Travel driving control device for vehicle

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

Vehicle driving control device

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

[0002] There are vehicles, such as four-wheel drive hybrid vehicles, in which the front and rear wheels are driven by an engine and a motor. Patent Document 1 discloses a four-wheel drive vehicle in which the front wheels are primarily driven by the engine and the rear wheels are driven by the motor as needed. Furthermore, the vehicle described in Patent Document 1 is equipped with a control system that, when the temperature of the rear-wheel drive motor is equal to or higher than a predetermined temperature, reduces the output of the motor compared to when the temperature is below the predetermined temperature, and increases the output of the engine accordingly, thereby ensuring the driving force of the entire vehicle.

[0003] The front wheels are fitted with a transaxle, which houses the transmission and differential in the power transmission path between the engine and the front wheels. The transaxle is filled with lubricating oil (hydraulic oil).

[0004] Japanese Patent Application Publication No. 9-329222

[0005] Among four-wheel drive hybrid vehicles, four-wheel drive vehicles have been developed that are equipped with a motor for front-wheel drive and a motor for rear-wheel drive, and in which the front wheels are driven by an engine and motor, and the engine drives a generator to generate electricity, while the rear wheels are driven by a motor.

[0006] In this way, in vehicles in which the front wheels are driven by an engine and a motor, the temperature (lubricant temperature) of the transaxle provided in the front-wheel drive system also tends to rise. In particular, in hybrid vehicles capable of series mode, power is transmitted within the transaxle simultaneously through two paths: between the engine and the generator, and between the motor and the front wheels, so the temperature of the lubricant in the transaxle tends to rise.

[0007] However, if the temperature of the lubricating oil in the transaxle rises excessively, problems arise such as a decrease in lubricating performance and an increase in the load on the transaxle.

[0008] The present invention has been made to solve these problems, and its purpose 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.

[0009] In order to achieve the above object, a vehicle driving control device of the present invention is characterized in that, in a vehicle that drives one of the front and rear first driving wheels by power transmitted from a first driving device via a transaxle and drives the other, second driving wheels by a second driving device, the vehicle driving control device includes: an output control unit that calculates a required output for vehicle driving, sets an output ratio between the first driving device and the second driving device, and calculates the output of the first driving device and the output of the second driving device based on the required output of the vehicle and the output ratio, a temperature detection unit that acquires an oil temperature of the transaxle, and a protection control unit that executes transaxle protection control to reduce the output ratio of the first driving device when the transaxle oil temperature is equal to or higher than a predetermined first threshold value, compared to when the transaxle oil temperature is below the first threshold value. As a result, when the temperature of the transaxle is equal to or higher than the first threshold value, the output of the first driving device is reduced, thereby reducing the driving force transmitted through the transaxle while maintaining the required output, thereby suppressing a temperature rise in the transaxle.

[0010] Preferably, the first driving device includes an engine and an electric motor, and the transaxle is connected to the engine, the electric motor, and a generator, and includes 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 an EV mode in which the first driving wheels are driven by the electric motor via the transaxle, and a parallel mode in which the first driving wheels are driven by the engine and the electric motor, and the protection control unit executes the transaxle protection control when the driving mode switching unit has switched to the series mode or the EV mode, and does not execute the transaxle protection control when the driving mode switching unit has switched to the parallel mode. As a result, in series mode or EV mode, transaxle protection control is executed to suppress temperature rise in the transaxle, while 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 executed, thereby suppressing unnecessary changes in the front and rear power ratio while driving and improving the vehicle's driving performance.

[0011] Preferably, the vehicle includes a regenerative power generation control unit that executes regenerative power generation by forcibly driving the first driving drive device with the rotational force of the first driving wheels to generate electricity when the vehicle is decelerating, and the protection control unit executes the transaxle protection control when the first driving drive device is powered, and does not execute the transaxle protection control when the regenerative power generation is being performed. This executes the transaxle protection control when the first driving drive device is powered, thereby suppressing a temperature rise in the transaxle, while not executing the transaxle protection control when regenerative power generation is being performed, which does not require output from the first driving drive device and results in a relatively small amount of power transmitted within the transaxle, thereby suppressing unnecessary changes in the front and rear output ratio while the vehicle is running, thereby improving the running performance of the vehicle.

