JPH0214931A - Differential limit controller for vehicle - Google Patents

Abstract

PURPOSE:To aim at facilitation of a tail slide at time of low speed and stabilization of a tail flow at time of high speed by controlling differential limiting torque in a direction where actual tire sliding velocity accords with desired tire sliding velocity. CONSTITUTION:A differential means 10 distributively transmits engine driving force to symmetrical driving wheels as allowing differential motion. A differential limiting mechanism 11 generates differential limiting torque by control external force. As a detecting means, there are provided with a turning time inner-outer tire discriminating means 142, left driving wheel and right driving wheel speed detecting means 143, 144 and a car speed detecting means 141. Desired tire sliding velocity, which keeps drive transmission force to a road surface and lateral force necessary for turning with mudirm speed time as a basis, has been set to a control means 13 in advance, and this control means 13 controls the differential limiting torque in a direction where actual tire sliding velocity accords with desired tire sliding velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a differential limiting torque that is applied by an external control force,
The present invention relates to a differential limiting control device for a vehicle that controls differential limiting according to predetermined control conditions.

(Prior Art) As a conventional vehicle differential limiting control device, for example, Japanese Patent Application Laid-open No. 103226/1982 (Japanese Patent Application No. 24467/1982)
The device described in No. 6) is known.

In this control device, a target outer wheel slip ratio that maintains the drive transmission force to the road surface and the lateral force necessary for turning is set in advance in the control means, and the actual outer wheel slip ratio is set in a direction that matches the target outer wheel slip ratio. The content is to control the differential limiting torque.

(Problem to be solved by the invention) However, in such a conventional device, since the outer wheel slip ratio is controlled to the same value regardless of the vehicle speed, the lateral force of the tire is also maintained in the same way regardless of the vehicle speed. .

However, considering human driving characteristics, there is a demand for a car that tailslides with less lateral force on the tires at low speeds, and a desire to ensure sufficient lateral force on the tires at high speeds to improve turning stability.

The present invention was made with attention to the above requirements, and it is common to develop a differential limiting control device that can facilitate tail sliding at low speeds and stabilize the tail flow at high speeds. This will be the subject of this study.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the differential limiting control device for a vehicle according to claim 1 uses a differential. A differential means that distributes and transmits the engine driving force to the left and right drive wheels while allowing the engine to drive, and a differential limiting mechanism that generates a differential limiting torque by an external control force.
A differential limiting control device for a vehicle, comprising a control means for increasing or decreasing differential limiting torque based on a signal from a predetermined detecting means, wherein the detecting means includes a vehicle speed detecting means, an inner/outer wheel identification detecting means during turning; , a left drive wheel speed detection means and a right drive wheel speed detection means, and the control means includes a target outer wheel slip that maintains the drive transmission force to the road surface and the lateral force necessary for turning with reference to medium speed. The speed is set in advance, and the control means is a means for controlling the differential limiting torque in a direction such that the actual outer ring sliding speed obtained from the detection signal matches the target outer ring sliding speed.

The differential limiting control device for a vehicle according to claim 2 further includes a differential means for distributing and transmitting engine driving force to left and right drive wheels while allowing a differential, and a differential means for generating a differential limiting torque by an external control force. In a differential limiting control device for a vehicle, comprising a motion limiting mechanism and a control means for increasing/decreasing differential limiting torque based on a signal from a predetermined detection means, the detection means includes a vehicle speed detection means, and a vehicle speed detection means, Ring identification detection means;
It has a left drive wheel speed detection means and a right drive wheel speed detection means,
A target outer wheel slip rate whose value decreases as the vehicle speed increases is set in advance in the control means, and the control means determines whether the actual outer wheel slip rate obtained from the detection signal matches the target outer wheel slip rate. The present invention is characterized in that the differential limiting torque is controlled in the direction of

(Function) The function of the differential limiting control device for a vehicle according to claim 1 will be described.

During a turn, the control means calculates the actual outer wheel slipping speed by subtracting the reference wheel speed based on the vehicle speed from the outer wheel speed, and this actual outer wheel slipping speed is the target outer wheel slipping speed, which is set in advance with reference to the middle speed. The differential limiting torque is controlled in the direction that coincides with , and in the direction that the difference between the outer wheel speed and the reference wheel speed converges to a constant value.

