A concentric slave cylinder (also known as a slave cylinder or release cylinder, CSC) is part of an automatic transmission and is an important component of a modern vehicle clutch system that works in conjunction with a throwout bearing (release bearing or locking bearing) to control the engagement and disengagement of the clutch or brake.

Concentric slave cylinders work by using compressed air or hydraulic pressure to control the position of the throwout bearing and thus the engagement and disengagement of the torque converter or clutch. This ensures smooth and efficient power transfer between the engine and transmission, while providing easy shifting and stopping. Here is how a concentric slave cylinder works:

Concentric slave cylinder working principle:

There is a hydraulic system in the automatic transmission, which consists of an oil pump, control valves, tubing and various hydraulic cylinders (including throw-out bearings).

1. hydraulic torque converter (Torque Converter): in the automatic transmission, the torque converter connects the engine and transmission, and plays the role of transmitting power. It contains a pumper wheel (pump), a turbine (transmission input shaft) and a guide wheel (locking wheel).

2. Concentric Slave Cylinder Location: The concentric slave cylinder is located on the torque converter housing and is connected to the throwout bearing, which is in direct contact with the guide wheel of the torque converter.

3. Engagement process: When the driver depresses the clutch pedal, the control system reduces the pressure on the concentric slave cylinders, causing the throwout bearing to release and no longer lock with the guide wheel. This allows engine power to be transferred to the transmission through the pump wheel and turbine of the torque converter.

4. Disengagement process: When the clutch pedal is released, the control system increases the pressure on the concentric slave cylinders, causing the throwout bearing to re-lock with the guide wheel, thus disconnecting the engine power for shifting or stopping.

5. Function of the control valve: The operation of the concentric slave cylinders is controlled by a control valve in the gearbox. The control valve regulates the pressure of the concentric slave cylinders according to the driver's operation and the vehicle's operating condition to achieve the engaging and disengaging actions.

When the driver depresses the clutch pedal, the control system reduces the pressure on the hydraulic throwout bearing so that the piston inside it pushes the release bearing, thus separating the engine from the gearbox. When the clutch pedal is released, the control system increases the pressure on the hydraulic throwout bearing, causing it to re-engage the engine and transmission. The following is a detailed description:

Concentric slave cylinder working process:

1. Concentric Slave Cylinders Structural Features:

   - Concentric structure: the concentric slave cylinder consists of two concentric cylinders with hydraulic pistons inside. The outer cylinder surrounds the inner cylinder and the inner cylinder surrounds the input shaft of the transmission.

2. hydraulic transmission:

   - When the driver depresses the clutch pedal, the Clutch Master Cylinder (CMC) transmits hydraulic pressure to the concentric slave cylinders through the master cylinder pistons.

   - Hydraulic pressure is applied to the piston of the inner cylinder, which moves the piston in the outer cylinder by hydraulic pressure.

3. Release the clutch:

   - The movement of the piston in the outer cylinder pushes the Release Arm, which in turn pushes the Pressure Plate to release the Clutch Disc, interrupting the transfer of power between the engine and the transmission.

4. Feedback Sensing:

   - Concentric slave cylinders are usually equipped with sensors or Electronic Control Units (ECUs) to sense their position and status in order to adjust the operation of the clutch system and optimise the driving experience.

The main advantages of concentric slave cylinders:

- Space efficiency: Concentric slave cylinders are typically more compact than traditional throwaway bearings, allowing for greater flexibility in vehicle design.

- Manoeuvrability and responsiveness: hydraulically operated, concentric slave cylinders provide more precise and smoother clutch operation, resulting in a more comfortable driver experience.

- Maintenance costs: Concentric slave cylinders typically have a longer service life and require less maintenance than conventional throwaway bearings.

Overall, a hydraulic throwout bearing is controlled by a hydraulic system that connects and disconnects the engine to the transmission to complete the gear shift process. Its operation relies on precise hydraulic control and interaction between components to ensure smooth vehicle operation and shift quality. Concentric slave cylinders are used in many modern vehicles as a modern solution to clutch systems, enhancing driving comfort and handling.