JPH05262254A - Vehicle with driving force distribution interlocking rear wheel steering device - Google Patents

Abstract

PURPOSE:To securely improve the cornering performance of a vehicle. CONSTITUTION:In a vehicle provided with a driving force distributing device 60 to regulate distribution of a driving force from an engine 2 to left and right rear wheels 6 and 7 and a rear wheel steering device 20 to steer the left and right rear wheels 6 and 7, the rear wheel steering device 20 is provided with main and auxiliary steering mechanisms 20A and 20B and a control amount setting means 25 to set a distribution control amount of the driving force distributing device 60 and set a steering control amount of the auxiliary steering mechanism 20B. The control amount setting means 25 sets a distribution control amount to a low value and meanwhile sets a steering control amount to a high value when lateral acceleration exerted on a vehicle is low and sets a distribution control amount to a high value and meanwhile sets a steering control amount to a low value when lateral acceleration is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle equipped with a rear-wheel steering device of the driving force distribution interlocking system, which comprises a rear-wheel left-right driving force distribution device and a rear-wheel steering device.

[0002]

2. Description of the Related Art Conventionally, steering of an automobile is performed by steering front wheels, but in recent years, in order to improve turning performance of a vehicle, not only front wheels but also rear wheels are steered. A four-wheel steering system has also been developed. In this four-wheel steering system, the rear-wheel steering angle is adjusted according to the steering angle (that is, the front-wheel steering angle). Reverse phase steering,
At high speeds, the in-phase steering in which the rear wheels are steered in phase with the front wheels is performed with an emphasis on the stability of the posture of the vehicle when turning.

On the other hand, a means has been proposed in which a turning moment is generated in a vehicle by making the driving forces of the left and right driving wheels uneven, not by turning the wheels, and the turning performance is improved by the turning moment. .. Here, the correlation between the lateral acceleration (hereinafter, abbreviated as lateral G) and the cornering force (hereinafter, abbreviated as CF) that occurs when the conventional general automobile turns is as shown in FIG. The cornering force is a force acting on the tire on the road surface in a direction perpendicular to the traveling direction.

As shown in FIG. 10, the CF size increases in direct proportion to the lateral G size.
If the size of the lateral G becomes a certain size or more, the rate of increase in the value of CF becomes dull. Therefore, in a turn in which a large lateral G value occurs (for example, when the vehicle turns at a high steering angle with a large steering angle), the CF sharply becomes dull, and when the vehicle is further accelerated or the steering wheel is further turned. It is also possible that there will be a sudden oversteering tendency.

By mounting the above-described four-wheel steering device and the driving force distribution device for the left and right driving wheels on an automobile and controlling them appropriately, such a sudden oversteering tendency can be suppressed. It is possible to improve the turning performance of the vehicle.

[0006]

By the way, considering the improvement of the turning performance of the vehicle, it is conceivable to use the rear wheel steering and the uneven distribution of the left and right driving forces together. In this case, the rear wheel steering is used. The issue is how to control the driving force. The present invention was devised in view of the above-mentioned problems, and is provided with a rear wheel steering device with a driving force distribution interlocking type, which can significantly improve the turning performance of a vehicle by using rear wheel steering together with driving force control. An object is to provide a vehicle device.

[0007]

Therefore, a vehicle with a driving force distribution interlocking type rear wheel steering system according to the present invention includes a driving force distribution device for distributing and adjusting the driving force from the engine to the left and right rear wheels.
In a vehicle having a rear wheel steering device for steering the left and right rear wheels, the rear wheel steering device steers the rear wheels at a predetermined front-rear steering angle ratio with respect to the steering amount of the vehicle. And a sub-steering mechanism capable of additionally turning-correcting the main steering mechanism, and the distribution control of the driving force distribution device based on the yaw rate of the vehicle in order to improve the steer characteristic of the vehicle. A control amount setting means for setting the steering amount of the sub-steering mechanism and for setting the steering amount is provided, and the control amount setting means sets the distribution control amount small when the lateral acceleration applied to the vehicle is small. On the other hand, the steering control amount is set large, and when the lateral acceleration is large, the distribution control amount is set large while the steering control amount is set small.

[0008]

In the vehicle with the driving force distribution interlocking type rear wheel steering device of the present invention described above, the control amount setting means sets the distribution control amount of the driving force distribution device and the steering control amount of the auxiliary steering mechanism. Improve the steering characteristics of the vehicle. The control amount setting means sets the distribution control amount small when the lateral acceleration applied to the vehicle is small, while setting the steering control amount large, and sets the distribution control amount large when the lateral acceleration is large. On the other hand, the steering control amount is set small.

Then, for the rear wheels steered by the main steering mechanism, the sub steering mechanism additionally steers and corrects this steering angle, and the control means responds to the control of the driving force distribution device. Then, the steering amount of the sub steering mechanism is controlled.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, a vehicle equipped with a driving force distribution interlocking type rear wheel steering device will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the schematic construction thereof, and FIG. FIG. 3 is a schematic diagram showing the structure of the main part, FIG. 3 is a flowchart showing the operation of the main part, and FIGS. 4 to 9 are graphs showing the control characteristics of the device.

