JP2003104186A - Acceleration slip control device for four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration slip control device for four-wheel drive vehicle, capable of preventing the shortage of braking torque and sufficiently conducting slip control when brake control is carried out for suppressing acceleration slip during traveling in a four-wheel drive state. SOLUTION: This acceleration slip control device comprises a slip controlling means executing brake control at the time of acceleration slip. The acceleration is provided with a temperature corresponding brake means, which decreases brake control amount to one acceleration slip wheel of front and rear wheels having a brake temperature exceeding a specified temperature and increases brake control amount to the other wheel of the front and rear wheels, during performing slip control, and in the four-wheel state, and in the case that the brake temperature of one of the front and rear wheels exceeds the specified temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of an acceleration slip control device for a four-wheel drive vehicle that performs a slip suppression control of an acceleration slip wheel by brake control.

[0002]

2. Description of the Related Art Conventionally, as an acceleration slip control device for a vehicle, when a driving wheel has an acceleration slip due to an excessive driving torque, a braking torque is applied by a braking device for the acceleration slip wheel to drive the drive transmitted from the engine. It is known to reduce torque and suppress acceleration slip.

[0003]

However, when the acceleration slip control device is applied to a four-wheel drive vehicle,
When 4 wheels are driven and acceleration slip occurs on 4 wheels during low μ road start or during acceleration, etc., when brake control is performed for 4 wheels, the brake temperature rises if the brake control is continued for a long time or frequently. However, there is a fear that the braking torque becomes insufficient due to the deterioration of the frictional characteristics of the friction material of the brake.

On the other hand, in order to prevent the braking torque from becoming insufficient, there are proposals to limit the brake control time or prohibit the brake control.

However, if the brake control time is limited or the brake control is prohibited, there is a problem that the slip control for suppressing the acceleration slip cannot be sufficiently performed.

An object of the present invention is to sufficiently perform the slip control while preventing the insufficient braking torque when the brake control is executed to suppress the acceleration slip during traveling in the four-wheel drive state. An object is to provide an acceleration slip control device for a four-wheel drive vehicle.

[0007]

In order to achieve the above object, according to the present invention, an acceleration slip control device having a slip control means for executing brake control at the time of acceleration slip is used. When the brake temperature of one of the front and rear wheels exceeds the specified temperature in the driving state, the brake control amount to one acceleration slip wheel of the front and rear wheels of which the brake temperature exceeds the specified temperature is decreased and A temperature-corresponding brake control means for performing brake control for increasing the brake control amount for the other wheel is provided.

[0008]

According to the present invention, when one of the front and rear wheels has a brake temperature exceeding the specified temperature, the brake of one of the front and rear wheels having the brake temperature exceeding the specified temperature is applied to the acceleration slip wheel. Since the control amount is reduced, the insufficient braking torque of the acceleration slip wheel, which tends to increase the brake temperature, is prevented. That is, if the brake control is continued as it is for the acceleration slip wheel in which the brake temperature is increasing, the brake temperature may become high and the braking torque may decrease. However, it is possible to prevent a shortage of braking torque by reducing the amount of braking heat generated by reducing the brake control amount of the acceleration slip wheel that tends to increase the brake temperature.

Further, since the brake control amount for increasing the brake control amount to the other of the front and rear wheels whose brake temperature has not reached the specified temperature is increased, the brake control amount for one acceleration slip wheel is decreased, Slip control for suppressing acceleration slip is sufficiently ensured. That is,
In the four-wheel drive state, since the front wheels and the rear wheels are in the engaged state, if the brake control amount is increased by the other acceleration slip wheel of the front and rear wheels, the rotation speed of the other axle of the front and rear wheels decreases In addition, the rotation speed of one of the front and rear wheels will also decrease.For example, when the brake control decrease amount and the brake control increase amount are made equal, an acceleration slip suppression effect equivalent to that in the case of performing normal brake control is obtained. Obtainable. Note that the fastening state does not matter the magnitude of the fastening force. That is, the case where the driving force distributions to the front wheels and the rear wheels are not equal is also included.

