JP2016108999A - Start control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly and steeply raise a rotation number of an engine while suppressing the generation of pre-ignition at a start of the engine.SOLUTION: A start control device (ECU 50) of an engine comprising a variable intake value mechanism 18 which can change the valve-closing timing of an intake valve 12 arranged at the engine 10 has a rotation-number steep rise control part 50a which controls the valve-closing timing of the intake valve 12 by the variable intake valve mechanism 18 so as to steeply raise an engine rotation number by increasing a suction air amount at a start of the engine. The rotation-number steep rise control part 50a estimates the limit valve-closing timing of the intake valve 12 at which pre-ignition for making an air-fuel mixture self-ignited is not generated prior to normal combustion start timing with spark ignition as a trigger, on the basis of an operation state of the engine 10, and controls the valve-closing timing of the intake valve 12 by imposing a limit on the timing so as not to exceed the limit valve-closing timing.SELECTED DRAWING: Figure 11

Description

  The present invention relates to an engine start control device that performs engine start control, and more particularly to an engine start control device including a variable intake valve mechanism that can change the closing timing of an intake valve provided in the engine. .

  2. Description of the Related Art Conventionally, in a sports car or the like, a technique has been proposed in which a sporty start feeling can be obtained by rapidly and rapidly decreasing an engine speed after the engine speed has been increased. For example, in Patent Document 1, when starting the engine, the ignition timing is advanced from the ignition timing at the time of idling, and the throttle valve is opened from the opening at the time of idling. Then, the ignition timing is retarded from the ignition timing at the time of idling, and the throttle valve is closed from the opening at the time of idling to increase the engine speed vigorously and then quickly and rapidly decrease the technology. Proposed.

JP 2013-231388 A

  However, in the technique described in Patent Document 1, the ignition timing is advanced when the engine is started. However, the control (in other words, the intake air amount is controlled to increase the effective compression ratio in order to increase the engine speed more quickly). When the control is increased, so-called pre-ignition in which the air-fuel mixture self-ignites before the normal combustion start timing triggered by spark ignition may occur. When pre-ignition occurs, as the combustion starts earlier, the combustion becomes sharper. As a result, the engine noise may increase or the piston or the like may be damaged. In order to suppress the occurrence of such pre-ignition, it is conceivable to apply a method of preventing the effective compression ratio from being increased (in other words, control to prevent the intake air amount from being increased). It will not be possible to quickly increase the engine speed.

  The present invention has been made to solve the above-described problems of the prior art, and at the time of starting the engine, it is possible to start the engine that can appropriately increase the engine speed while suppressing the occurrence of pre-ignition. An object is to provide a control device.

In order to achieve the above object, the present invention provides an engine start control device including a variable intake valve mechanism capable of changing a closing timing of an intake valve provided in an engine, and The engine has a speed increase control means for controlling the closing timing of the intake valve by a variable intake valve mechanism so as to increase the intake air amount and increase the engine speed rapidly. Based on the condition, estimate the limit closing timing of the intake valve that does not cause pre-ignition when the mixture self-ignites before the normal combustion start timing triggered by spark ignition, and this limit closing timing is not exceeded In this way, the valve closing timing of the intake valve is controlled by imposing restrictions.
In the present invention configured as above, when the intake valve closing timing is controlled so as to increase the intake air amount and rapidly increase the engine speed at the time of starting the engine, the limit closing timing should not be exceeded. Since the valve closing timing of the intake valve is controlled by restricting the intake valve, it is possible to appropriately increase the engine speed while suppressing the occurrence of pre-ignition. In particular, according to the present invention, when the intake air amount is increased, the intake valve having higher intake controllability (responsiveness) than controlling the throttle valve is controlled by the variable intake valve mechanism (the intake valve is a throttle valve). Therefore, the suppression of pre-ignition and the rapid increase of the engine speed can be achieved at a high level.

In the present invention, it is preferable that the engine speed increase control means does not limit the closing timing of the intake valve by the limit valve closing timing while the engine speed is less than the predetermined value, and the engine speed exceeds the predetermined value. Then, the closing timing of the intake valve is limited by the limit closing timing.
In the present invention configured as described above, the intake valve closing timing is limited by the limit closing timing only when the engine speed is equal to or greater than a predetermined value, and the engine speed is less than the predetermined value. Does not limit the closing timing of the intake valve by the limit closing timing. This is because when the engine speed is low, pre-ignition is unlikely to occur because the in-cylinder temperature is low. In addition, even if pre-ignition occurs, the time during which the engine speed is less than a predetermined value is considerably short (for example, only a few ignitions are performed in the engine), so that it is hardly affected by the pre-ignition. . According to the present invention, when the engine speed is less than a predetermined value, the intake valve is closed so as to sufficiently increase the intake air amount without imposing a restriction for suppressing pre-ignition. The timing can be controlled, and the engine speed can be effectively increased rapidly.

In the present invention, preferably, the rotation speed rapid increase control means controls the valve closing timing of the intake valve to the advance side within a range not exceeding the limit valve closing timing.
In the present invention configured as described above, the closing timing of the intake valve is advanced as much as possible within a range that does not exceed the limit closing timing, so that pre-ignition suppression and rapid increase in engine speed are appropriately realized. be able to.

In the present invention, preferably, the rotation speed rapid increase control means sets an effective compression ratio limit, which is an upper limit effective compression ratio at which pre-ignition does not occur, based on the engine rotation speed, the engine load, and the environmental conditions under which the engine is operated. Estimate and obtain the limit closing timing based on this effective compression ratio limit.
In the present invention configured as described above, an accurate limit closing timing can be applied, and pre-ignition can be effectively suppressed.

  According to the engine start control device of the present invention, when the engine is started, it is possible to appropriately increase the engine speed while suppressing the occurrence of pre-ignition.

1 is a schematic configuration diagram of an engine system to which an engine start control device according to an embodiment of the present invention is applied. It is a block diagram which shows the function structure of ECU by embodiment of this invention. It is explanatory drawing of the valve closing timing of the intake valve used in embodiment of this invention. It is a map in which the valve closing timing of the intake valve used in the embodiment of the present invention is defined. It is explanatory drawing which shows how to obtain | require the limit valve closing timing of an intake valve by embodiment of this invention. It is a time chart which shows the rotation speed rapid increase control at the time of start by embodiment of this invention. It is a map in which the current change rate limit value used in the embodiment of the present invention is defined. It is a time chart which shows the alternator power generation control at the start according to the embodiment of the present invention. It is a flowchart which shows the engine starting control by embodiment of this invention. It is a flowchart which shows the rotation speed rapid increase control at the time of start by embodiment of this invention. It is a flowchart which shows the target valve closing timing setting control by embodiment of this invention. It is a flowchart which shows the alternator power generation control at the time of start by embodiment of this invention.

  Hereinafter, an engine start control device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

<System configuration>
First, an engine system to which an engine start control device according to an embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an engine system to which an engine start control device according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the engine system 100 mainly includes an intake passage 1 through which intake air (air) introduced from the outside passes, intake air supplied from the intake passage 1, and a fuel injection valve 13 described later. An engine 10 (specifically, a gasoline engine) that generates a vehicle power by burning an air-fuel mixture with the supplied fuel, an exhaust passage 25 that discharges exhaust gas generated by combustion in the engine 10, and an engine Sensors 31 to 38 that detect various states related to the system 100 and an ECU (Electronic Control Unit) 50 that controls the entire engine system 100 are included.

  In the intake passage 1, in order from the upstream side, an air cleaner 3 for purifying intake air introduced from the outside, a throttle valve 5 for adjusting the amount of intake air (intake air amount) passing through, and the intake air supplied to the engine 10 temporarily. And a surge tank 7 for storing automatically.

  The engine 10 mainly supplies an intake valve 12 for introducing the intake air supplied from the intake passage 1 into the combustion chamber 11, a fuel injection valve 13 for injecting fuel toward the combustion chamber 11, and a supply to the combustion chamber 11. Spark plug 14 for igniting the mixture of the intake air and fuel, a piston 15 reciprocating by combustion of the air-fuel mixture in the combustion chamber 11, a crankshaft 16 rotated by reciprocating motion of the piston 15, and combustion And an exhaust valve 17 that exhausts exhaust gas generated by combustion of the air-fuel mixture in the chamber 11 to the exhaust passage 25.

