JP2003312287A - Torque allocation controller for four-wheeled-drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a vehicle to maintain its traveling performance without deteriorating traveling safety when a wheel speed signal shows abnormality. <P>SOLUTION: When the wheel speed signal shows no abnormality, a value given by adding a pre-torque set on the basis of a vehicle speed and a throttle opening to a compensation torque (ΔN torque) set on the basis of an average wheel speed difference ΔN between front wheels and rear wheels is set as an allocation torque given to a driven wheels RT3, RT4 (steps S2, S4, S6, S8). When the wheel speed signal shows abnormality, the pre-torque is set only on the basis of a throttle opening given when the vehicle speed is fixed to zero, the compensation torque is forced to be set to zero, and a pre-torque based only on the throttle opening is set as the allocation torque given to a driven wheels RT3, RT4 (steps S10, S12, S14, S8). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque distribution control device for a four-wheel drive vehicle, and more particularly to a control for ensuring four-wheel drive by continuing four-wheel drive when an abnormality occurs in a wheel speed signal. .

[0002]

2. Description of the Related Art Conventionally, a torque distribution control device for a four-wheel drive vehicle provided with a torque distribution device for distributing a driving force transmitted from an engine to driving wheels to driven wheels is one of front and rear wheel speed sensors. When an abnormality occurs in the wheel speed signal due to a failure or disconnection of those signal lines, a short circuit, etc., normally, continuing four-wheel drive control based on the wheel speed signal, which lacks reliability, deteriorates the steering stability, Since it impairs safety, the command value to the torque distribution device is switched to 0, and the distribution torque to the driven wheels is switched to 0, that is, 4
Control is performed to switch from wheel drive to two wheel drive.

[0003]

However, if the vehicle is switched to the two-wheel drive when the wheel speed signal is abnormal as described above, the abnormality occurs when the vehicle is required to drive the four wheels such as on a deep snowy road. In the subsequent two-wheel drive, the vehicle may not be able to travel, and running performance may not be secured.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to ensure the running performance without impairing the safety when an abnormality occurs in the wheel speed signal. .

[0005]

A torque distribution control device for a four-wheel drive vehicle according to claim 1 is provided with a torque distribution device for distributing a driving force transmitted from an engine to a drive wheel to a driven wheel. In the torque distribution control device of the above, if there is no abnormality in the wheel speed signal by the abnormality determining means for determining whether the wheel speed signal has abnormality, the vehicle speed, the throttle opening, and the front and rear wheels are determined. When the normal speed torque setting means for setting the command torque on the basis of the wheel speed difference and the abnormality judging means determine that the wheel speed signal is abnormal, the command torque is set only on the basis of the throttle opening. Abnormal torque setting means, and a distribution torque for outputting a command value corresponding to the torque set by the normal torque setting means or the abnormal torque setting means to the torque distribution device. Characterized in that it comprises a click setting means.

According to the torque distribution control device for a four-wheel drive vehicle of the first aspect, when an abnormality occurs in the wheel speed signal, the vehicle speed and the average wheel speed difference calculated based on the unreliable wheel speed signal are calculated. Since the distribution torque is set without using it and the torque distribution device is controlled using the set distribution torque as a command value, it is possible to secure the running performance without impairing the safety.

A torque distribution control device for a four-wheel drive vehicle according to a second aspect includes a torque distribution device for distributing the driving force transmitted from the engine to the drive wheels to the driven wheels. In the device, the abnormality determination means for determining whether there is no abnormality in the wheel speed signal, and when it is determined that there is no abnormality in the wheel speed signal by the abnormality determination means,
When the normal speed torque setting means for setting a command torque based on the vehicle speed, the throttle opening, and the wheel speed difference between the front and rear wheels and the abnormality determining means determine that the wheel speed signal is abnormal, a predetermined fixed value is set. Abnormal time torque setting means for setting a command torque based on the value, and abnormal time distribution for outputting a command value corresponding to the torque set by the normal time torque setting means or the abnormal time torque setting means to the torque distribution device. And a torque setting means.

