JPH0314416Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is a vehicle differential limiter that applies a differential resistance force using external fluid pressure and controls the differential limiter according to predetermined control conditions. Concerning control means.

(Prior art) As a differential device with a conventional differential limiting mechanism, for example, No. 321 of "Automotive Engineering Complete Book Volume 9 Power Transmission Device" (published by Sankaido Co., Ltd. on November 15, 1980)
Devices such as those described on pages 324 to 324 are known.

This conventional device uses a multi-plate friction clutch and a cam mechanism provided between the differential case and the side gear as a differential limiting mechanism. It was a torque proportional differential limiting mechanism that applied differential resistance force using the thrust force generated by the engine.

Note that the term "differential limiting mechanism" here refers to a mechanism that exhibits a differential limiting function, and a device usually referred to as a limited slip differential is a differential device that has a built-in differential limiting mechanism that functions as a differential limiting mechanism. When used simply as a differential device (differential means), it refers to a conventional differential device that does not have a limiting function.

(Problem to be solved by the invention) However, in such conventional devices, a differential resistance force is applied by the thrust force generated in proportion to the rotational speed difference between the left and right wheels, and the transfer ratio Rt is Because it had a uniquely defined configuration, even when turning when there is a difference in the rotation speed between the left and right wheels, a differential resistance force is generated from the beginning of the turn, and a larger drive torque is transmitted to the lower speed inner wheels than to the outer wheels. As a result, there was a problem in that the understeer tendency became very strong at the beginning of a turn.

In other words, when looking at the torque characteristics of the inner and outer wheels during a turn, as shown in Figure 9, it shows a strong understeer tendency in the early turning region A, and on the contrary shows an oversteer tendency in the later stages of the turn when the inner wheels slip. The vehicle had a so-called reverse steering characteristic, and the turning trajectory of the vehicle was as shown by the solid line B in FIG.

This conventional device is a differential device equipped with a preload type + torque proportional type differential limiting mechanism in which an initial torque Ti is applied by a disc spring or the like.

(Means for solving the problem) This invention uses a differential limiting function when driving on rough roads or low-friction roads where differential limiting is necessary, even when there is a difference in rotational speed between the left and right wheels. The purpose of this invention was to suppress the differential limiting function only when turning, and to solve the above-mentioned problems.To achieve this purpose, the present invention uses the following solutions and did.

The solution of the present invention will be described with reference to the conceptual diagram of the claim shown in FIG. 1, which includes a differential means 3 that distributes and transmits engine driving force to the left and right drive wheels 1 and 2 while allowing a differential, and the differential means 3, a differential limiting mechanism 4 that applies a differential resistance force using external fluid pressure, and a fluid pressure generating means 6 having an actuator 5 that controls fluid pressure supply to the differential limiting mechanism 4; Input sensor 7 that detects the driving state of the vehicle
and a control means 8 for outputting a control signal for increasing or decreasing the differential resistance force to the actuator 5 based on the signal from the input sensor 7, in which the input sensor 7 is a differential limiting control device for a vehicle. ,
It includes a steering angle sensor 701 that detects the steering angle, and a left wheel rotation speed sensor 702 and a right wheel rotation speed sensor 703 that detect the rotation speed of the left and right drive wheels 1 and 2. The control means 8 is configured to perform control to reduce the differential resistance force when a signal indicating that the rotational speed of the inner turning wheel is smaller than the rotational speed of the outer turning wheel is input.

(Function) Therefore, as described above, in the differential limiting control device for a vehicle of the present invention, when a signal indicating that the rotational speed of the inner wheel of the turn is smaller than the rotational speed of the outer wheel of the turn is inputted, the differential is activated. By using a means to reduce the resistance force, the differential resistance force is increased when differential restriction is necessary, such as when there is a rotational speed difference between the left and right wheels when driving straight, or when the inner wheel rotational speed is large when turning. The dynamic limiting effect improves straight-line stability and turning stability, and when turning on dry roads, etc., when the inner ring rotation speed is low, the differential resistance force is reduced and the tendency for understeer at the beginning of a turn due to the differential limiting effect is reduced. It can be prevented.

(Example) Hereinafter, an example 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 FIGS. 2 to 4, the embodiment device includes a differential device (differential means) 10, a multi-disc friction clutch mechanism (differential limiting mechanism) 11, and a hydraulic pressure generating device (fluid pressure generating means) 12. , a control unit (control means) 13, and an input sensor 14.
Each configuration 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 rotational speed difference in a driving state where a rotational speed difference occurs between the left and right wheels;
This device has a driving force distribution function that equally distributes and transmits the engine driving force to the left and right drive wheels.

