JPS63270975A - Piston - Google Patents

Abstract

PURPOSE:To produce an excellently durable piston by using polyamide for a sliding part of the piston to reduce friction between the piston and a cylinder, resulting in less wear quantity of the sliding part of the piston. CONSTITUTION:A piston rod 13 passes through a piston 12 made of polyamide reciprocating within a metal cylinder 11, and its one end is threedably attached to the piston 12 through a nut 14. A groove 15 formed on the outside surface of the piston 12 is filled with a grease 16 as early oiling for the piston 12, and its both sides are formed with a sliding surface respectively. Thus, since the sliding part 17 of the piston 12 is made of the polyamide low in the coefficient of friction, friction between the sliding part 17 of the piston 12 and the cylinder 11 can be reduced. The sliding part 17 of the piston 12 can therefore become less in its wear quantity to produce the excellently durable piston 12.

Description

[Detailed description of the invention] , Birth 1 Yuj ■ 1 minute! The present invention relates to a piston, particularly a piston used in a shock absorber using air.

FIG. 3 shows a sectional view of a conventional piston and cylinder. A piston rod 3 passes through a metal piston 2 that reciprocates inside a metal cylinder 1, and one end of the piston rod 3 is screwed onto the piston 2 by a nut 4.

A wear ring 5 is installed as a backing for the piston in one groove formed on the outer surface of the piston 2, and a seal backing 6 and an O-ring 7 are installed in the other grooves.

In addition, as one that does not use a backing for the piston,
For example, there is a piston made of oleoresin.

However, at present, these wear rings, seal backings, O-rings, pistons made of oil-impregnated resins, etc. do not have satisfactory durability (wear resistance). That is, there is a problem in that the durability decreases when the vertical movement speed of the piston increases or the pressure resistance required of the piston increases.

As an example of such problems, Table 1 shows the results of a durability test of the piston backing of a shock absorber using a seal backing as the piston backing. 5kgf/a
d, Shock absorber stroke is 13011II
This is for the case where the lifting/lowering speed of the I+1 piston is 1°13 m/sec, and the piston rises under pressure against gravity (hereinafter referred to as the rising side). Also, the first
Table (b) shows the case where the pressure is 5 kgf/ad, the stroke of the shock absorber is 130 fflI11, and the vertical speed of the piston is 1.5 m/sec, and the piston descends under pressure in the direction of gravity (hereinafter referred to as the descending side). ).

Table 1 (a) (unit: mm) However, A indicates the thickness of the seal backing, and B indicates the amount of wear of the seal backing.

In Table 1 (a) and the table below, the amount of wear is -
If the symbol is attached, it indicates that the backing or piston has worn out.

In Table 1 (a) and Table 1 (b) shown below,
The reason why the thickness of the seal backing increases when the number of reciprocations after the start of the test is 570,000 times and the amount of wear is marked with a 0 is because
It is thought that the seal backing was swollen due to a measurement error or due to grease or the like.

Table 1 (b) (unit: mm) However, A indicates the thickness of the seal backing, and B indicates the amount of wear of the seal backing.

FIGS. 4(a) and 4(b) are graphs of the wear amounts shown in Tables 1(a) and (b), respectively.

In addition, as another example of such problems,
Table 2 is a table showing the results of the durability test of the piston made of the oleoresin, and Table 2 (a) shows the results when the pressure is 5 kg.
f/cJ, shock absorber stroke is 130m
m, the lifting speed of the piston is 1°13 m/diameter,
This is for the rising side.

Table 2 (b) is for the downward side of the piston, where the pressure is 5 kgf/cj, the stroke of the shock absorber is 130 mm, and the vertical speed of the piston is 1.5 m/sec.

Table 2 (a) (unit: mm) B indicates the amount of wear on this piston.

In Table 2 (a) and Table 2 (b) shown below,
The reason why the thickness of the piston increased after 1.43 million reciprocations after the start of the test and the amount of wear was marked with a 10 is thought to be due to a measurement error or because the piston swelled due to grease etc. .

Table 2 (b) (unit: mm) However, A indicates the thickness of the piston made of oleoresin, and B indicates the amount of wear of this piston.

FIGS. 5(a) and 5(b) are graphs of the wear amount shown in Tables 2(a) and (b), respectively.

Based on Tables 1 and 2, 277 as a durability test
Table 3 shows the amount of wear after the piston has reciprocated 10,000 times.

