JP2003328786A - Control device for variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve power consumption of an electromagnetic brake and its service life in the variable valve timing mechanism which changes a rotation phase of a camshaft with respect to a cam sprocket in the direction of an advanced angle phase and a delayed angle phase by the braking force of two magnetic brakes. <P>SOLUTION: If the relative velocity of the camshaft becomes smaller than the predetermined value A and a primary delayed value of the relative velocity becomes smaller than the border value set up based on the maximum value of the relative velocity, the feedback gain of the rotation phase is reduced by a regular judgement. If the absolute value of the deviation between an actual rotation phase and a target value is below the predetermined value and the relative rotation velocity respect to the cam sprocket of the camshaft becomes approximately zero, both electromagnetic brakes are forcedly turned off. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a variable valve timing mechanism that changes the valve timing of an engine valve (intake / exhaust valve) of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a variable valve timing mechanism, as disclosed in Japanese Unexamined Patent Publication No. 2001-041013, the opening / closing timing of an engine valve is changed to a crank angle by changing the rotational phase of a camshaft with respect to a crankshaft. On the other hand, a configuration is known in which the angle is advanced and retarded.

In this system, an assembly angle adjusting mechanism for a driving rotary body integrated with a cam sprocket and a driven rotary body on the camshaft side is provided, and a rotary portion at one end is provided on one side of the drive rotary body and the driven rotary body. It has a link arm that is rotatably connected and has a slide part at the other end that is connected so as to be slidable in the radial direction by a radial guide provided on the other side, and rotates as the slide part moves in the radial direction. The positions of the parts are displaced relative to each other in the circumferential direction, and the assembling angle of the drive rotating body and the driven rotating body is relatively changed, and a spiral guide engaged with the slide part of the link arm is formed. The sliding portion is radially displaced by relatively rotating the formed guide plate in the deceleration direction or the acceleration direction by the braking force of the two electromagnetic brakes.

Hereinafter, the variable valve timing mechanism provided with the assembly angle adjusting mechanism having the above construction will be referred to as a spiral radial link type.

[0005]

By the way, in the variable valve timing mechanism of the spiral radial link type in which the retard angle change and the advance angle change are respectively generated by the two electromagnetic brakes as described above, the rotational phase converges near the target. Even if the energization of one electromagnetic brake is stopped based on this, as a result of the guide plate continuing relative rotation due to inertia, the rotational phase deviates from the target, and it is necessary to energize the other electromagnetic brake to absorb this. As a result, it is necessary to alternately energize the two electromagnetic brakes at a high speed even in a state where the two electromagnetic brakes converge near the target.

In the spiral radial link type variable valve timing mechanism, when the energization of the two electromagnetic brakes is off, the rotational phase at that time is substantially maintained. If the two electromagnetic brakes continue to be energized even after they converge to the vicinity, there is a problem that the above characteristics are not utilized and power consumption and brake life are deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to improve power consumption and brake life by enabling the electromagnetic brake to be turned off while maintaining a target rotational phase.

[0008]

Therefore, according to the first aspect of the invention, the deviation between the target value and the actual value of the rotational phase of the camshaft is less than a predetermined value, and the relative speed of the camshaft with respect to the cam sprocket is predetermined. 2 if less than or equal to value
It is configured to forcibly turn off the two electromagnetic brakes.

According to the above construction, the control deviation of the rotational phase is less than or equal to the predetermined value, and the relative speed of the camshaft with respect to the cam sprocket is less than or equal to the predetermined value even when the target rotational phase is reached. , When the phase change due to inertia is judged to be sufficiently small, the two electromagnetic brakes are forcibly turned off, and then the electromagnetic brakes are turned on until the control deviation of the rotational phase exceeds the predetermined value. Hold off.

Therefore, even if the electromagnetic brake is turned off, the target rotation phase can be maintained in the vicinity of the target phase without causing a rapid phase change, and the period during which the electromagnetic brake is turned off is provided, so that power consumption and brake life are reduced. Can be improved. According to the second aspect of the invention, the gain in the feedback control according to the control deviation of the rotation phase is changed to a smaller value when converged near the target than before the convergence.

According to the above configuration, the braking force of the electromagnetic brake is feedback-controlled with a relatively large gain until the rotational phase converges near the target. However, when the rotational phase converges near the target, the gain is changed to a smaller value. When the relative speed of the camshaft becomes equal to or lower than a predetermined value in the feedback control state by the gain, the power supply to the electromagnetic brake is cut off.

