JP2003193895A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the case that, in conjunction with idling speed feedback control after cold start, a decreased intake air amount, a worse catalyst warming condition and poor emission control result from small friction of an internal combustion engine. <P>SOLUTION: This control device for controlling an idling speed after starting the internal combustion engine having a catalyst arranged in an exhaust system for purifying exhaust emission performs speed feedback control for controlling an engine speed to a target speed by controlling the intake air amount depending on a difference between the target speed and an actual engine speed and sets such an ignition timing that an exhaust temperature is kept constant, depending on the engine intake air amount as a result of the speed feedback control. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to control for maintaining an engine speed at a target speed during idle operation after cold start of the engine (after cold start). The present invention relates to a control device that performs idle speed feedback control).

[0002]

2. Description of the Related Art A controller for maintaining an engine speed at a predetermined target speed during engine idle operation is generally known. For example, as an example of this type of control device, Japanese Patent Laid-Open No.
There is one described in Japanese Patent No. 222997. The device disclosed in the same publication carries out feedback control of the engine speed by adjusting the engine intake air amount so that the engine speed matches a predetermined target speed during idle operation, and makes the idle speed constant. In addition to maintaining the engine speed, if a failure occurs in the engine speed control by adjusting the engine intake air amount, feedback control of the engine speed by adjusting the ignition timing is performed to maintain the idle speed constant. I am trying.

[0003]

When performing feedback control of the engine speed by adjusting the engine intake air amount so that the engine speed matches the target speed during cold idle operation, friction may occur. In an internal combustion engine with a small value, the air correction amount by the feedback control becomes small. As a result, the amount of engine intake air also becomes small, which may deteriorate the warm-up state of the catalyst provided in the exhaust system. In that case, there arises a problem that the emission is deteriorated.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to suppress variations in emissions due to small friction of an internal combustion engine in idle speed feedback control after a cold start. An object of the present invention is to provide a control device for an internal combustion engine that can be reduced.

[0005]

In order to achieve the above object, according to a first aspect of the present invention, an idle speed after starting of an internal combustion engine in which a catalyst for purifying exhaust gas is arranged in an exhaust system. A device for controlling the engine rotation speed feedback control means for controlling the engine rotation speed to the target rotation speed by adjusting the intake air amount according to the difference between the target rotation speed and the actual engine rotation speed, Depending on the engine intake air amount as a result of the control by the rotation speed feedback control means,
There is provided an internal combustion engine control device comprising: an ignition timing setting unit that sets an ignition timing so that the temperature of exhaust gas becomes a constant temperature.

In the control device for an internal combustion engine according to the first aspect of the present invention configured as described above, the ignition timing is set with respect to the intake air amount so that the exhaust temperature is always constant. The variation in the catalyst warm-up state is reduced, and as a result, the emission variation is also reduced.

Further, according to the second aspect of the present invention, the ignition timing setting means determines the constant temperature according to the cooling water temperature and the intake air temperature at the time of starting the engine.

The exhaust gas temperature required to obtain a constant catalyst warm-up state varies depending on the catalyst temperature at the time of starting. That is, when the catalyst temperature at the start is high, the exhaust temperature may be relatively low, while when the catalyst temperature at the start is low, a relatively high exhaust temperature is required. In the control device for the internal combustion engine according to the second aspect of the present invention as described above, the target exhaust gas temperature is determined according to the cooling water temperature and the intake air temperature at the time of starting, which are a guide when estimating the catalyst temperature at the time of starting. Therefore, the variation in the catalyst warm-up state and the variation in the emission can be further reduced.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the overall construction of the present invention when applied to an internal combustion engine for automobiles. In FIG. 1, 1 is an internal combustion engine main body, 2 is a surge tank provided in an intake passage of the engine 1, 2a is an intake manifold connecting the surge tank 2 and an intake port of each cylinder, and 16 is an upstream side of the surge tank 2. Throttle valve located in the intake passage of
Reference numeral 7 is a fuel injection valve for injecting pressurized fuel into the intake port of each cylinder of the engine 1.

In the present embodiment, the throttle valve 16 is provided with an actuator 16a such as a stepper motor, and is of a type that takes an opening according to a control signal input from the ECU 10 described later. That is, as the throttle valve 16 of the present embodiment, a so-called electronically controlled throttle valve that can take an opening that is irrelevant to the accelerator pedal operation amount of the driver is used. Further, the throttle valve 16 is provided with a throttle opening sensor 17 which generates a voltage signal according to the operation amount (opening) of the throttle valve.

