The automobile clutch is installed between the engine and the transmission, that is, within the flywheel shell between the engine and the transmission. The clutch assembly is fixed to the rear plane of the flywheel by screws. During driving, the driver can step on or release the clutch pedal as needed, making the engine temporarily separated from and gradually engaged with the transmission, so as to cut off or transmit the power input from the engine to the transmission.
Composition and structure of clutch and operating principle
Diaphragm spring clutch is widely used in various types of cars, so here we will introduce its working principle and structure.
The clutch consists of friction plates, spring plates, pressure plates, and a power output shaft
The diaphragm spring clutch consists of an active part, a driven part, a pressing mechanism, and a steering mechanism. The active part consists of a flywheel, a clutch cover, and a pressure plate.
The clutch cover is fixed to the flywheel through bolts. To maintain the correct installation position, the clutch cover is positioned by positioning pins. The pressure plate and the clutch cover are connected by three or four sets of circumferentially distributed transmission plates to transmit torque. The transmission plates are made of spring steel and each set consists of two plates. One end of each plate is riveted to the clutch cover, and the other end is connected to the pressure plate with screws.
Construction of clutch
The driven part includes the driven disc and the driven shaft. The driven disc usually has a torsional vibration damper. The speed and torque transmitted from the engine to the transmission system vary periodically, causing torsional vibrations in the transmission system, which can subject the components of the transmission system to impactful alternating loads, reducing their life and causing damage to the components. The use of a torsional vibration damper can effectively prevent torsional vibrations in the transmission system. The structure of the driven disc with a torsional vibration damper is shown in the figure.
Disassembly diagram of the clutch cover and pressure plate: 1—Clutch cover; 2—Diaphragm spring; 3—Pressure plate; 4—Driving piece; 5—Driven plate; 6—Supporting ring.
Working principle of clutch
The clutch is used to transmit the torque stored on the engine flywheel to the transmission, to ensure that the appropriate driving force and torque are transmitted to the driving wheels under different driving conditions, which belongs to the category of powertrain. When in semi-engagement, the clutch allows a speed difference between the power input and output ends, which is achieved by the speed difference to transmit appropriate amounts of power.
In simple terms, the clutch is used to transmit power to the transmission by means of “separation” and “connection”.
Structure of clutch cover and pressure plate
Specific working principle of clutch
The outer circumference of the steel piece of the driven plate is riveted with a wavy spring steel piece, and the friction lining is riveted on the spring steel piece. The steel piece of the driven plate and the damping plate are riveted together, and there is a friction pad and a driven hub between them. The driven hub, the steel piece of the driven plate and the damping plate all have six round windows evenly distributed around their circumference. The damping spring is installed in the window hole.
Structure of the driven disc with torsional vibration damper
When the driven disc receives torque, the torque is transmitted from the friction lining to the steel piece of the driven disc, and then to the driven hub through the damping spring. At this time, the spring will be compressed, absorbing the torsional vibration transmitted from the engine.
The pressure-tightening mechanism is a diaphragm spring, which has several radial grooves to form an elastic lever. At the end of each groove, there is a circular hole through which the fixing rivets are passed and then fixed to the clutch cover. The diaphragm spring is equipped with steel wire supporting rings on both sides, which are the supporting points for the diaphragm spring to work. The outer edge of the diaphragm spring is connected to the pressure plate through the separating hook.
The working principle of the diaphragm spring clutch is shown in Figure 5.
When the clutch cover is not installed on the flywheel, the diaphragm spring is not stressed and is in a free state. At this time, there is a distance S between the clutch cover and the flywheel, as shown in Figure 5(a). When the clutch cover is fixed to the flywheel through bolts, the diaphragm spring is compressedively deformed at the supporting ring, and the outer circumference of the diaphragm spring exerts a clamping force on the pressure plate, making the clutch in an engaged state, as shown in Figure 5(b). When the clutch pedal is depressed, the separating bearing pushes the diaphragm spring, making it pivot around the supporting ring and move its outer circumference backward, pulling the pressure plate backward through the separating hook to separate the clutch, as shown in Figure 5(c).
Figure 5: Working principle of diaphragm spring clutch
Dynamic diagram of clutch working principle
As shown in Figure 6, the release mechanism of the diaphragm spring clutch is mainly composed of a release fork, a release bearing, and a release bearing seat. When the clutch pedal is depressed, the clutch control mechanism transfers the force to the release fork, which acts as a lever. The fulcrum of this “lever” is the support point of the release fork, which pushes the release bearing seat to press the release bearing against the diaphragm spring, causing the clutch to disengage. The fixed ring of the release bearing plays a role in connecting the release bearing seat and the release fork.
Figure 6: Clutch release mechanism
As can be seen from the above introduction, the diaphragm spring serves as both the compression spring and the release lever, simplifying the structure. Additionally, the spring characteristics of diaphragm springs are superior to those of cylindrical helical springs, making diaphragm spring clutches increasingly popular and widely used in various vehicle models.
