JPH075032B2 - Vehicular differential limiting controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle differential limiting control device that is used in a differential device of an automobile and controls a differential limiting amount.

(Prior Art) As a conventional differential device provided with a differential limiting means, for example, “Automotive Engineering Complete Book, Vol. 9 Power Transmission Device” (November 1980)
Devices such as those described on pages 321 to 324 of Sankaido Co., Ltd. on the 15th are known.

In this conventional device, a multi-disc friction clutch provided between a differential case and a side gear is used as a differential limiting means, and a cam mechanism of a pinion mate shaft portion due to a rotational speed difference between the left and right wheels is used for the multi-disc friction clutch. The thrust force generated in 1 is used as the clutch engaging force, and the clutch engaging force is used to generate the differential limiting torque (differential limiting amount).

(Problems to be Solved by the Invention) However, in such a conventional device, a certain amount of differential limiting amount is generated according to the driving torque and the initial torque of the multi-plate friction clutch. In addition, it is possible to transmit torque only to one wheel, and a high differential limiting amount can be obtained on a split μ road (a road where the road surface friction coefficient is different between the left and right wheels) where a high rotational speed difference occurs between the left and right wheels, resulting in running performance. However, there are problems as described below.

If the initial torque is set to a large value to improve running performance on split μ roads, when both the left and right wheels run on low μ roads, both drive wheels will slip at the same time and the cornering force of the tire will decrease, resulting in a Swinging is likely to occur, resulting in poor steering stability.

(Means for Solving Problems) The present invention has been made for the purpose of solving such conventional problems, and in order to achieve this object, the present invention uses the following means.

The solution means of the present invention will be described with reference to the conceptual diagram of the claims shown in FIG. 1. A differential limiting clutch means 1 provided between left and right drive wheels and engaged by an external control force, and a predetermined vehicle state detecting device. And a clutch control means 3 for increasing / decreasing the differential limiting amount with a control signal output based on the detection signal from the detecting means 2. The detection means 2 includes a non-driving wheel rotation speed detecting means 201, a left driving wheel rotation speed detecting means 202, and a right driving wheel rotation speed detecting means 203,
The clutch control means 3 controls the increasing direction of the differential limiting amount when the rotational speed of one of the left and right driving wheels or the left and right driving wheels becomes higher than that of the non-driving wheel. When the slip conditions of the left and right drive wheels both exceed the set slip condition that lowers the cornering force of the tire, the differential limit level is smaller than the differential limit amount given at that time or the differential limit is set to zero. It is characterized in that it is a means for controlling to reduce the amount.

(Operation) When traveling on a split μ road, etc., when the rotational speed of either the left or right driving wheel is higher than the non-driving wheel,
Alternatively, when the vehicle is traveling on a low friction coefficient road or the like and the rotational speeds of the left and right driving wheels are high with respect to the non-driving wheels, the clutch control means 3 performs control to gradually increase the differential limiting amount.

When the slip state of the left and right driving wheels exceeds the set slip state that reduces the cornering force of the tire during the differential limit amount increase control for suppressing the occurrence of the drive wheel slip due to the increase of the differential limit amount, the clutch control is performed. In the means 3, control is performed to reduce the differential limiting amount to a differential limiting amount level smaller than the differential limiting amount applied at that time, or from the differential limiting amount applied at that time to a differential limiting amount of zero. Control is performed to reduce the differential limiting amount.

In this way, by performing the control for gradually increasing or decreasing the differential limiting amount by controlling the engaging force with respect to the differential limiting clutch means 1, the differential limiting is rapidly applied like the differential lock control. There is no sudden change in the vehicle behavior caused by turning on or off.

The upper limit of the range in which the drive wheel slip suppression effect is exerted by increasing the differential limiting amount is the set slip state in which both the left and right drive wheel slip states reduce the cornering force of the tire. In order to secure the cornering force of the tire by reducing the amount in reverse, the drive performance is improved when a drive wheel slip occurs at a level that does not reduce the cornering force of the tire and the overdrive that reduces the cornering force of the tire. It is possible to achieve both improvement in steering stability in the wheel slip occurrence region.

(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 provided with a multi-plate friction clutch means that operates by external hydraulic pressure will be taken as an example.

First, the configuration of the embodiment will be described.

As shown in FIGS. 2 to 4, the embodiment device is a differential device.
10, multi-disc friction clutch means (differential limited clutch means) 1
1, a hydraulic pressure generator 12, a control unit (clutch control means) 13, and an input means 14, each of which will be described below.