As described above, according to the present invention,
When the brake control is performed to suppress the acceleration slip during traveling in the four-wheel drive state, the slip control can be sufficiently performed while preventing the decrease of the braking torque.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments for realizing an acceleration slip control device for a four-wheel drive vehicle according to the present invention will be described below.
A description will be given based on the first embodiment corresponding to claim 6.

(First Embodiment) First, the configuration will be described. FIG. 1 is a combined system diagram of VDC, TCS, and ABS to which the acceleration slip control device for a four-wheel drive vehicle according to the first embodiment is applied. The outline of each system will be briefly described.

VDC system (Vehicle Dynamics Controller)
ol System) reduces the sideslip of the vehicle that occurs during an emergency avoidance of a slippery road surface or an obstacle during driving, by reducing brake control and engine output control for each of the four wheels, and also improves turning performance and braking performance. This is a vehicle behavior control system that achieves both compatibility and improves running stability.

A TCS (Traction Control System) controls engine output (closes an electronically controlled throttle valve or cuts fuel) and brakes (rear or front / rear brake fluid pressure) when the slip amount of driving wheels becomes large. It is a system that suppresses acceleration slip by increasing the pressure).

The ABS (Anti-Rock Brake System) detects the number of wheel revolutions during braking and controls the braking force by electronic control to prevent the four wheels from locking, improving stability during sudden braking. A system that facilitates avoiding obstacles by operating the steering wheel.

In FIG. 1, 1 is an engine, 2 is an automatic transmission, 3 is a transmission output shaft, 4 is a transfer, 5 is a rear propeller shaft, 6 is a rear differential,
Reference numerals 7 and 8 denote rear drive shafts, 9 rear left wheels, 10 right rear wheels, 11 front propeller shafts, 12 front differentials, 13 and 14 front drive shafts, 15 left front wheels, 16 right front wheels, 17 Is 4WD
The actuator, 18 is a 4WD control unit,
Reference numeral 19 is a mode selection switch.

That is, in the two-wheel drive state, the left and right rear wheels 9,
This is a rear-wheel-drive four-wheel drive vehicle in which 10 is used as a drive wheel and a drive torque is distributed to the left and right front wheels 15 and 16 which are driven wheels by engaging a clutch in the transfer 4. A front / rear wheel drive force distribution control system is configured by the 4WD control unit 18 that outputs a control command to the 4WD actuator 17 by using a mode selection switch 19 or the like capable of selecting the two-wheel drive mode, the four-wheel drive mode, and the auto mode as input information. ing. When the two-wheel drive mode is selected, the driving torque is transmitted only to the left and right rear wheels 9 and 10 by releasing the clutch in the transfer 4. When the four-wheel drive mode is selected, the drive torque is transmitted to the left and right rear wheels 9 and 10 and the left and right front wheels 15 and 16 with equal distribution by engaging the clutch without slippage. When the auto mode is selected, for example, the front / rear wheel drive force distribution ratio of the drive torque is variably controlled by a clutch engagement force command proportional to the front / rear wheel rotation speed difference.

In FIG. 1, 20 is a brake pedal, 2
1 is a master cylinder, 22 is a steering angle sensor, 23 is a yaw rate / lateral G sensor, 24 is a left front wheel rotation sensor, 25 is a right front wheel rotation sensor, 26 is a left rear wheel rotation sensor, 27 is a right rear wheel rotation sensor, 28 Is a pressure sensor, 29 is VDC / T
CS / ABS control unit, 30 is engine control unit, 31 is automatic transmission control unit, 32 is electronically controlled throttle, 33 is VDC / T
CS / ABS brake actuator, 34 left front wheel brake unit, 35 right front wheel brake unit, 36
Is a left rear wheel brake unit, 37 is a right rear wheel brake unit, 38 is an ABS warning lamp, 39 is a VDC-OFF indicator lamp, and 40 is a SLIP indicator lamp.

