1.6.3 Inverted Tooth Chain (Silent Chain)
Silent Chains are used for the camshaft drive of the mid- to large-size motorcycle engines and automobile engines in the United States, the transfer-case drive in four-wheel-drive vehicles, and the primary drive between the engine and transmission, as well as in other high-speed applications (Figure 1.28).
Figure 1.28 Silent Chain
Construction and Features
- Silent Chains have a very simple construction: only plates and pins. Today's Silent Chains are actually an update of a 19th-century design. ANSI B29.2M-1982 regulates the standard pitch, width, and kilowatt ratings of the chains and sprockets.
- There are eight different pitches from 9.52 mm to 50.8 mm.
- The link plate receives tension and has a notch for engaging the sprockets. There is no notch on the guide plate. These plates act as guides for the sprockets.
- Pins may be round or have other shapes, such as D-shape (Figure 1.29).
- All of the chain components share the tension. Silent Chains have higher capacity than roller chains of the same width.
- Because the link plates of Silent Chain strike the sprocket at an angle, the impact and the noise are reduced (Figure 1.30). This is why these chains are called "silent." The higher the chain speed, the greater the difference from roller chains.
Figure 1.29 Silent Chain Components
Figure 1.30 Silent Chain Strikes the Sprocket at an Angle, Reducing Noise
The sprocket for Silent Chain is shaped like a gear. In the ANSI standard, the tooth working face is a straight line. But in HY-VO® Chains (see Applications Series below), an involute tooth is used for the sprocket.
Selection and Handling
- Silent Chains are good for high-speed transmission.
- If single- or multiple-strand roller chains are an option, they are less expensive. Wider Silent Chain becomes relatively competitive in price.
- Silent Chains must be lubricated during operation. Use an oil bath if the speed is less than 600 m/min. If the speed is more than 600 m/min., or if the shaft center distance is short, use a pump or forced lubrication. Silent Chains wear rapidly without lubrication.
- The notch on the plates can engage with the sprockets from only one direction. The chain is not for reversing applications.
- To select the right Silent Chain for your operation, refer to the manufacturer's catalog.
HY-VO® Chain is a unique type of Silent Chain. HY-VO stands for High Capacity, High Velocity, and Involute Tooth, and it is a registered trademark of Borg-Warner Automotive, Inc.
In Silent Chain, the pin and the plate rotate against each other. In HY-VO Chains, the pin is comprised of two pieces that have rotational contact. Due to the rotational contact of the pins, the wear life of the chain is increased. Also in HY-VO Chains, the contact point between the pins moves up when the chain engages the sprocket (Figure 1.31). This construction decreases chordal action (which was discussed in Basics Section 2.2.1), vibration, and noise.
Figure 1.31 HY-VO Chain