JPH0740754A - Differential limiting torque control device - Google Patents

Abstract

(57) [Summary] [Purpose] In a differential limiting torque control device that electronically controls the differential limiting torque between the left and right driving wheels based on the left and right driving wheel speed difference information, the left and right driving wheel speed difference proportional control and smooth steering. Make sure to escape from the stack while ensuring the start. [Configuration] When the vehicle speed is equal to or higher than a set vehicle speed or is lower than the set vehicle speed and the left / right drive wheel speed difference is smaller than a predetermined value, the differential limit torque determined according to the detected value of the left / right drive wheel speed difference is directly used as the target differential limit torque. When the vehicle speed is less than the set vehicle speed and the difference between the left and right driving wheel speeds is 1 degree or more,
Target differential limiting torque setting means e is provided which maintains the maximum value of the differential limiting torques determined according to the detected value of the left and right driving wheel speeds as the target differential limiting torque until the set vehicle speed is reached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential limiting torque control device for electronically controlling a differential limiting torque between left and right driving wheels based on left and right driving wheel speed difference information.

[0002]

2. Description of the Related Art Conventionally, as a limited differential torque control device, for example, one disclosed in Japanese Patent Application Laid-Open No. 1-215628 is known.

In the above-mentioned conventional source, the differential limiting torque component given with a larger value as the turning radius is larger and the lateral acceleration is larger, and the differential based on the left and right driving wheel slip amount (difference between the left and right driving wheel speed values) detected by the sensor. An apparatus for calculating a target differential limiting torque by the sum of the limiting torque components and performing control to obtain this target differential limiting torque is shown.

[0004]

However, in the above-mentioned conventional differential limiting torque control device by the left-right driving wheel speed difference proportional control, the differential limiting torque is applied in proportion to the occurrence of the left-right driving wheel speed difference. Since one of the left and right drive wheels is in the stack, it is not possible to expect high stack escape performance from the state in which one of the left and right drive wheels enters the stack.

That is, when one of the left and right driving wheels enters the stack, the differential limiting torque is applied based on the occurrence of the left and right driving wheel speed difference, and the engine driving force to the other driving wheel is increased. However, if the left and right drive wheel speed difference decreases due to the application of the differential limiting torque, the differential limiting torque weakens with the decrease, and it becomes impossible to escape from the severe stack.

Further, when the differential limiting torque is weakened at the time of such a stack exit, the control that the generation of the left-right drive wheel speed difference is increased and the differential limiting torque is strengthened is repeated, and hunting of the differential limiting torque is caused. .

The present invention has been made in view of the above problems, and an object of the present invention is to electronically control the differential limiting torque between the left and right driving wheels based on the left and right driving wheel speed difference information. In the dynamic limiting torque control device, it is intended to surely escape from the stack while ensuring the left-right drive wheel speed difference proportional control and smooth turning start.

[0008]

In order to achieve the above-mentioned object, in the differential limiting torque control device of the present invention, as shown in the claim correspondence diagram of FIG. Differential limiting torque applying means a for applying a differential limiting torque according to the above, left and right driving wheel speed difference detecting means b for detecting a left and right driving wheel speed difference, vehicle speed detecting means c for detecting a vehicle speed, and left and right driving Differential limit torque determining means d for determining a differential limit torque according to the detected wheel speed difference, and left and right drive when the vehicle speed is equal to or higher than the set vehicle speed or the vehicle speed is less than the set vehicle speed and the wheel speed difference is smaller than a predetermined value. The differential limiting torque determined according to the wheel speed difference detection value is directly used as the target differential limiting torque, the vehicle speed is less than the set vehicle speed, and the left-right driving wheel speed difference is 1
The target differential limit torque setting that maintains the maximum value of the differential limit torques determined according to the left and right drive wheel speed difference detection value as the target differential limit torque until the vehicle speed is reached Means e and differential limiting torque control means f for outputting a control command for obtaining the target differential limiting torque to the differential limiting torque applying means a are provided.