In FIG. 1, 11 is an exhaust manifold for connecting the exhaust ports of the respective cylinders to a common collective exhaust pipe 14, 20
Is a three-way catalyst arranged in the exhaust pipe 14, 13 is an upstream air-fuel ratio sensor arranged in the exhaust merging portion of the exhaust manifold 11 (upstream of the three-way catalyst 20), and 15 is an exhaust pipe downstream of the three-way catalyst 20. 14 is a downstream side air-fuel ratio sensor. The three-way catalyst 20 can simultaneously purify the three components of HC, CO, and NOx in the exhaust when the air-fuel ratio of the inflowing exhaust is near the stoichiometric air-fuel ratio. The air-fuel ratio sensors 13 and 15 are used to detect the exhaust air-fuel ratio when feedback controlling the fuel injection amount to the engine so that the engine air-fuel ratio becomes a predetermined target air-fuel ratio during normal engine operation.

In this embodiment, the surge tank 2 in the intake passage is provided with an intake pressure sensor 3 for generating a voltage signal according to the intake pressure (absolute pressure) in the surge tank, and the engine body 1 as well.
The water jacket 8 of the cylinder block is provided with a water temperature sensor 9 for generating an electric signal of an analog voltage according to the temperature of the cooling water. An air flow meter 7 for detecting the intake air amount (flow rate) is provided in the intake passage.
0 is attached. An intake air temperature sensor 73 for detecting the temperature of intake air is attached near the air cleaner in the intake passage.

The throttle valve opening sensor 1 described above is used.
7, intake pressure sensor 3, water temperature sensor 9, air-fuel ratio sensor 1
3, 15, air flow meter 70, and intake air temperature sensor 73
Output signal is input to an A / D converter 101 with a built-in multiplexer of the ECU 10, which will be described later.

Reference numerals 5 and 6 in FIG. 1 denote crank angle sensors arranged near the cam shaft and the crank shaft (not shown) of the engine 1, respectively. The crank angle sensor 5 generates a reference position detecting pulse signal at every 720 ° converted into a crank angle, and the crank angle sensor 6 generates a crank angle detecting pulse signal at every 30 ° crank angle.
The pulse signals of the crank angle sensors 5 and 6 are transmitted to the ECU 1
0 of the input / output interface 102, of which the output of the crank angle sensor 6 is the CPU 10 of the ECU 10.
3 is supplied to the interrupt terminal. The ECU 10 calculates the rotation speed (rotation speed) of the engine 1 based on the crank angle pulse signal interval from the crank angle sensor 6 and uses it for various controls.

Electronic control unit (ECU) 10 of engine 1
Is configured as, for example, a microcomputer, includes an A / D converter 101 with a built-in multiplexer, an input / output interface 102, a CPU 103, a ROM 104,
A RAM 105, a backup RAM 106 capable of storing and holding even when the main switch is turned off, a clock generation circuit 107, etc. are provided.

The ECU 10 performs basic control of the engine 1 such as fuel injection amount control of the engine 1 and ignition timing control based on the intake air amount, throttle valve opening, engine speed, etc. As will be described later, idle speed control is performed to maintain the engine speed at the target speed during engine idle operation.

In order to perform the above control, the ECU 10 executes an A / D conversion routine that is executed at regular time intervals, and an intake pressure signal from the intake pressure sensor 3, a throttle opening signal from the throttle opening sensor 17, and a water temperature sensor 9 from the intake air pressure signal. The cooling water temperature signal, the intake air amount signal from the air flow meter 70, and the intake air temperature signal from the intake air temperature sensor 73 are A / D converted and input.

The input / output interface 102 of the ECU 10 is connected to the fuel injection valve 7 via a drive circuit 108 to control the fuel injection amount and injection timing from the fuel injection valve 7. Further, the input / output interface 102 of the ECU 10 is connected to each spark plug 111 of the engine 1 via the ignition circuit 110, controls the ignition timing of the engine, and is connected to the actuator 16a of the throttle valve 16 via the drive circuit 113. The actuator 16a is driven to control the opening of the throttle valve 16.

Next, the idle speed control of this embodiment will be described. In the present embodiment, the ECU 10 performs idle speed control for maintaining the engine speed at a predetermined target speed during idle operation after engine startup. Normally, when the engine is started (when cranking is started), the fuel injection amount of the engine is corrected based on the cooling water temperature and the engine speed, and the basic injection amount is corrected according to the intake air temperature (atmospheric temperature) and atmospheric pressure. It is set to the added amount. After the cranking is started, it is determined that the engine speed exceeds a predetermined speed (for example, about 400 rpm) higher than the cranking speed (that is, combustion is started in each cylinder and the engine is in a complete explosion state). The fuel injection amount is set to an amount obtained by multiplying the basic fuel injection amount according to the engine intake air amount and the engine speed by a predetermined coefficient. The basic fuel injection amount is the fuel injection amount required to maintain the engine combustion air-fuel ratio at the stoichiometric air-fuel ratio. Further, the above-mentioned predetermined coefficient is for compensating the deterioration of the vaporization state of the fuel due to the adhesion of the injected fuel to the wall surface of the intake port at the time of engine start and the low temperature, and the above-mentioned predetermined coefficient is a value larger than 1 at the time of engine start. The engine combustion air-fuel ratio is set to the rich side of the stoichiometric air-fuel ratio.

