CN112576640B

CN112576640B - Clutch and method for searching clutch half-joint point

Info

Publication number: CN112576640B
Application number: CN201910939961.1A
Authority: CN
Inventors: 王泽伦; 张新桂; 余子林; 凌晓明; 周友; 刘维
Original assignee: Guangzhou Automobile Group Co Ltd
Current assignee: Guangzhou Automobile Group Co Ltd
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2023-02-24
Anticipated expiration: 2039-09-29
Also published as: CN112576640A

Abstract

The invention relates to the technical field of automobile clutch control, and discloses a clutch and a method for searching a clutch half-joint point, wherein the clutch comprises an outer hub, a main hub, a friction plate set, a piston and a balance piston; and a return spring group is arranged between the balance piston and the piston, and an elastic piece is arranged on a path of the piston for pushing the friction plate group to move axially. The method of finding a clutch half-engagement point comprises the steps of: filling oil into the pressure cavity; detecting and recording the pressure of the pressure cavity and the displacement of the piston in real time; drawing to form a spring stiffness curve; and reading a pressure point corresponding to a break point formed by the change of the spring stiffness, and judging that the pressure point is a half joint point. The semi-joint point searching method has the advantages that the semi-joint point searching is more accurate and visual, the control precision of the clutch is improved, the gear shifting smoothness is improved, meanwhile, the difficulty of KP point searching can be reduced, the testing efficiency is improved, and therefore the cost is reduced.

Description

Clutch and method for searching clutch half-joint point

Technical Field

The invention relates to the technical field of automobile clutch control, in particular to a clutch and a method for searching a clutch half-joint point.

Background

AT present, the automatic transmission has a wide application range, wherein the proportion of a hydraulic electric control Automatic Transmission (AT) and a double-clutch automatic transmission (DCT) is large. The control accuracy of the wet clutch, which is an important actuating mechanism for the gear shifting operation, directly influences the quality of the gear shifting process, and has the influence on improving the efficiency and reducing the oil consumption. The wet clutch generally comprises a friction plate set, a piston for pushing and pressing the friction plate set, a return spring and other parts, and continuous gear shifting operation without power interruption can be realized by accurately controlling the pressure of the wet clutch. Accurate control of the wet clutch relies on accurate identification of the half-joint point (KP point for short). The half-joint point is actually a pressure point at which the theoretical torque transmission capacity is 0 when the piston of the clutch is just in contact with the friction plate set under the action of oil pressure and a return spring.

Due to the difficulty of finding the half-engagement point, the prior art often relates the torque transfer capacity of the clutch to the pressure, artificially defining the pressure for a low torque transfer condition as the half-engagement point. At present, the following two methods are mainly adopted to search for half-junction points:

1. the method comprises the following steps of measuring a pressure point corresponding to the transmission of corresponding torque of the wet clutch, considering the KP point, and specifically: 1) Determining the self-dragging torque of the wet clutch under a specific working condition, namely, keeping the rotating speed of the input end of the clutch constant at 1000rpm, keeping the output end of the clutch fixed, setting the cooling flow of 1Lpm, and reading the self-dragging torque of the clutch through a torque sensor; 2) And on the basis of the measured dragging torque, artificially adding a certain numerical value of torque, and considering that the pressure corresponding to the clutch in the state of transmitting the corresponding torque is KP point pressure. If the drag torque of the wet clutch is measured to be 5nm, the pressure corresponding to the clutch in the state of transmitting 10nm torque is considered to be the KP point pressure. This approach ignores the tendency for drag torque to increase progressively as piston stroke becomes smaller. On the other hand, since the clutch output torque is not constant, there is a certain torque fluctuation, and there is a difference in how to determine that the determination value is reached.

