GAS COMPRESSOR

Abstract: A gas compressor has a cup-like casing (l). A driving shaft (5) is rotatably carried by a bottom (l0l) of the casing (l) and has a rotary plate (23) secured thereto. A driven shaft (l6) is disposed in the casing at an inclination angle of 20° against the driving shaft (5), supported by a bearing (4) provided on an end of the driving shaft (5), and driven by the driving shaft (5). A cylinder block (l2) is fixed to the driven shaft (l6) and has a cylinder bores (l22) receiving pistons (l3, l5) coupled with the rotary plate (23) so that the pistons (l3, l5) reciprocate in the cylinder bores (l22) upon rotation of the driving shaft (5). A side plate (3) is secured to an open end of said casing (l) and has a bore (30l) receiving a bearing (l7) for supporting one end of the driven shaft (l6). The bore (30l) is formed in the inside of a part (300) of the side plate which projects outside, so that a distance between the bearing (4) of the driving shaft (5) and the bearing (l7) in the bore is extended and stable.

Description: Background of the Invention The present invention relates to a gas compressor and, more particularly, to a gas compressor which has a rotary cylinder block with cylinder bores and pistons reciprocating in the cylinder bores upon rotation of the cylinder stock and which can be suitable mounted to a car. A typical conventional gas compressor which is provided with cylinders and pistons adapted to reciprocate in the cylinders by converting rotation of a driving shaft into axial motion is disclosed in Japanese Patent Laid-­ Open No. 9l383/l983. This gas compressor comprises a rotary swash plate secured to the driving shaft and an oscillation disk disposed on a driven shaft end and oscillatorily driven by the rotary swash plate. The rotary swash plate has a portion inclined with respect to the driving shaft, so that unbalanced force is apt to be caused on the driving shaft by the rotation of the rotary swash plate. The rotary swash plate suffers from various frictions caused between the rotary swash plate and the oscillation disk by oscillation of the oscillation disk and rotation of the rotary swash plate. This construction of the gas compressor makes vibrations and noises. Further, the gas compressor requires a complicated construction because of necessity of many parts. The Japanese Patent Laid-Open, further, discloses an improved gas compressor. However, the gas compressor has many defects left thereon. Summary of the Invention An object of the present invention is to provide a highly reliable gas compressor with reduced mechanical friction and less parts. Another object of the present invention is to provide a highly reliable gas compressor with less parts and with reduced mechanical friction by reducing the pressure acting upon a driven shaft. The present invention is characterized by a first casing defining a working chamber and rotatably carrying a driving shaft, a rotary plate disposed in the working chamber and fixed to the driving shaft so as to rotate in a plane substantially perpendicular to the driving shaft, the rotary plate being coupled with pistons to reciprocate, a second casing fixed to the first casing and having a bearing receiving recess, a high pressure recess and a low pressure recess, a driven shaft fixed to a cylinder block with cylinder bores receiving the pistons, rotatably supported by an end of the driving shaft and a bearing inserted in the bearing receiving recess at an inclination angle with respect to the driving shaft, and engaged with the driving shaft to be rotated, and a float valve plate disposed between the cylinder block and the second casing so as to form cylinder heads of the cylinder bores. In this gas compressor, discharge pressure of the compressed gas acts on a float valve plate which presses, in turn, the cylinder block end at about a cylinder bore center, so that a rotating moment is applied on the driven shaft. The rotating moment induces a load on the bearing in the bearing receiving recess of the second casing. The load becomes smaller as the distance between the supporting bearings of the driven shaft is lengthened. In this invention, since the bearing is disposed in the recess formed in the second casing, the above-mentioned distance between the two bearings is lengthened, as a result, the load is reduced. The end of the driving shaft is provided with the bearing for supporting the driven shaft. The bearing receives a resultant force from the cylinder block pressing force and the above-mentioned load, and the direction that the resultant force