JP2003206768A - Control device for variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide fail-safe handling when a sensor to detect a rotational phase in a variable valve timing mechanism to displace the rotational phase of a camshaft in the delay-angle direction or in the advance-angle direction by braking forces of two electromagnetic brakes. <P>SOLUTION: An electrification control duty ratio is decided in accordance with a cooling water temperature Tw related to a coil temperature when at least one of a crank angle sensor and a cam sensor to detect the rotational phase of the camshaft fails. Thereafter, valve timing is held at a most delay- angle position by intermittently performing electrification in accordance with the duty ratio against the electromagnetic coil to displace the valve timing in the delay-angle direction. <P>COPYRIGHT: (C)2003,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).

[0002]

2. Description of the Related Art Conventionally, as a variable valve timing mechanism, an assembling angle between a drive rotating body to which rotation is transmitted from a crankshaft of an internal combustion engine and a driven rotating body on a camshaft side is changed by an assembling angle adjusting mechanism. By doing so, a configuration is known in which the opening / closing timing of the engine valve is changed to the advance side and the retard side with respect to the crank angle.

For example, in the assembly angle adjusting mechanism of the variable valve timing mechanism disclosed in Japanese Patent Application Laid-Open No. 2001-041013, the rotating portion at one end is rotatably connected to one of the driving rotating body and the driven rotating body. At the same time, a slide arm at the other end is provided with a link arm that is slidably connected in the radial direction by a radial guide provided on the other side of the driving rotary body and the driven rotary body. The spiral guide is configured so that the position of the rotating portion is relatively displaced in the circumferential direction, and the assembling angle of the driving rotating body and the driven rotating body is relatively changed, and the sliding portion of the link arm engages. By controlling the relative rotation angle of the guide plate on which is formed by the braking force of the electromagnetic brake, the slide portion is displaced in the radial direction, and thus the valve timing is advanced / retarded. You have me.

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, the above-mentioned Japanese Unexamined Patent Application Publication No.
In the spiral radial link type variable valve timing mechanism disclosed in Japanese Patent Laid-Open No. 001-041013, since the guide plate is biased in the retard direction of the valve timing by the mainspring, the valve timing is changed by turning off the electromagnetic brake. It will return to the most retarded position which is the reference position.

However, Japanese Patent Application No. 20 previously filed by the applicant
In the case of controlling the advance direction and the retard direction with two electromagnetic brakes as in No. 01-319908, even if both electromagnetic brakes are turned off, the valve timing does not change. Fail-safe processing is required when detection of is impossible. Therefore,
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fail-safe process when it becomes impossible to detect an actual valve timing in a variable valve timing mechanism that controls advance and retard directions with two electromagnetic brakes. .

[0007]

Therefore, according to the invention of claim 1, the rotation phase of the camshaft with respect to the crankshaft of the internal combustion engine is changed in the advance direction and the retard direction by the braking force of the two electromagnetic brakes. In a variable valve timing mechanism for changing the valve timing of an engine valve, the two electromagnetic brakes are configured to be feedback-controlled based on the detection result of the valve timing of the engine valve, and the valve timing detection means is abnormal. When the above occurs, one of the two electromagnetic brakes is always energized to return the valve timing to the reference position.

According to the above configuration, the two electromagnetic brakes that change the rotational phase of the camshaft with respect to the crankshaft in the advance direction and the retard direction are feedback-controlled according to the actual valve timing, but the valve timing is detected. If an abnormality occurs in the means, the valve timing becomes unclear. Therefore, by constantly energizing one of the two electromagnetic brakes, the braking force is continuously applied in the advance direction or the retard direction of the rotation phase, The retard position or the most advanced position is returned to the reference position.

According to the second aspect of the invention, the valve timing of the engine valve is changed by changing the rotational phase of the camshaft with respect to the crankshaft of the internal combustion engine in the advance direction and the retard direction by the braking force of the two electromagnetic brakes. In the variable valve timing mechanism for changing, the two electromagnetic brakes are feedback-controlled based on the detection result of the valve timing of the engine valve, and when an abnormality occurs in the valve timing detecting means, In order to return the valve timing to the reference position, one of the two electromagnetic brakes is intermittently energized.