The vehicle with a driving force distribution interlocking type rear wheel steering device is provided with a driving force distribution device 60 and a rear wheel steering device 20. First, the driving force transmission system 1 in this vehicle
1, the driving force transmission system 1 receives the driving force from the engine 2 via a transmission or the like at a center differential 3 composed of planetary gears, and from the center differential 3 to the front wheel side. It is designed to be transmitted to the rear wheel side.

In particular, the center differential 3 is provided with a center differential differential limiting mechanism 24 capable of appropriately limiting the differential between the front and rear wheels. The differential limiting mechanism 24 is composed of a hydraulic multi-plate clutch here, and can control the distribution of the driving force to the front and rear wheels while limiting the differential between the front and rear wheels according to the supplied hydraulic pressure. , A device for controlling the distribution of the driving force between the front and rear wheels.

In this way, one of the driving forces distributed from the center differential 3 is transmitted from the drive shafts 12, 13 to the left and right front wheels 4, 5 through the front differential 10. On the other hand, the other driving force distributed from the center differential 3 is transmitted to the rear differential 11 via the propeller shaft 62, and the left and right rear wheels 6, 7 are transmitted through the rear differential 11.
To be transmitted to.

A driving force distribution device 60 including a speed change mechanism 26 and a multi-plate clutch mechanism 27 is provided at the rear differential 11. The multi-plate clutch mechanism 27 is of a hydraulic type, and the distribution of driving force to the left and right wheels can be adjusted by adjusting the hydraulic pressure. The hydraulic system of the multi-plate clutch mechanism 27 of the driving force distribution device 60, together with the hydraulic system of the multi-plate clutch mechanism 24 of the front-rear driving force control device described above, is a controller 16 as control amount setting means.
Is controlled by.

That is, the hydraulic system of the multi-plate clutch mechanism 27 and the hydraulic system of the multi-plate clutch mechanism 24 include an unillustrated hydraulic chamber attached to each clutch mechanism, an electric pump 28 and an accumulator 29 constituting a hydraulic source. A clutch hydraulic pressure control valve 61 for supplying a required amount of this hydraulic pressure to the hydraulic chamber. The opening of the clutch hydraulic pressure control valve 61 is controlled by the controller 16.

The controller 16 controls the opening of the clutch hydraulic pressure control valve 61 based on the information from the wheel speed sensor 17 and the steering angle sensor 18. Here, the main part of the driving force distribution device 60 will be explained. As shown in FIG. 2, an input shaft 62A provided at the rear end of the propeller shaft 62 and inputted with the rotational driving force, and input from the input shaft 62A. A left wheel rotating shaft (drive shaft for the left rear wheel 6) 14 and a right wheel rotating shaft (drive shaft for the right rear wheel 7) 15 that output the generated driving force are provided, and the left wheel rotating shaft 14 and the right wheel rotating shaft 14 are provided. A driving force distribution device 60 is interposed between the shaft 15 and the input shaft 62A.

The driving force distribution device 60 is configured as follows, while allowing the differential between the left wheel rotating shaft 14 and the right wheel rotating shaft 15 while allowing the left wheel rotating shaft 14 and the right wheel rotating shaft 1 to rotate.
The driving force transmitted to the gears 5 and 5 can be distributed to a required ratio. That is, the left wheel rotation shaft 14 and the input shaft 62
A and between the right wheel rotary shaft 15 and the input shaft 62A,
A speed change mechanism 26 and a multi-plate clutch mechanism 27 are respectively interposed, and the rotation speed of the left wheel rotary shaft 14 or the right wheel rotary shaft 15 is increased by the speed change mechanism 26 to be a hollow shaft as a driving force transmission auxiliary member. 63.

The multi-disc clutch mechanism 27 is interposed between the hollow shaft 63 and a differential case (hereinafter abbreviated as a differential case) 11A on the input shaft 62A side, and the multi-disc clutch mechanism 27 is engaged. By combining,
Driving force is supplied from the high speed side differential case 11A to the low speed side hollow shaft 63. This is because, as a general characteristic of the clutch plates arranged to face each other, torque is transmitted from a higher speed to a lower speed.

Therefore, for example, when the multi-plate clutch mechanism 27 between the right wheel rotary shaft 15 and the input shaft 62A is engaged, the driving force distributed to the right wheel rotary shaft 15 is input shaft 62A.
The driving force distributed to the left wheel rotary shaft 14 is decreased or increased by this amount, which is increased or decreased by the route from the side.
The above-described speed change mechanism 26 is configured by a so-called double planetary gear mechanism in which two planetary gear mechanisms are connected in series. The speed change mechanism 26 provided on the right wheel rotation shaft 15 will be described as an example as follows. Become.

