JPH054529A - Differential limit device for vehicle - Google Patents

Abstract

PURPOSE:To perform the differential control in response to the structural characteristic of a vehicle and the like by controlling the differential limit actions based on the differential rotating speeds of an inter-axle differential and inter- wheel differentials when the vehicle speed is a preset value or above, and controlling the differential limit actions based on the output of an engine when the vehicle speed is the preset value or below. CONSTITUTION:In the power transmission system of a vehicle, a central differential 20 is arranged on a transfer 12, and front and rear differentials 21, 22 are arranged on front and rear axles 15, 17 respectively. The differentials 20-22 are controlled by a differential control unit 43 respectively based on input signals from a throttle sensor 32, a brake switch 31 and a manual switch 44. The differential control unit 43 controls the differential limit actions based on the differential rotating speeds of the inter-axle differential 20 and the inter- wheel differentials 21, 22 when the vehicle speed is a preset value or above. It controls the differential limit actions based on the output of an engine 10 when the vehicle speed is the preset value or below.

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 specifically, to a vehicle operating condition,
The present invention relates to a differential limiting device capable of performing differential control adapted to structural characteristics.

[0002]

2. Description of the Related Art In general, a four-wheel drive vehicle is provided with a center differential provided between axles of the front and rear wheels, a front differential provided between front wheels, and a rear differential in order to compensate for a difference in trajectories of the front and rear wheels during turning. Each has a rear differential disposed between the wheels. Such a four-wheel drive vehicle is described in, for example, Japanese Patent Laid-Open No. 62-166114. This four-wheel drive vehicle is provided with a differential limiting device including a front differential, a rear differential, and a center differential whose operating states are locked and unlocked by hydraulic pressure. The 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 on the basis of these values, and makes various driving states. Correspondingly, the operating states of the front differential, the rear differential, and the center differential are set, thereby improving steering stability, braking performance, acceleration performance, and the like.

A differential limiting device of this type has been proposed which is configured to increase the transmission torque capacity in accordance with an increase in the rotational speed difference between the front and rear wheels (Japanese Patent Laid-Open No. 62-2).
61538). This differential limiting device gradually limits the differential action of the center differential device with an increase in the rotational speed difference between the front and rear wheels, and thereby attempts to ensure a smooth start of the vehicle when escaping from a rough road.

A differential limiting device constructed to control the transmission torque capacity based on the throttle opening and the vehicle speed has been proposed (Japanese Patent Laid-Open No. 63-57332). This type of differential limiting device controls the differential action of the center differential on the basis of the throttle opening and the vehicle speed, thereby preventing tire wear and deterioration of fuel consumption during high speed running.

[0005]

The differential limitation based on the difference in the rotational speeds of the front and rear wheels is a control that is performed to eliminate the slip that actually occurs, while it is based on the throttle opening. The differential limitation is a control that is performed to avoid possible slip. However, the slip characteristics of the vehicle actually differ depending on the driving conditions and the structural characteristics of the vehicle, and the above control methods are applicable to all driving conditions and the structural characteristics of the vehicle related to the arrangement of each differential. It is not possible. For example, when driving at low speed, is the difference in rotation speed caused by steering?
Alternatively, it is difficult to reliably determine whether the slip has occurred. Also, when traveling at high speed, the possibility of slippage due to depression of the accelerator is extremely low, and it is desirable to emphasize fuel consumption. Therefore, there is a demand for a differential limiting device that performs suitable differential control according to the driving state of the vehicle.

The present invention has been made in view of the above points, and an object of the present invention is to provide a differential limiting device capable of performing a differential control adapted to a driving state of a vehicle and structural characteristics. To do.

[0007]

In order to achieve the above object, the present invention relates to a differential limiting device for a vehicle, which performs differential limiting by setting the inter-axle differential and the inter-wheel differential in a locked state under predetermined conditions. A first differential limiting means provided on the differential for limiting the differential of the inter-axle differential; a second differential limiting means provided on the inter-wheel differential for limiting the differential of the inter-wheel differential; Differential control means for controlling the differential limiting operation of the first and second differential limiting means, wherein the differential control means includes the inter-axle differential and / or the inter-wheel differential when the vehicle speed exceeds a predetermined vehicle speed. The first differential limiting means and / or
Alternatively, the differential limiting operation of the second differential limiting means is controlled, and when the vehicle speed is equal to or lower than a predetermined vehicle speed, the difference between the first differential limiting means and / or the second differential limiting means is determined based on the output of the engine. Provided is a vehicle differential limiting device characterized by controlling a motion limiting operation.

