JP2591148B2 - Exhaust recirculation control device for diesel engine - Google Patents

Description

The present invention relates to an exhaust gas recirculation (hereinafter referred to as EG) of a diesel engine.
Also called R. ) Regarding the control device.

[Conventional technology]

Conventionally, an EGR passage communicating the exhaust passage and the intake passage is provided, 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 substantially constant. Further, there is known an exhaust gas recirculation control device for a diesel engine in which the opening degree of an intake throttle valve is adjusted by using a vacuum modulator or the like (for example, Japanese Utility Model Publication No. Sho 62-4).
No. 663, Japanese Utility Model Publication No. 55-100052).

[Problems to be solved by the invention]

However, Japanese Utility Model Publication No. Sho 62-4663 and Japanese Utility Model Sho 55-1000
In constant pressure control of the intake negative pressure as disclosed in Japanese Patent Publication No. 52,
Increase the intake negative pressure over almost the entire engine speed range
Increase the EGR rate (ratio of EGR gas to intake air) and reduce NOx
Although this can be reduced, the following problem may be caused.

That is, since only the vacuum modulator is used to perform the constant pressure control of the intake negative pressure, it is not possible to appropriately control whether to perform the constant pressure control or another fixed control according to the operating conditions. Therefore, for example, when constant pressure control is performed for all engine load regions,
There is a possibility that the amount of intake air is insufficient in the entire load range, causing inconvenience such as generation of black smoke.

Even with the conventional device, even if the intake throttle valve can be fully opened under certain operating conditions, the path length from the vacuum modulator to the actuator for driving the intake throttle valve is long. It is difficult to perform the switching with high responsiveness. If the switching is delayed, the increase in the amount of intake air is delayed, causing inconveniences such as black smoke and smoke. Further, if the switching from the full opening to the constant pressure control is delayed, the control to the target intake negative pressure by conversely reducing the intake air amount is delayed, and it is difficult to quickly set the predetermined EGR rate.

The present invention focuses on the above-described problems, and achieves an optimal map control in which intake negative pressure constant pressure control and intake throttle valve full-open control are combined in accordance with the operating conditions of the engine. It is an object of the present invention to improve control responsiveness when switching between a pressure constant pressure control region and an intake throttle valve fully open control region, prevent black smoke, smoke, etc. from occurring, and quickly control a target EGR rate.

[Means for solving the problem]

The exhaust gas recirculation control device for a diesel engine according to the present invention for this purpose includes an EGR passage communicating the exhaust passage and the intake passage, and has an intake throttle valve upstream of the EGR passage opening of the intake passage. Between an intake passage downstream of the intake throttle valve and an actuator for adjusting the opening degree of the intake throttle valve,
An exhaust gas recirculation control device for a diesel engine including a vacuum modulator that synthesizes a pressure from a pressure source and an atmospheric pressure in accordance with an intake negative pressure as a driving pressure to the actuator, wherein the vacuum modulator and the actuator include: A first switching valve for switching the driving pressure to the actuator between the pressure from the vacuum modulator and the pressure from the pressure source, and switching the driving pressure to the actuator between the pressure from the first switching valve and the atmospheric pressure; A second switching valve, wherein at least when the engine load is equal to or more than a first predetermined load, the first switching valve is switched to the vacuum modulator side and the second switching valve is switched to the first switching valve side. At a predetermined load or more, the first and second switching valves are connected to a control device so as to switch the second switching valve to the atmosphere side. Consisting of things.

[Action]

In such an exhaust gas recirculation control device, there are a constant pressure control region in which the opening of the intake throttle valve is adjusted so as to keep the intake negative pressure substantially constant, a control region in which the intake throttle valve is forcibly fully opened, and the like. Is set as an optimal map according to the engine operating state.