That is, the first sun gear 26A is fixed to the right wheel rotary shaft 15, and the first sun gear 26A is fixed.
A is meshed with a first planetary gear (planetary pinion) 26B on the outer periphery thereof. Further, the first planetary gear 26B is integrally fixed to the second planetary gear 26D, and is pivotally supported by a carrier 26F that is fixed to the casing (fixed portion) and does not rotate via a pinion shaft 26C provided on the carrier. .. As a result, the first planetary gear 26B and the second planetary gear 26D perform the same rotation about the pinion shaft 26C.

Further, the second planetary gear 26D is
The second sun gear 26E is meshed with a second sun gear 26E pivotally supported by the right wheel rotary shaft 15, and the second sun gear 26E is connected to a clutch plate 27A of the multi-plate clutch mechanism 27 via a hollow shaft 63. The other clutch plate 27B of the multi-plate clutch mechanism 27 is connected to the differential case 11A driven by the input shaft 62A.

In the structure of this embodiment, since the second sun gear 26E is formed to have a smaller diameter than the first sun gear 26A, the rotation speed of the second sun gear 26E is the same as that of the second sun gear 26E through the planetary gears 26B and 26D. The size of the sun gear 26A is larger than that of the first sun gear 26A, and the speed change mechanism 26 functions as a speed increasing mechanism. Therefore, when the rotational speed of the clutch plate 27A is higher than that of the clutch plate 27B and the multi-plate clutch mechanism 27 is engaged, a torque corresponding to the engaged state is input from the right wheel rotary shaft 15 side. It is adapted to be fed to the shaft 62A side. For this reason, the drive torque from the input shaft 62A becomes
Will be distributed more to

On the other hand, the transmission mechanism 26 and the multi-disc clutch mechanism 27 provided on the left wheel rotary shaft 14 are also constructed in the same manner. Therefore, when it is desired to distribute more of the drive torque from the input shaft 62A to the right wheel rotary shaft 15, the multi-plate clutch mechanism 27 on the left wheel rotary shaft 14 side is appropriately engaged according to the degree of distribution (distribution ratio). If it is desired to distribute more to the left wheel rotary shaft 14, the multiple disc clutch mechanism 27 on the right wheel rotary shaft 15 side is appropriately engaged according to the distribution ratio.

At this time, since the multi-plate clutch mechanism 27 is of a hydraulic drive type, the engagement state of the multi-plate clutch mechanism 27 can be controlled by adjusting the magnitude of hydraulic pressure, and the input shaft 62A to the left wheel rotary shaft 14 or The feed amount of the driving force to the right wheel rotating shaft 15 (that is, the left / right distribution ratio of the driving force) can be adjusted with appropriate accuracy. The left and right multi-plate clutch mechanisms 27 are set so as not to be completely engaged, and when one of the left and right multi-plate clutch mechanisms 27 is completely engaged, the other multi-plate clutch mechanism 27 slips. It is happening.

Next, the rear wheel steering device 20 of the present device will be described. The rear wheel steering device 20 includes the main steering mechanism 20.
It is constituted by A and the sub-steering mechanism 20B. The main steering mechanism 20A is configured to give a steering angle δm to the rear wheels at a predetermined front-rear steering angle ratio according to a front-wheel steering angle δf input by the handle 8. Then, in the present embodiment, when the handle 8 is rotated, this rotation is transmitted to the front wheel side steering gear box 21, and the front wheel is passed through the left and right tie rods 21A and 21B provided in the front wheel side steering gear box 21. Is designed to be steered. The vehicle outer ends of these tie rods 21A and 21B are knuckle arms (not shown) for the front wheels.
The front left and right wheels 4 and 5 are steered according to the rotation of the handle 8 by being attached using, for example, a ball joint or the like.

On the other hand, a steering shaft 8A for steering the rear wheels is provided from the front-wheel steering gear gearbox 21 toward the rear wheels, and the rotation of the steering wheel 8 is also transmitted to the steering shaft 8A. It is like this. A steering gear box 23 for steering the rear wheels is provided at the rear end of the steering shaft 8A, and the steering angle of the steering wheel 8 input from the steering shaft 8A is reduced at a predetermined reduction ratio to reduce the left and right rear wheels. The wheels 6 and 7 are steered.

This rear wheel steering steering gear gearbox 23 is composed of a pinion gear 23A and a rack 23B, and further, at both ends of the rack 23B, a rear wheel for transmitting a steering angle to the left and right rear wheels. Wheel side tie rod 2
3C and 23D are provided. Then, the pinion gear 23A provided in the steering gear gear box 23 for steering the rear wheels is rotated by the rotation angle input from the steering shaft 8A to transmit the turning angle to the rack 23B. Further, the rotation angle input from the steering shaft 8A is reduced by appropriately adjusting the number of teeth of the rack 23B and the pinion gear 23A.