According to the torque distribution control device for a four-wheel drive vehicle according to the second aspect, as in the torque distribution control device for a four-wheel drive vehicle according to the first aspect, when an abnormality occurs in the wheel speed signal,
The distribution torque is set without using the vehicle speed calculated based on the unreliable wheel speed signal and the average wheel speed difference, and the torque distribution device is controlled using this set distribution torque as a command value, thus ensuring safety. It is possible to ensure running performance without impairing

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual block diagram of a four-wheel drive vehicle equipped with a torque distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention.

In FIG. 1, a transaxle 14 is mounted on the output side of the engine 12. The transaxle 14 integrally includes a transmission, a transfer, and a front differential 16. The transaxle 14 transfers the driving force of the engine 12 to the axle shaft 18 via the front differential 16.
To drive the left and right front wheels RT1 and RT2, and output to the first propeller shaft 20. The first propeller shaft 20 is connected to the second propeller shaft 24 via a torque distribution device 22. When the torque distribution device 22 connects the first propeller shaft 20 and the second propeller shaft 24 so that torque can be transmitted, the driving force is transmitted to the rear differential 26, and is output from the rear differential 26 to the axle shaft 28 so that the left and right sides can be transmitted. The rear wheels RT3 and RT4 are driven.

The torque distribution device 22 includes a clutch plate 30 for transmitting torque from the first propeller shaft 20 to the second propeller shaft 24, and a clutch plate 3 (not shown).
And a pressing mechanism for pressing 0. This pressing mechanism acts on the clutch plate 30 with a pressing force according to a command value from the electronic control circuit 50. For example, when the command value increases the torque distribution from the first propeller shaft 20 to the second propeller shaft 24, the engagement force of the clutch plate 30 is increased and the torque of the first propeller shaft 20 is changed to the second propeller shaft. It is transmitted to the shaft 24. Further, the command value is from the first propeller shaft 20 to the second propeller shaft 24.
If the torque is not distributed to the second propeller shaft 24, the clutch plate 30 is separated so that the torque of the first propeller shaft 20 is not transmitted to the second propeller shaft 24. As described above, the torque distribution device 22 is configured to change the engaging force of the clutch plate 30 according to the magnitude of the command value and adjust the transmission torque from the first propeller shaft 20 to the second propeller shaft 24. .

Drive wheels RT1, RT2 and driven wheels RT3
RT4 has brakes B1, B2, B3, B4 respectively.
And wheel speed sensors S1, S2, S for detecting the wheel speed
3, S4 are provided. The wheel speed sensor S1,
S2, S3, S4 are brakes B1, B2, B3, B
4 also serves as a wheel speed sensor for an anti-lock brake system (ABS) that controls the 4 independently. Further, a steering wheel SW for operating the steering system of the vehicle
The steering column connected to is provided with a steering angle sensor S5 for detecting the steering angle. Further, the throttle body of the intake system of the engine 12 is provided with a throttle opening sensor S6 that detects the opening of the throttle valve 32 that adjusts the intake amount according to the depression amount of the accelerator pedal.

The electronic control circuit 50, as shown in FIG.
The torque distribution device 2 is connected to the wheel speed sensors S1, S2, S3, S4 and the throttle opening sensor S6.
Connected to 2. The electronic control circuit 50 includes a CPU 54 that performs various arithmetic processes for controlling the torque distribution device 22.
A ROM 56 in which a control program representing a calculation processing procedure by the CPU 54 is stored in advance; and a RAM 5 in which necessary data is read and written at any time during execution of the calculation processing of the CPU 54.
8 and the wheel speed sensors S1, S2, S3, S4, and the throttle opening sensor S6, and inputs a wheel speed signal and a throttle opening signal, and outputs a command value as a calculation result by the CPU 54 to the torque distribution device 22. And an input / output circuit 52.

Next, an example of main control performed by the electronic control circuit 50 on the torque distribution device 22 will be described with reference to FIG.

The CPU 54 includes wheel speed sensors S1 and S.
Based on the wheel speed signals from S2, S3 and S4, it is determined whether or not the wheel speed signals for each of the wheel speed sensors S1, S2, S3 and S4 are abnormal (step S2). The wheel speed sensors S1, S2, S3, S4 output signals according to the wheel speeds under normal conditions, but output signals that do not correspond to the wheel speeds under abnormal conditions such as sensor failure, signal line disconnection or short circuit. Then, the CPU 54 determines whether or not there is an abnormality for each wheel speed signal based on such a difference between the signals in the normal state and the abnormal state.