acts on the bearing approaches more the axis of the driving shaft as the load become smaller. In the present invention, the load is smaller so that the direction that the resultant force acts on the bearing of the driving shaft approaches more the axis of the driving shaft, and never go beyond 30° against the axis of the driving shaft. Therefore, the gas compressor is highly reliable. Other advantages are described referring to the accompanying drawings. Brief Description of the Drawings Fig. l is a sectional view of a gas compressor for a car according to an embodiment of the present invention; Fig. 2 is a sectional view of an assembly of a driving shaft and a rotary plate; Fig. 3 is a side view of a side plate; Fig. 4 is an enlarged sectional view of a part of Fig. l showing a sealing between the side plate and a float valve plate; Fig. 5 is a sectional view of the gas compressor taken along a line V-V of Fig. l; Fig. 6 is a plane view of the float valve plate used in the gas compressor; Fig. 7 is a sectional view of the float valve plate taken along a line VII-VII of Fig. 6; and Fig. 8 is a sectional view of the gas compressor for explaining forces applied on bearings. Description of a Preferred Embodiment The present invention will be described hereunder, referring to a preferred embodiment thereof shown in the accompanying drawings. In Fig. l showing a sectional view of a gas compressor, a cup-like casing l as a first casing comprises a bottom l0l and a cylindrical side wall l02 extending sideways from the bottom l0l at about ll0° with respect to an inner surface of the bottom l0l to form a working chamber 9 therein. At a central portion of the bottom l0l of the casing l, a bore is formed. A part l03 of the bore receives a radial bearing 6. A driving shaft 5 passes through the bottom l0l and is rotatably supported by the bearing 6. A mechanical sealing 8 is disposed between the inner surface of the bore l04 and the driving shaft 5 and fixed by a snap ring 7. The shaft 5 is driven by a driving mechanism disposed outside the cup-like casing l and connected to an outer end thereof. An inner end of the driving shaft 5 is provided with a rotary plate 23 at right angles against the axis of the driving shaft. At a central portion of the inner end of the driving shaft 5, a semispherical ball 4 as a bearing is secured to the driving shaft 5 through a bushing l0. A helical bevel gear 50l is formed at the inner end around the semispherical ball 4. The rotary plate 23 the back surface of which is supported to the casing l by thrust bearings 22 is fixed on the outer surface of the driving shaft 5. An aluminum alloy or the like is used for the rotary plate 23. As shown in Fig. 2, after the center portion is fitted to the driving shaft 5, the portion 23l near the center of the rotary plate 23 is pressed locally and vertically so that part of the material is plastically fluidized and caused to flow into a ring-like groove 502 that is formed in advance in the driving shaft 5, and both of these members are mechanically coupled by the pressing force occurring around the ring-like groove 502. In a front surface of the rotary plate 23, a plurality of spherically recessed bearing surfaces 232 are formed. The bearing surfaces 232 fluidly communicate with the back surface of the rotary plate 23 through lubrication oil passages 233. Referring back to Fig. l, a side plate 3 as a second casing is airtightly secured to the cup-like casing l through an O-ring 2 by means of screws so as to close the working chamber 9. The side plate 3 has a projection 300 projecting outside at the central portion. As shown in Fig. 3, in the inside of the side plate 3, a bearing receiving recess 30l is formed at a central portion. A high pressure recess 304 and a low pressure recess 302 each are formed around the bearing receiving bore 30l and communicate with a high pressure port 309 and a low pressure port 3l0, respectively. The high pressure recess 304 communicates with the bearing receiving recess 30l through a oil passage 305. A groove 306 for receiving a seal ring 20 is formed around the high pressure recess 304. Further, a groove 307 is formed around the periphery of the side plate 3 and receives the O-ring 2 (as shown in Fig. l). An area enclosed by the groove 306 for the seal ring 20 defines a high pressure chamber when closed by a float valve plate 2l which is described later. As shown in Fig. 4, the groove 306 is formed in a little recessed portion 3ll which defines the high pressure chamber so that a guide side wall 3l2 is formed outside the groove 306. Referring