These rear wheel side tie rods 23C, 23D
The outer end of the vehicle is located on the rear wheel side left and right wheels 6, as on the front wheel side.
The knuckle arm 7 (not shown) is attached using, for example, a ball joint or the like to steer the rear wheel side left and right wheels at a steering angle δm. Here, the control characteristic of the main steering mechanism 20A is a vehicle speed sensitive type as shown in the map of FIG. 7, and a gain K1 according to the vehicle speed V is set from this map. At this time, the vehicle speed V is detected by the wheel speed sensor 17. The rear wheel side turning angle δm is equal to the front wheel side turning angle δ.
It is set by the product of f and the gain K1.

The main steering mechanism 20A of the rear wheel steering device 20 is
With the configuration as described above, the rear wheels are steered at a predetermined turning angle δm (= K1 · δf) with respect to the turning angle δf of the front wheels. Next, the auxiliary steering mechanism 20B of the rear wheel steering device 20 will be described.
The drive force distribution device 60 described above applies to the rear wheel left and right wheels 6 and 7 that are mechanically steered by the main steering mechanism 20A.
The rear wheel steering angle δm is corrected in accordance with the running state of the vehicle in conjunction with. In particular, here, when the main steering mechanism 20A is steering in the same phase, the auxiliary steering mechanism 20B can slightly correct the phase to the opposite phase.

The structure of the sub-steering mechanism 20B will now be described. Inside the steering gear gearbox 23 for steering the rear wheels, a power cylinder 23E integrated with the rack 23B is provided. And this cylinder 23
In the E, oil chambers 30 and 31 partitioned by the spool 23F to the left and right are provided. When hydraulic oil is not supplied to the oil chambers 30 and 31, the spool 23F is always located in the center of the cylinder 23E. The left and right oil chambers 30, 3
Return springs 23G and 23H are respectively provided in
Is provided.

In this way, the position of the rack 23B is adjusted by the magnitude of the hydraulic pressure supplied to the left and right oil chambers 30 and 31 in the cylinder 23E. That is, when this hydraulic oil is driven, the left and right oil chambers 30, 31 are
The tie rods 23C and 23D move in the cylinder 23E against the urging forces of the return springs 23G and 23H, which are balanced in force, and the spool 23F moves in accordance with the hydraulic pressure of the hydraulic oil. It has become.

For example, by the main steering mechanism 20A, the rear wheels 6,
When the steering angle δm is given to the right side of 7, the pinion gear 2
The rack 23B and the power cylinder 23E are integrally moved by 3A to the left. And the sub-steering mechanism 20
A predetermined amount of hydraulic oil is stored in the left oil chamber 30 so that the rear wheels 6 and 7 are corrected to the opposite phase side by the correction steering angle δρ with respect to the rear wheel side steering angle δm according to the traveling state of the vehicle. It is being supplied.

When the hydraulic oil 30 is supplied to the left oil chamber, the hydraulic pressure moves the spool 23F to the right, causing the tie rods 23C and 23D to steer the left and right rear wheels 6 and 7 to the left. The turning angle δm is corrected to the opposite phase side. The setting of the corrected turning angle δρ corrected to the opposite phase side will be described below.

First, the vehicle speed V is detected by the wheel speed sensor 17, and the gains K2 and K3 are set corresponding to the vehicle speed V by the maps 1 and 2 in FIG. And
The time derivative δ of this turning angle δf from the front wheel side turning angle δf
f '(= dδf / dt) is calculated. Then, δρ is set by the following equation using the yaw rate deviation ΔY calculated by the control amount setting means 25 described later and the time differential value δf ′ of the turning angle δf. δρ = K2 · δf ′ + K3 · ΔY Here, the maps 1 and 2 in FIG. 9 will be described. In the map 1, the gain K2 is set, and in the map 2, the gain K3.
Is set. And maps 1 and 2
Both of them are set so that the control characteristics thereof change with the lateral acceleration (lateral G) of the vehicle as a parameter. The larger the lateral G of the vehicle, the smaller the gains K2 and K3 that are set. There is.

The actual steered angle δr of the rear wheels is calculated by determining the steered angle δm of the rear wheel by the main steered mechanism 20A and the sub steered mechanism 20.
Is calculated by the difference δr from the corrected turning angle δρ by B,
The steering angle δr is steered to the in-phase side. Therefore, the actual rear wheel steering angle δr is given by the following equation. δr = δm−δρ = K1 · δf−K2 · δf′−K3 · ΔY Then, the control characteristic of the auxiliary steering mechanism 20B is as shown in the map of FIG. That is, with respect to the turning angle δm set by the main turning mechanism 20A, the sub turning mechanism 20B can correct the range shown in FIG.

By the way, the sub-steering mechanism 20B is designed to be controlled by the hydraulic pressure of the hydraulic oil. This hydraulic system is integrated with the hydraulic system of the multi-plate clutch mechanism 27 of the driving force distribution device 60. Is installed in the vehicle. And
The hydraulic system of the sub-steering mechanism 20B is controlled by the controller 16 together with the hydraulic systems of the multiple disc clutch mechanisms 24 and 27 of the driving force control device described above.

