JP3966209B2 - Engine starter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine starting device that automatically stops an engine once during idling or the like and then automatically restarts the engine.
[0002]
[Prior art]
In recent years, fuel consumption reduction and CO ₂ In order to reduce emissions, an engine starter has been developed that automatically stops the engine when idling and then restarts the engine automatically when a restart condition such as a start operation is established. It is coming.
[0003]
When restarting automatically after stopping the engine in this way, it is required to start immediately according to the starting operation, etc., so the engine is started through cranking that drives the engine output shaft by the starting motor. The conventional general starting method that requires a considerable time to complete the starting operation is not preferable.
[0004]
Therefore, it is desirable to supply fuel to a specific cylinder of the engine in a stopped state to cause ignition and combustion so that the engine is instantly started with the energy. In this case, if the fuel is supplied to the cylinder in the expansion stroke while the engine is stopped to cause combustion, the energy of the combustion can be applied in the normal rotation direction of the engine. However, if the engine is in operation, combustion is performed after the combustion chamber is in a highly compressed state, and thus a large amount of energy can be obtained. Therefore, even if fuel is supplied into the combustion chamber at the low pressure and combustion is performed, energy necessary for starting is often not obtained sufficiently.
[0005]
As a countermeasure against such a problem, in a multi-cylinder engine, the first combustion is performed on a cylinder that is in the compression stroke when the engine is stopped, and the piston of the cylinder is pushed down to a position before the bottom dead center. After the cylinder piston approaches the top dead center, the cylinder pressure of the cylinder is increased, and fuel is injected into the cylinder in the expansion stroke to ignite and burn, thus causing the engine to rotate forward. Some have been devised so as to increase the combustion energy acting on the gas (see, for example, Patent Document 1).
[0006]
[Patent Document 1]
International Publication No. 01/81759 Pamphlet
[0007]
[Problems to be solved by the invention]
According to the starting device disclosed in Patent Document 1 described above, the engine is slightly reversed by the initial combustion in the cylinder in the compression stroke when the engine is stopped, and then the engine corrects due to the combustion in the cylinder in the expansion stroke when the engine is stopped. The cylinder in the compression stroke shifts to the expansion stroke through the compression top dead center due to the rotation, but if the top dead center of any cylinder is exceeded during the engine reverse rotation, the cylinder in the next expansion stroke Combustion makes it difficult to apply a driving force in the normal rotation direction of the engine, and the startability deteriorates.
[0008]
Therefore, engine reversal due to initial combustion in a cylinder in the compression stroke is required to be within a range that does not exceed the top dead center of any cylinder, but the momentum of movement in the reverse direction varies depending on the piston stop position etc. Therefore, there was a possibility that the top dead center of one of the cylinders could be exceeded due to engine reversal.
[0009]
In view of the above circumstances, the present invention increases the combustion energy by reversing the engine a little at the time of restarting the engine and then performing combustion in the cylinder in the expansion stroke, and at the time of the reversal. It is an object of the present invention to provide an engine starter that can prevent the top dead center of any cylinder from being exceeded and improve startability.
[0010]
[Means for Solving the Problems]
In the present invention, when a restart condition is established after the engine is stopped, fuel is supplied to a cylinder in a stroke in which the cylinder volume is reduced to perform ignition and combustion, thereby operating the engine in a reverse direction and then expanding the engine. In the engine starter that starts the engine by rotating it in the forward direction by burning in the cylinders in the stroke, at the initial start of operating the engine in the reverse direction, one of the cylinders exceeds the piston top dead center. Predicting means for predicting whether or not excessive operation in the reverse direction occurs, and reverse rotation until one of the cylinders reaches the piston top dead center when the predicting means predicts excessive operation in the reverse direction. Control means for executing combustion that gives a driving force in the forward direction of the engine during direction operation The predicting means examines the momentum of the movement of the piston in the reverse direction by detecting the angular velocity during the movement of the piston in the reverse direction, and the control means, when the momentum is greater than a predetermined value, As control for executing combustion that gives driving force in the forward direction of the engine, the intake valve of the cylinder in the intake stroke is closed when the engine is stopped, and fuel is supplied to the cylinder and ignited, so that the cylinder is stopped when the engine is stopped. It is designed to burn with a cylinder in the expansion stroke. .
[0011]
According to the present invention, when the engine is restarted, the engine is first reversed to some extent, the piston of the cylinder in the expansion stroke is raised and the in-cylinder pressure is increased, and then combustion is performed in the cylinder. The combustion pressure in the cylinder in the stroke is increased, and the combustion pressure effectively acts on the piston, and a driving force in the normal engine rotation direction is obtained.
[0012]
In such restart operation, By detecting the angular velocity during piston movement in the reverse direction, the momentum of movement of the piston in the reverse direction is checked, and either cylinder exceeds the piston top dead center depending on whether this momentum is greater than a predetermined value. It can be predicted whether or not excessive operation in the reverse direction will occur. And When it is predicted that excessive operation in the reverse direction will occur, combustion that provides driving force in the forward direction of the engine is performed during reverse direction operation, so that the movement of the piston in the reverse direction is suppressed, and either It is possible to prevent the cylinder top dead center from being exceeded, and to increase the driving force in the forward direction of the engine after the reverse rotation, thereby improving the startability.
