JPH0260874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a helical screw type compressor that allows liquid to flow in the axial direction. The present invention relates to a compressor comprising means for controlling the compressor.

BACKGROUND OF THE INVENTION Axial flow helical screw compressors having means for substantially equalizing the pressure of fluid being discharged with the pressure of fluid in the discharge region are disclosed in Lysholm's Patent No. 2,519,913 and Whitfield's Patent No.
No. 3,151,806 and Shaw Reissue Patent No. 29,283.

Schibbye axially displaceable slide valve for adjusting the capacity of screw compressors
Patent No. 3314597 by Mr. Kocher et al.
Disclosed in No. 3527548.

Shaw patent No. 4,222,716 discloses a helical screw rotary compressor having a slide valve member for controlling an output port and a shiftable cylindrical valve member disposed within the slide valve member to vary volumetric capacity. Tsusa is disclosed.

Shaw Reissue Patent No. 29,283 discloses a compressor having a displacement control slide valve member above the rotor and an undercompression/overcompression control slide below the rotor.

No. 4,249,866 to Shaw discloses a compressor having a slide valve member and condition responsive means for controlling its position.

Mr. Szymaszek's Patent No. 3924972 and No.
No. 4080110 describes state sensing and slide position;
Compressor slide valve members are disclosed whose position is controlled in response to circuitry that includes sensing of other parameters.

The internal compression ratio does not match the input and output compression ratios because the input and output gases affect the system variables and the internal gas is confined within the housing of varying dimensions. It must also be considered that system input and discharge pressures are sensed beyond the movement of the slide valve. Therefore, one of the objects of the present invention is to match the internal compression ratio of the compressor to the input and output compression ratios to improve efficiency.

Another object of the invention is to obtain maximum efficiency by:
By always obtaining the optimum position for the two parts of the compound valve (slide valve and slide stopper) where the internal compression ratio is the same as the external compression ratio, and simultaneously adjusting the capacity of the compressor according to the system situation. By controlling the position of the part. This purpose is achieved by detecting four variables, namely the position of each of the two parts of the compound valve, the suction pressure and the discharge pressure, and by feeding these values to the computer and according to a predetermined program of the computer. This is done by controlling the position of two parts of the compound valve.

Structure of the Invention The present invention provides an input/output method for inputting the internal compression ratio of a compressor.
The present invention relates to a control means for controlling the capacity of a compressor while matching the output compression ratio. this is,
This is achieved by mounting the two slides on the same axis and below the rotor so that their combined effective length exceeds the effective length of the rotor. This allows the end of one slide in the discharge area to be positioned to influence the compression ratio, and the spacing between the two slides to vary to provide the desired capacity. The physical position of each slide is monitored as well as the input and output pressures,
These four variables are sent to an electrical network with a computer programmed to programmatically control the position of the slide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, a helical screw compressor 10 includes a central rotor casing 11 and an input casing 1 connected in sealing relation to each other.
2 and an output section casing 13. The rotor casing has intersecting bores 15 and 16;
These provide a working space for intermeshed male and female helical rotors or screws 18 and 19, which are mounted for rotation about parallel axes by suitable bearings.

The rotor 18 includes a bearing (not shown) in the output part casing 13 and an input part casing 1.
The shaft 20 is rotatably mounted on a shaft 20 supported on a bearing 22 within the shaft 20. A shaft 20 extends outwardly from the output casing for connection to a motor (not shown) via a suitable coupling (not shown).

The compressor has an input passage 25 in the input casing 12, which communicates with the working space through a port 26. The discharge channel 28 in the output casing 13 is connected to ports 29 (at least one of which
part (in the output casing 13) communicates with the working space.

In the example considered here, in a horizontally oriented machine, the input ports 26 are primarily above the horizontal plane passing through the axis of the rotor, and the output ports 29 are primarily below this horizontal plane.

