Vehicle drive control system

Abstract

This invention relates to a vehicle 1 that travels by the driving of front wheels 4 by means of power transmitted from an engine 3 and a front motor 2 through a transaxle 7 and the driving of rear wheels 6 by means of a rear motor 5, and comprises: a hybrid controller unit 18 that computes a requested output for vehicle travel, sets an output ratio for the front wheels 4 and the rear wheels 6, and controls the output of the engine 3, the front motor 2, and the rear motor 5 on the basis of the requested output of the vehicle 1 and the output ratio; a T / A oil temperature sensor 30 that acquires the oil temperature of the transaxle 7; and a T / A protection control unit 50 that, when the oil temperature T of the transaxle 7 is greater than or equal to a first threshold value T1, executes a transaxle protection control for reducing the output ratio on the front wheels 4 side by more than when the oil temperature T of the transaxle 7 is less than the first threshold value T1.

Description

Technical Field

[0001] The present invention relates to a driving control technology for four-wheel drive vehicles.

Background Art

[0002] There are vehicles that drive the front and rear wheels of the vehicle by an engine and a motor, such as a four-wheel drive vehicle of a hybrid vehicle. Patent Document 1 discloses a four-wheel drive vehicle that mainly drives the front wheels by an engine and drives the rear wheels by a motor as needed. Further, the vehicle described in Patent Document 1 has a control system that reduces the output of the motor when the temperature of the motor for rear-wheel drive is above a predetermined temperature and increases the output of the engine by that amount to ensure the driving force of the entire vehicle.

[0003] In addition, on the front wheel side, a transaxle incorporating a transmission and a differential device is provided in the power transmission path between the engine and the front wheels. The transaxle is filled with lubricating oil (hydraulic oil). [[ID=2]]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, among four-wheel drive vehicles of hybrid vehicles, there has been developed a four-wheel drive vehicle that includes a motor for front-wheel drive and a motor for rear-wheel drive, drives the front wheels by an engine and a motor, can drive a generator by the engine to generate electricity, and drives the rear wheels by a motor.

[0006] Thus, in vehicles where the front wheels are driven by both an engine and a motor, the temperature of the transaxle (lubricating oil temperature) in the front-wheel drive system tends to rise. In particular, in hybrid vehicles capable of series mode, power is transmitted simultaneously within the transaxle through two paths: between the engine and the generator, and between the motor and the front wheels, which makes the temperature of the lubricating oil within the transaxle more prone to rising.

[0007] However, if the temperature of the lubricating oil inside the transaxle rises excessively, it can lead to problems such as reduced lubrication performance and increased load on the transaxle.

[0008] The present invention was made to solve these problems, and its objective is to provide a drive control device for a four-wheel drive vehicle that prevents the transaxle from overheating while ensuring the driving force of the entire vehicle. [Means for solving the problem]

[0009] To achieve the above objective, the vehicle driving control device of the present invention is used in a vehicle that drives either the front or rear first running wheel by transmitting power from a first driving device via a transaxle, and drives the other second running wheel by a second driving device. The first drive unit comprises an engine and an electric motor, and the engine, the electric motor and a generator are connected to the transaxle. The unit operates in at least one of the following modes: a series mode in which power is transmitted from the engine to the generator via the transaxle to drive and generate electricity, and power is transmitted from the electric motor to the first drive wheels via the transaxle to drive them, and an EV mode in which the first drive wheels are driven by the electric motor via the transaxle. A driving mode switching unit that switches between parallel mode, which drives the first driving wheel, The system includes: an output control unit that calculates the requested output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the second drive unit based on the requested output of the vehicle and the output ratio; a temperature detection unit that acquires the oil temperature of the transaxle; and a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, maintains the requested output and reduces the output ratio of the first drive unit to a level lower than when the oil temperature of the transaxle is below the first threshold, thereby executing transaxle protection control. The protection control unit, when the driving mode switching unit has switched to the series mode or EV mode, will then... The transaxle protection control is performed, and if the system is switched to parallel mode, the transaxle protection control is not performed. It is characterized by the following: This makes it possible to reduce the driving force transmitted to the transaxle by lowering the output of the first traction drive equipment while maintaining the required output when the transaxle temperature exceeds a first threshold, thereby suppressing the rise in transaxle temperature.

[0010] moreover, In series mode or EV mode, transaxle protection control is performed to suppress the rise in transaxle temperature. However, in parallel mode, where the amount of power transmitted within the transaxle is less than in series mode or EV mode, transaxle protection control is not performed. This suppresses unnecessary changes in the front-to-rear power ratio during driving, thereby improving the vehicle's driving performance.

