JPH02267330A - Exhaust gas recirculation control device for diesel engine - Google Patents

Abstract

PURPOSE:To improve the accuracy of judging abnormality by using a pressure sensor in common to detect both the driving pressure of an EGR actuator and the intake negative pressure and judging system abnormality when the detected intake negative pressure is out of the specified range at the time of non-EGR. CONSTITUTION:An EGR valve 7 driven by a diaphragm type actuator 8 is provided at the opening part, to an intake passage 4, of an EGR passage 6 for communicating an exhaust passage 5 with an intake passage 4, as well as an intake throttle valve 9 is provided at the intake passage, more on the upstream side than the EGR passage opening part 6a. This intake throttle valve 9 is controlled by an actuator 10 so as to keep intake negative pressure constant, thus functioning as a constant pressure control mechanism. At the time of non-EGR, a pressure sensor 14 for detecting the driving pressure of the actuator 8 at the time of EGR control is also used as a pressure sensor for detecting the intake negative pressure on the downstream side of the intake throttle valve 9, and when the detected intake negative pressure is out of the specified range, system abnormality is judged, and the intake throttle valve 9 is opened to full admission.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides exhaust gas recirculation a<hereinafter referred to as EG
(also referred to as R) relates to a control device.

[Conventional technology]

Conventionally, an exhaust passage and an intake passage are provided with an EGR passage that communicates with each other, and an intake throttle valve is provided upstream of the EGR passage opening of the intake passage, so that the negative pressure downstream of the intake throttle valve is kept approximately constant. An exhaust recirculation control device for a diesel engine is known in which the opening degree of an intake throttle valve is adjusted using a vacuum modulator or the like (for example, the
Publication No. 2-4663, Publication No. 1987-100052@
l).

[Problem to be solved by the invention]

However, the above-mentioned Japanese Utility Model Publication No. 62-4663 and Utility Model Publication No. 5
In the constant pressure control of intake negative pressure as disclosed in Publication No. 5-100052, the intake negative pressure is increased to increase the EGR rate (the ratio of EGR gas to intake air) over almost the entire engine speed range, and NOx However, if the system is not operating properly, the following problems may occur.

In other words, under operating conditions in which the intake throttle valve is controlled at a constant pressure so that the intake negative pressure is approximately constant, if the intake throttle valve deviates from the target control opening and operates unexpectedly, for example, the intake throttle valve should be throttled. If it is too high, system troubles such as excessive intake negative pressure may occur. Such system troubles, especially if the intake air volume is too restricted, may lead to the generation of black smoke, white smoke, etc. Moreover, the above-mentioned system troubles may occur, for example, when negative pressure piping is disconnected or system wiring is disconnected.

The present invention has focused on these problems, and uses a simple control mechanism to accurately detect system abnormalities.If there is no abnormality, a predetermined intake negative pressure constant pressure control is performed, and if an abnormality occurs, it is In particular, the purpose is to prevent inconveniences caused by excessively restricting intake air.

[Means to solve the problem]

The exhaust gas recirculation control device for a diesel engine according to the present invention that meets this objective includes an EGR passage that communicates an exhaust passage with an intake passage, an EGR valve that opens and closes the EGR passage, and a negative pressure that drives the EGR valve. Equipped with an actuator to
An intake throttle valve is provided upstream of the EGR passage opening of the intake passage, and the opening degree of the intake throttle valve can be adjusted by detecting negative pressure downstream of the intake throttle valve and keeping the negative pressure substantially constant. In an exhaust gas recirculation control device for a diesel engine equipped with a constant pressure control mechanism, the control device is provided with a non-EGR/constant pressure control region that operates the constant pressure control mechanism during non-EGR, and is used for detecting the driving pressure of the EGR valve actuator. The pressure sensor is also used as a pressure sensor that detects the intake negative pressure downstream of the intake throttle valve during non-EGR, and the control device is configured to control the intake negative pressure detected by the pressure sensor within a predetermined range. The system is equipped with a system abnormality determination circuit that determines that the system is abnormal when the intake throttle valve deviates from the intake throttle valve, and issues a signal to fully open the intake throttle valve.

