JPH0647388B2 - All-wheel independent steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is based on a steering angle of a steering wheel and a traveling speed of a vehicle. The present invention relates to a wheel independent steering device.

[Conventional technology]

Conventionally, most steering mechanisms of vehicles are connected left and right. In the case where the left and right wheels are connected, the tire turning angle cannot be determined with respect to the turning center, and each wheel is not adjusted to the ideal Ackermann turning angle when the vehicle is turning. .

A four-wheel steering system that steers the front wheels, which are the steered wheels, to steer the rear wheels together with the front wheels is disclosed in JP-A-59 / 59
No. 777969.

This four-wheel steering system increases the rear wheel steering angle in accordance with an increase in the front wheel steering angle when the front wheel steering angle is less than a set value, and increases the rear wheel steering angle in accordance with the increase in the front wheel steering angle when the front wheel steering angle is greater than the set value. It has an inflection point for maintaining or reducing the angle constant, and changes the rear wheel steering angle characteristic with respect to the front wheel steering angle in accordance with the vehicle speed, and the front wheel steering in accordance with the increase in the vehicle speed at the inflection point. The controller comprises a controller that controls the rear wheel steering device according to the characteristics of the rear wheel steering angle with respect to the front wheel steering angle that is changed to the side where the angle is small and the rear wheel is large.

Further, a steering apparatus for a vehicle in which a steering mechanical system of a steering theory is driven by a driver's rotating operation of a steering wheel is disclosed in Japanese Utility Model Laid-Open No. 60-43474.

The steering apparatus for an automobile has a steering wheel equipped with a steering actuator independently mounted on all wheels and provided with a reaction force actuator that increases or decreases a steering force according to a steering state, and a steering command direction signal and a steering wheel linked to the steering wheel. A steering command signal generator that outputs a command angle signal, a drive control circuit that receives the output signal of the generator as an input, and operates each of them belonging to the steering actuator, and at least a part of the same steering command signal A steering mode changeover switch for switching the output of each drive control circuit is provided, and the drive control circuit to which each steering actuator belongs is operated according to the Ackermann-Junt geometry.

[Problems to be solved by the invention]

However, conventionally, regarding the steering mechanism of the vehicle in which the left and right wheels are connected such that each wheel cannot be determined to have an ideal Ackerman turning angle, the uneven wear of the tire, the limit performance, the cornering performance, etc. are lowered, There was a problem.

The suspension geometry is regulated by each running condition such as straight running and turning, and is not in an ideal state under each running condition, so maneuverability,
There was a problem that the stability and the like became low.

Further, the four-wheel steering device disclosed in Japanese Patent Laid-Open No. 59-77969 mentioned above automatically changes the rear-wheel steering angle with respect to the front-wheel steering angle according to the vehicle speed, but the four-wheel steering is independent. Therefore, it has the same problems as described above.

Further, the steering apparatus disclosed in Japanese Utility Model Laid-Open No. 60-43474 is not one which controls the alignment of the suspension, that is, the camber angle, and is not adjusted so as to keep the ground tread constant, and moreover, it is manually operated. The mode is changed and therefore has the same problems as above.

Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide an all-wheel independent steering device having a variable suspension geometry device that improves steering stability performance during steering of a vehicle.

[Means for solving problems]

The present invention is configured as follows to achieve the above object. That is, the present invention is a steering stroke device connected to each knuckle provided on all running wheels, an upper link and a lower link of variable length, and a steering angle sensor for detecting the steering angle of the steering wheel,
The vehicle has a vehicle speed sensor that detects a traveling speed of the vehicle, and a control unit that controls the steering stroke device, the upper link, and the lower link based on detection signals from the steering angle sensor and the vehicle speed sensor. , Calculating the turning radius based on the vehicle speed and the steering angle to calculate the turning angle of the wheels to control the operation of the steering stroke device, and calculate the roll moment to calculate the moving load of each wheel, and based on the moving load It is configured by calculating a moving stroke of the wheel and controlling the operation of each upper link and each lower link so as to keep the camber angle of the suspension alignment and the ground tread constant based on the moving stroke of the wheel. The present invention relates to an all-wheel independent steering device.

[Action]

The present invention is configured as described above and operates as follows. That is, the turning radius is obtained based on the vehicle speed of the vehicle and the steering angle of the steering wheel, the steering angle is calculated by calculating the turning angle of the wheel, and the roll moment is calculated to obtain the moving load of each wheel. A movement stroke of the wheel is calculated based on the movement load, and operation control of each upper link and each lower link is performed so that the camber angle of the suspension alignment and the ground tread are kept constant based on the movement stroke of the wheel. To do. Therefore, since the camber angle and the ground tread are kept constant, the steering stability performance can be dramatically improved.

〔Example〕

Embodiments of an all-wheel independent steering device according to the present invention will be described below in detail with reference to the drawings.

