A method for obtaining the clutch pressure characteristic curve

Abstract

The present invention provides a method for obtaining the clutch pressure characteristic curve. The constitutive relationship of the friction plate assembly material is constructed based on the pressure characteristic curve of the friction plate assembly obtained through tests, and then the constitutive relationship of the friction plate assembly material is applied to the finite element simulation of the clutch system by using the finite element analysis method. Finally, the clutch pressure characteristic curve is obtained through simulation. The present invention combines experimental technical means with simulation technical means, only needs to conduct the pressure characteristic curve test of the friction plate assembly with a relatively short test period, and applies the constructed constitutive relationship of the friction plate assembly material to the finite element simulation of the clutch system, so as to quickly simulate and obtain a high-precision clutch pressure characteristic curve.

Description

Technical Field

[0001] The present invention belongs to the technical field of clutch characteristic curve calculation, and particularly relates to a method for obtaining the clutch pressure characteristic curve. Background Art

[0002] The main function of the clutch pressure characteristic curve is to control the worm angle according to the clutch pressure characteristic curve during the shifting process to control the engagement pressure of the clutch, so as to achieve precise control of shifting. The accuracy of the clutch pressure characteristic curve will directly affect the shifting quality.

[0003] In the existing product design process, usually two technical means are adopted to obtain the clutch pressure characteristic curve:

[0004] One is the experimental technical means: mainly obtaining the clutch pressure characteristic curve through the bench test of the clutch system. In the test, the worm in the actuator is rotated, and at the same time, the clutch clamping force is measured to calibrate the pressure of the clutch. This method has a long test cycle, requires a large number of physical prototypes, and has a high cost, and cannot fully meet the needs of product development.

[0005] The other is the simulation technical means: obtaining the clutch pressure characteristic curve by building a clutch system analysis model using the corresponding clutch module in the Amesim software (a complex system modeling and simulation platform in the multi-disciplinary field). However, the Amesim software cannot simulate the actual deformation of the clutch system, resulting in a large deviation between the simulation data and the real data, and cannot guarantee the accuracy of the clutch pressure characteristic curve. Summary of the Invention

[0006] In view of the defects existing in the above-mentioned prior art, the present invention provides a method for obtaining the clutch pressure characteristic curve, which combines the experimental technical means and the simulation technical means, only needs to conduct the pressure characteristic curve test of the friction plate assembly with a shorter test cycle, and applies the constitutive relationship of the friction plate assembly material to the finite element simulation of the clutch system, then the high-precision clutch pressure characteristic curve can be quickly obtained by simulation.

[0007] Combined with the accompanying drawings of the specification, the technical solution of the present invention is as follows:

[0008] A method for obtaining the clutch pressure characteristic curve, the method is: constructing the constitutive relationship of the friction plate assembly material according to the friction plate assembly pressure characteristic curve obtained through experiments, and then applying the finite element analysis method to endow the constitutive relationship of the friction plate assembly material to the finite element simulation of the clutch system, and finally obtaining the clutch pressure characteristic curve through simulation.

[0009] Further, the specific process of the method for obtaining the clutch pressure characteristic curve is as follows:

[0010] S1. Establish a finite element model of the clutch system;

[0011] S2. Define the properties of the finite element model of the clutch system. Among them, the constitutive relationship of the friction plate assembly material is constructed by the pressure characteristic curve of the friction plate assembly obtained through experiments;

[0012] S3. Define the contact between the components of the clutch system;

[0013] S4. Define the boundary conditions of the finite element model of the clutch system;

[0014] S5. Define the input parameters of the clutch system;

[0015] S6. Assign the constitutive relationship of the friction plate assembly material to the finite element simulation of the clutch system, and solve and calculate the finite element model of the clutch system;

[0016] S7. Compare and screen the results of the finite element model;

[0017] S8. Obtain the clutch pressure characteristic curve according to the screening results.

[0018] Furthermore, in the step S1, during the process of establishing the finite element model of the clutch system:

[0019] The input shaft 1, snap ring 2, limit baffle 3, first thrust bearing 4, ball cam 5, second thrust bearing 9, clutch pressure plate 10, clutch baffle 11, friction plate assembly 12, clutch housing 13, clutch seat 14, needle roller bearing 16, output shaft 17, limit block 18, tooth part of the worm wheel 7 and tooth part of the worm 8 are all modeled using first-order hexahedral elements;

[0020] The spoke part of the worm wheel 7, the spoke part of the worm 8 and the pressure plate 6 are all modeled using second-order tetrahedral elements;

[0021] The teeth and spokes of the worm wheel 7 and the teeth and spokes of the worm 8 are connected in a co-node form;