[Effect]

In such an exhaust recirculation control device, EGR is performed depending on the operating state of the engine. For example, in a relatively high load range, the opening of the intake throttle valve is controlled sufficiently large, and the intake air amount is also sufficiently large. A region that is secured and in which exhaust gas NOx, etc. can be kept within sufficient regulation values without performing EGR is set as a non-EGR/constant pressure control jB jJl region. When the operating conditions are in this range, there is no need to detect the EGR valve actuator drive pressure, so the pressure sensor is switched to intake negative pressure detection and detects the intake negative pressure. If the detected intake negative pressure is outside the predetermined range, this means that the intake throttle valve is outside the target control opening degree, so it is determined that the system is abnormal, and the intake throttle valve is fully opened. Fully opening the intake throttle valve ensures a sufficient amount of intake air, and prevents the generation of black smoke or the like due to over-throttling. Furthermore, in this control device, the pressure sensor can be used both for detecting the EGR valve actuator drive pressure and for detecting the intake negative pressure, so the control mechanism is simplified. Furthermore, since the intake negative pressure is detected in the non-EGR/constant pressure control m fil region, there is no pressure pulsation due to changes in the EGR valve opening during detection, and the detection accuracy is increased accordingly, and the accuracy of determining the above-mentioned abnormality is also improved.

〔Example〕

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

1 to 8 show an exhaust gas recirculation control device for a diesel engine according to an embodiment of the present invention. In the figure, 1 is a diesel engine body, 2 is a fuel injection pump, and 3 is an ECU (electronic control unit). 4 is an intake passage to the engine 1, 5 is an exhaust passage from the engine 1, and an EG connecting the air passage 5 and the intake passage 4
An R passage 6 is provided. An EGR valve 7 is provided at the opening 6a of the EGR passage 6 to the intake passage 4, and the EGR valve 7 is operated by an EGR valve actuator 8 having a diaphragm.

An intake throttle valve 9 is provided upstream of the EGR passage opening portion 6a of the intake passage 4. The opening degree of the intake throttle valve 9 can be adjusted by an actuator 10 having a diaphragm.

The control system for actuating actuator 8.10 is constructed as follows.

Reference numeral 11 denotes a vacuum pump, in which driving negative pressure is generated. The negative pressure from the vacuum pump 11 is EVR
It is introduced into V (electricity charge negative pressure regulating valve) 12 and VSV (vacuum switching valve) 13. EVRV
At step 12, introduction of negative pressure from the vacuum pump 11 to the actuator 8 is controlled.

A target value for the control negative pressure to be supplied to the BGR valve actuator 8 is calculated within the ECU 3 based on information on the engine operating state input from various sensors.

This target value is determined to be the EGR valve opening that provides the optimum EGR rate under the engine operating state at that time. The ECU 3 provides the EVRV 12 with a duty signal corresponding to the target value. The EVRV 12 adjusts the rate at which negative pressure from the vacuum pump 11 and atmospheric pressure are introduced into the actuator 8 in accordance with the duty signal. Also, during exhaust gas recirculation, the VS'iN5 supplies the control negative pressure to the pressure sensor 14, and the ECU 3 corrects the duty signal based on the deviation between the actual control negative pressure detected by the pressure sensor 14 and the target value. Then, feedback control B is performed so that the actual controlled negative pressure is once again equal to the target value. The VSV 15 supplies intake negative pressure to the pressure sensor 14 when exhaust gas recirculation is stopped. Further, when the pressure sensor 14 is used for EGR, the pressure sensor 14 is connected to the EGR valve actuator 8.
It is used for feedback control of the drive negative pressure.

The negative pressure downstream of the intake throttle valve 9 is introduced into the vacuum modulator 17 through the filter 16, and the opening degree of the intake throttle valve 9 can be adjusted via the vacuum modulator 17 and the actuator 10 so that the negative pressure is kept approximately constant. It has become. As shown in FIG. 2, the vacuum modulator 17 has a diaphragm valve structure, and negative intake pressure is introduced into a diaphragm chamber 19 provided with a spring 18, and another chamber 20 is communicated with the atmosphere. diaphragm 21
Negative pressure from the vacuum pump 11 is introduced into the valve body 22 of the valve body 22, and when the intake negative pressure is higher than the set value, the valve body 22 moves to the diaphragm chamber 19 side, and the negative pressure from the vacuum pump 11 is introduced into the valve body 22. is bled, the output negative pressure to the actuator 10 decreases, and the opening of the intake throttle valve 9 is adjusted in the opening direction until the intake negative pressure reaches a target value (set value). When the intake negative pressure is lower than the set value, the valve body 22
stops the negative pressure from bleeding from the vacuum pump 11,
The negative pressure from the vacuum pump 11 is directly output to the actuator 10, and the opening of the intake throttle valve 9 is adjusted in the closing direction until the intake negative pressure reaches a target value (set value). Therefore, these constitute a constant pressure control mechanism that adjusts the opening degree of the intake throttle valve 9 so as to keep the intake negative pressure substantially constant.

