JP2010255512A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce degree of dilution of engine oil and PM while improving fuel economy at cool engine. <P>SOLUTION: The engine control device (100) controls a direct injection type engine at valve timing including NOL at the partial load of the direct injection engine (10). The engine control device includes a dilution degree detection means (25) detecting degree of dilution of the engine oil, a period change means (23) capable of expanding NOL, and a control means (27) (i) controlling the period change means to expand NOL under a condition where the engine is cold and the detected dilution degree is higher than threshold and controlling fuel injection means (21) to inject fuel at a retardation side of injection possible period in the expanded NOL, and (ii) controlling the period change means to expand NOL under a condition where the engine is cold and the detected dilution degree is lower than the previous value and controlling fuel injection means to inject fuel a plurality of times during the injection possible period in the expanded NOL. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technical field of an engine control device that controls a direct injection engine mounted on, for example, an automobile.

  As this type of device, for example, in Patent Document 1, the first fuel injection by the fuel injection valve is performed as a small injection amount between the exhaust valve closing timing and the exhaust top dead center during the negative overlap period, An apparatus is disclosed that performs the second fuel injection by the fuel injection valve as the remaining injection amount during the intake stroke immediately after the intake valve opening timing.

  Alternatively, in Patent Document 2, the first fuel injection device performs the first fuel injection during the negative overlap period, and the second fuel injection device performs the second fuel injection during the intake stroke or the compression stroke. An apparatus is disclosed. In particular, it is described that the first fuel injection device is smaller in the injection rate and the total injection amount, which are the temporal change amounts of the injection amount, than the second fuel injection device.

  Alternatively, in Patent Document 3, when the detected knocking intensity exceeds a certain setting limit, the fuel injection timing during the negative overlap is retarded, and the detected combustion stability is a certain stability upper limit. An apparatus for advancing the fuel injection timing during the negative overlap when exceeding the above is disclosed.

  Alternatively, Patent Document 4 discloses a device that provides a negative overlap period during the intake stroke when the engine is cold, and injects fuel during the latter half of the period during which the negative pressure develops. Alternatively, in Patent Document 5, when engine oil dilution exceeds a predetermined allowable dilution, fuel injection timing, injection pressure, cooling water temperature, oil temperature, ignition timing, intake valve closing timing, etc. An apparatus for temporarily changing is disclosed.

JP 2001-82229 A Japanese Patent Laying-Open No. 2005-220839 JP 2001-207888 A JP 2007-247485 A JP-A-10-317936

  However, according to the background art described above, fuel consumption, dilution of engine oil, and PM (Particulate Matter) are not fully considered. Then, there is a technical problem that at least one of the degree of dilution of the engine oil and the degree of PM may be deteriorated particularly during cold weather.

  The present invention has been made in view of the above problems, and proposes an engine control device capable of reducing the degree of dilution of engine oil and the degree of PM while improving fuel efficiency when cold. This is the issue.

  In order to solve the above-described problems, an engine control apparatus according to the present invention uses a direct-injection engine having fuel injection means capable of injecting fuel into a cylinder when the direct-injection engine is partially loaded. An engine control device for controlling at a valve timing having a negative overlap period in which both the intake valve and the exhaust valve are closed, a dilution degree detecting means for detecting a dilution degree of the engine oil in the direct injection engine, A period changing means capable of extending the negative overlap period; and (i) changing the period to extend the negative overlap period on the condition that it is cold and the detected dilution is greater than a threshold. And control from a point of time when the exhaust valve is closed during the enlarged negative overlap period. Controlling the fuel injection means so as to inject the fuel on the retarded side until reaching the point, and (ii) on the condition that it is cold and the detected dilution is smaller than the threshold value. The period changing means is controlled so as to expand the negative overlap period, and the exhaust valve within the expanded negative overlap period is closed until the top dead center is reached. Control means for controlling the fuel injection means so as to inject the fuel a plurality of times.

