RECIPROCATORY PISTON TYPE COMPRESSOR WITH VALVE ASSEMBLIES HAVING ENHANCED PRESSURE RESPONSE CHARACTERISTICS

Abstract: A reciprocatory piston type compressor has suction valve assemblies incorporated between a suction gas chamber (9, 10) and each of cylinder bores (1a, 2a) in which reciprocatory pistons (25) are reciprocated to draw a refrigerant gas from the suction gas chamber (9, 10) into the cylinder bores (1a, 2a) and compress the refrigerant gas in response to an opening and closing of flat plate-like float type valve elements (26, 27), in axially extended valve chambers (6d), each of which is defined between a flat valve seat and a facing retainer unit, and discharge valve assemblies incorporated between a discharge gas chamber (11, 12) and each of the cylinder bores (1a, 2a) and having flat plate-like float type valve elements (30, 31) movable toward a position thereof seated on a valve seat and closing a discharge port and away from the valve seat to an open position restricted by a retainer.

Description: DESCRIPTION RECIPROCATORY PISTON TYPE COMPRESSOR WITH VALVE ASSEMBLIES HAVING ENHANCED PRESSURE RESPONSE CHARACTERISTICS TECHNICAL BACKGROUND The present invention relates to a reciprocatory piston type refrigerant compressor for a car air- conditioner, and more particularly to valve assemblies accommodated in a reciprocatory piston type refrigerant compressor and having enhanced pressure response characteristics when opening and closing a suction port through which a refrigerant gas is drawn from a suction gas chamber into a compression chamber, or a discharge port through which the refrigerant gas after compression is discharged from the compression chamber toward a discharge gas chamber of the reciprocatory piston type refrigerant compressor. PRIOR ART Many reciprocatory piston type compressors, such as a swash plate type compressor and a wobble plate type compressor are known. For example, U.S. Pat. No. 4,767,283 to Ikeda et al discloses a swash plate type compressor with double-acting reciprocatory pistons and suction and discharge valve assemblies employing reed valves made of metallic spring plate. Further, U.S. Patent Nos. 4,749,340, 4,764,091, and 4,781,540, all to Ikeda et al., disclose reed valve mechanisms for a reciprocatory piston type compressor having enhanced valve characteristics. Figure 34 shows a reed valve type discharge valve assembly accommodated in a swash plate operated reciprocatory piston type refrigerant compressor as disclosed in U.S. Pat. No. 4,767,283. As shown in Fig. 34, a cylinder bore 800 of the reciprocatory piston type compressor for compressing therein a refrigerant gas by a reciprocatory piston ( not shown ) is separated from a discharge gas chamber 803 by a valve plate.805 having a port, i.e., a discharge port 806 through which the refrigerant gas after compression is discharged from the cylinder bore 800 toward the discharge gas chamber 803. The discharge port 806 is openably closed by a reed valve 807 made of a thin metallic spring plate, and an amount of opening of the reed valve 807 is restricted by a retainer 109. The reed valve 807 and the retainer 809 are arranged between a housing having the above-mentioned discharge gas chamber 803 therein and the valve plate 805. The reed valve 807 is arranged in a manner such that it constantly closes the discharge port 806 until a pressure differential between pressures in the cylinder bore 800 and the discharge gas chamber 803 increases beyond a predetermined pressure level. Namely, when the pressure prevailing in the cylinder bore 800 becomes larger than the predetermined pressure level, the reed valve 807 is bent and moved away from the contact face of the valve plate 805 toward an open position thereof, to thereby open the discharge port 806, and thus the compressed refrigerant gas is discharged from the cylinder bore 800 toward the discharge gas chamber 803. In the above-described conventional valve assembly of the reciprocatory piston type compressor, the reed valve 807 is constantly at a closed position, and is bent from the closed position toward the open position thereof when a pressure differential between pressures acting on the opposite faces of the reed valve 807 sufficiently exceeds the above-mentioned predetermined pressure level that a self spring force urging the valve 807 toward the constantly closed position is overcome. Namely, the spring force of the reed valve 807 acts to provide a strong resistance to the opening of the reed valve 807, and therefore, the refrigerant gas is apt to be over-compressed in the cylinder bore 800, and therefore, a loss of power for driving the compressor occurs. Moreover, due to the over-compression of the refrigerant gas, when the reed valve 807 is moved away from the face of the valve plate, a speed of movement of the reed valve 807 is very fast, and accordingly, the reed valve 807 violently collides with the retainer 809 and generates an unfavourable noise. Further, when the reed valve 807 is employed by the valve assembly, a vibration of the reed valve 807 often occurs, and this causes a pulsative change in the pressure of the refrigerant gas discharged from the cylinder bore 800. This pulsative change in the discharge pressure is transmitted to an evaporator of an air-conditioning circuit, and thus a further noise is generated. Still further, when the reed valve 807 is moved from the closed to the opened position thereof by the pressure differential, the opening motion of the reed valve 807 is gradually transmitted from a free end thereof to an end portion thereof. Namely, the pressure response characteristics of the reed valve 807 are poor, and therefore, the flow of the compressed refrigerant gas is apt to be directed to the free end of the reed valve 807 through the discharge port 806. Accordingly, it is difficult to obtain a homogeneous flow of the compressed refrigerant gas from the cylinder bore 800 toward the discharge gas chamber 803 through the discharge port 806, and thus a high discharge efficiency at the discharging stage of the compressor cannot be obtained. Although the above-description of the prior art is made in connection with the discharge valve assembly of the reciprocatory piston type compressor, the conventional suction valve assembly of the same compressor also employs a reed valve, and accordingly, must suffer from similar problems. DISCLOSURE OF THE INVENTION Therefore, an object of the present invention is to obviate the problems encountered by the conventional valve assemblies accommodated in the reciprocatory piston type compressor. A further object of the present invention is to provide a reciprocatory piston type compressor provided with valve assemblies capable of exhibiting enhanced pressure response characteristics in the opening and closing operation thereof, when used as suction and/or discharge valve assemblies of the compressor. A still further object of the present invention is to provide a valve assembly for a reciprocatory piston type compressor provided with a freely movable float type valve element capable of moving from a port closed position toward a port open position, and vice versa, whereby an over-compression of the refrigerant gas is prevented. A further object of the present invention is to provide a reciprocatory piston type compressor having a valve assembly free from noise, and capable of deadening a pulsative change in the flow of the refrigerant gas. A still further object of the present invention is to provide a valve assembly for a reciprocatory piston type compressor able to enhance a volumetric efficiency of the compression of the reciprocatory piston type compressor. In accordance with the present invention, there is provided a reciprocatory piston type compressor including: a compressor body in the form of a combination of a cylinder block defining therein axially extended cylinder bores for compression chambers, and front and rear housings sealingly closing axial opposite ends of the cylinder block via front and rear valve plates, respectively; reciprocatory pistons driven so as to reciprocate in the cylinder bores to thereby compress a refrigerant gas in the compression chambers when the refrigerant gas before compression is sucked from a suction gas chamber, and to discharge the refrigerant gas after compression from the compression chambers toward a discharge gas chamber; a piston reciprocating mechanism for causing the reciprocation of the reciprocatory pistons when a rotative drive force is applied from outside the compressor body via a drive shaft rotatably supported in the compressor body; and a valve assembly provided with a suction valve assembly operative to closably open suction ports between the suction gas chamber and the compression chambers during suction strokes of the reciprocatory pistons, to thereby allow the refrigerant gas to be sucked from the suction chamber into the compression chambers, and a discharge valve assembly operative to closably open discharge ports between the compression chambers and the discharge gas chamber during discharge strokes of the reciprocatory pistons, to thereby allow the refrigerant gas to be discharged from the compression chamber toward the discharge chamber, characterized in that at least the suction valve assembly of the valve assembly comprises: a first unit for defining an open-ended valve chamber in each of the suction ports to be enclosed by an axially extended wall, the valve chamber having one open end thereof arranged adjacent to the suction gas chamber and provided with a flat valve seat formed to be extended in a plane perpendicular to the axially extended wall, and the other open end thereof axially spaced from the one open end and arranged adjacent to each of the compression chambers; an independent flat plate-like suction valve element arranged in the valve chamber to be freely movable toward and away from the valve seat in response to a pressure differential generated between pressures prevailing in each of the compression chambers and the suction chamber, the flat plate-like suction valve taking an open position thereof to establish a communication between each of the compression chamber and the suction gas chamber via each suction port when moved away from