JP2000087787A - Control device for cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel economy during idle operation by monitoring a load applied to an engine and by selecting stratified charge combustion when such a load increases as a result of auxiliaries being actuated in an idle state and when that load falls within the range through which stratified charge combustion is possible. SOLUTION: In a control device for a cylinder injection type internal combustion engine 1, in which fuel is directly injected into a combustion chamber 5 and which is equipped with control means 70 that selects either premixture combustion or stratified charge combustion according to operating conditions, the control means 70 selects stratified charge combustion if an external auxiliary load applied to the engine 1 as a result of auxiliaries 80 being actuated during idle operation does not exceed a predetermined value Pe0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a control device for a direct injection internal combustion engine mounted on a vehicle.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine mounted on a vehicle, in-cylinder injection in which fuel is directly injected into a combustion chamber in place of an intake pipe injection type in order to reduce harmful exhaust gas components and improve fuel efficiency. Various types of gasoline engines have been proposed. In a cylinder injection type gasoline engine, for example, during low load operation, fuel is injected mainly during the compression stroke,
A mixture having an air-fuel ratio close to the stoichiometric air-fuel ratio is locally formed around the ignition plug or in the cavity, and good combustion can be realized even with a lean air-fuel ratio as a whole (hereinafter, this is referred to as "stratified combustion"). . On the other hand, during medium-high load operation, fuel is injected during the intake stroke to form an air-fuel mixture with a uniform air-fuel ratio in the combustion chamber.
By burning a large amount of fuel (hereinafter referred to as "premixed combustion"
(Referred to as “acceleration”) or at the time of high-speed running.

[0003]

In such an engine, it is conceivable to set so that stratified combustion (lean operation) is performed at the time of idling to improve idle fuel efficiency. However, in the stratified combustion, when the fuel ratio to the air amount is increased to a certain degree or more, the air-fuel mixture around the ignition plug becomes too rich, causing misfiring or generating smoke. As a result, the air-fuel ratio in the combustion chamber when the maximum output of the stratified combustion is generated is leaner than the stoichiometric air-fuel ratio, and the maximum fuel amount that can be supplied during the stratified combustion is smaller than that at the time of the premixing. It is low. For this reason, when an external auxiliary load such as an air conditioner or power steering is applied during idling, there is a limit to increasing the fuel amount in response to this, and the output obtained during stratified combustion is not sufficient. And the engine speed may drop, and in some cases, engine stall may occur. Due to these factors, conventionally, when the external auxiliary equipment load is applied at the time of idling, the control of premixed combustion is performed, and the idling fuel efficiency cannot be improved as desired.

In a conventional port injection lean-burn internal combustion engine different from the above-described in-cylinder injection internal combustion engine, when an external accessory load is applied during idling operation, the rotation speed tends to fluctuate. A technology has been disclosed in which the lean operation is prohibited and the operation is shifted to a stoichiometric (stoichiometric air-fuel ratio) operation when the operation is performed (Japanese Patent Publication No. 60-17 / 1985).
234). However, in the above-described known example, the operation state is switched to the stoichiometric operation based only on the operation signals of the auxiliary devices (such as the air conditioner). There is a case where the state is switched, and there is a problem that it is difficult to improve idle fuel efficiency.

According to the present invention, even if the load on the engine increases due to the operation of the auxiliary equipment during idling operation, the load is monitored and the stratified combustion is selected if the load is within the range where the 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 fuel efficiency during idling operation.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a control means for injecting fuel directly into a combustion chamber and switching between premixed combustion and stratified combustion in accordance with an operation state is provided. In the control device for a direct injection internal combustion engine provided, the control means selects and executes stratified combustion when the external accessory load applied to the engine does not exceed a predetermined value due to the operation of the accessories during idling operation. Therefore, the stratified combustion state is continued even during the idling operation until the external auxiliary equipment load exceeds the predetermined value, and the fuel consumption is suppressed.

According to a second aspect of the present invention, there is provided a control apparatus for a direct injection type internal combustion engine, comprising a control means for directly injecting fuel into a combustion chamber and switching between premixed combustion and stratified combustion in accordance with an operation state. The control means selects and executes stratified combustion when the engine load applied to the engine by the operation of the air conditioner during idle operation does not exceed a predetermined value, and performs air conditioning of the air conditioner even when the engine load exceeds the predetermined value. If the load does not exceed the preset value, the operation of the air conditioner is stopped and the stratified combustion is selected and executed, so that the engine load does not exceed the predetermined value, and even if the load exceeds the preset value, the air conditioning load exceeds the set value. Until it exceeds, the stratified combustion state is continued even during idle operation, and fuel consumption is suppressed.

