But, this is the case in normal driving. So, how is the power disengagement done with a clutch? For the disengagement purpose, a special kind of spring is introduced in the pressure plate assembly. This spring is known as a diaphragm spring Fig To understand this diaphragm spring better, assume that the diaphragm spring motion is fixed around this circle. In this case, if you press the centre portion of the spring as shown, the outer portion should move in the opposite direction.
The diaphragm spring sits between pressure plate and cover. The outer portion of the diaphragm spring is connected to the pressure disc Fig:7A. This means, if you press the inner portion as shown, the pressure disc will move away from the friction disc Fig:7B. Thus the power flow will discontinue to the transmission.
This is exactly what happens when you press the clutch pedal. A hydraulic system transfers the clutch motion to the center of the diaphragm spring; when the diaphragm spring is pressed, the power flow is discontinued Fig:8A. During this time you can make a gear change; the clutch pedal is released after the gear change and the power flow continues again. These are used to smooth out the fluctuations and vibrations from the engine power output.
It is clear that the hub and disc are not directly connected. The engine power first reaches the disc, then it transfers to the springs and finally to the output hub.
This means that the springs will dampen out most of the power flow fluctuations from the engine and the motion transfer to the vehicle will be much smoother. Even in a car without a handbrake you can use this clutch technique to start while pointing uphill. In an uphill start, initially both the brake and clutch pedal are pressed while the engine is running.
The clutch bite can be experienced at your foot; it may feel like engine is shivering. At this point, even if you release the brake pedal, you can see the vehicle will not roll. The partially released clutch acts like a brake. A clutch works because of friction between a clutch plate and a flywheel. We'll look at how these parts work together in the next section.
In a car's clutch, a flywheel connects to the engine , and a clutch plate connects to the transmission.
When your foot is off the clutch pedal in a manual car, springs push the pressure plate against the clutch disc, which in turn presses against the flywheel. This locks the engine to the transmission input shaft, causing them to spin at the same speed.
The amount of force the clutch can hold depends on the friction between the clutch plate and the flywheel, and how much force the spring puts on the pressure plate. The friction force in the clutch works just like the blocks described in the friction section of How Brakes Work , except that the spring presses on the clutch plate instead of weight pressing the block into the ground.
When the clutch pedal is pressed, a cable or hydraulic piston pushes on the release fork. This in turn presses the release bearing , which disengages the engine from the transmission during gear shifts, against the middle of the diaphragm spring. As the middle of the diaphragm spring is pushed in, a series of pins near the outside of the spring causes the spring to pull the pressure plate away from the clutch disc.
This releases the clutch from the spinning engine. Note the springs in the clutch plate. These springs help to isolate the transmission from the shock of the clutch engaging. This design usually works pretty well, but it does have a few drawbacks. We'll look at common clutch problems and other uses for clutches in the following sections.
From the s to the s, you could count on getting between 50, and 70, miles 80, and , kilometers from your car's clutch. Clutches can now last for more than 80, miles , kilometers if you use them gently and maintain them well. If not cared for, clutches can start to break down at 35, miles 56, kilometers.
Trucks that are consistently overloaded or that frequently tow heavy loads can also have problems with relatively new clutches. The most common problem with clutches is that the friction material on the disc wears out. The friction material on a clutch disc is very similar to the friction material on the pads of a disc brake or the shoes of a drum brake — after a while, it wears away.
When most or all of the friction material is gone, the clutch will start to slip, and eventually it won't transmit any power from the engine to the wheels.
The clutch only wears while the clutch disc and the flywheel are spinning at different speeds. When they are locked together, the friction material is held tightly against the flywheel, and they spin in sync. It's only when the clutch disc is slipping against the flywheel that wearing occurs. So, if you are the type of driver who slips the clutch a lot, you'll wear out your clutch a lot faster.
Sometimes the problem is not with slipping, but with sticking. If your clutch won't release properly, it will continue to turn the input shaft. This can cause grinding, or completely prevent your car from going into gear. Some common reasons a clutch may stick are:. A "hard" clutch is also a common problem. All clutches require some amount of force to depress fully. If you have to press hard on the pedal, there may be something wrong. Sticking or binding in the pedal linkage, cable, cross shaft, or pivot ball are common causes.
Sometimes a blockage or worn seals in the hydraulic system can also cause a hard clutch. Another problem associated with clutches is a worn clutch release bearing , sometimes called a throw-out bearing. This bearing applies force to the fingers of the spinning pressure plate to release the clutch. If you hear a rumbling sound when the clutch engages, you might have a problem with the throw-out.
If you don't hear any noise during these four steps, then your problem is probably not the clutch. If you hear the noise at idle and it goes away when the clutch is pressed, it may be an issue in the contact point between the release fork and the pivot ball that supports it. There are many other types of clutches in your car and in your garage. An automatic transmission contains several clutches. It's the third pedal that you have to press in order to change gears. However, you might not know exactly what the clutch does, especially if you've only driven cars with automatic transmissions.
What is a clutch and why do you need one? Because your engine is always spinning, there has to be a way for the wheels to disengage so they can stop moving. This is where the clutch comes into play. It can disengage the wheels without killing the engine. Everyone knows that a car has an engine to power it, but not everyone is familiar with a clutch or how it works.
This mechanism both engages and disengages your power transmission from the driving shaft to the driven shaft. It connects rotating shafts, and there can be two or more of these under your hood. If you drive a manual transmission, the clutch is connected to both the shaft coming from the engine and the shafts that turn the wheels. While the motor is going to spin constantly, you don't want the wheels continually spinning. One of the rotating shafts is going to be connected to the engine or power unit, this will be the driving member, while the other rotating shaft, or driven member, provides output for work.
For example, a drill has a shaft that's driven by a motor and one that's driven by a drill chuck. HowStuffWorks explains that the clutch connects the shafts so they can be engaged spin at the same speed , slipping spinning at different speeds , or disengaged spinning at different speeds. Typically, you'll find that these motions are rotary; although, linear clutches are possible.
In order for your car to come to a stop without the entire engine having to shut off, the connection between the wheels and the motor has to be broken. Your clutch is made up of two main parts:. There are springs in place that keep pressure on a plate that pushes up against the clutch plate. These springs also push the clutch plate up against the flywheel.
When this happens, the engine's shaft is connected to the wheel shafts, making both turn at the same time , according to AAMCO. In order for the opposite to happen, you have to engage the clutch.
This presses down a release fork which pulls the pressure plate off of the clutch plate, essentially breaking the connection between the rotating engine and the moving wheels.
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