[0012] Preferably, the vehicle is provided with a skid suppression control unit that controls the rotational speeds of the first and second driving wheels to suppress skid when skid occurs, and the protection control unit executes the transaxle protection control when skid suppression control by the skid suppression control unit is active, and does not execute the transaxle protection control when skid suppression control by the skid suppression control unit is prohibited. In this way, by executing the transaxle protection control when skid suppression control is active, it is possible to suppress a temperature rise in the transaxle while ensuring vehicle driving stability.

[0013] Preferably, the vehicle includes a vehicle speed acquisition unit that acquires the vehicle's traveling speed, and the protection control unit reduces the required output by a predetermined amount set based on the traveling speed when the transaxle oil temperature is equal to or higher than a second threshold that is higher than the first threshold. This reduces the required output when the transaxle oil temperature becomes higher than the first threshold that changes the front-to-rear output ratio, thereby further reducing the power transmitted through the transaxle. This further suppresses temperature rise in the transaxle. Furthermore, because the required output is reduced based on vehicle speed, the amount of reduction in the required output can be appropriately set in response to changes in the effectiveness of suppressing temperature rise in the transaxle due to wind while the vehicle is traveling.

[0014] Preferably, the vehicle is provided with a skid suppression control unit that controls the rotational speeds of the first and second driving wheels to suppress skid when skid occurs, and the protection control unit executes the transaxle protection control when the oil temperature of the transaxle is equal to or higher than the second threshold, even when skid suppression control by the skid suppression control unit is prohibited. Thus, when the oil temperature of the transaxle is equal to or higher than the second threshold, which is higher than the first threshold, the transaxle protection control is executed, even when skid suppression control is prohibited, thereby suppressing a temperature rise in the transaxle.

[0015] Preferably, the protection control unit reduces the required output to a value greater than the maximum value of the predetermined amount when the transaxle oil temperature is equal to or greater than a third threshold value that is higher than the second threshold value. This further reduces the required output when the transaxle oil temperature becomes even higher than the second threshold value, thereby further reducing the power transmitted by the transaxle and further suppressing a rise in temperature of the transaxle.

[0016] Preferably, the vehicle control system includes a rotational speed detection unit that detects the rotational speeds of the front and rear wheels, and a slip suppression control unit that performs feedback control of the output ratio to suppress slip when slip of the front or rear wheels is detected based on the rotational speeds, and the protection control unit allows the feedback control even when the transaxle protection control is being executed, thereby preventing slip even when the transaxle protection control is being executed.

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

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

[0019] An embodiment in which the present invention is applied to a hybrid vehicle (hereinafter referred to as vehicle 1) will be described below. Fig. 1 is a diagram showing the overall configuration of a driving system of vehicle 1 in which a driving control device according to this embodiment is employed.

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

[0021] The output shaft of the engine 3 is connected via a transaxle 7 to a drive shaft 8, which is the drive shaft for the front wheels 4. The transaxle 7 has a case 7a containing a differential 7b and a clutch 9 that can connect and disconnect the power transmission path, 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 drive shaft 8, and when the clutch 9 is disconnected, the connection between the engine 3 and the front wheels 4 is cut off.

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

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

[0024] The front motor 2, rear motor 5, and motor generator 10 are, for example, three-phase AC motors, and are powered by a storage battery 15 for driving the vehicle. The storage battery 15 is formed from a secondary battery such as a lithium-ion battery, and includes a built-in battery monitoring unit 15a that calculates the charging rate and detects the temperature.

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

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

[0027] The vehicle 1 is equipped with a hybrid control unit 18 (output control unit) which is a control device for performing overall control of the vehicle 1. The hybrid control unit 18 is composed of input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. The 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) which detects the traveling speed (vehicle speed V) of the vehicle 1, and an accelerator position sensor (not shown) which detects the accelerator position, and detection and operation information from these devices is input.

[0028] 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 also 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 ​​from an accelerator opening sensor, a vehicle speed sensor 20, etc. The driving mode switching unit 51 sets the driving mode to parallel mode in a range where the efficiency of the engine 3 is high, such as a high-speed range. In a medium- to low-speed range, the driving mode is switched between EV mode and series mode based on the state of charge (SOC) of the storage battery 15, the required torque for driving the vehicle, etc.

[0029] In the 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 electric power from the storage battery 15 to propel the vehicle 1 .

[0030] In the series mode, the clutch 9 of the transaxle 7 is disengaged, and the engine 3 is operated to drive the motor generator 10, and the generated power and power from the storage battery 15 are used to drive the front motor 2 and the rear motor 5 to run the vehicle 1. Note that surplus power generated by the motor generator 10 is charged into the storage battery 15.

