JPH11132110A - Control device for EGR valve - Google Patents

Abstract

(57) [Problem] To provide an EGR valve that can be controlled with high resolution and high accuracy with high resolution, and to compensate for the complete closing of the valve, and to operate the closing position of the EGR valve and the valve driving motor. To provide an EGR valve control device capable of always performing accurate opening / closing control by reliably associating with an origin. SOLUTION: In addition to adopting a torque balance drive system for opening and closing a valve by a balance between a return torque by an urging means and a motor torque of a DC motor, a predetermined play is provided in a power transmission system between the DC motor and the valve. Forming
Further, an origin alignment processing unit 67 is provided for determining and coping with the operating position of the DC motor at the time when the valve starts to open.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas recirculation (EGR) provided in an exhaust gas recirculation system.
(rculation) valve control device.

[0002]

2. Description of the Related Art Conventionally, as a control device for an EGR valve of this type, for example, a device described in Japanese Patent Application Laid-Open No. 7-332168 is known.

In such a control device, the opening and closing of the EGR valve is controlled by a stepping motor such as a PM type, and the opening of the EGR valve is adjusted by controlling the stepping motor on a step angle basis. Further, a power transmission mechanism for transmitting the rotational force of the stepping motor to the EGR valve as a valve opening / closing force includes:
There is no play in the transmission system. Therefore, in order to make the closing position of the EGR valve coincide with the rotor origin of the stepping motor, spacers of various thicknesses are interposed at the connection portion between the valve body of the EGR valve and the motor case of the stepping motor, and the EGR valve The so-called shim adjustment is performed for the coupling distance between the body of the stepping motor and the body of the stepping motor.

[0004]

In the conventional control device using such a stepping motor, the opening of the EGR valve can be controlled only in steps of the step angle of the stepping motor. The resolution of the opening was limited. Furthermore, in stepping motor open control, there is a limit to the responsiveness because a step-out phenomenon may occur, and once step-out occurs, an error occurs in the control amount and reliability is lost. There was a problem of getting worse.

In addition, it is very troublesome to adjust the coupling distance between the body of the EGR valve and the body of the stepping motor so that the closed position of the EGR valve coincides with the rotor origin of the stepping motor. Moreover,
EG due to wear of EGR valve valves and seats
When the closed position of the R valve changes over time, the EGR
The open position of the valve and the origin of the rotor of the stepping motor deviate from each other, so that the valve cannot be completely closed, so that accurate opening / closing control of the EGR valve cannot be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to control the opening of an EGR valve with high resolution and high precision, to compensate for the complete closing of the valve, to close the EGR valve and to operate the valve driving motor. An object of the present invention is to provide an EGR valve control device capable of always performing accurate opening / closing control by reliably associating the origin with the origin.

[0007]

According to the first aspect of the present invention, a predetermined return torque is applied in the closing direction of the EGR valve by the urging means, and the EG is controlled by the DC motor.
A control device for an EGR valve which is provided with a variable motor torque in an opening direction of an R valve and is opened and closed by their torque balance, transmitting a motor torque of the DC motor to the EGR valve, and A power transmission system for forming a predetermined amount of play at the time of closing; a detecting means for detecting an operating position of the DC motor; and an initial operation controlling means for gradually increasing the motor torque of the DC motor from the time of closing the EGR valve. From the relationship between the change in the motor torque of the DC motor gradually increased by the initial operation control means and the change in the operation position of the DC motor detected by the detection means, the time at which the EGR valve starts to open. And a calculating means for obtaining an operating position of the DC motor.

According to a second aspect of the present invention, in the first aspect, the initial operation control means gradually increases the motor torque of the DC motor so as to reciprocate the DC motor in a maximum operation range and then gradually increases the motor torque. Decreasing, and the calculating means obtains an operating characteristic of the EGR valve from a relationship between a change in motor torque of the DC motor and a change in an operating position of the DC motor detected by the detecting means. I do.

The invention according to claim 3 is characterized in that, in claim 1 or 2, the initial operation control means controls the motor torque by performing PWM control on the DC motor.

[0010] The invention described in claim 4 is the invention according to claims 1 to 3.
In any one of the above, the power transmission system is connected to the EGR valve, and is pushed in one direction, so that the EGR valve is pressed.
A valve shaft for opening a GR valve, linearly moving in accordance with the operation amount of the DC motor, and facing the valve shaft with a predetermined play gap when the EGR valve is closed; With the increase,
A motor shaft that pushes the valve shaft in one direction after contacting the valve shaft.

[0011] The invention according to claim 5 is the invention according to claims 1 to 4.
In any one of the above, the DC motor can apply motor torque in the open direction and the close direction to the EGR valve by energizing in one direction and the other direction.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) A. First Embodiment "Configuration of EGR Valve" FIGS. 1 to 7 are views for explaining the first embodiment of the present invention. First, the configuration of the EGR valve will be described with reference to FIG.

