Vehicle transmission control system

Abstract

To achieve both prevention of oversteer and ensuring of a regeneration amount in a rear drive vehicle.SOLUTION: A vehicle transmission control device comprises: an engine 4; a motor 5; an automatic transmission 8; a friction brake system 3; and a control device (controller 20) which executes regenerative control and variable speed control while a vehicle is decelerated with brake force distributed to front wheels 2F and rear wheels through the friction brake system. The control device increases input torque of an input shaft 8a in accordance with a shift down so that an acceleration variation of the vehicle associated with the shift down becomes equal to a target acceleration variation. When determining an oversteer state during the shift down while the regenerative control is in execution, the control device maintains regenerative operation of the motor while increasing the input torque of the input shaft so as to reduce regenerative brake torque and causes the automatic transmission to perform the shift down with an increment amount of the input torque of the input shaft in accordance with the shift down larger than the increment amount when the oversteer state is not determined.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The technology disclosed herein relates to a shift control device for a vehicle.

Background Art

[0002] Patent Document 1 describes a control device for a hybrid vehicle. This hybrid vehicle includes an engine, a motor, and an automatic transmission. The engine and the motor are connected to the input shaft of the automatic transmission. This hybrid vehicle improves fuel consumption performance by causing the motor to perform a regenerative operation when the automatic transmission downshifts.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a rear-wheel drive vehicle in which the output shaft of the automatic transmission is connected to the rear wheels, when the motor performs a regenerative operation, regenerative braking torque is applied only to the rear wheels. Therefore, for example, when the motor performs a regenerative operation during deceleration and turning, the lateral force of the rear wheels decreases and the behavior of the vehicle tends to be in an oversteer state.

[0005] If the regenerative operation of the motor is stopped when the vehicle is in an oversteer state, the braking force corresponding to the regenerative braking torque is distributed to the front and rear wheels by the friction brake, so the lateral force of the rear wheels is restored and the oversteer state of the vehicle is eliminated. However, stopping the regenerative operation reduces the fuel consumption performance of the hybrid vehicle.

[0006] Note: There seems to be a mistake in the original text where line ID=27 is marked as "

発明の概要

[0007] The technology disclosed herein achieves both the suppression of oversteer in rear-wheel-drive vehicles and the securing of regenerative braking. [Means for solving the problem]

[0008] The inventors of this invention analyzed the relationship between the behavioral stability of a rear-wheel-drive vehicle and the amount of regenerative braking, and found that even if the amount of regenerative braking is reduced to a certain extent, the oversteer condition will be resolved after the vehicle starts to oversteer during deceleration, without having to reduce the amount of regenerative braking to zero.

[0009] On the other hand, when an automatic transmission downshifts, the torque to the rear wheels fluctuates due to the inertia torque generated by the automatic transmission during the downshift. Downshifting when a rear-wheel-drive vehicle is in an oversteer state may destabilize the vehicle's behavior.

[0010] As mentioned above, the torque of the rear wheels fluctuates as the automatic transmission downshifts, causing a change in the vehicle's acceleration. When the automatic transmission downshifts, control is performed to increase the input torque applied to the input shaft of the automatic transmission so that the vehicle's acceleration reaches the target acceleration. Further investigation by the inventors of the present invention revealed the following: In other words, if an oversteer condition of the vehicle is detected during the automatic transmission downshift, the amount of increase in the input torque of the input shaft is increased to a greater amount than the amount of increase when an oversteer condition is not detected, and the automatic transmission is then instructed to downshift. This suppresses torque fluctuations in the rear wheels, and the automatic transmission can downshift while suppressing instability in the vehicle's behavior.

[0011] Specifically, the technology disclosed herein relates to a vehicle transmission control device. This transmission control device is An engine mounted on a vehicle and generating the driving force for the vehicle, A motor that generates the driving force for the vehicle and supplies regenerative energy to the battery when the vehicle decelerates, An automatic transmission in which the input shaft is connected to the engine and the motor, and the output shaft is connected to the rear wheel, and the input rotation is changed to output at a gear ratio corresponding to the gear stage, A friction brake system that distributes braking force to the front and rear wheels in accordance with the driver's brake pedal operation, The system includes a controller that performs regenerative control, which applies regenerative braking torque to the rear wheels by causing the motor to perform regenerative operation, and shift control, which causes the automatic transmission to shift down by outputting a shift-down signal corresponding to the rotational speed of the input shaft to the automatic transmission, while the friction brake system is distributing braking force to the front and rear wheels during deceleration of the vehicle, The controller increases the input torque of the input shaft of the automatic transmission in accordance with the downshift so that the acceleration fluctuation of the vehicle accompanying the downshift of the automatic transmission becomes the target acceleration fluctuation. Furthermore, if the controller determines that the vehicle is in an oversteer state during the regenerative control and while the automatic transmission is downshifting, it maintains the regenerative operation of the motor while increasing the input torque of the input shaft of the automatic transmission so that the regenerative braking torque decreases, and causes the automatic transmission to downshift when the amount of increase in the input torque of the input shaft in accordance with the downshift is greater than the amount of increase when the oversteer state is not determined.

[0012] In this configuration, while the vehicle is decelerating and the friction brake system is distributing braking force to the front and rear wheels, the motor performs regenerative braking. This control is a regenerative coordinated control between the friction brake system and the motor. This regenerative coordinated control increases the regenerative energy stored in the battery. The regenerative braking torque from the motor is applied only to the rear wheels via the automatic transmission. The friction brake system distributes braking force to the front and rear wheels, taking into account the regenerative braking torque applied to the rear wheels. As a result, the braking force acting on the vehicle corresponds to the driver's brake pedal operation.

[0013] Furthermore, while the vehicle is decelerating, the controller outputs a downshift signal to the automatic transmission corresponding to the rotational speed of the input shaft. Upon receiving the downshift signal, the automatic transmission performs a downshift, changing the gear from a high gear to a low gear. During vehicle deceleration, the gear corresponding to the engine's operating state is selected.

[0014] If the system detects an oversteer condition during the regenerative braking coordinated control described above, while the automatic transmission is downshifting, the controller increases the input torque of the automatic transmission's input shaft to reduce the regenerative braking torque. This reduces the regenerative braking torque applied to the rear wheels, ensuring sufficient lateral force on the rear wheels, thus resolving the vehicle's oversteer condition. The friction brake system compensates for the reduced braking force due to the decrease in regenerative braking torque.

[0015] Although regenerative braking torque decreases, the motor's regenerative operation is maintained. Even when the vehicle is in an oversteer state, the amount of regeneration is secured as much as possible, which is advantageous for improving the vehicle's fuel efficiency.

[0016] Here, the controller increases the input torque of the input shaft of the automatic transmission in accordance with the downshift so that the vehicle's acceleration fluctuation associated with the downshift of the automatic transmission matches the target acceleration fluctuation. By increasing the input torque of the input shaft in accordance with the downshift of the automatic transmission, excessive shift shock is suppressed while the vehicle's acceleration fluctuation matches the target acceleration fluctuation.

[0017] If an oversteer condition is detected in the vehicle, the controller will cause the automatic transmission to downshift when the increase in input torque of the input shaft during the downshift is greater than the increase when an oversteer condition is not detected. This further suppresses torque fluctuations in the rear wheels during the downshift, thus preventing the vehicle's behavior from becoming unstable due to the downshift if an oversteer condition is detected during the downshift.

[0018] Therefore, this transmission control device can maintain the regenerative operation and stabilize the behavior of the vehicle.

[0019] When determining the oversteer state, the controller may increase the increase amount of the input torque of the input shaft by making the target acceleration fluctuation smaller than when the oversteer state is not determined.

[0020] By doing so, when determining the oversteer state, the torque fluctuation of the rear wheels associated with downshifting is suppressed, which is advantageous for stabilizing the behavior of the vehicle.

[0021] When the oversteer state of the vehicle diverges, the controller may cause the friction brake system to execute control to stabilize the behavior of the vehicle by applying braking force to the front wheels or the rear wheels.

[0022] That is, when the oversteer state of the vehicle diverges, it is possible to avoid the situation where the behavior of the vehicle becomes uncontrollable due to the operation of DSC (Dynamic Stability Control) or ABS (Anti-lock Brake System).

