WO2002014676A1

WO2002014676A1 - Method of controlling exhaust recirculation valve

Info

Publication number: WO2002014676A1
Application number: PCT/JP2000/005480
Authority: WO
Inventors: Satoshi Kawamura; Sotsuo Miyoshi; Toshihiko Miyake; Youichi Fujita
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2000-08-16
Filing date: 2000-08-16
Publication date: 2002-02-21
Also published as: JP4480938B2

Abstract

A motor for driving an exhaust recirculation valve of an exhaust recirculation system undergoes binary control when either the difference between a target value and the actual value or a function defined by the difference and the valve operating speed is large beyond a predetermined range. When the difference or the function is small within the range, on the other hand, the drive motor undergoes PI control. As a result, response and control are stabilized.

Description

Description Control method of exhaust gas recirculating pulp Technical field

The present invention relates to an exhaust gas recirculation system provided in an exhaust gas recirculation system.

EGR (ExhaustGasRecirculationi)). This relates to a valve control device. Background art

FIG. 1 is a configuration diagram in which a control valve 11 of an EGR valve is disposed in an exhaust gas recirculation passage c that connects an exhaust passage a and an intake passage b of an engine E. The control device of the EGR valve includes, for example, an engine controller unit (hereinafter referred to as an ECU) 51 that drives and controls a stepping motor M such as a hybrid PM type four-phase motor. The opening and closing of the control valve 11 is adjusted by performing open-loop control of the stepping motor M in increments of step angles.

By the way, such a control method using the stepping motor M can control the opening of the control valve 11 only in the unit of the step angle of the stepping motor M. Had a limited resolution. In the open-loop control of the stepping motor M, the step-out phenomenon may occur, which limits the responsiveness. There was a problem that the sex deteriorated.

Therefore, the conventional method of controlling an EGR valve uses a control valve 11 A predetermined return torque is applied in the opening or closing direction of 1 and the control valve 11 can be changed in the closing or opening direction by energizing one direction of the DC motor M (hereinafter referred to as "M"). The control valve 11 is opened and closed by applying a torque to the motor and the torque balance of the motor. A feedback control system that performs PID control of the motor based on the deviation of the motor, and an I-gain clear means of the feedback control system when the deviation falls within a predetermined allowable range. For example, it is described in Japanese Patent Application Laid-Open No. Hei 10-222609.

The method of driving the EGR valve using such a motor adopts a so-called torque balance method, in which a predetermined return torque is applied in the closing direction by a spring as a biasing means, and the motor is opened by driving the motor in the opening direction. A variable motor torque is applied in the direction, and opening and closing control is attempted by the torque balance.

In such a driving method, since the return torque is always applied to the EGR valve, the opening / closing position ( Shift amount).

Here, line A is the operating characteristic when the control valve 11 is opened by increasing the motor torque, and line B is the operating characteristic when the control valve 11 is closed by decreasing the motor torque, and the return torque is given. The inclination of the operating characteristics A and B changes according to the spring constant of the spring, and the operating characteristics A and B shift right and left in Fig. 2 depending on the magnitude of the set torque.

Now, in order to control the control valve 11 having such operating characteristics, it is necessary to simply calculate the deviation between input data corresponding to the target opening / closing position of the control valve 11 and detection data of the current opening / closing position of the control valve. P (proportional), I (integral) It is assumed that the control method is adopted. In this case, it becomes difficult to stabilize the control valve 11 at the target opening position in relation to the operation characteristics as shown in FIG.

That is, in order to increase the motor torque and open the control valve 11 to the target opening position, the P (proportional) gain and the I (integral) gain are required to execute the control along the operating characteristic A in FIG. Must be increased. However, when the motor torque is increased by PI control under such control, as soon as the control valve 11 opens to the target opening position, the deviation of the opening position of the control valve becomes “0”, The P component is "0", the I component is cleared, and the return torque causes the control valve 11 to start closing. At the initial stage when it starts to close (at the time of small deviation), since the P and I components are both small, the torque cannot overcome the return torque and the deviation becomes large. Then, even if the deviation increases to some extent and the motor torque and the return torque are balanced, the closing operation of the control valve 11 cannot be stopped suddenly due to the inertia of the motor M, and the control valve 11 is opened immediately. I can't do that. If the gain is increased so as to generate a relatively large motor torque even at the time of a small deviation, a vicious circle occurs, as shown in FIG. 3, which causes an increase in overshoot and undershoot.