As described above, even if the load on the engine increases during idling operation, stratified combustion is performed when the load allows stratified combustion, and the operation of the air conditioner is cut off when the load cannot stratified combustion. Accordingly, stratified combustion can be executed by reducing the load applied to the engine, so that the execution range of the stratified combustion can be extended during the idling operation, and the fuel consumption can be suppressed and the fuel efficiency during the idling operation can be improved.

[0009]

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 also 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 a piston 7 that reciprocates while sliding in the cylinder 6 at a position near the top dead center where fuel dew from the fuel injection valve 4 reaches. The theoretical compression ratio of the engine 1 is set higher (about 12 in this embodiment) than that of the intake pipe injection type. A DOHC 4-valve valve mechanism is adopted as the valve operating mechanism. An intake camshaft 11 and an exhaust camshaft 12 are rotatably provided above the cylinder head 2 to drive intake and exhaust valves 9 and 10, respectively. Is held.

The cylinder head 2 has two camshafts 1.
An intake port 13 is formed in a substantially upright direction so as to pass through between the intake ports 1 and 12, and the intake flow passing through the intake port 13 generates a reverse tumble flow described later in the combustion chamber 5. ing. The exhaust port 14 is formed in a substantially horizontal direction similarly to a normal engine, but a large-diameter EGR port 15 branches diagonally. In the figure, reference numeral 16 denotes a water temperature sensor for detecting a cooling water temperature TW, and 17 denotes a crank angle for outputting a crank angle signal SGT at a predetermined crank position (5 ° BTDC and ぴ 75 ° BTDC in this embodiment) of each cylinder. Reference numeral 19 denotes an ignition coil which outputs a high voltage to the ignition plug 3. A cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC is attached to a camshaft or the like that rotates at half the number of revolutions of the crankshaft, and discriminates which cylinder the crank angle signal SGT belongs to. .

An air cleaner 2 is connected to the intake port 13 via an intake manifold 21 having a surge tank 20.
2, an intake pipe 25 provided with a throttle body 23 and an idle speed control valve (hereinafter referred to as an idle adjustment valve) 24 of a stepper motor type. 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. A linear solenoid type large air bypass valve is provided in the pipe. (Referred to as an ABV valve) 27 is provided. Air bypass pipe 26
Has a flow passage area similar to that of the intake pipe 25, and ABV
When the valve 27 is fully opened, the required amount of intake air in the low to medium speed range of the engine 1 can flow. On the other hand, the idle adjustment valve 24 has a flow path bond smaller than the ABV valve 27, and uses the idle adjustment valve 24 when adjusting the intake air amount with high accuracy.

The throttle body 23 includes a butterfly type throttle valve 28 for opening and closing a flow path, a throttle sensor 29 for detecting accelerator opening information by detecting an opening degree θth of the throttle valve 28, and a fully closed state. An idle switch 30 for detecting is provided. Further, inside the air cleaner 22, an atmospheric pressure sensor 31 and an intake air temperature sensor 32 for obtaining an intake air density are provided, and output signals corresponding to the atmospheric pressure Pa and the intake air temperature Ta. Further, a Karman vortex airflow sensor 33 is disposed near the inlet of the intake pipe 25, and outputs a vortex generation signal proportional to the volume air flow rate Qa per intake stroke.

On the other hand, an O ₂ sensor 4
An exhaust pipe 43 provided with a three-way catalyst 42 and a muffler (not shown) is connected through an exhaust manifold 41 to which 0 is attached. The EGR port 15 is provided with a large-diameter EG.
The EGR valve 45 is connected downstream of the throttle valve 28 and upstream of the intake manifold 21 via an R pipe 44, and is provided with a stepper motor type EGR valve 45 in the pipeline.

The fuel tank 50 is installed at the rear of the vehicle body (not shown). Then, the fuel stored in the fuel tank 50 is sucked up by the electric low-pressure fuel pump 51,
The air is supplied to the engine 1 via the low-pressure feed pipe 52. The fuel pressure in the low-pressure feed pipe 52 is controlled by a first fuel pressure regulator 54 interposed in the return pipe 53.
Thus, the pressure is adjusted to a relatively low pressure (hereinafter, referred to as a low fuel pressure). The fuel supplied to the engine 1 is supplied to each fuel injection valve 4 via 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 the present embodiment, the high-pressure fuel pump 55 is of 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. Delivery pipe 57
The internal fuel pressure is regulated to a relatively high pressure (hereinafter, referred to as high fuel pressure) by a second fuel pressure regulator 59 interposed in the return pipe 58. In the drawing, reference numeral 60 denotes an electromagnetic fuel pressure switching valve attached to the second fuel pressure regulator 59, which relieves fuel in the ON state and supplies the fuel to the delivery pipe 5.
The fuel pressure in 7 is reduced to a predetermined value. Reference numeral 61 denotes a return pipe for returning the fuel, which has been lubricated or cooled by the high-pressure fuel pump 55, to the fuel tank 50.

