JP2701308B2 - Differential limit torque control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a differential limiting torque control device that variably controls a differential limiting torque between left and right driving wheels by externally controlling a clutch engagement force.

(Prior Art) Conventionally, as a differential limiting torque control device, a hydraulic multi-plate clutch is used as a differential limiting clutch, and the clutch engagement pressure is variably controlled by an external hydraulic control means, so that the differential limiting torque is controlled. There are known devices for controlling (for example, JP-A-62-103226, JP-A-62-103227, etc.).

In that case, in order to obtain sufficient drive torque during turning,
It is preferable to increase the differential limiting torque, and when the differential limiting torque is increased, power slide traveling can be performed in a high lateral acceleration state.

(Problems to be Solved by the Invention) However, in such a conventional differential limiting torque control device, for example, control is performed such that the larger the turning radius and the greater the lateral acceleration, the greater the differential limiting torque. In this case, although the driving torque at the time of turning can be sufficiently obtained and the turning drive performance can be improved, in a vehicle that can output a larger driving torque even at a high speed, if the driving torque increases during a high turning turn at a large turning radius, In addition, a problem arises in that the vehicle easily spins due to an increase in the spin moment based on the application of the differential limiting torque.

In other words, when the vehicle is accelerated by changing the longitudinal acceleration variously from a steady circular turning with a constant turning radius, the vehicle with differential limitation (FR
FIG. 4 shows a comparison of the type of yaw moment generated by the vehicle) based on the difference in turning radius.

According to this comparison characteristic diagram, when the differential limiting torque is applied, when the turning radius is small, the application of the differential limiting torque contributes to an increase in the driving torque on the turning inner wheel side and easily acts on the understeer side. When the radius is large, it can be seen that the application of the differential limiting torque contributes to an increase in the driving torque on the turning outer wheel side and easily acts on the oversteer side. However, since the vehicle speed is higher as the turning radius is larger, the vehicle is in a state where it is difficult to generate a further driving torque (for example, only about 0.1 G is output at 100 mR), and usually there is no problem.

However, in a vehicle equipped with a high-output engine, when the longitudinal acceleration is increased due to an increase in driving torque, a situation occurs in which a vehicle spin is likely to occur.

(Means for Solving the Problems) An object of the present invention is to provide a differential limiting torque control device that achieves both improvement of driving performance during turning and prevention of vehicle spin during large turning radius turning acceleration. It was made as.

In order to achieve the above object, the differential limiting torque control device of the present invention employs a differential limiting clutch 1 to control the differential force between the left and right driving wheels 2 and 3 as shown in the conceptual diagram of the claim. A vehicle provided with a differential limiting torque control means 4 capable of variably controlling a limiting torque and applying a differential limiting torque to improve driving performance even during turning, wherein the turning radius of the vehicle is large. A turning radius detecting means 5 for detecting the turning force and a longitudinal acceleration detecting means 6 for detecting a value corresponding to the longitudinal acceleration are provided. It is characterized in that the differential limiting torque is set to a target value, and the differential limiting torque is set to a smaller value as the value corresponding to the longitudinal acceleration on the acceleration side is larger, so as to perform control for weakening the differential limiting torque.

(Operation) At the time of turning, the differential limiting torque control unit 4 basically performs control for applying a differential limiting torque according to a turning radius, a lateral acceleration, and the like.

However, when turning with a large turning radius, the turning radius of which is large from the turning radius detecting means 5, the differential limiting torque control means 4 determines that the larger the turning radius is, the more the differential is determined according to the longitudinal acceleration equivalent value. Control for weakening the limit torque is performed.

Therefore, by applying the differential limiting torque during turning,
A large amount of drive torque is distributed to the drive wheels to improve drive performance. In addition, by monitoring the turning radius and the longitudinal acceleration equivalent value, the differential limit torque reduction correction control is performed as described above, thereby obtaining the differential limit torque. When a large turning radius is accelerated in a state where the vehicle is given a spin, generation of a spin moment accompanying an increase in longitudinal acceleration is suppressed, and vehicle spin can be prevented.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

 First, the configuration will be described.

The rear-wheel drive vehicle-based four-wheel drive vehicle to which the differential limiting torque control device of the first embodiment is applied, as shown in FIG.
Engine 10, transmission 11, transfer device
12, rear propeller shaft 13, rear differential
14, rear drive shafts 15,16, rear wheels 17,18, front propeller shaft 19, front differential 20,
Front drive shafts 21 and 22 and front wheels 23 and 24 are provided.

As the transfer device 12, a part-time 4WD
Equipment using the selective method that realizes
An electronically controlled torque split system that realizes 4WD and a viscous coupling system are installed.

The rear differential 14 has a built-in differential limiting clutch 25 (such as a wet multi-plate friction clutch) similar to the above-described known technology.