  In addition, the engine 10 has variable intake valve mechanisms 18 and variable exhaust valve mechanisms in which the operation timings (corresponding to valve phases) of the intake valve 12 and the exhaust valve 17 are variable valve timing mechanisms. 19 is variably configured. As the variable intake valve mechanism 18 and the variable exhaust valve mechanism 19, various known types can be applied. For example, the operation of the intake valve 12 and the exhaust valve 17 is performed using a mechanism configured in an electromagnetic or hydraulic manner. Change the timing.

  Further, the engine 10 is provided with an alternator 21 as a generator that is rotated by the output of the engine 10 to generate electric power. The alternator 21 charges the battery 22 with the generated power. The battery 22 is electrically connected to various components (including the ECU 50) in the vehicle, and supplies power to these components.

  The exhaust passage 25 is mainly provided with exhaust purification catalysts 26a and 26b having an exhaust gas purification function, such as a NOx catalyst, a three-way catalyst, and an oxidation catalyst. Hereinafter, when the exhaust purification catalysts 26a and 26b are used without being distinguished from each other, they are simply referred to as “exhaust purification catalyst 26”.

  The engine system 100 is provided with sensors 31 to 38 that detect various states relating to the engine system 100. Specifically, the air flow sensor 31 detects the intake air amount corresponding to the flow rate of the intake air passing through the intake passage 1, and the throttle opening sensor 32 detects the throttle opening that is the opening of the throttle valve 5. The pressure sensor 33 detects the intake manifold pressure (intake manifold pressure) corresponding to the pressure of the intake air supplied to the engine 10. The crank angle sensor 34 detects the crank angle in the crankshaft 16, the water temperature sensor 35 detects the water temperature that is the temperature of the cooling water that cools the engine 10, and the temperature sensor 36 is in the cylinder of the engine 10. The in-cylinder temperature that is the temperature is detected, and the cam angle sensors 37 and 38 detect the operation timing including the closing timing of the intake valve 12 and the exhaust valve 17, respectively. These various sensors 31 to 38 output detection signals S31 to S38 corresponding to the detected parameters to the ECU 50, respectively.

  The ECU 50 controls the components in the engine system 100 based on the detection signals S31 to S38 input from the various sensors 31 to 38 described above. Specifically, the ECU 50 supplies the control signal S5 to the throttle valve 5, controls the opening / closing timing and throttle opening of the throttle valve 5, supplies the control signal S13 to the fuel injection valve 13, and the fuel injection amount. Control the fuel injection timing, supply the control signal S14 to the spark plug 14, control the ignition timing, and supply the control signals S18, S19 to the variable intake valve mechanisms 18, 19, the intake valve 12 and the exhaust valve The control signal S21 is supplied to the alternator 21 to control the generated current of the alternator 21 and the like.

  Here, a functional configuration of the ECU 50 according to the embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, the ECU 50 according to the present embodiment functionally prohibits the control of the rapid rotation speed increase control unit 50a, the power generation control unit 50b, the fuel cut control unit 50c, the catalyst warm-up control unit 50d, and the control prohibition. Part 50e.

  The rotation speed rapid increase control unit 50 a performs control for rapidly increasing the engine rotation speed when the engine 10 is started. Specifically, the rotation speed rapid increase control unit 50a controls the closing timing of the intake valve 12 via the variable intake valve mechanism 18 so as to increase the intake air amount and increase the engine rotation speed (in this case). The rotation speed rapid increase control unit 50a functions as intake valve closing timing control means). In addition, the power generation control unit 50 b controls the power generation current of the alternator 21. Further, the fuel cut control unit 50 c controls the stop of fuel injection to the engine 10 and the restart of fuel injection to the engine 10. The catalyst warm-up control unit 50d performs control for activating the exhaust purification catalyst 26 at an early stage when the exhaust purification catalyst 26 is in an inactive state. When the temperature of the exhaust purification catalyst 26 needs to be raised when the engine 10 is started, specifically, when the control by the catalyst warm-up control unit 50d is performed, the control prohibiting unit 50e is a rotational speed rapid increase control unit 50a. Both stop control and stop of fuel injection by the fuel cut control unit 50c are prohibited.

  Thus, the ECU 50 corresponds to the “engine start control device” in the present invention.

<Control by ECU>
Next, the control performed by the ECU 50 in the embodiment of the present invention will be specifically described.

In the present embodiment, the ECU 50 performs control for rapidly increasing the engine rotational speed and realizing control for rapidly decreasing the engine rotational speed after the control in order to realize a sporty starting feeling when the engine 10 is started. Specifically, when the engine 10 starts up (assuming that it is after a complete explosion), the ECU 50 increases the intake air amount so that the engine speed rapidly increases toward the target speed. Thus, the valve closing timing of the intake valve 12 is controlled by the variable intake valve mechanism 18. Hereinafter, the control performed by the rotation speed rapid increase control unit 50a in this way is referred to as “starting rotation speed rapid increase control”.
Further, in order to rapidly reduce the engine speed after execution of the start-up speed increase control, the fuel cut control unit 50c of the ECU 50 stops the fuel injection to the engine 10 and the power generation control unit 50b of the ECU 50 Then, control for applying a load to the engine 10 by power generation by the alternator 21 is performed. Specifically, the power generation control unit 50b executes control to increase the power generation current of the alternator 21 in order to increase the load of the alternator 21. In this case, the power generation control unit 50b starts control to increase the power generation current of the alternator 21 during execution of the start-up rotation speed rapid increase control, and a large generation current is secured at the end of the start-up rotation speed rapid increase control. To be. Hereinafter, the control performed by the power generation control unit 50b is referred to as “starting alternator power generation control”.

Further, in the present embodiment, when the temperature of the exhaust purification catalyst 26 needs to be raised when the control prohibiting unit 50e of the ECU 50 is started, specifically, the control by the catalyst warm-up control unit 50d is performed. In this case, both the start-up speed rapid increase control by the rotational speed rapid increase control unit 50a and the stop of fuel injection by the fuel cut control unit 50c are prohibited (including alternator power generation control at start-up by the power generation control unit 50b).
Note that the catalyst warm-up control unit 50d of the ECU 50 operates an AWS (Accelerated Warm-up System) to activate the exhaust purification catalyst 26 at an early stage when the exhaust purification catalyst 26 is in an inactive state. This AWS increases the amount of intake air when the exhaust purification catalyst 26 is in an inactive state, for example, immediately after a cold start of the engine 10, for example, compared to when it is in an active state in the same operating state (for example, idle operation). In addition, the ignition timing is retarded beyond the compression top dead center. By doing so, the air-fuel mixture is burnt after the expansion stroke, the exhaust gas temperature and the exhaust heat quantity are increased, and the warming-up of the exhaust purification catalyst 26 is promoted.

  Hereinafter, the above-described start speed rapid increase control and start alternator power generation control will be specifically described.

(Starting speed rapid increase control)
First, an outline of the start-up rotation speed rapid increase control will be briefly described. When the engine 10 is started, the sudden increase control unit 50a of the ECU 50 increases the intake air amount so that the engine rotation speed rapidly increases toward the target rotation speed by the variable intake valve mechanism 18 to close the intake valve 12. Control to set the valve timing to the advance side. In this case, in the present embodiment, the rotation speed rapid increase control unit 50a estimates the limit closing timing of the intake valve 12 at which pre-ignition does not occur based on the operating state of the engine 10, and does not exceed the limit closing timing. In this way, the limit closing timing of the intake valve 12 is controlled to control the limit closing timing of the intake valve 12, that is, the closing timing of the intake valve 12 is advanced within a range not exceeding the limit closing timing.

  Here, the pre-ignition is an abnormal combustion phenomenon in which the air-fuel mixture self-ignites before the normal combustion start timing due to spark ignition due to the excessive increase in the temperature and pressure of the combustion chamber 11 or the like. is there. When pre-ignition occurs, combustion becomes steep due to the self-ignition of the air-fuel mixture at an early stage, so that there is a possibility that the engine noise becomes considerably loud and the piston 15 and the like are damaged. Therefore, in the present embodiment, the rapid rotation speed increase control unit 50a of the ECU 50 advances the closing timing of the intake valve 12 using the limit closing timing as described above in order to suppress the occurrence of such pre-ignition. Limit the degree of cornering. This limit valve closing timing is the valve closing timing of the intake valve 12 corresponding to the upper limit effective compression ratio at which pre-ignition does not occur (in other words, the upper limit intake air amount at which pre-ignition does not occur).