the valve seat, and a closing position thereof preventing a communication between each compression chamber and the suction gas chamber when moved toward and seated on the valve seat; a retainer unit arranged in the other open end of the valve chamber for retaining the flat plate-like valve element in the open position, to thereby allow the refrigerant gas to be sucked from the suction gas chamber into each compression chamber. Preferably, the discharge valve assembly of the valve assembly of the reciprocatory piston type compressor comprises: a second unit for defining an open ended valve chamber in each of the discharge ports to be enclosed by an axially extended wall, the valve chamber having one open end thereof arranged adjacent to each of the compression chambers and provided with a flat valve seat formed to be extended in a plane perpendicular to the axially extended wall, and the other open end thereof axially spaced from the one open end and arranged adjacent to the discharge gas chamber; an independent flat plate-like discharge valve element arranged in the valve chamber to be freely movable toward and away from the valve seat in response to a pressure differential generated between pressures prevailing in each of the compression chamber and the discharge gas chamber, the flat plate-like discharge valve element taking an open position thereof to establish a communication between each of the compression chamber and the discharge gas chamber via each discharge port when moved away from the valve seat, and a closing position thereof preventing the communication between each compression chamber and the discharge gas chamber when moved toward and seated on the valve seat; a retainer unit arranged in the other open end of the valve chamber for retaining the flat plate-like discharge valve element when the discharge valve element is moved to the open position thereof. DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be made apparent from the ensuing description of the embodiments with reference to the accompanying drawings wherein: Fig. 1 is a longitudinal cross-sectional view of a reciprocatory piston type compressor provided with valve assemblies according to the present invention; Fig. 2 is a cross-sectional view taken along the line I — I of Fig. 1; Fig. 3 is a partial cross-sectional view of suction and discharge valve assemblies of the valve assembly according to an embodiment of the present invention, and accommodated in the reciprocatory piston type compressor of Fig. 1, illustrating one state of the operation of the valve assembly; Fig. 4 is a partial flat view taken along the line W - IV of Fig. 3; Fig. 5 is a partial flat view taken along the line V - V of Fig. 3; Fig. 6 is the same view as Fig. 3, illustrating the other state of the operation of the valve assembly; Fig. 7 is a partial flat view of a valve assembly, i. e., a suction valve assembly according to another embodiment of the present invention, taken along the line W - W of Fig. 8; Fig. 8 is a cross-sectional view of the valve assembly of Fig. 7; Fig. 9 is a partial flat view of a valve assembly, i. e., a suction valve assembly according to a further embodiment of the present invention; Fig. 10 is a partial cross-sectional view of a valve assembly, i.e., a discharge valve assembly according to a further embodiment of the present invention; Fig. 11 is a partial flat view illustrating the plate-like valve element of the discharge valve assembly of Fig. 10; Fig. 12 is a flat view illustrating a modification of the valve element of Fig. 11; Fig. 13 is a partial cross-sectional view similar to Fig. 3 or 6, illustrating a valve assembly for a reciprocatory piston type compressor, according to a still further embodiment of the present invention; Fig. 14 is a partial flat view taken along the line X W - X 17 of Fig. 13; Fig. 15 is a partial cross-sectional view of a valve assembly, illustrating a modification of a retainer member employed by the valve assembly of Figs. 13 and 14; Fig. 16 is a partial cross-sectional view of a valve assembly, illustrating a different modification of a retainer member employed by the valve assembly of Figs. 13 and 14; Fig. 17 is a partial cross-sectional view of a valve assembly, illustrating a further different modification of a retainer member employed by the valve assembly of Figs. 13 and 14; Fig. 18 is a partial flat view of a valve assembly for a reciprocatory piston type compressor, according to a further embodiment of the present invention; Fig. 19 is a cross-sectional view taken along the line XI- XI of Fig. 18; Fig. 20 is a longitudinal cross-sectional view of a reciprocatory piston type compressor provided with valve assemblies according to the present invention; Fig. 21 is a partial cross-sectional view of a valve assembly according to a further embodiment of the present invention incorporated in a head portion of a reciprocatory piston of the compressor of Fig. 20; Fig. 22 is a partial front view taken along the line X X I - X X I of Fig. 21, illustrating the head portion of the reciprocatory piston of Fig. 21; Fig. 23 is a partial front view of a flat plate-like valve element capable of being used with the valve assembly of Fig. 21; Fig. 24 is a partial front view of another flat plate-like valve element capable of being used with the valve assembly of Fig. 21; Fig. 25 is a partial front view of a further flat plate-like valve element capable of being used with the valve assembly of Fig. 21; Fig. 26 is a partial front view similar to that of Fig. 22, illustrating a valve assembly according to a further embodiment of the present invention; Fig. 27 is a partial front view illustrating a valve assembly of the type accommodated in the head portion of a piston, according to a still further embodiment of the present invention; Fig. 28 is a partial cross-sectional view of a valve assembly according to a further embodiment of the present invention incorporated in a head portion of a reciprocatory piston of a reciprocatory piston type compressor; Fig. 29 is a perspective view of a cylindrical element used as an indispensable element of the valve assembly of Fig. 28; Fig. 30 is a partial cross-sectional view of a valve assembly according to a still further embodiment of the present invention incorporated in a valve plate of a reciprocatory piston type compressor; Fig. 31 is a perspective view of a cylindrical element used as an indispensable element of the valve assembly of Fig. 30; Fig. 32 is a partial cross-sectional view of a valve assembly according to a further embodiment of the present invention incorporated in a valve plate of a reciprocatory piston type compressor; Fig. 33 is a perspective view of a cylindrical element used as an indispensable element of the Valve assembly of Fig. 32; and Fig. 34 is a partial cross-sectional view of a discharge valve assembly for a reciprocatory piston type compressor according to the prior art. BEST MODE OF CARRYING OUT THE INVENTION Referring to Figs. 1 and 2, a reciprocatory piston type compressor is provided with front and rear cylinder blocks 1 and 2 axially connected together. The connected cylinder blocks 1 and 2 are sealingly closed at front and rear ends thereof by front and rear housings 7 and 8 attached thereto via front and rear valve plates 5 and 6 generally made of a light metallic material such as an aluminum alloy system. Namely, the front and rear cylinder blocks 1 and 2, and the front and rear housings 7 and 8 are axially tightly combined by screw bolts, to thereby form an axially extended compressor body. The compressor body has a swash plate chamber 4 formed therein at a connecting portion of the front and rear cylinder blocks 1 and 2. The compressor body also has a suction inlet 3 through which a refrigerant gas " G " circulating in an air- conditioning circuit enters the swash plate chamber 4. The front housings 7 and 8 are provided with suction gas chambers 9 and 10 in a radially inner region of these housings 7 and 8, and discharge gas chambers 11 and 12 in a radially outer region of these housings 7 and 8. The latter discharge gas chambers 11 and 12 are fluidly communicated with an outlet pipe 35 attached to the compressor body to discharge the refrigerant gas after compression toward the air-conditioning circuit. The front and rear cylinder blocks 1 and 2 are provided with axial suction passageways 38 formed therein to provide a fluid communication between the swash plate chamber 4 and the front and rear suction gas chambers 9 and 10. An axial drive shaft 18 is centrally rotatably supported in the compressor * body by rotary bearings 14 and 15 fitted in central bores If and 2f of the front and rear cylinder blocks 1 and 2. The drive shaft 18 is axially extended through a through- bore 5u of the front valve plate 5 and a central bore of a ring member 20 held by the front housing 7 via a stop ring 16 and a ring seal 20a. The drive shaft 18 is air- tightly sealed by a rubber seal ring 19 arranged between the drive shaft 18 and the ring member 20. A swash plate 23 is keyed on the drive shaft 18 at a position such that the swash plate 23 is rotated together with the drive shaft 18 in the swash plate chamber 4, and axially supported by thrust bearings 21 and 22 seated on shoulders of the front and rear cylinder blocks 1 and 2. The front and rear cylinder blocks 1 and 2 of the compressor body are provided with a plurality of pairs of axial cylinder bores la and 2a formed therein in such a manner that these cylinder bores la and 2a are arranged around and in parallel with the axis of rotation of the drive shaft 18. These cylinder bores la and 2a are provided as cylindrical chambers in which the refrigerant gas is compressed by a plurality of double-headed pistons 25 reciprocated in the cylinder bores la and 2a due to a rotation of the swash plate 23. Namely, the swash plate 23 is operatively connected with each of the reciprocatory pistons 25 via a pair of shoes 24 in the shape of a half-spherical ball, respectively, and thus when the swash plate 23 is rotated by the drive shaft 18, the rotation of the swash plate 23 causes a reciprocation of the piston 25 in the pair of cylinder bores la and 2a. Accordingly, the drive shaft 18, the swash plate 23, and the shoes 24 are