The steering angle sensor 22, yaw rate / lateral G sensor 23, left front wheel rotation sensor 24, right front wheel rotation sensor 2
5, sensor signals from the left rear wheel rotation sensor 26, the right rear wheel rotation sensor 27, and the pressure sensor 28 are VDC / TCS / A.
It is output to the BS control unit 29.

The VDC / TCS / ABS control unit 29 inputs various sensor signals and information from the engine 1, the automatic transmission 2, and the 4WD control unit 18, and determines the running state of the vehicle. And VDC /
Calculation of target brake fluid pressure required for TCS / ABS control,
It outputs the brake actuator drive signal and calculates the target engine torque.

The engine control unit 30
Is the VDC / TCS / ABS control unit 29
In response to a command from the engine, the throttle opening control for the throttle motor of the electronically controlled throttle 32 and the fuel cut control for the injector of the engine 1 are performed.

The VDC / TCS / ABS actuator 33 generates a brake hydraulic pressure when the VDC / TCS is operated, receives an actuator drive signal from the VDC / TCS / ABS control unit 29, and receives a brake unit 34 for each wheel. Adjust the brake fluid pressure to 35, 36 and 37 individually.

The brake units 34, 35 on the front wheels 15, 16 side are larger units than the brake units 36, 37 on the rear wheels 9, 10 side.
That is, the wheel brake unit of the vehicle is usually
Front wheel 1 against rear wheels 9 and 10 due to load movement during braking, etc.
A larger braking force is required for 5 and 16. For this reason,
On the front wheels 15 and 16 side, a large-diameter rotor / caliper size unit that can exert a large braking force is adopted, and at the same time, the heat dissipation of ventilated disks etc. with high heat dissipation so as to cope with high heat generation due to high load The excellent unit is adopted. On the other hand, since the load on the rear wheels 9 and 10 is lower than that on the front wheels 15 and 16, the front wheels 15 and 16
It has a smaller rotor / caliper size than the side,
Drum brakes are used. As a result, front wheel 1
When the same braking force is generated on the 5th and 16th sides, the load is increased and the amount of heat generation is increased. Further, when the drum brake is adopted, the heat dissipation is inferior, and therefore, in order to prevent insufficient braking torque, it is necessary to limit the usable upper limit temperature to a low value.

The VDC / TCS / ABS control unit 29 and the engine control unit 30
The automatic transmission control unit 31 and the steering angle sensor 22 are connected to each other by a CAN communication line (multiplex communication line).

Next, the operation will be described.

[Acceleration Slip Control Processing] FIG. 2 shows VDC /
6 is a flowchart showing a flow of acceleration slip control processing executed by the TCS / ABS control unit 29,
Each step will be described below.

In step S1, it is determined whether the slip control execution flag is set. Ie 4
The acceleration slip of the wheels is detected by calculating the slip ratio, slip ratio, etc. (acceleration slip detection means), and when this acceleration slip detection value becomes equal to or greater than the set slip control start threshold value, the slip control execution flag is set. Set. If the slip control execution flag is set, the process proceeds to step S2. If the slip control execution flag is not set, the process proceeds to RETURN and waits until the slip control execution flag is set.

In step S2, slip control (engine control, brake control) is executed (slip control means). That is, the target brake hydraulic pressure and the target engine torque required for the TCS control are calculated based on the set slip control execution flag. Then, after the processing of each step described below is completed, VDC / TCS / ABS
Brake control is performed by outputting an actuator drive signal to the brake actuator 33. On the other hand, VD
By outputting a command from the C / TCS / ABS control unit 29 to the engine control unit 30, engine control by throttle opening control and fuel cut control is performed.

In step S3, the brake temperature of the four wheels is estimated (brake temperature estimating means). Here, the temperature estimation of the brake units 34, 35, 36, 37 of the respective wheels is basically estimated by a value obtained by subtracting the temperature decrease due to the heat release of the traveling wind from the temperature increase due to the braking heat generation.
The details will be described later.

