JPS628221Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the improvement of the power steering system for automobiles.In particular, the cylinder system that generates the steering power is improved, and the maximum steering angle position of the tires, which is the end point of steering, is adjusted to this point. Previously, the resistance of the steering force was gradually increased so that the driver could feel it,
The present invention also relates to a device that can achieve this with a simple configuration.

2. Description of the Related Art As a steering device for automobiles, a power steering device called power steering is becoming commonly used not only for large vehicles but also for vehicles such as small passenger cars. In this power steering device, the cross-sectional area and maximum pressure of the cylinder of the hydraulic device are set so that sufficient power assistance can be obtained even in response to changes in the coefficient of friction of the road surface and fluctuations in loaded weight.

With the power steering device described above, when operating the steering wheel, the steering wheel can be steered with light force until it hits the mechanical stopper that determines the maximum turning angle of the tire, but when the driver hits the stopper, the driver is unable to operate the steering wheel unexpectedly. You will receive a large reaction force and have an unpleasant experience.

In addition, in the hydraulic system of a power steering system, when hydraulic pressure is supplied into the cylinder to provide power assistance, the hydraulic pump, which is the hydraulic pressure generating device, is equipped with a relief valve to prevent an excessive rise in hydraulic pressure. This relief pressure is normally set sufficiently high in anticipation of the aforementioned changes in road surface conditions and load weight changes, and in reality, a pressure of about 50 atm is sufficient considering the variation in production.
Pumps with high relief pressures of atmospheric pressure may also be made. In vehicles equipped with such high-pressure pumps, a high-pressure load is applied each time the stopper is hit at the end of the steering wheel operation, which can lead to fatigue of the strength members of each part of the cylinder device and shorten the lifespan of rubber hoses, seals, etc. Undesirable.

For this reason, it has been proposed to short-circuit the high-pressure chamber and low-pressure chamber in the cylinder device at the end of the handle operation, and for example, a short-circuit valve for this is proposed in U.S. Pat. No. 3,047,087, but this method requires a complicated structure. , it is also expensive and disadvantageous in terms of cost.
Furthermore, such a large-scale device poses a problem in terms of space, and has the disadvantage that it is difficult to accommodate a small vehicle such as a passenger car.

This invention was made in view of the above-mentioned technical problems in conventional power steering devices and to solve them.

The purpose of this invention is to gradually increase the steering force at the right or left end point of the steering wheel operation, starting just before the end point, so that the driver is warned that the end point is at or near the end point. To provide a device that has a simple configuration, is inexpensive, has reliable operation in advance, is highly reliable, and is durable.

The purpose of this invention is to bypass the pressure in the high-pressure chamber defined by the piston of the cylinder device to the low-pressure chamber before the end point of the steering wheel, thereby reducing the steering force before the end point of the steering wheel. To provide a device that includes a short-circuiting means that increases the weight of the device, prevents unnecessary load on cylinders, etc. due to high pressure generated near the end point of handle operation, and improves the life of the device.

In particular, the purpose of this invention is to provide two springs on the piston shaft on both sides of the piston, and near the end of the piston stroke, the springs are brought into contact with the end of the cylinder and compressed and deformed. The synergistic effect of the above-mentioned bypass action from the high pressure side to the low pressure side and the elastic action of this spring makes it possible to further increase the steering force and effectively prevent the piston from colliding suddenly with the end of the cylinder. We provide equipment that

A preferred embodiment of this invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall side sectional view of the main parts of the device according to this invention.

In the figure, 2 is a pinion provided on the operating rod 1 which is directly rotated by a steering handle (not shown), and this pinion 2 meshes with a rack 4 of a rack rod 3 configured to slide from side to side in the figure. Both ends of this rack rod 3 engage the steering wheels in the usual manner via tie rods.

The pinion 2 is formed with diagonal teeth, and the rack 4 is also formed with diagonal teeth correspondingly, and a thrust force is applied upward and downward according to the direction and magnitude of the torque applied to the pinion 2 by the operating rod 1. A four-way switching valve 5 is provided at the lower end of the operating rod 1 and is configured to act on the thrust force.

