JP2621032B2 - Fuel injection control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device, and more particularly to a fuel injection device that can maintain a target air-fuel ratio even when an exhaust gas recirculation device is operating.

[Conventional technology]

2. Description of the Related Art Some internal combustion engines include an electronically controlled fuel injection control device as a countermeasure against problems such as harmful exhaust components and fuel consumption rate. This fuel injection control device inputs changes in the engine operating state such as load, engine speed, cooling water temperature, intake air amount and the like as an electric signal, and controls the operation of the fuel injection valve according to the operating state of the internal combustion engine. , And controls fuel injection.

Some internal combustion engines include an exhaust gas recirculation device (EGR device) together with a fuel injection control device. This exhaust gas recirculation device has an EGR control valve for adjusting the amount of exhaust gas recirculation (EGR amount) in the intake system, dilutes the intake air by recirculating a part of the exhaust gas to the intake system, and increases the fire propagation speed and This is to reduce the maximum temperature of combustion to reduce NOx in exhaust gas.

An example of such an exhaust gas recirculation device is disclosed in
-124119. In this publication, a flow control valve which is operated in synchronization with a deviation signal from a control circuit is provided in an EGR recirculation passage to prevent surging (torque fluctuation) while recirculating a maximum amount of exhaust gas. Things.

[Problems to be solved by the invention]

By the way, in an internal combustion engine equipped with an exhaust gas recirculation device, by recirculating exhaust gas into the intake passage, the intake pipe negative pressure, which is the intake pipe pressure in the intake passage, is affected, and the set air-fuel ratio is reduced to the target air-fuel ratio. That is, the air-fuel ratio when the exhaust gas is not recirculated may be changed (shifted).

To eliminate this inconvenience, EG
A control pressure switching valve is provided in the middle of the operating pressure passage communicating with the pressure chamber of the R adjustment valve, and the on / off of the control pressure switching valve is sensed. Exhaust is recirculated only when the control pressure switching valve is on. As a result, a constant air-fuel ratio correction coefficient is output from the control circuit, thereby correcting a change in the set air-fuel ratio.

However, even in such air-fuel ratio correction control, as shown in FIG. 6, when exhaust gas is recirculated to the intake passage, the intake pipe negative pressure PB is affected despite the fact that the intake air amount Ga is constant. As a result, the intake pipe negative pressure decreases, so the fuel injection control device that incorporates the intake pipe negative pressure PB as a control Is increased, the fuel injection amount Gf also changes, that is, the fuel amount increases, and as a result, the air-fuel ratio is affected and shifts to the rich side, and the set air-fuel ratio becomes the target air-fuel ratio. And the inconvenience was not solved. That is, as shown in FIG.
Is constant, the change in the intake pipe negative pressure due to the recirculation of exhaust gas causes the amount of change (ΔA / F) in the air-fuel ratio to increase in proportion, resulting in the inconvenience of reduced flammability. Also, if the EGR rate changes over time due to factors such as clogging,
The variation of the EGR rate due to the regulating valve could not be absorbed, and as a result, the target air-fuel ratio could not be maintained.

[Object of the invention]

Therefore, an object of the present invention is to eliminate the inconvenience described above, predicting the change in the intake pipe pressure due to the recirculation of exhaust gas, predicting the change in the air-fuel ratio due to the influence of the intake pipe pressure, and calculating the change in the air-fuel ratio. An object of the present invention is to realize a fuel injection control device capable of ensuring the operating state of an internal combustion engine by correcting the target air-fuel ratio to obtain a target air-fuel ratio.

[Means for solving the problem]

In order to achieve this object, the present invention relates to a fuel injection control device for controlling the operation of a fuel injection valve in accordance with the operating state of an internal combustion engine to control the injection of fuel. During operation of the device, the exhaust gas recirculation device stops the recirculation of exhaust gas for a predetermined time, detects a change in the intake pipe pressure, and calculates an EGR rate by the exhaust gas recirculation device according to the change in the intake pipe pressure. In addition, a control means for calculating a change amount of the air-fuel ratio due to the recirculation of the exhaust gas according to the EGR rate, and controlling the fuel injection amount to correct the change amount of the air-fuel ratio to obtain the target air-fuel ratio is provided. And

[Action]

According to the structure of the present invention, the control means firstly stops the exhaust gas recirculation for a predetermined time when the exhaust gas recirculation device is operated, calculates a change in the intake pipe pressure, and calculates the EGR according to the change in the intake pipe pressure. The change rate of the air-fuel ratio due to the recirculation of exhaust gas is calculated in accordance with the EGR rate, and the change amount of the air-fuel ratio is corrected to obtain a target air-fuel ratio. As a result, the target air-fuel ratio can be maintained even during the operation of the exhaust gas recirculation device, and the operating state of the internal combustion engine can be ensured well.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