The principle of an all-wheel independent steering system according to the present invention is shown in FIG.

Further, in FIG. 2, a four-wheel independent steering device is generally indicated by reference numeral 1. The four-wheel independent steering device 1 has front wheels 2 and 2
And rear wheels 3 and 3, each of which is steered independently by a signal from the control unit 4.

Each of the wheels 2 and 3 has a knuckle 10, and an upper link 11, 12 and a lower link 13, 14 are attached to each knuckle 10. The strokes of the upper links 11, 12 and the lower links 13, 14 are adjusted by a signal from the control unit 4, and the stroke sensors 15, 16 of the upper links 11, 12 for detecting the strokes are respectively adjusted.
And the stroke sensors 17 of the lower links 13 and 14,
18 is provided.

A steering stroke device 9 is provided on each of the wheels 2 and 3, and a rack stroke sensor 8 for detecting the stroke length of the steering stroke device 9 is provided.
Is provided. Further, a vehicle speed sensor 6 for detecting the speed of the vehicle is provided. A steering angle / steering angular velocity sensor 7 for detecting the steering angle and the steering angular velocity of the steering wheel 5 is also provided. In the figure, 19 indicates a lateral acceleration sensor, and 20 indicates a longitudinal acceleration sensor.

In FIG. 1, in a vehicle in which all the traveling wheels are independently steered, a turning center O is a lateral extension from the center between the front wheels 2 and the rear wheels 3 of the vehicle, and the turning center depends on the vehicle speed. It moves to the rear (arrow) to determine the turning angle of each wheel. The symbol O indicates the turning center after the movement.

As means for giving this turning angle, the signals from the vehicle speed sensor and the steering angle sensor are input to the control unit,
The steering means for steering each traveling wheel, that is, each of the four wheels is controlled to determine the tire cutting angle of each traveling wheel. The state of the steering means is detected by the rack stroke sensor 8.

The above will be described below with reference to the flowchart in FIG.

When the main key is put into the engine and the engine is started and then turned on, the vehicle runs and the vehicle speed V is detected by the vehicle speed sensor 6 (step 61). Vehicle speed V
Is detected, the turning center O is determined and the backward movement amount X is processed. That is, X = AV, X = A · V ^1/2 , X = Y
(V) (step 62).

The steering wheel steering angle α is detected by the steering angle sensor 7 (step 63). When the steering angle α is detected,
The turning radius r is processed. That is, r = r ₀ (α) + AV
Alternatively, r = r ₀ (α) + n (V) (step 64).

When the turning radius is processed, the ideal Ackermann turning angle of each of the running wheels 2 and 3 is given (step 65). That is, the cutting angles for the inner wheels of the front wheels are as follows, and the same applies to the other running wheels.

However, f in β _fi means the front and i means the inner ring. S indicates a wheel base and t _f indicates a tread ftund. These processes are repeated.

The vehicle speed sensor 6, the steering angle sensor 7 and each traveling wheel are means for determining the turning angle of each traveling wheel and changing the length of the arm of each suspension so that the contact point of each traveling wheel does not change. Stroke sensors 8, 15, 16,
Input the signals of 17 and 18 to the control unit 4,
The steering unit that independently steers all the traveling wheels 2 and 3 is adjusted, and the cutting angles of the tires of the wheels 2 and 3 are ideal angles with respect to the turning center O. The Ackermann cutting angle β
Therefore, the stroke of each steering unit is determined.

The strokes of those steering units are detected by the rack stroke sensor 8.

The flowchart for the above will be described with reference to FIG.

The vehicle runs at the vehicle speed V by turning on the engine by inserting the main key into the engine and then turning it on. The vehicle speed V is detected by the vehicle speed sensor 6 (step 71). When the vehicle speed V is detected, the backward movement amount X of the turning center is processed. For example, if the vehicle speed increases, the backward movement amount is determined as a function of the vehicle speed. The center of rotation is moved backward as the vehicle speed increases (step 72).

That is, X = AV or X = r (V).

When the backward movement amount X is determined, the steering angle α of the steering wheel is detected by the steering angle sensor 7 (step 7
3). It is determined whether the steering wheel steering angle α is | α |> 0 or α = 0 (step 7).
4).

If | α |> 0, the radius gyration r is processed (step 75).

That is, r = r ₀ (α) + A (V).

When the turning radius r is processed, the ideal Ackermann cutting angle β _{fi of} each of the running wheels 2 and 3 is determined (step 7).
6). That is, However, f means the front and i means the inner ring.

The turning acceleration is calculated from the turning radius r and the vehicle speed V. That is, V ² / r is calculated (step 77). Then
The trim height H _C of each running wheel is calculated (step 7).
8).