[0014]
In particular, When the intake valve of the cylinder in the intake stroke is closed, the cylinder in the intake stroke becomes the same state as the cylinder in the expansion stroke, and combustion is performed in this cylinder and the expansion stroke cylinder. The operation is prevented and the driving force in the forward direction is increased.
[0018]
Further, it is preferable that the control means controls the fuel supply amount to the cylinder so that the air-fuel ratio at the time of combustion on the intake stroke cylinder side is equal to or lower than the stoichiometric air-fuel ratio. In this way, in the cylinder in the intake stroke, the driving force in the forward rotation direction is increased by appropriately making the air-fuel ratio rich.
[0020]
Further, in the present invention, it is preferable that the fuel supply to the cylinder in the stroke in which the cylinder volume is reduced when the engine is stopped and the fuel supply to the cylinder in the expansion stroke are performed at the same time. In this way, the fuel supply timing is made as early as possible to the cylinders in the expansion stroke, and it is possible to secure a time for vaporizing and atomizing the fuel between the fuel supply and ignition.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
1 and 2 show a schematic configuration of an engine according to an embodiment of the present invention. In these drawings, the engine body is composed of a cylinder head 1 and a cylinder block 2, and has a plurality of cylinders, and in the illustrated embodiment, has four cylinders 3A to 3D. A piston 4 is fitted into each of the cylinders 3 </ b> A to 3 </ b> D, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to a crankshaft 6 via a connecting rod.
[0023]
A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3 </ b> A to 3 </ b> D, and the tip of the plug faces the combustion chamber 5.
[0024]
Further, a fuel injection valve 8 that directly injects fuel into the combustion chamber 5 is provided at a side portion of the combustion chamber 5. The fuel injection valve 8 includes a needle valve and a solenoid (not shown). When a pulse signal is input, the fuel injection valve 8 is driven and opened for a time corresponding to the pulse width at the pulse input timing. It is comprised so that the quantity of fuel according to may be injected. The injection direction of the fuel injection valve 8 is set so as to inject fuel toward the vicinity of the spark plug 7. The fuel injection valve 8 is supplied with fuel via a fuel supply passage or the like by a fuel pump (not shown), and a fuel supply system so that a fuel pressure higher than the pressure in the combustion chamber during the compression stroke can be applied. Is configured.
[0025]
An intake port 9 and an exhaust port 10 are opened to the combustion chambers 5 of the respective cylinders 3A to 3D, and these ports 9 and 10 are equipped with an intake valve 11 and an exhaust valve 12, respectively. These intake valve 11 and exhaust valve 12 are driven by a valve operating mechanism. As will be described in detail later, the opening / closing timings of the intake and exhaust valves 11 and 12 of each cylinder are set so that each cylinder performs a combustion cycle with a predetermined phase difference.
[0026]
Furthermore, valve drive changing means 13 and 13 'are provided for the intake valve 11 and the exhaust valve 12, which can be switched between an operating state and a closed state. For example, as shown in FIG. 3, the valve drive changing means 13 and 13 ′ are slidably disposed in the housing 13 a made of a non-magnetic material and are integrally connected to the exhaust valve 12. And a pair of electromagnets 13c and 13d and return springs 13e and 13f provided at both upper and lower ends in the housing 13a.
[0027]
When the upper electromagnet 13c is energized, the armature core 13b is attracted upward to open the intake valve 11 or the exhaust valve 12, and when the lower electromagnet 13d is energized, the armature core 13b is moved downward. The intake valve 11 or the exhaust valve 12 is closed by the suction. According to such a structure, the energization timing of the electromagnets 13c and 13d is controlled, whereby the intake / exhaust valves 11 and 12 are opened / closed at a predetermined timing, and the energization state of the lower electromagnet 13d is maintained. When it is leaned, the intake / exhaust valves 11 and 12 are closed and stopped.
[0028]
Returning to FIG. 1, an intake passage 15 and an exhaust passage 16 are connected to the intake port 9 and the exhaust port 10. The intake passage 15 is provided with a throttle valve for adjusting the intake air amount. In this embodiment, a throttle valve 17 is provided in the branch intake passage 15a near the intake port 9 in order to improve the response of the intake air amount control. Is provided. That is, the intake passage 15 has a branch intake passage 15a for each cylinder downstream of the surge tank 15b, and the downstream end of each branch intake passage 15a communicates with the intake port 9 of each cylinder. In the vicinity of the downstream end, a throttle valve 17 comprising a multiple rotary valve for restricting the throttle of each branch intake passage 15a at the same time is disposed. The throttle valve 17 is driven by an actuator 18.