2. Calculating a half joint point through a pressure curve and a torque curve, and specifically comprising the following steps: 1) And measuring a torque pressure curve of the wet clutch by adjusting the pressure. If the rotating speed of the input end of the constant clutch is 1000rpm, the output end of the constant clutch is fixed, and the cooling flow of 1Lpm is given, the oil pressure is controlled to be increased from 0 to the maximum pressure which can be borne by the clutch. Drawing a pressure-torque curve of the process; 2) And processing the curve, for example, selecting a curve of 50% to 75% of the pressure (as shown in fig. 1), and making a reverse extension line according to the slope to intersect with the pressure coordinate axis at a point, wherein the point is regarded as a KP point. This method attempts to remove the effect of drag torque through analysis of the torque-pressure curve, but it is too theoretical and ignores the non-linear stiffness variation trend of the compression element during the elastic deformation phase.

The existing scheme depends on measuring the correlation between the transmission torque and the pressure of the wet clutch, and the influence of the dragging torque cannot be removed. However, the drag torque of the wet clutch changes along with the external environment, and if the cooling flow is larger, the drag torque is larger; the smaller the piston stroke. The greater the drag torque, etc. And considering that the tolerance accumulation of the individual clutch can affect the magnitude of the dragging torque, the selection precision of the KP point is limited.

Therefore, how to simplify the search for the half-joint point and improve the accuracy thereof is an important technical problem that needs to be solved by those skilled in the art at present.

Disclosure of Invention

The invention aims to provide a clutch and a method for searching a clutch half-joint point, which can enable the half-joint point to be searched more accurately and visually, are beneficial to improving the control precision of the clutch and the gear shifting smoothness, and can reduce the difficulty of searching a KP point and improve the test efficiency so as to reduce the cost.

In order to achieve the above object, in one aspect of the present invention, a clutch is provided, which includes an outer hub, a main hub, a friction plate set connected in the outer hub, a piston axially slidably connected to the main hub to press or release the friction plate set, and a balance piston connected to the main hub, wherein the balance piston, the main hub and the piston define a balance cavity, and a pressure cavity is formed between the piston and the main hub;

and a return spring group for abutting and compressing the piston when the piston moves towards the friction plate group in the axial direction is arranged between the balance piston and the piston, and an elastic piece is arranged on a path for pushing the friction plate group to move in the axial direction by the piston.

Preferably, the elastic element is connected to the outer hub and is arranged on one side of the friction plate group close to the piston.

Preferably, the elastic member is connected to a side of the piston facing the friction plate set.

Preferably, the friction plate set includes disc-shaped friction plates and steel plates arranged at intervals in sequence, and the elastic member is arranged between the friction plates and the steel plates.

Preferably, one side of the friction plate group, which is far away from the piston, is provided with a first clamp spring for axial limiting, and the elastic part is arranged between the first clamp spring and the friction plate group.

Preferably, the return spring set is precompressed between the balance piston and the piston; the elastic part adopts a corrugated spring arranged in the radial direction.

Preferably, the clutch further includes displacement detecting means for detecting axial displacement of the piston, and pressure detecting means for detecting an oil pressure of the pressure chamber.

As a preferred scheme, the displacement detection device adopts a displacement sensor, and the pressure detection device adopts a pressure sensor; the main hub is provided with a first oil duct communicated with the pressure cavity and a second oil duct communicated with the balance cavity; the displacement sensor is connected to the piston, and the pressure sensor is arranged in the first oil duct.

In another aspect of the present invention, there is also provided a method of finding a clutch half-engagement point, comprising the steps of:

filling oil into the pressure cavity;

detecting and recording the pressure of the pressure cavity and the displacement of the piston in real time;

drawing a curve of displacement along with pressure change according to the records of oil pressure and displacement to form a spring stiffness curve;

and reading a pressure point corresponding to a break point formed by the change of the spring stiffness, and judging that the pressure point is a half joint point.

In a further aspect of the present invention, there is provided a method of finding a clutch half-engagement point, comprising the steps of:

judging whether the conditions for entering the self-learning of the half-joint point are met: obtaining the idle time of the vehicle, and comparing the idle time with the preset time t 1;

if the idling time is greater than the preset time t1, entering self-learning of the half-joint point;

if the idling time is less than or equal to the preset time t1, the condition for entering the self-learning of the half joint point is not met, and the step of judging whether the condition for entering the self-learning of the half joint point is met is returned;

the semi-joint self-learning comprises the following steps:

filling oil into the pressure cavity;

reading a pressure point corresponding to a break point formed by the change of the spring stiffness, and judging that the pressure point is a half joint point;

and recording the information of the determined half joint to the vehicle CPU in real time, and simultaneously covering the recording of the last half joint in the vehicle CPU.