This differential device 10 is housed in a housing 16 that is attached to the vehicle body with stud bolts 15, and includes a ring gear 17, a differential case 18, and a pinion mate shaft 1.
9, differential pinion 20, side gear 21, 21'
It is equipped with

The differential case 18 has a tapered roller bearing 22,
It is rotatably supported by 22'.

The ring gear 17 is fixed to a differential case 18 and is connected to the propeller shaft 2.
3, and rotational driving force is input from this drive pinion 24.

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

The multi-plate friction clutch mechanism 11 includes the differential gear 1
0 between the drive input section and the drive output section,
This is a mechanism that applies differential resistance force using clutch engagement force generated by external hydraulic pressure.

This multi-plate friction clutch mechanism 11 includes a housing 1
6 and differential case 18, which include multi-plate friction clutches 27, 27',
Pressure rings 28, 28', reaction plates 29, 29', thrust bearings 30, 30',
It includes spacers 31, 31', a push rod 32, a hydraulic piston 33, an oil chamber 34, and a hydraulic port 35.

The multi-plate friction clutches 27, 27' include friction plates 27a, 27 fixed to the differential case (drive input section) 18 in the rotational direction.
a, a friction disk 27b fixed in the rotational direction to the side gears (drive output parts) 21, 21,
27'b, and pressure rings 28, 28' and reaction plates 29, 29' are arranged on both end faces in the axial direction.

The pressure rings 28, 28' are fitted to the pinion mate shaft 19 as members that receive the clutch fastening force, and their fitting portions have a rectangular cross section as shown in FIG. It is fitted to the shaft end 19a through square grooves 28a, 28'a, and has a structure in which no thrust force is generated due to a rotational difference, unlike the conventional torque proportional differential limiting mechanism.

The hydraulic piston 33 moves in the axial direction (rightward in the drawing) by hydraulic pressure supplied to the hydraulic port 35,
Both multi-plate friction clutches 27, 27' are engaged in accordance with the oil pressure level, and in one multi-disc friction clutch 27, the engagement force is transmitted from the push rod 32 to the spacer 31 to the thrust bearing 30 to the reaction plate 29. , are fastened using the pressure ring 28 as a reaction force receiver, and the other multi-plate friction clutch 27' is fastened using the fastening reaction force from the housing 16 as a fastening force.

The hydraulic pressure generating device 12 is an external device that generates hydraulic pressure to serve as a clutch engagement force, and includes a hydraulic pump 40, a pump motor 41, a pressure oil passage 42, and a check valve 4.
3. First drain oil passage 44, relief valve 4
5, reserve tank 46, second drain oil path 4
7, a switching valve 48, a valve solenoid (actuator) 49, and a pressure switch 50.

The pump motor 41 is a motor that is activated and deactivated by the energization signal i and de-energization signal o from the control unit 13, and is used when the pump is running and differential restriction is being performed or when differential restriction is being performed. When there is a possibility, the motor is in a rotating state based on the energization signal i, and when there is no need for differential restriction at all, such as when the vehicle is stopped, the motor is in a stopped state due to the energization release signal o.

The pressure oil passage 42 is an oil passage connected to a pressure oil pipe 51 that supplies pressurized oil 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 pressurized oil flowing through the pressure oil path 42 to the reserve tank 46 side for pressure regulation when the pressure is higher than a predetermined pressure.

The switching valve 48 is a valve that switches between supplying pressurized oil to the hydraulic port 35 side and returning it to the reserve tank 46, and transmits the control signal c from the control unit 13 to the valve solenoid 4.
9 receives it and operates.

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 pressurized oil is supplied to the hydraulic port 35.
When the control signal c is a power cutoff signal, the valve spring 53 switches to the side where the second drain oil passage 47 is communicated, and the pressurized oil is drained.

The pressure switch 50 is an input sensor for checking the pressure level of the pressure oil passage 42, and outputting a switch signal s to the control unit 13 when the pressure level is above a predetermined value to perform feedback control to lower the pressure level. .

The control unit 13 uses an in-vehicle microcomputer, and includes an input circuit 131,
RAM (random access memory) 132,
ROM (read only memory) 133,
CPU (Central Processing Unit) 1
34, a clock circuit 135, and an output circuit 136.

As the input sensor 14, a steering angle sensor 14 is used.
1. A left wheel rotation speed sensor 142 and a right wheel rotation speed sensor 143 are provided.