Each data is input to maintain a constant ground point and ground camber angle, to adjust the length of the arm of each of the suspension, so that the length of the arm is set length l _C (Step 79 ).

The length l of the suspension arm is detected by the suspension arm sensors 15, 16, 17, and 18 (step 80).

The difference between the detected suspension arm length l and the length l _C to be set is determined. That is, | l-l _C
If | = 0, the process moves to the next process, | l-l _C |> 0
If so, the suspension arm is fed back to the process of step 79 to change the length of the arm (step 81).

The trim height H is detected by the trim height sensor (step 82). The difference between the detected trim height H and the trim height H _C to be set is determined. That is,
If | H−H _C |> 0, it is fed back to the process of step 79 in order to change the length of the suspension arm. If | H−H _C | = 0, the process returns to the first process (step 83).

Further, the base point of the turning center O is set to be a lateral extension from the center between the front wheels 2 and the rear wheels 3 of the vehicle, and is fixed in the lateral direction without moving backward, and the steering angle of the steering wheel 5 and the vehicle speed are fixed. And the suspension stroke, the turning radius of the vehicle, in other words, the turning center for the wheels is always set on a fixed line in the center, and the wheels are moved by the difference in the turning radii. Input the data of the turning angle and the vehicle speed into the control unit.

Then, the cutting angle and the ground camber are controlled, the front and rear wheels are steered by the same angle, and the length of the suspension arm is changed so as to keep the ground tread constant. The length of the suspension arm is adjusted so as to make the Ackermann corner angle.

The above will be described with reference to the flowchart of FIG.

Start by inserting the main key into the engine and then turn it on. As the vehicle runs, the steering wheel steering angle α is input. It is detected by the steering angle sensor 7 (step 85). The vehicle speed V is detected by the vehicle speed sensor 6 (step 86). When the vehicle speed V and the steering angle α are detected, the turning radius r is processed (step 8).
7). That is, r (α) = r ₀ (α) + A (υ).

When the turning radius r is processed, the turning angles of the four wheels 2, 3 are calculated. That is, the following applies to the front and inner wheels, and the same applies to the other wheels (step 8).
8).

When the cutting angle β is calculated, each rack stroke γ (α)
_{fi, fo,-are} calculated (step 89), and the operation of the steering stroke device 9 is controlled based on the calculated strokes. Next, each rack stroke Γ (α) _{fi, fo, -is} detected by the rack stroke sensor 8 (step 90), and then the following equation is determined. That is, | γ (α) −Γ (α) |.

If | γ (α) −Γ (α) |> 0, the process is fed back to step 90.

If | γ (α) −Γ (α) | = 0, the process proceeds to the next process (step 91).

The roll moment is calculated (step 92). That is, M = (W / g) · (V ² / r) · h, where h is the height of the center of gravity and the moving load is calculated. For example, the amount of sinking such that the inner ring is depressed by 10 mm and the outer ring is raised by 16 mm is known (step 93). That is, the following applies to the front wheels, and the same applies to the rear wheels.

The stroke of each wheel is processed (step 9).
4). That is, the inner wheels of the front wheels are as follows, and the same applies to the other wheels.

The ground camber is controlled, and the length of each suspension arm is changed so that the ground tread does not change. The amount of change ΔL is calculated (step 95).

The change amount Δl of the arm length of each suspension is detected by the stroke sensors 15, 16, 17 and 18 (step 96).

| ΔL−Δl | is determined. That is, if | ΔL−Δl |> 0, the process proceeds to step 95.
Give feedback to.

If | ΔL-Δl | = 0, the process returns to the first process (step 97).

FIG. 3 shows an example of a mechanism for changing the length of the suspension arm. The device for changing the length of the arm is hydraulic. All running wheels or wheels 2,
The knuckle 10 attached to the upper end 3 of the knuckle 3 is connected to upper ends 11 and 12 of variable length at the upper part and lower links 13 and 14 of variable length at the lower part. Here, only the hydraulic device for adjusting the lengths of the lower links 13 and 14 will be described.

Pistons 22 are attached to the other ends of the lower links 13 and 14, and each piston slides in the cylinder 21. Oil from the oil tank 24 is sent to the cylinder 21 by the pump 25 through the check valve 26, the switching valve 23, and the one adjusting valve 28 into one chamber of the cylinder 21. The oil in the other chamber of the cylinder 21 is supplied to the other control valve 28 and the switching valve 23.
Through the oil tank 24.

This hydraulic pressure causes the piston 22 to slide to move the lower links 13 and 14, the stroke or length is changed, the knuckle 10 is moved, and the camber angles of the wheels 2 and 3 are adjusted (Fig. 5). reference). The length of the stroke at this time is detected by the stroke sensors 17 and 18.

A similar hydraulic device is also attached to the upper links 11 and 12. The hydraulic system of the upper links 11 and 12 and the hydraulic system of the lower links 13 and 14 work together to change the camper angle by the action described with reference to FIG. 5 described later.

