JPH0577842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a valve timing adjustment device that performs variable control of the opening and closing timing of intake and exhaust valves of an internal combustion engine.

Conventional technology The fourth valve timing adjustment device of this type
As shown in the figure, a cylindrical gear 3, at least one of which is a helical tooth, is provided between the timing pulley 1 and the camshaft 2 on the inner and outer peripheries.
The outer teeth 3a provided on the outer periphery are meshed with the inner teeth 1a provided on the inner periphery of the timing pulley 1, and the inner teeth 3b provided on the inner periphery are meshed with the outer teeth 2a provided on the outer periphery of the camshaft 2. The rotation of the timing pulley 1 can be transmitted to the camshaft 2, and the gear 3 is connected to the hydraulic pump 4a.
By moving the camshaft 2 in the axial direction with a gear drive mechanism 4 using a coil spring 4b or the like, the timing pulley 1 and the camshaft 2 are rotated relative to each other, and the opening/closing timing of the intake and exhaust valves by the camshaft 2 is controlled. It is known that the internal combustion engine is advanced or retarded depending on the operating status of the engine (for example, US Pat. No. 4,231,330). Note that 5 is a timing belt.

Problems to be Solved by the Invention The conventional valve timing adjustment device described above has a simple operation of moving the gear 3 in the axial direction of the camshaft 2 using hydraulic pressure or the like, and adjusts the timing according to the operating condition of the internal combustion engine, for example, during high-load operation. Sometimes, it is possible to delay the timing of closing the intake valve to increase the filling efficiency of the flammable mixture and obtain high output, and during low-load operation, by advancing the timing of closing the intake valve (earlier), residual burnt gas can be reduced. By reducing the amount of gas, it is possible to improve combustion stability and fuel efficiency.

However, since this valve timing adjustment device has a configuration in which the gear 3 meshes with the respective teeth of the timing pulley 1 and the camshaft shaft 2, a meshing gap called a so-called bump crush naturally exists between these meshes. . Therefore,
Due to the existence of this bounce, during operation, the spring force of the valve spring acts as an alternating load in the rotational direction or counter-rotation direction of the camshaft 2, causing fluctuations in the rotational torque of the camshaft 2, resulting in meshing noise. In some cases, the timing of opening and closing the intake and exhaust valves became unstable.

Means for Solving the Problems Therefore, in the present invention, the gears that connect the timing pulley and the camshaft are connected via an elastic member to a plurality of gear structures whose tooth traces are slightly shifted from each other. It is configured. Further, the elastic member is a rubber bush embedded in the gear assembly, and a plurality of gear assembly are connected by a thrust pin inserted into the rubber bush.

By slightly shifting the helix of the outer teeth and inner teeth of the gear components constituting the gear, and adjusting the apparent tooth thickness of each tooth when these gear components are connected, This gear is attached to the timing pulley and camshaft with zero backlash, and the valve timing adjustment device functions by preventing meshing noise caused by the presence of backlash.

Embodiment Next, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a divided perspective view of a gear 3, which is the gist of the present invention. The gear 3 is generally formed by cutting and dividing a long gear, and has the same outer teeth 3a and inner teeth 3b. , 3d, a cylindrical rubber bushing 3e as an elastic member is embedded in one of the gear components 3c, and a slide pin 3f connects the helical gear components 3c and 3d by being inserted into the rubber bushing 3e.
The gear components 3c, 3
A spacer 3g having a desired thickness is interposed between d and d.

The rubber bush 3e, in cooperation with the thrust pin 3f inserted therein, connects the gear components 3c, 3d to each other so as to be movable in the rotational and axial directions using the spring force of the rubber bush 3e. Here,
The mutual rotational and axial movement of the gear structures 3c and 3d increases the apparent tooth thickness of the teeth formed on the inner and outer circumferences of these gears, causing the inner teeth 1a of the timing pulley 1 and the outer teeth of the camshaft 2 to increase in thickness. This makes it possible to assemble the gear 3 to each tooth 2a with zero backlash.

In other words, since at least one of the teeth (both in this example) formed on the inner and outer circumferences is a helical tooth, the gear structure 3 cut and divided as described above
By connecting 3c and 3d with a width narrower than the cutting width, the mutual tooth traces are slightly shifted, and the apparent tooth thickness of the connected gear components 3c and 3d increases. I will do it.

Therefore, the gears 3 connected and constructed in this manner are separated, for example, to a size substantially the same as the cutting width, and meshed with the inner teeth 1a of the timing pulley 1 and the outer teeth 2a of the camshaft 2, respectively. As a result, each of the gear components 3c and 3d is configured to engage each of the inner teeth 1a of the timing pulley 1 and the outer teeth 2a of the camshaft 2 with spring force in the rotational direction and axial direction generated by the rubber bush 3e itself. It moves within the tooth groove in a direction that makes the meshing backlash zero, and the gear 3 is assembled to the timing pulley 1 and camshaft 2 with zero backlash. At this time, the spring force applied by the rubber bush 3e is not exhausted, and henceforth the assembled state with zero backlash is maintained. Incidentally, since at least one of the teeth formed on the inner and outer peripheries of the gear 3 is a helical tooth, each gear structure 3c,
When 3d is moved by the spring force of the rubber bush 3e and the backlash is zero, these teeth mesh with the teeth of the timing pulley 1 and camshaft 2 with a wedge action, so that torque is not transmitted to the rubber bush 3e. To rotationally drive a camshaft 2 without placing an excessive burden on the camshaft 2.

