A method for simulating temperature rise during slip, engagement and separation of a wet clutch

Abstract

The present invention provides a method for simulating the temperature rise of a wet clutch during slip, engagement and separation, the method comprising establishing a single friction pair geometric model of the wet clutch; establishing a computational fluid dynamics simulation analysis grid for the single friction pair geometric model; dividing the wet clutch slip, engagement and separation process into multiple stages in the fluid dynamics simulation analysis grid, setting the state of the first flow channel part and the state of the second flow channel part, the cooling flow rate and the surface heat source applied to the first flow channel part and the second flow channel part respectively for each stage, and executing multiple stages in a cycle; using the computational fluid dynamics simulation analysis grid, performing a temperature rise simulation analysis on the wet clutch to obtain the maximum temperature and average temperature curves of the steel plate and the friction lining over time. The present invention solves the problem that the flow rate provided in the existing clutch separation cooling stage is insufficient, which may cause the clutch to burn out due to excessive temperature after frequent separation and engagement cycles.

Description

Technical Field

[0001] The invention relates to the technical field of automobile simulation, and in particular to a method for simulating temperature rise during slip, engagement and separation of a wet clutch. Background Art

[0002] The wet clutch is a key power transmission component in the vehicle power system, and its cooling and lubrication conditions are very critical, because during the clutch shifting stage, sliding friction will occur between the clutch friction plate and the steel plate. If it is not properly lubricated, the clutch steel plate will turn blue, and even the clutch plate will burn and fail to transmit power. In the past, the oil supply of the clutch mainly depended on the experience of the clutch supplier. Generally speaking, more flow is required during the clutch slipping stage. Taking a certain model of clutch plate as an example, the supplier recommends that 1.5L / min~2L / min of lubricating oil should be provided during the clutch slipping stage, while the flow rate in the non-slipping stage is only 0.8L / min~1.2L / min. However, this flow rate is only a past experience value and is not targeted at specific clutch operating conditions. There may still be excessive cooling and lubrication or insufficient cooling and lubrication.

[0003] In addition, the clutch may not have overheating problems in a slip, engagement and separation cycle because the initial clutch temperature is low. However, after experiencing multiple identical or different cycles, the maximum clutch temperature will increase and reach a stable state. If the flow rate provided during the clutch separation cooling stage is insufficient, the clutch may overheat and burn after frequent separation and engagement cycles. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a temperature rise simulation method for the slip, engagement and separation processes of a wet clutch, which is used to solve the problem that insufficient flow is provided in the existing clutch separation cooling stage, which may cause the clutch to overheat and burn after frequent separation and engagement cycles.

[0005] The present invention provides a method for simulating temperature rise during sliding, engagement and separation of a wet clutch, the method comprising:

[0006] S11, establishing a single friction pair geometric model of the wet clutch, wherein the single friction pair geometric model comprises a steel sheet, a friction lining and a friction substrate, wherein the friction lining is arranged in contact with the friction substrate and faces the steel sheet, a first flow channel portion is arranged at both ends of the friction lining, and a second flow channel portion is arranged between the steel sheet and the friction lining;

[0007] S12, determining the curves of the transmission torque, the driving end speed, the driven end speed and the cooling flow rate of the wet clutch during a single sliding, engagement and separation process over time, and determining the initial temperature and cooling oil temperature of the wet clutch;

[0008] S13, establishing a computational fluid dynamics simulation analysis grid for the single friction pair geometric model;

[0009] S14, dividing the wet clutch slip, engagement and disengagement process into a plurality of stages in the fluid dynamics simulation analysis grid, setting the first flow channel portion state and the second flow channel portion state, the cooling flow rates and the surface heat source applied to the first flow channel portion and the second flow channel portion respectively for each stage, and executing the plurality of stages in a loop;

[0010] S15. Using the computational fluid dynamics simulation analysis grid, perform a temperature rise simulation analysis on the wet clutch to obtain curves of the maximum temperature and average temperature of the steel plate and the friction lining changing with time.

[0011] Furthermore, in the computational fluid dynamics simulation analysis grid, the number of grid layers in the thickness direction of each of the steel plates, each of the friction linings and each of the friction base plates is no less than two.

