JPH06144055A - Differentail limiter of automobile - Google Patents

Abstract

PURPOSE:To secure a car performance including traveling stability, controllability, roadability or the like by installing such a means as determining the operating order of respective differentials, and operating a differential limit ing means in the order of a center differential, a rear differential and a front differential. CONSTITUTION:A center differential 20 is installed in a space between both axles, a rear differential 22 in a space between both rear wheels and a front differential 21 in a space between both front wheels, respectively, and each magnetic multiple disk clutch is installed in these differentials 20, 21 and 22 as a differential limiting means. In addition, the device is provided with a differential control unit 43 into which each signal out of a throttle sensor 32, a brake switch 31 and each wheel speed sensor is inputted. On the basis of these input values, each differential current is fed to these differentials 20, 21 and 22 from the control unit 43. Each target current value is set to each differential, and on the basis of the current value supplied, each differential comes to antilocking, intermediate locking and complete locking states respectively. In this constitution, differential limits are carried out by the center differential 20, the rear differential 22 and the front differential 21 in order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle differential limiting device, and more particularly, to a vehicle differential limiting device capable of ensuring traveling stability during starting and acceleration.

[0002]

2. Description of the Related Art A four-wheel drive vehicle has a center differential disposed between the front and rear wheel axles, a front differential disposed between the front wheels, and a front differential to compensate for the difference in the trajectories of the front and rear wheels when turning. , And rear differentials arranged between the rear wheels. The function of these differentials makes it possible to eliminate the so-called tight corner braking phenomenon and the like. However, in cars equipped with these differentials,
If any of the four wheels spins when starting or accelerating, the driving force is not sufficiently transmitted to the other wheels, making stable starting and accelerating difficult, resulting in poor steering stability, braking, and acceleration. There was a problem of doing.

An example of a four-wheel drive vehicle for solving such a problem is disclosed in Japanese Patent Laid-Open No. 62-166114. This four-wheel drive vehicle is provided with a differential limiting device for a front differential, a rear differential, and a center differential whose operating states are locked and unlocked by hydraulic pressure. This differential limiting device inputs a wheel speed signal and a steering angle signal of each wheel to a control circuit, and makes a bad road determination, a straight traveling determination, an acceleration determination and a braking determination based on these values, and various running states. In response to this, the operation of the front differential, rear differential and center differential is controlled to improve steering stability, braking performance, acceleration performance, and the like.

Further, in this type of differential limiting device, there has been proposed a device configured to control the transmission torque capacity of the differential limiting device on the basis of the difference in the rotational speeds of the front and rear wheels (Japanese Patent Laid-Open No. 62-62160). ─166113). This differential limiting device is configured to reduce the transmission torque capacity when the rotational speed difference between the front and rear wheels is relatively small, thereby ensuring an appropriate differential action or differential limiting action according to the operating state. try to.

Further, there has been proposed a diff lock control device configured to detect the starting state of an automobile and automatically lock the center differential when the automobile starts (Japanese Patent Laid-Open No. 63-251327). This diff lock device eliminates the need for a driver's manual diff lock operation at the time of starting and attempts to secure a reliable diff lock operation at the time of starting.

[0006]

However, in such a differential limiting device, when the differentials are locked, a plurality of differentials are locked substantially synchronously, so that the drive torque fluctuates rapidly. A so-called torque shock may occur. Further, since all the differential limiting devices of the differentials lock or unlock at substantially the same time under substantially the same conditions, under certain operating conditions, all the limiting devices may cause hunting all at once. Conceivable. Furthermore, the differential limiting device generally includes an electromagnetic or hydraulically actuated multi-disc clutch that regulates the differential of each differential. When an electromagnetic type clutch is used as such a clutch, the clutch in each differential is reduced. Simultaneous operation of 1 may impose a sudden electrical load on the control system of the limited slip differential.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a differential limiting device for an automobile capable of suppressing a torque shock during traveling due to a differential lock operation. Especially.
Another object of the present invention is to provide an electrically operated differential limiting device that can avoid a sudden electrical load from being generated in the control system.

Another object of the present invention is to provide a vehicle differential limiting device capable of effectively preventing wheel slippage and contributing to vehicle stability, especially when the vehicle starts or accelerates.

[0009]

In order to achieve the above object, the present invention is premised on a differential limiting device for an automobile provided with a control system for limiting the differential of all of a plurality of differentials under a predetermined condition. The plurality of differentials includes a first differential provided between axles, a second differential provided between rear wheels, and a third differential provided between front wheels. First differential limiting means attached to limit differential of the first differential, and second differential limiting means attached to the second differential and limiting differential of the second differential. A third differential limiting means attached to the third differential for limiting the differential of the third differential; the first differential limiting means; When the differential limiting means and the third differential limiting means are all activated, the first differential limiting means, the second differential limiting means, and the third differential limiting means. And an operation order determining means for operating each differential limiting means in this order.

