This article will provide a clear, concise and easy-to-follow answer to the question how does the hydraulic clutch system work?
We will begin with a basic overview of clutch systems before a more detailed look at the components of hydraulic clutches and then the operation of a hydraulic clutch.
The Basics of Clutch Systems
A clutch is both the connector and disconnector between an engine or power source and, most commonly, the transmission or gearbox of a vehicle. The clutch allows for the smooth transfer of power within the transmission by disconnecting the flow of power from the engine to the wheels.
A hydraulic clutch differs from a mechanical clutch because, as the name suggests it uses high-pressured clutch fluid instead of the cable used in a mechanical clutch.
Components of a Hydraulic Clutch System
- Clutch master cylinder. This is the primary hydraulic cylinder, it houses the piston that is actuated by the clutch pedal. It is also connected to the hydraulic fluid reservoir and is where the fluid is pressurised.
- Clutch slave cylinder. This houses the push piston rod that is connected to the release fork.
- Hydraulic fluid reservoir. This contains the hydraulic clutch fluid which enters the master cylinder when the clutch pedal is pressed.
- The clutch pedal starts the clutch engagement process.
- Pressure pipe. This carries the pressurised fluid from the master cylinder to the slave cylinder.
- The clutch pressure plate pushes the clutch plate against the flywheel until the clutch pedal is pressed then the diaphragm spring pulls it away.
- Flywheel. This is connected to the engine’s crankshaft and the clutch pressure plate and transfers the power between the two until the pedal movement pulls it away.
- Release fork this puts pressure via the clutch shaft onto the release bearing when the clutch pedal is pressed.
- Clutch release bearing. The clutch pedal being pushed presses this against the diaphragm spring
- Splined sleeves sit between the friction lining of the clutch plate and the pressure plate. They enable the disengaging of the engine crankshaft and the pressure plate.
- Diaphragm spring. This curled spring keeps constant pressure on the clutch plate until the clutch pedal is depressed, and then it pulls it away.
- Clutch plate. This has friction linings on both sides which help control the flow of power between the flywheel on one side and the pressure plate on the other.
The Operation of a Hydraulic Clutch System
There are two parts to clutch operation; engagement and disengagement. We’ll explain more about these different phases below.
Clutch Disengagement
This part of the operation of hydraulic clutches initiates when clutch pedals are depressed. This causes the hydraulic clutch fluid in the clutch reservoir to be pressurised via the hydraulic piston in the master cylinder.
This high-pressure fluid transfers to the slave cylinder via the fluid-filled tube and then activates the piston in the slave cylinder which activates the clutch fork and the clutch release bearing. This puts pressure on the diaphragm spring which pulls the pressure plate away from the flywheel by retracting the splined sleeves.
This disruption of power enables the easy and smooth gear change.
Clutch Engagement
Following a gear change, the clutch pedal is released. This will initiate clutch engagement or the release of hydraulic pressure within the master and slave cylinders which in turn releases the diaphragm spring, release fork and release bearing so they can return to their original positions.
The pressure on the clutch plate starts again and the friction surface makes contact with the flywheel, which means the power transfer is resumed.
Conclusion
At MCH Hydraulics, we believe in helping people understand the basic principles of the hydraulic machinery that we all work with every day to help demystify hydraulic processes. We hope that this article has achieved that aim regarding hydraulic clutch systems today.
We would also like to remind you that hydraulic clutches, as with all hydraulic systems, need regular servicing and maintenance to keep them working safely and effectively.