According to the differential limiting device having such a structure, when the vehicle is traveling at a high speed where slipping is relatively unlikely to occur, when the slipping actually occurs, the differential is limited in order to eliminate the slipping. It can be performed. Further, in the above-described differential limiting device, during low-speed traveling in which slip is relatively likely to occur, the differential is limited in order to avoid possible slip when the output of the engine is increased. It can be performed.

In order to achieve the above object, the present invention is provided in an inter-axle differential in a differential limiting device for a vehicle, in which the inter-axle differential and the inter-wheel differential are locked in a locked condition under predetermined conditions.
First differential limiting means for limiting the differential of the axle differential and second differential limiting means provided for the wheel differential to limit the differential of the wheel differential, and the first and second differences. Differential control means for controlling the differential limiting operation of the motion limiting means, wherein the differential controlling means controls the differential limiting operation of the first differential limiting means based on the output of the engine, A differential limiting device for a vehicle, wherein the differential limiting operation of the second differential limiting means is controlled based on a differential rotation speed of a wheel-to-wheel differential.

According to the differential limiting device of this construction, the differential between the axles, which is relatively close to the engine and distributes the driving force to the front wheels and the rear wheels, limits the differential according to the output of the engine. This ensures that the driving force is distributed back and forth, and on the other hand, for the inter-wheel differential that is relatively close to the wheels and that distributes the driving force to the left and right wheels, for example, the left and right rear wheels, the other wheel, for example, , The differential is limited according to the rotational speed difference between the left and right rear wheels without affecting the left and right front wheels, thereby effectively suppressing the slip that occurs while ensuring the operability of the vehicle. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment 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 of the present invention. First, the power transmission system of the vehicle shown in FIG. 1 will be described. Reference numeral 10 denotes an engine. A transmission 11 is connected to the engine 10, and a transfer 12 is connected to the transmission 11. A front propeller shaft 13 for transmitting the output from the engine 10 to the front wheel side and a rear propeller shaft 14 for transmitting the output from the engine 10 to the rear wheel side are connected to the transfer 12, respectively. This front propeller shaft 13 has a front axle 1
A front wheel 16 is connected via 5. A rear wheel 18 is connected to the rear propeller shaft 14 via a rear axle 17. Further, the transfer 12 has a center differential 20 (hereinafter referred to as a center differential), the front axle 15 has a front differential 21 (hereinafter referred to as a front differential), and the rear axle 15 has a rear differential 22 (hereinafter referred to as a rear differential). That is) provided respectively.

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), and each wheel speed is input from the wheel speed sensor 30 to the ABS control unit 41. Reference numeral 43 denotes a differential control unit. The differential control unit 43 is connected with a manual switch 44 and a battery 45 for selecting a diff lock mode to be described later. The differential control unit 43 receives a throttle opening from the throttle sensor 32, a brake signal from the brake switch 31, a wheel speed of each wheel, and a mode signal from the manual switch 44. Based on each of these input values, the differential control unit 43
To the center differential 20, the front differential 21 to the front differential current, and the rear differential 22 to the rear differential current respectively. Based on these current values, the center differential 20, the front differential 21, and the rear differential 22 are in the unlocked state and the intermediate locked state. , It is in 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 by the electromagnetic multi-plate clutch 50, the differential 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 structure as that shown in FIG. Next, the control contents in each mode selected by the manual switch 44 will be described with reference to Table 1.

[0016]

[Table 1]

As shown in Table 1, in the "AUTO (A mode)" of the manual switch 44, the front differential 21 is in the unlocked state, and the center differential 20 and the rear differential 22 are in the automatic mode control. "C (C mode)"
In the above, the front differential 21 is unlocked, the center differential 20 is completely locked, and the rear differential 22 is in automatic mode control. In "R (R mode)", the front differential 21 is unlocked, and the center differential 20 and the rear differential 22 are completely locked. In "F (F mode)", the front differential 21 and the center differential 20
Also, all of the rear differential 22 are completely locked. Here, If is the front differential current, Ic is the center differential current, Ir is the rear differential current, and the numerical values are the current values thereof. The electromagnetic multiple disc clutches provided in each differential are provided with the differential current of these values. By being supplied, each differential is brought into a completely locked state.