[0012] Alternatively, the vehicle drive control device of the present invention is for a vehicle that drives either the front wheels or the rear wheels by transmitting power from a first drive device to one of the first running wheels via a transaxle, and drives the other second running wheel by a second drive device, The vehicle is equipped with a skid suppression control unit that controls the rotational speed of the first and second running wheels to suppress skidding when skidding occurs. The system includes: an output control unit that calculates a requested output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the second drive unit based on the requested output of the vehicle and the output ratio; a temperature detection unit that acquires the oil temperature of the transaxle; and a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, maintains the requested output and reduces the output ratio of the first drive unit to a level lower than when the oil temperature of the transaxle is below the first threshold. The protection control unit executes the transaxle protection control when the skidding suppression control by the skidding suppression control unit is effective, and does not execute the transaxle protection control when the skidding suppression control by the skidding suppression control unit is prohibited. It is characterized by the following: This allows for the implementation of transaxle protection control when skidding control is active, thereby ensuring vehicle stability while suppressing the temperature rise of the transaxle.

[0013] Alternatively, the vehicle drive control device of the present invention is for a vehicle that drives either the front wheels or the rear wheels by transmitting power from a first drive device to one of the first running wheels via a transaxle, and drives the other second running wheel by a second drive device, Vehicle speed acquisition unit that acquires the vehicle's travel speed The system includes: an output control unit that calculates the requested output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the second drive unit based on the requested output of the vehicle and the output ratio; a temperature detection unit that acquires the oil temperature of the transaxle; and a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, maintains the requested output and performs transaxle protection control that reduces the output ratio of the first drive unit compared to when the oil temperature of the transaxle is below the first threshold. If the oil temperature of the transaxle is above a second threshold, which is higher than the first threshold, the protection control unit reduces the requested output by a predetermined amount set based on the travel speed. It is characterized by the following: As a result, if the transaxle oil temperature rises above the first threshold that changes the front-to-rear power ratio, the requested power is reduced, further decreasing the power transmitted through the transaxle. This further suppresses the temperature rise of the transaxle. In addition, since the requested power is reduced based on the vehicle speed, the amount of reduction in the requested power can be appropriately set in response to changes in the effect of the airflow during vehicle travel on suppressing the temperature rise of the transaxle.

[0014] Preferably, the vehicle is equipped with a skid suppression control unit that controls the rotational speed of the first and second running wheels to suppress skidding when skidding occurs, and the protection control unit may execute the transaxle protection control even when the skid suppression control unit is prohibited from suppressing skidding if the oil temperature of the transaxle is above the second threshold. As a result, if the transaxle oil temperature is above the second threshold, which is higher than the first threshold, the transaxle protection control can be executed even if the lateral slip suppression control is disabled, thereby suppressing the rise in transaxle temperature.

[0015] Preferably, the protection control unit reduces the requested output to a value greater than the maximum value of the predetermined amount when the oil temperature of the transaxle is above a third threshold, which is higher than the second threshold. This further reduces the required power output when the transaxle oil temperature exceeds the second threshold, thereby further reducing the power transmitted through the transaxle and further suppressing the rise in transaxle temperature. [Effects of the Invention]

[0017] According to the driving control device of the present invention, when the oil temperature of the transaxle rises, the required output is secured to ensure the driving force of the vehicle, while the output of the first driving device is reduced to reduce the driving force transmitted to the transaxle, thereby suppressing the temperature rise of the transaxle and protecting the transaxle.

Brief Description of the Drawings

[0018] [Figure 1] This is an overall configuration diagram of the driving system of a vehicle in which the T / A oil temperature corresponding control device of this embodiment is adopted. [Figure 2] This is a flowchart showing the control procedure of the transaxle protection control executed in the T / A protection control unit. [Figure 3] This is a table summarizing the control contents of the transaxle protection control. [Figure 4] This is an explanatory diagram of the transition of each step in the transaxle protection control.

Modes for Carrying Out the Invention

[0019] Hereinafter, an embodiment in which the present invention is applied to a hybrid vehicle (hereinafter referred to as vehicle 1) will be described. FIG. 1 is an overall configuration diagram of the driving system of vehicle 1 in which the driving control device of this embodiment is adopted.

[0020] Vehicle 1 of this embodiment is a hybrid vehicle equipped with a front motor 2 (first driving device for running, electric motor), a rear motor 5 (second driving device for running), and an engine 3 (first driving device for running) as driving power sources. Vehicle 1 is a four-wheel drive vehicle configured to drive the front wheels 4 (first driving wheels) by the output of the front motor 2 or the output of the front motor 2 and the engine 3, and drive the rear wheels 6 (second driving wheels) by the output of the rear motor 5.

