Control device for a hybrid vehicle

Abstract

A control device and a control method for a hybrid vehicle are provided. The control device is applied to a hybrid vehicle that is provided with an engine, a motor generator, and a clutch. A CPU of the control device executes first start processing in which, in a case where the engine is started in a situation in which an increase amount of a torque demand value is smaller than an increase amount determination value, combustion in the engine is started after the engine rotation speed is increased to a motor rotation speed by engaging the clutch. The CPU executes second start processing in which, in a case where the engine is started in a situation in which the increase amount of the torque demand value is equal to or greater than the increase amount determination value, combustion in the engine is started before the engine rotation speed reaches the motor rotation speed after the crankshaft of the engine starts rotating by engaging the clutch.

Description

Technical Field

[0001] This disclosure relates to a control device and control method for hybrid vehicles. Background Technology

[0002] Japanese Patent Application Publication No. 2019-25985 discloses a control device for a hybrid vehicle equipped with an engine and an electric generator as power sources, and a clutch disposed between the engine and the electric generator. When the engine is started, this control device engages the clutch to connect the engine crankshaft and the drive shaft of the electric generator. This allows the crankshaft to rotate under the drive of the electric generator. Furthermore, once the crankshaft rotation begins under the drive of the electric generator, combustion in the engine is initiated.

[0003] When combustion in the engine begins after the crankshaft is started to rotate via an electric generator, as described above, advancing the combustion start timing allows for earlier engine starting, but it can easily cause vehicle vibration associated with engine starting. On the other hand, delaying the combustion start timing reduces the likelihood of this vibration, but it delays the completion of engine starting. Summary of the Invention

[0004] To address the aforementioned problems, according to a first aspect of this disclosure, a control device for a hybrid vehicle is provided. The hybrid vehicle includes an engine with a crankshaft and an electric generator with a drive shaft as power sources, and a clutch is provided between the crankshaft and the drive shaft. The control device includes an actuator for controlling the engine, the electric generator, and the clutch. The actuator is configured to perform a first starting process and a second starting process. The first starting process is as follows: when starting the engine under conditions where the increase in torque requirement relative to the power source is less than an increase determination value, combustion in the engine is initiated after the crankshaft speed (i.e., engine speed) is increased to the drive shaft speed (i.e., electric motor speed) by engaging the clutch. The second starting process is as follows: when starting the engine under conditions where the increase in torque requirement is greater than or equal to the increase determination value, combustion in the engine is initiated before the engine speed reaches the electric motor speed after the crankshaft begins to rotate by engaging the clutch.

[0005] To address the aforementioned problems, a control method for a hybrid vehicle is provided according to a second aspect of this disclosure. The hybrid vehicle includes an engine with a crankshaft and an electric generator with a drive shaft as power sources, and a clutch is provided between the crankshaft and the drive shaft. The control method includes: when starting the engine under conditions where the increase in torque requirement relative to the power source is less than a threshold value, engaging the clutch to increase the crankshaft speed (engine speed) to the drive shaft speed (electric motor speed) and then initiating combustion in the engine; and when starting the engine under conditions where the increase in torque requirement is greater than or equal to the threshold value, initiating combustion in the engine before the engine speed reaches the electric motor speed after the crankshaft begins to rotate by engaging the clutch. Attached Figure Description

[0006] Figure 1 This is a diagram showing a schematic structure of a hybrid vehicle equipped with a control device as one embodiment.

[0007] Figure 2 It is a timeline of the engine starting process using the first start-up procedure.

[0008] Figure 3 This is a timeline of the engine starting process using the second starting procedure.

[0009] Figure 4 This is a block diagram illustrating the multiple processes executed by the CPU of the aforementioned control device.

[0010] Figure 5 This is a flowchart illustrating the final decision-making process.

[0011] Figure 6 This is a time graph showing the progression of the accelerator opening. Detailed Implementation

[0012] The following is in accordance with Figures 1-6 This describes one embodiment of a control device for hybrid vehicles.

[0013] Figure 1 The diagram illustrates a schematic structure of a hybrid vehicle 500 equipped with a control device 100, which is an example of a control device for hybrid vehicles. Hereinafter, the hybrid vehicle 500 will be referred to as "vehicle 500".

[0014] <Vehicle Structure>

[0015] Vehicle 500 has an engine 10 and an electric generator 30 as power sources. Vehicle 500 also has a clutch 20 configured between the engine 10 and the electric generator 30 in the torque transmission path. The torque output from the engine 10 or the electric generator 30 is transmitted to multiple drive wheels 65 via a transmission 40 and a differential 60. It should be noted that the torque input from the vehicle's power source to the transmission 40 is called the "system shaft torque".

[0016] The engine 10 includes multiple fuel injection valves 12 for injecting fuel and multiple cylinders. Additionally, the engine 10 includes an intake passage 13 connected to the multiple cylinders and an electrically operated throttle valve 14 that adjusts the amount of air flowing in the intake passage 13. In the multiple cylinders, a mixture including air introduced from the intake passage 13 and fuel injected from the fuel injection valves 12 is burned. Exhaust gas generated by the combustion of the mixture is discharged from the multiple cylinders to an exhaust passage 16. A catalyst 17 for purifying the exhaust gas is provided in the exhaust passage 16.

[0017] The engine 10 includes a crankshaft 18, which serves as the output shaft of the engine 10. The crankshaft 18 rotates in a predetermined direction by utilizing the force obtained from the combustion of the air-fuel mixture in multiple cylinders. That is, the output torque of the engine 10, namely the engine torque Te, is output from the crankshaft 18.

[0018] The clutch 20 is connected to the crankshaft 18 of the engine 10. When the clutch 20 is engaged, torque transmission between the engine 10 and the electric generator 30 is possible. On the other hand, when the clutch 20 is disengaged, torque transmission between the engine 10 and the electric generator 30 is not possible.

[0019] It should be noted that in this embodiment, the clutch 20 can be fully engaged or slippery engaged. Full engagement is when the engagement force of the clutch 20 is greater than that of slippery engagement. The greater the engagement force of the clutch 20, the greater its torque capacity Tc. Therefore, when the clutch 20 is fully engaged, the torque transmission efficiency between the engine 10 and the electric generator 30 is relatively high. On the other hand, when the clutch 20 is slippery engaged, its torque capacity Tc is smaller compared to when it is fully engaged. Therefore, when the clutch 20 is slippery engaged, torque is transmitted between the engine 10 and the electric generator 30, but the torque transmission efficiency is low. That is, the clutch 20 is sometimes slippery engaged when the torque transmission efficiency between the engine 10 and the electric generator 30 is intentionally low.