The differential device 10 has a differential function of providing a speed difference between the left and right wheels in accordance with 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 to the left and right driving rear wheels. This is a device that has a driving force distribution function that distributes and transmits the signals evenly.

The differential device 10 is housed in a housing 16 attached to a vehicle body by a stud bolt 15, and has a ring gear 17, a differential case 18, a pinion mate shaft 19, a differential pinion 20, side gears 21, 21 '.
Is equipped with.

The former 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-disc friction clutch means 11 is provided between the drive input portion and the drive output portion of the differential device 10, is given a clutch engagement force by an external hydraulic pressure, and generates a differential limiting torque.

The multi-plate friction clutch means 11 is housed in the housing 16 and the differential case 18, and comprises multi-plate friction clutches 27, 27 ', pressure rings 28, 28', reaction plates 29, 29 ', thrust bearing 30. , 30 ', spacers 31,31', push rod 32, hydraulic piston 33,
An oil chamber 34 and a hydraulic port 35 are provided.

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 a member for receiving a clutch engaging 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 drive torque is not particularly generated like the conventional torque proportional type differential limiting means 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.

As shown in FIG. 4, the hydraulic pressure generating device 12 is an external device that generates hydraulic pressure to be a clutch engagement force, and is a hydraulic pump 40, a pump motor 41, a pump pressure oil passage 42, a drain oil passage 43, a control pressure oil passage. 44 and an electromagnetic proportional pressure reducing valve 46 having a valve solenoid 45 as a valve actuator.

The electric / electromagnetic proportional pressure reducing valve 46 supplies the differential oil of the pump pressure supplied from the hydraulic pump 40 via the pump pressure oil passage 42 to the control current signal (i) from the control unit 13,
A valve actuator that controls the pressure of the control oil pressure P proportional to the magnitude of the command current value i ^* and sends the control oil pressure P from the control pressure oil passage 44 to the oil pressure port 35 and the oil chamber 34 is controlled by the control current signal (i ) Is the valve solenoid of the electromagnetic proportional pressure reducing valve 46
Output for 45.

The control oil pressure P and the differential limiting torque T are in the relationship of T∝P · μ · n · r · A n; number of clutches r; average clutch radius A; pressure receiving area, and the differential limiting torque T is controlled. Proportional to hydraulic pressure P.

The control unit 13 is a control circuit that is the center of a vehicle-mounted microcomputer.
1, a memory 132, a CPU (central processing unit) 133, and an output interface circuit 134.

As the input means 14 to the control unit 13, the left front wheel rotation speed sensor 141 and the right front wheel rotation speed sensor 1 are used.
42, left rear wheel rotation speed sensor 143, right rear wheel rotation speed sensor 1
44 are provided.

The left front wheel rotation speed sensor 141 and the right front wheel rotation speed sensor 142 are means for detecting the rotation speeds of the left and right front wheels which are non-driving wheels, and the sensor 141 outputs the left front wheel rotation speed signal corresponding to the left front wheel rotation speed N _FL. (Nfl), the sensor 142 outputs a right front wheel rotation speed signal (nfr) corresponding to the right front wheel rotation speed N _FR .

The left rear wheel rotation speed sensor 143 and the right rear wheel rotation speed sensor 144 are means for detecting the rotation speeds of the left and right rear wheels, which are driving wheels, and from the sensor 143, the left rear wheel according to the left rear wheel rotation speed N _RL. The wheel rotation speed signal (nrl), and the sensor 144 outputs a right rear wheel rotation speed signal (nrr) according to the right rear wheel rotation speed N _RR .

Next, the operation of the embodiment will be described.

First, the differential flow of the differential limiting control in the control unit 14 will be described with reference to the flowchart shown in FIG.

In step 100, each wheel rotation speed sensor 141, 142, 143, 1
From the signal from 44, the left front wheel rotation speed N _FL , the right front wheel rotation speed N _FR , the left rear wheel rotation speed N _RL , and the right rear wheel rotation speed N _RR are read.

In step 101, the average wheel speed N _FAVE of the front wheels is calculated by the left front wheel rotation speed N _FL and the right front wheel rotation speed N _FR read in step 100.

The arithmetic expression is N _FAVE = (N _FL + N _FR ) / 2.

