JPH0345229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an EGR control device for an engine.

[Prior art]

Generally, an engine EGR control device lowers the combustion temperature of the engine by recirculating a portion of the exhaust gas to the intake side, thereby reducing NOx in the exhaust gas. In this way, the engine
Since EGR control is closely related to the fuel supply system, the amount of recirculation of exhaust gas must be controlled accurately and quickly according to the operating state of the engine.

However, changing the above-mentioned recirculation amount of exhaust gas inevitably changes the torque generated by the engine, especially when the above-mentioned target recirculation amount of exhaust gas is zero (hereinafter referred to as EGR-OFF). and the above target reflux amount is different from zero (hereinafter referred to as
When transitioning from one state (referred to as EGR-ON) to the other state, if the above-mentioned recirculation amount of exhaust gas is varied greatly and in a short period of time, large torque fluctuations will occur.
If the transition from EGR-OFF to EGR-ON is performed as described above, a large amount of exhaust gas will recirculate within a short period of time, inhibiting the intake of the air-fuel mixture, and a large amount of exhaust gas will be sucked into the cylinder, resulting in an extremely large amount of exhaust gas. Large torque fluctuations occur, but in conventional engine EGR control systems, sufficient consideration has not been given to the above-mentioned transient state, and therefore the EGR-ON to EGR-ON
During transition from OFF or EGR-OFF to EGR-ON,
There was a problem in that a large shock occurred when the change in the target recirculation amount was large.

[Purpose of the invention]

In view of such conventional problems, this invention
From EGR-ON to EGR-OFF or from EGR-OFF
It is an object of the present invention to provide an engine EGR control device that causes less shock even during transition to EGR-ON.

[Structure of the invention]

Therefore, as shown in the functional block diagram of FIG. 1, the present invention provides an engine EGR control system that
Based on the target recirculation amount of exhaust gas according to the operating state of the engine calculated by the target recirculation amount calculation means 31 and the recirculation amount of exhaust gas detected by the recirculation amount detection means 9, the control means 32 calculates a manipulated variable and drives the exhaust gas recirculation adjusting means 33 with the manipulated variable so that the recirculation amount becomes the target recirculation amount, and also adjusts the deviation according to the deviation between the target recirculation amount and the recirculation amount. The larger the amount, the more slowly the recirculation amount is driven to approach the target recirculation amount.

〔Example〕

Examples of the present invention will be described below.

FIG. 2 shows an engine according to an embodiment of the present invention.
Shows EGR control device. In the figure, 1 is an engine, and an exhaust passage 3 of the engine 1 is provided with a recirculation passage 4 for recirculating exhaust gas, and the recirculation passage 4 is provided with an adjustment valve 5 for adjusting the area of the passage. It is arranged. The regulating valve 5 is provided with a diaphragm device 6 for driving it, and the diaphragm device 6 is provided with a negative pressure introduction passage 7 that communicates the negative pressure chamber with the intake passage 2. A three-way valve 8 that switches between introducing negative pressure and introducing atmospheric pressure is interposed in the middle. Further, the diaphragm device 6 is provided with a position sensor 9 for detecting the position of the regulating valve 5.

In the figure, 10 is a negative pressure sensor that detects the negative pressure in the intake passage 2, 11 is a water temperature sensor that detects the temperature of cooling water, 12 is a crank angle sensor that detects the rotation angle of the crankshaft, and 13 is a gear but
This is a top position signal that becomes "1" when operated to the TOP position.

Furthermore, 14 is an input/output interface 15,
It is a control unit composed of a CPU 16 and a memory 17, and the memory 17 includes
In addition to the arithmetic processing program of the CPU 16, a map of the above target recirculation amount of exhaust gas according to the operating state of the engine, from EGR-ON to EGR-OFF or EGR-
Data and the like are stored that determine how slowly the recirculation amount is brought closer to the target recirculation amount during the transition from OFF to EGR-ON. Also the above CPU
16 is each sensor and switch signal 9,1 mentioned above.
The outputs of 0, 11, 12, and 13 are read through the input/output interface 15, and based on this information, the target recirculation amount is determined according to the operating state of the engine, and whether EGR-ON or EGR-OFF is selected.
The EGR mode is set, and if the EGR mode is not in transition, the operation amount is calculated based on the target recirculation amount and the recirculation amount so that the recirculation amount becomes the target recirculation amount. Sometimes, depending on the deviation between the target reflux amount and the reflux amount, the larger the deviation, the more slowly the operation amount is calculated so that the reflux amount becomes the target reflux amount. A control signal is applied to the three-way valve 8 via the interface 15 to perform feedback control.

In addition, in the above configuration, the CPU 16 functions as the target recirculation amount calculation means 31 and the control means 3 shown in FIG.
The recirculation passage 4, the regulating valve 5, the diaphragm device 6, the negative pressure introduction passage 7, and the three-way valve 8 constitute the exhaust gas recirculation adjustment means 33 shown in FIG. , the position sensor 9 serves as the reflux amount detection means shown in FIG.

In this embodiment, as is clear from FIG. 2, the pressure in the negative pressure chamber of the diaphragm device 6 is controlled by controlling the three-way valve 8, and the pressure in the reflux passage 4 is The recirculation amount of exhaust gas is adjusted by changing the cross-sectional area of the regulator valve 5, and the position of the regulator valve 5 (hereinafter referred to as lift position) is detected by a position sensor 9 that moves in conjunction with the regulator valve 5. The exhaust gas recirculation amount is indirectly detected. Therefore, in this embodiment, the recirculation amount is given as the lift position of the regulating valve 5, and the target recirculation amount is given as the position to which the regulating valve 5 should aim (hereinafter referred to as the target lift position), and is stored in the memory. The data of the target lift position is set in the target recirculation amount map No. 17.