[0022] Refine the mesh at the positions of the pressure plate raceway 19 on the pressure plate 6 and the worm wheel raceway 20 on the worm wheel 7;

[0023] The spring 15 is simulated by a spring element, and the spring 15 connects the clutch pressure plate 10 and the clutch seat 14; a first rigid constraint unit is established on the clutch pressure plate 10, and the slave nodes of the first rigid constraint unit select the nodes of the contact part between the clutch pressure plate 10 and the spring 15, and the master node of the first rigid constraint unit selects the geometric center point 21 of the clutch pressure plate; a second rigid constraint unit is established on the clutch seat 14, and the slave nodes of the second rigid constraint unit select the nodes of the contact part between the clutch seat 14 and the spring 15, and the master node of the second rigid constraint unit selects the geometric center point 22 of the clutch seat; one end of the spring element is connected to the geometric center point 21 of the clutch pressure plate, and the other end is connected to the geometric center point 22 of the clutch seat.

[0024] Furthermore, in the step S2, defining the finite element model attributes of the clutch system includes:

[0025] Defining the material properties of the inelastic components of the clutch system, including: elastic modulus and Poisson's ratio of the material;

[0026] Defining the spring properties, including: stiffness of the spring element and initial pressure;

[0027] Constructing the constitutive relationship of the friction plate assembly material through the pressure characteristic curve of the friction plate assembly obtained by experiments, and defining the material properties of the friction plate assembly, including: stress-strain curve and Poisson's ratio.

[0028] Furthermore, the specific process of defining the material properties of the friction plate assembly is:

[0029] A1. Measuring the pressure-axial deformation test curve of the friction plate assembly through experiments, and measuring the data of the pressure-axial deformation curve of the friction plate assembly;

[0030] A2. Obtaining the stress-strain curve and Poisson's ratio of the Marlow model;

[0031] The formula for obtaining the stress-strain curve of the Marlow model is specifically as follows:

[0032] ε m =L / L t

[0033] σ m =F / S t

[0034] In the above formula:

[0035] ε m is the strain in the Marlow model;

[0036] L is the axial deformation of the friction plate assembly, that is: during the friction plate assembly test, the distance change between the lower surface of the loading fixture and the upper surface of the fixed fixture;

[0037] L t is the initial axial thickness of the friction plate assembly;

[0038] σ m is the stress in the Marlow model;

[0039] F is the axial pressure acting on the friction plate assembly;

[0040] S t is the contact area between the loading fixture 23 and the friction plate assembly 12 during the test of the friction plate assembly;

[0041] Define the initial Poisson's ratio of the Marlow model as 0.49;

[0042] A3. Add the Marlow model as input data to the finite element analysis model of the friction plate assembly and define the hyperelastic material properties of the friction plate assembly.

[0043] Furthermore, in the step S3, defining the contact between the components of the clutch system includes:

[0044] The main connection forms between the components of the clutch system are: the limit baffle 3 is connected to the input shaft 1 through a spline and is limited by a snap ring 2; the friction plate assembly 12 is composed of two groups of friction plates stacked crosswise in sequence, where the inner diameter side of one group of friction plates is connected to the clutch seat 14 through a spline, and the outer diameter side of the other group of friction plates is connected to the clutch housing 13 through a spline; the clutch seat 14 is connected to the input shaft 1 through a spline; the clutch housing 13 is connected to the output shaft 17 through a spline; the remaining components are all connected in the form of contact;

[0045] During the clutch shifting process, the input rotation angle of the worm 8 is controlled to rotate the worm gear 7. Under the action of the spherical cam 5, the worm gear 7 moves towards the side close to the clutch pressure plate, thereby transmitting the pressure to the clutch pressure plate 10. The clutch pressure plate 10 presses the clutch baffle 11, and further the friction plate assembly 12 is pressed, and further the clutch seat 14 and the clutch housing 13 are connected through the pressed friction plate assembly 12, thereby realizing the connection between the input shaft 1 and the output shaft 17;

[0046] Assemble the model according to the actual installation position of the clutch system, create the contact of the snap ring 2 - limit baffle 3, pressure plate 6 - spherical cam 5, spherical cam 5 - worm gear 7, worm gear 7 - worm 8, clutch pressure plate 10 - clutch baffle 11, clutch baffle 11 - friction plate assembly 12, friction plate assembly 12 - clutch housing 13, clutch housing 13 - limit block 18, clutch housing 13 - output shaft 17, and clutch seat 14 - input shaft 1. The snap ring 2 is connected to the input shaft 1 as a whole, and the output shaft 17 is connected to the limit block 18 as a whole;

[0047] Define the bearing contact form as follows: The inner ring of the bearing is integrated with the connecting part, the outer ring of the bearing is integrated with the connecting part, the rolling elements are integrated with the inner ring of the bearing, and contact is defined between the rolling elements and the outer ring of the bearing.

