WO2002002924A1 - Control device of exhaust gas recirculating valve - Google Patents

Abstract

A control device of an exhaust gas recirculating device capable of preventing a flow detection sensor inside an intake passage from being affected by the operation of an exhaust gas recirculating valve provided in an exhaust gas recirculating system, wherein drive pulses of a frequency to reciprocate a valve disc (11) of the exhaust gas recirculating valve at a frequency not disturbing a vortex produced in a Karman air flow sensor disposed inside the intake passage are supplied to each phase coil of a stepping motor (1) driving the exhaust gas recirculating valve, preferably the frequency of the drive pulses should be 10 Hz or less and varied.

Description

 Description Control device for exhaust gas recirculation valve Technical field

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

EGR (ExhaustGasRecircuulatoion). "This is related to a valve control device. Background art

 FIG. 1 is a configuration diagram in which a valve element (open / close valve) 11 of an EGR valve is disposed in an exhaust gas recirculation circuit c that communicates an exhaust passage a and an intake passage b of the engine E. The control device of the EGR valve, for example, drives and controls a stepping motor 1 by an engine controller unit (hereinafter referred to as an ECU) 31, and opens and closes the valve body 11 by the stepping motor 1. By controlling the stepping mode 1, the valve body 11 is adjusted and held at the target opening position.

 The conventional EGR valve control device of this type applies a predetermined re-start torque in the valve closing direction of the valve body 11 by an urging means, and drives the stepping motor 1 in the valve-opening direction. A motor torque that varies the valve body 11 in the valve direction is applied, and the opening and closing of the valve body 11 is controlled by the torque balance.

FIG. 2 is a longitudinal sectional view in which a configuration of a control device of the EGR valve is partially cut away. In the figure, reference numeral 1 denotes a driving motor serving as a driving source, for example, a configuration in which a cylindrical mouth 4 in which four-phase excitation coils 2 are attached to 48 slots is arranged on the inner diameter side of the core 3. . The outer circumference of this row 4 is N A cylindrical magnet 5 having 24 poles alternately magnetized with poles and S poles is fitted. In addition, a threaded motor shaft 7 is provided on the inner diameter side of the mouth 4 through a female screw member 6, and the rotational movement of the mouth 4 is controlled by the motor shaft 7 through the female screw member 6. It has been converted into a vertical motion. A valve shaft 10 is connected to the lower end of the motor shaft 7 via two connecting plates 8 and 9, and a valve body 11 is fixed to the lower end of the valve shaft 10. By moving the valve body 11 up and down on the valve seat 12, the valve opening is adjusted. The upper connecting plate 8 is fixed to the lower end of the motor shaft 7, and the lower connecting plate 9 is fixed to the upper end of the valve shaft 10.

 Then, the L-shaped engaging claw 13 formed downward on the upper connecting plate 8 is engaged with the lower linking plate 9, and the valve body 11 is brought into close contact with the valve seat 12 even in the fully closed state. The motor shaft Ί and the upper link plate 8 can move in the valve closing direction. The lower link plate 9 is urged downward (to close the valve) by the outer compression coil spring 14 and the inner compression coil spring 15, and when the valve body 11 moves up and down (opens and closes), the two compression coils are moved. The lower connecting plate 9 is held by the springs 14 and 15 in a state where the lower connecting plate 9 is engaged with the engaging claws 13 of the upper connecting plate 8, and the valve shaft 10 is integrally formed with the motor shaft 7. Moves up and down. The opening of the valve seat 12 communicates with an inlet port 17 through which exhaust gas flows in from the exhaust pipe side and an outlet port 18 through which exhaust gas flows out to the surge tank side.

Next, the operation of the EGR valve will be described. When the energization to the excitation coil 2 of each phase of the stepping motor 1 is sequentially switched by the two-phase excitation method, the rotor 4 rotates and its rotational motion is changed to linear motion by the female screw member 6, and the motor shaft is rotated. It is transmitted to 7. At this time, when the rotation direction of the stepping motor 1 is the forward rotation direction, the motor shaft 7 is set to the outer compression coil. The valve body 11 moves upward by staking the spring force of the valve spring 14 and moves away from the valve seat 12 (valve opening direction) via the valve shaft 10. As a result, the inlet port 17 and the outlet port 18 communicate with each other, and by adjusting the distance (valve opening) between the valve body 11 and the valve seat 12, the amount of exhaust gas recirculation is adjusted. It is o

 On the other hand, when the rotation direction of the stepping motor 1 is the reverse direction, the motor shaft 7 moves downward (to close the valve), and the valve shaft 10 moves downward integrally with this. And the valve body 11 moves in the direction to approach the valve seat 12, and finally, the valve body 11 is fitted to and tightly attached to the valve seat 12, and becomes a fully closed state. After this, if the stepping wheel 1 rotates in the reverse direction, the motor shaft 7 moves further downward by staking the spring force of the inner compression coil spring 15 and the valve shaft 10 and the valve The body 12 is overstroked downward in the stroke of the inner compression coil spring 15. As a result, the valve element 11 is more strongly pressed against the valve seat 12, and the recirculation of the exhaust gas is reliably shut off.

