JP3755308B2 - In-cylinder injection type internal combustion engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a direct injection internal combustion engine mounted on a vehicle.
[0002]
[Prior art]
In a spark ignition internal combustion engine mounted on a vehicle, an in-cylinder injection type gasoline engine that directly injects fuel into a combustion chamber is used instead of an intake pipe injection type in order to reduce harmful exhaust gas components and improve fuel efficiency. Various proposals have been made. In a cylinder injection type gasoline engine, for example, during low load operation, fuel is injected mainly during the compression stroke, and an air-fuel mixture close to the stoichiometric air-fuel ratio is locally formed around the spark plug and in the cavity. Thus, good combustion can be realized even with a lean air-fuel ratio as a whole (hereinafter referred to as “stratified combustion”). On the other hand, during medium-high load operation, fuel is injected during the intake stroke, a uniform air-fuel ratio mixture is formed in the combustion chamber, and a large amount of fuel is burned (hereinafter referred to as an intake pipe injection type gasoline engine). This is referred to as “premixed combustion”), and it is possible to ensure the output required during acceleration or high-speed traveling.
[0003]
[Problems to be solved by the invention]
In such an engine, it is conceivable to set so as to improve idle fuel efficiency by performing stratified combustion (lean operation) during idling. However, in stratified combustion, if the fuel ratio to the air amount increases to some extent, the air-fuel mixture around the spark plug becomes too thick and misfires or smoke is generated. As a result, the air-fuel ratio in the combustion chamber when the maximum output of stratified combustion occurs is leaner than the stoichiometric air-fuel ratio, and the maximum amount of fuel that can be supplied during stratified combustion is smaller than that during premixing, resulting in a maximum output as well. It is low. For this reason, if an external auxiliary load such as an air conditioner or power steering is applied during idling, there is a limit to the amount of fuel that can be increased. The engine speed may drop, and engine stall may occur in some cases. Due to these factors, conventionally, control for premixed combustion is performed when an external auxiliary load is applied during idling, and the idle fuel consumption cannot be improved as expected.
[0004]
In a conventional port injection type lean combustion internal combustion engine different from the above-described cylinder injection type internal combustion engine, when an external auxiliary machine load is applied during idle operation, the rotation speed is likely to fluctuate. Discloses a technology for prohibiting lean operation and shifting to stoichiometric (theoretical air-fuel ratio) operation (Japanese Patent Publication No. 60-17234). However, in the above known example, since the operation state is switched to the stoichiometric operation based only on the operation signal of the auxiliary machinery (air conditioner etc.), the operation is actually performed even though the lean operation can be continued. There is a case where the state is switched, which causes a problem that it is difficult to improve the idle fuel consumption.
[0005]
Even when the load on the engine increases due to the operation of auxiliary equipment during idle operation, the present invention monitors the load and selects stratified combustion within the range where stratified combustion is possible. An object of the present invention is to provide a control device for a direct injection internal combustion engine that improves the fuel efficiency of the engine.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, there is provided an in-cylinder injection type internal combustion engine having a control means for injecting fuel directly into a combustion chamber and switching between premixed combustion and stratified combustion according to the operating state. In the control device, the control means selects and executes the stratified combustion when the engine load applied to the engine due to the operation of the air conditioner during idle operation does not exceed the predetermined value, and even when the engine load exceeds the predetermined value. If the air conditioning load of the air conditioning equipment does not exceed the preset setting value, the air conditioning equipment is stopped and the stratified combustion is selected and executed. Therefore, even if the engine load does not exceed the predetermined value, the air conditioning load Until the value exceeds the set value, the stratified combustion state is continued even during idling, and fuel consumption is suppressed .
[0008]
In this way, even if the load on the engine increases during idle operation, stratified combustion is performed when the load is capable of stratified combustion, and the engine is turned off when the load is not capable of stratified combustion. Since this load can be reduced and stratified combustion can be executed, the execution range of stratified combustion can be extended during idle operation, and fuel consumption can be suppressed to improve fuel efficiency during idle operation.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a control device for a direct injection gasoline engine according to the present invention mounted on a vehicle. The cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 4 together with an ignition plug 3 for each cylinder, so that fuel is directly injected into the combustion chamber 5. A hemispherical cavity 8 is formed on the top surface of the piston 7 that reciprocates while sliding in the cylinder 6 at a position where fuel spray from the fuel injection valve 4 reaches near the top dead center. The theoretical compression ratio of the engine 1 is set higher than that of the intake pipe injection type (about 12 in this embodiment). As the valve operating mechanism, a DOHC four-valve type is adopted, and an intake side camshaft 11 and an exhaust side camshaft 12 are rotatable at the upper part of the cylinder head 2 so as to drive the intake and exhaust valves 9 and 10, respectively. Is retained.