[0023] During deceleration of the vehicle when the friction brake system is not applying braking force to the front wheels and the rear wheels, the controller executes a second regenerative control to apply regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation. When the controller determines the oversteer state of the vehicle during the second regenerative control, the controller may maintain the regenerative operation.

[0024] For example, when the vehicle is decelerating with the driver's accelerator pedal off and the brake pedal off, the controller applies regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation (that is, the second regenerative control). The regenerative braking torque in this case may be, for example, a braking torque corresponding to an engine brake. This regenerative braking torque is relatively small.

[0025] During the second regenerative control, if the oversteer state of the vehicle is determined, the motor maintains the regenerative operation. As a result, the regenerative amount is ensured, which is advantageous for improving the fuel consumption performance of the vehicle.

[0026] When the controller determines the oversteer state of the vehicle during the second regenerative control and during the downshift of the automatic transmission, the controller maintains the regenerative operation of the motor and downshifts the automatic transmission in a state where the increase amount of the input torque of the input shaft according to the downshift is larger than the increase amount when the oversteer state is not determined.

[0027] Even when the oversteer state of the vehicle is determined during the second regenerative control, the controller suppresses the destabilization of the vehicle behavior associated with the downshift by relatively increasing the input torque of the input shaft according to the downshift while maintaining the regenerative operation of the motor, as described above.

[0028] When the oversteer state of the vehicle is resolved and during the downshift, the controller downshifts the automatic transmission in a state where the increase amount of the input torque of the input shaft according to the downshift is larger than the increase amount when the oversteer state is not determined.

[0029] Even after the oversteer state is resolved, there is a risk that the vehicle behavior may become unstable due to the downshift. Therefore, the automatic transmission downshifts in a state where the increase amount of the input torque of the input shaft is relatively increased. The destabilization of the vehicle behavior associated with the downshift is suppressed.

[0030] The controller receives signals from a first sensor that outputs a signal related to the vehicle behavior and a second sensor that outputs a signal related to the driver's steering operation, and determines the oversteer state of the vehicle. ru.

[0031] By determining an oversteer condition based on the signals from the first and second sensors, the controller can quickly and accurately determine the vehicle's behavior. [Effects of the Invention]

[0032] According to the aforementioned vehicle's transmission control device, it is possible to suppress oversteer in rear-wheel-drive vehicles while simultaneously ensuring sufficient regenerative braking. [Brief explanation of the drawing]

[0033] [Figure 1] Figure 1 shows a hybrid vehicle. [Figure 2] Figure 2 shows the fastening table for an automatic transmission. [Figure 3] Figure 3 is a block diagram of the gear shift control device. [Figure 4] Figure 4 is an overall flowchart of the control related to behavioral stability. [Figure 5] Figure 5 illustrates the control function related to behavioral stability. [Figure 6] Figure 6 is a flowchart of the first process. [Figure 7] Figure 7 shows the downshift points for each gear in an automatic transmission. [Figure 8] Figure 8 is a flowchart of the second process. [Figure 9] Figure 9 is a flowchart of the gear shift control process. [Figure 10] Figure 10 is a flowchart of the third process. [Figure 11] Figure 11 is a flowchart of the fourth process. [Figure 12] Figure 12 is a time chart showing the case where downshifting is delayed. [Figure 13] Figure 13 is a time chart showing the time it takes to release the K1 clutch of the automatic transmission as a result of delaying the downshift. [Figure 14] Figure 14 is a time chart showing what happens when oversteer is detected during a downshift. [Figure 15] Figure 15 is a flowchart showing a modified example of the second process. [Modes for carrying out the invention]

[0034] The following describes an embodiment of a vehicle's transmission control device with reference to the drawings. The transmission control device described here is illustrative.

[0035] (Hybrid vehicles) Figure 1 shows an automobile 1 (an example of a vehicle) to which the disclosed technology is applied. This automobile 1 is a hybrid automobile capable of running on electricity. The automobile 1 has a total of four wheels: two front wheels 2F and two rear wheels 2R. Friction brakes 31 are attached to the front wheels 2F and the rear wheels 2R to brake their rotation.

[0036] Automobile 1 is equipped with an engine 4 and a motor 5 as its power sources. These work together to drive the rear wheels 2R, thereby enabling automobile 1 to move. Automobile 1 is a rear-wheel-drive vehicle. In addition to being a power source, motor 5 is also used as a generator during regenerative braking.

[0037] As described later, this vehicle 1 is equipped with a high-voltage battery 9 with a rated voltage of 50V or less. Power supplied from this high-voltage battery 9, the motor 5 primarily assists the engine 4 in driving (a so-called mild hybrid vehicle). Vehicle 1 may also be a so-called plug-in hybrid vehicle that can receive power from an external power source.

[0038] In this automobile 1, the engine 4 is located at the front of the vehicle, and the drive wheels are located at the rear of the vehicle. In other words, this automobile 1 is a so-called FR (front-engine, rear-wheel drive) vehicle.

[0039] Automobile 1 is equipped with an engine 4, a motor 5, and as part of its drivetrain, a K0 clutch 6, an inverter 7, and an automatic transmission 8. Automobile 1 is also equipped with a controller 20 as part of its control system. Automobile 1 is also equipped with a friction brake system 3, including a friction brake 31, as part of its braking system.

[0040] (Drive system components) Engine 4 is, for example, an internal combustion engine that burns fossil fuels. Engine 4 is also a so-called four-stroke engine that generates rotational power by repeating the intake, compression, expansion, and exhaust cycles. Engine 4 can be of various types and forms, such as spark-ignition engines and compression-ignition engines, but the disclosed technology does not particularly limit the type or form of engine 4.

[0041] In this automobile 1, the engine 4 is positioned approximately in the center of the vehicle width direction, with the crankshaft 4a that outputs rotational power facing in the front-to-rear direction of the vehicle body. The automobile 1 is equipped with various devices and mechanisms associated with the engine 4, such as an intake system, an exhaust system, and a fuel supply system.

[0042] Motor 5 is a permanent magnet type synchronous motor driven by three-phase alternating current. Motor 5 is located in series behind the engine 4 via the K0 clutch 6. Motor 5 is also located in series in front of the automatic transmission 8.

[0043] The K0 clutch 6 is installed between the front end of the shaft 5a of the motor 5 and the crankshaft 4a of the engine 4. The K0 clutch 6 switches between a state in which the crankshaft 4a and shaft 5a are connected (connected state) and a state in which the crankshaft 4a and shaft 5a are separated (separated state).

[0044] The rear end of the motor 5's shaft 5a is connected to the input shaft 8a of the automatic transmission 8. Therefore, the engine 4 is connected to the automatic transmission 8 via the K0 clutch 6 and shaft 5a. By disengaging the K0 clutch 6, the engine 4 is disconnected from the automatic transmission 8.

[0045] While the vehicle 1 is in motion, the K0 clutch 6 is switched between an engaged state and an engaged state. For example, when the vehicle 1 is decelerating, the K0 clutch 6 may be put into the engaged state, and regeneration may be performed with the engine 4 disconnected.

[0046] The motor 5 is connected to a high-voltage battery 9 mounted on the vehicle as a power source via an inverter 7 and a high-voltage cable 40. In the case of this automobile 1, the high-voltage battery 9 is a DC battery with a rated voltage of 50V or less, specifically a 48V battery.

[0047] The high-voltage battery 9 supplies high-voltage DC power to the inverter 7. The inverter 7 converts this DC power into three-phase AC power and energizes the motor 5. This causes the motor 5 to rotate. The motor 5 also supplies regenerative energy back to the high-voltage battery 9.

[0048] The high-voltage battery 9 is also connected to the DC-DC converter 10 via a high-voltage cable 40. The DC-DC converter 10 converts 48V high-voltage DC power to 12V low-voltage DC power and outputs it. The DC-DC converter 10 (its output side) is connected to the low-voltage battery 11 (a so-called lead-acid battery) via a low-voltage cable 41.