  According to the engine control apparatus of the present invention, the engine control means controls a direct injection type engine provided with fuel injection means capable of injecting fuel such as gasoline fuel into the cylinder. The engine control means controls the direct-injection engine at a valve timing having a negative overlap period in which both the intake valve and the exhaust valve of the direct-injection engine are closed particularly when the direct-injection engine is partially loaded. . On the other hand, the engine control means typically controls the direct injection engine at normal valve timing (for example, priority is given to fuel efficiency) at the time of full load of the direct injection engine.

  The “negative overlap period” according to the present invention means that the intake valve is opened in the intake stroke from the timing when the exhaust valve is closed in the exhaust stroke in the operation cycle of the direct injection engine (that is, the exhaust valve is closed) ( That is, it means a period until the timing when the intake valve is opened).

  The dilution degree detecting means detects the dilution degree of the engine oil in the direct injection engine. Here, the “dilution degree” may be a percentage, a ratio, or a ratio, or may be any physical quantity or parameter relating to dilution of the engine oil. That is, it may mean a broad degree of dilution. The dilution of engine oil typically condenses out of the fuel supplied to the cylinder that did not contribute to combustion (ie, unburned fuel) and the water that is generated when the fuel burns. Water is generated by mixing into the engine oil along the wall surface of the cylinder bore.

  For example, the period changing means including a memory, a processor, etc. can expand the negative overlap period. Here, the “negative overlap period” is typically represented by the rotation angle (ie, crank angle) of the crankshaft of the direct injection engine. That is, the “negative overlap period” typically has a dimension of “degree CA (Crank Angle)”.

  For example, the control means including a memory, a processor, etc. controls the period changing means to expand the negative overlap period on the condition that (i) it is cold and the detected dilution is larger than the threshold. And (ii) controlling the fuel injection means so as to inject fuel on the retarded side from when the exhaust valve is closed within the expanded negative overlap period until reaching the top dead center; The control unit changes the period changing means so as to increase the negative overlap period on the condition that the detected dilution is smaller than the threshold value when the engine is cold and the exhaust valve is closed within the expanded negative overlap period. The fuel injection means is controlled so that the fuel is injected a plurality of times from the time when the state is reached until the top dead center is reached.

  The control means has a temperature sensor or the like, for example, detects the temperature of the cooling water of the direct injection type engine, and is based on the detected temperature or not (for example, the water temperature is less than 0 degrees Celsius). Determine whether. The control means controls the period changing means to extend the negative overlap period when it is determined that the time is cold. Here, “to increase the negative overlap period” means to increase compared to the negative overlap period when the direct injection engine is warm (that is, the negative overlap period becomes longer). is there. On the other hand, when it is determined that the time is not cold, the control means typically controls the period changing means so as not to extend the negative overlap period.

  When it is determined that the control means is cold, the control means further starts from the time when the exhaust valve is closed within the expanded negative overlap period, provided that the detected dilution is greater than the threshold. The fuel injection means is controlled so as to inject fuel on the retard side until the top dead center is reached. On the other hand, when it is determined that the control means is cold, the exhaust valve is closed in the expanded negative overlap period on condition that the detected dilution is smaller than the threshold. The fuel injection means is controlled so as to inject the fuel a plurality of times from the time point until the top dead center is reached.

  When fuel is injected a plurality of times, the control means, for example, the most advanced angle side and the most retarded angle between the time when the exhaust valve is closed and the top dead center within the expanded negative overlap period. The fuel injection means is controlled so as to inject fuel on the side (that is, the first and last time between when the exhaust valve is closed and when it reaches the top dead center).

  The "threshold value" according to the present invention, when it is determined that it is cold, from the time when the exhaust valve is closed in the expanded negative overlap period until the top dead center is reached, This is a value that determines whether to control the fuel injection means so as to inject the fuel on the retard side, or (ii) to control the fuel injection means to inject the fuel multiple times. Or a variable value corresponding to some physical quantity or parameter.