[0021] The output shaft of the engine 3 is connected to a drive shaft 8 which is the drive shaft of the front wheels 4 via a transaxle 7. The transaxle 7 incorporates a differential 7b and a clutch 9 capable of disconnecting and connecting the power transmission path in a case 7a, and is filled with lubricating oil. When the clutch 9 is connected, the driving force of the engine 3 is transmitted to the front wheels 4 via the transaxle 7 and the drive shaft 8, and when the clutch 9 is disengaged, the connection between the engine 3 and the front wheels 4 is disconnected.

[0022] The drive shaft of the front motor 2 is connected to the drive shaft 8 via the transaxle 7, and the driving force of the front motor 2 is transmitted from the transaxle 7 through the drive shaft 8 to the front wheel 4. In addition, a motor generator 10 is connected to the upstream side (engine 3 side) of the clutch 9 of the transaxle 7 in the power transmission direction, and generates electricity when the engine 3 is driven. The motor generator 10 also functions as a starter motor to start the engine 3 when the clutch 9 is disengaged. The rear motor 5 is connected to the drive shaft 12 of the rear wheel 6 via a reduction gear 11, and its driving force is transmitted from the reduction gear 11 through the drive shaft 12 to the rear wheel 6.

[0023] Engine 3 is connected to an engine control unit 14, which consists of input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. This engine control unit 14 controls the throttle opening, fuel injection amount, ignition timing, etc. of engine 3.

[0024] The front motor 2, rear motor 5, and motor generator 10 are, for example, three-phase AC motors, and a battery 15 for driving is provided as their power source. The battery 15 is composed of a secondary battery such as a lithium-ion battery and incorporates a battery monitoring unit 15a that calculates the charge level and detects the temperature.

[0025] The front motor 2 and motor generator 10 are connected to the battery 15 via the front motor control unit 16. The front motor control unit 16 is equipped with a front motor inverter 16a and a motor generator inverter 16b. The DC power from the battery 15 is converted to three-phase AC power by the front motor inverter 16a and the motor generator inverter 16b and supplied to the front motor 2 and motor generator 10. In addition, the regenerative power from the front motor 2 and the power generated by the motor generator 10 are converted to DC power by the front motor inverter 16a and the motor generator inverter 16b and charged to the battery 15.

[0026] The rear motor 5 is connected to the battery 15 via the rear motor control unit 17. The rear motor control unit 17 is equipped with a rear motor inverter 17a. The DC power from the battery 15 is converted to three-phase AC power by the rear motor inverter 17a and supplied to the rear motor 5, and the regenerative power from the rear motor 5 is converted to DC power by the rear motor inverter 17a and charged to the battery 15. Furthermore, vehicle 1 is equipped with a charger 13 that charges the battery 15 using an external power source.

[0027] Vehicle 1 is equipped with a hybrid control unit 18 (output control unit), which is a control device for the overall control of Vehicle 1. The hybrid control unit 18 consists of input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. This hybrid control unit 18 controls the operating states of the engine 3, front motor 2, motor generator 10, and rear motor 5, as well as the engagement / disengagement state of the clutch 9 of the transaxle 7. The input side of the hybrid control unit 18 is connected to a battery monitoring unit 15a, a front motor control unit 16, a rear motor control unit 17, an engine control unit 14, a vehicle speed sensor 20 (vehicle speed acquisition unit) that detects the driving speed (vehicle speed V) of Vehicle 1, and an accelerator opening sensor (not shown) that detects the accelerator opening, and detection and operation information from these devices is input.

[0028] Furthermore, the output side of the hybrid control unit 18 is connected to the front motor control unit 16, the rear motor control unit 17, the clutch 9 of the transaxle 7, and the engine control unit 14. The hybrid control unit 18 is equipped with a driving mode switching unit 51 that switches the driving mode of the vehicle 1 between EV mode, series mode, and parallel mode based on various detected values ​​such as the accelerator opening sensor and the vehicle speed sensor 20. The driving mode switching unit 51 sets the driving mode to parallel mode in areas where the engine 3 is highly efficient, such as high speeds. In the medium to low speed range, it switches between EV mode and series mode based on the charge level (SOC) of the battery 15 and the required torque for driving the vehicle.

[0029] In EV mode, the clutch 9 of the transaxle 7 is disengaged and the engine 3 is stopped, and the front motor 2 and rear motor 5 are driven by power from the battery 15 to move the vehicle 1.