Therefore, at low vehicle speeds where the reference wheel speed is a small value, the actual outer wheel speed is allowed to reach a speed level equal to the target outer wheel speed, which is a relatively large constant value, and the differential limiting torque is controlled to be higher. Thus, the tail slide is facilitated. In addition, at high vehicle speeds where the reference wheel speed is a large value, the actual outer wheel slipping speed is only allowed up to a speed level equal to the target outer wheel slipping speed, which is a relatively small constant value, and the differential limiting torque is controlled to be low. This ensures sufficient lateral force of the tire and stabilizes the tail.

The operation of the differential limiting control device for a vehicle according to the second aspect will be described.

During a turn, the control means calculates the actual outer wheel slip rate by dividing the value obtained by subtracting the reference wheel speed based on the vehicle speed from the outer wheel speed by the outer wheel speed. The differential limiting torque is controlled in a direction that matches the target outer wheel slip ratio, which is set as a value decreasing.

Therefore, at low vehicle speeds when the target outer wheel slip rate is a large value, a high actual outer wheel slip rate is allowed, the differential limiting torque is controlled to be high, and tail sliding is facilitated. Furthermore, at high vehicle speeds where the target outer wheel slip ratio is a small value, a high actual outer wheel slip ratio is not allowed.
The differential limiting torque is controlled to be low, ensuring sufficient lateral force of the tires and stabilizing the tail.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing this embodiment, an example will be taken of a differential limiting control device for an automobile equipped with a multi-disc friction clutch mechanism operated by external hydraulic pressure.

First, the configuration of the embodiment will be explained.

As shown in FIG. 1, the embodiment device includes a differential device (differential means) 10 and a multi-disc friction clutch mechanism (differential limiting mechanism) 11.
, a hydraulic pressure generator 12, and a control unit (control means) 13, and the input sensors 14 of the control unit 13 include a vehicle speed sensor 141 (vehicle speed detection means), a steering angle sensor 142 (inner and outer wheel identification detection means), and a left wheel It has a rotation speed sensor 143 (left drive wheel speed detection means) and a right wheel rotation speed sensor 144 (right drive wheel speed detection means).

Each configuration will be described below with reference to FIGS. 2 to 4.

The differential device 10 has a differential function of providing a speed difference between the left and right wheels according to the rotational speed difference in a driving state where a rotational speed difference occurs between the left and right wheels, and a differential function that equalizes the engine driving force to the left and right driving wheels. This is a device that has a driving force distribution function that distributes and transmits the driving force.

This differential device 10 is housed in a housing 16 that is attached to the vehicle body by a stud port 15, and includes a ring gear 17, a differential case 18,
It includes a binion mate shaft 19, a differential pinion 20, and side gears 21 and 21'.

On the first day of the differential case, the housing 16
It is rotatably supported by tapered roller bearings 22°22'.

The ring gear 17 is connected to a differential case 18.
The propeller shaft 23 is fixed to the propeller shaft 23 and meshes with a drive pinion 24 provided on the propeller shaft 23, from which rotational driving force is input.

The side gear 21.21° includes a left wheel drive shaft 25 and a right wheel drive shaft 2, which are drive output shafts.
6 is provided for each.

The multi-disc friction clutch mechanism 11 is provided between a drive input section and a drive output section of the differential gear 10, and is a mechanism that generates a differential limiting torque using a clutch engagement force generated by external hydraulic pressure.

The multi-plate friction clutch mechanism 11 is housed within a housing 16 and a differential case 18.
Multi-plate friction clutch 27.27' Pressure ring 2
8.28', reaction plate 29.29',
7. Last bearing 30.30' spacer 31.31',
It includes a bushing rod 32, a hydraulic piston 33, an oil chamber 34, and a hydraulic port 35.