  Such a threshold value is determined experimentally, empirically, or by simulation, for example, by determining the relationship between engine oil dilution and fuel consumption, and the degree of deterioration in fuel consumption is within an allowable range based on the determined relationship. The degree of dilution may be set as a value that is greater than or less than the degree of dilution by a predetermined value.

  According to the inventor's research, the following has been found. That is, PM emission increases as the amount of fuel injected into the cylinder increases on the piston. For this reason, it is often the case that the PM emission is suppressed by relatively advancing the fuel injection timing. On the other hand, when the engine is cold, the fuel injection timing is often retarded to suppress dilution of the engine oil. As a result, it is difficult to achieve both suppression of engine oil dilution during cold and suppression of PM emission.

  However, in the present invention, the control means controls the period changing means to enlarge the negative overlap period on the condition that (i) when cold and the detected dilution is larger than the threshold, and enlargement. The fuel injection means is controlled so as to inject fuel on the retarded side from when the exhaust valve is closed within the negative overlap period, until reaching the top dead center, and (ii) when cold And the period changing means is controlled to expand the negative overlap period on the condition that the detected dilution is smaller than the threshold value, and the exhaust valve is closed in the expanded negative overlap period. The fuel injection means is controlled so as to inject the fuel a plurality of times from the time point until the top dead center is reached.

  That is, in the present invention, when it is cold and the detected dilution is larger than the threshold value, even if the effect of suppressing PM emission is reduced, priority is given to suppression of dilution of engine oil and enlargement. The fuel injection means is controlled so as to inject fuel on the retarded side from when the exhaust valve is closed within the negative overlap period, until the top dead center is reached.

  The period from when the exhaust valve is closed to when it reaches top dead center is a period during which the pressure in the cylinder rises. For this reason, by injecting fuel during the period, the penetration (ie, penetration force) of the injected fuel becomes relatively short, and the amount of the injected fuel adhering to the piston can be suppressed. That is, PM emission can be suppressed.

  On the other hand, in the present invention, when it is cold and the detected dilution is smaller than the threshold value, even if the effect of suppressing dilution of engine oil is reduced, priority is given to suppression of PM emission and expansion. The fuel injection means is controlled to inject the fuel a plurality of times from the time when the exhaust valve is closed within the negative overlap period to the time when the top dead center is reached. By injecting the fuel a plurality of times, for example, dilution of the engine oil as compared with the case where the fuel is injected only once on the advance side from the time when the exhaust valve is closed to the top dead center Can be suppressed.

  Furthermore, fuel is injected before the top dead center when the detected dilution is larger or smaller than the threshold. As a result, vaporization of the fuel is promoted due to the relatively early injection of the fuel into the high temperature field, thereby improving the fuel efficiency.

  As a result of the above, according to the engine control apparatus of the present invention, it is possible to reduce the degree of engine oil dilution and the degree of PM while improving fuel efficiency when cold.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a block diagram which shows the structure of the engine control apparatus which concerns on embodiment of this invention. It is a conceptual diagram which shows notionally the relationship between valve timing and fuel injection timing. It is a flowchart which shows the control processing which the engine control apparatus which concerns on embodiment of this invention performs.

  Hereinafter, an embodiment of an engine control device according to the present invention will be described with reference to FIGS. 1 to 3.

  First, the configuration of the engine control apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the engine control apparatus according to this embodiment. In FIG. 1, for convenience of explanation, only members that are directly related to the present embodiment are shown, and the other members are not shown.

  In FIG. 1, a direct injection engine 10 controlled by an engine control device 100 includes a cylinder block 16, a piston 15 that reciprocates in the cylinder block 16, a cylinder head 17, and oil that stores engine oil EO (Engine Oil). A pan 18 is provided.

  The cylinder head 17 includes an intake valve 13, an exhaust valve 14, an injectable fuel injection valve 21, and a spark plug 22. The intake valve 13 can open and close the intake port 11 formed in the cylinder head 17 as an intake passage. The exhaust valve 14 can open and close the exhaust port 12 formed in the cylinder head 17 as an exhaust passage.

