JPH0310039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The invention relates to a method for axially moving a fluid such that it provides automatically variable volume ratios and is provided with means for injecting liquid refrigerant into the interlobe volume for cooling. This invention relates to a fluid spiral screw type compressor.

BACKGROUND OF THE INVENTION The present invention is disclosed by David A.
Murphy and Peter C. Spellar. Therefore, the inventor does not claim any right to the invention in the content of the application. The description of the parts in said application is used herein to exemplify the parts that may be used with the present invention.

The use of oil in screw-type compressors is traditionally used to seal gas leakage paths around the rotor, lubricate contact areas, and remove heat from the gas as it is compressed. It is known for its technology. In all systems except low compression ratio systems, some type of oil cooling method is commonly used to remove the heat of compression from the oil and gas so that the oil can be reinjected at a given temperature.

One method used for oil cooling is to inject liquid refrigerant into the interlobe volume of the threads before opening the threads to the discharge ports. The refrigerant is expanded from the compressor pressure through the expansion valve to a specified pressure in the threads. By regulating the flow of refrigerant, the heat released from the compressor is controlled to the desired level.

Schibbye, U.S. Pat. No. 3,432,089, discloses injecting lubricating oil through channel 114 into a compressor where the injection point changes with a percentage of the full load position of the slide valve, thereby providing volume adjustment. It is done.

Edstrom U.S. Pat. No. 3,738,780 discloses that alternative oil injection port locations are used for various fixed internal volume ratio compressors in which slide valves and plugs are used under the machine. There is.

No. 3,795,117 to Moody et al. discloses the use of injected liquid refrigerant to control the discharge temperature from a screw compressor.

US Pat. No. 3,869,227 to Kocher et al. discloses changing the location of a high pressure suction port to change mechanical capacity.

According to the disclosure of Herschler et al., U.S. Pat. , so that the amount of liquid varies depending on the capacity of the compressor. Also record the cooling liquid injection port, preferably for oil.

No. 3,885,402 to Moody et al. discloses a fixed internal volume ratio compressor that is equipped to determine the optimal point of injection.

U.S. Pat. No. 4,375,156 to Shaw discloses the use of liquid refrigerant to cool screw type compressors.

Means and Effects for Solving the Problem The present invention provides for injecting liquid refrigerant into the interlobe volume of a variable volume ratio screw compressor at one of two or more locations separated from the discharge point at different volume locations. and a means for automatically selecting an injection port that matches the internal volume ratio at which the compressor is operating.

This is accomplished by providing two or more liquid refrigerant input ports in the compressor wall adjacent to the discharge port. The input ports are first revealed by a thread, one of which is located further from the discharge port than the other ports, and is valved by a control means responsive to the internal volume ratio. The means are spaced apart such that they are operative to select a path for the liquid refrigerant to flow to a desired input port.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, a helical screw compressor 10 of the type disclosed in U.S. Pat. have. The rotor casing has intersecting bores 15 and 16 which interlock male and female helical rotors or screws 18 and 19, which are mounted for rotation about parallel axes by suitable bearings. It creates a working space for people to work together.

The rotor 18 includes a bearing (not shown) in the output part casing 13 and an input part casing 1.
2 is rotatably mounted to a supported shaft 20 with a bearing 22 in it. 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 and with parallel axes of bores 15 and 16 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 the cylinder 48 by an input section cover 51 that receives the reduced diameter end 52 of the cylinder 48 .

Mounted inside the input section cover 51 is a sleeve 54 having a bulkhead portion 55 at one end, which extends longitudinally towards the rotor casing. The slide stopper 33 is located at the end 40
It has a head 56 terminating in , 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, a piston 60 is fixed by suitable fixing means 61.

A fixed partition 62 is fixed to the cylinder 48 centrally between its ends, which divides the interior of the cylinder into an outer compartment 64 in which the piston 46 moves and an inner compartment 66 in which the piston 60 moves. Cylinder 48 has fluid ports 67 and 68 in close proximity to each side of septum 62, each of which is connected to compartment 62.
4 and 66. 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 it 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 through the end of port 38 that communicates with discharge portion 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 space between the slide valve and the slide stopper is to the output casing, the greater the capacity reduction from the maximum value.

A control system is provided for moving the slide valve and slide stop according to a predetermined program to accomplish the above objectives. To do this, four variables from the compressor are constantly sensed 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 has a movable element 91,
This extends through the wall of the rotor casing 11 and engages an angled slot 57 in the slide stop 33 to control the voltage divider network 92.
Work as 1. Potentiometer 94 has a movable element 95 that extends through cylinder cover 50 and engages rod 44 of slide valve 32 and serves as P2 to control voltage divider network 96. Split network 92 connects calibration resistor R1
and R2 to provide 1-5 volts to analog input module 98 via lines 100 and 101.
Provides DC signal. Similarly, voltage divider network 9
6 includes calibration resistors R3 and R4, and line 1
Analog input module 9 via 02 and 103
8 to provide a 1-5 volt DC signal.