In step S4, it is determined whether or not the vehicle is in the four-wheel drive state (drive state determination means). For example, when the information that the clutch engagement force is being output from the 4WD control unit 18 to the 4WD actuator 17 is input, it is determined that the vehicle is in the four-wheel drive state, the process proceeds to step S5, and the clutch engagement force is set. If the information indicating that the command is not output is input, it is determined that the vehicle is not in the four-wheel drive state, and the process proceeds to step S7.

In step S5, it is determined whether or not the brake units 34, 35 on the front wheels 15, 16 side are below a specified temperature (whether or not the front wheel brake temperature upper limit flag is reset). Here, the specified temperature is set for each type of brake unit to a limit temperature at which brake control can be performed without progress of insufficient braking torque. Then, if YES, the process proceeds to step S6, and if NO, the process proceeds to step S10.

In step S6, it is determined whether or not the brake units 36, 37 on the rear wheels 9, 10 side are below a specified temperature (whether or not the rear wheel brake temperature upper limit flag is reset). Here, like the front wheels 15 and 16, the specified temperature is set to a limit temperature at which brake control can be performed without progress of insufficient braking torque for each type of brake unit. If YES, then the process proceeds to step S8, N
If it is O, the process proceeds to step S9.

In step S7, similarly to step S6, it is determined whether or not the brake units 36, 37 on the rear wheels 9, 10 side are below a specified temperature (whether or not the rear wheel brake temperature upper limit flag is reset). Then, if YES, the process proceeds to step S8, and if NO, the process proceeds to step S10.

In step S8, normal brake control is executed (normal brake control means). That is, TCS
The brake fluid pressures of the brake units 34, 35, 36, 37 of the respective wheels are applied based on the calculation of the target brake fluid pressure required for control.

In step S9, the brake control of the rear wheels 9 and 10 is added to the front wheels 15 and 16 to perform brake control (temperature-corresponding brake control means). That is, the brake control amount of the rear wheels 9 and 10 is reduced, and the brake control amount of the front wheels 15 and 16 is increased by the amount of the brake control amount reduced on the rear wheels 9 and 10 side.

In step S10, if the brake control is being performed, the brake control is gradually ended and the normal brake is set (brake control limiting means). That is, if the brake control for suppressing the acceleration slip is being performed, the brake control is gradually ended and the normal braking state is restored.

[Brake Temperature Estimating Action] The temperature estimation of the brake units 34, 35, 36, 37 of the respective wheels is basically estimated by a value obtained by subtracting the temperature decrease due to running wind heat dissipation from the temperature increase due to braking heat generation. It That is, the approximate expression for obtaining the estimated temperature is represented by the following expression, for example. Estimated temperature = (1) Previous temperature + (2) Temperature increase amount- (3) Temperature decrease amount + (4) Various correction amounts (1) Previous temperature For the previous temperature, the previous estimated temperature is used. (2) Temperature rise The temperature rise is approximated by the following formula. {Brake braking force (pad area x pad μ x control hydraulic pressure)} x {movement distance between rotor and pad (2π x rotor effective radius x ω)} time integration (3) Temperature decrease It can be approximated by the amount of air passing through and the temperature. Here, the air volume is estimated by the estimated vehicle speed or the like obtained by ABS. The air temperature is a fixed value at room temperature, or if the vehicle has an outside air temperature sensor, the sensor value is used. When the temperature decrease is approximated using both the air volume and the outside air temperature, the accuracy is improved as compared with the case where the temperature decrease is approximated using only the air volume. (4) Various correction amounts There is a discrepancy between the temperature change amount calculated by the approximate temperature rise amount and the temperature decrease amount based on the actual measurement value on the actual vehicle and the table, and the actual temperature change amount under the same condition. In this case, the amount of deviation is obtained as various correction amounts.

