JPH0735132B2 - Vehicular differential limiting controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a case where differential limiting torque is applied by an external control force,
The present invention relates to a vehicle differential limiting control device that controls differential limiting according to a predetermined control condition.

(Prior Art) As a conventional vehicular differential limiting control device, for example, a device described in JP-A-62-103226 (Japanese Patent Application No. 60-244676) is known.

This control device presets a target outer wheel slip ratio for maintaining the drive transmission force to the road surface and the lateral force required for turning in the differential limiting control means, and the actual outer wheel slip ratio matches the target outer wheel slip ratio. It is the content of controlling the differential limiting torque in the direction of turning.

(Problems to be Solved by the Invention) However, in such a conventional vehicle differential limiting control device, the outer wheel slip ratio (the same applies to the outer wheel slip speed) is unique regardless of the magnitude of the accelerator operation amount. Since it is controlled so as to match the target value that has been set, even if the driver performs an acceleration operation by depressing the accelerator in the latter half of the turn at the time of turning, the vehicle behavior remains the same as it was before the accelerator depressing operation. As a result, the driver cannot control the amount of tail slide due to the amount of depression of the accelerator pedal, and there is a problem that the driver feels something wrong with the accelerator operation.

That is, regardless of the accelerator operation amount, when the outer wheels of the drive wheels are controlled so as to uniquely match the set target value, even if the acceleration operation is performed by depressing the accelerator, it is the same as before the depressing operation. The outer wheels of the driving wheels are in a slip state, and the same change in tire lateral force and the same amount of oversteer always occur, so that no change in vehicle behavior is observed.

The present invention has been made in view of the above-mentioned problems, and it is possible to control the tail slide amount by adjusting the amount of depression of the accelerator at the time of accelerating turning, and at the same time, it is possible to eliminate a feeling of strangeness in the accelerator operation. Is the development of.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and in order to achieve this object, the vehicular differential limiting control device of the present invention uses the claims of FIG. As shown in the corresponding diagram, a differential limiting mechanism 1 that is provided in a drive system that distributes and transmits the engine driving force to the left and right driving wheels while allowing differential, and a differential limiting mechanism 1 that generates a differential limiting torque by an external control force, and a predetermined limiting mechanism. In a vehicle differential limiting control device including a differential limiting control means 3 for increasing / decreasing differential limiting torque based on a signal from the detecting means 2, the vehicle speed detecting means 201 is used as the detecting means 2.
And a turning inner and outer wheel identification detecting means 202, a left driving wheel speed detecting means 203, a right driving wheel speed detecting means 204, and an accelerator operation amount detecting means 205, and the differential limiting control means 3 detects The actual outer wheel slip amount obtained from the signal is different in the direction that matches the target outer wheel slip amount, which increases as the accelerator operation amount increases within the range where the drive transmission force to the road surface and the lateral force required for turning are maintained. It is characterized by being means for controlling the motion limiting torque.

The outer wheel slip amount is a general term indicating the outer wheel slip ratio, the outer wheel slip speed, and the like.

(Operation) At the time of turning, the differential limiting control means 3 obtains the actual outer wheel slip amount based on the outer wheel speed and the vehicle speed, and this actual outer wheel slip amount is the target outer wheel slip amount determined based on the accelerator operation amount. In the same direction, that is, when the actual outer wheel slip amount is smaller than the target outer wheel slip amount, the differential limit torque is increased, and when the relationship is reversed, the actual outer wheel slip amount is reduced by decreasing the differential limit torque. Control is performed to converge the quantity.

Specifically, the operation when the accelerator pedal depression amount is increased in the latter half of turning to perform accelerated turning traveling will be described.

When the accelerator operation amount is small before depressing the accelerator,
The target outer wheel slip amount also becomes a small value, the allowable range of the outer wheel slip amount is narrow, and the differential limiting torque is low.
Although the driving force transmitted to the road surface is small, the tire lateral force is sufficiently secured and high turning stability is achieved.

When the accelerator is depressed, the target outer wheel slip amount becomes a high value according to the accelerator operation amount, and the allowable range of the outer wheel slip amount also increases according to the accelerator operation amount.

Due to this change in the target outer wheel slip amount, the differential limiting torque is controlled to become higher in accordance with the accelerator operation amount, and the minimum drive transmission force to the road surface that does not lead to vehicle spin and the lateral force necessary for turning. Although maintained, the tire lateral force decreasing tendency and the road driving force increasing tendency are simultaneously generated according to the accelerator operation amount, that is, the oversteer amount increases according to the accelerator operation amount, and the accelerator operation amount increases. The vehicle behavior in which the tail slide corresponding to the operation amount occurs is shown.