Compared with the prior art, the invention has the beneficial effects that:

the clutch comprises an outer hub, a main hub, a friction plate group connected in the outer hub, a piston which can be axially and slidably connected to the main hub to press or loosen the friction plate group, and a balance piston connected to the main hub, wherein a pressure cavity is formed between the piston and the main hub, a return spring group for abutting and compressing the piston when the piston moves axially towards the friction plate group is arranged between the balance piston and the piston, an elastic element is arranged on a path for the piston to push the friction plate group to move axially, after hydraulic oil is supplied to the pressure cavity, the piston overcomes the elastic force of the return spring to move axially towards the direction close to the friction plate group under the action of the oil pressure, in the process, the axial displacement of the piston and the size of the oil pressure in the pressure cavity are respectively detected, a curve of the piston displacement along with the change of the oil pressure cavity is drawn according to the detection result to form a spring stiffness curve, when the piston continues to move axially and the piston is in contact with the friction plate group (directly or indirectly contacts the elastic element through the elastic element), the elastic element on the path for pushing the friction plate group to be extruded, the elastic element to start to generate reverse acting force which is superposed with the stiffness of the spring, and simultaneously hinder the axial movement of the piston, so as to act on the slope of the piston, and the slope of the spring, thus the piston, the spring, the point, namely, the point of the broken point, and the broken point can be immediately occur. For the detection of the axial displacement of the piston and the detection of the oil pressure in the pressure cavity, in the off-line test, a tester can respectively detect the axial displacement and the oil pressure by adopting a displacement detection tool and a pressure detection tool; during the on-line test, the detection can be realized through the arrangement of the displacement sensor and the pressure sensor respectively. The clutch is simple in structure, the wet clutch body is optimized, the method for searching the KP points of the clutch is simple and easy to implement, the KP points can be found more visually and accurately only by providing oil pressure for the clutch, the influence of interference factors on the KP point searching is eliminated, the control precision of the wet clutch is improved, the gear shifting smoothness is improved, the efficiency is improved, the oil consumption is reduced, the test efficiency is improved, and the cost is reduced.

Drawings

FIG. 1 is a schematic diagram of a prior art half-joint calculated from pressure and torque curves;

FIG. 2 is a schematic structural diagram of a clutch according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a clutch according to a second embodiment of the present invention;

FIG. 4 is a schematic diagram of a method of finding a half-engagement point of a clutch in accordance with one embodiment of the present invention;

FIG. 5 is a schematic diagram of a pressure and displacement curve calculation half joint provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of a method of finding a half-engagement point of a clutch according to a second embodiment of the present invention.

Wherein, 10, outer hub; 11. a first clamp spring; 20. a main hub; 21. a second clamp spring; 22. a first oil passage; 23. a second oil passage; 30. a friction plate set; 31. a friction plate; 32. a steel sheet; 40. a piston; 41. a pressure chamber; 42. a balancing chamber; 43. a first seal ring; 44. a second seal ring; 50. a balance piston; 60. a displacement detection device; 70. a pressure detection device; 80. a return spring set; 90. an elastic member.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The first embodiment is as follows:

referring to fig. 2, a clutch of the present invention is schematically shown, which includes an outer hub 10, a main hub 20, a friction plate set 30, a piston 40, and a balance piston 50. The friction plate set 30 is connected in the outer hub 10, the piston 40 is axially slidably connected to the main hub 20 to compress or loosen the friction plate set 30, the balance piston 50 is connected to the main hub 20, a first seal ring 43 and a second seal ring 44 are arranged between the piston 40 and the main hub 20, so that the piston 40 and the main hub 20 are in interference seal, a pressure chamber 41 is formed between the piston 40 and the main hub 20, a balance chamber 42 is enclosed by the balance piston 50, the main hub 20 and the piston 40, a return spring set 80 is arranged between the balance piston 50 and the piston 40, and the piston 40 can be abutted and compressed when moving axially towards the friction plate set 30, so that the return spring set 80 can be compressed. It is important to provide the elastic member 90 on the path of the piston 40 pushing the friction plate set 30 to move axially, so that the elastic member 90 is directly or indirectly pressed during the axial movement of the piston 40, and the elastic member 90 generates a force resisting the axial movement of the piston 40 towards the friction plate set 30.

