JPH0813652B2 - Four-wheel steering system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering device capable of switching and selecting two kinds of steering modes, that is, a front-rear both-wheels reverse steering mode and a front-rear both-wheels same-direction steering mode.

2. Description of the Related Art Conventionally, a rigid axle type steering mechanism has a steering link configured to satisfy Ackermann theory in order to make a stable turn. That is, the steering link for steering the left and right wheels is configured such that the steering angle of the wheel inside the turning direction is larger than the steering angle of the wheel outside the turning direction.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Here, in a four-wheel steering device capable of switching and selecting two kinds of steering modes, a front and rear both-wheel reverse steering mode and a front and rear both-wheel same-direction steering mode, a front and rear both-wheel reverse steering When the mode is selected, the left and right front wheels and the rear wheels are steered so as to satisfy the Ackermann theory, and when the front and rear wheels same direction steering mode is selected, the steering angles of the four wheels are made equal. Need to steer.

However, when the steering link is configured to satisfy the Ackermann theory, the steering angles of the left and right wheels do not match when the front and rear wheels same-direction steering mode is selected, causing uneven wear of the wheels, When traveling on grass, it has the drawback of damaging the grass.

Similarly, when the steering link is configured so that the steering angles of the four wheels are the same when the front and rear wheels same direction steering mode is selected, the left and right wheels are selected when the front and rear wheels reverse direction steering mode is selected. Does not satisfy Ackermann's theory, wheels have skid, uneven wear of wheels occurs, and there is a drawback that grass is damaged when traveling on grass.

Means for Solving the Problems There are two kinds of front and rear wheels reverse steering mode in which front and rear wheels are steered in opposite directions, and front and rear wheels same direction steering mode in which front and rear wheels are steered in the same direction. In a work vehicle with a four-wheel vehicle body in which the steering mode is switchable and selectable, a steering arm that is connected to a first drive unit that is driven in the same steering mode for both front and rear wheels and that rotates in the left and right direction is provided. A sliding body attached to the steering arm so as to be slidable in the left-right direction by being connected to a second drive unit that is driven in the reverse steering mode for both wheels is provided, and can be pivoted to a kingpin integrally with the front wheel or the rear wheel. Attached to the arm and one end connected to this arm, and the other end connected to the sliding body so that the arm is steered at a steering angle satisfying the Atkaman theory. Link mechanisms for the front wheels and the rear wheels are formed by the tie rods, and the connecting points of the tie rods to the sliding body are respectively formed by the front wheels and the rear wheels when the steering arm rotates. The steering angles were set to be equal.

Operation During steering with the front-rear wheel reverse steering mode selected, the front and rear wheels are both steered to a steering angle that satisfies the Atkaman theory by sliding the sliding body in the left-right direction. Also, when steering in which the front and rear wheels are in the same direction steering mode, the front and rear wheels are steered to the same steering angle by rotating the sliding body left and right around the support shaft by the drive unit. Be directed.

Embodiment An embodiment of the present invention will be described with reference to the drawings. First,
A mower 4 is mounted between a front wheel 2 and a rear wheel 3 on the abdomen of an automatic traveling lawnmower 1 which is a work vehicle of a four-wheel vehicle so as to be vertically movable. Both the front wheels 2 and the rear wheels 3 are steerably provided, and a front wheel steering device 5 for traveling the front wheels 2 and a rear wheel steering device 6 for traveling the rear wheels 3 are provided. On the other hand, an induction cable 7 is buried underground in the work area where the automatic lawnmower 1 is driven, and the excitation current power supply device 8 is embedded in the induction cable 7.
Causes a low frequency current to flow, and an alternating magnetic field is generated from the induction cable 7. Further, the automatic traveling lawnmower 1 is provided with a sensor 9 for detecting the alternating magnetic field.

Next, the front wheel steering device 5 and the rear wheel steering device 6 will be described. The front wheel steering device 5 and the rear wheel steering device 6 have the same structure,
Only the front wheel steering device 5 will be described. Front wheel 2
Is connected to one end of an arm 11 so as to be rotatable about the axis of the king pin 10, and one end of a tie rod 12 is connected to the other end of the arm 11 so as to be rotatable.
A link mechanism 13 for steering the front wheels 2 is constituted by 12 and.