That is, the hydraulic system of the sub-steering mechanism 20B includes oil chambers 30 and 31, an electric pump 28 and an accumulator 29 which form a hydraulic pressure source, and the hydraulic pressure to the oil chambers 30 and 3 described above.
Clutch hydraulic control valve 61 for supplying the required amount to 1
It consists of Then, the clutch hydraulic pressure control valve 6
1 is controlled by the controller 16. In the controller 16, the wheel speed sensor 1
7. The opening of the clutch hydraulic pressure control valve 61 is controlled based on the information from the steering angle sensor 18.

The structure of the controller 16 will now be described. Part of the controller 16 is provided with a target yaw rate calculating means 22 for calculating a target yaw rate based on steering angle information and a control amount setting means 25 for setting a control amount. From the control amount setting means 25, the multi-plate clutch mechanism 2
A control signal for controlling 4, 27 and a control signal for controlling the sub-steering mechanism 20B are output.

As shown in FIG. 1, this vehicle has a vehicle speed sensor 17 as vehicle speed detecting means for detecting the vehicle speed of the vehicle.
A steering angle sensor 18 as steering angle detection means for detecting the steering angle of the steering wheel, and a yaw rate sensor 19 as actual yaw rate detection means for detecting the actual yaw rate of the vehicle. After the information is input to the controller 16, a required calculation is performed in the controller 16 based on each detection signal, and the control amount of each adjusting means 24 and 60 and the sub-steering mechanism 20B.
The control amount is calculated, and the set control signal is sent to the clutch hydraulic pressure control valve 61. Then, a predetermined amount of operating oil pressure is supplied to the center differential limiting mechanism 24 and the multiple disc clutch mechanism 27 according to the map of FIG.

The vehicle speed sensor 17 includes the drive shafts 12,
They are provided in the vicinity of 13, 14, 15 respectively, and can detect the rotation state of the drive shafts 12, 13, 14, 15; that is, the wheel speeds of the wheels 4, 5, 6, 7. ing. And in this controller 16,
Based on the information from each sensor, a control signal for controlling the driving force distribution of the left and right wheels and a control signal for controlling the auxiliary steering mechanism 20B are output while referring to the actual yaw rate.

That is, the control amount setting means 25 outputs the respective control command values EL and ER to the driving force distribution device 60 and the auxiliary steering mechanism 20B according to the yaw rate deviation and the derivative value of the yaw rate deviation. It has become. Here, the setting method of each control command value EL, ER in the control amount setting means 25 will be specifically described. The front wheel side turning angle (actual steering angle) δf detected by the steering angle sensor 18, the main rotation Rear wheel side turning angle δm by the steering mechanism 20A, vehicle speed sensor 17
4 wheel speeds V4, V5, V6, V detected by
7 and the actual yaw rate Y detected by the yaw rate sensor 19 are input to the controller 16.

The target yaw rate calculating means 22 calculates the target yaw rate Y ^{* according} to the following equation (1). ^{Y * = V · δf · (} 1-K1) / ^{[L (1 + A · V 2} ) ] (1) where, V is the wheel speed of the vehicle speed V4, V5, V6, V
7 is the average value, L is the vehicle wheel base, and A is the stability factor. The stability factor A is one of the vehicle speed sensitive elements like the feedback gains G1 and G2 described later. For example, the stability factor A is
Is determined according to a map as shown in FIG.

Further, the yaw rate deviation ΔY, which is the deviation between the target yaw rate Y ^* and the actual yaw rate Y, is calculated by the equation (2), and the yaw rate deviation differential value ΔY ′ is obtained.
Is calculated according to the equation (3). ΔY = Y ^* −Y (2) ΔY ′ = dΔY / dt (3) , The command value E by the control amount setting means 25 using the yaw rate deviation ΔY and the yaw rate deviation differential value ΔY ′.
L and ER are, for example, equations (3) and (4) as shown below.
Is calculated according to. EL = G1 × ΔY + G2 × ΔY '... (3) ER = -G1 × ΔY-G2 × ΔY' ... (4) Here, G1 and G2 are It is a vehicle speed sensitive element called feedback gain, and these feedback gains G
The values of 1 and G2 are determined according to the graphs shown in maps 1 and 2 of FIG. 8, for example.

The maps 1 and 2 shown in FIG. 8 will be described. The map 1 sets the gain G1 and the map 2 sets the gain G2. Similar to the maps 1 and 2 in FIG. 9, the maps 1 and 2 in FIG. 8 are set so that the control characteristics thereof change with the lateral G of the vehicle as a parameter. In this map, the lateral G of the vehicle is set. The larger the value of, the larger the values of the gains G1 and G2 that are set.

Then, the control signals of the above command values EL and ER are sent from the control amount setting means 25 to the clutch hydraulic pressure control valve 6.
1 is sent to the multi-plate clutch mechanism 27 and the sub-steering mechanism 20B according to the map of FIG. Regarding the control of the center differential differential limiting mechanism 24 and the driving force distribution device 60 as described above, a control signal is set as in the flowchart shown in FIG. 3, for example.