In FIG. 1, reference numeral 1 designates a valve body in which an exhaust gas passage interposed in an exhaust gas recirculation system is formed. The valve 11 moves upward as shown in FIG. The gas passage is closed and valve 1
The exhaust gas passage is opened when 1 moves downward and separates from the seat 12. Reference numeral 2 denotes a motor case in which the DC motor 20 is built. In the motor 20, 21 is the coil 2
Reference numeral 23 denotes a yoke provided with a magnet 24, and a rotor shaft 25 in which upper and lower shaft portions 25A and 25B are connected is formed at the center of the rotor 21. The upper shaft portion 25A is a bearing 2
The lower shaft portion 25B is rotatably supported on the valve body 1 by bearings 27. A commutator 28 is attached to the upper end of the rotor 21, and a motor brush 29 provided on the motor case 2 side is pressed against the commutator 28 by a brush spring 30.

Reference numeral 40 denotes a position sensor for detecting the rotational position of the rotor 21. In this embodiment, the position sensor 40 has a form in which the resistance value changes according to the rotational position of the rotor 21. That is, it has a resistor 41 attached to the motor case 2 side, and a brush plate 43 attached to the rotor shaft 25 and provided with a brush 42. 41 are slidably contacted. This position sensor 40
The motor brush 29 and the motor brush 29 are connected to a control device described later by the connector terminal 3.

A motor shaft 31 is screwed into the rotor shaft 25, and the motor shaft 31
Is stopped by a guide bush 13 on the body 1 side. Therefore, the motor shaft 31 moves up and down according to the amount of rotation of the rotor 21. A stopper plate 31 is attached to the rotor shaft 25, and the outer peripheral portion of the stopper plate 31 and the stopper portion 2 </ b> A formed on the inner peripheral surface of the motor case 2 come into contact with each other to rotate the rotor 21. The range is being regulated. A spiral spring 32 has an inner end 32A attached to the stopper plate 31 and an outer end 32B attached to the inside of the motor case 2. This spiral spring 32 urges the rotor 21 in one direction, and when the motor 20 is not driven,
The rotor 21 is held at a rotation limit position in one direction regulated by the stopper plate 31 and the stopper portion 2A. When the rotor 21 is at the rotation limit position in one direction, the motor shaft 31 moves to the upper limit position as shown in FIG. When the rotor 21 is driven to rotate in the other direction, the motor shaft 31 moves downward.

The lower end of the motor shaft 31 faces the upper end of the valve shaft 14 having the lower end to which the valve 11 is attached. An intermediate portion of the valve shaft 14 has a valve body 1 formed by a guide seal 15 and a guide plate 16.
The guide is movable up and down. 17 is a guide seal cover. A coil spring 19 is interposed between the spring seat 18 attached to the upper end of the motor shaft 14 and the valve body 1 to urge the shaft 14 upward, that is, in the closing direction of the valve 11.

B. "Driving method" The EGR valve thus configured is driven by a so-called torque balance method.

That is, a predetermined return torque is applied to the EGR valve in the closing direction of the valve 11 by the coil spring 19 as an urging means, and the direction of opening of the valve 11 is increased by energizing the DC motor 20 in one direction. A variable motor torque is applied, and the opening and closing of the valve 11 is controlled based on the torque balance. Motor torque is
When the motor shaft 31 that moves up and down according to the rotation amount of the rotor 21 pushes the valve shaft 14 downward,
It is transmitted to the valve 11. In the power transmission system for transmitting the motor torque to the valve 11 as described above, a play S at a predetermined interval is formed between the valve shaft 14 and the motor shaft 31 when the valve 11 is closed as shown in FIG. . That is, as shown in FIG. 1, the valve 11 is held in the closed position by the coil spring 19, and the rotor 21 is rotated to one rotation limit position by the spiral spring 32, and the motor shaft 31 is moved to the upper limit position. , A play S is formed between the opposing surfaces of the shafts 11 and 31.

In the case of such a torque balance driving method, the resolution of the adjustment opening of the valve 11 can be theoretically reduced to infinity by continuously controlling the torque generated by the DC motor 20. Further, the DC motor 20 does not generate a control error due to the step-out phenomenon as in the case of the stepping motor, so that the responsiveness can be improved as compared with the case where the stepping motor is used, and the reliability is also improved. Further, since a play S is formed at a predetermined interval between the valve shaft 14 and the motor shaft 31 in the power transmission system, even if the valve 11 and the seat 12 are worn, the valve 11 is completely removed. Closure will be compensated. The interval between the play S is set to, for example, about 0.2 mm in consideration of their wear.

The operating characteristics of the EGR valve having such a configuration have a hysteresis as shown in FIG. FIG.
The abscissa indicates the drive duty of the DC motor 20, and the ordinate indicates the sensor output value (voltage) of the position sensor 40 corresponding to the rotation position of the rotor 21. S1 is a sensor output value when the rotor 21 is at one of the rotation limit positions. Hereinafter, the position of the motor shaft 31 at this time is referred to as a “rotor origin”. S2 is a sensor output value when the motor shaft 31 is moved down from the rotor origin S1 by a play S, that is, when the valve 11 starts to open. Hereinafter, the position of the motor shaft 31 at this time is referred to as “valve origin. "

Lines A, A ', B,
The operation of the EGR valve in the control area on B ', C, C', D, D ', E, E' is as follows.