A VSV 23 and a VSV 24 are interposed between the vacuum modulator 17 and the actuator IO. V
The SV 23 selects either the negative pressure via the constant pressure control mechanism or the source pressure from the vacuum pump 11 as the output to the actuator 10 . (2) 5V24 selects either negative pressure from VSV23 or atmospheric pressure as the output to actuator 10.

The actuator 10 that adjusts the opening degree of the intake throttle valve 9 is
A chamber 27 divided by diaphragms 25 and 26 and communicating with the atmosphere, a chamber 28 into which pressure from the VSV 24 is introduced, and either negative pressure or atmospheric pressure from the vacuum pump 11 switched by the VSV 13 is introduced. It has a B chamber 29. A connecting rod 30 with the intake throttle valve 9 is provided on the diaphragm 25 side, and the diaphragm 2
Intake throttle valve 9 through the movement of Rondo 30 with the movement of 5
The opening degree is adjusted.

A spring 31 is provided in the A chamber 28, and a seat 32
diaphragm 25 on the rod 30 side (intake throttle valve 9
(opening direction).

A stopper member 33 is provided on the A chamber 28 side of the diaphragm 26.
is provided protrudingly, and the diaphragm 25 is connected to the diaphragm 2.
When it moves to the 6 side and comes into contact with the tip of the stopper member 33, it is possible to restrict further movement of the diaphragm 25 toward the diaphragm 26 side, thereby restricting the operation of the intake throttle valve 9 in the closing direction below the − constant opening degree. It has become.

Since this stopper member 33 is provided on the diaphragm 26, it moves with the movement of the diaphragm 26. Since the B chamber 29 is provided with a spring 34 that biases the diaphragm 26 in the direction of the diaphragm 25,
When atmospheric pressure is introduced into the chamber 29, the spring 3
4, the diaphragm 26 is pressed against the seat member 32 and the stopper member 33 is held in the position shown in FIG.
When negative pressure is introduced into the chamber 29 from the vacuum pump 11, the diaphragm 2 resists the force of the spring 34.
6 moves in a direction to reduce the size of chamber B 29, and accordingly, stopper member 33 is also moved in the same direction. Therefore, the opening degree of the intake throttle valve 9 is controlled by the movement of the diaphragm 25 by the stopper member 33.
can be changed to a regulation position where the opening degree is even lower (for example, fully closed).

EVRV12, VSV13.15.23.24 are EC
It is operated based on a command from U3. The ECU 3 receives an accelerator opening signal as an engine load signal from a lever opening sensor 35 attached to the fuel injection pump 2, an engine rotational speed from an engine rotational speed sensor 36, and also receives an accelerator opening signal as an engine load signal. A signal from an adjustment resistor 37 for adjusting the temperature, a signal from the pressure sensor 14, and a signal from the engine water temperature sensor 38 are manually input. Further E
The CU 3 receives a signal from a vehicle speed sensor 39, a neutral (N) position signal 40 in the case of a vehicle equipped with an automatic transmission, and a signal from an ignition switch 41 (engine on/off signal). The signal from the ignition switch 41 is also used as a signal for operating the 5v13. The ECU 3 further outputs a signal 42 to the near conditioner amplifier and a signal 43 to the automatic transmission.

Note that 44 represents a boost compensator for regulating the maximum value of the fuel injection amount using negative pressure, and 45 represents a fuel cut valve.

Configured as above! Control according to the present invention is performed as follows using the position.

First, the operation control of the intake throttle valve 9 will be explained with reference to Table 1 and FIGS. 3 to 6.

The opening degree of the intake throttle valve 9 is controlled via the actuator 10, and the operation of the actuator 10 is as follows: ■5v13.23
．． 24 and vacuum modulator 17. The operation mode of the intake throttle valve 9 is as shown in Table 1.

When the ignition switch 41 is switched from on to off, that is, when the engine is stopped, VS■13.23.
24 are turned off, and as shown in Figure 3, a constant negative pressure from the vacuum pump 11 sufficient to move the intake throttle valve 9 is introduced into both the A room 2 and the B room 29 (the diagonal lines in the figure). ), the intake throttle valve 9 is kept fully closed. Therefore, when the engine is stopped while it is running, the intake throttle valve 9 is fully closed to strongly restrict the amount of air intake, and the compression resistance of the engine, which is rotating due to inertia, is suppressed to a minimum, thereby reducing shock and vibration. The generation is suppressed and the engine is stopped quietly. At this time, the fuel supply is also cut off by the fuel cut valve 45, and combustion is stopped naturally and quietly.