When exhaust gas recirculation is performed during the constant pressure control, the intake negative pressure is stabilized, so that the predetermined EGR rate is easily maintained, and the exhaust gas purification performance is improved. In this constant pressure control region, the intake throttle valve opening is reduced on the low rotation side to reduce vibration and noise caused by intake air, and the intake throttle valve opening is increased on the high rotation side to secure a sufficient intake air volume. Is done.

At the time of switching from the constant pressure control region to the intake throttle valve fully open control region, the second switching valve is switched to a side for introducing atmospheric pressure to the intake throttle valve actuator, but this second switching valve is closest to the actuator. Since it is disposed at the position, the atmospheric pressure is quickly introduced into the actuator, and the control response to the intake throttle valve being fully opened is enhanced. When switching from the intake throttle valve fully open control area to the constant pressure control area,
Since the pressure from the vacuum modulator has already been introduced via the first switching valve to the second switching valve, the second
By switching the switching valve, it is possible to quickly shift to the predetermined constant pressure control. Since the control response at the time of transition between both areas is good,
Constant pressure control, intake throttle valve full-open control, and the like, which were the targets when setting the map, are reliably achieved.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

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

An intake throttle valve 9 is provided upstream of the EGR passage opening 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 operating the actuators 8 and 10 is configured as follows.

Reference numeral 11 denotes a vacuum pump, which generates a driving negative pressure. The negative pressure from the vacuum pump 11 is introduced into an EVRV (electric negative pressure regulating valve) 12 and a VSV (vacuum switching valve) 13. The EVRV 12 controls the introduction of the negative pressure from the vacuum pump 11 to the actuator 8. That is, based on the information of the engine operating state input from various sensors, the ECU 3
The target value of the control negative pressure to be supplied to is calculated. This target value is determined so as to be an EGR valve opening that gives an optimum EGR rate in the engine operating state at that time. The ECU 3 supplies a duty signal corresponding to the target value to the EVRV12. EV
The RV 12 adjusts the ratio of introduction of the negative pressure from the vacuum pump 11 and the atmospheric pressure to the actuator 8 according to the duty signal. At the time of exhaust gas recirculation, the VSV 15 is
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, and the actual control negative pressure matches the target value. Feedback control is performed as follows. The VSV 15 supplies the negative pressure of the intake air to the pressure sensor 14 when the 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 vacuum modulator 17 and the actuator 10 are controlled so that the negative pressure is maintained substantially constant.
The opening degree of the intake throttle valve 9 can be adjusted via the. As shown in FIG. 2, the vacuum modulator 17 has a diaphragm valve structure, and is introduced into a diaphragm chamber 19 provided with a spring 18 at a negative intake pressure, and the other chamber 20 is communicated with the atmosphere. Negative pressure from the vacuum pump 11 is introduced into the valve body 22 of the diaphragm 21.
When the intake negative pressure is higher than the set value, the valve body 22 moves toward the diaphragm chamber 19, the negative pressure from the vacuum pump 11 bleeds, the output negative pressure to the actuator 10 decreases, and the intake throttle valve 9 opens. Then, the opening is adjusted 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 bleeding of the negative pressure from the vacuum pump 11, and the negative pressure from the vacuum pump 11 is output to the actuator 10 as it is, and 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 for adjusting the opening of the intake throttle valve 9 so as to keep the intake negative pressure substantially constant.

A VSV 23 as a first switching valve and a VSV 24 as a second switching valve are interposed between the vacuum modulator 17 and the actuator 10. VSV23 is an actuator
The output to 10 is selected from either the negative pressure via the constant pressure control mechanism or the source pressure from the vacuum pump 11.
The VSV 24 selects the output to the actuator 10 from either the negative pressure from the VSV 23 or the atmospheric pressure. The VSV 24 as the second switching valve is provided at a position closest to the actuator 10.

