JP2005030241A - Control device for variable valve mechanism - Google Patents

Abstract

A control device for a variable valve mechanism capable of ensuring good controllability while minimizing power consumption and calculation load in feedback control.
In a configuration in which a valve operating state is changed by rotationally driving a control shaft by an actuator, a torque transmission means for allowing only torque transmission from the actuator side is provided between the output shaft and the control shaft of the actuator. . The deviation (absolute value) ERR between the target operating angle of the control shaft and the detected operating angle of the control shaft is compared with a predetermined value Δθ (S14). If ERR> Δθ, feedback is performed by proportional / integral / differential operation. The operation amount is calculated and output, and the drive of the actuator is controlled (S15, 16). On the other hand, if ERR ≦ Δθ, it is determined that the target operating angle has converged, and calculation / output of the feedback manipulated variable is stopped, and the integral manipulated variable at that time is held (S17, 18).
[Selection] Figure 11

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a variable valve mechanism that changes valve operating states (valve timing, valve lift amount, etc.) of an intake valve and an exhaust valve of an engine.
[0002]
[Prior art]
Patent Document 1 discloses a variable valve mechanism that has a control shaft that is rotationally driven by an actuator and changes the valve operating state of an intake valve or exhaust valve of an engine by changing the rotational position of the control shaft. There is something that was done.
[0003]
This includes a cam and a camshaft that open and close an intake valve or an exhaust valve by changing the rotational position (rotation angle) of a gear shaft (control shaft) installed in parallel with the camshaft by an electric motor (actuator). The rotational phase of the control disk of the inconstant velocity joint interposed between them is changed, thereby adjusting the valve timing and valve opening period of the intake valve or exhaust valve.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-88531
[Problems to be solved by the invention]
By the way, some load is applied to the control shaft as described above by a spring for biasing the control shaft or a structurally generated torque (effect of valve spring, etc.). When the rotational position of a certain control axis is controlled to a predetermined target position by an actuator, a controller that includes an integral element (performs an integral operation) is usually used to prevent the occurrence of a steady deviation.
[0006]
Here, when the rotational position of the control shaft coincides with a predetermined target position, the actuator controls the operation amount (the integral term in the feedback operation amount, hereinafter referred to as the integral operation amount) by the integral operation of the controller. It should have been calculated so as to generate a torque that can maintain the rotational position of the shaft at the predetermined target position.
[0007]
This integral operation amount is necessary to hold the control shaft at the target position even after the rotational position of the control shaft matches the target position when torque is transmitted between the control shaft and the actuator. However, when a transmission mechanism (means) that allows only torque transmission from the actuator side and prohibits (cuts off) torque transmission from the control shaft side is interposed between the control shaft and the actuator. In this case, since the rotational position of the control shaft is maintained as it is by this transmission mechanism (means), it can be said that the integral operation amount is no longer necessary.
[0008]
However, when the conventional controller is used as it is, even after the rotational position of the control shaft coincides with the target position (that is, even when the other operation amount such as the proportional operation amount becomes 0), the integral operation amount is Since the actuator is driven by the output, the power corresponding to that is wasted.
[0009]
On the other hand, if the target position matches, the integral manipulated variable is forced (or all manipulated variables including the integral manipulated variable are forcibly determined when the rotational position is within the predetermined range). It is conceivable that the actuator operation is stopped by setting the output feedback operation amount itself to 0 by setting it to 0. However, when the target value (target) position changes after that, Therefore, the calculation of the integral operation amount is performed again, and there is a problem that the convergence is deteriorated.
[0010]
The present invention has been made to solve such conventional problems, and it is possible to ensure good controllability (convergence) while minimizing power consumption and calculation load in feedback control. It is an object of the present invention to provide a control device for a variable valve mechanism.