[0010]
An intake port 13 is formed in the cylinder head 2 so as to pass between the camshafts 11 and 12 in a substantially upright direction, and an intake air flow passing through the intake port 13 will be described later in the combustion chamber 5. A reverse tumble flow is generated. The exhaust port 14 is formed in a substantially horizontal direction as in a normal engine, but a large-diameter EGR port 15 is branched obliquely. In the figure, 16 is a water temperature sensor that detects the cooling water temperature TW, and 17 is a crank angle that outputs a crank angle signal SGT at a predetermined crank position of each cylinder (in this embodiment, 5 ° BTDC and 75 ° BTDC). A sensor 19 is an ignition coil that outputs a high voltage to the spark plug 3. A cylinder discriminating sensor (not shown) that outputs a cylinder discriminating signal SGC is attached to a camshaft or the like that rotates at half the number of revolutions of the crankshaft to discriminate which cylinder the crank angle signal SGT belongs to. .
[0011]
An intake pipe 25 having an air cleaner 22, a throttle body 23, and a stepper motor type idle speed control valve (hereinafter referred to as an idle adjustment valve) 24 is connected to the intake port 13 via an intake manifold 21 having a surge tank 20. is doing. The intake pipe 25 is provided with a large-diameter air bypass pipe 26 that bypasses the throttle body 23 and introduces intake air into the intake manifold 21, and a linear solenoid type large air bypass valve is provided in the pipe line. 27 (referred to as an ABV valve) is provided. The air bypass pipe 26 has a flow passage area similar to that of the intake pipe 25, and the amount of intake air required in the low and medium speed range of the engine 1 can flow when the ABV valve 27 is fully opened. On the other hand, the idle adjustment valve 24 has a flow path note smaller than the ABV valve 27, and the idle adjustment valve 24 is used when adjusting the intake air amount with high accuracy.
[0012]
The throttle body 23 includes a butterfly throttle valve 28 that opens and closes a flow path, a throttle sensor 29 that detects accelerator opening information by detecting the opening θth of the throttle valve 28, and an idle that detects a fully closed state. A switch 30 is provided. Further, an atmospheric pressure sensor 31 and an intake air temperature sensor 32 for obtaining the intake air density are disposed inside the air cleaner 22 and output signals corresponding to the atmospheric pressure Pa and the intake air temperature Ta. Further, a Karman vortex type air flow sensor 33 is disposed in the vicinity of the inlet of the intake pipe 25 and outputs a vortex generation signal proportional to the volumetric air flow rate Qa per intake stroke.
[0013]
On the other hand, an exhaust pipe 43 including a three-way catalyst 42 and a muffler (not shown) is connected to the exhaust port 14 via an exhaust manifold 41 to which an O ₂ sensor 40 is attached. The EGR port 15 is connected to the downstream of the throttle valve 28 and the upstream of the intake manifold 21 via a large-diameter EGR pipe 44, and a stepper motor type EGR valve 45 is provided in the pipeline. It has been.
[0014]
The fuel tank 50 is installed at the rear of the vehicle body (not shown). The fuel stored in the fuel tank 50 is sucked up by an electric low-pressure fuel pump 51 and fed to the engine 1 side through a low-pressure feed pipe 52. The fuel pressure in the low-pressure feed pipe 52 is regulated to a relatively low pressure (hereinafter referred to as a low fuel pressure) by a first fuel pressure regulator 54 interposed in a pipe line of the return pipe 53. The fuel supplied to the engine 1 side is supplied to each fuel injection valve 4 through a high-pressure feed pipe 56 and a delivery pipe 57 by a high-pressure fuel pump 55 attached to the cylinder head 2. In the case of this embodiment, the high-pressure fuel pump 55 is a swash plate axial piston type, is driven by the exhaust side camshaft 12, and generates a high discharge pressure even when the engine 1 is idling. The fuel pressure in the delivery pipe 57 is regulated to a relatively high pressure (hereinafter referred to as a high fuel pressure) by a second fuel pressure regulator 59 interposed in the pipe line of the return pipe 58. In the figure, reference numeral 60 denotes an electromagnetic fuel pressure switching valve attached to the second fuel pressure regulator 59, which relieves the fuel in the ON state and lowers the fuel pressure in the delivery pipe 57 to a predetermined value. Reference numeral 61 denotes a return pipe that returns the fuel that has been lubricated or cooled to the high-pressure fuel pump 55 to the fuel tank 50.