[0009]

When the vehicle speed is equal to or higher than the set vehicle speed, or when the vehicle speed is less than the set vehicle speed and the vehicle starts to move with the left and right drive wheel speed difference smaller than the predetermined value, the differential limiting torque determination means d outputs the left and right drive wheel speed difference detection means b. The differential limiting torque is determined according to the detected value of the difference between the left and right driving wheel speeds, and the determined differential limiting torque is set as the target differential limiting torque by the target differential limiting torque setting means e. In the control means f, a control command for obtaining the target differential limiting torque is output to the differential limiting torque giving means a for giving the differential limiting torque between the left and right driving wheels.

Therefore, for example, when traveling on the left and right split μ roads, the differential limiting torque is applied between the left and right drive wheels on the basis of the occurrence of the left and right drive wheel speed difference, and the differential drive torque is applied to the drive wheels on the high μ road side. The engine drive torque is increased and high traction performance is demonstrated.

Further, for example, at the time of steering start, the difference in speed between the left and right driving wheels is smaller than that at the time of stacking, so that the differential limiting torque is applied between the left and right driving wheels based on the occurrence of the difference between the left and right driving wheels. Therefore, as will be described later, the tight corner braking phenomenon that occurs in the case of turning start when a large differential limiting torque is applied by peak hold is prevented, and a smooth start is secured.

When the vehicle speed is less than the set vehicle speed and the left-right drive wheel speed difference is equal to or larger than the predetermined value even at 1 degree, the left and right drive wheel speed difference detection means b outputs the right and left directions in the differential limiting torque determining means d. The differential limiting torque is determined according to the drive wheel speed difference detection value, and the target differential limiting torque setting means e
Among the determined differential limiting torques, the maximum value is maintained as the target differential limiting torque until the set vehicle speed is reached, and the differential limiting torque control means f drives the left and right control commands to obtain the target differential limiting torque by the peak hold. It is output to the differential limiting torque applying means a for applying the differential limiting torque between the wheels.

Therefore, the differential limiting torque control by the peak hold is performed only when the vehicle speed condition and the left and right driving wheel speed difference condition are both satisfied, and when one wheel enters the stack, the vehicle is completely moved. The maximum value of the differential limiting torque is maintained until the vehicle starts moving and the vehicle speed increases to the set vehicle speed, so that escape from the stack is secured.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure will be described.

FIG. 2 is an overall system diagram of a rear-wheel drive vehicle to which the differential limiting torque control device according to the embodiment of the present invention is applied.

In FIG. 2, 1 is an engine, 2 is a transmission, 3 is a propeller shaft, 4 is an electronically controlled limited slip differential (hereinafter abbreviated as electronically controlled LSD), 5 and 6 are rear wheels, and 7 and 8 are front wheels. Is.

The electronically controlled LSD 4 has a built-in differential limiting clutch 10 for generating a differential limiting torque between the left and right rear wheels 5 and 6 according to the clutch control pressure applied from the hydraulic unit 9.

The hydraulic unit 9 includes a hydraulic power source 11 and an LS.
And a D control valve 12. The hydraulic unit 9 and the differential limiting clutch 10 correspond to the differential limiting torque applying means a.

The LSD control valve 12 is controlled by the control current ILSD from the active LSD controller 13 to generate a clutch control pressure for the differential limited clutch 10.

In the active LSD controller 13, the left front wheel rotation speed NFL from the left front wheel rotation sensor 14 and
The right front wheel rotation speed NFR from the right front wheel rotation sensor 15, the left rear wheel rotation speed NRL from the left rear wheel rotation sensor 16, the right rear wheel rotation speed NRR from the right rear wheel rotation sensor 17, and the lateral acceleration sensor 18 From the longitudinal acceleration sensor 19, the longitudinal acceleration XG from the longitudinal acceleration sensor 19, the accelerator opening ACC from the accelerator opening sensor 20, the switch signal BS from the brake switch 21, and the ABS operation signal AS from the ABS controller 22. Is entered.