[0020] Clutch 20 is a hydraulically driven clutch. In such a clutch 20, the higher the hydraulic pressure supplied to clutch 20, i.e., the clutch hydraulic pressure Pc, the greater the engagement force of clutch 20. That is, by adjusting the clutch hydraulic pressure Pc, clutch 20 can be engaged either slipwise or fully. Furthermore, the higher the clutch hydraulic pressure Pc, the greater the torque capacity Tc of clutch 20, and therefore the higher the torque transmission efficiency between engine 10 and electric generator 30. In other words, when clutch 20 is engaged, by adjusting clutch hydraulic pressure Pc, torque capacity Tc is changed, and thus the torque transmission efficiency of clutch 20 is adjusted.

[0021] The electric generator 30 has a drive shaft 31 connected to the clutch 20. That is, when the electric generator 30 functions as an electric motor, the drive shaft 31 is rotated by power supplied from the battery via a converter. On the other hand, when the electric generator 30 functions as a generator, regenerative power corresponding to the rotation of the drive shaft 31 is generated in the electric generator 30, and this regenerative power is supplied to the battery via the converter. When the output torque of the electric generator 30 is set to "motor torque Tm", the sum of the torque input from the crankshaft 18 to the drive shaft 31 via the clutch 20 in the engine torque Te and the motor torque Tm becomes the system shaft torque Tsys.

[0022] The transmission device 40 includes a torque converter 41 and a transmission mechanism 46. The torque converter 41 includes a pump wheel 42, a turbine 43, and a lock-up clutch 44. The pump wheel 42 is connected to the drive shaft 31 of the electric generator 30. The turbine 43 is connected to the transmission mechanism 46. When the lock-up clutch 44 is in the open state, torque is transmitted from the pump wheel 42 to the turbine 43 via the working oil in the torque converter 41. On the other hand, when the lock-up clutch 44 is in the engaged state, torque is transmitted directly from the pump wheel 42 to the turbine 43 without via the working oil.

[0023] The transmission mechanism 46 is, for example, a stepped transmission mechanism. The transmission mechanism 46 has an input shaft 47 that receives torque from the torque converter 41 and an output shaft 48 that outputs torque. The input shaft 47 is connected to the turbine 43 of the torque converter 41. The transmission mechanism 46 outputs the torque input from the input shaft 47 in a reduced-speed state from the output shaft 48 toward the differential 60.

[0024] In this embodiment, the vehicle 500 includes an electric pump 80 and a hydraulic control circuit 90. The electric pump 80 pressurizes working oil and supplies it to the hydraulic control circuit 90. The hydraulic control circuit 90 supplies the high-pressure working oil supplied from the electric pump 80 to the transmission mechanism 46, the torque converter 41, and the clutch 20. For example, the hydraulic control circuit 90 has multiple oil control valves. By controlling the multiple oil control valves, the supply and discharge of working oil relative to the target of the working oil supply, as well as the hydraulic pressure of the working oil supplied to the target, are controlled. That is, the hydraulic control circuit 90 is configured to adjust the aforementioned clutch hydraulic pressure Pc.

[0025] Vehicle detection system

[0026] The detection system of vehicle 500 includes multiple sensors that output detection signals corresponding to the detection results to control device 100. Specifically, vehicle 500 includes a crankshaft angle sensor 111, an air flow meter 112, an accelerator opening sensor 113, an electric motor angle sensor 114, an input shaft sensor 115, and an oil temperature sensor 116. The crankshaft angle sensor 111 outputs a detection signal corresponding to the rotational speed of crankshaft 18, i.e., engine speed Ne. The air flow meter 112 detects the amount of air flowing in the intake passage 13, i.e., the intake air volume GA, and outputs a detection signal corresponding to its detection result. The accelerator opening sensor 113 detects the amount of accelerator pedal operation, i.e., accelerator opening ACCP, and outputs a detection signal corresponding to its detection result. The electric motor angle sensor 114 outputs a detection signal corresponding to the rotational speed of the drive shaft 31 of the electric generator 30, i.e., the electric motor speed Nm. The input shaft sensor 115 outputs a detection signal corresponding to the rotational speed of the input shaft 47 of the transmission mechanism 46, i.e., the input shaft speed Nat. The oil temperature sensor 116 detects the temperature of the working oil injected by the electric pump 80, i.e., the oil temperature TOIL, and outputs a detection signal corresponding to its detection result.

[0027] <Control Device>

[0028] The control device 100 includes a CPU 101, a ROM 102, and a RAM 103. The ROM 102 stores various control programs executed by the CPU 101. The RAM 103 stores the calculation results of the CPU 101. The CPU 101 controls the engine 10 and the electric generator 30 by executing the control programs. Furthermore, the CPU 101 controls the clutch 20 and the transmission 40 by controlling the electric pump 80 and the hydraulic control circuit 90. Therefore, in this embodiment, the CPU 101 corresponds to the "execution device".

[0029] It should be noted that the CPU101 calculates the engine speed Ne based on the detection signal Scr from the crankshaft angle sensor 111. The CPU101 calculates the engine load rate KL based on the engine speed Ne and the intake air volume GA.

[0030] CPU 101 derives the required torque value, TsR, relative to the vehicle's power source based on the accelerator opening (ACCP). The required torque value TsR is the torque input from drive shaft 31 to transmission 40. For example, CPU 101 derives the torque requirement TsR as a value that increases with the accelerator opening (ACCP). Furthermore, CPU 101 controls the vehicle's power source, namely engine 10 and electric generator 30, based on the required torque value TsR.

[0031] Vehicle 500 has an electric driving mode and a hybrid driving mode as driving modes. The electric driving mode is a mode in which torque is output solely from the engine 10 and the electric generator 30. Therefore, when the electric driving mode is selected, CPU 101 controls the electric generator 30 based on the torque requirement value TsR. When the electric driving mode is selected, since the engine 10 is not running, CPU 101 disengages the clutch 20.