[0049] The low-voltage battery 11 is connected to various electrical components via the low-voltage cable 41. The DC-DC converter 10 is also connected to the CAN (Controller Area Network) 12 via the low-voltage cable 41. As a result, the DC-DC converter 10 supplies low-voltage DC power to the CAN 12.

[0050] The automatic transmission 8 is a multi-stage automatic transmission (so-called AT). The automatic transmission 8 has an input shaft 8a at its front end, and this input shaft 8a is connected to the shaft 5a of the motor 5 as described above. The automatic transmission 8 has an output shaft 8b at its rear end, which rotates independently of the input shaft 8a.

[0051] Between the input shaft 8a and the output shaft 8b, a speed change mechanism consisting of a torque converter 8c, multiple planetary gear mechanisms, and multiple friction fastening elements is incorporated. Each friction fastening element is switched between a fastened state and a disfastened state by hydraulic pressure.

[0052] Figure 2 shows the fastening table for this automatic transmission 8. Circles in the table indicate fastening. This automatic transmission 8 incorporates three clutches consisting of a first clutch CL1, a second clutch CL2, and a third clutch CL3 as friction fastening elements, and two brakes consisting of a first brake BR1 and a second brake BR2.

[0053] The automatic transmission 8 uses hydraulic control to select and engage three elements from these three clutches and two brakes. In doing so, the automatic transmission's gears switch between forward gears from 1st to 8th gear, and reverse gears (reverse speed).

[0054] For example, in 1st gear, the first clutch CL1, the first brake BR1, and the second brake BR2 are engaged. When shifting up from 1st gear, the gear changes from 1st to 2nd gear by engaging the second clutch CL2 instead of the first clutch CL1. The gear changes from 2nd to 3rd gear by engaging the first clutch CL1 instead of the first brake BR1. The gear changes from 3rd to 4th gear by engaging the third clutch CL3 instead of the first clutch CL1.

[0055] Shifting up to 5th gear and beyond is done in the same way. Shifting down follows the reverse procedure of shifting up.

[0056] If the elements that should be fastened at each gear are not fastened, the input shaft 8a and the output shaft 8b will be disconnected (so-called neutral). Even if rotational power is input to the automatic transmission 8 from the drive source, that rotational power will not be output from the automatic transmission 8.

[0057] As described later, the automatic transmission 8 may be put into neutral while the vehicle 1 is decelerating. Specifically, when the automatic transmission 8 is in 2nd, 3rd, or 4th gear, the automatic transmission 8 is put into neutral by releasing the second clutch CL2. Also, when the automatic transmission 8 is in 5th, 6th, 7th, or 8th gear, the automatic transmission 8 is put into neutral by releasing the third clutch CL3. In the following explanation, these second clutch CL2 and third clutch CL3 may be collectively referred to as the K1 clutch. Releasing the K1 clutch while the vehicle 1 is decelerating means interrupting the power transmission between the input shaft 8a and the output shaft 8b of the automatic transmission 8, thereby putting the automatic transmission 8 into neutral.

[0058] As shown in Figure 1, the output shaft 8b of the automatic transmission 8 is connected to the differential gear 16 via a propeller shaft 15 that extends in the longitudinal direction of the vehicle body. The differential gear 16 is connected to a pair of drive shafts 17, 17 that extend in the width direction of the vehicle and are connected to the left and right rear wheels 2R, 2R. The rotational power output through the propeller shaft 15 is distributed by the differential gear 16 and then transmitted to each rear wheel 2R through this pair of drive shafts 17, 17.

[0059] (Speed ​​control device) Figure 3 is a block diagram of the transmission control device. The automobile 1 is equipped with the aforementioned controller 20 to control the movement of the automobile 1 by controlling the engine 4, motor 5, K0 clutch 6, automatic transmission 8, friction brake system 3, etc., in response to the driver's operation. The controller 20 consists of hardware such as a processor, memory, and interface, and software such as a database and control programs. Although Figure 3 shows a single controller 20 for the transmission control device, the controller of the transmission control device may be divided into a unit (PCM) that mainly controls the operation of the drive source (engine 4 and motor 5) and a unit (TCM) that mainly controls the operation of the K0 clutch 6 and automatic transmission 8. The PCM and TCM are connected by CAN 12 and configured to communicate with each other electrically.

[0060] The transmission control device is equipped with sensors that measure various parameters related to the vehicle's operation. Specifically, the transmission control device includes a vehicle speed sensor 51, a wheel speed sensor 52, a steering angle sensor 53, a yaw rate sensor 54, a brake pedal sensor 55, an accelerator pedal position sensor 56, an AT input torque sensor 57, and an AT input rotational speed sensor 58.

[0061] The vehicle speed sensor 51 outputs a signal corresponding to the vehicle speed of car 1. The wheel speed sensor 52 outputs a signal corresponding to the rotational speed of each of the four wheels 2F and 2R of car 1.

[0062] The steering angle sensor 53 outputs a signal corresponding to the rotation angle of the steering wheel 110 (see Figure 1) operated by the driver, i.e., the steering angle. The yaw rate sensor 54 outputs a signal corresponding to the yaw rate of the automobile 1.

[0063] The brake pedal sensor 55 outputs a signal corresponding to the degree to which the brake pedal 19 (see Figure 1) is pressed by the driver. The accelerator pedal position sensor 56 outputs a signal corresponding to the degree to which the accelerator pedal 18 (see Figure 1) is pressed by the driver.

[0064] The AT input torque sensor 57 outputs a signal corresponding to the input torque of the input shaft 8a of the automatic transmission 8. The AT input rotational speed sensor 58 outputs a signal corresponding to the rotational speed of the input shaft 8a of the automatic transmission 8.

[0065] The controller 20 receives the signals output by these sensors via CAN 12. The controller 20 outputs control signals via CAN 12 to the engine 4, inverter 7, K0 clutch 6, automatic transmission 8, and friction brake system 3. In this way, the controller 20 controls the engine 4, motor 5, K0 clutch 6, automatic transmission 8, and friction brake system 3.

[0066] (Control related to behavioral stability) <Overall control> Figure 4 shows the overall control of the vehicle's behavioral stability. Note that Figure 4, and the flowcharts in Figures 6, 8-11, and 8-15 (which will be explained later), basically relate to the control of vehicle 1 during deceleration.

[0067] Figure 5 illustrates the concept of the control functions related to the behavioral stability of automobile 1. Automobile 1 has three functions: active control, passive control, and DSC / ABS control. Active control functions to keep the grip force of wheels 2F and 2R within the friction circle illustrated in Figure 5. As long as the grip force of wheels 2F and 2R remains within the friction circle, the behavioral stability of automobile 1 is maintained. Active control is a control function for maintaining the behavioral stability of automobile 1.

[0068] The passive control system works by returning the grip force of wheels 2F and 2R back within the friction circle if the grip force of wheels 2F and 2R exceeds the friction circle, causing the behavior of car 1 to become unstable.

[0069] DSC / ABS control functions when the behavior of vehicle 1 is likely to diverge, in other words, when the grip force of wheels 2F and 2R is likely to exceed the circle with the largest diameter, by applying braking force to each wheel 2F and 2R through the friction brake 31, thereby bringing the grip force of wheels 2F and 2R back within the friction circle. DSC / ABS control can employ known technologies.

[0070] Automobile 1, which has three functions, can ensure the stability of the vehicle's behavior.

[0071] In the flow chart of Figure 4, in step S11 after the start, the controller 20 reads the sensor signal. The controller 20 determines the driving state of the vehicle 1. Then, the controller 20 executes the first process (step S12). The first process involves active control and switches the gear shift control according to the road surface μ. Details of the first process will be described later.

[0072] After the first process in step S12, the process moves to the second process (step S13) or the fourth process (step S15). The second process relates to passive control and concerns gear shift control when the vehicle 1 enters an oversteer state. Details of the second process will be described later.

[0073] After step S13, the process moves to either the third process (step S14) or the fourth process (step S15). The third process involves active control, switching the gear shift control according to the slip state of wheels 2F and 2R. Details of the third process will be described later. The fourth process is DSC / ABS control. Details of the fourth process will be described later.

