Endless belt power transmission systems or components – Positive drive pulley or guide roll
Patent
1989-02-17
1990-07-10
Bui, Thuy M.
Endless belt power transmission systems or components
Positive drive pulley or guide roll
474153, F16H 5530
Patent
active
049404504
DESCRIPTION:
BRIEF SUMMARY
Technical Field:
The present invention relates to a system for transmitting rotative power from a driver element to a driven element, and more particularly to a power transmission system employing a toothed belt and pulleys around which the toothed belt is trained. Background Art:
Generally, a train of gears or a coupling means for coupling a gear train and a rotatable shaft is employed to transmit the rotation of a driver shaft to a driven shaft. Such means for transmitting rotative power are however disadvantageous in that the number of parts required is increased as the distance between the driver and driven shafts becomes larger. On the other hand, a power transmission system using a belt is employed in many applications since it is free from the problem of the increased number of components needed.
A power transmission system using a toothed belt and toothed pulleys, in particular, can reliably keep constant the ratio between the rotational speeds of driver and driven shafts, and is used as a timing belt transmission device for use in an internal combustion engine.
More specifically, as shown in FIG. 15 of the accompanying drawings, an automotive internal combustion engine 1 has a crankshaft 2 projecting from the front wall of the engine. Rotative power from the crankshaft 2 is transmitted through a power transmission system using a toothed belt to a camshaft 3, an oil pump 4, a water pump (not shown), a balancer shaft (not shown), and the like. A pulley 6 mounted as a driver pulley on the crankshaft 2 transmits its rotative power through a toothed belt 9 to driven pulleys 7, 8 coupled to the accessories.
The tooth profile of the pulleys and toothed belt of the toothed belt transmission system is selected such that any loss of the rotative power transmitted between the pulleys and toothed belt when they mesh with each other will be minimized. Specifically, the tooth profile which is used should allow the pulley and the toothed belt to start meshing with each other simultaneously over entire meshing teeth in their longitudinal direction and also should prevent the meshing teeth from being displaced relatively to each other in their longitudinal direction. To meet these requirements, the teeth of conventional pulleys and toothed belts have had tooth profiles parallel to the longitudinal direction of the teeth, e.g., spur gear tooth profiles.
The problems to be solved by the present invention will be described below.
The belt is subject to large tension over the span between the pulley 6 on the crankshaft 2 and the pulley 7 adjacent thereto for driving an accessory. Between the pulleys 6, 7 and the toothed belt 9, intermeshing teeth start meshing with each other simultaneously over their entire longitudinal area to transmit rotative power. When these teeth of the belt and the pulleys mesh with each other, however, the intermeshing teeth hit each other and produce impact sounds, which vary with the rotational speeds of the pulleys.
The impact sounds are liable to amplify the vibration of the teeth belt 9, and the toothed belt 9 gives off noise due to resonance thereof upon the amplified vibration, resulting in a shortened belt life.
Japanese Utility Model Publication No. 55-19324 disclosed an improved power transmission system using a toothed belt. With the disclosed power transmission system, when a belt and a pulley start to mesh with each other, the tip of a tooth of the belt engages into a tooth groove in the pulley while the tooth tip is being elastically deformed. Then, a tooth tip of the pulley and the bottom of a tooth groove in the belt engage each other in a final period of the meshing cycle. The impact between the tooth tip of the pulley and the bottom of the tooth groove in the belt, which has maximized the level of the hitting sounds, can be dampened beforehand by the elastic deformation of the tooth of the belt.
However, the teeth of the pulley and belt are still nevertheless caused to start meshing with each other in the entire longitudinal direction of the teeth, and hence the level of th
REFERENCES:
patent: 4634409 (1987-01-01), Johnson et al.
patent: 4687261 (1987-08-01), Atkin
Asano Hiroshi
Hamada Hayato
Iwasa Seizo
Kinoshita Takeshi
Miyamura Noriyuki
Bui Thuy M.
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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