The actuator 10 for adjusting the opening degree of the intake throttle valve 9 includes:
Either a negative pressure or an atmospheric pressure from the vacuum pump 11 switched by the VSV 13 is introduced, and a chamber 27 that is divided by the diaphragms 25 and 26 and communicates with the atmosphere, an A chamber 28 into which the pressure from the VSV 24 is introduced, and the like. A room B 29 is provided.
A connecting rod 30 for connecting to the intake throttle valve 9 is provided on the diaphragm 25 side, and the opening degree of the intake throttle valve 9 is adjusted through the movement of the rod 30 accompanying the movement of the diaphragm 25. A spring 31 is provided in the A chamber 28 and urges the diaphragm 25 toward the rod 30 (in a direction in which the intake throttle valve 9 is opened) with respect to the seat portion 32.

A stopper member 33 protrudes from the A chamber 28 side of the diaphragm 26, and when the diaphragm 25 moves to the diaphragm 26 side and abuts against the tip of the stopper member 33, the diaphragm 25 is moved to the further diaphragm 26 side. , That is, the closing operation of the intake throttle valve 9 to a certain opening degree or less can be restricted.

Since the stopper member 33 is provided on the diaphragm 26, it moves with the movement of the diaphragm 26. B
The chamber 29 is provided with a spring 34 that urges the diaphragm 26 in the direction of the diaphragm 25. When the atmospheric pressure is introduced into the B chamber 29, the spring 34 presses the diaphragm 26 against the seat member 32 to stop the diaphragm 26. The member 33 is held at the position shown in FIG.
When the negative pressure from 11 is introduced, the diaphragm 26 moves in the direction to reduce the B chamber 29 against the force of the spring 34, and the stopper member 33 moves in the same direction accordingly. Has become. Therefore, the opening restriction position of the intake throttle valve 9 through the restriction of the movement of the diaphragm 25 by the stopper member 33 causes the intake throttle valve 9 to be further lowered (for example, fully closed) by the movement of the stopper member 33. It can be changed to the restriction position.

In this embodiment, the stopper member 33 is provided on the A chamber 28 side of the diaphragm 26, but the same function can be obtained by providing the stopper member 33 on the A chamber 28 side of the diaphragm 25.

The EVRV12, VSV13, 15, 23, 24 are operated based on a command from the ECU3. 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 and an engine speed from an engine speed sensor 36, respectively. Signal from adjustment resistor 37 for adjusting the degree, pressure sensor 14
And a signal from the engine water temperature sensor 38 are input. Further, the ECU 3 receives a signal from the vehicle speed sensor 39,
In a vehicle equipped with an automatic transmission, a neutral (N) position signal 40 and a signal from an ignition switch 41 (engine on / off signal) are input. The signal from the ignition switch 41 is VSV1
3 It is also used as a signal for operation. The ECU 3 further outputs a signal 42 to the air conditioner amplifier and a signal 43 to the automatic transmission.

Reference numeral 44 denotes a boost compensator for regulating the maximum value of the fuel injection amount by using negative pressure, and 45 denotes a fuel cut valve.

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

First, the operation control of the intake throttle valve 9 will be described 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, and the operation of the actuator 10 is controlled by VSVs 13, 23, 24 and a vacuum modulator 17. The operation modes of the intake throttle valve 9 are as shown in Table 1.

When the ignition switch 41 is switched from on to off, that is, when the engine is stopped, all of the VSVs 13, 23, and 24 are turned off, and as shown in FIG. A constant negative pressure from the vacuum pump 11 sufficient to move the pressure is introduced (the hatched portion in the figure indicates the introduction of the negative pressure), and the intake throttle valve 9 is kept fully closed. Therefore, when the running engine is stopped, the intake throttle valve 9 is fully closed, whereby the amount of air intake is greatly reduced, and the compression resistance of the engine rotating by inertia is suppressed to a small value to reduce the impact and vibration. The occurrence is suppressed and the engine is stopped quietly. At this time, the fuel supply is also cut by the fuel cut valve 45, and the combustion is stopped naturally and quietly.

