JPH0874676A - Exhaust gas recirculation control device - Google Patents

Abstract

PURPOSE: To provide an exhaust has recirculation control device which can easily control the opening of an EGR valve at the start of an engine. CONSTITUTION: A diesel engine 1 has an exhaust pipe 3 and an intake pipe 2 communicated with each other by an EGR pipe 10. An EGR valve 11 is provided in the EGR pipe 10 and can be adjusted to steps of opening. An ECU 27 digitizes an EGR command, multiplies the EGR command by a correction factor determined by engine water temperature at the start of the diesel engine 1, and during the warm-up of the diesel engine 1 subtracts an amount of damping every predetermined period, the amount of damping determined by engine water temperature at the start of the engine 1. The ECU 27 controls the opening of the EGR valve 11 based on the EGR command. Also, the ECU 27 computes an EGR command after the warm-up to control the opening of the EGR valve 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exhaust gas recirculation (hereinafter referred to as EG) for recirculating a part of engine exhaust gas to an intake system.
R) for a control device.

[0002]

2. Description of the Related Art In recent years, there has been a demand for additional use of EGR in medium and large-sized diesel vehicles equipped with an exhaust brake as a measure against NO _x . E for medium and large diesel engines
Since the GR valve has a large valve diameter and has a large hysteresis and poor controllability when continuous opening control is performed, in many cases, a stepwise EGR valve or a combination of an intake throttle and an exhaust throttle is under consideration.

Further, the present EGR device is used for improving startability and acceleration of warm-up (for example, JP-A-55-139960), and at the time of starting the engine, depending on the warm-up state of the engine. There is also a need to control the opening of the EGR valve.

In this case, depending on the initial engine state, E
It is necessary to determine the opening of the GR valve and control the opening according to the elapsed time.

[0005]

However, in order to satisfy this, many EGR valve opening maps corresponding to the engine water temperature are provided, and many opening maps are operated according to the elapsed time for each initial opening. It was very complicated because I needed a time map.

Therefore, an object of the present invention is to easily control the opening degree of the EGR valve when starting the engine.
It is to provide a GR control device.

[0007]

According to a first aspect of the present invention, as shown in FIG. 9, an EGR passage M1 which connects an exhaust system and an intake system of an engine is provided, and the EGR passage M1 is provided in the middle of the EGR passage M1. , EGR valve M2 that can be adjusted in steps
And an EGR command value calculating means M3 that digitizes the EGR command value and corrects it according to the warm-up state of the engine.
An opening degree control means M4 for controlling the opening degree of the EGR valve M2 based on the EGR command value by the EGR command value calculation means M3.
An EGR control device provided with and is the gist.

According to a second aspect of the present invention, the EGR command value calculating means M in the EGR control device according to the first aspect is provided.
The correction by 3 is performed by the engine temperature when the engine is started, and the correction coefficient determined by the engine temperature is EG
The gist is an EGR control device that multiplies the R command value and subtracts the amount of attenuation determined by the engine temperature every predetermined period.

According to a third aspect of the present invention, the EGR command value calculating means M in the EGR control device according to the first aspect is provided.
3 calculates the EGR command value during warm-up and the EGR command value after warm-up, and the correction is performed on the EGR command value during warm-up.
The main point is the control device.

[0010]

According to the first aspect of the present invention, the EGR command value calculating means M3 digitizes the EGR command value, and the EGR command value is corrected according to the warm-up state of the engine. The opening degree of the EGR valve M2 is controlled based on the EGR command value by the value calculation means M3.

As described above, the EGR command value is digitized, the EGR command value is corrected according to the warm-up state of the engine, and the opening degree of the EGR valve M2 is controlled by the corrected EGR command value. Therefore, the opening degree of the EGR valve is easily controlled without using a large number of EGR opening degree maps or a large number of time maps according to the engine water temperature as in the conventional case.

