Before discussing the working principle of Release Bearing, it is first necessary to clarify the position and role of Release Bearing in the automotive transmission system, especially the clutch system.

The release bearing, also known as clutch release bearing or hydraulic throwout bearing, is an important part that connects the clutch pedal with the clutch pressure plate, and is a key component in the clutch system of manual transmission. Its main function is to convert the movement of the clutch pedal into the movement of the clutch pressure plate when the driver operates the clutch pedal, so as to achieve the separation and combination of the clutch discs and enable the driver to shift gears smoothly. The release bearing is usually located near the transmission and is connected to the clutch master cylinder by a hydraulic or mechanical linkage.

Basic structure of the release bearing

The release bearing usually consists of the following key components:

Housing: protects the internal mechanism and is connected to the rest of the clutch system.

Balls or rollers: located inside the bearing to reduce friction and provide smooth rotation.

Inner ring: in contact with the clutch pressure plate or associated mechanism, transmits power.

Lubrication system (in some high end or specially designed bearings): ensures smooth running of the bearing and prolongs its service life.

Principle of operation of release bearings

The operating principle of the release bearing can be summarised in the following steps:

Initial state: the release bearing is at rest or slightly preloaded when the clutch is in the combined state, when the clutch disc is in close contact with the engine flywheel and power is transmitted.

Pedal operation: When the driver depresses the clutch pedal, the pedal transmits force to the release bearing via a series of linkages or a hydraulic system (in some models).

Bearing movement: The release bearing is subjected to an external force and begins to move in an axial direction. This movement process may be achieved by the rolling of balls or rollers between the inner and outer rings of the bearing, thus reducing friction and wear.

Pressure Plate Disengagement: As the release bearing moves, it pushes the clutch pressure plate backwards, separating the clutch disc from the engine flywheel and thus cutting off power transmission. The precise movement of the release bearing and sufficient thrust during this process are key to ensuring that the clutch disc can be fully disengaged.

Pedal release: When the driver releases the clutch pedal, the reverse force on the release bearing decreases or disappears, and the clutch pressure plate moves forward under the action of a spring or other resetting mechanism, allowing the clutch disc to re-unite with the engine flywheel and resume power transmission.

Lubrication (if any): In some designs, the release bearing may contain a lubrication system inside, such as hydraulic oil in a hydraulic release bearing. These lubricants serve to reduce friction, minimise wear and extend the life of the bearing during operation.

Special features of hydraulic release bearings

Hydraulic release bearings are a special type of release bearing that utilises hydraulic principles to release and engage the clutch. The hydraulic release bearing contains hydraulic oil chamber, piston and other hydraulic components inside. When the driver operates the clutch pedal, the hydraulic system drives the piston or related mechanism to move by changing the pressure of the hydraulic oil, which pushes the clutch pressure plate to disengage the clutch disc. This design improves smoothness and durability of operation because the hydraulic fluid provides better cushioning and lubrication.

Overall, the release bearing is one of the indispensable components of the clutch system, which achieves clutch disengagement and engagement through precise movement and thrust. The hydraulic release bearing further enhances the performance of this process by utilising hydraulic principles. The release bearing plays a vital role in the smooth operation of the automotive clutch system. Their reliable function ensures that drivers can shift gears without interrupting power transmission, helping to improve the overall driving experience and longevity of the vehicle's drivetrain.