JPH0223493Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a power steering device for agricultural tractors.

(b) Prior Art Technologies related to power steering mechanisms for traveling vehicles have been known to the public.

For example, there is a technique described in Japanese Utility Model Application Publication No. 48-102728.

However, this conventional technology is related to the power steering mechanism of vehicles that travel on flat areas, such as forklifts, and the left and right ends of the front axle are moved up and down in order to travel on rough terrain, such as agricultural tractors. This technology is essentially different from that of a power steering mechanism.

(c) Issues to be solved by the invention Agricultural tractors do not have four-wheel independent suspension, but instead have two front wheels and two rear wheels supported in a straight line by their respective axles.

In order to overcome uneven terrain, the front axle side is pivoted at the center of the aircraft using a center pin, and the front wheels at the left and right ends can rotate in opposite directions, independent of the rear wheels. has been done.

In such a structure, the front axle rotates left and right and up and down, and the front axle bracket is on the side of the aircraft supported by the rear wheels and is fixed, so if the front wheel rides on an uneven surface and rotates left and right and up and down, the front axle bracket rotates left and right and up and down. The tie rod that connects the knuckle arm and the bell crank on the hydraulic cylinder side of the front axle bracket is pulled toward the lower front wheel. Conversely, the raised front wheels push.

In the case of conventional manual steering, the operator compensated for this by holding the steering wheel loosely.

However, in the case of power steering equipment,
If the hydraulic control valve is set to neutral, even if the operator holds the steering wheel loosely, the hydraulic pressure will not be transmitted beyond the valve, so when the front wheels move left, right, up or down, the tie rod will not move even if you pull or push it. It doesn't move.

Therefore, if the front wheels are not rotated to their full turning angle, the front wheels automatically change the turning angle to absorb the amount of change caused by the left/right, up/down movement of the front axle.

If the cutting angle of the front wheel is small and the knuckle arm is not in contact with the rotation restriction stopper, this change can be absorbed by cutting the front wheel further by itself in this way.

However, if an attempt is made to turn with the front wheels turned to their full turning radius, and the hydraulic control valve returns to neutral, the front axle moves left and right, up and down, and the front wheels are forced to turn to limit the maximum turning angle. If there is a restriction stopper, the front wheel side will not be able to absorb the changes in the tie rod caused by this horizontal and vertical movement, and will forcefully pull the tie rod, causing the hydraulic cylinder to expand and contract, which may cause an abnormality in the hydraulic circuit. High pressure is generated, damaging the hydraulic cylinder device and hydraulic circuit control valve.

In order to eliminate this problem, recent power steering devices remove the rotation restriction stopper on the front wheel side and install this rotation restriction stopper on the bell crank or hydraulic cylinder device side to determine the minimum turning radius. Even if the front axle turns left, right, up or down, the tie rod and bell crank do not move, and the front wheels change the angle of rotation to absorb the movement.

However, with this configuration, a situation where the front wheels turn further inward than the position of the minimum turning radius in a flat state occurs when driving on rough terrain and the front axle moves left and right and up and down. It is necessary to determine the minimum turning radius when the vehicle is flat, leaving a minimum of
The problem was that the minimum turning radius became large.

In order to eliminate these problems, the present invention eliminates these problems by leaving the rotation regulating stopper on the front wheel side as is and installing a safety valve on the hydraulic cylinder device and hydraulic circuit side to absorb abnormally high pressure.

(d) Means for solving the problem The problems to be solved by this invention are as described above.
Next, means for solving the problem will be explained.

Due to the expansion and contraction of the hydraulic cylinder device A, the pivot pin 1
In a power steering mechanism that rotates a bell crank 6 that is pivotally supported at 0, and rotates a nutcle arm 16 via a tie rod 11 by the rotation of the bell crank 6, the bell crank 6 and the tie rod 11
The connecting portion O ₁ with L and 11R is offset upward with respect to the center M of vertical movement of the front axle 7, and further displaced backward with respect to the longitudinal center of the front axle 7, so that the inward movement of the knuckle arm 16 is performed. A rotation regulating stopper 17 that limits the cutting angle is attached to the front axle 7.
The hydraulic control valve 24 is switched when the front wheel on the restricted side rises on rough ground when the rotation regulating stopper 17 contacts the rotation regulating stopper 17 and the turning angle is restricted. without being done,
A safety valve B is provided on the inlet and outlet sides of the hydraulic cylinder device A to release abnormally high pressure generated by forcibly expanding and contracting the hydraulic cylinder device A from the nutcle arm 16, tie rod 11, and bell crank 6 side. It is.