According to the above configuration, by energizing either one of the two electromagnetic brakes, a braking force is applied in the advance direction or the retard angle direction to the reference position which is the most retarded position or the most advanced angle position. It should return, but it should be energized intermittently rather than energized at all times. In the invention according to claim 3, when an abnormality occurs in the valve timing detection means, the applied voltage for energizing one of the two electromagnetic brakes is set according to the temperature of the coil of the electromagnetic brake. It was configured.

According to the above construction, the applied voltage is set by the coil temperature, in other words, the coil resistance value. The setting of the applied voltage includes the setting of the average applied voltage by adjusting the duty ratio in the ON / OFF control of energization. In the invention according to claim 4, the temperature of the coil is estimated based on the cooling water temperature and / or the lubricating oil temperature of the engine.

According to the above arrangement, instead of directly detecting the coil temperature of the electromagnetic brake, the coil temperature is estimated based on the engine coolant temperature and / or the lubricating oil temperature, which is correlated with the coil temperature. . In the invention according to claim 5, the means for detecting the valve timing is a means for detecting a rotational phase difference between the crankshaft and the camshaft.

According to the above configuration, the valve timing is
Since it changes according to the change in the rotational phase difference between the crankshaft and the camshaft, feedback control of the electromagnetic brake is performed based on the detection result of the means for detecting the rotational phase difference, so that the target valve timing is controlled. However, if an abnormality occurs in the means for detecting the rotational phase difference and the rotational phase difference becomes unclear, the braking force by one of the two electromagnetic brakes is continuously applied to reach the most retarded angle position or the most advanced angle position. Try to return to the reference position.

According to a sixth aspect of the present invention, in the variable valve timing mechanism, the drive rotary body to which rotation is transmitted from the crankshaft of the internal combustion engine and the driven rotary body on the camshaft side are provided with an assembly angle adjusting mechanism. Is connected coaxially, and the valve timing of the engine valve is changed by changing the assembling angle between the drive rotating body and the driven rotating body by the assembling angle adjusting mechanism. The mechanism has a diameter in which a rotating portion at one end is rotatably connected to one of the drive rotating body and the driven rotating body, and a slide portion at the other end is provided at the other of the drive rotating body and the driven rotating body. A guide plate provided with a link arm slidably connected in a radial direction by a direction guide and having a spiral guide for displacing the sliding portion in a radial direction is provided by two electromagnetic brakes. By relative rotation with respect to the drive rotor, the position of the rotating portion circumferential direction is displaced relative to a structure for changing the assembly angle between the drive rotor and the driven rotor.

According to the above construction, the sliding force of the two electromagnetic brakes causes the guide plates to relatively rotate in the advance direction and the retard direction, whereby the slide portion of the link arm is displaced in the radial direction, and the displacement is accompanied by the displacement. A means for detecting valve timing in a configuration in which the position of the rotary portion of the link arm is relatively displaced in the circumferential direction, and the assembly angle between the driving rotary body and the driven rotary body, that is, the rotational phase of the camshaft with respect to the crankshaft changes. If the valve timing becomes unclear due to an abnormal condition, the relative force of the guide plate is returned to the position corresponding to the most retarded position or the most advanced position by continuously applying the braking force by one of the two electromagnetic brakes. To do so.

According to a seventh aspect of the present invention, the guide plate is rotationally transmitted through a planetary gear mechanism having a carrier member as an input element, one of a sun gear and a ring gear as an output element, and the other as a free element. And the above 2
One of the two electromagnetic brakes provides braking to the output element,
The other is configured to apply braking to the free element. According to the above configuration, when the free element is braked, the guide plate is accelerated, and conversely, when the output element is braked, the guide plate is decelerated.

[0017]

According to the invention described in claim 1, even if the actual valve timing becomes unknown, the braking force for displacing toward the reference position (the most advanced angle position or the most retarded angle position) is continuously applied. There is an effect that it can be surely returned to the reference position. According to the invention of claim 2, when the actual valve timing becomes unknown, the braking force for displacing toward the reference position (the most advanced angle position or the most retarded angle position) is intermittently generated, It is possible to return to the reference position and hold the position while suppressing wear and power consumption of the electromagnetic brake.