[0012] Furthermore, in step S14, the wet clutch slip, engagement and separation process is divided into a plurality of stages in the fluid dynamics simulation analysis grid, specifically including an engagement slip stage, a complete engagement stage, a separation process stage and a complete separation stage, wherein:

[0013] The engagement slip stage is from the initial moment of clutch engagement slip to the end moment of clutch slip, the complete engagement stage is from the end moment of clutch slip to the end moment of clutch engagement, the separation process stage is from the end moment of clutch engagement to the moment when the clutch is completely separated, and the complete separation stage is from the moment when the clutch is completely separated to the initial moment of clutch engagement slip in the next cycle.

[0014] Furthermore, the step of setting the state of the first flow channel portion and the state of the second flow channel portion, the cooling flow rates respectively applied by the first flow channel portion and the second flow channel portion, and the surface heat source for each stage specifically includes:

[0015] At the initial moment of engagement and slipping of the clutch, the second flow channel portion is not activated, and the steel plate is displaced toward the friction lining until it just contacts the friction lining;

[0016] In the engagement slip stage, from the initial moment of engagement slip of the clutch to the end moment of clutch slip, a surface heat source q(t, r) that varies with time t and contact surface radius r is applied between the contact surface of the steel plate and the friction lining, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0017] In the fully engaged stage, from the moment when the clutch slip ends to the moment when the clutch engagement ends, the second flow channel portion continues to be inactivated, the surface heat source applied between the steel plate and the friction lining contact surface is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0018] In the separation process stage, from the moment when the clutch engagement ends to the moment when the clutch is completely separated, the second flow channel portion continues to be inactivated, the surface heat source applied between the contact surface of the steel plate and the friction lining is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0019] When the clutch is completely disengaged, the second flow channel is activated to displace the steel plate in a direction opposite to the friction lining to a position just in the disengagement state;

[0020] In the complete separation stage, from the moment the clutch is completely separated to the initial moment of engagement and slipping of the clutch in the next cycle, the second flow channel portion continues to be activated, the surface heat source applied between the steel plate and the friction lining contact surface is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, a cooling flow Qc(t) is applied at the inlet of the first flow channel portion, and a cooling flow Qδ(t) is applied at the inlet of the second flow channel portion, and Qδ(t)=Q(t)-Qc(t).

[0021] Furthermore, the calculation formula of the surface heat source q(t, r) is specifically:

[0022] The M(t) is the transmission torque, the r is the contact surface radius of the steel plate and the friction lining, the Δω(t) is the speed difference between the driving end speed and the driven end speed, the A is the contact area between the steel plate and the friction lining, the a is the number of friction pairs of the wet clutch, and the r m is the average radius of the friction lining.

[0023] The implementation of the present invention has the following beneficial effects:

[0024] Through the present invention, according to the preset transmission torque, active end speed, driven end speed change curve with time and cooling flow, the steel plate temperature and friction lining temperature changes of the wet clutch in multiple sliding, engagement and separation processes are simulated and calculated. When the simulation shows that the temperature is too high, the transmission torque, active end speed, driven end speed, cooling flow and other related parameters can be adjusted in reverse to reduce the temperature rise of multiple sliding cycles, so as to solve the problem that the flow provided in the existing clutch separation cooling stage is insufficient, which may cause the clutch to have too high temperature and burn the plate after frequent separation and engagement cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flow chart of a method for simulating temperature rise during slip, engagement and separation of a wet clutch provided by an embodiment of the present invention.

[0027] Figure 2 It is a structural diagram of a single friction pair geometric model provided by an embodiment of the present invention.

[0028] Figure 3 It is a time curve diagram of torque transmission during a single sliding, engagement and separation process provided by an embodiment of the present invention.

[0029] Figure 4 It is a time curve diagram of the driving end rotation speed during a single sliding, engagement and separation process provided by an embodiment of the present invention.

[0030] Figure 5 It is a time curve diagram of the rotation speed of the driven end during a single sliding, engagement and separation process provided by an embodiment of the present invention.

[0031] Figure 6 It is a time curve diagram of the temperature of the steel sheet during multiple sliding, combining and separating processes provided by an embodiment of the present invention.