Therefore, while ensuring the convergence responsiveness to the target rotation phase, the relative speed of the camshaft with respect to the cam sprocket after the convergence becomes a predetermined value or less, the timing of turning off the electromagnetic brake is easily grasped, and power consumption and power consumption are reduced. The effect of improving the brake life can be obtained more reliably. According to a third aspect of the present invention, the variable valve timing mechanism to which the control device according to the first or second aspect is applied is provided with a guide plate having a spiral guide with which a slide portion of a link arm engages. Spiral radial link type variable that changes the assembling angle between the driving rotary body and the driven rotary body connected via the link arm by relatively rotating in the deceleration direction or the acceleration direction by the braking force of two electromagnetic brakes. The valve timing mechanism is used.

According to the above structure, in the spiral radial link type variable valve timing mechanism having a structure in which the rotational phase at that time is substantially maintained when both the electromagnetic brakes are de-energized, the rotational phase control deviation is The electromagnetic brake is forcibly turned off when the relative speed of the camshaft to the cam sprocket is equal to or lower than a predetermined value and equal to or lower than a predetermined value.

Therefore, the power consumption and the brake life can be improved by taking advantage of the characteristic of the spiral radial link type mechanism that the rotation phase at that time is substantially maintained when the two electromagnetic brakes are both turned off.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a vehicle internal combustion engine according to an embodiment, and an intake pipe 102 of the internal combustion engine 101.
The throttle motor 103a and throttle valve 1
An electronically controlled throttle 104 for opening and closing 03b is interposed, and the electronically controlled throttle 104 and the intake valve 10 are provided.
Air is sucked into the combustion chamber 106 via No. 5.

Combustion exhaust is discharged from the combustion chamber 106 to the exhaust valve 1.
It is discharged via 07, purified by the front catalyst 108 and the rear catalyst 109, and then discharged into the atmosphere. The intake valve 105 and the exhaust valve 107 are opened and closed by cams provided on the exhaust side cam shaft 110 and the intake side cam shaft 134, respectively, and the intake side cam shaft 134 changes the rotational phase with respect to the crankshaft 120. The variable valve timing mechanism VTC113 of the spiral radial link type that changes the valve timing by performing the above is provided.

In this embodiment, the variable valve timing mechanism VTC113 is provided only on the intake valve side, but instead of the intake valve side or together with the intake valve side, the variable valve timing mechanism VTC1 is provided on the exhaust valve side.
A configuration including 13 may be used. Further, an electromagnetic fuel injection valve 131 is provided in the intake port 130 on the upstream side of the intake valve 105 of each cylinder, and the fuel injection valve 131 is
When the valve is driven to open by the injection pulse signal from the ECU 114, the fuel adjusted to a predetermined pressure is supplied to the intake valve 1.
It jets toward 05.

Detection signals from various sensors are input to an engine control unit (ECU) 114 containing a microcomputer, and the electronically controlled throttle 104, variable valve timing mechanism VTC 113 and Fuel injection valve 1
31 and the like are controlled. The various sensors include an accelerator opening sensor APS116 that detects an accelerator opening and an air flow meter 1 that detects an intake air amount Q of the engine 101.
15, a crank angle sensor 117 that extracts a rotation signal from the crankshaft 120, a throttle sensor 118 that detects the opening TVO of the throttle valve 103b, the engine 1
A water temperature sensor 119 for detecting the cooling water temperature of 01, a cam sensor 132 for extracting a rotation signal from the intake side camshaft 134, and the like are provided.

The engine speed Ne is calculated in the ECU 114 based on the rotation signal output from the crank angle sensor 117. Next, the configuration of the variable valve timing mechanism VTC 113 will be described with reference to FIGS. The variable valve timing mechanism VTC113
Is composed of a cam shaft 134, a drive plate 2, an assembly angle adjusting mechanism 4, an actuator 15, and a VTC cover 6.

The drive plate 2 is a member that rotates when the rotation is transmitted from the engine 101 (crankshaft 120), and the assembly angle adjusting mechanism 4 includes an assembly angle between the camshaft 134 and the drive plate 2. And is operated by the actuating device 15. The VTC
The cover 6 is a cover that is attached across the front ends of the cylinder head and the rocker cover (not shown) and covers the front surface of the drive plate 2 and the assembly angle adjusting mechanism 4 and the peripheral area thereof.

A spacer 8 is fitted to the front end portion (left side in FIG. 2) of the cam shaft 134, and the spacer 8 is further provided with a flange portion 134 of the cam shaft 134.
The rotation is regulated by a pin 80 penetrating through f.
Further, a plurality of oil supply holes 134r are formed through the cam shaft 134 in the radial direction.