According to the invention of claim 2, claim 1
In addition to the effect of the invention described in (1), EGR command value calculation means M3
The EGR command value is multiplied by a correction coefficient determined by the engine temperature when the engine is started, and the attenuation amount determined by the engine temperature is subtracted every predetermined period.

In this way, the value obtained by multiplying the EGR command value by the correction value is subtracted by the attenuation amount every predetermined period. According to the invention of claim 3, in addition to the operation of the invention of claim 1, the EGR command value calculating means M3 calculates an EGR command value during warm-up and an EGR command value after warm-up,
The correction is performed on the EGR command value during warm-up.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the EGR control device of this embodiment. An intake pipe 2 and an exhaust pipe 3 are connected to the multi-cylinder diesel engine 1. A combustion chamber 4 of the multi-cylinder diesel engine 1 communicates with an intake pipe 2 via an intake valve 5. Further, the combustion chamber 4 is connected to the exhaust pipe 3
Is in communication with An injection nozzle 7 is attached to the multi-cylinder diesel engine 1 so that fuel can be injected from the injection nozzle 7 into the combustion chamber 4.

The row-type injection pump 8 is operated in conjunction with the accelerator pedal 9 so that the control rack operates and the row-type injection pump 8 is operated.
The fuel amount corresponding to the depression amount of the accelerator pedal 9 is pressure-fed to the injection nozzle 7, and the fuel is supplied from the nozzle 7 to the engine 1.

The exhaust pipe 3 and the intake pipe 2 communicate with each other through an EGR pipe 10 which constitutes an EGR passage. This EGR tube 10
An EGR valve 11 is provided midway. EGR valve 1
Reference numeral 1 has a valve body 13 fixed to a diaphragm 12, and the valve body 13 is biased by a spring 14 toward the valve closing side. or,
The EGR valve 11 has an actuation rod 16 fixed to a diaphragm 15, and the actuation rod 16 has a spring 17 for actuating the valve body 1
It is urged in a direction away from 3 (upward in the figure).
Further, the first pressure chamber 18 partitioned by the diaphragm 15 is connected to a pressure source by a communication pipe 19, and the communication pipe 1
A first solenoid valve 20 is provided in the middle of 9. Similarly, the second pressure chamber 21 partitioned by the diaphragm 15 is connected to a pressure source by a communication pipe 22, and a second solenoid valve 23 is provided in the communication pipe 22. Then, the pressures of the first and second pressure chambers 18 and 21 are adjusted by opening and closing the first and second solenoid valves 20 and 23, so that the EGR valve 11 can be switched between fully closed, half opened, and fully opened. It has become.

That is, by closing both solenoid valves 20 and 23 together, the valve element 13 is moved upward by the biasing force of the spring 14 and the EGR valve 11 is fully closed. When the first solenoid valve 20 is opened and the second solenoid valve 23 is closed, the first pressure chamber 18 becomes a high pressure and the operating rod 16 moves downward to move the valve body 13 against the biasing force of the spring 14. The EGR valve 11 is half open. Further, by opening the second electromagnetic valve 23 and opening (or closing) the first electromagnetic valve 20, the second pressure chamber 21 becomes high pressure and the valve body 13 moves downward against the biasing force of the spring 14. EGR valve 1
1 is fully open.

As described above, the opening of the EGR valve 11 can be adjusted in two steps. Multi-cylinder diesel engine 1
A water temperature sensor 24 for detecting the temperature of the engine cooling water is attached to the. The temperature of the engine cooling water corresponds to the engine temperature. A rack position sensor 25 that detects the position of a control rack (injection amount control member) is attached to the row-type injection pump 8. Further, the camshaft of the row-type injection pump 8 is drivingly connected to the crankshaft of the engine 1. The row-type injection pump 8 has the camshaft (crankshaft of the engine 1) rotation speed, that is, the engine rotation speed. Rotation speed sensor 26 for detection
Is provided.