The multi-plate friction clutch 27, 27'' includes friction plates 27a, 27'a fixed to the differential case 18 in the rotational direction, and side gears 21, 21'.
a friction disk 27b fixed in the rotational direction to;
27'b, and a pressure ring 28°28' and a reaction plate 29.29° are arranged on both end faces in the axial direction.

The pressure ring 28.28° is provided in a fitted state on the pinion mate shaft 19 as a member receiving the clutch engagement force, and the fitting portion is connected to the shaft having a square cross section as shown in FIG. It is fitted to the end portion 19a by square grooves 28a, 28°a, and has a structure in which no thrust force is generated due to a difference in rotation, unlike the conventional torque proportional differential limiting mechanism.

The hydraulic piston 33 moves in the axial direction (to the right in the drawing) by supplying hydraulic pressure to the hydraulic boat 35, and engages both multi-plate friction clutches 27, 27° according to the oil pressure level. In the plate friction clutch 27, the engagement force is transmitted from the bushing rod 32 to the spacer 31 to the thrust bearing 30 to the reaction plate 29, and the plate friction clutch 27 is engaged using the pressure ring 28 as a reaction force receiver. The fastening reaction force from the housing 16 becomes a fastening force and the fastening is performed.

The hydraulic pressure generating device 12 is an external device that generates hydraulic pressure as a clutch engagement force, and includes a hydraulic pump 40, a pump motor 41,
It includes a control pressure oil passage 42, a check valve 43, a first drain oil passage 44, a relief valve 45, a reserve tank 46, a second drain oil passage 47, a switching valve 48, a valve solenoid 49, and a pressure switch 50.

The pump motor 41 is a motor that is activated or deactivated by a motor signal (m) from the control unit 13, and is activated or deactivated when the vehicle is running and there is a possibility that differential restriction is being performed or differential restriction is being performed. When the vehicle is stopped, a motor signal (m) is output when the vehicle is energized, and when no differential restriction is required, such as when the vehicle is stopped, a motor signal (m) is output when the vehicle is not energized.

The control pressure oil passage 42 is an oil passage connected to a control pressure oil pipe 51 that supplies hydraulic oil at a control pressure to the hydraulic port 35, and is provided with an orifice 52 in the middle to slow the rise of oil pressure. .

The relief valve 45 is a valve that releases pressure to the reserve tank 46 side for pressure regulation when the pump pressure flowing through the control pressure oil path 42 is equal to or higher than a predetermined pressure.

The switching valve 48 is a valve actuator that switches between supplying pump pressure oil to the hydraulic port 35 side and returning it to the reserve tank 46. The switching valve 48 is actuated when the valve solenoid 49 receives a control signal (C) from the control unit 13. do.

When the control signal (c) is an energization signal, the electromagnetic force generated by the valve solenoid 49 overcomes the valve spring 53 and switches to the side that blocks the second drain oil passage 47, and pump pressure oil is supplied to the hydraulic boat 35. , control signal (c)
When is the power cutoff signal, the valve spring 53 switches to the side that communicates the second drain oil passage 47, the pump pressure oil is drained, and the duty signal, which is a repeated signal of energization and power cutoff, is changed to the control signal (c ), and hydraulic control is performed by controlling the energization or energization time.

The pressure switch 50 checks the pressure level of the control pressure oil passage 42, outputs a switch signal (S) to the control unit 13 when the pressure level is above a predetermined value, and serves as an input for feedback control to lower the pressure level. It is a sensor.

The control unit 13 uses an on-vehicle microcomputer, and includes an input circuit 131, a RAM (random, access, memory) 132, a ROM (read,
only, memory) 133, CPLI (central, processing, unit) 134, clock circuit 135,
An output circuit 136 is provided.

The vehicle speed sensor 141 is a sensor that detects vehicle speed by detecting the rotational speed of a transmission output shaft, the rotational speed of one or more driven wheels, a Doppler radar type ground vehicle speedometer, etc., and outputs a vehicle speed signal (V). .

The steering angle sensor 142 is a sensor that detects a steering angle based on displacement of a steering shaft, a steering linkage, etc., and outputs a steering angle signal (θ).