According to the third aspect of the present invention, even if the coil temperature is different, the necessary current for returning to the reference position can be secured, and the return to the reference position can be ensured. According to the invention described in claim 4, there is an effect that the coil temperature can be estimated by using a sensor which is often installed for other control, and the system cost can be reduced.

According to the fifth aspect of the present invention, the valve timing can be easily detected as the rotational phase difference between the crankshaft and the camshaft, and when an abnormality occurs in the rotational phase difference detection means, the electromagnetic brake is activated. There is an effect that the current can be surely returned to the reference position by energizing. According to the invention of claim 6, in the spiral radial link type variable valve timing mechanism for controlling the valve timing in the retard direction and the advance direction by using two electromagnetic brakes, even if the actual valve timing becomes unknown, There is an effect that it can be surely returned to the reference position.

According to the seventh aspect of the present invention, in a mechanism in which rotation is transmitted to the guide plate via the planetary gear mechanism so that speed increase / decrease of the guide plate can be controlled by two electromagnetic brakes, There is an effect that the valve timing can be surely returned to the reference position when the valve timing becomes unknown.

[0021]

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. A variable valve timing mechanism VTC 113 for changing the valve timing is provided.

In this embodiment, the variable valve timing mechanism VTC 113 is provided only on the intake valve side, but instead of the intake valve side or together with the intake valve side,
Variable valve timing mechanism VTC113 on the exhaust valve side
May be provided. 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 when the fuel injection valve 131 is driven to open by an injection pulse signal from the ECU 114, The intake valve 105 supplies the fuel adjusted to a predetermined pressure.
Jet toward.

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 Tw of 01, a cam sensor 132 for extracting a rotation signal from the intake 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 extending axially from the 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.

Further, as shown in FIG. 3, the drive plate 2 is formed with a timing sprocket 3 on the outer periphery of the rear portion thereof, the rotation of which is transmitted from the crankshaft 120 via a chain (not shown). Further, on the front end surface of the drive plate 2, three guide grooves 2g are formed in the outer diameter direction by connecting the through hole 2a and the outer periphery, and the guide groove 2g is similar to the shaft support portion 8d. 120 ° in the circumferential direction
It is arranged for each.

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 rotating body is constituted by the cam shaft 134 and the spacer 8, and the driving rotating body is constituted by the drive plate 2 including the timing sprocket 3.

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 its tip portion, 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 is radially displaced along the guide groove 2g, the pivot 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, and 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 to move.
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 radial movement of the cylindrical portion 14a in the assembling angle adjusting mechanism 4 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 circumference 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 provided 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. 5, a disc-shaped support panel 22a, a coil spring 22b, a retainer 22c, and a ball 22 are sequentially inserted. Further, the retainer 22c has a bowl-shaped supporting recess 2 that supports the ball 22 in a state where the ball 22 is projected at the front end.
2d is formed, 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 22b 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 move up and down. Direction engagement, and relative movement is possible in the extending direction of the spiral guide groove 28. Further, the spiral guide groove 28 is
As shown in FIGS. 4 and 5, the drive plate 2 is formed so as to gradually reduce its diameter along the rotational direction R.

Therefore, in the operation converting mechanism 40, when the guide plate 24 relatively rotates in the rotation direction R with respect to the drive plate 2 with the sphere 22 engaged with the spiral guide groove 28, the sphere 22 swirls. The guide portion 28 moves radially outward along the spiral shape of the guide groove 28, whereby the cylindrical portion 14a as the slide portion moves in the outer diameter direction shown in FIG. 4, and the rotating pin 81 connected to the link arm 14 is moved. Is pulled toward the guide groove 2g, and the camshaft 1
34 moves in the retard 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, if 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 lagging direction, whereby the planetary gear 33 rotates. 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 members 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 divided 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 each electromagnetic brake 26, 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 sun gear 30 is rotated at an increased speed as the timing sprocket 3 rotates.

The guide plate 24 is rotated in the rotation 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 instantaneously regulated 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 value (target rotational phase difference) of the camshaft 134 with respect to 20 is set, and the actual advance value detected from the detection signal of the crank angle sensor 117 and the detection signal of the cam sensor 132 and the target value are set. Based on the deviation and the direction of the deviation, the energization of the first electromagnetic brake 26 and the second electromagnetic brake 27 is feedback-controlled, and when the actual advance value matches the target, the energization of both electromagnetic brakes 26, 27 is performed. Stop and maintain the advanced position at that time.