The differential limiting torque control for variably controlling the differential limiting torque of the left and right rear wheels 17 and 18 by controlling the engagement force of the differential limiting clutch 25 controls the hydraulic control valve 30 by applying pressurized oil from an external hydraulic source. This is performed by setting the clutch engagement pressure to a predetermined value via the differential clutch 25. The external hydraulic pressure source includes a pump 31, a motor 32, an accumulator 33, a pressure switch 34, and a reservoir 35.

A predetermined valve drive signal (i) is supplied to the hydraulic control valve 30.
Is an electronic control circuit including a storage circuit (RAM, ROM), an arithmetic processing circuit (CPU), and the like.
The controller 40 includes a front right wheel speed sensor 41, a front left wheel speed sensor 42, a longitudinal acceleration sensor 43, and an accelerator opening sensor 44.
, The detection signals NFR, NFL, Xg, A are input.

The controller 40 also receives detection signals from other sensors 45 such as a lateral acceleration sensor, a right rear wheel speed sensor, and a left rear wheel speed sensor.

 Next, the operation will be described.

First, the flow of the differential limiting control operation in the controller 40 will be described with reference to the flowchart shown in FIG.

In step 100, the right front wheel speed NFR and the left front wheel speed NFL are read.

In step 101, the right front wheel speed NFR and the left front wheel speed NF
The turning radius R is obtained by calculation from L. still,
The arithmetic expression is as follows.

Where, tr; tread width ΔV; left / right rotation speed difference ΔV = | NFR−NFL | V; vehicle speed V = (NFR + NFL) / 2 In step 102, the right front wheel speed NFR and the left front wheel speed NFL
Thus, the lateral acceleration Yg is obtained by calculation. The arithmetic expression is as follows.

In step 103, the turning radius R and the lateral acceleration Yg are
The differential limiting torque target value ΔT ₁ is calculated by using the preset differential limiting torque target value map.

The differential limiting torque target value map corresponds to the step shown in FIG.
As described in 103 in the frame, turning radius as R increases, also as the lateral acceleration Yg increases, a higher differential limiting torque target value [Delta] T ₁ is set so as to obtain.

In step 104, the longitudinal acceleration Xg is read from the longitudinal acceleration sensor 43.

In step 105, the turning radius R in step 101, the differential limiting torque target value ΔT _{1 in} step 103,
Based on the longitudinal acceleration Xg at 104 and the preset final differential limiting torque target value map, a final differential limiting torque target value ΔT ^* is calculated.

Note that the final differential limiting torque target value map starts from the differential limiting torque target value ΔT ₁ and is small when the turning radius R is small, as described in the frame of step 105 in FIG. Regardless of the increase in the longitudinal acceleration Xg, the decrease rate of the target value is represented by a characteristic line with zero or small, and as the turning radius R increases, the decrease rate of the target value is represented by a large characteristic line with an increase in the longitudinal acceleration Xg. When the radius R is large and the longitudinal acceleration Xg is large, the final differential limiting torque target value ΔT ^* is compared with the differential limiting torque target value ΔT ₁ ^.
Is set to be the smallest.

In step 106, a valve drive signal (i) for obtaining the value of the final differential torque target value ΔT ^* obtained in step 105 is output from the controller 40 to the hydraulic control valve 30.

 Next, the operation during traveling will be described.

(B) When turning with a small turning radius When turning with a small turning radius, the controller 40 sets the differential limiting torque target value Δ in accordance with the turning radius R and the lateral acceleration Yg.
When T ₁ is determined (step 103), regardless occurs whether the longitudinal acceleration Xg, the differential limiting torque target value [Delta] T ₁
Of the final differential limiting torque target value ΔT
^It is set as ^* (step 105).

Accordingly, as the turning radius R is larger and the lateral acceleration Yg is larger, a control for applying a higher differential limiting torque is performed, so that the driving torque due to the differential rotation of the left and right rear wheels 17, 18 during turning is reduced. The outflow is prevented, and the driving performance is improved.

In addition, even during high-speed straight running where the turning radius R is infinite, a high differential limiting torque is applied, so that straight running stability is enhanced when a disturbance such as a cross wind acts.

Further, since a high differential limiting torque is applied even at the time of turning at a high lateral acceleration, power sliding traveling is also possible.

(B) When turning with a large turning radius When turning with a large turning radius, the controller 40 sets the differential limiting torque target value Δ in accordance with the turning radius R and the lateral acceleration Yg.
When T ₁ is determined (step 103), the larger the turning radius R, and as the longitudinal acceleration Xg is larger, the value subtracted by the large decline from the value of the differential limiting torque target value [Delta] T ₁ final It is set as the differential limiting torque target value ΔT ^* (step 105).

Therefore, the larger the turning radius R, the greater the longitudinal acceleration
Since the control for weakening the differential limiting torque according to Xg is performed, the occurrence of a spin moment due to an increase in the longitudinal acceleration Xg during a large turning radius turning acceleration with the differential limiting torque applied is suppressed, and the vehicle Spin is prevented.

