The main components of a clutch include: crankshaft, transmission input shaft, release bearing, flywheel, pressure plate, disc, support ring, drive belt and so on.
The clutch is located in the flywheel housing between the engine and the transmission, and the clutch assembly is fixed on the rear plane of the flywheel with screws, and the output shaft of the clutch is the input shaft of the transmission. In the process of automobile driving, the driver can according to the need to step on or release the clutch pedal, so that the engine and gearbox temporary separation and gradual engagement, in order to cut off or transfer the engine to the transmission input power. The clutch is a commonly used component in mechanical transmission, which can separate or engage the transmission system at any time. Its basic requirements are: smooth engagement, separation quickly and thoroughly; easy to adjust and repair; small external dimensions; small quality; good wear resistance and sufficient heat dissipation capacity; easy to operate and labor-saving, commonly used into the tooth embedded and friction type two categories.
Definition
Clutch, Hong Kong is commonly known as the polarized son, which is from the English Clutch, Taiwan is often used to leave the child or the Japanese クラッチ said, is the car or other power machinery engine power to switch to the axle of the device.
The clutch is installed between the engine and the transmission, and is an assembly that is directly connected to the engine in the automobile driveline. Usually the clutch is installed with the flywheel group of the engine crankshaft, and it is the component that cuts off and transmits power between the engine and the automobile driveline. Automobile from the start to normal driving throughout the process, the driver can according to the need to manipulate the clutch, so that the engine and the transmission system is temporarily separated or gradually engaged, in order to cut off or transfer the engine to the transmission system output power. Its role is to enable the engine and the transmission can be gradually engaged, thus ensuring a smooth start; temporarily cut off the link between the engine and the transmission, in order to shift gears and reduce the impact of shifting; when the car emergency braking can play a role in separating, to prevent overloading of the transmission and other drive systems, thus playing a certain role in the protection.
The clutch is similar to a switch, engagement or disengagement of power transmission, the clutch mechanism of its active part and the slave part can be temporarily separated, but also can be gradually engaged, and in the process of transmission, but also have the possibility of relative rotation. Rigid connection between the active and driven parts of the clutch is not possible. Any form of automobile has a clutch device, just different forms.
Classification
According to the analysis of "China Clutch Manufacturing Industry Production and Sales Demand and Investment Forecast Analysis Report Forward", clutches are divided into electromagnetic clutches, magnetic particle clutches, friction clutches and hydraulic clutches of four:
Electromagnetic clutches
Relying on the coil's on and off electric power to control the clutch's engagement and disengagement.
Electromagnetic clutches can be divided into: dry single electromagnetic clutch, dry multi-disc electromagnetic clutch, wet multi-disc electromagnetic clutch, magnetic particle clutch, rotary electromagnetic clutch and so on.
Electromagnetic clutch working mode can be divided into: energized combination and power-off combination.
Dry single-disc electromagnetic clutches: when the coil is energized, it generates magnetic force to absorb the "armature" plate, and the clutch is in the state of engagement; when the coil is de-energized, the "armature" pops back, and the clutch is in the state of disengagement.
Dry multi-disc, wet multi-disc electromagnetic clutches: the principle is the same as above, in addition to increase a few friction payment, the same volume of torque than the dry single-disc electromagnetic clutches, wet multi-disc electromagnetic clutches work must have oil or other coolant cooling.
Magnetic powder clutch
In the active and the slave placed between the magnetic powder is not energized when the powder is in a loose state, when energized, the magnetic powder is combined, the active and the slave rotate at the same time. Advantages: the torque can be adjusted by adjusting the current, allowing a large slip. Disadvantages: large temperature rise at large slip, relatively high price.
Differential electromagnetic clutch: clutch work, the master and slave part must exist a certain speed difference in order to have torque transfer. The size of the torque depends on the magnetic field strength and speed difference. The excitation current remains constant, the speed decreases dramatically with the increase of torque; the torque remains constant, the excitation current decreases, the speed decreases even more severely.
Differential electromagnetic clutch due to the master and slave parts without any mechanical connection, no wear and tear consumption, no magnetic powder leakage, no impact, adjusting the excitation current can change the rotational speed, as a stepless transmission, which is its advantage. The main disadvantage of this clutch is that the eddy current in the rotor generates heat, which is proportional to the speed difference. The efficiency at low speeds is very low, and the efficiency value is the ratio of the speeds of the master and slave shafts, i.e. η = n2/n1.
It is suitable for mechanical transmission systems with high-frequency action, and can be used to unite or disengage the slave part from the master part while the master part is in operation.