(Control Area on Line A) Spiral Spring 3
Due to the set torque of 2, the rotor 21 does not move. At this time, the rotor 21 is stopped at one rotation limit position by the set torque of the spiral spring 32, and a predetermined play S is provided between the motor shaft 31 and the valve shaft 14.
Are formed.

(Control Area on Line B) From time P1, the motor torque exceeds the set torque of the spiral spring 32, the rotor 21 rotates, and the motor shaft 31 moves downward accordingly.

(Control Area on Line C) Although the motor shaft 31 abuts on the valve shaft 14 from the time point P2, the rotation of the rotor 21 is stopped due to the return torque of the coil spring 19.

(Control Area on Line D) From point P3, the motor torque exceeds the return torque of the coil spring 19, the rotor 21 rotates, and the motor shaft 31 moves downward accordingly. On this line D, the valve 1
1 is controlled to open.

(Control Area on Line E) Rotation in the other direction of the rotor 21 is restricted by a stopper (stopper plate 31, stopper portion 2A) from the time point P4, and the rotor 21 does not rotate even if the motor torque increases. .

(Control area on line E ') Rotor bearings (such as bearings 26 and 27), brush 29,
Since there is friction in the contact portion such as the position sensor 40, the rotor 21 does not return even if the motor torque is reduced.

(Control Areas on Lines D ', C', B ', A') Appear as lines D, C, B, A slid by friction. On the line D ', the valve 11 is controlled to close.

Lines D and D 'during opening and closing operation of the valve 11
The inclination K changes according to the spring constant of the coil spring 19, and shifts right and left in FIG. 4 according to the magnitude of the set torque. The valve origin S2 corresponds to the valve 11 or the seat 1
2 will change due to wear, etc.
In order to control the opening of the valve with high accuracy, the valve origin S
It is important to grasp 2 accurately.

For example, when the interval of the play S is predicted to be a constant value of 0.2 mm, the sensor output So at the valve origin S2 is calculated based on the sensor output Si at the rotor origin S1 as follows. Can be estimated.

[0032]

S = Si + (△ S × 0.2) ΔS is the sensitivity of the sensor output to the unit rotation amount of the rotor 21 of the position sensor 40.

In this way, when the valve origin S2 is uniformly estimated, it is possible to cope with a change in the interval of the play S caused by wear of the valve 11 and the seat 12 and variations in the components of the EGR valve. However, there is a difference from the actual valve origin, which makes it difficult to control the opening of the valve 11 with high accuracy.

The present embodiment takes such circumstances into consideration,
Taking advantage of the torque balance driving method using a DC motor, the valve origin S
2 to accurately control the opening of the valve 11 with high accuracy.

C. [Control Device] FIG. 2 is a schematic configuration diagram of the entire control device, in which the motor 20 is chopper-controlled by a control unit 50 in the form of a microcomputer. That is, the voltage applied to the motor 20 is turned on and off at a constant cycle, and the FET (field effect transistor) 51 is switched by a PWM signal corresponding to a ratio (drive duty) between the on time and the off time per cycle. The average drive voltage applied to the motor 20 is controlled.

Reference numeral 52 denotes a battery, 53 denotes a Zener diode, and 54 denotes a diode. The current flowing through the motor 20 is limited to one direction. 55 is the control unit 50 and F
An interface with the ET 51, 56 is a control unit 50
This is a regulator for securing the driving voltage (5V) of the driving voltage.

The control section 50 receives a detection signal from an operation state quantity sensor 57 such as a crank angle sensor and a detection signal from a position sensor 40. 58 and 59 are interfaces. The position sensor 40 of the present example
A brush 42 is provided as a movable contact portion that moves on a resistor 41 to which a constant voltage (5 V) is applied. The brush 42 moves as the rotor 21 rotates, and A voltage corresponding to the rotational position of the rotor 21 is output as a detection signal. 60 is the resistor 4
1 is a voltage supply unit for applying a constant voltage.

FIG. 3 is a schematic block diagram for explaining a control system constituted by the control unit 50.

In FIG. 3, reference numeral 61 denotes an operation state quantity sensor 5.
7 is a target position calculation unit for obtaining the optimum opening / closing position of the EGR valve based on the detection signal of No. 7. Reference numeral 67 denotes an origin alignment processing unit, which performs an initial setting operation to be described later and the opening / closing position obtained by the target position calculation unit 61 and the valve origin S.
2 and a voltage corresponding to the target position (hereinafter, referred to as a “target value”) is output after obtaining the consistency. Reference numeral 62 denotes an A / D conversion of the detection signal of the position sensor 40.
The conversion unit converts the voltage (hereinafter, referred to as “current value”) corresponding to the current open / close position of the EGR valve. Based on the deviation between the target value and the current value, the PID
The control amount calculator 63 calculates a proportional component (P component) and an integral component (I
Component) and a differential component (D component) are calculated and output as a PID control amount (voltage). The PID control amount is converted by the drive duty calculator 64 into a drive duty of the DC motor 20 (PID control drive duty). The calculation unit 64 corrects {(PID control amount) / K} in consideration of the above-described gradient K of the operation characteristic due to the return torque in FIG. 4 to reduce the influence of the operation characteristic due to the return torque.