[0032] Figure 7 It is a time curve diagram of the friction lining temperature during multiple sliding, engagement and separation processes provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In this patent, the relationship between the steel sheet temperature and the friction lining temperature and time is simulated and calculated, and active intervention is performed when the steel sheet temperature or the friction lining temperature is too high. The specific implementation method is further described below in conjunction with the accompanying drawings and examples.

[0034] like Figure 1 As shown, an embodiment of the present invention provides a method for simulating temperature rise during slip, engagement and separation of a wet clutch, the method comprising:

[0035] S11. Establishing a single friction pair geometric model of the wet clutch.

[0036] refer to Figure 2 , Figure 2 The friction pair geometric model of the wet clutch is shown, and the single friction pair geometric model includes a steel plate, a friction lining and a friction base plate, wherein the friction lining is arranged in contact with the friction base plate and faces the steel plate, a first flow channel portion is arranged at both ends of the friction lining, and a second flow channel portion is arranged between the steel plate and the friction lining. The first flow channel portion and the second flow channel portion are used to supply oil to lubricate and cool the wet clutch.

[0037] S12, determining the curves of the change of the torque transmitted, the driving end speed, the driven end speed and the cooling flow rate of the wet clutch over time during a single sliding, engagement and separation process, and determining the initial temperature and cooling oil temperature of the wet clutch.

[0038] It should be noted that there is no restriction on the order of step S11 and step S12.

[0039] refer to Figure 3 , Figure 4 and Figure 5 , Figure 3 , Figure 4 and Figure 5 The curves showing the changes of the transmission torque, the driving end speed and the driven end speed with time during single sliding, engagement and separation are shown respectively, and the cooling flow rate does not change with time.

[0040] S13, establishing a computational fluid dynamics simulation analysis grid for the single friction pair geometric model.

[0041] It should be noted that in the computational fluid dynamics simulation analysis grid, the number of grid layers in the thickness direction of each steel plate, each friction lining and each friction substrate is no less than two. The purpose of this setting is to ensure the accuracy of the calculation results in subsequent steps.

[0042] S14. Divide the wet clutch slip, engagement and disengagement processes into a plurality of stages in the fluid dynamics simulation analysis grid, set the state of the first flow channel portion and the state of the second flow channel portion, the cooling flow rates and the surface heat source respectively applied to the first flow channel portion and the second flow channel portion for each stage, and execute the plurality of stages in a loop.

[0043] Specifically, the wet clutch slip, engagement and separation process is divided into multiple stages in the fluid dynamics simulation analysis grid, and the multiple stages include an engagement slip stage, a complete engagement stage, a separation process stage and a complete separation stage, wherein:

[0044] The engagement slip stage is from the initial moment of clutch engagement slip to the end moment of clutch slip, the complete engagement stage is from the end moment of clutch slip to the end moment of clutch engagement, the separation process stage is from the end moment of clutch engagement to the moment when the clutch is completely separated, and the complete separation stage is from the moment when the clutch is completely separated to the initial moment of clutch engagement slip in the next cycle.

[0045] Furthermore, the step of setting the states of the first flow channel portion and the second flow channel portion, the cooling flow rates respectively applied by the first flow channel portion and the second flow channel portion, and the surface heat source for each stage specifically includes:

[0046] From the initial moment when the clutch engages and slips, the second flow channel portion is not activated, and the steel plate is displaced toward the friction lining until it just contacts the friction lining;

[0047] In the engagement slip stage, from the initial moment of engagement slip of the clutch to the end moment of clutch slip, a surface heat source q(t, r) that varies with time t and contact surface radius r is applied between the contact surface of the steel plate and the friction lining, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0048] It should be noted that in the engagement slip stage, at the initial moment of engagement slip of the clutch, the speed difference between the driving end speed and the driven end speed is the largest, and at the end of clutch slip, the speed difference between the driving end speed and the driven end speed is the smallest.

[0049] It should be further explained that the active end refers to the steel sheet, and the passive end refers to the friction lining.

[0050] It should also be noted that the calculation formula for the surface heat source q(t, r) is specifically:

[0051] The M(t) is the transmission torque, the r is the contact surface radius of the steel plate and the friction lining, the Δω(t) is the speed difference between the driving end speed and the driven end speed, the A is the contact area between the steel plate and the friction lining, the a is the number of friction pairs of the wet clutch, and the r m is the average radius of the friction lining.