[0031] In the parallel mode, the clutch 9 of the transaxle 7 is connected, and the engine 3 is operated to transmit driving force from the transaxle 7 to the front wheels 4, and when there is excess engine driving force, it is regenerated by the front motor 2, and when there is insufficient engine driving force, the front motor 2 is assisted by using the power of the storage battery 15.

[0032] The hybrid control unit 18 also calculates the total required power output necessary for the vehicle 1 to travel based on the various detected amounts and operation information described above, and allocates this total required power output to the front motor 2 and rear motor 5 in EV mode and series mode, and to the front motor 2, engine 3, and rear motor 5 in parallel mode. The power output ratio between the front wheel side (front motor 2, engine 3) and the rear wheel side (rear motor 5) is calculated by the hybrid control unit 18. The power output ratio between the front wheel 4 side and the rear wheel 6 side is normally, for example, about 40-50:60-50.

[0033] The hybrid control unit 18 further sets the required torque for each of the front motor 2, engine 3, and rear motor 5 based on the required output power 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 reducer 11 from the rear motor 5 to the rear wheels 6, and outputs command signals to the front motor control unit 16, rear motor control unit 17, and engine control unit 14 so as to achieve each required torque.

[0034] The front motor control unit 16 and rear motor control unit 17 calculate target current values ​​to be passed through the coils of each phase of the front motor 2 and rear motor 5 to achieve the required torque based on command signals from the hybrid control unit 18. Then, based on the target current values, they control the switching of the front motor inverter 16a and rear motor inverter 17a to control the current values ​​of each coil to the target current values, thereby achieving the respective required torque. Note that the same is true when the motor generator 10 is generating power; the switching of the motor generator inverter 16b is controlled based on the target current value calculated from the required negative torque, thereby achieving the target current value.

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

[0036] The vehicle 1 also 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, 6 when decelerating. 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 when decelerating, thereby controlling the regenerative power generation.

[0037] Furthermore, the vehicle 1 is equipped with an anti-skid system (ASC). The anti-skid system uses an anti-skid control unit 53 provided in the hybrid control unit 18 to determine whether the vehicle 1 is skidding while it is running based on the rotational speeds of the wheels 4, 6, and if it determines that a skid has occurred, it controls the front, rear, left, and right brake devices independently to suppress the skid of the vehicle 1. The driver can restrict the function of the anti-skid system by turning off the ASC switch 61.

[0038] Furthermore, the hybrid control unit 18 of the vehicle 1 of this embodiment is provided with a slip suppression control unit 55 that performs feedback control of the output ratio, etc., in order to optimize slip (longitudinal slip) between the front and rear wheels of the vehicle 1 and slip (lateral slip) between the left and right wheels of the vehicle 1 in four-wheel drive. When slip of the wheels 4, 6 is detected based on the rotational speeds of the wheels 4, 6 detected by wheel speed sensors 54 (rotational speed detection units) provided on the wheels (front, rear, left, and right wheels) 4, 5, the slip suppression control unit 55 controls the output ratio between the front, rear, left, and right wheels to suppress slip.

[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 is equipped with a T / A protection control unit 50 (protection control unit) that executes transaxle protection control to suppress excessive temperature rise in the transaxle 7.

[0040] The transaxle protection control will be described below with reference to Figures 3 and 4. Figure 2 is a flowchart showing the control procedure of the transaxle protection control executed by the T / A protection controller 50. Figure 3 is a table summarizing the control contents of the transaxle protection control.

[0041] The transaxle protection control of this embodiment is executed when the power supply to the vehicle 1 is turned on. First, in step S10, if the vehicle is running, the process proceeds to step S20. If the vehicle is not running, i.e., if the vehicle is stopped, the process proceeds to step S110.

[0042] In step S20, it is determined whether the driving mode of the vehicle 1 is the EV mode or the series mode. If the driving mode is the EV mode or the series mode, the process proceeds to step S30. If the driving mode is not the EV mode or the series mode, i.e., if the driving mode is the parallel mode, the process proceeds to step S120.

[0043] In step S30, it is determined whether the vehicle 1 is in power running, that is, driven by the engine 3 or the motors 2 and 5. If the vehicle 1 is in power running, the process proceeds to step S40. If the vehicle 1 is not in power running, i.e., if regenerative power generation is being performed, 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 input in step S40 is equal to or greater than a first threshold value T1. The first threshold value T1 may be set appropriately, for example, to a value slightly lower than the maximum value of the allowable range of oil temperatures at which the operation and transmission efficiency of the transaxle 7 are not affected. If the oil temperature T is equal to or greater than the first threshold value T1, the process proceeds to step S60. If the oil temperature T is less than the first threshold value T1, the process proceeds to step S120.