Specifically, in this embodiment, the balance piston 50 is made of a steel material, and rubber is attached to the joint of the balance piston 50 and the piston 40 by a vulcanization process, so as to achieve interference fit as a sealing function. Balance piston 50 be provided with second jump ring 21 between balance piston 50 and the main hub 20, balance piston 50 realizes axial positioning through second jump ring 21, and balance piston 50 passes through second jump ring 21 and main hub 20 interference fit, as sealed effect. It will be appreciated that the second circlip 21, the first sealing ring 43 and the second sealing ring 44 may also be replaced by rubber vulcanization on the surface of the balance piston 50 or the piston 40, if desired.

To achieve the same object, referring to fig. 4, the present invention also provides a method for finding a clutch half-engagement point, comprising the steps of:

s1, filling oil into the pressure cavity 41;

s2, detecting and recording the pressure of the pressure cavity 41 and the displacement of the piston 40 in real time;

s3, drawing a curve of displacement changing along with pressure according to the records of oil pressure and displacement to form a spring stiffness curve;

and S4, reading a pressure point corresponding to a break point formed by the change of the spring stiffness, and judging that the pressure point is a half joint point.

Based on the clutch and the method for searching the clutch half joint point with the above technical characteristics, in step S1, hydraulic oil is supplied to the pressure chamber 41 to continuously increase the oil pressure, in step S2, the piston 40 gradually overcomes the elastic force of the return spring to axially move towards the friction plate set 30 under the action of the oil pressure, and meanwhile, the tester uses a tool with displacement detection function and a tool with oil pressure detection function to respectively detect the axial displacement of the piston 40 and the oil pressure in the pressure chamber 41 in real time and record the axial displacement and the oil pressure. In step S3, the displacement of the piston 40 is plotted against the oil pressure of the pressure chamber 41 based on the detected oil pressure and the displacement data record to form a spring rate curve (as shown in fig. 5). When the piston 40 continues to move axially and the piston 40 just starts to contact with the friction plate set 30 (directly or indirectly through the elastic member 90), the elastic member 90 located on the path where the piston 40 pushes the friction plate set 30 to move axially is squeezed, the elastic member 90 starts to generate a reverse acting force, which is superimposed on the stiffness of the return spring, and simultaneously forms a barrier to the axial movement of the piston 40, so that the slope of the spring stiffness curve acting on the piston 40 changes immediately, thereby generating a break point, in step S4, the pressure point corresponding to the break point is read, and the pressure point can be determined as the KP point. The clutch is simple in structure, the wet clutch body is optimized, the method for searching the KP point of the clutch is simple and easy to implement, the KP point can be found more visually and accurately only by providing oil pressure for the clutch, and the influence (such as drag torque) of interference factors on the KP point searching is eliminated, so that the control precision of the wet clutch is improved, the gear shifting smoothness is improved, the efficiency is improved, the oil consumption is reduced, the test efficiency is improved, and the cost is reduced.

The clutch and the method for finding the clutch half-engagement point of the embodiment are suitable for finding the clutch half-engagement point before the vehicle is used (such as during a clutch assembly offline testing process, or a transmission assembling process, or a transmission offline process). The KP point determined in step S4 may be recorded in the CPU of the vehicle equipped with the clutch by a manual entry method, and after the vehicle is put into use, the CPU of the vehicle controls the clutch based on the KP point information.

