JPH05125912A - Valve timing regulator for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent collision of a phase changing member against a stopper and keep a valve timing within an allowable range even at the time of a failure in a valve timing regulator for an internal combustion engine, for moving the phase changing member in the axial direction so as to change the valve timing. CONSTITUTION:A phase changing member is supported by a nut 7a of a ball screw. A shaft 7b of the ball screw is rotated by a motor so as to be moved together with the nut 7a in the axial direction. A spring 20 adapted to abut against the nut 7a is disposed in the vicinity of a moving limit on a delay angle side of the nut 7a. The movement of the nut 7a is resiliently stopped by the spring 20 in the vicinity of the moving limit, thus preventing collision against a stopper 19. Although the nut 7a is pressed toward the delay angle side by driving reaction of a camshaft at the time of a motor failure, the nut 7a cannot exceed an allowable moving range by energizing force of the spring 20, thereby preventing an inoperable situation due to an excessive delay angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing adjusting device for changing the intake / exhaust valve opening / closing timing of an internal combustion engine according to operating conditions.

[0002]

2. Description of the Related Art As a mechanism for variably controlling the valve timing of intake and exhaust valves in accordance with the rotational speed of an internal combustion engine, when a camshaft is driven from a crankshaft via a chain, gears, etc. It has been proposed to provide a means for changing the phases of the crankshaft and the camshaft in the path.

An example of this type of apparatus is, for example, Japanese Patent Laid-Open No. 59-59.
There is one disclosed in Japanese Patent Publication No. 87214. The device of the publication has a structure in which a sleeve on a hollow cylinder is connected to a timing pulley driven by a belt from a crankshaft, and another sleeve connected to the camshaft is rotatably fitted in the sleeve. ing. Slits are provided on both the inner and outer sleeves so as to intersect with each other, and a phase changing member rotatably supported by a nut of a ball screw is inserted through the slit intersecting portion to axially move together with the nut. It is designed to move. Since the phase changing member is in contact with the slit wall surfaces of both the inner and outer sleeves, the rotational torque to the pulley is transmitted from the outer sleeve to the inner sleeve via the phase changing member to rotate the cam shaft. Further, when the phase changing member is moved in the cam shaft axis direction, the respective sleeves rotate in the inclination direction of the slit, so that the rotational phase of the timing pulley (that is, the crank shaft) and the cam shaft can be changed.

The nut for supporting the phase changing member is movable in the axial direction with respect to the housing by a key provided in the axial direction but is fixed in the rotating direction and is connected to the shaft via a ball screw mechanism. The shaft of this ball screw is connected to an electric motor located on the side opposite to the cam shaft of the shaft. Therefore, by rotating the shaft of the ball screw by the electric motor, the nut moves in the cam shaft axial direction together with the phase changing member, and the rotational phase of the cam shaft and the timing pulley can be changed.

Further, a rigid stopper is arranged at a predetermined position in the nut moving direction to prevent the nut from moving beyond a predetermined operating range.

[0006]

However, in the case where the nut for moving the phase changing member is brought into contact with the rigid stopper to limit the operating range, as in the device of the above-mentioned Japanese Patent Laid-Open No. 59-87214. When the nut is moved to the limit of the operating range, the nut and the stopper may come into shock impact, and an excessive force may be applied to the driving force transmitting members such as the electric motor and the ball screw. There was a risk of damage.

To solve this problem, it is possible to limit the operating range of the nut by controlling the electric motor instead of limiting it by a mechanical stopper. That is, if the amount of phase change of the cam shaft is detected and the motor drive circuit is controlled and the motor is stopped when the amount of phase change reaches a predetermined value, the nut operating range is limited without bringing the nut into contact with the stopper. be able to.

However, also in this case, when an abnormality occurs in the electric motor or the control circuit, the nut moves beyond the operating range,
The above problem may occur due to the collision with the stopper. Further, even if there is no abnormality in the electric motor or the control circuit, the nut may move beyond the operating range due to overshoot during control and collide with the stopper. Torque due to the reaction force of the valve spring acts on the cam shaft during operation, and this reaction force torque is constantly applied to the phase changing member in the direction of moving the phase changing member toward the valve timing retard side. Therefore, when the motor is controlled so as to move the nut to the retard side, the above-mentioned overshoot is likely to occur.

If the stopper is installed at a sufficient distance from the operating range of the nut, it is possible to avoid collision between the nut and the stopper during the above-mentioned overshoot,
In this case, when the nut driving force is lost due to a failure of the electric motor or the like, the above-mentioned force in the retard angle direction applied to the phase changing member causes the nut to gradually move to the retard angle side, and the valve timing May exceed the permissible range and be retarded so that operation cannot continue.

The present invention solves the above problems and prevents excessive force from being applied to the member due to the collision between the nut and the stopper during the valve timing changing operation, and the operation can be continued even when the electric motor or the like fails. An object is to provide a valve timing adjusting device for an internal combustion engine.

