JPH0246789B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an exhaust gas recirculation device for an engine, and particularly to an exhaust gas recirculation device for an engine that performs exhaust gas recirculation during warm-up operation of the engine. [Prior art] Conventionally, diesel engines have been used to perform exhaust gas recirculation (EGR) during warm-up to improve warm-up performance, reduce noise and vibration, and suppress half-misfires to prevent the generation of HC. A warm-up EGR system is known (see Japanese Unexamined Patent Publication No. 41453/1983). By the way, when warming up the engine,
It is easy to cause so-called half-misfire, where some cylinders misfire.
If a half-misfire actually occurs, the exhaust gas temperature will drop, causing problems such as the effectiveness of warm-up being reduced. [Object of the Invention] An object of the present invention is to provide an engine EGR system that can ensure good warm-up performance by warm-up EGR even if a half-misfire occurs during warm-up operation. [Structure of the Invention] Therefore, the present invention provides a plurality of exhaust gas recirculation passages that open to exhaust passages of different cylinders, and
An exhaust gas recirculation valve is provided in each exhaust gas recirculation passage, and a sensor is provided that directly or indirectly detects the temperature of the exhaust gas flowing through the exhaust passage where the exhaust gas recirculation passage opens, and the exhaust gas temperature during engine warm-up is determined according to the output of the sensor. The warm-up ECR system is equipped with an exhaust recirculation control device that opens an exhaust recirculation valve installed in an exhaust recirculation passageway that opens into an exhaust passageway with a high temperature. That is, in the warm-up EGR system according to the present invention,
Higher temperature exhaust gas, that is, exhaust gas from cylinders that have not misfired, is recirculated to the intake side. [Effects of the Invention] According to the present invention, since higher temperature exhaust gas can be recirculated to the intake side, the intake air temperature can be effectively increased and the half-misfire prevention performance can be improved. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The diesel engine E shown in FIG.
Each cylinder 1 to 4 takes in fuel injected by a fuel injection pump 5 along with intake air from an intake passage 6, and passes through compression, explosion, and combustion strokes to an exhaust passage 7. exhaust gas. The exhaust manifold 8 that constitutes the connection part of the exhaust passage 7 with the engine body is connected to the first to fourth cylinders 1 to 4.
It has a structure in which the exhaust passages 9 to 12 connected to each other are gathered together and connected to a common intake passage 13, and the exhaust passage 9 of the first cylinder 1 and the exhaust passage 1 of the fourth cylinder 4 are connected to a common intake passage 13.
2, a first and second exhaust outlet 14,
15 are formed respectively. These first and second exhaust outlet ports 14 and 15 are connected to the first and second EGR passages 1
6 and 17, the first and second EGR passages 16 and 1 communicate with the intake passage 6 downstream of the intake throttle valve 18, respectively.
First and second EGR valves 19 and 20, which open and close on and off, are interposed in the middle of the valve 7, respectively. In this embodiment, these first and second EGR valves 19 and 20 are each configured as a diaphragm-operated on-off valve using intake negative pressure as an operating source.
The opening diameter d is set to be one step smaller than the opening diameter D of the second EGR valve 20 (d<D). Further, for each of the first and second EGR valves 19 and 20, control valves 21 and 22, which are electromagnetic solenoid valves for introducing or cutting off intake negative pressure, are connected to each intake negative pressure conduit 23 and 24, respectively. It is set up. These control valves 21 and 22 are connected to a microcontroller valve 27, which is an electromagnetic solenoid valve, which is interposed in an intake negative pressure conduit 26 of an actuator 25, which is provided to the intake throttle valve 18, and which is a diaphragm device operated by an intake negative pressure. It is controlled by a control unit 28 consisting of a computer. This control unit 28 includes a rotation sensor 29 provided for the fuel injection pump 5, a position sensor 30 provided for a control lever (not shown) of the pump 5, and a water temperature sensor for detecting the cooling water temperature of the engine E. 31 Furthermore, the following control is executed using each output of the first exhaust temperature sensor 32 installed in the exhaust passage 9 of the first cylinder 1 and the second exhaust temperature sensor 33 installed in the exhaust passage 12 of the fourth cylinder 4 as input data. do. FIG. 2 shows the control flow executed by the control unit 28. When the control is started, in step 101,
When the 5th speed switch (not shown in FIG. 1) is turned on or off, and it is determined in step 102 that the speed is not 5th, the water temperature sensor 31 is turned on in step 103.
sensor output is read. In addition, in the case of 5th gear, EGR is not performed at all, so the vehicle is returned to the starting side. In step 104, the engine cooling water temperature θ detected from the output of the water temperature sensor 31 is set to a preset water temperature, e.g.
℃, and if it is higher than this set water temperature (θ≧
60℃), transitions to normal EGR control after warm-up is completed,
If the water temperature is lower than the set water temperature, the warm-up according to the present invention
Shift to EGR control. () Warm-up EGR control First, in step 105, the engine coolant temperature θ is 60
If it is confirmed that the vehicle is being warmed up at a temperature lower than ℃, the vehicle speed signal detected by the vehicle speed sensor (not shown) is read in step 106, and it is determined whether the vehicle speed S is smaller than a preset vehicle speed So. Kaga step
107 will be judged. In addition, the set vehicle speed So is:
For example, set 8Km/H. If the vehicle speed is 8 km/h or higher, even if the engine cooling water temperature θ is lower than 60°C, the
Since the temperature will be 60℃ or higher, in this case, warm-up EGR
will not be carried out. When the vehicle speed S is lower than the set vehicle speed So (S<
In step 108, the outputs of the first and second exhaust temperature sensors 32 and 33 are read. In step 109, the exhaust temperature T 1 of the first cylinder 1 detected by the first exhaust temperature sensor ₃₂ and the exhaust temperature T 2 of the fourth cylinder 4 detected by the second exhaust temperature sensor ₃₃ are determined.
When T ₁ ≧ T ₂ , that is, when the exhaust temperature of the first cylinder 1 side is equal to or higher than the exhaust temperature of the fourth cylinder 4 side, the first EGR control valve 21 is opened and the first EGR control valve 21 is opened.
1Open the EGR valve 19 (step 110) and
2Keep the EGR control valve 22 closed and close the second EGR valve 20.
is set to “closed” (step 111). On the other hand, T ₁ < T ₂
In this case, close the first EGR valve 19 (step
112), open the second EGR valve 20 (step
113). Then, in step 114, the throttle valve control valve 27 is opened, and the intake throttle valve 18 is closed to a predetermined angle in order to generate a negative pressure downstream thereof that promotes the recirculation of exhaust gas. The warm-up EGR control described above compares the exhaust gas temperatures discharged from the first and fourth cylinders 1 and 4, and recirculates the exhaust gas having a higher temperature to the intake side. Note that in this embodiment, the first EGR valve 19 and the
2 Since the opening diameters of the EGR valves 20 are different, there may be a difference in the recirculation amount, but if the amount of closing of the intake throttle valve 18 is adjusted to cancel the difference in the opening diameter, the recirculation amount can be effectively reduced. can be made equal. () EGR control during normal operation If engine cooling water temperature θ is 60℃≦θ＜100℃, warm-up has been completed, so normal operation is possible.
Perform EGR control. In step 115, the output of the rotation sensor 29 is read, and in step 116, the rotation speed N is determined.
(rpm) is in the range of 700<N<3000 (rpm)
Step 117 when it is determined that it is in the EGR range
Further, the position of the control lever of the fuel injection pump 5 is read from the position sensor 30. Then, from this control lever position and the pump rotation speed, the load on the engine E at that time, actually the average effective pressure Pe, is calculated. (i) In the case of 0Kg/cm ² >Pe If it is determined in step 118 that 0Kg/cm ² >Pe, the first EGR valve 19, the second EGR valve 20, and the intake throttle valve 18 are all “closed”. (Steps 119, 120, 121). (ii) When 0≦Pe<5 (Kg/cm ² ) If Pe≧0 (Kg/cm ² ), step
In step 122, it is determined whether it is lower than 5 (Kg/cm ² ), and if so, that is, if 0≦Pe<5 (Kg/cm ² ), the small diameter first EGR valve 19 is “closed” in step 123. In step 124, the large-diameter second EGR valve 20 is opened, and a relatively large amount of EGR is performed by the large-diameter second EGR valve 20. Then, in step 125, Pe < 4.5 (Kg/cm ² )
If so, the intake throttle valve 18 is operated in the closing direction in step 126. In this case, the closing angle of the intake throttle valve 18 is controlled by controlling the duty ratio of the throttle valve control valve 27 according to the Pe value, and the EGR amount is controlled according to the load. On the other hand, if 4.5≦Pe<5 (Kg/cm ² ), the intake throttle valve 18 is opened in step 127. When the intake throttle valve 18 is opened, the intake negative pressure generated by the intake throttle valve 18 disappears, so the EGR amount is
It will be reduced by that amount. (iii) When 5≦Pe<6 (Kg/cm ² ) If it is determined in step 128 that Pe<6 (Kg/cm ² ), the small diameter first EGR valve 19 is “opened” in step 129. In step 130, the large diameter
2EGR valve 20 is “closed” and EGR amount is 4.5≦Pe
<5 (Kg/cm ² ), it is further reduced by one step. In this case, the intake throttle valve 18 is held in the "open" state (step 131). (iv) Case of Pe≧6 (Kg/cm ² ) In this case, the first and second EGR valves 19 and 20 are both “closed” and the intake throttle valve 18 is held “open” (step 132, 133, 134), the EGR is cut to ensure the required high output. The results of the above EGR control are shown in the table below.

