A method and device for calculating oil filling time of a clutch and a computer readable storage medium

Abstract

The application discloses a kind of calculation method, device and computer readable storage medium of clutch oiling time, the method comprises: selecting the geometric parameter of any section of oil passage of clutch as characteristic parameter, and set intermediate characteristic flow rate as the flow rate of the section oil passage previous time;Calculate the total along-path loss and total local loss of oil passage at the current time;Calculate the piston movement speed, piston displacement and piston acceleration at the current time;Calculate the average pressure of piston surface at the current time;Calculate characteristic flow rate;Determine whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than the preset threshold value, if yes, calculate the piston displacement and piston speed at the next time, and when the piston at the next time reaches half engagement point stroke, obtain the clutch oiling time;Otherwise, update the intermediate characteristic flow rate to the characteristic flow rate, and re-execute.The application can greatly improve the calculation efficiency, and provide a kind of fast evaluation method for oiling time in clutch design stage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of automobiles, and particularly relates to a clutch oil filling time calculation method, device and computer readable storage medium. BACKGROUND

[0002] In the design of a wet-type automatic clutch, the oil filling time is an important index for measuring the performance of the clutch and directly affects the gear shifting quality of the clutch. In the oil filling process of the clutch, the time from the start of oil filling of the clutch to the kiss point (half engagement point, hereinafter referred to as kp point) accounts for most of the total oil filling time. At present, only after the product design is completed, the clutch oil filling test can be performed through the production of a prototype to know the time of the clutch oil filling to the kp point. If the oil filling time is too long (especially at low temperature), it is necessary to repeatedly modify the oil passage or other related parameters to meet the requirements of the oil filling time.

[0003] The existing oil filling time analysis method is to establish a three-dimensional CFD model of the clutch control oil passage to perform simulation analysis, so as to obtain the time of the clutch oil filling to the kp point. The main shortcomings of the existing three-dimensional CFD analysis method are as follows: first, the model processing and calculation time is long, and the engineering application value will be greatly reduced; second, the method needs relevant CFD simulation experience, and it is difficult for general product engineers without CFD experience to apply. SUMMARY

[0004] The technical problem to be solved by the embodiments of the present application is to provide a clutch oil filling time calculation method, device and computer readable storage medium which can improve the calculation speed of the clutch oil filling time and are simple and easy to use.

[0005] To solve the above technical problems, the present application provides a clutch oil filling time calculation method, comprising:

[0006] Step S1, selecting the geometric parameters of any section of the oil passage of the clutch as characteristic parameters, and setting the intermediate characteristic flow rate as the flow rate at the previous moment of the section of the oil passage;

[0007] Step S2, calculating the total along-path loss and total local loss of the oil passage at the current moment according to the characteristic parameters, the intermediate characteristic flow rate, the clutch control parameters, the clutch body parameters, the oil passage geometric parameters and the oil parameters;

[0008] Step S3, calculating the piston movement speed, piston displacement and piston acceleration at the current moment;

[0009] Step S4, calculating the average piston surface pressure at the current moment according to the piston movement speed, piston displacement and piston acceleration at the current moment and the clutch body parameters;

[0010] Step S5, calculating a characteristic flow rate according to the clutch control parameter, the oil parameter, the average pressure of the piston surface at the current time, the total flow resistance and the total local loss of the oil gallery at the current time;

[0011] Step S6, judging whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value, if yes, executing step S7, otherwise executing step S8;

[0012] Step S7, calculating the piston displacement and the piston speed at the next time, and obtaining the oil filling time of the clutch when the piston displacement at the next time reaches the half engagement point stroke;

[0013] Step S8, updating the intermediate characteristic flow rate as the characteristic flow rate, and re-executing steps S2-S6.

[0014] Further, the step S1 selects the geometric parameters of the i (i∈{1, 2, 3, …}) section of the oil gallery of the clutch as the characteristic parameters, sets the intermediate characteristic flow rate as the flow rate of the section of the oil gallery at the previous time initializes the characteristic oil speed before oil filling piston acceleration a (0) = 0 m / s 2 , piston speed u (0) = 0 m / s, piston displacement x (0) = 0 m, and sets the time step as dt.