provided as a reciprocation drive mechanism of the reciprocatory pistons 25. The above-mentioned refrigerant compressor, is further provided with enhanced pressure response valve assemblies for drawing the refrigerant gas before compression from the suction gas chambers 9 and 10 into respective cylinder bores la and 2a for compressing by the reciprocatory pistons 25, and for discharging the compressed refrigerant gas from the cylinder bores la and 2a toward the discharge gas chambers 11 and 12. A description of the valve assemblies of a first embodiment will now be provided with respect to rear suction and discharge valve assemblies provided on the rear side of the compressor body, with reference to Fig. 3. Referring to Fig. 3, the rear valve plate 6 having plate member 6ι and 6 2 is provided with a suction port 6a for providing a communication between the suction gas chamber 10 and one of the cylinder bores 2a, and a discharge port 6h for providing a communication between the same cylinder bore 2a and the discharge gas chamber 12. The rear valve plate 6 is provided with a cylindrical valve chamber 6d ( a suction valve chamber ) defined between a flat ring-shape valve seat 6b extended to surround a part of each suction port 6a at a position adjacent to the suction gas chamber 10 and an opposite retainer portion 6c axially spaced from the valve seat 6b. Namely, the valve chamber 6d is arranged substantially in alignment with the suction port 6a, and a flat plate-like valve element 27 is arranged in the valve chamber 6d to act as a float type valve element freely movable between the valve seat 6b and the retainer 6c, to limit the movement of the valve element 27. Therefore, the suction port 6a, the above-mentioned valve seat 6b, the cylindrical valve chamber 6d, the flat plate-like valve element 27, and the retainer 6c are provided in combination to form a rear suction valve assembly able to control a fluid communication between the rear suction gas chamber 10 and one of the cylinder bores 2a. The rear valve plate 6 is also provided with a different cylindrical valve chamber 6k ( a discharge valve chamber ) defined between a flat ring-shape valve seat 6i extended to surround a part of each discharge port 6h at a position adjacent to the cylinder bore 2a and an opposite retainer 6j axially spaced from the valve seat 6i. Namely, the valve chamber 6k is arranged substantially in alignment with the discharge port 6h, and a flat plate-like valve element 31 is arranged within the valve chamber 6k to be freely movable between the valve seat 6i and the retainer 6j. Therefore, the discharge port 6h, the above-mentioned valve seat 6i, the cylindrical valve chamber 6k, the flat plate-like valve element 31, and the retainer 6j are provided in combination to form a rear discharge valve assembly able to open and close the rear discharge port 6h communicating between each cylinder bore 2 and the rear discharge gas chamber 12. As shown in Fig. 4, the retainer 6j of the discharge valve assembly includes a plurality of ( three in the example shown in Fig. 4 ) tongues radially inwardly extended from an end of axially extended wall portion of the valve chamber 6k toward the center of a large aperture spaced axially opposite to the discharge port 6h. These tongues of the retainer 6j are equiangularly arranged around the discharge port 6h, and as described later, each portion of the aperture extending between the neighbouring tongues of the retainer 6j provides a passageway to permit the refrigerant gas to flow therethrough when the valve element 31 is moved away from the valve seat 6i, i.e., the discharge valve assembly is in an open position thereof. As shown in Fig. 5, the retainer 6c of the suction valve assembly includes a plurality of similar tongues arranged equiangularly around the outer circumference of the valve chamber 6d. It can be understood from Fig. 1 that the front valve plate 5 consisting of two plate members in tight contact with one another is provided with front suction and discharge valve assemblies incorporated therein, similar to the above-mentioned rear suction and discharge valve assemblies. Namely, the front suction valve assembly for one of the cylinder bores la is provided with a cylindrical valve chamber 5d defined between a flat ring shape valve seat 5b extended to surround a suction port 5a, and an axially spaced retainer 5c. The front suction valve assembly is also provided with a flat plate-like valve element 26 in the shape of a float valve disposed in the valve chamber 5d to be freely movable between the valve seat 5b and the retainer 5c, to thereby open and close the suction port 5a. The retainer 5c includes a plurality of radial tongues similar to those shown in Fig. 5, to restrict the movement of the flat plate-like valve element 26 when moved away from the valve seat 5b. When the flat plate-like valve element 26 is moved toward the retainer 5c, i.e., to the open position, the cylinder bore la and the front suction chamber 9 are fluidly communicated through the suction port 5a and the valve chamber 5d. The front discharge valve assembly for one of the cylinder bores la is provided with a cylindrical valve chamber 5k defined between a flat ring shape valve seat 5i extended to surround a discharge port 5h, and a retainer 5j arranged to be axially spaced from the valve seat 5i. The front discharge valve assembly is further provided with a flat plate-like valve element 30 disposed to be freely movable between the valve seat 5i and the retainer 5j, to thereby open and close the discharge port 5h. When the front discharge valve assembly is opened, the refrigerant gas after compression is discharged from the compression chamber of the cylinder bore la toward the front discharge gas chamber 11 through the discharge port 5h and the valve chamber 5k. Since the flat plate-like valve elements 26, 27, 30 and 31 of the above-described front and rear suction and discharge valve assemblies are formed as an independent float-like valve element, respectively, movable between the two positions, i.e., a closed position stopping the flow of the refrigerant gas and an opened position permitting the refrigerant gas to flow, the respective valve elements 26, 27, 30 and 31 are able show enhanced pressure response characteristics in response to a pressure differential between a pressure prevailing in the suction or discharge chamber and that prevailing in each cylinder bore la or 2a. Each of these flat plate-like valve elements 26, 27, 30 and 31 of the front and rear suction and discharge valve assemblies may be made of a metallic material belonging to an iron system. Referring again to Figs. 1 and 2, when the swash plate 23 is rotated with the drive shaft 18 driven by an external rotation drive source, e.g., a car engine, the double headed reciprocatory pistons 25 are reciprocated in the front and rear cylinder bores la and 2a to alternately perform a suction and compression of the refrigerant gas. As best shown in Fig. 2, in the suction stroke of each of the pistons 25, the refrigerant gas G returned from the external air-conditioning circuit is drawn into the swash plate chamber 4 through the inlet port 3, and in turn, into the front suction chamber 9 and the rear suction chamber 10 via the suction passageways 38. At this stage, as will be understood from Figs. 1 and 3, the refrigerant gas, e.g., the gas in the rear suction chamber 10, is subjected to a suction due to the suction stroke of each piston 25 in the corresponding rear cylinder bore 2a. Namely, a pressure differential appears between a pressure in the rear suction chamber 10 and that in the cylinder bore 2a due to an increase in the volume of the cylinder bore 2a, and thus'the flat plate-like valve elements 27 and 31 are moved in the respective valve chambers 6d and 6k toward the cylinder bore 2a. Accordingly, the valve element 31 is seated on the valve seat 6i to close the rear discharge port 6h, and the valve element 27 is retained by the retainer 6c to open the rear suction port 6a. Therefore, the refrigerant gas before compression is drawn from the suction chamber 10 into the cylinder bore 2a having an increased volume thereof. When the reciprocatory movement of the reciprocatory piston 25 is switched from the suction stroke to the compression stroke in the cylinder bore 2a, the volume of the cylinder bore 2a is reduced to raise a gas pressure in the cylinder bore 2a, and thus the discharge valve element 31 is moved away from the valve seat 6i toward the retainer 6j within the valve chamber 6k until it is retained by the retainer 6j, to thereby open the rear discharge port 6h. Simultaneously, the suction valve element 27 is moved away from the retainer 6c toward the valve seat 6b within the valve chamber 6d, to thereby close the rear suction port 6a. Figure 6 shows a state wherein the rear discharge port 6h is opened by the valve element 31, and the rear suction port 6a is closed by the valve element 27. Accordingly, the refrigerant gas compressed by the piston 25 is discharged from the compression chamber of the cylinder bore 2a toward the rear discharge gas chamber 12 via the rear valve chamber 6k. The same operation of the front suction and discharge valve assemblies having the suction and discharge valve elements 26 and 30, the front valve chambers 5d and 5k, and the front retainers 5c and 5j, respectively, is performed in the same manner at the front side of the compressor in response to the reciprocation of the respective reciprocatory double headed pistons 25. Thus, the refrigerant gas drawn from the front suction chamber 9 into each front cylinder bore la is discharged from the cylinder bore la toward the front discharge gas chamber 11 via the front valve chamber 5k. The compressed gas in the front and rear discharge gas chambers 11 and 12 is further discharged from these chambers 11 and 12 toward the external air- conditioning circuit through the outlet passageway 35a of the outlet pipe 35 shown in Fig. 2, and circulated through the air-conditioning circuit. Since the above-described flat plate-like valve elements 26, 27, 30 and 31 of the front and rear suction and discharge valve assemblies incorporated in the front and rear valve plates 5 and 6 of the compressor can perform