[0011]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, torque transmission from the actuator side is permitted between the output shaft of the actuator and the control shaft in a configuration in which the valve operating state is changed by rotationally driving the control shaft by the actuator. On the other hand, a torque transmission means for prohibiting (cutting off) torque transmission from the control shaft side is provided, and at least an integration operation is performed when the control means for feedback controlling the actuator determines that the valve operating state has converged to the target. The calculation of the integral manipulated variable by the control and the output of the feedback manipulated variable including the integral manipulated variable are stopped, and the calculated value (integral manipulated variable) of the integral operation at that time is held.
[0012]
According to such a configuration, when the valve operating state converges to the target, the driving of the actuator is stopped, the calculation of the integral operation amount in the feedback control is stopped, and the integral operation amount calculated at that time (immediately before the stop) is held as it is. The
[0013]
As a result, the controllability (convergence) of the feedback control can be satisfactorily maintained while minimizing the power consumption and the calculation load. That is, the rotational position of the control shaft is held as it is by the torque transmission means if there is no torque transmission from the actuator side, so that the actuator drive is stopped by stopping the output of the feedback manipulated variable, and at the same time, the feedback By stopping the calculation of the operation amount (particularly, the integral operation amount), it is possible to suppress the power consumption and calculation load accordingly. Although the calculation of the integral operation amount stops, the integral operation amount immediately before the stop is maintained as it is, so that if the target changes after that, there is no need to calculate the integral operation amount from the beginning, and convergence to the target Good maintainability.
[0014]
According to the second aspect of the present invention, the rotational position of the control shaft correlated with the valve operating state is detected, and the control means detects the target rotational position corresponding to the target valve operating characteristic and the detected control shaft. The amount of feedback operation is calculated based on the deviation from the rotational position of the valve, and it is determined that the valve operating state has converged to the target when the deviation is equal to or less than a predetermined value.
[0015]
According to this configuration, rotational position detection means (potentiometer or the like) that detects the rotational position of the control shaft is employed as the valve operating state detection means, and the actuator is fed back so that the detected rotational position becomes the target rotational position. Become.
[0016]
Thus, in the configuration in which the valve operating state is changed by rotationally driving the control shaft by the actuator, the same effect as in the first aspect can be obtained with a relatively simple configuration. Further, since the convergence to the target is determined when the deviation between the target rotational position and the detected rotational position is less than or equal to a predetermined value, stable control can be realized by preventing hunting and the like.
[0017]
According to a third aspect of the present invention, the valve operating state is at least one of valve opening / closing timing (valve timing) and valve lift amount.
According to such a configuration, when feedback control is performed for a variable valve mechanism configured to change the valve timing and / or valve lift amount by rotationally driving the control shaft by an actuator, the power consumption and the calculation load are minimized. The controllability (convergence) can be maintained well.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an internal combustion engine for a vehicle according to a first embodiment of the present invention. In FIG. 1, an electronic control throttle 104 that opens and closes a throttle valve 103 b by a throttle motor 103 a is interposed in an intake passage 102 of the internal combustion engine 101, and combustion is performed via the electronic control throttle 104 and the intake valve 105. Air is sucked into the chamber 106.
[0019]
The combustion exhaust gas is discharged from the combustion chamber 106 through the exhaust valve 107, purified by the exhaust purification catalyst 108, and then released into the atmosphere through the muffler 109. Here, the exhaust valve 107 is driven by a cam 111 pivotally supported by the exhaust side camshaft 110 while maintaining a constant valve lift amount and a valve operating angle. The intake valve 105 serves as a variable valve mechanism. A valve lift amount and a valve operating angle are continuously changed by a VEL (Variable Valve Event and Lift mechanism) 112, and a valve timing is continuously changed by a VTC (Valve Timing Control mechanism) 113 as a variable valve mechanism. It is like that.
[0020]
In addition, an electromagnetic fuel injection valve 131 is provided in the intake port 130 upstream of the intake valve 105 of each cylinder. The combustion injection valve 131 receives an injection pulse signal from the control unit (C / U) 114. When the valve is driven to open, the fuel adjusted to a predetermined pressure is injected toward the intake valve 105.