 A ball IC 20 as a rotation sensor is arranged above the rotor 4 in the motor housing 19. This Hall IC 20 is obtained by integrating the Hall element and the amplification IC. On the other hand, at the upper end of the mouth 4, a rotation detecting magnetizing part 21 is formed as a rotation detecting part, in which the N pole and the S pole are alternately magnetized with a fixed bit. The rotation of the section 21 is detected by the Hall IC 20, and the rotation fluctuation when the stepping motor 1 goes out of synchronization is detected.

FIG. 3 is a block diagram of a drive control circuit (hereinafter referred to as ECU) 31 that outputs a drive pulse signal to the step coils 1a to 2d of each phase of the stepping motor 1. The drive control circuit 31 constantly monitors the operating state of the engine by detecting the central processing unit 32, storage circuits ROM and RAM, engine speed, intake pipe negative pressure (inner pressure), and water temperature. Operation status detection to judge Output section 37, a voltage level correction circuit 33 that amplifies the output signal from the operation state detection section 37 and corrects the output voltage to a required voltage, and outputs the signal output from the voltage level correction circuit 33 to A / A / D converter 34 for D-conversion, Kalman airflow sensor (AFS) 38 for detecting the intake air flow rate, and waveform shaping circuit 35 for shaping the output voltage from this Kalman airflow sensor 38 The drive circuit 36 converts the control signal for controlling the stepping motor 1 from the central processing unit 32 into a drive pulse signal, and supplies the drive pulse signal to the excitation coil 2 of each phase of the steering motor 1. It is provided.

 The storage circuit ROM stores a program for controlling the stepping module 1, and the central processing unit 32 drives the stepping module 1 in accordance with the control program stored in the storage circuit ROM. By controlling the opening and closing of the body 11, the flow rate of air passing through the exhaust gas recirculation passage is controlled.

 Next, the operation will be described.

 The central processing unit 32, which is the CPU of the drive control circuit 31, generates and outputs a drive signal for the stepping motor 1 according to the detection of the engine coolant temperature, the intake air amount of the engine, the engine speed, and the like. In step 36, a driving pulse is sequentially supplied to each phase of the exciting coil 2 of the stepping motor 1 based on the driving signal to operate the stepping motor 1.

This driving mode 1 rotates the row 4 according to the drive pulse. Rotation of the rotor 4 moves the motor shaft 7 screwed into the screw of the center hole of the mouth 4 in the axial direction, and the elastic force of the outer compression coil spring 14 and the inner compression coil spring 15 And drive the valve shaft 10 in the valve opening direction. On the other hand, when a drive pulse having an opposite polarity is supplied from the drive circuit 36 to the exciting coil 2 of the steering motor 1, the opening 4 is directed in the opposite direction. Rotate to move the valve shaft 10 in the direction to close the valve body 11.

 In this case, the drive circuit 36 outputs the duty-pulsed drive pulse to the excitation coil 2 of the preceding phase or the subsequent phase of the exciting phase when the mouth 4 is advanced by n steps, thereby setting the target value. At the position, the mouth is stepped to the target position between the n-step position and the n + 1 step position, or the target position between the n-step position and the n-1 step position, and the valve body 11 reciprocates. Move to get average flow rate.

 Since the conventional EGR valve control system is configured as described above, the duty is controlled by the drive pulse supplied to the stepping motor, so that the valve reciprocates around the target opening position and exhaust Fluid flowing from the return passage c to the intake passage b fluctuates. As a result, if a Kalman-type airflow sensor is provided in the intake passage b, the vortex generated in the Kalman-type airflow sensor is disturbed by the fluid fluctuation, and accurate flow rate detection cannot be performed. There were challenges.

 In other words, Kome-Kalman airflow sensors detect the frequency of vortices generated by the turbulence of the wake of an obstacle in the fluid, and use the characteristic that the higher the flow rate, the higher the frequency of the vortices. ing. Therefore, when the intake air volume of the engine is large, that is, when the engine speed is high or the load is high, the frequency of the vortex becomes very high with respect to the driving frequency of the stepping motor. It has no effect on the vortex of the airflow sensor, but the frequency of the vortex drops extremely at low rotation and low load, that is, in the idling state because the intake air volume is the smallest, and the frequency is usually 15 to 20 H Down to z.

Therefore, when the exhaust gas recirculation pulsation is set to 15 Hz or more, that is, the driving frequency of the stepping motor is set to 15 Hz or more, the vortex generated in the Kalman type air flow sensor and the exhaust gas recirculation pulsation are superimposed. Suction air The air flow may not be measured. In order to prevent this, it is necessary to set the exhaust gas recirculation pulsation always lower than the vortex frequency of the Kalman airflow sensor.

 When the engine speed or load is high, the frequency of the Karman vortex is high, so there is no problem even if the drive frequency of the stepping motor is increased.

However, in order to average the fluctuation flow rate of the exhaust gas recirculation, it is preferable to set the drive frequency to about 100 to 300 Hz, so it is necessary to vary the drive frequency according to the operating state of the engine. It is.