Centrally located below the bores 15 and 16 and having parallel axes is a longitudinally extending cylindrical recess 30 that communicates with both the input and output ports. ing.

Mounted for sliding movement within recess 30 is a composite valve member including a slide valve 32 and its cooperating member or slide stop 33. The inner surface 35 of the slide valve and the inner surface 36 of the slide stop face the outer periphery of the rotors 18 and 19 within the rotor casing 11.

The right end (as viewed in FIG. 1) of the slide valve has an opening 38 on its upper surface, which forms a radial port communicating with the output port 29. The left end 39 of the slide valve is flattened or shaped as desired to fit the right end 40 of the slide stop and the recess 30 is formed into bores 15 and 16 by engagement of the two adjacent ends of the slide valve and the slide stop. It has become sealed since then.

The slide valve has an internal bore 42 and a head 43 at one end thereof. rod 4
4, one end of which is fixed to the head 43 by the fixing means 45.
A rod 44 extends through the head and is connected at its other end to a piston 46. The piston is mounted for reciprocating movement within the body 47 of a cylinder 48, which is connected to the input casing 12 and extends axially therefrom. A cover or end plate 50 is attached to the outer end of cylinder 48. Input part casing 12
is connected to cylinder 48 by an input section cover 51 that receives a reduced diameter end 52 of cylinder 48 .

Mounted inside the input section cover 51 is a sleeve 54 having a partition wall portion 55 at one end.
, which extends longitudinally towards the rotor casing. The slide stopper 33 is located at the end 4
It has a head 56 ending in 0, which has an angled slot 57 on its underside, which slopes upwardly from left to right as viewed in the drawing. The axial length of the slot is sufficient to provide the desired maximum movement of the slide stop. From its head, the slide stop has a main portion 58 which is slidably received within the sleeve 54. At the other end of the slide stop, the piston 60 is fitted with suitable fixing means 61.
is fixed.

A fixed bulkhead 62 is fixed to the cylinder 48 centrally between its ends, which defines an outer compartment 64 within which the piston 46 moves;
It is divided into an internal compartment 66 in which the piston 60 moves.
Cylinder 48 has fluid ports 67 and 68 proximate each side of septum 62, which communicate with compartments 64 and 66, respectively. A fluid port 70 is provided at the outer end of cylinder 48 , which communicates with compartment 64 on the opposite side of piston 46 . At the inner end of cylinder 48 is a port 72 which communicates with a recess 73 provided in the outer end surface of bulkhead portion 55 of sleeve 54 and which communicates with port 68.
Fluid is introduced into and removed from the compartment 66 on the opposite side of the piston 60.

The internal bore 74 of the slide stop matches the diameter of the bore 42 of the slide valve 32 and communicates therewith. At the outer end of the slide stop there is a head 75 on which the piston 60 is mounted.

A self-load release coil spring 76 is connected to the coaxial bore 7
4 and 42 about the rod 44, the spring forces the slide valve 32 into the closed position and the slide stop into an abutting relationship with the bulkhead 62. In such a position, the slide valve and slide stop are separated by a maximum distance.

In operation, a working fluid, such as refrigerant gas, is admitted to the group of compressor rotors 18 and 19 by input 25 and port 26. The rotation of the rotor forms a chevron-shaped compression chamber that receives gas and gradually reduces in volume as the chamber moves toward the inner surface of the output casing 13. Fluid is discharged as the ridge of the rotor island defining the leading edge of the compression chamber passes the end of port 38 that communicates with discharge passage 28. When the slide valve 32 is located further away from the output casing 13, the compression ratio is reduced by enlarging the final compression chamber. On the other hand, if the slide valve is positioned towards the output casing when the slide valve and the slide stop are brought together, the opposite effect is obtained. Therefore, movement of the slide valve changes the compression ratio and changes the pressure of the gas discharged from the compressor.