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

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

[0048] In step S80, T / A protection control STEP 3 is executed. T / A protection control STEP 3 sets the front and rear wheel drive power distribution (output distribution) to 3:7 (T / A protection distribution). This T / A protection distribution of 3:7 maximizes the distribution to the rear wheels 6 within the range that allows for changes in vehicle characteristics such as straight-line stability, thereby limiting the distribution to the front wheels 4. Additionally, the overall vehicle output (required output) is suppressed to a constant output value Pmin. This output value Pmin is a value that reliably reduces the oil temperature T of the transaxle 7. Furthermore, an output suppression alarm is issued by the alarm device 60, such as an instrument panel or a voice alarm, to notify the driver of the vehicle 1 that output suppression is being performed. Then, this routine ends.

[0049] In step S90, T / A protection control STEP 2 is executed. T / A protection control STEP 2 sets the driving force distribution between the front and rear wheels to a T / A protection distribution of 3:7. It also suppresses the overall vehicle driving output (required output) based on the vehicle speed V. In this step, the suppression amount (predetermined amount) of the vehicle 1 driving output may be set within a range smaller than the suppression amount in T / A protection control STEP 3, and may decrease as the vehicle speed V increases, for example. Then, this routine ends.

[0050] In step S100, it is determined whether the ASC switch 61 is enabled. 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 prohibited, the process proceeds to step S120.

[0051] In step S110, T / A protection control STEP 1 is executed. T / A protection control STEP 1 sets the front and rear wheel drive power distribution to a T / A protection distribution of 3:7. Note that the driving output is not suppressed. Then, this routine ends.

[0052] In step S120, the T / A protection control is not executed (STEP 0). That is, the distribution ratio between the front and rear 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 tabulated in Figure 3. In this embodiment, as shown in Figure 3, the transaxle protection control is executed in any of the drive modes (Normal, ECO, Power mode, etc.) that change the output levels of the motors 2 and 5 and the engine 3 relative to the accelerator operation amount.

[0054] Regarding the driving mode, the transaxle protection control is executed in the EV mode or the series mode, but is not executed in the parallel mode. This is because in the 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] The transaxle protection control is executed during power running, but not during regeneration because the power transmitted through the transaxle 7 during regeneration is lower than during power running, so the temperature of the transaxle 7 does not exceed the allowable temperature.

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

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

[0058] However, when the oil temperature T is equal to or greater than the first threshold value T1 and less than the second threshold value T2, and the ASC switch 61 is OFF, the power distribution control and the power suppression control are not performed. This is because, since no warning is issued in STEP 1, the running stability of the vehicle 1 needs to be ensured by the ASC.

[0059] Furthermore, even when the output distribution in the above-mentioned T / A protection control STEP 1 to T / A protection control STEP 3 is T / A protection distribution 3:7, the slip suppression control unit 55 allows feedback control of the output ratio to operate in order to suppress slip between the left and right wheels of the vehicle.

[0060] The transition between T / A protection control STEP 0 to STEP 3 will be explained using Figure 4. As shown in Figure 4, from STEP 0, where the oil temperature T of the transaxle 7 is less than the first threshold value T1, the process proceeds to STEP 1, STEP 2, and STEP 3 as the oil temperature T rises.

[0061] When the oil temperature T is equal to or higher than the third threshold value T3 and T / A protection control STEP 3 is being executed, and then the oil temperature T drops below the third threshold value T3, T / A protection control STEP 2 is skipped and the process moves to T / A protection control STEP 1. This is because executing T / A protection control STEP 3 often causes the temperature of the transaxle 7 to drop, causing the oil temperature T to immediately drop from equal to or higher than the third threshold value T3 to below the second threshold value T2. Therefore, by ending output suppression control without executing output suppression control in response to vehicle speed, the number of control switches is reduced and the impact on driving is minimized as much as possible.

[0062] Furthermore, it is advisable to set the threshold values ​​T1 to T3 for determining each step to different values ​​when the oil temperature is rising and when the oil temperature is falling. For example, by setting the threshold values ​​T1 to T3 when the oil temperature is falling slightly smaller than the threshold values ​​T1 to T3 when the oil temperature is rising, the number of times the STEP is switched when the oil temperature fluctuates around the threshold value can be reduced, preventing unnecessary switching of the 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 travel, sets the output ratio between the front wheels 4 (front motor 2 and engine 3) and the rear wheels 6 (rear motor 5), 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 this output ratio.

