Vehicle transmission control device

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 to apply regenerative brake torque to rear wheels 2R through causing the motor to perform regenerative operation and variable speed control to variably change a transmission stage of the automatic transmission through outputting a variable speed signal according to a rotation speed of an input shaft to the automatic transmission while a vehicle is decelerated with brake force distributed to front wheels 2F and the rear wheels through the friction brake system. When determining an oversteer state of the vehicle with the regenerative control in execution, the control device: maintains the regenerative operation of the motor while increasing input torque of the input shaft of the automatic transmission so as to reduce the regenerative brake torque; and limits the transmission control between the input shaft and an output shaft for the automatic transmission.SELECTED DRAWING: Figure 15

Description

[Technical Field]

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

[0002] Patent Document 1 describes a control device for a hybrid vehicle. This hybrid vehicle is equipped with 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 aims to improve fuel economy by having the motor perform regenerative operation when the automatic transmission downshifts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-132432 Summary of the Invention [Problem to be solved by the invention]

[0004] In a rear-wheel drive vehicle, where the output shaft of the automatic transmission is connected to the rear wheels, when the motor performs regenerative braking, regenerative braking torque is applied only to the rear wheels. Therefore, when the motor performs regenerative braking while decelerating and turning, for example, the lateral force of the rear wheels decreases, and the vehicle's behavior is likely to become oversteered.

[0005] If the regenerative braking operation of the motor is stopped when the vehicle is in an oversteer state, the braking force equivalent 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 vehicle is no longer in an oversteer state. However, stopping the regenerative operation reduces the fuel efficiency of the hybrid vehicle.

[0006] Unfortunately, conventional hybrid vehicles do not take into consideration the regenerative operation that occurs when a rear-wheel drive vehicle oversteers, and are therefore unable to simultaneously suppress oversteer and ensure sufficient regeneration.

[0007] The technology disclosed herein achieves both suppression of oversteer in a rear-wheel drive vehicle and ensuring sufficient regeneration. [Means for solving the problem]

[0008] The inventors of the present application analyzed the relationship between the behavioral stability of a rear-wheel drive vehicle and the amount of regeneration, and found that after the vehicle begins to oversteer, the oversteer state can be resolved by reducing the amount of regeneration to a certain extent, even if the amount of regeneration does not decrease to zero.

[0009] However, depending on road conditions, etc., reducing the amount of regeneration may not resolve the oversteer condition easily, and during this time the engine speed may gradually decrease, causing the speed of the input shaft of the automatic transmission to reach the shift point. If the automatic transmission shifts down in this state, the torque to the rear wheels may fluctuate due to the inertia torque of the automatic transmission, which may cause the vehicle to behave unstable.

[0010] As a result of experiments conducted by the inventors of the present application, it was found that if a shift point in the automatic transmission is reached while the amount of regeneration is being reduced to eliminate an oversteer condition, cutting off the power transmission between the input shaft and output shaft of the automatic transmission prevents the automatic transmission from downshifting, thereby maintaining regeneration and stabilizing vehicle behavior.

[0011] Specifically, the technology disclosed herein relates to a vehicle gear shift control device. an engine mounted on a vehicle and generating driving force for the vehicle; a motor that generates a driving force for the vehicle and supplies regenerative energy to a battery when the vehicle is decelerating; an automatic transmission having an input shaft connected to the engine and the motor and an output shaft connected to a rear wheel, the automatic transmission shifting the input rotation at a gear ratio corresponding to a selected gear position and outputting the shifted rotation; a friction brake system that distributes braking force to the front wheels and the rear wheels so that braking is performed in accordance with the driver's brake pedal operation; a controller that executes regenerative control for applying regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation, and shift control for changing the gear position of the automatic transmission by outputting a shift signal to the automatic transmission according to the rotation speed of the input shaft, while the vehicle is decelerating and the friction brake system is distributing braking force to the front wheels and the rear wheels; If the controller determines that the vehicle is in an oversteer state during the regenerative control, it increases the input torque of the input shaft of the automatic transmission so as to reduce the regenerative braking torque, while maintaining the regenerative operation of the motor, and cuts off power transmission between the input shaft and the output shaft of the automatic transmission.

[0012] With this configuration, the motor performs regenerative operation while the vehicle is decelerating and the friction brake system is distributing braking force to the front and rear wheels. This control is regenerative cooperative control by the friction brake system and the motor. Regenerative cooperative control increases the regenerative energy stored in the battery. Regenerative braking torque by the motor is applied only to the rear wheels through 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 acting on the vehicle corresponds to the driver's brake pedal operation.

[0013] Furthermore, while the vehicle is decelerating, the controller outputs a shift signal to the automatic transmission according to the rotation speed of the input shaft. The automatic transmission receives the shift signal and changes the gear, i.e., performs a downshift from a higher gear to a lower gear. While the vehicle is decelerating, a gear corresponding to the operating state of the engine is selected.

[0014] If the controller determines that the vehicle is oversteering during the aforementioned regenerative cooperative control, it increases the input torque of the input shaft of the automatic transmission to reduce the regenerative braking torque. This reduces the regenerative braking torque applied to the rear wheels, ensuring lateral force at the rear wheels, and thus eliminating the oversteering state of the vehicle. The friction brake system compensates for the reduced regenerative braking torque by increasing braking force.

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

[0016] While the regenerative braking torque is reduced, power transmission between the input shaft and output shaft of the automatic transmission is cut off. In other words, the automatic transmission does not downshift. This prevents torque fluctuations at the rear wheels due to inertia torque of the automatic transmission that occurs when downshifting. This also prevents the vehicle from becoming unstable due to downshifting. It also prevents engine stalls during deceleration.

[0017] Therefore, this gear change control device can maintain regenerative operation and stabilize vehicle behavior.

[0018] The controller may interrupt the power transmission when the rotation speed of the input shaft reaches a downshift point after the input torque of the input shaft increases.

[0019] While the oversteer condition remains, it is difficult to downshift the automatic transmission. Meanwhile, since the engine speed gradually decreases during vehicle deceleration, if the automatic transmission is not downshifted, the engine speed will become too low, which may result in the engine stalling.