Each of these modes is arbitrarily selected by the driver. In A mode, front differential 2
Since No. 1 is in the unlocked state, it has little influence on the drivability and is excellent in operability, and is suitable for on-road traveling on a normal road such as an urban area. On the other hand, "F mode"
In, since the front differential 21, the center differential 20, and the rear differential 22 are all completely locked,
Operability is reduced, but driveability is excellent, making it suitable for off-road traveling on rough roads. The “C mode” and the “R mode” have characteristics between them and are selected according to the driver's preference.

Next, the control contents of the differential control unit 43 will be described with reference to FIGS. In these figures, the symbol P indicates each step in the flowchart. FIG. 3 is a flowchart showing a vehicle body speed calculation routine in the automatic mode control. As shown in FIG. 3, at P10, each wheel speed Nfr,
Input Nfl, Nrr, Nrl. Here, Nfr represents the wheel speed of the right front wheel, Nfl represents 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 P11, these wheel speeds Nfr, Nfl, Nrr,
The minimum value of Nrl is defined as the vehicle speed Vsp.

FIG. 4 is a flow chart showing a center differential differential rotation speed calculation routine in the automatic mode control. As shown in FIG. 4, at P20, each wheel speed Nfr,
Input Nfl, Nrr, Nrl. Next, in P21, the center differential differential rotation speed ΔNc, which is the rotation difference, is obtained. Figure 5
6 is a flowchart showing a rear differential differential rotation speed calculation routine in automatic mode control. As shown in FIG. 5, at P30, the wheel speeds Nrr and Nrl of the rear wheels are input. Next, at P31, the rear differential differential rotation speed ΔNr is obtained.

6 and 7 are flowcharts showing a center diff current setting routine in the automatic mode control. As shown in FIG. 6, the vehicle body speed V obtained as described above
sp is input (P40), it is determined whether the center differential current Ic is supplied (P41), and the center differential current Ic is determined.
Is not supplied, that is, when the center differential 20 is in the unlocked state, it is determined whether the vehicle body speed Vsp exceeds a predetermined speed, for example, 80 km / h (P4).
2). When the vehicle body speed Vsp exceeds 80 km / h, that is, when the vehicle is traveling at a relatively high speed, the desired center differential current Ica is obtained from the center differential differential rotation speed ΔNc (P43), while the vehicle body speed Vsp is When the speed is 80 km / h or less, that is, when the vehicle is traveling at a relatively low speed, the desired center differential current Ica is obtained from the throttle opening TVO (P44). Further, when the center differential current Ic is supplied and the center differential 20 is in the complete lock state or the intermediate lock state (P41), the center differential current I under different conditions.
Since ca may be reset, the current setting conditions are held, and when the center differential 20 is unlocked, the process proceeds to the determination of the vehicle body speed Vsp (P42).

FIG. 8 shows the current value Ica and the throttle opening TV.
9 is a diagram showing the relationship with O, and FIG. 9 is a diagram showing the relationship between the current value Ica and the center differential differential rotation speed ΔNc. As shown in the figure, the throttle opening TVO or the center differential differential rotation speed ΔNc is increased. Along with this, the current value Ica is set larger, and when the predetermined throttle opening TVO or the center differential differential rotation speed ΔNc is exceeded, the current value Ica is set to Imax, respectively.

The current value Ic thus obtained is set as the center differential current value Ic as shown in FIG. 7 (P
50). Further, it is determined whether or not the center differential current Ic is the maximum current value Imax (P51). Center differential current Ic is maximum current value Ima
When it is different from x, that is, when it is smaller than the maximum current value Imax, “Ic = Ic” is set in P52.
At this time, the center differential 20 is in an intermediate locked state. However, in the case of “Ic = 0”, the unlocked state is set. When the center differential current Ic has the maximum current value Imax, the timer is set to the initial value in P53, and the center differential current Ic is set to "Ic = Imax" in P54. At this time, the center differential 20 is completely locked. Then P
The timer is counted up at 55, and it is determined at P56 whether a predetermined time has elapsed. By this self-holding, the center differential 20 can be kept in the completely locked state for a predetermined time, and hunting due to a sudden change in the center differential differential rotation speed ΔNc or the throttle opening TVO can be avoided.