During deceleration, the VSV 13 is turned on and the B chamber 29 is opened to the atmosphere, and the VSV 23.24 is turned off and negative pressure from the vacuum pump 11 is introduced into the A chamber 28. At this time, as shown in FIG. 4, the diaphragm 26
The diaphragm 2 is held in a fixed position by the diaphragm 2.
5 is held at a position that abuts the tip of a stopper member 33 that is held at a fixed position together with the diaphragm 26, and the intake throttle valve 9 is held at a half-open position. By keeping the intake throttle valve 9 half-open, a predetermined amount or more of intake air is ensured even when the load is low, and intake muffled noise during deceleration is reduced.

At full load (acceleration), VSV13.24 is turned on, atmospheric pressure is introduced into both chamber A 28 and chamber B 29, and the fifth
As shown in the figure, the intake throttle valve 9 is kept fully open.

The intake air is not substantially throttled, ensuring a sufficient amount of intake air and suppressing smoke.

In medium and low load range, VSV13.23 on, VS
V24 is turned off, the B chamber 29 is opened to the atmosphere, the output negative pressure from the vacuum modulator 17 is introduced into the A chamber 28, and the opening degree of the intake throttle valve 9 is controlled so that the intake negative pressure becomes approximately constant pressure. Ru. Vacuum modulator 17 at this time
The operation is as described above.

Through this constant pressure control, a stable EGR rate can be obtained and the target exhaust gas purification performance can be obtained.

In the low speed (low rotation speed) low load range, each VSV13.
The operating modes of 23 and 24 are the same as the modes in the low load range mentioned above. However, since atmospheric pressure is introduced into the B chamber 29 and the diaphragm 26 and the stopper member 33 are held at the fixed positions shown in FIG. 2, the negative pressure introduced into the A chamber 28 from the vacuum modulator 17 As a result, the movement of the diaphragm 25 that attempts to move the intake throttle valve 9 in the closing direction is regulated by the tip of the stopper member 33, and the intake throttle valve 9 is ultimately kept in a half-open state. Therefore, a sufficient amount of air is ensured even at low rotational speeds, and the intake negative pressure is reduced. As a result, excessive EGR rate in the low rotational speed range is prevented when constant pressure control is adopted, which has been a problem in the past.

For each of the above-mentioned operating regions, if EGR operation and stop control are added and expressed as a map regarding engine speed and accelerator opening (load), the result will be as shown in FIG. 7. In FIG. 7, the shaded area is the constant pressure control area 101, the area 102 is the fully open area of the intake throttle valve 9, the area 103 is the half open area of the intake throttle valve 9, and the double shaded area 104 is the area A 28 of the actuator 10. Although the negative pressure from the vacuum modulator 17 is introduced to establish a constant pressure control system,
In reality, this is a region where the movement is regulated by the stopper member 33 and the intake throttle valve 9 is kept in a half-open state. EGR is turned on and off in the region between the operating boundary lines 111 and 112, and the EGR rate is optimal in the constant pressure control region. For example, during operation along the characteristic line 114, the opening degree of the intake throttle valve 9 is regulated to half open on the low rotational speed side, thereby preventing over-throttling. Operating boundaries 111 and 113
In the region 105 between the two, although the load is quite high, the intake throttle valve 9 is not fully open, and the intake noise can be reduced by controlling the intake throttle valve 9. Since this region is close to full load, EGR is turned off. In other words, the non-E'GR/constant pressure side in the present invention? It is set as 118N area.

A system abnormality is determined by the ECU 3 in this non-EGR/constant pressure side '4B wi region 105.

FIG. 8 and FIG. 9 show the flow of system abnormality determination. In step 201, it is determined whether EGR is on or off, and the EGR
When R is on, VSV15 is turned off and the pressure sensor is E.
Step 20: Detect the driving pressure for the GR valve actuator.
2), when EGR is off, in step 203 VSV2
4 is off.

■If 5v24 is on, go to step 202, VSV24
If it is off, it is determined in step 204 whether the VSV 23 is on. If the VSV 24 is off, the process goes to step 202, and if the VSV 24 is on, the process goes to step 205.

