Piston-rotation preventing structure for variable displacement swash plate type compressor

Abstract: A piston-rotation preventing structure for a variable displacement swash plate type compressor is disclosed. The piston-rotation preventing structure has a front housing and a cylinder block that constitute the housing of the compressor. The piston has a head portion and a jaw portion. The jaw portion is formed in the shape of an inverse U in such a way that a horizontal extension is horizontally extended from one side of the upper portion of the piston head portion and inside and outside jaws are respectively and vertically extended from both ends of the horizontal extension. The piston-rotation preventing structure comprises a pair of stopper grooves and a guide groove. The stopper grooves are extended along the upper surfaces of the horizontal extension and the piston head portion from the outer edge of the upper surface of the horizontal extension to a certain position on the upper surface of the piston head portion while being spaced apart from each other. The guide groove is longitudinally formed along the inner surface of the front housing over the stopper grooves to have the same width as the space between the stopper grooves.

Description: The present invention relates, in general, to variable displacement swash plate type compressors and, more particularly, to a piston-rotation preventing structure for a variable displacement swash plate type compressor that is capable of reducing the size and weight of its piston, thereby reducing the overall outside diameter of the compressor. In a typical variable displacement swash plate type compressor, a drive shaft is rotatably mounted in the interior of a front housing, a plurality of cylinder bores are formed in a cylinder block that is fixed to the front housing to constitute an entire compressor housing, and the corresponding number of pistons are respectively and reciprocatably received in cylinder bores. Each of such pistons comprises a piston head portion and a jaw portion. The piston head portion sucks and compresses refrigerant gas by its reciprocating movement in a cylinder bore. The jaw portion is formed in the shape of an inverse U in such a way that a horizontal extension is horizontally extended from one side of the upper portion of the piston head portion, inside and outside jaws are respectively and vertically extended from both ends of the horizontal extension, and a recess is defined by the horizontal extension and the inside and outside jaws. A swash plate is fitted around the drive shaft to be rotated together and the peripheral edge of the swash plate is inserted to the recess of the jaw portion, so that the piston constructed as described above is reciprocated forward and rearward by the rotation of a swash plate. For allowing the swash plate to be rotated without hindrance, two shoe pockets are respectively formed on the inner surfaces of the inside and outside jaws, and two semispherical shoes are respectively inserted into the shoe pockets to hold both surfaces of the peripheral edge of the swash plate. Additionally, a rotating prevention structure is formed on the piston so as to prevent the rotation of the piston due to the rotational resistance of the swash plate while the piston is reciprocated forward and reward. The document EP-A 0 689 735 discloses a piston rotation preventing structure for a variable displacement swash plate type compressor, said compressor having a front housing and a cylinder block that constitute a housing of said compressor, said piston having a head portion and a jaw portion, said jaw portion being formed in the shape of an inverse U in such a way that a horizontal extension is extending from one side of the upper portion of the piston head portion, and inside and outside jaws are respectively and vertically extending from both ends of the horizontal extension, said structure comprising a pair of stopper grooves extending along upper surfaces of said horizontal extension and said piston head portion from an outer edge of an upper surface of said horizontal extension to a certain position on an upper surface of said piston head portion while being spaced from each other, and also comprising a guide groove longitudinally formed along an inner surface of said front housing over said stopper grooves to have the same width as the space between the stopper grooves. Another one of conventional piston-rotation preventing structures for variable displacement swash plate type compressors is disclosed in U.S. Pat. No. 5,706,716. According to the patent, as is seen from Figure 5, a piston 7 includes two projections 73 formed on both sides of the web 72 of the bridge portion 71 and is inserted into a cylinder bore 91 formed in a cylinder block 9. When the piston 7 7 receives rotational resistance due to the rotation of a swash plate (not shown) and is about to be rotated while the piston 7 is reciprocated by the rotation of the swash plate, the projections 73 that are projected considerably out of the range of the diameter of the cylinder bore 91 come into contact with the inner surface of the front portion of the housing 10. As a result, the piston is prevented from being rotated. However, in the conventional piston-rotation preventing structure for a variable displacement swash plate type compressor, since the projections 73 are projected considerably out of the range of the diameter of the cylinder bore 91 or the outside diameter of the piston 7, not only the size and weight of the piston 7 but also the inside and outside diameters of the front portion of the housing 10 is increased. Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a piston-rotation preventing structure for a variable displacement swash plate type compressor that is capable of reducing the size and weight of its piston and, consequently, reducing the overall outside diameter of the compressor. In order to accomplish the above object, the present invention provides a piston-rotation preventing structure for a variable displacement swash plate type compressor, said compressor having a front housing and a cylinder block that constitute a housing of said compressor, said piston having a head portion and a jaw portion, said jaw portion being formed in the shape of an inverse U in such a way that an extension extends from the side portion of the piston head which comes into contact with the inside surface of the front housing, and inside and outside jaws are respectively extending perpendicularly from both ends of the extension, with a pair of stopper grooves extending along said extension and said piston head portion which comes into contact with the inside surface of the front housing, from an outer edge of said extension to a certain position on said piston head portion while being spaced apart from each other; and a guide groove longitudinally formed along an inner surface of said front housing over said stopper grooves to have the same width as a space between said stopper grooves, wherein said stopper grooves are situated within a range of an outside diameter of said piston or an inner diameter of said cylinder bore. In accordance with the present invention the stopper grooves are situated within the range of the outside diameter of the piston or the inner diameter of the cylinder bore. The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 a side view of a piston in which there is embodied a piston-rotation preventing structure for a variable displacement swash plate type compressor in accordance with the present invention; Figure 2 is a sectional view of a piston showing a state where the piston having the piston-rotation prevention structure of the present invention is inserted into a cylinder bore; Figure 3 is a sectional view of a piston showing the operation of the piston-rotation prevention structure of the present invention; Figure 4 is a sectional view of a compressor showing a variable displacement swash plate type compressor in which the piston-rotation prevention structure of the present invention is embodied; and Figure 5 is a sectional view showing a state where a piston having a piston-rotation prevention structure is inserted into a cylinder bore shown in US Pat. No. 5,706,716. Reference is made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. As illustrated in Figure 4, reference numeral 1 designates a variable displacement swash plate type compressor in accordance with the present invention. A drive shaft 14 is rotatably mounted in the interior of a front housing 11. A cylinder block 12 is fixed to the front housing 11 to form an entire compressor housing. A plurality of cylinder bores 13 are formed in the cylinder block 12, and the corresponding number of pistons 2 are respectively and reciprocatably received in the cylinder bores 13. As seen from Figure 1, each of such pistons 2 comprises a piston head portion 3 and a jaw portion 4. The piston head portion 3 sucks and compresses refrigerant gas by its reciprocating movement in a cylinder bore 13. The jaw portion 4 is formed in the shape of an inverse U in such a way that an extension 42 extends from the side portion of the piston head 3 which comes into contact with the inside surface of the front housing 11, and inside and outside jaws 41 and 43 are respectively extending perpendicularly from both ends of the extension 42, and a recess 44 is defined by the extension 42 and the inside and outside jaws 41 and 43. As shown in Figures 1 and 4, a swash plate 15 is fitted around a drive shaft 14 in an inclined state to be rotated together with the drive shaft 14, and the swash plate 15 is inserted to the recess 44 of the jaw portion 4 at its peripheral edge. Accordingly, as the swash plate 15 is rotated together with the drive shaft 14, the phase of the swash plate 15 is continuously changed