[0032] The hybrid driving mode is a mode in which torque is output from both the engine 10 and the electric generator 30. When the engine 10 is running, the CPU 101, with the clutch 20 engaged, controls the engine 10 and the electric generator 30 based on the torque requirement value TsR. When the hybrid driving mode is selected, the CPU 101 sometimes intermittently stops the operation of the engine 10. In this case, the CPU 101, with the clutch 20 disengaged, controls the electric generator 30 based on the torque requirement value TsR.

[0033] When the engine 10 is stopped while the hybrid driving mode is selected, if the accelerator pedal opening (ACCP) increases and the torque requirement value (TsR) increases, the CPU 101 may sometimes restart the engine 10. In this case, the CPU 101 not only starts the engine 10 but also engages the clutch 20. In this embodiment, when starting the engine 10, the CPU 101 selects either a first starting process or a second starting process and starts the engine 10 by executing the selected process.

[0034] Reference Figure 2 Let's explain the first startup process.

[0035] In the first starting process, if engine 10 is required to start at time t11, clutch 20 is engaged. In this case, clutch 20 is engaged by slip engagement. CPU 101 increases clutch hydraulic pressure Pc by controlling electric pump 80 and hydraulic control circuit 90. This increases the engagement force of clutch 20. If the engagement force increases, then... Figure 2As shown in (A), the torque capacity Tc of clutch 20 increases. If clutch 20 slips into engagement, the electric motor torque Tm is input to crankshaft 18. Thus, engine 10 is started by electric generator 30, therefore... Figure 2 As shown in (B), the engine speed Ne increases. Furthermore, the engine speed Ne rises to the electric motor speed Nm. Consequently, the clutch hydraulic pressure Pc is increased, and the torque capacity Tc of clutch 20 is increased. Thus, clutch 20 is fully engaged.

[0036] It should be noted that the timing of making the engine speed Ne essentially the same as the electric motor speed Nm is also called the "synchronization timing of clutch 20". At the synchronization timing of clutch 20 or at a timing t12 slightly later than the synchronization timing, combustion in engine 10 begins. That is, combustion in engine 10 begins after clutch 20 is fully engaged.

[0037] Reference Figure 3 Let's explain the second startup process.

[0038] In the second starting process, if the engine 10 is required to start at time t21, the clutch 20 is engaged. In this case, the clutch 20 is engaged by slip engagement. The CPU 101 increases the clutch hydraulic pressure Pc by controlling the electric pump 80 and the hydraulic control circuit 90. As a result, the engagement force of the clutch 20 increases. If the engagement force increases, then... Figure 3 As shown in (A), the torque capacity Tc of clutch 20 increases. If clutch 20 slips into engagement, the electric motor torque Tm is input to crankshaft 18. Thus, engine 10 is started by electric generator 30, therefore... Figure 3 As shown in (B), the engine speed Ne increases.

[0039] In the second start-up process, unlike the first start-up process, combustion in the engine 10 begins at a time t22 before the engine speed Ne reaches the electric motor speed Nm. In this embodiment, combustion in the engine 10 begins at a time when the crankshaft 18 has rotated one revolution based on the start-up of the electric generator 30, or at a time when the crankshaft 18 has rotated two revolutions.

[0040] Therefore, after time t22, the engine speed Ne increases sharply due to both the starting of the electric generator 30 and the increase in engine torque Te. If the engine 10 is started, the torque capacity Tc of the clutch 20 is adjusted before the engine speed Ne reaches the electric motor speed Nm. That is, the CPU 101 reduces the clutch hydraulic pressure Pc by controlling the hydraulic control circuit 90. Thus, from time t23, the torque capacity Tc of the clutch 20 is reduced. If the torque capacity Tc is reduced, the torque transmitted from the crankshaft 18 to the drive shaft 31 via the clutch 20 becomes smaller. As a result, the torque transmission efficiency of the clutch 20 becomes lower. Thus, during the period from the start of combustion of the engine 10 until the engine speed Ne reaches the electric motor speed Nm, the engine torque Te transmitted to the drive shaft 31 is adjusted by adjusting the torque capacity Tc of the clutch 20. As a result, the sharp increase in the electric motor speed Nm is suppressed.

[0041] If, at time t24, the engine speed Ne becomes substantially equal to the electric motor speed Nm, then the clutch hydraulic pressure Pc is increased through the control of the hydraulic control circuit 90 by the CPU 101. The result is as follows: Figure 3 As shown in (B), the torque capacity Tc of clutch 20 is increased. Therefore, clutch 20 is fully engaged, and thus the torque transmission efficiency of clutch 20 becomes maximum.

[0042] <Processes performed when starting the engine>

[0043] Reference Figures 4-6 The process executed by CPU 101 when starting engine 10 will be explained.

[0044] like Figure 4 As shown, CPU 101 executes torque capacity prediction processing M11 and turbine speed prediction processing M13. Additionally, CPU 101 executes first decision value candidate setting processing M15, second decision value candidate setting processing M17, setting processing M19, and provisional selection processing M21. Furthermore, CPU 101 executes incremental decision value setting processing M23, final decision processing M25, and startup processing M27.

[0045] <Torque Capacity Prediction Processing>

[0046] The torque capacity prediction process M11 derives the predicted value of the clutch 20's torque capacity Tc, i.e., the predicted torque capacity Tce. The predicted torque capacity Tce is the torque capacity Tc of the clutch 20 at the synchronization timing when the engine 10 is started using the second starting process. When the engine 10 is started using the second starting process, the CPU 101 adjusts the command value of the clutch hydraulic pressure Pc in a predetermined manner. The actual response of the clutch hydraulic pressure Pc to changes in the command value can be inferred to some extent based on the motor speed Nm, the system shaft torque Tsys, and the input shaft speed Nat.

[0047] Therefore, in the torque capacity prediction processing M11, CPU101 derives the predicted torque capacity Tce based on the motor speed Nm, system shaft torque Tsys, and input shaft speed Nat. For example, it can be inferred that the higher the motor speed Nm, the more delayed the synchronization timing of clutch 20. Therefore, CPU101 derives the predicted torque capacity Tce as a value that decreases with increasing motor speed Nm. Similarly, it can be inferred that the higher the system shaft torque Tsys, the more delayed the synchronization timing of clutch 20. Therefore, CPU101 derives the predicted torque capacity Tce as a value that decreases with increasing system shaft torque Tsys. Furthermore, it can be inferred that the higher the input shaft speed Nat, the more delayed the synchronization timing of clutch 20. Therefore, CPU101 derives the predicted torque capacity Tce as a value that decreases with increasing input shaft speed Nat.