In the embodiment, the spacer 3g is the gear structure 3
It is useful for determining the gap when connecting c and 3d with a desired gap. In other words, this spacer 3
By changing the thickness of g, rubber bushing 3
The spring force in each direction applied to the gear components 3c and 3d can be arbitrarily selected by e. However, as is clear from the above description, this spacer 3g is not so important for eliminating bumpiness when the gear 3 is assembled. Therefore, it is possible to eliminate the spacer 3g depending on the method of connecting the gear components 3c and 3d, and the elimination of the spacer 3g does not significantly affect the effects of the present invention.

FIG. 3 shows a state in which the gear 3 is mounted between the timing pulley 1 and the camshaft 2 so as to be slidable in the axial direction of the camshaft 2 as described above. The gear 3 is driven by a gear drive mechanism 4. The gear drive mechanism 4 includes a hydraulic pump 4a that supplies hydraulic pressure to one end of the gear 3 via a pressure receiving piston 4c, and a hydraulic pump 4a that supplies hydraulic pressure to one end of the gear 3.
It consists of a return spring 4b attached to the other side, and during high load operation, the hydraulic pump 4
Hydraulic pressure is supplied from a to one end side of the gear 3 through a hydraulic passage 4d provided in the camshaft 2, and when the gear 3 moves to the right in FIG. 3 while compressing the return spring 4b due to the oil pressure, the timing pulley 1
On the other hand, the camshaft 2 rotates in one direction to advance the timing of closing the intake valve, thereby increasing the filling efficiency. Also, during low load operation, the hydraulic pump 4a
When the supply of hydraulic pressure to one end of the gear 3 is stopped, the gear 3 moves to the left in FIG. 3 by the spring force of the return spring 4b, and the camshaft 2 rotates in the other direction relative to the timing pulley 1. By delaying the timing of closing the intake valve (reducing valve overlap), the amount of residual burnt gas is reduced, improving combustion stability and fuel efficiency.

Although the embodiment shown in the drawings uses a hydraulic pump for the gear drive mechanism 4, a step motor or the like may be used instead of the hydraulic pump to drive the gear 3.
It may be configured to move in the axial direction of the camshaft 2.

Effects of the Invention As explained above, the present invention provides a gear 3 that connects the timing pulley 1 and the camshaft 2.
Since a plurality of gear components 3c, 3d whose lines are slightly shifted from each other are connected via an elastic member, the gear components 3c, 3d forming the gear 3
The apparent tooth thickness of the teeth formed on the inner and outer peripheries of the gear 3 is adjusted, and the gear 3 is assembled to each of the inner teeth 1a of the timing pulley 1 and the outer teeth 2a of the camshaft 2 with a backlash of zero. be able to. Therefore, it is possible to prevent the occurrence of meshing noise due to the presence of backlash, and it is also possible to stabilize the timing of opening and closing the intake and exhaust valves. Furthermore, even if the finishing accuracy of the gear 3 and the inner teeth 1a of the timing pulley 1 and the outer teeth 2a of the camshaft 2 that mesh with the gear 3 are made low, no unevenness will occur in the meshing, so the valve timing adjustment device Since there is no deterioration in the functionality of the device, manufacturing becomes easy and manufacturing costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of the gear component of a gear used in the valve timing adjustment device of the present invention, Fig. 2 is a partially fragmented sectional view of the assembled state, and Fig. 3
The figure is a sectional view of a valve timing adjustment device showing an embodiment of the present invention, and FIG. 4 is a sectional view of a conventional valve timing adjustment device. 1...Timing pulley, 1a...Inner tooth,
2...Camshaft, 2a...Outer tooth, 3...
Gear, 3a...outer tooth, 3b...inner tooth, 3
c, 3d...Gear structure, 3e...Elastic member (rubber bushing), 3f...Thrust pin.

Claims (1)

[Scope of Claims] 1. A cylindrical gear 3 in which at least one of the teeth provided on the inner and outer circumferences is a helical tooth is provided between the timing pulley 1 and the camshaft 2.
The outer teeth 3a provided on the outer periphery of the timing pulley 1 are meshed with the inner teeth 1a provided on the inner periphery of the timing pulley 1, and the inner teeth 3b provided on the inner periphery are meshed with the outer teeth 2a provided on the outer periphery of the camshaft 2. The rotation of the timing pulley 1 can be transmitted to the camshaft 2, and the gear 3 is moved in the axial direction of the camshaft 2 by the gear drive mechanism 4, thereby rotating the camshaft 2 relative to the timing pulley 1. In the valve timing adjustment device for an internal combustion engine in which the timing of opening and closing of the intake and exhaust valves can be changed by the camshaft 2, the gear 3 has a plurality of gear components 3c and 3d whose tooth traces are slightly shifted from each other, and is made of an elastic member. A valve timing adjustment device for an internal combustion engine, characterized in that the valve timing adjustment device is configured to be connected via a valve 3e. 2. Valve timing adjustment for an internal combustion engine according to claim 1, wherein the elastic member is a rubber bushing 3e embedded in a gear assembly, and a plurality of gear assembly are connected by a thrust pin 3f inserted into the rubber bushing. Device.