Next, with reference to FIG. 3, the reason why the closing timing of the intake valve 12 is controlled to the advance side as the engine speed rapid increase control in the embodiment of the present invention will be described. FIG. 3 shows the crank angle in the horizontal direction, and schematically shows the operation timing of the intake valve 12 and the exhaust valve 17. Specifically, graphs G11 and G12 show the operation timing of the intake valve 12, and graph G13 shows the operation timing of the exhaust valve 17.
Here, the time during which the intake valve 12 is opened (the time from opening to closing) is not changed by the operation of the variable intake valve mechanism 18, and the opening timing and closing of the intake valve 12 are not changed. A configuration in which the timing changes is illustrated (the same applies to the variable exhaust valve mechanism 19).

  A graph G12 shown in FIG. 3 shows the operation timing of the intake valve 12 applied when the engine 10 is normally started (corresponding to the case where the engine 10 is started without executing the rapid rotation speed increase control at startup). ing. As shown in the graph G12, when the engine 10 is normally started, the operation timing of the intake valve 12 is set to the retard side in order to reduce pump loss and the like. In this way, since the intake valve 12 is closed after bottom dead center, the intake valve 12 is opened during the compression operation by the piston 15, and therefore the intake air is discharged from the cylinder through the intake valve 12 in accordance with the compression operation. As a result, the amount of intake air is reduced. During normal starting, the intake valve 12 is opened after top dead center and the intake valve 12 is closed after bottom dead center to reduce the amount of intake air, thereby making the throttle valve 5 open easily. Yes.

  In contrast, in the present embodiment, when the engine speed rapid increase control is performed, as shown in the graph G11, the operation timing of the intake valve 12 applied when the engine 10 is started is shown in the normal start shown in the graph G12. It is set to an advance side with respect to the operation timing of the intake valve 12 that is sometimes applied (see arrow A11). By doing so, the intake valve 12 is closed near the bottom dead center, and therefore, the intake valve 12 is closed during the compression operation by the piston 15. Will not be discharged, and a large amount of intake air will be secured. Therefore, in the present embodiment, when the engine 10 is started, the sudden increase controller 50a of the ECU 50 sets the operation timing of the intake valve 12 at the normal start in order to increase the intake air amount so as to increase the engine speed rapidly. In particular, the closing timing of the intake valve 12 is set to an advance side relative to the normal start. However, although the effective compression ratio increases as the intake air amount increases, the possibility of pre-ignition increases when the effective compression ratio becomes too high. The closing timing of the intake valve 12 is advanced within a range where no ignition occurs.

  By the way, due to the inertia of the intake air flowing from the intake passage 1 toward the engine 10, the intake air may be introduced into the cylinder of the engine 10 even after the bottom dead center. Specifically, when the engine speed is high, the flow rate of intake air is large, so that intake air is introduced into the cylinder even at the timing after the bottom dead center, for example, as indicated by reference numeral L11 in FIG. The Rukoto. In this case, as the engine speed increases, the inertia of the intake air increases, and the timing at which the intake air is introduced into the cylinder moves toward the retarded side even after the bottom dead center. Therefore, in a region where the engine speed is high, a sufficient intake air amount can be secured to increase the engine speed even if the closing timing of the intake valve 12 is retarded.

Therefore, in the present embodiment, the engine speed rapid increase control unit 50a advances the closing timing of the intake valve 12 as described above while the engine speed is less than the predetermined value that is less than the target engine speed. Control is performed (see arrow A11), and control is performed to retard the closing timing of the intake valve 12 (see arrow A12) when the engine speed exceeds the predetermined value. In this case, the rotation speed rapid increase control unit 50a moves according to the increase in the engine rotation speed, and sets the closing timing of the intake valve 12 in accordance with the timing at which intake air is introduced into the cylinder even after bottom dead center. Retard.
The above-mentioned predetermined value is, for example, 1600-1800 rpm when the target rotational speed is 2300 rpm (revolution per minute). Hereinafter, this predetermined value is referred to as a “first threshold value”. The first threshold value is set based on the engine speed at which the intake air is introduced into the cylinder even after the bottom dead center due to the inertia of the intake air even when the closing timing of the intake valve 12 is retarded.

  On the other hand, when the engine speed reaches the target speed by the control of the closing timing of the intake valve 12 as described above (that is, the start-up speed rapid increase control), the engine load is reduced by closing the throttle valve 5 or the like. Since the flow rate of the intake air becomes small, the timing at which the intake air is introduced into the cylinder moves toward the advance side even after the bottom dead center. Therefore, as described above, if the valve closing timing of the intake valve 12 is retarded before the engine speed reaches the target speed, the intake air amount is reduced after the engine speed reaches the target speed. Since the engine speed is small, the engine speed decreases rapidly.

Next, with reference to FIG. 4, a map that defines the closing timing of the intake valve 12 to be set (corresponding to the intake VVT phase) used in the embodiment of the present invention will be described.
FIG. 4A shows the engine speed in the horizontal direction and the engine load in the vertical direction, and the closing timing of the intake valve 12 used in the normal control without performing the start-up speed rapid increase control is shown. A predetermined map (hereinafter referred to as “normal control map”) is schematically shown. FIG. 4B shows the engine speed in the horizontal direction and the engine water temperature in the vertical direction, and the closing timing of the intake valve 12 used when the engine speed rapid increase control at the start is performed. 1 schematically shows a map (hereinafter referred to as “starting speed rapid increase control map”). Note that “·” in FIGS. 4A and 4B represents specific numerical values defined in the map instead.

  As shown in FIG. 4A, in the normal control map, generally, in the region where the engine speed is low to medium speed, the valve closing timing of the intake valve 12 is advanced as the engine speed increases. In the region where the engine speed is equal to or higher than the medium speed, the valve closing timing of the intake valve 12 is determined to be retarded as the engine speed increases. In the normal control map, generally, the valve closing timing of the intake valve 12 is advanced as the engine load increases. Such a normal control map considers the inertia of the intake air and takes into account the time required for the stroke in the engine 10 according to the engine speed (the higher the speed, the shorter the stroke time). Regardless of the state, the intake air amount is substantially constant (that is, the effective compression ratio is substantially constant), and the valve closing timing of the intake valve 12 is determined so as to ensure fuel efficiency and achieve stable rotation of the engine 10. .

  On the other hand, as shown in FIG. 4 (B), in the starting speed rapid increase control map, generally, the higher the engine speed (assumed only for low to medium speeds), It is determined that the closing timing of the intake valve 12 is advanced. Specifically, in the starting speed rapid increase control map, the valve closing timing is set on the advance side in the same operation state as in the normal control map. Further, in the map for starting speed rapid increase control, it is generally determined that the closing timing of the intake valve 12 is advanced as the engine water temperature increases.

  Next, with reference to FIG. 5, a description will be given of a limit closing timing applied to the closing timing of the intake valve 12 in order to suppress the occurrence of pre-ignition in the embodiment of the present invention. FIG. 5A shows a diagram for explaining a calculation method of the limit valve closing timing, and FIG. 5B schematically shows a map used when calculating the limit valve closing timing. In FIG. 5B, only the tendency of numerical values defined in the map is shown, and specific numerical values are not shown.

  In the present embodiment, as shown in FIG. 5A, the ECU 50 (specifically, the rotational speed rapid increase control unit 50a), the engine rotational speed, the fuel octane number, the in-cylinder temperature of the engine 10, and the engine 10 Based on the intake manifold pressure (corresponding to the engine load), an effective compression ratio limit which is an upper limit directional compression ratio at which pre-ignition does not occur is obtained using a predetermined arithmetic expression and map. In this case, the rapid rotation speed increase control unit 50a determines that pre-ignition is likely to occur when the engine speed is a predetermined value (for example, 2000 rpm) or less, that pre-ignition is likely to occur when the octane number is low, and that the pre-ignition temperature is high. The effective compression ratio limit is obtained in consideration of the tendency that ignition is likely to occur and pre-ignition is likely to occur if the intake manifold pressure is high. For example, the method disclosed in Japanese Patent No. 5360121 can be applied to a specific method for obtaining the effective compression ratio limit.