As shown in FIG. 3, the spacer 8 includes a disk-shaped locking flange 8a, a circular pipe portion 8b axially extending from a front end surface of the locking flange 8a, and a front end of the locking flange 8a. A shaft support portion 8d is formed which is a surface and extends from the base end side of the circular pipe portion 8b in three directions in the outer diameter direction and in which a press-fitting hole 8c parallel to the axial direction is formed. The shaft support portion 8d and the press-fitting holes 8c are arranged at intervals of 120 ° in the circumferential direction, as shown in FIG.

An oil supply hole 8r for supplying oil is formed through the spacer 8 in the radial direction. The drive plate 2 is formed in a disk shape having a through hole 2a formed in the center thereof, and is rotatably assembled to the spacer 8 in a state in which axial displacement is restricted by a locking flange 8a. ing.

As shown in FIG. 3, the drive plate 2 has a cam sprocket 3 to which rotation is transmitted from the crankshaft 120 via a chain (not shown) on the outer periphery of the rear portion thereof. It rotates together with 3. Further, the front end surface of the drive plate 2 connects the through hole 2a and the outer periphery with three guide grooves 2 in the outer diameter direction.
g is formed, and the guide grooves 2g are arranged every 120 ° in the circumferential direction, like the shaft support portion 8d.

An annular cover member 2c is fixed to the outer peripheral portion of the front end surface of the drive plate 2 by welding or press fitting. In the present embodiment, the driven rotary body is constituted by the cam shaft 134 and the spacer 8, and the drive rotary body is the drive plate 2 including the cam sprocket 3.
Composed by.

The assembly angle adjusting mechanism 4 includes the camshaft 1
34 is arranged on the front end side of the drive plate 2 and the drive plate 2, and changes the relative angle of assembly between the cam shaft 134 and the drive plate 2. The assembly angle adjusting mechanism 4 has three link arms 14 as shown in FIG.

Each of the link arms 14 is provided with a cylindrical portion 14a as a slide portion at the tip thereof, and an arm portion 14b extending from the cylindrical portion 14a in the outer diameter direction. A housing hole 14c is formed through the cylindrical portion 14a, while a rotation hole 14d as a rotation portion is formed through the base end of the arm portion 14b.

The link arm 14 includes the spacer 8
The turning hole 14 is attached to the turning pin 81 that is tightly press-fitted into the press-fitting hole 8c, and is attached so as to be rotatable about the turning pin 81. On the other hand, the cylindrical portion 14a of the link arm 14 is inserted into a guide groove 2g as a radial guide of the drive plate 2 and is attached to the drive plate 2 so as to be movable (sliding) in the radial direction.

In the above structure, when the cylindrical portion 14a receives an external force and slides in the radial direction along the guide groove 2g, the rotation pin 81 is displaced in the radial direction of the cylindrical portion 14a by the link action of the link arm 14. The cam shaft 134 is moved by the displacement of the rotation pin 81 in the circumferential direction by an angle corresponding to the drive plate 2.
It will rotate relative to.

FIGS. 4 and 5 show the operation of the assembling angle adjusting mechanism 4. As shown in FIG. 4, the cylindrical portion 14a is arranged on the outer peripheral side of the drive plate 2 in the guide groove 2g. In some cases, the pivot pin 81 at the base end portion may cause the guide groove 2
It is pulled to a position close to g, and this position is the most retarded position. On the other hand, as shown in FIG.
When a is arranged on the inner peripheral side of the drive plate 2 in the guide groove 2g, the rotating pin 81 is pushed in the circumferential direction and moves away from the guide groove 2g, and this position is the most advanced position.

The movement of the cylindrical portion 14a in the assembly angle adjusting mechanism 4 in the radial direction is performed by the actuating device 15, and the actuating device 15 includes an actuation conversion mechanism 40 and an acceleration / deceleration mechanism 41. There is. The operation conversion mechanism 40 includes a sphere 22 held by the cylindrical portion 14a of the link arm 14,
And a guide plate 24 provided coaxially to face the front surface of the drive plate 2.
Is a mechanism that converts the rotation of the above into a radial displacement of the cylindrical portion 14a of the link arm 14.

The guide plate 24 is supported on the outer periphery of the circular pipe portion 8b of the spacer 8 so as to be relatively rotatable via a metallic bush 23. On the rear surface of the guide plate 24, there is formed a spiral guide groove 28 as a spiral guide which has a substantially semicircular cross section and is displaced in the radial direction along with the displacement in the circumferential direction. Is formed with an oil supply hole 24r for supplying oil penetrating in the front-rear direction.

