JPH0140372Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a piston, and particularly to a high-pressure side piston of a two-stage compressor.

(Prior Art) A piston that reciprocates within a cylinder is connected to a connecting rod via a piston pin. This piston pin is usually supported by a pair of piston boss holes formed in the peripheral wall of the piston, and is fixed to the piston so as not to come off from the piston.

Conventionally, the piston pin was fixed to the piston in the following manner. That is, the inner diameter of the pair of piston boss holes is made smaller than the outer diameter of the piston pin, and when the piston pin is fixed, the piston is heated to expand the piston boss hole, and then the piston pin is inserted, The piston is then cooled and the piston pin is tightened, a so-called shrink fit.

(Problems to be solved by the invention) As mentioned above, in the above conventional example, two of the piston pins supported by a pair of piston boss holes
Because the parts were fixed together by shrink fitting, there were the following inconveniences.

In other words, when the piston is cooled after heating, the diameter normally decreases uniformly, but if the piston pin is inserted into the piston boss hole, the gap between the piston boss hole and the piston pin becomes smaller, causing friction between the two. After cooling, the piston will:
As shown in FIG. 3, the piston pin is deformed into an oval cross-section with the longitudinal direction of the long axis extending in the direction of extension, which causes abnormal noise. In the figure, a shows the outline of the piston during heating, b shows the outline of the deformed piston after cooling, and c shows the outline of the undeformed piston.

In addition, as mentioned above, in the above conventional example, since the two parts of the piston pin are shrink-fitted, the piston pin cannot be inserted into the piston boss hole until the piston is heated. It required a special jig.

In view of these problems, the present invention facilitates assembly by allowing the piston pin to be inserted into one of the piston boss holes before heating the piston. The aim is to suppress deformation as much as possible.

(Means for Solving the Problems) In order to solve the above problems, the present invention has one of the piston boss holes that support the piston pin has an inner diameter that can be shrink-fitted to the piston pin, and the other has an inner diameter that can be shrink-fitted to the piston pin. The idea is to make the inner diameter so that it can be tightened.

(Function) After inserting a piston pin into a piston boss hole having an inner diameter that allows for a loose fit, the piston is heated to expand the piston boss hole, and then, after inserting the piston pin into the expanded piston boss hole, the piston The piston pin is fixed to the piston by shrink fitting one part of the piston pin and loosely fitting the other part.

(Embodiment) The present invention will be explained below with reference to an embodiment shown in the drawings. As shown in FIG. , and the boss holes 1a and 1b are arranged so that their axes coincide with each other.

The piston boss holes 1a, 1b are for supporting the piston pin 2, and the piston boss holes 1a, 1b are for supporting the piston pin 2.
The inner diameters of 1b are different from each other. That is, the inner diameter of one of the boss holes 1a, 1b is smaller than the outer diameter of the piston pin 2, and the inner diameter of the other boss hole 1b is larger than the outer diameter of the piston pin 2. In this way, the relative dimensional relationship between the piston boss holes 1a, 1b and the piston pin 2 is set by
This is to fix the piston pin 2 to the piston by shrink fitting in one piston boss hole 1a and by loose fit in the other piston boss hole 1b.

Therefore, the difference between the inner diameter of one piston boss hole 1a and the outer diameter of piston pin 2 is set within a range that allows shrink fit, and
The difference between the inner diameter of b and the outer diameter of the piston pin 2 is set within a range that allows tight fit.

By setting the relative dimensional relationship between the piston boss holes 1a, 1b and the piston pin 2 in this way, it is possible to insert the piston pin 2 into the other piston boss hole 1b when assembling the piston pin 2. ,
When the piston is heated in this state, the boss hole 1a
expands, allowing the piston pin 2 to be inserted. Finally, when the piston is cooled by natural cooling or forced cooling, the boss hole 1a
will contract, and the piston pin 2 will be shrink-fitted.

When the piston is cooled, a gap is formed between the other piston boss hole 1b and the piston pin 2, so even if the piston contracts, no frictional resistance is generated between them. does not interfere with the contraction of

(Effects) As is clear from the above, in the present invention, in relation to the piston pin, one piston boss hole has an inner diameter that allows a shrink fit, and the other piston boss hole has an inner diameter that allows a loose fit. It becomes possible to insert the piston pin into the other piston boss hole before heating, and therefore shrink fitting can be performed without the need for a jig, which facilitates assembly.

In addition, as mentioned above, the other piston boss hole is
Since it has an inner diameter that allows for a loose fit in relation to the piston pin, there is no frictional resistance between the two even when the piston is retracted.
Compared to the conventional example in which both parts are shrink-fitted, deformation of the piston is suppressed as much as possible.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the piston according to the present invention, Figure 2 is a sectional view of the piston according to the present invention;
The figure is a sectional view of the piston pin, and FIG. 3 is a sectional view showing the state of deformation of the piston. 1a, 1b... Piston boss hole, 2... Piston pin.

Claims (1)

[Scope of utility model registration request] A piston in which one of the piston boss holes supporting a piston pin has an inner diameter that allows a shrink fit to the piston pin, and the other has an inner diameter that allows a clearance fit.