[0020] Therefore, if the rotation speed of the input shaft of the automatic transmission reaches the downshift point without the vehicle's oversteer state being resolved, the controller cuts off the power transmission between the input shaft and output shaft of the automatic transmission. This prevents the engine from stalling and also prevents the vehicle's oversteer state from worsening. If the vehicle's oversteer state is resolved before the rotation speed of the input shaft reaches the downshift point, the automatic transmission will downshift when it reaches the downshift point.

[0021] The controller may be configured to cause the friction brake system to perform control to stabilize the behavior of the vehicle by applying braking force to the front wheels or the rear wheels when the oversteer state of the vehicle diverges.

[0022] In other words, if the vehicle begins to oversteer, the DSC (Dynamic Stability Control) or ABS (Anti-lock Brake System) will be activated to prevent the vehicle's behavior from becoming uncontrollable.

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

[0024] For example, when the driver releases the accelerator pedal and brake pedal and the vehicle is decelerating, the controller applies regenerative braking torque to the rear wheels by causing the motor to perform regenerative operation (i.e., second regenerative control). In this case, the regenerative braking torque may be, for example, a braking torque equivalent to engine braking. This regenerative braking torque is relatively small.

[0025] If the vehicle is determined to be in an oversteer state during the second regenerative control, the motor maintains regenerative operation. This ensures a sufficient amount of regeneration, which is advantageous for improving the fuel efficiency of the vehicle.

[0026] The controller may be configured to interrupt the power transmission when it determines that the vehicle is in an oversteer state during the second regenerative control and the rotation speed of the input shaft reaches a downshift point.

[0027] Even if the controller determines that the vehicle is oversteering during the second regenerative control, it will interrupt the power transmission of the automatic transmission when the automatic transmission reaches the downshift point, as described above. This prevents the vehicle's behavior from becoming unstable when the downshift occurs.

[0028] The controller may be configured to cause the friction brake system to perform control to stabilize the behavior of the vehicle by applying braking force to the front wheels or the rear wheels when the oversteer state of the vehicle diverges.

[0029] This prevents the vehicle from becoming uncontrollable.

[0030] The controller may receive signals from a first sensor that outputs a signal related to the behavior of the vehicle and a second sensor that outputs a signal related to the steering operation of the driver, and determine whether the vehicle is in an oversteer state.

[0031] By determining whether the vehicle is oversteered based on the signals from the first and second sensors, the controller can quickly and accurately determine the behavior of the vehicle. [Effects of the Invention]

[0032] According to the above-described vehicle speed change control device, it is possible to suppress oversteer in a rear-wheel drive vehicle while ensuring a sufficient amount of regeneration. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows a hybrid vehicle. [Figure 2] Figure 2 shows the engagement table for an automatic transmission. [Figure 3] FIG. 3 is a block diagram of the gear change control device. [Figure 4] FIG. 4 is a flowchart showing the overall control relating to behavioral stability. [Figure 5] FIG. 5 is a diagram illustrating the control function related to behavioral stability. [Figure 6] FIG. 6 is a flowchart of the first process. [Figure 7] FIG. 7 shows downshift points for each gear position of an automatic transmission. [Figure 8] FIG. 8 is a flowchart of the second process. [Figure 9] FIG. 9 is a flowchart of the gear shift control. [Figure 10] FIG. 10 is a flowchart of the third process. [Figure 11] FIG. 11 is a flowchart of the fourth process. [Figure 12] FIG. 12 is a time chart showing a case where the downshift is delayed. [Figure 13] FIG. 13 is a time chart showing the case where the K1 clutch of the automatic transmission is released as a result of delaying the downshift. [Figure 14] FIG. 14 is a time chart showing a case where oversteer is determined during a downshift. [Figure 15] FIG. 15 is a flowchart according to a modified example of the second process. DETAILED DESCRIPTION OF THE INVENTION

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle gear shift control device will be described below with reference to the drawings. The gear shift control device described here is an example.

[0035] (Hybrid vehicle) FIG. 1 shows an automobile 1 (an example of a vehicle) to which the disclosed technology is applied. The automobile 1 is a hybrid automobile that can run on electric power. The automobile 1 has a total of four wheels: front wheels 2F and rear wheels 2R. Friction brakes 31 are attached to the front wheels 2F and rear wheels 2R to brake their rotation.

[0036] The automobile 1 is equipped with an engine 4 and a motor 5 as drive sources. These work together to drive the rear wheels 2R, thereby propelling the automobile 1. The automobile 1 is a rear-wheel drive vehicle. The motor 5 is used not only as a drive source but also as a generator during regeneration.

[0037] As will be described later, this automobile 1 is equipped with a high-voltage battery 9 having a rated voltage of 50 V or less. The motor 5 runs by mainly assisting the engine 4 with the power supply from the high-voltage battery 9 (a so-called mild hybrid vehicle). Note that the automobile 1 may also be a so-called plug-in hybrid vehicle that can receive power from an external power source.

[0038] In the case of this automobile 1, the engine 4 is disposed at the front of the body, and the drive wheels are disposed at the rear of the body, that is, this automobile 1 is a so-called FR vehicle.

[0039] In addition to an engine 4 and a motor 5, the automobile 1 is equipped with a K0 clutch 6, an inverter 7, and an automatic transmission 8 as drive system devices. The automobile 1 is also equipped with a controller 20 as a control system device. The automobile 1 is also equipped with a friction brake system 3 including a friction brake 31 as a braking system device.

[0040] (Drive system device) The engine 4 is, for example, an internal combustion engine that burns fossil fuel. The engine 4 is also a so-called four-stroke engine that generates rotational power by repeating cycles of intake, compression, expansion, and exhaust. There are various types and forms of engine 4, such as spark ignition engines and compression ignition engines, but the technology disclosed herein is not particularly limited to the type or form of the engine 4.

[0041] In this automobile 1, the engine 4 is disposed in the approximate center in the width direction of the vehicle, with the crankshaft 4a that outputs rotational power facing 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] The motor 5 is a permanent magnet synchronous motor driven by three-phase AC. The motor 5 is arranged in series behind the engine 4 via a K0 clutch 6. The motor 5 is also arranged in series in front of the automatic transmission 8.

[0043] The K0 clutch 6 is disposed 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 the shaft 5a are connected (connected state) and a state in which the crankshaft 4a and the shaft 5a are separated (separated state).

[0044] A rear end of the shaft 5a of the motor 5 is connected to an 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 the shaft 5a. The engine 4 is separated from the automatic transmission 8 by disengaging the K0 clutch 6.