to Fig. l, the bearing receiving bore 30l has a radial bearing l7 fitted therein. The depth of the bearing receiving bore 30l is as twice as the bearing width. A driven shaft l6 has a semispherical bearing l9 secured to an end thereof. A helical bevel gear l6l is formed in the driven shaft l6 around the bearing l9. The driven shaft l6 has an oil passage l62 axially formed over the whole length thereof. The driven shaft l6 is inserted in the working chamber 9 and supported at both ends by the semispherical bearing 4 and the radial bearing l7 so as to incline at an angle of 20° with respect to the driving shaft 5. The helical bevel gear l6l of the driven shaft l6 is meshed with the helical bevel gear 50l formed in the driving shaft 5, whereby the rotation of the driving shaft 5 is transferred to the driven shaft l6. A cylinder block l2 is made of a light alloy such as aluminum alloy and has a mounting hole l2l at its center and a plurality of cylinder bores l22 of through holes arranged equiangularly as shown in Fig. 5. The cylinder block l2 is mounted on the driven shaft l6 not to be moved relatively, and disposed in the working chamber 9 of the cup-like casing l. A plurality of piston devices l5, as shown in Fig. l, each have a piston l3 slidablely inserted in the cylinder bore l22, a piston rod l3l and a steel ball l4. The piston l3 and the piston rod l3l are formed integrally from an aluminium alloy to reduce the weight. The rod l3l is inserted in a hole of the steel ball l4 and secured to the steel ball l4 by plastic deformation of the rod member as shown Fig. 2. The steel ball l4 of the piston device l5 is rotatably fitted into the recessed bearing surface 232, and an open end portion 234 of the recessed bearing surface 232 is pinched thereby to prevent the steel ball l4 from coming off therefrom by a champing force. The float valve plate 2l with check valves 25, constituting cylinder heads is disposed between the end of the cylinder block l2 and the inside of the side plate 3 with a small gap between the side wall l02 of the casing l and the periphery of the float valve plate 2l. The float valve plate 2l is constructed as shown in Figs. 6, 7. Namely, as a whole, the float valve plate 2l has a horseshoe-like shape and it is made of steel plate. The float valve plate 2l has a two projections 2ll and 2l3 which a little project from the surface surrounding the projections. The projection 2ll is for positioning and guiding itself and inserted into a guide recess 308 made in the side plate 3. The projection 2l3 is movably fitted in the guide side wall 3l2 formed around the seal ring groove 306 of the side plate 3 so as to cover the high pressure chamber 3ll including the high pressure recess 304. The projection 2l3 of the float valve plate 2l has valve holes 2l4 and screw holes 2l5. The valve 25 is mounted by screws screwed in the screw holes 2l5 to cover the valve holes 2l4. The float valve plate 2l is mounted on the side plate 3 as shown in Fig. 4. The projection 2l3 is inserted in the recessed portion 3ll of the side plate 3, guided by the guide side wall 3l2 of the recessed portion 3ll and the guide recess 308, and abutted on the seal ring 20 to define the high pressure chamber as previously mentioned. The float valve plate 2l is moved vertically to the float valve plate surface by the high pressure applied on the float valve plate 2l. Even if the above-mentioned float valve plate 2l is shifted by the pressure applied on the valve plate 2l to the cylinder block side, the seal ring 20 is prevented from going out from the seal ring groove 306 because the projection 2l3 of the float valve plate 2l is guided by the guide side wall 3l2 of the side plate 3 and the overlapping relation between the guide side wall 3l2 of the side plate 3 and the projection side wall 2l8 of the float valve plate 2l is kept. Therefore, the durability of the seal ring 20 can be extended greatly and the seal ring 20 has a stable sealing function. The gas compressor having such a seal mechanism is enhanced greatly in reliability. A low pressure area is outside the high pressure chamber enclosed by the seal ring groove 306 and communicates with the low pressure recess 302 communicating with a low pressure port 3l0. Further, a through-hole l9l formed in the semi­ spherical bearing l9 is communicated with the passage 305 formed in the side plate 3 through the passage l62 formed in the driven shaft l6, thereby forming an oil supply passage led to the bearings 4, l9. A bush 24 is disposed between the driven shaft l6 and the bottom of the bearing receiving recess 