[0015] Further, the clutch control parameters include: spring stiffness K, kp point stroke L, design main oil pressure P t ; the clutch body parameters include: piston outer diameter R out , piston inner diameter R in , piston area A, piston mass M; the oil gallery geometric parameters include: the length H n of each section of the oil gallery, the hydraulic diameter D n of the oil gallery and the oil gallery area A n (subscript n represents the flow passage section with different hydraulic diameters, n = 1, 2, 3, …); the oil parameter includes oil viscosity μ and oil density ρ.

[0016] Further, let the time t = t + dt, and the step S2 calculates the total flow resistance of the oil gallery at time t according to the following formula

[0017]

[0018]

[0019]

[0020]

[0021] wherein A i is the oil passage area of the i-th oil passage selected as a characteristic parameter, is the Reynolds number of the n-th oil passage at t, is the frictional loss coefficient of the n-th oil passage at t, is the frictional loss of the n-th oil passage at t.

[0022] total local loss is calculated as follows:

[0023]

[0024]

[0025] wherein A i is the oil passage area of the i-th oil passage selected as a characteristic parameter, ζ n is the local loss coefficient of the n-th oil passage, is the local loss of the n-th oil passage at t.

[0026] Further, the step S3 calculates and updates the piston movement speed u (t) , the displacement x (t) and the acceleration a (t) according to the following formulas:

[0027] piston movement speed

[0028] piston displacement x (t) = x (t-dt) + u (t) dt;

[0029] piston acceleration a (t) = 2(u (t) dt - u (t-dt) dt) / dt 2 .

[0030] Further, the step S4 calculates the average pressure of the piston surface according to the following formula:

[0031]

[0032] wherein F y is the pre-tightening force of the piston spring, F m is the frictional force of the piston, F c is the centrifugal force of the piston; the centrifugal force F c of the piston is calculated by the following formula:

[0033]

[0034] wherein ω is the rotational angular velocity of the clutch, and r0 is the radius at which the pressure oil enters the oil cylinder.

[0035] Further, the step S5 calculates and updates the characteristic oil flow rate according to the following formula:

[0036]

[0037] Further, the step S6 specifically comprises: comparing the updated characteristic oil flow rate with the intermediate characteristic flow rate , and if the absolute value of the difference between the two is less than 1e-4 m / s, the step S7 is executed, and if the absolute value of the difference between the two is greater than or equal to 1e-4 m / s, the step S8 is executed.

[0038] Further, the step S7 updates the piston displacement u (t+dt) and the piston velocity x (t+dt) at the next time according to the following formula:

[0039] u (t+dt) = u (t) + a (t) dt

[0040] x (t+dt) = x (t) + u (t) dt.

[0041] Further, the step S7 further comprises: comparing the piston displacement x (t+dt) with the size of the kp point stroke L, and if the piston displacement x (t+dt) is greater than or equal to the kp point stroke L, the time t+dt corresponding to the piston displacement x (t+dt) is taken as the clutch oil filling time; and if the piston displacement x (t+dt) is less than the kp point stroke L, the step S1 is returned to, the intermediate characteristic flow rate is set, and the steps S2-S7 are re-executed.

[0042] The embodiment of the present application also provides a calculation device for clutch oil filling time, comprising:

[0043] An initialization module is configured to select the geometric parameters of any oil passage of the clutch as characteristic parameters, and set the intermediate characteristic flow rate as the flow rate at the previous time of the oil passage;

[0044] A first calculation module is configured to calculate the total along-path loss and the total local loss of the oil passage at the current time according to the characteristic parameters, the intermediate characteristic flow rate, the clutch control parameters, the clutch body parameters, the oil passage geometric parameters and the oil parameters.