[0021]
A C / U 114 having a built-in microcomputer includes a water temperature sensor 115 for detecting the coolant temperature Tw of the engine 101, an accelerator opening sensor APS116 for detecting the accelerator opening, an air flow meter 117 for detecting the intake air amount Qa, and a crankshaft. Detection signals are input from various sensors such as a crank angle sensor 118 that extracts a rotation signal from the cam, a cam sensor 119 that detects the rotation position of the intake camshaft, and a throttle sensor 120 that detects the opening TVO of the throttle valve 103b.
[0022]
The engine rotation speed Ne is calculated based on a rotation signal output from the crank angle sensor 118.
Then, the C / U 114 sets the target valve operating state (valve timing, valve lift amount, etc.) of the intake valve 105 according to the operating state, and controls the VEL 112 and the VTC 113 so as to be in this target valve operating state.
[0023]
Here, the structure of the VEL 112 will be described.
2 to 4, the VEL 112 includes a pair of intake valves 105, 105, a hollow cam shaft 13 that is rotatably supported by the cam bearing 14 of the cylinder head 11, and a shaft mounted on the cam shaft 13. Two eccentric cams 15, 15 that are supported rotating cams, a control shaft 16 that is rotatably supported by the same cam bearing 14 above the cam shaft 13, and a control cam 17 on the control shaft 16. A pair of rocker arms 18 and 18 supported in a swingable manner, and a pair of independent rocking cams 20 and 20 disposed at upper ends of the intake valves 105 and 105 via valve lifters 19 and 19, respectively. It is configured with.
[0024]
The eccentric cams 15 and 15 and the rocker arms 18 and 18 are linked by link arms 25 and 25, and the rocker arms 18 and 18 and the rocking cams 20 and 20 are linked by link members 26 and 26. Yes.
[0025]
As shown in FIG. 5, the eccentric cam 15 has a substantially ring shape and includes a small-diameter cam main body 15a and a flange portion 15b integrally provided on the outer end surface of the cam main body 15a. A cam shaft insertion hole 15 c is formed through the shaft, and the shaft center X of the cam body 15 a is eccentric from the shaft center Y of the cam shaft 13 by a predetermined amount.
[0026]
The eccentric cam 15 is press-fitted and fixed to the camshaft 13 on both outer sides that do not interfere with the valve lifter 19 via camshaft insertion holes 15c, and the outer peripheral surface 15d of the cam body 15a has the same cam profile. Is formed.
[0027]
As shown in FIG. 4, the rocker arm 18 is bent in a substantially crank shape, and a central base portion 18 a is supported by the control cam 17 in a self-rotating manner.
A pin hole 18d into which a pin 21 connected to the tip end of the link arm 25 is press-fitted is formed at one end 18b protruding from the outer end of the base 18a, while the inner end of the base 18a is formed. A pin hole 18e into which a pin 28 connected to one end portion 26a (described later) of each link member 26 is press-fitted is formed in the other end portion 18c projecting from the portion.
[0028]
The control cam 17 has a cylindrical shape, is fixed to the outer periphery of the control shaft 16, and the position of the axis P1 is eccentric from the axis P2 of the control shaft 16 by α as shown in FIG.
[0029]
The swing cam 20 has a substantially horizontal U shape as shown in FIGS. 2, 6, and 7, and a cam shaft 13 is fitted into a substantially annular base end portion 22 so as to be rotatably supported. A support hole 22a is formed through, and a pin hole 23a is formed through the end 23 located on the other end 18c side of the rocker arm 18.
[0030]
Further, a base circle surface 24a on the base end portion 22 side and a cam surface 24b extending in an arc shape from the base circle surface 24a toward the end edge side of the end portion 23 are formed on the lower surface of the swing cam 20. The circular surface 24 a and the cam surface 24 b come into contact with predetermined positions on the upper surfaces of the valve lifters 19 in accordance with the swing position of the swing cam 20.
[0031]
That is, when viewed from the valve lift characteristics shown in FIG. 8, as shown in FIG. 2, the predetermined angular range θ1 of the base circle surface 24a becomes the base circle section, and the predetermined angular range from the base circle section θ1 of the cam surface 24b. θ2 is a so-called ramp section, and further, a predetermined angle range θ3 from the ramp section θ2 of the cam surface 24b is set to be a lift section.