  A combustion chamber 19 is formed in a space surrounded by the intake valve 13, the exhaust valve 14, the cylinder head 17, the cylinder block 16 and the piston 15. The fuel injection valve 21 is provided in the combustion chamber 19 at a position where fuel stored in a fuel tank (not shown) can be directly injected.

  The engine control apparatus 100 includes a variable valve timing system (VVT) 23 that can change the opening / closing timing of each of the intake valve 13 and the exhaust valve 14, and coolant water LLC (Long Life Coolant) that flows inside the cylinder block 16. A temperature sensor 24 for detecting the temperature of the engine, a viscosity sensor 25 for detecting the viscosity of the engine oil EO, a rotational speed sensor 26 for detecting the rotational speed of the direct injection engine 10, and an ECU (Electronic Control Unit) 27. Yes.

  The “fuel injection valve 21”, “variable valve timing mechanism 23”, “viscosity sensor 25”, and “ECU 27” according to the present embodiment are respectively referred to as “fuel injection means” and “period change means” according to the present invention. , “Dilution degree detection means” and “control means”. In the present embodiment, various electronic control ECUs 27 are used as part of the engine control apparatus 100.

  The ECU 27 as a part of the engine control device 100 detects, for example, an amount of depression of an accelerator pedal (not shown), an opening degree of a throttle valve (not shown), etc. during the operation, and the direct injection engine 10 It is determined whether the operation is full load (ie, full throttle) or partial load (ie, partial throttle).

  When it is determined that the vehicle is operating at full load, the ECU 27 controls the variable valve timing mechanism 23 so as to achieve, for example, a valve timing that maximizes fuel efficiency, and injects fuel so that fuel is injected at an appropriate time. The valve 21 is controlled. Various known modes can be applied to the valve timing and fuel injection timing during full load operation.

  On the other hand, when it is determined that the partial load operation is being performed, the ECU 27 controls the variable valve timing mechanism 23 so that the valve timing has a negative overlap period.

  In the present embodiment, in particular, when it is determined that the operation is a partial load operation, the ECU 27 as a part of the engine control device 100 acquires the temperature of the cooling water LLC via the temperature sensor 24 and sets the acquired temperature to the acquired temperature. Based on this, the negative overlap amount (hereinafter referred to as “NOL amount” as appropriate) and the fuel injection timing, which are the length of the negative overlap period, are changed. The NOL amount typically has a dimension of “degree CA”.

  Here, the NOL amount and the fuel injection timing during the partial load operation will be described with reference to FIG. FIG. 2 is a conceptual diagram conceptually showing the relationship between the valve timing and the fuel injection timing. FIG. 2 (a) shows the valve timing and fuel injection timing for suppressing PM emission when cold, and FIG. 2 (b) shows the valve timing for suppressing dilution of engine oil when cold. FIG. 2C shows the valve timing and the fuel injection timing when it is not cold. “EX”, “IN”, “BDC”, and “TDC” in FIG. 2 respectively indicate “a period during which the exhaust valve 14 is open”, “a period during which the intake valve 13 is open”, and “bottom death”. "Point" and "(exhaust) top dead center".

  When the acquired temperature is lower than, for example, 0 degrees Celsius, the ECU 27 acquires the rotational speed of the direct injection engine 10 via the rotational speed sensor 26 and, for example, determines the opening of the throttle valve and the direct injection engine 10. The load of the direct injection engine 10 is acquired based on the speed of the vehicle to be mounted. Subsequently, the ECU 27 calculates a NOL amount that maximizes the length of the negative overlap period based on the acquired rotation speed and load, and is variable so that the valve timing has the calculated NOL amount. The valve timing mechanism 23 is controlled.

  At this time, the ECU 27 calculates the degree of dilution of the engine oil EO based on the viscosity of the engine oil EO acquired via the viscosity sensor 25, and changes the fuel injection timing according to the calculated degree of dilution.