[0048] It should be noted that when the engine 10 is stopped, the clutch 20 is in the open state, so the CPU 101 obtains the motor torque Tm as the system shaft torque Tsys.

[0049] <Turbine Speed ​​Prediction Processing>

[0050] Turbine speed prediction processing M13 is the process that derives the predicted value of the turbine speed 43, namely the predicted turbine speed Nte. The speed of turbine 43 is set as the "turbine speed". The predicted turbine speed Nte is assumed to be the turbine speed at the synchronization timing of clutch 20 when the engine 10 is started using the second starting process. Since the turbine 43 of torque converter 41 is connected to the input shaft 47 of transmission mechanism 46, the turbine speed and the input shaft speed Nat are essentially the same. That is to say, the predicted turbine speed Nte can also be considered a predicted value of the input shaft speed Nat.

[0051] In the turbine speed prediction processing M13, CPU101 derives the predicted turbine speed Nte from the input shaft speed Nat by subtracting the deceleration correction value ΔNat. The deceleration correction value ΔNat is a value determined according to the specifications of the vehicle 500's drive system.

[0052] <Handling of First Judgment Value Candidate Settings>

[0053] The first determination value candidate setting process M15 derives a first shaft torque determination value TsysTh1, which is one of the candidate values ​​for the shaft torque determination value, by referring to the first mapping MAP1. The first mapping MAP1 is a mapping that shows the relationship between the predicted turbine speed Nte and the system shaft torque Tsys. In the first mapping MAP1, when the predicted turbine speed Nte is less than the first reference speed Nte1, the system shaft torque Tsys corresponding to the predicted turbine speed Nte becomes a positive value. Specifically, when the predicted turbine speed Nte is less than the first reference speed Nte1, the system shaft torque Tsys corresponding to the predicted turbine speed Nte increases as the predicted turbine speed Nte decreases. On the other hand, when the predicted turbine speed Nte is greater than or equal to the first reference speed Nte1, the system shaft torque Tsys corresponding to the predicted turbine speed Nte becomes a negative value. Specifically, when the predicted turbine speed Nte is greater than or equal to the first reference speed Nte1, the absolute value of the system shaft torque Tsys corresponding to the predicted turbine speed Nte increases as the predicted turbine speed Nte increases.

[0054] In the first determination value candidate setting process M15, CPU101 derives the system shaft torque Tsys corresponding to the predicted turbine speed Nte by referring to the first mapping MAP1. Furthermore, CPU101 sets the system shaft torque Tsys derived by referring to the first mapping MAP1 as the first shaft torque determination value TsysTh1.

[0055] It should be noted that, as detailed later, the first mapping MAP1 is the mapping used when the predicted torque capacity Tce is less than the reference torque capacity Tcb. When the predicted torque capacity Tce is less than the reference torque capacity Tcb, if the system shaft torque Tsys is greater than or equal to the first shaft torque determination value TsysTh1 set with reference to the first mapping MAP1, then even if the engine 10 is started using the second starting process, the vibration caused by the starting of the engine 10 can be suppressed.

[0056] <Second Judgment Value Candidate Setting Processing>

[0057] The second decision value candidate setting process M17 derives a second shaft torque decision value TsysTh2, which is one of the candidate values ​​for the shaft torque decision value, by referring to the second mapping MAP2. The second mapping MAP2 is a mapping showing the relationship between the predicted turbine speed Nte and the system shaft torque Tsys. In the second mapping MAP2, when the predicted turbine speed Nte is less than the second reference speed Nte2, the system shaft torque Tsys corresponding to the predicted turbine speed Nte becomes a positive value. Specifically, when the predicted turbine speed Nte is less than the second reference speed Nte2, the system shaft torque Tsys corresponding to the predicted turbine speed Nte increases as the predicted turbine speed Nte decreases. On the other hand, when the predicted turbine speed Nte is greater than or equal to the second reference speed Nte2, the system shaft torque Tsys corresponding to the predicted turbine speed Nte becomes a negative value. Specifically, when the predicted turbine speed Nte is greater than or equal to the second reference speed Nte2, the absolute value of the system shaft torque Tsys corresponding to the predicted turbine speed Nte increases as the predicted turbine speed Nte increases. It should be noted that the second reference speed Nte2 is set to a value larger than the first reference speed Nte1.

[0058] In the second determination value candidate setting process M17, CPU101 derives the system shaft torque Tsys corresponding to the predicted turbine speed Nte by referring to the second mapping MAP2. Furthermore, CPU101 sets the system shaft torque Tsys derived by referring to the second mapping MAP2 as the second shaft torque determination value TsysTh2.

[0059] It should be noted that, as detailed later, the second mapping MAP2 is used when the predicted torque capacity Tce is greater than or equal to the reference torque capacity Tcb. When the predicted torque capacity Tce is greater than or equal to the reference torque capacity Tcb, if the system shaft torque Tsys is greater than or equal to the second shaft torque determination value TsysTh2 set with reference to the second mapping MAP2, then even if the engine 10 is started using the second starting process, the vibration caused by the starting of the engine 10 can be suppressed.

[0060] Furthermore, a first shaft torque determination value TsysTh1 is set in the first determination value candidate setting process M15, and a second shaft torque determination value TsysTh2 is set in the second determination value candidate setting process M17. Both the first shaft torque determination value TsysTh1 and the second shaft torque determination value TsysTh2 are torques corresponding to the predicted turbine speed Nte. In this embodiment, the first mapping MAP1 and the second mapping MAP2 are created such that the second shaft torque determination value TsysTh2 is larger than the first shaft torque determination value TsysTh1. It should be noted that the dashed line in the graph representing the second mapping MAP2 is a line showing the relationship between the predicted turbine speed Nte and the system shaft torque Tsys in the first mapping MAP1.

[0061] <Settings and Processing>

[0062] Setting process M19 involves setting one of the first axis torque determination value TsysTh1 and the second axis torque determination value TsysTh2 as the axis torque determination value TsysTh. In setting process M19, CPU 101 sets the axis torque determination value TsysTh based on the predicted torque capacity Tce. Specifically, when the predicted torque capacity Tce is less than the reference torque capacity Tcb, CPU 101 sets the first axis torque determination value TsysTh1 as the axis torque determination value TsysTh. On the other hand, when the predicted torque capacity Tce is greater than or equal to the reference torque capacity Tcb, CPU 101 sets the second axis torque determination value TsysTh2 as the axis torque determination value TsysTh. Therefore, when the predicted torque capacity Tce is large, a value larger than the value smaller than the predicted torque capacity Tce is set as the axis torque determination value TsysTh.

