JPH0374222A - Distribution control device for drive force - Google Patents

Abstract

PURPOSE:To improve the stability of a vehicle by prohibiting control of a rear differential clutch, when the ratio of engine output torque to rear transmitting torque is under a prescribed threshold value, or when the ratio is not under the prescribed threshold value at deceleration. CONSTITUTION:A control means 10 computes the output torque T of an engine 20 from the output of an engine speed sensor 11, a throttle opening sensor 16, and rotating speed sensors 5-8 of four wheels, and computes the rear transmitting torque TOUT by controlling a center clutch 1. When the ratio T/TOUT is under a prescribed threshold value To, or when the ratio is over the threshold value To at deceleration, control of a rear differential clutch 2 is prohibited. Therefore, a differential limiting device is actuated against control of the clutch 2 in the running condition at usual acceleration, and at deceleration actuation the differential limiting device is prohibited and only a rear differential gear 24 is actuated, hereby, respective wheels output torque according to the road surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a driving force distribution control device that can vary torque distribution between left and right rear wheels.

[Prior Art] As a technique related to this type of driving force distribution control device, there is a technique disclosed in Japanese Patent Application Laid-Open No. 1784-37.

This technology includes vehicle speed sensors, steering angle sensors, braking sensors,
Even if the driver puts the rear differential gear into lock mode based on signals from the speed difference sensor, kickdown sensor, etc., depending on the conditions, it can be switched to unlock mode to prevent shocks, improve durability, and provide tight corner braking. This is to prevent the decrease.

[Problem to be solved by the invention] However, when the driver selects the automatic control mode, depending on the conditions, the mode is switched to the unlock mode, which prevents shock generation, improves durability, and reduces tight corner braking. No function was selected to prevent this. However, in general, the road surface does not always have a uniform μ on the left and right sides, and a rotation difference occurs between the left and right wheels. In such a case, if the differential of the rear differential is limited, the vehicle may sway from side to side. This is particularly noticeable when the road surface μ is low on one side or in some places, and in such cases it becomes almost difficult to make corrections using the steering wheel.

In addition, in 4WD vehicles, when torque is not transmitted to the rear wheels, or when only a small amount of torque is transmitted,
It is pointless to limit the differential movement of the rear differential, and this results in repeated unnecessary control, which is disadvantageous in terms of the durability of the differential limiting device.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a driving force distribution control device that prohibits meaningless control of the differential clutch during deceleration in a vehicle having a variable torque clutch in the differential.

[Means for Solving the Problems] The driving force distribution control device according to the present invention uses the output of an engine rotation speed sensor, the output of a throttle opening sensor, and the output of a rotation detection sensor that detects the rotation speed of each of the four wheels. ,
The engine output torque is calculated, and the rear transmission torque is calculated by controlling a center clutch arranged between the front wheels and the rear wheels that adjusts the rear transmission torque, and the ratio between the engine output torque and the rear transmission torque is calculated. is below a predetermined threshold, when the ratio between the engine output torque and the rear transmission torque is not below a predetermined threshold, and during deceleration, control of the rear differential clutch is prohibited.

[Operations] In the present invention, engine output torque is calculated by an engine rotation speed sensor, a throttle opening sensor, and four wheel rotation detection sensors, and the rear transmission torque is calculated by using an engine rotation speed sensor, a throttle opening sensor, and four wheel rotation detection sensors. Rear transmission torque is calculated based on the control pressure of the center clutch to be adjusted, and when the ratio of engine output torque and rear transmission torque is below a predetermined threshold, At least when the vehicle is decelerating, the control of the rear differential clutch is stopped, and the prohibition of rear differential clutch control is not prohibited, which would be meaningless.

[Embodiment] Hereinafter, a driving force distribution control device according to an embodiment of the present invention will be described.

FIG. 1 is an overall configuration diagram of a driving force distribution control device according to an embodiment of the present invention, and FIG. 2 is a hydraulic system diagram of the driving force distribution control device according to an embodiment of the present invention.