a required valve motion in response to only a pressure differential between pressures prevailing in the front and rear cylinder bores la and 2a, and the front and rear suction and discharge gas chambers 9, 10, 11 and 12, the movement of these valve elements is very quick in comparison with the conventional reed valve. Namely, the valve assemblies can show enhanced pressure response characteristics, and therefore, an over-compression of the refrigerant gas can be advantageously avoided. Further, due to a quick movement of the discharge valve elements 30 and 31 when opening the front and rear discharge ports 5h and 6h, a reduction of pulsative changes in the pressure of the refrigerant gas discharged from the compressor toward the external air- conditioning circuit is obtained. When a test was conducted with the conventional reed valve type valve assembly and the described float valve type valve assembly, it was confirmed that, during the rotation of the drive shaft 18 at 3,000 r.p.m., the conventional valve assembly indicated a noise level at 72 dB due to an over-compression of 12 kgf/cm 2 . The valve assembly of the present invention, however, indicated a lower noise level at 72 dB due to a reduced over-compression of 7 kgf/cm 2 . Further, since the flat plate-like valve elements 26, 27, 30 and 31 of the front and rear suction and discharge valve assemblies are provided as float-like elements freely and independently movable in the respective cylindrical valve chambers 5d, 5k, 6d, and 6k, these valve elements 26, 27, 30 and 31 can permit the refrigerant gas to flow while passing all around the periphery of the respective valve elements. Therefore, when these flat plate-like valve elements 26, 27, 30, and 31 are moved away from the respective valve seats 5b, 5i, 6b, and 6i to open the suction and discharge ports 5a, 5h, 6a, and 6h, a homogeneous flow of the refrigerant gas is formed in the respective suction and discharge ports 5a, 5h, 6a, and 6h, and accordingly, the suction and discharge efficiency of the refrigerant gas is very high. The above-described suction and discharge valve assemblies are compactly incorporated in the front and rear valve plates 5 and 6, and both end faces of each of the valve plates 5 and 6, e.g., the end faces 6x of the valve plate 6 ( Fig. 3 ), are flat faces. Thus, the axial length and the outer diameter of the compressor body accommodating therein the above-described valve assemblies can be greatly reduced compared with the compressor accommodating therein the conventional suction and discharge reed valve assemblies, i.e., it is possible to obtain a compact reciprocatory piston type compressor. Conversely, when the above-described valve assemblies are accommodated in a reciprocatory piston type compressor having the same size as the conventional reciprocatory piston type compressor, it is possible to obtain an increase in the compression efficiency by increasing a compression stroke of the respective pistons 25 in the front and rear cylinder bores la and 2a of the front and rear cylinder blocks 1 and 2. Figures 7 and 8 illustrate another embodiment of the valve assembly able to be accommodated in a reciprocatory piston type compressor similar to the compressor of Figs. 1 and 2. The valve assembly of Figs. 7 and 8 is the same as the afore-mentioned valve assembly of Figs. 3 through 6 in that it is incorporated in front and rear valve plates of the compressor. Nevertheless, the valve assembly of this embodiment is characterized in that it includes a retainer member 45 separately produced and fixedly attached to an end face of the valve plate, e.g. , an end face of the front valve plate 5* . The retainer 45 has a ring-like retainer portion 45a and a plurality of ( four in the embodiment in Figs. 7 and 8 ) radial legs 45b for fixing the retainer 45 to an counter-bore portion 5r of the valve plate 5' . The method of fixing of the retainer 45 to the valve plate 5* may be a press-fitting method or a welding method. The ring-like retainer portion 45a has an outer diameter smaller than that di of the circular flat plate-like valve element 26, and can contribute to a stable retention of the flat plate-like valve element 26 when the valve element 26 is moved toward the retainer 45 to open the suction port 5a of the valve plate 5* . The stable retention of the flat plate-like valve element 26 is advantageous from the viewpoint of preventing a local abrasion of the retainer 45, and accordingly, a long operation life of the valve assembly is ensured. The stable retention of the flat plate-like valve element 26 is also advantageous from the viewpoint of constantly stabilizing the movement of the flat plate-like valve element 26 in the valve chamber 5d from the port opening position toward the port closing position and vice versa. As a result, the flat plate-like valve element 26 is stably seated on the valve seat 5b, and therefore, a prevention of occurrence of a pulsative change in a pressure of the refrigerant gas can be enhanced * compared with the embodiment of Figs. 3 through 6. It should be understood that the retainer 45 may be used with the discharge valve assembly incorporated in the front and rear valve plates of the compressor. A test was conducted with respect to compressors accommodating therein the valve assemblies of Figs. 3 through 6 and of Figs. 7 and 8, and it was confirmed that, when the drive shaft 18 of each of the test compressors was rotated at 3,000 r.p.m, the pulsative change in the discharge pressure of the refrigerant gas was approximately 0.09 kgf/cm 2 with the valve assembly of Figs. 3 through 6, but was approximately only 0.06 kgf/cm 2 with the valve assembly of Figs. 7 and 8. The retainer 45 of the valve assembly of Figs. 7 and 8 may be made of an abrasion-resistant material, such as a metal of a steel system. Further, the retainer 45 may be coated by an elastic material, to thereby reduce noise generated by a collision of the valve element 26 with the retainer 45. Figure 9 illustrates another embodiment of the valve assembly, e.g., the suction valve assembly incorporated in the front valve plate 5' . This valve suction valve assembly is different from the valve assembly of Figs. 7 and 8 in that the shape of a retainer 47 is further improved over the afore-described retainer 45. Namely, the retainer 47 includes a central retainer portion 47a, a plurality of radial legs 47b by which the retainer 47 is fixed to the counter-bore portion 5r of the valve plate 5' , and a plurality of radial extensions 47c. The retainer 47 is physically more rigid than the retainer 45, and the central retainer portion 47a and the radial legs and extensions 47b and 47c are able to contribute to a stable retention of the flat plate-like valve element 26. Thus, the movement of the flat plate-like valve element 26 from the port opening position to the port closing position and vice versa within the valve chamber * 5d is constantly stabilized, and therefore, the valve element 26 can be stably and accurately seated on the valve seat 5b. Accordingly, the pressure response characteristics of the valve assembly can be enhanced. Figures 10 and 11 illustrate a further embodiment of the valve assembly incorporated in the front and rear valve plates of a reciprocatory piston type compressor similar to the compressor of Figs. 1 and 2. Referring to Figs. 10 and 11, the valve assembly, i.e., the front discharge valve assembly incorporated into the front valve plate 5 is provided with a cylindrical valve chamber 5k enclosed by a cylindrical wall 5m, and defined between a flat valve seat 5i and a retainer 5j. The flat valve seat 5i is formed as a flat face extended around a central discharge port 5h. The discharge valve assembly is also provided with a flat plate-like circular valve element 26' having an circular periphery 26a and a plurality of through-holes 26c formed therein and used as passageways 26b for the refrigerant gas. The circular valve element 26' is arranged in the valve chamber 5k to be movable between two positions, i.e., a position seated on the valve seat 5i ( the position closing the discharge port 5h ) and an axially spaced position in which it is retained by the retainer 5j ( the position opening the discharge port 5h ), and the movement of the valve element 26* is smoothly guided by the cylindrical wall 5m of the valve chamber 5k. Namely, the entire periphery 26a of the valve element 26' is in constant smooth contact with the cylindrical wall 5m of the valve chamber 5k. A central portion of the circular flat plate-like valve element 26' acts to tightly close the discharge port 5h when the valve element 26* is seated on the valve seat 5i. When the valve element 26' άs moved away from the valve seat 5i toward the retainer 5j, the refrigerant gas after compression is discharged toward the discharge gas chamber 11 through the passageways 26b of the valve element 26* . The valve assembly of Figs. 10 and 11 having the circular flat plate-like valve element 26' is characterized in that, since the movement of the valve element 26' is constantly smoothly guided by the cylindrical wall 5m of the valve chamber 5k, any play in the valve element 26' can be prevented during the movement of the valve element 26* between the port opening and closing positions. Accordingly, the flat plate-like valve element 26* per se and the cylindrical wall 5m of valve chamber 5k are physically durable and provide a long operation life of the valve assembly. Further, the valve plate 5 defining the valve chamber 5k therein can be made of a less abrasion-resistant but lighter metallic material such as an aluminum alloy. Thus, the valve assembly provided with the valve element 26* accommodated therein can contribute to a reduction in the weight of the compressor. Although the above-described valve assembly is constructed as a discharge valve assembly incorporated in the valve plate 5, it will be readily understood that the same construction can be applied to the construction of a suction valve assembly incorporated in the valve plates of the reciprocatory piston type compressor. Figure 12 illustrates a modification of the circular flat plate-like valve element accommodated in the suction or discharge valve assembly incorporated in the front