When the active part and the follower are in a separated state, the active part rotates and the follower is stationary; when the active part and the follower are in a jointed state, the active part brings the follower to rotate.
Widely used in machine tools, packaging, printing, textile, light industry, and office equipment.
Electromagnetic clutches are generally used in ambient temperature -20-50 ℃, humidity less than 85%, no explosion hazardous media, its coil voltage fluctuations do not exceed the rated voltage ± 5%.
Friction clutch
Friction clutch is the most widely used and the longest history of a clutch, it is basically by the active part, the slave part, the pressure mechanism and the manipulation mechanism of four parts. The master, slave part and pressure mechanism is to ensure that the clutch is in the state of engagement and can drive the power of the basic structure, and the clutch manipulation mechanism is mainly to make the clutch separation device. In the process of disengagement, depressing the clutch pedal first eliminates the free play of the clutch during the free stroke, and then generates the separation gap during the working stroke and the clutch disengages. In the process of engagement, gradually release the clutch pedal, the pressure plate moves forward under the action of the pressure spring, firstly eliminates the separation clearance, and acts on the pressure plate, the driven disc and the flywheel working surface with sufficient pressure force; after that, the release bearing moves backward under the action of the reset spring, generates the free play, and the clutch engages.
Fluid clutches
Fluid clutches use fluid (generally oil) as the transmission medium, compared with mechanical clutches, in addition to various changes in the transmission characteristics, but also mainly to absorb the vibration and shock generated by the rotation of the active and driven shafts.
The structure of the hydraulic clutch includes an input shaft with a speed-increasing gear train; a working fluid flow chamber consisting of an impeller, a driven wheel and an impeller housing; an output shaft with a driven wheel, and the driven wheel and the impeller can be operatively combined; generally the impeller housing and the impeller are composed of materials with small specific gravity and large stress tolerance range to reduce the centrifugal stress.
Principle
For manual gearboxes, the clutch is an important part of the car's powertrain, and it is responsible for cutting off and connecting power to the engine. In the city road or complex road driving, the clutch has become one of the most frequently used parts, and the use of the clutch is a direct reflection of the driving level of high and low, but also play a protective effect of the vehicle. How to use the clutch correctly, to master the principle of the clutch in order to use the clutch to solve the problem in special circumstances, is each driving manual gearbox models of the car friends should master.
The so-called clutch, as the name suggests, is the use of "away" and "together" to transfer the right amount of power. The clutch consists of a friction plate, a spring plate, a pressure plate, and a power output shaft. It is located between the engine and the transmission, and it is used to transfer the torque stored on the engine flywheel to the transmission to ensure that the vehicle transmits the right amount of driving force and torque to the drive wheels under different driving conditions, which is part of the category of powertrain. In semi-linkage, the power input end of the clutch and the power output end are allowed to have a speed difference, that is, the transmission of the right amount of power is realized through its speed difference.
The clutch is divided into three operating states, namely, non-linkage with the clutch depressed, full linkage without depressing the clutch, and semi-linkage with the clutch partially depressed. When the vehicle starts, the driver depresses the clutch, and the movement of the clutch pedal pulls the pressure plate backward, that is, the pressure plate is separated from the friction plate, and at this time, the pressure plate is not in contact with the flywheel at all, and there is no relative friction. When the vehicle in normal driving, the pressure plate is tightly squeezed in the flywheel friction plate, at this time the pressure plate and the friction plate between the friction is the largest, the input shaft and the output shaft to maintain a relative static friction, the two rotational speeds are the same. The last is the semi-linked state of the clutch, pressure plate and friction plate friction is less than the full linkage state. At this time, the clutch pressure plate and the friction plate on the flywheel is a state of sliding friction, the flywheel speed is greater than the speed of the output shaft, the power transmitted from the flywheel partially transferred to the gearbox. This state is equivalent to a soft connection between the engine and the drive wheel.
Generally speaking, the clutch plays a role in the vehicle start and shift, at this time there is a speed difference between the first and second axle of the gearbox, and the engine power must be cut off from the first axle, so that the synchronizer can keep the speed of the first axle synchronized with the second axle. After the gears are put in, the first shaft is combined with the engine power through the clutch, so that the power can continue to be transmitted. In the clutch, there is also an indispensable cushioning device. It consists of two discs similar to the flywheel to together, in the disc on the rectangular groove, in the groove arranged spring, in the case of intense impact, the spring between the two discs each other elastic effect, buffer external stimuli, effective protection of the engine and clutch.
