JP2005214302A - Valve control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve control device capable of performing good valve closing operation and reducing motor driving circuit loss during PWM control. <P>SOLUTION: A returning torque which moves a control valve in either of a valve opening direction or a valve closing direction is applied to an EGR valve. The valve control device comprises a valve driving motor 13 which applies a motor torque counteracting a returning torque to an exhaust gas circulation valve, and a motor driving circuit 12 which controls driving of a valve driving motor by PWM control to control opening and closing of the EGR valve in proportion to torque balance of the returning torque and the motor torque. Furthermore, the motor driving circuit has PWM switch elements 41 and 43 that controls the valve driving motor under PWM control, and non-PWM switch elements 42a and 44a which turns ON to bring a motor winding of the valve driving motor into a short-circuit state when PWM control elements are OFF. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a valve control device, for example, a valve control device used for opening / closing control of an exhaust gas recirculation valve (hereinafter referred to as an EGR (Exhaust Gas Recirculation) valve) provided in an exhaust gas recirculation system in a vehicle. It is about.

  Generally, a vehicle is provided with an exhaust gas recirculation passage that communicates an exhaust passage from an engine and an intake passage, and an EGR valve for opening and closing the exhaust gas recirculation passage is disposed in the exhaust gas recirculation passage. When controlling the EGR valve, the engine controller unit (hereinafter referred to as ECU) controls the opening of the exhaust gas recirculation passage by controlling the opening and closing of the EGR valve by driving the motor, for example. ing.

  By the way, when the EGR valve is controlled to open and close using a motor, a predetermined return torque is applied in the opening or closing direction of the EGR valve by an urging means such as a spring, and the EGR valve is closed or opened by the motor. A motor torque that varies in the direction is applied. The EGR valve is controlled to open and close by these torque balances (see, for example, Patent Document 1).

  On the other hand, a chopper drive is used to drive and control the motor, the voltage applied to the motor is turned on and off at a predetermined cycle, and a PWM signal according to the ratio of the on time and off time per cycle, for example, an electrolytic effect transistor (FET) is switched to control the average drive voltage applied to the motor. When the FET is on, a current flows only on the motor side, and the motor rotates to a position that matches the return torque of the urging means to open and close the EGR valve (for example, Patent Documents). Reference 2: hereinafter referred to as a conventional example).

In a conventional valve control device, when a motor is driven by PWM control, a switching element such as an FET is turned on to return a back electromotive force to a motor coil, thereby improving power efficiency in PWM control.

  Further, in the conventional valve control device, when the driving of the motor is stopped and the EGR valve is operated to be closed by the urging means, the switch element is maintained in the OFF state and the EGR valve is closed by the urging means. The counter electromotive force generated when the rotor is driven by the movement of the motor is prevented from flowing back to the motor coil, so that the brake torque is not generated in the motor, thereby improving the power efficiency in PWM control and EGR. Responsiveness when closing the valve is good.

Japanese Patent Publication No. WO02 / 14676 republished patent publication (page 4, FIGS. 7 and 8) JP 2001-342906 A (paragraph (0010) to paragraph (0019), FIGS. 1 to 6)

  Since the conventional valve control device is configured as described above, considering that the EGR valve is disposed in the exhaust gas recirculation passage, the EGR valve is exposed to a high temperature and the friction load at the time of opening and closing the valve fluctuates. Then, especially during the valve closing operation, the EGR valve cannot be accurately positioned at the predetermined closed position, and the valve moves from the predetermined closed position, so-called overshoot occurs. When overshoot occurs, the valve collides with the valve stopper, which makes it difficult to perform a good valve closing operation.

  Further, in the conventional valve control device, when the switch element is turned off during PWM control, the back electromotive force from the motor is prevented from flowing back to the motor coil, so that brake torque is not generated. However, there has been a problem in that the back electromotive force increases the loss of the motor drive circuit, and this heat generation adversely affects the EGR valve.