(E) Embodiments The problems to be solved by the present invention and the means for solving them are as described above. Next, the detailed structure of the present invention will be explained based on the attached drawings.

Fig. 1 is a plan view of the front axle bracket, Fig. 2 is a partial sectional view of the front, Fig. 3 is a plan view of the front axle, Fig. 4 is a sectional view of the safety valve B, and Fig. 5 is the safety valve B. FIG. 6 is an overall hydraulic circuit diagram of the power steering device of the present invention.

The bell crank 6 is rotated by the hydraulic cylinder device A in the front axle bracket 1, and the left and right tie rods 11L and 11R are connected to the connecting portion _O1 of the bell crank 6, and the left and right tie rods 1 are connected to the connecting portion O1 of the bell crank 6.
Katsukuru arm 16L, 1 at the tip of 1L, 11R
6R are connected, and the king pins 18L and 18R are rotated.

Front wheel 22L with king pins 18L and 18R,
It is rotating 22R.

The hydraulic cylinder device A is composed of a hydraulic cylinder 4 and a piston rod 3.
The piston rods 3, 3 protrude from both sides of the piston so that the amount of oil chambers on both sides does not change. Also, generally the hydraulic cylinder 4 side is fixed and the piston rod 3 side slides.
In the present invention, the piston rod 3 is pivotally connected to the front left corner of the front axle bracket 1 at the portion 3a,
The hydraulic cylinder 4 side is supported by a pivot pin 4a between a bell crank 6 and a bell crank pivot body 5 in a loosely fitted manner.

The bell crank pivot 5 is fixed to the bell crank 6 with bolts 14, 14. bell crank 6
is pivotally supported to the front axle bracket 1 by a pivot pin 10.

2 is a flexible pipe, which bends the pressure oil sent from the rear engine side by creating a U-shaped rotating part in the front part of the front axle bracket, and runs it along the hydraulic cylinder device from the front, and connects it to the adapter 2c. is sending oil to. 2a and 2b are oil distribution pipes.

At the rear end of the bell crank 6, there are two connecting portions _O1 having eyeglass-shaped openings, and the ball joint portions of the left and right tie rods 11L and 11R are pivotally supported in these holes.

As shown in FIGS. 2 and 3, in the present invention, as in the conventional art, a stopper 17 for restricting the rotation of the knuckle arm 16 is provided between the knuckle arm 16 on the front wheel side and the front axle 7 side to prevent the front wheel from breaking any further. ing. The knuckle arm 16 is fixed to a king pin 18.

As shown in Fig. 3, the minimum turning radius is the state in which the knuckle arm 16 is in contact with the rotation regulating stopper 17, and when the vehicle is traveling on flat ground in this state, the tie rod will rotate the bell crank 6 and the knuckle arm 16 at the 11L' position. It is tied.

If the left side of the front axle falls into the recess from this state, the relationship between the knuckle arm 16 and the front wheel 22L will not change because it is restricted by the rotation restriction stopper 17, so the tie rod 11L can be moved to 11.
L'', the pivot point of the tie rod 11 and bell crank 6, which had moved to _O2 on flat ground, is forcibly returned to the connecting part _O3 .

The bell crank 6 is rotated by the steering handle 23 to the full turning radius of _O2 .
After the rotation, the steering handle 23 returns the hydraulic control valve 24 to the neutral position, so when the bell crank 6 rotates from this state, the compression side of the hydraulic cylinder device becomes abnormally high pressure.

In this invention, the safety valves B shown in Figures 4 and 5 are installed at the inlet and outlet of the hydraulic cylinder device A as shown in Figure 6 in order to release the abnormally high pressure at this time and prevent damage to the equipment. be.