or rear valve plate 5 or 6. The circular flat plate-like valve element 26* of Fig. 12 is modified from the valve element of Figs. 10 and 11 in such a manner that four quadrilateral through- bores 26c used as fluid passageways 26b of the refrigerant gas are equiangularly arranged around .a central portion of the valve element 26' . The operation and advantageous effect of the valve assembly of Fig. 12 is approximately similar to those of the valve assembly of Figs. 10 and 11. Figures 13 and 14 illustrate a further embodiment of the suction and discharge valve assemblies capable of being incorporated in each of the front and rear valve plates of a reciprocatory piston type compressor similar to the compressor of Figs. 1 and 2. Referring to Figs. 13 and 14, the valve assemblies, i.e., the suction valve assembly arranged between a rear suction gas chamber 10 and a rear cylinder bore 2a, and the discharge valve assembly arranged between the rear cylinder bore 2a and a rear discharge gas chamber 12 are incorporated in a rear valve plate 6* . The respective valve assemblies accommodate a separately made circular retainer member 49 therein fixedly attached to a counter-bore portion 6e of the valve plate 6* as shown in Fig. 13. The retainer 49 is provided with an outer ring¬ like portion 49a and a plurality of ( four in the shown embodiment ) radial retaining tongues 49b equiangularly arranged with respect to a center of the retainer 49, and is characterized in that the respective radial retaining tongues 49b are provided with projections 49c formed to be axially projected from a free end of each tongue 49b toward a valve chamber 6d or 6k, so that a flat plate-like valve element 27 or 31 may make a point contact with the retainer 49 when the valve element 27 or 31 is moved from a flat valve seat 6b or 6i toward the retainer 49. Namely, in the suction and discharge valve assemblies of Figs. 13 and 14, the flat plate¬ like valve elements 27 and 31 are always prevented from making a surface contact with the associated retainer 49, and therefore, it is possible to prevent the flat plate-like valve elements 27 and 31 from being adhered to the retainers 49 by a lubricant oil contained -in the refrigerant gas. Namely, a delay in the separating movement of the the valve element 27 of the suction valve assembly from the retainer 49 at the start of the discharge stroke of the piston 25, and a delay in the separating movement of the valve element 31 of the discharge valve assembly from the retainer 49 at the start of the suction stroke of the piston 25 can be cancelled, and accordingly, a volumetric efficiency of the compression and discharge of the refrigerant gas can be maintained at a high level. Figures 15 through 17 illustrate various modifications of the retainer 49 of the suction and discharge valve assemblies of Figs. 13 and 14. The retainer member 49 of Fig. 15 has a plurality of projections 49d by which, e.g., a flat plate-like valve element 31 of the discharge valve assembly is permitted to make a point contact with the projections 49d of the retainer member 49. The projections 49d are formed by bending respective free ends of the radial retaining tongues 49b at right angles. The radial retaining tongues 49b per se are radially extended from a ring-like portion 49a of the retainer 49. The projections 49d of the retainer member 49 therefore contribute to obtaining the same advantageous effect as that of the projections 49c of the retainer 49 of Figs. 13 and 14. The retainer 49 of Fig. 16 has a plurality of projections 49e enabling the valve element 31 to make a point contact therewith, and therefore, the same advantageous effect as the afore-described projections 49c and 49d of the retainer 49 can be obtained. The projections 49e of the retainer 49 are formed by bending the radial tongues 49b to that they are downwardly inclined toward the inside of the valve chamber 6k. The retainer 49 of Fig. 17 has a plurality of radial tongues 49b having inner faces 49f which are roughened to prevent the flat plate-like valve element 31 from coming into close contact with the retainer 49 when the valve element 31 is. moved away from the valve seat 6i toward a position retained by the retainer 49. Figures 18 and 19 illustrate another embodiment of the suction and discharge valve assemblies, i.e., the rear discharge valve assembly incorporated in the rear valve plate 6' in the case of the shown embodiment. The discharge valve assembly of Figs. 18 and 19 is provided with a flat plate-like retainer member 49 formed as a separate element from the valve plate 6', and a cylindrical flat plate-like valve element 31' arranged in a valve chamber 6k. The discharge valve assembly of this embodiment is characterized in that the valve element 31* is provided with a face facing the retainer member 49 and having an annular projection 31a formed therein. Therefore, when the flat plate-like valve element 31* is moved from the valve seat 6i surrounding the discharge port 6h toward the retainer 49 until it comes into contact with radial projections 49b extended from the ring portion 49a, only a line contact occurs between the annular projection 31a of the flat plate-like valve element 31' and the radial projections 49b of the retainer member 49. Thus, it is possible to prevent the valve element 31' from being adhered to the face of the radial tongues 49b of the retainer 49 when the valve element 31' is moved to the port opening position in contact with the retainer 49, and accordingly, enhanced pressure responsive characteristics of the valve assembly can be obtained. Figure 20 illustrates a reciprocatory piston type compressor provided with suction and discharge valve assemblies according to a further embodiment of the present invention. The compressor of Fig. 20 is provided with front and rear cylinder blocks 101 and 102 axially combined together. Both axial ends of the combined cylinder blocks 101 and 102 are sealingly closed by front and rear housings 107 and 108, via front and rear valve plates 105 and 106 made of a light metallic material belonging to an aluminum alloy system. The front and rear cylinder blocks 101 and 102, and the front and rear housings 107 and 108 are axially connected by a plurality of screw bolts to form a compressor body. The compressor body is provided with a swash plate chamber 104 formed therein at the connecting portion of the front and rear cylinder blocks 101 and 102. The swash plate chamber 104 is fluidly communicated with a suction gas inlet 103 through which a refrigerant gas is introduced into the compressor body. The front and rear housings 107 and 108 are provided with front and rear discharge chambers 111 and 112, respectively. An axial drive shaft 118 is rotatably supported by the compressor body via rotary bearings 114 and 115, and rubber seals 116 and 117 held in an axially extended central bore of the compressor body. The drive shaft 118 is outwardly extended through the front housing 107, and is supported by a radial bearing 119 mounted in a central portion of the front housing 107. The drive shaft 118 is also sealed by a shaft seal 120 arranged adjacent to the radial bearing 119. A swash plate 123 is mounted on the rotatable drive shaft 118 at a position such that the swash plate 123 is rotated in the swash plate chamber 104, and axially supported by the front and rear cylinder blocks 101 and 102 via thrust bearings 121 and 122. The compressor body is further provided with a plurality of pairs of axial cylinder bores 101a and 102a arranged around and in parallel with an axis of rotation of the drive shaft 118. A plurality of reciprocatory double headed hollow pistons 125 are slidably fitted in the cylinder bores 101a and 102a, and engaged with the swash plate 123 via respective pairs of shoes 124. As shown in Fig. 20, each of the above-described double headed hollow pistons 125 is made of aluminum alloy, and is provided with a pair of inner chambers 125a formed in both head portions to be constantly communicated with the swash plate chamber 104. Thus, the refrigerant gas is able to flow from the swash plate chamber 104 into the two inner chambers 125a of the piston 125. The double headed hollow piston 125 is also provided with suction ports 125b formed in each of the opposite end faces of the two head portions for providing a fluid communication between the swash plate chamber 104 and the cylinder bores 101a and 102a via the inner chambers 125a when a pair of suction valve assemblies incorporated in the end faces of the double headed hollow piston 125. Figures 21 and 22 typically illustrates, on a large scale, the detailed construction of one of the suction valve assemblies incorporated in the head end faces of the piston 125. As shown in Figs. 21 and 22, a cylindrical head member 125' is embedded in the end face of the piston 125 by a threaded engagement and a mechanical staking method so that the cylindrical head member 125' is integrally assembled in the head end face of the piston 125. The cylindrical head member 125' is provided with a valve chamber 125f of the suction valve assembly formed beforehand therein, and contains a flat -plate-like valve element 126 in the valve chamber 125f freely movable between a flat valve seat 125c formed to be extended around the suction port 125b and a retainer 125e spaced from the valve seat 125c. The valve element 126 is formed as a substantial triangular plate element having three guide portions 126a in smooth contact with a cylindrical wall 125d of the valve chamber 125f, and three passage forming portions 126b forming three passageways 127 between the portions 126b and the cylindrical wall 125d of the valve chamber 125f for the refrigerant gas. Thus, the triangular valve element 126 can stably be moved in the valve chamber 125f without any play between a port closing position closing the suction port 125b and a port opening position where the valve element 126 rests on the retainer 125e of the cylindrical member 125'. The retainer 125e includes a plurality of, e.g., three, retaining tongues arranged equiangularly around the valve chamber 125 . The front and rear valve plates 105 and 106 of the compressor are provided with discharge ports 105b and 106b formed therein to provide a fluid