[Brake TCS control action] When the slip control is being executed, and the four wheels are being driven, in the brake control start range, the brake units 34, 3 on the front wheels 15, 16 side.
Brake units 36 and 37 on the side of 5 and the rear wheels 9 and 10
Indicates that the brake temperature is equal to or lower than the specified temperature, so in the flowchart of FIG. 2, step S1 → step S2 →
The flow proceeds from step S3 → step S4 → step S5 → step S6 → step S8 to step S8.
Then, the brake control of four wheels that suppresses a normal acceleration slip is performed.

If this brake control is continued as it is, the brake unit 3 on the rear wheels 9 and 10 side.
6 and 37, the brake temperature rises slowly on the front wheels 15 and 16 side where large brake units 34 and 35 are adopted, and the brake units 36 and 37 on the rear wheels 9 and 10 side first.
Since the brake temperature of the above exceeds the specified temperature, in the flowchart of FIG. 2, step S1 → step S2
→ Step S3 → Step S4 → Step S5 → Step S6 → Step S9
9, the brake control amount of the rear wheels 9 and 10 is reduced, and the brake control amount of the front wheels 15 and 16 is changed to the rear wheels 9 and 10.
Brake control is executed to increase the amount of the brake control reduced on the side.

Further, if the brake control is continued as it is, the brake temperature on the side of the front wheels 15 and 16 in which the large brake units 34 and 35 are adopted also exceeds the specified temperature. Therefore, in the flowchart of FIG. Step S1 → Step S2 → Step S3 → Step S4
→ Step S5 → Step S10
In step S10, the brake control is gradually ended, and the normal braking state (the state in which the braking force is applied only based on the brake operation) is returned.

On the other hand, when the slip control is being executed and the four-wheel drive state such as the rear-wheel drive state is not established, step S1 → step S2 → step S3 → step S4 → step S7 in the flowchart of FIG. In step S7, it is determined whether or not the brake temperatures of the brake units 36, 37 on the rear wheels 9, 10 side are equal to or lower than the specified temperature. If the temperature is equal to or lower than the specified temperature, the process proceeds to step S8 to perform normal acceleration slip. If the brake control for suppressing the above is performed and the temperature exceeds the specified temperature, the process proceeds to step S10 to gradually end the brake control and return to the normal brake state.

[Brake Control Operation in Rigid 4-Wheel Drive State] In the rigid 4-wheel drive state in which the front and rear wheels are directly connected, the driver fully depresses the accelerator pedal 20 (accelerator opening 100%), and four wheels The operation in the case where the driving torque transmitted to the vehicle becomes excessive and all four wheels fall into the acceleration slip state, and the brake control is performed to suppress the acceleration slip will be described with reference to the time chart shown in FIG.

First, as shown in the vehicle speed / wheel speed characteristics,
When the slip control execution flag is set at t1 when the acceleration slip state in which the wheel speed greatly exceeds the vehicle body speed and the acceleration slip detection value becomes equal to or more than the set slip control start threshold value, the normal slip state is set. Brake control is started. That is, the brake temperature of the front and rear wheels (estimated temperature)
While monitoring the rear brake unit 36, 37
The front wheel (FR) and the rear wheel (RR) are provided to the front wheel side brake units 34 and 35 and the rear wheel side brake units 36 and 37 until time t2 when the brake temperature of the vehicle reaches the specified temperature.
As shown in the brake control hydraulic pressure characteristic of No. 3, the brake control hydraulic pressure having the same characteristic according to the acceleration slip situation is applied.