The command value EL is determined by the driving force distribution device 60.
Is a signal indicating the magnitude of the hydraulic pressure supplied to the left-side multi-plate clutch mechanism 27, and in the sub-steering mechanism 20B, the magnitude of the hydraulic pressure supplied to the left-side oil chamber 30 in the cylinder 23E. It is a control signal shown. Similarly, the command value ER is a signal indicating the magnitude of the hydraulic pressure supplied to the multiple disc clutch mechanism 27 on the right wheel side in the driving force distribution device 60, and the cylinder 2 in the auxiliary steering mechanism 20B.
It is a control signal indicating the magnitude of the hydraulic pressure supplied to the right oil chamber 31 in 3E.

From the maps 1 and 2 shown in FIG. 8, for example, when the lateral G of the vehicle is small, the gains G1 and G2 are set to small values. Then, according to equations (3) and (4), E
The values of L and ER are set to be small, so that the movement of the driving force between the left and right wheels is small. On the other hand, focusing on the steering wheel operation at this time, for example, in the initial stage of turning, the front wheel side turning angle δf
Since the time differential value δf ′ (that is, the steering wheel angular velocity) is large, the rear wheel side turning angle δr (= K1 · δf−K2 ·
δf′−K3 · ΔY) momentarily becomes a negative value, and the rear wheels steer in reverse phase with respect to the front wheels. And then
As the steering wheel angular velocity decreases, the steering direction of the rear wheels changes to the in-phase side.

Therefore, in such a turn in which the lateral G does not occur so much, the driving force movement between the left and right by the driving force distribution device 60 is relatively small.
Further, in the rear-wheel steering angle control by the rear-wheel steering device 20, control is performed in which the rear wheels are momentarily turned in the opposite phase at the initial stage of turning and then in the same phase. That is, in a turn in which the lateral G does not occur much, the turning performance of the vehicle is more affected by the rear wheel steering device 20 than by the driving force distribution device 60.

Further, the control of the driving force distribution device 60 is reduced when the lateral G is small, because it is also considered to reduce the load on the left and right multi-plate clutch mechanisms 27. Next, a case where a large lateral G occurs due to turning of the vehicle will be described. At this time, the values of the gains G1 and G2 are set to relatively large values according to the maps 1 and 2 of FIG.

The values of the gains K2 and K3 are set to relatively small values according to the maps 1 and 2 in FIG.
Therefore, the driving force distribution device 60 performs driving force distribution control between the left and right, and operates to give a turning moment to the vehicle. At this time, the rear wheel steering angle is gain K
Since the values of 2 and K3 are small, the gain K1 steers to the in-phase side, for example.

As a result, a turn having a large lateral G (for example,
When the steering angle is steered at a high speed), the influence of the driving force distribution device 60 is larger than that of the rear wheel steering device 20. That is, in such a case, the turning moment is appropriately applied to the vehicle by the left and right driving force distribution. Further, while the yaw rate of the vehicle is being fed back so as to approach the target yaw rate, the distribution of the driving force between the wheels on the inner wheel side and the wheels on the outer wheel side is adjusted in accordance with the steering state of the vehicle, so that it is possible to turn in the direction in which the vehicle tries to turn. The turning moment of is properly controlled.

Here, in the multi-plate clutch mechanism 27,
The driving force corresponding to the control signals of the command values EL and ER is determined by, for example, the map shown in FIG. In this map, the neutral dead zone width α is provided, and the command values EL, E
When R is a small value in the dead zone, the driving force distribution between the left and right wheels is not changed. The neutral dead zone is provided in a region where EL and ER are close to 0, and when noise is mixed into the signals input to the sensors 17, 18, and 19 when the vehicle is traveling due to disturbance from the road surface or the like. In order to stabilize the control by suppressing the excessive control for the minute control signal output by the noise.

Therefore, when EL and ER are small values near 0, the driving torque corresponding to the command values EL and ER of the control signal is set to 0 and the driving force distribution between the left and right wheels is not changed. It is like this. A vehicle with a driving force distribution-linked rear wheel steering device as an embodiment of the present invention is
Since the operation is performed as described above, for example, the command values EL and ER of the control signal are set according to the flowchart shown in FIG. 3, and the driving force distribution device 60 and the rear wheel steering device 20 are controlled. To describe the flowchart of FIG. 3, first, in step S1, the front wheel side turning angle (actual steering angle) δf, the rear wheel side turning angle δm, and the wheel speeds V4, V of the four wheels.
5, V6, V7 and the actual yaw rate Y are input to the controller 16.

Next, in step S2, the above equation (1)
Then, the target yaw rate Y ^* is calculated. Also,
In step S3, the yaw rate deviation ΔY and the yaw rate deviation differential value Δ are calculated in accordance with the above equations (2) and (3).
Y'is calculated. Next, in step S4, the command value E is calculated by the control amount setting means 25 according to the equations (3) and (4).
L and ER are calculated.