Rear differential current I in automatic mode control
The setting of r is also performed in the same manner as the setting of the center differential current Ic. That is, when the vehicle body speed Vsp is higher than the predetermined speed, the desired rear differential current Ira is obtained from the rear differential differential rotation speed ΔNr, while the vehicle speed Vsp
When the vehicle is traveling at a low speed below a predetermined speed, the desired rear differential current Ira is obtained from the throttle opening TVO. Although illustration and detailed description of a specific control current value setting routine are omitted, the center differential current values Ica and Ic shown in FIGS. 6 to 9 are rear differential current values Ira, respectively.
And Ir, and the center differential differential rotation speed Δ
Replace Nr with rear differential center differential differential speed ΔNr,
Further, one of ordinary skill in the art will readily appreciate upon consideration of the above description of the center differential current.

As described above, in the above embodiment, the center differential current Ic and the rear differential current Ir in the automatic mode control are controlled.
Is set under different conditions depending on whether or not the vehicle body speed Vsp exceeds a predetermined speed. When the vehicle body speed Vsp exceeds the predetermined speed and the vehicle is traveling at a relatively high speed, the desired center differential current is set. Ica and the rear differential current Ira are obtained from the center differential differential rotation speed ΔNr, respectively. On the other hand, when the vehicle body speed Vsp is a predetermined speed or less and the vehicle is traveling at a relatively low speed, the desired center differential current Ica and the rear differential current Ira are obtained. Each is calculated from the throttle opening TVO. Therefore, at the time of high-speed running where slippage is relatively unlikely to occur, only when slippage actually occurs, control for increasing the center differential current Ic and the rear differential current Ir, that is, control that emphasizes fuel consumption can be performed. On the other hand, on the other hand, during low-speed traveling in which slip is relatively likely to occur, control for increasing the center differential current Ic and the rear differential current Ir in order to avoid possible slip.
That is, it is possible to perform the acceleration-oriented control according to the engine output.

10 and 11 are flow charts showing a modification of the above embodiment, and FIG. 12 is a current value Ica.
FIG. 6 is a diagram showing a relationship between the rear differential differential rotation speed ΔNr. In this example, with respect to the center differential 20 arranged on the upstream side of the drive torque transmission path, that is, relatively close to the engine,
A desired center differential current Ica is obtained from the throttle opening TVO, and on the other hand, with respect to the rear differential 22 arranged on the downstream side of the drive torque transmission path, that is, relatively close to the wheels, the desired rear differential current Ira is calculated from the rear differential differential speed ΔNr. Ask.

In the center differential current Ic setting routine in the automatic mode control, first, a desired center differential current Ica is obtained from the throttle opening TVO as shown in FIG. 8 and set as the center differential current value Ic (P60).
Further, it is determined whether or not the center differential current Ic is the maximum current value Imax (P61). Center differential current I
When c is different from the maximum current value Imax, that is, when it is smaller than the maximum current value Imax, “Ic
= Ic ". At this time, the center differential 20 is in an intermediate locked state, and in the case of "Ic = 0", it is in an unlocked state. On the other hand, when the center differential current Ic is the maximum current value Imax, the timer is set to the initial value, the center differential current Ic is set as "Ic = Imax" (P63, 64), and the timer is counted up (P6).
5, 66).

In the routine for setting the rear differential current Ir in the automatic mode control, first, the desired center differential current Ira is set to the rear differential differential rotation speed ΔN as shown in FIG.
It is obtained as a function of r and set as the rear differential current value Ir (P70). Further, it is determined whether or not this rear differential current Ir is the maximum current value Imax (P71). When the rear differential current Ir is different from the maximum current value Imax, that is, when it is smaller than the maximum current value Imax, "Ic = Ic" is set in P72. At this time, the rear differential 20
Is in an intermediate lock state, and in the case of "Ic = 0", is in an unlock state. On the other hand, when the rear differential current Ir is the maximum current value Imax, the timer is set to the initial value, the center differential current Ic is set as "Ic = Imax" (P73, 74), and the timer is counted up (P
75, 76).