[0032]
The link arm 25 includes an annular base portion 25a and a projecting end 25b projecting at a predetermined position on the outer peripheral surface of the base portion 25a. At the center position of the base portion 25a, the cam body 15a of the eccentric cam 15 is provided. A fitting hole 25c is formed on the outer peripheral surface so as to be freely rotatable, and a pin hole 25d through which the pin 21 is rotatably inserted is formed in the protruding end 25b.
[0033]
Further, the link member 26 is formed in a straight line having a predetermined length, and circular pin ends 26a and 26b are provided with pin holes 18d in the other end 18c of the rocker arm 18 and the end 23 of the swing cam 20, respectively. Pin insertion holes 26c and 26d through which end portions of the respective pins 28 and 29 press-fitted into the screw holes 23a are rotatably inserted are formed. Note that snap rings 30, 31, and 32 that restrict the axial movement of the link arm 25 and the link member 26 are provided at one end of each of the pins 21, 28, and 29.
[0034]
In such a configuration, the valve lift amount can be changed as shown in FIGS. 6 and 7 depending on the positional relationship between the axis P2 of the control shaft 16 and the axis P1 of the control cam 17, and the control shaft By rotating 16, the position of the axis P <b> 2 of the control shaft 16 relative to the axis P <b> 1 of the control cam 17 is changed.
[0035]
FIG. 10 shows a schematic configuration of the rotation drive mechanism of the control shaft 16. As shown in this figure, the rotation of the output shaft (rotary shaft) of the DC servo motor (actuator) 201 is transmitted to the control shaft 16 via the transmission mechanism 202. By changing the operating angle by the DC servo motor 201, the valve lift amount (and the valve operating angle) of the intake valves 105, 105 change continuously (see FIG. 9).
[0036]
The transmission mechanism 202 includes a first gear (worm) 203 provided on the output shaft of the DC servo motor 201 and one end of a gear shaft 204 installed in parallel with the control shaft 16 so as to mesh with the first gear 203. A second gear (worm wheel) 205 provided on the side, a third gear 206 provided on the other end side of the gear shaft 204, and a fourth gear provided on the control shaft 16 so as to mesh with the third gear 206. And a so-called worm gear type reduction gear. Alternatively, the gear 204 shaft, the second gear 205, and the third gear 206 may be omitted, and the fourth gear 207 may be configured as a worm wheel so that the first gear 203 directly drives the fourth gear 207 directly.
[0037]
Thus, in this embodiment, since the worm gear type reduction gear is used as the transmission mechanism 202, torque (including torque generated due to the structure of the VEL 112) that causes the control shaft 16 to rotate on the VEL 112 side is generated. However, the rotation of the control shaft 16 is prevented, and this rotational torque is not transmitted to the DC servo motor 201 side.
[0038]
Under such a configuration, the C / U 114 detects the operating angle (rotational position) VCS_ANGL of the control shaft 16 by the potentiometer-type operating angle sensor 208 provided at the tip of the control shaft 16, and this detected operating angle. The DC servo motor (actuator) 201 is feedback-controlled so that VSC_ANGL becomes the target operating angle (target rotational position) TGVEL, thereby mainly controlling the valve lift amount of the intake valve 105. The operating angle sensor 208 may be, for example, a Hall IC non-contact type sensor in addition to the potentiometer type.
[0039]
On the other hand, as the VTC 113, a known variable valve timing mechanism configured to change the rotational phase of the camshaft with respect to the crankshaft can be used. Therefore, although detailed description is omitted, the C / U 114 includes the crank angle sensor 118 and The valve timing is controlled by detecting the rotation phase VTCNOW of the intake camshaft based on the detection signal of the cam sensor 119 and performing feedback control of the VTC 113 (actuator thereof) so that the detected rotation phase becomes the target rotation phase TGVTC. .
[0040]
Here, feedback control of the VEL 112 by the C / U 114 will be described. FIG. 11 is a flowchart of feedback control of the VEL 112, which is executed every predetermined time (for example, 10 msec).