[0045] The K0 clutch 6 is switched between an engaged state and a disengaged state while the automobile 1 is traveling. For example, when the automobile 1 is decelerating, the K0 clutch 6 may be disengaged 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 driving 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 50 V or less, specifically 48 V.

[0047] The high-voltage battery 9 supplies high-voltage DC power to the inverter 7. The inverter 7 converts the DC power into three-phase AC and supplies it to the motor 5, thereby driving the motor 5 to rotate. The motor 5 also supplies regenerative energy to the high-voltage battery 9.

[0048] The high-voltage battery 9 is also connected to a DC-DC converter 10 via a high-voltage cable 40. The DC-DC converter 10 converts high-voltage DC power of 48 V into low-voltage DC power of 12 V and outputs it. The DC-DC converter 10 (its output side) is connected to a 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 a low-voltage cable 41. The DC-DC converter 10 is also connected to a CAN 12 (Controller Area Network) 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, which 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 from the input shaft 8a.

[0051] A transmission mechanism consisting of a torque converter 8c, multiple planetary gear mechanisms, and multiple frictional engagement elements is installed between the input shaft 8a and the output shaft 8b. Each frictional engagement element is switched between an engaged state and a disengaged state by hydraulic pressure.

[0052] 2 shows an engagement table for the automatic transmission 8. Circles in the table indicate engagement. The automatic transmission 8 incorporates three clutches, a first clutch CL1, a second clutch CL2, and a third clutch CL3, as frictional engagement elements, and two brakes, a first brake BR1 and a second brake BR2.

[0053] The automatic transmission 8 uses hydraulic control to selectively engage three of these three clutches and two brakes, thereby switching the gears of the automatic transmission between forward gears (1st to 8th gears) and reverse gear (reverse gear).

[0054] For example, in first gear, the first clutch CL1, first brake BR1, and second brake BR2 are engaged. When shifting up from first gear, the gear shifts from first gear to second gear by engaging the second clutch CL2 instead of the first clutch CL1. The gear shifts from second gear to third gear by engaging the first clutch CL1 instead of the first brake BR1. The gear shifts from third gear to fourth gear by engaging the third clutch CL3 instead of the first clutch CL1.

[0055] Shifting up to 5th gear and above is done in the same way. To shift down, follow the reverse procedure to shifting up.

[0056] When an element that should be engaged in each gear is not engaged, the input shaft 8a and the output shaft 8b are disconnected (so-called neutral). Even if rotational power is input to the automatic transmission 8 from the drive source, the rotational power is not output from the automatic transmission 8.

[0057] As will be described later, the automatic transmission 8 may be placed in neutral while the vehicle 1 is decelerating. Specifically, when the automatic transmission 8 is in second, third, or fourth gear, the second clutch CL2 is disengaged to place the automatic transmission 8 in neutral. Also, when the automatic transmission 8 is in fifth, sixth, seventh, or eighth gear, the third clutch CL3 is disengaged to place the automatic transmission 8 in neutral. In the following description, the second clutch CL2 and the third clutch CL3 may be collectively referred to as the K1 clutch. Disengaging the K1 clutch while the vehicle 1 is decelerating means that power transmission between the input shaft 8a and the output shaft 8b of the automatic transmission 8 is interrupted to place the automatic transmission 8 in neutral.

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

[0059] (Gear change control device) FIG. 3 is a block diagram of a gear change control device. The automobile 1 is equipped with the above-mentioned controller 20 to control the engine 4, motor 5, K0 clutch 6, automatic transmission 8, friction brake system 3, etc. in response to driver operation and thereby control the running of the automobile 1. The controller 20 is composed of hardware such as a processor, memory, and interface, and software such as a database and control programs. Note that while the gear change control device in FIG. 3 shows one controller 20, the controller of the gear change control device may be divided into a unit (PCM) that primarily controls the operation of the drive source (engine 4 and motor 5) and a unit (TCM) that primarily controls the operation of the K0 clutch 6 and automatic transmission 8. The PCM and TCM are connected by a CAN 12 and are configured to be able to communicate electrically with each other.

[0060] The gear change control device is equipped with sensors that measure various parameters related to vehicle driving. Specifically, the gear change control device is equipped with 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 opening sensor 56, an AT input torque sensor 57, and an AT input rotation speed sensor 58.

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

[0062] The steering angle sensor 53 outputs a signal corresponding to the rotation angle of the steering wheel 110 (see FIG. 1) operated by the driver, that is, 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 depression of the brake pedal 19 (see FIG. 1) operated by the driver. The accelerator opening sensor 56 outputs a signal corresponding to the depression of the accelerator pedal 18 (see FIG. 1) operated 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 rotation speed sensor 58 outputs a signal corresponding to the rotation speed of the input shaft 8a of the automatic transmission 8.

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

[0066] (Control related to behavioral stability) <Overall control> Fig. 4 shows the overall control relating to the behavioral stability of the automobile 1. The flows in Fig. 4 and Figs. 6, 8-11, and 15, which will be explained later, basically relate to the control of the automobile 1 when it is decelerating.

[0067] FIG. 5 shows the concept of the control functions related to the behavioral stability of the automobile 1. The automobile 1 has three functions: active control, passive control, and DSC / ABS control. The active control functions to keep the grip force of the wheels 2F and 2R within the friction circle shown in FIG. 5. If the grip force of the wheels 2F and 2R remains within the friction circle, the behavioral stability of the automobile 1 is maintained. The active control is a control for maintaining the behavioral stability of the automobile 1.

[0068] The passive control functions to bring the grip force of the wheels 2F and 2R back into the friction circle when the grip force of the wheels 2F and 2R exceeds the friction circle and the behavior of the automobile 1 becomes unstable.

[0069] The DSC / ABS control functions when the behavior of the automobile 1 is about to diverge, in other words, when the grip force of the wheels 2F, 2R is about to exceed the circle with the largest diameter, by the friction brake system 3 applying braking force to each of the wheels 2F, 2R through the friction brakes 31, thereby returning the grip force of the wheels 2F, 2R to within the friction circle. Known technology can be used for the DSC / ABS control.

[0070] The automobile 1 having the three functions can ensure the stability of the vehicle's behavior.

[0071] In the flow of FIG. 4, in step S11 after the start, the controller 20 reads the sensor signals. The controller 20 determines the running state of the automobile 1. Thereafter, the controller 20 executes a first process (step S12). The first process involves active control, and switches the gear change control depending on the road surface μ. The first process will be described in detail later.