Next, the operation will be explained in detail using FIGS. 3 and 4. Here, FIG. 3 is a flowchart of EGR control by the CPU 16.

The CPU 16 first initializes the registers in the CPU 16 (step 18), and then reads each sensor and switch signal 9 to 13 as input information via the interface 15 (step 19).
Based on the input information, a target lift position Po that provides a target recirculation amount according to the operating state of the engine is read from the memory 17 (step 20). Step 21
Then, depending on whether the above target lift position Po is 0 or not, EGR-OFF or EGR-ON is selected.
Set the EGR mode, compare the EGR mode set last time and the EGR mode set this time, and check the EGR
Determine whether the mode has changed (step 22),
If there is no transition to EGR mode, do nothing and proceed to step
The process proceeds to step 24, but if there is a transition, the coefficient α is initialized to 0 (step 23). In step 24, the target lift position Po and the lift position P read in step 19 are calculated from the memory 17 based on the difference |Po−P|
Read the increment Δα of the coefficient α that determines the degree of slowness when transitioning to EGR mode (step 24), update the coefficient α by adding the increment Δα (step 25), and increase the coefficient α by Δα. As a result, it is determined whether the coefficient α exceeds 1 or 0 (step 26). If the coefficient α does not exceed 1 or 0, nothing is done and the process proceeds to step 28, but if it exceeds 1 or 0, the process proceeds to step 28. The coefficient α is set to 1 and 0 (step 27). In step 28, the temporary target lift position Po' is updated according to the difference equation given by Po'(k)=αPo(k)+(1-α)Po'(k-1)-(1). Step 28), calculates the operation amount MA based on the difference between this temporary target lift position Po' and the lift position P (Step 29), and calculates the operation amount MA.
A corresponding control signal is output to the three-way valve 8 via the interface 15 (step 30), and step 19
Return to

According to the above procedure, after the EGR mode changes and a predetermined time has elapsed, that is, if there is no transient state, the coefficient α becomes 1 and 0, and is calculated by equation (1). Since the tentative target lift position Po' matches the true target lift position Po calculated according to the operating state of the engine, the above lift position P, which gives the amount of recirculation of exhaust gas, gives the target amount of recirculation of exhaust gas. It is controlled to be the target lift position Po, but if the EGR mode changes, the coefficient α is set to 0 at the time of the change, so this coefficient α is successively increased until it reaches 1 and then 0 (1 ) The temporary target lift position Po′ calculated by the formula does not match the true target lift position Po. During this time, the above lift position P is a temporary target lift position Po′ that is different from the true target lift position Po. Therefore, the recirculation amount of exhaust gas does not become the target recirculation amount, but as the coefficient α approaches 1 or 0, the recirculation amount approaches the target recirculation amount. However, as shown in FIG. 4, the increment Δα of the coefficient α is set to become smaller as the deviation |Po−P| becomes larger.
The above deviation in the transient state where the EGR mode has changed｜Po
The larger −P| is, the more slowly the recirculation amount approaches the target flow rate.

In the device of this embodiment as described above, when changing the EGR mode, the larger the deviation between the exhaust gas recirculation amount and the target recirculation amount, the more slowly the recirculation amount approaches the target recirculation amount. Shocks caused by engine torque fluctuations when changing modes can be minimized.

The control according to the present invention described above is effective when the deviation between the target reflux amount and the actual reflux amount is relatively large, so it should be applied only when the deviation is greater than a predetermined value. It's okay.

〔Effect of the invention〕

As described above, according to the present invention, in the EGR control device, the larger the deviation of the exhaust gas recirculation amount from the target recirculation amount, the more slowly the recirculation amount approaches the target recirculation amount. This has the effect of minimizing shocks caused by engine torque fluctuations when there is a large change in flow rate.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
FIG. 2 shows an engine according to an embodiment of the present invention.
FIG. 3 is a block diagram of the EGR control device, FIG. 3 is a flowchart of arithmetic processing by the CPU 16 in the device, and FIG. 4 is a diagram showing the slowness of response when changing the EGR mode in the device. 1... Engine, 9... Reflux amount detection means, 31
...Target reflux amount calculation means, 32...Control means, 3
3...Exhaust gas recirculation adjustment means, 16...CPU.

Claims (1)

[Claims] 1 Exhaust gas recirculation adjustment means for adjusting the amount of exhaust gas recirculation, target recirculation amount calculation means for calculating the amount of recirculation of exhaust gas according to the operating state of the engine, and recirculation amount detection means for detecting the amount of recirculation of exhaust gas. Then, a manipulated variable is calculated so that the actual recirculation amount detected by the recirculation amount detection means becomes the target recirculation amount calculated by the target recirculation amount calculation means, and the exhaust gas recirculation adjustment is performed using the manipulated variable. In an EGR control device having a control means for driving a device, when the target reflux amount changes, the larger the deviation, the smaller the amount per time, depending on the deviation between the target reflux amount and the actual reflux amount. An EGR control device for an engine, characterized in that the amount of change starts changing the actual recirculation amount to approach the target recirculation amount, and then gradually increases the amount of change per time.