How one-way bearings work

A one-way bearing is a bearing that can rotate freely in one direction and lock in the other direction. One-way bearings are also called overrunning clutches, but they are named according to different industries and different functions. The metal shell of the one-way bearing contains many rollers, needles or balls, and the shape of its rolling seat (hole) enables it to roll in one direction only, and will produce a lot of resistance in the other direction ( so-called "one-way").

Technical principle

A one-way bearing is a bearing that can rotate freely in one direction and lock in the other direction. The metal shell of the one-way bearing contains many rollers, needles or balls, and the shape of its rolling seat (hole) allows it to roll in one direction only, and will produce a lot of resistance in the other direction.

The working principle of the one-way bearing:

1. Wedge type design

This wedge type one-way overrunning clutch is generally composed of an inner ring, an outer ring, a wedge block group, a wedge block cage, a strong spring and a bearing. The wedges transfer force from one raceway to the other by wedging between the inner and outer rings. Wedges have two diagonal diameters (the distance from one corner of the wedge to the other diagonally), one of which is larger than the other. Wedge action occurs when the inner and outer rings rotate relative to each other and force the wedges to have a larger vertical position on a relatively large cross-section.

2. The action of the self-locking angle wedge 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 larger 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 wedges are designed with a low initial self-locking angle to ensure absolute engagement from the start. As the torque increases, a radial force is created on the wedge that deflects the wedge raceway, causing the wedge to roll to a new position. Wedges are often designed with a self-locking angle that increases gradually, as it goes from the overrun position to the maximum load bearing position. The relatively large self-locking angle reduces the radial force produced by the wedge, thus allowing greater torque to be transmitted as long as the elongation and Brinell hardness limits are required.

3. Slope and roller design

The slope and roller type one-way clutch basically consists of an outer ring with a cylindrical inner diameter, an inner ring with a slope, and a set of rollers that are respectively subjected to spring force and are always in close contact with the inner and outer rings. As long as the rotation of one of the raceways in its direction of motion has an effect on the other, this arrangement inherently ensures the immediateness of the overrunning speed and the immediate driveability.

The use of this type of one-way clutch can be suitable for overrunning, indexing and anti-reverse use in various environments.

When used as an overrunning one-way clutch, the ramp-type roller one-way clutch will be installed in such a way that the outer ring is used as the overrunning member. This is very important for high speed overtaking. In the use of inner ring overrunning, the centrifugal force acting on the rollers will cause the overrunning speed to be limited.

When used as a non-return one-way clutch, a sloped roller one-way clutch in which only the inner ring rotates is suitable for relatively low speeds. If the required speed is higher than the recommended speed, it is recommended to use a sprag type one-way clutch.

When used as an indexing one-way clutch, the outer ring is often seen as the oscillating element, and the inner ring is often seen as the slave element. Otherwise, the inertia of the rollers and springs will cause errors, especially at high frequency indexing. The use of diluted oil and strong springs provides high-speed indexing accuracy and high quality.