[0072] After the first process in step S12, the process proceeds to a second process (step S13) or a fourth process (step S15). The second process relates to passive control, and relates to gear shift control when the automobile 1 is in an oversteer state. The second process will be described in detail later.

[0073] After step S13, the process proceeds to a third process (step S14) or a fourth process (step S15). The third process is related to active control, and shift control is switched depending on the slip state of the wheels 2F, 2R. The third process will be described in detail later. The fourth process is DSC / ABS control. The fourth process will be described in detail later.

[0074] <First process> 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. 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 μ is not low, that is, if the road surface μ is high and the grip of the wheels 2F, 2R is likely to remain within the friction circle, the controller 20 executes normal gear shift control. First, in step S22, the controller 20 determines whether the driver is depressing 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 depressing 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 depressing the brake pedal 19, the process proceeds to step S24.

[0076] When the driver depresses the brake pedal 19, the controller 20 executes regenerative cooperative control to provide a part of the braking force required by the driver with the regenerative braking torque of the motor 5. 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 a downshift point for the automatic transmission 8. FIG. 7 illustrates downshift points for each gear of the automatic transmission 8. The horizontal axis of FIG. 7 represents vehicle speed, and the vertical axis represents the rotation speed of the input shaft 8a of the automatic transmission 8. The first shift point S1 is set to a constant rotation speed of the input shaft 8a for each gear, regardless of 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 traveling in sixth gear, the rotation speed of the input shaft 8a of the automatic transmission 8 reaches the first shift point S1 when the vehicle speed is just under 60 km / h, causing the automatic transmission 8 to downshift from sixth gear to fifth gear. As a result of the downshift, the rotation speed of the input shaft of the automatic transmission 8, in other words, the rotation speed of the motor 5, becomes higher than the first shift point S1. When the driver is depressing the brake pedal 19 and the controller 20 is executing regenerative cooperative control, the rotation speed of the motor 5 during regenerative operation can be maintained high by setting the downshift point to the first shift point S1. A high motor rotation speed increases the amount of regeneration, thereby improving the fuel efficiency of the automobile 1.

[0078] When the driver is not depressing the brake pedal 19, the controller 20 does not perform regenerative cooperative control. The motor 5 applies regenerative braking torque equivalent to engine braking to the rear wheels 2R to perform regenerative operation. When the driver is not depressing the brake pedal 19 and the deceleration state is in progress, the driver may depress the accelerator pedal 18, which may change to an acceleration request. If the rotation speed of the input shaft 8a of the automatic transmission 8 is maintained high by setting the downshift point to the first 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 of the automatic transmission 8. As shown in Fig. 7, the rotation 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 rotation speed of the input shaft 8a of the automatic transmission 8 during deceleration becomes relatively lower, ensuring sufficient driving force when the driver requests acceleration.

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

[0081] In contrast to normal control where the road surface μ is not low, when the road surface μ is low, the grip force of the wheels 2F, 2R exceeds the friction circle and the behavior of the automobile 1 tends to become unstable. Therefore, the controller 20 performs control to prevent the behavior of the automobile 1 from becoming unstable due to the gear 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, and if the vehicle 1 is not accelerating (No), the process proceeds to step S27.

[0083] If the vehicle 1 is accelerating, the automatic transmission 8 upshifts as the vehicle speed and / or the rotation speed of the input shaft 8a of the automatic transmission 8 increases. The accelerating vehicle 1 will eventually decelerate, and the automatic transmission 8 downshifts during deceleration. When the automatic transmission 8 downshifts, torque fluctuations at the rear wheels 2R occur due to the inertia torque of the automatic transmission 8. If the road surface μ is low, torque fluctuations at the rear wheels 2R due to downshifts may cause the behavior of the vehicle 1 to become unstable. Therefore, in step S26, the controller 20 suppresses upshifts. Specifically, the controller 20 prohibits the automatic transmission 8 from upshifting from sixth gear to seventh gear and from seventh gear to eighth gear. In step S26, the automatic transmission 8 reaches a maximum of sixth gear. Limiting the highest gear of the automatic transmission 8 reduces the frequency of downshifts during subsequent deceleration. This reduces the opportunities for the behavior of the vehicle 1 to become unstable.

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

[0085] As mentioned above, upshifting to seventh and eighth gears is prohibited, so the highest gear is sixth gear. Moreover, the downshift point is the third gear change point S3. Therefore, in step S27, the automatic transmission 8 does not downshift unless the vehicle speed drops to approximately 40 km / h, as shown by the white arrow in Figure 7. Because downshifting is not performed at high vehicle speeds, it is possible to prevent the behavior of the automobile 1 from becoming unstable.

[0086] In the following step S28, the controller 20 disengages the K1 clutch when the rotation speed of the input shaft 8a of the automatic transmission 8 becomes lower than the third shift point S3. As described above, the K1 clutch is a clutch formed by a frictional engagement element of the automatic transmission 8, and when the K1 clutch is disengaged, power transmission between the input shaft 8a and output shaft 8b of the automatic transmission 8 is interrupted. Disengagement of the K1 clutch reduces the torque applied to the rear wheels 2R, thereby suppressing instability in the behavior of the automobile 1 and avoiding engine stall due to a further decrease in the rotation speed of the engine 4.

[0087] After the active control when the road surface μ is low, the process proceeds to the fourth processing.

[0088] <Second process> FIG. 8 is a flowchart of the second process. As described above, the second process is passive control. In step S31 after the start, the controller 20 determines whether the oversteer determination is established. The controller 20 determines whether the automobile 1 is in an oversteer state, for example, based on the deviation between an estimated yaw rate that can be calculated from the vehicle speed and steering angle and an actual yaw rate based on a signal from the yaw rate sensor 54. If the deviation between the estimated yaw rate and the actual yaw rate is equal to or greater than a predetermined value, the controller 20 may determine that the automobile 1 is in an oversteer state. If the determination in step S31 is No, that is, if the automobile 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 automobile 1 is in an oversteer state, the process proceeds to step S32.

[0089] In step S32, the controller 20 determines whether brake regeneration is being performed, that is, whether the driver is depressing the brake pedal 19. If the determination in step S32 is Yes, the process proceeds to step S33, and if the determination in step S32 is No, the process proceeds to step S34 without proceeding to step S33.