On the other hand, a hydraulic cylinder 14 serving as a second drive unit is provided at the center of the automatic traveling lawnmower 1 in the left-right direction. The rod 16
The tip end of is connected to a steering arm 18 that is rotatable around a support shaft 17 provided in the center of the automatic lawnmower 1 in the left-right direction. Furthermore, one end of the rod 19 is a spindle
A hydraulic cylinder 21, which is a first drive unit supported rotatably in the front-rear direction around 20, is provided. A cylinder body 22 of the hydraulic cylinder 21 has a steering arm 18
Are rotatably connected. Therefore, the hydraulic cylinder 14
When driving, the cylinder body 15 slides in the left-right direction, and when driving the hydraulic cylinder 21, the hydraulic cylinder 14 rotates in the left-right direction around the support shaft 17 together with the steering arm 18.

In the cylinder body 15, the other ends of the pair of left and right tie rods 12 are rotatably connected at predetermined intervals. That is, when the cylinder body 15 moves in the left-right direction, the link mechanism 13 steers the steering angle between the front wheels 2 and the rear wheels 3 so as to satisfy the Atkaman theory (see FIG. 5). Arm 18
When the cylinder body 15 is rotated by the rotation, the shaft attachment point of the tie rod 12 set at a predetermined interval also rotates. The interval dimension of the shaft landing points of each tie rod 12 is set so that the steering angles of the front wheels 2 and the rear wheels 3 become equal by the movement of the shaft landing points (see FIG. 4).

Next, a solenoid valve for driving the hydraulic cylinder 14
23, 24 and solenoid valve 2 for driving the hydraulic cylinder 21
3,25 and are provided. These solenoid valves 23, 24, 25 are
Based on the detection result from the sensor 9, it is connected to a control device 26 which selects between the front and rear wheels reverse steering mode and the front and rear wheels same direction steering mode and calculates a necessary steering angle. The solenoid valve 23 is connected to an oil tank 29 via a hydraulic pump 27 and a filter 28.

In such a configuration, when the control device 26 determines that the steering in the front and rear wheels in the same direction steering mode is appropriate based on the detection result from the sensor 9, the first
As shown in the figure, the solenoid valve 23 is turned off and the hydraulic pump
The oil discharged from 27 is supplied to the solenoid valve 25. The solenoid valve 25 is connected to the front and rear hydraulic cylinders 21, and the control device 26 controls the solenoid valve 25 to drive the hydraulic cylinder 21 and rotate the steering arm 18 around the support shaft 17. Since the oil passages are arranged so that the steering arm 18 turns in the opposite direction on the front wheel 2 side and the rear wheel 3 side, the front wheel 2 and the rear wheel 3 are shown by solid lines in FIG. Thus, the steering is performed in the same direction and at the same steering angle.

Next, based on the detection result from the sensor 9, the control device
When 26 determines that the steering in the front and rear wheels reverse steering mode is appropriate, the solenoid valve 23 is turned on and the oil solenoid valve 24 discharged from the hydraulic pump 27 is supplied. The solenoid valve 24 is connected to the front and rear hydraulic cylinders 14, and the solenoid valve 24 is controlled by the control device 26 so that the cylinder body 15 of the hydraulic cylinder 14 slides in the left-right direction. The front wheel 2 and the rear wheel 3 connected through the link mechanism 13 by the sliding motion of the cylinder body 15 are steered to the steering angle satisfying the Ackermann theory as shown by the solid line in FIG.

Here, as shown in FIG. 6, the dimension "a" from the support shaft 17 to the hydraulic cylinder 14 is 130 mm, the distance "b" between the connecting portions of the left and right tie rods 12 to the cylinder body 15 is 50 mm, and the left and right kingpins are Dimension "c" between 10 is 610 mm, left and right kingpin 10
The distance "d" between the straight line connecting them and the hydraulic cylinder 14 is 120 m
m, tie rod 12 length dimension "L ₁ " is 352.5 mm, arm 11
If the steering wheel is operated in the same direction steering mode with the front and rear wheels in the same direction when the length dimension "L ₂ " of the left wheel is 110 mm, and the steering angle "α" of the right wheels 2 and 3 is 45 °, the left wheel The steering angle “β” of 2 and 3 is 43 °, which satisfies α≈β. on the other hand,
When steering in the reverse steering mode for both front and rear wheels, the steering angle "β '" of the left wheels 2 and 3 is 30 when the steering angle "α'" of the right wheels 2 and 3 is 45 °. And satisfies Ackermann theory.