Next, the operation will be described.

[Differential Limiting Torque Control Operation Processing] FIG. 3 is a flow chart showing the flow of the differential limiting torque control operation processing performed by the active LSD controller 13. Each step will be described below.

In step 30, the left front wheel rotation speed NFL, the right front wheel rotation speed NFR, the left rear wheel rotation speed NRL, and the right rear wheel rotation speed NRR.
And lateral acceleration YG is read.

In step 31, the left front wheel rotation speed NFL, the right front wheel rotation speed NFR, the left rear wheel rotation speed NRL, and the right rear wheel rotation speed NRR.
From left front wheel speed VFL, right front wheel speed VFR and left rear wheel speed V respectively
RL and the right rear wheel speed VRR are calculated.

In step 32, the vehicle body speed VF is determined by selecting the smaller one of the left front wheel speed VFL and the right front wheel speed VFR (corresponding to the vehicle speed detecting means c), and the left and right front wheel speed difference ΔVF.
Is calculated by the absolute value of the difference between the left front wheel speed VFL and the right front wheel speed VFR, and the left / right rear wheel speed difference ΔVR is the left rear wheel speed VRL and the right rear wheel speed V
Calculated by the absolute value of the difference in RR, and the front and rear wheel speed difference ΔVFR
Is calculated from the difference between the rear wheel speed average value VRA and the front wheel speed average value VFA.

In step 33, a turning locus left / right rear wheel speed difference ΔVR 'caused by a turning locus difference between the inner and outer wheels during turning is calculated by the following equation.

ΔVR ′ = K2 · VF / R K2; constant Here, the turning radius R is determined, for example, by the following arithmetic expression according to the magnitude of the lateral acceleration YG.

I) YG ≤ YGO
YGO; for example, 0.05 [G] R = VF / (K1 · ΔVF) K1; Constant ii) YG> YGO At R = VF ² / YG step 34, a correction factor from the left and right rear wheel speed difference ΔVR by detecting the turning locus The left / right rear wheel speed difference ΔVRR for control is calculated by the following formula for subtracting the left / right rear wheel speed difference ΔVR ′ (corresponding to the left / right drive wheel speed difference detection means b).

ΔVRR = ΔVR−ΔVR ′ In step 35, the differential limiting torque TΔV proportional to the left / right rear wheel speed difference is calculated by the following equation (corresponding to the differential limiting torque determining means d).

TΔV = CΔVRR C is a constant. For example, as shown in FIG. 4, the constant is changed to C1 and C2 according to the vehicle speed VF, and the differential limitation for the left / right rear wheel speed difference ΔVRR for control is limited. The constant C, which is the control gain of the torque TΔV, may be set to a smaller constant C2 (<C1) than the constant C1 in the low speed range in order to achieve stability due to the ease of correction steering in the high speed range.

In step 36, it is judged whether the vehicle speed VF is equal to or higher than the set vehicle speed x.

Here, the set vehicle speed x is, for example, x
A value of about 5 km / h is given.

In step 43, the peak hold flag PHF indicating whether or not the peak hold control is in progress is PHF =
Set to 0.

At step 44, it is judged if the peak hold flag PHF is PHF = 0.

At step 45, the control left / right rear wheel speed difference Δ
It is determined whether VRR is greater than or equal to the set left / right rear wheel speed difference y.

Here, the set left / right rear wheel speed difference y is given a large value such as y = 5 km / h, which only occurs during stacking.

At step 46, the peak hold flag PHF is set to PHF = 1 (during peak hold control).

At step 47, each wheel speed VFL of the four wheels,
It is determined whether VFR, VRL and VRR are all zero.

In step 48, it is judged whether or not the time has continued for 1 second or more.