When it is determined that all the wheel speed signals are normal, pre-torque calculation is executed to obtain pre-torque (step S4). Here, in the pre-torque calculation, the command torque (Nm) is obtained based on the vehicle speed (km / h) obtained based on each wheel speed signal and the throttle opening (%) obtained based on the throttle opening signal. Done by. This command torque is a basic torque transmitted to the driven wheels RT3, RT4, and the driven wheels RT3, RT4 rotate at a torque suitable for the running state of the vehicle estimated from the vehicle speed and the throttle opening for each vehicle or vehicle type. The value is set so that it can be represented by, for example, a three-dimensional feedforward map shown in FIG. The pre-torque may be stored in the ROM 56 as map data in advance, or may be obtained by a predetermined arithmetic expression. Next, the CPU 54 sets Δ
N torque calculation is executed to obtain ΔN torque (step S6). Here, the ΔN torque calculation is performed by the two front wheels RT1,
Wheel speed difference between front and rear wheels (average wheel speed difference) as a result of subtracting the average value of wheel speeds of the two rear wheels RT3 and RT4 (average wheel speed of the rear wheels) from the average value of wheel speeds of the RT2 (front wheel average wheel speed) , ΔN) based on the torque (ΔN torque) of the driven wheels RT3, RT4. This ΔN torque is a correction torque that is added to the above-described basic torque, that is, the pretorque, and is a torque suitable for the running state of the vehicle estimated from the average wheel speed difference ΔN between the front wheels RT1 and RT2 and the rear wheels RT3 and RT4. A value is set and can be represented by, for example, a two-dimensional feedback map shown in FIG. It should be noted that this ΔN torque may be stored in advance in the ROM 56 as map data, or may be calculated by the CPU 54 by a predetermined arithmetic expression, like the pre-torque. Next, the ΔN torque is added to the pre-torque, and the final driven wheels RT3 and RT4 are finally obtained.
Then, the transmission torque is calculated (step S8). That is, the distributed torque is obtained according to the vehicle speed, the throttle opening, and the difference between the average wheel speeds of the front and rear wheels. The calculated distribution torque is output as a command value to the torque distribution device 22, and the torque distribution device 22 distributes the torque according to the command value.

On the other hand, if it is determined in step S2 that any of the wheel speed signals is abnormal, the vehicle speed is fixed to 0 (step S10), and pre-torque calculation is executed.
A pre-torque is obtained (step S12). The pre-torque calculation here is different from the pre-torque calculation in step S4, and since the vehicle speed is fixed at 0, the command torque is obtained based only on the throttle opening. It is also possible to prepare a map for an abnormality based only on the throttle opening in advance separately from the feedforward map and use this map to obtain the pretorque. Next, the CPU 54 executes the ΔN torque calculation to obtain the ΔN torque (correction torque).
Unlike the ΔN torque calculation in step S6, the N torque calculation fixes ΔN torque to 0 (step S14).
Next, ΔN torque is added to the pre-torque to obtain the final driven wheel torque (distributed torque) (step S
8) Here, since the ΔN torque is 0, the distributed torque is equal to the pre-torque. Therefore,
The distribution torque takes a value depending only on the throttle opening, and this distribution torque is output to the torque distribution device 22 as a command value.