In this way, a feedback control system for PID controlling the DC motor 20 based on the deviation between the target value and the current value is configured. The drive duty from the PID control system is added to compensate for the drive duty from the feedforward control system described later, and becomes the drive duty of the DC motor 20.

Reference numeral 65 denotes a feed forward control unit.
The drive duty of the DC motor 20 corresponding to the target value is calculated and output from the relationship between the sensor output value (target value) such as the lines D and D 'in FIG. 4 and the drive duty. The control unit 65 of the present example calculates and outputs a different drive duty according to the rotation direction of the DC motor 20, that is, the detection direction of the opening movement direction detection unit 66 that detects the opening and closing direction of the valve 11. That is, when the valve 11 is opened, the drive duty corresponding to the target value is calculated from the relationship of the line D in FIG.
Is closed, the drive duty corresponding to the target value is calculated from the relationship of the line D 'in FIG. Detection unit 66
Compares the current value with the current value one time before the current value, and detects the rotation direction of the DC motor 20 based on whether the difference is positive or negative. Thus, a feedforward control system that controls the DC motor 20 according to the current value is configured.

The driving duties from each of the feedback control system and the feedforward control system are added and output as a motor driving duty. Therefore, the drive voltage for generating the motor torque corresponding to the return torque is always applied by the feedforward control system according to the opening / closing direction of the valve 11, and the deviation between the current value and the target value due thereto (excess or insufficient feedforward control). Minutes)
, The feedback control system performs PID control. As a result, regardless of the opening and closing direction of the valve 11, the amount of feedback control can be made relatively small, and the occurrence of vibration can be suppressed.

D. “Initial setting operation of control device” The origin matching processing unit 67 functions as an initial operation control unit and a calculation unit of the valve origin S2, and performs valve opening at the time of engine start in order to enable highly accurate opening control of the valve 11. After accurately grasping the origin S2, the opening / closing position obtained by the target position calculation unit 61 is made consistent with the valve origin S2.

FIG. 5 shows a main routine for reading the valve origin S2. First, the drive duty of the motor 20 is set to "0" (step S1).
The timer interrupt of the interrupt processing routine of FIG. 6 is set (step S2), and the interruption of the interrupt processing routine of FIG. 6 is permitted (step S3). The timer interrupt interval is, for example, 20 msec, and the interrupt processing routine of FIG. 6 is repeatedly executed at the interval. Then, by means of a flag check or the like, a notification of the end of the origin reading process by the interrupt processing routine of FIG. 6 is waited (step S4), and after that, the timer interrupt is released (step S5).

In the interrupt processing shown in FIG. 6, first, the motor 2 is driven by the currently set drive duty D (t).
0 is driven (step S11), and the sensor output value S (t) of the position sensor 40 at that time is read (step S12). In the first interrupt processing, when the drive duty is set to “0” in step S1 of FIG. 4, that is, the drive duty D (t) is set to “0”.
, The sensor output value S (t) at that time is stored as the rotor origin S1 (steps S13 and S1).
4) The drive duty D (t) is increased by one step (step S15). The drive duty is, for example, 100
When% is represented by 8 bits, (100/255)%
Can be set as one stage.

In the next interrupt processing, step S13
To step S16, and the difference ΔS between the sensor output values S (t−1) and S (t) between the previous time and this time is obtained. If the difference ΔS is equal to or smaller than the reference value (15 mV), it is determined that the rotor 21 does not move on the line A in FIG. 4 and the value of the counter C is reset to “0” (step S17, S18), drive duty D
(T) is increased by one step (step S15). On the other hand, when the difference ΔS exceeds the reference value (15 mV), B in FIG.
It is determined that the rotor 21 has rotated on the line, and the value of the counter C is incremented (steps S17 and S1).
9). And when the value of the counter C is 8 or less,
The drive duty D (t) is increased by one step with the value (step S15).

When the value of the counter C exceeds 8, when the
It is determined that it has entered the middle line C, and the sensor output values S (t−10) and S (t−1) from 10 times to 13 times before
1), the average of S (t-12) and S (t-13), that is, the average of a plurality of sensor output values on line B in FIG. 4, is stored as the valve origin S2 (step S21). . Thereafter, the drive duty D (t) is returned to "0" to stop the motor 20 (step S22), and the end of the origin reading process is notified by a flag or the like (step S23).

