JPH024861Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a piston for a power steering device, and more particularly, to a piston for a power steering device that is lightweight and has sufficient strength.

``Prior Art'' Conventionally, as a piston of a power steering device, a wormshaft hole into which a wormshaft linked to a steering handle is inserted, a cylindrical sliding surface that slides on the inner peripheral surface of a cylinder, and a sector gear. It is known that the device is equipped with an interlocking rack.
Publication No. 14934).

Furthermore, conventionally, in order to reduce weight, an annular sliding surface is left at both ends of the piston, an annular groove recess is formed in the entire other sliding surface, and a horizontal hole is formed from the easy side to the back side. A drilled one has been proposed (Utility Model Application Publication No. 171381/1981).

``Problem to be solved by the invention'' However, in the case of a piston with the latter configuration, the weight can be reduced by using the above-mentioned configuration, but when the rack provided at a predetermined position of the piston meshes with the sector gear, The drawback was that the piston was not strong enough to withstand the pressing force.

"Means for Solving the Problem" In view of the above circumstances, the present invention provides a wormshaft hole into which a wormshaft that is linked to a steering wheel is inserted, a sliding surface that comes into sliding contact with the inner circumferential surface of a cylinder, In a piston of a power steering device, the piston is provided with a rack that meshes with a sector gear, wherein the sliding surface is an annular sliding surface formed at both ends of the piston in the axial direction, and an annular sliding surface formed on the back side of the rack. an axial sliding surface that substantially connects the annular sliding surfaces, and recesses are provided at both axial positions of the piston, excluding the positions where the sliding surfaces are formed and the positions where the racks are formed. The bottom surface of each recess is formed as a flat surface, and a horizontal hole is formed that communicates with the wormshaft hole and penetrates from the flat surface of one recess to the flat surface of the other recess.

"Function" According to this configuration, firstly, since the sliding surface in the axial direction is formed on the back side of the rack,
The reaction force from the sector gear meshing with the rack can be received by the sliding surface in the axial direction, thereby ensuring the necessary and sufficient strength of the piston.

Second, by forming both the recesses and the lateral hole, the weight of the piston can be reduced.

Thirdly, both of the recesses are formed on both sides of the piston in the axial direction, the bottom surface of each recess is formed as a flat surface, and the horizontal hole is passed through from the flat surface of one recess to the flat surface of the other recess. Therefore, these recesses and horizontal holes can be easily formed.

Therefore, with the above-described configuration, the invention of the present application can secure the necessary and sufficient strength of the piston, reduce the overall weight of the piston, and provide a piston that is easy to process.

"Example" The present invention will be explained below with reference to the illustrated example.
1 and 2, a piston 1 has a wormshaft hole 2 in its shaft portion into which a wormshaft (not shown) is inserted, and a rack 3 on one side of its outer circumferential surface that engages with a sector gear (not shown). As is well known in the art, the wormshaft is linked to a steering wheel, and the sector gear is linked to a steering wheel. Both ends of the piston 1 are formed with annular sliding surfaces 4 and 5 that make sliding contact with the cylinder into which the piston is fitted, and the sliding surface 4 on the front side, that is, on the opposite side from the steering handle, has two surfaces inside the cylinder. An annular groove 6 is formed into which a sealing member that partitions the chamber is fitted.

Further, the piston 1 has an axial sliding surface 7 formed on the rear side of the rack 3 so as to be substantially continuous from one sliding surface 4 to the other sliding surface 5. , 5, and 7, a recess 8 is formed in the side surface of the piston 1. In this embodiment, an annular groove 9 connecting the recesses 8 on both sides is formed on the outer peripheral surface of the rack 3 except for the part where the rack 3 is formed, and an annular groove 9 is formed in the direction perpendicular to the worm shaft hole 2. A lateral hole 10 is bored through this and opens into each of the recesses 8.

In the piston having the above configuration, the recess 8 is formed on both sides of the piston 1, the annular groove 9 is formed on the outer peripheral surface of the rack 3, and the horizontal hole 10 is formed through the piston 1. 9
Compared to a conventional high-output piston in which an annular groove is formed around the entire circumference at the position , or a piston in which a lateral hole corresponding to the above-mentioned lateral hole 10 is further bored in the conventional high-output piston, the concave portions 8 on both sides are By forming this, the overall weight can be reduced. In addition, compared to a conventional low-output piston in which the width of the annular groove formed in a conventional high-output piston is expanded to a part or all of the rack 3 side, the reaction force applied to the rack 3 is reduced by the axial sliding on the rear side. Since it can be received by the moving surface 7, it can withstand high output. Therefore, according to this embodiment, it is possible to obtain a lightweight piston 1 for high output.

In this embodiment, grooves 11 and 15 for supplying lubricating oil are formed on the sliding surface 7. In particular, the grooves 11 and 14 are made slightly wider to facilitate machining of the surface connected to the recess 8. I have to. In the illustrated embodiment, the ratio of the sliding surface 7 to the total length in the axial direction, that is, the ratio between the total length and the length obtained by subtracting the lengths of the arcuate portions at both ends and the lengths of all grooves 6 and 11 to 15 from the total length is approximately If the wide grooves 11, 14 are made the same as the other grooves 12, 13, 15, the above ratio will be about 83%. On the other hand, the above ratio in a conventional piston with an annular groove is about 40 to 50% at most, and the piston of the above embodiment has a large percentage of the sliding surface 7.
It is understood that From this perspective, the above percentage should be set at 60% or more, more preferably 70%.
If it is above 80%, it can support high output.
With the above configuration, the sliding surface 7 is almost secured to the maximum extent. Of course, the cross-sectional shape of the above-mentioned lubricating oil supply grooves can be set as appropriate, and in order to achieve high output, the number of grooves should be reduced as much as possible, the width should be narrow, and the grooves should be spaced apart from each other in the length direction. It is desirable to provide them in a distributed manner.

Next, in a piston 20 as another embodiment shown in FIGS. 3 and 4, the annular groove 9 in the above-mentioned embodiment is omitted and that portion is used as a sliding surface 21. The other configurations are the same as those of the above-described embodiment, and the same parts are designated by the same reference numerals.
According to the configuration of this embodiment, it becomes possible to cope with even higher output.

``Effects of the invention'' As described above, according to the invention, it is possible to ensure the necessary and sufficient strength of the piston, while at the same time reducing the overall weight of the piston, and moreover, it is possible to provide a piston that is easy to process. Effects can be obtained.

[Brief explanation of the drawing]

Figure 1 is a side view showing one embodiment of the present invention;
The figure is a sectional view taken along the - line in Fig. 1, Fig. 3 is a side view showing another embodiment, and Fig. 4 is a - line in Fig. 3.
It is a sectional view along a line. 1, 20... Piston, 2... Wormshaft hole, 3... Rack, 4, 5, 7, 21... Sliding surface, 8... Recess, 10... Lateral hole.

Claims (1)

[Claims for Utility Model Registration] A power steering system comprising a wormshaft hole into which a wormshaft interlocked with a steering handle is inserted, a sliding surface that slides on the inner peripheral surface of a cylinder, and a rack that meshes with a sector gear. In the piston of the device, the sliding surface is substantially continuous with an annular sliding surface formed at both axial ends of the piston and an annular sliding surface formed on the back side of the rack. and a sliding surface in the axial direction, and recesses are formed at both sides of the piston in the axial direction, excluding the positions where the sliding surface and the rack are formed, so that the bottom surface of each recess is a flat surface. A piston for a power steering device, further comprising a lateral hole communicating with the wormshaft hole and penetrating from the flat surface of one recess to the flat surface of the other recess.