[0064] When the oil temperature T of the transaxle 7 becomes equal to or higher than the first threshold value T1, the T / A protection control section 50 provided in the hybrid control unit 18 executes power distribution control as transaxle protection control, setting the power ratio between the front wheels 4 (front motor 2 and engine 3) and the rear wheels 6 (rear motor 5) to 3:7. Since the power ratio between the front wheels 4 and the rear wheels is normally about 40-50:60-50, when the oil temperature T becomes equal to or higher than the first threshold value T1, the power ratio between the front wheels 4 becomes smaller than when the oil temperature T is less than the first threshold value T1.

[0065] As a result, when the oil temperature T of the transaxle 7 becomes equal to or higher than the first threshold value T1, the output of the front motor 2 and the engine 3 is reduced to reduce the power transmitted through the transaxle 7, thereby suppressing the temperature rise of the transaxle 7.

[0066] Furthermore, although the output ratio on the front wheels 4 side is reduced by executing the output distribution control in the transaxle protection control, the total output on the front wheels 4 side and the rear wheels 6 side is maintained. This ensures the driving output of the vehicle 1 and makes it possible to suppress a decrease in the driving performance of the vehicle 1.

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

[0068] As a result, when in EV mode or series mode, the transaxle protection control suppresses the temperature rise of the transaxle 7 as described above, while 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 executed, thereby preventing unnecessary changes to the front / rear power ratio or unnecessary reductions in power output while the vehicle is traveling, and suppressing a decrease in the driving performance of the vehicle 1.

[0069] Furthermore, during powered driving in which the vehicle is driven by the 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), but during regenerative driving in which regenerative power is generated, the transaxle protection control is not executed. As a result, during regenerative driving in which output from the front motor 2 is not required, unnecessary transaxle protection control is not executed, thereby suppressing a decline in the driving performance of the vehicle 1.

[0070] Furthermore, the transaxle protection control switches between STEP 1 to STEP 3 based on the oil temperature T of the transaxle 7. When the oil temperature T of the transaxle 7 is equal to or greater than the first threshold value T1 and equal to or less than the second threshold value T2, only the output distribution control out of the output distribution control and the output suppression control is performed, thereby suppressing the temperature rise of the transaxle 7 as described above and ensuring the driving output of the vehicle as a whole.

[0071] When the oil temperature T of the transaxle 7 is equal to or greater than the second threshold value T2 and equal to or less than the third threshold value T3, in STEP 2, output distribution control and output suppression control are performed, thereby suppressing the output of the entire vehicle. This further reduces the power transmitted through the transaxle 7, thereby further suppressing the temperature rise of the transaxle 7. In addition, because the required output is reduced based on the vehicle speed V, it is possible to set the reduction in the required output to the minimum necessary in accordance with the effect of suppressing the temperature rise of the transaxle 7 due to traveling wind.

[0072] If the oil temperature T of the transaxle 7 is equal to or higher than the third threshold value T3, output suppression control is performed in STEP 3, which further suppresses the output compared to STEP 2. This further reduces the power transmitted through the transaxle 7, thereby further suppressing the temperature rise of the transaxle 7.

[0073] Furthermore, the vehicle 1 is equipped with an ASC that prevents skidding, and an ASC switch 61 that restricts the function of the ASC. When the ASC switch 61 is OFF, the transaxle protection control is not executed in STEP 1.

[0074] Specifically, by executing transaxle protection control when the ASC switch 61 is ON and the ASC function is enabled, it is possible to suppress a temperature rise in the transaxle 7 while ensuring the driving stability of the vehicle 1 through the ASC function. On the other hand, by not executing transaxle protection control (power distribution control that fixes the front / rear power ratio) when the ASC switch 61 is OFF, it is possible to suppress a deterioration in the driving performance of the vehicle 1.

[0075] Note that the restriction of transaxle protective control based on this ASC switch 61 is performed only in STEP 1, but is not restricted in STEPs 2 and 3 where the oil temperature T of the transaxle 7 is equal to or higher than the second threshold T2. In STEPs 2 and 3, the notification device 60 issues a warning to the driver, so that the driver can take appropriate action by notifying them that transaxle protective control will be executed to change the front / rear power ratio or suppress output. Therefore, the transaxle protective control can suppress a rise in temperature of the transaxle 7.