[0029]
An air flow sensor 20 that detects the amount of intake air is provided in the common intake passage 15c of the intake passage 15 upstream of the surge tank 15b. The crankshaft 6 is provided with a crank angle sensor that detects its rotation angle. In this embodiment, as will be described in detail later, crank angle signals that are out of phase with each other by a certain amount are output. Two crank angle sensors 21 and 22 are provided. Further, a cylinder identification sensor 23 is provided which can provide a cylinder identification signal by detecting a specific crank angle of the engine. In addition to this, as a detection element necessary for engine control, a water temperature sensor 24 for detecting the temperature of the engine cooling water, an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount), and the like are provided. .
[0030]
An ECU (engine control unit) 30 receives signals from the sensors 20 to 25, outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 8, and supplies the ignition device with a signal. While outputting an ignition timing control signal, the control signal is output to the valve drive changing means 13. A signal for controlling the throttle opening is output to the actuator 18 of the throttle valve 17. Furthermore, a signal for controlling the driving of the starter (starting motor) 31 is output when necessary.
[0031]
When a predetermined engine stop condition is satisfied during idling, the engine is automatically stopped by stopping fuel supply or the like, and when the engine restart condition is subsequently satisfied, the engine is automatically restarted. If the piston stop position is within a specific range when the engine is restarted, fuel is first supplied to the cylinders in the compression stroke when the engine is stopped, causing ignition and combustion to start the engine in a reverse direction. After that, the engine is rotated in the normal rotation direction by starting combustion in the cylinder in the expansion stroke, and is started.
[0032]
Further, the ECU 30 predicts whether or not an excessive operation in the reverse rotation direction such that any cylinder exceeds the piston top dead center occurs at the initial start of operating the engine in the reverse rotation direction, and the prediction means 30a. When the excessive operation in the reverse rotation direction is predicted by the control means 30b, the control means 30b for executing the combustion for applying the driving force in the normal rotation direction during the reverse rotation operation until any cylinder exceeds the piston top dead center. Is included.
[0033]
In this embodiment, as described above, initial combustion for engine reverse rotation in the cylinder in the compression stroke when the engine is stopped and combustion for engine forward rotation in the cylinder in the expansion stroke when the engine is stopped are performed. Then, when the cylinder that was in the compression stroke when the engine was stopped has shifted to the expansion stroke, the first restart control mode in which re-combustion is performed in the cylinder, and the second restart control in which the re-combustion is not performed And a third restart control mode in which starting is performed by combustion in a cylinder in an expansion stroke while assisting by a starter (starting motor) 31 without performing initial combustion in a cylinder in a compression stroke when the engine is stopped, It executes selectively according to the stop position of the piston. When either the first restart control mode or the second restart control mode is selected, the functions as the prediction unit 30a and the control unit 30b are exhibited.
[0034]
Control of engine stop and restart by the ECU 30 will be described with reference to FIGS. In the following description, a cylinder in the intake stroke is abbreviated as an intake cylinder, a cylinder in the compression stroke is a compression cylinder, a cylinder in the expansion stroke is abbreviated as an expansion cylinder, and a cylinder in the exhaust stroke is abbreviated as an exhaust cylinder.
[0035]
The process shown in the flowchart of FIG. 4 starts from a state where the engine is operated, and the ECU 30 first determines whether or not an idle stop condition is satisfied in step S1. This determination is made based on the vehicle speed, engine temperature (engine cooling water temperature), etc., for example, the stopped state where the vehicle speed is 0 continues for a predetermined time or more, the engine temperature is within the predetermined range, and the engine is stopped The idle stop condition is established when there is no particular inconvenience in making it.
[0036]
When the idle stop condition is satisfied, the fuel supply to each cylinder of the engine is stopped (step S2), then the throttle valve 17 is once opened to a predetermined opening degree (step S3), and then the engine speed is set to be equal to or lower than the predetermined speed. This state is maintained until it reaches (step S4), and if it is equal to or lower than the predetermined rotational speed, the throttle valve 17 is closed (step S5).
[0037]
Subsequently, it is determined in step S6 whether or not the engine has been stopped. When the engine is stopped, the stop position is determined in step S7 based on detection of the stop position of the piston by a stop position detection routine shown in FIG. It is determined whether it is within the range. In this case, in the expansion cylinder when the engine is stopped, the piston stop position is a range A indicated by hatching in FIG. 5, that is, a range corresponding to the middle stage of the expansion stroke is set as a predetermined range. If it is within the predetermined range A, it is determined in step S8 whether or not the piston stop position is on the TDC (top dead center) side of the expansion cylinder when the engine is stopped.
[0038]
When it is confirmed that the stop position of the piston 4 is within the predetermined range A and on the TDC side (within the range A1) based on the determinations at the steps S7 and S8, the second position shown in FIG. When the routine (R1) of the 1 restart control mode is executed and it is confirmed that the stop position of the piston 4 is within the predetermined range A and within the range A2 on the BDC side (bottom dead center side). Executes the routine (R2) of the second restart control mode. When it is confirmed that the stop position of the piston 4 is outside the predetermined range A, the routine (R3) of the third restart control mode is executed.