The input circuit 131 is a circuit that converts the input signals (θ), (n), and (nr) from the input sensor 14 into digital signals that can be processed by the CPU.

The RAM 132 is a readable and writable memory, and input signals from the sensors 141, 142, and 143 are written therein, and information is written in the middle of calculation by the CPU 134.

The ROM 133 is a read-only memory in which information necessary for arithmetic processing by the CPU 134 is stored in advance, and is read-only from the CPU 13 as necessary.
It is read from 4.

The CPU 134 is a device that performs arithmetic processing on various input information according to predetermined processing conditions.

The clock circuit 135 is a circuit that sets the calculation processing time of the CPU 134.

The output circuit 136 is a circuit that outputs a control signal c based on a duty signal to the valve solenoid 49, which is an actuator, based on a calculation result signal from the CPU 134.

The steering angle sensor 141 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 142 is provided on the left wheel side drive shaft 25, etc., and is a sensor that detects the rotation speed of the driving left wheel, and outputs a rotation speed signal (n).

The right wheel rotation speed sensor 143 is provided on the right wheel side drive shaft 26 or the like, and is a sensor that detects the rotation speed of the driving right wheel, and outputs a rotation speed signal (nr).

The steering angle sensor 141 is a sensor that determines whether the steering is correct, that is, whether the vehicle is traveling straight or when turning, and it is also a sensor that determines whether the left or right wheels are inner or outer depending on the turning direction when turning. be.

In addition, the left wheel rotation speed sensor 142 and the right wheel rotation speed sensor 143 measure the rotation speed difference (rotational speed difference) between the left and right wheels when traveling straight, and between the inner and outer wheels when turning.
It is used as a sensor to determine the

Next, the operation of the embodiment will be explained.

First, the operation of the embodiment will be described with reference to a flowchart (FIG. 6) showing the operational flow of differential limiting control.

(b) When traveling straight The flow of control operations when traveling straight is step 20.
0→Step 201→Step 204.

In other words, when driving straight, the duty is set at step 204.
A 100% control signal is output, and the differential between the left and right wheels is limited, ensuring straight-line stability of the vehicle.

Note that in step 200, the input signals (θ),
(n) and (nr) are read.

In step 201, the steering angle θ is set to θ=0 based on the steering angle signal (θ) read in step 200.
(when traveling straight) or θ=0 (when turning) is determined.

(b) When turning The flow of control operations when turning is from step 200→
The process proceeds from step 201 to step 208. In step 208, it is determined which of the left and right wheels is the inner ring and which is the outer ring, and the process proceeds to step 209 or step 210.

Then, in step 211, whether the inner and outer ring rotational speed difference (Ni-No) is (Ni-No)≧0 or (Ni-No)<
If (Ni-No)≧0, that is, if the inner ring rotational speed Ni is greater than the outer ring rotational speed No, the process proceeds to step 204, where the duty=
100% control signal c is output, (Ni−No)<0
In other words, the inner ring rotation speed Ni is the outer ring rotation speed
If it is smaller than No, proceed to step 212;
In this step 212, a predetermined rotational speed difference between the inner and outer rings is determined.
It is determined whether it is smaller or larger than Nt, (Ni−No)
If <Nt, the process proceeds to step 207 and the control signal c with duty=0 is output, and if Nt<(Ni-No)<
If it is 0, proceed to step 213 and step 214, and set the predetermined duty ratio (duty = 100%).
A control signal c according to the following) is output.

In step 213, step 209 or step 21 is selected from a map (FIG. 5) showing the relationship between the rotational speed difference between the inner and outer wheels and the duty, which is stored in advance in the ROM 133 of the control unit 13.
The duty is searched based on the calculation result at 0.

For example, when the difference in rotational speed between the inner and outer wheels is _-N2 , the duty D= _D2 .

In this way, differential resistance is always applied during normal straight-line driving, and like a normal limited slip differential, it improves straight-line performance on rough roads, and also improves straight-line performance on rough roads. Even if the vehicle gets stuck in ice or snow, the increased drive torque on the low speed side improves the ability to escape.

Furthermore, at the beginning of a turn, the rotational speed of the inner ring becomes smaller than the rotational speed of the outer ring due to the difference in turning radius.

Therefore, in the flowchart of FIG. 6, the control operation flow reaches step 207 or step 214, and even if there is a difference in rotational speed, the control operation operates in the direction of reducing or eliminating the differential resistance force, and the differential The tendency of understeer at the beginning of a turn due to resistance force is eliminated.