  Thereafter, the rotational speed rapid increase control unit 50a refers to the map shown in FIG. 5B to determine the limit closing timing of the intake valve 12 corresponding to the effective compression ratio limit determined as described above. In this map, the larger the effective compression ratio limit is, the more the limit valve closing timing is set to be on the more advanced side.In other words, the smaller the effective compression ratio limit is, the more the limit valve closing timing is on the more retarded side. It is determined to be.

In the present embodiment, the rapid rotation speed increase control unit 50a of the ECU 50 limits the closing timing of the intake valve 12 by the limit closing timing only when the engine speed is equal to or higher than a predetermined value (for example, 500 rpm). . That is, the rotation speed rapid increase control unit 50a does not limit the closing timing of the intake valve 12 by the limit closing timing while the engine rotation speed is less than the predetermined value. This is because when the engine speed is low, pre-ignition is unlikely to occur because the in-cylinder temperature is low. Even if pre-ignition occurs, the time during which the engine speed is less than a predetermined value is considerably short (for example, only a few ignitions are performed while the engine speed is less than 500 rpm). This is because it is hardly affected by the ignition.
Hereinafter, the predetermined value is referred to as a “second threshold value”. The second threshold value is set based on the engine speed at which pre-ignition is unlikely to occur or the engine speed at which no problem occurs even if pre-ignition occurs.

  Next, with reference to FIG. 6, the engine speed rapid increase control according to the embodiment of the present invention will be described more specifically. FIG. 6 is a time chart showing an example of the start-up rotation speed rapid increase control according to the embodiment of the present invention. In FIG. 6, the graph G21 shown above shows the change over time of the engine speed. In addition, graphs G22 and G23 shown below in FIG. 6 indicate the time change of the closing timing of the intake valve 12 (corresponding to the intake VVT phase). Specifically, the graph G22 shows the limit closing timing of the intake valve 12, and the graph G23 is the target closing timing of the intake valve 12 (substantially the same as the actual closing timing of the intake valve 12). Is shown.

  First, at time t21, the control for starting the engine 10 is started, for example, when the ignition signal is switched from OFF to ON. Specifically, as shown in the graph G21, the engine 10 is cranked by the starter from time t21 to time t22 (see arrow A21). For example, the engine speed is increased to about 200 rpm by cranking.

Then, from time t22, in the engine 10, fuel is injected from the fuel injection valve 13 and ignited by the spark plug 14, and the air-fuel mixture burns, whereby the engine speed increases. In this case, the rotational speed rapid increase control unit 50a of the ECU 50 increases the intake air amount so that the engine rotational speed increases rapidly toward the target rotational speed N22, as shown in the graph G23. Set the time to the advance side. Specifically, the rotational speed rapid increase control unit 50a obtains a limit closing timing at which no pre-ignition occurs as shown in the graph G22 based on the operating state of the engine 10, and advances the target closing timing of the intake valve 12. When making the angle, a limit is imposed so as not to exceed the limit closing timing, that is, the target valve closing timing of the intake valve 12 is advanced as much as possible within a range not exceeding the limit closing timing (see arrows A22 and A23). Thereby, generation | occurrence | production of preignition is suppressed, and an engine speed will rise rapidly (refer arrow A24).
Although not shown in FIG. 6, the rotational speed rapid increase control unit 50 a advances the ignition timing from the normal start in addition to the control for advancing the closing timing of the intake valve 12 as described above. The engine speed is increased rapidly by performing control to make the angle and control to make the throttle opening larger than that at the normal start.

  Thereafter, at time t23, the engine speed reaches the first threshold value N21 that is less than the target speed N22. At this time, the rotation speed rapid increase control unit 50a retards the target valve closing timing of the intake valve 12 (see arrow A25). Thus, even if the target valve closing timing is retarded, the engine speed is high, and the intake air amount is secured by the inertia of the intake air, so that the rapid increase in the engine speed is maintained (see arrow A26).

  Thereafter, the engine speed reaches the target speed N22. In this case, the rotational speed rapid increase control unit 50a directly uses the engine rotational speed corresponding to the detected value of the crank angle sensor 34 to determine whether or not the engine rotational speed has reached the target rotational speed N22. Instead, it is determined whether or not the engine speed has reached the target speed N22 based on the time elapsed since the engine speed has reached the first threshold value N21. Specifically, the rotational speed rapid increase control unit 50a sets a time (estimated time) required from the time when the engine speed reaches the first threshold value N21 to the target speed N22 set in advance, or from that time. When the predetermined time T21 has elapsed since the engine speed reached the first threshold value N21 using the predetermined time T21, which is a longer time (time t24), the engine speed has reached the target speed N22. to decide. At this time, the ECU 50 controls the closing of the throttle valve 5 so as to rapidly decrease the engine speed, the control for stopping the fuel injection to the engine 10 (fuel cut), and the start time alternator for the generated current of the alternator 21. (Strictly speaking, the alternator power generation control at the start is started during the execution of the rapid rotation speed increase control at the start). In addition, when the fuel injection to the engine 10 is resumed (specifically, when a predetermined return condition is satisfied), the ECU 50 should suppress an increase in the engine speed due to the resumption of the fuel injection. Then, the closing timing of the intake valve 12 is further retarded (see arrow A27).

  As described above, the crank angle sensor determines whether or not the engine speed has reached the target speed N22 based on the time elapsed since the engine speed has reached the first threshold value N21. This is because the following problems may occur if this determination is made using the engine speed corresponding to the detected value of 34 directly. First, when the determination is made using the engine speed directly, the engine speed does not reach the target speed N22 due to the oil applied to the engine 10 and the engine speed reaches the target speed. By continuing to determine that N22 has not been reached, there may be a problem in that subsequent control (specifically, control for rapidly reducing the engine speed) is not performed. Secondly, if the determination is made by directly using the engine speed, the determination takes time, and there may be a problem that the engine speed cannot be reduced in a short time. . Third, when the determination is made using the engine speed directly, whether or not the engine speed has reached the target speed N22 when the engine speed increases or decreases across the target speed N22. There may be a problem that it is difficult to make an appropriate decision.

(Alternator power generation control at start-up)
Next, the alternator power generation control at the start will be specifically described. In the present embodiment, the power generation control unit 50b of the ECU 50 causes the power generation current of the alternator 21 to be a predetermined value when the engine speed reaches the target speed or immediately after the target speed is reached by the above-described start-up rotation speed rapid increase control. Control is performed to increase the generated current of the alternator 21 so as to be equal to or greater than the value (preferably, the generated current is the maximum value). In this case, the power generation control unit 50b starts control to increase the power generation current of the alternator 21 during the start-up rotation speed rapid increase control.

  Thus, the reason for starting the control to increase the generated current of the alternator 21 during the execution of the start-up rotation speed rapid increase control is as follows. In order to rapidly reduce the engine speed after the engine speed is rapidly increased by the engine speed rapid increase control at the time of starting the engine, the generated current of the alternator 21 is increased as much as possible at the timing at which the engine speed should be decreased. It is desirable to keep it. Preferably, the generated current of the alternator 21 is set to a maximum value. In this case, it is difficult to immediately set the generated current of the alternator 21 to the maximum value, and it takes time until the generated current of the alternator 21 is set to the maximum value. Therefore, in the present embodiment, the power generation control unit 50b starts control to increase the power generation current of the alternator 21 during the start-up rotation speed rapid increase control. Specifically, the power generation control unit 50b performs a predetermined value (for example, 350 rpm. Hereinafter, the predetermined value is referred to as a “third threshold value”) with the engine speed being less than the target speed by the start-up speed rapid increase control. When the value reaches, control for increasing the generated current of the alternator 21 is started.

  Further, in the present embodiment, the power generation control unit 50b sets the third threshold value of the engine speed for starting the control for increasing the power generation current of the alternator 21 from the engine speed corresponding to the third threshold value to the alternator 21. When the control for increasing the generated current is started, the engine in which the generated current of the alternator 21 accurately reaches the maximum value when the engine speed reaches the target speed or immediately after reaching the target speed. Set to the number of revolutions. Preferably, since the time until the generated current of the alternator 21 reaches the maximum value varies depending on the state of the alternator 21, the engine that starts the control to increase the generated current of the alternator 21 according to the state of the alternator 21 is started. It is preferable to change the third threshold value of the rotational speed. By doing so, the generated current of the alternator 21 can be accurately reached to the maximum value when the engine speed reaches the target speed or immediately after reaching the target speed.

