JPH07247915A - Exhaust reflux control device of diesel engine - Google Patents

Abstract

PURPOSE:To realize stable EGR control against small load fluctuation by setting an EGR target value based on engine speed and a load and an EGR target value based on car speed and changing proportion of the car speed and selectively using the EGR target values in accordance with a travelling state. CONSTITUTION:An engine speed detection means 2 and an engine load detection means 3 are furnished in a diesel engine to control EGR gas quantity by a valve means 1 at the time of refluxing a part of exhaust gas in an intake system, and a first EGR target value is set 4 in accordance with detected engine speed and a detected load. Additionally, a car speed detection means 5 is furnished, changing proportion of car speed is detected, and a second EGR target value is set 7 in accordance with the car speed and the car speed changing proportion. A valve means 1 is controlled by an exhaust reflux control means 9 by selecting 8 one of the first and second EGR target values in accordance with a driving state, that is, the car speed and the changing proportion of the car speed and in accordance with the selected EGR target value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for a diesel engine for vehicles.

[0002]

2. Description of the Related Art In a vehicle diesel engine, NOx
In order to reduce the above, an exhaust gas recirculation (EGR) device that recirculates a part of the exhaust gas to the intake system is adopted.

As a conventional exhaust gas recirculation device, there is, for example, the one described in Nissan Motor Co., Ltd. New Car Manual, Bluebird (U31-1), published in September 1991. This is exhaust gas from an exhaust passage (EGR The EGR valve is installed in the exhaust gas recirculation passage leading the gas), the intake throttle valve is installed in the intake passage upstream of the opening of the exhaust gas recirculation passage, and the engine speed and control lever opening (or fuel injection amount) are set in the control device. Has an EGR map in which EGR data is set on the grid of the
The amount of gas is controlled.

Since the EGR map set by the engine speed and the control lever opening in this way reflects the operating state of the engine, a large amount of EGR is set in a low load range or the like in accordance with the operating state of the engine. It can be performed with good response, and EGR can be quickly cut when the load is high.

[0005]

SUMMARY OF THE INVENTION However, the conventional device as described above has the following problems while being able to perform control with good responsiveness according to the operating state of the engine. Discovered.

That is, when the vehicle travels at a constant speed on a fixed ground and travels at a relatively large acceleration, a slight load change in the almost same traveling state or almost the same acceleration state causes E
The GR region fluctuated, which sometimes switched the EGR control.

Therefore, in such a case, the EGR control cannot be performed accurately, NOx cannot be sufficiently reduced, and the exhaust gas varies.

According to the present invention, when the vehicle is traveling under the influence of a minute load change, the vehicle speed E is less influenced by the load change.
The purpose is to solve the above problems by controlling GR.

[0009]

A first aspect of the present invention is a vehicle equipped with a valve means 1 for controlling the amount of EGR gas recirculated from an exhaust passage of an engine to an intake system via an exhaust gas recirculation passage as shown in FIG. In a diesel engine for automobiles, means 2 for detecting the engine speed, means 3 for detecting the engine load, and EGR based on the engine speed and the load
First EGR target value setting means 4 for setting the target value, means 5 for detecting the vehicle speed of the vehicle, means 6 for detecting the change rate of the vehicle speed, and EGR based on the vehicle speed and the change rate of the vehicle speed.
Second EGR target value setting means 7 for setting a target value, and the first and second EGs according to the vehicle speed and the change rate of the vehicle speed.
Target value selection means 8 for selecting one of the EGR target values set by the R target value setting means 4, 7, and the selected EGR
An exhaust gas recirculation control means 9 for driving the valve means 1 based on the target value is provided.

In a second aspect of the invention, the target value selection means 8 is
The second EG is operated at a predetermined constant speed and at a predetermined acceleration.
The EGR target value set by the R target value setting means 7 is selected.

In a third aspect of the invention, the valve means 1 comprises an EGR valve provided in the exhaust gas recirculation passage and an intake throttle valve provided in the intake passage upstream of the opening of the exhaust gas recirculation passage.

[0012]

[Effect] Even if there is a slight load change when the vehicle is running, the effect on the vehicle speed is small, so the vehicle speed does not change much.

According to the first aspect of the invention, the EGR target value based on the engine speed and the load, and the EGR target value based on the vehicle speed and the change rate of the vehicle speed are set, and the running state is calculated from the change rate of the vehicle speed and the vehicle speed. To determine this EGR
Select one of the target values, and based on that EGR target value, EGR
I do.