[0045] a second calculation module, configured to calculate a piston movement speed, a piston displacement and a piston acceleration at a current time;

[0046] a third calculation module, configured to calculate a piston surface average pressure at the current time according to the piston movement speed, the piston displacement and the piston acceleration at the current time and clutch body parameters;

[0047] a fourth calculation module, configured to calculate a characteristic flow rate according to clutch control parameters, oil parameters, the piston surface average pressure at the current time, an oil passage total along loss and a total local loss at the current time;

[0048] a judging module, configured to judge whether an absolute value of a difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value;

[0049] an obtaining module, configured to calculate a piston displacement and a piston speed at a next time when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than the preset threshold value, and obtain a clutch oil filling time when the piston displacement at the next time reaches a half engagement point stroke;

[0050] an updating module, configured to update the intermediate characteristic flow rate to the characteristic flow rate and re-perform corresponding functions of the first calculation module, the second calculation module, the third calculation module, the fourth calculation module and the judging module when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is greater than or equal to the preset threshold value.

[0051] The application further provides a computer readable storage medium, which comprises a stored computer program; wherein the computer program controls a device where the computer readable storage medium is located to perform the clutch oil filling time calculation method when running.

[0052] The application has the following beneficial effects: the calculation of a series of empirical formulas instead of complex three-dimensional CFD analysis can greatly improve the calculation efficiency, and provides a fast evaluation method for the oil filling time in the clutch design stage; the influence of the change of a parameter on the oil filling time can be evaluated, which is beneficial to finding suitable clutch parameters, oil passage parameters and oil parameters and the like in the design stage. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0054] Figure 1 FIG. 1 is a flowchart of a method for calculating oil filling time of a clutch according to an embodiment of the present application.

[0055] Figure 2 FIG. 2 is a graph of piston displacement versus time according to an embodiment of the present application. DETAILED DESCRIPTION

[0056] The following description of the embodiments is provided with reference to the drawings, which are used to illustrate specific embodiments of the present application that can be implemented.

[0057] Referring to FIG. 1, Figure 1 The method for calculating oil filling time of a clutch according to an embodiment of the present application comprises the following steps.

[0058] In step S1, a geometric parameter of any section of the oil passage of the clutch is selected as a characteristic parameter, and an intermediate characteristic flow rate is set as the flow rate at the previous time of the section of the oil passage.

[0059] In step S2, the total head loss and the total local loss of the oil passage at the current time are calculated according to the characteristic parameter, the intermediate characteristic flow rate, the clutch control parameter, the clutch body parameter, the oil passage geometric parameter and the oil parameter.

[0060] In step S3, the piston movement speed, the piston displacement and the piston acceleration at the current time are calculated.

[0061] In step S4, the average piston surface pressure at the current time is calculated according to the piston movement speed, the piston displacement and the piston acceleration at the current time and the clutch body parameter.

[0062] In step S5, the characteristic flow rate is calculated according to the clutch control parameter, the oil parameter, the average piston surface pressure at the current time, the total head loss and the total local loss of the oil passage at the current time.

[0063] In step S6, it is determined whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value, and if so, step S7 is executed, otherwise, step S8 is executed.

[0064] In step S7, the piston displacement and the piston speed at the next time are calculated, and when the piston at the next time reaches the half-engagement point stroke, the oil filling time of the clutch is obtained.

[0065] In step S8, the intermediate characteristic flow rate is updated to the characteristic flow rate, and steps S2-S6 are re-executed.

[0066] The embodiment can be used to quickly evaluate the time required for the clutch to be filled with oil to the kp point after the primary design of the main oil pressure, spring stiffness, oil parameters, clutch size and oil inlet flow channel size is completed, thereby providing a reference basis for clutch oil filling design. Specifically, in the embodiment, the clutch control parameters include: spring stiffness K, kp point stroke L, design main oil pressure P t ; the clutch body parameters include: piston outer diameter R out , piston inner diameter R in , piston area A, piston mass M; the oil channel geometric parameters include: the length H n of each section of the oil channel, the hydraulic diameter D n of the oil channel and the oil channel area A n (subscript n represents the flow channel section with different hydraulic diameters, n = 1, 2, 3, …); the oil parameters include oil viscosity μ and oil density ρ.