  Further, in the present embodiment, the power generation control unit 50b increases the target voltage of the battery 22 when the control for increasing the power generation current of the alternator 21 as described above is performed, and the amount of charge that can be accepted by the battery 22 is increased. Increase, in other words, increase the upper limit of power generation.

  Furthermore, in this embodiment, the power generation control unit 50b functions as a current change rate limiting unit, sets a current change rate limit value according to the deviation between the target voltage of the battery 22 and the actual voltage, and sets the current change rate limit value of the alternator 21. The generated current of the alternator 21 is increased while limiting the change rate of the generated current to less than the current change rate limit value. In particular, in the present embodiment, the power generation control unit 50b is in a normal state (meaning a case where the start-up rotation speed rapid increase control is not performed; the same applies hereinafter) when the start-up rotation speed rapid increase control is performed. Rather, the current change rate limit value is increased to relax the limitation on the change rate of the generated current of the alternator 21.

  With reference to FIG. 7, the current change speed limit value will be described in detail. FIG. 7 shows a map in which the current change rate limit value used in the embodiment of the present invention is defined. In FIG. 7, the horizontal axis indicates the deviation between the target voltage and the actual voltage of the battery 22 (target voltage−actual voltage), and the vertical axis indicates the current change speed limit value. Specifically, the graph G31 shows a map of the current change speed limit value that is used during normal time when the engine speed rapid increase control is not performed, and the graph G32 is used when the engine speed rapid increase control is performed. A map of current change speed limit values is shown.

  As shown in the graph G31, the map of the current change speed limit value used in the normal state is such that the current change speed limit value decreases as the deviation decreases in a region where the deviation between the target voltage and the actual voltage is less than a predetermined value. (In other words, the limit imposed on the change rate of the generated current is set to be large), whereas in the region where the deviation between the target voltage and the actual voltage is a predetermined value or more, Regardless of the deviation, the current change rate limit value is set to be constant (that is, the limit imposed on the change rate of the generated current is set to be constant). On the other hand, as shown in the graph G32, the map of the current change speed limit value used when the engine speed rapid increase control is performed is larger as the deviation increases over the entire range of deviation between the target voltage and the actual voltage. The current change rate limit value is set to be large (that is, the limit imposed on the change rate of the generated current is set to be small).

Here, as described above, the limitation on the change rate of the generated current of the alternator 21 using the current change rate limit value is due to the overshoot (excessive voltage rise) of the voltage of the battery 22. This is to prevent it. If an overshoot of the voltage of the battery 22 occurs, a fault is erroneously determined by exceeding the guaranteed voltage of the control unit of the battery 22, the bulb life of the lamps in the vehicle is shortened, or the battery 22 is excessive. Since it becomes charged, overshooting is prevented by using a current change speed limit value. However, troubles due to overshoot occur when the amount of overshoot is large or when the overshoot occurs for a long time. Problems caused by excessive overshoot are not particularly problematic.
Therefore, in the present embodiment, when starting speed rapid increase control is performed, the current change rate limit value is made larger than normal (see graph G32), and the limit of the change rate of the generated current of the alternator 21 is relaxed. By doing so, priority is given to an increase in the generated current of the alternator 21 over the prevention of the overshoot of the voltage of the battery 22, and the generated current is quickly reached to the maximum value. If such a large current change speed limit value is continuously used, overshooting of the voltage of the battery 22 is likely to occur. However, in this embodiment, only in a region where the deviation between the target voltage and the actual voltage is relatively large. In the region where the current change speed limit value is larger than that in the normal time and the deviation between the target voltage and the actual voltage is relatively small, the current change speed limit value is decreased as in the normal time (see graphs G31 and G32). When the actual voltage approaches the target voltage, the limit of the change rate of the generated current is strengthened to prevent overshoot.

  Next, the alternator power generation control at the start time according to the embodiment of the present invention will be described more specifically with reference to FIG. FIG. 8 is a time chart showing an example of start alternator power generation control according to the embodiment of the present invention.

  In FIG. 8, a graph G41 shows the actual voltage of the battery 22 when the start alternator power generation control according to this embodiment is executed, and the graph G42 does not execute the start time alternator power generation control according to this embodiment. The actual voltage of the battery 22 is shown as a comparative example. Further, the graph G43 shows the engine speed when both the start speed rapid increase control and the start alternator power generation control according to the present embodiment are executed, and the graph G44 shows the start speed rapid increase according to the present embodiment. The engine speed when only control is executed (that is, when alternator power generation control at start-up is not executed) is shown as a comparative example. A graph G45 shows a target current of the alternator 21 when the start alternator power generation control according to the present embodiment is executed, and a graph G46 shows a case where the start time alternator power generation control according to the present embodiment is executed (that is, the graph). The graph G47 shows the actual current of the alternator 21 when the current is controlled based on the target current shown in G45, and the graph G47 shows the actual current of the alternator 21 when the start-time alternator power generation control according to this embodiment is not executed. Is shown as a comparative example.

First, at time t41, the control for starting the engine 10 is started, for example, when the ignition signal is switched from OFF to ON, and the engine 10 is cranked by the starter. Thereafter, in the engine 10, fuel is injected from the fuel injection valve 13 and is ignited by the spark plug 14 to burn the air-fuel mixture. At this time, as described above, the rotation speed rapid increase control unit 50a executes the engine speed rapid increase control. Thereby, the engine speed increases, and when the engine speed reaches the third threshold value N41 at time t42, the power generation control unit 50b starts to increase the target current of the alternator 21 as shown in the graph G45. .
In this case, the power generation control unit 50b applies a map of the current change speed limit value in which the restriction on the current change speed is relaxed, which is used when the engine speed rapid increase control is performed (see graph G32 in FIG. 7). The target current of the alternator 21 is increased. As a result, the target current of the alternator 21 greatly increases as indicated by an arrow A44 attached to the graph G45, and as a result, the alternator 21 follows the target current as indicated by an arrow A45 attached to the graph G46. The actual current increases greatly. As indicated by an arrow A41 attached to the graph G41, the actual voltage of the battery 22 increases toward the target voltage V41 (an example in which the target voltage V41 is substantially constant is shown in FIG. 8).

  When the alternator power generation control at start-up according to the present embodiment is not executed, the actual current of the alternator 21 hardly increases (see graph G47), and the actual voltage of the battery 22 hardly increases (see graph G42). .

  After this, immediately after the engine speed reaches the target speed by the start-up speed rapid increase control, as shown in the graph G46, the actual current of the alternator 21 becomes almost the maximum value. Therefore, when the maximum load due to the power generation of the alternator 21 is applied to the engine 10, the engine speed rapidly decreases as indicated by an arrow A42 attached to the graph G43. Specifically, the engine speed decreases with a steeper slope than when the alternator power generation control at the time of start is not executed (see arrow A43 attached to the graph G44).

<Processing flow>
Next, a processing flow performed by the ECU 50 in the embodiment of the present invention will be described with reference to FIGS.

  FIG. 9 is a flowchart showing engine start control according to the embodiment of the present invention. This flow is repeatedly executed by the ECU 50 at a predetermined cycle.

  First, in step S101, the ECU 50 determines whether there is a request for starting the engine 10. For example, the ECU 50 determines whether or not there is a request for starting the engine 10 based on an ignition signal on / off, a signal corresponding to an operation of a brake pedal and / or an accelerator pedal, and the like. As a result, when it is determined that there is no request for starting the engine 10 (step S101: No), the process returns to step S101. In this case, the ECU 50 repeats the determination in step S101 until it is determined that there is a request for starting the engine 10.

  On the other hand, when it is determined that there is a request for starting the engine 10 (step S101: Yes), the process proceeds to step S102, and the ECU 50 is a request corresponding to the restart after the engine automatic stop. It is determined whether or not. That is, the ECU 50 determines whether or not there is a request to restart the engine 10 after the engine 10 is automatically stopped by idling stop. As a result, when it is determined that the start request of the engine 10 is a request corresponding to the restart after the engine is automatically stopped (step S102: Yes), the process proceeds to step S103, and the ECU 50 is in the state of being automatically stopped. 10 is restarted.