[0090] As described above, when the driver is decelerating with the brake pedal 19 depressed, regenerative cooperative control is executed in which part of the braking force required 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 wheels 2R of the automobile 1, which is a rear-wheel drive vehicle. As a result, the lateral force of the rear wheels 2R decreases, and the behavior of the automobile 1 is prone to oversteer.

[0091] Therefore, in step S33, the controller 20 executes torque-up control. Specifically, the input torque of the input shaft 8a of the automatic transmission 8 is increased so that the regenerative braking torque of the motor 5, which had been providing part of the braking force of the friction brake 31, is eliminated. The torque-up control corresponds to the end of the regenerative cooperative control. The friction brake system 3 compensates for the braking force resulting from the elimination of the regenerative braking torque with the braking force of the friction brake 31. Note that even after the regenerative cooperative control is terminated, the regenerative braking torque equivalent to the engine brake caused by releasing the accelerator remains, and the regenerative operation of the motor 5 itself continues. Even if the automobile 1 is in an oversteer state, the amount of regeneration is secured, which is advantageous for improving the fuel efficiency of the automobile 1.

[0092] The regenerative braking torque applied to the rear wheels 2R is reduced, ensuring lateral force at the rear wheels 2R, which eliminates the oversteer state of the automobile 1. The deviation between the estimated yaw rate and the actual yaw rate is reduced. The behavior of the automobile 1 can be stabilized while ensuring as much regeneration as possible. After step S33, the process proceeds to step S34.

[0093] In step S32, when regenerative braking is not performed, that is, when the vehicle is decelerating without the driver pressing the brake pedal 19, second regenerative control is performed, which performs regenerative braking equivalent to engine braking, and regenerative cooperative control is not performed, so torque increase in step S33 is not performed. Even when the process moves from step S32 to step S34, the motor 5 is performing 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 automobile 1 is diverging. For example, the controller 20 may determine that the unstable behavior of the automobile 1 is diverging when 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 not shifting gears (i.e., out of gear). If the automatic transmission 8 is not shifting gears (i.e., if Yes), the process proceeds to step S36. If the automatic transmission 8 is shifting gears (i.e., if No), the process proceeds to step S310.

[0096] In step S36, the controller 20 delays downshifting of the automatic transmission 8. In other words, even if the running state of the automobile 1 reaches the downshift point, the controller 20 prohibits downshifting of the automatic transmission 8 until the oversteer state of the automobile 1 is resolved. As described above, downshifting of the automatic transmission 8 involves torque fluctuations at the rear wheels 2R, which may further destabilize the behavior of the automobile 1. However, by prohibiting downshifting, the behavior of the automobile 1 is prevented from becoming further unstable. The downshift point is the first shift point S1 or the second shift point S2 of normal shift control.

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

[0098] In step S38, the controller 20 determines whether the rotation speed of the input shaft 8a of the automatic transmission 8 has reached the third shift point S3. If the rotation speed of the input shaft 8a has reached the third shift point S3, the process proceeds to step S39. If not, the process proceeds to the fourth process. As described above, the third shift point S3 is a downshift point that takes engine stall into consideration.

[0099] In step S39, the controller 20 disengages the K1 clutch of the automatic transmission 8, similarly to step S28 of the first processing. This makes it possible to suppress engine stall. After that, the process proceeds to the fourth processing.

[0100] In this way, if the vehicle 1 enters an oversteer state while decelerating due to the regenerative cooperative control or the second regenerative control, the downshift of the automatic transmission 8 is delayed. This prevents the behavior of the vehicle 1 from becoming further unstable due to the downshift. Furthermore, if the downshift of the automatic transmission 8 is delayed, the rotation speed of the input shaft 8a of the automatic transmission 8 decreases, which may cause the engine to stall. However, once the rotation speed of the input shaft 8a of the automatic transmission 8 reaches the limit rotation speed (i.e., the third shift point S3), power transmission between the input shaft 8a and output shaft 8b of the automatic transmission 8 is interrupted, thereby preventing the engine from stalling.

[0101] On the other hand, if the vehicle 1 is in an oversteer state and the automatic transmission 8 is in the process of downshifting (if No in step S35), or if a delayed downshift is to be performed after the oversteer state of the vehicle 1 is resolved (if No in step S34), the controller 20 executes gear shift control during oversteer determination in step S310. The 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 as a result of the downshift. In the gear shift control during oversteer determination in step S310, the input torque of the input shaft 8a of the automatic transmission 8 is increased compared to that during normal gear shift control, i.e., the input torque when oversteer is not determined, so that torque fluctuations at the rear wheels 2R corresponding to the inertia are suppressed. As a result of the relative increase in the input torque, torque fluctuations are suppressed even when a downshift is performed, and the instability of the vehicle 1's behavior caused by the downshift is suppressed.

[0102] In the following step S311, the controller 20 determines whether or not regenerative braking is in progress, and if so, the process proceeds to step S312. On the other hand, if not, the process proceeds from step S311 to a fourth process.

[0103] In step S312, the controller 20 stops the regenerative cooperative control, and the braking force that was provided by the regenerative braking torque of the motor 5 is secured by the friction brake 31, thereby achieving deceleration that matches the braking required by the driver. Note that even after the regenerative cooperative control ends, the regenerative braking torque corresponding to the engine brake caused by the accelerator release remains, and the regenerative operation of the motor 5 itself continues.

[0104] <Gear shift processing> 9 is a flowchart of the gear shift control. After starting, in step S41, the controller 20 reads the AT input torque and the AT input rotation speed. The process then proceeds to steps S42 and S44.

[0105] In step S42, the controller 20 sets a target acceleration fluctuation when the automatic transmission 8 shifts gears. The target acceleration fluctuation is a target value for the acceleration fluctuation that occurs in the automobile 1 when the automatic transmission 8 shifts gears. Basically, the higher the AT input rotation speed, the larger the target acceleration fluctuation is set. When the AT input rotation speed is high, it is acceptable for the driver to feel an upshift or downshift. The target acceleration fluctuation is determined from the gear position of the automatic transmission 8 and the AT input rotation speed, based on a relational expression or map set for each of the upshift and downshift.

[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 is shifting gears.

[0107] Meanwhile, in step S44, the controller 20 sets a target shift time for shifting the automatic transmission 8. Basically, the higher the AT input rotation speed, the shorter the target shift time is set. When the AT input rotation 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 rotation speed, based on a relational expression or map set for each of the upshift and downshift.