  The present invention has been made to solve the above-described problems, and can always perform the valve closing operation satisfactorily, and can reduce the loss of the motor drive circuit and suppress the heat generation during the PWM control. An object of the present invention is to obtain a valve control device that can be used.

  In the valve control device according to the present invention, a PWM switch element that performs PWM control and a non-PWM switch element that performs non-PWM control are connected in series, and a terminal of the motor is connected between connection points of both switch elements. And a motor drive circuit that turns on all of the non-PWM switch elements to short-circuit the motor windings.

  According to this invention, the motor drive circuit is configured to include a PWM switch element that performs PWM control of the motor, and a non-PWM switch element that is turned on when the PWM control element is in the off state and shorts the motor winding of the motor. Therefore, it is possible to prevent overshoot during the valve closing operation and perform a good valve closing operation, and further, it is possible to reduce heat loss by reducing the loss of the motor drive circuit during PWM control. effective.

Embodiment 1 FIG.
FIG. 1 shows a valve control apparatus according to Embodiment 1 for carrying out the present invention. In FIG. 1, a valve control device 10 (hereinafter simply referred to as a control device) 10 includes a controller 11, a motor drive circuit (hereinafter simply referred to as a drive circuit) 12, a valve drive motor 13 and an EGR valve (in FIG. 1). A valve position sensor 14 for detecting the position (not shown) is provided, and the control device 10 is given a target position for designating the valve position (opening) as a target position signal.

The above-described valve position sensor 14 includes, for example, a movable contact portion (not shown) that moves on a resistor (not shown) to which a constant voltage is applied. It moves according to the rotation of the rotor, and a voltage according to the moving position of the motor shaft described later is output from the movable contact portion as a valve position signal indicating the position of the EGR valve.

The valve position signal output from the valve position sensor 14 is given to the subtractor 15, and a deviation between the target position signal and the valve position signal is obtained by the subtracter 15, and this deviation is given to the controller 11. Then, the controller 11 generates a PWM control signal corresponding to the deviation and gives the PWM control signal to the drive circuit 12.

  As will be described later, the drive circuit 12 controls the valve drive motor 13 according to the PWM control according to the PWM control signal, and the valve drive motor 13 drives the EGR valve to change its opening degree.

  Referring now to FIG. 2, FIG. 2 is a cross-sectional view schematically showing the EGR valve 20, and this EGR valve 20 is disposed in an exhaust gas recirculation system. The EGR valve 20 includes a valve housing 21, and a passage 22 that defines a part of the exhaust gas recirculation passage is defined in the valve housing 21. A motor case 23 is disposed at the upper end of the EGR valve 20, and the valve drive motor 13 is accommodated in the motor case 23.

  Although not shown, the valve drive motor 13 has a rotor around which a coil is wound and a yoke having a magnet. A motor shaft 24 is screwed to the rotor, and the rotor is rotated according to the rotation of the rotor. The motor shaft 24 moves in the vertical direction in the figure.

  The upper end of the valve shaft 25 is positioned corresponding to the lower end of the motor shaft 24, and this valve shaft 25 extends in the valve housing 21 in the vertical direction in the figure. The valve shaft 25 is guided to the valve housing 21 by a guide seal 26 and a guide plate 27 so as to be movable up and down. A control valve 28 and a guide seal cover 29 are attached to the valve shaft 25.

  A spring seat 30 is disposed at the upper end of the valve shaft 25, and a return spring 31, which is an urging means, is disposed between the spring seat 30 and the guide plate 27. 14 is biased upward, that is, in the closing direction of the control valve 28.

  In the illustrated EGR valve 20, a predetermined return torque is applied in the valve closing direction of the control valve 28 by the return spring 31, and the motor torque is applied in the valve opening direction of the control valve 28 in response to energization of the valve drive motor 13. And the valve shaft 25, that is, the control valve 28 is driven by the torque balance of the return torque and the motor torque, and the passage 22 is controlled to open and close. When the control valve 28 moves upward and comes into contact with the valve stopper (valve seat) 32, the passage 22 (that is, the exhaust gas recirculation passage) is closed, and the control valve 28 moves downward and the valve stopper 32 is moved. When leaving, the exhaust gas recirculation passage is opened.

