JPH02267331A - Exhaust gas recirculation control device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent an excessive EGR ratio in the area of low engine speed by providing a stopper mechanism for regulating the opening of an intake throttle valve with a constant pressure control mechanism and controlling the opening regulating position to be changed according to the engine operating state. CONSTITUTION:An EGR valve 7 driven by an 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 the intake passage 4, as well as an intake throttle valve 9 is provided at the intake passage 4, more on the upstream side than the EGR passage opening part 6a. This intake throttle valve 9 is controlled by the actuator 10 so as to keep intake negative pressure constant, thus functioning as a constant pressure control mechanism. The actuator 10 is provided with a chamber 27 divided into diaphragms 25, 26 and communicated with the atmospheric air and chambers 28, 29 communicated with the negative pressure or the atmospheric air, as well as a stopper member 33 is protrusively provided on the chamber 28 side of the diaphragm 26, and the closing action of the intake throttle valve 9 is regulated by the member 33 to be the fixed opening or less.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to exhaust gas recirculation (hereinafter referred to as EG) of diesel engines.
(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
(Japanese Utility Model Publication No. 2-4663, Japanese Utility Model Application Publication No. 55-100052), in the above-mentioned constant pressure control mechanism for the intake negative pressure, in order to prevent the intake throttle valve from being throttled below a certain opening degree, An exhaust gas recirculation control device provided with a fixed stopper is also known (Japanese Unexamined Patent Publication No. 115841/1984).

Furthermore, a device is known in which the intake throttle valve is closed when the key switch is opened (off) (Japanese Patent Application Laid-open No. 57-1999).
18430).

[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 over almost the entire engine speed range to increase the EGR rate (the ratio of EGR gas to intake air) and reduce NOx. Although it is possible to measure the above, it may lead to the following problems, especially at low rotation speeds.

In other words, in order to keep the intake negative pressure constant, the lower the rotation speed, the more it is necessary to throttle the intake throttle valve, which reduces the amount of intake air. If the opening degree) is the same, the EGR rate will inevitably increase as the rotation speed becomes lower. Therefore, unless the BGR valve lift amount is precisely controlled with a minute opening degree, an appropriate EGR rate cannot be obtained, and in some cases, the EGR rate becomes excessive. Therefore, if the pressure is controlled to a constant negative pressure that achieves the required EGR rate in the high rotation speed range, the EGR rate will tend to be excessive in the low rotation speed range.Excessive EGR rate will cause problems such as the generation of black smoke and misfires. .

On the other hand, if the pressure is controlled to a constant negative pressure such that the required EGR rate is achieved on the low rotation speed side, the EGR rate will become too low on the high rotation speed side, and the target exhaust gas purification performance such as NOx reduction rate may not be achieved. There is.

To solve this problem, as disclosed in JP-A-56-115841, providing a stopper to prevent the intake throttle valve from being throttled below a certain opening degree prevents the intake air amount from being throttled too much. Since it can be prevented, the above E in the low rotation speed range
This is considered to be an effective method to avoid the problem of excessive GR rate.

However, if a fixed stopper is provided as in JP-A-56-115841, the intake throttle valve cannot be throttled below the opening regulated by the stopper no matter what state the engine is in. However, in this case, the following excellent effects of intake throttle valve control would be abandoned. In other words, as disclosed in Japanese Unexamined Patent Publication No. 57-18430, by closing the intake throttle valve when the engine is stopped (when the key is off), the amount of intake air is kept extremely small and the engine rotates due to inertia. This reduces compression resistance, suppresses shock and vibration, and allows the engine to shut down quietly. This effect cannot be obtained unless the intake throttle valve can be fully closed when the engine is stopped.

The present invention focuses on the various problems mentioned above, and makes it possible to control the EGR rate to an optimum EGR rate that is high but not excessive over the entire engine speed range, and also to respond to engine operating conditions such as acceleration/deceleration and when the engine is stopped. It is an object of the present invention to provide an exhaust gas recirculation side '<B device that can control the intake throttle to an optimal intake throttle state.

[Means to solve the problem]

The exhaust recirculation control device for a diesel engine according to the present invention that meets this purpose is an EGR system that connects an exhaust passage and an intake passage.
and an intake throttle valve upstream of the BGR passage opening of the intake passage, and the intake throttle valve is opened so as to know the negative pressure downstream of the intake throttle valve and keep the negative pressure substantially constant. In an exhaust recirculation control device for a diesel engine equipped with a constant pressure control mechanism that can adjust the opening degree of the intake throttle valve, either the actuator that adjusts the opening degree of the intake throttle valve or the intake throttle valve itself is controlled to have an opening degree of the intake throttle valve below a certain degree. The stopper mechanism is provided with a stopper mechanism that can restrict the closing direction of the intake throttle valve, and that can change the restriction position to a lower opening than the constant opening according to engine operating conditions.