[0108] In the next step S45, the controller 20 calculates the AT input rotation gradient from the set target shift time. The AT input rotation gradient is the rate of change of the rotation speed of the input shaft 8a when the automatic transmission 8 shifts gears.

[0109] After steps S43 and S45, the process proceeds to step S46. In step S46, the controller 20 determines whether or not the calculated AT output torque and / or AT input rotation slope needs to be corrected. As in step S310 of the second process described above, when the vehicle 1 performs a gear change in an oversteer state, torque fluctuations at the rear wheels 2R that accompany downshifting must be suppressed 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 rotation slope is corrected. Specifically, in gear change control when oversteer is determined, correction is performed to suppress torque fluctuations at the rear wheels 2R, in other words, to flatten the AT output torque. When an oversteer state is determined, the target acceleration fluctuation is made smaller than when an oversteer state is not determined. After correction, the process proceeds to step S48. On the other hand, if the determination in step S46 is No, that is, if the normal gear shift control does not require correction, the process proceeds to step S48 without proceeding to step S47.

[0110] Note that the correction in step S47 is also performed in the first coordinated shift control in step S54 and the second coordinated shift control in step S55 of the third process described below, and torque fluctuations in the rear wheel 2R during gear shifting are suppressed.

[0111] In step S48, the controller 20 calculates the AT input torque based on the AT output torque and the AT input rotation slope. The AT input torque is the torque input to the input shaft 8a of the automatic transmission 8, and is adjusted mainly by the motor 5. When a downshift is performed in step S310 of the second process described above, the correction made in step S47 results in the increase in the AT input torque being greater than the increase during a normal downshift (i.e., when an oversteer state is not determined and no correction is made).

[0112] Once the AT input torque is calculated, in the following step S49, the controller 20 calculates the oil pressure to be supplied to the frictional engagement elements of the automatic transmission 8 so as to correspond to the calculated AT input torque. By supplying oil pressure to the frictional engagement elements in accordance with the set oil pressure, the automatic transmission 8 downshifts or upshifts.

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

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

[0115] In step S56, the controller 20 executes normal shift control. That is, because the wheels 2F, 2R are not in a slip state and the vehicle 1 is traveling straight, there is little 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 shift control flow of FIG. 9 is not performed.

[0116] On the other hand, in steps S52, S54, and S55, if the wheels 2F, 2R are in a slipping state or the automobile 1 is in a turning state, and the automatic transmission 8 changes gears in this state, causing the torque of the rear wheel 2R to fluctuate, there is a risk of the behavior of the automobile 1 becoming unstable. Therefore, the controller 20 performs control so that the behavior of the automobile 1 does not become unstable.

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

[0118] When brake regeneration is being performed, the controller 20 executes coordinated control of the friction brake system 3, the motor 5, and the automatic transmission 8. Specifically, in step S54, the automatic transmission 8 executes gear shift control so as to suppress torque fluctuations at the rear wheels 2R that accompany gear shifting. In step S54, the correction of step S47 in the gear shift control flow of FIG. 9 is performed. In addition, the friction brake system 3 and / or the motor 5 impart torque to the rear wheels 2R to compensate for torque fluctuations that occur during gear shifting. As a result, the behavior of the automobile 1 is prevented from becoming unstable.

[0119] When brake regeneration is not being performed, the controller 20 executes cooperative control of the motor 5 and the automatic transmission 8. In step S55, the automatic transmission 8 executes gear shift control so as to suppress torque fluctuations at the rear wheels 2R that accompany gear shifting. In step S55, the correction of step S47 in the gear shift control flow of FIG. 9 is also performed. In addition, the motor 5 applies torque to the rear wheels 2R to compensate for torque fluctuations that occur during gear shifting. As a result, the behavior of the automobile 1 is prevented from becoming unstable.

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

[0121] <Fourth Process> 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 automobile 1 is diverging. If the unstable behavior of the automobile 1 is diverging, the process proceeds to step S62. If the unstable behavior of the automobile 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 on. If the driver is depressing the brake pedal 19 (i.e., if Yes), the process proceeds to step S63, and if the driver is not depressing the brake pedal 19 (i.e., if No), the process proceeds to step S64.

[0123] In step S63, since the brake is on, DSC control or ABS control is executed to converge the unstable behavior of the automobile 1. In step S64, since the brake is off, DSC control is executed to converge the unstable behavior of the automobile 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 described with reference to the time charts of Figures 12 to 14. Each time chart includes changes in the brake pedal operation amount and brake fluid pressure, changes in the steering angle (measured value of the steering angle sensor 53), changes in the gear position, changes in the yaw rate (measured value of the yaw rate sensor 54), changes in the regenerative braking torque, changes in the AT input torque, changes in the transmission ratio of the automatic transmission 8, and changes in the AT input rotation speed.

[0126] First, FIG. 12 is a time chart for prohibiting downshifting of the automatic transmission 8 until the oversteer state of the automobile 1 is resolved. At time t1, the driver begins to depress the brake pedal 19. The controller 20 starts regenerative cooperative control. Based on a signal from the controller 20, the friction brake system 3 reduces the brake fluid pressure in accordance with the amount of operation of the brake pedal 19, as indicated by the dashed dotted line. The braking force of the friction brake 31 is reduced accordingly. The motor 5 increases the regenerative braking torque to compensate for the reduction in the braking force of the friction brake 31. This ensures regenerative energy, which is advantageous for improving the fuel efficiency of the automobile 1. As 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 turn the steering wheel 110. As a result, the steering angle gradually increases. The automobile 1 begins to turn, and the yaw rate gradually increases.

[0128] At time t3, the automobile 1 enters an oversteer state, and the deviation between the actual yaw rate and the estimated yaw rate increases. 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 the motor 5, which had been providing part of the braking force of the friction brake 31, disappears. This reduces the regenerative braking torque. Note that even after time t3, the regenerative braking torque equivalent to the engine brake caused by the accelerator being released remains, and the regenerative operation of the motor 5 itself continues. Furthermore, the hydraulic pressure of the friction brake 31 is increased to compensate for the decrease in the regenerative braking torque of the motor 5.

