Abstract:
A gas compressor of the variable volume type having a rotary plate which is rotated to move recesses therein communicating with a compression chamber of a cylinder relative to communication ports formed in a front side block fixed to the one side of the cylinder so that the volume of the compression chamber may be made variable in accordance with the fast or slow running state of the gas compressor. The rotary plate is moved rotatably by means of a self-contained and self-actuated hydraulic cylinder which is driven by oil within the compressor in response to the intake pressure of the compressor&#39;s intake chamber.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a gas compressor to be used with a car cooler or air conditioner and, more particularly, to a gas compressor in which the volume of its compression chamber is made variable. 
     2. Description of the Prior Art 
     Usually, a gas compressor to be used for cooling the automobile or the like is arranged in parallel with an engine so that it may be driven through a V-belt by the crankshaft pulley of the engine, and it is connected to or disconnected from the driving force by means of an electromagnetic clutch which is disposed on the compressor side. 
     As a result, the volume of the gas compressor of the above-specified type is increased in proportion to the r.p.m. of the engine. This in turn causes the gas compressor to be driven at a high speed, in case the automobile runs at a high speed, thereby to relatively overcool the automobile compartment and to raise the shortcoming that the power consumption is also increased in proportion to the running speed. This tendency is serious 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 &#34;volume-variable type&#34; gas compressors in which the volume of the compression chamber for the coolant gas is varied in accordance of the compressor the driving speed thereof. 
     For example, the volume of the compression chamber can be made variable by controlling the opening of a bypass hole, which is formed in a position suitably displaced in the rotational direction of a rotor with respect to an intake port. 
     In the gas compressor of this type, the coolant gas, once confined in the compression chamber, is bypassed to an intake side after it has been compressed to some extent. Therefore, such a gas compressor has been noted to have an inferior compression efficiency and the drawback that the discharge temperature of the coolant gas rises especially at highspeed, i.e., small-volume run. 
     To overcome these shortcomings the gas intake compressor developed in recent years is of the type in which the intake capacity to be sucked in from an intake port of a front side block of the compressor is made variable by using a rotary plate as the front side plate, by forming this rotary plate with a recess communicating with the intake port, and by rotating the rotary plate a predetermined angle. In the gas compressors as developed, most have a means for controlling the rotary plate that are constructed such that the temperature of the air to be blown out of the automobile compartment or an evaporator is sensed by means of a thermostat so that the rotary plate may be turned by the drive of a motor attached to the compressor when the temperature drops to, or lower than, a set level of the thermostat. This raises certain defects in that the construction is complicated and large-sized due to the motor which is added. 
     For example, in U.S. Pat. No. 4,137,018, it is disclosed that a control plate is mounted between a cylinder and a front side block, and that the shaft 220 which gears with the control plate 200 (in the patent) drives the control plate 200. In this mechanism, however, another drive means for driving shaft 220 is required. It is not specifically described in the specification that this mechanism is controlled automatically. Provided that the control plate 200 is controlled automatically, the mechanism will be complicated on the whole, and will not be simplified and compact. 
     SUMMARY OF THE INVENTION 
     The present invention has been conceived in view of the background described above and provides a gas compressor of the so-called &#34;variable volume type&#34;, in which the volume of the compression chamber for confining and compressing a coolant gas is made variable in accordance with the high and low running speeds so that the volume of the compression chamber is controlled in accordance with the intake pressure of an intake chamber while a control mechanism therefor is simplified and also made compact. 
     In order to achieve the above-specified object, according to the present invention, there is provided a gas compressor with comprises: 
     a cylinder (4) formed into a substantially elliptic or round shape; 
     a front side block (5) in which a communicating port or ports (12) is formed, and a rear side block (6), the two blocks being fixed to the two sides of the cylinder; 
     a rotor (9) fitted rotatably in a cylinder chamber (13) which is defined by the cylinder and the two side blocks, and carrying a plurality of vanes (8) mounted to protrude and retract radially from the rotor; 
     a rotary valve plate (10) borne rotatably within a predetermined angular range in the inner face of the front side block; 
     an intake chamber (15) which is defined between a front head (3) and the front side block (5); 
     and driving means (21) for rotatably moving the rotary valve plate, being driven by oil in the compressor in accordance with the intake pressure of the intake chamber, and rotatably moving the rotary valve plate to move an intake port or ports (16) communicating with the cylinder chamber (13) relative to the communicating port (12) so that the volume of a compression chamber may be made variable in accordance with the running state of the gas compressor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal section showing the overall construction of the gas compressor according to the present invention; 
     FIG. 2 is a longitudinal section showing a first embodiment of the gas compressor according to the present invention; 
     FIG. 3 is a transverse section showing the rotating mechanism of the first embodiment; 
     FIG. 4 is a longitudinal section taken along line A--A of FIG. 3; 
     FIG. 5 is a transverse section showing the gas compressor when in the low-speed run; 
     FIG. 6 is a transverse section showing the gas compressor when in the high-speed run; and 
     FIG. 7 is a longitudinal section showing a second embodiment of the gas compressor according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     FIGS. 1 to 4 show a first embodiment of the gas compressor to which the present invention is applied. 