In this embodiment, regarding the center differential 20,
The desired center differential current Ica is obtained from the throttle opening TVO, while the desired rear differential current Ira for the rear differential 22 is obtained from the rear differential differential rotation speed ΔNr. Thus, for the center differential 20 which is relatively close to the engine and which distributes the driving force to the front wheels 16 and the rear wheels 18, by limiting the differential according to the output of the engine, the driving force is reliably distributed to the front and rear. Further, regarding the rear differential 22 that is relatively close to the wheels and distributes the driving force to the left and right rear wheels 18, by limiting the differential according to the rotational speed difference between the left and right rear wheels 18, Therefore, the rear wheels 18 can be prevented from slipping without affecting the vehicle operation.

The present invention is not limited to the above embodiments, and various modifications and changes are possible, and these are also included in the present invention within the scope of the invention described in the claims. Needless to say. For example, in the above embodiment, both the center differential current and the rear differential current are set under different conditions depending on whether or not the vehicle body speed Vsp exceeds a predetermined speed, but other settings regarding the rear differential current are made. A method, for example, a setting method of obtaining from the rear differential differential rotation speed ΔNr regardless of the vehicle body speed Vsp may be adopted.

[0031]

As described above, according to the present invention,
It is possible to provide a differential limiting device capable of performing differential control adapted to the driving state of the vehicle and its structural characteristics.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a vehicle control device including a differential limiting device of the present invention.

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

FIG. 3 is a flowchart showing a vehicle body speed calculation routine in automatic mode control.

FIG. 4 is a flowchart showing a center differential differential rotation speed calculation routine in automatic mode control.

FIG. 5 is a flowchart showing a rear differential differential rotation speed calculation routine in automatic mode control.

FIG. 6 is a flowchart showing a center differential current setting routine in auto mode control.

FIG. 7 is a flowchart showing a center differential current setting routine in automatic mode control.

FIG. 8 is a diagram showing a relationship between a center differential current value and a throttle opening.

FIG. 9 is a diagram showing a relationship between a center differential current value and a center differential differential rotation speed.

FIG. 10 is a flowchart showing a modified example of a center differential current setting routine in auto mode control.

FIG. 11 is a flowchart showing a modified example of a rear differential current setting routine in auto mode control.

FIG. 12 is a diagram showing a relationship between a rear differential current value and a rear differential differential rotation speed.

[Explanation of symbols]

16 front wheel 18 rear wheel 20 center differential (center differential) 21 front differential (front differential) 22 rear differential (rear differential) 30 wheel speed sensor 31 brake switch 32 throttle sensor 41 anti-skid braking device control unit 43 differential control・ Unit 44 Manual switch 50 Electromagnetic multi-plate clutch

Continued front page    (72) Inventor Yoshitaka Kimura             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Naoji Masuda             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation

Claims (3)

[Claims] 1. A differential limiting device for a vehicle, wherein an inter-axle differential and an inter-wheel differential are locked under a predetermined condition to limit the differential. The differential limiting device is provided in the inter-axle differential and limits the differential of the inter-axle differential. First differential limiting means and a second differential limiting means provided on the inter-wheel differential and limiting the differential of the inter-wheel differential, and controlling the differential limiting operation of the first and second differential limiting means. And a differential control means for controlling the first differential limiting means based on the differential rotation speed of the inter-axle differential and / or the inter-wheel differential when the vehicle speed exceeds a predetermined vehicle speed. And / or controlling the differential limiting operation of the second differential limiting means, and when the vehicle speed is equal to or lower than a predetermined vehicle speed, based on the output of the engine, the first differential limiting There is provided a differential limiting device for a vehicle, characterized by controlling the differential limiting operation of the means and / or the second differential limiting means. 2. A differential limiting device for a vehicle, wherein the differential between the axles and the differential between the wheels are locked under a predetermined condition to limit the differential. The differential is provided in the differential between the axles and limits the differential of the differential between the axles. First differential limiting means and a second differential limiting means provided on the inter-wheel differential and limiting the differential of the inter-wheel differential, and controlling the differential limiting operation of the first and second differential limiting means. Differential control means for performing the first differential control based on the output of the engine.
The differential limiting operation of the differential limiting means is controlled, and the differential limiting operation of the second differential limiting means is controlled based on the differential rotation speed of the inter-wheel differential. Restriction device. 3. The differential limiting device for a vehicle according to claim 1, wherein the inter-wheel differential is a rear-wheel differential.