[0039]
FIG. 6 shows a stop position detection routine. When this routine starts, the ECU 30 examines the first crank angle signal CA1 (signal from the first crank angle sensor) and the second crank angle signal CA2 (signal from the second crank angle sensor), and the first crank angle signal. It is determined whether the second crank angle signal CA2 is low when CA1 rises or the second crank angle signal CA2 is high when the first crank angle signal CA1 falls. In short, by determining whether the phase relationship between these signals CA1 and CA2 is as shown in FIG. 7 (a) or FIG. 7 (b), it is determined whether the engine is rotating forward or reverse. Is discriminated (step S11).
[0040]
That is, at the time of forward rotation of the engine, as shown in FIG. 7A, the second crank angle signal CA2 is generated with a phase delay of about a half pulse width with respect to the first crank angle signal CA1, thereby the first crank angle signal. The second crank angle signal CA2 becomes Low when CA1 rises, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, during reverse rotation of the engine, as shown in FIG. 7B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, so On the contrary, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls. Therefore, if the determination in step S11 is YES, the CA counter for measuring the crank angle change in the forward rotation direction of the engine is increased (step S12). If the determination in step S11 is NO, the CA counter is decreased. (Step S13). Then, the stop position is obtained by examining the value of the CA counter when the engine is stopped (step S14).
[0041]
FIG. 8 shows a routine of the first restart control mode that is executed when the determination in step S7 in the flowchart of FIG. 4 is YES. FIGS. 9 and 10 show the cycle and combustion operation of each cylinder when controlled by the first restart control mode, and FIG. FIG. 10 shows a case where it is predicted that the dead center will not be exceeded (reverse rotation will not be excessive). FIG. 10 shows that there is a possibility that the bottom dead center of the compression cylinder will be exceeded in step S26 described later (reverse rotation is excessive). The predicted case is shown.
[0042]
9 and 10 show the case of a four-cylinder four-cycle engine. 1-NO. When it is called four cylinders, the cycle consisting of intake, compression, expansion, and exhaust strokes is NO. 1 cylinder, NO. 3 cylinders, NO. 4-cylinder, NO. Since it is performed with a phase difference of 180 ° in crank angle in order of two cylinders, for example, when the engine is stopped as in the examples of FIGS. If one cylinder is in the compression stroke, NO. The two cylinders have an expansion stroke, NO. The three cylinders have an intake stroke, NO. The four cylinders are in the exhaust stroke. The routine of FIG. 8 will be described with reference to FIGS.
[0043]
In this routine, in step S21, the ECU 30 first determines whether a predetermined engine restart condition is satisfied, and waits if the engine restart condition is not satisfied.
[0044]
When the engine restart condition is satisfied (when the determination in step S21 is YES) such as when the accelerator operation for starting is performed from the stop state or when the battery voltage is lowered, the piston is turned on in step S22. Based on the stop position, the air amounts of the compression cylinder (NO.1 cylinder in FIGS. 9 and 10) and the expansion cylinder (NO.2 cylinder in FIGS. 9 and 10) are calculated. That is, the combustion chamber volume of each cylinder is obtained from the stop position, and when the engine is stopped, the engine is stopped after several revolutions after the fuel cut, so that each cylinder is filled with fresh air, In addition, since the cylinder pressure of each cylinder becomes substantially atmospheric pressure while the engine is stopped, the amount of air is obtained from the combustion chamber volume.
[0045]
Subsequently, in step S23, a fuel injection amount is obtained so that the calculated air amount of the compression cylinder becomes a predetermined air-fuel ratio, and fuel injection to the cylinder is performed with the injection amount (F11 in FIGS. 9 and 10). I do. In this case, the predetermined air-fuel ratio is set to a lean air-fuel ratio larger than the stoichiometric air-fuel ratio so that surplus air remains even after the first combustion in the cylinder. Further, in step S24, a fuel injection amount is obtained so that the calculated air amount of the expansion cylinder becomes a predetermined air-fuel ratio (theoretical air-fuel ratio or the vicinity thereof), and fuel injection to the cylinder with the injection amount (FIG. 9). , F12) in FIG.
[0046]
Further, in step S25, ignition of the cylinder (I11 in FIGS. 9 and 10) is performed after the time set in consideration of the fuel vaporization time after fuel injection into the compression cylinder. Thus, combustion is performed in the compression cylinder, the piston of the cylinder is pushed down by the combustion pressure, and the engine is reversed.