  Alternatively, return torque may be applied in the valve opening direction of the control valve 28 by the return spring 31, and motor torque may be applied in the valve closing direction of the control valve 28 by the valve drive motor 13.

  By the way, in the controller 11, for example, a PI control amount is obtained according to the above-described deviation, a drive duty is obtained based on the PI control amount, and this drive duty is given to the drive circuit 12 as a PWM control signal. . The drive circuit 12 turns on and off the voltage applied to the valve drive motor 13 in accordance with the PWM control signal at a predetermined cycle, and according to the ratio of the on time to the off time per cycle (drive duty: PWM control signal). The switching element (not shown in FIG. 1) is switched by the PWM signal to control the average driving voltage applied to the valve driving motor 13.

  FIG. 3A is a diagram illustrating an example of the drive circuit 12 together with the valve drive motor 13. In the illustrated example, the valve drive motor 13 is a DC motor. In FIG. 3A, the drive circuit 12 has first to fourth switch elements 41 to 44, and is a first bypass element in parallel with the first to fourth switch elements 41 to 44, respectively. To fourth diodes 45 to 48 are arranged.

  The first and second switch elements 41 and 42 are connected in series, and similarly, the third and fourth switch elements 43 and 44 are connected in series. The first and second switch elements 41 and 42 and the third and fourth switch elements 43 and 44 are arranged in parallel.

  A motor terminal of the valve drive motor 13 is connected between the connection point of the first and second switch elements 41 and 42 and the connection point of the third and fourth switch elements 43 and 44, and the first and third The switch elements 41 and 43 are connected to a reference voltage source (constant voltage source) Vref, and the second and fourth switch elements 42 and 44 are grounded.

  The drive circuit 12 shown in FIG. 3A is shown as a conventional example, and the drive circuit 12 used in Embodiment 1 of the present invention has a configuration shown in FIG. 4A described later. The circuit configuration is the same, but the functions of the second and fourth switch elements and the method for on / off control of the first to fourth switch elements are different as will be described later.

Next, the operation will be described.
First, in order to easily understand the energization control of the valve drive motor 13 according to the first embodiment, the energization control of the conventional valve drive motor 13 will be described with reference to FIGS. 3 (a) and 3 (b). When drive control (PWM) of the valve drive motor 13 is performed, for example, the first and fourth switch elements 41 and 44 are PWM-controlled (that is, on / off controlled).

  When the valve drive motor 13 is energized, the first and fourth switch elements 41 and 44 are turned on. As a result, as indicated by solid line arrows in FIG. 3A, a current is supplied from the reference voltage source Vref. Im flows in the order of the first switch element 41, the valve drive motor 13, and the fourth switch element 44, and the valve drive motor 13 is driven.

  On the other hand, when the first and fourth switch elements 41 and 44 are turned off, the current Im is changed to the second diode 46, the valve drive motor 13, and the third diode as shown by the solid arrows in FIG. It will flow in the order of 47. That is, in the PWM control, when the first and fourth switch elements 41 and 44 are off, the current Im flows through the second and third diodes 46 and 47.

  Now, assuming that the forward voltage of the second and third diodes 46 and 47 is Vf, in PWM control, the power loss P of the drive circuit 12 when the first and fourth switch elements 41 and 44 are OFF is , P = 2 × Im × Vf.

  In general, the forward voltage Vf of the diode is 0.6V to 0.7V. For example, if Im = 2A, the drive circuit 12 when the first and fourth switch elements 41 and 44 are OFF. The power loss P is P = 2 × 2A × 0.6V to 0.7V = 2.4W to 2.7W.

