JP2006200387A - Control device for variable valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a variable valve system capable of acquiring a rotating angular velocity of a motor without a large delay and with a high degree of precision, thereby achieving accurate PWM control of motor current in consideration of counter electromotive voltage of the motor. <P>SOLUTION: Effective driving voltage of a motor is acquired from voltage of a driving power source in a motor and counter electromotive voltage estimated from a rotating angular velocity of the motor. A duty ratio in PWM control is set from the effective driving voltage and applied voltage corresponding to a current command value. A hysteresis processing is provided to detected data of the rotating angle employed to compute the rotating angular velocity, whereby a noise component superimposing on the detected signal of the rotating angle is eliminated by valve spring reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a variable valve mechanism that makes an opening characteristic of an engine valve variable by drive control of a motor.

Patent Document 1 discloses a variable valve mechanism that makes a lift of an engine valve variable with an operating angle by rotationally driving a control shaft by a motor.
JP 2001-003773 A

By the way, in the variable valve mechanism, a counter electromotive voltage is generated by the rotation of the motor. Therefore, in order to accurately control the motor current by PWM control, the switching duty ratio is set in consideration of the counter electromotive voltage. It is desirable to decide.
The counter electromotive voltage can be estimated from the rotational angular velocity of the motor.
However, noise is superimposed on the detection signal of the angle sensor that detects the rotation angle of the motor due to the load acting on the control shaft due to the valve spring reaction force or the like.

For this reason, if the rotational angular velocity is obtained by differentiating the rotational angle information detected by the angle sensor and the counter electromotive voltage is estimated from the rotational angular velocity, the counter electromotive voltage cannot be accurately estimated, resulting in the motor current. There was a problem that it was not possible to control with high precision.
Here, if the detection signal from the angle sensor is differentiated after being processed by a low-pass filter, the influence of noise can be suppressed. In this case, the phase of the estimated value of the rotational angular velocity is relative to the actual rotational angular velocity. There was a problem that it was greatly delayed.

  The present invention has been made in view of the above problems, and can determine the rotational angular velocity of the motor with high accuracy without a large delay, so that variable control that can accurately perform PWM control in consideration of the back electromotive force of the motor. An object of the present invention is to provide a control device for a valve mechanism.

Therefore, according to the present invention, there is provided a control device for a variable valve mechanism that varies an opening characteristic of an engine valve by motor drive control, and obtains a rotation angular velocity based on a rotation angle of the motor detected by an angle sensor. , Estimating the back electromotive voltage of the motor based on the rotational angular velocity, setting a control signal of the motor current based on the back electromotive voltage,
A hysteresis processing signal that changes in response to a change exceeding a predetermined width of the detection result by the angle sensor is generated, and the rotational angular velocity is obtained based on the hysteresis processing signal.

According to the above configuration, even if the detection signal of the angle sensor fluctuates within the predetermined width around the actual rotation angle due to noise superposition, the hysteresis processing signal does not fluctuate corresponding to the noise superposition. As a result, the noise component is removed from the detection signal of the angle sensor.
When a change exceeding the fluctuation range due to noise occurs, the hysteresis processing signal changes in response, the rotation angular velocity at that time is obtained, and the back electromotive force is estimated from the rotation angular velocity.

  Therefore, the rotational angular velocity (counterelectromotive voltage) can be obtained by eliminating the influence of noise, and the motor angular control (counterelectromotive voltage) does not cause a large phase delay, and the motor drive control (PWM control) is accurate. It can be done well.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating a variable valve mechanism in the embodiment.
A variable valve mechanism 1 shown in FIG. 1 is a mechanism that changes the lift of an engine valve together with the operating angle, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-107725. In this embodiment, the variable valve mechanism 1 is applied to an intake valve. An example is shown.

  The variable valve mechanism 1 includes an intake valve 11 slidably provided on a cylinder head (not shown) and a drive shaft 2 rotatably supported by a cam bracket (not shown) on the cylinder head. A drive eccentric cam 3 fixed to the drive shaft 2 by press-fitting or the like, and a control which is rotatably supported by the same cam bracket at a position above the drive shaft 2 and arranged in parallel with the drive shaft 2 A shaft 12, a rocker arm 6 as an intermediate member swingably supported by the control eccentric cam 18 of the control shaft 12, and a swing cam 9 that comes into contact with the tappet 10 disposed at the upper end of the intake valve 11; It has.