1 to 5 show an embodiment of the present invention.
In the figure, 2 is an internal combustion engine, 4 is an air cleaner, 6 is a throttle body, 8 is a body intake passage, 10 is a fuel injection valve, 12 is a throttle valve, 14 is an intake manifold, 16 is a manifold intake passage, 18 is an intake port, 20 is a combustion chamber, 22 is an exhaust manifold, 24 is a manifold exhaust passage, 26 is an exhaust pipe, 28 is a pipe exhaust passage, and 30 is a catalytic converter. The fuel injection valve 10 constituting the fuel injection control device 32 is disposed in the body intake passage 8 on the upstream side of the throttle valve 12. The fuel in the fuel tank 34 is supplied to the fuel injection valve 10. That is, the fuel in the fuel tank 34 is supplied to the fuel supply passage 38 by the fuel pump 36.
After that, it is filtered by the fuel filter 40 and sent to the fuel injection valve 10.

The fuel supply passage 38 is provided with a fuel pressure regulator 42 for regulating the fuel pressure acting on the fuel injection valve 10 at a constant level. The fuel pressure regulator 42 is connected to a fuel pressure passage opening to the manifold intake passage 16 downstream of the throttle valve 12.
Activated by intake pipe pressure from 44.

An exhaust gas recirculation device (EG)
(R device) 46, an exhaust intake port 50 which is one end of an EGR recirculation passage 48 is open. An exhaust gas recirculation port 52, which is the other end of the EGR recirculation passage 48, opens into the manifold intake passage 16 downstream of the throttle valve 12. In the middle of this EGR recirculation passage 48, the EGR
An adjustment valve 54 is provided. The pressure chamber 5 of this EGR regulating valve 54
6, the pressure passage 58 for operation of the EGR valve 54 is connected.

The operating pressure passage 58 communicates the pressure chamber 56 of the EGR valve 54 with the body intake passage 8 on the upstream side of the throttle valve 10. In the middle of the operating pressure passage 58, the EGR modulator 60 and the control pressure switching valve 62 (VS
V). The EGR modulator 60,
The exhaust pressure from the EGR recirculation passage 48 acts on the internal diaphragm chamber 66 via the exhaust pressure passage 64 to control the pressure acting on the pressure chamber 56 of the EGR regulating valve 54. The control pressure switching valve 62 is operated by control means 80 described later, and opens and closes the operation pressure passage 58.

A pressure sensor is provided via a detection pressure passage 68 to detect an air pipe negative pressure which is an intake pipe pressure in the manifold intake passage 16.
The air cleaner 4 is provided with an intake air temperature sensor 72 for detecting the intake air temperature. Further, a water temperature sensor 76 for detecting a temperature of a cooling water in a cooling water passage 74 formed in the intake manifold 14 is attached to the intake manifold 14. Further, the exhaust manifold 22, 0 ₂ sensor 78 for detecting the oxygen concentration in the exhaust gas
Is installed.

The fuel injection valve 10, fuel pump 36, the pressure sensor 70, intake air temperature sensor 72, such as a water temperature sensor 76,0 ₂ sensor 78 is in communication with the control unit (EVC) 80.

The control means 80 turns off the control pressure switching valve 62 or the EGR modulator 60 for a predetermined time during which the NOx does not change when the exhaust gas recirculation device 46 is operated to recirculate exhaust gas to the manifold intake passage 16. That is, the exhaust gas recirculation is stopped, the amount of change in the intake pipe negative pressure is detected, the EGR rate is calculated in accordance with the change in the intake pipe negative pressure, and the air-fuel ratio due to the exhaust gas recirculation is calculated in accordance with the EGR rate. The amount of change is calculated, and the amount of fuel injection is controlled so as to correct the amount of change in the air-fuel ratio to obtain a target air-fuel ratio (air-fuel ratio when exhaust gas is not recirculating).

The EGR rate is Is determined.

The control unit 80 includes a throttle switch 82 for detecting the degree of opening of the throttle valve 10, an ignition coil 84 for detecting an ignition signal and an engine speed, a battery 86 for detecting a voltage state, and a downstream side of the throttle valve 12. The first negative pressure switching valve 90 is provided in the middle of a bypass passage 88 having one end opened to the manifold intake passage 16 and the other end opened to the air cleaner 4, and is parallel to the first negative pressure switching valve 90 in the short circuit passage 92. The second provided in
The negative pressure switching valve 94 and the like are in communication. Reference numeral 96 is a starter, 98 is a distributor, 100 is a canister, 102 is an evaporative fuel passage, 104 is a blow-by gas passage, and 106 is
PCV valve.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

The program starts (step
102) Then, it is first determined whether or not the exhaust gas recirculation device 46 is operating (step 104). If the exhaust gas recirculation device 46 is not operating and the result of step 104 is NO, END
(Step 114).