  On the other hand, when it is determined that the start request of the engine 10 is not a request corresponding to restart after automatic engine stop (step S102: No), the process proceeds to step S104, and the ECU 50 requests the temperature of the exhaust purification catalyst 26 to be increased. It is determined whether or not there is. That is, the ECU 50 determines whether or not there is an AWS operation request for activating the exhaust purification catalyst 26 at an early stage. As a result, when it is determined that there is a request to raise the temperature of the exhaust purification catalyst 26 (step S104: Yes), the process proceeds to step S105, and the ECU 50 performs normal start control (normal Start control). That is, the control prohibition unit 50e of the ECU 50 prohibits both the control by the rapid rotation speed increase control unit 50a and the stop of the fuel injection by the fuel cut control unit 50c, and executes the normal start control. In this case, the catalyst warm-up control unit 50d of the ECU 50 operates the AWS so as to activate the exhaust purification catalyst 26 in an inactive state at an early stage. Specifically, the catalyst warm-up control unit 50d increases the intake air amount and exceeds the compression top dead center in order to quickly warm up the exhaust purification catalyst 26 by increasing the exhaust gas temperature (exhaust heat amount). To retard the ignition timing.

  On the other hand, if it is determined that there is no request to raise the temperature of the exhaust purification catalyst 26 (step S104: No), the process proceeds to step S106, where the ECU 50 suddenly increases the engine speed and then rapidly decreases the engine speed. Thus, in order to realize a sporty starting feeling when the engine is started, the engine speed rapid increase control according to the present embodiment is executed.

  Next, with reference to FIG. 10, the engine speed rapid increase control executed in step S106 of FIG. 9 will be described. FIG. 10 is a flowchart showing the engine speed rapid increase control according to the embodiment of the present invention. This flow is mainly executed by the rotational speed rapid increase control unit 50a of the ECU 50.

  First, in step S201, the rotational speed rapid increase control unit 50a cranks the engine 10 with a starter, and during that time, cylinder identification is performed based on the detection signal patterns of the crank angle sensor 34 and the cam angle sensor 37. I do. As a result, when cylinder identification is completed (step S201: Yes), it progresses to step S202, and when cylinder identification is not completed (step S201: No), it returns to step S201.

  Next, in step S202, the rotational speed rapid increase control unit 50a determines whether or not to end the cranking of the engine 10 and permit the fuel injection of the engine 10. As a result, when fuel injection is permitted (step S202: Yes), the process proceeds to step S203. In this case, the rotational speed rapid increase control unit 50a injects fuel into the cylinder to be injected based on the result of cylinder identification in step S201, and ignites the air-fuel mixture. On the other hand, when fuel injection is not permitted (step S202: No), the process returns to step S202.

  Next, in step S203, the rotation speed rapid increase control unit 50a performs control (target closure) for setting the target valve closing timing of the intake valve 12 to the advance side in order to increase the intake air amount and increase the engine rotation speed rapidly. Valve timing setting control). And after setting the target valve closing timing of the intake valve 12 by this target valve closing timing setting control, it progresses to step S204.

  Here, the target valve closing timing setting control executed in step S203 of FIG. 10 will be described with reference to FIG. FIG. 11 is a flowchart showing target valve closing timing setting control according to the embodiment of the present invention. This flow is executed by the rotational speed rapid increase control unit 50a of the ECU 50.

  First, in step S301, the rotation speed rapid increase control unit 50a acquires the operating state of the engine 10. Specifically, the rotational speed rapid increase control unit 50a performs the engine rotational speed corresponding to the crank angle detected by the crank angle sensor 34, the intake manifold pressure (corresponding to the engine load) detected by the pressure sensor 33, the water temperature The water temperature detected by the sensor 35, the in-cylinder temperature detected by the temperature sensor 36, and the like are acquired.

  Next, in step S302, the rotational speed rapid increase control unit 50a refers to the start rotational speed rapid increase control map shown in FIG. 4B, and corresponds to the engine rotational speed and water temperature acquired in step S301. The closing timing of the intake valve 12 to be acquired is acquired. Hereinafter, the valve closing timing acquired from the map (including not only the starting speed rapid increase control map but also the normal control map) will be referred to as “base valve closing timing” as appropriate.

  Next, in step S303, the rotational speed rapid increase control unit 50a obtains the limit closing timing of the intake valve 12 by the procedure shown in FIGS. 5 (A) and 5 (B). Specifically, the engine speed rapid increase control unit 50a first obtains an effective compression ratio limit based on the engine speed, octane number, in-cylinder temperature, and intake manifold pressure, and thereafter, as shown in FIG. With reference to the map, a limit valve closing timing corresponding to the obtained effective compression ratio limit is obtained. The octane number may be estimated based on the detection value of the vibration sensor provided in the engine 10. For example, when the vibration intensity detected by the vibration sensor is large, it can be estimated that the octane number is small.

  Next, in step S304, the rotational speed rapid increase control unit 50a determines whether or not the base valve closing timing acquired in step S302 is a valve closing timing on the advance side with respect to the limit valve closing timing obtained in step S303. To do. As a result, when the base valve closing timing is more advanced than the limit valve closing timing (step S304: Yes), the process proceeds to step S305, and the engine speed rapid increase control unit 50a sets the engine speed to the second threshold (for example, 500 rpm). ) Determine whether it is above. As a result, when the engine speed is equal to or greater than the second threshold (step S305: Yes), the process proceeds to step S306. In this case, since the engine speed is equal to or higher than the second threshold value, there is a situation where pre-ignition may occur, and the situation where pre-ignition occurs becomes a problem. In addition, since the base valve closing timing is more advanced than the limit valve closing timing, if this base valve closing timing is applied to the target valve closing timing of the intake valve 12, there is a high possibility that pre-ignition will occur. Therefore, in step S306, the rotational speed rapid increase control unit 50a sets not the base valve closing timing determined from the starting rotational speed rapid increase control map, but the limit valve closing timing that can suppress pre-ignition, as a target of the intake valve 12. Set the valve closing time.

  On the other hand, when the base valve closing timing is not advanced from the limit valve closing timing (step S304: No), or when the engine speed is not equal to or higher than the second threshold (step S305: No), the process proceeds to step S307. If the base valve closing timing is not an advance side of the limit valve closing timing, even if this base valve closing timing is set to the target valve closing timing of the intake valve 12, pre-ignition does not occur. In addition, when the engine speed is not equal to or higher than the second threshold value, the possibility of occurrence of pre-ignition is very low, and even when pre-ignition occurs, there is no particular problem. Therefore, in step S307, the rotational speed rapid increase control unit 50a sets the base valve closing timing determined from the starting rotational speed rapid increase control map to the target valve closing timing of the intake valve 12 as it is.

  Next, returning to FIG. 10, the control after step S204 will be described. In step S204, the rotation speed rapid increase control unit 50a sets the target opening (target throttle opening) of the throttle valve 5 and the target ignition timing of the spark plug 14. In this case, from the viewpoint of rapidly increasing the engine speed, the engine speed rapid increase control unit 50a sets the throttle opening larger than that at the normal start to the target throttle opening and the ignition timing advanced from the normal start. Is set to the target ignition timing.

  Next, in step S205, the rotational speed rapid increase control unit 50a performs the intake valve 12, throttle valve 5, based on the target valve closing timing set in step S203, the target throttle opening set in step S204, and the target ignition timing. And each of the spark plugs 14 is controlled.

  Next, in step S206, the rotation speed rapid increase control unit 50a determines whether or not the engine rotation speed is equal to or greater than a third threshold value (for example, 350 rpm). As a result, when the engine speed is not greater than or equal to the third threshold value (step S206: No), the process returns to step S203, and the control after step S203 is performed again.

  On the other hand, when the engine speed is equal to or greater than the third threshold (step S206: Yes), the process proceeds to step S207, where the engine speed rapid increase control unit 50a performs the start alternator power generation control flag for executing the start alternator power generation control. Is set to “1”. Thereby, the start alternator power generation control for increasing the power generation current of the alternator 21 is executed in parallel with the start time rotation speed rapid increase control. The details of the start alternator power generation control will be described later (see FIG. 12).