The drive eccentric cam 3 and the rocker arm 6 are linked by a link arm 4, and the rocker arm 6 and the swing cam 9 are linked by a link member 8.
The drive shaft 2 is driven by a crankshaft of an internal combustion engine via a timing chain or a timing belt.
The drive eccentric cam 3 has a circular outer peripheral surface, the center of the outer peripheral surface is offset from the axis of the drive shaft 2 by a predetermined amount, and the annular portion of the link arm 4 is rotatable on the outer peripheral surface. Is fitted.

The rocker arm 6 has a substantially central portion supported by the control eccentric cam 18 so as to be swingable, and an arm portion of the link arm 4 is linked to one end of the rocker arm 6 via a connecting pin 5. The upper end portion of the link member 8 is linked to the end portion via the connecting pin 7.
The control eccentric cam 18 is eccentric from the axis of the control shaft 12, whereby the rocking center of the rocker arm 6 changes according to the angular position of the control shaft 12.

The rocking cam 9 is fitted to the outer periphery of the drive shaft 2 and is rotatably supported, and a lower end portion of the link member 8 is linked to an end portion extending laterally via a connecting pin 17. ing.
On the lower surface of the swing cam 9, a base circle surface concentric with the drive shaft 2 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface come into contact with the upper surface of the tappet 10 according to the swing position of the swing cam 9.

That is, the base circle surface is a section where the lift amount of the intake valve 11 becomes 0 as a base circle section. When the swing cam 9 swings and the cam surface contacts the tappet 10, the intake valve 11 gradually moves. It will lift.
A slight ramp section is provided between the base circle section and the lift section.

As shown in FIG. 1, the control shaft 12 is configured to rotate within a predetermined angle range by a DC servo motor 13 which is a lift / operation angle control actuator provided at one end.
The DC servo motor 13 is controlled by a control signal from the controller 50 and rotationally drives the control shaft 12 via the worm gear 15.

Here, the rotation angle of the control shaft 12 is detected by an angle sensor 14 composed of, for example, a potentiometer, and the DC servo motor 13 is closed-loop controlled based on the detected actual control state.
The operation of the variable valve mechanism 1 will be described. When the drive shaft 2 rotates, the link arm 4 moves up and down by the cam action of the drive eccentric cam 3, and the rocker arm 6 swings accordingly.

The swing of the rocker arm 6 is transmitted to the swing cam 9 via the link member 8, and the swing cam 9 swings.
The tappet 10 is pressed by the cam action of the swing cam 9, and the intake valve 11 is lifted.
Here, when the angle of the control shaft 12 is changed by being rotationally driven by the DC servo motor 13, the center position of the rocker movement of the rocker arm 6 is moved to change the initial position of the rocker arm 6. The initial swing position of the is changed.

For example, if the control eccentric cam 18 is positioned upward in the figure, the rocker arm 6 is positioned upward as a whole, and the end of the swing cam 9 on the side of the connecting pin 17 is relatively lifted upward. Become.
That is, the initial position of the swing cam 9 is inclined in a direction in which the cam surface is separated from the tappet 10.
Therefore, when the swing cam 9 swings as the drive shaft 2 rotates, the base circle surface is kept in contact with the tappet 10 for a long time, and the period during which the cam surface is in contact with the tappet 10 is short.

Therefore, the lift amount of the intake valve 11 is reduced as a whole, and the angle range from the opening timing to the closing timing of the intake valve 11, that is, the operating angle is also reduced.
Conversely, assuming that the control eccentric cam 18 is positioned downward in the figure, the rocker arm 6 is positioned downward as a whole, and the end of the swing cam 9 on the side of the connecting pin 17 is relatively pushed downward. It becomes a state.

That is, the initial position of the swing cam 9 is inclined in a direction in which the cam surface approaches the tappet 10.
Therefore, when the swing cam 9 swings as the drive shaft 2 rotates, the portion that contacts the tappet 10 immediately shifts from the base circle surface to the cam surface.
Accordingly, the lift amount of the intake valve 11 increases as a whole, and the operating angle of the intake valve 11 also increases.