An electronic control unit (hereinafter referred to as an ECU) 27 as EGR command value calculating means and opening control means 27
The rack position sensor 25 of the injection pump 8, the rotation speed sensor 26, and the water temperature sensor 24 of the engine 1 are connected to the
The ECU 27 inputs signals from these sensors to detect the rack position R of the injection pump 8, the engine speed Ne, and the engine cooling water temperature THW. Further, the ECU 27 inputs a starter signal (STA) to detect the drive of the starter.

Further, the ECU 27 is connected to the first and second solenoid valves 20 and 23, and the first and second solenoid valves are provided on the basis of the signals from the sensors 24, 25 and 26 and the starter signal.
The solenoid valves 20, 23 are opened and closed to control the opening degree of the EGR valve 11.

Next, the operation of the EGR valve control device constructed as described above will be described. FIG. 2 shows a process (flow chart) executed by the ECU 27. This routine is started every predetermined time. This process will be described with reference to the timing chart shown in FIG.

In step 101, the ECU 27 determines the engine speed Ne, the rack position R, the water temperature THW, and the starter signal S.
Take in engine parameters such as TA. And EC
U27 determines in step 102 whether or not the water temperature THW has become 80 ° C. or higher, and if the water temperature THW is less than 80 ° C., it is determined that the warm-up has not been performed and the process proceeds to step 103. ECU2
In step 103, the starter signal STA determines in step 103 whether or not the engine is starting. When the starter signal STA is ON (see FIG. 8).
Before t1), the steps 104, 105,
The processing of 106 and 107 is executed. In step 104, the correction coefficient K according to the water temperature THW is set using the map shown in FIG. 3, and in step 105, the attenuation amount dE according to the water temperature THW is set using the map shown in FIG. In step 106, the EGR command value EG during warming up according to the engine speed Ne and the rack position R is used using the map shown in FIG.
Calculate RC. In step 107, step 104
The correction coefficient K calculated in step 106 is multiplied and corrected by the EGR command value EGRC during warming up calculated in step 106, and the value is set as the EGR command value (count value) C _EGR , and the step 10
Go to 8. However, the EGR command value (count value) C
_EGR is a value of "256" or less.

In step 108, the ECU 27 determines the electromagnetic valve command value for the count value which is the EGR command value C _EGR using the map shown in FIG. 7 and sets it in the output stage. That is, when (1) the EGR command value C _EGR is “0”, the first
The solenoid valve 20 is closed and the second solenoid valve 23 is closed.
(2) When the EGR command value _CEGR is "1" to "128", the first solenoid valve 20 is opened and the second solenoid valve 23 is closed. (3) EGR command value _CEGR is "129" to "2"
At 56 ", the first solenoid valve 20 is opened (or closed) and the second solenoid valve 23 is opened. Here, when the engine is started, the engine water temperature THW and the engine speed Ne are low, and the rack position R is on the small injection amount side.
The GR command value _CEGR is in the range of "129" to "256", and the first solenoid valve 20 is opened (or closed) and the second solenoid valve 23 is opened. As a result, the EGR valve 11 is fully opened and the EGR flow rate is maximized.

At step 108, the EG
A solenoid valve command value setting means for replacing the R command value _CEGR with the solenoid valve command value is configured. Before timing t1 in FIG. 8, steps 101 to 108 in FIG. 2 are repeated.

As described above, the starter signal ON is used to determine that the engine 1 is in the starting state, and at the time of starting, the EGR command value EG corresponding to the engine speed Ne and the rack position R is set.
The EGR command value C _EGR is set by multiplying the correction coefficient K determined by RC and the engine water temperature THW.

On the other hand, when the ECU 27 determines in step 103 that the engine is warming up after the starter is turned off (timing t1 in FIG. 8), it is determined in step 109 whether the EGR command value C _EGR is larger than "0". Determine whether it is "0"
If it is larger, the previous EGR command value C is determined in step 110.
_The attenuation amount dE calculated in step 105 is subtracted from _EGR, and the process proceeds to step 108. Like this step 1
In the process of 10, the attenuation amount d is _calculated from the previous EGR command value C _EGR.
The value obtained by subtracting E becomes the EGR command value C _{EGR of} this time.