[0030] In series mode, the clutch 9 of the transaxle 7 is disengaged, and the engine 3 is operated to drive the motor generator 10. The generated power, along with power from the battery 15, drives the front motor 2 and rear motor 5 to move the vehicle 1. Any surplus power generated by the motor generator 10 is charged into the battery 15.

[0031] In parallel mode, the clutch 9 of the transaxle 7 is engaged, and the engine 3 is driven to transmit driving force from the transaxle 7 to the front wheels 4. When there is excess engine driving force, it is regenerated by the front motor 2, and when there is insufficient engine driving force, the power from the battery 15 is used to assist the front motor 2.

[0032] Furthermore, the hybrid control unit 18 calculates the total required output necessary for the vehicle 1 to run based on the various detected quantities and operating information described above, and distributes this total required output to the front motor 2 side and the rear motor 5 side in EV mode and series mode, and to the front motor 2 side, the engine 3 side and the rear motor 5 side in parallel mode. The output ratio between the front wheels (front motor 2, engine 3) and the rear wheels (rear motor 5) is calculated by the hybrid control unit 18. The output ratio between the front wheels 4 side and the rear wheels 6 side is typically around 40-50:60-50, for example.

[0033] The hybrid control unit 18 further sets the required torque for the front motor 2, engine 3, and rear motor 5 based on the requested output allocated to each, the gear ratio of the transaxle 7 from the front motor 2 to the front wheels 4, the gear ratio of the transaxle 7 from the engine 3 to the front wheels 4, and the gear ratio of the reduction gear 11 from the rear motor 5 to the rear wheels 6, and outputs command signals to the front motor control unit 16, the rear motor control unit 17, and the engine control unit 14 to achieve each of the requested torques.

[0034] The front motor control unit 16 and the rear motor control unit 17 calculate target current values ​​to be supplied to the coils of each phase of the front motor 2 and rear motor 5 in order to achieve the required torque, based on command signals from the hybrid control unit 18. Then, based on the target current values, the front motor inverter 16a and the rear motor inverter 17a are switched to control the current value of each coil to the target current value, thereby achieving the required torque. The same procedure is followed when the motor generator 10 is generating power; the motor generator inverter 16b is switched to control based on the target current value obtained from the required torque on the negative side, thereby achieving the target current value.

[0035] The engine control unit 14 calculates target values ​​such as throttle opening, fuel injection amount, and ignition timing based on command signals from the hybrid control unit 18 to achieve the required torque, and achieves the required torque through control based on these target values.

[0036] Furthermore, vehicle 1 has a regenerative power generation function that generates electricity by forcibly driving the front motor 2 and rear motor 5 with the rotational force of the wheels 4 and 6 during deceleration. The hybrid control unit 18 is equipped with a regenerative power generation control unit 52 that controls the load on the front motor 2 and rear motor 5 via the front motor control unit 16 during deceleration, and controls the regenerative power generation.

[0037] Furthermore, vehicle 1 is equipped with an Anti-Skid Control (ASC) system. The Anti-Skid Control system, via an Anti-Skid Control Control Unit 53 located within the Hybrid Control Unit 18, determines whether vehicle 1 is skidding while in motion based on the rotational speed of each wheel 4, 6, etc. If skidding is detected, it independently controls the front, rear, left, and right brake systems to suppress the skidding of vehicle 1. The function of the Anti-Skid Control system can be restricted by the driver turning off the ASC switch 61.

[0038] Furthermore, the hybrid control unit 18 of the vehicle 1 in this embodiment is equipped with a slip suppression control unit 55 that provides feedback control of the output ratio, etc., in order to properly control the slip between the front and rear wheels (longitudinal slip) and the slip between the left and right wheels (lateral slip) of the vehicle 1 in four-wheel drive. The slip suppression control unit 55 detects slip in the wheels 4 and 6 based on the rotational speed of each wheel 4 and 6 detected by wheel speed sensors 54 (rotational speed detection unit), etc., provided on each wheel 4 and 5, and suppresses slip by controlling the output ratio of the front and rear left and right wheels.

[0039] The vehicle 1 of this embodiment is equipped with a T / A oil temperature sensor 30 (temperature detection unit) that detects the lubricating oil temperature (oil temperature) of the transaxle 7. The hybrid control unit 18 includes a T / A protection control unit 50 (protection control unit) that performs transaxle protection control to suppress excessive temperature rise of the transaxle 7.

[0040] The transaxle protection control will be explained below using Figures 3 and 4. Figure 2 is a flowchart showing the control procedure for transaxle protection control performed by the T / A protection control unit 50. Figure 3 is a table summarizing the control contents of the transaxle protection control.