Generally, as a method for maintaining the engine speed during idle operation at a predetermined target speed, the engine speed feedback is performed by adjusting the engine intake air amount so that the engine speed matches the target speed. Control is performed.
In the engine speed feedback control by adjusting the intake air amount, when the engine speed is lower than the target engine speed, the opening degree of the throttle valve 16 is increased (the engine intake air amount is increased) to increase the engine speed. Is higher than the target rotation speed, the rotation speed is maintained at the target rotation speed by performing feedback control to reduce the opening degree of the throttle valve 16 (reduce the intake air amount) to reduce the rotation speed.

However, as described above, in an internal combustion engine with a small friction, the air correction amount by the feedback control becomes small, and as a result, the intake air amount becomes small, so that the catalyst provided in the exhaust system is warmed up. Not promoted,
The problem arises that emissions are worse.

Therefore, in the present embodiment, the ignition timing is set so that the exhaust temperature becomes a constant temperature with respect to the intake air amount obtained as a result of the idle speed feedback control by adjusting the intake air amount, Variations in the catalyst warm-up state are reduced, and as a result, variations in emissions are reduced.

FIG. 2 shows that the exhaust temperature is kept constant during idle operation.
Intake air amount and ignition timing required to maintain
It is a characteristic view showing the relationship of. That is, the curve L₁Is exhaust
Temperature to T₁Of the intake air amount and ignition timing to maintain
Relationship, curve L₂Is the exhaust temperature T ₂Inhalation empty to maintain
Relationship between volume and ignition timing, curve L₃Is the exhaust temperature T₃To
The relationship between the amount of intake air to maintain and the ignition timing
Shows, T₁, T₂And T₃Is T₁<T₂<T₃In a relationship
is there. The specific numerical value is determined by the test.
It will be.

As is apparent from this figure, when the intake air amount decreases, the ignition timing is retarded, while when the intake air amount increases, the ignition timing is advanced to maintain the exhaust temperature at a constant temperature. be able to. Further, the exhaust gas temperature required to obtain a constant catalyst warm-up state differs depending on the catalyst temperature at the time of starting. For example, if the catalyst temperature at startup is high, the target exhaust temperature needs to be set along a curve L ₁ that achieves a relatively low exhaust temperature, while if the catalyst temperature at startup is low. The target exhaust temperature needs to be set along the curve L ₃ that achieves a relatively high exhaust temperature.

Since the catalyst temperature at the start can be estimated by the cooling water temperature and the intake air temperature at the start,
In the present embodiment, at the time of start-up, a diagram for determining the target exhaust temperature THE according to the cooling water temperature THW detected by the water temperature sensor 9 and the intake air temperature THA detected by the intake temperature sensor 73 A map as shown in 3 is provided in advance. In addition, the concrete numerical value is
It will be decided by the test.

Further, in this embodiment, the ignition timing SA based on the equal exhaust temperature line shown in FIG. 2 is determined according to the determined target exhaust temperature THE and the intake air amount QA detected by the air flow meter 70. A map as shown in FIG. 4 for determining is set in advance. The specific numerical value is determined by the test.
The specific control in this embodiment will be described below.

FIG. 5 is a flowchart showing the processing procedure of the target exhaust temperature setting routine. This routine is executed once by the ECU 10 when the engine is started. First, at step 152, the cooling water temperature THW detected by the water temperature sensor 9 and the intake air temperature THA detected by the intake air temperature sensor 73 are read.

Next, at step 154, the target exhaust gas temperature THE according to the read cooling water temperature THW and intake air temperature THA is determined by referring to the map of FIG. Then, this routine ends.

FIG. 6 is a flow chart for explaining the processing procedure of the idle speed feedback control routine. This routine is executed by the ECU 10 at regular time intervals. In the control of FIG. 6, the difference between the target idle speed NE ₀ and the current engine speed NE DNE (= NE ₀ −N
E), and the integrated value of DNE (integrated value) IDNE, DNE
Intake air amount correction amount EQ using the time change rate DDNE of
Is equal to EQ = α ₁ * DNE + α ₂ * IDNE + α ₃ * D
Calculated as DNE. The value of the target intake air amount is increased or decreased according to the correction amount EQ. That is, the engine intake air amount is the difference DNE between the target rotational speed NE ₀ and the actual rotational speed NE.
The proportional-integral-derivative (PID) control is performed based on

First, at step 202, it is judged if the engine is currently idle. In the present embodiment, it is determined that the engine is currently in idle operation when the accelerator pedal operation amount of the driver is zero (the driver does not step on the accelerator pedal). If it is determined in step 202 that the idle operation is not currently being performed, the idle speed control is not necessary, and thus the process ends, while if it is determined that the idle operation is currently being performed, the process proceeds to step 204.