The discharge pressure transducer 82 and the suction pressure transducer 86 each transmit the received signal to one
-5V DC signal and line 104-10
4 to an analog input module 98.

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 signals received from the feedback potentiometers 90 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. Line 135 connects valve 130 to liquid port 72 and line 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 left view of the valve, i.e. from "P" to "B" and thus through the conduit 136 to the left side of the piston 60. Valve 130 is positioned so as to simultaneously apply hydraulic pressure to the piston, and simultaneously send oil from "A" to "T" from the opposite side of the piston, through conduit 135, and at valve 130, and drain oil to the drain pipe. . This forces the piston and its associated slide stop to the right in the drawing.

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 opposite 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 4, and then move the slide valve to the right as seen in the drawing.
31 is located. Solenoid 1 of valve 131
26, fluid flows from "P" to "A", applies pressure through fluid port 67, and drains oil from "B" to "T" through fluid port 70, and slides. Valve 1, moving the valve to the left.
31 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 setpoint is entered into microcomputer 110 by appropriate switches 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 microcomputer 110 selects the appropriate position of slide stop 33 based on information received from discharge pressure transducer 82 and suction pressure transducer 86, as well as refrigerant and compressor characteristics. be. 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 the motor driving the compressor to avoid drawing too much current to the motor driving the compressor. This transducer 140 is connected by lines 141 and 142 to an analog input module 98 which is connected to the microcomputer 110. 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 from loading and unloading is typically pulsed in a time proportional configuration such that the response rate of the slide valve changes with the magnitude of the error in the displacement control signal.

The signal from the potentiometer 90 associated with the slide valve 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 stopper and slide valve potentiometers determines whether a conflict or overlap condition exists between the desired mechanical position of the slide stopper and the actual mechanical position of the slide valve. used for making judgments. 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 mutually arranging the slide valve and the slide stop with respect to the rotor casing, the desired variation of the compression ratio is obtained, so that the compressor is "loaded" or "loaded" as obtained by various parameters. No load.

Although hydraulic means for moving the slide stop and slide valve are described, other means known to those skilled in the art may also be used. For example, electric step motors or step motor driven hydraulic means can be used if desired.

The distance to this point for the example is 1982 9
4,516,914, filed on May 20, 2006, and more particularly describes the compressor environment in which the present invention is applied or used.

Further, FIG. 5 will be explained. The compressor central rotor casing 11 has a pair of ports 150
and 151 on the side wall of the output part casing 13
It is isolated from the end wall. port 1
50 is positioned such that this port communicates with the threaded portion of the anterior interlobe volume that communicates with port 151 . The interlobe volume is lower than port 150 when port 151 is first exposed to the interlobe volume.
It can be seen that when first exposed to the interlobe volume, it is larger. Therefore, when the internal volume ratio is relatively small, port 150 is closed and port 151 is open. Various locations on either side or end walls may be used for ports 150 and 151.

Input port 150 is connected by line 152 to valve 153 which is operated by solenoid 154 . Similarly, input valve 151 is connected to valve 153 by conduit 155. Valve 153 connects liquid coolant line 15
6 through a thermal expansion valve 157 to a line 158 which connects to a source of liquid coolant.

To control solenoid 154, the system shown in FIG. 4 is used. As previously mentioned, the system of FIG. 4 includes a cross-sectional view of a helical screw compressor with dual slides for volume ratio and capacity control. The present invention is used to introduce liquid refrigerant into the compression region of a screw compressor prior to releasing compressed vapor.

To control the introduction of liquid refrigerant, a fifth output 160 from the microcomputer is provided, which output 160 is connected to control the operation of the solenoid 154 as shown. Thus, when the machine changes from one internal volume ratio to another, the flow of liquid refrigerant is changed from one input port to another by a valve 153 controlled by a solenoid 154. , output 160. Output 160 serves to energize or deenergize solenoid 154 to allow refrigerant to enter the compressor housing via either input port 150 or input port 151. The supply of liquid is controlled by a thermal expansion valve 157 which detects the discharge temperature of the discharge channel 28 by a sensor 159.

Therefore, for a compressor with a fixed built-in volume ratio, such as that of Moody et al., U.S. Pat. has been done. For example, for compressors with low internal volume ratios, the ports are located closer to the beginning of compression than for machines designed to operate with high internal volume ratios. As a result, the power required to compress this refrigerant can be reduced, increasing the overall efficiency of the compressor.