In the figure, the driving force of an engine 20 mounted on an automobile is transmitted to the front wheels via a transmission 21 and a front wheel differential gear 22. Further, the driving force of the engine 20 is transmitted to the rear wheels via the transmission 21 and the center clutch 1 consisting of a variable torque clutch (friction multi-disc clutch) that operates as a driving force distribution means controlled by the action of the control valve 3. be done. That is, the driving force of the engine 20 is transferred to the transmission 21.
, a center clutch 1 , a rear differential clutch 2 consisting of a variable torque clutch that operates as a driving force distribution means controlled by the functions of a control valve 4 , and a rear wheel differential gear 24 , and then transmitted to the rear wheels. and,
The front wheel differential gear 22 controls the distribution of driving force between the left and right front wheels, and the center clutch 1, the rear differential clutch 2, and the rear differential gear 24 control the distribution of driving force between the left and right rear wheels.

In addition, the control valve 3 and the control valve 4 are as shown in FIG.
The center clutch is controlled by the control means 10 and adjusts the amount of oil in the oil tank fed to the clutch release cylinder 14 and the clutch release cylinder 15 via the pump 12 and regulator 13 by adjusting the amount of return to the oil tank. 1 and rear differential clutch 2 set the torque distribution to the wheels.

The rotational speed of the four wheels is detected by rotation detection sensors 5, 6, and 7°8, and the steering angle (rotation angle) of the steering wheel is detected by a steering angle detection sensor 9.
A rotation speed of 0 is detected by the engine rotation speed sensor 11.

The throttle opening is determined by the throttle opening sensor 16.
has been detected in Each rotation detection sensor 5.6. 7.
8 and steering angle detection sensor 9, engine rotation speed sensor 11
The output of the throttle opening sensor 16 is input to the control means 10.

The control means 10 includes the rotation detection sensor 5, 6°7.8
In response to the outputs of the steering angle detection sensor 9, engine speed sensor 11, and throttle opening sensor 16, the center clutch 1 and rear differential clutch 2, which distribute torque between the front and rear wheels, are controlled as follows.

FIG. 3 is a flowchart for controlling the driving force distribution control device according to an embodiment of the present invention.

4 to 8 are explanatory diagrams of characteristic maps stored in the control means 10 included in the driving force distribution control device of this embodiment. Figure 4 shows the rear differential clutch output oil pressure Po, P for the rear wheel left-right rotation difference 11 N r.
This is a map for setting r' characteristics, and FIG. 5 is a map for setting rear differential clutch output oil pressure Pr characteristics with respect to time t. In addition, Fig. 6 is a map for setting the center clutch output oil pressure Pc characteristic with respect to the excitation current i, and Fig. 7
The figure is a map for setting the rear transmission torque T out characteristic with respect to the center clutch output oil pressure Pc, and FIG. 8 is the map for setting the rear differential clutch output oil pressure Pr characteristic with respect to time t.

The control means 10 executes a predetermined driving force distribution control (not shown), and this routine is executed every predetermined time, for example, every two
It is called every Qms.

First, when this routine is called every predetermined time,
In step S1, the engine rotation speed sensor 11 and the rotation detection sensor 5.6. 7.8 and throttle opening sensor 11
, engine rotation speed NEC, wheel speed of 4 wheels VwL - Vw
4 and throttle opening θ. In step S2, the estimated actual vehicle speed control V is calculated from the wheel speeds Vwl to Vw4 of the four wheels,
The engine output torque T is calculated from the read engine speed NEC and throttle opening θ. That is, the engine output torque T is T=f (NEC, θ, V
).