[0067] For ease of description, the geometric parameters of the first section of the oil channel of the clutch are selected as the characteristic parameters in the embodiment, that is, n = 1, and the geometric parameters of the section of the oil channel are: the oil channel length H1, the oil channel hydraulic diameter D1 and the oil channel area A1, and the intermediate characteristic flow velocity is set as the flow velocity of the previous moment of the section of the oil channel , that is The initial characteristic oil velocity before oil filling is set as The piston acceleration a (0) = 0 m / s 2 , the piston velocity u (0) = 0 m / s, the piston displacement x (0) = 0 m, and the time step is set as dt.

[0068] Let t = t + dt, and the total along-path loss of the oil channel at time t is calculated according to the following formula:

[0069]

[0070]

[0071]

[0072]

[0073] In the above formulas (1) to (4), n = 1, 2, 3, …, indicating the oil channel sections with different hydraulic diameters; in formula (1), Re is the Reynolds number of the n-th section of the oil channel at time t, in formula (2), f is the along-path loss coefficient of the n-th section of the oil channel at time t, and in formula (3), h is the along-path loss of the n-th section of the oil channel at time t.

[0074] Total local loss The calculation method is as follows:

[0075]

[0076]

[0077] In formulas (5) and (6), n = 1, 2, 3, …, representing oil channel sections with different hydraulic diameters; ζ n is the local loss coefficient of the nth oil channel, and in formula (6), ζ is the local loss of the nth oil channel at time t.

[0078] It can be understood that if the geometric parameters of the second oil channel are selected as the characteristic parameters, A1 in formulas (1), (3), and (5) is replaced by A2, and so on, A1 in formulas (1), (3), and (5) can be rewritten as A i , i ∈ {1, 2, 3, …}, A i is the oil channel area of the ith oil channel selected as the characteristic parameter, and the rewritten formulas (1), (3), and (5) are as follows:

[0079]

[0080]

[0081]

[0082] The embodiment does not limit which section of the oil channel the geometric parameters are selected as the characteristic parameters.

[0083] In step S3, the piston movement speed u (t) , the displacement x (t) , and the acceleration a (t) are calculated and updated according to the following formulas:

[0084] The piston movement speed u

[0085] The piston displacement x (t) = x (t-dt) + u (t) dt;

[0086] The piston acceleration a (t) = 2 (u (t) dt - u (t-dt) dt) / dt 2 .

[0087] It should be noted that steps S2 and S3 do not have a specific execution order and can be performed simultaneously.

[0088] Step S4 calculates the average pressure on the piston surface according to the following formula

[0089]

[0090] Where F y is the pre-tightening force of the piston spring, F m is the friction force of the piston, and F c is the centrifugal force of the piston. The centrifugal force F c of the piston is calculated by the following formula:

[0091]

[0092] Where ω is the rotational angular velocity of the clutch, and r0 is the radius at which the pressure oil enters the oil cylinder.

[0093] Step S5 calculates and updates the characteristic oil flow rate according to the following formula

[0094]

[0095] Step S6 judges whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value. Specifically, the updated characteristic oil flow rate is compared with the intermediate characteristic flow rate . If the absolute value of the difference between the two is less than 1e-4 m / s, it is considered that the calculation converges, and step S7 is executed. If the absolute value of the difference is greater than or equal to 1e-4 m / s, it is considered that the calculation does not converge, and step S8 is executed.