In FIG. 4, another example of the mechanism for changing the length of the suspension arm is shown. The device for changing the arm length is a screw. Only the lower links 13 and 14 will be described as in the case of the hydraulic system.

One ends of lower links 13 and 14 are connected to the knuckle 10, and female screws 30 are formed at the other ends of the lower links 13 and 14. A rotary shaft 33 having a male screw 29 is screwed into the female screw 30. The rotary shaft 33 is attached to the body 31 via a bearing 34, and the motor 3
The rotation is controlled by 2. Stroke sensors 17 and 18 are provided for the lower links 13 and 14, respectively.

The rotation shaft 33 is rotated by the rotation of the motor 32, the strokes of the lower links 13 and 14 are changed, and the knuckle 1
Move 0 to change and adjust the camber angle of the wheels.

As the stroke sensors 17 and 18, there are those that use a permanent magnet to detect the stroke length depending on the position of the magnet, or convert the resistance value into the stroke. It may be one and is not limited. Of course, the upper links 11 and 12 are also provided with the same screw changing device as that shown in FIG.
The operation is similar to that of the hydraulic system shown in FIG.

Next, the operation of changing the camber angle will be described with reference to FIG. Hydraulic pressure is applied to the cylinders 21 of the upper links 11 and 12 to extend the upper links 11 and 12,
When the lower links 13 and 14 are contracted, the wheels 2 and 3 are indicated by the arrow B.
It tilts in the direction and becomes a positive camber.

In contrast to the above, extend the lower links 13 and 14,
When the upper links 11 and 12 are contracted, the wheels 2 and 3 incline in the direction of arrow C to become a negative camber. These states are the stroke sensors 1 of the upper links 11 and 12.
5, 16 and the stroke sensors 17, 18 of the lower links 13, 14 detect the signals and feed them back to the control unit 4 (see FIG. 2).

〔The invention's effect〕

Since the all-wheel independent steering system according to the present invention is configured as described above, it has the following effects. That is, since this all-wheel independent steering device has the above-mentioned configuration,
It is possible to control by changing the turning angle of all the running wheels under each running condition, the suspension geometry, that is, the camber angle of each wheel, and it is possible to independently maintain the ground tread of each wheel independently. The steering stability performance can be dramatically improved.

[Brief description of drawings]

1 is an explanatory view for explaining the principle of the present invention, and FIG. 2 is a schematic plan view showing an all-wheel independent steering device according to the present invention,
FIG. 3 is a schematic view showing an example of a mechanism for changing the length of the suspension arm, FIG. 4 is a schematic view showing another example of a mechanism similar to FIG. 3, and FIG. 5 is a camber angle change. It is a schematic diagram showing a mechanism. FIG. 6 is a flowchart for explaining a case where the turning center in the all-wheel independent steering device according to the present invention is moved rearward according to the vehicle speed, and FIG. 7 is a flowchart for explaining the turning center in the all-wheel independent steering device according to the present invention depending on the vehicle speed. 8 and FIG. 8 is a flow chart for explaining a case where the arm length is adjusted so as to give an ideal Ackermann turning angle, and FIG. 8 shows the turning center in the all-wheel independent steering device according to the present invention as the front wheel of the vehicle. The flow chart in the case of controlling the cutting angle and the ground tread by locating it on the extension in the lateral direction from the center of the rear wheel is shown. 1 ... 4-wheel independent steering device (all-wheel independent steering device), 2, 3
…… Wheels, 4 …… Control unit, 5 …… Steering wheel, 6 …… Vehicle speed sensor, 8 …… Rack stroke sensor, 9 …… Steering stroke device, 10 …… Knuckle, 11, 12 …… Upper link (suspension) Arm), 13, 14 ... Lower link (suspension arm), 15, 16, 17, 1.
8 ... Stroke sensor.

Claims (1)

[Claims] 1. A steering stroke device connected to each knuckle provided on all traveling wheels, an upper link and a lower link having variable lengths, a steering angle sensor for detecting a steering angle of a steering wheel, and a traveling speed of a vehicle. It has a vehicle speed sensor for detecting and a control unit for controlling the steering stroke device, the upper link and the lower link based on the detection signals from the steering angle sensor and the vehicle speed sensor, and the control unit includes the vehicle speed and the steering angle. Based on the above, the turning radius is calculated, the turning angle of the wheel is calculated to control the operation of the steering stroke device, the roll moment is calculated to calculate the moving load of each wheel, and the moving stroke of the wheel based on the moving load is calculated. Alignment of the suspension based on the moving stroke of the wheel Camber angle and to keep the ground tread constant, the all-wheel independent steering device, characterized in that consisted be operated controls and the respective lower link and the upper link.