【table】

[Table] As described above, in this embodiment, the first and second EGR valves 19 and 20, which control the EGR amount according to the load of the engine E, are used to warm up the engine in the normal EGR region.
During EGR, the exhaust gas has a higher temperature than EGR
can be carried out, and the combustion from a half-misfired cylinder can be carried out.
Since EGR can be avoided, warm-up EGR can be made effective, and warm-up performance can be improved and half-misfires can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 shows an engine according to an embodiment of the present invention.
EGR system configuration diagram, Figure 2 is a flowchart of EGR control. E... Engine, 1 to 4... Cylinder, 16, 17
...1st, 2nd EGR passage, 19,20...1st,
2nd EGR valve, 28...control unit, 3
1... Water temperature sensor, 32, 33... First and second exhaust temperature sensors.

Claims (1)

[Scope of Claims] 1. An engine that is provided with an exhaust recirculation passage that communicates the exhaust passage and intake passage of the engine via an exhaust recirculation valve, and that when the engine is warmed up, the exhaust recirculation valve is opened to perform exhaust recirculation. The exhaust gas recirculation device includes a plurality of exhaust gas recirculation passages that open to the exhaust passages of different cylinders, and each exhaust gas recirculation passage is equipped with an exhaust gas recirculation valve, and the temperature of the exhaust gas flowing through the exhaust passage that each exhaust recirculation passage opens is controlled. The exhaust recirculation control device is equipped with a sensor that detects a signal related to the sensor, and an exhaust recirculation control device that opens an exhaust recirculation valve interposed in an exhaust recirculation passage that opens into an exhaust passage where the exhaust gas temperature is high during engine warm-up operation according to the output of the sensor. An engine exhaust recirculation device characterized by: