HEAT LOAD ESTIMATE DEVICE AND HEAT LOAD ESTIMATE METHOD FOR FRICTION ENGINE ELEMENT

Abstract

A heat load estimating device (40) for a friction engagement element (C1, C2, B1, B2) applied to a vehicle comprising a transmission (26) which includes the friction engagement element (C1, C2, B1, B2) operating with hydraulic pressure, and which is designed to estimate a heat load (y1, y2) when at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element (C1, C2, B1, B2) at the time of shifting the transmission (26) is considered to be the heat load (y1, y2), wherein the heat load estimating device (40) comprises: a storage device (46) designed to store mapping data (DM) defining a mapping, wherein the mapping comprises as an input variable (x) a speed variable (x1) which is a variable indicating a relative speed (Nr) of elements of the friction engagement element (C1, C2, B1, B2) rotating relative to each other during the shifting operation of the transmission (26), and a hydraulic pressure variable (x2) which is a variable indicating the hydraulic pressure applied to the friction engagement element (C1, C2, B1, B2) during the shifting operation of the transmission (26), and comprising as an output variable (y) the heat load (y1, y2); and an execution device (42, 44) designed to perform a calculation process for calculating a value of the output variable (y) by determining a value of the input variable (x) and entering the value into the figure and a change process for changing an execution mode of the calculation process during the shifting operation of the transmission (26), where: a time period from the start of a torque phase to the completion of the shifting process in the transmission (26) is divided into several predetermined time periods (Z1-Z4); the storage device (46) is designed to store several of the imaging data (DM), each defining the different imaging according to the time interval; and the execution device (42, 44) is designed to perform a process for selecting the mapping data (DM) according to the time interval when the calculation process is executed, as the change process.

Description

[0001] The present invention relates to a heat load estimation device and a heat load estimation method for a friction engagement element.

[0002] JP 2010-38225 A describes a device that estimates the temperature of a friction engagement element based on the relative rotational speed of elements of the friction engagement element rotating relative to each other, the input torque of the friction engagement element, and the motor speed.

[0003] For a better understanding of the present invention, reference is also made to US 2004 / 0242360A1 and US 8744706B2.

[0004] For the friction engagement element, it is desirable to accurately estimate the heat load, such as temperature, heat generation or development quantity, or seizing / friction welding or non-seizing. Therefore, the present invention provides a heat load estimation device and a heat load estimation method that accurately estimate the heat load, such as temperature, heat generation quantity, or seizing or non-seizing, in the friction engagement element.

[0005] A first aspect of the present invention relates to a device applied to a vehicle comprising a transmission including a friction engagement element operating under hydraulic pressure, and designed to estimate a thermal load when at least one of the following is considered to be the thermal load: temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element at the time of transmission shifting. This thermal load estimating device for the friction engagement element comprises an implementing device and a storage device. The storage device is designed to store mapping data that defines a mapping.The diagram includes, as an input variable, a speed variable, which is a variable indicating the relative speed of elements of the friction engagement element that rotate relative to each other during the transmission shifting process, and a hydraulic pressure variable, which is a variable indicating the hydraulic pressure applied to the friction engagement element during the transmission shifting process. The output variable is the thermal load. The device is designed to perform a calculation process to determine a value of the output variable by determining a value of the input variable and inputting that value into the diagram, and a modification process to change the execution mode of the calculation process during the transmission shifting process, specifically within a time span from the start of a torque phase to its completion.The end of the shifting process in the transmission can be divided into several predetermined time intervals. The storage device can be designed to store multiple mapping data sets, each defining a different mapping according to the time interval. The execution device can be designed to perform a process for selecting the mapping data according to the time interval when the calculation process is executed.

[0006] The higher the relative rotational speed between elements of the friction engagement component that rotate relative to each other, the greater the amount of heat generated by the friction engagement component. Furthermore, the amount of heat generated by the friction engagement component increases with the hydraulic pressure applied to the friction engagement component during the switching process. Therefore, according to the heat load estimation device for the friction engagement component of the first aspect, the rotational speed variable, which represents the relative rotational speed in relation to the amount of heat generated in the friction engagement component during the switching process, and the hydraulic pressure variable, which represents the hydraulic pressure, are used as input variables. These input variables are fed into the diagram defined by the diagram data to calculate the heat load described above.Since the state of the friction element changes from the released state to the engaged state during the switching process, the heat generation state of the friction element also changes in different ways during the switching process. Therefore, the execution mode of the calculation process for determining the heat load during the switching process is modified. Consequently, the heat load of the friction element can be estimated accurately.

[0007] Since, according to the heat load estimation device for the friction engagement element of the first aspect, the imaging data can be specialized for the respective predetermined time periods, the heat load of the friction engagement element can be estimated exactly.

[0008] In the thermal stress estimation device for the friction element of the first aspect, several of the time intervals can include at least a first, second, third, or fourth time interval. Here, the first time interval can be the period from the start of the torque phase until the friction element's engagement gap in the transmission is cleared. The second time interval can be the period from the closing of the friction element's engagement gap until the start of an inertia phase in the transmission. The third time interval can be the period from the start of the inertia phase until a differential value of the rotational speed of an input shaft of the transmission is equal to or less than a certain value.The fourth time period can be a time period after the difference value of the input shaft rotational speed becomes equal to or less than the determined value and until the input shaft rotational speed reaches a synchronous speed after the switching process is completed.

[0009] The inventors of the present invention have confirmed that the heat generation state of the friction engagement element differs during the switching process in each of the first, second, third, and fourth time intervals. Therefore, according to the heat load estimation device for the friction engagement element of the first aspect, the heat load in each time interval can be accurately estimated by considering at least one of the first to fourth time intervals as the aforementioned multiple time intervals.

[0010] In the heat load estimation device for the friction engagement element of the first aspect, the execution device can be designed to prevent input of the input variable into the figure from the start of the application of hydraulic pressure to the friction engagement element until the start of a torque phase in the gearbox (26) as the change process, and the execution device can be designed to perform a process for inputting the input variable into the figure after the start of the torque phase.

[0011] When the shifting process is initiated, the friction element is subjected to hydraulic pressure. However, until the torque phase in the transmission begins, no sliding occurs between the rotating elements of the friction element, making heat generation unlikely. Therefore, according to the first aspect of the heat load estimation device for the friction element, input variables into the diagram are prohibited during the period when heat generation in the friction element is unlikely, i.e., until the start of the torque phase. After the start of the torque phase, when heat is generated in the friction element, the input variables are allowed into the diagram.Therefore, when calculating the heat load, the time period in which heat generation by the friction engagement element is unlikely is excluded, so that the heat load of the friction engagement element can be estimated exactly.

[0012] In the heat load estimator for the friction element of the first aspect, the input variable can include an oil temperature variable, which is a variable indicating the temperature of the hydraulic oil supplied to the friction element. If the temperature of the hydraulic oil changes, the ambient temperature of the friction element changes, thus changing the amount of heat generated by the friction element.

[0013] Since the oil temperature variable is included in the input variable of the heat load estimation device for the friction element of the first aspect, the heat load is calculated taking into account the influence of the hydraulic oil temperature on the amount of heat generated. Therefore, the heat load can be calculated with higher accuracy than if the oil temperature variable were not included in the input variable.

[0014] In the heat load estimation device for the friction engagement element of the first aspect, the hydraulic pressure applied to the friction engagement element can be changed so that the hydraulic pressure is higher the higher the output torque of a drive motor of the vehicle, and the input variable includes a torque variable that is a variable indicating the output torque.

[0015] According to the heat load estimation device for the friction engagement element of the first aspect, an increase in hydraulic pressure when the output torque of the drive motor is high, for example in a situation where sudden acceleration is required, shortens the time the friction engagement element needs to change from the disengaged state to the engaged state. This, in turn, reduces the time required for shifting and enables faster shifting. Here, if the hydraulic pressure is variably adjusted according to the output torque, the output torque depends on the amount of heat generated by the friction engagement element. In this respect, the heat load is calculated in the same configuration, taking into account the influence of the output torque on the amount of heat generated, since the torque variable is included in the input variable.Therefore, the heat load can be calculated with higher accuracy than if the torque variable is not included in the input variable.

[0016] In the heat load estimation device for the friction engagement element of the first aspect, the transmission can include several of the friction engagement elements, and the input variable can include a switching variable that specifies the friction engagement elements that are brought into engagement during the switching operation.

[0017] Since, according to the heat load estimation device for the friction engagement element of the first aspect, the input variable includes the switching variable, the heat load of the friction engagement elements that come into engagement during the switching process can be calculated exactly.

[0018] A second aspect of the present invention relates to a heat load estimation method for a friction engagement element, applied to a vehicle comprising a transmission containing the friction engagement element operating with hydraulic pressure, and estimating a heat load when at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element at the time of transmission shifting is considered the heat load, wherein the period from the start of a torque phase to the completion of the shifting operation in the transmission is divided into several predetermined time intervals. The above heat load estimation method comprises: (i) storing mapping data defining a mapping, wherein the mapping takes as an input variable a speed variable, which is a variable representing a relative speed of elements of the friction engagement element,(ii) specifies the rotation of the friction engagement element relative to each other during the transmission shifting process, and includes a hydraulic pressure variable, which is a variable that specifies the hydraulic pressure applied to the friction engagement element during the transmission shifting process, and includes the heat load as an output variable, wherein several of the mapping data, each defining a different mapping, can be stored according to each of the several time periods; (ii) execute a computation process to calculate a value of the output variable by determining a value of the input variable and inputting the value into the mapping; and (iii) execute a modification process to change a mode of the computation process during the transmission shifting process, wherein the modification process can be a process for selecting the mapping data according to each of the several time periods when the computation process is executed.

[0019] According to the heat load estimation method for the friction element of the second aspect, the rotational speed variable, which specifies the relative rotational speed with respect to the amount of heat generated in the friction element during the switching operation, and the hydraulic pressure variable, which specifies the hydraulic pressure, are used as input variables. These input variables are fed into the diagram defined by the diagram data to calculate the heat load described above. Since the state of the friction element changes from the disengaged state to the engaged state during the switching operation, the heat generation state of the friction element changes in different ways during the switching operation. Thus, the execution mode of the calculation process for calculating the heat load during the switching operation is modified. Therefore, the heat load of the friction element can be estimated accurately.

[0020] Another aspect of the present invention relates to a device applied to a vehicle comprising a transmission including a friction engagement element operating under hydraulic pressure, and designed to estimate a thermal load when at least one of the following is considered to be the thermal load: temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element at the time of transmission shifting. This thermal load estimating device for the friction engagement element comprises an implementing device and a storage device. The storage device is designed to store mapping data that defines a mapping.The diagram includes as an input variable a speed variable, which is a variable that indicates a relative speed of elements of the friction engagement element that rotate relative to each other during the shifting process of the transmission, and a hydraulic pressure variable, which is a variable that indicates the hydraulic pressure with which the friction engagement element is subjected during the shifting process of the transmission, and as an output variable the heat load.The execution device is designed to perform a calculation process for determining a value of the output variable by determining a value of the input variable and entering the value into the diagram, and a modification process for changing an execution mode of the calculation process during the transmission shifting operation, wherein the execution device is designed to prevent input of the input variable into the diagram from the start of the hydraulic pressure supply to the friction engagement element until the start of a torque phase in the transmission; and the execution device is designed to perform a process for entering the input variable into the diagram after the start of the torque phase.

[0021] Another aspect of the present invention relates to a heat load estimation method for a friction engagement element, which is applied to a vehicle comprising a transmission containing the friction engagement element operating with hydraulic pressure, and which estimates a heat load when at least one temperature, one heat generation quantity, or one seizing or non-seizing in the friction engagement element at the time of transmission shifting is considered the heat load, wherein the heat load estimation method is characterized in that it comprises: storing mapping data defining a mapping, wherein the mapping as an input variable is a speed variable, which is a variable indicating a relative speed of elements of the friction engagement element that rotate relative to each other during the transmission shifting process, and a hydraulic pressure variable, which is a variable indicating the hydraulic pressure.the friction engagement element is subjected to pressure during the transmission's shifting process, and includes the heat load as an output variable; executing a calculation process to determine a value of the output variable by determining a value of the input variable and inputting the value into the diagram; and executing a modification process to change a mode of the calculation process during the transmission's shifting process, wherein the execution device is designed to prevent input of the input variable into the diagram from the start of the hydraulic pressure supply to the friction engagement element until the start of a torque phase in the transmission as the modification process; and the execution device is designed to execute a process for inputting the input variable into the diagram after the start of the torque phase.

[0022] The following describes the features, advantages, and technical and industrial significance of exemplary embodiments of the invention with reference to the accompanying drawings, in which the same reference numerals denote the same elements and wherein: Fig. 1 a diagram showing a configuration of a heat load estimating device for a friction engagement element according to an embodiment as an example of the present invention; Fig. 2 is a block diagram showing a process carried out by a control device according to the embodiment; Fig. 3A is a time diagram showing a change in a setpoint translation ratio up to the time of switching of the embodiment; Fig. 3B is a timing diagram showing a change in an input wave speed up to the time of switching; Fig. 3C is a time graph showing a change in output torque up to the time of switching; Fig. 3D is a time diagram that shows a change in a hydraulic pressure setpoint up to the time of switching; Fig. 3E is a time diagram showing a change in a unit of heat generation up to the time of switching; Fig. 3F is a time graph that shows a change in the total amount of heat generated up to the time of switching; Fig. 4 is a flowchart showing a procedure of a process carried out by the control device according to the embodiment; and Fig. 5 is a flowchart showing a procedure of a process carried out by the control device according to the embodiment.