For example, as shown in fig. 2, in a specific embodiment in which the elastic member 90 is connected to the outer hub 10 and is disposed on a side of the friction plate set 30 close to the piston 40, when the piston 40 continues to move axially and the piston 40 just starts to contact the friction plate set 30, the piston 40 starts to contact the elastic member 90, and at this time, the elastic resultant force acting on the piston 40 is a reaction force generated when the elastic member 90 and the stiffness of the return spring are superimposed, so that the spring stiffness curve acting on the piston 40 is bent, and the pressure point corresponding to the bent point is determined as the KP point. In the present embodiment, the elastic member 90 is connected to the outer hub 10 by a spline.

For example, the elastic element 90 is connected to a side of the piston 40 facing the friction plate set 30, and when the piston 40 drives the elastic element 90 to continuously move axially towards the friction plate set 30, the elastic element 90 on the piston 40 first contacts the friction plate set 30, and the elastic element 90 contacts the friction plate set 30 to generate elastic deformation, so that a break point appears on a spring stiffness curve.

Illustratively, the friction plate set 30 includes a disk-shaped friction plate 31 and a steel plate 32 which are sequentially arranged at intervals, the elastic member 90 is arranged between the friction plate 31 and the steel plate 32, when the piston 40 axially moves to contact the friction plate set 30, thrust is generated on the friction plate set 30, and under the thrust, the friction plate 31 and the steel plate 32 press the elastic member 90, so that the elastic member 90 elastically deforms, and thus a spring stiffness curve is broken. Similarly, one side of the friction plate group 30, which is away from the piston 40, is provided with a first snap spring 11 for axial limiting, and the elastic member 90 may also be arranged between the first snap spring 11 and the friction plate group 30, when the piston 40 axially moves to contact the friction plate group 30, the thrust force applied to the friction plate group 30 is conducted forward, so that the elastic member 90 is squeezed by the friction plate group 30 and the first snap spring 11 and elastically deforms, thereby causing a break point to appear on the spring stiffness curve. Therefore, in the process that the piston 40 presses the friction plate set 30, only by arranging one elastic member 90 (one elastic member is arranged on the basis of the return spring set 80) on the moving path of the piston 40 or the friction plate set 30, when the piston 40 just contacts (directly contacts or indirectly contacts) the friction plate set 30, the spring stiffness curve acting on the piston 40 changes, so that the pressure point corresponding to the break point can be quickly found, and the KP point is determined.

Specifically, the return spring set 80 is pre-compressed and disposed between the balance piston 50 and the piston 40, the return spring set 80 is an element formed by a plurality of small coil springs distributed circumferentially around an axis, when hydraulic oil is filled into the pressure chamber 41, the oil pressure can push the piston 40 to generate a tendency of moving axially toward the friction plate set 30, because the return spring is pre-compressed and disposed between the balance piston 50 and the piston 40, when the oil pressure is small, the displacement of the piston 40 is 0, and when the pressure of the hydraulic oil is increased to be greater than the pre-tightening force of the return spring, the piston 40 can be pushed to start moving axially, and the return spring is further compressed. When the clutch needs to be disengaged, the oil pressure in the pressure chamber 41 is reduced, so that the elastic force provided by the return spring is greater than the pressure of the hydraulic oil, and the piston 40 axially moves in the direction away from the friction plate set 30 under the action of the elastic force of the return spring, so that the piston 40 is disengaged from the friction plate set 30. The elastic member 90 is a corrugated spring arranged in a radial direction, the surface of the corrugated spring has corrugations and has certain rigidity, and when the piston 40 moves to just contact with the friction plate set 30 in the axial direction, the corrugated spring arranged in the radial direction is extruded to generate elastic deformation, so that an elastic force opposite to the moving direction of the piston 40 is generated, and a broken point is generated on a curve of the displacement of the piston 40 along with the pressure change of the pressure chamber 41.

Example two:

referring to fig. 3, another clutch of the present invention is schematically shown, and the clutch of the present embodiment is different from the first embodiment in that: the clutch in the present embodiment further includes displacement detecting means 60 for detecting axial displacement of the piston, and pressure detecting means 70 for detecting the oil pressure of the pressure chamber.