[0048] In the step S4, the boundary conditions of the finite element model of the clutch system are defined specifically as follows:

[0049] Restrain all degrees of freedom of the input shaft 1 at the position of the input shaft end face 28 and the output shaft 17 at the position of the output shaft end face 29.

[0050] Furthermore, in the step S5, the worm rotation angle of the worm 8 is used as the input parameter of the clutch. Among them, the calculation formula of the worm rotation angle of the worm 8 is as follows:

[0051] α = i × β

[0052] In the above formula:

[0053] α is the worm rotation angle;

[0054] i is the transmission ratio of the worm and worm gear;

[0055] β is the tooth angle of the worm gear;

[0056] Input the worm rotation angle applied to the worm into the finite element analysis model of the clutch system.

[0057] Furthermore, in the step S6, use finite element analysis software to solve and calculate the finite element model of the clutch system, and obtain the finite element model results including: the axial pressure of the friction plate assembly, the axial deformation of the friction plate assembly, the input rotation angle of the worm, and the friction plate assembly.

[0058] Furthermore, in the step S7, extract the axial pressure and axial deformation data of the friction plate assembly, and form a simulation curve of the axial pressure and axial deformation of the friction plate assembly. Compare the simulation curve with the test curve of the pressure and axial deformation of the friction plate assembly, and screen the qualified finite element model result data. The screening process is as follows:

[0059] First: Discretize the simulation curve and the test curve into multiple comparison points with the same abscissa;

[0060] Then: Compare the ordinates of the comparison points. When the ordinate errors of all comparison points are less than the preset error range, the pressure of the friction plate assembly and the axial deformation of the friction plate assembly corresponding to the simulation curve are both qualified data; when the ordinate errors of all comparison points are not all less than the preset error range, reduce the Poisson's ratio of the material in the Marlow model, and re-solve and calculate the finite element model of the clutch system until the ordinate errors of all comparison points are less than the preset error range;

[0061] Finally: According to the qualified friction plate assembly pressure data, the corresponding worm input rotation angle data is extracted as qualified data.

[0062] Furthermore, in the step S8, based on the axial pressure of the qualified friction plate assembly and the contact area parameter between the friction plate assembly and the clutch housing extracted from the clutch system model, the corresponding clutch pressure value is obtained, and the clutch pressure characteristic curve is drawn according to the obtained qualified worm input rotation angle and clutch pressure value.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] 1. The method for obtaining the clutch pressure characteristic curve of the present invention constructs the constitutive relationship of the friction plate assembly material according to the friction plate assembly pressure characteristic curve, and applies it to the finite element simulation of the clutch system, effectively improving the simulation accuracy of the clutch pressure characteristic curve.

[0065] 2. The method for obtaining the clutch pressure characteristic curve of the present invention can quickly obtain the clutch pressure characteristic curve under different numbers of friction plate groups by applying the finite element method on the basis of obtaining the constitutive relationship of the friction plate assembly material.

[0066] 3. The method for obtaining the clutch pressure characteristic curve of the present invention only needs to conduct the friction plate assembly pressure characteristic curve test, and does not need to conduct the clutch system pressure characteristic curve test, effectively reducing the physical prototypes required for the test, simplifying the test process, being beneficial to cost saving and shortening the R & D cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 is a flow block diagram of the method for obtaining the clutch pressure characteristic curve of the present invention;

[0068] Figure 2 is a schematic structural diagram of the clutch system;

[0069] Figure 3 is a schematic diagram of the pressure plate raceway in the clutch system;

[0070] Figure 4 is a schematic diagram of the worm raceway in the clutch system;

[0071] Figure 5 is a schematic diagram of the installation position of the first thrust bearing and the spring in the clutch system;

[0072] Figure 6 is Figure 5 a partial enlarged view of the installation position A of the first thrust bearing in

[0073] Figure 7 isFigure 5 Partial enlarged view of the installation position B of the middle spring between the clutch pressure plate and the clutch seat;

[0074] Figure 8 Schematic diagram of the test curve of the pressure and axial deformation of the friction plate assembly;

[0075] Figure 9 Schematic diagram of the loading fixture and the fixing fixture during the test of the friction plate assembly;

[0076] Figure 10 Schematic diagram of the stress-strain curve of the Marlow model;

[0077] Figure 11 Schematic diagram of the end face of the input shaft and the end face of the output shaft in the clutch system;

[0078] Figure 12 Schematic diagram of the end face of the worm wheel in the clutch system;

[0079] Figure 13 Schematic diagram of the clutch pressure characteristic curve obtained by the method described in the present invention.