[0041] The transaxle protection control in this embodiment is performed when the vehicle 1 is powered on. First, in step S10, if the vehicle is in motion, proceed to step S20. If the vehicle is not in motion, i.e., if the vehicle is stopped, proceed to step S110.

[0042] In step S20, it is determined whether the driving mode of vehicle 1 is EV mode or series mode. If the driving mode is EV mode or series mode, the process proceeds to step S30. If the driving mode is neither EV mode nor series mode, i.e., parallel mode, the process proceeds to step S120.

[0043] In step S30, it is determined whether vehicle 1 is in powered operation, driven by engine 3 and motors 2 and 5. If it is in powered operation, the process proceeds to step S40. If it is not in powered operation, i.e., regenerative power generation is in progress, the process proceeds to step S120.

[0044] In step S40, the oil temperature T of the transaxle 7 is input from the T / A oil temperature sensor 30. Then, the process proceeds to step S50.

[0045] In step S50, it is determined whether the oil temperature T entered in step S40 is equal to or greater than the first threshold T1. The first threshold T1 can be appropriately set to a value slightly lower than the maximum allowable oil temperature range that does not cause problems with the operation or transmission efficiency of the transaxle 7. If the oil temperature T is equal to or greater than the first threshold T1, the process proceeds to step S60. If the oil temperature T is less than the first threshold T1, the process proceeds to step S120.

[0046] In step S60, it is determined whether the oil temperature T entered in step S40 is greater than or equal to the second threshold T2. The second threshold T2 should be set to a value higher than the first threshold T1, within the allowable range of the oil temperature T of the transaxle 7. If the oil temperature T is greater than or equal to the first threshold T1, the process proceeds to step S60. If the oil temperature T is less than the first threshold T1, the process proceeds to step S100.

[0047] In step S70, it is determined whether the oil temperature T entered in step S40 is greater than or equal to the third threshold T3. The third threshold T3 should be set appropriately to a value higher than the second threshold T2 and close to the highest value within the allowable range of the transaxle 7 oil temperature. If the oil temperature T is greater than or equal to the third threshold T3, the process proceeds to step S80. If the oil temperature T is less than the first threshold T1, the process proceeds to step S90.

[0048] In step S80, T / A protection control STEP3 is executed. T / A protection control STEP3 sets the front and rear wheel drive force distribution (output distribution) to 3:7 (T / A protection distribution). This T / A protection distribution of 3:7 is the setting that gives the largest distribution to the rear wheels 6 while allowing for changes in vehicle characteristics such as straight-line stability, and limits the distribution to the front wheels 4. In addition, the overall output of the vehicle (required output) is suppressed to a certain output value Pmin. This output value Pmin is a value that ensures the oil temperature T of the transaxle 7 decreases. Furthermore, an output suppression warning is issued via the instrument panel or other notification device 60, informing the driver of vehicle 1 that output suppression is being performed. Then, this routine ends.

[0049] In step S90, T / A protection control STEP2 is executed. T / A protection control STEP2 sets the front and rear wheel torque distribution to a T / A protection distribution of 3:7. It also suppresses the overall vehicle output (requested output) based on the vehicle speed V. In this step, the amount of suppression (determined amount) of the vehicle's output should be set to be smaller than the suppression amount in T / A protection control STEP3, for example, decreasing as the vehicle speed V increases. Then, this routine is terminated.

[0050] In step S100, it is determined whether the ASC switch 61 is enabled or disabled. If the ASC switch 61 is ON, i.e., the skid suppression control is ON, the process proceeds to step S110. If the ASC switch 61 is OFF, i.e., the skid suppression control by the skid suppression control unit 53 is disabled, the process proceeds to step S120.

[0051] In step S110, T / A protection control STEP1 is executed. T / A protection control STEP1 sets the front and rear wheel torque distribution to a T / A protection distribution of 3:7. Note that the driving output is not suppressed. Then, this routine is terminated.

[0052] In step S120, T / A protection control is not performed (STEP0). That is, the front-to-rear distribution ratio of the vehicle is the normal distribution (approximately 40-50:60-50), and the driving output is not suppressed. Then, this routine ends.

[0053] The control details of the transaxle protection control described above are shown in Figure 3. In this embodiment, as shown in Figure 3, transaxle protection control is performed in all of the drive modes (Normal, ECO, Power mode, etc.) that change the degree of output of motors 2 and 5 and engine 3 in response to accelerator input.

[0054] Regarding the driving mode, transaxle protection control is performed in EV mode or series mode, but not in parallel mode. This is because in parallel mode, the front wheels 4 are driven by both the engine 3 and the front motor 2, and the output of the front motor 2 is suppressed, so the oil temperature of the transaxle 7 does not exceed the allowable temperature.