communication between each pair of cylinder bores 101a and 102a and the front and rear discharge gas chambers 111 and 112 in response to the reciprocation of the double headed pistons 125. These discharge ports 105b and 106b are closably opened by conventional reed valves 130 and 131 retained by retainer gaskets 128 and 129. The description of the operation of the compressor of Figs. 20 through 22 will be provided hereunder. When the refrigerant gas returned from an external air-conditioning circuit is introduced into the swash plate chamber 104 via the inlet port 103, the refrigerant gas is further introduced into the inner chambers 125a of the respective pistons 125. Due to the rotation of the drive shaft 118 and the swash plate 104, the double headed pistons 125 are reciprocated in the cylinder bores 101a and 102a to perform suction, compression and discharge strokes thereof, in that order. In response to the suction stroke of the piston 125, a pressure level in one of the cylinder bores 101a and 102a is reduced, and a pressure differential is generated between that cylinder bore and one of the inner chambers 125a of the piston 125. Therefore, the valve element 126 is moved from the port closing position resting on the valve seat 125c toward the port opening position resting on the retainer 125e, to thereby permit the refrigerant gas before compression to be drawn into one of the cylinder bores 101a and 102a in which the piston 125 carries out the suction stroke thereof. Subsequently, the drawn refrigerant gas is compressed by the piston 125 in one of the cylinder bores 101a and 102a during the compression stroke of the piston 125. Accordingly, a pressure level in that one cylinder bore 101a or 102a is increased, and thus the valve element 126 of the suction valve assembly is moved from the port opening position thereof toward the port closing position thereof. Then, the compressed refrigerant gas is discharged from one of the cylinder bores 101a and 102a toward the related discharge gas chamber 111 or 112 via the discharge port 105b or 106b opened by the discharge reed valve 130 or 131. The compressed refrigerant gas is further discharged from the discharge gas chambers 111 and 112 toward the external air-conditioning circuit. The described suction valve assemblies provided with flat plate-like valve elements 126 and incorporated in both head end faces of the respective double headed hollow pistons 125 can exhibit the same various advantageous effects as exhibited by the afore- described suction valve assemblies incorporated in the front and rear valve plates of the reciprocatory piston type compressor. Namely, the stable and smooth movement of the triangular plate-like valve element 126 in the valve chambers 125f is effective for preventing the valve element 126 per se and the inner wall of the valve chamber 125f from being mechanically damaged during the operation of the compressor, and accordingly, a mechanical durability of both the suction valve assemblies and the compressor is enhanced to thereby guarantee the long operation life of the compressor. Further, the valve elements 126 of the suction valve assemblies are provided as float type valve elements, and thus high pressure response characteristics of the valve assemblies can be obtained. Namely, a quick opening and closing operation of each valve element 126 is obtained in response to only a generation of a pressure differential between pressures acting on both faces of each valve element 126, and therefore, an over- compression of the refrigerant can be avoided, to thereby increase a compression efficiency of the compressor. Moreover, since a homogeneous flow of the refrigerant gas is obtained in the valve chambers 125f and the suction ports 125b of the suction valve assemblies, a pulsative change in the flow of the refrigerant gas can be remarkably reduced. The triangular plate-like valve elements 126 of the suction valve assembly incorporated in each head end face of the piston 125 may be variously modified as shown in Figs. 23, 24, and 25. A valve element 226 of Fig. 23 has circular guide portions 226a and one or two passage forming portions 225b. A valve element 326 of Fig. 24 is formed as an oval plate-like element having two round guide portions 326a and two curved passage forming portions 326b. A valve element 426 of Fig. 25 is formed as a star-like shaped element having four guide portions 426a and four passage forming portions 426b. Figure 26 illustrates another suction valve assembly capable of being incorporated in a head end face of a double headed hollow piston 125, similar to the piston 125 of the afore-described suction valve assemblies of Figs. 20 through 22. The suction valve assembly of Fig. 26 has a circular flat plate-like valve element 526 arranged to be movable in a valve chamber 525f formed in an end face of the piston 125. The inner wall of the valve chamber 525f is provided with four circular engraved portions 525g and four circular guide faces 525d in smooth. contact with four circular guided portions 526a of the circular flat plate-like valve element 526. The valve element 526 is further provided with four passage forming portions 526b defining passageways 527 for the flow of the refrigerant gas in cooperation with the four circular engraved portions 525g of the end face of the piston 125. A retainer formed in the end face of the piston 125 includes four retaining tongues 525e to perform a stable retention of the valve element 526 when moved to the port opening position from the port closing position resting on the valve seat ( not shown in Fig. 26 ). The suction valve assembly of Fig. 26 is able to exhibit the same advantageous effects as the afore- described suction valve assemblies of Figs. 20 through 22. Figure 27 is a modification of the suction valve assembly of Fig. 26. Namely, the suction valve assembly of Fig. 27 is provided with a valve chamber 625f formed in an end face of the double headed piston 125 and having a square wall 625d. The valve assembly is further provided with a circular flat plate-like valve element 526 movable in the valve chamber 625f enclosed by the square wall 625d. Since four portions 526a of the valve element 526 are in constant smooth contact with the square wall 625d of the valve chamber 625f, the movement of the flat plate-like valve element 526 can be always stable. Thus, the suction valve assembly of Fig. 27 is able to exhibit enhanced pressure responsive characteristics when moved between the port closing position wherein the valve element 526 closes the suction port 125b, and the port opening position resting on the retainer having four retaining tongues 625e. Figures 2S and 29 illustrate a further embodiment of the suction valve assembly of the type incorporated in an end face of a double headed hollow piston made of a metallic material belonging to an aluminum and aluminum alloy system. Referring to Figs. 28 and 29, the suction valve assembly is provided with a suction port 125b formed in an end face of the piston 125 to be communicated with an inner chamber 125a of the piston 125. The end face of the piston 125 is counterbored to provide a cylindrical recess 125g in coaxial with the suction port 125b. In the cylindrical recess 125g, a hollow open ended cylindrical element 626 made of a metallic material belonging to an iron system, and provided with a central bore 626a and apertures 626b formed in a bottom face, is tightly fitted by an engagement of an annularly extended raised portion 626e of the cylindrical element 626 with an annular groove formed in a cylindrical wall of the recess 125g. The cylindrical element 626 may be formed with an axial slit to enable the tight fitting of the element 626 in the cylindrical recess 125g as shown in Fig. 29. The cylindrical element 626 is further provided with a cylindrical valve chamber 626f and a retainer having four radial projections 626c. Namely, the cylindrical element 626 is provided for constructing indispensable elements and parts of the suction valve assembly. A valve element 126 in the shape of a circular plate-like element made of an iron system metallic material is arranged in the valve chamber 626f. In accordance with the above-described embodiment of the suction valve assembly incorporated in each end face of the double headed hollow piston 125, since the movable valve element 126 and the cylindrical element 626 provided with the valve chamber 626f enclosed by the cylindrical wall 626d and the retaining projections 626c are made of the same strong metallic material belonging to an iron system, a high mechanical durability of the suction valve assembly can be obtained. Further, the employment of the iron cylindrical element 626 can protect the aluminum piston 125 from being damaged by the valve element 126 because the quickly moving valve element 126 comes into strong contact with only the valve seat 125c of the piston 125 during the operation of the compressor. The use of the iron cylindrical element 626 also contributes to a reduction in the manufacturing cost of the suction valve assembly. Figures 30 and 31 illustrate a further embodiment of a discharge valve assembly. In the discharge valve assembly of Figs. 30 and 31, a cylindrical element 726 having a bottom face in which a central aperture 726a and passages 726b are formed is fitted in the valve plates, e.g., the front valve plate 105 having a discharge port 105b, and used for a forming a valve chamber 726e enclosed by a cylindrical wall 726d, and a plurality of retaining projections 726c of the discharge valve assembly. A valve element 727 is arranged in the cylindrical element 726. It should be understood that the cylindrical element 726 is made of an iron system metallic material, and tightly fitted in the valve plate 105 at a position in registration with the discharge port 105b of the valve plate 105. The cylindrical element 726 is further provided with a plurality of small through-holes 726f located at a position adjacent to the face of the valve plate 105 facing the discharge gas chamber 111. These small through-holes 726f are effective for separating an oil component from the refrigerant gas. It will be easily understood that the discharge valve assembly of Figs, 30 and 31 employing