[Effect]

In such an exhaust recirculation control device, there is a constant pressure control that adjusts the opening of the intake throttle valve to keep the intake negative pressure approximately constant depending on the engine operating condition, and a constant pressure control mechanism. Control is selected to maintain the intake throttle valve at a constant opening such as half open or fully closed.

When exhaust gas recirculation is performed during constant pressure control, since the intake negative pressure is stable, the EGR rate is easily maintained at a predetermined level, and the exhaust gas purification performance is improved. If the engine enters the low rotation speed range with this constant pressure control, there is a risk that the EGR rate will become excessive as mentioned above, but the intake throttle valve is forced to close to a certain opening (for example, half open) by the stopper mechanism. Since the intake throttle is restricted and the amount of intake air is secured, EGR
Excessive rates are prevented. Additionally, depending on the engine operating conditions, for example when the engine is stopped, the restriction position by the stopper mechanism is changed to the lower opening side of the intake throttle valve (for example, the fully closed position), which greatly suppresses the amount of intake air and makes it quieter. This makes it possible to stop the engine.

Furthermore, by regulating the intake throttle valve to the above-mentioned constant opening position even during deceleration, etc., it is possible to ensure an appropriate amount of intake air and reduce intake noise.

〔Example〕

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

1 and 2 show an exhaust recirculation control device for a diesel engine according to an embodiment of the present invention. In FIG. 0, 1 is a diesel engine main body, 2 is a fuel injection pump, and 3 is an ECU (electronic control equipment) is shown. 4 is an intake passage to the engine 1, 5 is an exhaust passage from the engine 1, and an EGR connecting the exhaust passage 5 and the intake passage 4.
A passage 6 is provided. An EGR valve 7 is provided at the opening 6a of the EGR passage 6 to the intake passage 4.
The EGR valve 7 has an actuator 8 having a diaphragm.
It is designed to be operated by.

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 (electric negative pressure regulating valve) 12 and VSV (vacuum switching valve) 13 . EVRV
At 12, the introduction of negative pressure from the vacuum pump 11 to the actuator 8 is controlled.

That is, the target value of the control negative pressure to be supplied to the EGR valve actuator 8 is calculated within the ECU 3 based on information on the engine operating state inputted 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. EC
U3 converts the duty signal corresponding to the above target value to EVRV.
Give to 12. 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 vsvts 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. Actual system? B Feedback control is performed so that the negative pressure reaches the target value. (5) 5V15 supplies intake negative pressure to the pressure sensor 14 when exhaust gas recirculation is stopped.

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 IO, and the opening of the intake throttle valve 9 is adjusted in the closing direction until the intake plate 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 1°. 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 . The VSV 24 selects either the negative pressure from the VSV 23 or the atmospheric pressure as the output to the 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 A 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
Through the movement of the rod 30 with the movement of the intake throttle valve 9
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 2G.
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 becomes possible to restrict further movement of the diaphragm 25 toward the diaphragm 26 side, and therefore prevent the intake throttle valve 9 from operating in the closing direction below a certain opening degree. ing.

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 open).

In this embodiment, the stopper member 33 is replaced by the diaphragm 26.
Although it is provided on the A chamber 28 side of the diaphragm 25, the same function can be obtained even if it is provided on the A chamber 28 side of the diaphragm 25 as shown at 33A in FIG. Alternatively, it may be provided integrally with the rod 30 constituting the intake throttle valve member as shown in 33B in FIG.

EVRV12, VSV13.15.23.24ha, 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 temperature, a signal from a pressure sensor 14, and a signal from an engine water temperature sensor 38 are 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 VSvI3. 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.

The operation of the device configured as above will be explained.

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 an actuator 10.
11, and the operation of the actuator 10 is as follows:■S■13.
23, 24 and vacuum modulator 17. The operation mode of the intake throttle valve 9 is shown in Table-1.
It becomes like this.

When the ignition switch 41 is switched from on to off, that is, when the engine is stopped, ■s■13.23.
24 are all turned off, and as shown in FIG.
, B chamber 29, a constant negative pressure from the vacuum pump 11 sufficient to move the intake throttle valve 9 is introduced (the shaded area in the figure indicates the introduction of negative pressure), and the intake throttle valve 9 is kept fully closed. Ru. Therefore, when the engine is stopped while it is running, the intake throttle valve 9 is fully opened 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 small level, causing shocks and vibrations. is suppressed and the engine is quietly stopped. At this time, the fuel supply is also cut off by the fuel cant 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.

This constant pressure control keeps the intake negative pressure stable and prevents a shortage of intake air, so that a predetermined EGR rate can be achieved and the target exhaust gas purification performance can be achieved.