According to the differential limiting device having such a configuration, the differential timing between the rear axles and the operation timing of the first differential limiting means provided on the differential between the axles for limiting the differential of the inter-axle differential are controlled. A third differential that is provided in the differential timing of the second differential limiting means for limiting the differential between the rear wheels and the differential between the front wheels and limits the differential between the front wheels. The differential timing of the limiting means does not match.

Further, the first to third differential limiting means are always the first differential limiting means, the second differential limiting means, and the third differential limiting means.
The differential limiting means will be operated in that order.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing an overall configuration of a vehicle control device according to an embodiment of the present invention. First, the power transmission system of the vehicle shown in FIG. 1 will be described. 10 is an engine, and this engine 10 has a transmission 1
1 is connected, and a transfer 12 is connected to this transmission 11. The transfer 12 includes a front propeller shaft 13 for transmitting the output from the engine 10 to the front wheels and a rear propeller shaft for transmitting the output to the rear wheels.
The propeller shafts 14 are connected to each other. A front wheel 16 is connected to the front propeller shaft 13 via a front axle 15. A rear wheel 18 is connected to the rear propeller shaft 14 via a rear axle 17. Transfer 1
2 is a center differential 20 (hereinafter referred to as center differential), and the front axle 15 is a front differential.
A differential 21 (hereinafter referred to as a front differential) and a rear axle 15 are provided with a rear differential 22 (hereinafter referred to as a rear differential).

A wheel speed sensor 30 for detecting the wheel speed of each wheel is attached to each front wheel 16 and each rear wheel 18. Reference numeral 31 is a brake switch, and the brake switch 31 detects ON / OFF of the brake. Reference numeral 32 denotes a throttle sensor, which detects the throttle opening of the engine 10.

Reference numeral 40 denotes an engine control unit, and the throttle opening is input from the throttle sensor 32 to the engine control unit 40. Reference numeral 41 is a control unit for an anti-skid brake device (hereinafter referred to as an ABS control unit). The wheel speed sensor 30 inputs each wheel speed to the ABS control unit 41. Reference numeral 43 is a differential control unit, and a battery 45 is connected to the differential control unit 43. A throttle opening from the throttle sensor 32, a brake signal from the brake switch 31, and a wheel speed of each wheel are input to the differential control unit 43. Based on each of these entered values,
From the differential control unit 43,
A center differential current is supplied to the center differential 20, a front differential current is supplied to the front differential 21, and a rear differential current is supplied to the rear differential 22, respectively. Based on these current values, the center differential 2 is supplied.
0, the front differential 21 and the rear differential 22 are in an unlocked state, an intermediate locked state, and a completely locked state.

FIG. 2 is a sectional view showing an electromagnetic multi-plate clutch provided on the center differential. The center differential 20 is provided with an electromagnetic multi-plate clutch 50, and the electromagnetic multi-plate clutch 50 brings the center differential 20 into an unlocked state, an intermediate locked state, and a completely locked state. The electromagnetic multi-plate clutch 50 may be of any type as long as it can limit the differential between the front propeller shaft 13 and the rear propeller shaft 14. An example thereof is shown in FIG. In FIG. 2, the electromagnetic multi-plate clutch 50 is composed of a clutch plate 51 composed of a plurality of inner discs and an outer disc, and an actuator 52 for generating a pressing force on the clutch plate 51. 53 is a bearing,
Reference numeral 54 is a transmission member that is transmission-connected to one propeller shaft, and 55 is a transmission member that is transmission-connected to the other propeller shaft. The actuator 52 uses the magnetic force generated when a current flows through the solenoid 56 to cause the armature 5 to move.
7 is configured to press the clutch plate 51.
In this electromagnetic multi-plate clutch 50, the solenoid 56
Is proportional to the pressing force for frictionally engaging the clutch plate 51, that is, the torque generated in the electromagnetic multi-plate clutch 50, the differential rotation speed of the center differential 20 should be continuously changed by increasing or decreasing the current. You can The front differential 21 and the rear differential 22 are also provided with an electromagnetic multi-plate clutch, but the description thereof is omitted because it has the same configuration as that shown in FIG.