In step 37, the differential limiting torque TΔV
Filter processing is performed on the differential limited torque filter value T
It is referred to as F.

In this filtering process, the differential limiting torque TΔV one control cycle before is stored, and the limiter is set so that the difference from the differential limiting torque TΔV this time does not exceed a predetermined difference on the increasing side and the decreasing side. It is done by applying.

In step 38, the differential limiting torque filter value TF obtained in step 37 is set as the target differential limiting torque T ^* .

In step 39, the differential limiting torque TΔV
Is greater than or equal to the differential limiting torque maximum value Tmax. The initial value of the differential limiting torque maximum value Tmax is Tma.
When x = 0, and when the control is switched to the control from step 43 to step 37 during the control, Tmax = 0 is reset.

In step 40, the differential limiting torque TΔV satisfying TΔV ≧ Tmax is the differential limiting torque maximum value Tma.
Set as x.

In step 41, the maximum differential torque limit value Tmax obtained in step 40 is the target differential torque limit T
Set as ^* .

The above steps 36 to 41 and steps 43 to 48 correspond to the target differential limiting torque setting means e.

In step 42, the control current ILSD for obtaining the target differential limiting torque T ^* set in step 38 or 41 is output to the LSD control valve 12 (corresponding to the differential limiting torque control means f).

[Driving above the set vehicle speed x] Set vehicle speed x
When traveling as described above, in the flowchart of FIG. 3, step 30 → step 31 → step 32 → step 33 →
The flow proceeds in the order of step 34 → step 35 → step 36 → step 43 → step 37 → step 38 → step 42, and the filtered differential limiting torque TΔ
Differential limit torque control is performed in proportion to the difference between the left and right rear wheel speeds at which V is obtained.

Therefore, for example, when the vehicle runs on the left / right split μ road that satisfies the condition of the set vehicle speed x or more, the differential limiting torque between the left and right rear wheels 5, 6 is generated based on the occurrence of the control left / right rear wheel speed difference ΔVRR. Is given, the engine driving torque to the rear wheels on the high μ road side is increased, and high traction performance is exhibited.

Further, when the vehicle travels at the set vehicle speed x or higher, the differential limiting torque TΔV is limited by the increasing side and the decreasing side, so that the sudden increase and the sudden decrease of the differential limiting torque are suppressed. In addition, a sudden change in vehicle behavior due to a sudden increase or decrease in the differential limiting torque is prevented during traveling on the left and right split μ roads.

[Starting at a speed lower than the set vehicle speed x] When the vehicle starts at a speed lower than the set vehicle speed x, the control left / right rear wheel speed difference ΔVRR is small and does not satisfy the condition of step 45. Therefore, in the flowchart of FIG. Step 31 → Step 32 → Step 33 → Step 34 → Step 35 → Step 36 → Step 44 → Step 45 → Step 3
The flow goes from 7 to step 38 to step 42,
Differential limit torque control is performed in proportion to the left and right rear wheel speed difference that can obtain the filtered differential limit torque TΔV.

Therefore, for example, at the time of steering start in which the control left / right rear wheel speed difference ΔVRR is small, the differential limiting torque is generated between the left / right rear wheels 5, 6 based on the control left / right rear wheel speed difference ΔVRR. As will be described later, the tight corner braking phenomenon that occurs in the case of turning start when a large differential limiting torque is applied by peak hold is prevented, and a smooth start is ensured.

[When the stack escapes below the set vehicle speed x] When the stack escapes when the vehicle speed is below the set vehicle speed x, step 30 → step 31 → step 3 in the flowchart of FIG.
2 → step 33 → step 34 → step 35 → step 36 → step 44 → step 45 → step 46
The flow proceeds in the order of step 39 → step 40 → step 41 → step 42, and the differential limiting torque maximum value Tmax of the differential limiting torque TΔV proportional to the left and right rear wheel speed difference is set as the target differential limiting torque T ^*. Differential limiting torque control is performed by peak hold, which is maintained until x.