 The present invention has been made in order to solve the conventional problems described above.The present invention does not disturb the vortex generated in the Kalman type air flow sensor, performs accurate flow rate detection, and performs accurate control. The purpose of the present invention is to obtain a control device for an exhaust gas recirculation valve that can be used. Disclosure of the invention

 A control device for an exhaust gas recirculation valve according to the present invention includes a valve shaft having an on-off valve, a return spring for urging the valve shaft in a closing direction, and a motor acting on the valve shaft. A stepping motor for driving the tshaft in the valve opening direction; and control means for controlling the driving of the steering motor. The control means includes a Kalman-type system disposed in an intake passage for each phase coil of the steering motor. A drive pulse is supplied to the stepping motor at a frequency such that the valve reciprocates in a cycle that does not disturb the vortex generated in the airflow sensor.

 As a result, the flow rate can be accurately detected by a Kalman-type air outlet sensor provided in the intake passage.

The control device for an exhaust gas recirculation valve according to the present invention is such that the frequency of the drive pulse supplied to the stepping motor is set to 10 Hz or less. The same effect can be obtained.

 The exhaust gas recirculation valve control device according to the present invention is characterized in that the frequency of the drive pulse supplied to the stepping motor is changed in accordance with the opening of the throttle valve. _

 As a result, the flow rate in the intake passage, that is, the flow rate can be increased as the flow rate increases, so that the reciprocating operation of the valve element can be appropriately controlled.

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

 Fig. 2 is a vertical cross-sectional view of the EGR valve driven by a stepping motor.

 FIG. 3 is a drive control circuit diagram of the steering mode.

 FIG. 4 is a schematic explanatory view of an engine exhaust system according to 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

The drive control circuit for outputting a drive pulse signal to the excitation coil 2 of each phase of the stepping motor 1 according to the present invention is the same as the conventional drive control circuit shown in FIG. In other words, the central processing unit 32, which is the CPU of the drive control circuit 31, has a target opening degree for obtaining the exhaust gas recirculation amount determined according to the engine cooling water temperature, the amount of intake air of the engine, the engine speed, and the like. Is supplied to the stepping motor 1 through the drive circuit 36, After the target opening is obtained, the valve body 11 is alternately supplied with one drive pulse for driving the valve opening direction up to that time and one drive pulse for driving the valve body in the valve closing direction. In the evening, advance to the target position between the n-step position and the n + 1 step position or the target position between the n-step position and the n-1 step position, and reduce the valve body 11 at the target opening position. Move back and forth to obtain the average flow rate.

 In this case, the cycle in which the valve body 11 reciprocates is set to a frequency that does not disturb the vortex generated in the Kalman airflow sensor disposed in the intake passage b, and the intake air flow rate decreases as described above, Since the frequency drops to 15 to 20 Hz, the frequency is set lower, for example, 10 Hz or less.

 As described above, according to the first embodiment, the valve element 11 reciprocates in a cycle that does not disturb the vortex generated in the Leman-type airflow sensor provided in the intake passage b. Can be detected. Embodiment 2

 FIG. 4 is a schematic explanatory view of an engine exhaust system according to the present invention. In FIG. 4, S is a throttle valve provided in the intake passage b, and the opening state of the throttle valve S is detected by a throttle position sensor (TPS) 39 mounted on the valve shaft. I do. As a method of detecting the operating state of the engine, first, a method of knowing the operating state by "inner pressure and engine speed" and a method of knowing by "the throttle valve setting and engine speed" The latter detection is performed by the throttle position sensor 39. The detection signal is sent to the CPU 32 to determine the driving frequency of the stepping motor according to the operating state of the engine. That is, the frequency of the driving pulse supplied to the stepping motor 1 is changed.

As described above, according to the second embodiment, the flow rate flowing through the intake passage, In other words, the frequency can be increased as the flow rate increases, so that the reciprocating operation of the valve element can be appropriately controlled. Industrial applicability

 As described above, the control device for an exhaust gas recirculation valve according to the present invention is characterized in that when returning a part of the exhaust gas from the exhaust passage a to the intake passage b, the flow rate fluctuation in the intake passage b is a Kalman type air flow. It is suitable for accurate flow rate detection because it does not adversely affect the flow sensor.

Claims

The scope of the claims 1. A valve shaft having an on-off valve, a return spring for urging the valve shaft in the closing direction, and a stepping motor for driving the motor shaft acting on the valve shaft in the valve opening direction. And control means for controlling the driving of the stepping motor. The control means controls each step coil of the stepping motor to generate a cycle that does not disturb the vortex generated in the Kalman airflow sensor disposed in the intake passage. A driving pulse having a frequency such that the valve body reciprocates in the stepping motor is supplied to the stepping motor. 2. The control device for an exhaust gas recirculation valve according to claim 1, wherein the frequency of the drive pulse supplied to the steering motor is set to 10 Hz or less. 3. The exhaust gas recirculation valve control device according to claim 1, wherein the frequency of the drive pulse supplied to the steering motor is changed according to the opening degree of the throttle valve.