Then, as shown in the brake temperature characteristics of the front wheels (FR) and the rear wheels (RR), the brake temperatures of the brake units 36, 37 on the rear wheel side approach the specified temperature before the front wheel side, and the brake temperature of t2 Brake unit 3 on the rear wheel side at this point
When the brake temperatures of the brake wheels 6 and 37 reach the specified temperature, the brake control hydraulic pressure to the brake units 36 and 37 on the rear wheel side is reduced, and the decrease in the brake control hydraulic pressure is applied to the brake units 34 and 35 on the front wheel side. Brake control to be added to the control hydraulic pressure is started. That is, the slip control execution flag is reset by the accelerator release operation t3
Up to the point of time, as shown in the brake control fluid pressure characteristic of the front wheel (FR), the brake control fluid pressure added to the front wheel side brake units 34, 35 by the reduction amount (hatching portion) on the rear wheel side is added. The brake control fluid pressure due to the low pressure is applied to the brake units 36 and 37 on the rear wheel side, as indicated by the brake control fluid pressure characteristics of the rear wheel (RR).

By this front brake control distribution increase control, the brake temperature of the front wheel side brake units 34, 35 increases the brake control hydraulic pressure from time t2 to time t3 as shown in the FR brake temperature characteristic. The brake temperature rises due to a slightly larger gradient than before. On the other hand, the brake temperature of the brake units 36, 37 on the rear wheel side is, as shown in the RR brake temperature characteristic,
During the period from t2 to time t3, the brake temperature gradually decreases with a temperature decreasing gradient with respect to the temperature increasing gradient before the brake control hydraulic pressure decreases.

As described above, for the rear wheel brake units 36 and 37 in which the brake temperature tends to rise, even if the brake temperature exceeds the specified temperature, if the brake control is continued as it is, the brake temperature becomes high and the braking torque becomes insufficient. May become. However, when the brake units 36, 37 on the rear wheel side exceed the specified temperature, the brake control hydraulic pressure is reduced, so that the temperature decrease amount due to heat radiation exceeds the temperature increase amount due to braking heat generation, and the brake unit on the rear wheel side is increased. 36, 37
Since the brake temperature of 1 is turned down, insufficient braking torque is prevented.

At the same time, in order to execute the brake control for increasing the brake control hydraulic pressure to the brake units 34, 35 on the front wheel side where the brake temperature has not reached the specified temperature,
Slip control that suppresses acceleration slip is sufficiently ensured while reducing the brake control hydraulic pressure of the brake units 36 and 37 on the rear wheel side. That is, in the four-wheel drive state, since the front wheels and the rear wheels are in the engaged state, increasing the brake control hydraulic pressure on the front wheel side reduces the rotation speed of the front wheel side axle, resulting in the rear wheel side. The number of rotations of the axle also decreases, and when the decrease amount of the brake control hydraulic pressure and the increase amount of the brake control hydraulic pressure are equalized as in the first embodiment, the case where the brake control is performed on four wheels is performed. An equivalent acceleration slip suppression effect (brake TCS effect) can be obtained.

Since the front and rear wheels are in the engaged state in the four-wheel drive state, even if the rear wheels 9 and 10 accelerate and slip, the brake control is performed only by the front wheel side brake units 34 and 35 having a sufficient heat capacity from the beginning. Although there is an idea that it may be performed, it is not preferable because of the following reasons. The first reason is that the brake TCS effect is more efficiently achieved when the braking force is directly applied to the acceleration slip wheel. The second reason is that the front wheel side brake units 34, 3
If the brake control is performed only by 5, the drive system such as the differential gear will be overloaded.

Next, the effect will be described.

(1) When the slip control is executed, the four wheels are driven, and the brake temperature of the rear wheels exceeds the specified temperature, the brake to the rear wheels whose brake temperature exceeds the specified temperature. Since the control fluid pressure is reduced and the brake control fluid pressure for the front wheels is increased, braking is performed when braking control is performed to suppress acceleration slip during traveling in four-wheel drive. The slip control can be sufficiently performed while preventing the torque shortage.

(2) At the time of executing the slip control, in the four-wheel drive state, the brake temperature of the front wheels 15 and 16 is below the specified temperature, and the brake temperature of the rear wheels 9 and 10 exceeds the specified temperature. In this case, the brake control hydraulic pressure of the rear wheels 9 and 10 is reduced, and the brake control hydraulic pressure of the front wheels 15 and 16 is increased by the brake control hydraulic pressure reduced on the rear wheels 9 and 10 side. Therefore, in the four-wheel drive vehicle in which the brake units 34 and 35 having a larger heat capacity than the brake units 36 and 37 on the rear wheel side are mounted on the front wheel side, the normal brake control is switched to the temperature-corresponding brake control. Even if the brake TCS is almost the same
It can be effective.