Therefore, control suitable for the traveling state can be performed, and the influence on the control due to a minute load change during EGR based on the vehicle speed and the change rate of the vehicle speed can be prevented.

In the second aspect of the invention, EGR is performed based on the EGR target value based on the vehicle speed and the change rate of the vehicle speed during the predetermined constant speed traveling and the predetermined acceleration traveling.

Therefore, it is possible to accurately prevent the influence of minute load fluctuations on the control, and to ensure proper control of the EGR.

In the third aspect of the invention, the EGR valve which is provided in the exhaust gas recirculation passage and the intake throttle valve which is provided in the intake passage upstream of the opening of the exhaust gas recirculation passage are used to reach the EGR target value.
Can be done.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, 20 is an engine, 21 is an intake passage, 22 is an exhaust passage, and 23 is an exhaust gas recirculation passage that connects the exhaust passage 22 to the intake passage 21.

An opening 25 is formed in the exhaust gas recirculation passage 23 on the upstream side of the manifold 24 in the intake passage 21, and a diaphragm type EGR valve 26 is interposed in the opening 25.

Diaphragm type first and second intake throttle valves 27 and 28 are provided in the intake passage 21 upstream of the opening 25 of the exhaust gas recirculation passage 23.

EGR valve 26, first and second intake throttle valve 2
The operating negative pressure from the vacuum pump 29 is introduced to the valves 7 and 28 through the negative pressure passage, and the first and second EGR control solenoid valves 31 and 32 are provided to the negative pressure passage 30 to the EGR valve 26.
Is provided.

Turning on (opening) the first EGR control solenoid valve 31
At the same time, operating negative pressure is supplied to the EGR valve 26, and it is turned off (closed).
At that time, the supply is cut off, and the second EGR control solenoid valve 32
The operating negative pressure is diluted by the atmosphere when the
The dilution is blocked at N (closed).

The EGR valve 26 is fully closed when both the first and second EGR control solenoid valves 31, 32 are OFF, and is half-opened when only the first EGR control solenoid valve 31 is ON, When both are turned on, it is fully opened.

First and second intake throttle control solenoid valves 35 and 36 are provided in the negative pressure passages 33 and 34 to the first and second intake throttle valves 27 and 28, respectively.

The first and second intake throttle valves 27 and 28 are O of the first and second intake throttle control solenoid valves 35 and 36, respectively.
When N (open), operating negative pressure is supplied and fully closed, then OFF
When it is closed, its supply is shut off and it is fully opened.

The opening degree of the accelerator 37 is detected by an accelerator opening sensor 38, and the engine 2 is detected according to the accelerator opening degree.
The fuel injection pump 39 that injects fuel to 0 is provided with a rotation speed sensor 40 that detects the engine rotation speed from the shaft rotation.

The vehicle speed is detected by the vehicle speed sensor 41, and the cooling water temperature of the engine 20 is detected by the water temperature sensor 42.

The signals from the sensors 38 and 40 to 42 are supplied to the control unit 43 which is a microcomputer.
Entered in.

The control unit 43 is provided with a vehicle running state determination map (FIG. 4), an engine operating state determination map (FIG. 5), and EGR maps (FIGS. 6 to 8) in which EGR control data is set. .

The control unit 43 controls the first and second EGs based on the signals from the sensors 38, 40 to 42 and according to the determination maps and EGR maps.
R control solenoid valves 31, 32, first and second intake throttle control solenoid valves 35, 36 are driven, that is, EGR valve 26, first, second
The intake throttle valves 27 and 28 are controlled to perform EGR control.

Reference numeral 44 is a catalyst device.

Next, the control contents of the control unit 43 will be explained based on the flowchart of FIG. 3. First, in step 1, the engine speed and accelerator opening are read, and in step 2, fuel injection is performed based on the engine speed and accelerator opening. Calculate the amount (engine load).

In step 3, the vehicle speed is read, and in step 4, the rate of change in vehicle speed is calculated from the change in vehicle speed over time.

In step 5, the vehicle speed and the change rate of the vehicle speed (Δ
Based on the vehicle speed), the vehicle traveling state is determined based on the vehicle traveling state determination map shown in FIG.

The vehicle speed is lower than the predetermined value V ₀ , and the rate of change of the vehicle speed is -X _R <Δ vehicle speed <0 or X ≤ Δ vehicle speed ≤ X ₁ (-
If X _R , X, X ₁ are predetermined values), it is determined that the vehicle is decelerating or slowly accelerating, or traveling on a gentle slope, and the routine proceeds to step 6.

