JPS6233042Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a drive device for a camshaft in an internal combustion engine.

For example, in an OHC (overhead valve) type engine, power transmission between the crankshaft and camshaft is as follows:
Generally, this has been done using a chain-wound transmission mechanism, but in recent years, there has been a tendency for cog belts (toothed timing belts), which are excellent in quietness and are lightweight, to be adopted in place of the above-mentioned chains.

Figures 1 and 2 show the conventional camshaft drive device used for this cog belt.
3 is a toothed crankshaft pulley fixed to the tip of the crankshaft 2, 3 is a toothed camshaft pulley fixed to the tip of the camshaft 4, and 5 is a toothed portion 5a on the inner peripheral surface, which is wound around both pulleys 1 and 3. 6 is a cylindrical tension pulley that presses against the outer peripheral surface of the cog belt 5 on the slack side to apply a predetermined tension to the cog belt 5;
Reference numeral 7 denotes a V-belt type pulley for driving auxiliary equipment, which is fixed to overlap the camshaft pulley 3.

By the way, in a device using such a cog belt 5, unlike in the case of a chain, it is necessary to restrict the movement of the cog belt 5 in the width direction to prevent it from falling off the pulleys 1 and 3. Belt guiding flanges 8, 8 are provided at both ends of the pulley 1 to regulate the movement described above.

However, when the flanges 8, 8 are provided in this way, as shown in detail in FIG. 3, the direction of motion of the cog belt 5 and the direction of motion of the flange 8 intersect, and the hatched portion in FIG. Due to the high-speed contact between the cog belts 5 and 5, a harsh vibration noise (rubbing sound) is generated from this portion, which considerably impairs the level of quietness achieved by using the cog belt 5.

This idea was made in view of these circumstances, and the movement of the cog belt in the width direction is restricted by forming the tension pulley, which is attached to the slack side and back side of the cog belt, into a chain shape. The purpose of this is to remove the belt guiding flanges at both ends of the pulley and prevent noise generation due to relative movement between the cog belt and the flange portion at the flanges.

Hereinafter, one embodiment of this invention will be described in detail based on the drawings.

4 and 5 show a camshaft drive device according to this invention, where 11 is a toothed crankshaft pulley fixed to the tip of the crankshaft 12, and 13 is a toothed camshaft pulley fixed to the tip of the camshaft 14. Pulley, 15 is both pulley 1
The crankshaft pulley 11 is a cog belt having toothed portions 15a on the inner circumferential surface wound around the crankshaft pulleys 1 and 13, and the crankshaft pulley 11 is not provided with a flange for guiding the belt.

Tension pulleys 16 and 17 are rotatably supported by the frame 18 and press against the back surface of the cog belt 15 on the slack side, and are pressed inward by a spring or hydraulic pressure (not shown). Or, the cog belt 15 is fixed in advance with being pressed inward,
This applies a predetermined tension to the cog belt 15. Here, one tension pulley 16 is formed in the shape of a concave central part, and therefore the cog belt 15 is always attached to this tension pulley 1.
6 toward the center, and its movement in the width direction is restricted. In other words, even if the cog belt 15 tries to move in the width direction due to some kind of disturbance, it will be pulled back to the center where it will be more stable.
This prevents it from falling off. The other tension pulley 17 is formed in a barrel shape with a swollen center in the opposite direction to the tension pulley 16, and compensates for the uneven tension of the cog belt 15 caused by the tension pulley 16 in the width direction. It is designed so that even tension can be obtained. These tension pulleys 16 and 17 are made of, for example, engineering plastic, and their dents and bulges are exaggerated in the drawings, but in reality, a sufficient effect can be obtained with just a few pulleys.

Therefore, according to the above configuration, as a result of removing the belt guiding flanges from the pulleys 11 and 13, the vibration noise generated from the pulleys 11 and 13, the cog belt 15, etc. due to the contact between the flanges and the cog belt 15 is reduced. is completely prevented.

In addition, the cog belt 1 by the tension pulley 16
5 If the uneven tension in the width direction is slight, the barrel-shaped tension pulley 17 can be omitted.

As explained above in detail, according to the camshaft drive device of this invention, there is no need to provide a belt guide flange on the toothed pulley of the crankshaft and camshaft, noise caused by this can be eliminated, and the engine This makes it possible to achieve even lower noise levels.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a conventional camshaft drive device, Fig. 2 is a front view of the same, Fig. 3 is an enlarged view of its main parts, Fig. 4 is a side view showing an embodiment of this invention, Fig. 5 The figure is a front view of the same. 11...Crankshaft pulley, 13...Camshaft pulley, 15...Cog belt, 16...Tsut type tension pulley, 17...Barrel type tension pulley.

Claims (1)

[Scope of utility model registration request] In a camshaft drive device in which a cog belt is wound around toothed pulleys fixed to the crankshaft and the camshaft, respectively, the tension pulley, which presses against the back surface of the cog belt on the slack side of the cog belt, has a concave central portion. A camshaft drive device characterized in that the cog belt is formed in a pinched shape to restrict movement of the cog belt in the width direction.