Then, in step S 5, the control amount setting means 25 sends the control signals of the command values EL and ER to the clutch hydraulic pressure control valve 61. Then, such control operation is repeated in a predetermined cycle. As a result,
Control signals of the command values EL and ER are sent from the controller 16 to the clutch hydraulic pressure control valve 61, and a predetermined operating hydraulic pressure is output to the driving force distribution device 60 and the auxiliary steering mechanism 20B and transmitted to the left wheel and the right wheel. When the driving force to be adjusted is adjusted to the required state, the steering angle on the rear wheel side is also controlled, and the driving force is distributed according to the driving state of the vehicle.

By distributing the driving force to the outer wheel side of the vehicle more than to the inner wheel side by such control, the driving force distribution between the left and right wheels is positively controlled at the same time when turning.
Turn the rear wheel at a steering angle that corresponds to the steering angle of the steering wheel,
Further, since the rear wheel side turning angle at this time is corrected with respect to the driving force distribution and the rear wheel side is steered, the turning performance can be improved.

Specifically, when the lateral acceleration (lateral G) is small, the rear wheel steering device 20 momentarily steers the rear wheels to the opposite phase at the start of turning, and then steers the rear wheels to the same phase side. Therefore, the responsiveness in the yaw direction is improved, the center-of-gravity slip angle is reduced, and the vehicle attitude during turning is stable. When the lateral G is large, a torque difference is generated between the left and right wheels by the driving force distribution device 60 to generate a yaw moment, and the yaw rate of the vehicle is fed back so as to approach the target yaw rate, depending on the steering state of the vehicle. Since the driving force distribution between the inner wheel side wheel and the outer wheel side wheel is adjusted, the turning moment in the direction in which the vehicle is about to turn is appropriately controlled.

The auxiliary steering mechanism 20B of the rear wheel steering device
Thus, the turning of the vehicle is promoted, the turning characteristics of the vehicle are improved, and the response in the yaw direction and the response in the lateral G direction are improved. Further, by making the steering characteristic of the vehicle neutral steering, the limit value of the turning performance of the vehicle is improved, and the vehicle controllability near the limit when turning can be improved.

By using this device, the turning characteristics of the vehicle, such as understeer and oversteer, can be
It is possible to approach ideal steer characteristics such as neutral steer. Further, since the yaw rate feedback control and the rear wheel steering angle control are controlled by using the same hydraulic system, the hydraulic system of this device can be made small, simple, and surely interlocked.

In this embodiment, the driving force distribution device 6
A hydraulic multi-disc clutch mechanism 27 is provided as 0, but as the driving force distribution device 60, in addition to the multi-disc clutch mechanism, a friction clutch, a VCU (viscus coupling unit), and an HCU (hydro-hydraulic). Other couplings such as a lick coupling unit) can also be used.

In the case of a friction clutch, it is conceivable that the engaging force is adjusted by hydraulic pressure or the like similarly to the multi-disc clutch mechanism. In particular, in this friction clutch, the one in which the torque transmission direction is one direction (the respective It may be possible to install it in the direction of torque transmission. Also, this VCU and HCU
A conventional type having a constant power transmission characteristic may be considered, but a type capable of adjusting the engaging force and the power transmission characteristic by hydraulic pressure or electromagnetic force is suitable.

Further, the main steering mechanism 20A does not have to have the control characteristics shown in the map of FIG. 7, and for example, even if the control characteristics do not steer to the opposite phase side, there is no problem. .. A driving force distribution device 60 is added to the front diff 10 portion to control the two driving force distribution devices 60 on the front side and the rear side at the same time to adjust the driving force distribution between the left and right wheels. It is also conceivable to configure.

With such a structure, the turning performance of the vehicle can be further improved by controlling the distribution of the driving force to the left wheel side and the right wheel side.

[0064]

As described in detail above, according to the vehicle with the driving force distribution interlocking type rear wheel steering device of the present invention, a driving force distribution device for distributing and adjusting the driving force from the engine to the left and right rear wheels, In a vehicle having a rear wheel steering device for steering the left and right rear wheels, the rear wheel steering device steers the rear wheels at a predetermined front-rear steering angle ratio with respect to the steering amount of the vehicle. And a sub-steering mechanism capable of additionally turning-correcting the main steering mechanism, and the distribution control of the driving force distribution device based on the yaw rate of the vehicle in order to improve the steer characteristic of the vehicle. A control amount setting means for setting the steering amount of the sub-steering mechanism and for setting the steering amount is provided, and the control amount setting means sets the distribution control amount small when the lateral acceleration applied to the vehicle is small. While setting the steering control amount However, when the lateral acceleration is large, the distribution control amount is set large while the steering control amount is set small, so that the driving force distribution control between the left and right wheels at the time of turning according to the lateral acceleration, It is possible to improve the turning performance of the vehicle by integrally controlling the two control means of the steering angle control corresponding to the steering angle on the rear wheel side, and to make the turning characteristic, for example, the neutral steer.