Table 3 However, the oleoresin piston refers to a piston made of oleoresin.

As is clear from Table 3, the amount of wear on the piston made of seal parts king and oleoresin is extremely large, and as is clear from Figures 4 and 5, as the number of reciprocations of the piston increases, There is no tendency for the amount of wear to increase and become saturated. In other words, as the number of reciprocations of the piston is further increased, the amount of wear increases accordingly.

Note that substantially similar results to those in Tables 1 and 2 were obtained for O-rings, wear rings, and the like.

Therefore, there is a problem that seal backings, O-rings, wear rings, pistons, etc. made of oil-impregnated resins do not have sufficient durability.

The gist of the structure of the piston of the present invention, which is used for occupancy, is to use polyamide for the sliding portion.

The amount of wear on the sliding parts of pistons using starch polyamide is reduced.

FIG. 1 shows a longitudinal sectional front view of an embodiment of the present invention. A piston rod 13 passes through a polyamide piston 12 that reciprocates inside a metal cylinder 11, and one end of the piston rod 13 is fixed to the piston 12 by a nut 14.

Grease 6 is loaded into a groove 15 formed on the outer surface of the piston 12 as initial lubrication for the piston.

Sliding portions 17 are formed on both sides of the groove 15 of the piston 12. Note that the cylinder may be made of any metal such as iron, aluminum alloy, or stainless steel.

Table 4 shows the durability test of the piston of the present invention (grease 16
Table 4 (a) shows the results when the pressure is 5 ktrf/crl, the stroke of the shock absorber is 130 nm, and the vertical speed of the piston is 1.13 m.
/second for the rising side of the piston. Table 4 (b) shows the pressure on the descending side of the piston, where the pressure is 5 kgf/aa, the stroke of the shock absorber is 130 mm, and the lifting/lowering speed of the piston is 1.5/sec.

Table 4 (a) (Unit: WIII+) However, A indicates the diameter of a piston made of polyamide, and B indicates the amount of wear of this piston.

Table 4 (b) (unit: mm) However, A indicates the diameter of a piston made of polyamide, and B indicates the amount of wear of this piston.

FIGS. 2(a) and 2(b) are graphs of the wear amounts shown in Tables 4(a) and (b), respectively.

Based on FIG. 2, Table 5 shows the amount of wear on the sliding portion 17 after 2.77 million reciprocations of the piston were performed as a durability test.

Table 5 The amount of wear shown in Table 5 is extremely small compared to the amount of wear shown in Table 3. Furthermore, as is clear from FIG. 2, after the initial wear, the amount of wear does not continue to increase as the number of reciprocations of the piston increases, but shows a tendency for the amount of wear to become saturated. In other words, this shows that even if the number of reciprocations of the piston is further increased, the amount of wear does not increase any further.

That is, the piston according to the present invention has satisfactory durability without lubrication.

In addition, in this example, the piston itself is made of polyamide, but the piston itself is made of metal as in the conventional case.
A piston in which the piston ring or the sliding part corresponding to the piston ring is made of polyamide also exhibits the same durability.

Further, although the above description has been made regarding a piston that makes reciprocating motion, it goes without saying that the same durability can be achieved even when polyamide is used for the sliding parts of a piston that makes rotational motion.

As explained above, according to the present invention, since the sliding portion of the piston is made of polyamide with a low coefficient of friction,
There is less friction between the sliding part of the piston and the cylinder,
Therefore, it is possible to obtain a piston with a small amount of wear on the sliding portion of the piston, that is, with good durability.

[Brief explanation of the drawing]

FIG. 1 shows a longitudinal sectional front view of an embodiment of the present invention. Second
Figures (a) and (b) are graphs of the wear amounts shown in Tables 4 (a) and (b), respectively. Third
The figure shows a longitudinal sectional front view of a conventional piston. Figure 4 (a
) and (b) are Table 1 (a) and (b), respectively.
This is a graph of the amount of wear shown in . Figure 5 (
a) and (b) are Table 2 (a) and (b), respectively.
) is a graph of the amount of wear shown in . 1.11...Cylinder, 2.12...Piston, 5
... Wearing, 6... Seal backing, 7.
...0 ring, 15...groove, 16...grease, 1
7...Sliding part. Figure 1 Figure 3

Claims (1)

[Claims] (1) A piston characterized by using polyamide for the sliding part.