In step 102, the average wheel speed N _FAVE of the front wheels obtained in step 101, and the left rear wheel rotation speed N _RL and the right rear wheel rotation speed N _RR read in step 100, for each of the left and right rear wheels. The rotational speed differences ΔN _L and ΔN _R with respect to the average wheel speed of the front wheels are calculated.

The calculation formula is as follows.

ΔN _L = N _RL −N _FAVE ΔN _R = N _RR −N _{FAVE In} step 103, it is determined whether at least one of the rotational speed differences ΔN _L and ΔN _R obtained in step 102 is greater than or equal to the set rotational speed difference ΔN _0. Done.

When ΔN _L ≧ ΔN ₀ or ΔN _R ≧ ΔN ₀ in step 103, the process proceeds to step 104, and in step 103 ΔN _L ≧ ΔN ₀ and ΔN _L ≧ ΔN ₀
When N _R ≧ ΔN _0, the process proceeds to step 107.

In step 104, the slip ratios S _L and S _R with respect to the average wheel speed of the front wheels for each of the left and right rear wheels are calculated.

The calculation formula is as follows.

S _L = N _RL / N _FAVE S _R = N _RR / N _{FAVE In} step 105, the slip ratio obtained in step 104 is calculated.
It is determined whether both S _L and S _R exceed the set slip ratio S ₀ . In step 105, S _L > S ₀ and S _R > S
_If it is _0, the process proceeds to step 107, and otherwise, the process proceeds to step 106.

In step 106, YES is determined in step 103,
When NO is determined in step 105, the differential limiting torque T
A control current signal (i) that gradually increases is output.

In step 107, when it is determined as NO in step 103 or when YES is determined in steps 103 and 105, the control current signal (i) that makes the differential limiting torque T zero.
Is output.

Next, the differential limiting control operation in various traveling modes will be described.

(B) When traveling on a high friction coefficient road When traveling on a high friction coefficient road such as a dry asphalt road, proceed to step 100 → step 101 → step 102 → step 103, as long as the vehicle is traveling by normal accelerator work. Since there is almost no drive wheel slip, it is determined to be NO in this step 103, and the routine proceeds to step 107.

Therefore, a normal traveling state is achieved in which the differential limiting amount is not generated.

However, even if the vehicle is traveling on a high friction coefficient road, if a drive wheel slip occurs during sudden transmission by suddenly depressing the accelerator pedal or during sudden acceleration, NO is determined in step 103 and the drive wheel slip is determined. A differential limiting amount may occur in order to suppress

(B) Running on low friction coefficient roads When running on low friction coefficient roads such as rain roads, ice and snow roads,
Step 100 → Step 101 → Step 102 → Step 103
Since the tires are slippery even when traveling with normal accelerator work, the rotational speed difference ΔN _L , ΔN with respect to the average wheel speed of the front wheels for each of the left and right rear wheels.
_{When R} occurs, YES is determined in this step 103,
Go to step 104.

Then, in step 104, the slip ratios S _L and S _R are calculated for each of the left and right rear wheels, and step 105
Then, it is judged whether both of the slip ratios S _L and S _R obtained in step 104 exceed the set slip ratio S ₀ , but immediately after the start of the drive wheel slip, the set slip ratio S ₀ is set.
Since it has not reached the above, it is judged as NO in step 105,
At step 106, the control current signal (i) is output so as to gradually increase the differential limiting torque T. Here, the control current signal (i) gradually increases the output current value so that the current output current value i new becomes i new = i old + Δi when the previous output current value is i old. It is a thing.

Then, YES is determined in step 103, and N is determined in step 105.
As long as it is determined to be O, the flow of steps 100 to 106 is repeated, the differential limiting torque T gradually increases, and the drive wheel slip is suppressed. Next, if it is determined NO at step 103 by the action of suppressing the drive wheel slip, the routine proceeds to step 107, where the differential limiting torque T is released.

Further, although the differential limiting torque T is given in step 105, the accelerator is operated in the stepping direction,
The friction coefficient on the road surface suddenly drops, and YES at step 105.
If it is determined that the differential limit torque T is released, the process immediately proceeds to step 107.

This is because, as shown in FIG. 6, when the slip ratios S _L and S _R exceed the set slip ratio S ₀ , the cornering force CF of both tires on the driving side is reduced, and the tail swing occurs. Easy to reach, cornering force with each tire on the left and right
This is because securing the CF improves steering stability.

