Early automobile clutches actually came from other mechanical equipment. According to some information, the first-generation clutch was a flat belt (personally inferred that it should be the kind of centrifugal clutch on a scooter). However, the transmission efficiency of the belt is too low and the wear is very serious, especially in rainy days, the power transmission is more prone to problems. As the gearbox increases, the clutch will continue to withstand greater torque, so people invented a variety of clutches, including the forerunner of modern clutches-clutches based on the principle of friction.
Since the clutch needs to switch between disengagement and engagement, the spring must be an essential element. Card friends who have been driving for a long time know that the previous truck clutches used coil springs, some in the middle, and some in the outer ring. But the current clutch does not have these springs, but replaced with a set of plates with claws.
In fact, these claws are also a kind of springs, which are called "diaphragm springs".
The diaphragm spring clutch was born in the research room of General Motors in 1936 and mass-produced in the United States in the late 1930s. It began to be applied to some single European models in the mid-1950s. The Porsche 356, BMW 700 and DKW Munga were the first German-made cars equipped with a diaphragm spring clutch. Mass production of diaphragm spring clutches began in 1965 on the Opel Rekrod model.
In the past few years, the variety of diaphragm spring clutches has been able to fully cover the domestic demand for heavy, medium, light, sedan, mini and agricultural models. So, why use a diaphragm spring instead of a coil spring?
Everyone knows that the tighter the coil spring is pressed, the greater the elasticity-that is, the deeper the clutch pedal is, the harder it is. But the diaphragm spring is different. When it deforms to a certain degree, its elastic force is the largest, and then it continues to deform, the elastic force will decrease instead-that is to say, the deeper the clutch pedal is stepped on, the heavier it is not necessarily.
For overloaded vehicles, it is obvious that the coil spring can provide greater elastic force to press the clutch plate and ensure the power output. However, for standard vehicles, excessive elasticity is not required. At this time, if the loading point of the diaphragm spring is selected, the clutch pedal can be made lighter and labor-saving, and driver fatigue can be reduced while ensuring the compression force.
At the same time, for the coil spring clutch, as the friction plate wears down, the spring deformation will definitely become smaller, so the pressing force will definitely gradually decrease, but the diaphragm spring will first become larger and then decrease.
For example, when the clutch is installed, the spring is pressed to position b; when the clutch is stepped on, the spring is pressed to position c; after a period of wear, the spring returns to position a, at this time:
For the coil spring: the force of stepping on the clutch pedal will become heavier and heavier; the pressing force will become smaller after the clutch disc is worn out.
For the diaphragm spring: the force of stepping on the clutch pedal will be lighter and lighter; the pressing force will increase after the clutch disc is worn out;
Therefore, the diaphragm spring clutch is more comfortable and more reliable than the coil spring.
In the early years, heavy-duty truck clutches used two friction plates, that is, two-plate clutches, in order to be able to transmit greater torque. However, the two friction plates are likely to cause the problem of incomplete separation. Therefore, with the improvement of material technology in recent years, heavy trucks have gradually changed to single-plate clutches.
In addition, if you have disassembled the clutch, you may have seen that some clutches will release the clutch after the release bearing presses the "claw" in the middle of the clutch, while some require the release bearing to pull the "claw" out. These are actually two types of clutches: pull clutch and push clutch. The claws of the pull-type clutch face inward and push outwards.
Due to structural problems, in the case of the same pressure plate size, the pull clutch can use a larger diameter diaphragm spring to provide greater compression force and transmit more torque; or when the same torque is transmitted, Use a smaller size. Therefore, the structure of the pull-type diaphragm spring is more compact and the advantages are more obvious.
Having said so much before, many people may be a little confused. Let’s summarize, clutches can be divided into these categories:
1) According to the number of driven discs, clutches can be divided into single-plate clutches, double-plate clutches, multi-plate clutches, etc.;
2) According to the spring type, the clutch can be divided into cylindrical spiral spring clutch, conical spiral spring clutch, diaphragm spring clutch, etc.;
3) According to the spring arrangement form, the coil spring clutch can be divided into a peripheral spring clutch, a central arrangement spring clutch, etc.;
4) According to the direction of force, the clutch can be divided into push clutch and pull clutch.