JPS6135372B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention stores the EGR amount in the form of the output value of the displacement detector of the EGR valve for each operating condition, and uses a displacement detector that actually measures the stored displacement detector output value while the engine is running. Concerning a computer-controlled exhaust gas recirculation system that is programmed to match output values. Recently, in the exhaust gas recirculation system of internal combustion engines,
In order to perform ideal EGR amount control, the EGR amount determined by the engine operating conditions, especially the load, is stored in a memory circuit in the form of some parameter, and the EGR amount corresponding to the load can be obtained during actual operation. Computer-controlled EGR systems have appeared that allow for An example of such a system is
The output value of the EGR valve displacement detector is stored for each combination of intake air amount and engine rotation speed that represent the engine load, and the intake air amount and engine rotation speed are measured during actual operation. Some devices are programmed to read a detector output value corresponding to the displacement detector, and to match this read value with the actually measured displacement detector output value. Since the output value of the EGR valve displacement detector immediately corresponds to the EGR amount, the EGR amount can be controlled according to the engine load, resulting in an ideal
EGR effect can be obtained. By the way, this displacement detector is normally a potentiometer that outputs an electric signal according to the position of the valve stem of the EGR valve.
It works to divide the voltage applied across the potentiometer over the EGR rate range from 0% EGR rate without EGR operation to the maximum EGR rate. By the way, in this case, since the EGR amount is expressed as a difference with respect to the reference voltage of EGR zero, that is, the zero point, it is necessary to adjust the reference voltage at the time of manufacture so that it is always constant in order to obtain an accurate EGR amount. However, such adjustment during the manufacturing process causes complexity, and the reference voltage fluctuates with continued use, so it is not possible to
It is also necessary to perform maintenance so that the zero point of the displacement detector remains constant during EGR, that is, when the EGR valve is closed. The purpose of the present invention is to provide a novel computer-controlled EGR system that eliminates the need for zero point adjustment of the displacement detector, thereby reducing system costs.
The purpose is to provide an EGR control method. In FIG. 1, 10 is an engine body of an internal combustion engine, into which air-fuel mixture is introduced from an intake pipe 14 into a combustion chamber 12, and exhaust gas as a result of combustion flows into an exhaust chamber 16.
taken out. Reference numeral 18 denotes an EGR passage connecting the exhaust pipe 16 to the intake pipe 14, and there is a valve device on this passage 18 for controlling the flow rate of recirculated exhaust gas flowing therethrough.
An EGR valve 20 is provided. This EGR valve 20 is a negative pressure operated type having a valve body 22 facing a valve seat 24 and connected to a diaphragm 28 by a valve stem 26. A negative pressure chamber 30 is formed on the side surface of the diaphragm 28 opposite to the valve body 22, and the diaphragm 28 is inserted into the negative pressure chamber 3.
A spring 32 is arranged to bias the valve body 22 away from the valve seat 24, ie, to open and close. Therefore, depending on the negative pressure level in the chamber 30, the valve body 22 and the valve seat 2
The position relative to 4 changes and the EGR amount is controlled.
In order to control the negative pressure level in the negative pressure chamber 30, this chamber is connected to a negative pressure port 42 bored in the intake pipe 14 via a passage 36, a throttle 81, a negative pressure on/off valve 38, and a passage 40. , a passage 44, a throttle 82, and an atmosphere opening/closing valve 46 communicate with the atmosphere. Both the negative pressure on-off valve 38 and the atmospheric on-off valve 46 are electromagnetic valves having two ports a and b, and when in the open position, ports a and b are electrically connected, and when in the closed position, the ports a and b are electrically connected. and b are separated. There are three combinations of operation of these two valves 38 and 46 as shown in the table below. That is,