[0023] The following are embodiments relating to a heat load estimation device and a heat load estimation method for a friction engagement element with reference to the Fig. 1 to 5 described. As it is in Fig. As shown in Figure 1, a power splitting device 20 is mechanically connected to a crankshaft 12 of an internal combustion engine 10 of the vehicle VC. The power splitting device 20 divides the power of the internal combustion engine 10, a first motor-generator 22, and a second motor-generator 24. The power splitting device 20 includes a planetary gear mechanism. The crankshaft 12 is mechanically connected to a carrier CR of the planetary gear mechanism, a rotating shaft 22a of the first motor-generator 22 is mechanically connected to a sun gear S, and a rotating shaft 24a of the second motor-generator 24 and an input shaft 27 in an automatic transmission 26 are mechanically connected to a ring gear R. The output voltage of a first inverter 23 is applied to the terminal of the first motor-generator 22. The output voltage of a second inverter 25 is applied to the terminal of the second motor-generator 24.

[0024] The automatic transmission 26 is a multi-stage transmission comprising several hydraulically actuated friction engagement elements, such as a first clutch C1, a second clutch C2, a first brake B1 and a second brake B2, several planetary gear mechanisms, and a one-way clutch F1. In the automatic transmission 26, the gear stage can be selected by combining the engaged and disengaged states of the first clutch C1, the second clutch C2, the first brake B1, and the second brake B2, as well as the combination of the rotation limiting and rotation enabling states controlled by the one-way clutch F1. The automatic transmission 26 of the present embodiment is a transmission with four forward gears and one reverse gear. However, the number of gears can be changed as needed.

[0025] The basic structure of the friction engagement element is almost identical and is a well-known design. Specifically, the friction engagement element consists of a first plate and a second plate, which rotate relative to each other, arranged alternately, and a friction material is attached to one of the plates. When the friction engagement element is not subjected to hydraulic pressure, the first and second plates are separated, and torque transmission between them is interrupted.

[0026] However, when the friction element is subjected to hydraulic pressure, the engagement clearance PCtc, which is the clearance between the first and second plates, is eliminated. This brings the friction element into the state immediately before engagement, i.e., into a contact or packing state. If, after this contact, the hydraulic pressure is further increased, the first and second plates begin to engage with each other, so that the relative rotational speed of the first and second plates gradually decreases and the torque capacity of the friction element increases. Finally, when the relative rotational speed between the first and second plates becomes zero, the friction element is in a fully engaged state.

[0027] Drive wheels 30 are mechanically connected to an output shaft 27 of the automatic transmission 26. Furthermore, an output shaft 32a of an oil pump 32 is mechanically connected to the carrier CR. The oil pump 32 circulates the oil in an oil pan 34 as lubricating oil to the power splitting device 20 and supplies it to the automatic transmission 26 as hydraulic oil. The pressure of the hydraulic oil delivered by the oil pump 32 is adjusted by a hydraulic pressure control circuit 28 in the automatic transmission 26, and the hydraulic oil is used, for example, to supply hydraulic pressure to the friction engagement element or to apply hydraulic pressure to the friction engagement element. The hydraulic pressure control circuit 28 comprises several solenoid valves 28a and is a circuit that regulates the flow state of the hydraulic oil and the hydraulic pressure of the hydraulic oil by energizing the respective solenoid valves 28a.

[0028] A control device 40 controls the internal combustion engine 10 and actuates various operating units of the internal combustion engine 10 to regulate torque, exhaust gas component ratio, and the like, the controlled variables of which are . Furthermore, the control device 40 controls the first motor-generator 22 and actuates the first inverter 23 to regulate torque, speed, and the like, the controlled variables of which are . Furthermore, the control device 40 controls the second motor-generator 24 and actuates the second inverter 25 to control torque, speed, and the like, the controlled variables of which are .

[0029] When the control device 40 controls the above-mentioned controlled variables, the control device 40 refers to the output signal Scr of a crank angle sensor 50, the output signal Sm1 of a first rotation angle sensor 52, which detects the rotation angle of the rotating shaft 22a of the first motor generator 22, and the output signal Sm2 of a second rotation angle sensor 54, which detects the rotation angle of the rotating shaft 24a of the second motor generator 24. Furthermore, the control device 40 refers to the oil temperature Toil, which is the temperature of the hydraulic oil detected by an oil temperature sensor 56, the vehicle speed SPD detected by a vehicle speed sensor 58, and the accelerator actuation amount ACCP, which is the depressurization amount of an accelerator pedal 60 detected by an accelerator sensor 62.

[0030] The control device 40 comprises a central processing unit (CPU) 42, a read-only memory (ROM) 44, a storage device 46, which is an electrically rewritable, non-volatile memory, and a peripheral circuit 48, which can communicate with each other via a local network 49. Here, the peripheral circuit 48 includes a circuit that generates a clock signal defining the internal operation, a power supply circuit, a reset circuit, and the like. The control device 40 controls the control variables when the CPU 42 executes the program stored in the ROM 44. The CPU 42 and the ROM 44 form an execution device.

[0031] Fig. Figure 2 shows a process that is carried out by the control device 40. The in Fig. The process shown in 2 is realized when the CPU 42 repeatedly executes the program stored in the ROM 44, for example in a predetermined cycle.

[0032] The drive torque setting process M6 is a process for receiving the accelerator actuation amount ACCP as an input and setting the drive torque setpoint Trq*, which is a setpoint of the torque to be applied to the drive wheels 30, to a larger value when the accelerator actuation amount ACCP is comparatively large.

[0033] The drive force distribution process M8 is a process for setting the torque setpoint Trqe* for the internal combustion engine 10, the torque setpoint Trqm1* for the first motor-generator 22, and the torque setpoint Trqm2* for the second motor-generator 24 based on the drive torque setpoint Trq*. The torque corresponding to these torque setpoints Trqe*, Trqm1*, and Trqm2* is generated by the internal combustion engine 10, the first motor-generator 22, and the second motor-generator 24, respectively, so that the torque applied to the drive wheels 30 is the value corresponding to the drive torque setpoint Trq*.