In this embodiment, the full stroke of the valve 11 is 5 mm, the maximum change width of the sensor output value S is 4 V, and one stage of the drive duty is (100/255)%. Of the sensor output value S is 15.6 mV. Actually, the change width of the drive duty on line D in FIG.
And the sensor output value S per one stage of the drive duty has a variation width several times as large as 15.6 mV. Therefore, by setting the determination reference value in step S17 to 15 mV, the presence / absence of movement of the rotor 21 could be reliably determined. Further, in this example, it is expected that the drive duty is increased by about six steps at the maximum on the line B in FIG. Therefore, when the criterion of the counter C in step S20 is set to eight times, it is determined whether the vehicle has entered the line B and the line D in FIG. I was able to judge for sure.

The origin matching processing unit 67 matches the valve origin S2 thus accurately recognized with the target opening / closing position obtained by the target position calculating unit 61. That is,
As in the following equation, the target value calculated by the target position calculation unit 61 is defined as SA, and the value of the valve origin S2 is added to the value SA to obtain a consistent target value SB.

[0050]

## EQU2 ## SB = SA + S2 The origin alignment treatment section 67 outputs the target value SB with the valve origin S2 being "0". As a result, the opening of the valve 11 can be controlled with high accuracy.

Immediately after the rotor origin S1 and the valve origin S2 are obtained, the origin check processing of FIG. 7 may be executed.

That is, the valve origin S2 and the rotor origin S
It is determined whether or not the difference between the sensor output values of No. 1 is 10 mV or more (step S31). If the determination is affirmative, it is determined that the sensor output is normal and the process ends. On the other hand, when a negative determination is made, it is determined that the interval of the play S between the valve shaft 14 and the motor shaft 31 is so small that the valve 11 may not be able to be completely closed. I do. That is, the power supply relay of the motor 20 is turned off to stop driving the motor 20 (step S32), and the engine controller is notified that the EGR valve is not operating, and the warning lamp is turned on to notify the driver (step S33, S3
4).

(Second Embodiment) FIGS. 8 to 13 are views for explaining a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the case of the present example, the origin alignment processing unit 67 and the maximum displacement amount alignment processing unit 68 in FIG.
Medium rotor origin S1, valve origin S2, maximum displacement point S
3, and the drive duties D3, D4, D5 are determined to recognize the valve operating characteristics of the EGR valve.
The R valve is controlled.

FIG. 9 shows a main routine for reading the valve operating characteristics. First, the drive duty of the motor 20 is set to "0" (step S4).
1), the flag F is cleared (step S42). Then, a timer interrupt of a series of interrupt processing routines of FIGS. 10 and 11 is set (step S43),
The interruption of the interruption processing routine is permitted (step S44). The timer interrupt interval is, for example, 20 msec, and a series of interrupt processing routines shown in FIGS. 10 and 11 are repeatedly executed at the interval. Then, by means of a flag check or the like, the process waits for notification of the end of the reading process of the valve operating characteristics by the interrupt process routine (step S45), and after that, releases the timer interrupt (step S4).
6).

In the series of interrupt processing in FIGS. 10 and 11, the processing in FIG.
Steps S51 to S61 are the same as steps S11 to S21 in FIG. 6 described above, and FIG.
This is a process in which 54A, S56A, S62, and S63 are added. A step S45A sets the flag F to "A" after the rotor origin S1 is set in the step S54. In step S56A, the flag F is determined after step S56, and when the flag F is "A", the process proceeds to step S57, and when it is not "A", the process proceeds to step S57.
Go to step S64. In step S62, after the valve origin S2 is set in step S61, the drive duty D (t-9) nine times before is stored as the drive duty D3 at the point P3 in FIG. Step S63
Sets the flag F to "D" thereafter. This “D” means that the control status is on the line D in FIG.

In the interrupt processing at the latter stage of FIG.
First, the flag F is determined in step S64, and if it is "D", the following processing is performed. That is, when the difference ΔS between the sensor output values S (t−1) and S (t) at the previous time and this time is equal to or more than the reference value (15 mV), the rotor 21 rotates on the line D in FIG. Is determined to have been performed, the value of the counter C is reset to “0” (steps S65 and S66), and then the drive duty D (t) is set to 1
The step is raised (step S55). On the other hand, when the difference ΔS is smaller than the reference value (15 mV), it is determined that the rotor 21 has stopped moving on the E line in FIG. 4, and the value of the counter C is incremented (steps S65 and S6).
7). If the value of the counter C is equal to or less than 10, the drive duty D (t) is increased by one step with the value (steps S68 and S55). When the value of the counter C exceeds 10, the sensor output values S (t), S (t-1), S (t-2), and S (t) from this time to three times before are output.
-3), that is, the average of a plurality of sensor output values on the line E in FIG. 4, is stored as the maximum displacement point S3 in FIG. 4 (steps S68, S69). Thereafter, the drive duty D (t-11) eleventh before is stored as the drive duty D4 at the point P4 in FIG. 4 (step S70), and the flag F is set to "E" (step S71).