On the other hand, if the exhaust gas recirculation device 46 is operated and the answer is YES in step 104, that is, if the EGR region α in FIG.
In (the area surrounded by the lines Y, A, B, and C), the control pressure switching valve 62 is turned on and off for a predetermined time during which NOx does not change, so that the intake air by the recirculation of the exhaust gas from the exhaust gas recirculation port 52 is obtained. Control means 80 for the amount of change ΔPB in tube negative pressure
In step 106, it is determined whether the EGR is stable. EGR is not stable and NO in step 106
In step 108, in step 108, the previous negative pressure change amount ΔP
The fuel injection amount (time) is corrected by the correction coefficient of B.

Further, if the EGR is stabilized and the result of step 106 is YES, the amount of change ΔPB in the intake pipe negative pressure due to the recirculation of exhaust gas is detected (step 110). That is, in FIG. 5, a change in the intake pipe negative pressure is detected in a region β (region indicated by a two-dot chain line) in which EGR is stably performed.

Next, at step 112, the change amount ΔP of the intake pipe negative pressure
The EGR rate is calculated based on the correction coefficient of B, the change amount of the air-fuel ratio is calculated based on the EGR rate, and the fuel injection amount (time) is corrected to the target air-fuel ratio. At this time, for example, as shown in a separate table, as the change amount (change amount) ΔPB of the negative pressure increases, the correction coefficient is increased to the minus side, and the fuel injection amount (time) is reduced. Can be set to the target air-fuel ratio while preventing the shift to the rich side.

In the above case, the relationship between the time for turning off the exhaust gas recirculation device 46, that is, the time for turning off the control pressure switching valve 62 and the NOx of exhaust gas, is as shown in FIG. It is necessary to determine the off-time of 46 in a region where NOx does not increase and in a region where the amount of change in the intake pipe negative pressure can be sensed.

As a result, even when the air is recirculated into the exhaust manifold intake passage 16, the target air-fuel ratio can be maintained, and the operating state of the internal combustion engine 2 can be ensured well.

Further, it is practical because it can cope with a change over time in the EGR rate (for example, clogging).

Further, since the air-fuel ratio control can be performed on software of the control unit (ECU) 80, the cost can be reduced.

In the above-described embodiment, the amount of change in the intake pipe negative pressure is detected by controlling the on / off operation of the control switching valve 12, but as shown by the two-dot chain line in FIG. It is also possible to perform 60 by operation control.

〔The invention's effect〕

As apparent from the detailed description above, according to the present invention, the amount of change in the intake pipe pressure due to the recirculation of exhaust gas is calculated, the amount of change in the air-fuel ratio due to the influence of the intake pipe pressure is calculated, and the amount of change in the air-fuel ratio is calculated. By correcting and setting the target air-fuel ratio, the operating state of the internal combustion engine can always be satisfactorily ensured.

Further, according to the configuration of the present invention, it is possible to cope with a temporal change of the EGR rate due to factors such as clogging, which is practically advantageous.

Further, the air-fuel ratio can be controlled on the software of the control means (ECU), and the cost can be reduced.

[Brief description of the drawings]

1 to 5 show an embodiment of the present invention, FIG. 1 is a schematic diagram of a fuel injection control device, FIG. 2 is a block diagram of the device in this embodiment, and FIG. 3 explains the operation of this embodiment. FIG. 4 is a diagram showing the relationship between the time when the control pressure switching valve is momentarily turned OFF and NOx of exhaust gas, and FIG. 5 is a diagram showing the relationship between the engine speed and the intake pipe negative pressure. FIG. 6 is a diagram showing various characteristic changes at the time of exhaust gas recirculation in the related art. FIG. 7 is a diagram showing the relationship between a change in intake pipe negative pressure and a change in air-fuel ratio (deviation) in the related art. In the figure, 2 is an internal combustion engine, 10 is a fuel injection valve, 12 is a throttle valve, 16 is a manifold intake passage, 32 is a fuel injection device, 46 is an exhaust recirculation device, 48 is an EGR recirculation passage, 52 is an exhaust recirculation port, Five
4 is an EGR regulating valve, 58 is an operating pressure passage, 60 is an EGR modulator, 62 is a control pressure switching valve, 70 is a pressure sensor, 78 is
0 ₂ sensor, and 80 denotes a control unit.

Claims (1)

(57) [Claims] A fuel injection control device for controlling the operation of a fuel injection valve in accordance with the operation state of an internal combustion engine to control the injection of fuel, wherein the exhaust gas is recirculated to an intake system when an exhaust gas recirculation device is operated. The recirculation of the exhaust gas by the recirculation device is stopped for a predetermined time to detect a change in the intake pipe pressure, and the EGR rate by the exhaust gas recirculation device is calculated according to the change in the intake pipe pressure. A fuel injection control device for calculating a change amount of an air-fuel ratio due to recirculation of exhaust gas, and controlling a fuel injection amount so as to correct the change amount of the air-fuel ratio to obtain a target air-fuel ratio. .