[0063] <Tentative Selection Process>

[0064] The provisional selection process M21 is a process that provisionally selects either the first start-up process or the second start-up process based on the shaft torque determination value TsysTh and the system shaft torque Tsys. In the provisional selection process M21, the CPU 101 provisionally selects the first start-up process when the system shaft torque Tsys is less than the shaft torque determination value TsysTh. On the other hand, the CPU 101 provisionally selects the second start-up process when the system shaft torque Tsys is greater than or equal to the shaft torque determination value TsysTh.

[0065] <Increased Scale Judgment Value Setting Processing>

[0066] The increment determination value setting process M23 is the process of setting the increment determination value ΔTsRTh, which will be described later. In the increment determination value setting process M23, the CPU 101 sets the increment determination value ΔTsRTh based on the predicted torque capacity Tce, oil temperature TOIL, and the transmission stage Z selected by the transmission mechanism 46. In this embodiment, the CPU 101 sets the value of the increment determination value ΔTsRTh, which is the reference value ΔTsRThb modified based on the predicted torque capacity Tce, oil temperature TOIL, and transmission stage Z, as the increment determination value ΔTsRTh.

[0067] CPU 101 sets the value that decreases as the predicted torque capacity Tce decreases as the first correction gain G1. CPU 101 sets the value that decreases as the oil temperature TOIL increases as the second correction gain G2. CPU 101 sets the value that decreases as the transmission stage Z selected by the transmission mechanism 46 becomes higher as the third correction gain G3. It should be noted that the multiple correction gains G1, G2, and G3 are set to values ​​greater than 0 (zero) and less than 1. Furthermore, CPU 101 sets the product of the reference increment determination value ΔTsRThb, the first correction gain G1, the second correction gain G2, and the third correction gain G3 as the increment determination value ΔTsRTh.

[0068] <Final Decision Processing>

[0069] The final decision to handle M25 was made when the engine 10 was actually required to be started.

[0070] Reference Figure 5 Let's explain the final decision processing M25. The CPU 101 executes the final decision processing M25 repeatedly for each specified control loop.

[0071] In step S11, CPU 101 determines whether there is a starting requirement for engine 10. If there is no starting requirement (S11: No), CPU 101 temporarily terminates the final decision process M25. On the other hand, if there is a starting requirement (S11: Yes), CPU 101 moves the process to step S13. In step S13, CPU 101 determines whether the first starting process has been tentatively selected in the tentative selection process M21. If the first starting process has been tentatively selected (S13: Yes), CPU 101 moves the process to step S15. On the other hand, if the second starting process has been tentatively selected (S13: No), CPU 101 moves the process to step S19.

[0072] In step S15, CPU 101 determines whether there is spare capacity in the motor torque Tm. In this embodiment, CPU 101 derives the maximum value of the motor torque Tm when the engine 10 starts, i.e., the maximum motor torque at startup. Specifically, CPU 101 uses the torque requirement value TsR based on the accelerator opening ACCP to derive a predicted value of the system shaft torque when the engine 10 needs the most power at startup. Next, CPU 101 derives the maximum motor torque at startup by summing the predicted value of the system shaft torque with the reaction torque of the starting torque. Furthermore, if the electric generator 30 can output the maximum motor torque at startup, CPU 101 determines that there is spare capacity in the motor torque Tm. On the other hand, if the electric generator 30 cannot output the maximum motor torque at startup, CPU 101 determines that there is no spare capacity in the motor torque Tm. Furthermore, if it is determined that there is spare capacity in the motor torque Tm (S15: Yes), CPU 101 moves the processing to step S21. On the other hand, if it is determined that there is no spare force in the motor torque Tm (S15: No), the CPU101 moves the processing to step S17.

[0073] In step S17, the CPU 101 determines whether the increase in the torque requirement value TsR, ΔTsR, is greater than or equal to the increase determination value ΔTsRTh. When the engine 10 is required to start while the driver of the vehicle 500 is operating the accelerator pedal, the CPU 101 determines whether the increase in the torque requirement value, ΔTsR, is greater than or equal to the increase determination value ΔTsRTh based on the increase in the accelerator opening ACCP. For example, the CPU 101 determines whether the increase in the torque requirement value, ΔTsR, is greater than or equal to the increase determination value ΔTsRTh based on the increase in the accelerator opening ACCP, ΔACCP, over a specified period.

[0074] like Figure 6As shown, CPU 101 obtains the current value ACCP1 of the accelerator opening ACCP and the reference accelerator opening ACCP at a time interval TA from the current time point backwards. The reference time TA is the length of the aforementioned specified period. CPU 101 derives the increment ΔACCP of the accelerator opening from the current value ACCP1 minus the reference accelerator opening ACCPb as the increment ΔACCP of the accelerator opening within the specified period. Furthermore, if the increment ΔACCP of the accelerator opening is greater than or equal to the increment determination value ΔACCPth, CPU 101 determines that the increment ΔTsR of the torque requirement value is greater than or equal to the increment determination value ΔTsRTh. On the other hand, if the increment ΔACCP of the accelerator opening is less than the increment determination value ΔACCPth, CPU 101 determines that the increment ΔTsR of the torque requirement value is less than the increment determination value ΔTsRTh.

[0075] It should be noted that, in this embodiment, the increment determination value ΔTsRTh is variable based on the predicted torque capacity Tce, oil temperature TOIL, and transmission stage Z mentioned above. Therefore, a value that increases with the increase determination value ΔTsRTh is set as the opening increment determination value ΔACCPth.

[0076] return Figure 5 If the increase in torque requirement value ΔTsR is greater than or equal to the increase determination value ΔTsRTh (S17: Yes), the CPU 101 moves the processing to step S19. On the other hand, if the increase in torque requirement value ΔTsR is less than the increase determination value ΔTsRTh (S17: No), the CPU 101 moves the processing to step S21.

[0077] In step S19, CPU 101 determines the second start-up process as a process to start engine 10. After that, CPU 101 ends the final decision process M25.

[0078] In step S21, CPU 101 determines the first start-up process as a process to start the engine 10. After that, CPU 101 ends the final decision process M25.