Referring to fig. 6, another method for finding a clutch half-engagement point according to the present invention is schematically shown, which is applied to the clutch in the second embodiment, and is different from the method for finding a clutch half-engagement point in the first embodiment, and the method for finding a clutch half-engagement point in the first embodiment may also be applied to a vehicle, and before the step S1, the method further includes the step S0: judging whether the self-learning condition of the half joint is met: and acquiring the idle time of the vehicle, and comparing the idle time with the preset time t 1.

if the idle time is less than or equal to the preset time t1, the condition of entering the self-learning of the half-joint point is not met, and the step S0 is returned to be continuously executed;

the semi-joint self-learning comprises the following steps:

step S1; step S2; step S3; step S4; and

and S5, recording the information of the judged half joint to the vehicle CPU in real time, and covering the last recording of the half joint in the vehicle CPU.

That is, after the condition for entering the half joint point self-learning is satisfied, the execution of step S1 is started, and steps S2, S3, S4, and S5 are sequentially executed.

Specifically, the KP self-learning method comprises the following steps: steps S1, S2 are performed in sequence, and in step S2, the pressure of the pressure chamber 41 and the displacement of the piston 40 are detected in real time using the displacement detecting means 60 and the pressure detecting means 70 of the clutch, respectively, and the detected data are transmitted to the vehicle CPU; continuing to execute the step S3, drawing a curve of displacement changing along with the pressure by the vehicle CPU according to the oil pressure and displacement data recorded in real time to form a spring stiffness curve; and then, executing the steps S4 and S5, recording new KP point information by the vehicle CPU, covering the original KP point and finishing the KP point self-learning process. In the subsequent use of the automobile, the pressure detecting device 70 transmits the oil pressure information of the pressure chamber 41 to the vehicle CPU, and when the oil pressure of the pressure chamber 41 recognized by the vehicle CPU is equal to the pressure value corresponding to the KP point recorded by the vehicle CPU, the vehicle CPU determines that the clutch is in the semi-engaged state.

The clutch and the method of finding a clutch half-engagement point in the present embodiment are different from the clutch and the method of finding a clutch half-engagement point in the first embodiment, and the greatest difference is that the clutch and the method of finding a clutch half-engagement point in the first embodiment are suitable for finding a half-engagement point before use of the vehicle (during a offline test), while the clutch in the second embodiment has the displacement detecting means 60 and the pressure detecting means 70, and the method of finding a clutch half-engagement point in the present embodiment is also suitable for finding a half-engagement point in use of the vehicle. In the embodiment, the driving intention is judged by comparing the idle time with the preset time t1, and if the idle time is greater than the preset time t1, the KP point self-learning is started; if the idle time is less than or equal to the preset time t1, the condition for entering the self-learning of the half joint point is not met, and the initial stage of the step S0 is returned. Through KP point self-learning, the vehicle CPU records the latest measured KP point information, and in the subsequent driving process, the vehicle CPU takes the KP point information recorded at the latest time as the basis for judging KP points, so that the KP point information recorded by the vehicle CPU is continuously updated and always best accords with the actual condition of the current vehicle. Because the clutch is provided with the displacement detection device 60 and the pressure detection device 70, KP point self-learning can be conveniently carried out at any time, so that the accuracy of KP points when a vehicle is used every time is kept, and the problem that the KP point judgment is not accurate due to the fact that a vehicle CPU still takes the KP point measured before the clutch is off the line or in the assembly process of a gearbox as a judgment basis after the KP points are changed due to the change of IP (protection level) characteristics of an electromagnetic valve, the abrasion of the clutch and other factors is avoided.

The value of t1 can be set as required, so that KP point self-learning is completed once in the process of each driving cycle.

Further, the displacement detecting device 60 employs a displacement sensor, which may be a contact sensor or a non-contact sensor. In this embodiment, the displacement sensor is connected to the piston 40 for detecting the length of the axial displacement of the piston 40. The pressure detection device 70 is a pressure sensor, the main hub 20 is provided with a first oil passage 22 and a second oil passage 23, the first oil passage 22 is communicated with the pressure chamber 41, the second oil passage 23 is communicated with the balance chamber 42, the pressure sensor is arranged in the first oil passage 22, and the oil pressure of the first oil passage 22 is the same as the oil pressure of the pressure chamber 41, so that the oil pressure detected by the pressure sensor is the oil pressure of the pressure chamber 41.