In step 6, based on the engine speed and the fuel injection amount, the corresponding E from the first EGR map of FIG.
Read GR control data. In the first EGR map,
Control data I to VI for performing target EGR by region
Is set, and the control data of the corresponding region is read based on the engine speed and the fuel injection amount.

On the other hand, in step 5, the rate of change in vehicle speed is 0.
When ≦ Δ vehicle speed <X or X ₁ <Δ vehicle speed, or when the vehicle speed is equal to or higher than the predetermined value V ₀ , the process proceeds to step 7.

In step 7, the engine operating state at that time is examined from the engine speed and the fuel injection amount based on the engine operating state determination map of FIG. 5, and the running state under the conditions of the vehicle speed and the change rate of the vehicle speed is determined. judge.

When the engine speed and the fuel injection amount are smaller than the predetermined values X ₃ and Y _{3 and} are not in the high speed and high load region, that is, when the engine output is in the predetermined range, the vehicle speed and the rate of change of the vehicle speed are fixed. It is determined that the vehicle is traveling at a constant speed or is traveling at a relatively large acceleration, and the process proceeds to step 8.

In step 8, the corresponding EGR control data is read from the second EGR map of FIG. 7 based on the vehicle speed and the rate of change of the vehicle speed. In the second EGR map, control data I to VI for performing the target EGR are set for each area, and the control data of the corresponding area is read based on the vehicle speed and the change rate of the vehicle speed.

When the engine speed, the fuel injection amount are equal to or more than the predetermined values X ₃ and Y ₃ and the high speed and high load range is determined in step 7, it is determined that the vehicle is running suddenly or on an uphill road.
Go to step 9.

At step 9, the control data VI (without EGR) is read from the third EGR map of FIG. In this case, the map of FIG. 9 may be used as the third EGR map, and the control data V may be selected when not in such a high speed and high load region.

Then, at step 10, according to the EGR control data I to VI, the first and second EGR control solenoid valves 31, 32, the first and second intake throttle control solenoid valves 3 are provided.
A control signal is output to 5, 36.

First and second for each control data I to VI
EGR control solenoid valves 31, 32, the control contents of the first and second intake throttle control solenoid valves 35, 36, and the EGR valve 26,
The operating states of the first and second intake throttle valves 27 and 28 are shown in FIG.
Shown in.

With such a configuration, the running state of the vehicle is determined from the vehicle speed and the rate of change of the vehicle speed, and the engine speed and the engine speed are used when the vehicle is decelerating, slowly accelerating, or traveling on a gentle slope. The first EGR depending on the fuel injection amount
Control data is selected from the map, and the solenoid valves 31, 32, 35, 36, the EGR valve 26, and the intake throttle valves 27, 28 are controlled based on the control data to perform the target EGR.

Therefore, EGR control is performed with good response in response to changes in the engine operating state.

On the other hand, when the vehicle is traveling at a constant speed or on a relatively large acceleration, the control data is selected from the second EGR map according to the vehicle speed and the rate of change of the vehicle speed, and each electromagnetic wave is selected based on the control data. Valves 31, 32, 35, 36,
The EGR valve 26 and the intake throttle valves 27 and 28 are controlled to perform the target EGR.

In this case, the engine speed and the fuel injection amount fluctuate due to minute load fluctuations during traveling, but the vehicle speed and the rate of change of the vehicle speed do not fluctuate.

As a result, stable EGR control can be obtained during constant-speed running on a fixed ground, where control is difficult to stabilize due to minute load fluctuations, and during comparatively large acceleration running.

In FIG. 11, for example, from the area of control data IV
Solenoid valves 31, 3 during acceleration traveling that switches to V range
2, 35, 36 operation, fuel injection amount, engine speed,
In the case of the change of the vehicle speed and NOx, in the conventional case, the fuel injection amount and the engine speed may change to the area without EGR (the area of the control data VI). NOx is accurately reduced without switching from the area to the area VI of the control data.

Therefore, EGR is performed with high accuracy in accordance with the engine operating state and the vehicle running state, and NOx
Is sufficiently reduced, and clean exhaust gas is secured.

