The clutch pedal is probably the most important part of the transmission in a car. It connects the transmission to the flywheel of the engine. However, the big question is how does a clutch pedal work?
This varies depending on the type of mechanism and the type of gearbox of the car. However, the basic operating principles always remain the same .New drivers and car owners are interested in many questions related to clutch pedals. How does a clutch pedal work? Why is it needed at all?
Can't you just connect the engine to the gearbox? Why there is simply no clutch pedal in automatic cars? The questions are endless and here you will find the answers.
First, the absence of a clutch pedal in automatic cars does not mean that there is no clutch pedal. Actually, it is built into the box itself and has a different structure. Secondly, it is technically possible to connect the gearbox and the engine directly. Nevertheless, in this case, the gearbox will last no more than two days.
The car will move in jerks, and to stop you will have to turn off the engine. When the clutch is released too quickly the car jerks forward - this is something that happens to many new drivers. However, if you know what is a clutch pedal, and how does it work, you can also learn how to avoid it. Let's dive in!
What is a clutch pedal?
To understand how a clutch works, you need to know what it is and how it works. First of all, the clutch housing is connected to the engine crankcase which is how it has control over the vehicle.
The main elements of a clutch are a driven friction disk and a pressure plate. They are either pressed against each other or separated under the influence of the drive. The pressure plate is huge and is firmly fixed in the casing and does not have a coupling with the gearbox shaft.
On the other hand, the driven friction disc is much thinner. Additionally, it is located on the gearbox shaft splines which, on the one hand, provides its rigid coupling, and on the other, allows it to move along the shaft.
In working condition, the two discs under the pressure and the release are tightly connected and transmit the torque from the engine to the input shaft. If they are disconnected, the torque is interrupted, and accordingly, the driven friction disk stops rotating.
What is the function of a clutch pedal?
After engaging the first gear, the input shaft of the box is connected directly to a running engine. If the clutch does not work properly, here are a few scenarios that might happen:
- The motor will not have enough force to cope with the applied full load, it will stall;
- The power unit has enough power to overcome the load. It will result in a strong jerk of the machine forward;
- If at this moment you increase the speed by pressing the gas pedal, the torque of the crankshaft can break the teeth of the gears of the gearbox.
The reason is that without a clutch, it is impossible to get on the road normally. Moreover, you will not even turn on the first speed. The direct joining of two shafts will give the jerk. In addition, shifting to higher gears will also be impossible and so on.
By the way, while we are talking about driving, check out our other blog post that covers some great safety tips that every driver should know.
Hence, the conclusion is that a clutch integrated between the input shaft of the gearbox and the engine crankshaft is needed to smoothly connect one unit to another. Thanks to it, the torque force is not transferred to the transmission immediately, but gradually. For example, when releasing the clutch after switching speeds, you usually feel an increasing effort. This is when you also can turn up the gas so that the car does not stall.
In cars with an automatic transmission, there is no clutch pedal since the intermediary unit acts without the participation of the driver. However, switching is performed by a hydraulic or electric drive.
How does it work?
It is easy to understand how a clutch pedal works if you consider it in a "cause-effect" format i.e. how the driver's actions affect the operation of the unit and the car as a whole:
- To engage the clutch, the driver moves the gear lever to neutral, depress the pedal, and selects the gear. After that, the engine will start running and the engine flywheel will start to rotate. However, the driven disc is not yet in contact with the flywheel which is why the car remains in place.
- The driver releases the clutch pedal just a bit, after which the car begins to move very slowly. The driven disc, which had previously remained static, comes into contact with the flywheel under the action of the pressure disc springs. The coefficient of rotation of the flywheel is very high. Upon contact, it accelerates the driven disc. The speed of the disc increases, the rotations are transmitted to the drive wheels with which it is directly connected.
- The driver does not take any action while holding the clutch pedal but it also does not release it completely. The flywheel and the driven disc continue to touch. The speed of rotation of the disc increases and after a while, the elements rotate at the same speed. The vehicle continues to move at an increased speed.
- The driver slowly releases the pedal, removing their foot from it. It causes pressure on discs, and the flywheel rotates at the same speed. It transmits torque from the engine first to the gearbox, and then to the wheels. Finally, the clutch is fully engaged and the vehicle is moving smoothly at a steady speed.
Types of clutch pedals
Most modern cars use a dry, single-plate, always-on clutch. Despite that this type of clutch pedal is the most practical one, there are still other types of clutch pedals you may want to know:
- There are two main types of clutches: dry and wet. The first one uses friction to engage and is not lubricated with oil while the second one, as its name suggests, is lubricated with oil. The wet type of clutches can mostly be found in motorcycles and bikes. If you want to learn more about this type of clutch pedal, check out this article here.
- Another classification criterion divides clutches by the number of flows into single-flow and double-flow. Single-flow clutches transmit the rotation of the engine to only one element. Single-flow clutches are present in most models of passenger cars.
On the other hand, a two-way clutch can be found in those cars with a robotic-type automatic gearbox There is no need to talk about noticeable differences. The only difference is that two-flow systems transfer two shaft rotations.
- If you take as a basis the number of driven discs in the clutch, then there will also be only two options – single-plate and multi-plate clutches.
- Clutches also differ based on the type of drive that is used to control the unit. Here you will find the mechanical, hydraulic, electric, and combined clutches. The main difference between them is which element acts as a "transmitter" of rotation from the engine to the gearbox. And of course, there is also a difference in terms of cables, cylinders, fluid, electric motors, etc.
The clutch disc is made of a special friction composite material. Thanks to heat-resistant components, such material can withstand temperatures up to several hundred degrees. The disc has spring plates and friction linings that are attached to it with rivets or glue.
As already mentioned, clutch pedals can be dry or wet, depending on the type of friction. In dry clutch pedals, air acts as a working medium, while the wet clutch pedals are lubricated with oil.
In passenger cars, a diaphragm-type pressure spring is usually used to move the driven disc away from the engine flywheel. It can be flat or tapered. In the central part, there are about twenty petals, on which the release bearing presses when the pedal is pressed.
In case you are facing some disability, this type of clutch might be helpful for you: If by now, you have realized that the issue you are facing is not the clutch, but you still want to reduce the vibrations then check out our other blog post to find out the best harmonic balancers for cars.
Clutch pedals in automatic transmission
Clutch in its classical sense consists of two dry discs interacting with each other after pressing the pedal. However, it is also used in "automatic vehicles" despite that it is a little bit different. That type of clutch depends on the type of automatic transmission.
How a clutch works is different for cars with a classic "automatic" and cars with a robotic system. In fact, clutch pedals in "automatic car" work with the help of special couplings, turbines, and oil pressure.
The clutch pedal is an integral part of every vehicle. Therefore, it is important to know what is it and how it works even if you are not that into cars but would like to learn to drive. It is important to know how the clutch pedal works because you never know when this knowledge might serve you to fix your car on the road.
However, if you are not that savvy with cars and you are not in an urgent situation, then perhaps it's best if you take your car to a car service and they will take care of it.