If it is determined in step S72 after the negative determination in step S64 that the flag F is "E", the following processing is performed. That is, the difference ΔS between the sensor output values S (t−1) and S (t) between the previous time and the present time.
Is equal to or more than the reference value (−15 mV), it is determined that the rotor 21 does not move on the E line in FIG.
Is reset to "0" (steps S73 and S73).
74), the drive duty D (t) is reduced by one stage (step S75). On the other hand, the difference ΔS is equal to the reference value (−15 m
If it is smaller than V), it is determined that the rotor 21 is moving on the line D 'in FIG. 4, and the value of the counter C is incremented (steps S73, S76). And
When the value of the counter C exceeds 8, the drive duty D (t-9) nine times before is stored as the drive duty D5 at the point P5 in FIG. 4 (step S78). Thereafter, the drive duty D (t) is returned to "0" to stop the motor 20 (step S79), and the completion of reading the valve operating characteristics is notified by a flag or the like (step S80).

As described above, the operating characteristics of the EGR valve shown in FIG. 4 can be recognized by obtaining the rotor origin S1, the valve origin S2, the maximum displacement point S3, and the drive duties D3, D4, D5. On the basis of,
The EGR valve can be controlled with high accuracy. Also, the linearity error of the sensor 40 and the sensor 40
And the stopper of the rotor 21 (stopper plate 31,
A control problem caused by an assembly error of the stopper portion 2A), for example, an unnecessary current continues to flow through the motor 20 because the target value when the valve 11 is fully opened deviates greatly from the maximum displacement point S3. Such problems can be avoided.

The drive duty D3 at the point P3, the valve origin S2, the drive duty D4 at the point P4, the maximum displacement point S3, and the drive duty D5 at the point P5.
Using the maximum displacement point S3 and F3 in FIG.
Equation (1) of the control straight line can be obtained. X
Is the horizontal axis, Y is the vertical axis, and K is the slope.

[0061]

(Equation 3)

By obtaining the straight line F in this manner, more precise control can be performed particularly in response to the temperature dependency of the EGR valve. That is, in the EGR valve configured as shown in FIG. 1, BH such as ferrite used as a field magnet of the motor 20 is used.
The characteristics have a temperature dependence, and the resistance of a conductor used as an armature coil also has a temperature dependence. Therefore, the torque characteristic of the motor 20 has a temperature dependence, and the EGR valve driven by the balance between the motor torque and the return torque of the motor 20 necessarily has a temperature dependence in the operation characteristic. Will be. When the engine is started, obtaining such a control straight line F for the EGR valve enables control corresponding to the temperature dependency.

Further, the abnormality of the EGR valve can be diagnosed, including the abnormal output of the motor 20 caused by excessive friction or coil disconnection due to an abnormal assembly of the EGR valve. FIG. 12 shows an example of a process for such an abnormality diagnosis, which is executed immediately after the operation characteristic of the EGR valve is obtained.

First, it is determined whether or not the drive duty D3 at the point P3 in FIG. 4 is greater than 40% (step S91). If the determination is affirmative, the motor 21 is disconnected and the commutator is in contact. It is determined that the drive duty D3 has become abnormally large due to a defect or the like, and error processing is performed (step S94). That is, the power supply relay in the power supply line of the motor 20 is turned off, the motor 20 is disabled, and the fact that the EGR valve is not operated is notified to the engine controller, and the warning lamp is turned on to notify the driver.

Next, it is determined whether or not the maximum displacement point S3 is smaller than 4.3 V (step S92). If the determination is affirmative, the maximum valve opening due to some abnormal interference of the sensor 21 or the movable part is determined. It is determined that the degree has become abnormally small, and error processing is performed (step S94). As a result,
It can be avoided that a large current continues to flow through the motor 20.

Next, during the drive duties D4 and D5,
That is, the hysteresis width at the maximum valve opening is 15
It is determined whether it is greater than% (step S93). If the determination is affirmative, it is determined that the friction of the movable portion has become abnormally large, and error processing is performed (step S94). As a result, deterioration of controllability due to occurrence of hunting can be avoided.

The maximum displacement amount matching processing unit 6 in FIG.
8 performs a maximum displacement amount matching process as shown in FIG. 13 based on the maximum displacement point S3.

That is, when the target value of the control is the maximum displacement point S3
Is exceeded, the target value is changed to the maximum displacement point S3 (steps S101, S102). By limiting the maximum target value to the maximum displacement point S3 in this manner, a problem occurs when the target value exceeds the maximum displacement point S3, that is, the motor 20 is driven by the stopper plate 31 and the stopper portion 2A.
Since the drive current continues to flow unnecessarily to the motor 20 while the motor is restricted to the rotation limit position, it is possible to avoid a problem that heat is generated and a temperature failure is caused.