The sphere 22 is placed in the spiral guide groove 28.
Are engaged. That is, the accommodating hole 14c formed in the cylindrical portion 14a of the link arm 14 has a structure shown in FIGS.
As shown in FIG. 2, a disk-shaped support panel 22a, a coil spring 22b (elastic body), a retainer 22c, and a ball 2 are provided.
2 (spherical member) are sequentially inserted.

The retainer 22c has a bowl-shaped support recess 22d for supporting the ball 22 in a state where the ball 22 is projected at the front end.
And a flange 22f on which the coil spring 22b is seated is formed on the outer circumference. In the assembled state shown in FIG. 2, the coil spring 22
b is compressed, the support panel 22a is pressed against the front surface of the drive plate 2, and the sphere 22 is pressed against the spiral guide groove 28 to engage in the vertical direction, and the extending direction of the spiral guide groove 28. It is possible to move relative to.

The spiral guide groove 28 is shown in FIG.
As shown in FIG. 5, the diameter of the drive plate 2 is gradually reduced along the rotational direction R of the drive plate 2. Therefore, in the operation conversion mechanism 40, the guide plate 24 is driven by the drive plate 2 while the ball 22 is engaged with the spiral guide groove 28.
Relative to the rotation direction R, the sphere 22 moves radially outward along the spiral shape of the spiral guide groove 28, whereby the cylindrical portion 14a as the slide portion moves in the outer radial direction shown in FIG. Then, the rotating pin 81 connected to the link arm 14 is attracted so as to approach the guide groove 2g, and the cam shaft 134 moves in the retard angle direction.

On the contrary, when the guide plate 24 rotates relative to the drive plate 2 in the direction opposite to the rotation direction R from the above state, the sphere 22 moves radially inward along the spiral shape of the spiral guide groove 28. As a result, the cylindrical portion 14a as the slide portion moves in the inner diameter direction shown in FIG.
The rotation pin 81 connected to the link arm 14 is pushed in a direction away from the guide groove 2g, and in this case, the cam shaft 134 moves in the advance direction.

Next, the acceleration / deceleration mechanism 41 will be described in detail. The acceleration / deceleration mechanism 41 includes the guide plate 24.
With respect to the drive plate 2, and the guide plate 24 is moved (accelerated) in the rotation direction R side with respect to the drive plate 2, or the guide plate 24 is rotated with respect to the drive plate 2 in the rotation direction R. It is moved (decelerated) to the opposite side, and is provided with a planetary gear mechanism 25, a first electromagnetic brake 26, and a second electromagnetic brake 27.

The planetary gear mechanism 25 includes a sun gear 30.
, A ring gear 31, and a planetary gear 33 meshed with both gears 30, 31. As shown in FIGS. 2 and 3, the sun gear 30 includes a guide plate 24.
Is integrally formed on the inner circumference on the front side of the. The planetary gear 33 is rotatably supported by a carrier plate 32 fixed to the front end of the spacer 8.

The ring gear 31 is formed on the inner circumference of an annular rotating body 34 which is rotatably supported outside the carrier plate 32. The carrier plate 32 is fitted to the front end of the spacer 8,
With the washer 37 abutting on the front end, the bolt 9 is passed through and fastened to the cam shaft 134 to be fixed.

A braking plate 35 having a braking surface 35b facing forward is screwed to the front end surface of the rotating body 34. A braking plate 36 having a braking surface 36b facing forward is also fixed to the outer periphery of the guide plate 24 integrally formed with the sun gear 30 by welding or fitting.

Therefore, in the planetary gear mechanism 25, assuming that the planetary gear 33 revolves together with the carrier plate 32 without rotating, the first electromagnetic brake 26 and the second electromagnetic brake 26.
When the electromagnetic brake 27 is inactive, the sun gear 30 and the ring gear 31 rotate at the same speed in a free state. When only the first electromagnetic brake 26 is braked from this state, the guide plate 24 rotates relative to the carrier plate 32 (relative to the camshaft 134) in the direction behind (the direction opposite to the R direction in FIGS. 4 and 5). Then, the drive plate 2 and the cam shaft 134 are relatively displaced in the advance direction shown in FIG.

On the other hand, when only the second electromagnetic brake 27 is braked, a braking force is applied only to the ring gear 31, and the ring gear 31 rotates relative to the carrier plate 32 in the delay direction, whereby the planetary gear 33 rotates about its own axis. The rotation of the planetary gears 33 speeds up the sun gear 30, the guide plate 24 rotates relative to the drive plate 2 in the rotation direction R side, and the drive plate 2 and the camshaft 134 rotate in the retard direction shown in FIG. Will be done.