the cylindrical element fitted in the valve plate of the compressor can exhibit the same advantageous effects as the afore-mentioned suction valve assemblies of Figs. 28 and 29 incorporated in the end faces of the double headed hollow piston of the compressor. Figures 32 and 33 illustrate a still further embodiment of a discharge valve assembly incorporated in the valve plate, e.g., the front valve plate 105, and including a separately made cylindrical element 726' . The cylindrical element 726' of the discharge valve assembly of Figs. 32 and 33 is tightly fitted in a counter-bore 105e of the valve plate 105 from the side adjacent to a cylinder bore.101a. The cylindrical element 726' is provided with a bottom face 726'g in which a central bore 726'a is formed as a discharge port for the compressed refrigerant gas. A valve seat 726'g is extended to surround the central bore 726'a, i.e., the discharge port. A bottom 105d of the counter-bore 105e is provided as a retainer, and a flat plate-like valve element 727 is arranged in a valve chamber 726*e formed in the cylindrical element 726' . The valve element 727 can be freely moved between a port closing position whereat it rests on the valve seat 726'g and a port opening position whereat the element 727 rests on the retainer 105d. The cylindrical element 726' is also provided with a plurality of small through-holes 726'f though which the compressed refrigerant gas flows from the cylinder bore 101a toward the discharge gas chamber 111 when the discharge port 726'a is opened by the valve element 727. Namely, the compressed gas is led to the discharge gas chamber 111 through an annular passageway 125f and a guide passageway 125g formed in the valve plate 105. This discharge valve assembly of Figs. 32 and 33 can exhibit the same advantageous effects as the afore¬ mentioned discharge valve assembly of Figs. 30 and 31. From the foregoing description of the preferred embodiments of the present invention, it will be understood that the reciprocatory piston type compressor accommodating valve assemblies therein which employ freely and smoothly movable valve elements can exhibit enhanced pressure response characteristics. Thus, an over-compression of the refrigerant gas is avoided, and a pulsative change in the flow of the refrigerant gas can be suppressed. Further, a long operation life of the valve assembly and the compressor is ensured. It should be understood that many modification and variations of the present invention will occur to persons skilled in the art without departing from the scope and spirit of the present invention claimed in the attached claims.

Claims: CLAI S 1. A reciprocatory piston type compressor including: a compressor body in the form of a combination of a cylinder block defining therein axially extended cylinder bores for compression chambers, and front and rear housings sealingly closing axial opposite ends of the cylinder block via front and rear valve plates, respectively; reciprocatory pistons driven so as to reciprocate in the cylinder bores to thereby compress a refrigerant gas in the compression chambers when the refrigerant gas before compression is sucked from a suction gas chamber and to discharge the refrigerant gas after compression from the compression chambers toward a discharge gas chamber; a piston reciprocating mechanism for driving the reciprocation of the reciprocatory pistons when a rotative drive force is applied thereto from outside the compressor body via a drive shaft rotatably supported in the compressor body; and a valve assembly provided with a suction valve assembly operative to closably open suction ports between the suction gas chamber and the compression chambers during suction strokes of the reciprocatory pistons to thereby allow the refrigerant gas to be sucked from the suction chamber into the compression chambers, and a discharge valve assembly operative to closably open discharge ports between the compression chambers and the discharge gas chamber during discharge strokes of the reciprocatory pistons to thereby allow the refrigerant gas to be discharged from the compression chamber toward the discharge chamber, characterized in that at least said suction valve assembly of said valve assembly comprises: first means for defining an open ended valve chamber in each of said suction ports to be enclosed by.an axially extended wall, the valve chamber having one open end thereof arranged adjacent to said suction " gas chamber and provided with a flat valve seat formed to be extended in a plane perpendicular to the axially extended wall, and the other open end thereof axially spaced from the one open end and arranged adjacent to each of said compression chambers; an independent flat plate-like suction valve element arranged in said valve chamber to be freely movable toward and away from said valve seat in response to a pressure differential generated between pressures prevailing in each of said compression chamber and said suction chamber, said flat plate-like suction valve taking an open position thereof to establish a communication between said compression chamber and said suction gas chamber via each of said suction ports when moved away from said valve seat, and a closing position thereof preventing the communication between said compression chamber and said suction gas chamber when moved toward and seated on said valve seat; retainer means arranged in said other open end of said valve chamber for retaining said flat plate-like valve element moved to said open position to thereby allow said refrigerant gas to be sucked from said suction gas chamber into said each compression chamber. 2. A reciprocatory piston type compressor according to claim 1, wherein said discharge valve assembly of said valve assembly comprises: second means for defining an open ended valve chamber in each of said discharge ports to be enclosed by an axially extended wall, the valve chamber having one open end thereof arranged adjacent to each of said compression chambers and provided with a flat valve seat formed to be extended in a plane perpendicular to the axially extended wall, and the other open end thereof axially spaced from the one open end and arranged adjacent to the discharge gas chamber; an independent flat plate-like discharge valve element arranged in said valve chamber to be freely movable toward and away from said valve seat in response to a pressure differential generated between pressures prevailing in each of said compression chamber and said discharge gas chamber, said flat plate- like discharge valve element taking an open position thereof to establish a communication between said compression chamber and said discharge gas chamber via each of said discharge ports when moved away from said valve seat, and a closing position thereof preventing the communication between said compression chamber and said discharge gas chamber when moved toward and seated on said valve seat; retainer means arranged in said other open end of said valve chamber for retaining said flat plate-like discharge valve element when said discharge valve element is moved to said open position thereof. 3. A reciprocatory piston type compressor according to claim 2, wherein: said suction gas chamber comprises a front suction gas chamber formed in said front housing of said compressor body, and a rear suction gas chamber formed in said rear housing of said compressor body; said discharge gas chamber comprises: a front discharge gas chamber formed in said front housing, and a rear discharge gas chamber formed in said rear housing of said compressor body; said suction valve assembly of said valve assembly comprises: a front suction valve assembly incorporated in said front valve plate arranged between a front end of said cylinder block and said front housing and allowing said refrigerant gas to be sucked from said front suction gas chamber into said compression chambers during a suction stroke of said reciprocatory pistons, said front valve plate having plate portions thereof surrounding said respective suction ports formed . therein, each of said plate portions being said first means for defining said valve chamber; and a rear suction valve assembly incorporated in said rear valve plate arranged between a rear end of said cylinder block and said rear housing and allowing said refrigerant gas to be sucked from said rear suction gas chamber into said compression chambers during a suction stroke of said reciprocatory pistons; and said discharge valve assembly of said valve assembly comprises: a front discharge valve assembly incorporated in said front valve plate arranged between said front end of said cylinder block and said front housing and allowing said refrigerant gas to be compressed in and discharged from said compression chambers toward said front discharge gas chamber during compressing and discharging strokes of said reciprocatory pistons, said front valve plate having further plate portions thereof surrounding said respective discharge ports formed therein, each of said further plate portions being said second means for defining said valve chamber; and a rear discharge valve assembly incorporated in said rear valve plate arranged between said rear end of said cylinder block and said rear housing and allowing said refrigerant gas to be compressed in and discharged from said compression chambers toward said rear discharge gas chamber during compressing and discharging strokes of said reciprocatory pistons, said rear valve plate having further plate portions thereof surrounding said respective discharge ports formed therein, each of said further plate portions being said second means for defining said valve chamber. 4. A reciprocatory piston type compressor according to claim 3, wherein said retainer means of each of said front and rear suction valve assemblies comprises a plurality of tongues integral with said axially extended wall, said plurality of tongues being extended radially from said axially extended wall and arranged in said other open end of said valve chamber of each of said front and rear suction valve assemblies, and wherein said retainer means of each of said front and rear discharge valve assemblies comprises a plurality of tongues integral with said axially extended wall, said plurality of tongues being extended radially from said axially extended wall and arranged at said other open end of said valve chamber of each of said front and rear discharge valve assemblies. 