The left wheel rotation speed sensor 143 is provided on the left wheel side drive shaft 25 or the like, and is a sensor that detects the rotation speed of the driving left wheel, and outputs a rotation speed signal (nl).

The right wheel rotation speed sensor 144 is a sensor that is provided on the right wheel side drive shaft 26 or the like, detects the rotation speed of the driving right wheel, and outputs a rotation speed signal (nr).

Here, in a first embodiment corresponding to claim 1, the RO
M133 has a target outer wheel veri speed Δ that maintains the drive transmission force to the road surface and the lateral force necessary for turning at medium speeds (60 km/h).
ω. (=9.8 rad/s) is stored and set in advance.

The overspeed Δω is the amount of over-rotation due to wheel slip defined by the following equation.

Δω=ω-(V/r) However, r: tire diameter, ω: wheel speed, V: vehicle speed, and the relationship with slip rate S is: S = 1- (V/rc, +) = 1 (V/ r△
ωv) This target outer ring sliding speed △ω. = 9.8rad
/s, when the vehicle speed is 30km/h, the slip rate S is
is 26.1%, and when the vehicle speed is 60 km/h, the slip rate S is 15%, and when the vehicle speed is 90 km/h, the slip rate S is 10.5%.

In addition, the slip ratio S and the tire-road friction coefficient μ in Fig. 5
In relation to this, when the slip ratio is around 15%, the friction coefficient μ between the tire and the road surface is the largest and the driving force is easily transmitted to the road surface. Furthermore, the smaller the slip ratio S, the higher the cornering force (proportional to lateral force) CF.

Next, the operation of the first embodiment will be explained.

First, the operational flow of the differential limiting control in the control unit 13 of the first embodiment will be described with reference to the flowchart shown in FIG.

(b) When turning right When turning right, the outer wheel rotational speed ω due to the difference in turning radius
L (left wheel rotation speed) is inner wheel rotation speed ω.

At the beginning of a turn, etc., when the rotational speed of the right wheel is larger than the rotational speed of the right wheel, the flow is as follows: step 200 → step 201 → step 202 → step 203 - step 204, and in step 204, a control signal (C
) is output.

Note that the rotation speed signals (nl) and (nr) are input from each rotation speed sensor 142, 143, and it is possible to compare the rotation speeds ω and ω7 by looking at the number of rotations per unit time. .

Step 200 includes a vehicle speed signal (V
), steering angle signal (θ), left and right wheel rotation speed signal (nl)
, (nr) reading step.

In step 201, the vehicle speed V and the rotational speed ω5 of the left and right wheels are determined based on the input signals read in step 200. ω8, the sliding speed of the left and right wheels, which are the inner and outer wheels, is △ω5. Δ
This is a calculation step for calculating ω9.

The calculation formula is It is.

Step 202 is a determination step in which it is determined whether the vehicle is turning to the right or to the left, based on the steering angle θ read in step 200.

Step 203 is the left wheel rotation speed ωL (outer wheel rotation speed)
This is a judgment step in which the magnitude of the right wheel rotational speed ω, (inner wheel rotational speed) is compared.

Next, during a right turn, in the later stages of the turn, when the inner wheel rotational speed ω9 becomes larger than the outer wheel rotational speed ω due to inner wheel slip, the process proceeds to step 200 - step 201 → step 202 → step 203 → step 205. ,
In this step 205, the outer ring sliding speed Δω or the target outer ring sliding speed Δω is determined. A judgment is made as to whether it is larger or smaller than △ω1〉△ω. In the case of Δω, <Δω. In this case, the process proceeds to steps 207 and 208, where a control signal (c) for increasing the differential limiting torque is output, and Δω,=Δω. In this case, the process returns from step 207 to step 200, and the control signal (C) at that time is output as is without any change.

For example, the outer ring slipping speed △ω is the target outer ring slipping speed Δ
If it is larger than ω0, as shown in FIG. 7, by reducing the differential limiting torque Tc to TCI-+TC2, the outer ring sliding speed Δω is transferred to the target velocity Δω.

Conversely, if Δω1<Δω0, the outer ring sliding speed Δω is changed to the target outer ring sliding speed Δω by increasing the differential limiting torque Tc from Tc1 to Tc2. is controlled in a direction that approaches .