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

[0130] The torque increase described above reduces the regenerative braking torque applied to the rear wheels 2R, ensuring lateral force at the rear wheels 2R, which helps to eliminate the oversteer state of the automobile 1. When the oversteer state of the automobile 1 is eliminated at time t4, the controller 20 causes the automatic transmission 8 to execute a delayed downshift (proceeding from step S34 to step S310). Specifically, the increase in 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 torque fluctuations at the rear wheels 2R due to the inertia caused by the downshift, preventing the behavior of the automobile 1 from returning to instability immediately after the oversteer state is eliminated.

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

[0132] When the automatic transmission 8 downshifts after the oversteer state of the automobile 1 is resolved, normal shift control may be executed instead of the shift control executed when oversteer is determined. In other words, the torque increase of the motor 5 during downshifting may be suppressed.

[0133] Fig. 13 is a time chart for prohibiting downshifting of the automatic transmission 8 until the oversteer state of the automobile 1 is resolved. The time chart of Fig. 13 differs from the time chart of Fig. 12 in that the AT input rotation speed reaches the third shift point S3.

[0134] In the time chart of FIG. 13, as in the time chart of FIG. 12, the driver begins to depress the brake pedal 19 at time t1, the driver begins to steer the steering wheel 110 at time t2, and the automobile 1 enters an oversteer state at time t3. In order to end the regenerative cooperative control, the controller 20 increases the input torque of the input shaft 8a of the automatic transmission 8 (torque up) so that the regenerative braking torque of the motor 5, which had been providing part of the braking force of the friction brake 31, disappears. This reduces the regenerative braking torque. Note that the regenerative operation of the motor 5 itself continues even after time t3. The gear shift of the automatic transmission 8 is delayed.

[0135] As the automobile 1 decelerates, the AT input rotation speed gradually decreases, and at time t4, the AT input rotation 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. This decreases the AT input rotation speed, 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] The oversteer state is resolved by increasing the torque of the input shaft 8a. After the oversteer state is resolved, the automatic transmission 8 downshifts.

[0137] Fig. 14 is a time chart showing a case where the automobile 1 is in an oversteer state while the automatic transmission 8 is shifting gears. In the time chart of Fig. 14, as in the time chart of Fig. 12, the driver starts to depress the brake pedal 19 at time t1, and starts to steer the steering wheel 110 at time t2. The controller 20 performs regenerative cooperative control.

[0138] At time t3, the AT input rotation speed reaches the first shift point S1, so the automatic transmission 8 downshifts. Since the automobile 1 is turning, the first coordinated shift control (step S54) of the third process is executed. As shown in FIG. 14, the hydraulic pressure of the friction brake 31 is adjusted after time t4 in accordance with the downshift of the automatic transmission 8.

[0139] At time t5 during the gear shift, the automobile 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 up) to stop the regenerative cooperative control, and also increases the torque of the motor 5 to make the input torque of the input shaft 8a of the automatic transmission 8 higher than that during normal gear shift control. The torque up for stopping the regenerative cooperative control and the torque up for the gear shift may be performed substantially simultaneously or at different times. By ensuring the lateral force of the rear wheels 2R and suppressing torque fluctuations during the gear shift, the instability of the behavior of the automobile 1 is prevented from worsening. The hydraulic pressure of the friction brake 31 is increased to compensate for the decrease in the regenerative braking torque of the motor 5. The motor 5 also performs regenerative operation with a regenerative braking torque equivalent to engine braking.

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

[0141] (Variation) Figure 15 shows a modified example of the second process. This modified example differs from the flow of Figure 8 in that the downshift is not delayed. In step S71 after the start, the controller 20 determines whether or not the oversteer determination is established. 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 regenerative braking is being performed. If the determination in step S72 is Yes, the process proceeds to step S73, and if the determination in step S72 is No, the process proceeds to step S74 without proceeding to step S73.

[0143] In step S73, the controller 20 executes torque-up control. This ends the regenerative cooperative control. The regenerative braking torque applied to the rear wheels 2R is reduced, ensuring lateral force at the rear wheels 2R, and the oversteer state of the automobile 1 is resolved. After step S73, the process proceeds to step S74. From step S74 onwards, the motor 5 performs regenerative operation with a regenerative braking torque equivalent to engine braking when the accelerator is released. Even if the automobile 1 is in an oversteer state, the amount of regeneration is ensured as much as possible, which is advantageous for improving the fuel efficiency of the automobile 1.

[0144] In step S74, the controller 20 determines whether the unstable behavior of the automobile 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 not shifting gears. If the automatic transmission 8 is not shifting gears (i.e., if the answer is Yes), the process proceeds to step S76. If the automatic transmission 8 is shifting gears (i.e., if the answer is No), the process proceeds to step S710.

[0146] In step S76, the controller 20 determines whether the rotation speed of the input shaft 8a of the automatic transmission 8 has reached the first shift point S1. If the rotation speed of the input shaft 8a has reached the first shift point S1, the process proceeds to step S77; if not, the process proceeds to the fourth process. As described above, the first shift point S1 is the downshift point when regenerative cooperative control is being executed. Note that in step S76, the controller 20 may also determine whether the rotation 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 behavior of the automobile 1 due to downshifting is suppressed.

[0148] In this way, in the second process according to the modified example, when the automobile 1 is in an oversteer state, the K1 clutch is released and the automatic transmission 8 is not shifted down. This prevents the behavior of the automobile 1 from becoming further unstable due to gear changes. In addition, engine stalls can be avoided.

[0149] On the other hand, if the automobile 1 is in an oversteer state and the automatic transmission 8 is in the process of downshifting (if No in step S75), or if a downshift is performed after the oversteer state of the automobile 1 is resolved (if No in step S74), the controller 20 executes gear change control when an oversteer is determined in step S710. Even if a downshift is performed, torque fluctuations are suppressed, so that the behavior of the automobile 1 is prevented from becoming more unstable.

[0150] In the following step S711, the controller 20 determines whether or not regenerative braking is in progress, and if so, the process proceeds to step S712. On the other hand, if not, the process proceeds from step S711 to a fourth process.

[0151] In step S712, the controller 20 stops the regenerative cooperative control, and ensures the braking force that was provided by the regenerative braking torque of the motor 5 by the friction brake 31, thereby achieving deceleration that matches the braking required by the driver.

[0152] The disclosed technology is not limited to the above-described embodiment, but includes various other configurations. For example, the configuration of the automobile 1 is an example. The configuration can be changed as appropriate depending on the specifications.