An air conditioner 80 which is an example of auxiliary equipment and is an air conditioner circulates a refrigerant compressed by an 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 via a belt. An electromagnetic clutch 86 is mounted on this pulley, so that the drive system between the AC compressor 81 and the pulley can be intermittently connected. A refrigerant passage 84 serving as a low-pressure pipe connecting the condenser 82 and the evaporator 83 is provided with a condenser 8.
A refrigerant pressure sensor 85 serving as an external accessory load detecting means for detecting a change in the external accessory load by detecting the refrigerant pressure Acp passing through the pressure sensor 85 is mounted.

An ECU (Electronic Control Unit) 70 as control means is installed in the vehicle interior. This ECU 7
0 includes an input / output device (not shown), a storage device (ROM, RAM, non-volatile RAM, etc.) for storing a control program, a control map, and the like, a central processing unit (CPU), a timer counter, and the like. Has comprehensive control. The input side of the ECU 70 has an engine 1
Air-conditioning equipment, power steering equipment,
Switches for detecting the operation status of the automatic transmission and the like, that is, air conditioner switch (A / C / SW) 34, power steering switch (P / S / SW) 35, inhibitor switch / (INH / SW) 36, refrigerant pressure The sensors 85 are connected to each other and supply each detection signal to the ECU 70. In addition to the various sensors and switches described above, a large number of switches and sensors (not shown) are connected to the input side of the ECU 70, and an electromagnetic clutch 86, various warning lights, devices and the like are also provided on the output side. It is connected.

The ECU 70 determines the fuel injection mode, the fuel injection amount, the fuel injection end timing, the ignition timing, the amount of EGR gas introduced, etc., based on the input signals from the various sensors and switches described above. The drive control of the fuel injection valve 4, the ignition coil 19, the EGR valve 45, and the like is performed.

A control procedure for switching the operating state of the engine according to the operation of the accessories during the idling 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 determines the engine speed N based on the crank angle signal generation time interval from the crank angle sensor 17 in step S1 of FIG.
e, the throttle valve opening θth detected by the throttle sensor 29, the intake air intake amount Qa per intake process detected by the air flow sensor 33, and the refrigerant pressure Acp detected by the refrigerant pressure sensor 85 are read. Next, the ECU 70 determines whether or not the vehicle is in an idling operation state in step S2.
Then, the operation mode is set according to the target average effective pressure Ev according to the throttle valve opening θth and the engine speed Ne, and the operation mode according to the engine speed Ne, and the processing ends. For example, when the vehicle is running at low to medium speeds, the intake stroke injection mode is selected so as to be in a lean region or a stoichiometric feedback region (stoichiometric air-fuel ratio feedback control region) based on the intake stroke injection mode (premixed combustion) in FIG. Fuel is injected so as to have a predetermined air-fuel ratio.

When the ECU 70 determines in step S2 that the vehicle is in the idling operation state, it proceeds to step S3.
For example, it is determined whether or not the air conditioner switch 34 is turned on. If the air conditioner switch 34 is off, the process proceeds to step S15. If the air conditioner switch 34 is turned on, a timer (not shown) is activated in step S4 to start the engine 1. The stoichiometric operation is waited for a predetermined time. In this case, it is unknown 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 why the predetermined time elapses in step S4 is for a self-check to surely execute the stoichiometric operation here, and is not more than one second in terms of time.

After a lapse of a predetermined time in step S4, the ECU 70 determines in step S6 a load Pe corresponding to, for example, the throttle valve opening θth and the intake air amount Qa from an engine load map 90 previously stored in the storage device.
Is calculated, and the process proceeds to step S7. The load Pe is the total load applied to the engine 1 at the time of idling, and the fuel supply amount (target air-fuel ratio) and the ignition timing are set based on the load Pe.

In step S7, the load Pe and a predetermined value Pe0 stored in the storage device in advance (hereinafter, "predetermined value Pe0").
If the load Pe does not exceed the predetermined value Pe0, the flow proceeds to step S8, the operation is switched to the lean operation, and the flow returns to step S1. The predetermined value Pe0 is an index that allows the lean operation (stratified combustion) during the idling operation, and is a lower limit value at which the engine 1 does not stop even if the lean operation is performed unless the load Pe exceeds this value. That is, even when the air conditioner 80 operates, there is a case where the load of the external auxiliary equipment due to the operation of the air conditioner is not necessarily increased until the lean operation of the load Pe becomes impossible due to the temperature setting and the relationship with the outside air temperature. For this reason, even when the air conditioner 80 is operated during the idling operation, if the load Pe has a margin, the lean operation is executed to suppress the fuel consumption.