[0096] Step S7 updates the piston displacement u (t+dt) and the piston velocity x (t+dt) at the next time according to the following formula:

[0097] u (t+dt) = u (t) + a (t) dt

[0098] x (t+dt) = x (t) + u (t) dt

[0099] Further, since the kp point stroke L is known at the time of design, the updated piston displacement x (t+dt) is compared with the kp point stroke L. If the piston displacement x (t+dt) is greater than or equal to the kp point stroke L, the time t+dt corresponding to the piston displacement x (t+dt) is taken as the clutch oil filling time. In the case where the piston displacement x (t+dt)The steps of calculating the relationship between the current time and the piston displacement within the stroke L" of the kp point can be obtained by the above calculation method, and according to the relationship, a piston displacement-time change diagram can be output, as shown in FIG. 3. Figure 2

[0100] If the piston displacement x (t+dt) is less than the stroke L of the kp point, return to step S1, set the intermediate characteristic flow rate (which is known at this time ), and re-execute steps S2-S7.

[0101] It can be known from the foregoing description that different oil filling times can be obtained by changing some clutch parameters, oil passage parameters or oil parameters, for example, changing the hydraulic diameter D n of the oil passage, and finally the clutch oil filling time will also change, therefore, the present application can also evaluate the influence of the parameter change on the oil filling time, which is beneficial to finding suitable clutch parameters, oil passage parameters and oil parameters in the design stage.

[0102] The method of the embodiment can be implemented in Matlab software or other programming software, and after inputting the related clutch parameters, oil passage parameters and oil parameters, the above calculation, judgment and other processes are executed by the program.

[0103] Corresponding to the clutch oil filling time calculation method of the first embodiment of the present application, the second embodiment of the present application also provides a clutch oil filling time calculation device, which comprises:

[0104] An initialization module is configured to select the geometric parameters of any section of the oil passage of the clutch as the characteristic parameters, and set the intermediate characteristic flow rate as the flow rate at the previous moment of the section of the oil passage;

[0105] A first calculation module is configured to calculate the total friction loss and total local loss of the oil passage at the current moment according to the characteristic parameters, the intermediate characteristic flow rate, the clutch control parameters, the clutch body parameters, the oil passage geometric parameters and the oil parameters;

[0106] A second calculation module is configured to calculate the piston movement speed, the piston displacement and the piston acceleration at the current moment;

[0107] A third calculation module is configured to calculate the average piston surface pressure at the current moment according to the piston movement speed, the piston displacement and the piston acceleration at the current moment and the clutch body parameters;

[0108] A fourth calculation module is configured to calculate the characteristic flow rate according to the clutch control parameters, the oil parameters, the average piston surface pressure at the current moment, the total friction loss and the total local loss of the oil passage at the current moment;

[0109] ​a judging module configured to judge whether an absolute value of a difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value;

[0110] an obtaining module configured to, when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than the preset threshold value, calculate a piston displacement and a piston speed at a next time point, and obtain the clutch oil filling time when the piston displacement at the next time point reaches a half engagement point stroke;

[0111] an updating module configured to, when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is greater than or equal to the preset threshold value, update the intermediate characteristic flow rate to the characteristic flow rate, and perform corresponding functions by the first calculating module, the second calculating module, the third calculating module, the fourth calculating module and the judging module again.

[0112] For working principles and processes of the computing device for the clutch oil filling time according to the embodiment, refer to the foregoing description of the first embodiment of the present application, and details are not repeated here.

[0113] The third embodiment of the present application further provides a computer readable storage medium, which comprises a stored computer program; wherein the computer program controls a device where the computer readable storage medium is located to perform the computing method for the clutch oil filling time as described above when running. Preferably, the computer program can be divided into one or more modules / units (such as computer program 1, computer program 2, …), which are stored in the memory and executed by the processor to complete the present application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe execution processes of the computer program in the device.

[0114] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can also be any conventional processor. The processor is a control center of the device, and connects various parts of the device by using various interfaces and lines.

[0115] The memory mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required by a function, etc., and the data storage area can store relevant data, etc. In addition, the memory can be a high-speed random access memory, and can also be a non-volatile memory such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., or can be another volatile solid-state storage device.

[0116] It should be noted that the above device can include, but is not limited to, a processor, a memory, and the like, which can be understood by those skilled in the art.