The compressor is configured to controllably vary its volumetric capacity while controlling its compression ratio. Therefore, as described below, the slide valve and slide stopper input and input the internal compression ratio of the compressor when controlling the volumetric capacity.
Controlled to match the output compression ratio. Third
As shown in the figure, when the slide valve and slide stopper are separated from each other, the space between them communicates with the intermeshed rotors 18 and 19, and the input pressure in the compression chamber between the rotors is working fluid can be maintained in communication with the input via slot 78 and passageways (not shown) in casing 11, thereby reducing the amount of fluid that is compressed. Therefore, maximum capacity can be obtained when the slide valve and slide stopper are in an abutting relationship. The closer the output casing is from the space between the slide valve and the slide stopper, the greater the capacity reduction from the maximum value.

Control System The compressor of the present invention is equipped with a control system that moves the slide valve and slide stopper according to a predetermined program to achieve the above purpose. To do this, from the compressor
Two variables are sensed at all times and fed into the electrical network. The output casing 13 thus has a plug opening 80 connected by a conduit 81 to a discharge pressure transducer 82 . Input casing 12 has a plug opening 84 connected by a conduit 85 to a suction pressure transducer 86 . The potentiometer 90 is
It has a movable element 91 which extends through the wall of the rotor casing 11 and which engages the inclined slot 57 of the slide stop 33 and serves as P1 to control the voltage divider network 92. Potentiometer 94 has a movable element 95 that extends through cylinder cover 50 and engages rod 44 of slide valve 32, serving as P2 to control voltage divider network 96. Voltage divider network 92 includes calibration resistors R1 and R2 and provides a 1-5 volt DC signal to analog input module 95 via lines 100 and 101. Similarly, voltage divider network 96 includes calibration resistors R3 and R4 and provides a 1-5 volt DC signal to analog input module 98 via lines 102 and 103.

The discharge pressure transducer 8 and the suction pressure transducer 86 each receive and transmit signals 1--
Convert to 5V DC signal and connect lines 104-107
The signal is supplied to the analog input module 98 via the .

The module 98 converts the signal it receives into a digital signal and sends it to the microcomputer 110.
supply to The microcomputer 110 has a program 112 with predetermined characteristics so that the output of the computer achieves desired control of the slide valve 32 and slide stopper 33. A suitable readout or display 114 is connected to the microcomputer 110 and indicates the position of the slide valve and slide stop based on the signals received from the feedback potentiometers 9 and 94.

Four control signals are sent from the microcomputer 110 via outputs 116, 117, 118 and 119. Therefore, the two signals sent from voltage divider networks 92 and 96 and the two signals sent from discharge pressure and suction pressure transducers 82 and 86 in response to slide stop and slide valve positions are analog The signals are passed through the input module to the microcomputer 110 where they are processed and provide the appropriate outputs 116-119. Outputs 116 and 117 are connected to solenoids 120 and 121 via lines 122 and 123, respectively. Outputs 118 and 119
are connected to solenoids 125 and 126 via lines 127 and 128, respectively.

Solenoids 120 and 121 are control valve 130
via which a hydraulic circuit for positioning the slide stop 33 is controlled. Solenoids 125 and 12
6 controls a hydraulic circuit that positions the slide valve 32 via a control valve 131.

Control valve 130 is connected by line 134 to a source of pressurized oil or other suitable pressurized liquid from the compressor's pressurized lubrication system. Conduit 135 connects valve 130 to fluid port 72 and conduit 136
connects valve 130 to fluid port 68. The oil drain line 137 is connected to the input area of the compressor.

Control valve 131 is connected to a source of pressurized oil by line 134 and drained by line 137. Conduit 138 connects valve 131 to fluid port 6
7 and conduit 139 connects valve 131 to fluid port 70 .

In operation, energizing the solenoid 120 of the valve 130 causes fluid to flow according to the diagram on the left side of the valve, i.e. from "P" to "P" and thus through the conduit 136 to the piston 60. Valve 130 is positioned so as to simultaneously apply oil pressure to the left side and drain oil from the opposite side of the piston through conduit 135 and from "A" to "T" at valve 130 and into the drain pipe. Ru. This allows the piston and its associated slide stop to be seen in the drawings.