[0080] In the figure:

[0081] 1 - Input shaft, 2 - Snap ring, 3 - Limit baffle, 4 - First thrust bearing, 5 - Ball cam, 6 - Pressure plate,

[0082] 7 - Worm wheel, 8 - Worm, 9 - Second thrust bearing, 10 - Clutch pressure plate, 11 - Baffle of the clutch, 12 - Friction plate assembly, 13 - Clutch housing, 14 - Clutch seat, 15 - Spring assembly, 16 - Needle bearing, 17 - Output shaft, 18 - Limit block, 19 - Pressure plate raceway, 20 - Worm wheel raceway, 21 - Geometric center point of the clutch pressure plate, 22 - Geometric center point of the clutch seat 23 - Loading fixture 24 - Fixing fixture

[0083] 25 - Bearing outer ring, 26 - Rolling element, 27 - Bearing inner ring, 28 - End face of the input shaft, 29 - End face of the output shaft. Detailed implementation manners

[0084] To clearly and completely describe the technical solution and its specific working process of the present invention, in combination with the accompanying drawings of the specification, the detailed implementation manners of the present invention are as follows:

[0085] In the present invention, unless otherwise clearly specified or defined, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0086] In the present invention, unless otherwise clearly specified or defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0087] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0088] The present invention discloses a method for obtaining the clutch pressure characteristic curve. The method is to obtain the pressure characteristic curve of the friction plate assembly through experiments, and construct the constitutive relationship of the friction plate assembly material (i.e., the relationship between the stress tensor and the strain tensor). Then, by applying the finite element method, the constitutive relationship of the friction plate assembly material is applied to the finite element simulation of the clutch system. Finally, the clutch pressure characteristic curve under different numbers of friction plate groups is obtained through simulation.

[0089] As Figure 1 shown, the specific process of the method for obtaining the clutch pressure characteristic curve according to the present invention is as follows:

[0090] S1. Establish a finite element model of the clutch system;

[0091] In this step S1, using finite element analysis software, solid mesh elements are adopted to model the components in the clutch system. To ensure the number of nodes in the established model and the simulation accuracy:

[0092] As Figure 2 shown, in the clutch system, the input shaft 1, snap ring 2, limit baffle 3, first thrust bearing 4, ball cam 5, second thrust bearing 9, clutch pressure plate 10, clutch baffle 11, friction plate assembly 12, clutch housing 13, clutch seat 14, needle roller bearing 16, output shaft 17, limit block 18, tooth part of the worm wheel 7 and tooth part of the worm 8 are all modeled using first-order hexahedral elements;

[0093] The spoke part of the worm wheel 7, the spoke part of the worm 8 and the pressure plate 6 are all modeled using second-order tetrahedral elements;

[0094] The teeth and spokes of the worm wheel 7 and the teeth and spokes of the worm 8 are connected in a co-node form;

[0095] As Figure 2 、 Figure 3 and Figure 4 shown, the mesh at the position of the pressure plate raceway 19 on the pressure plate 6 and the worm wheel raceway 20 on the worm wheel 7 is refined;

[0096] The spring 15 is simulated through a spring element (SPRINGA element). As Figure 2 、 Figure 5 and Figure 7 shown, the spring 15 is used to connect the clutch pressure plate 10 and the clutch seat 14. A first rigid constraint (rbe2) element is established on the clutch pressure plate 10. The slave nodes of the first rigid constraint element select the nodes at the contact part between the clutch pressure plate 10 and the spring 15, and the master node of the first rigid constraint element selects the geometric center point 21 of the clutch pressure plate; A second rigid constraint (rbe2) element is established on the clutch seat 14. The slave nodes of the second rigid constraint element select the nodes at the contact part between the clutch seat 14 and the spring 15, and the master node of the second rigid constraint element selects the geometric center point 22 of the clutch seat; One end of the spring element is connected to the geometric center point 21 of the clutch pressure plate, and the other end is connected to the geometric center point 22 of the clutch seat.

[0097] S2. Define the properties of the finite element model of the clutch system;

[0098] In this step S2, defining the properties of the finite element model of the clutch system includes:

[0099] (1) Define the material properties of the inelastic components in the clutch system:

[0100] As Figure 2As shown, the inelastic components of the clutch system include: input shaft 1, snap ring 2, limit baffle 3, first thrust bearing 4, ball cam 5, pressure plate 6, worm gear 7, worm 8, second thrust bearing 9, clutch pressure plate 10, clutch baffle 11, clutch housing 13, clutch seat 14, needle roller bearing 16, output shaft 17, and limit block 18;

[0101] The material properties of the inelastic components include: material elastic modulus E = 210000 Mpa, Poisson's ratio μ = 0.3;