[0034] In the gear ratio setpoint adjustment process M10, the gear ratio setpoint Vsft*, which is the setpoint of the gear ratio of the automatic transmission 26, and a shift variable ΔVsft, which indicates whether the gear ratio is being shifted up or down, are set based on the drive torque setpoint Trq* and the vehicle speed SPD. Thus, for example, if the gear ratio setpoint Vsft* indicates third gear and the shift variable ΔVsft indicates upshifting, this means that the shift type is a shift from third gear to fourth gear. The gear ratio setpoint Vsft* and the shift variable ΔVsft are shift variables that indicate the friction engagement element that is brought into engagement during shifting.

[0035] The hydraulic pressure setpoint adjustment process M12 calculates the oil pressure setpoint P0*, which is the base value of the hydraulic pressure setpoint set by the solenoid valves used for switching. This calculation is based on the drive torque setpoint Trq*, the oil temperature Toil, the gear ratio setpoint Vsft*, and the switching variable ΔVsft when the gear ratio is switched. This hydraulic pressure setpoint adjustment process M12 is implemented when the CPU 42 performs a map calculation of the hydraulic pressure setpoint P0* in a state where the map data, in which the drive torque setpoint Trq*, the gear ratio setpoint Vsft*, the switching variable ΔVsft, and the oil temperature Toil are input variables and the oil pressure setpoint P0* is an output variable, is pre-stored in ROM 44.When the drive torque setpoint Trq* is high, for example in a situation requiring sudden acceleration, the time required for the friction engagement element to disengage and move from the disengaged state to the engaged state is reduced by increasing the hydraulic pressure. This shortens the shifting time and enables faster shifting. Therefore, when the drive torque setpoint Trq* is high, the calculated hydraulic pressure setpoint P0* is set to a higher pressure than when the drive torque setpoint Trq* is low. Furthermore, the hydraulic pressure setpoint adjustment process M12 calculates the final hydraulic pressure setpoint P* by adjusting the hydraulic pressure setpoint P0* with various values.

[0036] The current conversion process M18 is a process for converting the hydraulic pressure setpoint P* into the current setpoint I*, which is the setpoint of the current flowing through the solenoid valves 28a. When the value of the gear ratio setpoint Vsft* changes, the control device 40 changes the current setpoint I* of the solenoid valves 28a corresponding to the friction engagement element, whose engagement is initiated in accordance with the gear ratio setpoint Vsft* and the switching variable ΔVsft, thus switching the friction engagement element from the released state to the engaged state.

[0037] The Fig. 3A to 3F show changes in various values ​​during the switching process. Fig. 3A is a time diagram showing a change in the setpoint translation ratio Vsft*, Fig. 3B is a timing diagram showing a change in the input shaft rotational speed Nin, Fig. 3C is a time graph that shows a change in the output torque Trqout, Fig. 3D is a time diagram that shows a change in the hydraulic pressure setpoint P*, Fig. 3E is a time graph showing a change in the unit heat output ΔQ, which is the amount of heat produced per unit of time, and Fig. 3F is a time diagram showing a change in the total heat output Qs, which is a value obtained by integrating the unit heat output ΔQ.

[0038] As it is in the Fig. 3A and Fig. As shown in 3D, if the value of the translation ratio setpoint Vsft* changes at time t1, the hydraulic pressure setpoint P*, which is a target value of the hydraulic pressure with which the friction engagement element is acted upon, which is to be engaged in the current switching process, is output at time t2.

[0039] The hydraulic pressure setpoint P* is first adjusted to activate the rapid activation control, so that the hydraulic pressure setpoint P* is increased once and the hydraulic pressure is applied to the friction engagement element (time t2). This rapid activation control is a well-known method for temporarily increasing the hydraulic pressure to quickly supply hydraulic oil to the friction engagement element when it is moved from the disengaged state to the engaged state. After the hydraulic pressure setpoint P* has been set to the activation pressure Pa for the specified time, it is then reduced to the specified standby pressure Pw (time t3). This standby pressure Pw is the hydraulic pressure required to perform the engagement process described above.

[0040] Subsequently, once a specified time has elapsed since the start of the hydraulic pressure supply at time t2, and the time required to determine that the initial setup is complete has also elapsed (time t5), a wobble control is executed, gradually increasing the hydraulic pressure setpoint P* from the standby pressure Pw. During this wobble control, the input shaft speed Nin begins to change towards the synchronous speed after switching due to the start of the inertia phase (time t6).

[0041] Then, at time t8, when the input shaft speed Nin reaches synchronous speed after the switching operation, the hydraulic pressure setpoint P* is abruptly increased to the engagement pressure Pk, which is the pressure required to prevent slippage of the friction engagement element, thus completing the switching operation.

[0042] The torque phase is started at time t4, which is the time between the start of the hydraulic pressure supply at time t2 and the completion of the engagement at time t5, so that the output torque Trqout transmitted to the output shaft 27out of the automatic transmission 26 begins to decrease. Then, when the inertia phase is started at time t6, the output torque Trqout begins to increase.

[0043] Since the state of the friction engagement element changes from the released state to the engaged state during the switching process, the heat generation state of the friction engagement element changes in different ways during the switching process. In particular, as described in the Fig. As shown in Figures 3A to 3F, the time interval from the start of the hydraulic pressure supply to the friction engagement element until the start of the torque phase in the automatic transmission 26 (the time interval from time t2 to time t4) is considered the initial time interval Z0. During this initial time interval Z0, the shifting process and the supply of hydraulic pressure to the friction engagement element are initiated. However, during the time interval until the start of the torque phase, no sliding occurs between the first and second plates of the friction engagement element, which rotate relative to each other, so it is unlikely that heat is generated in the friction engagement element.

[0044] The time from the start of the hydraulic pressure supply until time t2, and from the start of the torque phase until time t4, correlates with the engagement clearance PCtc of the friction element, and so on. Therefore, the engagement clearance PCtc is measured until the automatic transmission 26 is dispatched, and the measured value is stored in the storage device 46. Since the engagement clearance PCtc increases with the increasing frequency of engagement of the friction element, the value of the engagement clearance PCtc is updated to reflect this change over time. Based on this updated value of the engagement clearance PCtc, the time interval TZ0 from the output of the hydraulic pressure setpoint P* until the start of the torque phase is calculated. Thus, it can be determined that the initial time interval Z0 exists if the time elapsed since the output of the hydraulic pressure setpoint P* is within the time interval TZ0.