[0079] <Startup Process>

[0080] Startup process M27 is the process of starting engine 10. CPU 101 starts engine 10 using the startup process determined in final decision process M25. If the startup process determined in final decision process M25 is a first startup process, CPU 101 executes the first startup process as startup process M27. If the startup process determined in final decision process M25 is a second startup process, CPU 101 executes the second startup process as startup process M27.

[0081] <Function and Effects of This Implementation Method>

[0082] When the hybrid driving mode is selected and the engine 10 is stopped, if the torque demand value TsR increases due to the driver operating the accelerator pedal, the engine 10 may need to be started. The control device 100 performs a first start process or a second start process as a process for starting the engine 10.

[0083] When starting engine 10 using the first starting process, such as using Figure 2 As explained, combustion begins in the engine 10 after the engine speed Ne rises to the electric motor speed Nm. Therefore, fluctuations in the electric motor speed Nm caused by starting the engine 10 can be easily suppressed using the electric generator 30 and the clutch 20. When starting the engine 10 using the first starting process, the abrupt change in the electric motor speed Nm caused by the sudden increase in engine speed Ne can be suppressed, thus vibrations caused by starting the engine 10 are less likely to occur in the vehicle 500. However, during the period until the engine speed Ne rises to the electric motor speed Nm, combustion does not begin in the engine 10, therefore the completion of starting the engine 10 is delayed.

[0084] When starting engine 10 using the second starting process, such as using Figure 3 As explained, combustion begins in engine 10 when the engine speed Ne is less than the electric motor speed Nm. Therefore, it is difficult to suppress the fluctuation in electric motor speed Nm caused by starting engine 10 using the electric generator 30 and clutch 20. As a result, vibrations caused by starting engine 10 are more likely to occur in vehicle 500. However, since engine 10 is started before engine speed Ne reaches electric motor speed Nm, starting engine 10 can be completed earlier.

[0085] Here, we will explain in detail why vibrations caused by starting the engine 10 are more likely to occur in the vehicle 500 when the second starting process is performed compared to when the first starting process is performed. Immediately after the initial combustion in the engine 10 (more specifically, immediately after the initial detonation), the engine torque Te and the torque capacity Tc of the clutch 20 deviate, thus causing a deviation in the rate of increase of the engine speed Ne. If the electric motor speed Nm is sufficiently high, the deviation in the rate of increase of the engine speed Ne will converge, thus minimizing deviation in the synchronization timing of the clutch 20. On the other hand, if the electric motor speed Nm is relatively low, the deviation in the rate of increase of the engine speed Ne is less likely to converge, thus causing a deviation in the synchronization timing of the clutch 20. Vibrations caused by starting the engine 10 can be mitigated by the electric motor torque Tm. However, due to the response delays of the crankshaft angle sensor 111 and the electric motor angle sensor 114, as well as the response delay of the electric motor torque Tm, it is necessary to predict the synchronization timing of the clutch 20 based on the rate of increase of the engine speed Ne. In the first starting process, since combustion in the engine 10 does not occur before the synchronization timing, the increase rate of engine speed Ne is low, and the increase rate does not deviate much. As a result, the synchronization timing of the clutch 20 can be predicted with high accuracy, and therefore vibrations caused by the starting of the engine 10 are less likely to occur.

[0086] In contrast, during the second starting process, the rate of increase in engine speed Ne deviates, making it impossible to accurately predict the synchronization timing of clutch 20. Therefore, by... Figure 3 The timing t23 shown is used to temporarily reduce the torque capacity Tc of the clutch 20 in an attempt to suppress vibrations caused by the starting of the engine 10. However, if a second starting process is performed when the motor torque Tm is relatively low, the synchronization timing of the clutch 20 may sometimes occur before the timing t23 when the reduction of torque capacity Tc begins. In this case, the reduction of torque capacity Tc cannot keep up, thus causing vibrations caused by the starting of the engine 10.

[0087] The greater the increase in torque requirement ΔTsR, the greater the acceleration of vehicle 500. With a high acceleration of vehicle 500, compared to a low acceleration, the occupants of vehicle 500 are less likely to experience discomfort due to vibrations generated within the vehicle. When starting engine 10 using the first starting process, the combustion in engine 10 begins later than when starting engine 10 using the second starting process. Therefore, in the first starting process, vibrations caused by starting engine 10 are less likely to increase, while in the second starting process, vibrations caused by starting engine 10 are more likely to increase. Furthermore, when the increase in torque requirement ΔTsR is large, it is desirable to complete the starting of engine 10 as early as possible to rapidly increase engine torque Te.

[0088] In this embodiment, when starting the engine 10, if the increase in torque requirement value ΔTsR is greater than or equal to the increase determination value ΔTsRTh, the engine 10 is started by a second starting process. In this case, the starting of the engine 10 can be completed earlier, and the occupants are less likely to feel uncomfortable with the vibration of the vehicle 500 caused by the starting of the engine 10. On the other hand, when starting the engine 10, if the increase in torque requirement value ΔTsR is less than the increase determination value ΔTsRTh, the engine 10 is started by a first starting process. In this case, there is a delay in the completion of the starting of the engine 10, but the vibration caused by the starting of the engine 10 is less likely to occur in the vehicle 500.

[0089] Therefore, the control device 100 can simultaneously suppress the discomfort felt by the occupants during the start-up of the engine 10 and ensure the early completion of the start-up of the engine 10.

[0090] It should be noted that, in this embodiment, the following effects can be further obtained.

[0091] (1) When the increase in torque requirement value ΔTsR is greater than or equal to the increase determination value ΔTsRTh, the second starting process is executed, thus the engine 10 is started earlier. That is, a state in which the system shaft torque Tsys can be increased using the engine torque Te can be created earlier. Therefore, the response delay of the increase in system shaft torque Tsys relative to the increase in torque requirement value TsR can be suppressed. On the other hand, when the increase in torque requirement value ΔTsR is less than the increase determination value ΔTsRTh, the rate of increase in system shaft torque Tsys can also be made less large. Therefore, the engine 10 is started by the first starting process. Therefore, when rapid acceleration of vehicle 500 is not required, the generation of vibration associated with the starting of engine 10 can be suppressed, and correspondingly, the occupants are less likely to feel unpleasant when the engine 10 is started.

