One way sprag bearing technical principle

One way sprag bearing is a kind of bearing that can rotate freely in one direction and lock in the other direction. The metal shell of one way sprag bearing contains many rollers, needles or balls, and the shape of its rolling seat (cavity) makes it only roll in one direction, but it will produce great resistance in the other direction (so-called "one-way").

How one way sprag bearing works

1. Ramp and Roller Design

The slope and roller type one-way clutch is basically composed of an outer ring with a cylindrical inner diameter, an inner ring with a slope, and a set of rollers that bear spring force respectively and are always in close contact with the inner and outer rings. This arrangement essentially ensures immediacy of overrun speed and guarantees immediate actuation capability as long as rotation of one of the raceways in its direction of motion affects the other.

The use of this type of one-way clutch can be used for overrunning, indexing and non-return in various environments.

When used as an overrunning one-way clutch

Ramp roller one-way clutches will be mounted in such a way that the outer race acts as the overrunning member. This is very important for high-speed overtaking. In the application of inner ring overrunning, the centrifugal force acting on the rollers will cause the overrunning speed to be limited.

When used as a backstop one-way clutch

A ramped roller one-way clutch with only the inner ring turning is suitable for relatively low speeds. If the required speed is higher than the recommended speed, it is recommended to use the sprag type one-way clutch.

When used as an indexing one-way clutch

The outer ring is often seen as a swing element, and the inner ring is often seen as a slave element. Otherwise, the inertia of the rollers and springs will cause errors, especially when indexing at high frequencies. The use of diluted lubricating oil and strong spring provides high-speed indexing accuracy and high quality.

2. wedge design

This wedge type one-way overrunning clutch is generally made up of inner ring, outer ring, wedge group, wedge cage, powerful spring and bearing. Wedges transmit force from one raceway to the other by wedging between the inner and outer rings. Wedges have two diagonal diameters, (that is, the distance from one corner of the wedge to the opposite corner) one of which is larger than the other. Wedging occurs when the inner and outer rings rotate relative to each other, forcing the wedge to have a greater vertical position over a larger cross-section.

3. The self-locking angle wedge action mainly depends on the wedging and self-locking angle of the wedge between the inner and outer rings. The basic concept of the wedge one-way clutch requires that the friction coefficient of the wedge is related to the sudden torque generated by the inner ring in the driving direction, and this friction value must be greater than the tangent of the self-locking angle. If conditions are not safe, wedging will not occur.

The self-locking angle is determined by the structure of the wedge, and the points on the inner and outer rings are respectively connected with the wedge.

The wedge is designed with a very low initial self-locking angle to ensure absolute engagement from the start. As the torque increases, a radial force is exerted on the wedge that deflects the wedge raceway, causing the wedge to roll to a new position. Wedges are often designed to have a progressively increasing self-locking angle as it progresses from the overrun position to the maximum load bearing position. A relatively large self-locking angle can reduce the radial force generated by the wedge, thus allowing a large torque to be transmitted as long as the elongation and Brinell hardness limit requirements are met.

One way sprag bearing main application: Textile machinery; Printing machinery; Automobile industry; Household appliances; Money detector.

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