[0047]
Next, in step S26, as a process for performing the function of the predicting means 30a, it is predicted whether or not the compression cylinder bottom dead center will not be exceeded by the reverse rotation. In this case, the momentum of the movement of the piston in the reverse rotation direction is examined, for example, the angular velocity during the movement of the piston in the reverse rotation direction is detected by measuring the cycle of the crank angle signal from the crank angle sensors 21 and 22, and this angular velocity is If it is below the predetermined value, it is determined that the compression cylinder bottom dead center is not exceeded (YES in step S26), and if the angular velocity is higher than the predetermined value, the compression cylinder bottom dead center may be exceeded (NO in step S26). Is determined. Alternatively, the piston position of the compression cylinder when the engine is stopped is checked. If this position is more than a predetermined amount from the bottom dead center, it is determined that the compression cylinder bottom dead center is not exceeded (YES in step S26), and this position is the bottom dead center. If it is less than the predetermined amount, it may be determined that there is a possibility that the bottom dead center of the compression cylinder may be exceeded (NO in step S26).
[0048]
If it is predicted that the bottom dead center of the compression cylinder will not be exceeded, in step S27, after detecting the edge of the crank angle signal (rising or falling edge of the crank angle signal), a predetermined delay time has elapsed and the expansion cylinder is Ignition is performed (I12 in FIG. 9).
[0049]
Thus, in the first stroke until any cylinder reaches the top dead center after the engine restarts, the compression cylinder is ignited and burned, and the engine reverses to some extent, and then the expansion cylinder ignites and burns. And the engine rotates normally.
[0050]
Then, in step S28, a start assist execution determination, which will be described in detail later, is performed, and in step S29, a predetermined air-fuel ratio (theoretical air-fuel ratio or the vicinity thereof) is calculated with respect to the calculated remaining air amount of the compression cylinder when the engine is stopped. The fuel is injected so as to become (F21 in FIG. 9). In this case, the remaining air amount is obtained by subtracting the amount of air consumed by the initial combustion (combustion by ignition in step S25) from the air amount of the compression cylinder calculated in step S23. Thus, the fuel injection amount is obtained so that the theoretical air fuel ratio or an air fuel ratio in the vicinity thereof is obtained.
[0051]
In step S30, ignition (I21 in FIG. 9) is performed when the compression cylinder when the engine is stopped exceeds the top dead center. That is, in the second stroke in which the compression cylinder is in the expansion stroke when the engine is stopped, recombustion is performed in this cylinder.
[0052]
Thereafter, in step S31, the control shifts to normal control. In other words, in the third and subsequent strokes when the exhaust cylinder is in the compression stroke when the engine is stopped, fuel is injected into each cylinder sequentially at an appropriate time such as the intake stroke and then expanded from the compression cylinder. I ignite near the top dead center when going to the stroke to make it burn.
[0053]
Further, when the determination in step S26 is NO (when it is predicted that there is a possibility that the compression cylinder bottom dead center may be exceeded due to reverse rotation), the following processing is performed as the function of the control means 30b. The processes of steps S32 to S38 are performed.
[0054]
In step S32, the intake and exhaust valves 11 and 12 of the intake cylinder (NO. 3 cylinder in FIG. 10) are closed to form an expansion cylinder. That is, since the piston movement is the same between the intake cylinder and the expansion cylinder (NO. 2 cylinder in FIG. 10), if the intake and exhaust valves 11 and 12 of the intake cylinder are closed, the combustion chamber of the cylinder is in the same state as the expansion cylinder. It becomes. In order to change the intake cylinder to an expansion cylinder, at least the intake valve 11 should be closed. However, when the intake cylinder approaches the top dead center due to reverse rotation of the engine (the advance side of the exhaust valve close timing). In order to avoid the exhaust valve 12 from opening when the intake and exhaust valves 11 and 12 are both closed, it is preferable to keep them closed.
[0055]
Subsequently, in step S33, the air amount of the cylinder is calculated according to the closing timing of the intake / exhaust valve, and the fuel injection amount is set so that the predetermined air / fuel ratio (theoretical air / fuel ratio or the vicinity thereof) is equal to the air amount. The fuel injection (F13 in FIG. 10) with respect to the cylinder is executed with the obtained injection amount. In step S34, before the compression cylinder exceeds the bottom dead center, ignition (I12, I13 in FIG. 10) is performed on the expanded cylinder and the expanded intake cylinder so that combustion occurs in these cylinders. Let it be done.
[0056]
Next, in step S35, as in step S29, the amount of air remaining in the compression cylinder when the engine is stopped is obtained, and fuel is injected so that a predetermined air-fuel ratio (theoretical air-fuel ratio or the vicinity thereof) is obtained. (F21 in FIG. 10). In step S36, the exhaust valve of the cylinder is opened before the intake cylinder (cylinder made into an expansion cylinder; NO. 3 cylinder) when the engine is stopped reaches the bottom dead center. As a result, the second stroke (originally the compression stroke) of the cylinder is converted to an exhaust stroke, and the burned gas is discharged.
[0057]
Further, in step S37, when the compression cylinder when the engine is stopped exceeds the top dead center, the cylinder is ignited (I21 in FIG. 10), so that the cylinder is recombusted. In step S38, the exhaust valve 12 is closed and the normal control is returned to when the intake cylinder (cylinder with expansion stroke; NO. 3 cylinder) when the engine is stopped reaches the original exhaust valve closing timing.