     This gas compressor is constructed of a compressor body 1, an open ended type casing 2 enclosing the body 1 gastight, and a front head 3 fixed to the open end face of said casing 2. 
     The aforementioned compressor body 1 is comprised of a cylinder 4 formed to have a generally elliptic inner periphery (see FIGS. 5 and 6), and front and rear side blocks respectively, 5 and 6, fixed to the two sides of cylinder 4. In the elliptic chamber 13 of the cylinder thus formed, there is rotatably fitted in a horizontal direction a solid, cylindrical rotor 9 which is integral with a rotor shaft 7 and carries on its outer circumference five vanes 8 enabled to protrude and retract radially from the rotor 9 (see FIGS. 5 and 6. 
     On the inner face of the aforementioned front side block 5, there is borne displaceable valve means in the form of a generally disk-shaped rotary valve plate 10 which is made relative to side block 5 angularly displaceable within a predetermined angular range. 
     Moreover, the aforementioned rotary plate 10 is formed in its peripheral edge with a valve opening or recess 11, through which coolant gas communication is provided between communication holes 12 in the front side block 5 and cylinder compression chamber 13. 
     In operation, as the intake pressure drops when the gas compressor is running at a high speed, the recess 11 of the rotary plate 10 is moved clockwise to reduce the volume thereof and to raise the intake pressure. Due to a rise in intake pressure in a low-speed run, on the other hand, the rotary valve plate 10 can rotate so that the recess 11 may move counterclockwise to maximize the volume. The means for driving the rotary plate 10 will be described hereinafter. 
     Thus, when the motor 9 is rotationally driven by rotor shaft 7 through conventional drive means (not shown), a coolant gas, which is introduced under a low pressure from an intake port 14 formed in the front head 3 into an intake chamber 15, is sucked, as indicated by solid arrows in FIG. 1, into the cylinder chamber 13 via intake ports 16 and both the communication holes 12 formed in the front side block 5 in diametrically opposed positions of 180 degrees and (see FIG. 3). Then, the gas is compressed to a high pressure and is supplied through a discharge port 17 and a discharge valve 18 (see FIGS. 5 and 6) and further through a communication hole, which 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 with a phase difference of 90 degrees from the aforementioned communication holes 12, to an oil separator 19 which is formed at the back of said block 6, until it is discharged, as indicated by broken arrow in FIG. 1, from the rear space of the casing 2 to the outside through a discharge port 20. Denoted at numeral 35 appearing in the drawing is oil under a high pressure, which is used in the present invention as a fluid drive source for driving the rotary plate 10. 
     Next, an essential portion of the present invention, i.e., the drive means for driving the rotary valve plate 10, will be described, especially with reference to FIGS. 2 and 4. 
     First, there is arranged in the front head 3 a hydraulic drive means piston 21 which is caused to protrude and retract in a direction perpendicular to the axis of the compressor. The hydraulic piston member 21 has front head portion 21a open to and communicating with the intake chamber 15 which is defined by said front head 3 and the front side block 5. At an intermediate portion of the piston member 21, there is formed a gap or gap chamber 22 into which is introduced the oil 35 at the side of the compressor via an oil passage (not shown) formed in the front head 3 and communicating with oil passage 23a, 23b, 23c. The rear portion of the piston 21 communicates with the outside ambient atmosphere. Front head 3 is arranged with pressure-responsive control valve means comprising a spool valve member 24 for opening and closing the oil passage. The spool valve member 24 is constructed of a cylinder 25 which is enabled to protrude and retract and which has its front end opened to and communicating with the intake chamber 15 and its rear end opened to the outside ambient atmosphere, and a spring 26 which is fitted in cylinder 25 and which has a predetermined spring force. Moreover, the spool valve member 24 is caused to move back and forth in front head 3 by the force difference between the intake pressure in the intake chamber 15 and the force of the spring 26 so that with the back and forth movement of the spool valve a communication port or groove 27a may accordingly alternately establish communication between oil passage 23a and 23b. Moreover, the hydraulic piston 21 is formed at its head end with an engagement portion 28, in which is loosely fitted the leading end of a drive pin 29 anchored upright from the rotary valve plate 10 and projecting into the intake chamber 15. Drive pin 29 extends through a cam groove 30 which is formed in an arcuate shape in the front side block 5. 
     Next, the operations of the rotary plate 10 will be described especially with reference to FIGS. 3 to 6. 
