JPH0579306A - Valve timing adjusting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To miniaturize the above device by carrying out movement of a phase changing member of a valve timing adjusting mechanism in the axial direction by way of using a shaft and by supporting the shaft with a nut connected to the shaft. CONSTITUTION:A phase changing member 7 is interposed between a sprocket 2 driven from a crankshaft and a cam shaft 1, and the cam shaft 1 and the sprocket 2 are engaged to each other through helical splines 5, 6. A ball screw mechanism furnished with a shaft 17 and a nut 18 is used to move the phase changing member 17 in the axial direction. The nut 18 is supported against a housing 12 free to rotate by its both end parts 18a, 18b, and a wheel gear 19 is fitted on the roughly central outer periphery of these support parts. It is made needless to provided a bearing separately by way of supporting the shaft 17 with the nut 18, and the device is miniaturized.

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 the sleeve connected to the camshaft is rotatably fitted in the sleeve. .. 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.

Further, 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 at the same time, is mounted on the shaft via a ball screw mechanism. It is connected. The shaft of the 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.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-59-87
In the structure of rotating the shaft to move the nut in the axial direction like the device of Japanese Patent No. 214, a bearing that rotatably supports the shaft with respect to the housing is required. For this reason, there is a problem that a space for installing the bearing is required, and the device becomes large in size, which deteriorates mountability. Further, in the device of the publication, since the nut and the phase changing member are supported by the shaft in a cantilever manner, the rigidity of the shaft protruding portion in the direction perpendicular to the axis of the shaft is insufficient, and the phase changing member with respect to the axis. There is a problem that the phase changing member tends to be inclined and the phase changing member cannot be smoothly moved in the axial direction.

In view of the above problems, the present invention makes it possible to reduce the bearing space for supporting the shaft in a valve timing adjusting device that changes the camshaft rotation phase by moving the phase changing member in the axial direction, thereby enabling downsizing of the device. In addition, it is an object of the present invention to provide a valve timing adjusting device capable of preventing the phase changing member from inclining with respect to the axis.

[0007]

According to the present invention, it is formed between a crankshaft and a camshaft of an internal combustion engine, and is arranged between two coaxially provided rotary members, which move in the axial direction. Internal combustion engine that includes a phase changing member that relatively rotates the two rotating members to change the rotational phase between the crank shaft and the cam shaft, and a phase control mechanism that moves the phase changing member in the axial direction. In the valve timing adjusting device for an engine, the phase control mechanism has a nut rotatably supported on an outer peripheral portion thereof and prevented from moving in the axial direction,
A drive mechanism for rotationally driving the nut, and a shaft which has one end coupled to the phase changing member and which is supported by being engaged with a threaded portion of the nut inner peripheral surface via a threaded portion provided on an outer peripheral portion. The shaft timing is held non-rotatably, and the valve timing adjusting device for an internal combustion engine is characterized in that the shaft is moved in the axial direction according to the rotation of the nut to move the phase changing member in the axial direction. Provided.

[0008]

Since the shaft is supported by the nut via the threaded portion, it is not necessary to separately provide a bearing for supporting the shaft. Further, since the entire surface of the shaft in the longitudinal direction is supported at the engaging portion with the nut, the rigidity of the shaft in the direction perpendicular to the axis of the shaft is increased and the inclination of the phase changing member with respect to the axis can be prevented.

Further, since a wheel gear is provided on the outer circumference of the nut and the nut is driven via a worm, a nut driving device such as an electric motor can be arranged at right angles to the axis, so that the length in the axial direction of the device can be further shortened. Further, if the nut and the shaft are connected via a ball screw mechanism, the shaft supporting accuracy can be further improved and the operation can be facilitated.

[0010]

DETAILED 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 that opens and closes an intake and exhaust valve (not shown) of the internal combustion engine, and 2 is a sprocket that is synchronously driven by a crankshaft (not shown) of the internal combustion engine via a chain.

The sprocket 2 is fitted to the camshaft 1 at the bore 2a provided at the center, and is held on the camshaft 1 by the camshaft sleeve 3 and the bolt 4.
The camshaft sleeve 3 is fixed by a pin 3a so as to rotate integrally with the camshaft 1, but the sprocket 2 is held so as to be slidably rotatable with respect to the camshaft 1 and the camshaft sleeve 3.

A cylindrical sprocket sleeve 10 is integrally attached to the sprocket 2 concentrically with the cam shaft 1. Helical splines 5 and 6 having opposite twist angles are provided on the inner peripheral surface of the sprocket sleeve 10 and the outer peripheral surface of the camshaft sleeve 3, respectively. Between the sprocket sleeve 10 and the camshaft sleeve 3, the sprocket sleeve 1 is provided on the outer peripheral surface and the inner peripheral surface, respectively.
There is provided a cylindrical phase changing member 7 in which splines 10a and 10b which engage with the spline 5 of 0 and the spline 6 of the camshaft sleeve 3 are formed.