[0153] In each of the flows 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 transmission control device an engine 4 mounted on the automobile 1 and generating driving force for the automobile 1; a motor 5 that generates a driving force for the automobile 1 and supplies regenerative energy to a high-voltage battery 9 when the automobile 1 is decelerated; an automatic transmission 8 having an input shaft 8a connected to the engine 4 and the motor 5 and an output shaft 8b connected to the rear wheel 2R, which changes the speed of the input rotation at a gear ratio corresponding to a selected gear position and outputs the rotation; a friction brake system 3 that distributes braking force to the front wheels 2F and the rear wheels 2R so that braking is performed in accordance with the operation of a brake pedal 19 by a driver; a controller (20) that executes, during deceleration of the automobile (1) while the friction brake system (3) is distributing braking force to the front wheels (2F) and the rear wheels (2R), regenerative control for applying regenerative braking torque to the rear wheels (2R) by causing the motor (5) to perform a regenerative operation, and gear shift control for changing the gear position of the automatic transmission (8) by outputting a gear shift signal to the automatic transmission (8) according to the rotation speed of the input shaft (8a), If the controller 20 determines that the automobile 1 is in an oversteer state (Yes in step S71) during the regenerative control (Yes in step S72), it increases the input torque of the input shaft 8a of the automatic transmission 8 while maintaining the regenerative operation of the motor 5 so as to reduce the regenerative braking torque (step S73), and cuts off the power transmission between the input shaft 8a and the output shaft 8b of the automatic transmission 8 (step S77).

[0155] This allows the gear change control device to maintain regenerative operation and stabilize vehicle behavior.

[0156] After the input torque of the input shaft 8a is increased, when the rotation speed of the input shaft 8a reaches a downshift point, the controller 20 interrupts the power transmission (step S77).

[0157] This can prevent the engine from stalling.

[0158] When the oversteer state of the automobile 1 diverges, the controller 20 causes the friction brake system 3 to execute control to stabilize the behavior of the vehicle by applying braking force to the front wheels 2F or the rear wheels 2R (Figure 11).

[0159] If the oversteer state of the automobile 1 becomes excessive, the DSC or ABS is activated to prevent the behavior of the automobile 1 from becoming uncontrollable.

[0160] the controller 20 executes a second regenerative control to apply a regenerative braking torque to the rear wheels 2R by causing the motor 5 to perform a regenerative operation during deceleration of the automobile 1 when the friction brake system 3 is not applying a braking force to the front wheels 2F and the rear wheels 2R; If the controller 20 determines that the automobile 1 is in an oversteer state during the second regenerative control, the controller 20 maintains the regenerative operation (No in step S72).

[0161] This ensures a sufficient amount of regeneration, which is advantageous for improving the fuel efficiency of the automobile 1.

[0162] If the controller 20 determines during the second regenerative control that the automobile 1 is in an oversteer state and the rotation speed of the input shaft 8a reaches the downshift point, the controller 20 cuts off the power transmission (step S77).

[0163] During the second regenerative control, the power transmission of the automatic transmission 8 is also cut off, so that the behavior of the automobile 1 can be prevented from becoming unstable.

[0164] When the oversteer state of the automobile 1 diverges, the controller 20 causes the friction brake system 3 to execute 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).

[0165] This makes it possible to prevent the behavior of the automobile 1 from becoming uncontrollable even during the second regenerative control.

[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 whether the automobile 1 is in an oversteer state (step S71).

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

[0168] 1. Automobiles (vehicles) 19 Brake pedal 110 Steering Wheel 20 Controller 2F front wheel 2R rear wheel 3 Friction Brake System 4 Engine 5 motors 53 Steering angle sensor (second sensor) 54 Yaw rate sensor (first sensor) 8 Automatic Transmission 8a Input shaft 8b Output shaft 9 High Voltage Battery

Claims

1. an engine mounted on a vehicle and generating driving force for the vehicle; a motor that generates a driving force for the vehicle and supplies regenerative energy to a battery when the vehicle is decelerating; an automatic transmission having an input shaft connected to the engine and the motor and an output shaft connected to a rear wheel, the automatic transmission shifting the input rotation at a gear ratio corresponding to a selected gear position and outputting the shifted rotation; a friction brake system that distributes braking force to the front wheels and the rear wheels so that braking is performed in accordance with the driver's brake pedal operation; a controller that executes regenerative control for applying regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation, and shift control for changing the gear position of the automatic transmission by outputting a shift signal to the automatic transmission according to the rotation speed of the input shaft, while the vehicle is decelerating and the friction brake system is distributing braking force to the front wheels and the rear wheels; When the controller determines that the vehicle is in an oversteer state during the regenerative control, the controller increases the input torque of the input shaft of the automatic transmission so that the regenerative braking torque decreases, while maintaining the regenerative operation of the motor, and cuts off the power transmission between the input shaft and the output shaft of the automatic transmission.

2. 2. The vehicle gear shift control device according to claim 1, The controller interrupts the power transmission when the rotation speed of the input shaft reaches a downshift point after the input torque of the input shaft increases.

3. 2. The vehicle gear shift control device according to claim 1, The controller controls the friction brake system to stabilize the behavior of the vehicle by applying braking force to the front wheels or the rear wheels when the oversteer state of the vehicle diverges.

4. 2. The vehicle gear shift control device according to claim 1, the controller executes a second regenerative control to apply a regenerative braking torque to the rear wheels by causing the motor to perform a regenerative operation during deceleration of the vehicle when the friction brake system is not applying a braking force to the front wheels and the rear wheels; The vehicle shift control device, wherein the controller maintains the regenerative operation when it determines that the vehicle is in an oversteer state during the second regenerative control.

5. 5. The vehicle gear shift control device according to claim 4, A vehicle shift control device, wherein the controller cuts off the power transmission when it determines that the vehicle is in an oversteer state during the second regenerative control and the rotation speed of the input shaft reaches a downshift point.

6. 6. The vehicle gear shift control device according to claim 5, The controller controls the friction brake system to stabilize the behavior of the vehicle by applying braking force to the front wheels or the rear wheels when the oversteer state of the vehicle diverges.

7. 2. The vehicle gear shift control device according to claim 1, The controller receives signals from a first sensor that outputs a signal related to the behavior of the vehicle and a second sensor that outputs a signal related to the steering operation of the driver, and determines whether the vehicle is in an oversteer state.

Images