5. A reciprocatory piston type compressor according to claim 3, wherein said retainer means of each of said front and rear suction valve assemblies comprises a generally flat retainer member fixedly attached to each of said front and rear valve plates at a position adjacent to said other open end of said valve chamber of each of said front and rear suction valve assemblies, and wherein said retainer means of each of said discharge valve assemblies comprises a generally flat retainer member fixedly attached to each of said front and rear valve plates at a position adjacent to said other open end of said valve chamber of said discharge valve assembly. 6. A reciprocatory piston type compressor according to claim 3, wherein said retainer means of each of said front and rear suction valve assemblies is provided with a plurality of projection-like retaining portions making a point contact with a plurality of portions of said flat plate-like suction valve element when said suction valve element is moved to said open position thereof, and wherein said retainer means of each of said front and rear discharge valve assemblies is provided with a plurality of projection-like retaining portions making a point contact with a plurality of portions of said- flat plate-like discharge valve element when said discharge valve element is moved to said open position thereof. 7. A reciprocatory piston type compressor according to claim 3, wherein said flat plate-like suction valve element of each of said front and rear suction valve assemblies is provided with an axially projecting portion formed therein and making a line contact with said retainer means of each of said front and rear suction valve assemblies when said suction valve element is moved to said open position thereof, and wherein said flat plate-like discharge valve element of each of said front and rear discharge valve assemblies is provided with an axially projecting portion formed therein and making a line contact with said retainer means of each of said front and rear discharge valve assemblies when said discharge valve element is moved to said open position thereof. •8. A reciprocatory piston type compressor according to claim 3, wherein said retainer means of each of said front and rear suction valve assemblies is provided with a plurality of contact faces that are roughened to provide a readily separable contact with a plurality of portions of said flat plate-like suction valve element when said suction valve element is moved to said open position thereof, and wherein said retainer means of each of said front and rear discharge valve assemblies is provided with a plurality of contact faces that are roughened to provide a readily separable contact with a plurality of portions of said flat plate-like discharge valve element when said discharge valve element is moved to said open position thereof. 9. A reciprocatory piston type compressor according to claim 3, wherein said flat plate-like suction valve element of each of said front and rear suction valve assemblies is provided with at least two peripheral portions in constant smooth contact with said axially extended wall of said open ended valve chamber, and passage-defining portions capable of cooperating with said axially extended wall of said open ended valve chamber to define a passage for allowing said refrigerant gas before compression to flow from said front or rear suction gas chamber toward each of said compression chambers when said suction valve element is moved from said valve seat, and wherein said flat plate¬ like discharge valve element of each of said front and rear discharge valve assemblies is provided with at least two peripheral portions in constant smooth contact with said axially extended wall of said open ended valve chamber, and a passage-defining portions capable of cooperating with said axially extended wall of said open ended valve chamber to define a passage for allowing said refrigerant gas after compression to flow from each of said compression chambers toward one of said front and rear discharge gas chambers when said discharge valve element is moved from said valve seat. 10. A reciprocatory piston type compressor according to claim 3, wherein said flat plate-like suction valve element of each of said front and rear suction valve assemblies has a substantially central portion operative to closably open one of said suction ports, an entire peripheral portion extended to surround said central portion and being in constant smooth contact with said axially extended wall of said valve chamber during the movement of said suction valve element between said open and closing positions thereof, and an intermediate portion extending between said central portion and said entire peripheral portion and having at least one aperture permitting said refrigerant gas before compression to flow from said front or rear suction gas chamber to each of said compression chambers when said valve element is moved away from said valve seat, and wherein said flat plate-like discharge valve element of each of said front and rear discharge valve assemblies has a substantially central portion operative to closably open one of said discharge ports, an entire peripheral portion extended to surround said central portion and being in constant smooth contact with said axially extended wall of said valve chamber during the movement of said discharge valve element between said open and closing positions thereof, and an intermediate portion extending between said central portion and said entire peripheral portion and having at least one aperture permitting said refrigerant gas after compression to flow from said one of each of said compression chambers toward one of said front and rear discharge gas chambers when said discharge valve element is moved away from said valve seat. 11. A reciprocatory piston type compressor according to claim 1, wherein: said compressor body is provided with a swash plate chamber formed therein to house a rotatable swash plate and receive said refrigerant gas before compression returned from an external air-conditioning circuit; said reciprocatory pistons comprise double headed hollow pistons, each having a chamber therein acting as said suction gas chamber always in communication with said swash plate chamber, and opposite cylindrical front and rear head portions; said piston reciprocating mechanism comprises said drive shaft, said swash plate mounted on said drive shaft, and shoes operatively engaging said swash plate with said double headed hollow pistons; said suction valve assembly of said valve assembly comprises front and rear suction valve assemblies incorporated in said front and rear head portions of each of said double headed hollow pistons, and said first means of said suction valve assembly comprises each of said front and rear head portions of said each double headed hollow piston. 12. A reciprocatory piston type compressor according to claim 11, wherein each of said double headed hollow pistons comprises a hollow cylindrical element tightly embedded in a cylindrical recess of each of said front and rear head portions thereof, said hollow cyindrical element having an axially extended cylindrical inner wall therein formed as said axially extended wall of said valve chamber and axially spaced opposite ends thereof between which said valve chamber is formed, said hollow cylindrical element further having a bottom portion arranged at one of said axially opposite ends thereof and formed as said retainer means. 13. A reciprocatory piston type compressor according to claim 12, wherein said recess of each of said front and rear head portions of said double headed hollow piston is provided with a bottom thereof formed as said valve seat, and wherein said flat plate-like valve element and said hollow cylindrical element are made of a metallic material of an iron system, respectively. 14. A reciprocatory piston type compressor according to claim 12, wherein said bottom portion of said hollow cylindrical element formed as said retainer means has apertures permitting said refrigerant gas to flow therethrough. 15. A reciprocatory piston type compressor according to claim 11, wherein said compressor body is provided with front and rear gas chambers in said front and rear housings, respectively, and wherein said discharge valve assembly of said valve assembly comprises front and rear discharge valve assemblies incorporated in said front and rear valve plates, said second means of said discharge valve assembly comprises plate portions of said front and rear plates, respectively, surrounding front and rear discharge ports opening toward said front and rear discharge gas chambers. 16. A reciprocatory piston type compressor according to claim 15, wherein each of said front and rear discharge valve assemblies is provided with -hollow cylindrical elements tightly embedded in cylindrical recesses of each of said front or rear valve plate and arranged adjacent to said discharge ports of said front or rear valve plate, each of said hollow cyindrical element having an axially extended cylindrical inner wall therein formed as said axially extended wall of said valve chamber and axially spaced opposite ends thereof between which said valve chamber is formed, said hollow cylindrical element further having a bottom portion arranged at one of said axially opposite ends thereof and formed as said retainer means. 17. A reciprocatory piston type compressor according to claim 16, wherein said flat plate-like valve element and said hollow cylindrical element embedded in one of said front and rear valve plates are made of a metallic material of an iron system, respectively.

Inventors: FUJII TOSHIRO, IKEDA HAYATO, KAWAMURA HISATO, MURAKAMI KAZUO, UMEMURA SATOSHI, YOKOMACHI NAOYA, FUJII, TOSHIRO, IKEDA, HAYATO, KAWAMURA, HISATO, MURAKAMI, KAZUO, UMEMURA, SATOSHI, YOKOMACHI, NAOYA
Applicants: TOYODA AUTOMATIC LOOM WORKS, KABUSHIKI KAISHA TOYODA JIDOSHOKKI SEISAKUSHO
Application year: 1992
Main classification: F04B39
IPC codes: F04B27, F04B39