In consideration of such a situation, a configuration of a control method of the control valve 11 by a so-called torque balance driving method using the motor M will be described with reference to FIGS. In FIG. 4, reference numeral 1 denotes a valve body in which a passage forming a part of an exhaust gas recirculation passage c interposed in the exhaust gas recirculation system is formed, and the control valve 11 moves upward as shown in the figure. Then, the exhaust gas recirculation passage c is closed by coming into contact with the seat 12, and the exhaust recirculation passage c is opened by moving the control valve 11 downward and separating from the seat 12.

Reference numeral 2 denotes a motor case containing a motor M. In this mo overnight case 2 , 21 is a rotor around which a coil 22 is wound, 23 is a yoke provided with a magnet 24, and the lower end of the rotor 21 is rotatable to the valve body 1 by a bearing 27. It is supported by.

A motor shaft 31 is screwed into the inside of the rotor 21, and the motor shaft 31 is prevented from rotating by a guide bush 13 of the body 1. Therefore, the motor shaft 31 moves up and down according to the amount of rotation of the rotor 21. A valve shaft 14 is in contact with the lower end of the motor shaft 31, and an intermediate portion of the valve shaft 14 is moved up and down on the valve body 1 by the guide seal 15 and the guide plate 16. It is freely guided, and a control valve 11 is attached to the lower end of the valve shaft 14.

17 is a guide seal cover. Between the spring seat 18 attached to the upper end of the valve shaft 14 and the guide plate 16, the valve shaft 14 is urged upward, that is, in the closing direction of the control valve 11. For this, a spring 19 is interposed.

The control valve 11 configured as described above is driven by the torque balance method as described above. That is, the EGR valve is provided with a predetermined return torque in the valve closing direction of the control valve 11 by the return spring 19 as an urging means, and the valve opening direction of the control valve 11 is supplied by one-way energization of the motor M. A variable motor torque is applied to the motor, and the control valve 11 is controlled to open and close by the torque balance.

FIG. 5 is a circuit block diagram showing an engine controller unit 51 (referred to as an ECU) for supplying a control signal to the motor M. Reference numeral 50 denotes a control in the form of a computer having a microphone port for determining a motor drive voltage. , 52 is a battery, 53 is a motor drive voltage converter that converts the output of the controller 50 and supplies it to the motor M. It is composed of a diode 53b with current flowing in only one direction, an FET (electrolytic effect transistor) 53c, and an interface 53d provided between the control unit 50 and the FET 53c. Have been. Reference numeral 56 denotes a regulation for securing the drive voltage (5 V) of the control unit 50.

The control unit 50 includes sensors provided at various parts of the vehicle, for example, a detection signal from an operation state quantity sensor 57 such as a crank angle sensor, and a detection signal from the position sensor 40, respectively. Is entered via The position sensor 40 of this example includes a movable contact part 42 that moves on a resistor 41 to which a constant voltage (5 V) is applied from a voltage supply part 60. As the rotor 21 moves with the rotation of the rotor 21, a voltage corresponding to the moving position of the motor shaft 31 is output from the movable contact portion 42 as a detection signal.

The motor drive voltage converter 53 turns on and off the voltage applied to the motor M in a fixed cycle, and the FET is controlled by a PWM signal corresponding to the ratio (drive duty) between the on-time and the off-time per cycle. The average drive voltage applied to the motor M is controlled by switching the 5 3c.

FIG. 6 is a configuration diagram of the control unit 50. In FIG. 6, reference numeral 61 denotes a target position calculation unit for determining an optimal opening / closing position of the control valve 11 based on a detection signal of the operating state sensor 57, and a voltage corresponding to the target position. (Hereinafter referred to as “target value”). 62 outputs an AZD conversion unit (hereinafter referred to as “current value”) that performs AZD conversion of the detection signal of the position sensor 40. 7 1 is the addition / subtraction unit between the target value and the current value. 6 3 is the PI control amount (voltage) that combines the proportional component (P component) and the integral component (I component) based on the deviation between the target value and the current value. What is the PI control amount calculation unit that outputs the data? 1 Control amount calculation section 63 This is a drive duty calculation unit for calculating

Next, the operation will be described.