Therefore, the peak hold flag PHF is set to PH under two conditions of the vehicle speed condition and the left and right rear wheel speed difference condition.
Since F = 0 is rewritten to PHF = 1, the peak hold control is performed only when the vehicle is stuck. For example, the peak hold control is also performed when the vehicle is started as in the case where the determination is made only based on the vehicle speed condition. Is prevented.

Then, for example, as shown in FIG. 5, when the left rear wheel 5 of the left and right rear wheels 5, 6 is in the stack, the differential limiting torque based on the occurrence of the control left / right rear wheel speed difference ΔVRR. The maximum value Tmax is kept high until the vehicle starts to move completely and the vehicle body speed VF increases to the set vehicle speed x, so that the increase in the engine drive torque to the right rear wheel 6 is ensured until the vehicle completely escapes from the stack and is high. The stack escape performance is demonstrated.

[When Stopping from Evacuation from Stack] When the vehicle is stopped and then started to travel instead of directly starting from the stack escape, steps 47 and 48 are performed.
In, the state where the wheel speed of each four wheels is zero is 1 sec.
It is judged that it is the time to stop after completing the escape from the stack depending on whether it is continuous for a while.
The routine proceeds from step 48 to step 43, and the peak hold flag PHF is rewritten from PHF = 1 to PHF = 0.

As a result, the peak hold function is released early without waiting for the vehicle speed condition in step 36 to be satisfied, and thereafter the differential limitation is released to ensure a smooth start. become.

[When traveling from stack escape] When the vehicle speed becomes equal to or higher than the set vehicle speed x after the stack escape, the flow proceeds from step 36 to step 43 → step 37 → step 38, and the maximum differential limiting torque that has been given up to that point is reached. The value Tmax is switched to the differential limiting torque TΔV proportional to the left / right rear wheel speed difference, and there is a risk that the vehicle behavior will change suddenly due to a large difference in torque.

However, in step 37, the differential limiting torque TΔV (Tmax in this case) one control cycle before is obtained.
If the difference between the differential limiting torque TΔV proportional to the left / right rear wheel speed difference this time is greater than or equal to a predetermined value, the contents are filtered, so that even if there is a large difference in the commanded differential limiting torque, The torque is controlled to be gradually reduced in accordance with the filter processing, and sudden changes in vehicle behavior are prevented when traveling from the stack escape.

Next, the effect will be described.

(1) In the differential limiting torque control device for electronically controlling the differential limiting torque between the left and right rear wheels 5, 6 based on the left and right rear wheel speed difference information, when the vehicle body speed VF is equal to or higher than the set vehicle speed x, or When the vehicle body speed VF is less than the set vehicle speed x and the control left / right rear wheel speed difference ΔVRR is less than the set left / right rear wheel speed difference y, the differential limiting torque TΔ determined according to the control left / right rear wheel speed difference ΔVRR
V is the target differential limiting torque T ^* as it is, and the vehicle speed VF
Is less than the set vehicle speed X and the control left / right rear wheel speed difference ΔVRR is greater than or equal to the set left / right rear wheel speed difference y, the maximum value Tmax of the differential limiting torque TΔV determined according to the control left / right rear wheel speed difference ΔVRR
The target differential limiting torque T ^* is set as the device that performs the stack-compatible control that maintains the vehicle speed x until the set vehicle speed x is reached. Therefore, it is possible to reliably escape the stack while ensuring the left / right rear wheel speed difference proportional control and smooth steering start. You can

(2) As a condition for ending the peak hold control, in addition to the vehicle speed condition in step 36, the continuous wheel speed zero condition in steps 47 and 48 is added. In the case of entering, the peak hold control can be released early and the normal left / right rear wheel speed difference proportional control can be restored.