[0055] Transaxle protection control is performed during powering, but not during regenerative braking. This is because the power transmitted to the transaxle 7 is lower during regenerative braking than during powering, so the temperature of the transaxle 7 does not exceed the allowable temperature.

[0056] In transaxle protection control, if the oil temperature T of the transaxle 7 is less than the first threshold T1, STEP 0 (no power distribution control and power suppression control) is executed; if the oil temperature T is greater than or equal to the first threshold T1 and less than the second threshold T2, STEP 1 is executed; if the oil temperature T is greater than or equal to the second threshold T2 and less than the third threshold T3, STEP 2 is executed; and if the oil temperature T is less than the third threshold T3, STEP 3 is executed.

[0057] In STEP 1, the output distribution is set to a T / A protection distribution of 3:7 (output distribution control). In STEP 2, the power distribution is set to a T / A protection distribution of 3:7, and power is suppressed based on the vehicle speed V (power distribution control and power suppression control). Furthermore, the notification device 60 displays a warning to the driver that power suppression is being performed. In STEP 3, the power distribution is set to a T / A protection distribution of 3:7, and the power is suppressed to a constant value lower than in STEP 2 (power distribution control and power suppression control). Furthermore, a warning display is shown to the driver indicating that power suppression is being performed. The warning at this time should be stronger than the warning in STEP 2.

[0058] However, if the oil temperature T is between the first threshold T1 and the second threshold T2 and the ASC switch 61 is OFF, output distribution control and output suppression control will not be performed. This is because, since no warning is issued in STEP 1, it is necessary to ensure the driving stability of vehicle 1 by the Anti-Skid Control (ASC) system.

[0059] Furthermore, even when the output distribution in the above T / A protection control STEP1 to T / A protection control STEP3 is set to a T / A protection distribution of 3:7, the slip suppression control unit 55 allows the output ratio feedback control to operate in order to suppress slip between the left and right wheels of the vehicle.

[0060] The transitions between T / A protection control STEP0 and STEP3 are explained using Figure 4. As shown in Figure 4, the process progresses from STEP 0, where the oil temperature T of the transaxle 7 is below the first threshold T1, to STEP 1, STEP 2, and STEP 3 as the oil temperature T increases.

[0061] If the oil temperature T drops below the third threshold T3 while the T / A protection control STEP3 is being executed, the system skips T / A protection control STEP2 and proceeds to T / A protection control STEP1. This is because executing T / A protection control STEP3 often causes the transaxle 7 temperature to drop, causing the oil temperature T to quickly fall below the second threshold T2 from above the third threshold T3. Therefore, the system terminates the output suppression control without executing output suppression control based on vehicle speed, thereby minimizing the number of control switches and reducing the impact on driving.

[0062] Furthermore, the threshold values ​​T1-T3 used for determining each step should be set to different values ​​for when the oil temperature is rising and when it is falling. For example, by setting the threshold values ​​T1-T3 for when the oil temperature is falling slightly smaller than the threshold values ​​T1-T3 for when the oil temperature is rising, the number of STEP switching cycles when the oil temperature fluctuates near the threshold can be suppressed, thereby preventing unnecessary switching of power distribution and power suppression, and improving driving stability.

[0063] As described above, the vehicle 1 according to this embodiment is a four-wheel drive vehicle in which the front wheels 4 are driven by power transmitted from the front motor 2 and engine 3 via the transaxle 7, and the rear wheels 6 are driven by the rear motor 5. The hybrid control unit 18 of the vehicle 1 calculates the required output for vehicle driving and sets the output ratio between the front wheel 4 side (front motor 2 and engine 3 side) and the rear wheel 6 side (rear motor 5 side), and calculates the outputs of the front motor 2, engine 3 and rear motor 5 based on the required output of the vehicle 1 and the said output ratio.

[0064] The T / A protection control unit 50 in the hybrid control unit 18 performs output distribution control as transaxle protection control when the oil temperature T of the transaxle 7 exceeds a first threshold T1, setting the output ratio between the front wheel 4 side (front motor 2 and engine 3 side) and the rear wheel 6 side (rear motor 5 side) to 3:7. The output ratio between the front wheel 4 side and the rear wheel side is normally around 40-50:60-50, so when the oil temperature T exceeds the first threshold T1, the output ratio of the front wheel 4 side becomes smaller than when the oil temperature T is below the first threshold T1.

[0065] This allows the output of the front motor 2 and engine 3 to be reduced when the oil temperature T of the transaxle 7 exceeds the first threshold T1, thereby reducing the power transmitted to the transaxle 7 and suppressing the temperature rise of the transaxle 7.