In addition, left wheel torque T Ll,t at differential limiting torque TCI
T1. The right wheel torque TR is T□1. Also, differential limiting torque T. The left wheel torque TL at No. 2 is TL2, and the right wheel torque T8 is TR. Furthermore, the characteristic line T in FIG. 7 shows the engine torque.

(0) When turning to the left When turning to the left, the flow of control operations is exactly the same, except that the relationship between the inner and outer wheels is opposite to that for turning to the right.

In other words, at the beginning of a turn, etc. when the outer wheel rotational speed ω8 is larger than the inner wheel rotational speed ω, step 200 → step 2
01 → Step 202 → Step 209 → Step 21
The flow becomes 0.

In addition, in the later stages of turning when the outer ring rotational speed ω is smaller than the inner ring rotational speed ω, step 200 → step 2
01 → Step 202 → Step 209 → Step 21
1, the outer ring slipping speed Δω8 and the target outer ring slipping speed Δω. What is the relationship between the flow from step 211 to step 212, the flow from step 211 to step 213 to step 214, and the flow from step knob 211 to step 2?
Step 13→Step 200.

As explained above, in the vehicle differential limiting control device of the embodiment, the effects described below can be obtained.

■ When turning, the difference in rotational speed between the inner and outer rings is compared, and when the relationship is greater than the rotational speed of the inner ring, a control signal (C) is output that sets the differential limiting torque Tc to zero. , strong understeer tendency is prevented at the beginning of a turn when this relationship occurs.

■ Outer ring rotational speed <When there is a relationship between inner ring rotational speed, actual outer ring sliding speed ΔωL or Δω8 and target outer ring sliding speed Δω. The actual outer ring sliding speed Δω or Δω8 is the target outer ring sliding speed Δω. Since the vehicle is controlled in a direction that matches the above, in the latter half of the turn where this relationship occurs, the following turning characteristics are exhibited in each vehicle speed range.

At low vehicle speeds, the target slip ratio increases when converted to slip ratio, and lateral force decreases, making it easier to tail slide, making it easier to control the accelerator.

At medium vehicle speeds, the target slip ratio or almost the optimum slip ratio is obtained when converted to a slip ratio, and the maximum road surface drive transmission force is obtained, as well as the necessary and sufficient lateral force.

At high vehicle speeds, the target slip ratio becomes low when converted to slip ratio, and although the road surface drive transmission force becomes low, the lateral force increases, so stable turning performance is achieved.

■ Target sliding speed Δω. It is only necessary to set one value, and calculation of slip speed does not require division like slip ratio, so the storage capacity of the control unit is small and the calculation process is simple. This gives an advantage in terms of equipment cost.

Next, a second embodiment of the apparatus corresponding to the second aspect of the invention will be described.

As for the device configuration, as shown in FIG. 8, the target slip ratio S is stored in the ROM 133 as the vehicle speed V increases.
A target slip ratio calculation formula for reducing the value of A is stored and set in advance.

This slip rate S is the ratio of wheel slip to wheel speed defined by the following equation.

ω−■ S=·100(%) ω Note that the other configurations are the same as those of the device of the first embodiment, so explanations thereof will be omitted.

As shown in FIG. 9, the flow of differential limiting processing operation is as follows: In step 215, the target slip ratio SA is calculated based on the vehicle speed V,
Nos. 5, 207, 211, and 213 are different from the prior application in that the judgment is made based on this target thrift rate SA.

That is, in the case of the earlier application, JP-A-62-103226,
The difference is that the processing is performed using a target slip ratio SA which is a constant value regardless of the vehicle speed, whereas the processing is performed using a target slip ratio SA that decreases according to the vehicle speed V.

Effectively, the target sliding speed Δω is determined by setting the actual sliding speed Δω to a constant value. The result is the same as in the case of matching , and effectively the effects (1) and (2) described above in the first embodiment device can be obtained.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, in the example, a preferable example was shown in which the control conditions include control based on the rotational speed difference between the inner and outer wheels during a turn, and the understeer tendency can be prevented at the beginning of a turn. It may also be possible to control only the following.