In this embodiment, the carrier plate 32 is an input element, the sun gear 30 is an output element, and the ring gear 31 is a free element. The first electromagnetic brake 26 and the second electromagnetic brake 27 are the braking surfaces 36b, 35b of the braking plates 36, 35 described above, respectively.
Circular pipe members 26r, 27r that are arranged in a double manner inside and outside so as to face each other and are supported on the back surface of the VTC cover 6 in a floating state in which only rotation is restricted by pins 26p, 27p.
have.

Coils 26c and 27c are housed in these circular pipe members 26r and 27r, and friction materials 26b and 27b that are pressed against the braking surfaces 35b and 36b when the coils 26c and 27c are energized are mounted. Has been done. The circular pipe members 26r and 27r and the braking plates 35 and 36 are made of a magnetic material such as iron so as to form a magnetic field when the coils 26c and 27c are energized.

On the other hand, since the VTC cover 6 does not cause leakage of magnetic flux when energized, the friction materials 26b and 27b are made permanent magnets and adhered to the braking plates 35 and 36 when de-energized. To prevent this, it is made of a non-magnetic material such as aluminum. The relative rotation between the guide plate 24 provided with the sun gear 30 as an output element of the planetary gear mechanism 25 and the drive plate 2 is restricted by the assembly angle stopper 60 at the most retarded position and the most advanced position. Has become.

Further, in the planetary gear mechanism 25, the braking plate 3 provided integrally with the ring gear 31.
A planetary gear stopper 90 is provided between the carrier 5 and the carrier plate 32. By the way, the operation conversion mechanism 40 described above holds the position of the cylindrical portion 14a of the link arm 14, and the drive plate 2 and the cam shaft 134 are held.
Since the relative assembly position with respect to and does not change, the configuration will be described.

From the drive plate 2 to the camshaft 13
The driving torque is transmitted to the shaft 4 through the link arm 14 and the spacer 8, but the fluctuation torque of the cam shaft 134 due to the reaction force from the engine valve (the intake valve 105) is transferred from the cam shaft 134 to the link arm 14. , Is input as a force F from the rotating pin 81 in the direction connecting the pivot points of both ends of the link arm 14.

The cylindrical portion 14a of the link arm 14 is
Since the sphere 22 which is guided in the radial direction along the guide groove 2g as a radial guide and which projects from the cylindrical portion 14a to the front is engaged with the spiral guide groove 28, each link arm 14 is The force F input through the guide groove 2g is supported by the left and right walls of the guide groove 2g and the spiral guide groove 28 of the guide plate 24.

Therefore, the force F input to the link arm 14 is decomposed into two component forces FA and FB which are orthogonal to each other, and these component forces FA and FB are combined into the spiral guide structure 2.
The outer peripheral wall of 8 and the one wall of the guide groove 2g are received in a direction substantially orthogonal to each other, and the cylindrical portion 1 of the link arm 14 is received.
4a is prevented from moving along the guide groove 2g,
This prevents the link arm 14 from rotating.

Therefore, after the guide plate 24 is rotated by the braking force of the electromagnetic brakes 26 and 27 and the link arm 14 is rotated to a predetermined position, basically, the braking force is not continuously applied. Even if the position of the link arm 14 is maintained, that is, the drive plate 2 and the cam shaft 134 are
The rotation phase of can be maintained as it is. The force F is not limited to acting in the outer diameter direction, but may act in the opposite inner diameter direction. At this time, the component force FA,
FB is the inner wall of the spiral guide groove 28 and the guide structure 2
It is received at a right angle to the other side of g.

Hereinafter, the variable valve timing mechanism VT will be described.
The operation of C113 will be described. When controlling the rotation phase of the crankshaft and the camshaft 134 to the retard side,
The second electromagnetic brake 27 is energized. Second electromagnetic brake 2
7, the friction material 27b of the second electromagnetic brake 27 is energized.
Comes into frictional contact with the braking plate 35, a braking force acts on the ring gear 31 of the planetary gear mechanism 25, and the cam sprocket 3
The sun gear 30 is rotated at a higher speed with the rotation of.

The guide plate 24 is rotated in the rotational direction R side with respect to the drive plate 2 by the accelerated rotation of the sun gear 30, and the sphere 22 supported by the link arm 14 is formed with the spiral guide groove 28. Move to the outer circumference.
This movement toward the retard angle side is performed by the assembling angle stopper 60 as shown in FIG.
It is regulated at the most retarded position shown in.

Further, as described above, when the rotation of the ring gear 31 is braked by the second electromagnetic brake 27, the rotation is not regulated instantaneously but is allowed while allowing a predetermined amount of rotation. The rotation of the ring gear 31 is restricted by the planetary gear stopper 90 when the value becomes a predetermined amount. On the other hand, when the mounting angle of the camshaft 134 is displaced in the advance direction, the first brake 26 is energized.