[0045] Furthermore, the time interval from the start of the torque phase in the automatic transmission 26 until the engagement of the friction element is released (the time interval from time t4 to time t5) is considered the first time interval Z1. The time from the start of the hydraulic pressure supply at time t2 until the engagement is closed at time t5, that is, the time until the engagement is complete, also correlates with the engagement clearance PCtc and the like. Therefore, based on the updated value of the engagement clearance PCtc, the time interval TZ1 is calculated from the output of the hydraulic pressure setpoint P* until the engagement is closed. Thus, it can be determined that the first time interval Z1 exists when the time elapsed since the output of the hydraulic pressure setpoint P* is a time between time interval TZ0 and time interval TZ1.

[0046] Furthermore, the time interval from the closing of the engagement gap of the friction element until the start of the inertia phase in the automatic transmission 26 (the time interval from time t5 to time t6) is considered the second time interval Z2. When the inertia phase starts, the input shaft speed Nin changes significantly. Therefore, it can be determined that the second time interval Z2 exists while the time elapsed since the output of the hydraulic pressure setpoint P* exceeds the aforementioned time interval TZ1 and changes significantly until the input shaft speed Nin changes. In the present embodiment, the speed of the input shaft 27in is designed to be equal to the speed of the second motor generator 24. Therefore, the CPU 42 calculates the input shaft speed Nin based on the output signal Sm2.

[0047] Furthermore, the time interval from the start of the inertia phase until the difference in the input shaft speed Nin of the automatic transmission 26 becomes equal to or less than the determined value α (the time interval from time t6 to time t7), that is, the time interval from the start of the inertia phase until the change in the input shaft speed Nin of the automatic transmission 26 stabilizes, is considered the third time interval Z3. It can be determined that the third time interval Z3 exists after the second time interval Z2 has elapsed and until the difference in the input shaft speed Nin becomes equal to or less than the determined value α mentioned above.

[0048] Furthermore, the time interval from the moment when the difference value of the input shaft speed Nin becomes equal to or less than the value α determined above, until the moment when the input shaft speed Nin reaches synchronous speed after the switching process is complete (the time interval from time t7 to time t8) is considered the fourth time interval Z4. From the moment when it is determined that the difference value of the input shaft speed Nin is equal to or less than the value α determined above, until the moment when the input shaft speed Nin reaches synchronous speed after the switching process is complete, it can be determined that the fourth time interval Z4 is currently in effect.

[0049] The inventors of the present invention have confirmed that the heat generation state of the friction engagement element differs for the respective time intervals Z1, Z2, Z3, and Z4. Therefore, the control device 40 of the present embodiment estimates the heat load, such as temperature, heat generation quantity, and seizing or non-seizing, in the friction engagement element up to the time of switching and changes the execution mode of the calculation process to calculate the heat load during the switching process. Such processing is described below. The control device 40, which performs the following processes, forms a heat load estimation device for the friction engagement element.

[0050] Fig. Figure 4 shows a procedure of a process carried out by the control device 40 according to the present embodiment. The in Fig. The process shown in Figure 4 is implemented when the CPU 42 repeatedly executes the program stored in ROM 44, for example, in a predetermined cycle. It should be noted that the step number of each process is subsequently represented by a number preceded by an "S".

[0051] In the series of processes that took place in Fig. As shown in Figure 4, CPU 42 first determines whether the switching operation is currently being carried out (S10). Then, if it is determined that the switching operation is not currently being carried out, CPU 42 temporarily terminates this process.

[0052] If, however, it is determined that the switching operation is currently being carried out, CPU 42 determines whether the current state is the initial time interval Z0 (S20). Then, if it is determined that the current state is the initial time interval Z0 (S20: YES), CPU 42 temporarily terminates this process.

[0053] If, however, it is determined that the current state is not the initial time interval Z0 (S20: NO), the CPU 42 executes a determination process to ascertain various values ​​(S30). In particular, the relative rotational speed Nr, the hydraulic pressure setpoint P*, the oil temperature Toil, the accelerator actuation amount ACCP, the gear ratio setpoint Vsft*, and the switching variable ΔVsft are determined.

[0054] The relative speed Nr is the speed of the first plate relative to the second plate of the friction engagement element, which rotate relative to each other during the shifting process of the automatic transmission 26, and is the difference between the input shaft speed Nin and the product "output shaft speed Nout × gear ratio after shifting". The CPU 42 calculates the output shaft speed Nout based on the vehicle speed SPD. Furthermore, the gear ratio setpoint Vsft* is inserted into the "gear ratio after shifting".

[0055] The CPU 42 then performs a selection process to select one of the four types of imaging data DM stored in the memory device 46 (S40).

[0056] Fig. Figure 5 shows the procedure of the selection process.

[0057] When this selection process is initiated, CPU 42 determines whether the current state is the first time interval Z1 (S41). If it is determined that the current state is indeed the first time interval Z1 (S41: YES), CPU 42 selects the first mapping data (S44) and temporarily terminates this process. The first mapping data is used to estimate the amount of heat generated and whether the friction element seizes or does not seize during the first time interval Z1. It is a trained model that was trained using the data from the first time interval Z1 as its training data.

[0058] If process S41 determines that the current state is not the first time interval Z1 (S41: NO), CPU 42 determines whether the current state is the second time interval Z2 (S42). If it is determined that the current state is the second time interval Z2 (S42: YES), CPU 42 selects the second mapping data (S45) and temporarily terminates this process. The second mapping data is used to estimate the amount of heat generated and whether the friction element is seizing or not seizing during the second time interval Z2. It is a trained model that was trained using the data from the second time interval Z2 as its training data.

[0059] If process S42 determines that the current state is not the second time interval Z2 (S42: NO), CPU 42 determines whether the current state is the third time interval Z3 (S43). Then, if it is determined that the current state is the third time interval Z3 (S43: YES), CPU 42 selects the third mapping data (S46) and temporarily terminates this process. The third mapping data is used to estimate the amount of heat generated and whether the friction element is seizing or not seizing during the third time interval Z3. This data is a trained model that was trained using the data from the second time interval Z3 as training data.

[0060] If process S42 determines that the current state is not the third time interval Z3 (S43: NO), CPU 42 selects the fourth mapping data (S47) and temporarily terminates this process. The fourth mapping data is used to estimate the amount of heat generated and whether the friction element is seizing or not in the fourth time interval Z4 and is a trained model that was trained using the data from the second time interval Z4 as training data.

[0061] If the mapping data DM are selected in this way, then the CPU 42 sets each value determined in the process of S30 to the input variables for the mapping defined by the selected mapping data DM (S50).

[0062] This means that the CPU 42 sets the relative speed Nr to the input variable x(1), sets the hydraulic pressure setpoint P* to the input variable x(2), sets the oil temperature Toil to the input variable x(3), sets the accelerator actuation amount ACCP to the input variable x(4), sets the gear ratio setpoint Vsft* to the input variable x(5) and sets the switching variable ΔVsft to the input variable x(6).

