Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
2000-06-15
2001-12-04
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
C092S186000, C092S159000
Reexamination Certificate
active
06324960
ABSTRACT:
This application is based on Japanese Patent Application Nos. 11-168591 and 11-185638 filed Jun. 15 and Jun. 30, 1999, respectively, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piston used for a swash plate type compressor.
2. Discussion of the Related Art
As a piston for a swash plate type compressor, there are known various types of pistons each of which has (a) a head portion which is slidably fitted in a cylinder bore formed in a cylinder block, (b) a neck portion which engages a swash plate, and (c) a connecting portion which connects the head portion and the neck portion. An example of such pistons is disclosed in JP-A-9-203378. In the swash plate type compressor piston disclosed in this publication, the head portion has a through-hole formed therethrough in a direction substantially parallel to the circumferential direction of the cylinder block. The surfaces of this through-hole which face in a direction intersecting the centerline of the piston are substantially flat or convexed towards the centerline, for easy removal of the piston from a casting mold or a forging die after the piston is formed by casting or forging.
Usually, the swash plate type compressor is lubricated by a lubricant oil in a liquid or mist phase contained or dispersed in a refrigerant gas or other gas to be compressed. The lubricant oil is delivered together with the gas into the crank chamber, for lubricating the contacting surfaces of the swash plate and the shoes, the contacting surfaces of the shoes and the pistons, and the contacting surfaces of the pistons and the cylinder bores. In some cases, the lubricant oil separated from the gas by a separator is delivered in a liquid state into the crank chamber through a rotary drive shaft by which the swash plate is rotated. This lubricant is splashed within the crank chamber and is eventually turned into a mist state. The known swash plate type compressor tend to suffer from a shortage of the lubricant oil, and an accordingly low degree of slidability of the swash plate, shoes, pistons and cylinder bore. In particular, the cylinder bores located at relatively high positions in the cylinder block and the pistons fitted therein are likely to suffer from insufficient lubrication and relatively low slidability. Since the specific gravity of the lubricant is larger than that of the gas to be compressed, the lubricant is sufficiently delivered to the cylinder bores and pistons located at relatively low positions in the cylinder block, and to the corresponding shoes. However, the lubricant oil is less likely to be sufficiently delivered to the cylinder bores, pistons and shoes which are located at the relatively high positions.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the slidability of a piston used for a swash plate type compressor. This object may be achieved by a piston for a swash plate type compressor, which is constructed according to any one of the following forms or modes of the present invention, each of which is numbered like the appended claims and depends from the other form or forms, where appropriate, to indicate and clarify possible combinations of technical features of the present invention, for easier understanding of the invention. It is to be understood that the present invention is not limited to the technical features and their combinations described below. It is also to be understood that any technical feature described below in combination with other technical features may be a subject matter of the present invention, independently of those other technical features.
(1) A piston for a swash plate type compressor, including a head portion slidably fitted in a cylinder bore formed in a cylinder block of the compressor, a neck portion slidably engaging a swash plate of the compressor, and a connecting portion connecting the head and neck portions, wherein the head portion has an inner surface which faces towards a centerline of the piston and which has at least one recess formed therein, the inner surface being located and the at least one recess being configured such that the at least one recess can accommodate a liquid when the piston is fitted in the cylinder bore.
The piston for a swash plate type compressor, which is constructed according to the above form (1) of this invention, has one or more recesses capable of accommodating a liquid when the piston is fitted in the corresponding cylinder bore. In this arrangement, a lubricant oil dispersed in a mist state within the crank chamber of the compressor is accumulated or accommodated in the at least one recess, and is splashed by a reciprocating movement of the piston, so that the lubricant is delivered between the cylinder bore and the piston, and between the swash plate and the piston, more specifically, between the swash plate and the shoes, and between the shoes and the piston. Accordingly, the contacting surfaces of the cylinder bore and the piston and the contacting surfaces between the swash plate and the piston can be sufficiently lubricated, assuring a smooth operation of the swash plate type compressor.
When the swash plate type compressor is not in operation, that is, when the piston is placed in a non-operated state, the lubricant oil which has been dispersed or suspended during operation of the compressor is settled and accumulated in the at least one recess. When the operation of the swash plate type compressor is initiated, that is, when the reciprocating movement of the piston is initiated, the lubricant oil accumulated in the at least one recess is splashed out to be supplied in between the piston and the swash plate and between the piston and the cylinder bore, for effectively lubricating their contacting surfaces. The lubricant oil is accumulated in the at least one recess also while the piston is reciprocated. That is, the lubricant oil is splashed out of the at least one recess while at the same time the oil is accumulated in the at least one recess, so that the at least one recess functions to deliver the lubricant oil even while the compressor is in operation. Thus, the compressor can be held in a fully lubricated condition throughout the operation of the compressor. The improved slidability of the piston is effective to prevent a local wear or removal of the coating on the outer circumferential surface of the piston, advantageously resulting in a prolonged service life of the piston. In addition, the provision of the at least one recess is effective to reduce the weight of the piston.
Usually, the swash plate type compressor is installed such that the axis of rotation of the rotary drive shaft, namely, the centerline of the cylinder block extends in the horizontal direction. In some cases, the centerline of the cylinder block is not completely parallel to the horizontal direction, and is more or less inclined with respect to the horizontal plane, depending upon the environment in which the compressor is installed. However, the compressor is usually installed with its centerline held substantially horizontal. In this usual orientation of the compressor, a plurality of cylinder bores are arranged along a circle whose center lies on the centerline of the cylinder block, such that the cylinder bores extend in parallel with the centerline of the cylinder block. The piston is slidably fitted in each cylinder bore. The angular phase of each piston about the centerline of the cylinder block is determined by the angular position or vertical position of the corresponding cylinder bore. The piston fitted in the cylinder bore at a relatively high position in the cylinder block has an angular phase in which the neck portion is open in the downward direction for engagement with the swash plate, while the piston fitted in the cylinder bore at a relatively low position has an angular phase in which the neck portion is open in the upward direction for engagement with the swash plate. Thus, the pistons fitted in the respective cylinde
Enokijima Fuminobu
Hoshida Takahiro
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Leslie Michael
Lopez F. Daniel
Morgan & Finnegan , LLP
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