By engaging the splines 5 and 6 with the phase changing member 7, the phase changing member 7 rotates together with the sprocket 2 and the cam shaft 1 to transmit the rotation of the sprocket 2 to the cam shaft 1, and the phase changing member 7 is rotated during the rotation. By sliding in the cam shaft axial direction, the splines 5 and 6
The engaging position of the phase change member 7 and the sprocket 2
The camshaft 1 can be relatively rotated in the opposite directions along the tooth traces of the splines 5 and 6. Therefore, by controlling the axial position of the phase changing member 7, the phase of the camshaft 1 with respect to the sprocket 2 (and the crankshaft) can be adjusted during operation.

A ball screw mechanism provided with a shaft 17 and a nut 18 is used as a phase control mechanism for moving the phase changing member 7 in the axial direction. The shaft 17 and the nut 18 are configured such that threads provided on the outer circumference of the shaft 17 and the inner circumference of the nut 18 mesh with each other via balls 18c, and the ball 18c is circulated by mutual rotation of the shaft 17 and the nut 18. Circulation mechanism (not shown).

The nut 18 is rotatably supported by the housing 12 at both ends 18a and 18b, and the ring-shaped wheel gear 1 is provided around the outer periphery of the center of these supporting portions.
9 is fitted. In this embodiment, the bearing portion 18a of the nut 18 is a cylindrical bearing portion 12a formed on the inner surface of the housing.
Is supported in the radial direction by the shaft, and the nut 18 is prevented from moving in this direction by the axis-perpendicular surface 12b. Further, the support portion 18b of the nut 18 is attached to the housing 12 by the bolt 13
It is supported on the housing 12 via a stopper 13 fixed by c, and is supported in the radial direction by a cylindrical bearing portion 13a of the stopper 13 and is prevented from moving in the axial direction by an axis-perpendicular surface 13b.

The wheel gear 19 is integrally fixed to the nut 18 of the ball screw by a key 19a and a nut 19b. Reference numeral 21 in the drawing denotes a worm that meshes with the wheel gear 19. The worm 21 is the housing 12
It is connected to a rotating shaft of an electric motor 20 such as a stepper motor supported by the. The rotational torque of the electric motor 20 is transmitted to the nut 18 via the wheel gear 19 to rotationally drive the nut 18.

On the other hand, the shaft 17 of the ball screw is connected to the phase changing member 7 via the ball bearing 16 at the end on the camshaft 1 side, and holds the phase changing member 7. The inner race of the ball bearing 16 is the shaft 1
7 is fixed to the shaft 17 by a stepped portion 17a and a circlip 17b. Therefore, the phase changing member 7
Is rotatably held on the shaft 17 and moves integrally with the shaft 17 in the axial direction.

A stopper pin 14 is press-fitted into the end of the shaft 17 opposite to the ball bearing 16 perpendicularly to the axis, and the protruding end of the stopper pin 14 engages with a key groove 12c provided in the housing 12. Together, the shaft 17 is held so as to be movable with respect to the housing 12 in the cam shaft axis direction, and the rotation of the shaft 17 is prevented.

The housing 12 is fixed to the cylinder head 15 of the internal combustion engine with bolts 15a and supports the above ball screw mechanism. Next, the operation of the valve timing adjusting device of this embodiment will be described. During operation, when the valve timing changing operation is not performed, the phase changing member 7 rotates together with the sprocket sleeve 10 and the camshaft sleeve 3, and the sprocket 2 and the camshaft 1
And rotate together. When it is necessary to change the valve timing according to the operating conditions, drive the electric motor 20,
The worm 21 is rotated by a predetermined amount. The rotation of the worm 21 is transmitted to the nut 18 via the wheel gear 19, which causes the nut 18 to rotate with respect to the housing 12 at a predetermined reduction ratio. As mentioned above, the nut has a vertical surface 12
Since the axial movement is blocked by b and 13b, the nut does not move in the axial direction due to the rotation. The rotation of the nut 18 is transmitted to the shaft 17 by the ball 18c, but the rotation of the shaft 17 is blocked by the stopper pin 14.
Moves in the axial direction of the cam shaft 1. Therefore the shaft 17
The phase changing member 7 connected to the shaft 17 through the ball bearing 16 rotates with respect to the shaft 17 while rotating.
Along with the axial movement, helical splines 5, 6 and 1
Due to the meshing action with 0a and 10b, the rotation phase with the sprocket 2 (that is, the crankshaft) camshaft 1 changes, and the valve timing is changed.

During operation of the engine, lubricating oil is supplied to the lubricating oil supply hole 22 from a lubricating oil pump (not shown) of the engine, and the key groove 12c is provided via the lubricating oil passages 22a and 22b.
After lubricating the meshing portions of the nut 18 support portions 18a and 18b, the worm 21, and the wheel gear 19, forced lubrication is performed through the lubricating oil drain hole 23, so that the sliding resistance at each sliding portion is increased. Is reduced, and the phase changing operation is performed smoothly in combination with the effect of the ball screw.

