VARIABLE VOLUME GAS COMPRESSOR

Abstract: A variable volume gas compressor comprising a compressor body (1) having an intake chamber (15), a cylinder chamber (13), and an angularly movable member (10) having gas passage means (11,16) therein; the gas passage means (11,16) being adapted to control communication between the intake chamber (15) and the cylinder chamber (13), and the effective volume of the gas passage means(11,16) altering as a result of angular movement of the angularly movable member (10) so as to alter the effective volume of a compression space (8 a ); compression means (8,9) in the cylinder chamber (13) for compressing a gas in the compression space (8 a ); and drive means (21,29) for effecting angular movement of the angularly movable member (10) characterised in that the drive means (21,29) are fluid-operated drive means which effect angular movement of the angularly movable member (10) in dependence upon the intake pressure in the intake chamber (15).

Description: The present invention relates to a variable volume gas compressor and, although it is not so restricted, it relates more particularly to a gas compressor for use with a car cooler. It has been known to use a gas compressor for cooling an automobile or the like, the gas compressor being arranged in parallel with the engine of the automobile so that it may be driven through a V-belt by the crankshaft pulley of the engine. The gas compressor has been connected to or disconnected from the drive thereto by means of an electromagnetic clutch which is disposed at the side of the compressor. As a result, the volume of a gas compressor of the kind described above depends upon the rotational speed of the engine. This in turn means that the gas compressor will be driven at a high speed if the automobile runs at a high speed, with the result that the passenger compartment of the automobile is overcooled and the power consumption is increased in proportion to the running speed. This is a serious drawback, especially in a gas compressor of the rotary type. In order to eliminate this defect, there have been proposed a variety of the so-called "volume-variable type" gas compressors in which the volume of the compression chamber of a coolant gas is varied in accordance with the driving speed thereof. For example, it has been proposed that the volume of the compression chamber should be made variable by controlling the opening of a bypass passage which is formed in a rotor so that it may be angularly displaced with respect to an intake port. In a gas compressor of this type, however, the coolant gas disposed in the compression chamber is by-passed to an intake side of the compressor after it has been compressed to some extent. Therefore, the gas compressor has rather poor compression efficiency and there is the drawback that the discharge temperature of the coolant gas rises especially at high-speed, i.e. during small-volume operation of the compression chamber. A gas compressor has also been suggested in which the capacity of the intake to be drawn in from an intake port of a front side block of the compressor is made variable by mounting a rotary plate on a front side plate of the compressor, and by forming this rotary plate with a recess which communicates with the intake port, the rotary plate being rotatable through a predetermined angle. In such a gas compressor, however, the angular position of the rotary plate depends mainly upon the temperature of the air which is to be blown out of the automobile compartment or on the temperature of an evaporator, such temperature being sensed by means of a thermostat. The rotary plate may thus be turned by the drive of an additional motor attached to the compressor when the temperature drops to or lower than a set level of the thermostat. This construction, however, is large and complicated because of the provision of the additional motor. For example, in U.S. Patent Specification No. 4,137,018, it is disclosed that a control plate is mounted between a cylinder and a front side block, and that a shaft 220 which is in gear with a control plate 200 drives the latter. In this mechanism, however, another drive means for driving the shaft 220 is required. There is no suggestion in this specification that this mechanism should be controlled automatically. Even if the control plate 200 were controlled automatically, however, the mechanism would be complicated and could not be simplified and made compact. According, therefore, to the present invention, there is provided a variable volume gas compressor comprising a compressor body having an intake chamber, a cylinder chamber, and an angularly movable member having gas passage means therein; the gas passage means being adapted to control communication between the intake chamber and the cylinder chamber, and the effective volume of the gas passage means altering as a result of angular movement of the angularly movable member so as to alter the effective volume of a compression space; compression means in the cylinder chamber for compressing a gas in the compressor space; and a drive means for effecting angular movement of the angularly movable member characterised in that the drive means are fluid-operated drive means which effect angular movement of the angularly movable member in dependence upon the intake pressure