[0063] In the present embodiment, the input variable x(1) is a speed variable indicating the relative speed Nr. The input variable x(2) is a hydraulic pressure variable indicating the hydraulic pressure applied to the friction engagement element during the shifting process of the automatic transmission 26. The input variable x(3) is an oil temperature variable indicating the temperature of the hydraulic oil supplied to the friction engagement element. The input variable x(4) is a torque variable indicating the output torque of the onboard drive motor. Since the accelerator actuation amount ACCP is a value related to the output torque of the onboard drive motor, the accelerator actuation amount ACCP is used as a torque variable in the present embodiment. However, the drive torque setpoint Trq* can also be used as this torque variable.The input variables x(5) and x(6) are switching variables that indicate the friction engagement element that is engaged during the switching process.

[0064] The CPU 42 then inserts the input variables x(1), x(2), x(3), x(4), x(5) and x(6) into the diagram to calculate the value of the output variable y(i) (S60).

[0065] In the present embodiment, a function approximator is described by way of example as shown in the figure, and in particular a fully connected, forward-facing neural network with an intermediate layer is described by way of example. In particular, the values ​​of the nodes in the intermediate layer are determined by substituting "m" values ​​into the activation function f. The "m" values ​​are values ​​obtained by transforming the input variables x(1) to x(6) in the process of S50, and the input variable x(0), which serves as a bias parameter, is determined by the linear map defined by the coefficient wFjk (j = 1 to m, k = 0 to 6). Furthermore, the values ​​of the output variables y(1) and y(2) are determined by substituting the values ​​obtained by transforming each of the values ​​of the nodes in the intermediate layer into the activation function g based on the linear map defined by the coefficient wSij (i = 1, 2).In the present embodiment, a hyperbolic tangent is described as the activation function f by way of example. Furthermore, the ReLU function is described by way of example in the activation function g for the section corresponding to the output variable y(1), and the softmax function is described by way of example for the section corresponding to the output variable y(2).

[0066] The output variables y(1) and y(2) are variables that specify the heat load on the friction element, and output variable y(1) specifies the unit heat generation quantity ΔQ. Furthermore, output variable y(2) specifies a value for determining whether the friction element seizes or not.

[0067] The CPU 42 then updates the total heat generation quantity Qs by adding the unit heat generation quantity ΔQ specified by the output variable y(1) to the currently calculated total heat generation quantity Qs (S70). Next, the CPU 42 calculates the temperature rise of the friction element by multiplying the total heat generation quantity Qs updated in S70 by the heat capacity C of the friction element, which is the target of this calculation. Simultaneously, the CPU 42 adds the calculated temperature rise to the currently calculated temperature Tk of the friction element to update the temperature Tk of the friction element (S80). The heat capacity C is a predetermined value obtained in advance. Furthermore, the initial value of the temperature Tk of the friction element can be, for example, the oil temperature Toil.

[0068] The CPU 42 then determines whether the value specified by the output variable y(2) is equal to or greater than the determined threshold value Yref (S90). The threshold value Yref is preset to a value that can appropriately determine whether seizing has occurred in the friction engagement element when the value of the output variable y(2) is equal to or greater than the threshold value Yref.

[0069] If the determined value specified by the output variable y(2) is less than the threshold Yref (S90: NO), CPU 42 temporarily terminates this process. However, if the determined value specified by the output variable y(2) is equal to or greater than the threshold Yref (S90: YES), CPU 42 determines that a jam has occurred on the friction element engaged in the current switching operation (S100) and temporarily terminates this process.

[0070] The following describes the operations and effects of the present embodiment.

[0071] (1) The higher the relative rotational speed Nr between the first and second plates of the friction element, which rotate relative to each other, the greater the amount of heat generated by the friction element. Furthermore, the higher the hydraulic pressure applied to the friction element during the switching operation, the greater the amount of heat generated by the friction element. Therefore, in the present embodiment, the rotational speed variable, which specifies the relative rotational speed Nr with respect to the amount of heat generated in the friction element during the switching operation, and the hydraulic pressure variable specified by the hydraulic pressure setpoint P* are used as input variables. These input variables are fed into the diagram defined by the diagram data to calculate the thermal load, such as the amount of heat generated, the temperature, or whether the friction element seizes or does not seize.Since the state of the friction engagement element changes from the released state to the engaged state during the switching process, the heat generation state of the friction engagement element changes in different ways during the switching process. Therefore, in the present embodiment, the change process for modifying the execution mode of the calculation process for calculating the heat load is carried out during the switching process.

[0072] In particular, the inventors of the present invention have confirmed that the heat generation states of the friction engagement element during the switching process are different in the first time period Z1, the second time period Z2, the third time period Z3 and the fourth time period Z4.

[0073] Therefore, the time span from the start of the torque phase to the completion of the shifting process in the automatic transmission 26 (which is in the Fig. The time span shown in 3A to 3F (from time t4 to time t8) is divided into several predetermined time spans, namely the first time span Z1, the second time span Z2, the third time span Z3, and the fourth time span Z4, as described above. The storage device 46 stores several mapping data sets, each defining a different mapping in accordance with the individual time spans, namely the first mapping data, the second mapping data, the third mapping data, and the fourth mapping data. As part of the modification process, the CPU 42 performs a selection process during the execution of the computation process. Since each of the mapping data sets can be specialized for each predetermined time span, the thermal load on the frictional engagement element can thus be estimated exactly.

[0074] Since, as described above, the heat generation state of the friction engagement element changes variously during the switching process, the structure of the diagram tends to be complex if the heat load is calculated using a simple diagram over the entire switching period. However, in the present embodiment, the structure of the diagram can be easily simplified because the diagram data can be specialized for each of the aforementioned predetermined time periods.

[0075] (2) At the start of the shifting process, the supply of hydraulic pressure to the friction engagement element is initiated. However, until the start of the torque phase in the automatic transmission 26, no sliding occurs between the first plate and the second plate of the friction engagement element, which rotate relative to each other, so that heat generation of the friction engagement element is unlikely.

[0076] Therefore, the CPU 42 executes the following process as a change process, which differs from the change process above. That is, in the initial time period Z0, which is the time period from the start of the supply of hydraulic pressure to the friction engagement element until the start of the torque phase in the automatic transmission 26, if in the Fig. 4 S20 shown, a positive determination is made, which in Fig. The processes shown in S30 are not executed. This means that the input of input variables into the diagram is prevented. However, if the switching operation is currently being carried out (S10: YES in Fig. 4) and it is determined that the current state is not the initial time interval Z0 (S20: NO in Fig. 4), the in Fig. The processes shown in Figure 4 are executed from S30 onwards to perform the process of inputting the input variables into the diagram. That is, the process of inputting the input variables into the diagram is executed after the start of the torque phase. Thus, in the present embodiment, inputting the input variables into the diagram is prohibited during the period in which heat generation in the frictional engagement element is unlikely, i.e., until the start of the torque phase. Conversely, after the start of the torque phase, during which heat generation in the frictional engagement element occurs, the input variables are entered into the diagram. Therefore, when calculating the heat load, the period in which heat generation of the frictional engagement element is unlikely is excluded, allowing the heat load of the frictional engagement element to be estimated accurately.