[0052] In the fully engaged stage, from the moment when the clutch slip ends to the moment when the clutch engagement ends, the second flow channel portion continues to be inactivated, the surface heat source applied between the steel plate and the friction lining contact surface is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0053] It should be noted that, in the fully engaged stage, the rotation speed of the driving end is equal to the rotation speed of the driven end.

[0054] In the separation process stage, from the moment when the clutch engagement ends to the moment when the clutch is completely separated, the second flow channel portion continues to be inactivated, the surface heat source applied between the contact surface of the steel plate and the friction lining is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion;

[0055] It should be noted that the moment when the clutch is completely disengaged refers to the moment when the steel plate and the friction lining just break away from contact. At this time, the speed of the driven end drops to zero, while the driving end still maintains the original driving end speed.

[0056] When the clutch is completely disengaged, the second flow channel is activated to displace the steel plate in a direction opposite to the friction lining to a position just in the disengagement state;

[0057] In the complete separation stage, from the moment the clutch is completely separated to the initial moment of engagement and slipping of the clutch in the next cycle, the second flow channel portion continues to be activated, the surface heat source applied between the steel plate and the friction lining contact surface is 0, the active end rotates according to the active end speed and the driven end does not rotate, a cooling flow Qc(t) is applied at the inlet of the first flow channel portion, and a cooling flow Qδ(t) is applied at the inlet of the second flow channel portion, and Qδ(t)=Q(t)-Qc(t).

[0058] It should be noted that the Qc(t) calculation formula is specifically:

[0059] Q c (t) = Q(t) × A c / (A c +A δ ), Q(t) is the curve of the change of cooling flow rate over time, A c is the inlet area of ​​the first flow channel, and A δ is the inlet area of ​​the second flow channel.

[0060] In this embodiment, combined with Figure 3 , Figure 4 and Figure 5 , during the slip, engagement and separation process of the wet clutch, one cycle is 14s, the transmission torque M(t) is 150Nm in the time period from 0s to 8s, linearly decreases from 150Nm to 0Nm in the time period from 8s to 8.3s, and remains at 0Nm in the time period from 8.3s to 14s; the active end speed ω1(t) is maintained at 1200rpm in one cycle, the driven end speed ω2(t) rises linearly from 0rpm to 1200rpm between 0s and 2s, then maintains 1200rpm from 2s to 8s, and linearly decreases from 1200rpm to 0rpm between 8s and 8.3s; the cooling flow curve Q(t), in this example, is maintained at 1L / min in one cycle; the number of cycles n=6, and the transmission torque, active end speed, driven end speed and flow changes in each cycle are the same. In this example, the clutch initial temperature T0 and the cooling oil temperature Toil of the clutch are both 120°C; the second flow channel part is activated at 8.3s, and the steel plate is displaced in the opposite direction of the friction lining to a position just in the separation state. The cooling flow rate applied at the inlet of the first flow channel part is changed to 0.65L / min, and the cooling flow rate of 0.35L / min is applied at the inlet of the flow channel between the steel plate and the friction lining.

[0061] S15. Using the computational fluid dynamics simulation analysis grid, perform a temperature rise simulation analysis on the wet clutch to obtain curves of the maximum temperature and average temperature of the friction lining and the friction substrate changing with time.

[0062] By performing simulation analysis on the embodiment described in the above step S14, curves of the maximum temperature and the average temperature of the steel plate and the friction lining changing with time are obtained respectively; Figure 6 is the maximum temperature and average temperature variation curve of the steel sheet, Figure 7 It is the maximum temperature and average temperature variation curve of the friction lining.

[0063] It should be further explained that if the simulation calculation shows that the temperature of the steel plate or friction lining is too high, it is necessary to actively intervene in the relevant parameters determined in step S12 so that the simulation calculation result of the final step S15 ensures that the wet clutch can operate stably without the problem of excessive temperature of the steel plate or friction lining.