[0102] (2) Define the properties of spring 15:

[0103] Define the spring element stiffness K = 150 N / mm, initial pressure F a = 410 N;

[0104] (3) Define the material properties of the friction plate assembly 12:

[0105] Define the material properties of the friction plate assembly 12 through the Marlow model in the hyperelastic constitutive equation of rubber materials, including: stress-strain curve and Poisson's ratio μ;

[0106] Convert the friction plate assembly pressure and axial deformation test curve measured through experiments, as Figure 8 shown, into a stress-strain curve, and endow the finite element model of the friction plate assembly through the hyperelastic constitutive equation of rubber materials. The specific process is as follows;

[0107] A1. Measure the friction plate assembly pressure and axial deformation test curve through experiments, as Figure 8 shown. The data of the friction plate assembly pressure and axial deformation curve measured through experiments are shown in Table 1 below:

[0108] Table 1

[0109]

[0110]

[0111] A2. Obtain the stress-strain curve and Poisson's ratio of the Marlow model;

[0112] The formula for obtaining the stress-strain curve of the Marlow model is as follows:

[0113] ε m = L / L t

[0114] σ m = F / S t

[0115] In the above formula:

[0116] εm is the strain in the Marlow model;

[0117] L is the axial deformation of the friction plate assembly, that is: during the friction plate assembly test, the distance change between the lower surface of the loading fixture 23 and the upper surface of the fixed fixture 24, as Figure 9 shown;

[0118] L t is the initial axial thickness of the friction plate assembly, where L t = 36 mm;

[0119] σ m is the stress in the Marlow model;

[0120] F is the axial pressure acting on the friction plate assembly;

[0121] S t is the contact area between the loading fixture 23 and the friction plate assembly 12 during the friction plate assembly test, as Figure 8 shown, where S t = 6700 mm 2 ;

[0122] The stress-strain curve data of the Marlow model obtained according to the above formula is shown in Table 2 below, and the obtained stress-strain curve of the Marlow model is as Figure 10 shown;

[0123] Table 2

[0124] Serial number Marlow model strain Marlow model stress / MPa 1 0.0000 0.0000 2 0.0056 0.0150 3 0.0064 0.0299 4 0.0067 0.0449 5 0.0072 0.0597 6 0.0083 0.1195 7 0.0094 0.1792 8 0.0100 0.2389 9 0.0108 0.2988 10 0.0114 0.3583 11 0.0119 0.4181 12 0.0122 0.4778 13 0.0128 0.5375 14 0.0131 0.5974 15 0.0136 0.6568 16 0.0139 0.7165 17 0.0142 0.7762 18 0.0144 0.8359 19 0.0147 0.8956 20 0.0150 0.9554 21 0.0153 1.0150 22 0.0156 1.0751 23 0.0158 1.1348 24 0.0161 1.1945 25 0.0164 1.2539 26 0.0167 1.3139 27 0.0169 1.3733 28 0.0172 1.4329 29 0.0175 1.4925

[0125] Define the initial Poisson's ratio of the Marlow model as 0.49;

[0126] A3. Add the Marlow model as input data to the friction plate assembly finite element analysis model and define the hyperelastic material properties of the friction plate assembly.

[0127] S3. Define the contact between the components of the clutch system;

[0128] In this step S3, the main connection form between the components of the clutch system is:

[0129] The limit baffle 3 is connected to the input shaft 1 through a spline and is limited by a snap ring 2;

[0130] The friction plate assembly 12 is composed of two groups of friction plates stacked crosswise in sequence. The inner diameter side of one group of friction plates is connected to the clutch seat 14 through a spline, and the outer diameter side of the other group of friction plates is connected to the clutch housing 13 through a spline;

[0131] The clutch seat 14 is connected to the input shaft 1 through a spline;

[0132] The clutch housing 13 is connected to the output shaft 17 through a spline;

[0133] All the other components are connected in a contact form;

[0134] In this step S3, the shifting process is achieved by controlling the input rotation angle of the worm 8 to rotate the worm gear 7. Due to the action of the spherical cam 5, the worm gear 7 moves towards the side close to the clutch pressure plate (i.e., Figure 2 the right side in ), thereby transmitting the pressure to the clutch pressure plate 10. The clutch pressure plate 10 presses the clutch retainer 11, and then the friction plate assembly 12 is pressed. In the pressed friction plate assembly 12, the two groups of friction plates are in frictional connection with each other. Furthermore, the clutch seat 14 and the clutch housing 13 are connected through the pressed friction plate assembly 12, thus realizing the connection between the input shaft 1 and the output shaft 17;