The initial position of the control eccentric cam 18 continuously changes according to the rotation angle of the control shaft 12, and accordingly, the lift characteristics of the intake valve 11 change continuously.
That is, the lift and the operating angle can be continuously expanded and contracted simultaneously.
Here, the configuration of the controller 50 will be described with reference to a control block diagram shown in FIG.

A detection signal (output voltage) from the angle sensor 14 is input to an angle signal input unit 501, and the angle signal input unit 501 converts the detection signal (output voltage) into rotation angle data of the control shaft 12. Output.
The rotation angle data of the control shaft 12 is input to the motor current command generation unit 502.
The motor current command generation unit 502 receives an angle command (target angle) of the control shaft 12 that is separately calculated based on the engine operating state, and the angle command and the actual angle detected by the angle sensor 14. Based on the motor current command (target motor current) is calculated and output.

The PWM duty calculator 503 receives the motor current command and calculates a duty ratio for switching the power supply to the DC servo motor 13 so that the current flowing through the DC servo motor 13 becomes the command value.
The duty ratio is input to the PWM signal generation circuit 504, and the PWM signal generation circuit 504 outputs a switching pulse (PWM pulse) having the duty ratio to the switching circuit 505.

The switching circuit 505 switches ON / OFF of power supply from the drive power supply 506 to the DC servo motor 13 in accordance with a switching pulse (PWM pulse).
By the way, in order to flow the current according to the motor current command to the DC servo motor 13 with high accuracy, the PWM duty calculation unit 503 reverses the voltage of the drive power supply 506 and the rotation of the DC servo motor 13. The duty ratio is determined based on the electromotive voltage.

In the PWM duty calculator 503, the duty ratio is
Duty ratio = (Voltage VM to be applied to the motor) / (Effective voltage VA usable for driving the motor)
Calculate as
As for the voltage VM to be applied to the motor, assuming that the DC resistance of the DC servo motor 13 is RM and the motor current command value is ICMD,
VM = ICMD × RM
Is calculated as

That is, the voltage VM to be applied to the motor can be obtained from the motor current command value ICMD by storing the DC resistance RM of the DC servo motor 13 as known data in advance.
On the other hand, the effective voltage VA that can be used for driving the motor is a value obtained by subtracting the counter electromotive voltage generated with the rotation of the DC servo motor 13 from the voltage of the drive power source 506.

The voltage of the drive power source 506 is detected by a drive voltage detector 507 and output to the PWM duty calculator 503.
Further, the counter electromotive voltage generated with the rotation of the DC servo motor 13 is calculated by the counter electromotive voltage calculation unit 508 based on the rotational angular velocity of the DC servo motor 13 and output to the PWM duty calculation unit 503.

The back electromotive voltage calculation unit 508 receives the rotational angular velocity data obtained by the rotational speed calculation unit 509, and the back electromotive voltage calculation unit 508 multiplies the rotational angular velocity data by a constant stored in advance. Thus, the counter electromotive voltage is obtained, and this is output to the PWM duty calculator 503.
The rotational speed calculation unit 509 obtains rotational angular velocity data by differentiating the rotational angle data of the control shaft 12 output from the angle signal input unit 501.

Note that the rotation speed calculation unit 509 calculates the difference between the latest rotation angle and the rotation angle before a certain time (for example, 10 ms) as data indicating the rotation angular speed.
Here, between the angle signal input unit 501 and the rotation speed calculation unit 509, a hysteresis processing unit 510 that performs a hysteresis process for removing noise from the rotation angle data is provided.

A load due to a valve spring reaction force or the like acts on the control shaft 12 where the angle sensor 14 detects the rotation angle, and thereby noise is superimposed on the detection signal of the angle sensor 14 (see FIG. 3).
For this reason, if the rotational angular velocity is directly calculated from the detection result of the angle sensor 14, the fluctuation of the noise component is picked up (see FIG. 4), and the rotational angular velocity calculation accuracy is greatly reduced. The estimation accuracy is lowered and cannot be adjusted to the motor current command value.

Therefore, by calculating the rotation angular velocity based on the rotation angle signal after removing the noise by the hysteresis processing unit 510, the estimation accuracy of the back electromotive voltage is ensured and the motor current command value can be adjusted with high accuracy. is there.
Next, details of processing contents in the hysteresis processing unit 510 will be described with reference to the flowchart of FIG.