As described above, in the torque distribution control system for a four-wheel drive vehicle according to the first embodiment, the drive force transmitted from the engine 12 to the drive wheels RT1, RT2 is driven wheel RT.
In the torque distribution control device for a four-wheel drive vehicle that includes the torque distribution device 22 that distributes to the motors 3, RT4, abnormality determination means for determining whether or not there is an abnormality in the wheel speed signal (step S
2) and the abnormality determining means (step S2) determines that there is no abnormality in the wheel speed signal, the normal time pre-torque setting means (step S4) for setting the pre-torque based on the vehicle speed and the throttle opening, and the abnormality. When it is determined by the determination means (step S2) that the wheel speed signal has no abnormality, the correction torque (based on the average wheel speed difference ΔN obtained by subtracting the average wheel speed of the two rear wheels from the average wheel speed of the two front wheels). When the normal speed correction torque setting means (step S6) for setting ΔN torque) and the abnormality determination means (step S2) determine that there is an abnormality in the wheel speed signal, the throttle opening when the vehicle speed is fixed to 0 There is an abnormality in the wheel speed signal by the abnormal pre-torque setting means (steps S10 and 12) for setting the pre-torque based on only the above and the abnormality determination means (step S2). If it is determined that the correction torque is set to 0, the correction torque setting means (step S14) at the time of abnormality and the abnormality determination means (step S2)
If it is determined that the wheel speed signal is normal, the normal torque correction torque setting means (step S4) is set to the pretorque set by the normal time pretorque setting means (step S4).
6) Addition of the correction torque set by
3, the distribution torque to RT4 is set, a command value according to the set distribution torque is output to the torque distribution device 22, and it is determined by the abnormality determination means (step S2) that there is an abnormality in the wheel speed signal. In case of abnormality, the correction torque set by the abnormal correction torque setting means (step S14) is 0.
Based on the above, the pre-torque set by the abnormal pre-torque setting means (steps S10, 12) is set as the distribution torque to the driven wheels RT3, RT4, and the torque distribution device 22 sets the command value according to the set distribution torque. And a distribution torque setting means (step S8) for outputting to.

According to this torque distribution control device for a four-wheel drive vehicle, when an abnormality occurs in the wheel speed signal, the distribution is performed without using the vehicle speed calculated based on the unreliable wheel speed signal and the average wheel speed difference. Since the torque is set and the torque distribution device is controlled by using the set distribution torque as a command value, it is possible to secure the running performance without impairing the safety.

Next, another example of main control performed by the electronic control circuit 50 on the torque distribution device 22 (second embodiment).
Will be described with reference to FIG.

First, the CPU 54, similarly to step S2 of the above-described control example, each wheel speed sensor S1, S2, S3.
Based on the wheel speed signal from S4, the wheel speed sensor S1,
It is determined whether or not there is an abnormality in the wheel speed signal for each of S2, S3 and S4 (step S22).

When it is determined that all the wheel speed signals have no abnormality, the pre-torque calculation is executed to obtain the pre-torque (step S4) as in step S4 of the control example described above.
24). The processing content of step S24 is the same as the processing content of step S4. Next, CPU
Similarly to step S6 of the above-described control example, 54 executes the ΔN torque calculation to obtain the ΔN torque (correction torque) (step S26). The processing content of step S26 is the same as the processing content of step S6.
Next, as in step S8 of the above-described control example, the ΔN torque is added to the pre-torque to obtain the final driven wheels RT3, RT.
The torque of 4 (distributed torque) is calculated (step S2).
8). That is, in step S28, as in step S8, the distributed torque is obtained according to the vehicle speed, the throttle opening, and the average wheel speed difference between the front and rear wheels. The calculated distribution torque is output as a command value to the torque distribution device 22, and the torque distribution device 22 distributes the torque according to the command value.

On the other hand, when it is determined in step S22 that one of the wheel speed signals is abnormal, the distribution torque is set to a fixed value (step S30). Here, the fixed value corresponds to the torque that can ensure the running performance, and is a value that is experimentally obtained in advance. This fixed torque is output to the torque distribution device 22 as a command value, and the torque distribution device 22 distributes torque according to this command value.