[0117] As can be seen from the above description, compared with the prior art, the beneficial effects of the present application are that: by using a series of empirical formula calculations instead of complex three-dimensional CFD analysis, the calculation efficiency can be greatly improved, a quick evaluation method for oil filling time is provided in the clutch design stage, the influence of changes in individual parameters on the oil filling time can be evaluated, and it is beneficial to find suitable clutch parameters, oil passage parameters, oil product parameters, etc. in the design stage.

[0118] The above disclosure is only the preferred embodiment of the present application, and of course cannot limit the scope of the right of the present application, so the equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.

Claims

1. A method of calculating oil filling time of a clutch, characterized by, The method comprises the following steps: Step S1, selecting the geometric parameters of any section of the oil passage of the clutch as characteristic parameters, and setting the intermediate characteristic flow rate as the flow rate of the section of the oil passage at the previous time; Step S2, calculating the total flow resistance loss and the total local loss of the oil passage at the current time according to the characteristic parameters, the intermediate characteristic flow rate, the clutch control parameters, the clutch body parameters, the oil passage geometric parameters and the oil parameters; Step S3, calculating the piston movement speed, the piston displacement and the piston acceleration at the current time; Step S4, calculating the average piston surface pressure at the current time according to the piston movement speed, the piston displacement and the piston acceleration at the current time and the clutch body parameters; Step S5, calculating the characteristic flow rate according to the clutch control parameters, the oil parameters, the average piston surface pressure at the current time, the total flow resistance loss and the total local loss of the oil passage at the current time; Step S6, judging whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value, if yes, executing Step S7, otherwise executing Step S8; Step S7, calculating the piston displacement and the piston speed at the next time, and obtaining the clutch oil filling time when the piston displacement at the next time reaches the half engagement point stroke; Step S8, updating the intermediate characteristic flow rate as the characteristic flow rate, and re-executing Steps S2-S6; The step S1 selects the geometric parameters of the i-th section of the oil passage of the clutch as the characteristic parameters, i∈{1, 2, 3, …}, and sets the intermediate characteristic flow rate as the flow rate of the previous moment of the section of the oil passage Initialize the characteristic flow rate before oil filling Piston acceleration a (0) = 0 m / s 2 , piston speed u (0) = 0 m / s, piston displacement x (0) = 0 m, and set the time step as dt; The clutch control parameters include spring stiffness K, kp point stroke L and design main oil pressure P t The clutch body parameters include piston outer diameter R out , piston inner diameter R in , piston area A and piston mass M; The oil passage geometric parameters include the length H n of each section of the oil passage, the hydraulic diameter D n of the oil passage and the oil passage area A n , the subscript n represents the flow passage section with different hydraulic diameters, n = 1, 2, 3, …; The oil parameters include oil viscosity μ and oil density ρ; The step S5 calculates and updates the characteristic flow rate according to the following equation wherein, P is the average piston surface pressure, is the total in-line loss of the oil gallery at time t, is the total local loss.

2. The method of claim 1, wherein, Letting the time instant t = t + dt, the step S2 calculates the total in-line loss at the time instant t according to the following formula wherein A i is the oil passage area of the i-th oil passage selected as a characteristic parameter, is the Reynolds number of the n-th oil passage at time t, is the friction loss coefficient of the n-th oil passage at time t, is the friction loss of the n-th oil passage at time t. Total local loss is calculated as follows: wherein A i is the oil passage area of the i-th oil passage selected as a characteristic parameter, ζ n is the local loss coefficient of the n-th oil passage, is the local loss of the n-th oil passage at time t.

3. The method of claim 2, wherein, Said step S3 calculates and updates the piston motion velocity u according to the following formula (t) , the displacement x (t) and the acceleration a (t) : Piston movement speed Piston displacement x (t) = x (t-dt) + u (t) dt; Piston acceleration a (t) = 2(u (t) dt-u (t-dt) dt) / dt 2 .

4. The method of claim 3, wherein, The step S4 calculates the average pressure on the piston surface according to the following formula Among them, F y F is the preload force of the piston spring. m For the frictional force of the piston, F c The centrifugal force of the piston; the centrifugal force F of the piston c Calculated using the following formula: Wherein, ω is the rotational angular velocity of the clutch, and r0 is the radius of the pressure oil entering the oil cylinder.