     In case the intake pressure of the intake chamber 15 is equal to or higher than a predetermined level, the hydraulic piston 21 and the spool valve member 24 will be located in the positions shown in FIG. 3, and the rotary valve plate 10 is located in the position shown in FIG. 5. In this state, the pressure of the gas in the intake chamber 15 acts on a working area of the front portion of the piston 21 to urge the piston 21 rearwardly. When the compressor comes into its highspeed running ranges, the intake pressure in the intake chamber 15 drops to a level lower than the predetermined level so that the spool valve member 24 has its cylinder 25 protruding into chamber 15 in the direction indicated by the arrow in FIG. 3. At this point the intake pressure in the intake chamber 15 is weaker than the biasing force of the biasing spring 26 in the cylinder 25, thus providing communication between the oil passages 23a and 23b via the communication port or groove 27a. As a result, the oil 35 at the side of the compressor has its speed controlled to a suitable value, while being throttled via oil passage 23 (i.e., 23a and 23b) by the axial clearance of the hydraulic piston 21, and the oil pressure is applied to a working area of the intermediate portion of the piston 21 via the gap chamber 2 so that the hydraulic piston 21 is caused to protrude by that oil pressure to push the drive pin 29 fitted loosely in the engagement portion 28 of the hydraulic piston 21 in the direction, as indicated by arrow in FIG. 3. As drive pin 29 rotates on its axis along the cam groove 30, the rotary valve plate 10 also rotates or angularly displaces between the positions shown in FIG. 5 (low speed) and FIG. 6 high speed because it is made integral with the drive pin 29. 
     Thus, when in a high-speed run, i.e., in case the intake pressure in the intake chamber 15 drops, the rotary valve plate 10 is caused to angularly displace by the operations described above thereby reducing the volume confining the coolant in the compression chamber so that the intake pressure can be held at a constant level (which may preferably be about 2 Kg/cm 2 ). 
     If intake pressure in the intake chamber 15 exceeds a predetermined level, the cylinder 25 is caused to retract to establish communication of an oil passage 23c with the communication groove 27b so that the oil fed to the gap 22 of the hydraulic piston 21 is returned to a lower-pressure chamber to thereby retract the hydraulic piston 21. As a result, the coolant confining volume of the compression chamber is enlarged. 
     At this time, the spool valve member 24 has already retracted to the position shown in FIG. 3, while blocking the communication between the oil passages 23a and 23b, so that no oil is fed to the hydraulic piston 21. Member 36 appearing in the drawing denotes a stopper for limiting the stroke of the spool valve 24. 
     Denoted at numeral 31 is which a thrust bearing which fitted on one side of the rotary plate 10 for smoothing the rotational motions of the same. 
     Next, a second embodiment of the gas compressor according to the present invention will be described with reference to FIG. 7. 
     The second embodiment is identical to the foregoing embodiment except for the drive means for the rotary valve plate 10, and the following description is directed only to the drive means. 
     In the second embodiment, a hydraulic piston 21&#39; is directed like the foregoing embodiment at a right angle with respect to the axis of the compressor and similarly has one end 21a opened to the intake chamber. Moreover, this hydraulic piston 21&#39; has its side formed with a gear rack portion 32, with which is meshed by an intermediate pinion 33. Pinion 33 is borne rotatably in a hole (not shown) of front side block 5&#39; while extending therethrough. In a rotary valve plate 10&#39; at the side of the front side block 5&#39;, on the other hand, there is concentrically borne plate pinion 34 which has a smaller diameter than that of the rotary valve plate 10&#39;. Plate pinion 34 meshes with the aforementioned intermediate pinion 33. 
     As a result, responsive to the difference between the intake pressure in the intake chamber 15 and the force of the spring 26 of the spool valve member 24, the hydraulic piston 21&#39; is caused to protrude and retract so that the intermediate pinion 33 meshing with gear the rack portion 32 is accordingly rotated thereby. Responsive to these rotations of the intermediate pinion 33, the plate pinion 34 is also rotated so that the rotary valve plate 10&#39; is in turn angularly displaced a predetermined angle because the plate 10&#39; is made integral with the plate pinion 34. 
     As in the first embodiment, the intake portion is moved so that the volume of the compression chamber of the coolant gas can be made continuously variable to hold the intake pressure at a constant level. 
     As has been described hereinbefore, the gas compressor according to the present invention is directed to a variable volume type, which is always run at an optimum volume. This is accomplished by rotating the rotary plate borne on the inner side of the front side block in a manner 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 due to the running condition thereby controlling the effective volume for the compression in the cylinder chamber. For this operation, the hydraulic piston is moved back and forth through operation the spool valve, which is caused to differentiate in accordance with the intake pressure in the intake chamber, so that the rotary plate may be rotated by the protrusion and retraction of the hydraulic piston. As a result, it is possible to provide a remarkably practical gas compressor which can be freed from the problem of the rise in the discharge temperature of the coolant gas when it is run at small volume, as has been experienced by the volume variable type gas compressors of the prior art. Additionally, the present gas compressor has its construction made simpler than that in which the rotary plate is controlled by the system, and the present compressor can effect the control of the rotary plate compactly because the control does not resort to a motor attached to the compressor.