in the intake chamber. Thus in a variable volume gas compressor according to the present invention, when used with a car cooler, the volume of its compression space for confining and compressing a coolant gas may be made variable in accordance with the high and low running speeds of the car so that the volume of the compression space may be controlled in accordance with the intake pressure of the intake chamber. Preferably, the angularly movable member is always set by the drive means in an angular position such that the gas entering the compression space is at a substantially constant pressure. The drive means preferably comprises a fluid-operated piston which is slidably mounted in a part of the compressor body and which is connected to the angularly movable member by connecting means, and valve means for controlling the fluid pressure acting on the fluid-operated piston in dependence upon the intake pressure in the intake chamber, one end of the fluid-operated piston being open to the pressure in the intake chamber, the said fluid pressure urging the fluid-operated piston towards the intake chamber. The connecting means may comprise a pin fixed to the angularly movable member, the pin being loosely mounted in engagement means provided on the fluid-operated piston. Alternatively, the connecting means may comprise a rack and pinion drive between the fluid-operated piston and the angularly movable member. Thus the rack may be formed on one side of the fluid-operated piston, the rack meshing with an intermediate pinion which meshes with a further pinion fixed concentrically to the angularly movable member. The valve means may comprise a hollow piston which is slidably mounted in a part of the compressor body, the hollow piston containing a spring which urges the hollow piston towards the intake chamber, one end of the hollow piston being open to the pressure in the intake chamber, the hollow piston controlling the flow of the pressure fluid to and/or from the fluid-operated piston. The compression means may comprise a rotor which is rotatably mounted in the cylinder chamber and which has radially movable vanes which are engageable with the wall of the cylinder chamber. The compressor body preferably has a cylinder block which is disposed between side blocks, said cylinder block and side blocks collectively defining the cylinder chamber, the angularly movable member being constituted by a plate which is mounted for angular movement on one of the side blocks. The intake chamber is preferably provided on the side of said one side block remote from the cylinder chamber, the said one side block having a port therein for establishing communication between the intake chamber and an intake port in the plate which communicates with the cylinder chamber. The invention is illustrated, merely by way of example, in the accompanying drawings, in which:- Figure 1 is a longitudinal section showing the overall construction of a first embodiment of a gas compressor according to the present invention, Figure 2 is a transverse section showing the first embodiment of the gas compressor according to the present invention, Figure 3 is a longitudinal section showing a portion of the first embodiment, Figure 4 is a longitudinal section taken along line A-A of Figure 3, Figure 5 is a longitudinal section showing a portion of the gas compressor of Figures 1-4 when used in a low-speed run, Figure 6 is a longitudinal section similar to Figure 5 but showing the gas compressor when used in a high-speed run, and Figure 7 is a transverse section showing a second embodiment of a gas compressor according to the present invention. Terms such as "front", "rear", "right", "left", "horizontal", "clockwise" and "counter-clockwise", as used in the description below, are to be understood to refer to directions as seen in the accompanying drawings. Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figures 1 to 6 show a first embodiment of a gas compressor of variable volume according to the present invention. The gas compressor of Figures 1-6 comprises a compressor body 1, a casing 2 which is open at one end, and a front head 3 which is fixed to the open end face of the casing 2. The compressor body 1 is enclosed in a gas-tight manner within the casing 2 and front head 3. The compressor body 1 is composed of a cylinder 4 which is formed to have a generally elliptical inner periphery in cross section (although it may, if desired be circular in cross-section) and front and rear side blocks 5 and 6 which are respectively fixed to the opposite sides of the cylinder 4. In the elliptical cross sectional chamber 13 of the cylinder 4 thus formed, there is rotatably mounted a solid, cylindrical rotor 9 which is rotatable about an horizontal axis. The rotor 9 is fixed to or is integrated with a rotor shaft 7 and carries on its outer circumference five vanes 8 which are radially movable towards and away from the said outer circumference. The vanes 8, which engage the wall of the cylinder chamber 13, may thus be moved into and out of the compression space 8 a provided partly in the cylinder chamber 13. On the inner face of the front side block 5, there is mounted a generally disk-shaped rotary plate 10 which is capable of being moved angularly within a predetermined angular range. The rotary plate 10 is formed at its