Shoe for compressors

This application claims the benefit of Japanese Patent Application No. 2006-251008 and Japanese Patent Application No. 2006-251012 both filed on Sep. 15, 2006, which are incorporated herein by reference.

The present invention relates to a shoe for compressors.

In a compressor provided with a swash plate and a piston, a pair of longitudinal shoes for compressors can be provided between the swash plate and the piston. The respective shoes comprise a base portion and a semi-spherical portion made integral with the base portion. The base portion includes a swash-plate sliding contact surface in sliding contact with the swash plate. The semi-spherical portion includes a bearing-seat sliding contact surface in sliding contact with a bearing seat, which is provided concavely on the piston.

With the compressor constructed in the manner described above, a drive shaft rotates whereby the swash plate rotates synchronously and the piston reciprocates in a cylinder bore through the shoes. Thereby, suction, compression, and discharge strokes of refrigerant gas are performed on a head side of the piston. In the meantime, the swash-plate sliding contact surface of the base portion of the shoe comes into sliding contact with a surface of the swash plate and the bearing-seat sliding contact surface of the semi-spherical portion of the shoe comes into sliding contact with a bearing surface of the piston.

General shoes are semi-spherical in shape such that a base portion and a semi-spherical portion are solid and integral with each other. Generally, such shoes are manufactured by subjecting a wire material of, for example, SUJ2 (JIS G4805) to cutting, press working, polishing, etc.

On the other hand, shoes made lightweight by forming a cavity between a base portion and a semi-spherical portion are known (for example, JP-A-2005-90385, JP-A-2002-31051, JP-A-2-119686, JP-A-2002-39058, JP-A-2001-263225, JP-UM-A-6-40385). By using shoes of this kind for compressors, in which a swash plate can be changed in inclination, it is possible to decrease a reciprocating inertial force of a piston, thus enabling achieving an improvement in capacity controllability. Also, shoes of this kind can realize reduction in motive power for driving of a compressor, lightening of the compressor, etc.

With the conventional, known shoes described above, however, lightening is realized by a cavity but there is a fear with respect to practical strength.

That is, while suction, compression, and discharge strokes of refrigerant gas are performed in a compressor, a swash-plate sliding contact surface of a base portion of a shoe comes into sliding contact with a surface of a swash plate and a bearing-seat sliding contact surface of a semi-spherical portion of the shoe comes into sliding contact with a bearing surface of a piston. Therefore, a force acting in a direction, in which the base portion and the semi-spherical portion approach each other, acts much on the shoe.

The shoes disclosed in JP-A-2002-31051, JP-A-2-119686, JP-A-2002-39058, JP-A-2001-263225, or JP-UM-A-6-40385 described above are hard to sustain the force and there is a fear of deformation in a direction, in which the base portion and the semi-spherical portion approach each other, due to use over a long term. In this case, gap is generated between the swash plate and the base portion of the shoe, or between the semi-spherical portion of the shoe and a bearing seat of the piston to lead to generation of abnormal noise and an obstacle to smooth operation.

In this respect, it is thought that the shoe disclosed in JP-A-2005-90385 is improved as compared with the other shoes since the base portion and the semi-spherical portion are connected to each other by a hollow connecting portion, which passes through centers of the both portions and extends in a central direction thereof. Since the hollow connecting portion in this shoe is hollow, however, it is not possible as well to eradicate insufficiency in practical strength.

The invention has been thought of in view of the conventional situation and has its object to provide a shoe for compressors, in which lightening and practical strength can be made compatible with each other.

The invention provides a shoe for compressors, comprising a base portion having a swash-plate sliding contact surface in sliding contact with a swash plate and a semi-spherical portion made integral with the base portion and having a bearing-seat sliding contact surface in sliding contact with a bearing seat, which is in the form of a spherical surface and provided concavely on a piston.

In this shoe according to the invention, a cavity is formed between the base portion and the semi-spherical portion of the shoe. Also, in this shoe according to the invention, the base portion and the semi-spherical portion are connected to each other by a solid connecting portion, which passes through centers of the both portions and extends in a central direction of the both portions. Lightening of the shoe according to the invention is realized by the cavity formed between the base portion and the semi-spherical portion. Also, the shoe can ensure practical strength since the base portion and the semi-spherical portion are connected to each other by the solid connecting portion, which passes through centers of the both portions and extends in a central direction of the both portions, and the connecting portion sustains a force acting in a direction, in which the base portion and the semi-spherical portion are caused to approach each other.

Accordingly, the shoe according to the invention can make lightening and practical strength compatible with each other. Therefore, the shoe can perform effects of suppression of abnormal noise of a variable displacement type swash plate compressor, an improvement in durability, etc. in addition to effects of an improvement in capacity controllability of the compressor, reduction in motive power, lightening, etc.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.