(3) In performing the differential limiting torque control proportional to the left / right rear wheel speed difference, the differential limiting torque TΔV obtained by the calculation is filtered, and the differential limiting torque TΔV one control cycle before and this time The limiter is set so that the difference between the differential limiting torque TΔV and the differential limiting torque TΔV does not exceed a predetermined difference on the increasing side and the decreasing side. This causes a sudden increase or decrease in the differential limiting torque during traveling on the left and right split μ roads. It is possible to prevent a sudden change in the vehicle behavior, and also to prevent a sudden change in the vehicle behavior due to a sudden decrease in the differential limiting torque when the vehicle starts traveling after exiting the stack.

Although the embodiments have been described above with reference to the drawings, the specific configuration is not limited to the embodiments, and modifications and additions within the scope of the present invention are included in the present invention. Be done.

For example, in the embodiment, the example in which the differential limiting torque is applied by the hydraulic multi-plate clutch has been shown, but if the differential limiting torque can be variably controlled by the control command from the outside, the electromagnetic clutch. And so on.

In the embodiment, the example in which the start vehicle speed condition and the end vehicle speed condition of the stack-corresponding control are given at the same set vehicle speed is shown. You may make it return to the control corresponding to a drive wheel speed difference.

[0068]

As described above, according to the present invention, the vehicle speed is set in the differential limiting torque control device that electronically controls the differential limiting torque between the left and right driving wheels based on the left and right driving wheel speed difference information. When the vehicle speed is equal to or more than the vehicle speed or less than the set vehicle speed and the left / right drive wheel speed difference is smaller than a predetermined value, the differential limit torque determined according to the detected value of the left / right drive wheel speed difference is directly set as the target differential limit torque and the vehicle speed is set to the set vehicle speed. When the difference between the left and right drive wheel speeds is less than a predetermined value even if it is less than 1, the maximum value among the differential limit torques determined according to the detected value of the left and right drive wheel speeds is set as the target differential limit torque. Since the device is provided with the target differential limiting torque setting means for maintaining the vehicle speed, the effect of being able to reliably escape the stack while ensuring the left-right drive wheel speed difference proportional control and smooth steering start is obtained. From That.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a differential limiting torque control device of the present invention.

FIG. 2 is an overall system diagram of a rear wheel drive vehicle to which the differential limiting torque control device of the embodiment is applied.

FIG. 3 is a flowchart showing a flow of a differential limiting torque control operation process performed by the active LSD controller of the embodiment apparatus.

FIG. 4 is a differential limiting torque characteristic diagram proportional to the left / right rear wheel speed difference in the embodiment apparatus.

FIG. 5 is an operation explanatory view showing a stack escape state in the embodiment apparatus.

[Explanation of symbols]

 a differential limiting torque applying means b left and right drive wheel speed difference detecting means c vehicle speed detecting means d differential limiting torque determining means e target differential limiting torque setting means f differential limiting torque controlling means

Claims (1)

[Claims] 1. A differential limiting torque applying means, which is provided between the left and right driving wheels, for applying a differential limiting torque according to a control command from the outside, and a left and right driving wheel speed difference for detecting a left and right driving wheel speed difference. Detection means, vehicle speed detection means for detecting the vehicle speed, differential limit torque determination means for determining the differential limit torque according to the left / right drive wheel speed difference detection value, and vehicle speed above or below the set vehicle speed or below or below the set vehicle speed. When the left-right drive wheel speed difference is smaller than a predetermined value, the differential limit torque determined according to the left-right drive wheel speed difference detection value is directly used as the target differential limit torque, and the vehicle speed is less than the set vehicle speed and the left-right drive wheel speed is set. When the difference is equal to or more than the predetermined value even once, the target differential that maintains the maximum value of the differential limit torques determined according to the detected value of the left and right drive wheel speeds as the target differential limit torque until the set vehicle speed is reached. Limit torque setting means, the eye Differential limiting torque control apparatus characterized by comprising a differential limiting torque control means for outputting a control command differential limiting torque is obtained in the differential limiting torque applying means.