[0041]
In FIG. 11, in S11, the operating angle VCS_ANGL of the control shaft 16 detected by the operating angle sensor 208 is read.
In S12, the target operating angle TGVEL is set such that the valve operating characteristic of the intake valve 105 becomes a target valve operating state set based on the engine operating conditions (load / rotation).
[0042]
In S13, an absolute value ERR (= | TGVEL−VCS_ANGL |) of the deviation between the target operating angle TGVEL and the detected operating angle VCS_ANGL is calculated.
In S14, the ERR (absolute value of deviation) is compared with a predetermined value Δθ or less. If the ERR exceeds the predetermined value Δθ, the process proceeds to S15.
[0043]
In S15, the feedback manipulated variable U is calculated by proportional (P), integral (I), and differential (D) operations based on the ERR, as shown in the following equation.
U = Up + Ui + Ud
Up = Gp * ERR
Ui = Gi * ERR * Ts + Uiz
Ud = Gd * (ERR−ERRz) / Ts
However, Up: proportional manipulated variable (proportional term), Ui: integral manipulated variable (integral term), Ud: differential manipulated variable (derivative term), Gp: proportional gain, Gi: integral gain, Gd: differential gain, Ts: control Period, ERRz: previous value (absolute value) of deviation.
[0044]
In S16, the calculated feedback operation amount U is output, the drive of the DC servo motor 201 is controlled, and this flow is finished.
On the other hand, if the ERR is equal to or smaller than the predetermined value Δθ in S14, it is determined that the valve operating state of the intake valve 105 has converged to the target, the process proceeds to S17, and the calculation of the feedback manipulated variable U is stopped.
[0045]
Then, in S18, the integration operation amount Ui remains at the previous value Uiz (Ui = Uiz), and this flow ends. Therefore, in this case, the feedback operation amount U is not output (the actuator 201 is not driven).
[0046]
As described above, in this embodiment, when the ERR is equal to or smaller than the predetermined value Δθ, it is determined that the valve operating state of the intake valve 105 has converged to the target, and calculation and output of the feedback manipulated variable U are stopped. However, in the case of the predetermined value Δθ≈0, when it is determined that the target has converged, the proportional manipulated variable Up and the differential manipulated variable Ud are also substantially zero, so the feedback manipulated variable U in this case And stopping the output have the same meaning as stopping the calculation and output of the integral operation amount Ui.
[0047]
The integral operation amount Ui is for obtaining a torque necessary for maintaining the operating angle of the control shaft 16 at the target operating angle. As described above, in the present embodiment, Since a worm gear type reduction gear is provided as a transmission mechanism between the VEL 112 (the control shaft 16 thereof), the control shaft 16 is mechanically prevented from rotating in reverse.
[0048]
Therefore, after the operating angle of the control shaft 16 coincides with the target operating angle, the operation amount for holding this, that is, the integral operation amount Ui is not required.
Therefore, when it is determined that the ERR is equal to or less than the predetermined value Δθ and the valve operating state of the intake valve 105 has converged to the target, the feedback manipulated variable U (the integral manipulated variable Ui when Δθ≈0) is calculated. In addition, the output is stopped to minimize power consumption and calculation load.
[0049]
On the other hand, if the integral manipulated variable Ui is cleared (to 0) when the feedback manipulated variable U is calculated and the output is stopped, the integral manipulated variable Ui is calculated again from the beginning when the target changes thereafter. It is extremely inefficient.
[0050]
Therefore, although the calculation of the feedback manipulated variable U (integrated manipulated variable Ui) is stopped, it is necessary when the target is subsequently changed by holding the integral manipulated variable Uiz at that time (immediately before the stop). The integral operation amount Ui can be calculated quickly, and early convergence of the valve operating state of the intake valve 105 to the target is realized.
[0051]
As a result, it is possible to improve power consumption by minimizing power consumption and calculation load, and to ensure good controllability (convergence).