If the crank angle sensor 117 and / or the cam sensor 132 fails and the actual advance value (actual valve timing) cannot be detected, feedback control to the target advance value can be performed. If the valve timing disappears and the valve timing at the time of failure is left as it is, the operability may be impaired depending on the operating conditions, and the valve timing may gradually change when the electromagnetic brake is de-energized. There is also a nature.

Therefore, in this embodiment, as shown in the flow chart of FIG. 6, the power supply to the electromagnetic brakes 26, 27 is controlled. In the flowchart of FIG. 6, in step S1, the crank angle sensor 117 is
And / or it is determined whether or not the cam sensor 132 is out of order. For the above failure, disconnection / short circuit of the sensor circuit,
In addition, a change in the output pattern due to a lack of a detected portion or the like is included.

Further, regarding the failure of the crank angle sensor 117 and / or the cam sensor 132, which is the valve timing detecting means, the advance value (rotational phase difference) calculated as described below shows a change which is normally impossible. It can be judged based on whether or not. When both the crank angle sensor 117 and the cam sensor 132 are normal, the process proceeds to step S2, and based on the detection signals from the crank angle sensor 117 and the cam sensor 132, the advance value of the rotational phase of the camshaft 134 with respect to the crankshaft 120 is set. To detect.

The advance angle value is detected, for example, by measuring the time or angle from the reference crank angle position detected by the crank angle sensor 117 to the reference cam angle position detected by the cam sensor 132. In step S3, the target of the advance angle value is set based on the operating conditions of the engine.
In step S4, the first electromagnetic brake 26 and the second electromagnetic brake are based on the deviation between the actual advance value detected in step S2 and the target advance value set in step S3 and the direction of the deviation. Feedback control of energization to 27 is performed.

Specifically, when the actual valve timing is ahead of the target, the second electromagnetic brake 27
On the contrary, when the actual valve timing is on the retard side with respect to the target, the first electromagnetic brake 26 is energized, and the ON / OFF of the energization to each electromagnetic brake is duty controlled. The duty ratio at this time is proportionally / integrally / differentially controlled according to the absolute value of the deviation, and the average applied voltage (braking force) is controlled according to the absolute value of the deviation.

On the other hand, if it is determined in step S1 that the crank angle sensor 117 and / or the cam sensor 132 is out of order, the process proceeds to step S5. In step S5,
The cooling water temperature Tw is detected based on the detection signal from the water temperature sensor 119. In step S6, the duty ratio for energizing the second electromagnetic brake 27 is determined based on the cooling water temperature Tw.

The cooling water temperature Tw is determined by the electromagnetic brake 2
In step S6, the coils 26c and 27c are referred to by previously storing the optimum duty ratio corresponding to the coil temperature estimated from the cooling water temperature Tw in correlation with the temperatures of the coils 26c and 27c. The duty ratio (average applied voltage) is set so that a substantially constant current can be obtained even if the temperature (resistance value) is different.

In the present embodiment, the duty ratio is an ON time ratio, and the higher the cooling water temperature Tw,
The ON time ratio is increased to increase the average applied voltage. In the present embodiment, the coil temperature is estimated based on the cooling water temperature Tw. However, when a sensor for detecting the temperature of the lubricating oil of the engine is provided, the coil temperature may be between the lubricating oil temperature and the coil temperature. Since there is a correlation, it is possible to set the duty ratio based on the lubricating oil temperature so that a substantially constant current can be obtained even if the coil temperature (resistance value) differs. Furthermore, the cooling water temperature Tw and the lubricating oil temperature can be set. And the coil temperature can be estimated to determine the duty ratio.

However, in a simple manner, the second electromagnetic coil 27 may be energized with a constant duty ratio (average applied voltage) regardless of the temperature condition. In step S7, the duty control signal having the duty ratio determined in step S6 is continuously output to the switching means that controls the energization of the second electromagnetic brake 27, and the second electromagnetic brake 27
Always energize.