Therefore, when the vehicle makes an accelerated turn, a tail slide corresponding to the accelerator operation amount occurs, so that the driver can control the tail slide amount from the accelerator work.

Further, when the accelerator operation is performed at the time of turning, the accelerator operation and the change in the vehicle behavior show a corresponding relationship, so that the uncomfortable feeling of the accelerator operation is eliminated.

(Examples) Hereinafter, examples of the present invention will be described in detail with reference to the drawings. In describing this embodiment, a differential limiting control device for a rear-wheel drive vehicle equipped with a multi-plate friction clutch mechanism operated by external hydraulic pressure will be taken as an example.

First, the configuration of the embodiment will be described.

FIG. 2 shows an overall schematic view of the embodiment apparatus, including a differential 10, a multi-plate friction clutch mechanism (differential limiting mechanism) 11,
A hydraulic pressure generator 12 and a control unit (differential limitation control means) 13 are provided, and as the input sensor 14 of the control unit 13, a vehicle speed sensor 141 (vehicle speed detecting means) and a steering angle sensor 142 (inner and outer wheel identification detecting means). And left wheel rotation speed sensor 143 (left drive wheel speed detection means) and right wheel rotation speed sensor 1
44 (right drive wheel speed detection means) and accelerator opening sensor 145
(Accelerator operation amount detection means).

Each configuration will be described below with reference to FIGS. 3 to 5.

The differential 10 has a differential function of providing a speed difference between the left and right wheels according to the difference in rotation speed in a traveling state in which a difference in rotation speed occurs between the left and right wheels, and the engine driving force is evenly distributed to the left and right drive wheels. This is a device having a driving force distribution function for distribution transmission.

This differential 10 is housed in a housing 16 attached to a vehicle body by a stud bolt 15, and includes a ring gear 17, a differential case 18,
A pinion mate shaft 19, a differential pinion 20, and side gears 21 and 21 'are provided.

The differential case 18 is rotatably supported on the housing 16 by tapered roller bearings 22 and 22 '.

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

The side gears 21 and 21 'are respectively provided with a left wheel side drive shaft 25 and a right wheel side drive shaft 26 which are drive output shafts.

The multi-plate friction clutch mechanism 11 includes the differential 10
Is a mechanism that is provided between the drive input unit and the drive output unit and that generates the differential limiting torque by the clutch engagement force by the external hydraulic pressure.

The multi-plate friction clutch mechanism 11 is housed in the housing 16 and the differential case 18, and includes a multi-plate friction clutch 27, 27 ', pressure rings 28, 28', reaction plates 29, 29 ', thrust bearing 30, 30 ', spacers 31, 31', push rod 32, hydraulic piston 33, oil chamber 3
4, equipped with hydraulic port 35.

The multi-plate friction clutches 27, 27 'are friction plates 27 fixed in the rotational direction to the differential case 18.
a, 27'a and friction discs 27b, 27'b fixed to the side gears 21, 21 'in the rotational direction,
Pressure rings 28, 28 'and reaction plates 29, 29' are arranged on both end surfaces in the axial direction.

The pressure rings 28, 28 'are provided in a fitted state on the pinion mate shaft 19 as members for receiving a clutch fastening force, and the fitting portion has a rectangular cross section as shown in FIG. Square grooves 28a, 28 'with respect to the end 19a
The structure is such that the thrust force due to the rotation difference is not generated unlike the conventional torque proportional type differential limiting mechanism by fitting by a.

The hydraulic piston 33 moves in the axial direction (to the right in the drawing) by the hydraulic pressure supplied to the hydraulic port 35, and the multi-plate friction clutch
27, 27 'are engaged according to the hydraulic pressure level, and one multi-plate friction clutch 27 has a fastening force of push rod 32 →
Spacer 31 → Thrust bearing 30 → Reaction plate 29
And is fastened by the pressure ring 28 as a reaction force receiver.
The fastening reaction force from is used as the fastening force for fastening.

The hydraulic pressure generation device 12 is an external device that generates hydraulic pressure that serves as a clutch engagement force, and is a hydraulic pump 40, a pump motor 41, a control pressure oil passage 42, a check valve 43, a first drain oil passage 44, a relief valve 45, a reserve tank. 46, 2nd drain oilway 4
7, switching valve 48, valve solenoid 49, pressure switch 5
It has 0 and.