  Here, referring to FIGS. 4A and 4B, in the first embodiment, in order to reduce the power loss P in the drive circuit 12, the energization control to the valve drive motor 13 is performed as follows. Do. 4 (a) and 4 (b), the same components as those in FIGS. 3 (a) and 3 (b) are denoted by the same reference numerals, and FIGS. 4 (a) and 4 (b). In the example shown, switch elements (for example, FETs (field effect transistors)) capable of reverse conduction are used as the second and fourth switch elements (switch elements located on the lower side in the drawing). For this reason, reference numerals 42a and 44a are assigned to the second and fourth switch elements, respectively.

  When the valve drive motor 13 is driven and controlled, the first and third switch elements 41 and 43 are PWM-controlled (the first and third switch elements 41 and 43 are PWM switch elements). Now, paying attention to the first switch element 41, when energizing the valve drive motor 13, for example, the first switch element 41 is turned on (the third switch element 43 is in the off state), and the fourth The switch element 44a is turned on.

  Then, the second switch element 42a is turned off, and the current Im is supplied from the reference voltage source Vref to the first switch element 41, the valve drive motor 13, and the fourth as shown by the solid line arrow in FIG. The valve drive motor 13 is driven in the order of the switch elements 44a.

  When the first switch element 41 is turned off, the second switch element 42a is turned on (at this time, the fourth switch element 44a is kept on). As described above, since the second and fourth switch elements 42a and 44a are switch elements capable of reverse conduction, as shown by solid line arrows in FIG. 4B, the counter electromotive force generated in the valve drive motor 13 is obtained. As a result, the current Im flows back through the second switch element 42a, the valve drive motor 13, and the fourth switch element 44a, and the motor winding (coil) of the valve drive motor 13 is short-circuited.

  Now, assuming that the on-resistance values of the second and fourth switch elements 42a and 44a are Ron, in PWM control, the power loss P of the drive circuit 12 when the first switch element 41 is off is P = 2. × Im × Im × Ron.

  In general, since the on-resistance value Ron when the switch element is an FET is about 2 mΩ to 30 mΩ, assuming that Im = 2A, the power loss P of the drive circuit 12 when the first switch element 41 is off. Is P = 2 × 2A × 2A × 2 mΩ to 30 mΩ = 0.008 W to 0.12 W, and the power loss can be greatly reduced as compared with the PWM control described with reference to FIGS. .

  Further, in the PWM control described with reference to FIGS. 3A and 3B, the first and fourth switch elements 41 and 44 are turned on and off, and the first and fourth switch elements 41 and 44 are turned off. At this time, since the current Im flows in the order of the second diode 46, the valve drive motor 13, and the third diode 47, the braking force is not generated in the valve drive motor 13 and the control valve 28 (FIG. 2) is closed. 5, even if braking is started at the braking start determination position, as indicated by reference numeral 51 in FIG. 5, overshoot occurs, and the position of the control valve 28 is attenuated while oscillating and positioned at the valve closing position. Therefore, the valve closing operation cannot be performed satisfactorily.

  That is, assuming that the target position is given as indicated by reference numeral 52 in FIG. 6, even if the target position changes from the fully open position to the fully closed position, the position of the motor shaft (that is, the position of the control valve 28) is the target position. As shown by reference numeral 53 in FIG. 6, the overshoot occurs, and the position of the control valve 28 is attenuated while oscillating and positioned at the closed position, as indicated by reference numeral 53 in FIG.

  On the other hand, in the PWM control described with reference to FIGS. 4A and 4B, the first and second switch elements 41 and 42a are controlled to be turned on / off, and the second switch element 41 is turned off when the first switch element 41 is turned off. The switch element 42a is turned on, and the current Im is recirculated with the second switch element 42a, the valve drive motor 13, and the fourth switch element 44a to short-circuit the motor winding of the valve drive motor 13.

  As a result, a braking force (braking force) is generated in the valve drive motor 13, and when the control valve 28 is positioned at the closed position, when braking is started at the braking start determination position, as indicated by reference numeral 54 in FIG. The position of the control valve 28 is gradually attenuated and positioned at the valve closing position without causing overshoot, and the valve closing operation can be performed satisfactorily. The second and fourth switch elements 42a and 44a described above function as non-PWM switch elements.