[0011]

According to the present invention, two rotations are arranged on the camshaft driving force transmission path between the crankshaft and the camshaft of an internal combustion engine and are coaxial with each other. A member and a phase changing member that is disposed between the two rotating members and that relatively moves the two rotating members by moving in the axial direction to change the rotational phase between the crank shaft and the cam shaft. A valve timing adjusting device for an internal combustion engine, comprising: a phase control mechanism that moves the phase changing member in an axial direction within a predetermined operating range, wherein the phase is changed when the phase changing member moves near the predetermined operating range limit. There is provided a valve timing adjusting device for an internal combustion engine, which is provided with an elastic member that elastically restricts the movement of the changing member.

[0012]

The movement of the phase changing member is elastically restricted in the vicinity of the operating range limit, so that no impact force is applied to the driving force transmitting member. Further, the stopping force applied to the phase changing member by the elastic member is as follows when the phase changing member moves beyond the operating range.
Since it increases according to the moving distance, it is possible to keep the overshoot at the time of moving the phase changing member to a minimum. Furthermore,
Even when the driving force of the phase changing member is lost, the phase changing member is held at a position where the reaction torque of the cam shaft and the reaction force of the elastic member are in balance, so the retard amount does not exceed the allowable range.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the valve timing adjusting device of the present invention. In the figure, reference numeral 1 is a cam shaft for opening and closing an intake / exhaust valve (not shown) of the internal combustion engine, and 3 is a crankshaft 13 of the internal combustion engine to a timing belt
It is a cam pulley that is driven to rotate synchronously via. The cam pulley 3 is fitted so as to be rotatable relative to the cam shaft 1, and a cylindrical portion 3a extending in the axial direction is formed on the side surface of the cam pulley 3.

Further, a cylindrical member 2 is integrally fixed to the end of the camshaft 1 concentrically with the camshaft 1 by bolts, and the cylindrical portion 3 of the cam pulley 3 facing each other.
Helical splines 4a and 4b having opposite twist angles are formed on the inner peripheral surface of the cylinder a and the outer peripheral surface of the cylindrical member 2, respectively. A cylindrical piston 5 is arranged between the inner peripheral surface of the cylindrical portion 3a and the outer peripheral surface of the cylindrical member 2. Helical splines 5a and 5b which mesh with the helical splines 4a and 4b are formed on the outer peripheral surface and the inner peripheral surface of the piston 5, respectively.

A ball screw mechanism for moving the piston 5 in the axial direction is shown by reference numeral 7 in its entirety in the drawing. A shaft 7b forming a screw portion of the ball screw 7 is rotatably supported by a bearing 11 with respect to the housing 17, and a nut 7a of the ball screw 7 rotatably holds the piston 5 via the bearing 6. .

A worm wheel 10 is provided on the shaft 7b of the ball screw 7, and the housing 17
Worm 9 fixed to the drive shaft of the motor 8 attached to the
Meshes with. The shaft 7b of the ball screw 7 is prevented from moving in the axial direction by a stopper member (not shown), while the nut 7a is held by a key (not shown) so as to be movable in the axial direction but not rotatable.
Therefore, by rotating the shaft 7b by the motor 8 via the worm 9 and the worm wheel 10, the nut 7a can be moved in the axial direction.

During operation, the driving force of the camshaft 1 is transmitted from the helical spline 4a provided on the cylindrical portion 3a of the cam pulley 3 via the piston 5 to the helical spline 4b of the cylindrical member 2 fixed to the camshaft 1. Piston 5
Is rotating integrally with the cam pulley 3 and the cam shaft 1 while meshing with the cylindrical portion 3a of the cam pulley 3 and the cylindrical member 2 fixed to the cam shaft 1. When the nut 7a moves in the axial direction, the piston 5 moves in the axial direction together with the nut 7a while rotating with the camshaft 1. Therefore, the meshing positions of the helical splines 5a and 5b of the piston 5 and the helical splines 4a and 4b move along the tooth traces of the respective splines, and the cam pulley 3 and the camshaft 1 rotate relatively, and the crankshaft Thirteen
The phase of the camshaft 1 with respect to changes. In this embodiment, when the piston 5 moves to the motor 8 side, the valve timing is retarded, and when it moves to the camshaft 1 side, the valve timing is advanced.

Further, in this embodiment, the cam shaft 1 and the crank shaft 13 have angular position sensors 15,
16 are provided. The angular position sensors 15 and 16 are protrusion-shaped markers 15a and 16a provided on their respective axes.
Is detected by an electromagnetic pickup and a signal is output. As shown in FIG. 2, the relative angular position θ of the cam shaft 1 (valve timing advance The angle amount or the retard angle amount) can be detected.

Reference numeral 14 in the drawing denotes a control circuit for performing valve timing control. The control circuit 14 rotates the motor 8 through a drive circuit (not shown), and controls the valve timing according to the operating conditions of the internal combustion engine. For this purpose, the control circuit 14 includes the cam angle position sensor 1
5 and the crank angle position sensor 16 respectively input the angular position signals, and the operating parameter sensor group 1
The intake air amount, the throttle valve opening, etc., which are parameters representing the engine speed and the load condition, are input from 8.