[0135] In this step S3, according to the actual installation position of the clutch system, the model is assembled to create contacts between the snap ring 2 - the limit baffle 3, the pressure plate 6 - the spherical cam 5, the spherical cam 5 - the worm gear 7, the worm gear 7 - the worm 8, the clutch pressure plate 10 - the clutch retainer 11, the clutch retainer 11 - the friction plate assembly 12, the friction plate assembly 12 - the clutch housing 13, the clutch housing 13 - the limit block 18, the clutch housing 13 - the output shaft 17, and the clutch seat 14 - the input shaft 1; the snap ring 2 is integrally connected to the input shaft 1; the output shaft 17 is integrally connected to the limit block 18;

[0136] In this step S3, the bearing contact form is defined as:

[0137] As Figure 2 , Figure 5 and Figure 6 shown, taking the first thrust bearing 4 as an example, the inner ring 27 of the bearing is integrally connected to the connecting part, the outer ring 25 of the bearing is integrally connected to the connecting part, the rolling element 26 is integrally connected to the inner ring 27 of the bearing, and the contact is defined between the rolling element 26 and the outer ring 25 of the bearing;

[0138] In addition, the contact form between the second thrust bearing 9 and the needle bearing 16 is the same as that of the first thrust bearing 4;

[0139] S4. Define the boundary conditions of the clutch system finite element model;

[0140] In this step S4, as Figure 2 and Figure 11 shown, the input shaft 1 and the output shaft 17 are fixed, that is: all degrees of freedom of the input shaft 1 at the input shaft end face 28 and the output shaft 17 at the output shaft end face 29 are constrained.

[0141] S5. Define the input parameters of the clutch system;

[0142] In this step S5, the worm 8 is driven to rotate by the shift motor, and then the worm 8 drives the worm wheel 7 to rotate. As the worm wheel 7 rotates, a corresponding axial force is applied to the clutch pressure plate 10 on its axial side, so as to realize the input of the axial force of the clutch system. Therefore, the worm angle of the worm 8 is used as the input parameter of the clutch. The calculation formula of the worm angle of the worm 8 is as follows:

[0143] α = i × β

[0144] In the above formula:

[0145] α is the worm angle;

[0146] i is the transmission ratio of the worm and worm wheel;

[0147] β is the tooth angle of the worm wheel, as Figure 12 shown;

[0148] According to the above formula, when the transmission ratio of the worm and worm wheel = 90 and the tooth angle of the worm wheel is used to calculate the worm angle β of the worm 8 = 70°, the calculated worm angle α = 6300°;

[0149] The worm angle applied to the worm 8 is input into the finite element analysis model of the clutch system.

[0150] S6. Solve and calculate the finite element model of the clutch system;

[0151] In this step S6, finite element analysis software such as ABAQUS / Standard is used to solve and calculate the finite element model of the clutch system, and the finite element model results including the axial pressure of the friction plate assembly, the axial deformation of the friction plate assembly, the input rotation angle of the worm, and the friction plate assembly are obtained;

[0152] S7. Compare and screen the finite element model results;

[0153] In this step S7, the axial pressure and axial deformation data of the friction plate assembly 12 are extracted, and a simulation curve of the axial pressure and axial deformation of the friction plate assembly is formed. The simulation curve is compared with the test curve of the pressure and axial deformation of the friction plate assembly measured by the test in the previous step S2, and the qualified finite element model result data are screened. The screening process is as follows:

[0154] First: The simulation curve and the test curve are respectively discretized into 10 comparison points with the same abscissa, as Figure 13 shown;

[0155] Then: Compare the vertical coordinates of 10 comparison points. When the vertical coordinate errors of all 10 comparison points are less than 5%, the pressure of the friction plate assembly and the axial deformation of the friction plate assembly corresponding to the simulation curve are both qualified data;

[0156] Finally: According to the qualified friction plate assembly pressure data screened, extract the corresponding worm input rotation angle data as qualified data;

[0157] In this step S7, during the screening process, if the vertical coordinate errors of the 10 discrete comparison points on the selected simulation curve and the test curve are not all less than 5%, then decrease the Poisson's ratio μ of the material in the Marlow model by a step of 0.01, and return to step S5 to re-solve and calculate the finite element model of the clutch system until the vertical coordinate errors of all 10 comparison points are less than 5%, and obtain the final Poisson's ratio μ of the material in the Marlow model; The process of adjusting the Poisson's ratio μ of the material in the Marlow model is shown in Table 3 below:

[0158] Table 3

[0159]

[0160]

[0161] As shown in Table 3 above, when the Poisson's ratio μ is 0.44, the corresponding errors are all less than 5%. Therefore, it is determined that the final Poisson's ratio μ of the material in the Marlow model is 0.44.