The switching valve 5 is switched by the thrust force generated by the pinion 2 when the handle is operated, and is set to supply and discharge hydraulic oil from a hydraulic pump (not shown) to left and right chambers partitioned by a piston in a cylinder, which will be described later. The hydraulic pump is driven by an engine, and is equipped with a known flow control valve so that the amount of oil supplied remains substantially constant even when the rotational speed changes, and the switching valve is installed so that the amount of oil supplied is substantially constant even when the rotational speed changes. ,
A so-called open center valve is used to allow pressurized oil from the pump to flow freely into the tank.

This switching valve 5 is connected to a hydraulic pump and is also connected to left and right chambers partitioned by a piston, which will be described later, through an external piping line 6 such as a hose, and in the drawing, 7 is a bearing of the operating rod 1, and 8 is a sealing material. .

The rack rod 3 is slidably fitted into a cylindrical casing 10, and the casing 10 is divided into left and right members 11 and 12 at a suitable midpoint, with a cylinder 13 interposed between them, and both ends of the cylinder 13 are connected to the left and right members. Screw connections 14, 15 at opposite ends of 11, 12
16 is a locking nut screwed into this threaded joint 15 of the cylinder 13 so as to contact the end of one member 12.

A piston 17 is provided in the part of the rack rod 3 located in the cylinder 13, so that the rack shaft 3 is used as a piston shaft, and the outer diameter of the piston 17 is set to be slightly smaller than the inner diameter of the cylinder 13. It is configured so that it does not come into direct contact with the inner periphery of the cylinder 13. An annular groove 18 is formed in the center of the outer circumference of the piston 17, and a seal ring 19 made of polytetrafluoroethylene resin or the like is fitted into this groove 18. Hydraulic chamber A is partitioned to the left and right in the axial direction of piston 17,
B is formed. The left and right chambers A and B are divided by the above, and seal members 22 and 2 are provided at the ends of stopper portions 20 and 21 formed at the left and right ends of the cylinder 13 of the left and right members 11 and 12, respectively.
3, and constitute independent chambers A and B on the left and right sides in the axial direction with the piston 17 in between.

Cushion springs 24 and 25 are wound around the outer periphery of the rack rod 3 so as to be located on both sides of the piston 17, and one ends of the springs 24 and 25 are brought into contact with the side surface of the piston 17. Furthermore, the rack rod 3 is provided with a shallow groove 2 at a position away from the end of the cylinder formed by the stopper portions 20 and 21 toward the piston 17.
6, 26 are formed, and the other ends of the springs 24, 25 are engaged with the grooves 26 and are locked in contact with the circlip 27 provided on the rack rod 3. It is attached to the rack rod 3 at a distance from the terminal end.

Hydraulic oil supply and discharge ports 28 and 2 are provided at the axial ends of the cylinder 13 of the left and right members 11 and 12.
9 is provided, and the supply/discharge ports 28 and 29 are connected to the switching valve 5 by a pipe 6. This supply/discharge port 2
8 and 29 communicate with the left and right chambers A and B, respectively, but in the illustrated example, the supply/discharge port 28 on the left side of the figure is connected to the stopper part 20 provided at the end of the cylinder 13 as shown in FIG. It is configured to communicate with the chamber A via a passage 31 provided in a spacer 30 which also serves as a spacer.

On the outer periphery of both ends of the cylinder 13, in front of the connection part of the supply/discharge ports 28 and 29, and at the screw joint 1
There is a shallow annular groove 32, 3 in the pilot part between 4 and 15.
3 are formed, and these grooves 32, 33 communicate with internal chambers A, B, respectively, through bypass holes 34, 35 and 36, 37 provided respectively. The grooves 32, 33 are formed with a slightly shorter length in the axial direction, and each groove 32, 3
Bypass holes 34 and 35 provided in each of 3 and 3
6 and 37 are provided with an interval in the axial direction, and the above grooves and holes constitute a bypass communication path at both ends of the cylinder 13.