  Specifically, as shown in FIG. 2 (a), the ECU 27 performs the negative overlap period on the condition that the calculated dilution is not more than a specified value as an example of the “threshold value” according to the present invention. In the period from the time when the exhaust valve 14 is closed to the top dead center (hereinafter referred to as “injectable period” as appropriate), in each of the most advanced angle side and the most retarded angle side of the injectable period The fuel injection valve 21 is controlled so as to inject fuel. The injectable period is determined by the positional relationship between the NOL amount and the piston 15.

  By controlling the fuel injection valve 21 in this way, it is possible to suppress the emission of PM, and compared to the case where the fuel is injected only once at the most advanced angle side of the injection possible period, the engine oil EO The deterioration of the degree of dilution can be suppressed. Furthermore, since the period from when the exhaust valve 14 is closed to the top dead center (that is, the injection possible period) is a period during which the pressure in the combustion chamber 19 increases, the penetration of the injected fuel Becomes relatively short, and the amount of injected fuel adhering to the piston 15 can be suppressed. For this reason, PM discharge can be further suppressed.

  In addition, by controlling the fuel injection valve 21 so as to inject fuel during the negative overlap period, it is not affected by the airflow generated when at least one of the intake valve 13 and the exhaust valve 14 is opened. , Fuel can be injected.

  On the other hand, the ECU 27 sets the fuel injection valve 21 to inject fuel at the most retarded angle side of the injectable period, as shown in FIG. Control. By controlling the fuel injection valve 21 in this way, it is possible to suppress deterioration of the dilution of the engine oil EO.

  In addition, the calculation method of the dilution degree of engine oil EO is not restricted to the method of calculating based on the viscosity of engine oil EO mentioned above. For example, various known modes such as calculating or estimating the dilution degree of the engine oil EO based on the number of fuel injections, the temperature of the engine oil EO, and the like can be applied.

  When the acquired temperature is higher than, for example, 0 degrees Celsius, the ECU 27 calculates the NOL amount that minimizes the pump loss and the heat loss due to unburned fuel (so-called unburned loss). The variable valve timing mechanism 23 is controlled so that the valve timing has a NOL amount. At this time, as shown in FIG. 2C, the ECU 27 controls the fuel injection valve 21 so as to inject fuel on the most advanced angle side of the injectable period. By controlling the fuel injection valve 21 in this way, the time during which the injected fuel is exposed to the high-temperature gas in the combustion chamber 19 becomes relatively long, and vaporization of the injected fuel can be promoted. That is, fuel consumption can be improved.

  In the present embodiment, as shown in FIG. 2, the negative overlap period in the case of cold time (see FIGS. 2A and 2B) is not in the cold time (FIG. 2C). It is set to be longer than the negative overlap period in the reference). That is, at the cold time, the variable valve timing mechanism 23 is controlled by the ECU 27 as a part of the engine control apparatus 100 so as to extend the negative overlap period.

  Next, control processing executed by the engine control apparatus 100 configured as described above will be described with reference to the flowchart of FIG. This control process is periodically executed at regular or irregular intervals mainly when a vehicle equipped with the direct injection engine 10 controlled by the engine control apparatus 100 is running.

  In FIG. 3, first, the ECU 27 as a part of the engine control device 100 determines the rotational speed of the direct injection engine 10 via the rotational speed sensor 26 when the direct injection engine 10 is in partial load operation. While acquiring, the load of the direct injection type engine 10 is detected or calculated (step S101).

  Next, the ECU 27 acquires the temperature of the cooling water LLC via the temperature sensor 24. Subsequently, the ECU 27 determines whether or not it is cold (step S102). Whether or not it is cold may be determined, for example, based on whether or not the acquired temperature is lower than 0 degrees Celsius.

  When it is determined that the time is cold (step S102: Yes), the ECU 27 acquires the viscosity of the engine oil EO via the viscosity sensor 25 and calculates the dilution degree of the engine oil EO (step S103). Subsequently, the ECU 27 determines whether or not the calculated dilution degree is equal to or less than a specified value (step S104).