Furthermore, at the beginning of a turn, the centrifugal force applied to the vehicle causes the inner wheels to lift up and slip, so the rotational speed of the inner wheels tends to become faster than the rotational speed of the outer wheels.

Therefore, in the flowchart of FIG. 6, the flow of the control operation reaches step 204, where the control operation moves in the direction of applying the maximum differential resistance, so even if the inner wheel slips, the other outer wheel can drive. Improves turning acceleration.

The torque characteristics of the inner and outer wheels during this turn are as shown in Figure 7. At the beginning of the turn (up to the ◎ position), the torque of the inner and outer wheels is the same as there is no differential resistance applied, and the Late period (after ◎ position)
In this case, the driving torque on the outer wheel side increases due to the application of differential resistance force.

Further, the turning trajectory becomes a trajectory as shown by the dotted line C in FIG. 8, and although the oversteer tendency in the late stages of the turns remains, the understeer tendency in the early stages of the turns is eliminated.

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 embodiment, when the inner wheel rotational speed is smaller than the outer wheel rotational speed during turning, a control example is shown in which the differential resistance force is reduced up to a certain predetermined rotational speed difference, and when it exceeds the differential resistance force, the differential resistance force is eliminated. The differential resistance force may be eliminated all at once in consideration of the delay in hydraulic response, or it may be reduced gradually as in the embodiment.

Furthermore, even if the inner ring rotational speed is lower than the outer ring rotational speed, the differential resistance remains applied until a small speed difference region within the rotational speed difference that does not exhibit a high understeer tendency, and when the speed difference exceeds this speed difference region. The differential resistance force may be reduced.

(Effects of the invention) As explained above, in the vehicle differential limiting control device of the present invention, when a signal indicating that the rotational speed of the inner wheel during turning is smaller than the rotational speed of the outer wheel during turning is input, Since this is a means to reduce the dynamic resistance force, the differential resistance force is increased when differential restriction is necessary, such as when there is a difference in rotational speed between the left and right wheels when driving straight, or when the inner wheel rotational speed is large when turning.
The differential limiting action improves straight-line stability and turning stability, and when turning on dry roads, etc., when the inner ring rotation speed is low, the differential resistance force is reduced, and the differential limiting action reduces the tendency for understeer at the beginning of the turn. This has the effect of being able to prevent this.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a claim showing a vehicle differential limiting control device of the present invention, Fig. 2 is a sectional view showing a differential unit of an embodiment of the device of the invention, and Fig. 3 is a view taken in the Z direction of Fig. 2. , FIG. 4 is a diagram showing the hydraulic pressure generating device and control device of the embodiment device, FIG. 5 is a relationship diagram between the rotational speed difference between the inner and outer wheels and the duty, which is stored in advance in the control unit of the embodiment device, and FIG. 6 is a diagram showing the duty. The figure is a flowchart showing the flow of the differential limiting control operation of the embodiment device, FIG. 7 is a diagram of inner and outer wheel torque characteristics in the embodiment device, and FIG. 8 is a turning locus diagram of a vehicle equipped with the embodiment and the conventional device. , FIG. 9 is a diagram showing the torque characteristics of the inner and outer wheels in the conventional device. DESCRIPTION OF SYMBOLS 1... Drive left wheel, 2... Drive right wheel, 3... Differential means, 4... Differential limiting mechanism, 5... Actuator, 6... Fluid pressure generation means, 7... Input sensor,
701... Steering angle sensor, 702... Left wheel rotation speed sensor, 703... Right wheel rotation speed sensor, 8... Control means.

Claims (1)

[Scope of Claim for Utility Model Registration] A differential means for distributing and transmitting engine driving force to left and right drive wheels while allowing differential movement, and a differential resistance force provided in the differential means that uses external fluid pressure to generate a differential resistance force. a fluid pressure generating means having an actuator that controls fluid pressure supply to the differential limiting mechanism; an input sensor that detects the operating state of the vehicle; A differential limiting control device for a vehicle, comprising: a control means for outputting a control signal for increasing or decreasing a resistance force to the actuator, the input sensor being a steering angle sensor for detecting a steering angle; It includes a left wheel rotation speed sensor and a right wheel rotation speed sensor that detect the rotation speed, and when a signal indicating that the inner wheel rotation speed of the turning wheel is smaller than the rotation speed of the outer wheel of the turn is input from these input sensors during turning. A differential limiting control means for a vehicle, characterized in that the control means performs control to reduce differential resistance force.