Next, with reference to FIGS. 3 to 10, how the differential control unit 43 controls the locked state of each differential in the first embodiment of the present invention will be described. 3 to 9, the symbol P indicates each step in the flowchart. FIG. 3 is a flowchart showing a differential rotation calculation routine of the center differential 20. As shown in FIG. 3, at P30, the wheel speeds Nfr, Nfl, Nrr, Nrl are input. Here, Nfr is the wheel speed of the right front wheel, Nfl is the wheel speed of the left front wheel,
Nrr represents the wheel speed of the right rear wheel, and Nrl represents the wheel speed of the left rear wheel. Next, at P31, each of these wheel speeds N
Maximum value of fr, Nfl, Nrr, Nrl Max (Nfr, Nfl, Nrr,
The difference between Nrl) and the minimum value Min (Nfr, Nfl, Nrr, Nrl) is calculated, and this is defined as the differential rotation speed ΔNc of the center differential 20.

FIG. 4 is a flowchart showing a differential rotation speed calculation routine of the rear differential 22. As shown in FIG.
At P40, the rear wheel speeds Nrr and Nrl are input. Next, at P41, the absolute value of the difference between the wheel speeds Nrr and Nrl of the rear wheels is calculated and used as the differential rotation speed ΔNr of the rear differential 22.
FIG. 5 is a flowchart showing a differential rotation speed calculation routine of the front differential 21. As shown in FIG. 5, at P50, the wheel speeds Nrr and Nrl of the rear wheels are input. Next, at P51, the absolute value of the difference between the wheel speeds Nrr and Nrl of the front wheels is calculated and used as the differential rotation speed ΔNf of the front differential 21.

6 to 8 are a center differential 20 and a rear differential.
22, target current values Ica, I of the front differential 21
It is a flowchart for determining ra and Ifa.
These target current values Ica, Ira, Ifa are the differential rotation speeds ΔNc, ΔNr, ΔN of the respective differentials 20, 22, 21.
It is uniquely determined as a function of f according to the map shown in FIG. That is, for example, when a certain differential rotation speed ΔNc of the center differential 20 is determined, based on the control map of FIG.
Target current Ica of the center differential 20 corresponding to the ΔNc
Is determined.

Next, referring to FIG. 9, the differential control unit 43 includes the center differential 20, the rear differential 22,
A specific process for controlling the locked state of the front differential 21 will be described. At P91, the differential rotation speed ΔN of each of the center differential 20, rear differential 22, and front differential 21
Input c, ΔNr, and ΔNf. Next, in P92, it is determined whether the differential rotation speed ΔNc of the center differential 20 is 0 or not. If the differential rotation speed ΔNc of the center differential 20 is 0, the control ends without locking any of the differentials. On the other hand, when the differential rotation speed ΔNc of the center differential 20 is not 0, the target current value I of the center differential 20 corresponding to the differential rotation speed ΔNc determined by the above-described method.
ca is set (P93). Further, the target current value Ica is made to flow through the electromagnetic multi-plate clutch 50 provided on the center differential 20, and the center differential 20 is brought into a predetermined locked state.

Then, after a lapse of a predetermined time T1, at P95,
It is determined whether or not the differential rotation speed ΔNr of the rear differential 22 is zero.
If the differential rotation speed ΔNr of the rear differential 22 is 0, the control is terminated without locking either the rear differential 22 or the front differential 21. On the other hand, the differential rotation speed Δ of the rear differential 22
When Nr is not 0, the target current value Ira of the rear differential 22 corresponding to the differential rotation speed ΔNr is set (P9).
6). Further, the target current value Ira is supplied to the electromagnetic multi-plate clutch provided on the rear differential 22, and the rear differential 22 is brought into a predetermined locked state.

Then, after a predetermined time T2 has elapsed, at P98,
It is determined whether or not the differential rotation speed ΔNf of the front differential 21 is 0. If the differential rotation speed ΔNf of the front differential 21 is 0, the control is terminated without locking the front differential 21. On the other hand, when the differential rotation speed ΔNf of the front differential 21 is not 0, the target current value Ifa of the front differential 21 corresponding to the differential rotation speed ΔNf is set (P99).
Further, the target current value Ifa is made to flow through the electromagnetic multi-plate clutch provided in the front differential 21, the front differential 21 is brought into a predetermined locked state, and the control of the differential control unit 43 which is the control means of the differential limiting device is controlled. Ends.

Next, a second embodiment of the present invention will be described. In the present embodiment, the wheel speeds Nfr, Nfl, Nr of the respective wheels are
The difference between the maximum value Max (Nfr, Nfl, Nrr, Nrl) and the minimum value Min (Nfr, Nfl, Nrr, Nrl) of r and Nrl is calculated, and this is defined as the differential rotation speed ΔN. Fig. 11 shows the rotation speed ΔN
Fit the control map shown in, center differential 20, rear differential
22, target currents Ica, Ira, Ifa of the front differential 21
Is determined and the target currents are caused to flow through the electromagnetic multi-disc clutches provided in the respective differentials to control the differential limiting operation of the center differential 20, the rear differential 22, and the front differential 21. A major difference from the first embodiment is that a common differential rotation speed ΔN is applied to each differential of the center diff 20, the rear diff 22, and the front diff 21, and the center diff 20 is included in the control map.
This is the point where three lines showing the respective target currents for the rear differential 22 and the front differential 21 are drawn.