[0077] (3) If the temperature of the hydraulic oil changes, the ambient temperature of the friction element changes, thus changing the amount of heat generated by the friction element. Since, in the present embodiment, the oil temperature (Toil) is included in the input variable as an oil temperature variable, which specifies the temperature of the hydraulic oil, the heat load is calculated taking into account the influence of the hydraulic oil temperature on the amount of heat generated. Therefore, the heat load can be calculated with higher accuracy than if the oil temperature variable were not included in the input variable.

[0078] (4) In the present embodiment, the hydraulic pressure setpoint P* is variably adjusted depending on the output torque of the onboard propulsion machine. When the hydraulic pressure is variably adjusted according to the output torque, the magnitude of the output torque is related to the amount of heat generated by the friction engagement element. Since, in the present embodiment, the above input variables include the accelerator actuation amount ACCP as a torque variable that specifies the output torque of the onboard propulsion machine, the heat load is calculated taking into account the influence of the output torque on the amount of heat generated. Therefore, the heat load can be calculated with higher accuracy than if the torque variable were not included in the input variables.

[0079] (5) Since the input variables include the gear ratio setpoint Vsft* and the switching variable ΔVsft as the switching variables that specify the friction engagement element that is brought into engagement during the switching operation, the heat load of the friction engagement element that is brought into engagement during the switching operation can be calculated exactly.

[0080] The present embodiment can be modified to be implemented as follows. The present embodiment and modifications thereof described above can be combined within a technically consistent range.

[0081] As can be seen from the hatched areas in Fig. As shown in Figure 3E, the total heat generation quantity Qs1 in the first time interval Z1, the total heat generation quantity Qs2 in the second time interval Z2, the total heat generation quantity Qs3 in the third time interval Z3, and the total heat generation quantity Qs4 in the fourth time interval Z4 can be calculated as output variables. In this case, the mean value, the maximum value in each time interval, or a set of values ​​immediately after the start of the interval and immediately after the end of the interval can be used as the values ​​of the input variables x(1), x(2), x(3), and x(4).

[0082] A value that is in Fig. The curve CR shown in 3F, which replicates the total heat generation quantity Qs, can be used as an output variable.

[0083] At least one of the following time intervals can be set: Z1 (first), Z2 (second), Z3 (third), and Z4 (fourth), and imaging data corresponding to the set time interval can be prepared. Even in this case, the thermal load on the friction element can be accurately estimated within the set time interval.

[0084] The output variable y(1), the output variable y(2) and the calculation of the temperature Tk can each be omitted.

[0085] The vehicle VC includes a communication device. The vehicle VC and the external data analysis center can communicate with each other via the communication device and the external network. The data analysis center includes a CPU, a ROM, a storage device, and a communication device. The CPU of the data analysis center can execute the selection and computation processes described above. In this case, the computational load on the vehicle VC's CPU 42 can be reduced compared to the case where the vehicle VC's CPU 42 performs the selection and computation processes described above.

[0086] At least one of the input variables—oil temperature, torque, or shift frequency—can be omitted. Furthermore, additional variables related to thermal stress can be added to the input variables.

[0087] The activation function shown in the figure above is just one example; other functions can also be used.

[0088] The neural network described here is an example of a neural network with only one intermediate layer. However, the number of intermediate layers can be two or more.

[0089] The term "neural network" is used as an example of a fully connected, forward-directed neural network. However, the term "neural network" is not limited to this. For example, a recurrent neural network can also be used as a neural network.

[0090] The function approximator, as represented by the mapping, can be a regression equation. This corresponds to the neural network described above without an intermediate layer.

[0091] The execution device is not limited to an execution device comprising the CPU 42 and the ROM 44 that performs software processing. For example, the execution device may comprise a dedicated hardware circuit (for example, an application-specific integrated circuit (ASIC), etc.) that executes hardware processes instead of at least some of the software processes that are executed in the embodiment above. That is to say, the execution device need only have one of the following configurations (a) to (c): (a) A configuration with a processing device that executes all of the above-mentioned processes according to a program, and a program storage device such as a ROM for storing the program.(b) A configuration with a processing device that executes some of the above processes according to a program, a program storage device, and a dedicated hardware circuit that executes the remaining processes. (c) A configuration with a dedicated hardware circuit that executes all of the above processes. Here, the above configurations may include multiple software execution devices, comprising a processing device, a program storage device, and multiple dedicated hardware circuits.

[0092] Vehicle VC is not limited to series / parallel hybrid vehicles. For example, vehicle VC can be a series hybrid vehicle or a parallel hybrid vehicle. Vehicle VC is not limited to a vehicle with an internal combustion engine and a motor-generator as its onboard propulsion system. For example, a vehicle with an internal combustion engine but no motor-generator, or with a motor-generator but no internal combustion engine, can be used.