In this embodiment, the nut 18 of the ball screw is rotationally driven to move the shaft 17 in the axial direction so as to change the phase.
It is possible to support by 8 and the shaft 1
Therefore, it is possible to reduce the axial length of the device because it is not necessary to separately provide a bearing for the device No. 7. Further, the nut 18 is supported by the housing 12 at both ends 18a and 18b,
Since it is driven to rotate at substantially the center through the wheel gear 19, the tilting moment applied to the nut 18 by the driving force applied to the wheel gear 19 is applied to both ends 18a, 1a.
The shaft center of the nut 18 can be held with high precision.

The shaft 17 is held by the ball screw with respect to the nut with high bearing accuracy.
Since 7 is supported over the entire region in the longitudinal direction of the engaging portion with the nut 18, the radial rigidity of the shaft protruding portion is increased as compared with the conventional cantilever structure with two-point support.
Further, in the present embodiment, since the worm 21 is used to drive the nut, the electric motor 20 can be arranged in the direction perpendicular to the axial line, so that the axial dimension of the device can be further shortened. ..

Further, in the present embodiment, by adopting the worm 21, the reduction ratio of the rotation of the nut 18 can be set large, and the driving resistance can be reduced by adopting the ball screw so that the torque of the electric motor 20 can be set small. Therefore, it is possible to perform an extremely smooth phase changing operation using a small electric motor. Next, FIG. 2 shows another embodiment of the valve timing adjusting device of the present invention. In the above-described embodiment, the supporting portions 18a and 18b of the nut 18 are constituted by sliding bearings by oil lubrication to simplify the structure and reduce the cost, but in the present embodiment, the supporting portions 18a and 18b of the nut 18 are provided. Angular contact ball bearing 2
The difference is that the structure is supported by 5, 26. According to the present embodiment, since the ball bearings 25 and 26 are used, the driving resistance, especially the starting torque is greatly reduced, so that there is an advantage that the phase changing operation can be performed more smoothly.

Although not shown, an inexpensive sintered oil-impregnated bearing may be used to support the supporting portions 18a and 18b of the nut 18, and a bearing structure having a production cost and a required operation accuracy may be provided. You can choose.

[0025]

According to the present invention, the phase changing member of the valve timing adjusting device is axially moved using a shaft,
Since the shaft is configured to be supported by the nut connected to the shaft via the screw portion, it is not necessary to separately provide a bearing for supporting the shaft, the device can be downsized, and the axis of the phase changing member can be achieved. There is an advantage that the device can be operated smoothly by preventing the inclination against.

Further, by structuring the nut to be driven via the worm, the electric motor can be downsized and the length in the axial direction of the device can be reduced, and the device can be further downsized. Furthermore, if the ball screw mechanism is used to connect the nut and the shaft, the operation of the device can be further facilitated and the shaft support accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of an embodiment of a valve timing adjusting device of the present invention.

FIG. 2 is a sectional view showing the structure of another embodiment of the valve timing adjusting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cam shaft 2 ... Sprocket 7 ... Phase change member 12 ... Housing 14 ... Stopper pin 16 ... Ball bearing 17 ... Shaft 18 ... Nuts 18a, 18b ... Bearing part 19 ... Wheel gear 20 ... Electric motor 21 ... Worm

Claims (3)

[Claims] 1. A rotary shaft formed between a crank shaft and a cam shaft of an internal combustion engine, arranged between two coaxially provided rotary members, and moved in the axial direction so that the two rotary members are opposed to each other. A valve timing adjusting device for an internal combustion engine, comprising: a phase changing member that rotates to change a rotational phase between a crank shaft and a cam shaft; and a phase control mechanism that moves the phase changing member in an axial direction. The phase control mechanism includes a nut rotatably supported on the outer peripheral portion thereof, which is prevented from moving in the axial direction, a drive mechanism which rotationally drives the nut, and one end of which is connected to the phase changing member and which has an outer peripheral portion. A shaft that is supported by and is supported by a threaded portion of the nut inner peripheral surface via a threaded portion provided on the shaft, the shaft being held non-rotatably, and being axially responsive to rotation of the nut. Move The valve timing control apparatus for an internal combustion engine, characterized in that moving the serial phase change member in the axial direction. 2. The nut is rotatably supported by bearings provided at both ends of the outer periphery of the nut so as to be prevented from moving in the axial direction, and meshes with a wheel gear provided on the outer periphery of the nut. 2. The valve timing adjusting device for an internal combustion engine according to claim 1, wherein the valve timing adjusting device is rotationally driven from a drive source via a worm. 3. The valve timing adjusting device for an internal combustion engine according to claim 1, wherein the nut inner peripheral surface and the shaft outer peripheral surface are engaged with each other via a ball screw mechanism.