[0058]
The start assist execution determination performed in step S28 of FIG. 8 will be described based on FIG. When the execution determination routine is started, it is determined in step S41 whether or not the engine speed Ne at the time point after the combustion of the expansion cylinder is equal to or higher than a preset reference speed, and it is determined as NO. If this is the case, in step S42, start assist control is performed to assist the restart by driving the starter 31.
[0059]
If it is determined YES in step S41 and it is confirmed that the engine speed is equal to or higher than the reference speed, the engine is restarted in step S43 with the brake switch turned off. It is determined whether or not. When it is determined YES in step S43, and it is confirmed that the restart condition is satisfied with the brake switch turned off by releasing the foot from the brake pedal with the intention of starting the vehicle In step S44, whether the accelerator switch is turned on within a predetermined time from when the brake switch is turned off, or whether the required torque at the time of restarting the engine is large due to an uphill state or the like. Determine whether.
[0060]
If YES is determined in step S44 and it is confirmed that the required torque at the time of restarting the engine is large, in step S45, the current time from the start of engine restart, that is, the engine speed is the reference speed. It is determined whether or not the elapsed time until the time is equal to or longer than a preset first reference time T1. If it is determined as YES in step S45, it is determined that there is a high possibility that engine restart will fail, and the process proceeds to step S42 to perform start assist control.
[0061]
If it is determined NO in step S44 and it is confirmed that the required torque at the time of restarting the engine is small, the elapsed time from the start of engine restart to the current time is determined in step S46 as the first time. It is determined whether or not the time is equal to or longer than a second reference time T2 set to a time longer than the reference time T1. If it is determined as YES in step S46 and it is confirmed that there is a high possibility that the restart of the engine will fail, the process proceeds to step S42 to perform start assist control.
[0062]
On the other hand, NO is determined in step S43, and the engine restart condition is satisfied because the air conditioner is activated or the battery capacity is reduced without the driver intending to start the vehicle. Is confirmed, it is determined in step S47 whether or not the elapsed time from the engine restart start time to the current time is equal to or longer than a third reference time T3 set to a time longer than the second reference time T2. judge. If it is determined as YES in step S47 and it is confirmed that there is a high possibility that the engine restart will fail, the process proceeds to step S42 to perform start assist control.
[0063]
If the determination in step S45, S46, or S47 is NO, the elapsed time until the engine speed becomes equal to or higher than the reference speed is short, and it is recognized that the restart is successful. Return without doing.
[0064]
The details of the routine of the second restart control mode (no recombustion) executed when the determination in step S8 in the flowchart of FIG. 3 is NO are omitted, but the first restart control mode is omitted. Substantially the same processing as steps S21 to S27, S31, S32 to S34, S36, and S38 of the routine is performed. However, in the processing corresponding to step S23, the air-fuel ratio of the compression stroke cylinder obtained from the map in accordance with the stop position of the piston is substantially stoichiometric or richer than that.
[0065]
FIG. 12 shows a routine of the third restart control mode (motor assist) that is executed when the determination in step S7 in the flowchart of FIG. 4 is NO. In this routine, the ECU first determines in step S51 whether a predetermined engine restart condition is satisfied, and waits if the engine restart condition is not satisfied.
[0066]
When the engine restart condition is satisfied (when the determination in step S51 is YES), the starter 31 starts to be driven in step S52, and the air amounts of the compression cylinder and the expansion cylinder are calculated based on the piston stop position in step S53. In step S54, fuel is injected so that the air-fuel ratios of the compression cylinder and the expansion cylinder are close to the theoretical air-fuel ratio. In step S55, after the time set in consideration of the fuel vaporization time has elapsed after the fuel injection of the expansion cylinder, the cylinder is ignited.
[0067]
Next, in step S56, the compression cylinder is ignited when the predetermined crank angle is reached. Then, the drive of the starter 31 is stopped (step S57), and the routine proceeds to normal control (step S58).
[0068]
According to the apparatus of the present embodiment as described above, the engine is automatically stopped when the engine stop condition is satisfied when the engine is in a predetermined idle state that does not require the output of the engine. When the engine is stopped, in the compression cylinder, as the piston approaches the top dead center, the air in the cylinder is compressed and pressure is applied in the direction of pushing back the piston, which reverses the engine and lowers the piston of the compression cylinder. When pushed back to the dead center side, the piston of the expansion cylinder moves to the top dead center side, and accordingly, the air in the cylinder is compressed, and the piston of the expansion cylinder is pushed back to the bottom dead center side by the pressure. In this way, the piston vibrates to some extent and then stops. At this time, in the compression cylinder and the expansion cylinder, the closer the piston is to the top dead center, the greater the force to push it back, so the piston stop position is closer to the middle of the stroke It is often a position.
[0069]
In this way, when the engine restart condition is satisfied after the engine is automatically stopped, the engine is restarted. In this case, the piston position of the expansion cylinder when the engine is stopped is within a predetermined range A ( 5), the first restart control mode routine (FIG. 8) or the second restart control mode routine is executed, so that the engine is slightly reversed by ignition and combustion in the compression cylinder. Then, the engine is driven in the forward direction by ignition and combustion in the expansion cylinder.