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, and area 1
02 is the fully open region of the intake throttle valve 9, region 103 is the half open region of the intake throttle valve 9, and double hatched region 104 is the region where the negative pressure from the vacuum modulator 17 is introduced into the A chamber 28 of the actuator 10, resulting in the operation of constant pressure control characteristics. Although it holds true,
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 boundaries 111 and 112, and in the region 105 between the 0 operating boundaries 111 and 113, where the optimum EGR rate is achieved in the constant pressure control region.
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, E
GR is turned off.

The relationship between the engine speed in the constant pressure control region 101 and the region 104 (for example, on the characteristic line 114 (for example, no-load characteristic line) in FIG. 7), intake negative pressure, EGR rate, and NOx reduction rate is shown below. , the broken line in Figure 0 as shown in Figure 8 is the characteristic when there is no intake throttle valve,
- The dotted chain line shows the characteristic by conventional constant pressure control, and the solid line shows the characteristic by the present invention. In particular, portions a, b, and c that diverge from the conventional constant pressure control characteristics show the characteristics when the intake throttle valve 9 is kept in a half-open state via the stopper member 33, and the intake throttle valve 9 The downstream intake negative pressure is reduced as the engine speed decreases, and the EGR rate is maintained at a high level as a whole, while an excessive state in the low speed range is avoided.

Further, in the above embodiment, a diaphragm 25 connected to the intake throttle valve and a diaphragm 26 not connected are provided in the actuator lO, and the stopper member 33, 33 on one diaphragm faces the other diaphragm.
Since A and 33B are provided, both constant pressure control and constant opening degree control can be performed using one actuator 10 and one intake throttle valve 9.30.

In the above embodiment, a stopper mechanism including the stopper member 33 is incorporated into the actuator 10, but the mechanism is not limited to this, and for example, a stopper member that can move in and out of the intake passage may be provided to control the movement of the intake throttle valve itself. It is also possible to directly regulate and change the regulating position.

〔Effect of the invention〕

As explained above, when using the exhaust recirculation control device for a diesel engine according to the present invention, a stopper mechanism capable of regulating the opening of the intake throttle valve equipped with a constant pressure control mechanism is provided, and the opening regulation position is adjusted depending on the engine operating condition. Since it is possible to change the EGR rate according to the current speed, it is possible to prevent excessive EGR rate in the low rotation speed range, which was a problem with conventional constant pressure control, and to control the EGR rate to the optimum level without excessive over the entire rotation speed range. become.

Further, depending on the engine operating conditions, for example, when the engine is stopped, the restriction position by the stopper mechanism can be changed to fully open the intake throttle valve, so that shocks and vibrations can be suppressed and the engine can be stopped quietly. Furthermore, it is possible to reduce intake noise during deceleration and suppress smoke during acceleration.

[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. 4 is a partial configuration diagram showing a fully closed control state of the intake throttle valve. FIG. 5 is a partial configuration diagram showing a fully open control state of the intake throttle valve. A partial configuration diagram showing the intake negative pressure constant pressure control state of the throttle valve, Fig. 7 is a map showing the intake throttle valve and EGR control i1 state in terms of engine speed and accelerator opening, and Fig. 8 shows the engine speed and intake air. Negative pressure, EGR rate, NOx
FIG. 9 is a partial sectional view showing a modification of the device shown in FIG. 2; FIG. 10 is a partial sectional view showing still another modification of the device shown in FIG. 2. 1... Diesel engine 2... Fuel injection pump 3... ECU (electronic control unit W) 4...
・Intake passage 5... Exhaust passage 6... EGR passage 7... EGR valve 8... EGR actuator 9...
Intake throttle valve 10... Actuator 11... Vacuum pump 12... EVRV (electricity bill 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 33.33A, 33B...Stopper member 35.
... Lever opening sensor 36 ... Engine rotation speed sensor 41 ...
・Ignition switch 45...Fuel cut valve is bent.

Claims (1)

[Claims] 1. An EGR passage that communicates an exhaust passage and an intake passage is provided, and an intake throttle valve is provided upstream of the EGR passage opening of the intake passage, and negative pressure downstream of the intake throttle valve is detected and the negative pressure is reduced. In an exhaust recirculation control device for a diesel engine equipped with a constant pressure control mechanism capable of adjusting the opening degree of an intake throttle valve to maintain a constant value, the invention provides a method for controlling either an actuator that adjusts the opening degree of the intake throttle valve or the intake throttle valve itself. a stopper that is capable of regulating the closing direction operation of the intake throttle valve below a certain opening degree, and that is capable of changing the regulating position to a lower opening side of the intake throttle valve than the constant opening degree according to engine operating conditions; An exhaust recirculation control device for a diesel engine characterized by being provided with a mechanism.