(Third Embodiment) The feedforward control unit 65 may determine the drive duty on the assumption of the straight line F in FIG. That is, the straight line F is an imaginary straight line having a slope K rising from an intermediate DF between the drive duties D3 and D6 at the rising points P3 and P6 of the lines D and D ', and considering the slope K and the intermediate drive duty DF. , ｛(Sensor output value corresponding to target value)
/ K + DF} to reduce the effect of return torque on operating characteristics. Therefore, from the relationship between the target value such as the straight line F and the drive duty of the DC motor 20, the drive duty for offset control corresponding to the target value can be calculated regardless of the rotation direction of the DC motor 20.

As a result, the torque difference between the lines D and F and between the lines D 'and F is less likely to be affected by disturbance, and the EGR valve can be easily controlled stably.

(Fourth Embodiment) The lines D, D 'and F in FIG. 5 described above can be obtained by learning.

The acquisition procedure is as follows. Each time the target value substantially matches the current value within a predetermined unit time, the current target value and the drive duty of the DC motor 20 are stored.
After obtaining a predetermined number of drive duty data for one target value, an average value of the drive duty for each target value is obtained one by one. Then, the slopes K of the lines D, D ', and F and the drive duties D3, D6, and DF at the time of rising are approximated from the average value for each target value. When the data on the lines D, D ', and F obtained as described above becomes outdated, the data is recalculated and updated.

(Fifth Embodiment) In order to generate a motor torque in the opposite direction to the return torque by the feedback control system, the DC motor 20 is controlled not only in one direction but also in the same direction as the return torque. In order to generate the motor torque described above, the DC motor 20 may be energized in other directions. In that case, the PID control amount when the energization control of the DC motor 20 is performed in one direction is set to plus, and the PID control amount when
The energization control of the DC motor 20 in the other direction may be performed according to the control amount. As described above, by generating the motor torque in the same direction as the return torque, the response in the closing direction of the valve 11 is improved.

FIG. 14 is an explanatory diagram of a circuit configuration example in the case where the DC motor 20 is bidirectionally energized as described above.
In the case of this example, four sets of transistors 71, 72, 73,
74 and diodes 75, 76, 77, 78, and the DC motor 2
0 is chopper-controlled. That is, when controlling the energization of the DC motor 20 in one direction, the transistor 71 is turned on, the transistor 72 is switched by the PWM signal, and when controlling the energization of the DC motor 20 in the other direction, the transistor 73 is turned on. , The transistor 74 is switched by the PWM signal. 81, 82, 83 and 84 are transistors 7
1, 72, 73, and 74 and the control unit 50.

(Sixth Embodiment) Since the interval of the play S does not change in a short time, the detection operation of the valve origin S2 is performed when the engine is started or when the engine is turned off (OF).
F) It may be performed only at the time. This shortens the time when the EGR valve becomes inoperable.
It is preferable to make it controllable.

In order to shorten the detection time of the valve origin S2, the drive duty is increased by one stage from the drive duty near the point P2 in FIG. 4 rather than by one stage from "0". Is preferred. For example, the drive duty D1 at the point P1 in FIG.
%, When the drive duty D2 at the point P2 is 26%, the valve origin S2 can be detected in a short time by changing the drive duty in a small range including 24% to 26%. FIG. 15 is a flowchart for explaining a detection operation when the initial drive duty at the time of detecting the valve origin is set to be large, and is executed in the engine state.

First, the motor 20 is driven by outputting the drive duty DA at the start of the valve origin detection operation (step S111). The drive duty DA is, for example, 24% when the drive duty D1 at the point P1 in FIG.
If the drive duty D2 at the time point P2 is about 26%, it is set to about 22%. Then, the drive duty is increased by one step (step S11).
2). The degree of the increase is, for example, 30% per 1%.
It is set to the extent that it is raised over 0 msec. If the degree of the increase is too large, the motor shaft 31 vigorously hits the valve shaft 14 and the valve origin S2
The detection accuracy is deteriorated, and if the degree is too small, the detection time becomes long.

Thereafter, it is determined whether or not the change width of the sensor output value has reached a predetermined reference change width Sw (step S1).
13). The change width Sw of the comparison standard is, for example, the play S
If the distance between the two (see FIG. 1) is about 0.2 mm,
The variation width of the sensor output required to open the valve 11 by 0.1 mm is set. Then, when the sensor output value exceeds the change width Sw, it is determined that the rotor 21 has rotated on the line B in FIG. 4, and in step S114, the current and previous sensor output values S (t) And S (t-1)
Is determined to be equal to or smaller than a predetermined reference difference ΔSc. When the difference exceeds the reference difference ΔSc, it is determined that the rotor 21 is rotating on the line B in FIG. 4, and the counter C1 is cleared (step S115). The difference between the sensor output values S (t) and S (t-1) is a predetermined reference difference △ Sc
In the following cases, it is determined that the rotor 21 does not move on the line C in FIG. 4, and the counter C1 is incremented (step S116). The reference difference ΔSc is, for example,
It is set to be equal to or less than the change width of the sensor output value when the valve 11 is opened by 18 μm.