When a target value is given from the outside, the current value detected by the position sensor 40 and the target value are added / subtracted by the addition / subtraction unit 71 to obtain a deviation. The PI control amount calculation unit 63 calculates the PI control amount from the obtained deviation and outputs it to the drive duty calculation unit 64.The drive duty calculation unit 64 calculates the drive duty based on the PI control amount. And supply it to Moryu M.

Since the conventional method of controlling the exhaust gas recirculation valve is configured as described above, there is a problem that the response is low because of the PI control.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is intended to improve the responsiveness, secure operation stability in the vicinity of a target value, and prevent an overshoot / undershoot. It is intended to provide a method for controlling a gas recirculation valve. Disclosure of the invention

According to a control method of an exhaust gas recirculation valve according to the present invention, a biasing means applies a return torque to an opening / closing valve in one direction in a valve opening direction or a valve closing direction, and the motor is opposed to the return torque in a moment. A torque is applied overnight, and the valve is opened and closed by the torque balance of these two torques. If the deviation is small and within the specified range, control is switched to PI control.

As a result, when the deviation is large, high-speed operation is performed by binary control, so that the response is excellent, and near the target value where the deviation is small, low-speed operation is performed by PI control. No operational stability can be ensured.

The control method of the exhaust gas recirculation valve according to the present invention is based on the binary control. When shifting to I control, PI control is started using the stable manipulated variable in the previous PI control stored in memory.

Thus, when shifting from the binary control to the PI control, the change in the manipulated variable is small, and the switching operation from the binary control to the PI control can be stably performed. The method for controlling the exhaust gas recirculation valve according to the present invention Is a binary control if the function value determined by the deviation between the target value and the present value of the on-off valve and the opening / closing speed of the on-off valve is large and out of the specified range, and PI control if the function value is small and within the specified range. And

As a result, when the function value is large, high-speed operation is performed by binary control, and excellent responsiveness is achieved. Near the target value with a small function value, low-speed operation is performed by PI control, resulting in overshoot and undershoot. -A stable operation without any trouble can be secured.

In the control method of the exhaust gas recirculation valve according to the present invention, the threshold value that shifts from PI control to binary control is wider than the threshold value that shifts from binary control to PI control. -As a result, the switching operation from PI control to binary control can be performed smoothly and stably. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic explanatory view of an engine exhaust system.

Fig. 2 is a characteristic diagram of the motor torque versus the open / close position of the control valve in the EGR valve of the torque balance drive system.

Fig. 3 is a characteristic diagram showing the relationship between time and the operating position of the motor shaft.

Figure 4 shows a longitudinal section I of the EGR valve. FIG. 5 is a configuration diagram of a control device using a so-called torque balance driving method using a motor.

FIG. 6 is a configuration diagram of a control unit in the control device.

FIG. 7 is a configuration diagram of a control unit that implements the control method of the present invention.

FIG. 8 is a flowchart illustrating a control method according to the first embodiment of the present invention.

FIG. 9 is a diagram for explaining the valve opening operation.

FIG. 10 is a flowchart illustrating a control method according to Embodiment 2 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in order to explain this invention in greater detail, the preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1

FIG. 7 is a block diagram of a control unit for implementing the control method of the present invention. In FIG. 7, reference numeral 61 denotes a control valve based on the detection signal of the lotus rotation state sensor 57.

11 A target position calculation unit for obtaining the optimal open / close position, and outputs a voltage (hereinafter, referred to as a “target value”) corresponding to the target position. 62 outputs an A / D converter (hereinafter, referred to as “current value”) for A / D converting the detection signal of the position sensor 40. 7 1 is the addition / subtraction unit between the target value and the current value. 6 3 is the PI control amount (voltage) that combines the proportional component (P component) and the integral component (I component) based on the deviation between the target value and the current value. PI control amount calculation unit that outputs the detected value, 65 is a binary control amount calculation unit, 66 detects the deviation between the target value and the current value, and if the detected deviation is outside the predetermined range, the switching switch is used.