Next, in step S3, the rear transmission torque Tout is determined from the target output oil pressure Pc that controls the center clutch 1 that is currently being output. As shown in the characteristic diagram of FIG. 6, this rear transmission torque Tout is determined by the fact that the excitation current i that excites the center clutch 1 during the current drive force distribution control is proportional to the target output oil pressure Pc that controls the center clutch 1. It is calculated from The target output oil pressure Pc that controls the center clutch 1 in step S4 is proportional to the torque that transmits energy to the rear wheels via the center clutch 1, as shown in the characteristic diagram of FIG. 7, and Tout = f'' (Pc). Since there is the following relationship, the rear transmission torque Tout is determined from this target output oil pressure Pc.

In step S5, it is determined whether the ratio Tout/T between the engine output l/lux T and the rear transmission torque Tout is less than or equal to a predetermined threshold To, and the ratio Tout/T between the engine output torque T and the rear transmission torque Tout is determined to be a predetermined value. When it is greater than the threshold value To, it is determined in step S6 whether the vehicle is currently decelerating based on the progress of the estimated actual vehicle speed limit V obtained from the four wheel speeds Vwl to Vw4.

If it is determined in step S6 that deceleration is not currently occurring, it is not necessary to set the upper limit output oil pressure Po of the rear differential clutch 2 to an output oil pressure for torque transmission that is larger than that for transmitting the rear transmission torque Tout, so step S7
The upper limit output oil pressure Po of the rear differential clutch 2 that can transmit an operating torque equivalent to the rear transmission torque Tout currently transmitted to the rear wheels is determined. In this embodiment, the second-limit output oil pressure Po is calculated from the rear transmission torque Tout. That is, the upper limit output oil pressure Po is Po=f(Tout)-f(Pc).

In step S8, the target output oil pressure Pr' of the differential clutch 2 is determined from the map shown in FIG. To do this, first, calculate the rear wheel left and right rotation difference JNr as dNr =
1 Vw3-Vw41, and using it, the sequential target output oil pressure Pr' to be sequentially output from the rear differential clutch 2 is determined. In order to prevent the target output oil pressure Pr' from changing rapidly in step S,
As shown in FIG. 5, the oil pressure gradient KL is determined according to the difference between the previous target output oil pressure Pro and the current sequential target output oil pressure Pr'.
The output is changed so that the effect is gradually transmitted to the vehicle.

-4, in step S5, the ratio Tout/T of the engine output torque T and the rear transmission torque Tout is set to a predetermined threshold To
When it is determined that the engine speed is below, or when it is determined in step S6 that deceleration is currently occurring, the target output oil pressure Pr is sequentially set to Pr=O in order to prohibit the operation restriction in step S10.

However, if Pr = 0 suddenly, the running feeling of the vehicle will not be good, so as shown in Fig. 8, the oil pressure is adjusted according to the difference between the previous sequential target output oil pressure Pro and the current sequential target output oil pressure Pr = 0. The gradient is increased by 2 and the target output oil pressure Pr is gradually set to 0. Then, in step 811, the excitation current i corresponding to the current target output oil pressure Pr is sequentially output.

In this way, the driving force distribution control device of this embodiment has the engine rotation speed sensor 11 that detects the rotation speed of the engine 20.
, a throttle opening sensor 16 that detects the throttle opening, and a rotation detection sensor 5 that detects the rotational speed of each of the four wheels.
, 6, 7.8, a center clutch 1 arranged between the engine 20 and the rear wheels, which adjusts the rear transmission torque, and a rear differential gear 24 and rear differential clutch, which adjusts the drive torque of the rear wheels. 2, the engine output torque T is calculated by the engine rotation speed sensor 11, the throttle opening sensor 16, and the four wheel rotation detection sensors 5, 6, 7.8, and the rear transmission torque Tout is calculated by controlling the center clutch 1. When the ratio between the engine output torque T and the rear transmission torque Tout is less than or equal to a predetermined threshold TO, or when the ratio between the engine output torque T and the rear transmission torque Tout is greater than the predetermined threshold To. The vehicle is equipped with a control means 10 that prohibits control of the rear differential clutch 2 during deceleration.