During deceleration, the VSV 13 is turned on, the B chamber 29 is opened to the atmosphere, the VSVs 23 and 24 are turned off, and a 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 is moved toward the seat 32 and held at a fixed position, and the diaphragm 25 is
At the same time, the intake throttle valve 9 is held at a half-open position, while being held at a position where it contacts the tip of the stopper member 33 held at a fixed position. By keeping the intake throttle valve 9 in a half-open state, an intake air amount equal to or more than a predetermined amount is ensured even when the load is low, and the intake muffled sound during deceleration is reduced.

At full load (during acceleration), VSV13, 24 are turned on,
Atmospheric pressure is introduced into both the chambers A and B, and the intake throttle valve 9 is kept in a fully open state as shown in FIG. The intake air is not substantially restricted, a sufficient amount of intake air is secured, and smoke suppression and the like are realized.

In the middle and low load ranges, VSV13 and 23 are turned on and VSV24 is turned off. The B chamber 29 is open to the atmosphere, the A chamber 28 receives the output negative pressure from the vacuum modulator 17, and the intake negative pressure is substantially constant. The opening degree of the intake throttle valve 9 is controlled so that The operation of the vacuum modulator 17 at this time is as described above. This constant pressure control keeps the intake negative pressure stable and prevents the shortage of intake air volume.
The EGR rate can be easily obtained, and the target exhaust gas purification performance can be obtained.

In low speed (low speed) low load range, each VSV13, 2
The operation modes of 3, 24 are the same as those in the low load range. However, since the atmospheric pressure is introduced into the chamber B and the diaphragm 26 and the stopper member 33 are maintained at the fixed positions shown in FIG. 2, the negative pressure introduced into the chamber A from the vacuum modulator 17 is obtained. By the intake throttle valve 9
The movement of the diaphragm 25 to move the diaphragm 25 in the closing direction is restricted by the tip of the stopper member 33, and the intake throttle valve 9 is maintained in the half-open state. Therefore, a sufficient amount of air is ensured even at a low rotation speed, and the intake negative pressure is reduced. As a result, when the constant pressure control, which is a conventional problem, is employed, an excessive EGR rate in a low rotational speed range is prevented.

The respective areas of the constant pressure control, the intake throttle valve fully open and the half open control are set in the ECU 3 as a map relating to the engine load and the engine speed as shown in FIG. 7, for example.

In the map shown in FIG. 7, the first predetermined load 201
When the above occurs, VSV23 is applied to the vacuum modulator 17 side
SV24 is switched to VSV23 side, intake throttle valve half-open control area 2
From 03 enters the constant pressure control area 204. When the load exceeds the second predetermined load 202, the VSV 24 is switched to the side where the atmospheric pressure is introduced into the actuator 10, and enters the intake throttle valve fully open control region 205. This switching control is performed by comparing the current load (Accp) with the first predetermined load 201 (Accp1) and the second predetermined load 202 (Accp2), as shown in FIGS. 8 and 9. It is performed according to the flow. In the control of the VSV 24 shown in FIG. 8, the second predetermined load (Accp2) is read in step 301, the current load (Accp) is compared with Accp2 in step 302, and when Accp> Accp2, step 303 is executed. VSV24 is turned on and the actuator 10
Atmospheric pressure is introduced. If Accp> Accp2,
In step 304, the VSV 24 is turned off. VSV2 shown in Fig. 9
In the control of 3, the first predetermined load (Ac
cp1) is read and compared with the current load (Accp) in step 402. In step 402, Accp <A
At the time of ccp1, VSV23 is turned off (step 403), and VSV2
4 is turned off, the original pressure from the vacuum modulator 11 is introduced into the actuator 10, and the intake throttle valve 9 is half-opened. When Accp1 <Accp <Accp2, in step 404, the VSV23 is turned on and the VSV24 is turned off, and the above-described constant pressure control is performed.