When the solenoid 121 of the valve 130 is energized, fluid will flow according to the diagram shown on the right side of the valve, i.e. from "P" to "A", through the conduit 135 to the right side of the piston 60. Apply hydraulic pressure and push it to the left, and at the same time send oil from the other side of the piston through the conduit 136 and from "B" to "T" at the valve and drain the oil to the oil drain pipe. , valve 130 is positioned.

Similarly, energizing solenoid 125 of valve 131 causes fluid to flow from "P" to "B", applying pressure through fluid port 70, and applying pressure to fluid port 6.
Drain the oil from "A" to "T" through step 7, and move the slide valve to the right as seen in the drawing.
31 is located. Solenoid 1 of valve 131
When 26 is energized, fluid flows from "P" to "A", applying pressure through fluid port 67, and draining oil from "B" to "T" through fluid port 70, causing the slide valve to open. valve 13 to move it to the left.
1 is located.

When the compressor is used in a refrigeration system, it is usually desired to operate the slide valve to maintain a certain suction pressure, commonly referred to as a "set point." Optionally, other parameters such as the temperature of the product being processed in the refrigeration system associated with the compressor may be used as a factor influencing the position of the slide valve and thus the capacity of the compressor. good. In the system of the present invention, the desired set point is entered into microcomputer 110 by a suitable switch connected to a control panel (not shown) associated with display 114. The control panel also includes structures for controlling the mode of operation, such as automatic or manual, and the operation of the slide stop, slide valve, and compressor. A readout or display device 114 from the microcomputer 110 operates based on the signals it receives. The necessary electrical connections are made between the control panel and microcomputer 110 to perform the desired functions by means well known in the art.

A program associated with the microcomputer 110 controls the discharge pressure transducer 82.
and selects the appropriate position of slide stop 33 based on information received from suction pressure transducer 86 and refrigerant and compressor characteristics. This program is created to control the position of slide valve 32 based on suction pressure transducer 86 or other suitable volume indications.

Therefore, the control system senses four variables at all times: discharge pressure, suction pressure, slide stopper position, and slide valve position, and the signals received by microcomputer 110 can be programmed as required. The slide stop and slide valve are moved in the appropriate direction until balanced with respect to the slide stop position and slide valve established at 112.

In systems using electric motors, a motor current transducer 140 is connected to such a motor (not shown) to avoid excessive current flowing through the motor driving the compressor. This transducer 140 is connected to the line 14
1 and 142, the microcomputer 1
10 is connected to an analog input module 98 connected to 10. The microcomputer 110 prevents the slide valve 32 from loading the compressor to the point where the motor current exceeds a predetermined limit; programmed to reduce it.

The slide valve 32 operates as a floating type controller. The slide valve 32 may be moved to load or unload in response to a displacement control signal derived, for example, from the suction pressure transducer 86, but not precisely in response to any other signal or control. It is not placed in a certain position. The volume control signal is typically based on suction pressure, but may include other parameters such as product temperature, as discussed above. The output due to loading or unloading is usually
In a time proportional configuration, the pulses are such that the response rate of the slide valve changes with the magnitude of the error in the displacement control signal.

Potentiometer 9 combined with slide valve
The signal from 0 is not used to control the position of the valve. However, this signal is used to indicate its position, and such position can be used for other purposes, including starting the compressor with no load at all, or starting the compressor in a multi-compressor configuration. used for sequencing.

In contrast, the slide stopper is controlled to an accurate position as described above. Feedback from the potentiometer 94 is used to determine when the slide stop is in the desired position.

Feedback from both the slide stop and slide valve potentiometers determines whether a conflict or overlap condition exists between the desired mechanical position of the slide stop and the actual mechanical position of the slide valve. It is used to judge. If a conflict condition exists, the slide valve is temporarily repositioned and a slide stop positioning procedure is performed.