[0076] Furthermore, when four-wheel drive feedback control (longitudinal slip suppression control / lateral slip suppression control) is executed, output distribution control is not performed and feedback control is allowed, thereby ensuring rough road escape performance when slipping.

[0077] Although the description of the embodiment has been completed, the aspects of the present invention are not limited to this embodiment. For example, the various execution conditions (travel mode, powering operation, ASC, etc.) of the transaxle protection control in the above embodiment may be determined based on only some of them.

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

[0079] The present invention can be widely applied to four-wheel drive vehicles in which one of the front wheels or rear wheels is driven via a transaxle and the other is driven without a transaxle, and can also be applied to plug-in hybrid vehicles (PHEVs) that can be externally charged or externally powered.

[0080] REFERENCE SIGNS LIST 1 Vehicle 2 Front motor (first driving device) 3 Engine (first driving device) 4 Front wheels (first driving wheels) 5 Rear motor (second driving device) 6 Rear wheels (second driving wheels) 7 Transaxle 8 Drive shaft 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 unit 52 Regenerative power generation control unit 53 Skid suppression control unit 54 Wheel speed sensor (rotation speed detection unit) 55 Slip suppression control unit

Claims

1. A vehicle in which one of the front and rear wheels, a first running wheel, is driven by a first driving device via a transaxle, and the other, a second running wheel, is driven by a second driving device, an output control unit that calculates a required output for vehicle running, sets an output ratio between the first driving device and the second driving device, and calculates the output of the first driving device and the output of the second driving device based on the required output of the vehicle and the output ratio; a temperature detection unit for acquiring an oil temperature of the transaxle; a protection control unit that executes transaxle protection control when an oil temperature of the transaxle becomes equal to or higher than a predetermined first threshold value, the protection control maintaining the required output and reducing an output ratio on the first driving device side compared to when the oil temperature of the transaxle is lower than the first threshold value; A vehicle drive control device comprising:

2. The first driving device includes an engine and an electric motor, The engine, the electric motor, and the generator are connected to the transaxle, 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 the generator and generate electricity, and an EV mode in which the first driving wheels are driven by the electric motor via the transaxle, and a parallel mode in which the first driving wheels are driven by the engine and the electric motor, The protection control unit executes the transaxle protection control when the driving mode switching unit switches to the series mode or the EV mode, and does not execute the transaxle protection control when the driving mode switching unit switches to the parallel mode.

2. The vehicle drive control device according to claim 1.

3. a regenerative power generation control unit that performs regenerative power generation by forcibly driving the first driving device by a rotational force of the first running wheel when the vehicle is decelerating, The protection control unit executes the transaxle protection control when the first driving device is powered, and does not execute the transaxle protection control when the regenerative power generation is being performed.

2. The vehicle drive control device according to claim 1.

4. The vehicle is provided with a skid suppression control unit that controls the rotation speeds of the first running wheels and the second running wheels when a skid occurs in the vehicle to suppress the skid, The protection control unit executes the transaxle protection control when the skid suppression control by the skid suppression control unit is active, and does not execute the transaxle protection control when the skid suppression control by the skid suppression control unit is prohibited.

2. The vehicle drive control device according to claim 1.

5. A vehicle speed acquisition unit that acquires a traveling speed of the vehicle, The protection control unit reduces the required output by a predetermined amount that is set based on the traveling speed when the oil temperature of the transaxle is equal to or higher than a second threshold value that is higher than the first threshold value.

2. The vehicle drive control device according to claim 1.

6. The vehicle is provided with a skid suppression control unit that controls the rotation speeds of the first running wheels and the second running wheels when a skid occurs in the vehicle to suppress the skid, When the oil temperature of the transaxle is equal to or higher than the second threshold value, the protection control unit executes the transaxle protection control even when the skid suppression control by the skid suppression control unit is prohibited.

6. The vehicle drive control device according to claim 5.

7. The protection control unit reduces the required output to a value greater than the maximum value of the predetermined amount when the oil temperature of the transaxle is equal to or greater than a third threshold value that is higher than the second threshold value.

7. The vehicle drive control device according to claim 5 or 6.

8. a rotation speed detection unit for detecting the rotation speeds of the front wheels and the rear wheels; a slip suppression control unit that, when slip of the front wheels or the rear wheels is detected based on the rotation speed, feedback controls the output ratio so as to suppress slip, The protection control unit allows the feedback control even when the transaxle protection control is being executed.

2. The vehicle drive control device according to claim 1.