[0070]
That is, according to the example shown in FIGS. By igniting and burning after fuel injection to one cylinder, the piston of this cylinder is pushed down and the engine is rotated in reverse, so that the NO. In two cylinders, the piston approaches top dead center, the air in the cylinder is compressed and the in-cylinder pressure rises, ignition is performed in this state, and the fuel already injected into the cylinder burns, A relatively large combustion pressure acts on the piston of the expansion cylinder, and the driving force in the normal engine rotation direction is increased.
[0071]
By the way, at the time of the reverse rotation, the driving force due to the initial combustion in the compression cylinder (NO.1 cylinder) when the engine is stopped is too large, and the piston top dead center (the compression cylinder of the compression cylinder) of the expansion cylinder (NO.2 cylinder) when the engine is stopped. If the piston bottom dead center) is exceeded, even if ignition and combustion are performed in the expansion cylinder when the engine is stopped, the driving torque in the normal direction of the engine cannot be obtained and the engine cannot be started.
[0072]
Therefore, in the apparatus according to the present embodiment, it is predicted whether or not an excessive operation that exceeds the bottom dead center of the compression cylinder will occur at the initial stage of reverse rotation. .2 cylinder), combustion is performed in an expanded intake cylinder (NO. 3 cylinder), and combustion in these expanded cylinder and intake cylinder is performed during reverse movement. Yes. Thereby, before reaching the top dead center of the piston of the expansion cylinder (piston bottom dead center of the compression cylinder), the movement in the reverse piston direction is stopped by the combustion of the expansion cylinder and the intake cylinder, and the driving force in the normal rotation direction Therefore, the probability of a successful restart will be greatly increased.
[0073]
If the piston position of the expansion cylinder when the engine is stopped is in the range A1 closer to the top dead center than the intermediate portion in the predetermined range A, the piston of the compression cylinder is closer to the bottom dead center. Since the torque required to move to the vicinity of the dead center is reduced and the amount of air in the compression cylinder is increased, the fuel injection amount is controlled so that the air-fuel ratio of the cylinder is lean. As a result, surplus air remains in the cylinder even after the initial combustion for reverse rotation, so fuel corresponding to this surplus air is injected, and when the cylinder moves to the expansion stroke, recombustion is performed, and startability Is increased. On the other hand, if the piston position of the expansion cylinder when the engine is stopped is in the range A2 closer to the bottom dead center than the middle portion in the predetermined range A, the piston of the compression cylinder is closer to the top dead center. A relatively large torque is required to move to the vicinity of the dead center, and the amount of air in the compression cylinder is relatively small. Therefore, the fuel is set so that the air-fuel ratio of the cylinder becomes the stoichiometric air-fuel ratio or richer than this. The injection amount is controlled, and in this case, the recombustion is not performed.
[0074]
Further, as described above, the piston position when the engine is stopped is often within the above range A, and in most cases when the engine is restarted, it is better to control the first restart control mode or the second restart control mode. However, in some rare cases, the piston position when the engine is stopped may deviate from the above range A, so that the expansion cylinder is at the top dead center side (exhaust cylinder bottom dead center side) of the above range A. If it is too close, the amount of movement in the reverse direction of the engine cannot be taken sufficiently, and the amount of air in the expansion cylinder is reduced, so that the torque obtained by combustion in the expansion cylinder is reduced, and the above range A If it is too close to the bottom dead center side of the expansion cylinder (exhaust cylinder top dead center side), the amount of air in the exhaust cylinder will be small, so that sufficient torque for engine reversal will not be obtained. Restart according to the first restart control mode is difficult in these cases.
[0075]
Therefore, when the piston position when the engine is stopped is out of the range A, the third restart control mode is executed and the starter assists the start.
[0076]
In addition, the specific structure of the apparatus of this invention is not limited to the said embodiment, A various change is possible. Other embodiments are described below.
[0077]
In the embodiment shown in FIG. 8, in the control in the case where it is predicted that there is a possibility that the compression cylinder bottom dead center may be exceeded due to the reverse rotation, in step S34, the ignition and combustion of the expanded cylinder and the expanded intake cylinder are simultaneously performed. However, the combustion of both cylinders may be slightly shifted in time. In particular, the expansion cylinder may inject fuel at an early timing such as at the start of restart and ignite at an appropriate timing, but the intake cylinder may exceed the compression cylinder bottom dead center due to reverse rotation. After it is predicted that the fuel is injected after the intake valve is closed, it is necessary to ignite after the time for vaporization and atomization has elapsed, so ignition is performed later than the expansion cylinder, It is preferable to cause combustion.
[0078]
If the air-fuel ratio of the intake cylinder set in step S33 in FIG. 8 is somewhat richer than the stoichiometric air-fuel ratio, it is advantageous to increase the driving force in the forward rotation direction.