When the second electromagnetic brake 27 is energized,
A braking force that relatively rotates the guide plate 24 in a direction that retards the assembling angle of the camshaft 134 is applied, and the camshaft 134 is kept at the most retarded position (reference position) by always energizing. Crank angle sensor 117 and / or cam sensor 1
If 32 is out of order, the valve timing becomes unknown and feedback control to the target cannot be performed.
Moreover, if the engine is advanced, the operability of the engine may be impaired depending on the operating condition.

Therefore, by constantly driving in the retard direction, even if the actual valve timing cannot be detected, the valve timing is displaced and held at the most retard position. As a result, the crank angle sensor 11
Even if the valve 7 and / or the cam sensor 132 fails and feedback control of the valve timing is disabled, it is possible to avoid a significant deterioration in drivability.

The flowchart of FIG. 7 shows the electromagnetic brake 2
2nd Embodiment of energization control to 6 and 27 is shown. In the flowchart of FIG. 7, step S11 to step S1
The process of No. 4, that is, the feedback control when both the crank angle sensor 117 and the cam sensor 132 are normal is the same as the above-described steps S1 to S4, and the description thereof is omitted here.

In step S11, the crank angle sensor 11
7 and / or the cam sensor 132 is determined to be defective, the process proceeds to step S15, the cooling water temperature Tw is detected, and in the next step S16, the second electromagnetic brake 27 is sent based on the cooling water temperature Tw. It determines the duty ratio when controlling the energization of. The processes of steps S15 and S16 are the same as steps S5 and S6 of the flowchart of FIG.

At step S17, the step S16 is performed.
Second electromagnetic brake 27 based on the duty ratio determined in
Energization control is started. Then, the next step S18
Then, it is determined whether or not a preset energization time has elapsed after the start of energization. In addition, the energization time is the same as the camshaft 1
It is set based on the maximum time required to displace the assembly angle of 34 to the most retarded position.

Here, until the energization time elapses,
The energized state of the second electromagnetic brake 27 based on the duty ratio determined in step S16 is continued, and when the energized time has elapsed, the process proceeds to step S19 to stop energizing the second electromagnetic brake 27. When the energization is stopped in step S19, in the next step S20, it is determined whether or not a preset energization interval time has elapsed, and the energization stop state is held for the energization interval time, and then the step S19 is performed.
Return to 15.

Therefore, in the above configuration, if the crank angle sensor 117 and / or the cam sensor 132 fails, the second
When the electromagnetic brake 27 is energized for the energization time, the energization is stopped for the energization interval time, and then the energization is repeated for the energization time. The energization interval time is set based on the time required for the assembly angle of the camshaft 134 to deviate to the extent that it affects drivability in a state where energization to the electromagnetic brakes 26 and 27 is stopped. Within the energization interval time, even if the energization of the electromagnetic brakes 26, 27 is stopped, the valve timing is set so as not to shift so as to affect the drivability.

According to the second embodiment, when the crank angle sensor 117 and / or the cam sensor 132 malfunctions and the valve timing is displaced to and held at the most retarded position which is the reference position, it is displaced in the retarded direction. Since the second electromagnetic brake 27 is energized intermittently, it is possible to suppress wear and power consumption of the second electromagnetic brake 27 while holding the second electromagnetic brake 27 at the most retarded position.

In the above embodiment, the valve timing is detected as the rotational phase difference of the cam shaft 134 based on the crank angle sensor 117 and the cam sensor 132. However, for example, the relative rotation of the guide plate 24 with respect to the driving rotating body is detected. The position may be detected, and the valve timing detecting means is not limited to the crank angle sensor 117 and the cam sensor 132. Even if the valve timing detecting means is different, the most retarded angle position can be obtained by the same control as in the above embodiment. It can be displaced to the (reference position).

Further, in the above embodiment, the spiral radial link type variable valve timing mechanism having a structure in which the guide plate having the spiral guide is relatively rotated in the advance direction and the retard direction by the two electromagnetic brakes is a target. However, the variable valve timing mechanism is not limited to the spiral radial link type, and may be any variable valve timing mechanism configured to change the rotational phase of the camshaft with respect to the crankshaft in the advance direction and the retard direction by the braking force of the two electromagnetic brakes. It is possible to obtain the same effect by applying the same fail-safe control.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a variable valve timing mechanism in the embodiment.