Claims

[1] A heat load estimating device (40) for a friction engagement element (C1, C2, B1, B2) applied to a vehicle comprising a transmission (26) which includes the friction engagement element (C1, C2, B1, B2) operating with hydraulic pressure, and which is designed to estimate a heat load (y1, y2) when at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element (C1, C2, B1, B2) at the time of shifting the transmission (26) is considered to be the heat load (y1, y2), wherein the heat load estimating device (40) comprises: a storage device (46) designed to store mapping data (DM) defining a mapping, wherein the mapping comprises as an input variable (x) a speed variable (x1) which is a variable indicating a relative speed (Nr) of elements of the friction engagement element (C1, C2, B1, B2) rotating relative to each other during the shifting operation of the transmission (26), and a hydraulic pressure variable (x2) which is a variable indicating the hydraulic pressure applied to the friction engagement element (C1, C2, B1, B2) during the shifting operation of the transmission (26), and comprising as an output variable (y) the heat load (y1, y2); and an execution device (42, 44) designed to perform a calculation process for calculating a value of the output variable (y) by determining a value of the input variable (x) and entering the value into the figure and a change process for changing an execution mode of the calculation process during the shifting operation of the transmission (26), where: a time period from the start of a torque phase to the completion of the shifting process in the transmission (26) is divided into several predetermined time periods (Z1-Z4); the storage device (46) is designed to store several of the imaging data (DM), each defining the different imaging according to the time interval; and the execution device (42, 44) is designed to perform a process for selecting the mapping data (DM) according to the time interval when the calculation process is executed, as the change process.[2] Heat load estimation device (40) according to claim 1, wherein several of the time intervals (Z1-Z4) comprise at least a first time interval (Z1), a second time interval (Z2), a third time interval (Z3) or a fourth time interval (Z4), wherein the first time interval (Z1) is a time interval from the start of the torque phase until the closing of an engagement gap of the friction engagement element (C1, C2, B1, B2) in the transmission (26), the second time interval (Z2) is a time interval from the closing of the engagement gap of the friction engagement element (C1, C2, B1, B2) until the start of an inertia phase in the transmission (26), the third time interval (Z3) is a time interval from the start of the inertia phase until a differential value of a rotational speed (Nin) of an input shaft (27in) of the transmission (26) is equal to or less than a certain value, and the fourth time period (Z4) is a time period,after the difference in rotational speed (Nin) of the input shaft (27in) becomes equal to or less than the specified value and until the rotational speed of the input shaft (27in) reaches a synchronous rotational speed (Nin) after the switching process is complete. [3] Heat load estimating device (40) for a friction engagement element (C1, C2, B1, B2) applied to a vehicle comprising a transmission (26) comprising the friction engagement element (C1, C2, B1, B2) operating with hydraulic pressure, and designed to estimate a heat load (y1, y2) when at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element (C1, C2, B1, B2) at the time of shifting the transmission (26) is considered to be the heat load (y1, y2), wherein the heat load estimating device (40) comprises: a storage device (46) designed to store mapping data (DM) defining a mapping, wherein the mapping comprises as an input variable (x) a speed variable (x1) which is a variable indicating a relative speed (Nr) of elements of the friction engagement element (C1, C2, B1, B2) rotating relative to each other during the shifting operation of the transmission (26), and a hydraulic pressure variable (x2) which is a variable indicating the hydraulic pressure applied to the friction engagement element (C1, C2, B1, B2) during the shifting operation of the transmission (26), and comprising as an output variable (y) the heat load (y1, y2); and an execution device (42, 44) designed to perform a calculation process for calculating a value of the output variable (y) by determining a value of the input variable (x) and inputting the value into the diagram, and a modification process for changing an execution mode of the calculation process during the shifting operation of the transmission (26), wherein the The execution device (42, 44) is designed to prevent input of the input variable (x) into the diagram from the start of the supply of hydraulic pressure to the friction engagement element (C1, C2, B1, B2) to the start of a torque phase in the gearbox (26) as the change process; and the execution device (42, 44) is designed to perform a process for inputting the input variable (x) into the figure after the start of the torque phase. [4] Heat load estimating device (40) according to one of claims 1 to 3, wherein the input variable (x) comprises an oil temperature variable which is a variable that indicates a temperature (Toil) of a hydraulic oil supplied to the friction engagement element (C1, C2, B1, B2). [5] Heat load estimating device (40) according to one of claims 1 to 4, wherein the hydraulic pressure with which the friction engagement element (C1, C2, B1, B2) is acted upon is changed such that the hydraulic pressure is higher the higher the output torque of a drive motor of the vehicle, and the input variable (x) comprises a torque variable (x4) which is a variable indicating the output torque. [6] Heat load estimating device (40) according to any one of claims 1 to 5, wherein: the transmission (26) comprises several of the friction engagement elements (C1, C2, B1, B2); and the input variable (x) includes a switching variable (x5, x6) that specifies the friction engagement elements (C1, C2, B1, B2) that are engaged during the switching process. [7] A heat load estimation method for a friction engagement element (C1, C2, B1, B2) applied to a vehicle comprising a transmission (26) containing the friction engagement element (C1, C2, B1, B2) operating with hydraulic pressure, estimating a heat load (y1, y2) where at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element (C1, C2, B1, B2) at the time of shifting the transmission (26) is considered as the heat load (y1, y2), wherein the time from the start of a torque phase to the completion of the shifting operation in the transmission (26) is divided into several predetermined time intervals (Z1-Z4), and wherein the heat load estimation method characterized by is that it includes: Storing mapping data (DM) that defines a mapping, wherein the mapping includes as an input variable (x) a speed variable (x1) that is a variable that specifies a relative speed (Nr) of elements of the friction engagement element (C1, C2, B1, B2) that rotate relative to each other during the shifting operation of the transmission (26), and a hydraulic pressure variable (x2) that is a variable that specifies the hydraulic pressure with which the friction engagement element (C1, C2, B1, B2) is subjected during the shifting operation of the transmission (26), and includes as an output variable (y) the heat load (y1, y2), wherein several of the mapping data (DM), each defining a different mapping, can be stored according to each of the several time intervals (Z1-Z4); Executing a computation process to calculate a value of the output variable (y) by determining a value of the input variable (x) and inputting the value into the diagram; and Executing a change process to change a mode of the calculation process during the shifting operation of the transmission (26), wherein the change process may be a process to select the mapping data (DM) according to each of the several time spans (Z1-Z4) when the calculation process is executed. [8] Heat load estimation method for a friction engagement element (C1, C2, B1, B2) applied to a vehicle comprising a transmission (26) containing the friction engagement element (C1, C2, B1, B2) operating with hydraulic pressure, and estimating a heat load (y1, y2) where at least one temperature, heat generation quantity, or seizing or non-seizing in the friction engagement element (C1, C2, B1, B2) at the time of shifting the transmission (26) is considered as the heat load (y1, y2), wherein the heat load estimation method characterized by is that it includes: Storing mapping data (DM) that defines a mapping, wherein the mapping includes as an input variable (x) a speed variable (x1) which is a variable that specifies a relative speed (Nr) of elements of the friction engagement element (C1, C2, B1, B2) that rotate relative to each other during the shifting operation of the transmission (26), and a hydraulic pressure variable (x2) which is a variable that specifies the hydraulic pressure with which the friction engagement element (C1, C2, B1, B2) is subjected during the shifting operation of the transmission (26), and includes as an output variable (y) the heat load (y1, y2); Executing a computation process to calculate a value of the output variable (y) by determining a value of the input variable (x) and inputting the value into the diagram; and Executing a change process to change a mode of the calculation process during the gear shifting process (26), wherein: the execution device (42, 44) is designed to prevent input of the input variable (x) into the diagram from the start of the supply of hydraulic pressure to the friction engagement element (C1, C2, B1, B2) to the start of a torque phase in the gearbox (26) as the change process; and the execution device (42, 44) is designed to perform a process for inputting the input variable (x) into the figure after the start of the torque phase.

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