Further, in this embodiment, the maximum retard amount and the maximum advance amount of the valve timing are set, and the control circuit 14
Controls the motor 8 so that the nut 7a does not move beyond this range. Further, in this embodiment, a spring 20 that elastically restricts the movement of the nut 7a is arranged on the retard side of the movement range of the nut 7a.

FIG. 3 is an enlarged view of a portion where the spring 20 is installed. In the present embodiment, the spring 20 is a coil spring having a shape surrounding the shaft 7b of the ball screw 7, and one end thereof has a stopper wall 19 provided in the housing 17.
Is fixed to the nut 7a, and the other end is brought into contact with the nut 7a. In the present embodiment, when the spring 20 is in the free state, the free end of the spring 20 is located on the advance side from the maximum retard position (point a in FIG. 3,) of the nut 7a. The spring is designed to be compressed by a predetermined amount when moving to.

For this reason, in this embodiment, the elastic force of the spring 20 acts before the nut 7a reaches the maximum retard position (point a in FIG. 3,) and presses the nut 7a toward the advance side.
Overshoot is prevented when the nut 7a moves, and the stopper 19 and the nut 7a do not collide. Also,
When the nut 7a cannot be driven due to an abnormality in the motor 8 or the like, the nut 7a is pushed toward the retard side by the reaction force acting on the camshaft 1. Because it stops at the point where the force balances,
The situation in which the nut 7a moves in the retard direction is prevented. In this embodiment, the free length of the spring 20 is adjusted so that the position where the nut 7a stops due to the balance between the camshaft reaction force and the spring elastic force is on the advance side from the maximum retard position (point a in FIG. 3). The spring constant is set to prevent the valve timing from being retarded beyond the allowable range even when the motor 8 is abnormal, and the operation can be continued.

Next, FIG. 4 shows another embodiment of the present invention. In this embodiment, the nut 7a does not move in the axial direction and the shaft 7 does not move.
The valve timing is changed by moving b in the axial direction. In FIG. 4, the nut 7a is rotatably held with respect to the housing 17 and is prevented from moving in the axial direction. The shaft 7b is supported by the engaging portion 21 with the nut 7a, and is prevented from rotating with respect to the housing 17 by a rotation prevention pin (not shown). The piston 5 is rotatably held at the end of the shaft 7b via a bearing 6. The nut 7a is rotationally driven by a motor 8 via a worm wheel 10 provided on the outer periphery of the nut 7a. Also in this embodiment, by providing the spring 20 between the retard side end of the shaft 7b and the housing 17, the same effect as the embodiment of FIG. 1 can be obtained.

In the above embodiment, the springs 20 are provided only on the retard side of the nut 7a or the shaft 7b, but not on the advance side. This is because the nut 7a and the shaft 7b are constantly urged toward the retard side by the reaction force of the cam shaft described above during operation,
Overshoot is unlikely to occur when moving on the advance side, and the possibility of collision with the stopper is low even if the spring 20 is not provided. Further, even when the motor fails, these members are pushed in the retard direction, and therefore the advance angle is increased. This is because it is not necessary to provide a means for restraining the directional movement.

In the above embodiment, the case where the nut 7a and the shaft 7b are driven by the motor 8 via the worm 10 has been described.
The same can be applied to the case where b is driven by a motor using a spur gear and the piston 5 is driven hydraulically.

[0026]

The valve timing adjusting device of the present invention is
By providing the elastic member for preventing the phase changing member from moving beyond the axial movement range, it is possible to prevent an impact force from being applied to the phase changing member drive mechanism due to a collision with the stopper, and these members are prevented. It is possible to prevent the life of the engine from decreasing and to prevent the failure, and to maintain the valve timing within the allowable range even when the drive source fails, so that the operation can be continued.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a method for detecting valve timing.

FIG. 3 is an enlarged view of a main part of FIG.

FIG. 4 is a view similar to FIG. 3, showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cam shaft 3 ... Cam pulley 4a, 4b ... Helical spline 5 ... Piston 5a, 5b ... Helical spline 7 ... Ball screw 7a ... Nut 7b ... Shaft 8 ... Motor 9 ... Worm 10 ... Worm wheel 20 ... Spring

Claims (1)

[Claims] 1. A rotary member which is disposed on a camshaft driving force transmission path between a crankshaft and a camshaft of an internal combustion engine and which is coaxial with each other, and between the rotary members. And a phase changing member that changes the rotational phase between the crank shaft and the cam shaft by rotating the two rotating members relative to each other by moving in the axial direction, and the phase changing member within a predetermined operating range. In a valve timing adjusting device for an internal combustion engine including a phase control mechanism that moves in the axial direction, an elasticity that elastically restricts the movement of the phase changing member when the phase changing member moves to near the predetermined operating range limit. A valve timing adjusting device for an internal combustion engine, comprising a member.