30l of the side plate 3 in order to damp the thrust force and to distribute the lubricant. In the arrangement described above, as the driving shaft 5 is rotated by, for example, an internal combustion engine, the rotary plate 23 is rotated in synchronism with the driving shaft 5, followed by rotation of the driven side of the helical bevel gears 50l, l6l, that is, the driven shaft l6 and the cylinder block l2. When the cylinder block l2 and the rotary plate 23 rotate synchronously clockwise, for example, as shown in Fig. 3, one of the cylinder bores l22 reaches the leading edge 2l7 of the float valve plate 2l. when further a little rotates, the cylinder bore l22 is closed by the float valve plate 2l and the piston in the bore l22 starts a compression stroke. When the cylinder bore l22 further rotates and reaches the valve holes 2l4, the compressed gas starts to discharge through the valve holes 2l4. When the cylinder bore l22 goes beyond the trailing edge 2l6 of the float valve plate 2l after the cylinder bore leaves the valve hole 2l4, the cylinder bore l22 closed by the float valve plate 2l starts to open and to suck a gas from the low pressure area. The cylinder block l2 further rotates and the cylinder block l22 go beyond the leading edge 2l7 of the float valve plate 2l, and when it is closed by the float valve plate 2l as mentioned above, the gas in the cylinder bore starts to be compressed. Thus, the piston l3 in the cylinder bore l2 is in the compression stroke when the cylinder bore l2 is closed by the float valve plate 2l, and when the cylinder bore l2 is opened, the piston l3 is in the suction stroke. Thus, the gas is sucked, compressed and discharged according to the rotation of the cylinder block l2. Next, when the high pressure recess 304 attains the high pressure, the high pressure is applied on the float valve 2l enclosed by the seal ring 20 so that the float valve 2l is pushed to the end surface of the cylinder block l2 and seals by itself airtightly the cylinder bore l22. Accordingly, so long as the high pressure recess 304 is at the high pressure, the float valve 2l is pushed always to the cylinder block l2 and air-tightness is always kept stably by its own force with the cylinder block l2. As described above, since sealing is made by the own force of the float valve plate, there is no need to separately dispose any push means and this arrangement is extremely simple and has high reliability and producibility. The float valve plate 2l is enough if it is disposed only on the high pressure side, so that the float valve has the horseshoe like shape, as in the embodiment, the dimension of which is a little larger than the area enclosed by the seal ring 20. However, around shape may be used for the horseshoe. When the float valve plate 2l is used for only the high pressure side, its weight is reduced. And the sealing performance can be further improved. In the normal operation state of a gas compressor a car for air cooler, the cooling medium and the lubricant are mixed and compressed. Therefore, when the high pressure is established in the high pressure chamber, the lubricant is simultaneously supplied to the semispherical bearing l9 through the oil supply passages. The oil jetted from the bush 24 lubricates the bearing l7, too, and lubrication can be kept smoothly by itself. Since this oil supply passage is formed inside the originally necessary components, it can be formed simply without any trouble and its appearance is also good. Next, in the construction in which the driven shaft l6 which is fixed to the cylinder block is extended up to the inside of the side plate 3 and supported rotatably through the bearing l7, forces acting on the bearings 4l7 will be explained with reference to Fig. 8. When a discharge pressure of high pressure is applied on the float valve plate 2l, the float valve plate 2l presses the cylinder block l2 by force P o . The force P o produces a moment in the cylinder block l2 and the driven shaft l6. Considering equilibrium of the moment at the center of the semispherical ball 4 the following equation is established to keep a fixed position of the cylinder block l2: P o ·l o = P₁·l₁ , wherein P o : force acting on the cylinder block l2, caused by discharge pressure (kgf) l o : distance between the central axis of the driven shaft l6 and the central axis of the cylinder bore l22 (mm) P₁: force acting upon the bearing l7 (kgf) l₁: distance from the center of the semispherical ball 4 to the center of the bearing l7 (mm) ϑ : direction of resultant force acting upon the semispherical ball 4 (degree). Therefore, the force P₁ acting upon the bearing is: The direction of resultant force (ϑ) is Accordingly, in comparison with a construction in which a fixed shaft is disposed on the side plate and a cylinder block is supported rotatably by the fixed shaft within the cylinder block through a bearing, the force acting upon the bearing and the direction of the resultant force are reduced by 50% for P₁ and by 40% for ϑ, respectively. The direction of resultant force ϑ is necessary to be at most 30°. Namely, the bearing l7 is necessary to be spaced from the semispherical ball 4 by more than l.7 times the distance l o . If it is beyond 30°, a bearing function by the spherical ball l4 is very unstable. The depth of the bearing receiving recess 30l is preferable more than one and half times the width of the bearing l7. As described above, since the force acting upon the bearing and stress acting upon the semispherical ball can be reduced drastically as illustrated in the embodiment described above, there can be obtained a cylinder block rotation type compressor having reduced friction, extended life and high reliability.

Claims: 1. A gas compressor in which pistons are inserted in cylinder bores formed in a cylinder block so as to reciprocate therein by reciprocating force converted from rotation of a driving shaft carried rotatably, thereby providing a compressed gas upon rotation of said driving shaft, characterized by comprising a first casing defining a working chamber therein and rotatably carrying said driving shaft; a rotary plate disposed in said working chamber and secured to said driving shaft so as to rotate in a plane substantially perpendicular to said driving shaft according to rotation of said driving shaft, said rotary plate having coupling portions circularly arranged equiangularly spaced from each other and coupled with piston rods of said pistons at said coupling portions; a second casing fixed to said first casing so as to close said working chamber, said second casing having a bearing receiving recess, a high pressure recess and a low pressure recess; a driven shaft disposed in said working chamber and rotatably supported by an end of said driving shaft and a bearing provided within said bearing receiving recess of said second casing with an inclination with respect to said driving shaft, said driven shaft being engaged with said driving shaft at said end thereof so as to rotate according to rotation of said driving shaft, said cylinder block being fixed to said driven shaft such that said cylinder bores are substantially in parallel with said driven shaft, whereby said pistons are reciprocated in said cylinder bores upon the rotation of said driving shaft; and a float valve plate having a valve hole, disposed between said cylinder block and said second casing and constituting cylinder heads of said cylinders in which a gas is subjected to compression, said float valve plate defining a high pressure chamber including said high pressure recess in cooperation with said second casing and being pressed on said cylinder block by a high pressure established in said high pressure chamber through said valve hole. 2. A gas compressor according to claim l, wherein said second casing has a projection projecting outside at a central portion thereof, and said bearing receiving recess is formed inside said projection of said second casing. 3. A gas compressor according to claim 2, wherein said driving shaft has a semispherical ball as a bearing at a central portion of said end thereof disposed in said working chamber, and said bearing disposed in said bearing receiving recess of said second casing is spaced from the center of said semispherical ball by at least l.7 times the distance between a central axis of said driven shaft and a central axis of said cylinder bore. 4. A gas compressor according to claim 3, wherein said bearing receiving recess has a depth of more than about 2 times the width of said bearing to be inserted therein and said bearing is inserted in the deepest position of said bearing receiving recess. 5. A gas compressor according to claim 3, wherein said driven shaft has an oil passage passing therethrough and said second casing has an oil passage formed therein communicating between said high pressure recess and said bearing receiving recess, whereby said semispherical ball is lubricated by lubrication oil supplied from said high pressure recess through said oil passages. 