In the case of Figures 2 and 3, the left wheel is stuck in a recess during a left turn _. tries to move further to the right.

The reason why the cutting angle of the front wheels tends to change when going from flat ground to uneven ground is that the center of vertical movement M of the front axle 7 is the center M of the center pin 8.
On the other hand, the connection part O ₁ of the tie rod 11 is located above and away from this M, so they do not match, and the connection part O ₁ of the bell crank 6 and the tie rod 11 is also This is because the distance between the pivot points of the knuckle arm 16 and the tie rod 11 changes due to left and right vertical movement since it is deviated rearward.

Furthermore, since the connecting part _O1 between the tie rod 11 and the bell crank 6 is not constant and its position changes depending on the turning radius, the position between the tie rod 16 and the tie rod 11 is not constant.
The distance between them also changes depending on their turning radius.

The center of the pivot pin 10 of the bell crank 6 and the pivot center M of the front axle 7 are shifted by a distance a.

In Figures 4 and 5, the safety valves are the left and right check valves 20L and 20R, and the relief valve 19.
When abnormally high pressure is applied to one oil chamber, the relief valve 19L or 19R is
R is opened and the pressure oil that spouts out is check valve 20.
It is configured to enter the other oil chambers through L and 20R, and both oil chambers are configured so that they are not always in a negative pressure state.

In FIG. 6, 28 is an engine, 27 is a hydraulic pump, 25 is a hydraulic oil tank, and 26 is a low pressure relief valve and flow control valve for the hydraulic oil. 29 is a hydraulic control valve, and 23 is a steering handle.

(f) Effects of the invention Since the invention is constructed as described above, it has the following effects.

First, the center of vertical movement M of the front axle
The forced movement of the tie rod due to the vertical movement of the front axle, which occurs due to the difference in the connection part _O1 between the nutcle arm and the tie rod, can be absorbed by the safety valve provided at the inlet and outlet of the hydraulic cylinder A. As a result, the hydraulic cylinder device A is no longer destroyed.

Second, since the safety valve B absorbs the energy, the rotation restriction stopper 17 can be provided at the full rotation range of the front wheel 22, and even though the power steering mechanism is used, the turning radius can be reduced compared to the conventional one. This allows the same range as manual steering.

Thirdly, in the case of conventional power steering, there was no safety valve, so the hydraulic cylinder could not absorb it, so the rotation of the bell crank was restricted, and the rotation was always restricted before the rotation range of the front wheels. However, since we left some room for the front axle to move up and down from its position, the minimum turning radius would become larger even when driving on flat ground where there is no need to provide that much room. It had been left behind. The present invention has completely solved this problem.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the front axle bracket. FIG. 2 is also a partially sectional view of the front. FIG. 3 is a plan view of the front axle. FIG. 4 is a sectional view of safety valve B. Figure 5 is a circuit diagram of safety valve B. FIG. 6 is an overall hydraulic circuit diagram of the power steering device of the present invention. A...Hydraulic cylinder device, B...Safety valve, 7
L, 7R...Front axle, 11...Tie rod, 16...Knuckle arm, 17...Rotation regulating stopper, 18...King pin, 22...Front wheel.

Claims (1)

[Scope of utility model registration request] Due to the expansion and contraction of the hydraulic cylinder device A, the pivot pin 1
In a power steering mechanism that rotates a bell crank 6 that is pivotally supported at 0, and rotates a nutcle arm 16 via a tie rod 11 by the rotation of the bell crank 6, the bell crank 6 and the tie rod 11
The connecting portion O ₁ with the front axle 7 is displaced upwardly with respect to the center M of vertical movement of the front axle 7, and further displaced backwardly with respect to the longitudinal center of the front axle 7, thereby causing the inward cutting of the knuckle arm 16. A rotation regulating stopper 17 that limits the angle is provided on the side of the front axle 7 to release abnormal high pressure generated by forcibly expanding and contracting the hydraulic cylinder device A from the side of the knuckle arm 16, tie rod 11, and bell crank 6. A power steering device for an agricultural tractor, characterized in that a safety valve B is provided on the inlet and outlet sides of a hydraulic cylinder device A.