Up to step 204, it can be determined whether the current operating region is in the non-EGR/constant pressure control region 105.

When in the non-EGR/constant pressure control I SJI region 105, the VSV 15 is turned on in step 205, and the detection by the pressure sensor 14 is switched to the intake negative pressure side. Then, the pressure sensor 14 detects the intake negative pressure VP1. M is detected and read (step 206), and in step 207 it is determined whether the detected pressure is within a predetermined range (between Pl and P2). If it is within the range, it is determined that the system is OK (step 208), and if it is outside the range, it is determined that the system is abnormal and it is stored (step 209).

When VSV24 is off, constant pressure control is possible.
When the intake throttle valve 9 is on, the intake throttle valve 9 is fully opened.
As shown in the figure, if it is determined that the system is abnormal in the above determination and storage flow, 5V24 is turned on (steps 210 and 211), and the intake throttle valve 9 is fully opened. If the system is normal, normal control as described above is performed (step 212 in FIG. 9).

In this manner, when a system abnormality occurs, the intake throttle valve 9 is forcibly opened fully, ensuring a sufficient amount of intake air regardless of the operating conditions.

〔Effect of the invention〕

As explained above, when using the diesel engine exhaust recirculation control device of the present invention, the constant pressure side i! I
It is possible to ensure a stable EGR rate with the f mechanism, and in the event of a system abnormality, a simple control system that shares a pressure sensor can accurately detect the system abnormality in the non-EGR/constant pressure control region. This can be detected, the intake throttle valve can be fully opened to ensure a sufficient amount of intake air, and the generation of black smoke, white smoke, etc. can be appropriately prevented. Furthermore, by sharing the pressure sensor, the control system of the present invention can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an exhaust recirculation control device for a diesel engine according to an embodiment of the present invention, FIG. 2 is an enlarged partial configuration diagram of the system shown in FIG. 1, and FIG. 3 is an intake throttle valve shown in FIG. 1. Fully closed! ! FIG. 4 is a partial configuration diagram showing the half-open control state of the intake throttle valve. FIG. 5 is a partial configuration diagram showing the fully open control state of the intake throttle valve. FIG. 6 is a partial configuration diagram showing the intake throttle valve fully open control state. FIG. 7 is a partial configuration diagram showing the negative pressure constant pressure control state; FIG. 7 is a map showing the control state of the intake throttle valve and EGR in terms of engine speed and accelerator opening; FIGS. 8 and 9 are flowcharts of control in the present invention. , is. 1... Diesel engine 2... Fuel injection pump 3... ECU (electronic control unit) 4...
・Intake passage 5... Exhaust passage 6... EGR passage 7... EGR valve 8... EGR actuator 9...
Intake throttle valve 10...Intake throttle valve actuator 11...
...Vacuum pump 12...EVRV (electric negative pressure regulating valve) 13
．． 15.23.24...VSV (vacuum switching valve) 14...Pressure sensor 17...Vacuum modulator 21.25.
26...Diaphragm 32...Seat portion 33...Stopper member 35...Lever opening sensor 36...Engine speed sensor 41.・・・・・・
・Ignition switch inch 45 Fuel cut valve patent Applicant Patent attorney representing Toyota Motor Corporation 1) Tsuneo Fuchi (and 1 other person) Iku Toheya Zentan

Claims (1)

[Claims] 1. EGR passage that communicates the exhaust passage and the intake passage;
The EGR valve opens and closes the GR passage and uses negative pressure to
The intake passage includes an actuator that drives the GR valve, and has an intake throttle valve upstream of the EGR passage opening of the intake passage, and detects negative pressure downstream of the intake throttle valve and maintains the negative pressure substantially constant. In an exhaust gas recirculation control device for a diesel engine equipped with a constant pressure control mechanism capable of adjusting the opening degree of a throttle valve, the control device is provided with a non-EGR/constant pressure control region that operates the constant pressure control mechanism during non-EGR, and The pressure sensor for detecting the driving pressure of the EGR valve actuator is connected to the non-E
A pressure sensor that detects the intake negative pressure downstream of the intake throttle valve is also used during GR, and the control device detects a system abnormality when the intake negative pressure detected by the pressure sensor deviates from a predetermined range. 1. An exhaust gas recirculation control device for a diesel engine, comprising a system abnormality determination circuit that determines that the intake throttle valve is fully open and issues a signal to fully open the intake throttle valve.