  In the example shown in FIGS. 4A and 4B, the drive circuit 12 when a DC motor is used as the valve drive motor 13 has been described. However, a three-phase motor may be used as the valve drive motor 13. . In this case, for example, the drive circuit shown in FIG.

  Referring to FIG. 7, the illustrated drive circuit 12 includes first to sixth switch elements 61 to 66, and the first and second switch elements 61 and 62 are connected in series. The third and fourth switch elements 63 and 64 are connected in series, and the fifth and sixth switch elements 65 and 66 are connected in series. A connection point U between the first and second switch elements 61 and 62, a connection point V between the third and fourth switch elements 63 and 64, and a connection point W between the fifth and sixth switch elements 65 and 66. The three-phase terminals of a valve drive motor (three-phase motor) 13 are connected to each.

  In the illustrated example, the second switch element 62, the fourth switch element 64, and the sixth switch element 66 located on the lower side in the figure are switch elements (non-PWM switches) capable of reverse conduction such as FETs. Element). The first switch element 61, the third switch element 63, and the fifth switch element 65 are connected to the reference voltage source Vref, and the second switch element 62, the fourth switch element 64, and the sixth switch element The switch element 66 is grounded.

  Here, referring to FIGS. 8A and 8B, when the valve drive motor 13 is driven and controlled, the first switch element 61, the third switch element 63, and the fifth switch element 65 are PWM control is performed (the switch elements 61, 63, and 65 are PWM switch elements).

  Now, paying attention to the first switch element 61, when the first switch element 61 is turned on, the sixth switch element 66 is also turned on. As a result, as shown by a solid arrow in FIG. In addition, the current Im flows from the reference voltage source Vref in the order of the first switch element 61, the valve drive motor 13, and the sixth switch element 66.

  Although not shown, the first to third switch elements 61 to 63 and the fourth to sixth switch elements 64 to 66 are selectively turned on / off by PWM control, thereby driving the valve. The motor 13 is driven and controlled.

  In the OFF period of the PWM control, as shown in FIG. 8B, the second switch element 62, the fourth switch element 64, and the sixth switch element 66 are turned on, and the first switch element 61 is turned on. The third switch element 63 and the fifth switch element 65 are turned off. As described above, since the second switch element 62, the fourth switch element 64, and the sixth switch element 66 are switch elements capable of reverse conduction, as shown by solid line arrows in FIG. The current Im caused by the counter electromotive force generated in the valve drive motor 13 circulates through the second switch element 62, the valve drive motor 13, the fourth switch element 64, and the sixth switch element 66, and the valve drive motor 13 The coil (motor winding) is short-circuited.

  As described above, also in the drive circuit 12 shown in FIG. 7, during the PWM control off period, the motor winding of the valve drive motor 13 that is a three-phase motor is short-circuited, and the current is supplied to the second switch element 62 and the valve drive. Since the motor 13, the fourth switch element 64, and the sixth switch element 66 are recirculated, the power loss of the drive circuit 12 is extremely reduced as described in FIGS. Can do.

  Further, even when the drive circuit 12 shown in FIG. 7 is used, a braking force is generated in the valve drive motor 13, and when the control valve 28 is positioned at the closed position, the position of the control valve 28 is gradually attenuated and overshoots. It will be positioned at the valve closing position without causing a chute, and the valve closing operation can be performed satisfactorily.

  In the above description, the drive circuit 12 when the valve drive motor 13 is a DC motor or a three-phase motor has been described, but the same applies when the valve drive motor 13 is an N-phase (N is an integer of 2 or more) motor. Thus, the first embodiment can be applied. For example, when using an N-phase motor, the number of switch elements is 2N, and as shown in FIG. 7, a pair of switch elements are connected in series to form a series body. Are connected in parallel, connected to the reference voltage source Vref and grounded, and the connection points of the series bodies are connected to the N-phase terminals, respectively. In this case, as described above, a switch element capable of reverse conduction such as an FET is used as the switch element located on the lower side.