[0079]
Further, in the above embodiment, when it is predicted that there is a possibility of exceeding the compression cylinder bottom dead center due to the reverse rotation, the intake valve of the intake cylinder is closed and combustion is performed in both the intake cylinder and the expansion cylinder. However, it is also possible to close the intake valve of the intake cylinder without performing fuel supply, ignition, and combustion to the intake cylinder. Even in this case, the pressure in the cylinder during the intake stroke rises by closing the intake valve during reverse rotation operation, and resistance to reverse rotation operation increases, and the reaction force of being compressed by reverse rotation An action of assisting forward rotation by pushing back the piston is obtained.
[0080]
In the above embodiment, the engine is operated in the reverse direction by causing combustion in the compression cylinder at the initial stage of restart. Instead, the exhaust valve of the cylinder in the exhaust stroke when the engine is stopped is used. The cylinder may be closed to form a compression cylinder, and fuel may be supplied to the exhaust cylinder that has been compressed to cause ignition and combustion. In short, fuel is supplied to a cylinder that is in the process of reducing the cylinder volume. The engine can be operated in the reverse direction by performing ignition and combustion.
[0081]
【The invention's effect】
As described above, according to the engine starter of the present invention, at the time of restart, the predicting means for predicting whether or not excessive operation in the reverse rotation direction occurs at the initial start of operating the engine in the reverse rotation direction, and the prediction means Control means for executing combustion that provides a driving force in the forward direction of the engine during the reverse direction operation until any cylinder reaches the top dead center of the piston when the excessive operation in the reverse direction is predicted by Therefore, the expansion stroke cylinder is compressed by the reverse rotation so as to increase the driving force due to the combustion in the expansion stroke, and the excessive operation in the reverse rotation direction in which one of the cylinders exceeds the piston top dead center. Can be effectively prevented. Accordingly, the probability of successful restart can be greatly increased.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an engine equipped with a starting device according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of the engine.
FIG. 3 is a cross-sectional view showing an example of valve drive changing means.
FIG. 4 is a flowchart of control for stopping and restarting the engine by the control means.
FIG. 5 is an explanatory diagram showing setting of a range for selecting a restart control mode according to a piston position when the engine is stopped.
FIG. 6 is a flowchart showing a process for detecting a piston position when the engine is stopped.
7A and 7B show crank angle signals from two crank angle sensors, where FIG. 7A is a signal when the engine is rotating forward and FIG. 7B is a signal when the engine is rotating backward.
FIG. 8 is a flowchart showing a first restart control mode.
FIG. 9 shows the cycle of each cylinder at the time of engine restart, fuel supply, ignition timing, etc., and it is predicted that the compression cylinder bottom dead center will not be exceeded by the operation in the engine reverse rotation direction at the initial stage of restart. It is explanatory drawing which shows what is based on control in the case of.
FIG. 10 shows the cycle of each cylinder at the time of engine restart, fuel supply, ignition timing, etc., and there is a possibility that the compression cylinder bottom dead center may be exceeded by the operation in the engine reverse rotation direction at the initial stage of restart. It is explanatory drawing which shows what is by control in case that is predicted.
FIG. 11 is a flowchart showing a start assist execution determination process.
FIG. 12 is a flowchart showing a second restart control mode.
[Explanation of symbols]
3A-3D cylinder
4 Piston
5 Combustion chamber
7 Spark plug
8 Fuel injection valve
30 ECU
30a Predictive means
30b Control means
31 Starter

Claims (3)

When the restart condition is established after the engine is stopped, the cylinder is in the expansion stroke after the engine is operated in the reverse direction by supplying fuel to the cylinder in the stroke in which the cylinder volume is reduced to perform ignition and combustion. In the engine starting device for starting the engine by rotating the engine in the normal rotation direction by performing combustion in
A predicting means for predicting whether or not an excessive operation in the reverse rotation direction occurs such that any cylinder exceeds the top dead center of the piston at the initial start of operating the engine in the reverse rotation direction;
Control for executing combustion that provides driving force in the forward direction of the engine during reverse direction operation until any of the cylinders reaches the top dead center of the piston when excessive operation in the reverse direction is predicted by the predicting means. and means,
The prediction means examines the momentum of movement of the piston in the reverse direction by detecting the angular velocity during movement of the piston in the reverse direction,
When the momentum is greater than a predetermined value, the control means closes the intake valve of a cylinder that is in the intake stroke when the engine is stopped and controls the fuel in the cylinder as a control for executing combustion that gives a driving force in the forward rotation direction of the engine. Is supplied and ignited so that the cylinder is burned together with the cylinder in the expansion stroke when the engine is stopped . The control means, the air-fuel ratio at the time of combustion in the intake stroke cylinder side so as to below the stoichiometric air-fuel ratio, engine starting system according to claim 1, wherein the controlling the fuel supply quantity for that cylinder. 3. The engine according to claim 1, wherein fuel is supplied to a cylinder in a stroke in which the cylinder volume is reduced when the engine is stopped and fuel is supplied to a cylinder in an expansion stroke at the same time. Starter.

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