[0074] <First Processing> Figure 6 is a flowchart of the first process. In step S21 after the start, the controller 20 determines whether the road surface μ is low or not. The controller 20 determines whether the road surface μ is lower than a predetermined value based on the vehicle speed, wheel speed, steering angle, and / or yaw rate. If the determination in step S21 is No, that is, if the road surface μ is not low, the process proceeds to step S22. If the determination in step S21 is Yes, that is, if the road surface μ is low, the process proceeds to step S25.

[0075] If the road surface friction coefficient (μ) is not low, that is, if the road surface friction coefficient is high and the grip of wheels 2F and 2R tends to remain within the friction circle, the controller 20 performs normal gear shift control. First, in step S22, the controller 20 determines whether the driver is pressing the brake pedal 19. The controller 20 makes this determination based on the signal from the brake pedal sensor 55. If the determination in step S22 is Yes, that is, if the driver is pressing the brake pedal 19, the process proceeds to step S23. If the determination in step S22 is No, that is, if the driver is not pressing the brake pedal 19, the process proceeds to step S24.

[0076] When the driver is pressing the brake pedal 19, the controller 20 performs regenerative coordinated control, which uses the regenerative braking torque of the motor 5 to supply a portion of the braking force requested by the driver. In addition, the hydraulic pressure of the friction brake 31 is reduced by the amount of the regenerative braking torque of the motor 5.

[0077] In step S23, the controller 20 selects the first shift point S1 as the downshift point for the automatic transmission 8. Figure 7 illustrates the downshift points for each gear of the automatic transmission 8. In Figure 7, the horizontal axis represents the vehicle speed, and the vertical axis represents the rotational speed of the input shaft 8a of the automatic transmission 8. The first shift point S1 is set to a constant rotational speed of the input shaft 8a for each gear, regardless of the vehicle speed. The first shift point S1 is higher than the second shift point S2 and the third shift point S3, which will be described later. For example, when driving in 6th gear, the rotational speed of the input shaft 8a of the automatic transmission 8 reaches the first shift point S1 when the vehicle speed is slightly less than 60 km / h, so the automatic transmission 8 shifts down from 6th gear to 5th gear. Along with the downshift, the rotational speed of the input shaft of the automatic transmission 8, in other words, the rotational speed of the motor 5, becomes higher than the first shift point S1. When the driver is pressing the brake pedal 19 and the controller 20 is performing regenerative cooperative control, setting the downshift point to the first gear shift point S1 allows the rotational speed of the motor 5 during regenerative operation to be maintained at a high level. A high motor rotational speed increases the amount of regeneration, thus improving the fuel efficiency of the vehicle 1.

[0078] If the driver is not pressing the brake pedal 19, the controller 20 does not perform regenerative braking control. The motor 5 applies regenerative braking torque equivalent to engine braking to the rear wheels 2R and performs regenerative operation. In a deceleration state where the driver is not pressing the brake pedal 19, the driver may press the accelerator pedal 18, which may change the request to acceleration. If the rotational speed of the input shaft 8a of the automatic transmission 8 is kept high by setting the downshift point to the first gear shift point S1, there is a risk that sufficient driving force may not be secured when the driver requests acceleration.

[0079] Therefore, in step S24, the controller 20 selects the second shift point S2 as the downshift point for the automatic transmission 8. As shown in Figure 7, the rotational speed of the input shaft 8a of the automatic transmission 8 is lower at the second shift point S2 than at the first shift point S1. As a result, the rotational speed of the input shaft 8a of the automatic transmission 8 is relatively lower during deceleration, so sufficient driving force can be secured when the driver requests acceleration.

[0080] After the normal control in step S23 or step S24, the process moves to the second process.

[0081] In contrast to normal control where the road surface friction coefficient (μ) is not low, when the road surface μ is low, the grip force of wheels 2F and 2R exceeds the friction circle, making it easy for the behavior of the vehicle 1 to become unstable. Therefore, the controller 20 performs control to prevent the behavior of the vehicle 1 from becoming unstable due to the shifting operation of the automatic transmission 8.

[0082] First, in step S25, the controller 20 determines whether or not the vehicle 1 is accelerating. If the vehicle 1 is accelerating (Yes), the process proceeds to step S26; if the vehicle 1 is not accelerating (No), the process proceeds to step S27.

[0083] If vehicle 1 is accelerating, the automatic transmission 8 will shift up as the vehicle speed and / or the rotational speed of the input shaft 8a of the automatic transmission 8 increase. Vehicle 1, while accelerating, will eventually decelerate, and during deceleration, the automatic transmission 8 will shift down. When the automatic transmission 8 shifts down, the torque fluctuation of the rear wheels 2R is caused by the inert shuttle of the automatic transmission 8. If the road surface friction coefficient (μ) is low, the torque fluctuation of the rear wheels 2R associated with the downshift may destabilize the behavior of vehicle 1. Therefore, in step S26, the controller 20 suppresses the upshift. Specifically, the controller 20 prohibits the automatic transmission 8 from shifting up from 6th gear to 7th gear, and from 7th gear to 8th gear. In step S26, the automatic transmission 8 will be at a maximum of 6th gear. Limiting the maximum gear of the automatic transmission 8 reduces the frequency of downshifts during subsequent deceleration. This reduces the opportunities for the behavior of vehicle 1 to become unstable.

[0084] Step S27 corresponds to the deceleration of the vehicle 1. As the vehicle speed and / or the rotational speed of the input shaft 8a of the automatic transmission 8 decreases, the automatic transmission 8 performs a downshift. The controller 20 performs the downshift when the vehicle speed is as low as possible in order to avoid as much instability as possible in the behavior of the vehicle 1 caused by the downshift. Specifically, the controller 20 selects the third shift point S3 as the downshift point of the automatic transmission 8. The third shift point S3 is lower than the first shift point S1 and the second shift point S2, as shown in Figure 7.

[0085] As mentioned above, since shifting up to 7th and 8th gear is prohibited, the maximum speed is 6th gear. Moreover, the downshift point is the third gear shift point S3. For this reason, in step S27, the automatic transmission 8 will not downshift until the vehicle speed drops to about 40 km / h, as shown by the white arrow in Figure 7. Since downshifting does not occur at high vehicle speeds, the instability of the vehicle 1's behavior can be suppressed.

[0086] In the subsequent step S28, the controller 20 disengages the K1 clutch when the rotational speed of the input shaft 8a of the automatic transmission 8 falls below the third gear shift point S3. As mentioned above, the K1 clutch is a clutch composed of friction engagement elements of the automatic transmission 8, and when the K1 clutch is disengaged, power transmission between the input shaft 8a and the output shaft 8b of the automatic transmission 8 is interrupted. Disengaging the K1 clutch reduces the torque applied to the rear wheel 2R, thereby suppressing instability in the behavior of the automobile 1 and preventing engine stall due to a further decrease in the rotational speed of the engine 4.

[0087] After active control in the case of low road surface friction coefficient, the process moves to the fourth step.

[0088] <Second Processing> Figure 8 is a flowchart of the second process. As mentioned above, the second process is passive control. In step S31 after the start, the controller 20 determines whether or not an oversteer determination has been made. The controller 20 determines whether or not the vehicle 1 is in an oversteer state based on the difference between the estimated yaw rate, which can be calculated from the vehicle speed and steering angle, and the actual yaw rate based on the signal from the yaw rate sensor 54. If the difference between the estimated yaw rate and the actual yaw rate is greater than or equal to a predetermined value, the controller 20 may determine that the vehicle 1 is in an oversteer state. If the determination in step S31 is No, that is, if the vehicle 1 is not in an oversteer state, passive control is not performed. The process proceeds to the third process. On the other hand, if the determination in step S31 is Yes, that is, if the vehicle 1 is in an oversteer state, the process proceeds to step S32.

[0089] In step S32, the controller 20 determines whether or not brake regeneration is being performed. In other words, it determines whether or not the driver is pressing the brake pedal 19. If the determination in step S32 is Yes, the process proceeds to step S33; if the determination in step S32 is No, the process does not proceed to step S33 but proceeds to step S34.