  As described above, according to the first embodiment, when PWM control of the valve drive motor is performed, when the PWM switch element is in the off state, the non-PWM switch element is turned on to short-circuit the motor winding of the valve drive motor. Thus, there is an effect that it is possible to prevent the overshoot during the valve closing operation and perform a good valve closing operation.

  According to the first embodiment, the present invention can be applied to valve drive motors of all phases by simply increasing the number of PWM switch elements and non-PWM switch elements in accordance with the number of phases of the valve drive motor. Is very easy.

  According to the first embodiment, since the non-PWM switch element is configured by a switch element that can conduct in both directions, the effect of greatly reducing the heat loss of the motor drive circuit when the motor winding is short-circuited. There is.

  According to the first embodiment, when the non-PWM switch element is turned on, a closed circuit including the non-PWM switch element and the motor is formed, and the motor is braked by returning current to the closed circuit. With such a circuit configuration, the braking force of the motor can be obtained.

It is a block diagram which shows the valve control apparatus by Embodiment 1 of this invention. It is sectional drawing which shows roughly the structure of an example of the valve controlled by the valve control apparatus shown in FIG. It is a figure for demonstrating an example of the conventional motor drive circuit, (a) is a figure for demonstrating the flow of the electric current at the time of supplying with electricity to a valve drive motor, (b) is when PWM control is an OFF period. It is a figure for demonstrating the flow of an electric current. It is a figure for demonstrating an example of the motor drive circuit used with the valve | bulb control apparatus by Embodiment 1 of this invention, (a) is a figure for demonstrating the flow of the electric current when supplying with electricity to a valve drive motor, (B) is a figure for demonstrating the flow of the electric current at the time of PWM control being an OFF period. FIG. 5 is a diagram showing a change in valve position during valve closing operation in the motor drive circuit shown in FIG. 3 and the motor drive circuit shown in FIG. 4. It is a figure which shows the target position at the time of using the motor drive circuit shown in FIG. 3, and an actual valve position. It is a figure for demonstrating the other example of the motor drive circuit used with the valve | bulb control apparatus by Embodiment 1 of this invention. FIG. 8 is a diagram for explaining the operation of the motor drive circuit shown in FIG. 7, (a) is a diagram for explaining the flow of current when the valve drive motor is energized, and (b) is a diagram in which PWM control is in the off period. It is a figure for demonstrating the flow of the electric current at the time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Valve control apparatus, 11 Controller, 12 Motor drive circuit, 13 Valve drive motor, 14 Valve position sensor, 15 Subtractor, 20 EGR valve, 21 Valve housing, 22 Passage, 23 Motor case, 24 Motor shaft, 25 Valve shaft , 26 guide seal, 27 guide plate, 28 control valve, 29 guide seal cover, 30 spring seat, 31 return spring, 32 valve stopper, 41-44 switch element, 42a, 44a switch element, 45-48 diode, 61-66 Switch element.

Claims (4)

  A return torque for moving the valve in the valve opening direction or the valve closing direction, and a motor for applying a motor torque opposite to the return torque to the valve, the torque balance between the return torque and the motor torque. In a valve control device that controls opening and closing of the valve according to the above, a PWM switch element that performs PWM control and a non-PWM switch element that performs non-PWM control are connected in series, and a terminal of the motor is connected between the connection points of both switch elements. A valve control device comprising: a motor drive circuit that turns on all of the non-PWM switch elements during an off period of the PWM switch elements to short-circuit the motor windings.   2. The valve control device according to claim 1, wherein when the motor is an N (N is an integer of 2 or more) phase motor, N PWM switch elements and N non-PWM switch elements are provided.   The valve control device according to claim 2, wherein the non-PWM switch element is configured by a switch element that is conductive in both directions. When the non-PWM switch element is turned on, a closed circuit including the non-PWM switch element and the motor is formed,
3. The valve control device according to claim 2, wherein the motor is braked by returning current to the closed circuit.

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