The pump motor 41 is a motor that is activated / deactivated according to a motor signal (m) from the control unit 13, and may be running or may be performing differential limiting. When the motor signal (m) is supplied when the motor is energized, the motor signal (m) is supplied when the motor is not energized when no differential limitation is required such as when the vehicle is stopped.

The control pressure oil passage 42 is an oil passage connected to a control pressure oil pipe 51 for supplying hydraulic oil of a control pressure to the hydraulic pressure port 35, and an orifice 52 is provided on the way to moderate the rise of hydraulic pressure. .

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

The switching valve 48 is a valve actuator for switching between supplying pump pressure oil to the hydraulic port 35 side and returning it to the reserve tank 46, and a valve solenoid 49 receives a control signal (c) from the control unit 13. Operate.

When the control signal (c) is the energization signal, the electromagnetic force from the valve solenoid 49 switches to the side that overcomes the valve spring 53 and shuts off the second drain oil passage 47, and the pump pressure oil is supplied to the hydraulic port 35. When the control signal (c) is a power interruption signal, the valve spring 53 causes the second drain oil passage.
47 is switched to the communication side, the pump pressure oil is drained, and the hydraulic signal is controlled by controlling the energization or interruption time by using the duty signal, which is a repeated signal of energization and interruption, as the control signal (c). It

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 level, and is an input for performing feedback control for lowering the pressure level. It is a sensor.

The control unit 13 is an electronic control circuit using a vehicle-mounted microcomputer, and includes an input circuit 131, a memory 132 such as RAM and ROM, a CPU 133, and an output circuit 134.

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

The steering angle sensor 142 is a sensor that detects a steering angle by displacement of a steering shaft, a steering linkage, or the like, and outputs a steering angle signal (θ).

The left wheel rotation speed sensor 143 includes the left wheel drive shaft 2
A sensor that is provided on the vehicle 5 or the like and detects the rotation speed of the driving left wheel outputs a rotation speed signal (nl).

The right wheel rotation speed sensor 144 includes the right wheel drive shaft 2
A sensor provided on 6 or the like, which detects the rotation speed of the driving right wheel, outputs a rotation speed signal (nr).

The accelerator opening sensor 145 is a sensor provided at a throttle valve position of the engine or the like and detects an accelerator opening Acc, and outputs an accelerator opening signal (Acc).

Below, as the target outer wheel slip amount, the target outer wheel slip ratio S _A
The differential limiting torque control in the first embodiment (FIGS. 6 to 8) which is controlled based on the above, and the second embodiment (FIGS. 9 and 10 which is controlled based on the target outer wheel slip speed Δω _A) The differential limiting torque control in FIG.

The differential limiting torque control operation of the first embodiment will be described.

First, the slip ratio S is the slip ratio of the wheel speed ω to the vehicle speed V defined by the following equation.

And in the first embodiment, the control unit 13
As shown in FIG. 7, an arithmetic expression for increasing the target outer wheel slip ratio S _A as the accelerator opening Acc increases is preset.

The target outer wheel slip ratio S _A has a slip ratio of about 15 as shown in the relationship characteristics between the slip ratio S and the tire-road friction coefficient μ and the relationship characteristics between the slip ratio S and the cornering force CF in FIG. % The friction coefficient μ between the tire and the road surface is the largest and it is easy to transmit the driving force to the road surface.
Cornering force CF (proportional to tire lateral force) is low. Further, when the slip ratio S is small, it is difficult to transmit the driving force to the road surface, but it is set in consideration of the relationship that a high cornering force CF can be obtained.

Next, the flow of the differential limiting control operation in the first embodiment will be described with reference to the flow chart shown in FIG.

(A) When turning right When turning right and when the left wheel rotation speed ω _L, which is the outer wheel side, is equal to or higher than the right wheel rotation speed ω _R , which is the inner wheel side, due to the difference in turning radii The flow proceeds in the order of 80 → step 81 → step 82 → step 83 → step 84 → step 85, and in step 85, the control signal (c) for making the differential limiting torque zero is output.

In step 80, the vehicle speed signal (v), the steering angle signal (θ), and the left and right wheel speed signals (nl) are input from the input sensor 14.
(Nr) and accelerator opening signal (Acc) are read.

In step 81, the target outer wheel slip ratio S _A is calculated from the relationship shown in FIG. 7 based on the accelerator opening Acc by the following calculation formula.