Next, to explain its operation, FIG. 1 shows this device in a straight running state. Let's now move Rack Rod 3 to the right by operating the steering wheel. When the handle is operated, the operating rod 1 is moved up and down by the engagement of the pinion 2 and the rack 4, and the switching valve 5 is switched. As a result, hydraulic oil is pressurized into the supply/discharge port 28 on the left side of the figure, and the
The hydraulic pressure inside increases, the rack lever 3 moves to the right via the piston 17, and the hydraulic oil in the right chamber B flows to the supply/discharge port 2.
It is discharged from 9. As a result, the right movement of the rack rod 3 is assisted by hydraulic power, and can be easily steered with a light handle operation.

When the tire is steered to the maximum turning angle by operating the steering wheel, as shown in FIG. 3, the end of the spring 25 on the right side of the figure that was locked by the circlip 27 moves to the stopper portion 21 at the end of the cylinder stroke. As a result, the spring 25 is compressed and deformed, and the resistance due to its cushioning action is propagated to the lock lever 3, making it difficult to operate the handle and avoiding a sudden collision of the piston 17 with the end of the cylinder. In addition, prior to this, the seal ring 19 of the piston 17 passes through the bypass hole 36 on this side, and as a result, this hole 36, the groove 33,
The high pressure chamber A and the low pressure chamber B communicate through the hole 37, and the chamber A
The oil pressure in chamber A is bypassed and leaks to the chamber B side, and as a result, the oil pressure in chamber A decreases.

Therefore, the auxiliary power decreases by this amount, the sliding resistance of the rack lever 3 increases, and the steering becomes heavier. Thereafter, the spring 25 comes into contact with the stopper 21 and the resistance increases, and at the end the spring 25 buckles and comes to a stop. During this time, as the seal ring 19 passes through the bypass hole 36 as described above, the hydraulic pressure decreases. The handle gradually becomes heavier, and the synergistic effect with the spring 25 provides a feeling of operating the handle that gradually becomes heavier.

In this way, the piston 17 does not directly hit the stopper at the end of the steering wheel operation, but the resistance to the steering wheel operation is gradually increased from this point onward, and the driver feels this.

In the above, the positional relationship between the holes 36 and 37 that leak hydraulic oil near the end of the steering is as follows:
7 slides to the right in the figure, the seal ring 19 passes through the hole 36 in the front, connecting the chambers A and B, and then when the piston 17 reaches the end point on the right side, the hole 37 also connects the chambers A and B. The holes 34 and 35 on the left side of the figure are provided outside the seal ring 19.
symmetrically and in the same positional relationship.

Although the explanation has been given above regarding the rightward movement of the rack rod 3, the leftward movement also operates symmetrically to the above.

FIG. 4 shows a device in which the opening area of the bypass passage described above is substantially increased as the seal ring passes.

In the figure, since the basic configuration is exactly the same as above, the same parts are given the same reference numerals.

In the illustration, only the right side portion of the cylinder 13 is shown as in FIG. 3, but the left side is similarly constructed symmetrically.

In this device, the bypass holes 36 and 37 provided at the end of the cylinder are replaced by bypass holes 136 and 1.
The cylinder 1 having bypass holes 136 and 137 is provided adjacently with a short distance as 37.
An annular groove 133 is provided on the outer periphery of the relevant portion of 3, and this groove 133 is directly communicated with a passage 138 of a cast hole provided at a connection portion with the supply/discharge port 29.

By providing the holes 136 and 137 adjacent to each other in this way, the seal ring 19 first passes through the hole 136 in front near the end of the steering stroke, and the chambers A and B are formed by the hole 136, the groove 133, and the passage 138. communication,
Similarly to the above, the oil pressure decreases and steering resistance occurs.
After the seal ring 19 passes through this hole 136,
The oil in chamber A, where the seal ring 19 passes through the adjacent hole 137, leaks through each hole 136, 137, and the oil leakage cross-sectional area becomes the combined size of the holes 136, 137, increasing the resistance. becomes more and more
After that, the spring 25 collides with the stopper 21,
As the cushioning action takes place, the resistance increases further.