In this control map, in particular, the constant pressure control region 20
4 to the fully open control area 205, the actuator 10
Is switched to the atmospheric pressure side, the atmospheric pressure is quickly introduced into the actuator 10, and the switching to the full open control is performed with extremely high responsiveness.
Therefore, shortage of the intake air amount is prevented, and generation of black smoke and the like is prevented. In addition, from the fully open control area 205 to the constant pressure control area 2
At the time of shifting to 04, the control pressure from the vacuum modulator 17 has been introduced in advance to the position of VSV24, and VSV2
By switching 4 to the VSV 23 side, the pressure from the vacuum modulator 17 is quickly introduced into the actuator 10. Therefore, constant pressure control is quickly performed without substantially delaying control, and a predetermined EGR rate is easily achieved.

With respect to the above control region, a map relating to the engine speed and the accelerator opening (load) can be set as shown in FIG. 10 in addition to the EGR operation and stop control. Tenth
In the figure, the shaded area is the constant pressure control area 101, and the area 1 is the constant pressure control area.
02 is the fully open region of the intake throttle valve 9, and region 103 is the intake throttle valve 9.
The half-open area, the double-hatched area 104, the negative pressure from the vacuum modulator 17 is introduced into the A chamber 28 of the actuator 10 and the operation of the constant pressure control system is established, but in reality, the movement is restricted by the stopper member 33, This is an area where the intake throttle valve 9 is kept in a half-open state. On / off of the EGR is turned on in a region between the operating boundary lines 111 and 112, and an optimum EGR rate is set in a constant pressure control region. An area 105 between the operating boundary lines 111 and 113 is an area where the intake throttle valve 9 is not fully opened but the intake noise can be reduced by controlling the intake throttle valve 9 although the load is considerably high. Since this region is near full load, EGR is turned off.

In the control in the constant pressure control regions 101 and 104 (for example, on the characteristic line 114 (for example, the characteristic line at no load) in FIG. 7), as described in the control in the low speed (low rotational speed) low load region described above. , In the low speed range,
The intake throttle valve 9 can be fixedly controlled to a half-open state while performing the EGR, and an excessive EGR rate in a low rotation speed region can be prevented.

Furthermore, in the control device of the present invention, various controls can be performed according to the operating state of the engine. For example, during rapid acceleration (accelerator opening increases more than a predetermined amount within a predetermined time)
In addition, by detecting this, the intake throttle valve 9 is forcibly fully opened for a predetermined period of time, so that generation of smoke due to transient excessive EGR rate and insufficient intake air amount can be prevented. Such control is performed according to a control flow as shown in, for example, FIG. 11 to FIG.

In the control flow of the transient determination counter (CTRAP1) shown in FIG.
p) and the load (Acpp) before 10 msec are read, and it is determined from the difference between them whether or not the vehicle is undergoing rapid acceleration. If the vehicle is undergoing rapid acceleration, the intake throttle valve is provided for a predetermined time, for example, 10 msec × 50. 9 is forcibly controlled to be fully opened. At the time of rapid acceleration, whether or not the load Acpp before 10 msec
Is determined by whether the current load Accp has increased by 4% or more. If it is determined that the vehicle is accelerating suddenly,
For example, 50 is stored in TRAP1, and the value of CTRAP1 is determined in step 601 as to whether or not CTRAP1 is not 0, as shown in the flow chart of the 10 msec routine in FIG.
In 02, for example, it is decremented once every 10 msec. If it is determined that the vehicle is temporarily accelerated suddenly, CTRAP1 ≠ 0 for 10 msec × 50. Then, in the control flow of the VSV 24 shown in FIG. 11, the engine speed (NE) and the load (Accp) are read in step 701, and it is determined in step 702 whether or not CTRAP1、0. If CTRAP1 ≠ 0), V
When the SV 24 is turned on, the intake throttle valve 9 is fully opened for a predetermined period of time, and when it is not during rapid acceleration, predetermined control is performed in step 704 according to the above-described map.