Therefore, the differential limiting device operates to control the rear differential clutch 2 during normal speed-up driving conditions, and during deceleration, the differential limiting device is prohibited from operating and operates only as the rear differential gear 24. Therefore, even when driving at deceleration on a road where uniform μ cannot be obtained on the left and right sides of the road surface, each wheel outputs torque according to the road surface, and the rear differential gear does not limit the differential. There is no chance of being dumped. Particularly, even when the road surface μ is low on one side or in some places, it is possible to significantly prevent the vehicle from wobbling and improve the stability of the vehicle. In particular, in 4WD vehicles, engine output torque T and rear transmission torque Tou
According to the ratio to t, when the rear transmission torque Tout is small, the operation of the differential limiting device is prohibited, thereby avoiding unnecessary operation of the differential limiting device and protecting the differential limiting device.

By the way, in the above embodiment, the center clutch 1 and the rear differential clutch 2 are used, but when the present invention is implemented, it can also be used to control the operation limiting device of a 2WD rear differential.

[Effects of the Invention] As described above, the driving force distribution control device of this embodiment includes an engine rotation speed sensor that detects the engine rotation speed, a throttle opening sensor that detects the throttle opening degree, and four
The engine output torque is calculated by a rotation detection sensor that detects the rotation speed of each wheel, and the rear transmission torque is calculated by controlling the center clutch that adjusts the rear transmission l and torque, which is installed between the engine and the rear wheels. is calculated, and when the ratio of the engine output torque and rear transmission torque is less than a predetermined threshold, or when the ratio of the engine output torque and rear transmission torque is not less than a predetermined threshold but the vehicle is decelerating, the rear differential is This prohibits clutch control.

Therefore, under normal driving conditions, the differential limiting device operates,
During deceleration, the differential limiting device is prohibited from operating and operates as a normal differential gear.
The stability of the vehicle can be improved.

In particular, in 4WD vehicles, unnecessary operation of the differential limiting device is avoided by prohibiting its operation when the rear transmitted torque is small, depending on the ratio between the engine output l/lux and the rear transmitted torque. The device can be protected.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a driving force distribution control device according to an embodiment of the present invention, FIG. 2 is a hydraulic system diagram of a driving force distribution control device according to an embodiment of the present invention, and FIG. 3 is a diagram of the hydraulic system of a driving force distribution control device according to an embodiment of the present invention. A flowchart for controlling the driving force distribution control device of one embodiment, and FIGS. 4 to 8 are explanatory diagrams of characteristic maps stored in the control means included in the driving force distribution control device of this embodiment, Figure 4 is a map for setting output oil pressure characteristics with respect to rear wheel left and right rotation difference.
Fig. 5 is a map for setting the output oil pressure characteristics with respect to time, Fig. 6 is a map for setting the output oil pressure characteristics with respect to exciting current,
FIG. 7 is a map for setting rear transmission torque characteristics with respect to output oil pressure, and FIG. 8 is a map for setting output oil pressure characteristics with respect to time. In the figure, 1: Center clutch 2: Rear differential clutch 5.6.7.3: Rotation detection sensor 5 10: Control means 11: Engine rotation speed sensor 16: Throttle opening detection sensor 24: Rear differential gear. In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Between the engine rotation speed sensor that detects the engine rotation speed, the throttle opening sensor that detects the throttle opening degree, the rotation detection sensor that detects the rotation speed of each of the four wheels, and the engine and the rear wheels. A center clutch that adjusts the rear transmission torque, a rear differential gear and rear differential clutch that adjusts the rear wheel drive torque, and the engine rotation speed sensor, throttle opening sensor, and four wheel rotation detection sensors. Calculate engine output torque; Calculate rear transmission torque by the center clutch control; When the ratio of the engine output torque to the rear transmission torque is less than or equal to a predetermined threshold, the ratio of the engine output torque to the rear transmission torque is 1. A driving force distribution control device, comprising: control means for prohibiting control of a rear differential clutch when the pressure is not below a predetermined threshold value and during deceleration.