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 flowchart showing a first embodiment of valve timing control.

FIG. 7 is a flowchart showing a second embodiment of valve timing control.

[Explanation of symbols]

2 ... Drive plate 2g ... Guide groove 3 ... Timing sprocket 4 ... Assembly angle adjustment mechanism 6 ... VTC cover 8 ... Spacer 14 ... Link arm 15 ... Actuator 24 ... Guide plate 25 ... Planetary gear mechanism 26 ... First electromagnetic brake 27 ... Second electromagnetic brake 28 ... Spiral guide groove 30 ... Sun gear 31 ... Ring gear 32 ... Carrier plate 33 ... Planetary gear 35 ... Braking plate 36 ... Braking plate 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 117 ... Crank angle sensor 119 ... Water temperature sensor 120 ... crankshaft 132 ... Cam sensor 134 ... Camshaft

Continued front page    F-term (reference) 3G016 AA19 DA03 DA23 DA27 GA06                 3G018 BA32 CA04 CA16 DA45 DA66                       EA23 FA02 FA07 GA39                 3G092 AA11 DA01 DA02 DA10 DF05                       DG09 EA03 EA04 EA13 FB02                       HE00Z HE03Z HE08Z                 3G301 HA19 JB01 JB07 LA07 NE11                       NE12 NE16 PE00Z PE03Z                       PE08Z

Claims (7)

[Claims] 1. A variable valve timing mechanism for changing a valve timing of an engine valve by changing a rotational phase of a camshaft with respect to a crankshaft of an internal combustion engine in an advance direction and a retard direction by braking forces of two electromagnetic brakes. In the above, the two electromagnetic brakes are configured to be feedback-controlled based on the detection result of the valve timing of the engine valve, and the valve timing is set to the reference position when an abnormality occurs in the valve timing detection means. A control device for a variable valve timing mechanism, characterized in that one of the two electromagnetic brakes is always energized in order to return it. 2. A variable valve timing mechanism for changing a valve timing of an engine valve by changing a rotational phase of a camshaft with respect to a crankshaft of an internal combustion engine by advancing and retarding directions by braking forces of two electromagnetic brakes. In the above, the two electromagnetic brakes are configured to be feedback-controlled based on the detection result of the valve timing of the engine valve, and the valve timing is set to the reference position when an abnormality occurs in the valve timing detection means. A control device for a variable valve timing mechanism, characterized in that one of the two electromagnetic brakes is intermittently energized to return. 3. An applied voltage for energizing one of the two electromagnetic brakes when an abnormality occurs in the valve timing detection means is set according to the temperature of a coil of the electromagnetic brake. The control device for the variable valve timing mechanism according to claim 1 or 2. 4. The control device for the variable valve timing mechanism according to claim 3, wherein the temperature of the coil is estimated based on a cooling water temperature and / or a lubricating oil temperature of the engine. 5. The means for detecting the valve timing comprises:
The control device for the variable valve timing mechanism according to claim 1, wherein the control device is means for detecting a rotational phase difference between the crankshaft and the camshaft. 6. The variable valve timing mechanism, wherein a drive rotating body to which rotation is transmitted from a crankshaft of an internal combustion engine and a driven rotating body on the camshaft side are coaxially connected via an assembly angle adjusting mechanism, A configuration for changing the valve timing of the engine valve by changing the assembly angle of the drive rotating body and the driven rotating body by the assembly angle adjusting mechanism, wherein the assembly angle adjusting mechanism has one end A part 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. By rotating the guide plate on which the guide is formed with respect to the drive rotating body by two electromagnetic brakes, the position of the rotating portion is relatively displaced in the circumferential direction, so that the drive rotating body and the driven rotating body are separated from each other. The control device for the variable valve timing mechanism according to any one of claims 1 to 5, characterized in that the assembly angle is changed. 7. The guide plate is configured so that rotation is transmitted via a planetary gear mechanism having a carrier member as an input element, one of a sun gear and a ring gear as an output element, and the other as a free element. 7. The control device for the variable valve timing mechanism according to claim 6, wherein one of the electromagnetic brakes applies braking to the output element and the other applies braking to the free element.