  When it is determined that the calculated dilution is equal to or less than the specified value (step S104: Yes), the ECU 27 determines that the negative overrun is based on the rotation speed acquired in the process of step S101 and the detected or calculated load. The NOL amount that maximizes the length of the lap period is calculated (step S105), and the variable valve timing mechanism 23 is controlled so that the valve timing has the calculated NOL amount.

  In parallel with the process of step S105, the ECU 27 calculates the amount of fuel to be injected from the fuel injection valve 21 (ie, the injection amount) (step S106). In addition, the well-known various aspects are applicable to the calculation method of injection quantity.

  Next, the ECU 27 calculates the most advanced position of the injectable period based on, for example, the NOL amount calculated in the process of step S105, the relationship of the piston 15, and the like. Subsequently, the ECU 27 sets the calculated most advanced position as a first injection SOI (Start Of Injection) (step S107).

  Concurrently with the process of step S107, the ECU 27 calculates the most retarded position of the available injection timing, and sets the calculated most retarded position as the second injection SOI (step S108). The ECU 27 controls the fuel injection valve 21 so as to inject fuel in the set first injection SOI and second injection SOI.

  When it is determined in the process of step S104 that the calculated dilution is greater than the specified value (step S104: No), the ECU 27 determines the rotation speed acquired in the process of step S101 and the detected or calculated load. Based on this, a NOL amount that maximizes the length of the negative overlap period is calculated (step S109), and the variable valve timing mechanism 23 is controlled so that the valve timing has the calculated NOL amount. In parallel with the process of step S109, the ECU 27 calculates the injection amount (step S110).

  Next, the ECU 27 calculates the most retarded position of the injectable period based on, for example, the NOL amount calculated in the process of step S109, the relationship of the piston 15, and the like. Subsequently, the ECU 27 sets the calculated most retarded angle position as the injection SOI (step S111). The ECU 27 controls the fuel injection valve 21 so as to inject fuel at the set injection SOI.

  If it is determined in step S102 that it is not cold (step S102: No), the ECU 27 calculates the NOL amount that minimizes the pump loss and the unburned loss (step S112). The ECU 27 controls the variable valve timing mechanism 23 so that the valve timing has the calculated NOL amount.

  In parallel with the process of step S112, the ECU 27 calculates the injection amount (step S113). Next, the ECU 27 calculates the most advanced position of the injectable period based on the NOL amount calculated in the process of step S112, the relationship of the piston 15, and the like, for example. Subsequently, the ECU 27 sets the calculated most advanced angle position as the injection SOI (step S114). The ECU 27 controls the fuel injection valve 21 so as to inject fuel at the set injection SOI.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and is accompanied by such a change. An engine control device is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Direct injection type engine, 11 ... Intake port, 12 ... Exhaust port, 13 ... Intake valve, 14 ... Exhaust valve, 15 ... Piston, 16 ... Cylinder block, 17 ... Cylinder head, 18 ... Oil pan, 19 ... Combustion chamber , 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Variable valve timing mechanism, 24 ... Temperature sensor, 25 ... Viscosity sensor, 26 ... Revolution sensor, 27 ... ECU

Claims (1)

A negative overlap period in which a direct injection engine having fuel injection means capable of injecting fuel into a cylinder is closed when both the intake valve and the exhaust valve of the direct injection engine are closed when the direct injection engine is partially loaded. An engine control device that controls at a valve timing having
Dilution detection means for detecting the dilution of engine oil in the direct injection engine;
A period changing means capable of expanding the negative overlap period;
(I) Controlling the period changing means to expand the negative overlap period on the condition that it is cold and the detected dilution is greater than a threshold, and the expanded negative overlap period Controlling the fuel injection means so as to inject the fuel on the retarded side from the time when the exhaust valve is closed to the top dead center, and (ii) when cold, and On the condition that the detected dilution is smaller than the threshold value, the period changing means is controlled to expand the negative overlap period, and the exhaust valve is closed in the expanded negative overlap period Control means for controlling the fuel injection means so as to inject the fuel a plurality of times from the point of time until the top dead center is reached. Engine control device.

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