S _A = f (Acc) = k × Acc (k; proportional constant) In step 82, the vehicle speed V read in step 80 is read.
And the rotational speeds ω _L and ω _R of the left and right wheels, the slip ratios S _L and S _R of the left and right wheels are calculated by the following calculation formula.

In step 83, it is determined whether the vehicle is turning right or turning left based on the steering angle θ read in step 80.

In step 84, the magnitudes of the left wheel rotation speed ω _L (outer wheel rotation speed) and the right wheel rotation speed ω _R (inner wheel rotation speed) are compared.

Next, during a right turn, in the latter stage of turning when the inner wheel rotation speed ω _R becomes higher than the outer wheel rotation speed ω _L due to inner wheel slip, the routine proceeds from step 84 to step 86, where the actual outer wheel slip ratio S _L is It is determined whether the target outer wheel slip ratio S _{A is} greater than or less than the target outer wheel slip ratio S _{A, and} it is determined in step 88 whether the actual outer wheel slip ratio S _L is equal to the target outer wheel slip ratio S _A.

Then, when S _L > S _A , the routine proceeds to step 87, where the control signal (c) for reducing the differential limiting torque is output, and S _L <S _A
If S _L = S _A , the control signal (c) for increasing the differential limiting torque is output, and if S _L = S _A , the control signal (c) at that time is held and output. The actual outer wheel slip ratio S _L is controlled to match the target outer wheel slip ratio S _A by repeating the reduction, holding, and holding.

(B) When making a left turn In the case of making a left turn, the relationship of the inner and outer wheels is just the reverse of the case of making a right turn, and the flow of control operation is exactly the same.

That is, in the initial stage of turning when the outer wheel rotation speed ω _R is higher than the inner wheel rotation speed ω _L , step 80 → step 81 → step
The flow is 82 → step 83 → step 90 → step 91.

Further, in the latter stage of turning when the outer wheel rotation speed ω _R is smaller than the inner wheel rotation speed ω _L, etc., the flow proceeds from step 92 to step 93 in accordance with the relationship between the actual outer wheel slip ratio S _L and the target outer wheel slip ratio S _A. The flow proceeds in the order of 92 → step 94 → step 95, and the flow proceeds in the order of step 92 → step 94 → step 80.

Next, a description will be given of the operation when the accelerator pedaling amount is increased in the latter half of the turning operation in the first embodiment to perform accelerated turning travel.

When the accelerator operation amount is small before the accelerator pedal is depressed, that is, when the accelerator opening Acc is small, the target outer wheel slip ratio S _A also becomes a small value, the allowable range of the outer wheel slip amount is narrow, and the differential limiting torque is low. Although the driving force transmitted to the road surface is small, the tire lateral force is sufficiently secured and high turning stability is achieved.

Then, when the accelerator is depressed, the target outer wheel slip ratio S _A becomes a high value according to the accelerator opening Acc, and the allowable range of the outer wheel slip amount also increases according to the accelerator opening Acc.

Due to this change in the target outer wheel slip ratio S _A , the differential limiting torque is controlled to increase according to the accelerator opening Acc, and the minimum drive transmission force to the road surface that does not lead to vehicle spin etc. and the lateral force required for turning are obtained. Although the force is maintained, as shown by the arrow in Fig. 6, the decreasing tendency of the tire lateral force (cornering force) and the increasing tendency of the driving force transmitted to the road surface simultaneously progress according to the accelerator opening Acc. Occurs in.

That is, the vehicle behavior is shown in which the amount of oversteer increases in accordance with the accelerator operation amount and the tail slide corresponding to the accelerator operation amount occurs.

As described above, in the vehicle differential limiting control system according to the first embodiment, the effects listed below can be obtained together.

When accelerating and turning, the tail slide corresponding to the accelerator operation amount occurs, so that the driver can control the tail slide amount by adjusting the accelerator pedal.

When the accelerator operation is performed during turning, the accelerator operation and the vehicle behavior change show a corresponding relationship, so that a feeling of strangeness in the accelerator operation is eliminated.

When turning, the rotation speeds of the inner and outer wheels are compared, and when the relationship of outer wheel rotation speed> inner wheel rotation speed is satisfied, the differential limiting torque is controlled to zero, so there is a tendency for strong understeer at the beginning of turning when this relationship occurs. To be prevented.

Next, the differential limiting torque control operation of the second embodiment will be described.

First, the slip velocity Δω is the over-rotation amount due to wheel slip defined by the following equation.