[0162] S8. Obtain the clutch pressure characteristic curve according to the screening result;

[0163] In this step S8, according to the qualified finite element model result data screened in step S7, and taking the input rotation angle of the worm as the abscissa and the clutch pressure value as the ordinate, draw the clutch pressure characteristic curve, as Figure 13 shown;

[0164] The clutch pressure value is calculated based on the axial pressure of the friction plate assembly screened as qualified and the contact area parameter CFN between the friction plate assembly and the clutch housing extracted from the clutch system model.

[0165] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0166] The specific embodiments of the present invention described above do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for obtaining the clutch pressure characteristic curve, characterized in that: The method is as follows: construct the constitutive relationship of the friction plate assembly material according to the pressure characteristic curve of the friction plate assembly obtained through experiments, and then apply the finite element analysis method to endow the constitutive relationship of the friction plate assembly material to the clutch system finite element simulation. Finally, obtain the clutch pressure characteristic curve through simulation; Among them, the specific process of the method for obtaining the clutch pressure characteristic curve is as follows: Step S1: Establish a finite element model of the clutch system; Step S2: Define the attributes of the finite element model of the clutch system. Among them, construct the constitutive relationship of the friction plate assembly material according to the pressure characteristic curve of the friction plate assembly obtained through experiments; Step S3: Define the contact between the components of the clutch system; Step S4: Define the boundary conditions of the finite element model of the clutch system; Step S5: Define the input parameters of the clutch system; Step S6: Endow the constitutive relationship of the friction plate assembly material to the clutch system finite element simulation, and solve and calculate the finite element model of the clutch system; Step S7: Compare and screen the results of the finite element model; Step S8: Obtain the clutch pressure characteristic curve according to the screening results; In the said step S5, the worm rotation angle of the worm (8) is used as the input parameter of the clutch. Among them, the calculation formula of the worm rotation angle of the worm (8) is as follows: α＝i×β In the above formula: α is the worm rotation angle; i is the worm and worm gear transmission ratio; β is the worm gear tooth angle; Input the worm rotation angle applied to the worm into the clutch system finite element analysis model; In the said step S6, use finite element analysis software to solve and calculate the finite element model of the clutch system, and obtain the finite element model results including: the axial pressure of the friction plate assembly, the axial deformation of the friction plate assembly, the input rotation angle of the worm, and the friction plate assembly; In the said step S7, extract the axial pressure and axial deformation data of the friction plate assembly, and form a simulation curve of the axial pressure and axial deformation of the friction plate assembly. Compare the simulation curve with the test curve of the pressure and axial deformation of the friction plate assembly, and screen the qualified finite element model result data. The screening process is as follows: First: Discretize the simulation curve and the test curve into multiple comparison points with the same abscissa; Then: Compare the ordinates of the comparison points. When the ordinate errors of all comparison points are less than the preset error range, the pressure of the friction plate assembly and the axial deformation of the friction plate assembly corresponding to the simulation curve are both qualified data; when the ordinate errors of all comparison points are not all less than the preset error range, reduce the Poisson's ratio of the material in the Marlow model, and re-solve and calculate the finite element model of the clutch system until the ordinate errors of all comparison points are less than the preset error range; Finally: According to the qualified friction plate assembly pressure data screened, extract the corresponding worm input rotation angle data as qualified data.

2. The method for obtaining a clutch pressure characteristic curve as described in claim 1, characterized in that: In the said step S1, during the process of establishing the finite element model of the clutch system: The input shaft (1), snap ring (2), limit baffle (3), first thrust bearing (4), ball cam (5), second thrust bearing (9), clutch pressure plate (10), clutch baffle (11), friction plate assembly (12), clutch housing (13), clutch seat (14), needle roller bearing (16), output shaft (17), limit block (18), the tooth part of the worm gear (7) and the tooth part of the worm (8) are all modeled using first-order hexahedral elements; The spoke part of the worm gear (7), the spoke part of the worm (8), and the pressure plate (6) are all modeled using second-order tetrahedral elements; The teeth and spokes of the worm gear (7) and the teeth and spokes of the worm (8) are connected in a co-node form; Refine the mesh at the positions of the pressure plate raceway (19) on the pressure plate (6) and the worm gear raceway (20) on the worm gear (7); The spring (15) is simulated by a spring element, and the spring (15) connects the clutch pressure plate (10) and the clutch seat (14); a first rigid constraint unit is established on the clutch pressure plate (10), and the slave node of the first rigid constraint unit selects the node at the contact part of the clutch pressure plate (10) and the spring (15), and the master node of the first rigid constraint unit selects the geometric center point (21) of the clutch pressure plate; a second rigid constraint unit is established on the clutch seat (14), and the slave node of the second rigid constraint unit selects the node at the contact part of the clutch seat (14) and the spring (15), and the master node of the second rigid constraint unit selects the geometric center point (22) of the clutch seat; one end of the spring element is connected to the geometric center point (21) of the clutch pressure plate, and the other end is connected to the geometric center point (22) of the clutch seat.