[0090] When the driver is pressing the brake pedal 19 during deceleration, as mentioned above, regenerative cooperative control is performed in which a portion of the braking force requested by the driver is supplied by the regenerative braking torque of the motor 5. The regenerative braking torque of the motor 5 is applied only to the rear wheel 2R of the rear-wheel-drive vehicle 1. As a result, the lateral force on the rear wheel 2R decreases, making the behavior of the vehicle 1 prone to oversteer.

[0091] Therefore, in step S33, the controller 20 performs torque-up control. Specifically, it increases the input torque of the input shaft 8a of the automatic transmission 8 so that the regenerative braking torque of the motor 5, which had been supplying part of the braking force of the friction brake 31, is eliminated. Torque-up control corresponds to the end of regenerative cooperative control. The friction brake system 3 compensates for the braking force lost due to the elimination of regenerative braking torque with the braking force of the friction brake 31. Even after the regenerative cooperative control ends, regenerative braking torque equivalent to engine braking due to the release of the accelerator remains, and the regenerative operation of the motor 5 continues. Even if the vehicle 1 enters an oversteer state, the amount of regeneration is secured, which is advantageous for improving the fuel efficiency of the vehicle 1.

[0092] As the regenerative braking torque applied to the rear wheel 2R decreases and lateral force is secured on the rear wheel 2R, the oversteer condition of vehicle 1 begins to resolve. The deviation between the estimated yaw rate and the actual yaw rate begins to decrease. The behavior of vehicle 1 can be stabilized while securing as much regeneration as possible. After step S33, the process proceeds to step S34.

[0093] Furthermore, in step S32, when brake regeneration is not performed, that is, when the driver is not pressing the brake pedal 19 during deceleration, a second regenerative control is performed that provides regenerative braking equivalent to engine braking, and since regenerative coordinated control is not performed, the torque increase in step S33 does not occur. Even when the process transitions from step S32 to step S34, the motor 5 performs regenerative operation with regenerative braking torque equivalent to engine braking when the accelerator is released.

[0094] In step S34, the controller 20 determines whether the unstable behavior of the vehicle 1 is diverging. The controller 20 may determine that the unstable behavior of the vehicle 1 is diverging, for example, if the deviation between the estimated yaw rate and the actual yaw rate is increasing. If the determination in step S34 is Yes, the process proceeds to step S35. If the determination in step S34 is No, the process proceeds to step S310.

[0095] In step S35, the controller 20 determines whether the automatic transmission 8 is shifting gears (i.e., out of gear). If the automatic transmission 8 is not shifting gears (i.e., Yes), the process proceeds to step S36. If the automatic transmission 8 is shifting gears (i.e., No), the process proceeds to step S310.

[0096] In step S36, the controller 20 delays the downshift of the automatic transmission 8. That is, even when the vehicle 1 reaches the downshift point, the controller 20 prohibits the downshift of the automatic transmission 8 until the oversteer condition of the vehicle 1 is resolved. As mentioned above, the downshift of the automatic transmission 8 is accompanied by torque fluctuations in the rear wheels 2R, which may further destabilize the behavior of the vehicle 1, but prohibiting the downshift suppresses further destabilization of the vehicle 1's behavior. The downshift point is normally the first gear shift point S1 or the second gear shift point S2 of the gear shift control.

[0097] In the following step S37, the controller 20 determines whether the oversteer condition of the vehicle 1 has been resolved. The controller 20 may determine that the oversteer condition of the vehicle 1 has been resolved if the deviation between the estimated yaw rate and the actual yaw rate falls below a predetermined value. If the oversteer condition of the vehicle 1 has been resolved, the process proceeds to the fourth process. If the oversteer condition of the vehicle 1 has not been resolved, the process proceeds to step S38.

[0098] In step S38, the controller 20 determines whether the rotational speed of the input shaft 8a of the automatic transmission 8 has reached the third shift point S3. If the rotational speed of the input shaft 8a has reached the third shift point S3, the process proceeds to step S39; otherwise, the process proceeds to the fourth process. As mentioned above, the third shift point S3 is a downshift point that takes engine stall into consideration.

[0099] In step S39, the controller 20 releases the K1 clutch of the automatic transmission 8, similar to step S28 of the first process. This prevents engine stalling. The process then proceeds to the fourth process.

[0100] Thus, if the vehicle 1 enters an oversteer state while decelerating using regenerative cooperative control or second regenerative control, the downshift of the automatic transmission 8 is delayed. This prevents the vehicle's behavior from becoming even more unstable due to the downshift. Furthermore, if the downshift of the automatic transmission 8 is delayed, the rotational speed of the input shaft 8a of the automatic transmission 8 decreases, which could lead to engine stall. However, once the rotational speed of the input shaft 8a of the automatic transmission 8 reaches the limit rotational speed (i.e., the third gear shift point S3), the power transmission between the input shaft 8a and the output shaft 8b of the automatic transmission 8 is interrupted, thus preventing engine stall.

[0101] On the other hand, if the vehicle 1 is in an oversteer state and the automatic transmission 8 is downshifting (if step S35 is No), or if the delayed downshift is performed after the oversteer state of the vehicle 1 has been resolved (if step S34 is No), the controller 20 performs gear shift control in step S310 when oversteer is detected. Details of this gear shift control will be described later. Simply put, the torque of the rear wheels 2R fluctuates due to the inertia of the automatic transmission 8 when downshifting. In the gear shift control in step S310 when oversteer is detected, the input torque of the input shaft 8a of the automatic transmission 8 is increased compared to the input torque during normal gear shift control, i.e., when oversteer is not detected, so that the torque fluctuation of the rear wheels 2R due to inertia is suppressed. As a result of the relatively increased amount of input torque, torque fluctuations are suppressed even when downshifting is performed, and the deterioration of the instability of the vehicle 1's behavior due to downshifting is suppressed.

[0102] In the following step S311, the controller 20 determines whether or not brake regeneration is in progress. If it is Yes, the process proceeds to step S312. On the other hand, if it is No, the process proceeds from step S311 to the fourth process.

[0103] In step S312, the controller 20 discontinues regenerative cooperative control and secures the braking force that was previously provided by the regenerative braking torque of the motor 5 using the friction brake 31, achieving a deceleration that matches the braking required by the driver. Even after the regenerative cooperative control ends, the regenerative braking torque equivalent to the engine braking that occurs when the accelerator is released remains, and the regenerative operation of the motor 5 continues.

[0104] <Speed ​​change processing> Figure 9 is a flowchart of the gear shift control. In step S41 after starting, the controller 20 reads the AT input torque and the AT input rotational speed. The process then proceeds to steps S42 and S44, respectively.

[0105] In step S42, the controller 20 sets the target acceleration fluctuation for shifting gears of the automatic transmission 8. The target acceleration fluctuation is the target value of the acceleration fluctuation that occurs in the vehicle 1 when the automatic transmission 8 shifts gears. Basically, the higher the AT input rotational speed, the larger the target acceleration fluctuation is set to be. When the AT input rotational speed is high, it is acceptable for the driver to feel the shift up or down. The target acceleration fluctuation is determined from the gear position of the automatic transmission 8 and the AT input rotational speed, based on the relational formula or map set for each of the up and down shifts.

[0106] In the following step S43, the controller 20 calculates the AT output torque from the set target acceleration fluctuation. The AT output torque is the torque fluctuation of the output shaft 8b when the automatic transmission 8 shifts gears.

[0107] Meanwhile, in step S44, the controller 20 sets the target shift time for the automatic transmission 8 during gear changes. Basically, the higher the AT input rotational speed, the shorter the target shift time is set. When the AT input rotational speed is high, it is required that the upshift or downshift be completed quickly. The target shift time is determined from the gear position of the automatic transmission 8 and the AT input rotational speed, based on the relational formula or map set for upshifts and downshifts, respectively.

[0108] In the following step S45, the controller 20 calculates the AT input rotational slope from the set target shift time. The AT input rotational slope is the rate of change of the rotational speed of the input shaft 8a during gear shifting of the automatic transmission 8.