periphery with recesses 11 and is also formed with an intake port 16 through which communication is provided between communication holes 12 of the front side block 5 and the cylinder chamber 13. Since the intake pressure drops when the gas compressor is running at a high speed, the rotary plate 10 (by means described below) moves clockwise so that the recesses 11 and intake port 16 reduce the effective volume of the compression space 8 a and thus raise the intake pressure of the cylinder chamber 13. Due to a rise of the intake pressure in a low-speed run, on the other hand, the rotary plate 10 can rotate so that the recesses 11 and intake port 16 may move counter-clockwise to maximize the said volume. Thus, when the rotor 9 is rotated, a coolant gas, which is introduced under a low pressure from an intake port 14 formed in the front head 3 is sucked into an intake chamber 15, as indicated by solid arrows in Figure 1 and thus into the cylinder chamber 13 via both the communication holes 12, which are formed in the front side block at diametrically opposed positions, and the intake port 16. The gas is then compressed to a high pressure and is supplied through a discharge port 17 (Figures 5 and 6 ) and a discharge valve 18 and further through a communication hole. The latter extends into the gap between the cylinder 4 and the inner periphery of the casing 2 and is formed in the rear side block 6 at an angle of 90 degrees to the communication holes 12, so as to extend to an oil separator 19 which is formed at the back of the block 6. The compressed gas is discharged, as indicated by a broken line in Figure 1, from the rear space of the casing 2 to the outside through a discharge port 20. The compressor body 1 is provided with an oil reservoir 35 the oil in which is maintained under a high pressure by means not shown, the oil being used as a drive source for driving the rotary plate 10. The drive means for driving the rotary plate 10 will now be described with reference to Figures 2 and 4. An hydraulic piston 21 is slidably mounted in a cylindrical portion 3 a of the front head 3 so that it can be moved towards and away from the axis of the compressor in a direction perpendicular to the said axis. The hydraulic piston 21 has a head 21 a disposed within the intake chamber 15, the latter being defined by the front head 3 and the front side block 5. The hydraulic piston 21 has a shoulder 21 b which defines with the cylindrical portion 3 a a gap 22 into which is introduced the oil from the reservoir 35 at the side of the compressor via an oil passage 23 formed in the front head 3. The head 3 is provided with a spool valve 24 for opening or closing the oil passage 23. The spool valve 24 comprises a hollow piston 25 which is slidably mounted in a cylindrical portion 3 b of the front head 3 so as to be movable towards and away from the intake chamber 15. One end of the spool valve 24 is open to the intake chamber 15, the other end thereof being open to the outside. A spring 26 is disposed in the hollow piston 25 so as to urge the latter towards the intake chamber 15 with a predetermined spring force. The hollow piston 25 of the spool valve 24 is caused to move back and forth in the front head 3 in accordance with the difference between the intake pressure in the intake chamber 15 and the force of the spring 26. This back and forth movement of the hollow piston 25 causes an annular communication groove 27 a therein to be moved into and out of a position in which it establishes communication between portions 23 a and 23 b of the oil passage 23. The hydraulic piston 21 is formed at its leading end with an engagement portion 28 in which is loosely fitted the leading end of a drive pin 29. The latter is fixed in the rotary plate 10 so as to extend at right angles therefrom and into the intake chamber 15. The drive pin 29 extends through a cam groove 30 which is formed in an arcuate shape in the front side block 5. The operation of the rotary plate 10 will now be described with reference to Figures 3 to 6. When the intake pressure of the intake chamber 15 is equal to or higher than a predetermined level, the hydraulic piston 21 and the hollow piston 25 of the spool valve 24 are located in the positions shown in Figure 3, and in this case the rotary plate 10 will be located in the position shown in Figure 5. When the compressor comes into a high-speed running range, the intake pressure in the intake chamber 15 first drops to a level lower than the predetermined level so that the hollow piston 25 of the spool valve 24 moves in the direction indicated by an arrow X. When the intake pressure in the intake chamber 15 becomes weaker than the force of the spring 26 in the hollow piston 25, there will be communication between the portions 23 a and 23 b of the oil passage 23 via the communication groove 27 a . As a result, the oil which is under pressure in the oil reservoir 35 and which is throttled in the course of passing through the oil passage 23 (i.e. through the portions 23 a and 23 b of the oil passage 23) passes to the axial clearance between the hydraulic piston 21 and the cylindrical portion 3 a to fill up the gap 22 at the back of the hydraulic piston 21. The hydraulic piston 21 is thus caused to move towards the intake chamber 15 by the oil pressure, at a speed which is controlled