(C) When traveling on split μ road When traveling on a split μ road where the road surface friction coefficients of the left and right wheels are different, the flow of control operation is the same as when traveling on the low friction coefficient road.

In step 103, it is determined whether the rotational speed difference ΔN _L , ΔN _R with respect to the average wheel speed of the front wheels for each of the left and right rear wheels has occurred, and at least one of them satisfies this condition. By proceeding from step 104 → step 105 → step 106.

When YES is determined in step 105, similarly to the above, the process proceeds to step 107, the differential limiting torque T is released, and the steering stability is enhanced.

As described above, the following effects can be obtained with the vehicle differential limiting control device of the embodiment.

Since it is a device that increases the differential limiting torque T when one of the left and right rear wheels, which is the driving wheel, or the left and right rear wheels, which are the non-driving wheels, has a high rotational speed, it is possible to drive on a split μ road or the like. When the rear wheel rotation speed of one of the left and right rear wheels is high with respect to the front wheel, and when the vehicle is traveling on a low friction coefficient road and the rotation speed of both left and right rear wheels is high with respect to the front wheel. In either case, the differential limiting torque is increased, and the drive wheel slip can be effectively suppressed.

The slip ratios S _L and S _{R of the} left and right rear wheels are both set.
_{Since the} device for canceling the differential limiting torque T when the _value exceeds ₀ is used, even if the slip of the driving wheels is suppressed by the increase of the differential limiting torque T, when the slips of the left and right rear wheels are still increased, It is possible to improve steering stability by suppressing the decrease in cornering force CF and preventing the tail swing.

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 determination of the slip ratio of the left and right driving wheels is shown as S _L > S ₀ and S _R > S ₀ , but (S _L + S _R ) / 2>
It may be S ₀ .

Further, in the embodiment, the electromagnetic proportional pressure reducing valve is shown as the actuator, but an example in which an opening / closing electromagnetic valve or the like is used and a hydraulic pressure control is performed by using a control signal as a duty signal may be performed.

(Effects of the Invention) As described above, in the vehicle differential limiting control device of the present invention, the clutch control means for controlling the increase / decrease of the differential limiting amount is provided for the left and right driving wheels with respect to the non-driving wheels. When either one of them or the rotational speed of the left and right drive wheels becomes high, the differential limiting amount is controlled to increase, and the slip state of the left and right drive wheels together reduces the cornering force of the tire during this differential limiting amount increasing control. When the set slip state is exceeded, the differential limit amount is smaller than the differential limit amount given at that time. Improving driving performance when a drive wheel slip occurs at a level that does not reduce the cornering force of the tire without causing a sudden change in vehicle behavior, and improves cornering of the tire. It is possible to obtain the effect that both improvement in steering stability in the excessive drive wheel slip occurrence region where the driving force is reduced can be achieved.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a differential limiting control device for a vehicle according to the present invention, FIG. 2 is a sectional view showing a differential device incorporating a differential limiting means of an embodiment device of the present invention, and FIG. 2 is a view in the Z direction, FIG. 4 is a view showing a hydraulic pressure generating device and a control device of the embodiment device, FIG. 5 is a flow chart diagram showing a flow of differential limiting control operation in a control unit of the embodiment device,
FIG. 6 is a characteristic diagram of the road surface friction coefficient and the cornering force with respect to the slip ratio. 1 ... Differential limiting clutch means 2 ... Detection means 201 ... Non-driving wheel rotation speed detecting means 202 ... Left driving wheel rotation speed detecting means 203 ... Right driving wheel rotation speed detecting means 3 ... Clutch control means

Claims (1)

[Claims] 1. A differential limiting clutch means provided between left and right drive wheels, which is engaged by a control force from the outside, a predetermined detecting means for detecting a vehicle state, and a detection signal from the detecting means. And a clutch control means for increasing / decreasing the limited differential amount by a control signal output by the control signal output from the vehicle. The clutch control means includes speed detection means and right drive wheel rotation speed detection means, and the clutch control means controls the differential limiting amount when the rotation speed of one of the left and right drive wheels or the left and right drive wheels increases. If the slip condition of the left and right drive wheels exceeds the set slip condition that lowers the cornering force of the tire during this differential limiting amount increase control, it is given at that time. Vehicular differential limiting control apparatus characterized by up differential limiting amount smaller differential limiting levels or differential limiting amount zero is a means for controlling to decrease the differential limiting amount.