and, consequently, the piston 2 is reciprocated forward and rearward in a cylinder bore 13. For allowing the swash plate 15 to be rotated without hindrance, two shoe pockets 45 are respectively formed on the inner surfaces of the inside and outside jaws 41 and 43, and two semispherical shoes 46 are respectively inserted into the shoe pockets 45 to hold both surfaces of the peripheral edge of the swash plate 15. In accordance with the present invention, in order to prevent the piston 2 from being rotated by rotational resistance due to the rotation of the swash plate 15 during the reciprocation of the piston 2, two stopper grooves 47 are extending on the upper surfaces of the horizontal extension 42, and the piston head portion 3 which comes into contact with the inside surface of the front housing 11 from the outer edge of said extension 42 to a certain position on said piston head portion 3, while being spaced apart from each other, as shown in Figures 1 and 3. Therefore, the stopper grooves 47 are situated within the range of the outer diameter of the piston 2 or the inside diameter of the cylinder bore 13. Additionally, in correspondence to the stopper grooves 47, a guide groove 17 is longitudinally formed on the inner surface of the front housing 11 over said stopper grooves 47 to have the same width as the space between the stopper grooves 47. The length of the stopper grooves 47 is preferably larger than that of the piston stroke. Meanwhile, the length of the guide groove 17 should be designed so that the front ends of the stopper grooves 47 do not deviate from the guide groove 17 during the reciprocation of the piston 2. As a result, while the piston 2 starts from a normal state and is reciprocated forward and rearward in the cylinder bore 13 by the rotation of the swash plate 15, the piston 2 receives rotational resistance due to the rotation of the swash plate 15. However, since the stopper groove 47 that stands behind in a rotating direction comes into contact with the inside surface 18 of the front housing 11 adjacent to the guide groove 17 as shown at A of Figure 3, the piston 2 is prevented from being rotated. At this time, as is seen at B of Figure 3, the stopper groove 47 that is preceding in a rotating direction does not come into contact with the inside surface 18 of the front housing 11. As described above, the present invention provides a piston-rotation preventing structure for a variable displacement swash plate type compressor, in which there are provided a pair of stopper grooves that do not deviate from the range of the inside diameter of the cylinder bore and are extended axially, instead of conventional projections that are projected out of the range of the inside diameter of the cylinder bore. As a result, the piston is reduced in its size and weight in comparison with the conventional piston, thereby lowering the manufacturing cost of the piston. The present invention provides a piston-rotation preventing structure for a variable displacement swash plate type compressor, in which a pair of stopper grooves do not deviate from the range of the inside diameter of the cylinder bore 13 and the inside and outside diameters of its front housing 11 can be reduced, thereby reducing the overall outside diameter of the compressor. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the invention as disclosed in the accompanying claims.

Claims: A piston-rotation preventing structure for a variable displacement swash plate type compressor, said compressor having a front housing (11) and a cylinder block (12) that constitute a housing of said compressor, said piston (2) having a head portion (3) and a jaw portion (4), said jaw portion (4) being formed in the shape of an inverse U in such a way that an extension (42) extends from the side portion of the piston head (3) which comes into contact with the inside surface of the front housing (11), and inside and outside jaws (41, 43) are respectively extending perpendicularly from both ends of the extension (42), with a pair of stopper grooves (47) extending along said extension (42) and said piston head portion (3) which comes into contact with the inside surface of the front housing (11), from an outer edge of said extension (42) to a certain position on said piston head portion (3) while being spaced apart from each other; and a guide groove (17) longitudinally formed along an inner surface of said front housing (11) over said stopper grooves (47) to have the same width as a space between said stopper grooves (47), characterised in that said stopper grooves (47) are situated within a range of an outside diameter of said piston (2) or an inner diameter of said cylinder bore.

Inventors: AHN HEW NAM, AHN, HEW NAM, Ahn, Hew Nam, Dormit.of Halla Climate Control Corp
Applicants: HALLA CLIMATE CONTROL CORP, HALLA CLIMATE CONTROL CORP.
Application year: 2000
Main classification: F04B27
IPC codes: F04B27, F04B39