to a suitable value, so as to push the drive pin 29 which is fitted loosely in the engagement portion 28 of the hydraulic piston 21 in the direction indicated by an arrow Y. The drive pin 29 rotates on its axis while passing along the cam groove 30 so that the rotary plate 10 also rotates to the position shown in Figure 6 because it is secured to (or integral with) the drive pin 29. Thus, when an automobile provided with a compressor as shown in Figures 1-6 is in a high-speed run, i.e. when the intake pressure in the intake chamber 15 drops, the rotary plate 10 is caused to rotate by the operations described above so as to reduce the effective volume of the coolant which is confined in the compression space 8 a so that the intake pressure can be held at a constant level (which may preferably be about 2 Kg/cm²). If the intake pressure in the intake chamber 15 exceeds a predetermined level, the hollow piston 25 is caused to retract so as to establish communication between an oil passage 23 c and a communication groove 27 b . The oil fed to the gap 22 is thus returned to a pressure chamber (not shown), thus enabling the hydraulic piston 21 to retract. As a result, the coolant confining volume of the compression space is enlarged. At this time, the hollow piston 25 of the spool valve 24 has already retracted to the position shown in Figure 3, while blocking the communication between the oil passages 23 a and 23 b , so that no oil is fed to the gap 22. A stopper 36 is provided for controlling the stroke of the hollow piston 25 of the spool valve 24. A thrust bearing 31 is mounted on one side of the rotary plate 10 for smoothing rotational motion of the latter. As will be appreciated, in operation the angular position of the rotary plate 10 is continuously set by the intake pressure of the intake chamber 15 so as to set the intake port 16, which communicates with the cylinder chamber 13, relative to the communication holes 12 which are formed in the front side block 5 so that the effective volume of the compression space 8 a varies in accordance with the state of operation of the gas compressor. By this means, the rotary plate 10 is always set such that the gas entering the compression space 8 a is at a substantially constant pressure. Next, a second embodiment of a gas compressor according to the present invention will now be described with reference to Figure 7. The construction of Figure 7 is generally similar to that of Figures 1-6 and for this reason will not be described in detail, like reference numerals indicating like parts. In the embodiment of Figure 7, however, a hydraulic piston 21' is employed which, as in the embodiment of Figures 1-6, extends at right angles to the axis of the compressor and has one end thereof open to the intake chamber 15. The hydraulic piston 21' has its side formed with a rack portion 32 which meshes with an intermediate pinion 33. The intermediate pinion 33 is rotatably mounted in a hole which extends through a front side block 5'. On a rotary plate 10' at the side of the front side block 5', there is concentrically mounted a pinion 34 which has a smaller diameter than that of the rotary plate 10'. The pinion 34 meshes with the intermediate pinion 33. As a result, the position of the piston 21' is set by the difference between the intake pressure of the intake chamber 15 and the force of the spring 26 of the spool valve 24. Movement of the piston 21' causes the intermediate pinion 33 which meshes with the rack portion 32, to be correspondingly rotated. Such rotation of the intermediate pinion 33, moreover, causes rotation of the pinion 34 so that the rotary plate 10' is rotated through a predetermined angle because the plate 10' is made integral with the pinion 34. As in the embodiment of Figures 1-6, an intake port (not shown) in the rotary plate 10' is moved so that the volume of the compression space for the coolant gas can be made continuously variable so as to hold the intake pressure at a constant level. The gas compressors shown in the drawings are of the variable volume type which can always be run at an optimum volume by rotating the rotary plate 10, 10' mounted on the inner side of the front side block 5, 5' so as to hold the intake pressure at a constant level at all times in accordance with the change in the intake pressure of the intake chamber 15 due to the running conditions, thereby to control the effective volume for the compression in the cylinder chamber 13. For this operation, the hydraulic piston 21, 21' is moved back and forth by the operation of the spool valve 24 which is responsive to the intake pressure in the intake chamber 15 so that the rotary plate 10, 10' is rotated by movement of the hydraulic piston 21, 21'. As a result, it is possible to provide a remarkably practical gas compressor which obviates the problem of the rise in the discharge temperature of the coolant gas when operating in small volume conditions, as has been experienced by the variable volume type gas compressor of the prior art. The construction of a gas compressor according to the present invention can be made simpler than that in which the rotary plate is controlled by a temperature responsive system. Moreover, the control of the rotary plate can be compact because the control does not comprise a motor attached to the compressor.