[0066] Furthermore, the power distribution control in the transaxle protection control reduces the power ratio of the front wheels 4, but the total power output of the front wheels 4 and rear wheels 6 is maintained. This ensures the driving output of vehicle 1 and suppresses a decrease in the driving performance of vehicle 1.

[0067] Vehicle 1 can switch between driving modes such as EV mode, series mode, and parallel mode. However, when in EV mode or series mode, transaxle protection control (output distribution control, output suppression control) is performed, while when in parallel mode, transaxle protection control is not performed.

[0068] As a result, in EV mode or series mode, the transaxle protection control suppresses the temperature rise of the transaxle 7 as described above. On the other hand, in parallel mode, where the amount of power transmitted within the transaxle 7 is less than in EV mode or series mode and the temperature of the transaxle 7 is less likely to rise, unnecessary transaxle protection control is not performed. This prevents unnecessary changes in the front-to-rear power ratio and unnecessary reductions in power while the vehicle is running, thereby suppressing a decrease in the driving performance of the vehicle 1.

[0069] Furthermore, during powered driving, when the vehicle is driven by engine 3 and motors 2 and 5, the temperature rise of the transaxle 7 is suppressed by transaxle protection control (output distribution control, output suppression control). However, during regenerative driving, when regenerative power generation is performed, transaxle protection control is not executed. As a result, during regenerative driving, when output from the front motor 2 is not required, unnecessary transaxle protection control is not executed, thereby suppressing a decrease in the driving performance of vehicle 1.

[0070] Furthermore, the transaxle protection control switches between STEP1 and STEP3 based on the oil temperature T of the transaxle 7. When the oil temperature T of the transaxle 7 is between the first threshold T1 and the second threshold T2, only the power distribution control is performed among the power distribution control and power suppression control. As a result, the temperature rise of the transaxle 7 is suppressed as described above, while the overall driving output of the vehicle is ensured.

[0071] If the oil temperature T of the transaxle 7 is between the second threshold T2 and the third threshold T3, output suppression control is performed along with output distribution control as STEP 2, and the output of the entire vehicle is suppressed. This further reduces the power transmitted through the transaxle 7, thereby further suppressing the temperature rise of the transaxle 7. Furthermore, since the requested output is reduced based on the vehicle speed V, it becomes possible to set the reduction in the requested output to the minimum necessary amount, in line with the temperature rise suppression effect of the transaxle 7 due to airflow.

[0072] If the oil temperature T of the transaxle 7 is above the third threshold T3, the output suppression control of STEP3 is performed, which further suppresses the output than STEP2. This further reduces the power transmitted through the transaxle 7 and further suppresses the temperature rise of the transaxle 7.

[0073] Furthermore, vehicle 1 is equipped with ASC to prevent skidding and an ASC switch 61 to restrict the function of ASC, but when the ASC switch 61 is OFF, transaxle protection control is not performed in STEP 1.

[0074] More specifically, when the ASC switch 61 is ON and the ASC function is enabled, transaxle protection control is executed, which ensures the driving stability of the vehicle 1 due to the ASC function while suppressing the temperature rise of the transaxle 7. On the other hand, when the ASC switch 61 is OFF, transaxle protection control (output distribution control that fixes the front-to-rear output ratio) is not executed, which suppresses a decrease in the driving performance of the vehicle 1.

[0075] Furthermore, the transaxle protection control based on this ASC switch 61 is only performed in STEP 1. In STEP 2 and STEP 3, when the oil temperature T of the transaxle 7 is above the second threshold T2, the transaxle protection control is not restricted. In STEP 2 and STEP 3, the notification device 60 warns the driver, allowing the driver to be informed that transaxle protection control, which changes the front-to-rear power ratio or suppresses power output, will be executed and to take appropriate action. Therefore, the temperature rise of the transaxle 7 can be suppressed by the transaxle protection control.

[0076] Furthermore, when performing feedback control (longitudinal slip suppression control / lateral slip suppression control) in four-wheel drive, output distribution control is not performed, and feedback control is permitted, thus ensuring the ability to escape rough terrain during slippage.

[0077] This concludes the description of the embodiments, but the embodiments of the present invention are not limited to these embodiments. For example, the various execution conditions for transaxle protection control in the above embodiment (driving mode, power operation, ASC, etc.) may be determined by only a portion of them.

[0078] Furthermore, although the above embodiment applies the present invention to a hybrid vehicle in which the driving mode of vehicle 1 can be switched between EV mode, series mode, and parallel mode, it may be applied to any vehicle capable of any of these driving modes.