In step S1, the angle signal input unit 501 is more current than the value obtained by adding the hysteresis width HysWidth stored in advance to the previous value of the rotation angle HysCenter (hysteresis processing signal) output from the hysteresis processing unit 510 to the rotation speed calculation unit 509. It is determined whether or not the detected rotation angle VEL # ANGL0 is large.
If VEL # ANGL0> HysCenter + HysWidth, the process proceeds to step S2, and the rotation angle signal HysCenter is updated according to the following equation.

HysCenter = VEL # ANGL0−HysWidth
On the other hand, when VEL # ANGL0 ≦ HysCenter + HysWidth, the process proceeds to step S3.
In step S3, it is determined whether or not the latest rotation angle VEL # ANGL0 detected by the angle signal input unit 501 is smaller than the value obtained by subtracting the hysteresis width HysWidth from the previous value of the rotation angle HysCenter.

If VEL # ANGL0 <HysCenter−HysWidth, the process proceeds to step S4, and the rotation angle HysCenter is updated according to the following equation.
HysCenter ＝ VEL # ANGL0 ＋ HysWidth
When it is determined in step S3 that VEL # ANGL0 ≧ HysCenter−HysWidth, that is, HysCenter−HysWidth ≦ VEL # ANGL0 ≦ HysCenter + HysWidth, and the rotation angle VEL # ANGL0 is the previous value ± of the rotation angle HysCenter. When it is within the dead zone of the hysteresis width HysWidth, the process proceeds to step S5.

In step S5, the rotation angle HysCenter is held at the previous value.
The hysteresis width HysWidth is set to substantially the same value as the amplitude of the noise component, and the rotational speed calculation unit 509 obtains the rotational angular speed by differentiating the rotational angle HysCenter.
According to the above configuration, when the rotation angle VEL # ANGL0 output from the angle signal input unit 501 does not show a change exceeding the hysteresis width HysWidth, that is, the rotation angle VEL # ANGL0 is an actual rotation angle due to superposition of noise components. When the angle fluctuates around the center, the rotation angle HysCenter remains constant without changing in response to the fluctuation (see FIG. 6).

In addition, when the rotation angle VEL # ANGL0 shows a change exceeding the hysteresis width HysWidth (noise component amplitude), the rotation angle HysCenter is equivalent to the change of the rotation angle VEL # ANGL0 exceeding the hysteresis width HysWidth. Is changed in response (see FIG. 6).
Therefore, the rotation angle HysCenter after the hysteresis processing is a signal obtained by removing a noise component from the rotation angle VEL # ANGL0 (see FIG. 3), and the rotation angular velocity is not calculated based on fluctuation due to noise superposition, The detection accuracy of the rotational angular velocity is improved (see FIG. 7).

Further, since the detection accuracy of the rotational angular velocity is improved, the estimation accuracy of the back electromotive force is improved, and the current of the DC servo motor 13 can be adjusted to the motor current command value with high accuracy.
In addition, when the rotation angle VEL # ANGL0 shows a change exceeding the fluctuation range due to the noise component, the rotation angle HysCenter immediately changes in response (see FIG. 6), so the estimated value of the rotation angular velocity with respect to the actual rotation angular velocity. Does not cause a large phase delay, and deterioration of controllability due to a phase shift can be avoided.

In the above embodiment, the hysteresis width HysWidth is a fixed value. However, when the amplitude of the noise component changes due to a change in the valve spring reaction force due to the lift amount, the hysteresis width HysWidth is set to the rotation angle HysCenter. It can be set as the structure changed according to (lift amount).
FIG. 8 is a control block diagram showing the second embodiment having the above-described configuration.

The control block diagram of FIG. 8 differs from the control block diagram of FIG. 2 only in that a hysteresis width setting unit 511 is added.
The hysteresis width setting unit 511 receives the rotation angle HysCenter output from the hysteresis processing unit 510, sets the hysteresis width HysWidth variably according to the rotation angle HysCenter, and outputs it to the hysteresis processing unit 510. To do.