[0015]
An air conditioner 80, which is an example of an auxiliary machine and is an air conditioner, circulates the refrigerant compressed by the AC compressor 81 via a condenser 82 and an evaporator 83. The AC compressor 81 is provided with a pulley (not shown) connected to the engine 1 side via a belt. An electromagnetic clutch 86 is attached to this pulley so that the drive system between the AC compressor 81 and the pulley can be intermittently connected. A refrigerant pressure 84 serving as an external auxiliary load detecting means for detecting a change in the external auxiliary load by detecting the refrigerant pressure Acp passing through the condenser 82 is provided in the refrigerant passage 84 serving as a low pressure pipe portion connecting the condenser 82 and the evaporator 83. A sensor 85 is attached.
[0016]
An ECU (electronic control unit) 70 as a control means is installed in the passenger compartment. The ECU 70 includes an input / output device (not shown), a storage device (ROM, RAM, nonvolatile RAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), a timer counter, and the like. 1 overall control. On the input side of the ECU 70, switches for detecting the operation status of an air conditioner device, a power steering device, an automatic transmission, etc., which become a load on the engine 1 during operation, that is, an air conditioner switch (A / C / SW) 34, power steering A switch (P / S • SW) 35, an inhibitor switch • (INH • SW) 36, and a refrigerant pressure sensor 85 are connected to each other, and each detection signal is supplied to the ECU 70. In addition to the various sensors and switches described above, the ECU 70 is connected to a number of switches and sensors (not shown) on the input side, and an electromagnetic clutch 86, various warning lights, devices, and the like are also provided on the output side. It is connected.
[0017]
The ECU 70 determines the fuel injection end time, the ignition timing, the introduction amount of EGR gas, and the like based on the input signals from the various sensors and switches described above, and the fuel injection valve. 4. Drive control of the ignition coil 19, the EGR valve 45, etc.
[0018]
A control procedure for switching the operating state of the engine in accordance with the operation of the auxiliary machinery during idle operation will be described.
The flowchart shown in FIG. 3 is executed by the ECU 70 every time a crank angle signal is output from the crank angle sensor 17. The ECU 70 detects the engine speed Ne detected from the crank angle signal generation time interval from the crank angle sensor 17 in step S1 of FIG. 3, the throttle valve opening θth detected by the throttle sensor 29, and the air flow sensor 33 detects one. The intake air amount Qa per intake process and the refrigerant pressure Acp detected by the refrigerant pressure sensor 85 are read. Next, the ECU 70 determines whether or not the engine is in an idling operation state in step S2, and if not in the idling operation state, the ECU 70 proceeds to step S15 and proceeds to a target average effective pressure Ev according to the throttle valve opening θth and the engine speed Ne. Then, the operation mode according to the engine speed Ne is set and the process ends. For example, during low and medium speed traveling, the intake stroke injection mode is selected so as to be in the lean region or stoichiometric feedback region (theoretical air-fuel ratio feedback control region) in the intake stroke injection mode (premixed combustion) in FIG. Fuel is injected so that a predetermined air-fuel ratio is obtained.
[0019]
When it is determined in step S2 that the engine is in the idling state, the ECU 70 determines, for example, whether or not the air conditioner switch 34 is turned on in step S3. When the air conditioner switch 34 is turned off, the ECU 70 proceeds to step S15. When it is turned on, a timer (not shown) is operated in step S4, and the engine 1 is once stoichiometrically operated to wait for a predetermined time. It is unclear how much load is applied to the engine 1 when the air conditioner switch 34 is turned on, and the stoichiometric operation is performed as a safety measure for preventing engine stall. The reason for waiting for the elapse of the predetermined time in step S4 is for a self-check for surely executing the stoichiometric operation here, which is 1 second or less in terms of time.
[0020]
When a predetermined time has elapsed in step S4, the ECU 70 calculates, for example, a load Pe according to the throttle valve opening θth and the intake air intake amount Qa from the engine load map 90 stored in advance in the storage device in step S6. Proceed to S7. The load Pe is a total load applied to the engine 1 during idling, and the fuel supply amount (target air-fuel ratio) and ignition timing are set based on the load Pe.
[0021]
In step S7, the load Pe is compared with a predetermined value Pe0 (hereinafter referred to as “predetermined value Pe0”) stored in advance in the storage device. If the load Pe does not exceed the predetermined value Pe0, the process proceeds to step S8. Then, the operation is switched to the lean operation and returns to step S1. The predetermined value Pe0 is an index that is allowed for lean operation (stratified combustion) during idle operation. If the load Pe does not exceed this value, the predetermined value Pe0 is a lower limit value that does not stop the engine 1 even when lean operation is performed. In other words, even if the air conditioner 80 is activated, there is a case where the external auxiliary load due to the air conditioner operation is not necessarily increased until the lean operation is impossible with respect to the load Pe due to the relationship between the temperature setting and the outside air temperature. For this reason, even when the air conditioner 80 is operated during the idle operation, if there is a margin in the load Pe, the lean operation can be executed to suppress fuel consumption.