At step 204, the engine speed NE is read. Next, at step 206, the target speed N
The difference DNE between E ₀ and NE is the difference DN in step 208.
The integrated value IDNE (integrated value) of E is further calculated in step 210.
Then, the time change rate DDNE of the difference DNE is calculated. Note that DNE _i-1 in step 210 is the DNE value at the time of the previous execution, and is updated in step 212 in preparation for the next execution.

In step 214, the DNE, IDN
Based on the values of E and DDNE, the value of the intake air amount correction amount EQ is calculated as EQ = α ₁ * DNE + α ₂ * IDNE + α ₃ * DDNE. Here, α ₁ , α ₂ , and α ₃ are a proportional term coefficient, an integral term coefficient, and a differential term coefficient, respectively, which are positive constant values.

In step 216, the target intake air amount Q _T of the engine is calculated as Q _T = Q _CAL + EQ, and the opening of the throttle valve 16 is adjusted so as to obtain the target intake air amount Q _T. Note that Q _CAL is the basic intake air amount,
It is a value determined by a preset relationship based on the engine speed NE and the throttle valve opening.

Next, at step 218, the value of the intake air amount QA detected by the air flow meter 70 is read. Finally, in step 220, the target ignition timing SA (represented by the crank angle up to the compression top dead center of each cylinder) according to the target exhaust temperature THEE that has already been obtained and the read intake air amount QA is The ignition circuit 110 is set so as to obtain the target ignition timing determined by referring to the map of FIG. Then, this routine ends.

[0036]

As described above, according to the present invention,
In idle speed feedback control after cold start, due to the small friction of the internal combustion engine,
A situation in which the intake air amount decreases, the catalyst warm-up state deteriorates, and the emission deteriorates can be avoided by maintaining the exhaust temperature constant.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration when the present invention is applied to an internal combustion engine for automobiles.

FIG. 2 is a characteristic diagram showing a relationship between an intake air amount and an ignition timing, which is necessary to maintain a constant exhaust gas temperature during idle operation.

FIG. 3 is a diagram showing a map for determining a target exhaust temperature THE according to a cooling water temperature THW and an intake air temperature THA.

FIG. 4 is a diagram showing a map for determining an ignition timing SA according to a target exhaust temperature THE and an intake air amount QA.

FIG. 5 is a flowchart showing a processing procedure of a target exhaust temperature setting routine.

FIG. 6 is a flowchart illustrating a processing procedure of an idle speed feedback control routine.

[Explanation of symbols]

1. Main body of internal combustion engine 2 ... surge tank 2a ... intake manifold 3 ... Intake pressure sensor 5, 6 ... Crank angle sensor 7 ... Fuel injection valve 8 ... Water jacket 9 ... Water temperature sensor 10 ... ECU 11 ... Exhaust manifold 13 ... Upstream air-fuel ratio sensor 14 ... Collecting exhaust pipe 15 ... Downstream air-fuel ratio sensor 16 ... Throttle valve 16a ... Actuator 17 ... Throttle opening sensor 20 ... Three-way catalyst 70 ... Air flow meter 73 ... Intake air temperature sensor 101 ... A / D converter with built-in multiplexer 102 ... Input / output interface 103 ... CPU 104 ... ROM 105 ... RAM 106 ... Backup RAM 107 ... Clock generation circuit 108 ... Driving circuit 110 ... Ignition circuit 111 ... Spark plug 113 ... Driving circuit

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Claims (2)

[Claims] 1. A device for controlling an idle speed after starting of an internal combustion engine in which a catalyst for purifying exhaust gas is arranged in an exhaust system, the device being controlled according to a difference between a target speed and an actual engine speed. By adjusting the intake air amount, the rotation speed feedback control means for controlling the engine rotation speed to a target rotation speed, and the exhaust gas temperature depending on the engine intake air quantity as a result of the control by the rotation speed feedback control means. An ignition timing setting means for setting an ignition timing so as to maintain a constant temperature, and a control device for an internal combustion engine. 2. The control device for an internal combustion engine according to claim 1, wherein the ignition timing setting means determines the constant temperature in accordance with a cooling water temperature and an intake air temperature at engine startup.