  In the hysteresis width setting unit 511, in the variable valve mechanism 1 having the above configuration, when the angle of the control shaft 12 is in the vicinity of the middle position of the variable range, the valve spring reaction force becomes the largest and the noise amplitude becomes the largest. Correspondingly, when the rotation angle HysCenter is near the middle position of the variable range, the hysteresis width HysWidth is set to the largest value (see FIG. 9).

The flowchart of FIG. 10 shows the processing contents in the hysteresis processing unit 510 and the hysteresis width setting unit 511.
In step S11, the hysteresis width HysWidth is set based on the rotation angle HysCenter. In steps S12 to S16, the hysteresis width HysWidth set in step S11 is used in the same manner as in steps S1 to S5. Update the rotation angle HysCenter.

According to the second embodiment, the minimum hysteresis width HysWidth can be set in response to the change in the amplitude of noise according to the rotation angle. While suppressing, it can prevent picking up a noise component and presuming rotation angular velocity.
The structure of the variable valve mechanism 1 is not limited to that shown in FIG. 1, and the engine valve whose open characteristic is variable by the variable valve mechanism 1 is not limited to the intake valve. The opening characteristics of the variable engine valve are not limited to the lift and the operating angle.

The perspective view which shows the variable valve mechanism in embodiment. The block diagram which shows the control function of the controller in 1st Embodiment. The figure which shows the superimposition state of the noise with respect to an angle detection value. The figure which shows the characteristic of the angular velocity data calculated using the angle data before a hysteresis process. The flowchart which shows the control function of the controller in 1st Embodiment. The figure which shows the correlation with the sensor detection value in embodiment, and the angle data after a hysteresis process. The figure which shows the characteristic of the angular velocity data calculated using the angle data after a hysteresis process. The block diagram which shows the control function of the controller in 2nd Embodiment. The figure which shows the correlation with the angle data and hysteresis width after the hysteresis process in 2nd Embodiment. The flowchart which shows the control function of the controller in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Variable valve mechanism, 11 ... Intake valve, 12 ... Control shaft, 13 ... DC servo motor, 14 ... Angle sensor, 501 ... Angle signal input part, 502 ... Motor current command generation part, 503 ... PWM duty calculation part, 504... PWM signal generation circuit, 505... Switching circuit, 506... Drive power supply, 507... Drive voltage detection unit, 508 .. back electromotive force calculation unit, 509. Part

Claims (6)

A control device for a variable valve mechanism that varies an opening characteristic of an engine valve by driving control of a motor,
An angle sensor for detecting a rotation angle of the motor; obtaining a rotation angular velocity of the motor based on the rotation angle detected by the angle sensor; estimating a back electromotive voltage of the motor based on the rotation angular velocity; While setting a control signal of the motor current based on the back electromotive voltage,
A control device for a variable valve mechanism, wherein a hysteresis processing signal that changes in response to a change exceeding a predetermined width of a detection result by the angle sensor is generated, and the rotational angular velocity is obtained based on the hysteresis processing signal.   An effective driving voltage in the motor is obtained from the back electromotive voltage and the power supply voltage of the motor, and a duty ratio for switching voltage application to the motor is set so that a target motor current can be obtained with the effective driving voltage. The control apparatus for a variable valve mechanism according to claim 1.   When the latest detection result of the angle sensor is the previous value of the hysteresis processing signal ± the dead band of the predetermined width, the hysteresis processing signal is held at the previous value, and the latest detection result of the angle sensor is the 3. The control apparatus for a variable valve mechanism according to claim 1, wherein when the dead zone is exceeded, the hysteresis processing signal is increased or decreased by an amount corresponding to the latest detection result of the angle sensor exceeding the dead zone.   The control device for a variable valve mechanism according to any one of claims 1 to 3, wherein the predetermined width is variably set according to the rotation angle.   The control device for a variable valve mechanism according to any one of claims 1 to 4, wherein the variable valve mechanism makes a lift of the engine valve variable according to a rotation angle of the motor.   The variable valve mechanism is rotationally driven by a crankshaft of an engine, a drive shaft having a drive cam fixed to the outer periphery thereof, a rocker arm that swings by rotation of the drive cam linked to one end, and the other end of the rocker arm A rocking cam that opens the engine valve in linkage with a portion is provided, and a rocking fulcrum of the rocker arm is changed by drive control of the motor. Control device for variable valve mechanism.

Images