Further, in the embodiment, an example using a multi-plate friction clutch was shown as the differential limiting mechanism, but an electromagnetic clutch or the like may be used as long as it is a variable torque clutch.

Furthermore, the characteristics of the slip ratio SA set based on the vehicle speed V are not limited to those that change linearly as shown in FIG. 8 in the embodiments. i.e. medium speed (e.g. 60 km
/h), the slip rate may be set to about 15%, and it may be set so that it is small in a region where the vehicle speed is lower than that and becomes high in a region where the vehicle speed is higher than that.

(Effects of the Invention) As described above, the vehicle differential limiting control device of the present invention according to claims 1 and 2 secures the drive transmission force to the road surface during medium-speed turns and is necessary for turning. In addition to ensuring sufficient lateral force, the common effects of facilitating tail sliding during low-speed turns and stabilizing the tail flow during high-speed turns can be obtained.

In addition to the above-mentioned effects, the differential limiting control device for a vehicle according to claim 1 only needs to set one value for the target slipping speed, and the calculation of the slipping speed can also be performed based on the slip rate, etc. Since no division is required, the storage capacity of the control means is small, and the arithmetic processing is simple, which is advantageous in terms of device cost.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram showing a differential limiting control device for a vehicle according to an embodiment, and FIG. 2 is a sectional view showing a differential device section of the embodiment device.
3 is a view taken in the Z direction of FIG. 2, FIG. 4 is a diagram showing the hydraulic pressure generator and control device of the embodiment device, and FIG. 5 is a target outer ring slip that is stored in advance in the control unit of the embodiment device. Figure 6 is a relationship diagram between slip ratio, road surface friction coefficient, and cornering force for determining speed.
A flowchart showing the flow of the differential limiting control operation in the device of the embodiment, FIG. 7 is a diagram of the torque characteristics of the inner and outer wheels in the device of the first embodiment, and FIG. 8 is a set slip rate characteristic with respect to vehicle speed in the device of the second embodiment. 9 are flowcharts showing the flow of the differential limiting control operation in the second embodiment device. 10...Differential device (differential means) 11...Multi-plate friction clutch mechanism (differential limiting mechanism) 12...Hydraulic pressure generator 3...Control unit (control means) 4...Input sensor 41...Vehicle speed sensor C (vehicle speed detection means) 42...-Steering angle sensor (inner and outer wheel identification detection means) 43...Left wheel rotation speed sensor (left drive wheel speed detection means) 44...Right wheel rotation speed sensor (Right drive wheel speed detection means)

Claims (1)

[Claims] 1) Differential means that distributes and transmits engine driving force to left and right drive wheels while allowing differential, a differential limiting mechanism that generates differential limiting torque by external control force, and predetermined detection. A differential limiting control device for a vehicle, comprising: a control means for increasing/decreasing differential limiting torque based on a signal from the means; The control means has a wheel speed detection means and a right drive wheel speed detection means, and the control means has a target outer wheel slipping speed in advance that maintains the drive transmission force to the road surface and the lateral force necessary for turning, with medium speed as a reference. The differential limiting torque for a vehicle is set in advance, and the control means is a means for controlling the differential limiting torque in a direction in which the actual outer wheel sliding speed obtained from the detection signal matches the target outer wheel sliding speed. Control device. 2) A differential means that distributes and transmits the engine driving force to the left and right drive wheels while allowing a differential, a differential limiting mechanism that generates differential limiting torque by an external control force, and a differential control mechanism based on a signal from a predetermined detection means. A differential limiting control device for a vehicle comprising a control means for increasing or decreasing differential limiting torque, wherein the detecting means includes a vehicle speed detecting means, an inner/outer wheel identification detecting means during turning, a left driving wheel speed detecting means, and a right driving wheel speed detecting means. drive wheel speed detection means; the control means has a target outer wheel slip ratio whose value decreases as the vehicle speed increases; A differential limiting control device for a vehicle, comprising means for controlling differential limiting torque in a direction in which a slip rate matches the target outer wheel slip rate.