[0109] After steps S43 and S45, the process proceeds to step S46. In step S46, the controller 20 determines whether or not correction of the calculated AT output torque and / or AT input rotational inclination is necessary. As described in step S310 of the second process above, when the vehicle 1 shifts gears in an oversteer state, it is necessary to suppress the torque fluctuation of the rear wheel 2R associated with the downshift in order to stabilize the behavior of the vehicle 1. In this case, the controller 20 determines in step S46 that correction is necessary. If the determination in step S46 is Yes, the process proceeds to step S47, where the calculated AT output torque and / or AT input rotational inclination are corrected. Specifically, in gear shift control when oversteer is detected, correction is made so that the torque fluctuation of the rear wheel 2R is suppressed, or in other words, so that the AT output torque becomes flat. When an oversteer state is detected, the target acceleration fluctuation is made smaller than when an oversteer state is not detected. After the correction, the process proceeds to step S48. On the other hand, if the decision in step S46 is No, that is, in normal gear shift control where no correction is needed, the process does not proceed to step S47 but proceeds to step S48.

[0110] Furthermore, in the first cooperative gear shift control in step S54 and the second cooperative gear shift control in step S55 of the third process described later, the correction in step S47 is also performed to suppress torque fluctuations of the rear wheel 2R during gear shifting.

[0111] In step S48, the controller 20 calculates the AT input torque based on the AT output torque and the AT input rotational inclination. The AT input torque is the torque input to the input shaft 8a of the automatic transmission 8, and the AT input torque is mainly adjusted by the motor 5. When a downshift is performed in step S310 of the second process described above, the amount of increase in the AT input torque is greater than the amount of increase during a normal downshift (i.e., when an oversteer condition is not detected and no correction is applied) as a result of the correction performed in step S47.

[0112] Once the AT input torque is calculated, in the following step S49, the controller 20 calculates the hydraulic pressure to be supplied to the friction engagement elements of the automatic transmission 8 to correspond to the calculated AT input torque. By supplying hydraulic pressure to the friction engagement elements according to the set hydraulic pressure, the automatic transmission 8 performs a downshift or upshift.

[0113] <Third Processing> Figure 10 is a flowchart of the third process. As mentioned above, the third process is active control. In step S51 after the start, the controller 20 determines whether a slip determination has been made. The controller 20 may determine the slip state of each wheel 2F and 2R based, for example, on the vehicle speed and wheel speed. If the determination in step S51 is Yes, that is, if it is determined that wheels 2F and 2R are slipping, the process proceeds to step S52. If it is No, that is, if it is determined that wheels 2F and 2R are not slipping, the process proceeds to step S53.

[0114] In step S53, the controller 20 determines whether a turning determination has been made. The controller 20 may determine the turning state of the vehicle 1 based, for example, on the steering angle and the yaw rate. If the determination in step S53 is Yes, that is, if it is determined that the vehicle 1 is in a turning state, the process proceeds to step S52. If the determination is No, that is, if it is determined that the vehicle 1 is not in a turning state, the process proceeds to step S56.

[0115] In step S56, the controller 20 performs normal gear shift control. That is, since wheels 2F and 2R are not in a slipping state and the vehicle 1 is moving straight, there is a low possibility that the vehicle 1 will become unstable when the automatic transmission 8 shifts gears. In step S56, the correction in step S47 in the gear shift control flow of Figure 9 is not performed.

[0116] On the other hand, in steps S52, S54, and S55, if wheels 2F and 2R are in a slipping state, or if the vehicle 1 is in a turning state, and the automatic transmission 8 shifts gears in this state, causing the torque of the rear wheel 2R to fluctuate, the behavior of the vehicle 1 may become unstable. Therefore, the controller 20 performs control to prevent the behavior of the vehicle 1 from becoming unstable.

[0117] First, in step S52, the controller 20 determines whether or not brake regeneration is being performed. If the answer is Yes, indicating that brake regeneration is in progress, the process proceeds to step S54. On the other hand, if the answer is No, indicating that brake regeneration is not in progress, the process proceeds to step S55.

[0118] When regenerative braking is performed, the controller 20 performs coordinated control of the friction brake system 3, the motor 5, and the automatic transmission 8. Specifically, in step S54, the automatic transmission 8 performs gear shift control so as to suppress torque fluctuations in the rear wheels 2R associated with gear shifting. In step S54, the correction in step S47 of the gear shift control flow in Figure 9 is performed. In addition, the friction brake system 3 and / or the motor 5 apply torque to the rear wheels 2R to compensate for torque fluctuations during gear shifting. As a result, instability in the behavior of the vehicle 1 is suppressed.

[0119] If regenerative braking is not being performed, the controller 20 performs coordinated control of the motor 5 and the automatic transmission 8. In step S55, the automatic transmission 8 performs gear shift control so as to suppress torque fluctuations in the rear wheels 2R associated with gear shifting. In step S55, the correction in step S47 of the gear shift control flow in Figure 9 is also performed. In addition, the motor 5 applies torque to the rear wheels 2R to compensate for torque fluctuations during gear shifting. As a result, instability in the behavior of the automobile 1 is suppressed.

[0120] After the third process, the process proceeds to the fourth process.

[0121] <Fourth Processing> Figure 11 is a flowchart of the fourth process. The fourth process is DSC / ABS control. In step S61 after the start, the controller 20 determines whether the unstable behavior of the vehicle 1 is diverging. If the unstable behavior of the vehicle 1 is diverging, the process proceeds to step S62. If the unstable behavior of the vehicle 1 is not diverging, DSC / ABS control is not necessary, and the fourth process ends.

[0122] In step S62, the controller 20 determines whether the brake is applied or not. If the driver is pressing the brake pedal 19 (i.e., Yes), the process proceeds to step S63; if the driver is not pressing the brake pedal 19 (i.e., No), the process proceeds to step S64.

[0123] In step S63, since the brakes are applied, DSC control or ABS control is executed to stabilize the unstable behavior of vehicle 1. In step S64, since the brakes are released, DSC control is executed to stabilize the unstable behavior of vehicle 1.

[0124] If the unstable behavior of the automobile 1 is resolved by the control intervention in step S63 or step S64, the fourth process ends.

[0125] <Control Example> Next, the second process will be explained with reference to the time charts in Figures 12-14. Each time chart includes changes in brake pedal operation amount and brake fluid pressure, changes in steering angle (measured by steering angle sensor 53), changes in gear position, changes in yaw rate (measured by yaw rate sensor 54), changes in regenerative braking torque, changes in AT input torque, changes in the transmission ratio of the automatic transmission 8, and changes in AT input rotational speed.

[0126] First, Figure 12 is a time chart showing the case where downshifting of the automatic transmission 8 is prohibited until the oversteer condition of the automobile 1 is resolved. At time t1, the driver starts pressing the brake pedal 19. The controller 20 starts regenerative cooperative control. Based on the signal from the controller 20, the friction brake system 3 lowers the brake fluid pressure in relation to the amount of operation of the brake pedal 19, which is shown by the dashed line. The braking force of the friction brake 31 decreases by that amount. The motor 5 increases the regenerative braking torque to compensate for the decrease in the braking force of the friction brake 31. This ensures that regenerative energy is secured, which is advantageous for improving the fuel efficiency of the automobile 1. Because the regenerative braking torque increases, the torque input to the input shaft 8a of the automatic transmission 8 decreases.

[0127] At time t2, the driver begins to steer the steering wheel 110. Consequently, the steering angle gradually increases. As the car 1 begins to turn, the yaw rate gradually increases.

[0128] At time t3, vehicle 1 enters an oversteer state, and the deviation between the actual yaw rate and the estimated yaw rate becomes large. In order to terminate the regenerative cooperative control, the controller 20 increases the input torque of the input shaft 8a of the automatic transmission 8 (torque increase, step S33) so that the regenerative braking torque of motor 5, which had been supplying part of the braking force of the friction brake 31, is eliminated. As a result, the regenerative braking torque is reduced. However, even after time t3, the regenerative braking torque equivalent to the engine braking due to releasing the accelerator remains, and the regenerative operation of motor 5 itself continues. In addition, the hydraulic pressure of the friction brake 31 is increased to compensate for the decrease in the regenerative braking torque of motor 5.

[0129] As vehicle 1 decelerates, the AT input rotational speed gradually decreases. After time t3, even if the AT input rotational speed reaches the first gear shift point S1, that is, the gear shift point set in the case of regenerative cooperative control, the controller 20 does not cause the automatic transmission 8 to perform a downshift. The downshift of the automatic transmission 8 is delayed (step S36).