Here, in the process of step 106, EGR during warming up from the engine speed Ne and the rack position R is performed.
Warm-up EGR command value calculation means for calculating the command value is configured. Further, the processing of step 104 constitutes a correction coefficient calculating means for calculating the correction coefficient K of the EGR command value according to the starting water temperature THW. In addition, step 1
In the processing of 05, the attenuation amount setting means for setting the attenuation amount of the EGR command value according to the starting water temperature THW is configured. Further, the processing of step 107 constitutes an EGR command value correcting means for correcting the EGR command value with the correction coefficient K. Further, the processing of step 110 constitutes EGR command value attenuating means for subtracting the amount of attenuation from the EGR command value corrected by the correction coefficient K.

During the period from t1 to t2 in FIG.
Steps 101 → 102 → 103 → 109 → 110 →
108 → 101 ... is repeated. At this time, while maintaining the EGR valve 11 in the fully open state (the maximum EGR flow rate), E
The GR command value C _EGR is subtracted by the attenuation amount dE.

When the EGR command value C _EGR becomes "128" or less in step 108 (timing t2 in FIG. 8), the first solenoid valve 20 is opened and the second solenoid valve 23 is closed in FIG. As a result, the EGR valve 11
Is half open, and the EGR flow rate is also halved.

Even during the period from t2 to t3 in FIG.
Steps 101 → 102 → 103 → 109 → 110 →
108 → 101 ... is repeated. At this time, the EGR command value C _EGR is subtracted by the attenuation amount dE while the EGR valve 11 is maintained in the half-open state (the EGR flow rate is half the maximum amount).

As described above, after the shift to the non-starting state, that is, during warm-up, the attenuation amount dE determined by the starting-time water temperature THW is subtracted,
EGR command value C _EGR Further, the subtraction is continued until the EGR command value C _EGR after the subtraction becomes “0”.

Further, when the EGR command value C _EGR becomes "0" or less in step 109 (timing t3 in FIG. 8), the ECU 27 determines in step 111 the EGR command value C
_{The EGR} command value C _{EGR is set} to “0” so that the EGR does not become a negative value. After that, the ECU 27 proceeds to step 108. Since C _EGR = 0 at this time, the first solenoid valve 20 is closed and the second solenoid valve 23 is closed. As a result, the EGR valve 11 is fully closed and the EGR flow rate is also "0".

During the period from t3 to t4 in FIG.
Steps 101 → 102 → 103 → 109 → 111 →
108 → 101 ... is repeated. At this time, the EGR command value _CEGR is guarded at "0", and the EGR valve 11 is maintained in the fully closed state (EGR flow rate is "0").

On the other hand, when the water temperature THW becomes 80 ° C. or higher in step 102 (timing t4 in FIG. 8), the ECU 27 shifts to step 112 after warming up and proceeds to FIG.
The EGR command value EGRH after warm-up, which is determined from the engine speed Ne and the rack position R, is calculated using the map of 1).

Here, in the process of step 112, EGR after warming up from the engine speed Ne and the rack position R is performed.
A post-warm EGR command value calculation means for calculating a command value is configured.

Further, the ECU 27 sets the EGR command value EGRH after warming up to the EGR command value C _{EGR in} step 113, and proceeds to step 108. In step 108, if the EGR command value C _EGR is “129” or more at this time, the first solenoid valve 20 is opened (or closed) and the second solenoid valve 23 is opened. As a result, the EGR valve 11 is fully opened and the EGR flow rate is maximized.

In step 102, the engine water temperature THW is used to determine whether the engine is warming up or after warming up. During warming up, the EGR command value at step 110 is used, and after warming up, step 1 is performed.
EGR command value switching means for switching to the EGR command value in 13 is configured.