  Next, in step S209, the rotation speed rapid increase control unit 50a determines whether or not the engine rotation speed is equal to or higher than a first threshold value (for example, 1800 rpm). As a result, when the engine speed is not equal to or higher than the first threshold (step S209: No), the process returns to step S203, and the control after step S203 is performed again.

  On the other hand, when the engine speed is equal to or higher than the first threshold value (step S209: Yes), the process proceeds to step S210, and the rotation speed rapid increase control unit 50a refers to the normal control map shown in FIG. Then, the closing timing of the intake valve 12 corresponding to the current engine speed and engine load is acquired, and this closing timing is set as the target closing timing. In this case, the rotational speed rapid increase control unit 50a normally sets the target valve closing timing set on the advance side based on the starting rotational speed rapid increase control map by the target valve closing timing setting control (see FIG. 11) in step S203. The valve closing timing retarded based on the control map is set as a new target valve closing timing.

  Next, in step S211, the rotation speed rapid increase control unit 50a determines whether or not a predetermined time has elapsed since the engine rotation speed has reached the first threshold value. The rotational speed rapid increase control unit 50a determines whether or not the engine rotational speed has reached the target rotational speed by making this determination. As a result, when the predetermined time has not elapsed since the engine speed reached the first threshold value (step S211: No), the process returns to step S204, and the control after step S204 is performed again.

  On the other hand, when the predetermined time has elapsed since the engine speed reached the first threshold (step S211: Yes), the ECU 50 performs control for rapidly decreasing the engine speed in step S212 and thereafter. First, in step S212, the ECU 50 (specifically, the fuel cut control unit 50c) starts fuel cut control, that is, stops fuel injection into the engine 10. Next, in step S213, the ECU 50 further delays the valve closing timing (base valve closing timing) set in step S210 in order to suppress an increase in the engine speed due to the subsequent restart of fuel injection. The timing is set to the target valve closing timing of the intake valve 12. The control of step S213 is not limited to the control of step S213 after the control of step S212, and the control of step S212 may be performed after the control of step S213, that is, the target closing with the base valve closing timing retarded. The fuel injection may be stopped after the valve timing is set.

  Next, in step S214, the ECU 50 determines whether or not the engine speed is greater than or equal to a fourth threshold value. This determination is performed in order to determine whether or not the control (fuel cut or the like) for rapidly decreasing the engine speed may be finished and the state may be shifted to a normal idling state. This determination corresponds to determining whether or not a return condition for resuming fuel injection is satisfied. From such a viewpoint, the fourth threshold value used for the determination may be set to a rotational speed slightly higher than the idle rotational speed in consideration of the case where an air conditioner load or the like is present. For example, when the idle speed is about 550 rpm, the fourth threshold value may be set to about 700 rpm.

  If the result of determination in step S214 is that the engine speed is not greater than or equal to the fourth threshold (step S214: No), the process returns to step S212, and the control after step S212 is performed again. In this case, the ECU 50 continues the fuel injection stop state and continues the state in which the target valve closing timing of the intake valve 12 is retarded.

  On the other hand, when the engine speed is equal to or greater than the fourth threshold (step S214: Yes), the process proceeds to step S215, and the ECU 50 (specifically, the fuel cut control unit 50c) stops the fuel cut control, that is, the engine 10 Resume fuel injection to.

  Next, in step S216, the ECU 50 sets the start alternator power generation control flag to “0”. Thus, when the start alternator power generation control flag is set to “0”, the start alternator power generation control for rapidly decreasing the engine speed is terminated (see FIG. 12).

  Next, in step S217, the ECU 50 performs control to return various control values used for the intake valve 12, the throttle valve 5, the spark plug 14, and the like to control values (base set) to be applied during normal control.

  Next, the alternator power generation control at the start time according to the embodiment of the present invention will be described with reference to FIG. FIG. 12 is a flowchart illustrating alternator power generation control at start time according to the embodiment of the present invention. This flow is executed by the power generation control unit 50b of the ECU 50.

  First, in step S401, the power generation control unit 50b determines whether or not the start alternator power generation control flag is 1. Here, the power generation control unit 50b determines whether or not start alternator power generation control for rapidly decreasing the engine speed is to be executed. As described above, the start alternator power generation control flag is set to “1” in step S207 shown in FIG.

  If the start alternator power generation control flag is not 1 as a result of the determination in step S401 (step S401: No), the process proceeds to step S412 and the power generation control unit 50b displays a map of current change speed limit values used during normal operation (the graph of FIG. Referring to G31), the current change rate limit value (hereinafter, the current change rate limit value set based on the map of the graph G31 in FIG. 7) is determined according to the deviation between the target voltage and the actual voltage of the battery 22. This is called “first current change speed limit value”). In step S 413, the power generation control unit 50 b sets the target voltage to be applied at the normal time (hereinafter referred to as “normal time target voltage”) as the target voltage of the battery 22. The power generation control unit 50b controls the power generation of the alternator 21 based on the first current change speed limit value and the normal target voltage set as described above.

  On the other hand, if the start alternator power generation control flag is 1 (step S401: Yes), the process proceeds to step S402, and the power generation control unit 50b increases the amount of charge that the battery 22 can accept, in other words, the power generation amount. In order to increase the upper limit, a voltage increased from the normal target voltage is set as a target voltage (hereinafter referred to as “starting target voltage”). For example, the power generation control unit 50b sets the voltage increased to the vicinity of the maximum voltage of the battery 22 as the starting target voltage.

  Next, in step S <b> 403, the power generation control unit 50 b acquires the actual voltage of the battery 22. For example, the power generation control unit 50b estimates the actual voltage of the battery 22 based on the voltage input from the battery 22 to the ECU 50.

  Next, in step S404, the power generation control unit 50b obtains a deviation (starting target voltage−actual voltage) between the starting target voltage set in step S402 and the actual voltage acquired in step S403.

  Next, in step S405, the power generation control unit 50b refers to the current change speed limit value map (see graph G32 in FIG. 7) used when the engine speed rapid increase control is performed, and the deviation obtained in step S404. The current change rate limit value (hereinafter, the current change rate limit value set based on the map of the graph G32 in FIG. 7 is referred to as “second current change rate limit value”).

  Next, in step S406, the power generation control unit 50b increases the target current of the alternator 21 within the range of the second current change speed limit value set in step S405. That is, the power generation control unit 50b increases the power generation current of the alternator 21 while limiting the speed of change of the power generation current of the alternator 21 to be less than the second current change speed limit value.

  Next, in step S407, the power generation control unit 50b determines whether or not the start alternator power generation control flag is zero. Here, the power generation control unit 50b determines whether or not to terminate the start alternator power generation control for rapidly decreasing the engine speed. As described above, the start alternator power generation control flag is set to “0” in step S216 shown in FIG.

  As a result of the determination in step S407, if the start alternator power generation control flag is 0 (step S407: Yes), the process proceeds to step S409. In this case, the power generation control unit 50b ends the start-time alternator power generation control for rapidly reducing the engine speed, and after step S409, the target current of the alternator 21, the target voltage of the battery 22, and the like are Control to return to the target value.

  On the other hand, if the start alternator power generation control flag is not 0 (step S407: No), the process proceeds to step S408, and the power generation control unit 50b determines whether the deviation between the start target voltage and the actual voltage is less than a predetermined value. Determine. Here, the power generation control unit 50b determines whether or not the actual voltage of the battery 22 has substantially reached the target voltage at start-up. In the alternator power generation control at the time of start illustrated in FIG. 12, since the target voltage of the battery 12 is increased (step S402), in order to prevent overshoot of the voltage of the battery 12, the predetermined value used in the determination of step S407 is set. It is better to set a value larger than 0. On the other hand, when the target voltage of the battery 12 is not increased during the alternator power generation control at the start, for example, when the normal target voltage is set to the target voltage, an overshoot is allowed to some extent and used in the determination of step S408. The predetermined value may be set to almost zero.

  As a result of the determination in step S408, if the deviation between the starting target voltage and the actual voltage is not less than the predetermined value (step S408: No), the process returns to step S403 and the above-described control after step S403 is performed again. In this case, the power generation control unit 50b acquires the current actual voltage, sets a second current change rate limit value corresponding to the actual voltage, and falls within the range of the second current change rate limit value. Thus, the target current of the alternator 21 is increased.