[0092] (2) In this embodiment, during the phase when starting the engine 10 is not required, either a first starting process or a second starting process is provisionally selected as the process for starting the engine 10. Specifically, if the system shaft torque Tsys is less than the shaft torque determination value TsysTh, the first starting process is provisionally selected. If the system shaft torque Tsys is greater than or equal to the shaft torque determination value TsysTh, the second starting process is provisionally selected.

[0093] Here, when the system shaft torque Tsys is above the shaft torque judgment value TsysTh, even if the engine speed Ne increases sharply, the motor speed Nm is not easily affected. That is, the vibration caused by starting the engine 10 is not easily generated in the vehicle 500.

[0094] Furthermore, when the engine 10 is required to start under the condition that the second starting process is tentatively selected, the engine 10 will still be started by the second starting process even if the increase in torque requirement value ΔTsR is less than the increase determination value ΔTsRTh. Therefore, it is possible to complete the starting of the engine 10 as early as possible while suppressing driver dissatisfaction during engine 10 starting. In addition, it is possible to increase the chances of starting the engine 10 using the second starting process.

[0095] On the other hand, when the engine 10 is required to start under the condition that the first start-up process is tentatively selected, and the increase in torque requirement value ΔTsR is less than the increase determination value ΔTsRTh, the engine 10 is started by the first start-up process. That is, the first start-up process is executed when the system shaft torque Tsys is small and vibration is likely to occur in the vehicle 500 when the engine 10 is started. When the engine 10 is started using the first start-up process, vibration is less likely to occur in the vehicle 500, so the occupants are less likely to feel uncomfortable when the engine 10 is started.

[0096] (3) When the torque capacity Tc of the clutch 20 decreases under the assumption that the engine 10 is started using the second starting process, it is easier to use the clutch 20 to change the engine torque Te when the engine torque Te rises sharply. That is, the smaller the torque capacity Tc is under the assumption that the engine 10 is started using the second starting process, the less likely vibration caused by the starting of the engine 10 will occur in the vehicle 500. Therefore, in this embodiment, the predicted value of the torque capacity under the assumption that the engine 10 is started using the second starting process, i.e., the value that the predicted torque capacity Tce is smaller as much as possible, is set as the increase determination value ΔTsRTh. Thus, when it can be predicted that the torque capacity Tc can be reduced when the engine 10 is started using the second starting process, it is easier to perform the second starting process. That is, it is possible to increase the chance of performing the second starting process while suppressing the generation of vibration in the vehicle 500 when the engine 10 is started.

[0097] (4) When the oil temperature is low and the working oil viscosity is low, the clutch hydraulic pressure Pc is easily adjusted. That is, when a decrease in clutch hydraulic pressure Pc is indicated, the decrease begins quickly. On the other hand, when the oil temperature is low and the working oil viscosity is high, the clutch hydraulic pressure Pc is not easily adjusted. That is, the responsiveness of clutch hydraulic pressure Pc when a decrease in clutch hydraulic pressure Pc is indicated is low. Even for example, in Figure 3 As shown at timing t23, in order to reduce the torque capacity Tc of clutch 20, the clutch hydraulic pressure Pc is indicated to decrease, but the start of the decrease in clutch hydraulic pressure Pc is also delayed. As a result, the engine speed Ne is high before the torque capacity Tc actually decreases, thus making it easier to generate vibrations caused by starting the engine 10.

[0098] In this embodiment, the value that decreases as the oil temperature TOIL increases is set as the increment determination value ΔTsRTh. Therefore, when the oil temperature TOIL is high and the clutch hydraulic pressure Pc has high responsiveness, it is easier to perform the second starting process. That is, it is possible to increase the opportunity to perform the second starting process while suppressing vibrations generated in the vehicle 500 during engine 10 startup.

[0099] (5) When a high-speed transmission stage Z is selected as the transmission stage Z of the transmission mechanism 46, the vibration caused by starting the engine 10 is less likely to increase compared to the case where a low-speed transmission stage Z is selected as the transmission stage Z of the transmission mechanism 46. In this embodiment, the value that the higher the speed of the transmission stage Z selected by the transmission mechanism 46 is, the smaller the increase determination value ΔTsRTh is set. Therefore, the higher the speed of the transmission stage Z is, the easier it is to perform the second starting process. That is, it is possible to suppress the vibration generated in the vehicle 500 when the engine 10 is started while increasing the opportunity to perform the second starting process.

[0100] <Example of Change>

[0101] The above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0102] Alternatively, the increment determination value ΔTsRTh may not be variable based on the gear Z selected by the transmission mechanism 46. In this case, the vehicle 500 may also be a structure without a transmission device.

[0103] Alternatively, the increment determination value ΔTsRTh may not be variable based on the oil temperature TOIL. In this case, an electromagnetically driven clutch may be used as the clutch configured between the engine 10 and the electric generator 30.

[0104] Alternatively, the incremental determination value ΔTsRTh can be made variable without relying on the aforementioned predicted torque capacity Tce.

[0105] In the above embodiments, the increment determination value ΔTsRTh is variable based on the predicted torque capacity Tce, the transmission stage Z, and the oil temperature TOIL. On the other hand, the length of the specified period is fixed, but not limited to this. For example, the increment determination value ΔTsRTh may be fixed, and the length of the specified period may be variable based on at least one of the parameters: the predicted torque capacity Tce, the transmission stage Z, and the oil temperature TOIL. For example, the smaller the predicted torque capacity Tce, the longer the length of the specified period. Furthermore, for example, the longer the specified period may be, the higher the transmission stage Z is on the high-speed side. Additionally, for example, the longer the specified period may be, the higher the oil temperature TOIL.

[0106] When vehicle 500 has an automatic speed control function, sometimes other control devices besides control device 100 request acceleration of vehicle 500. These other control devices include, for example, a control device that controls the brakes of vehicle 500, and a control device that generates various commands related to automatic driving. In this case, control device 100 derives a torque request value TsR based on the request or command from the other control device. Furthermore, it uses the increase in torque request value ΔTsR at this time to determine whether to execute a first start-up process or a second start-up process.

[0107] In the above embodiment, when there is no requirement to start the engine 10, either the first start process or the second start process is temporarily selected as the process to start the engine 10 by the provisional selection process M21, but it is not limited to this. That is, the provisional selection process M21 may not be executed.