[0130] As a result of the aforementioned torque increase, the regenerative braking torque applied to the rear wheel 2R decreases, and lateral force is secured on the rear wheel 2R, thus resolving the oversteer state of the vehicle 1. At time t4, once the oversteer state of the vehicle 1 is resolved, the controller 20 causes the automatic transmission 8 to perform the delayed downshift (transition from step S34 to step S310). Specifically, the increased torque of the motor 5 increases the input torque of the input shaft 8a of the automatic transmission 8 compared to normal shift control (see the "increase" arrow). This suppresses the torque fluctuation of the rear wheel 2R due to inertia during downshifting, thus preventing the vehicle 1 from becoming unstable immediately after the oversteer state is resolved.

[0131] Then, at time t5, the downshift of automatic transmission 8 is completed.

[0132] Furthermore, when the automatic transmission 8 downshifts after the oversteer condition of automobile 1 has been resolved, the normal gear shift control may be performed instead of the gear shift control used when oversteer was detected. In other words, the increase in torque of motor 5 during downshifting may be suppressed.

[0133] Figure 13 is a time chart showing the case where downshifting of the automatic transmission 8 is prohibited until the oversteer condition of vehicle 1 is resolved. The time chart in Figure 13 differs from the time chart in Figure 12 in that the AT input rotational speed reaches the third gear shift point S3.

[0134] In the time chart of Figure 13, as in the time chart of Figure 12, the driver begins to press the brake pedal 19 at time t1, the driver begins to steer the steering wheel 110 at time t2, and the car 1 enters an oversteer state at time t3. The controller 20 increases the input torque of the input shaft 8a of the automatic transmission 8 (torque increase) so that the regenerative braking torque of the motor 5, which was supplying part of the braking force of the friction brake 31, is eliminated in order to terminate the regenerative cooperative control. This reduces the regenerative braking torque. The regenerative operation of the motor 5 continues even after time t3. The shifting of the automatic transmission 8 is delayed.

[0135] As the vehicle 1 decelerates, the AT input rotational speed gradually decreases, and at time t4, the AT input rotational speed reaches the third shift point S3. The third shift point S3 is a downshift point that takes engine stall into consideration. The controller 20 disengages the K1 clutch of the automatic transmission 8. As a result, the AT input rotational speed decreases, and the transmission ratio, which is the speed ratio between the input shaft 8a and the output shaft 8b of the automatic transmission 8, decreases.

[0136] Furthermore, the oversteer condition is resolved by increasing the torque of the input shaft 8a. After the oversteer condition is resolved, the automatic transmission 8 performs a downshift.

[0137] Figure 14 is a time chart showing what happens when the vehicle 1 enters an oversteer state while the automatic transmission 8 is shifting gears. In the time chart of Figure 14, as in the time chart of Figure 12, the driver starts pressing the brake pedal 19 at time t1, and the driver starts steering the steering wheel 110 at time t2. The controller 20 performs regenerative braking control.

[0138] At time t3, the AT input rotational speed reaches the first shift point S1, so the automatic transmission 8 performs a downshift. Since the vehicle 1 is turning, the first cooperative shift control of the third process (step S54) is executed. As illustrated in Figure 14, the hydraulic pressure of the friction brake 31 is adjusted from time t4 onwards in accordance with the downshift of the automatic transmission 8.

[0139] At time t5 during gear shifting, the vehicle 1 enters an oversteer state. As per steps S310-S312 of the second process, the controller 20 increases the input torque of the input shaft 8a of the automatic transmission 8 (torque increase) in order to discontinue regenerative cooperative control, and also increases the input torque of the input shaft 8a of the automatic transmission 8 compared to normal gear shift control by increasing the torque of the motor 5. The torque increase for discontinuing regenerative cooperative control and the torque increase for gear shifting may be performed substantially simultaneously or with a timing difference. By securing lateral force on the rear wheels 2R and suppressing torque fluctuations during gear shifting, the deterioration of the vehicle 1's behavior is prevented. In addition, the hydraulic pressure of the friction brake 31 is increased to compensate for the decrease in the regenerative braking torque of the motor 5. Furthermore, the motor 5 performs regenerative operation with a regenerative braking torque equivalent to engine braking.

[0140] Then, at time t6, the downshift of automatic transmission 8 is completed.

[0141] (modified version) Figure 15 shows a modified version of the second process. This modified version differs from the flow in Figure 8 in that it does not delay the downshift. In step S71 after the start, the controller 20 determines whether or not an oversteer determination has been made. If the determination in step S71 is No, passive control is not performed. If the determination in step S71 is Yes, the process proceeds to step S72.

[0142] In step S72, the controller 20 determines whether or not brake regeneration is being performed. If the determination in step S72 is Yes, the process proceeds to step S73; if the determination in step S72 is No, the process does not proceed to step S73 but proceeds to step S74.

[0143] In step S73, the controller 20 performs torque-up control. This terminates the regenerative cooperative control. The regenerative braking torque applied to the rear wheel 2R decreases, and lateral force on the rear wheel 2R is secured, thus resolving the oversteer state of the vehicle 1. After step S73, the process proceeds to step S74. From step S74 onward, the motor 5 performs regenerative operation with a regenerative braking torque equivalent to engine braking when the accelerator is released. Even if the vehicle 1 is in an oversteer state, the amount of regeneration is secured as much as possible, which is advantageous for improving the fuel efficiency of the vehicle 1.

[0144] In step S74, the controller 20 determines whether the unstable behavior of the vehicle 1 is diverging. If the determination in step S74 is Yes, the process proceeds to step S75. If the determination in step S74 is No, the process proceeds to step S710.

[0145] In step S75, the controller 20 determines whether the automatic transmission 8 is shifting gears or not. If the automatic transmission 8 is not shifting gears (i.e., Yes), the process proceeds to step S76. If the automatic transmission 8 is shifting gears (i.e., No), the process proceeds to step S710.

[0146] In step S76, the controller 20 determines whether the rotational speed of the input shaft 8a of the automatic transmission 8 has reached the first shift point S1. If the rotational speed of the input shaft 8a has reached the first shift point S1, the process proceeds to step S77; otherwise, the process proceeds to the fourth process. As mentioned above, the first shift point S1 is the downshift point when regenerative cooperative control is being performed. In addition, in step S76, the controller 20 may also determine whether the rotational speed of the input shaft 8a of the automatic transmission 8 has reached the second shift point S2.

[0147] In step S77, the controller 20 disengages the K1 clutch of the automatic transmission 8. Since the automatic transmission 8 does not downshift, the instability of the vehicle 1's behavior caused by downshifting is suppressed.

[0148] Thus, in the second modification, when the vehicle 1 is in an oversteer state, the K1 clutch is released and the automatic transmission 8 does not downshift. This suppresses further instability of the vehicle 1's behavior due to gear changes. In addition, engine stall can be avoided.

[0149] On the other hand, if the vehicle 1 is in an oversteer state and the automatic transmission 8 is downshifting (if step S75 is No), or if the downshift is performed after the oversteer state of the vehicle 1 has been resolved (if step S74 is No), the controller 20 performs gear shift control in step S710 when oversteer is detected. Since torque fluctuations are suppressed even when downshifting is performed, the deterioration of the instability of the vehicle 1's behavior is suppressed.

[0150] In the following step S711, the controller 20 determines whether or not brake regeneration is in progress. If it is Yes, the process proceeds to step S712. On the other hand, if it is No, the process proceeds from step S711 to the fourth process.

[0151] In step S712, the controller 20 discontinues regenerative cooperative control and secures the braking force that was previously supplied by the regenerative braking torque of the motor 5 using the friction brake 31, thereby achieving a deceleration that matches the braking required by the driver.

[0152] The disclosed technology is not limited to the embodiments described above, but also encompasses various other configurations. For example, the configuration of automobile 1 is illustrative. Its configuration can be modified as appropriate depending on the specifications.

[0153] In the flows shown in Figures 4, 6, 8-11, and 15, it is possible to change the order of the steps, omit some steps, or add other steps.