[0079] The present invention can be broadly applied to four-wheel drive vehicles in which either the front wheels or the rear wheels are driven via a transaxle, while the other is driven without a transaxle. Furthermore, it is applicable to plug-in hybrid vehicles (PHEVs) that can be charged or powered externally. [Explanation of Symbols]

[0080] 1 vehicle 2. Front motor (first drive device for traction) 3. Engine (First drive unit for traction) 4. Front wheels (first running wheels) 5. Rear motor (second drive unit for traction) 6. Rear wheels (second running wheels) 7 transaxle 8 drive shafts 10. Motor Generator (Generator) 18. Hybrid Control Unit (Output Control Unit) 20. Vehicle speed sensor (vehicle speed acquisition unit) 30 T / A oil temperature sensor (temperature detection unit) 50 T / A Protection Control Unit (Protection Control Unit) 51 Driving mode switching section 52 Regenerative Power Generation Control Unit 53 Side-slip suppression control unit 54 Wheel speed sensor (rotation speed detection unit) 55 Slip suppression control unit

Claims

1. In a vehicle in which one of the first running wheels, either the front or rear wheels, is driven by power transmitted from a first running drive device via a transaxle, and the other second running wheel is driven by a second running drive device, The first drive unit comprises an engine and an electric motor, The transaxle is connected to the engine, the electric motor, and the generator. A driving mode switching unit that switches between at least one of a series mode in which power is transmitted from the engine to the generator via the transaxle to drive and generate electricity, and power is transmitted from the electric motor to the first driving wheel via the transaxle to drive the first driving wheel, and an EV mode in which the electric motor drives the first driving wheel via the transaxle, and a parallel mode in which the engine and the electric motor drive the first driving wheel, An output control unit calculates the required output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the output of the second drive unit based on the required output of the vehicle and the output ratio. A temperature detection unit that acquires the oil temperature of the transaxle, The system includes a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, performs transaxle protection control that maintains the requested output and reduces the output ratio of the first drive unit compared to when the oil temperature of the transaxle is below the first threshold, The protection control unit executes the transaxle protection control when the driving mode switching unit switches to the series mode or EV mode, and does not execute the transaxle protection control when the driving mode is switched to the parallel mode. A vehicle drive control device characterized by the following features.

2. A vehicle in which one of the front wheels or the rear wheels is driven by power transmitted from a first drive unit via a transaxle, and the other second wheel is driven by a second drive unit, The vehicle is equipped with a skid suppression control unit that controls the rotational speed of the first and second running wheels to suppress skidding when skidding occurs. An output control unit calculates the required output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the output of the second drive unit based on the required output of the vehicle and the output ratio. A temperature detection unit that acquires the oil temperature of the transaxle, The system includes a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, performs transaxle protection control that maintains the requested output and reduces the output ratio of the first drive unit compared to when the oil temperature of the transaxle is below the first threshold, The protection control unit executes the transaxle protection control when the skidding suppression control by the skidding suppression control unit is effective, and does not execute the transaxle protection control when the skidding suppression control by the skidding suppression control unit is prohibited. A vehicle drive control device characterized by the following features.

3. A vehicle in which one of the front wheels or the rear wheels is driven by power transmitted from a first drive unit via a transaxle, and the other second wheel is driven by a second drive unit, A vehicle speed acquisition unit that acquires the vehicle's travel speed, An output control unit calculates the required output for vehicle operation, sets the output ratio between the first drive unit and the second drive unit, and calculates the output of the first drive unit and the output of the second drive unit based on the required output of the vehicle and the output ratio. A temperature detection unit that acquires the oil temperature of the transaxle, The system includes a protection control unit that, when the oil temperature of the transaxle exceeds a predetermined first threshold, performs transaxle protection control that maintains the requested output and reduces the output ratio of the first drive unit compared to when the oil temperature of the transaxle is below the first threshold, If the oil temperature of the transaxle is above a second threshold, which is higher than the first threshold, the protection control unit reduces the requested output by a predetermined amount set based on the travel speed. A vehicle drive control device characterized by the following features.

4. The vehicle is equipped with a skid suppression control unit that controls the rotational speed of the first and second running wheels to suppress skidding when skidding occurs. The protection control unit executes the transaxle protection control even when the lateral slip suppression control by the lateral slip suppression control unit is prohibited, if the oil temperature of the transaxle is above the second threshold. The vehicle driving control device according to feature 3.

5. The protection control unit reduces the requested output to a value greater than the maximum value of the predetermined amount if the oil temperature of the transaxle is above the third threshold, which is higher than the second threshold. A vehicle drive control device according to feature 3 or 4.

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