6. A gas compressor according to claim 3, wherein said float valve plate contacts the inside of said second casing through a seal ring disposed around said high pressure recess, thereby providing a high pressure chamber, and the outside of a peripheral portion of said float valve plate communicating with said low pressure recess. 7. A gas compressor according to claim 6, wherein said second casing has a groove formed around said high pressure recess for receiving said seal ring, an outside wall of said groove serving as a guide wall, and said float valve plate has a projection a little projecting, said projection being inserted in said groove and guided by said guide wall so as to sandwich said seal ring. 8. A gas compressor according to claim 3, wherein said driving shaft has a bevel gear around said semispherical ball and said driven shaft has a bevel gear engaged with said bevel gear of said driving shaft. 9. A gas compressor comprising: a first casing having a bottom and a side wall extending sidewise from one side of said bottom to form a working chamber; a driving shaft passing through said bottom of said first casing and carried rotatably thereby through a radial bearing, one end of said driving shaft being disposed in said working chamber and having a bearing secured thereon and a bevel gear formed around said bearing; a rotary plate, disposed in said working chamber, rotatably supported at a back side thereof by said bottom of said first casing through thrust bearings and secured to said driving shaft so as to be substantially perpendicular to said driving shaft, said rotary plate having a plurality of semispherical bearing portions on a front side thereof; a second casing secured to an open end of said first casing so as to close said working chamber, and having a bearing receiving recess in a central portion of the inside thereof, a high pressure recess communicating with a high pressure port and a low pressure recess communicating with a low pressure port, said second casing having a projection projecting outside and said bearing receiving recess being formed in the inside of said projection, a driven shaft inclined at a predetermined angle with respect to said driving shaft and rotatably supported by said bearing of said driving shaft and a bearing disposed in said bearing receiving recess of said second casing, said driven shaft having a bevel gear meshed with said bevel gear of said driving shaft; a cylinder block having a central hole and a plurality of cylinder bores formed therein equiangularly with each other so as to surround said central hole, said cylinder block receiving said driven shaft through said central hole and secured thereto; a plurality of pistons inserted in said cylinder bores, respectively, and connected to said rotary plate with piston rods of said pistons being coupled with said bearing portions of said rotary plate; and a float valve plate disposed between said cylinder block and said second casing to close said cylinder bores in which said pistons are in compression stroke, said float valve plate abutting on said second casing through a seal ring arranged around said high pressure recess forming a high pressure chamber communicating with one of said cylinder bores through a valve hole formed in said float valve plate, and being pressed against said cylinder block by a high pressure established in said pressure chamber. l0. A gas compressor according to claim 9, wherein said bearing disposed in said bearing receiving recess of said second casing is distant from said bearing secured to said end of said driving shaft by at least l.7 times the distance between the central axis of said driven shaft and the central axis of said cylinder bore. 11. A gas compressor according to claim 9, wherein said bearing receiving recess has a depth as twice as the width of said bearing inserted therein. 12. A gas compressor according to claim 9, wherein said driven shaft has an oil passage formed therein so as to pass therethrough and said second casing has an oil passage formed therein so as to fluidly connect said high pressure recess and said bearing receiving recess, whereby oil is supplied from said high pressure recess to said bearing provided on said end of said driving shaft. 13. A gas compressor according to claim 9, wherein said second casing has a guide wall formed along a groove for said seal ring around said high pressure recess and said float valve plate has a float projection guided by said guide wall of said second casing so that said seal ring is prevented from expanding outside.

Inventors: KANAMARU, HISANOBU, OKAZAKI, MASAHARU, SASAYA, KAZUSHI
Applicants: HITACHI, LTD.
Application year: 1987
Main classification: F04B27
IPC codes: F04B27