(3) When the slip control is executed, the four wheels are driven, and the brake temperatures of the front wheels 15 and 16 are below the specified temperature and the brake temperatures of the rear wheels 9 and 10 are below the specified temperature, Since the brake control according to the acceleration slip is performed on the front and rear wheels 15, 16, 9, and 10, the braking force is directly applied to the acceleration slip wheels in the brake temperature range where the insufficient braking torque does not pose a problem. Therefore, a high brake TCS effect can be achieved.

(4) When the slip control is being executed, the four wheels are being driven, and the brake temperature of the front wheels 15 and 16 exceeds the specified temperature, the brake control is gradually ended if the brake control is in progress. The brake unit 3 has a sufficient heat capacity because it is returned to the normal braking state.
In a four-wheel drive vehicle in which the front wheels 4 and 35 are mounted, braking torque shortage can be reliably prevented without affecting the vehicle behavior due to a sudden brake release at the end of brake control.

(5) Since the brake temperature is estimated according to the value obtained by subtracting the heat radiation amount from the braking heat generation amount, it is possible to reliably estimate the brake temperature that changes with the passage of the brake operation time.

(6) The temperature increase due to the braking heat is calculated based on the braking force of the brake, and the temperature decrease due to the heat radiation approximated by the amount of air passing through the brake unit is calculated.
Since the temperature increase amount is added to the previous temperature and the temperature decrease amount is subtracted from this added value, the brake temperature at this time is estimated. Therefore, it is possible to accurately estimate the brake temperature that changes with the passage of the brake operation time. it can.

(Other Embodiments) The acceleration slip control system for a four-wheel drive vehicle according to the present invention has been described above based on the first embodiment, but the specific construction is limited to this first embodiment. It is not intended that modifications and additions of the design are allowed without departing from the gist of the invention according to each claim of the claims.

For example, in the first embodiment, an example of application to a four-wheel drive vehicle equipped with an electronically controlled 4WD system capable of arbitrarily changing the torque distribution between the front and rear wheels has been shown, but the two-wheel drive state and the four-wheel drive state are shown. It can also be applied to a four-wheel drive vehicle equipped with a part-time type 4WD system that switches ON / OFF. That is, any system that can realize the 4WD state in which the front wheel axle and the rear wheel axle are fastened is included.

In the first embodiment, the failsafe of temperature estimation is not mentioned, but the brake control continuous operation time (for example, 10 se) which is clearly abnormal is known.
In the case of c), the brake control may be prohibited. In this case, the reliability of the unit can be improved.

In the first embodiment, an example of application to a four-wheel drive vehicle in which a brake unit having a larger heat capacity than the brake unit on the rear wheel side is mounted on the front wheel side has been shown. It can also be applied to a four-wheel drive vehicle equipped with a unit. Further, when the brake temperature on the front wheel side reaches the specified temperature first, the brake control amount of the brake unit on the front wheel side may be decreased and the brake control amount of the brake unit on the rear wheel side may be increased. .

[Brief description of drawings]

FIG. 1 is a combined system diagram of VDC, TCS, and ABS to which an acceleration slip control device for a four-wheel drive vehicle according to a first embodiment is applied.

FIG. 2 is a flowchart showing a flow of an acceleration slip control process executed by a VDC / TCS / ABS control unit in the acceleration slip control device for the four-wheel drive vehicle of the first embodiment.

FIG. 3 is a time chart showing a brake control operation in a rigid four-wheel drive state in a vehicle equipped with an acceleration slip control device for a four-wheel drive vehicle of the first embodiment.

