Clutch is an integral part of any modern car. It is this node that takes on all the colossal loads and bumps. Devices on vehicles with a manual gearbox experience a particularly high voltage . As you already understood, in today's article we will consider the principle of operation of the clutch, its design and purpose.
Item Feature
The clutch is a power clutch that transmits torque between the two main components of the car: the engine and gearbox. It consists of several disks. Depending on the type of force transfer, these couplings can be hydraulic, friction or electromagnetic.
Appointment
The automatic clutch is designed to temporarily disconnect the transmission from the engine and smoothly grind them. The need for it arises as the movement begins. Temporary separation of the motor and gearbox is necessary during subsequent switching speeds, as well as during sudden braking and vehicle stopping.
While the machine is moving, the clutch system is mostly on. At this time, it transfers power from the engine to the gearbox, and also protects gearboxes from various dynamic loads. Those that arise in the transmission. Thus, the load on it increases as the engine brakes, with a sharp engagement of the clutch, a decrease in the speed of the crankshaft or when the vehicle collides with bumps in the road (pits, bumps, and so on).
Classification of the connection of the leading and driven parts
Grip is classified according to several criteria. According to the connection of the leading and driven parts, it is customary to distinguish the following types of devices:
- Frictional.
- Hydraulic.
- Electromagnetic
By type of creation of push forces
On this basis, the clutch types are distinguished:
- With a central spring.
- Centrifugal.
- With peripheral springs.
- Semi-centrifugal.
By the number of driven shafts of the system are single, double and multi-disk.
By type of drive
All of the above types of clutches (with the exception of centrifugal ones) are closed, that is, constantly turned off or on by the driver when switching speeds, stopping and braking the vehicle.
At the moment, friction type systems have gained great popularity. Such nodes are used both on cars and on trucks, as well as on buses of small, medium and large class.
2-disk clutches are used only on large-capacity tractors. They are also installed on high-capacity buses. Multi-disk is practically not used by automakers at the moment. Previously, they were used on heavy trucks. It is also worth noting that fluid couplings as a separate unit on modern machines will not be used. Until recently, they were used in car boxes, but only in conjunction with a friction element installed in series.
As for electromagnetic clutches, they are currently not widely used in the world. This is due to the complexity of their design and costly maintenance.
The principle of operation of the clutch with a mechanical drive
It is worth noting that this unit has the same principle of operation, regardless of the number of driven shafts and the type of pressure generation. An exception is the type of drive. Recall that it happens mechanical and hydraulic. And now we will consider the principle of operation of a clutch with a mechanical drive.
How does this node work? In working condition, when the clutch pedal is not affected, the driven disc is sandwiched between the pressure and the flywheel. At this time, the transmission of torque to the shaft is due to friction. When the driver presses the foot on the pedal, the clutch cable moves in the basket. Next, the lever rotates relative to its mounting location. After that, the free end of the fork begins to press on the release bearing. The last, moving to the flywheel, is to press on the plates that move the pressure plate. At the moment, the driven element is released from pressing forces and thus the clutch is disconnected.
Next, the driver freely makes a gear shift and begins to gradually release the clutch pedal. After that, the system again engages the driven disk with the flywheel. As the pedal is released, the clutch engages and the shafts are ground. After a while (a couple of seconds), the unit fully begins to transmit torque to the engine.
The latter drives the wheels through the flywheel. It is worth noting that the clutch cable is present only on nodes with a mechanical drive. The nuances of the design of another system will be described in the next section.
The principle of operation of the hydraulic clutch
Here, unlike the first case, the force from the pedal to the mechanism is transmitted through the fluid. The latter is contained in special pipelines and cylinders. A device of this type of clutch is somewhat different from a mechanical one. At the splined end of the drive shaft of the transmission and the steel casing fixed to the flywheel, 1 driven disk is installed.
Inside the casing there is a spring with a radial lobe. It serves as a release lever. The control pedal is then suspended on the axis of the body bracket. A pusher of the main cylinder is also attached to it on a swivel joint. After the node is turned off and the gear changes, a spring with radial petals returns the pedal to its original position. By the way, the clutch diagram is shown in the photo on the right.
But that's not all. In the design of the node there is both a main and a clutch slave cylinder. Both elements are very similar in design. Both consist of a housing, inside of which there is a piston and a special pusher. As soon as the driver depresses the pedal, the clutch master cylinder is activated . Here, with the help of a pusher, the piston moves forward, so that the pressure inside increases. Its subsequent movement leads to the fact that the liquid penetrates into the working cylinder through the discharge channel. So, thanks to the impact of the pusher on the plug, the unit is turned off. At that time, when the driver starts to release the pedal, the working fluid flows back. This action engages the clutch. This process can be described as follows. First, a check valve opens, which compresses the spring. Next is the return of fluid from the working cylinder to the main. As soon as the pressure in it becomes less than the force of pressing the spring, the valve closes, and excess fluid pressure forms in the system. This is the leveling of all the gaps that are in a certain part of the system.
What is the difference between the two drives?
The main advantage of systems with a mechanical drive is the simplicity of design and low maintenance. However, unlike their counterparts, they have a lower efficiency.
Hydraulic clutch (photo of it is presented below), due to its high performance, provides smoother turning on and off nodes.
However, this type of nodes is much more complicated in design, because of which they are less reliable in operation, more whimsical and costly to maintain.
Clutch requirement
One of the main indicators of this unit is its high ability to transmit torque forces. To assess this factor, a concept such as “the value of the coefficient of safety of adhesion” is used.
But, in addition to the main indicators that relate to each node of the machine, a number of other requirements are presented to this system, among which it should be noted:
- Smooth on. When operating a car, this parameter is provided by qualified control of the elements. However, some structural details are designed to increase the degree of smooth engagement of the clutch assembly, even with minimal driver qualifications.
- "Clean" shutdown. This parameter implies a complete shutdown, in which the torque forces on the output shaft correspond to a value close to zero or close to it.
- Reliable power transmission from the transmission to the engine under any operating and operating conditions. Sometimes with an underestimated value of the safety factor, the clutch begins to slip. Which leads to increased heating and wear of the parts of the mechanism. The higher the coefficient, the greater the mass and size of the node. Most often, this value is about 1.4-1.6 for cars and 1.6-2 for trucks and buses.
- Convenience of management. This requirement is generalized to all vehicle controls and is specified in the form of a characteristic of the pedal stroke and the degree of effort required to completely disengage the clutch. At present, Russia has a limit of 150 and 250 N for cars with and without power amplifiers, respectively. The pedal itself often does not exceed the mark of 16 centimeters.
Conclusion
So, we examined the device and the principle of operation of the clutch. As you can see, this node is of great importance for the car. The operability of the entire vehicle depends on its performance. Therefore, you should not tear the clutch, abruptly removing the foot from the pedal when moving. In order to preserve the details of the unit as much as possible, it is necessary to smoothly release the pedal and not practice prolonged shutdowns of the system. So you provide a long and reliable operation of all its elements.