[0022]
If the load Pe exceeds the predetermined value Pe0 in step S7, the ECU 70 proceeds to step S9, where the refrigerant pressure Acp (air conditioning load) of the refrigerant passage 84 (low pressure pipe section) and the refrigerant pressure setting previously stored in the storage device are set. Compared with the value Acp0 (hereinafter referred to as “set value Acp0”), if the refrigerant pressure Acp is higher than (or exceeds) the set value Acp0, the outside air temperature is high and the air conditioner 80 is actively operated at a high load. Assuming that it is, the routine proceeds to step S10, switches to stoichiometric operation, and returns to step S1. By doing in this way, the engine stall by the increase in the refrigerant pressure Acp can be prevented.
[0023]
If the refrigerant pressure Acp is lower than the set value Acp0 in step S9 (when it does not exceed), it is assumed that the air conditioner 80 is not operating actively at a low external temperature and a low load, and the routine proceeds to step S11 and the electromagnetic clutch 86 is advanced. To turn off the air conditioner 80 and switch to lean operation (stratified combustion). This lean operation is performed until the predetermined time in step S13 has elapsed. As described above, even if the air conditioner 80 is once activated, the load Pe applied to the engine 1 is reduced if the operation condition of the air conditioner 80 is stopped appropriately and the operation of the air conditioner 80 is stopped in a timely manner. The range is increased and fuel consumption can be further suppressed.
[0024]
When a predetermined time elapses in step S13, the ECU 70 connects the electromagnetic clutch 86 in step S14, operates the air conditioner again, returns to step S1, captures the latest information, and switches the operating state along each step as described above. Control is executed sequentially. In this way, once the air conditioner 80 that has been cut is operated again, an increase in the temperature in the passenger compartment can be suppressed.
[0025]
Here, the predetermined time in step S13 is a time until the vehicle interior temperature exceeds a certain temperature after the air conditioner 80 is stopped. Furthermore, although it is after the predetermined time has elapsed here, it may be a time during which the vehicle interior temperature does not exceed the set temperature. In the present embodiment, the load Pe is selected from the engine load map 90 according to the engine speed Ne and the intake air intake amount Qa in step S6, but the present invention is not limited to this and is selected by another routine. Alternatively, the calculated value may be taken in at an appropriate time. Further, in this embodiment, the air conditioning load is estimated from the refrigerant pressure in the refrigerant passage 84 serving as the low-pressure pipe section, but may be estimated from the refrigerant pressure in the refrigerant path connecting the AC compressor 81 serving as the high-pressure pipe section and the condenser 82. . Alternatively, the outside air temperature or the passenger compartment temperature may be measured and compared with the air conditioner set temperature.
[0026]
【The invention's effect】
According to the present invention, even when the engine load on the engine increases during idle operation, the load is switched to stratified combustion when the load is capable of stratified combustion, and when the engine load during idle operation cannot allow stratified combustion, By switching off the air conditioning equipment, the load on the engine is reduced, so it is possible to switch to stratified combustion, increase the execution range of stratified combustion during idle operation, and improve fuel efficiency during idle operation by suppressing fuel consumption. I can plan .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a control device for a direct injection internal combustion engine according to the present invention.
FIG. 2 is a diagram showing a determination map for a fuel injection mode.
FIG. 3 is a flowchart showing an engine control procedure according to the present invention.
[Explanation of symbols]
1 In-cylinder injection type internal combustion engine 70 Control means 80 Air-conditioning equipment (auxiliaries)
Pe load Pe0 Predetermined value Acp Air conditioning load (refrigerant pressure in low-pressure piping)
Set value of Acp0 refrigerant pressure

Claims (1)

In a control apparatus for a direct injection type internal combustion engine having control means for injecting fuel directly into a combustion chamber and switching between premixed combustion and stratified combustion according to the operating state, the control means is an air conditioner during idle operation If the engine load on the engine due to the operation of the engine does not exceed a predetermined value, the stratified combustion is performed, and even if the engine load exceeds the predetermined value, the air conditioning load of the air conditioner exceeds a preset set value. A control apparatus for a direct injection internal combustion engine, characterized by stopping the operation of the air conditioner and performing the stratified combustion when there is not .

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