3. The method for obtaining the clutch pressure characteristic curve according to claim 1, characterized in that: In the step S2, defining the finite element model attributes of the clutch system includes: Defining the material attributes of the inelastic components of the clutch system, including: material elastic modulus and Poisson's ratio; Defining the spring attributes, including: spring element stiffness and initial pressure; Construct the constitutive relationship of the friction plate assembly material through the pressure characteristic curve of the friction plate assembly obtained by experiments, and define the material attributes of the friction plate assembly, including: stress-strain curve and Poisson's ratio.

4. The method for obtaining the clutch pressure characteristic curve according to claim 3, characterized in that: The specific process of defining the material attributes of the friction plate assembly is: A1. Measure the test curve of the pressure of the friction plate assembly and the axial deformation through experiments, and measure the data of the pressure of the friction plate assembly and the axial deformation curve; A2. Obtain the stress-strain curve and Poisson's ratio of the Marlow model; The formula for obtaining the stress-strain curve of the Marlow model is specifically as follows: ε m = L / L t σ m = F / S t In the above formula: ε m is the strain in the Marlow model; L is the axial deformation of the friction plate assembly, that is: during the test of the friction plate assembly, the change in the distance between the lower surface of the loading fixture and the upper surface of the fixed fixture; L t is the initial axial thickness of the friction plate assembly; σ m is the stress in the Marlow model; F is the axial pressure acting on the friction plate assembly; S t During the test of the friction plate assembly, it is the contact area between the loading fixture (23) and the friction plate assembly (12). Define the initial Poisson's ratio of the Marlow model as 0.49; A3. Add the Marlow model as input data to the finite element analysis model of the friction plate assembly, and define the hyperelastic material attributes of the friction plate assembly.

5. The method for obtaining the clutch pressure characteristic curve according to claim 1, wherein: In the step S3, the contact between the components of the clutch system is defined as: The main connection forms between the components of the clutch system are as follows: The limit baffle (3) is connected to the input shaft (1) through a spline and is limited by a snap ring (2); the friction plate assembly (12) is composed of two sets of friction plates stacked crosswise in sequence. The inner diameter side of one set of friction plates is connected to the clutch seat (14) through a spline, and the outer diameter side of the other set of friction plates is connected to the clutch housing (13) through a spline; the clutch seat (14) is connected to the input shaft (1) through a spline; the clutch housing (13) is connected to the output shaft (17) through a spline; the remaining components are all connected in a contact form. During the clutch shifting process, the input rotation angle of the worm (8) is controlled to rotate the worm gear (7). Under the action of the spherical cam (5), the worm gear (7) moves towards the side close to the clutch pressure plate, thereby transmitting the pressure to the clutch pressure plate (10). The clutch pressure plate (10) presses the clutch baffle (11), and further the friction plate assembly (12) is pressed, and then the clutch seat (14) and the clutch housing (13) are connected through the pressed friction plate assembly (12), thereby realizing the connection between the input shaft (1) and the output shaft (17). Assemble the model according to the actual installation position of the clutch system, create the contact of the snap ring (2) - limit baffle (3), pressure plate (6) - spherical cam (5), spherical cam (5) - worm gear (7), worm gear (7) - worm (8), clutch pressure plate (10) - clutch baffle (11), clutch baffle (11) - friction plate assembly (12), friction plate assembly (12) - clutch housing (13), clutch housing (13) - limit block (18), clutch housing (13) - output shaft (17), and clutch seat (14) - input shaft (1). The snap ring (2) is integrally connected to the input shaft (1), and the output shaft (17) is integrally connected to the limit block (18). Define the bearing contact form as: The inner ring of the bearing is integrally connected to the connecting part, the outer ring of the bearing is integrally connected to the connecting part, the rolling element is integrally connected to the inner ring of the bearing, and the contact is defined between the rolling element and the outer ring of the bearing. In the step S4, the boundary conditions of the clutch system finite element model are specifically defined as: Restrain all degrees of freedom of the input shaft (1) at the position of the input shaft end face (28) and the output shaft (17) at the position of the output shaft end face (29).

6. The method for obtaining the clutch pressure characteristic curve according to claim 5, wherein: In the step S8, based on the axial pressure of the friction plate assembly screened as qualified, and the contact area parameter between the friction plate assembly and the clutch housing extracted from the clutch system model, the corresponding clutch pressure value is obtained, and the clutch pressure characteristic curve is drawn according to the obtained qualified input rotation angle of the worm and the clutch pressure value.

Images