[Table] In state A, the chamber 30 of the EGR valve 20 is separated from the negative pressure port and communicated with the atmospheric pipe 48 through the throttle 82. Therefore, the chamber 30 gradually becomes atmospheric pressure, and the spring 32 pushes the diaphragm 28 to the left so that the valve body 22 moves away from the valve seat 24. As a result, the EGR amount is controlled to increase. In the state shown in (b), the chamber 30 of the EGR valve 20 is isolated from both the negative pressure source and the atmospheric pressure source. Therefore, the pressure in the chamber 30 does not change and the valve body 22 does not move relative to the valve seat 24. Thus, the amount of EGR neither increases nor decreases. In state C, the chamber 30 of the EGR valve 20 is separated from the atmospheric pipe 48 and communicates with the negative pressure port 42 through the throttle 81. Therefore, the diaphragm 28 is pulled to the right against the spring 32, and the valve body 22 moves toward the valve seat 24.
The EGR amount is controlled in a decreasing direction. The EGR valve 20 is equipped with a displacement detector 50.
This displacement detector 50 is a potentiometer driven by the valve stem 26, and outputs a voltage corresponding to the opening amount between the valve body 22 and the valve seat 24, in other words, the EGR amount. That is, as shown in FIG. 2, the displacement detector 50 is a variable resistor R, the movable part of which moves together with the valve stem 26. Therefore, a voltage obtained by dividing the power supply voltage appears at the output terminal. That is,
If the position of the solid line 26' in the figure is the zero point where the valve body 22 is seated on the valve seat 24 and EGR is not performed, then
When the valve body 22 undergoing EGR is away from the valve seat 24, the movable part of the variable resistor R is positioned as shown by the broken line, and the voltage appearing at its output terminal changes. In this way, it is possible to obtain an output according to the amount of EGR. An intake air amount sensor 52, an engine rotation speed sensor 54, and a vehicle speed sensor 56 are provided to detect engine operating conditions. 58 is a control computer which opens and closes negative pressure in response to signals from the displacement detector 50 of the EGR valve 20, as well as signals from the intake air amount sensor 52, rotation speed sensor 54, and vehicle speed sensor 56 for detecting operating conditions. It works to drive the valve 38 and the atmospheric opening/closing valve 46. The throttles 81 and 82 each represent the opening speed of the EGR valve.
Determine the valve closing speed. Incidentally, since the configuration of the computer 58 itself is well known, it will not be described in detail. The basic concept of EGR control by the computer 58 is as follows. As described above, the output voltage of the potentiometer R of the displacement detector 50 is taken as a numerical value representing the EGR amount. This output voltage value corresponding to the EGR amount is experimentally determined in advance for each engine negative pressure determined by the combination of the intake air amount Ga and the engine rotational speed N, and the result is stored in the memory. During operation of the engine, electrical signals representing Ga and N are input to the computer 58 from the intake air amount sensor 52 and the rotational speed sensor 54, respectively.
Then, the computer 58 outputs one output value of the displacement detector corresponding to one combination of Ga and N.
Read the EGR amount. On the other hand, the computer 58 receives an output value indicating the actually measured EGR amount from the displacement detector 50. Therefore, computer 58
is the read displacement detector output value and the measured 〓〓〓〓
The negative pressure on/off valve 38 and the atmosphere on/off valve 46 are driven so that they match.
As a result, the EGR amount can be matched to the engine load. The basic principle of computer control of EGR in the present invention is as described above, but one of the conventional problems is that zero point adjustment of the displacement detector was required during manufacturing or maintenance. This is because, as mentioned immediately with reference to FIG. 2, displacement detection is performed using a potentiometer, and the EGR is measured at its zero point, that is, the voltage difference with respect to the reference voltage when the valve body 22 is seated on the valve seat 24.
Although this represents a quantity, this reference voltage cannot be kept constant as assembled due to tolerances of the parts. In the present invention, in order to eliminate the need for such adjustment, the valve body 22 where EGR operation is not performed is connected to the valve seat 22.
The computer 58 is programmed to store the output value of the displacement detector 50 when the driver is seated on the vehicle and use this as the zero point at the start of EGR. The method of the present invention employing such a principle will be explained below with reference to the flowchart of FIG. When the engine starts operating, the computer first determines whether EGR is being performed in step 62 by detecting, for example, whether the vehicle speed V is greater than 5 km/h. If “NO”, that is, it is determined that EGR is not being performed, the displacement detector 5
