Patent Application
20080261738
This invention relates generally to chain transmission systems and more particularly to chain transmission systems wherein one portion of elements engages a front side of a chain used is such system and another portion of elements in the system engage a backside of the chain.
As is known in the art, chain driven systems (i.e., chain transmission systems) have many applications, such as for example, in motor vehicles. In one such application, a drive sprocket is mounted to the drive shaft of the vehicle's internal combustion engine. A chain has links engaging the teeth of the drive sprocket and teeth of a driven sprocket mounted to a camshaft of the engine. Thus, rotation of the engine drives the engine's camshaft.
In some chain transmission systems additional sprockets are driven. For example, a sprocket may be connected to the links to drive a water pump. In some applications, the water pump pulley is driven by the backside of the chain. In another application, the backside of the chain may be used to engage an idler sprocket that spins but does no work other than to direct or guide the motion of the chain. This is possible with a standard roller chain, but this type of drive creates high levels of chain mesh noise and vibration. An inverted tooth or silent chain can reduce mesh noise, but the chain becomes very wide, heavy, and is prone to stretch over time if back drive teeth are added. The guiding of the chain also becomes an issue with chain teeth on both sides. Another technique is to use a roller chain and a toothed rubberized sprocket or a metal cushion ring sprocket.
In accordance with the present invention, a chain transmission system is provided having a drive sprocket, a driven sprocket, a chain having a front side engaging teeth on the drive sprocket and teeth on the driven sprocket, and a rotary wheel having rubber outer surface. A backside of the chain engages the rubber outer surface of the driven wheel.
With such an arrangement, because the teeth are removed from the central back-drive sprocket and over-molded with rubber, the back drive can be driven through friction from the relative smooth backside of a silent chain. This back drive on the flat side is similar to how a cogged belt is used to back drive a sprocket. This enables the incorporation of a silent chain into the design which reduces chain mesh noise and eliminates all mesh frequency noise from the central, back-driven sprocket.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Referring now to
It should be noted that the teeth 24, 28, and 30 engage the front side 50 of the chain 20. The engine 12 also includes a rotary wheel 40, here connected for example to a water pump, not shown, driven by the backside 52 of the chain 20, engaging a toothless rubberized outer surface 60 of the wheel 40, as shown more clearly in
Referring now to
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