In step S7, the load Pe becomes a predetermined value P
If it exceeds e0, the ECU 70 proceeds to step S9, in which the refrigerant pressure Acp (air-conditioning load) of the refrigerant passage 84 (low-pressure pipe) and the refrigerant pressure set value Accp0 stored in the storage device in advance.
(Hereinafter, referred to as “set value Acp0”), and when the refrigerant pressure Acp is higher than (exceeds) the set value Acp0, the air conditioner 80 is actively operated at a high external temperature and a high load. If it is determined that the vehicle is running, the process proceeds to step S10, switches to the stoichiometric operation, and returns to step S1. By doing so, engine stall due to an increase in the refrigerant pressure Acp can be prevented.

When the refrigerant pressure Acp is lower than the set value Acp0 (when it does not exceed) in step S9, it is considered that the outside air temperature is low and the air conditioner 80 is not actively operating at a low load, and the process proceeds to step S11. The electromagnetic clutch 86 is disengaged 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 elapses. As described above, even if the air conditioner 80 is once operated, the operating condition of the air conditioner 80 is checked and the load Pe applied to the engine 1 is reduced if the operation of the air conditioner 80 is stopped in a timely manner. The range is increased and fuel consumption can be further reduced.

After a predetermined time has elapsed in step S13, the ECU 70 operates the air conditioner again by connecting the electromagnetic clutch 86 in step S14, returns to step S1, fetches the latest information, and operates according to each step as described above. The state is switched and the control is sequentially executed. By operating the air conditioner 80 once turned off again in this manner, a rise in the temperature in the vehicle compartment can be suppressed.

Here, the predetermined time in step S13 is a time from when the air conditioner 80 is stopped to when the vehicle interior temperature exceeds a certain temperature. Further, although the predetermined time has elapsed here, the vehicle interior temperature may not exceed the set temperature. Further, in the present embodiment, in step S6, the engine speed Ne and the intake air amount Qa
Although the load Pe is selected from the engine load map 90 in accordance with the above, the present invention is not limited to this, and a load selected or calculated by another routine may be appropriately interrupted and fetched. Further, in the present embodiment, the air conditioning load is estimated from the refrigerant pressure in the refrigerant passage 84 serving as the low-pressure pipe, but may be estimated from the refrigerant pressure in the refrigerant passage connecting the AC compressor 81 and the condenser 82 serving as the high-pressure pipe. . Alternatively, the outside air temperature or the vehicle interior temperature may be measured and compared with the air conditioner set temperature.

[0026]

According to the first aspect of the present invention, even if the load of the external auxiliary equipment on the engine increases during idling operation,
In the case of an external auxiliary load capable of stratified combustion, the load is switched to the stratified combustion, so that the idling operation can be switched to the stratified combustion for a long time, and the fuel consumption can be suppressed.
Fuel efficiency can be improved during idling.

According to the second aspect of the present invention, even if the engine load on the engine increases during idling operation, if the load allows stratified combustion, the engine is switched to stratified combustion, and the engine load during idling is reduced to stratified combustion. If the air conditioner cannot be tolerated, the load on the engine is reduced by turning off the air conditioner, so that it is possible to switch to the stratified combustion, and to increase the execution range of the stratified combustion during the idling operation, thereby suppressing fuel consumption. Fuel efficiency can be improved during idling.

[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 of a fuel injection mode.

FIG. 3 is a flowchart showing an engine control procedure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 In-cylinder injection internal combustion engine 70 Control means 80 Air conditioning equipment (auxiliary equipment) Pe load Pe0 Predetermined value Acp Air conditioning load (refrigerant pressure of low-pressure piping) Acp0 Refrigerant pressure set value

Continued on front page F term (reference) 3G093 AB00 BA19 CA04 CA08 DA03 DA05 DA06 DA07 DA09 DB08 DB09 DB11 DB24 EA05 EB05 3G301 HA01 HA04 HA13 HA16 JA02 KA07 KA10 LB04 MA11 PA01Z PA05Z PA09Z PA10Z PA11Z PD03Z PE03Z PE05Z PE08Z08

Claims (2)

[Claims] 1. A control device for a direct injection internal combustion engine, comprising: control means for directly injecting fuel into a combustion chamber and switching between premixed combustion and stratified combustion in accordance with an operation state. A control device for a direct injection internal combustion engine, wherein the stratified combustion is performed when an external accessory load applied to the engine during operation does not exceed a predetermined value due to an operation of accessories. 2. A control apparatus for a direct injection internal combustion engine, comprising: a control means for directly injecting fuel into a combustion chamber and switching between premixed combustion and stratified combustion in accordance with an operation state. When the engine load applied to the engine due to the operation of the air conditioner during operation does not exceed a predetermined value, the stratified combustion is performed, and even when the engine load exceeds the predetermined value, the air conditioning load of the air conditioner is set in advance. A controller for stopping the operation of the air conditioner and performing the stratified combustion if the set value is not exceeded.