As a result, the braking force acts on the guide plate 24, and the guide plate 24 rotates in the direction opposite to the rotation direction R with respect to the drive plate 2, and the camshaft 13
4, the mounting angle is displaced to the advance side. This movement toward the advance angle side is restricted by the assembling angle stopper 60 at the most advanced angle position shown in FIG. 5, and when the rotation of the guide plate 24 is restricted, the planetary gear 33 rotates and the ring gear 31 increases. Although it is rotated at a high speed, when the rotation amount reaches a predetermined amount, the rotation is restricted by the planetary gear stopper 90.

The ECU 114 uses the crankshaft 1
A target advance angle value (target rotation phase) of the camshaft 134 with respect to 20 is set based on operating conditions of the engine, and the first electromagnetic brake 26 and the second electromagnetic brake 27 are energized based on the target advance angle value. It is designed for feedback control. Specifically, the feedback control is performed as shown in the control block diagram of FIG.

In FIG. 6, the actual advance value (actual rotation phase) θ detected based on the detection signal of the crank angle sensor 117 and the detection signal of the cam sensor 132, and the target advance value (target rotation phase). ) Θd is input to the sliding mode controller (SMC) 201. The S
In MC201, the linear term Peq and the nonlinear term Unl are calculated based on the error amount (control deviation), and the control signal U (the manipulated variable) is calculated according to the following equation based on the gain Keq of the linear term and the gain Knl of the nonlinear term. Calculate

U = Keq × Peq + Knl × Unl The manipulated variable has a plus / minus sign, and which of the electromagnetic brakes 26 and 27 should be energized is determined according to the sign. The control signal U from the SMC 201 is input to the self-holding utilization control unit 202, and the self-holding utilization control unit 202 should output the control signal U as it is, or force the control signal U to 0. , Determines whether or not to de-energize both electromagnetic brakes 26 and 27, and outputs a final control signal to the electromagnetic brakes 26 and 27.

Further, the self-holding utilization control section 202 is
Whether or not the gains Keq and Knl are switched is determined, and each of the gains Keq and Knl is switched to a value before convergence or a value after convergence. Here, the calculation of the linear term Peq and the nonlinear term Unl by the SMC 201 will be described in detail.

First, assuming that the friction coefficients of the electromagnetic brakes 26 and 27 are μc, the radius is rc, the attraction force of the coil is P, the moment of inertia of the guide plate 24 is Jsp, and the friction coefficient of the sphere 22 is μb, You can set the physical formula.

[0060]

[Equation 1] Converting the above equation into a state equation,

[0061]

[Equation 2] Where the error amount is

[0062]

[Equation 3] Then the switching function is

[0063]

[Equation 4] And the linear term becomes

[0064]

[Equation 5] Calculate as. When the target value changes stepwise, the second-order differential value of the target value instantaneously becomes a large value, and as a result, the operation amount also becomes extremely large and does not converge, and when the target value does not change, the target value does not change. Since the second derivative of is 0,
If the second derivative of the target value is ignored in the equation of the linear term of Equation 5,

[0065]

[Equation 6] Becomes In addition, the non-linear term, using the chattering prevention coefficient δ,

[0066]

[Equation 7] Calculate as. Next, the self-holding utilization control unit 202
Details of the processing contents in step S1 will be described with reference to the flowchart in FIG.

In step S1, it is determined whether or not the absolute value of the relative speed of the cam shaft 134 with respect to the cam sprocket 3 is smaller than a predetermined value A (for example, 200 deg / s). When the absolute value of the relative speed is greater than or equal to the predetermined value A, the process proceeds to step S7, where the gains Keq and Knl
The output of the SMC 201 is directly output to the electromagnetic brakes 26 and 27 while the value of is held at the value before convergence.

On the other hand, if it is determined in step S1 that the absolute value of the relative velocity is smaller than the predetermined value A, it is determined that the relative velocity has substantially converged to the vicinity of the target, and the process proceeds to step S2. In step S2, it is determined whether or not the first-order lag processing value of the absolute value of the relative speed is smaller than a border value (threshold value), and if the first-order lag processing value is equal to or more than the border value, go to step S7. By proceeding, the gain K
While holding the values of eq and Knl at the values before convergence, SMC20
The output of No. 1 is directly output to the electromagnetic brakes 26 and 27.