By providing the holes 136 and 137 adjacent to each other as described above, the oil outflow cross-sectional area is substantially changed as the steering stroke moves toward the end near the end, thereby gradually reducing the resistance. By increasing the size, you can gradually make the steering wheel heavier.

Although the illustrated embodiment has been described in detail above, the flow of oil into and out of the chambers is determined by the opening area of the hole, and by setting this, the resistance at the end of the steering wheel operation can be arbitrarily set. , the driver is made to feel that the steering wheel is at the end of the steering wheel, and the driver is made to do this gradually, and the settings are appropriately set so that the weight gradually increases.

Also, in the device shown in Figure 4, two holes are provided adjacent to each other, but if the stroke is large depending on the vehicle model, the number of holes may be greater than this, and by providing a plurality of holes, the resistance can be increased step by step. Can be done.

As is clear from the above explanation, according to this invention, at the right or left end point of the steering wheel operation, the steering force gradually becomes heavier from before the end point, giving the driver advance notice that the end point is near. Therefore, it is possible to prevent a situation where the vehicle directly hits the stopper at the end point and receives an impact, and to obtain an end point notice device that is effective for driving operations.

Also, according to this invention, the above-mentioned advance notice is configured to reduce the power auxiliary hydraulic pressure by providing a passage that communicates the chambers divided by the pistons near the end of the steering operation, so a special short circuit valve is not required. This can be achieved with a simple configuration, making it possible to obtain the device at a low cost and easily.In addition, since the rooms communicate with each other with a simple configuration, the operation is reliable and reliable, there is no breakdown, and it is excellent in terms of maintenance. This prevents unnecessary load on the product and improves its durability and lifespan.

In particular, according to this invention, two springs are disposed on both sides of the piston shaft, one end of which is in contact with the side surface of the piston, and the other end of the spring is separated from the end of the cylinder toward the piston and is engaged with the piston shaft. Near the end of the piston stroke, the other end comes into contact with the end of the cylinder and the spring is compressed, so the elastic force of this spring is added to the steering force of the steering wheel, and the high pressure generated by the passage described above is In addition to leaking oil from the chamber to the low-pressure chamber, the steering force can be made heavier, and it is also possible to more effectively prevent the piston from colliding with the end of the cylinder, making it effective for power steering devices. and is extremely practical.

[Brief explanation of the drawing]

The drawing shows one embodiment of this invention.
The figure is a side sectional view of the main part of the device, Fig. 2 is an enlarged sectional view of the main part of Fig. 1, Fig. 3 is a sectional view of the main part of Fig. 2 showing the progress of operation, and Fig. 4 shows the opening area of the piston. FIG. 4 is a cross-sectional view similar to FIG. 3 of the device adapted to be increased by the progression of . In the drawing, 3 is the rack rod which is the piston shaft, 1
3 is a cylinder, 17 is a piston, 19 is a sealing member, 27 is a circlip that is a locking member, 2
4, 25 are springs, 32 to 37 and 133,
136 to 138 are passages, and A and B are chambers.

Claims (1)

[Claim for Utility Model Registration] A passage in the cylinder wall near the end of the piston stroke of a hydraulic cylinder that performs power-assisted operation, which communicates between the high pressure chamber and low pressure chamber of the cylinder, which are partitioned by the piston that has reached the vicinity of the end of the stroke. In a power steering system for an automobile equipped with a piston, two springs are provided on both sides of the piston with one end of each abutting against the side surface of the piston that is integrated with the piston shaft. A stopper is provided on the piston shaft that abuts on the other end of each of the springs, and the piston first opens the passage near the end of its stroke to communicate between the high pressure chamber and the low pressure chamber, and then the other end of the spring comes into contact with the stopper. A power steering device for a motor vehicle, comprising: a locking member that restricts the other end of the spring so that the spring is in contact with the spring and thereafter compressed.