In other words, in the yaw moment characteristic shown in FIG. 4, when turning with a small turning radius of about 30 mR or a turning radius of only 0.1 G at a large turning radius of 100 mR, the spin moment is also small, which is not a problem. A vehicle equipped with an output engine.
When the speed increases from 2G to 0.3G, the spin moment also increases according to the longitudinal acceleration Xg, and a situation arises in which vehicle spin is likely to occur.

However, at the time of turning with a large turning radius, control is performed such that the differential limiting torque is weakened as the longitudinal acceleration Xg increases. The amount of increase in the spin moment with respect to the increase in Xg is reduced, and the increase in the spin moment is reduced from the dotted line characteristic to the one-dot chain line characteristic, thereby preventing the occurrence of vehicle spin.

As described above, the following effects can be obtained in the differential limiting torque control device of the first embodiment.

Based on the differential limiting control according to the turning radius R and the lateral acceleration Yg, the larger the turning radius R, the longer the longitudinal acceleration
Control that weakens the differential limiting torque according to Xg is effective for vehicles equipped with a large output engine, improving drive performance during turning and preventing vehicle spin during large turning radius turning acceleration. Can be achieved.

Since the differential limiting control base is a control for applying a differential limiting torque in accordance with the turning radius R and the lateral acceleration Yg, high-speed straight-running stability is improved on a highway, and power sliding traveling is enabled.

Next, a differential limiting torque control device according to a second embodiment will be described.

The device of the second embodiment detects the longitudinal acceleration Xg,
This is an example in which the value of the accelerator opening A is detected by estimation as a longitudinal acceleration equivalent value.

Accordingly, as a flow of the differential limiting control operation, as shown in FIG. 5, the accelerator opening A is read in place of the longitudinal acceleration Xg in step 107, and the accelerator opening is read in place of the longitudinal acceleration Xg in step 108. The final differential limiting torque target value ΔT ^* is obtained using the degree A as a parameter.

Note that the configuration of the second embodiment device and other functions and effects are the same as those of the first embodiment device, and thus description thereof will be omitted.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and any change or the like without departing from the gist of the present invention is included in the present invention.

For example, in the embodiment, an example in which the turning radius R and the lateral acceleration Yg are obtained by calculation based on the left and right front wheel speeds has been described.
The detection may be performed using a steering angle sensor, a vehicle speed sensor, a lateral acceleration sensor, or the like.

Further, in the embodiment, as an example of the detection of the longitudinal acceleration Xg, the example of the direct detection and the example of the indirect detection by the accelerator opening A have been described, but the engine intake torque and the throttle opening which can detect the driving torque of the engine are used. The longitudinal acceleration Xg may be estimated, and further, the longitudinal acceleration Xg may be detected including an accelerator opening change rate, a throttle opening change rate, and the like that affect the occurrence of the vehicle longitudinal acceleration Xg.

(Effects of the Invention) As described above, in the differential limiting torque control device of the present invention, the differential limiting torque control means sets a higher differential limiting torque target value as the turning radius is larger. ,
Since the differential limiting torque target value is controlled so as to decrease the differential limiting torque by setting the target value to be smaller as the value corresponding to the longitudinal acceleration on the acceleration side is larger, the driving performance at the time of turning is improved and the turning radius is increased at the time of turning acceleration. Thus, an effect of achieving both of the above and the prevention of vehicle spin can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a claim showing a differential limiting torque control device of the present invention, and FIG. 2 shows a rear wheel drive-based four-wheel drive vehicle to which the differential limiting torque control device of the first embodiment is applied. FIG. 3 is a flowchart showing the flow of the differential limiting operation in the controller of the first embodiment. FIG. 4 is a yaw moment characteristic diagram acting on the vehicle when the turning radius is changed.
FIG. 5 is a flowchart showing the flow of the differential limiting operation in the controller of the second embodiment. DESCRIPTION OF SYMBOLS 1 ... Differential limit clutch 2,3 ... Left and right drive wheels 4 ... Differential limit torque control means 5 ... Turn radius detection means 6 ... Longitudinal acceleration detection means

Claims (1)

(57) [Claims] A differential limiting torque control means capable of variably controlling a differential limiting torque between left and right driving wheels by controlling an engagement force of a differential limiting clutch, and applying the differential limiting torque even during turning. A vehicle having improved driving performance by providing a turning radius detecting means for detecting a magnitude of a turning radius of the vehicle, and a longitudinal acceleration detecting means for detecting a value corresponding to a longitudinal acceleration; The limiting torque control means sets the differential limiting torque target value to be higher as the turning radius is larger, and weakens the differential limiting torque by setting this differential limiting torque target value to a smaller value as the value corresponding to the longitudinal acceleration on the acceleration side is larger. A differential limiting torque control device, which is a means for performing control.