For screw-type compressors with variable volume ratios, optimal positions of the ports are given for obtaining various internal volume ratios in the range of the compressor. When the machine changes from one internal volume ratio to another, the flow of liquid refrigerant is changed from one internal port to another by a conditionally activated valve.
Thus, when the internal volume ratio is small, the injection is
This occurs at a location further from the discharge than when the internal volume ratio is large.

Although the invention discloses two port positions in the illustrative embodiment, more than two port positions can be used if the range of volume ratios requires.

Thus, the configuration and operation can maintain a constant discharge temperature from the compressor with minimal loss of efficiency, as desired.

[Brief explanation of the drawing]

1 is a cross-sectional view of a screw compressor as disclosed in U.S. Pat. No. 4,516,914 filed September 10, 1982; FIG. 3 is a sectional view showing a part of the structure, and FIG. 3 is a view similar to FIG. 1, but shows the slide valve and slide stopper in a different position from FIG. 5 is a schematic diagram including a control circuit according to the invention as used in the compressor shown in FIG.
-5 is a reduced cross-sectional view showing a port of a compressor according to the invention; 10... Spiral screw type compressor, 11
...Rotor casing, 12...Input section casing, 13...Output section casing, 15, 16...
Bore, 18, 19... spiral rotor (screw),
20...Shaft, 25...Input channel, 26...
Port, 28...Discharge channel, 29...Port, 3
0... 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 bulkhead, 64...External compartment, 66...Internal compartment, 67, 68...Port,
70, 72...port, 73...recess, 74...
...Bore, 75...Head, 76...Coil spring, 7
8...Slot, 80, 84...Plug opening, 8
2... Discharge pressure transducer, 86... Suction pressure transducer, 90, 94... Potentiometer, 92, 96... Voltage division network, 98
... Analog input module, 110 ... Microcomputer, 112 ... Program, 114
...Display device, 116, 117, 118, 119
... Output, 120, 121 ... Solenoid, 12
5,126... Solenoid, 130,131...
Control valve, 150, 151... Port, 152, 1
56,158...Pipeline, 153,157...Valve,
154... Solenoid.

Claims (1)

Claims: 1. Intermeshing helical rotors 18, 19 are mounted on mutually parallel axes in a housing with intersecting cylindrical bores, said rotors and housing being The housing has a high pressure end wall 13 at one end of the housing and a low pressure end wall 12 at the other end, the low pressure end wall 12 having an input suction opening as the input to the compressor. 13 and said high pressure end wall has an output discharge opening 28 as the output of the compressor, means 32, 33 for varying the internal volume ratio of said compressor; a first port 150 and a second port 151 in the housing for liquid refrigerant injection, the two ports being exposed to the interlobe volume at selected locations of the rotor; and the first liquid refrigerant injection port 150 is provided such that the inter-lobe volume becomes relatively large when the inter-lobe volume is first exposed to the first port. and a port 151 for injecting the second liquid refrigerant.
are arranged such that the interlobe volume is relatively small when the rotor is first exposed to the second port, whereby the interlobe volume is relatively small when the rotor is exposed to the second port. the liquid refrigerant is selectively introduced into one or the other of the first or second liquid refrigerant injection ports; Means for doing so 153, 154, 156, 15
A screw type compressor characterized by comprising: 7,158. 2. The compressor of claim 1, wherein the means for varying the internal volume ratio operates automatically in response to one or more operating conditions of the compressor. 3. The compressor of claim 2, wherein the means responsive to the internal volume ratio controls means for selectively introducing liquid refrigerant into the port. 4. A compressor according to claim 3, wherein said means for selectively introducing liquid refrigerant into one or the other of said two ports is valve means and electrical means for operating said valve means. 5. The means for varying the internal volume ratio of the compressor comprises a slide valve member mounted for axial movement within the recess means, the slide valve member being in sealing relation with the rotor. an inner surface and a discharge surface at one end adjacent the high pressure end wall and a rear surface at the other end; and further movable axially within the recess means. a slide stop member mounted so as to have an inner surface in sealing relationship with the rotor and a front surface;
The front face of the slide stop member is connected to the rear face of the slide valve member to form a continuous composite member selectively actuated to close the axially extending recess means relative to the input opening. the slide valve member and the slide stopper member are spaced apart from each other to form an opening of various sizes and axial positions therebetween that communicates with the input opening; A compressor according to claim 1, which can be used as a compressor. 6. Means for injecting oil into the interlobe volume at selected locations to seal and lubricate the rotor and to cool the working gas in the compressor, and means for cooling the oil. injecting liquid refrigerant into the interlobe volume at one of two or more predetermined positions at which the interlobe volume varies and before the interlobe volume moves to the discharge location. The compressor of claim 1, wherein the compressor selects its position in response to said predominant internal volume ratio. 7. The position selected for injection is far from the discharge position when the internal volume ratio is relatively small, and the position selected for injection is close to the discharge position when the internal volume ratio is relatively large. A compressor according to scope item 6.