In the control map shown in FIG. 11, line C shows the target current Ica for the center differential 20, line R shows the target current Ira for the rear differential 22, and line F shows the target current Ifa for the front differential 21, respectively. That is, in this control map, the maximum value Ma of the wheel speeds Nfr, Nfl, Nrr, Nrl of each wheel is
x (Nfr, Nfl, Nrr, Nrl) and minimum value Min (Nfr, Nfl,
When the value of ΔN, which is the difference between (Nrr, Nrl), is determined, the three differential target currents Ica, Ira, Ifa of the center differential 20, the rear differential 22, and the front differential 21 are determined at once. As is clear from the state of the three lines in this control map, when the ΔN is small, the center differential 20
The electric current flows only through the electromagnetic multi-disc clutch of, and as ΔN increases, the electromagnetic multi-disc clutch of the rear differential 22 and then,
Electric current flows through the electromagnetic multi-plate clutch of the front differential 21. Therefore, the differential limit control of each differential according to this control map limits the differential of each differential in the order of the center differential 20, the rear differential 22, and the front differential 21, as in the first embodiment. It will be.

The present invention is not limited to the above embodiments, and various modifications and variations can be made within the technical scope described in the claims. Further, the present invention relates to control when limiting the differential of the differential and bringing the differential into the locked state, and the differential in the locked state is unlocked by various other control methods. Is.

[0025]

As described above, according to the present invention,
By preventing the respective differentials from simultaneously performing the lock operation, it becomes possible to provide a differential limiting device for an automobile capable of suppressing a torque shock during traveling due to the differential lock operation.

Further, according to the present invention, in the differential limiting device provided with the electrically operated differential limiting means, by preventing the respective differential limiting means from operating at the same time,
It is possible to prevent a transiently excessive load from occurring in the electrical system of the differential limiting device. Further, according to the present invention, the differential of the center differential is limited first to effectively cancel the slip of the wheels and preferentially secure the stability of the vehicle body. This is particularly effective when the vehicle starts or accelerates.

Next, since the operation of the rear differential which has a relatively small influence on the maneuverability is restricted, the maneuverability becomes excellent as compared with the case where the operation of the front differential is restricted first. And finally, limit the operation of the front differential,
Make it the most crossing condition. Therefore, the present invention is an automotive differential limiting device that limits the actuation of the differential by first giving priority to stability, then maneuverability, and finally runnability.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an overall configuration of a vehicle control device to which a differential limiting device of the present invention is applied.

FIG. 2 is a sectional view showing an electromagnetic multi-plate clutch provided on a center differential.

FIG. 3 is a flowchart showing a center differential differential rotation speed calculation routine.

FIG. 4 is a flowchart showing a rear differential differential rotation speed calculation routine.

FIG. 5 is a flowchart showing a front differential differential rotation speed calculation routine.

FIG. 6 is a flowchart showing a routine for setting a center differential target current.

FIG. 7 is a flowchart showing a routine for setting a rear differential target current.

FIG. 8 is a flowchart showing a routine for setting a target current of the front differential.

FIG. 9 is a flowchart showing operation control of a center differential, a rear differential, and a front differential.

FIG. 10 is a control map applied to the first embodiment of the present invention.

FIG. 11 is a control map applied to the second embodiment of the present invention.

[Explanation of symbols]

 20 Center differential (Center differential) 21 Front differential (Rear differential) 22 Rear differential (Rear differential) 43 Differential control unit 50 Electromagnetic multi-disc clutch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Shitani 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (1)

[Claims] 1. A differential limiting device for an automobile, comprising a control system for limiting differentials of all of a plurality of differentials under a predetermined condition, wherein the plurality of differentials are a first differential provided between axles, It is composed of a second differential provided between the rear wheels and a third differential provided between the front wheels, which is attached to the first differential and limits the differential of the first differential. A differential limiting means, a second differential limiting means attached to the second differential for limiting differential of the second differential, and a third differential attached to the third differential. All of the third differential limiting means for limiting differential, the first differential limiting means, the second differential limiting means, and the third differential limiting means When it is dynamic,
The first differential limiting means, the second differential limiting means, and the operation order determining means for operating each differential limiting means in this order. Differential limiting device.