[Explanation of symbols]

1 engine 2 automatic transmission 3 Transmission output shaft 4 transfer 5 Rear propeller shaft 6 rear differential 7,8 Rear drive shaft 9 left rear wheel 10 right rear wheel 11 Front propeller shaft 12 front differential 13,14 Front drive shaft 15 left front wheel 16 right front wheel 17 4WD actuator 18 4WD control unit 19 Mode selection switch 20 brake pedal 21 master cylinder 22 Rudder angle sensor 23 Yaw rate / transverse G sensor 24 Left front wheel rotation sensor 25 Right front wheel rotation sensor 26 Left rear wheel rotation sensor 27 Right rear wheel rotation sensor 28 Pressure sensor 29 VDC / TCS / ABS control unit 30 engine control unit 31 Automatic transmission control unit 32 electronically controlled throttle 33 VDC / TCS / ABS brake actuator 34 Left front wheel brake unit 35 Right front wheel brake unit 36 Left rear wheel brake unit 37 Right rear wheel brake unit 38 ABS warning light 39 VDC-OFF indicator light 40 SLIP indicator light

Claims (6)

[Claims] 1. An acceleration slip detection means for detecting an acceleration slip of a wheel, and a slip control means for executing a brake control for applying a braking torque to an acceleration slip wheel when the acceleration slip detection value is equal to or more than a slip control start threshold value. In an acceleration slip control device including, a brake temperature estimating means for estimating a brake temperature of each wheel, a drive state detecting means for detecting whether or not the vehicle is in a four-wheel drive state, and a slip control execution time, and With four-wheel drive, and
If one of the front and rear wheels has a brake temperature that exceeds the specified temperature, the brake control amount for one of the front and rear wheels that accelerates and slips the brake temperature is decreased, An acceleration slip control device for a four-wheel drive vehicle, comprising: a temperature-corresponding brake control means for performing a brake control for increasing the brake control amount. 2. The acceleration slip control device for a four-wheel drive vehicle according to claim 1, wherein the temperature-corresponding brake control means performs the slip control, is in a four-wheel drive state, and has a front wheel brake temperature. Is less than the specified temperature and the brake temperature of the rear wheels exceeds the specified temperature, the brake control amount of the rear wheels is reduced and the brake control amount of the front wheels is reduced by the amount of the brake control amount reduced on the rear wheel side. An acceleration slip control device for a four-wheel drive vehicle, which is characterized by performing brake control to be added. 3. The acceleration slip control device for a four-wheel drive vehicle according to claim 2, wherein the slip control is executed, the four-wheel drive state is set, and
When the brake temperature of the front wheels is equal to or lower than the specified temperature and the brake temperature of the rear wheels is equal to or lower than the specified temperature, normal brake control means is provided for performing brake control on the front and rear wheels according to the acceleration slip. Acceleration slip control device for wheel drive vehicle. 4. The acceleration slip control device for a four-wheel drive vehicle according to claim 2 or 3, wherein the slip control is performed, the four-wheel drive state is set, and
Acceleration slip control of a four-wheel drive vehicle, characterized in that when the brake temperature of the front wheels exceeds a specified temperature, brake control limiting means is provided for gradually ending the brake control and returning to a normal brake state if the brake control is in progress. apparatus. 5. The acceleration slip control device for a four-wheel drive vehicle according to any one of claims 1 to 4, wherein the brake temperature estimating means brakes according to a value obtained by subtracting a heat radiation amount from a braking heat generation amount. An acceleration slip control device for a four-wheel drive vehicle, which estimates temperature. 6. The acceleration slip control device for a four-wheel drive vehicle according to claim 5, wherein the brake temperature estimating means calculates a temperature increase amount due to braking heat generation based on the brake braking force, and passes through the brake unit. A four-wheeled vehicle characterized in that the current brake temperature is estimated by calculating the temperature decrease due to heat dissipation approximated by the air volume, adding the temperature increase to the previous temperature, and subtracting the temperature decrease from this added value. Acceleration slip control device for driving vehicle.