In the above, the control for the VEL 112 for changing the valve lift amount of the intake valve 105 has been described. However, the same applies to the case where the VEL 112 is used on the exhaust valve side, and the rotation position of the control shaft is changed by the actuator. As long as the valve operating state is changed, the valve lift amount is not limited. For example, it is applied to a variable valve mechanism (VTC; Valve Timing Control mechanism) configured to change the valve timing (opening / closing timing). May be.
[0052]
Further, the transmission mechanism 202 only needs to be configured to permit only torque transmission from the actuator side to the control shaft and prohibit (shut off) torque transmission from the control shaft side, and is not limited to a worm gear type reduction gear. Absent.
[0053]
Further, technical ideas other than the claims that can be grasped from the above embodiment will be described together with the effects thereof.
The control apparatus for a variable valve mechanism according to any one of claims 1 to 3, wherein the torque transmission mechanism includes a worm fixed to an output shaft of the actuator, and a worm wheel meshing with the worm. It is characterized by being a worm gear type reduction gear configured to include.
[0054]
Thus, by providing a worm gear type speed reducer between the output shaft of the actuator and the control shaft, torque transmission from the actuator side to the control shaft is permitted and rotational torque other than the torque transmitted from the actuator side is allowed. Therefore, it is possible to easily prevent the control shaft from rotating (torque transmission from the control shaft side to the actuator side can be prohibited).
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an internal combustion engine in an embodiment. FIG. 2 is a cross-sectional view (AA cross-sectional view in FIG. 3) of a VEL (Variable valve Event and Lift mechanism) in an embodiment of the present invention.
FIG. 3 is a side view of the VEL.
FIG. 4 is a plan view of a VEL.
FIG. 5 is a perspective view showing an eccentric cam used for VEL.
6 is a cross-sectional view (a cross-sectional view taken along the line BB in FIG. 3) showing the action of the VEL during low lift.
7 is a cross-sectional view (a cross-sectional view taken along the line BB in FIG. 3) showing an operation of the VEL during high lift.
FIG. 8 is a valve lift characteristic diagram corresponding to the base end surface of the swing cam and the cam surface in VEL.
FIG. 9 is a characteristic diagram of valve timing and valve lift according to VEL.
FIG. 10 is a perspective view showing a rotation drive mechanism of a control shaft in VEL.
FIG. 11 is a flowchart showing feedback control of VEL.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 16 ... Control shaft, 101 ... Internal combustion engine, 105 ... Intake valve, 112 ... VEL (variable valve mechanism), 114 ... C / U (control unit), 132 ... Cam sensor, 208 ... Operating angle sensor

Claims (3)

A control device for a variable valve mechanism that has a control shaft that is rotationally driven by an actuator and changes the valve operating state of an intake valve or an exhaust valve of an internal combustion engine by changing the rotational position of the control shaft,
Torque is provided between the output shaft of the actuator and the control shaft, and transmits torque corresponding to the rotational torque of the output shaft of the actuator to the control shaft, while torque from the control shaft to the output shaft of the actuator Torque transmission means for prohibiting transmission of
A valve operating state detecting means for detecting the valve operating state;
Control means for performing feedback control of the actuator so that the valve operation state becomes a predetermined target valve operation state by a control operation including an integration operation,
When the control means determines that the valve operating state has converged to the target valve operating state, it stops at least the calculation of the integral operation amount by the integration operation and the output of the feedback operation amount including the integration operation amount. In addition, a control apparatus for a variable valve mechanism that holds an integral operation amount at that time. The valve operating state detecting means detects a rotational position of the control shaft corresponding to the valve operating state;
The control means calculates the feedback manipulated variable based on a deviation between a target rotational position corresponding to the target valve operating state and a detected rotational position, and when the deviation becomes a predetermined value or less, the valve 2. The control apparatus for a variable valve mechanism according to claim 1, wherein the operation state is determined to have converged to the target valve operation state. The control apparatus for a variable valve mechanism according to claim 1 or 2, wherein the valve operating state is at least one of a valve opening / closing timing and a valve lift amount.

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