By adding the control for forcibly opening the intake throttle valve 9 at the time of rapid acceleration, as shown in FIG. 14, the intake throttle valve 9 is fully opened at a very early stage as compared with the determination control using only the map. It can be performed. Therefore, it is possible to cope with a sudden and transient increase in load very quickly, and it is possible to reliably prevent an excessive EGR rate and an insufficient intake air amount at the time of rapid acceleration.

〔The invention's effect〕

As described above, when the exhaust gas recirculation control device for a diesel engine according to the present invention is used, the first and second switching valves are provided in addition to the vacuum modulator, and the switching valves are arranged at optimal positions for control. , So that control can be performed according to the optimal map according to the operating state of the engine, so that the optimal intake air amount is always controlled according to the engine operating state, and the target EGR rate is accurately controlled during EGR. When the control area of the map changes, the control state can be switched with good responsiveness. Therefore, it is possible to reliably prevent the generation of black smoke or the like due to the shortage of the intake air amount, and to perform the desired EGR during the EGR.
The rate can be easily achieved.

[Brief description of the drawings]

1 is an overall configuration diagram of an exhaust gas recirculation control device for a diesel engine according to one embodiment of the present invention, FIG. 2 is an enlarged partial configuration diagram of the system of FIG. 1, and FIG. 3 is an intake throttle valve of FIG. FIG. 4 is a partial configuration diagram showing a half-open control state of the intake throttle valve, FIG. 5 is a partial configuration diagram showing a full-open control state of the intake throttle valve, and FIG. FIG. 7 is a partial configuration diagram showing the control state of the intake negative pressure and the constant pressure of the throttle valve. FIG. 7 is a map showing the control state of the intake throttle valve with respect to the engine speed and the accelerator opening. FIG. FIG. 9 is a control flowchart of the VSV 23 based on the map of FIG. 7, FIG. 10 is a map showing an example of control of the intake throttle valve and the EGR, showing a relationship between an engine speed and an accelerator opening, and FIG. VSV24 related to an example of rapid acceleration control FIG. 12 is a flowchart of the rapid acceleration determination, FIG. 13 is a flowchart of the rapid acceleration control of the intake throttle valve fully open time, and FIG. 14 is a case where the rapid acceleration control of FIGS. 11 to 13 is added. 5 is a time chart showing the control characteristics of FIG. DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Fuel injection pump 3 ... ECU (Electronic control device) 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 (electric negative pressure regulating valve) 13, 15 VSV (vacuum switching valve) 14 Pressure sensor 17 Vacuum modulator 21, 25, 26 ... diaphragm 23 ... VSV 24 as the first switching valve 24 ... VSV as the second switching valve 32 ... seat 33 ... stopper member 35 ... lever opening degree sensor 36 ... engine speed sensor 41 … Ignition switch 45… Fuel cut valve Accp1… First predetermined load Accp2… Second predetermined load

Claims (1)

(57) [Claims] An EGR passage for communicating an exhaust passage and an intake passage, an intake throttle valve upstream of the EGR passage opening of the intake passage, and an intake passage downstream of the intake throttle valve and the intake throttle. An exhaust gas recirculation control device for a diesel engine including a vacuum modulator for synthesizing a pressure from a pressure source and an atmospheric pressure according to an intake negative pressure as a driving pressure for the actuator, between the actuator and an actuator for adjusting a valve opening degree A first switching valve for switching a driving pressure to the actuator between the pressure from the vacuum modulator and a pressure from a pressure source between the vacuum modulator and the actuator, and a driving pressure to the actuator A second switching valve for switching between the pressure from the first switching valve and the atmospheric pressure;
Above the predetermined load, the first switching valve is switched to the vacuum modulator side, the second switching valve is switched to the first switching valve side, and above the second predetermined load, the second switching valve is switched to the atmosphere side. An exhaust gas recirculation control device for a diesel engine, wherein the first switching valve and the second switching valve are connected to a control device.