Then, when the value of the counter C1 becomes 25 or more, the average value of the sensor outputs of a total of 25 points on the line C at the 25 count times is obtained, and this is set as the valve origin S2. For example, when the control cycle of the processing routine of FIG. 15 is 4 msec, 100 msec (4
When the valve 11 is continuously stopped (msec × 25 times), the valve origin S2 is obtained.

[0080]

As described above, the first aspect of the present invention employs a torque balance drive system in which the valve is opened and closed by the balance between the return torque by the urging means and the motor torque of the DC motor. A predetermined play is formed in the power transmission system between the motor and the valve, and the operating position of the DC motor at the time when the valve starts to open is obtained, whereby the opening of the EGR valve is controlled with high resolution and high accuracy. In addition to enabling the valve to be completely closed and ensuring that the EGR valve is closed and the operating origin of the valve driving motor, the opening and closing control can always be performed accurately.

According to a second aspect of the present invention, the DC motor is reciprocated in the maximum operating range, and the operating characteristics of the EGR valve are obtained from the relationship between the motor torque and the operating position of the DC motor. Accurate grasp of the operation characteristics enables more precise control.

According to a third aspect of the present invention, the DC motor
Chopper control can be performed by the WM signal.

According to a fourth aspect of the present invention, a play gap is formed between the opposing surfaces of the motor shaft and the valve shaft of the DC motor, so that these shafts can be used.
A power transmission system that compensates for complete closing of the valve can be simply configured.

According to the fifth aspect of the present invention, the responsiveness of the EGR valve in the direction in which the return torque is applied can be improved by controlling the DC motor to generate the motor torque in the same direction as the return torque. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an EGR valve according to a first embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of a control unit according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a control unit in FIG. 2;

FIG. 4 is an explanatory diagram of an operation characteristic of the EGR valve of FIG. 1;

FIG. 5 is a flowchart illustrating a main routine for an origin reading process of a control unit in FIG. 2;

FIG. 6 is a flowchart illustrating an interrupt process of a control unit in FIG. 2;

FIG. 7 is a flowchart illustrating an origin check process of a control unit in FIG. 2;

FIG. 8 is a block diagram of a control unit according to a second embodiment of the present invention.

9 is a flowchart for explaining a main routine for processing of reading valve operating characteristics of a control unit in FIG. 8;

FIG. 10 is a flowchart illustrating an interrupt process of a control unit in FIG. 8;

FIG. 11 is a flowchart illustrating an interrupt process of a control unit in FIG. 8;

FIG. 12 is a flowchart illustrating an abnormality diagnosis process of a control unit in FIG. 8;

FIG. 13 is a flowchart illustrating a maximum displacement amount matching process of a control unit in FIG. 8;

FIG. 14 is an explanatory diagram of a DC motor drive circuit according to a fifth embodiment of the present invention.

FIG. 15 is a flowchart for explaining a detection operation of a valve origin in a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Valve 12 Seat 19 Spring (biasing means) 20 DC motor 40 Position sensor 50 Control part 61 Target position calculation part 62 A / D conversion part 63 PID control amount calculation part 64 Drive duty calculation part 65 Feedforward control part 66 Opening direction Detector 67 Origin matching processor 68 Maximum displacement matching processor

Claims (5)

[Claims] An EG which is provided with a predetermined return torque in a closing direction of an EGR valve by an urging means, and a variable motor torque in an opening direction of an EGR valve by a DC motor, and is opened and closed by their torque balance.
A control device for an R valve, comprising: a power transmission system that transmits a motor torque of the DC motor to the EGR valve, and forms a predetermined amount of play when the EGR valve is closed; Detecting means for detecting, initial operation control means for gradually increasing the motor torque of the DC motor from the time the EGR valve is closed, and a change in the motor torque of the DC motor gradually increased by the initial operation control means; Calculating means for obtaining an operating position of the DC motor at the time when the opening of the EGR valve is started from a relationship with a change in an operating position of the DC motor detected by the detecting means. Control device. 2. The initial operation control means gradually increases the motor torque of the DC motor so as to reciprocate the DC motor in a maximum operation range, and then gradually decreases the motor torque. 2. The EGR according to claim 1, wherein an operating characteristic of the EGR valve is obtained from a relationship between a change in motor torque and a change in an operating position of the DC motor detected by the detecting unit. 3.
Valve control device. 3. The EGR valve control device according to claim 1, wherein the initial operation control means controls the motor torque by performing PWM control on the DC motor. 4. The power transmission system is connected to the EGR valve, the valve shaft opens the EGR valve by being pushed in one direction, and is linearly moved according to an operation amount of the DC motor. A motor shaft that opposes the valve shaft with a predetermined play gap when the valve is closed, and that pushes the valve shaft in one direction after coming into contact with the valve shaft as the motor torque of the DC motor increases. The control device for an EGR valve according to any one of claims 1 to 3, further comprising: 5. The DC motor according to claim 1, wherein the DC motor can apply motor torque in an opening direction and a closing direction to the EGR valve by energizing in one direction and another direction. EGR valve control device.