Among the various accessories of the clutch, the strength of the pressure plate spring, the coefficient of friction of the friction plate, the diameter of the clutch, the position of the friction plate, and the number of clutches are the key factors that determine the performance of the clutch. The greater the stiffness of the spring, the higher the coefficient of friction of the friction plate, and the larger the diameter of the clutch, the better the clutch performance will be.
Typical clutch operating process
Diaphragm spring type clutch, its work can be divided into three processes: working, disengagement and engagement.
1, the working process. The use of diaphragm springs installed between the clutch cover and pressure plate, so that it produces pre-compression deformation of the pressure formed on the pressure plate to make the clutch master and slave part of the pressure, that is, the clutch is in a state of engagement. Engine power through the crankshaft and crankshaft as one of the flywheel, clutch cover and pressure plate to the slave disk, and then through the slave disk spline sleeve to the input shaft of the transmission. This process is characterized by the same torque and speed transmitted by the master and slave parts of the clutch, and there is no speed difference between the master and slave parts and no slippage.
2, separation process. The driver presses the clutch pedal, the pedal moves left, the push rod moves left, and the diaphragm spring separator plate is pushed left through the cylinder and the working cylinder. Affected by this diaphragm spring and fixed in the clutch cover support pins as a fulcrum so that the big end to the right, while the role of the separation plate by pulling the pressure plate to the right. Eventually reach the driven disc and flywheel, pressure plate between each gap, the clutch to realize the separation, so the clutch separation process is over.
The work of the clutch is characterized by the process of separation: after the separation of the engine power and movement can not be transmitted to the driven disc. The active part remains synchronized with the engine speed, while the driven part decreases rapidly.
3, engagement process. The driver releases the clutch pedal in the return spring under the action of the pedal back to its original position, while driving the push rod and release bearing back. That is, the engagement process maneuvering mechanism movement is the inverse process of the separation process. When the release bearing and the diaphragm spring separation plate between the gap and the diaphragm spring pressure plate on the driven plate, the engagement process is over, the clutch resumed the function of transmitting power.
Role
1. Ensure a smooth start
This is the primary function of the clutch. Before the car starts, it is natural to start the engine first. When the car starts, it accelerates gradually from a completely stationary state. If the driveline (which links the entire car) is rigidly linked to the engine, then the transmission is put into gear, the car will suddenly rush forward, but not start. This is because the car from a standstill to forward, has a large inertia, the engine caused by a large moment of resistance. Under the action of this moment of inertia, the engine speed in the instantaneous sharp drop to the lowest stabilized speed (generally 300-500RPM) below, the engine is off and can not work, of course, the car can not start.
Therefore, we need the help of the clutch. After the engine starts, before the car starts, the driver first presses the clutch pedal, separates the clutch, disengages the engine and the driveline, and then puts the transmission into gear, and then gradually releases the clutch pedal, so that the clutch gradually engages. In the process of engagement, the engine by the resistance torque gradually increased, it should be gradually step on the accelerator pedal at the same time, that is, gradually increase the amount of fuel supply to the engine, so that the engine speed is always maintained at the lowest stable speed, without stalling. At the same time, due to the clutch engagement degree of tightness gradually increased, the engine through the transmission system to drive the wheel torque will gradually increase to the traction is enough to overcome the resistance to start, the car that is from a standstill to start moving and gradually accelerate.
2. Smooth gearshift
In the process of automobile driving, in order to adapt to the changing driving conditions, the transmission system often need to change different gears to work. Realization of gear transmission shift, generally is toggle gear or other gear mechanism, so that the original gear of a gear pair out of the transmission, and then make another gear gear pair into the work. Before shifting gears must step on the clutch pedal, interrupt the power transmission, easy to make the original gear meshing vice disengagement, at the same time to make the new gear meshing vice meshing parts of the speed gradually tend to synchronize, so that into the meshing of the impact can be greatly reduced, so as to achieve a smooth gear change.
3. Prevent overloading of the driveline
When the car for emergency braking, if there is no clutch, the engine will be rigidly connected to the driveline and dramatically reduce the speed of rotation, and therefore all the moving parts of which will produce a large moment of inertia (the value of which may be greatly exceeded by the maximum torque of the engine when working normally), the driveline caused by more than the bearing capacity of the load, and make the Damage to the machine parts. With a clutch, this danger can be eliminated by the relative motion that may be generated between the active and driven parts of the clutch. Therefore, clutches are needed to limit the maximum torque to which the driveline can be subjected and thus ensure safety.