[0064] The implementation of the present invention has the following beneficial effects:

[0065] Through the present invention, according to the preset transmission torque, active end speed, driven end speed change curve with time and cooling flow, the steel plate temperature and friction lining temperature changes of the wet clutch in multiple sliding, engagement and separation processes are simulated and calculated. When the simulation shows that the temperature is too high, the transmission torque, active end speed, driven end speed, cooling flow and other related parameters can be adjusted in reverse to reduce the temperature rise of multiple sliding cycles, so as to solve the problem that the flow provided in the existing clutch separation cooling stage is insufficient, which may cause the clutch to have too high temperature and burn the plate after frequent separation and engagement cycles.

[0066] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for simulating temperature rise during sliding, engagement and separation of a wet clutch, characterized in that: The method comprises: S11, establishing a single friction pair geometric model of the wet clutch, wherein the single friction pair geometric model comprises a steel sheet, a friction lining and a friction substrate, wherein the friction lining is arranged in contact with the friction substrate and faces the steel sheet, a first flow channel portion is arranged at both ends of the friction lining, and a second flow channel portion is arranged between the steel sheet and the friction lining; S12, determining the curves of the transmission torque, the driving end speed, the driven end speed and the cooling flow rate of the wet clutch during a single sliding, engagement and separation process over time, and determining the initial temperature and cooling oil temperature of the wet clutch; S13, establishing a computational fluid dynamics simulation analysis grid for the single friction pair geometric model; S14, in the fluid dynamics simulation analysis grid, the slip, engagement and separation process of the wet clutch is divided into a plurality of stages, the plurality of stages including an engagement slip stage, a complete engagement stage, a separation process stage and a complete separation stage; at the initial moment of engagement slip of the clutch, the second flow channel portion is not activated, and the steel plate is displaced toward the friction lining until it is just in contact with the friction lining; in the engagement slip stage, from the initial moment of engagement slip of the clutch to the end moment of clutch slip, a surface heat source q(t, r) that varies with time t and contact surface radius r is applied between the contact surface of the steel plate and the friction lining, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion; in the complete engagement stage, from the end moment of clutch slip to the end moment of clutch engagement, the second flow channel portion is continuously not activated, the surface heat source applied between the steel plate and the friction lining contact surface is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and in the first A cooling flow Q(t) is applied at the inlet position of a flow channel portion; in the separation process stage, from the moment when the clutch engagement ends to the moment when the clutch is completely separated, the second flow channel portion is continuously inactivated, the surface heat source applied between the contact surface of the steel plate and the friction lining is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, and a cooling flow Q(t) is applied at the inlet position of the first flow channel portion; at the moment when the clutch is completely separated, the second flow channel portion is activated to displace the steel plate in the opposite direction to the friction lining to a position in a just-separated state; in the complete separation stage, from the moment when the clutch is completely separated to the initial moment when the clutch engages and slips in the next cycle, the second flow channel portion is continuously activated, the surface heat source applied between the contact surface of the steel plate and the friction lining is 0, the active end rotates according to the active end speed and the driven end rotates according to the driven end speed, a cooling flow Qc(t) is applied at the inlet position of the first flow channel portion, and a cooling flow Qδ(t) is applied at the inlet of the second flow channel portion, wherein Qδ(t)=Q(t)-Qc(t); S15. Using the computational fluid dynamics simulation analysis grid, perform a temperature rise simulation analysis on the wet clutch to obtain curves of the maximum temperature and average temperature of the steel plate and the friction lining changing with time.

2. The method according to claim 1, characterized in that: In the computational fluid dynamics simulation analysis grid, the number of grid layers in the thickness direction of each of the steel plates, each of the friction linings and each of the friction base plates is no less than two.

3. The method according to claim 1, characterized in that: The calculation formula of the surface heat source q(t, r) is specifically: The M(t) is the transmission torque, the r is the contact surface radius of the steel plate and the friction lining, the Δω(t) is the speed difference between the driving end speed and the driven end speed, the A is the contact area between the steel plate and the friction lining, the a is the number of friction pairs of the wet clutch, and the r m is the average radius of the friction lining.

4. The method according to claim 1, characterized in that: The Qc(t) calculation formula is specifically: Q c (t) = Q(t) × A c / (A c +A δ ), Q(t) is the curve of the change of cooling flow rate over time, A c is the inlet area of ​​the first flow channel, and A δ is the inlet area of ​​the second flow channel.

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