If it is determined in step S2 that the first-order delay processing value is smaller than the border value, the process proceeds to step S3. As described above, only when the conditions of steps S1 and S2 are satisfied, it is determined that the steady state has been entered, so that the steady state (convergence) is obtained.
A margin time is provided until the determination is made, and the process proceeds to step S3 after the steady state is surely achieved.

The border value (threshold value) to be compared with the first-order lag processing value is set according to the flowchart of FIG. In the flowchart of FIG. 8, in step S11, it is determined whether or not the first-order lag processing value of the relative speed is larger than the previous value. If it is larger than the last value, the process proceeds to step S12, and the first-order lag processing of this time is performed. The value is stored as the maximum value.

On the other hand, when the first-order lag processing value is equal to or smaller than the previous value and the first-order lag processing value starts to decrease,
In step S13, it is determined whether the first-order lag processing value is equal to or less than a predetermined value X (for example, 10 deg / s). If the first-order lag processing value is not equal to or less than the predetermined value X, step S14 is performed.
Proceed to and keep the maximum value stored.

If it is determined in step S13 that the first-order delay processing value is less than or equal to the predetermined value X, step S15.
Then, the process proceeds to and the first-order lag processing value this time is reset to the maximum value. Then, in step S16, it is determined whether or not a predetermined ratio (for example, 60%) of the maximum value is a predetermined value Y (for example, 55 deg / s) or more, and a predetermined ratio of the maximum value (for example, 6%).
If 0%) is greater than or equal to the predetermined value Y, the process proceeds to step S17, a predetermined ratio of the maximum value (for example, 60%) is set to the border value, and the predetermined ratio of the maximum value (for example, 60%) is set to the predetermined value Y. If it is smaller than, go to step S18,
The predetermined value Y is set to the border value.

When the border value is set as described above, the maximum value of the first-order lag processing value differs depending on the magnitude of the change in the target value, so the timing for starting the control using the gain after convergence (steady-state) Timing of judgment)
The optimum timing can be set according to the magnitude of the change in the target value, and the timing is limited by the predetermined value Y.

When it is determined in step S2 that the first-order lag processing value is smaller than the border value, it is determined that the steady state is reached, and the process proceeds to step S3. In step S3,
The gains Keq and Knl are switched from the values before the convergence until then to the values after the convergence which are set to smaller values. By changing the gains Keq and Knl to smaller values and performing feedback control as described above, the operations of the electromagnetic brakes 26 and 27 are suppressed, and when the relative speed is approximately 0, the electromagnetic brake k is reduced.
It is easy to grasp the timing of turning off (energizing) 26 and 27.

When the gains Keq and Knl are changed to smaller values, the absolute value of the error amount is set to the predetermined value B in step S4.
It is determined whether or not (for example, 0.5 deg) or less, and when the absolute value of the error amount exceeds the predetermined value B, the process proceeds to step S7, and the output of the SMC 201 is directly output to the electromagnetic brakes 26 and 27. . On the other hand, when the absolute value of the error amount becomes equal to or smaller than the predetermined value B (for example, 0.5 deg), the process proceeds to step S5, and it is determined whether or not the absolute value of the relative speed is smaller than the predetermined value C.

The predetermined value C << predetermined value A, and the predetermined value C is, for example, about 5 deg / s. When the absolute value of the relative speed is smaller than the predetermined value C (for example, 5 deg / s) and it can be considered that the relative speed is substantially 0, the process proceeds to step S6, and what is the output of the SMC 201 at that time? Regardless of this, the control signals to the electromagnetic brakes 26 and 27 are forcibly set to 0 to cut off the energization.

When the process proceeds to step S6, the error amount is sufficiently small and the relative speed is substantially 0. Therefore, the change in the rotational phase due to inertia is sufficiently small, and the electromagnetic brakes 26 and 27 are turned off. However, the electromagnetic brakes 26 and 27 can be maintained in the off state as they are without being greatly deviated from the target. If the electromagnetic brakes 26 and 27 can be held in the off state, the electromagnetic brake 2
It is possible to reduce power consumption of the electromagnetic brakes 6 and 27 and extend the life of the electromagnetic brakes 26 and 27.

Before the change of the target value occurs, when the electromagnetic brakes 26 and 27 are turned off and the error amount gradually increases and exceeds the predetermined value B, feedback control using the gain after convergence is performed. The output of the control signal is restarted (see FIG. 9). In the above embodiment, the sliding mode is used for the feedback control, but the proportional / integral / derivative control may be used.