  On the other hand, when the deviation between the starting target voltage and the actual voltage is less than the predetermined value (step S408: Yes), the process proceeds to step S409. Also in this case, the power generation control unit 50b ends the start-time alternator power generation control for rapidly decreasing the engine speed, and after step S409, the target current of the alternator 21, the target voltage of the battery 22, and the like are Control to return to the target value.

  Next, in step S409, the power generation control unit 50b refers to a current change speed limit value map (see graph G31 in FIG. 7) used during normal time, as in step S412 described above. A first current change rate limit value corresponding to the deviation from the voltage is set.

  Next, in step S410, the power generation control unit 50b sets the starting target voltage to a predetermined value in order to return the starting target voltage set in step S402 (the target voltage increased from the normal target voltage) to the normal target voltage. Decrease by width. In this case, the power generation control unit 50b gradually decreases the target voltage at start. By doing so, for example, when the headlight is turned on or when the air conditioning is operated at maximum, the voltage of the battery 22 changes suddenly, causing a flickering of the light or a change in air conditioning performance (blower air volume). Is prevented.

  Next, in step S411, the power generation control unit 50b determines whether or not the current target voltage of the battery 22 has decreased below the normal target voltage by reducing the start target voltage in step S410. That is, the power generation control unit 50b determines whether or not the target voltage of the battery 22 has returned to the normal target voltage. As a result, when the target voltage is not less than the normal target voltage (step S411: No), the process returns to step S410, and the power generation control unit 50b continuously decreases the target voltage of the battery 22.

  On the other hand, when the target voltage is less than the normal target voltage (step S411: Yes), the process proceeds to step S413, and the power generation control unit 50b sets the normal target voltage to the target voltage of the battery 22. Thereafter, the power generation control unit 50b controls the power generation of the alternator 21 based on the first current change speed limit value and the normal target voltage.

<Effect>
Next, functions and effects of the engine start control device according to the embodiment of the present invention will be described.

  According to the present embodiment, when the engine is started, in order to advance the closing timing of the intake valve 12 in order to increase the intake air amount and rapidly increase the engine speed, the limit is closed so as not to exceed the limit closing timing. Is imposed to advance the closing timing of the intake valve 12, so that the engine speed can be increased rapidly while suppressing the occurrence of pre-ignition. In particular, according to this embodiment, when the intake air amount is increased, the intake valve 12 having higher intake controllability (responsiveness) than controlling the throttle valve 5 is controlled by the variable intake valve mechanism 18 (intake air). Since the valve 12 is closer to the inside of the cylinder than the throttle valve 5 and the intake responsiveness is high), preignition suppression and rapid increase in engine speed can be achieved at a high level.

  Further, according to this embodiment, when the engine speed reaches the first threshold value near the target speed by the start-up speed rapid increase control, the valve closing timing of the intake valve 12 is retarded. Therefore, while the engine speed is increasing toward the target speed, the intake air amount is secured by the inertia of the intake air, so that the rapid increase in the engine speed can be appropriately maintained, and thereafter After the engine speed reaches the target speed, a state in which the intake air amount is reduced due to a reduction in the inertia (flow velocity) of the intake air is formed, so that the engine speed can be appropriately and rapidly reduced. Therefore, it is possible to appropriately realize both a rapid increase in engine speed and a rapid decrease in engine speed thereafter. Therefore, it is possible to appropriately realize a sporty start feeling.

  Further, according to the present embodiment, the fuel injection is stopped after the engine speed reaches the target rotational speed by the start-up rotational speed rapid increase control, and then the intake valve 12 is closed before the fuel injection is restarted. Is retarded. Therefore, the amount of intake air can be reduced when the fuel injection is resumed, and an increase in the engine speed can be appropriately suppressed when the fuel injection is resumed.

  Further, in the present embodiment, when the exhaust purification catalyst 26 needs to be heated, the fuel cut control (stop of fuel injection) is prohibited in order to secure the emission with priority given to the temperature increase of the exhaust purification catalyst 26. In this embodiment, if the fuel cut control is not performed when the engine speed rapid increase control is performed, it is difficult to rapidly decrease the engine speed that has been rapidly increased, and an appropriate start feeling cannot be realized. Therefore, when the fuel cut control is prohibited, the engine speed rapid increase control is also prohibited. As described above, according to the present embodiment, when the exhaust purification catalyst 26 needs to be warmed, both the start-up engine speed rapid increase control and the fuel cut control are prohibited, and the exhaust purification catalyst 26 need not be warmed. In this case, since the engine speed sudden increase control and the fuel cut control are executed, the engine speed rapid increase control that provides a sporty start feeling while ensuring emissions (ie, the engine speed rapid increase control with sharpness) Can be realized appropriately.

  Further, according to the present embodiment, since the engine speed is reached by the power generation of the alternator 21 after the engine speed reaches the target speed by the start-up speed rapid increase control, the engine speed that has rapidly increased is appropriately set. It can be lowered rapidly. By using the power generation of the alternator 21 in this way, there is no need to reduce the intake air amount while the engine speed is increasing in order to decrease the engine speed. It is possible to appropriately achieve both a rapid decrease in the rotational speed. In particular, according to the present embodiment, taking into account a response delay in the change in the generated current of the alternator 21, the increase in the generated current of the alternator 21 is started during the start-up rotation speed rapid increase control. When the number reaches the value, the generated current of the alternator 21 can be increased, and the subsequent rapid decrease in the engine speed can be effectively realized. Further, according to the present embodiment, the power generated by the alternator 21 when the engine speed is reduced is charged to the battery 22, so that the engine speed is reduced only by reducing the intake air amount. Fuel consumption can be improved.

<Modification>
The variable intake valve mechanism 18 shown in the above-described embodiment increases the intake air amount by advancing the closing timing of the intake valve 12 and retards the closing timing of the intake valve 12. The variable valve timing mechanism is of a type that lowers the intake air amount, but the intake air amount is increased by retarding the closing timing of the intake valve 12, and the intake timing is increased by advancing the closing timing of the intake valve 12. There is also a type of variable valve timing mechanism that reduces the amount of air, and the present invention is also applicable to the latter type of variable valve timing mechanism.

DESCRIPTION OF SYMBOLS 1 Intake passage 5 Throttle valve 10 Engine 11 Combustion chamber 12 Intake valve 13 Fuel injection valve 14 Spark plug 16 Crankshaft 17 Exhaust valve 18 Variable intake valve mechanism 19 Variable exhaust valve mechanism 21 Alternator 22 Battery 25 Exhaust passage 26a, 26b Exhaust purification catalyst 34 Crank angle sensor 37, 38 Cam angle sensor 50 ECU
50a Speed increase control unit 50b Power generation control unit 50c Fuel cut control unit 50d Catalyst warm-up control unit 50e Control prohibition unit 100 Engine system

Claims (4)

An engine start control device including a variable intake valve mechanism capable of changing a closing timing of an intake valve provided in an engine,
A rotation speed rapid increase control means for controlling the closing timing of the intake valve by the variable intake valve mechanism so as to increase the intake air amount and rapidly increase the engine rotation speed when starting the engine;
Based on the operating state of the engine, the engine speed rapid increase control means is configured to prevent the pre-ignition of the air-fuel mixture before the normal combustion start timing triggered by spark ignition, and the intake valve limit closing timing And controlling the intake valve closing timing by imposing a limit so as not to exceed the limit closing timing.   When the engine speed is equal to or higher than the predetermined value without limiting the closing timing of the intake valve by the limit valve closing timing while the engine speed is less than the predetermined value, The engine start control device according to claim 1, wherein the closing timing of the intake valve is limited by the limit closing timing.   3. The engine start control device according to claim 1, wherein the rotation speed rapid increase control means controls the closing timing of the intake valve to an advance side within a range not exceeding the limit closing timing.   The speed increase control means estimates an effective compression ratio limit, which is an upper limit effective compression ratio at which the pre-ignition does not occur, based on an engine speed, an engine load, and an environmental condition in which the engine is operated. The engine start control device according to any one of claims 1 to 3, wherein the limit valve closing timing is obtained based on a compression ratio limit.

Images