Operation state in which 67, 67b is switched to the binary control variable calculation section, and when the deviation is within the specified range, the switching switches 67a, 67b are switched to the PI control variable calculation section 63. It is a switching unit. As shown in FIG. 9, the specified range W is set to a size corresponding to the range of the deviation of the target position X that can be allowed.

Next, the operation will be described.

FIG. 8 is a flowchart illustrating a control method according to the first embodiment. When a target value is given from the outside, the current value detected by the position sensor 40 and the target value are added and subtracted by the addition / subtraction unit 71. To calculate the deviation (steps ST1, ST2). The control area is determined based on the obtained deviation (step ST 3), and it is determined whether it is the PI control area based on the determination result (step ST 4). If NO, the switching switches 67 a and 67 b are calculated as binary control amounts. Switching to the section 65, the calculation of the binary control amount operation direction is performed (step ST5). On the other hand, if the above judgment is YES, the switching switches 67a and 67b are switched to the PI control amount calculating section 63 to calculate the PI operation manipulated variable (step ST6). Then, a driving force is supplied to the motor M via the driving duty calculating section 64 (step ST 7).

As described above, according to the first embodiment, when the deviation is large and out of the specified range, high-speed operation can be performed by the binary control. When the deviation is small and within the specified range, PI operation is performed. Operational stability can be ensured

Embodiment 2.

FIG. 10 is a flow chart for explaining a control method according to Embodiment 2 of the present invention. When a target value is given from the outside, the adder / subtracter 7 subtracts the current value detected by the position sensor 40 from the target value. The deviation is obtained by adding and subtracting 1 (step ST11, ST12). Next, the operating speed of the on-off valve is obtained by subtracting the previous current value from the current value (step ST13), and the obtained bias The control area is determined by the function value determined from the difference and the speed (step ST14), and the PI control area is determined from the determination result (step ST15). If NO, the switching switches 67a, 67b Is switched to the binary control amount calculation section 65 (step ST16). On the other hand, if the above determination is YES, the switching switches 67a and 67b are switched to the PI control amount calculating section 63 (step ST17). Then, a driving force is supplied to the motor M via the driving duty calculation section 64 (step ST18).

As described above, according to the second embodiment, when the function value is large and out of the specified range, high-speed operation can be performed by the binary control, and when the function value is small and within the specified range, PI control is performed. Since the operation stability can be ensured, the valve opening / closing operation can be performed at higher speed and the stability can be improved. Embodiment 3-In Embodiments 1 and 2, when shifting from the binary control to the PI control, the PI control is started using the stable operation amount at the time of the previous PI control stored in the memory. By doing so, when shifting from binary control to PI control, the change in the manipulated variable is small, and the switching operation from binary control to PI control can be performed stably. Embodiment 4.

The threshold for shifting from PI control to binary control is wider than the threshold for shifting from binary control to PI control. In this way, when shifting from PI control to binary control, the switching operation can be performed smoothly and stably. In each of the above embodiments, PI control has been described. Therefore, PID control may be used because it is a kind of PI control. Industrial applicability

As described above, in the control method of the exhaust gas recirculation valve according to the present invention, a part of the exhaust gas in the exhaust passage a is returned to the intake passage b in a rapid response to a change in the operating state of the engine. Especially suitable for.

Claims

The scope of the claims

1. A return torque for moving the on-off valve in one direction of the valve opening or valve closing direction by the urging means, and a motor torque opposite to the above-mentioned return torque in the motor and the motor, and a torque balance of these two torques. When the deviation between the target value for opening or closing the valve and the current value is greater than the specified value, the control is switched to binary control.If the deviation is smaller than the specified value, the control is switched to PI control. A method for controlling an exhaust gas recirculation valve.

2. When shifting from the binary control to the PI control, the PI control is started using the operation amount that was stable in the previous PI control and stored in the memory, wherein the PI control is started. Exhaust gas recirculation valve control method.

3. Binary control when the function value of the deviation between the target value and the current value of the on-off valve and the on-off speed of the on-off valve is large, and PI control when the function value is small. 2. The method for controlling an exhaust gas recirculation valve according to claim 1.

4. The control method for an exhaust gas recirculation valve according to claim 1, wherein a threshold value for shifting from the PI control to the binary control is wider than a threshold value for shifting from the binary control to the PI control.