For simplicity, the gain switching is omitted, the error amount is sufficiently small, and the relative speed is approximately 0.
The electromagnetic brakes 26 and 27 may be turned off when it becomes. Furthermore, technical ideas other than the claims that can be understood from the above embodiment will be described below along with their effects. (A) In the control device for the variable valve timing mechanism according to claim 2, the variable valve timing is characterized in that the convergence to the vicinity of the target is judged based on a comparison between the first-order lag processing value of the relative speed and a threshold value. Mechanism control device.

According to the above structure, the value having a first-order lag with respect to the actual relative speed is compared with the threshold value to judge the convergence state in which the relative speed decreases. Therefore, the margin time is set after the convergence, and it is possible to avoid the determination of convergence before the convergence completely. (B) In the control device for the variable valve timing mechanism according to the item (ii), the threshold value is set based on the maximum value of the relative speed.

According to the above configuration, the threshold value to be compared with the first-order lag processing value of the relative speed is changed based on the maximum value of the relative speed correlated with the magnitude of the target change. Therefore, the timing of the convergence determination is set appropriately according to the magnitude of the target change, and the convergence determination can be performed more reliably.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an internal combustion engine.

FIG. 2 is a sectional view showing a variable valve timing mechanism.

FIG. 3 is an exploded perspective view of the variable valve timing mechanism.

FIG. 4 is a cross-sectional view taken along the line AA of FIG. 2 showing an operation of a main part of the variable valve timing mechanism.

5 is a cross-sectional view taken along the line AA of FIG. 2 showing the operation of the main part of the variable valve timing mechanism.

FIG. 6 is a control block diagram showing details of feedback control of an electromagnetic brake.

FIG. 7 is a flowchart showing the processing contents of a self-holding utilization control unit.

FIG. 8 is a flowchart showing setting of a threshold value (border value) used for determination of a steady state in the self-holding utilization control unit.

FIG. 9 is a timing chart showing control characteristics in the embodiment.

[Explanation of symbols]

2 ... Drive plate, 2g ... Guide groove, 3 ... Cam sprocket, 4 ... Assembly angle adjusting mechanism, 14 ... Link arm, 15
... operating device, 24 ... guide plate, 25 ... planetary gear mechanism, 26 ... first electromagnetic brake, 27 ... second electromagnetic brake, 28 ... spiral guide groove, 40 ... operation conversion mechanism, 41
... acceleration / deceleration mechanism, 101 ... internal combustion engine, 105 ... intake valve, 113 ... variable valve timing mechanism VTC, 114
… Engine control unit, 120… Crankshaft, 134… Camshaft

Continued front page    F-term (reference) 3G018 AB07 AB17 BA32 CA04 CA12                       DA20 DA21 DA71 DA81 FA07                       GA03 GA27 GA37                 3G092 AA11 DA01 DA02 DA08 DG03                       DG09 EA02 EA08 EA13 EC02                       FA36 HA01Z HA06Z HA13Z                       HE01Z HE03Z HE08Z HF08Z

Claims (3)

[Claims] 1. A variable valve timing mechanism for changing a valve timing of an engine valve by changing a rotational phase of a cam shaft with respect to a cam sprocket in an advance direction and a retard direction by braking forces of two electromagnetic brakes. When the deviation between the target value and the actual value of the rotational phase of the camshaft is less than or equal to a predetermined value, and the relative speed of the camshaft with respect to the cam sprocket is less than or equal to the predetermined value, the two electromagnetic brakes are forced to operate. Control device for variable valve timing mechanism characterized by controlling off 2. The feedback control of the braking force of the two electromagnetic brakes according to the deviation between the target value and the actual value of the rotational phase of the camshaft, wherein the gain of the feedback control is near the target. 2. The control device for the variable valve timing mechanism according to claim 1, wherein the value is changed to a value smaller than that before convergence when the variable valve timing mechanism converges. 3. A drive rotary body in which the variable valve timing mechanism rotates integrally with the cam sprocket,
The driven rotary body on the camshaft side is coaxially connected via an assembly angle adjustment mechanism, and the assembly angle of the drive rotor and the driven rotary body is changed by the assembly angle adjustment mechanism. Of the assembly angle adjusting mechanism, wherein the rotating portion at one end is rotatably connected to one of the drive rotating body and the driven rotating body,
The spiral part for displacing the slide part in the radial direction is provided with a link arm whose slide part at the other end is slidably connected in the radial direction by a radial guide provided on the other of the driving rotary body and the driven rotary body. The guide plate on which the guide is formed is relatively rotated in the deceleration direction and the speed-up direction with respect to the drive rotating body by two electromagnetic brakes, whereby the position of the rotating portion is relatively displaced in the circumferential direction, and the drive rotation The control device for the variable valve timing mechanism according to claim 1 or 2, wherein the assembly angle between the body and the driven rotary body is changed.