After the warm-up after t4 in FIG.
Steps 101 → 102 → 112 → 113 → 108 →
Repeat 101 ... Thus, the engine water temperature T
When the HW rises and becomes equal to or higher than the warm-up determination temperature of 80 ° C., the EGR command value EGRH after warming
Control as _EGR .

As described above, in this embodiment, the command value of the EGR valve 11 is set to the continuous count value C _EGR , the count value is set according to the engine speed Ne and the rack position R, and the water temperature THW and the elapsed time are set. According to the correction, the count value is converted into the opening command at the output stage. That is, the EGR command value is converted into a numerical value, correction is made according to the warm-up state of the engine, and the opening degree of the EGR valve 11 is controlled based on the EGR command value C _EGR . Therefore, EGR can be easily performed without using many EGR opening degree maps and many time maps according to the engine water temperature as in the conventional case.
The opening degree of the valve 11 can be controlled. Further, it is possible to easily bring the EGR valve 11 which can be adjusted to a stepwise opening close to a control close to continuous, and at the same time construct a system with improved controllability and control flexibility.

Further, the EGR command value is multiplied by the correction coefficient K determined by the engine water temperature at the time of starting the engine 1, and the attenuation amount dE determined by the water temperature is subtracted every predetermined period, so that an appropriate correction is performed. be able to.

The present invention is not limited to the above embodiment. For example, although the load is detected at the rack position in the above embodiment, the accelerator opening or the nozzle opening period may be used.

In the above embodiment, the opening of the EGR valve 11 has two stages of half-opening and full-opening, but it may be performed in two or more stages.

[0043]

As described in detail above, according to the inventions described in claims 1 and 3, the excellent effect that the opening degree of the EGR valve can be easily controlled at the time of engine starting is exhibited.

According to the invention of claim 2, claim 1
In addition to the effects of the invention described in (1), appropriate correction can be performed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an EGR control device according to an embodiment.

FIG. 2 is a flowchart for explaining the operation.

FIG. 3 is a map for calculating a correction coefficient according to the cooling water temperature.

FIG. 4 is a map for calculating an attenuation amount according to a cooling water temperature.

[Fig. 5] EG during warm-up from engine speed and rack position
It is a map for calculating an R command value.

[Fig. 6] EG after warm-up from engine speed and rack position
It is a map for calculating an R command value.

FIG. 7 is an explanatory diagram showing correspondence between an EGR command value, a solenoid valve state, and an EGR flow rate.

FIG. 8 is a timing chart showing operation timings for explaining the operation.

FIG. 9 is a claim correspondence diagram.

[Explanation of symbols]

1 ... Diesel engine, 2 ... Intake pipe, 3 ... Exhaust pipe, 1
0 ... EGR pipe forming EGR passage, 11 ... EGR valve,
27 ... ECU as EGR command value calculating means and opening control means

Claims (3)

[Claims] 1. An EGR passage that connects an exhaust system and an intake system of an engine, an EGR valve that is provided in the middle of the EGR passage and that can adjust the opening degree stepwise, and digitizes an EGR command value. In addition, EGR command value calculating means for making a correction according to the warm-up state of the engine and opening control means for controlling the opening of the EGR valve based on the EGR command value by the EGR command value calculating means are provided. A characteristic exhaust gas recirculation control device. 2. The correction by the EGR command value calculating means is performed by the engine temperature at the time of starting the engine, the EGR command value is multiplied by a correction coefficient determined by the engine temperature, and the attenuation amount determined by the engine temperature is predetermined. The exhaust gas recirculation control device according to claim 1, wherein the exhaust gas recirculation control device subtracts each period. 3. The EGR command value calculation means is set to E during warm-up.
The exhaust gas recirculation control device according to claim 1, wherein the GR command value and the EGR command value after warm-up are calculated, and the correction is performed on the EGR command value during warm-up.