It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as being fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In summary, the clutch of the present invention includes an outer hub, a main hub, a friction plate set, a piston, and a balance piston, and an elastic member is disposed on a path along which the piston pushes the friction plate set to move axially. A method for searching the semi-joint point of clutch features that the oil is slowly filled in pressure cavity, the axial displacement of piston and the oil pressure in pressure cavity are respectively detected, and the stiffness curve of spring is formed by drawing. The clutch is simple in structure, the wet clutch body is optimized, the method for searching the KP of the clutch is simple and easy to implement, the KP is found more visually and accurately, and the influence (such as drag torque) of interference factors on the KP searching is eliminated, so that the control precision of the wet clutch is improved, the gear shifting smoothness is improved, the efficiency is improved, the oil consumption is reduced, the test efficiency is improved, and the cost is reduced. In addition, by adding the displacement detection device and the pressure detection device in the clutch and adding the KP point self-learning method in the method for searching the half joint point of the clutch, KP point information can be measured and recorded again in an automobile used each time, the accuracy of the KP point is effectively ensured, the problem that the vehicle CPU judges the KP point inaccurately due to the factors such as the change of the IP characteristic of the electromagnetic valve, the abrasion of the clutch and the like is avoided, and the method has high application and popularization values.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A clutch is characterized by comprising an outer hub, a main hub, a friction plate group connected in the outer hub, a piston axially and slidably connected to the main hub to press or release the friction plate group, and a balance piston connected to the main hub, wherein the balance piston, the main hub and the piston define a balance cavity, and a pressure cavity is formed between the piston and the main hub;

a return spring group for abutting and compressing the piston when the piston moves axially towards the friction plate group is arranged between the balance piston and the piston, and an elastic piece is arranged on a path for pushing the friction plate group to move axially by the piston;

a first clamp spring for axial limiting is arranged on one side, away from the piston, of the friction plate set, and the elastic part is arranged between the first clamp spring and the friction plate set;

the clutch further comprises displacement detection means for detecting axial displacement of the piston, and pressure detection means for detecting oil pressure of the pressure chamber;

drawing a curve of piston displacement along with the change of the oil pressure of the pressure cavity according to the detection result of the displacement detection device and the detection result of the pressure detection device so as to form a spring stiffness curve of the movement of the piston;

when the piston moves along the axial direction and just starts to contact with the friction plate set, the elastic piece starts to be extruded and generates reverse acting force on the piston, so that the spring stiffness curve has a break point, and a KP point is determined according to the pressure of the break point.

2. The clutch of claim 1, wherein the resilient member is connected to the outer hub and is disposed on a side of the set of friction plates adjacent the piston.

3. A clutch according to claim 1, characterized in that the elastic element is connected to the side of the piston facing the set of friction plates.

4. The clutch according to claim 1, wherein the set of friction plates includes disc-shaped friction plates and steel plates arranged at intervals in sequence, and the elastic member is disposed between the friction plates and the steel plates.

5. The clutch according to any one of claims 1 to 4, wherein the return spring set is provided precompressed between the balance piston and the piston; the elastic part adopts a corrugated spring arranged in the radial direction.

6. The clutch according to claim 1, wherein the displacement detecting means employs a displacement sensor, the pressure detecting means employs a pressure sensor,

the main hub is provided with a first oil duct communicated with the pressure cavity and a second oil duct communicated with the balance cavity; the displacement sensor is connected to the piston, and the pressure sensor is arranged in the first oil duct.

7. A method for finding a clutch half-engagement point, characterised by being implemented with a clutch according to any one of claims 1-6, comprising the steps of:

filling oil into the pressure cavity;

8. A method of finding a clutch half-engagement point, comprising the steps of:

judging whether the self-learning condition of the half joint is met: obtaining the idle time of the vehicle, and comparing the idle time with the preset time t 1;

the semi-joint self-learning comprises the following steps:

filling oil into the pressure cavity;