[0108] For example, when the engine 10 is required to start, it is possible to determine whether the system shaft torque Tsys is greater than or equal to the shaft torque determination value TsysTh and whether the increase in the torque requirement value ΔTsR is greater than or equal to the increase in the increase in the torque requirement value ΔTsRTh. Furthermore, if at least one of the following conditions is met: the system shaft torque Tsys is greater than or equal to the shaft torque determination value TsysTh and the increase in the torque requirement value ΔTsR is greater than or equal to the increase in the increase in the torque requirement value ΔTsRTh, then the second starting process is preferably executed. On the other hand, if neither the system shaft torque Tsys is greater than or equal to the shaft torque determination value TsysTh nor the increase in the torque requirement value ΔTsR is greater than or equal to the increase in the increase in the torque requirement value ΔTsRTh is met, then the first starting process is preferably executed.

[0109] Alternatively, for example, when the engine 10 is required to start, a determination can be made as to whether the increase in the torque requirement value ΔTsR is greater than or equal to the increase determination value ΔTsRTh. If the increase in the torque requirement value ΔTsR is greater than or equal to the increase determination value ΔTsRTh, a second start-up process is executed. On the other hand, if the increase in the torque requirement value ΔTsR is less than the increase determination value ΔTsRTh, a first start-up process is executed. In this case, the process to be executed is determined from the first and second start-up processes regardless of the magnitude of the system shaft torque Tsys.

[0110] exist Figure 5 In the final decision process M25 shown, the determination in step S15 can also be omitted.

[0111] It is also possible to have multiple first mappings MAP1 corresponding to the motor speed Nm. In this case, in the first determination value candidate setting process M15, the first mapping MAP1 corresponding to the current motor speed Nm is selected from the multiple first mappings MAP1. Furthermore, by referring to the selected first mapping MAP1, the system shaft torque Tsys corresponding to the predicted turbine speed Nte is set as the first shaft torque determination value TsysTh1.

[0112] It is also possible to have multiple second mappings MAP2 corresponding to the motor speed Nm. In this case, in the second determination value candidate setting process M17, the second mapping MAP2 corresponding to the current motor speed Nm is selected from the multiple second mappings MAP2. Furthermore, the system shaft torque Tsys corresponding to the predicted turbine speed Nte is set as the second shaft torque determination value TsysTh2 based on the second mapping MAP2 selected by the parameters.

[0113] In the above embodiment, the electric pump 80 and hydraulic control circuit 90, which supply working oil to the transmission device 40, also serve as the hydraulic supply system to the clutch 20, but are not limited thereto. The device for supplying hydraulic pressure to the clutch 20 may also be provided independently of the electric pump 80 and hydraulic control circuit 90.

[0114] The transmission device can also be a structure without a torque converter.

[0115] The transmission mechanism can also be a continuously variable transmission (CVT). In this case, it is best to set the increment judgment value ΔTsRTh according to the transmission ratio of the transmission mechanism.

[0116] The control device 100 is not limited to having a circuit with a CPU and ROM configured to perform software processing. That is, the control device 100 may be any of the structures described in (a) to (c) below.

[0117] (a) The control device 100 includes one or more processors that perform various processes according to a computer program. The processor includes a CPU and memories such as RAM and ROM. The memories store program code or instructions configured to cause the CPU to perform processes. Memory, or computer-readable medium, includes all usable media that can be accessed using a general-purpose or special-purpose computer.

[0118] (b) The control device 100 has one or more dedicated hardware circuits for performing various processes. Examples of dedicated hardware circuits include application-specific integrated circuits (ASICs) or FPGAs. It should be noted that ASIC is an abbreviation for "Application Specific Integrated Circuit" and FPGA is an abbreviation for "Field Programmable Gate Array".

[0119] (c) The control device 100 includes a processor that executes a portion of the various processes according to a computer program and dedicated hardware circuitry that executes the remaining processes in the various processes.

Claims

1. A control device for a hybrid vehicle, wherein, The hybrid vehicle has an engine with a crankshaft and an electric generator with a drive shaft as power sources, and a clutch is provided between the crankshaft and the drive shaft. The control device includes an actuator for controlling the engine, the electric generator, and the clutch. The actuator is configured to perform a first start-up process and a second start-up process. The first starting process is as follows: when starting the engine under conditions where the increase in torque requirement relative to the power source is less than the increase determination value, the crankshaft speed (i.e., engine speed) is increased to the drive shaft speed (i.e., electric motor speed) by engaging the clutch, and then combustion in the engine begins. The second starting process is as follows: when starting the engine under conditions where the increase in the required torque value is greater than or equal to the increase determination value, after the crankshaft begins to rotate by engaging the clutch, combustion in the engine is initiated before the engine speed reaches the electric motor speed. The actuator is configured to perform the second start-up process when starting the engine, provided that at least one of the following conditions is met: the shaft torque of the drive shaft, i.e., the system shaft torque, is above the shaft torque determination value or the increase in the torque requirement value is above the increase determination value; and on the other hand, to perform the first start-up process when neither the system shaft torque is above the shaft torque determination value nor the increase in the torque requirement value is above the increase determination value.

2. A control device for a hybrid vehicle, wherein, The hybrid vehicle has an engine with a crankshaft and an electric generator with a drive shaft as power sources, and a clutch is provided between the crankshaft and the drive shaft. The control device includes an actuator for controlling the engine, the electric generator, and the clutch. The actuator is configured to perform a first start-up process and a second start-up process. The first starting process is as follows: when starting the engine under conditions where the increase in torque requirement relative to the power source is less than the increase determination value, the crankshaft speed (i.e., engine speed) is increased to the drive shaft speed (i.e., electric motor speed) by engaging the clutch, and then combustion in the engine begins. The second starting process is as follows: when starting the engine under conditions where the increase in the required torque value is greater than or equal to the increase determination value, after the crankshaft begins to rotate by engaging the clutch, combustion in the engine is initiated before the engine speed reaches the electric motor speed. The actuator is configured such that the smaller the predicted value of the clutch torque capacity is when the engine is started using the second starting process, the smaller the value is, the greater the increase determination value is.

3. The control device for hybrid vehicles according to claim 2, The hybrid vehicle has a hydraulically driven clutch as the clutch. The actuator is configured to set the increase determination value as the value that decreases as the temperature of the clutch working oil increases.

4. The control device for a hybrid vehicle according to claim 2 or 3, The hybrid vehicle is equipped with a transmission, and the electric generator is arranged between the clutch and the transmission in the torque transmission path. The actuator is configured to set the increment determination value as smaller as the speed stage selected by the transmission device is on the higher speed side.

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