Δω = ω− (V−r) where r is the tire diameter, ω is the wheel speed, V is the vehicle speed, and the relationship with the slip ratio S is S = 1− (V / rω) = 1− (V / r △ ωV) Becomes

Then, as shown in FIG. 9, an arithmetic expression is set in advance that is proportional to the accelerator opening Acc and obtains the target outer wheel slip speed Δω _A of about 6 to 12 rad / s when the accelerator opening Acc is 100%. There is.

Also, the equations for the slip speeds Δω _L and Δω _R of the left and right wheels are Is.

As shown in Fig. 10, the flow of the differential limiting torque control operation is to change the actual outer wheel slip ratio S _L or S _R to the target outer wheel slip ratio S corresponding to the accelerator opening degree only by changing the slip ratio to the slip speed. _The description is omitted because it is the same as in the first embodiment in which it matches with _A. Further, effectively, the above in the first embodiment device,
The effects of and are obtained.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and the present invention can be applied even if there is a design change or the like within a range not departing from the gist of the present invention. included.

For example, in the embodiment, the control condition includes the control by the rotational speed difference between the inner and outer wheels at the time of turning, and the preferable example in which the understeer tendency can be prevented at the initial stage of turning is shown, but only the control of the outer wheel slip speed and the outer wheel slip ratio is performed. It may be one.

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

Further, although the linear characteristic is shown as the accelerator opening-corresponding characteristic shown in FIGS. 7 and 9, it may be a curved characteristic, a step diagram characteristic, or the like, and the characteristic can be selected by the driver. Is also good.

Further, the example in which the inner and outer wheels are identified by the turning direction based on the detection of the steering angle has been shown, but it may be identified by the lateral acceleration, the left and right front wheel rotation speed, or the like.

(Effects of the Invention) As described above, in the vehicular differential limiting control device of the present invention, the actual outer wheel slip amount obtained by the detection signal is such that the lateral force necessary for turning and the drive transmission force to the road surface. As the means for controlling the differential limiting torque in the direction that matches the target outer wheel slip amount that increases with the increase in the accelerator operation amount within the range that maintains the force It is possible to obtain the effect of enabling the control of and also eliminating the discomfort in accelerator operation.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims showing a vehicular differential limiting control device of the present invention, FIG. 2 is an overall schematic diagram showing a differential limiting control device of an embodiment, and FIG. 3 is a differential of an example device. FIG. 4 is a cross-sectional view showing a portion, FIG.
FIG. 5 is a diagram showing a hydraulic pressure generation device and a control device of the embodiment apparatus, and FIG. 6 is a road surface friction coefficient with respect to a slip ratio for determining a target outer wheel slip ratio (target outer wheel slip speed) in the embodiment apparatus and FIG. 7 is a relational characteristic diagram of the cornering force, FIG. 7 is a control map diagram of a target outer wheel slip ratio in the first embodiment device, and FIG. 8 is a flowchart diagram showing a flow of differential limiting control operation in the first embodiment device, FIG. 9 is a control map diagram of a target outer wheel slip velocity in the second embodiment device, FIG.
The drawing is a flow chart showing the flow of the differential limiting control operation in the device of the second embodiment. 1 ... Differential limiting mechanism 2 ... Detection means 201 ... Vehicle speed detection means 202 ... Inner / outer wheel identification detection means 203 ... Left drive wheel speed detection means 204 ... Right drive wheel speed detection means 205 ... Accelerator operation amount Detecting means 3 ... Differential limiting control means

Claims (1)

[Claims] 1. A differential limiting mechanism, which is provided in a drive system for distributing and transmitting an engine driving force to left and right driving wheels while allowing differential, and a differential limiting mechanism for generating a differential limiting torque by an external control force, and a predetermined detecting means. A differential limiting control device for a vehicle that controls increasing / decreasing the differential limiting torque based on the signal of the above-mentioned signal, wherein the detecting means is a vehicle speed detecting means, a turning inner / outer wheel identification detecting means, and a left side. It has a driving wheel speed detecting means, a right driving wheel speed detecting means, and an accelerator operation amount detecting means, and the differential limiting control means is such that the actual outer wheel slip amount obtained by the detection signal is equal to the drive transmission force to the road surface. A vehicle difference characterized by being means for controlling the differential limiting torque in a direction corresponding to a target outer wheel slip amount that increases in accordance with an increase in accelerator operation amount within a range in which a lateral force required for turning is maintained. Dynamic limit control device .