Read the output value Lreal from 0 and set it as Lo and store it in the memory. Next, in step 66, the negative pressure on/off valve 38 is opened and the atmospheric air on/off valve 46 is closed. Then, the valve body 22 moves in the direction of the valve seat 24, as explained in ○C in the previous table. Next, in step 68, the process returns to step 62 and repeats the same process, so that the valve body 22 is finally seated on the valve seat 24. Therefore, the value of Lo obtained in step 64 corresponds to the position of the valve stem 26 when the EGR valve 20 is fully closed, and this is the zero point. Next, when the vehicle is driving at a speed of 5 km/h or higher and EGR is performed, the determination result in step 62 becomes "YES" and step 70 is entered. Here, the difference Lc between the actually measured output value Lreal of the displacement detector 50 and the aforementioned Lo is calculated.
Since Lo is the output value of the potentiometer 50 when the EGR valve 20 is fully closed as described above, it is the differential voltage with respect to this. This means that Lc accurately represents the amount of EGR. In the next step 71, one displacement detector output value is determined for one combination of the intake air amount Ga and the engine rotation speed N detected by the sensors 54 and 56.
Read Lref from memory. In step 72, it is determined whether the actually measured output value Lc is larger than the read value Lref. If the answer is "NO", it means that the actual EGR amount, ie, Lc, is smaller than the set EGR amount Lref. In this case, in step 74, it is determined whether Lref - Lc is larger than the control dead width Ld. . This result is “YES”
If so, it is necessary to increase the EGR amount, so in step 76 the negative pressure on/off valve 38 is closed, and the atmospheric on/off valve 4 is closed.
6, that is, the state of ○A in the previous table. As a result, the valve body 22 moves away from the valve seat 24.
EGR amount increases. Judgment at step 74 is “NO”
In other words, the set EGR amount, or Lref, and the measured EGR amount, or Lc.
If the difference between the two valves 38 and 46 is not large enough to require control, step 78 is entered, where the two valves 38 and 46 are both closed, as shown in Table ○B, and as a result, the valve body 22 does not move. . In this way, the control dead width Ld
Here, preferable control is possible by providing an EGR valve and holding the EGR valve. The judgment at step 72 is “YES”, that is, the actual
If the EGR amount is greater than the set EGR amount,
First, in step 80, the process is similar to step 74 described above.
It is determined whether the difference in EGR amount is larger than the control dead width Ld. If this is "NO", there is no need to control the EGR amount, so in step 78, both the negative pressure on-off valve 36 and the atmosphere on-off valve 46 are kept closed as shown in the above table. If the judgment in step 80 is "YES", the measured EGR amount, ie, Lc, is too larger than the set EGR amount, ie, Lref, so in step 66, the on-off valves 38 and 46 are switched to the state of ○C to reduce the EGR amount. urge As described above, in the EGR control method of the present invention, the output value of the displacement detector 50 during non-EGR, that is, Lo is stored, and the difference Lc between this and the output value Lreal of the displacement detector during EGR is calculated. Therefore, accurate EGR control can be performed without adjusting the zero point of the displacement detector 50. This is an advantage in terms of manufacturing and maintenance costs.

[Brief explanation of the drawing]

Figure 1 is an overall schematic diagram of the computer-controlled EGR system of the present invention, Figure 2 is a principle diagram of the displacement detector, and Figure 3 is a diagram of the principle of the displacement detector.
〓〓〓〓
The figure is a flowchart showing the method of the present invention. 20...EGR valve, 50...displacement detector, 58...calculator. 〓〓〓〓

Claims (1)

[Claims] 1 The displacement detector output value of the EGR valve is stored for each operating condition of the internal combustion engine, and while the engine is running, one stored displacement detector output value Lref corresponding to that operating condition is read out. In an exhaust gas recirculation control method that opens and closes an EGR valve based on a value Lref and an actually measured displacement detector output value Lreal,
The EGR valve displacement detector output value Lo actually measured during non-EGR operation is stored, and the difference Lreal−Lo obtained by subtracting this stored value Lo from the displacement detector output value Lreal actually measured during EGR operation is calculated as the difference Lreal−Lo. An exhaust gas recirculation control method characterized by opening and closing an EGR valve depending on the magnitude of a displacement detector output value Lref.