In addition, in the present embodiment, the case where the switching selection between the front-rear both-wheels same-direction steering mode and the front-rear both-wheels reverse-direction steering mode is automatically performed by the control device 26 has been described, but by an artificial operation such as a radio control operation. It may be switched.

EFFECTS OF THE INVENTION As described above, the present invention has a front / rear wheel reverse steering mode in which the front wheels and the rear wheels are steered in opposite directions, and a front and rear wheel same direction steering mode in which the front wheels and the rear wheels are steered in the same direction. In a work vehicle with a four-wheel vehicle body in which two steering modes are switchably selectable, a steering arm that is connected to a first drive unit that is driven in the same-direction steering mode for front and rear wheels and that rotates in the left-right direction Is provided
Both front and rear wheels are equipped with a sliding body that is connected to the second drive unit that is driven in the reverse steering mode and is attached to the steering arm slidably in the left and right directions. A freely attached arm and one end is connected to this arm and the other end is connected to the sliding body so that it can be steered at a steering angle satisfying the Atkaman theory. Link mechanisms of the tie rods are connected to the sliding body so that the steering angles of the front wheels and the rear wheels are equal when the steering arm is rotated. The front and rear wheels satisfy the Ackermann theory by sliding the sliding body to the left and right when steering with the front and rear wheels reverse steering mode selected. The front and rear wheels can be rotated in four directions by rotating the sliding body in the left and right directions around the support shaft by the drive unit when steering in which the front and rear wheels same direction steering mode is selected. The wheels can be steered at the same steering angle. Therefore, with a very simple structure, it is possible to perform smooth turning steering by the front and rear wheels reverse steering mode and steering by the front and rear wheels same direction steering mode. In addition, it is possible to prevent uneven wear of the front wheels and the rear wheels, and to prevent damage to the grass even when steering on the grass.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a plan view showing a front and rear steering device and its control mechanism, FIG. 2 is an enlarged plan view showing a front wheel steering device, and FIG. Is a side view of an automatic traveling lawnmower adopting the four-wheel steering device of the present invention, FIG. 4 is a plan view for explaining steering states of front wheels and rear wheels in the front-rear both-wheel steering mode, and FIG. FIG. 6 is a plan view for explaining the steering state of the front wheels and the rear wheels in the front and rear wheels reverse steering mode, and FIG. 6 is an explanatory diagram for explaining a specific steering angle. 1 ... Work vehicle, 2 ... Front wheel, 3 ... Rear wheel, 13 ... Link mechanism, 14 ... Sliding body, 17 ... Spindle, 21 ... Drive unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takefumi Yoshizawa 1-1-1, Ishishiba, Matsumoto-shi, Nagano Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto factory (72) Inventor Michihiro Watanabe 1-1-1, Ishishiba, Matsumoto-shi, Nagano No. Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto Factory (72) Inventor Isamu Harada 1-1-1, Ishishiba, Matsumoto City, Nagano Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto Factory (56) Reference JP 62-116358 (JP, A) )

Claims (1)

[Claims] 1. Two types of steering modes: a front and rear wheel reverse steering mode in which front and rear wheels are steered in opposite directions, and a front and rear wheel same direction steering mode in which front and rear wheels are steered in the same direction. In a work vehicle with a four-wheel vehicle body that is switchably selectable, a front and rear wheels are provided with a steering arm that is connected to a first drive unit that is driven in the same-direction steering mode and that rotates in the left and right directions. A sliding body that is connected to the second drive unit that is driven in the reverse steering mode and that is slidably mounted in the left-right direction is provided on the steering arm, and is rotatably mounted on the kingpin integrally with the front wheel or the rear wheel. And a tie rod having one end connected to the arm and the other end connected to the sliding body so as to be steered at a steering angle satisfying the Azkerman theory. Link mechanisms for the front wheels and the rear wheels are respectively formed by and the steering points of the front wheels and the rear wheels when the steering arm rotates the connection points of these tie rods to the sliding body. A four-wheel steering device characterized in that the intervals are set so that the corners are equal.