Claims: 1. A variable volume gas compressor comprising a compressor body (1) having an intake chamber (15), a cylinder chamber (13), and an angularly movable member (10) having gas passage means (11,16) therein; the gas passage means (11,16) being adapted to control communication between the intake chamber (15) and the cylinder chamber (13), and the effective volume of the gas passage means (11,16) altering as a result of angular movement of the angularly movable member (10) so as to alter the effective volume of a compression space (8a); compression means (8,9) in the cylinder chamber (13) for compressing a gas in the compression space (8a); and drive means (21,29) for effecting angular movement of the angularly movable member (10) characterised in that the drive means (21,29) are fluid-operated drive means which effect angular movement of the angularly movable member (10) in dependence upon the intake pressure in the intake chamber (15). 2. A compressor as claimed in claim 1 characterised in that the angularly movable member (10) is always set by the drive means (21,29) in an angular position such that the gas entering the compression space (8a) is at a substantially constant pressure. 3. A compressor as claimed in claim 1 or 2 characterised in that the drive means (21,29) comprises a fluid operated piston (21) which is slidably mounted in a part (3) of the compressor body (1) and which is connected to the angularly movable member (10) by connecting means (28-30), and valve means (24) for controlling the fluid pressure acting on the fluid-­ operated piston (21) in dependence upon the intake pressure in the intake chamber (15), one end of the fluid-operated piston (21) being open to the pressure in the intake chamber (15), the said fluid pressure urging the fluid-operated piston (21)towards the intake chamber (15). 4. A compressor as claimed in claim 3 characterised in that the connecting means (28-30) comprises a pin (29) fixed to the angularly movable member (10), the pin (29) being loosely mounted in engagement means (28) provided on the fluid-operated piston (21). 5. A compressor as claimed in claim 3 characterised in that the connecting means comprises a rack (32) and pinion (33) drive between the fluid-operated piston (21) and the angularly movable member (10'). 6. A compressor as claimed in claim 5 characterised in that the rack (32) is formed on one side of the fluid-operated piston (31), the rack (32) meshing with an intermediate pinion (33) which meshes with a further pinion (34) fixed concentrically to the angularly movable member (10'). 7. A compressor as claimed in any of claims 3-6 characterised in that the valve means (24) comprises a hollow piston (25) which is slidably mounted in a part (3) of the compressor body (1), the hollow piston (25) containing a spring (26) which urges the hollow piston (25) towards the intake chamber (15),one end of the hollow piston (25) being open to the pressure in the intake chamber (15), the hollow piston (25) controlling the flow of the pressure fluid to and/or from the fluid-operated piston (21). 8. A compressor as claimed in any preceding claim characterised in that the compression means (8,9) comprises a rotor (9) which is rotatably mounted in the cylinder chamber (13) and which has radially movable vanes (8) which are engageable with the wall of the cylinder chamber (13). 9. A compressor as claimed in any preceding claim characterised in that the compressor body (1) has a cylinder block (4) which is disposed between side blocks (5,6), said cylinder block (4) and side blocks (5,6) collectively defining the cylinder chamber (13), the angularly movable member being constituted by a plate (10) which is mounted for angular movement in one of the side blocks (5,6). 10. A compressor as claimed in claim 9 characterised in that the intake chamber (15) is provided on the side of said one side block (5) remote from the cylinder chamber (13), the said one side block (5) having a port (12) therein for establishing communication between the intake chamber (15) and an intake port (16) in the plate (10) which communicates with the cylinder chamber (13). 11. A gas compressor of variable volume comprising: a cylinder (4) formed into a substantially elliptical or round shape; a front side block (5), in which a communicating port (12) is formed, fixed to one side of said cylinder and a rear side block (6) fixed to the other side; a rotor (9) fitted rotatably in a cylinder chamber (13) which is defined by said cylinder (4) and said two side blocks (5,6), and carrying a plurality of vanes (8) enabled to protrude and retract radially thereof; a rotary plate (10) borne rotatably within a predetermined angular range on the inner face of said front side block (5); an intake chamber (15) which is defined between a front head (3) and the front side block (5); driving means (21) for moving rotatably said rotary plate (10), the driving means (21) being driven by oil within said compressor in accordance with the intake pressure of said intake chamber (15) and the driving means (21) moving rotatably said rotary plate (10) to move an intake port (16) communicating with said cylinder chamber (13) relative to said communicating port (12)(formed in the front side block) so that the volume of a compression chamber (8a) may be made variable in accordance with the running state of said gas compressor.

Inventors: ASAI, JUNICHI C/O SEIKO SEIKI K.K., KOBAYASHI, TAKESHI C/O SEIKO SEIKI K.K.
Applicants: SEIKO SEIKI KABUSHIKI KAISHA
Application year: 1986
Main classification: F04C29
IPC codes: F04C28, F04C18