[0154] (summary) Therefore, the vehicle's transmission control device is An engine 4 mounted on automobile 1 and generating the driving force for the automobile 1, A motor 5 generates the driving force for the vehicle 1 and supplies regenerative energy to the high-voltage battery 9 when the vehicle 1 decelerates, An automatic transmission 8 has an input shaft 8a connected to the engine 4 and the motor 5, and an output shaft 8b connected to the rear wheel 2R, and outputs the input rotation at a gear ratio corresponding to the selected gear. A friction brake system 3 distributes braking force to the front wheels 2F and the rear wheels 2R so that braking is applied in response to the driver's operation of the brake pedal 19, The system includes a controller 20 that performs regenerative control, which applies regenerative braking torque to the rear wheel 2R by causing the motor 5 to perform regenerative operation, and shift control, which causes the automatic transmission 8 to shift down by outputting a shift-down signal corresponding to the rotational speed of the input shaft 8a to the automatic transmission 8, while the friction brake system 3 is distributing braking force to the front wheel 2F and the rear wheel 2R during deceleration of the automobile 1, The controller 20 increases the input torque of the input shaft 8a of the automatic transmission 8 in accordance with the downshift so that the acceleration fluctuation of the automobile 1 accompanying the downshift of the automatic transmission 8 becomes the target acceleration fluctuation (step S48). The controller 20 also determines that the vehicle 1 is in an oversteer state (Yes in step S31 or S71) during regenerative control (Yes in step S32 or S72) and during downshifting of the automatic transmission 8 (No in step S35 or S75), and maintains the regenerative operation of the motor 5 while increasing the input torque of the input shaft 8a of the automatic transmission 8 so that the regenerative braking torque decreases (step S33 or S73). At the same time, it causes the automatic transmission 8 to downshift when the amount of increase in the input torque of the input shaft 8a in accordance with the downshift is greater than the amount of increase when the oversteer state is not determined (step S310 or S710, step S47).

[0155] This allows the transmission control system to maintain regenerative braking and stabilize the vehicle's behavior.

[0156] When the controller 20 determines that an oversteer state is occurring, it increases the amount of increase in the input torque of the input shaft 8a by reducing the target acceleration fluctuation compared to when an oversteer state is not determined (step S47).

[0157] By doing this, when an oversteer condition is detected, the torque fluctuation of the rear wheel 2R associated with downshifting is suppressed, which is advantageous for stabilizing the behavior of car 1.

[0158] If the oversteer state of the automobile 1 diverges, the controller 20 causes the friction brake system to perform control to stabilize the behavior of the automobile 1 by applying braking force to the front wheels 2F or the rear wheels 2R (Figure 11).

[0159] If the oversteer condition of vehicle 1 diverges, the DSC or ABS will activate to prevent the vehicle's behavior from becoming uncontrollable.

[0160] The controller 20 performs a second regenerative control, which applies regenerative braking torque to the rear wheel 2R by causing the motor 5 to perform a regenerative operation while the automobile 1 is decelerating and the friction brake system 3 is not applying braking force to the front wheel 2F and the rear wheel 2R. If the controller 20 determines that the vehicle 1 is in an oversteer state during the second regenerative control, it maintains the regenerative operation (No in step S32 or step S72).

[0161] This ensures that the amount of regenerative energy is maintained, which is advantageous for improving the fuel efficiency of vehicle 1.

[0162] If the controller 20 determines that the automobile 1 is in an oversteer state during the second regenerative control and while the automatic transmission 8 is downshifting, it maintains the regenerative operation of the motor 5 and causes the automatic transmission 8 to downshift when the amount of increase in the input torque of the input shaft 8a, which is adjusted to match the downshift, is greater than the amount of increase when the oversteer state is not determined (step S310 or step S710).

[0163] Even during the second regenerative control, the regenerative operation of motor 5 is maintained, and the instability of the vehicle's behavior due to downshifting is suppressed by increasing the input torque of input shaft 8a.

[0164] The controller 20, when downshifting after the oversteer state of the automobile 1 has been resolved, causes the automatic transmission 8 to downshift when the amount of increase in the input torque of the input shaft 8a corresponding to the downshift is greater than the amount of increase when the oversteer state is not detected (No. in step S34 or step S74, step S310 or step S710).

[0165] Even after the oversteer condition is resolved, the instability of vehicle 1's behavior due to downshifting is suppressed.

[0166] The controller 20 receives signals from a yaw rate sensor 54 that outputs a signal related to the behavior of the automobile 1 and a steering angle sensor 53 that outputs a signal related to the driver's steering operation, and determines the oversteer state of the automobile 1 (step S31 or step S71).

[0167] The controller 20 can quickly and accurately determine the behavior of the automobile 1. [Explanation of symbols]

[0168] 1. Automobile (vehicle) 19 Brake pedal 110 Steering Wheel 20 Controllers 2F Front Wheel 2R rear wheel 3. Friction Brake System 4 engines 5 Motors 53. Steering angle sensor (second sensor) 54 Yaw rate sensor (first sensor) 8 Automatic transmission 8a Input axis 8b Output shaft 9 High-voltage battery

Claims

1. An engine mounted on a vehicle and generating the driving force for the vehicle, A motor that generates the driving force for the vehicle and supplies regenerative energy to the battery when the vehicle decelerates, An automatic transmission in which the input shaft is connected to the engine and the motor, and the output shaft is connected to the rear wheel, and the input rotation is changed to output at a gear ratio corresponding to the gear stage, A friction brake system that distributes braking force to the front and rear wheels in accordance with the driver's brake pedal operation, The system includes a controller that performs regenerative control, which applies regenerative braking torque to the rear wheels by causing the motor to perform regenerative operation, and shift control, which causes the automatic transmission to shift down by outputting a shift-down signal corresponding to the rotational speed of the input shaft to the automatic transmission, while the friction brake system is distributing braking force to the front and rear wheels during deceleration of the vehicle, The controller receives signals from a first sensor that outputs a signal relating to the vehicle's behavior and a second sensor that outputs a signal relating to the driver's steering operation, and determines whether the vehicle is in an oversteer state. The controller increases the input torque of the input shaft of the automatic transmission in accordance with the downshift so that the acceleration fluctuation of the vehicle accompanying the downshift of the automatic transmission becomes the target acceleration fluctuation. The controller also determines that the vehicle is in an oversteer state during the regenerative control and while the automatic transmission is downshifting, and maintains the regenerative operation of the motor while increasing the input torque of the input shaft of the automatic transmission so as to reduce the regenerative braking torque, and causes the automatic transmission to downshift when the amount of increase in the input torque of the input shaft in accordance with the downshift is greater than the amount of increase when the oversteer state is not determined.

2. In the vehicle gear control device described in claim 1, The aforementioned controller is a vehicle gear shift control device that, when an oversteer state is detected, increases the amount of increase in the input torque of the input shaft by reducing the target acceleration fluctuation compared to when an oversteer state is not detected.

3. In the vehicle gear control device described in claim 1, The controller is a vehicle gear shift control device that, when the vehicle's oversteer condition diverges, causes the friction brake system to perform control to stabilize the vehicle's behavior by applying braking force to the front wheels or the rear wheels.

4. In the vehicle gear control device described in claim 1, The controller performs a second regenerative control, which applies regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation while the vehicle is decelerating and the friction brake system is not applying braking force to the front and rear wheels. The controller is a vehicle gear shift control device that maintains the regenerative operation if it determines that the vehicle is in an oversteer state during the second regenerative control.

5. In the vehicle gear control device described in claim 4, The aforementioned controller, when it determines that the vehicle is in an oversteer state during the second regenerative control and the automatic transmission is downshifting, maintains the regenerative operation of the motor and causes the automatic transmission to downshift when the amount of increase in the input torque of the input shaft, which is adjusted to match the downshift, is greater than the amount of increase when the oversteer state is not determined.

6. In the vehicle gear control device described in claim 1, The controller, when downshifting after the oversteer condition of the vehicle has been resolved, A vehicle gear shift control device that causes the automatic transmission to downshift when the amount of increase in the input torque of the input shaft corresponding to the downshift is greater than the amount of increase when an oversteer condition is not detected.

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