The system also includes arrangement to allow manual positioning of both the slide valve and the slide stop by operating appropriate controls indicated on the control panel.

By positioning the slide valve and slide stop relative to each other and the rotor casing, the compressor can be "loaded" or "unloaded" as required by various parameters. It will be understood by those skilled in the art that the compression ratio can be varied as desired. Although hydraulic means for moving the slide stop and slide valve have been described above, it will be apparent that other means known to those skilled in the art may also be used. If desired, for example, electric step motors or hydraulic means guided by step motors can also be used.

Advantages of the Invention As mentioned above, the present invention has the advantage that improved control of the compressor allows for more efficient operation.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a screw-type compressor according to the present invention, with one part cut away for clarity, and FIG. The sectional view shown, FIG. 3, is a view similar to FIG. 1, but showing the slide valve and slide stopper in a different position from FIG.
FIG. 4 is a schematic diagram including a control circuit. 10... Spiral screw type compressor, 11...
Rotor casing, 12...Input section casing, 1
3... Output part casing, 15, 16... Bore, 1
8, 19...Spiral rotor (screw), 20...Shaft, 25...Input channel, 26...Port, 28...
discharge channel, 29...port, 30...recess, 32...
Slide valve, 33... Slide stopper, 42... Bore, 43... Head, 44... Rod, 45... Fixing means, 46... Piston, 47... Body, 48... Cylinder, 50... Cover, 54... Sleeve, 55... Partition part, 57... Slot, 58... Main part, 60... Piston, 62... Fixed partition, 64... External compartment, 66
...Internal compartment, 67, 68...Port, 70, 72...
Port, 73... recess, 74... bore, 75... head, 76... coil spring, 78... slot, 80,
84...Plug opening, 82...Discharge pressure transducer, 86...Suction pressure transducer, 90,
94... Potentiometer, 92, 96... Voltage divider network, 98... Analog input module, 110
...Microcomputer, 112...Program,
114...Display device, 116, 117, 118, 1
19...Output, 120, 121...Solenoid, 12
5,126...Solenoid, 130,131...Control valve.

Claims (1)

Claims: 1. Intermeshing helical rotors are mounted on mutually parallel axes in a housing with intersecting cylindrical bores, a high pressure end wall at one end of the housing, and a high pressure end wall at the other end. has a low pressure end wall having an input opening as the input of the compressor, and the high pressure end wall having a discharge opening as the output of the compressor and extending axially. a recess is provided in the housing in open communication with the bore, and a slide valve member is mounted for axial movement within the recess, the slide valve member having an inner surface in sealing relationship with the rotor. has
The slide valve member has a discharge surface at one end adjacent the high pressure end wall and a rear surface at the other end, and further includes a slide stopper member that extends axially within the recess. the slide stop member is movably mounted, the slide stop member has an inner surface in sealing relationship with the rotor, the slide stop member has a front surface, the front surface of the slide stop member is connected to the input section. the slide valve member and the slide stop member engage a rear surface of the slide valve member to form a continuous composite member selectively actuated to close the axially extending recess relative to the opening; , between these,
A screw type compressor of various sizes and axial positions which can be separated from each other to form an opening communicating with the input opening, comprising: a first means for sensing the pressure of the discharge opening; a second means for sensing the pressure of the slide stopper member; a third means for sensing the position of the slide stopper member; a fourth means for sensing the position of the slide valve member; means for controlling the movement of the slide stopper member and the slide valve member in response to the sensing means of 4, the means for controlling the movement being responsive to and proportional to the first and second means. pressure sensor means operative to provide an electrical output of said third and fourth
electronic circuit means operative to provide an electrical output proportional thereto in response to the means, and connected to the outputs of the first, second, third and fourth means;
A screw type compressor characterized by comprising electronic computer means for controlling the movement of the slide stopper member and the slide valve member in response to the output.