As described above, in the torque distribution control device for a four-wheel drive vehicle according to the second embodiment, the driving force transmitted from the engine 12 to the drive wheels RT1 and RT2 is driven wheel RT.
In the torque distribution control device for the four-wheel drive vehicle, which includes the torque distribution device 22 for distributing to 3 and RT4, abnormality determination means for determining whether or not there is an abnormality in the wheel speed signal (step S
22) and the abnormality determining means (step S22) determines that there is no abnormality in the wheel speed signal, the normal time pre-torque setting means (step S24) for setting the pre-torque based on the vehicle speed and the throttle opening, and the abnormality. When it is determined by the determination means (step S22) that the wheel speed signal has no abnormality, the correction torque (based on the average wheel speed difference ΔN obtained by subtracting the average wheel speed of the two rear wheels from the average wheel speed of the two front wheels) ( Normal-time correction torque setting means (step S26) for setting ΔN torque) and abnormality determination means (step S2)
When it is determined that there is no abnormality in the wheel speed signal by 2),
The correction torque set by the normal-time correction torque setting means (step S26) is added to the pre-torque set by the normal-time pre-torque setting means (step S24) to set the distribution torque to the driven wheels RT3, RT4. Normal-time distribution torque setting means for outputting a command value corresponding to the distributed torque to the torque distribution device 22 (step S28)
Then, when it is determined by the abnormality determination means (step S22) that the wheel speed signal is abnormal, a fixed value torque is set as the distribution torque to the driven wheels RT3, RT4, and a command value according to the set distribution torque. Is output to the torque distribution device 22 at the abnormal time distribution torque setting means (step S30).

According to the torque distribution control device for a four-wheel drive vehicle as well, when an abnormality occurs in the wheel speed signal, the distribution is performed without using the vehicle speed calculated based on the unreliable wheel speed signal and the average wheel speed difference. Since the torque is set and the torque distribution device is controlled by using the set distribution torque as a command value, it is possible to secure the running performance without impairing the safety.

[0027]

According to the torque distribution control device for a four-wheel drive vehicle of the present invention, when an abnormality occurs in the wheel speed signal, it is possible to ensure traveling stability while ensuring traveling stability.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram of a four-wheel drive vehicle equipped with a torque distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention.

FIG. 2 is a block diagram of an electronic control circuit.

FIG. 3 is a flowchart showing an example of main control performed by the electronic control circuit on the torque distribution device.

FIG. 4 is an explanatory diagram of a feedforward map.

FIG. 5 is an explanatory diagram of a feedback map.

FIG. 6 is a flowchart showing another example of main control performed by the electronic control circuit on the torque distribution device.

[Explanation of symbols]

12 engine 22 Torque distribution device RT1, RT2 drive wheels RT3, RT4 driven wheel S2 abnormality determination means S4 Normal pre-torque setting means S6 Normal time correction torque setting means S8 distribution torque setting means S10, 12 Pre-torque setting means in case of abnormality S14 Abnormality correction torque setting means S22 Abnormality determination means S24 Normal pre-torque setting means S26 Normal time correction torque setting means S28 Normal distribution torque setting means S30 Abnormal torque distribution torque setting means

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3D043 AA04 AA10 AB01 AB17 EA02                       EA16 EA42 EB03 EE02 EE06                       EE07 EF02 EF14

Claims (2)

[Claims] 1. A torque distribution control device for a four-wheel drive vehicle, comprising a torque distribution device for distributing a driving force transmitted from an engine to driving wheels to driven wheels, wherein an abnormality for determining whether or not there is an abnormality in a wheel speed signal. And a normal-time torque setting means for setting a command torque based on a vehicle speed, a throttle opening, and a wheel speed difference between the front and rear wheels when it is determined by the abnormality determining means that the wheel speed signal has no abnormality. When it is determined by the abnormality determination means that there is an abnormality in the wheel speed signal, torque abnormality setting means for setting the command torque based only on the throttle opening,
Torque distribution of a four-wheel drive vehicle, comprising: distribution torque setting means for outputting a command value corresponding to the torque set by the normal time torque setting means or the abnormal time torque setting means to the torque distribution device. Control device. 2. A torque distribution control device for a four-wheel drive vehicle, comprising a torque distribution device for distributing a driving force transmitted from an engine to driving wheels to driven wheels, wherein an abnormality for determining whether or not there is an abnormality in a wheel speed signal. And a normal-time torque setting means for setting a command torque based on a vehicle speed, a throttle opening, and a wheel speed difference between the front and rear wheels when it is determined by the abnormality determining means that the wheel speed signal has no abnormality. When the abnormality determining means determines that the wheel speed signal is abnormal, the abnormal torque setting means for setting the command torque based on a predetermined fixed value, and the normal torque setting means or the abnormal torque setting means Torque distribution for a four-wheel drive vehicle, comprising: an abnormal-time distribution torque setting means for outputting a command value according to the torque set in 1. to the torque distribution device. The control device.