Specifically, when the lateral acceleration (lateral G) is small, the rear wheel steering device steers the rear wheels to the opposite phase for a moment at the start of turning, and thereafter the rear wheels steer to the same phase side. , The response in the yaw direction is improved, the center of gravity slip angle is reduced,
A stable vehicle posture can be obtained when turning. When the lateral G is large, the driving force distribution device causes a torque difference between the left and right wheels to generate a yaw moment, and the yaw rate of the vehicle is fed back so that the yaw rate approaches the target yaw rate. Since the driving force distribution between the wheels on the side of the vehicle and the wheels on the side of the outer wheel is adjusted, the turning moment in the direction in which the vehicle is about to turn is appropriately controlled.

The sub-steering mechanism of the rear wheel steering system promotes the turning of the vehicle, improves the turning characteristics of the vehicle, and improves the response in the yaw direction and the response in the lateral G direction. By using this device, the turning characteristic of the vehicle, for example, the understeer or oversteer, can be approximated to the ideal steer characteristic such as neutral steer.

Further, since the yaw rate feedback control and the rear wheel steering angle control are controlled by using the same hydraulic system, the hydraulic system of this device can be made compact, simple and surely interlocked.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a vehicle with a driving force distribution interlocking type rear wheel steering device as an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a main part of a driving force transmission system in a vehicle with a driving force distribution interlocking type rear wheel steering device as one embodiment of the present invention.

FIG. 3 is a flow chart showing an operation of a main part in a vehicle with a driving force distribution interlocking type rear wheel steering device as one embodiment of the present invention.

FIG. 4 is a map relating to control amount setting in a vehicle with a driving force distribution-linked rear wheel steering device as one embodiment of the present invention.

FIG. 5 is a map relating to control amount setting in a vehicle with a driving force distribution interlocking type rear wheel steering device as one embodiment of the present invention.

FIG. 6 is a map relating to control amount setting in a vehicle with a driving force distribution-linked rear wheel steering device as one embodiment of the present invention.

FIG. 7 is a map relating to control amount setting in a vehicle with a driving force distribution interlocking type rear wheel steering device as one embodiment of the present invention.

FIG. 8 is a map relating to control amount setting in a vehicle with a driving force distribution interlocking type rear wheel steering device as one embodiment of the present invention.

FIG. 9 is a map relating to control amount setting in a vehicle with a driving force distribution-linked rear wheel steering device as one embodiment of the present invention.

FIG. 10 is a graph showing a correlation between lateral acceleration (lateral G) and cornering force (CF) in a general vehicle.

[Explanation of symbols]

 1 Driving force transmission system 2 Engine 3 Center differential 4,5 Front wheel 6,7 Rear wheel 8 Handle 8A Steering shaft 10 Front differential 11 Rear differential 11A Differential case 12, 13, 14, 15 Drive shaft 16 Controller as control means 17 Wheel speed sensor 18 Steering Angle Sensor 19 Yaw Rate Sensor 20 Rear Wheel Steering Device 20A Main Steering Mechanism 20B Sub Steering Mechanism 21 Front Wheel Side Steering Gear Gear Box 21A, 21B Front Wheel Side Tie Rod 22 Target Yaw Rate Calculation Means 23 Rear Wheel Side Steering Gear Gear Box 23A Pinion gear 23B Racks 23C, 23D Rear wheel side tie rod 23E Power cylinder 24 Center differential limiting mechanism 25 Control amount setting means 26 Transmission mechanism 26A First sun gear 26B First planetary gear 26 Pinion shaft 26D Second planetary gear 26E Second sun gear 26F Carrier 27 Multi-plate clutch mechanism 27A Clutch plate 27B Clutch plate 28 Electric pump 29 Accumulator 30,31 Oil chamber 60 Driving force distribution device 61 Clutch hydraulic control valve 62 Propeller shaft 62A Input Shaft 63 Hollow shaft

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Claims (1)

[Claims] 1. A vehicle having a drive force distribution device for distributing and adjusting drive force from an engine to the left and right rear wheels, and a rear wheel steering device for steering the left and right rear wheels, wherein the rear wheel steering device comprises: A main steering mechanism that steers the rear wheels at a predetermined front-rear steering angle ratio with respect to the steering amount of the vehicle, and a sub-steering mechanism that can additionally steer the main steering mechanism. Control amount setting means is provided for setting the distribution control amount of the driving force distribution device based on the yaw rate of the vehicle to improve the steering characteristic of the vehicle and for setting the steering control amount of the auxiliary steering mechanism. The control amount setting means sets the distribution control amount small when the lateral acceleration applied to the vehicle is small, while setting the steering control amount large and setting the distribution control amount large when the lateral acceleration is large. While turning the above A vehicle equipped with a drive force distribution interlocking rear wheel steering device, characterized in that the control amount is set small.