When the control data I is as shown in FIG. 10, the EGR valve 26 is fully opened, and the first and second intake throttle valves 2 are
7, 28 are fully closed, the EGR valve 26 is fully opened when the control data II is set, and only the first intake throttle valve 27 is fully closed, and the EGR valve 26 is half-open when the control data III is set and the first intake throttle is set. Only the valve 27 is fully closed. As the first and second intake throttle valves 27, 28 are fully closed, the suction negative pressure becomes larger and a large amount of EGR is performed.

When the control data is IV, the EGR valve 26,
The first and second intake throttle valves 27 and 28 are fully opened, and when the control data is V, the EGR valve 26 is half-opened and the first and second intake throttle valves 27 and 28 are fully opened. In this case, the smaller the opening of the EGR valve 26, the smaller amount of EGR is performed.

Thus, the first and second intake throttle valves 27,
Since 28 is provided, fine control can be obtained with the EGR valve 26.

[0056]

As described above, according to the first aspect of the present invention, in the vehicle diesel engine provided with the valve means for controlling the EGR gas amount recirculated from the exhaust passage of the engine to the intake system through the exhaust gas recirculation passage, Means for detecting the engine speed, means for detecting the engine load, first EGR target value setting means for setting the EGR target value based on the engine speed and load, and vehicle speed detection Means for detecting the change rate of the vehicle speed, and a second E for setting the EGR target value based on the vehicle speed and the change rate of the vehicle speed.
GR target value setting means, target value selecting means for selecting one of the EGR target values set by the first and second EGR target value setting means in accordance with the vehicle speed and the change rate of the vehicle speed, and the selected EGR target Since the exhaust gas recirculation control means for driving the valve means based on the value is provided, good EGR control suitable for the engine operating state and the vehicle running state can be performed, and NOx can be sufficiently reduced.

According to the second aspect of the present invention, E is obtained when the vehicle is traveling at a predetermined constant speed and traveling at a predetermined acceleration influenced by minute load fluctuations.
GR control can be performed stably, and NOx can be reduced accurately.

According to the third invention, the target E is set by the valve means.
Fine control over GR becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention.

FIG. 2 is a configuration cross-sectional view of an example.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a characteristic diagram showing a determination map of a vehicle traveling state.

FIG. 5 is a characteristic diagram showing a determination map of an engine operating state.

FIG. 6 is a characteristic diagram showing a first EGR map.

FIG. 7 is a characteristic diagram showing a second EGR map.

FIG. 8 is a characteristic diagram showing a third EGR map.

FIG. 9 is a characteristic diagram showing another example of a third EGR map.

FIG. 10 is a table showing a control operation of each valve.

FIG. 11 is an explanatory diagram showing operating characteristics during accelerated traveling.

[Explanation of symbols]

 20 engine 21 intake passage 22 exhaust passage 23 exhaust gas recirculation passage 25 opening 26 EGR valve 27 first intake throttle valve 28 second intake throttle valve 31 first EGR control solenoid valve 32 second EGR control solenoid valve 35 First intake throttle control solenoid valve 36 Second intake throttle control solenoid valve 37 Accelerator 38 Accelerator opening sensor 39 Fuel injection pump 40 Rotation speed sensor 41 Vehicle speed sensor 43 Control unit

Claims (3)

[Claims] 1. A vehicle diesel engine including valve means for controlling the amount of EGR gas recirculated from an exhaust passage of an engine to an intake system via an exhaust gas recirculation passage, the means for detecting an engine speed, and A means for detecting the load, and EGR based on the engine speed and the load
First EGR target value setting means for setting a target value, means for detecting a vehicle speed of the vehicle, means for detecting a change rate of the vehicle speed, and an EGR target value is set based on the vehicle speed and the change rate of the vehicle speed. Second EGR target value setting means, target value selecting means for selecting one of the EGR target values set by the first and second EGR target value setting means in accordance with the vehicle speed and the rate of change of the vehicle speed, and selecting An exhaust gas recirculation control device for a diesel engine, comprising: an exhaust gas recirculation control device that drives the valve device based on the EGR target value. 2. The diesel engine according to claim 1, wherein the target value selecting means selects the EGR target value set by the second EGR target value setting means during predetermined constant speed traveling and predetermined acceleration traveling. Exhaust gas recirculation control device. 3. The diesel engine according to claim 1, wherein the valve means comprises an EGR valve installed in the exhaust gas recirculation passage and an intake throttle valve installed in the intake passage upstream of the opening of the exhaust gas recirculation passage. Exhaust gas recirculation control device.