5. The method of claim 3, wherein, The step S6 specifically includes: comparing the updated characteristic flow rate with the intermediate characteristic flow rate and if the absolute value of the difference is less than 1e-4 m / s, executing the step S7, and if it is greater than or equal to 1e-4 m / s, executing the step S8.

6. The method of claim 5, wherein, Said step S7 updates the piston speed u at the next time instant according to the following formula (t+dt) and the piston displacement x (t+dt) : u (t+dt) = u (t) + a (t) dt x (t+dt) = x (t) + u (t) dt.

7. The method of claim 6, wherein, The step S7 further comprises: comparing the piston displacement x (t+dt) with the size of the kp point stroke L, if the piston displacement x (t+dt) is greater than or equal to the kp point stroke L, then the piston displacement x (t+dt) corresponding time t+dt as the clutch oil filling time; if the piston displacement x (t+dt) is less than the kp point stroke L, then return to step S1, set the intermediate characteristic flow rate and re-execute steps S2-S7.

8. A device for calculating oil filling time of a clutch, characterized by comprising: The method comprises the following steps: An initialization module is configured to select the geometric parameters of any section of the oil passage of the clutch as characteristic parameters, and set the intermediate characteristic flow rate as the flow rate of the section of the oil passage at the previous time; A first calculation module is configured to calculate the total flow resistance loss and the total local loss of the oil passage at the current time according to the characteristic parameters, the intermediate characteristic flow rate, the clutch control parameters, the clutch body parameters, the oil passage geometric parameters and the oil parameters; A second calculation module is configured to calculate the piston movement speed, the piston displacement and the piston acceleration at the current time; A third calculation module is configured to calculate the average piston surface pressure at the current time according to the piston movement speed, the piston displacement and the piston acceleration at the current time and the clutch body parameters; A fourth calculation module is configured to calculate the characteristic flow rate according to the clutch control parameters, the oil parameters, the average piston surface pressure at the current time, the total flow resistance loss and the total local loss of the oil passage at the current time; A judgment module is configured to judge whether the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than a preset threshold value; An obtaining module is configured to, when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is less than the preset threshold value, calculate the piston displacement and the piston speed at the next time, and obtain the clutch oil filling time when the piston displacement at the next time reaches the half engagement point stroke; An updating module is configured to, when the absolute value of the difference between the characteristic flow rate and the intermediate characteristic flow rate is greater than or equal to the preset threshold value, update the intermediate characteristic flow rate as the characteristic flow rate, and re-execute the corresponding functions of the first calculation module, the second calculation module, the third calculation module, the fourth calculation module and the judgment module. The initialization module selects the geometric parameters of the i-th section of the oil passage of the clutch as the characteristic parameters, i∈{1, 2, 3, …}, and sets the intermediate characteristic flow rate as the flow rate of the previous moment of the section of the oil passage The initialization characteristic flow rate before oil filling Piston acceleration a (0) = 0 m / s 2 Piston speed u (0) = 0 m / s, piston displacement x (0) = 0 m, and the time step is set as dt; The clutch control parameters include spring stiffness K, kp point stroke L and design main oil pressure P t The clutch body parameters include piston outer diameter R out , piston inner diameter R in , piston area A and piston mass M; the oil passage geometric parameters include the length H n of each oil passage, the hydraulic diameter D n of the oil passage and the oil passage area A n , the subscript n represents the flow passage section with different hydraulic diameters, n = 1, 2, 3, …; the oil parameters include oil viscosity μ and oil density ρ; The fourth calculation module calculates and updates the characteristic flow rate according to the following formula wherein, is the average piston surface pressure, is the total in-line loss of the oil gallery at time t, is the total local loss.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium comprises a stored computer program; wherein the computer program, when executed, controls a device in which the computer readable storage medium is located to perform the clutch oil filling time calculation method according to any one of claims 1-7.

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