JPS61207887A - Variable liquid coolant injection port locator for screw type compressor equipped with automatic variable volume ratio - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention provides an automatic variable volume ratio and a method for axially discharging a bulk body in which a means is provided for injecting a liquid refrigerant into the interlobe volume for cooling. This article relates to a screw type compressor.

BACKGROUND OF THE INVENTION The present invention is described in U.S. patent application Ser.
A, Murphy and Peter C, 5pella
Particularly suitable for use with the invention by R. Therefore, the present inventor does not claim any benefit of the invention in the content of the above 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 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.

5chibby, U.S. Pat. No. 3,432. '089 discloses injecting lubricating oil into a compressor via channel 1)4, in which the injection point changes with a percentage of the full load position of the slide valve, thereby providing capacity adjustment. .

Editro+s 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 the slide valve and plug are located at the base of the machine. used in

In U.S. Pat. No. 3,795,1)7 to Moody et al.
The use of injected liquid refrigerant to control the discharge temperature from a screw compressor is disclosed.

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

US Pat. No. 3,874,828 to Herschler et al.
According to the disclosure in No. 1, the screw type compressor has a manually adjustable capacity control valve, and the action of this valve not only changes the port position to control the capacity, but also changes the amount of liquid in the compressor. Change the size so that it changes depending on the capacity. Also record the cooling liquid injection port, preferably for oil.

In U.S. Pat. No. 3,885.402 to Moody et al.
A fixed internal volume ratio compressor is disclosed that is equipped to determine the optimal point of injection.

US Pat. No. 4,375,156 of 5ha- discloses the use of liquid refrigerant to cool a screw compressor.

SUMMARY OF THE INVENTION 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 means for automatically selecting an injection port that corresponds to the internal volume ratio at which the compressor is operating.

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

Illustrating the accompanying drawings, U.S. Patent Application No. 416.768
A helical screw compressor 10 of the type disclosed in No.
are a central rotor casing 1), an input casing 12 and an output casing 1 connected to each other in a sealed relationship.
It has 3. The rotor casing has intersecting bores 15 and 16 for interlocking male and female helical rotors or screws 18 and 19, which are mounted for rotation about parallel axes by suitable bearings. It forms the working space of

Rotor 18 is rotatably mounted on a shaft 20 supported by a bearing (not shown) in output casing 13 and a bearing 22 in input casing 12 . A shirt 20 extends outwardly from the output casing for connection to a motor (not shown) via a suitable coupling (not shown).

This compressor has an input passage 2 in an input part casing 12.
5, which communicates with the working space by a port 26. The discharge channel 28 in the output casing 13 is connected to a port 29 (at least a portion of which is connected to the output casing 1
3) 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 1).

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; Suitably flat or otherwise shaped, the recess 30 is sealed off from the bores 15 and 16 by engagement of the two adjacent ends of the slide valve and slide stop.

The slide valve has an internal bore 42 and a head 43 at one end thereof. The rod 44 is connected at one end to the head 43 by a fixing means 45, through which the rod 44 extends, and at the other end is connected to a piston 46. The piston is attached to reciprocate within the body 47 of a cylinder 48, and the cylinder 48 is connected to the input casing 12 and extends from there in the axial direction.

A cover or end plate 50 is attached to the outer end of cylinder 48. The input casing 12 is connected to the cylinder 48 by an input 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 stop 33 has a head 56 terminating in an end 40, which has an inclined 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 allow 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 stopper, a piston 60 is fixed by suitable fixing means 61.

The cylinder 48 has a fixed bulkhead 62 centrally located between its ends.
is fixed, 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 proximate each side of septum 62, which communicate with compartments 64 and 66, respectively. cylinder 48
A fluid port 70 is provided at the outer end of the piston 46 , which communicates with the compartment 64 on the opposite side of the piston 46 . At the inner end of the cylinder 48 is a port 72 which communicates with a recess 73 provided in the outer end face of the septum portion 55 of the sleeve 54 to provide fluid flow to the compartment 66 on the opposite side of the piston 60 with respect to the port 68. introduce or remove.

The internal bore 74 of the slide stop matches the bore 42 of the slide valve 32 in diameter 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-unloading coil spring 76 connects the coaxial bores 74 and 4.
2 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 septum 62. In such a position, the slide valve and slide stopper are separated by a maximum distance.

In operation, a working fluid, such as a refrigerant gas, enters the input section 25.
and into the group of compressor rotors 18 and 19 by port 26. The rotation of the rotor forms a chevron-shaped compression chamber, which receives gas and whose volume gradually decreases 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 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 discussed below, the slide valve and slide stopper are controlled to match the internal compression ratio of the compressor to the input and output compression ratios when controlling volumetric capacity. As shown in FIG. 3, 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 can be maintained in communication with the input via the slot 78 and the flow path (not shown) in the casing 1), thereby reducing the amount of fluid to be 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. Therefore, the output part casing 13
It has a plug opening 80 connected to a discharge pressure quadrangle juicer 82 by. The input part casing 12 is
Suction pressure quadrangle juicer 86 by conduit 85
It has a plug opening 84 connected to the plug opening 84 .

The potentiometer 90 has a movable element 91 that extends through the wall of the rotor casing 1) and engages the inclined slot 57 of the slide stop 33 as Pl to control the voltage divider network 92. work. Potentiometer 94 has a movable element 95 that extends through cylinder cover 50 and engages loft 44 of slide valve 32 to control voltage divider circuit w496.
The voltage divider circuit 1i192, which acts as a calibration resistor R
1 and R2 to provide a 1-5 volt DC signal to analog input module 98 via lines 100 and 101. Similarly, voltage divider network 96 includes calibration resistor R
-3 and R4 to provide a 1-5 volt DC signal to analog input module 98 via lines 102 and 103.

The discharge pressure quadrant juicer 82 and the suction pressure quadrant juicer 86 each convert the received signal to a 1-5V DC signal and provide it to the analog input module 98 via lines 104-107.

The module 98 converts the signal it receives into a digital signal and provides it to the microcomputer 1)0! do. The microcomputer 1)0 has a program 1)2 with predetermined characteristics, so that the output of the computer achieves desired control of the slide valve 32 and the slide stopper 33. A suitable readout or display device 1) 4 is connected to the microcomputer 1) 0 and indicates the position of the slide valve and slide stop on the basis of the signals received from the feedback potentiometers 90 and 94.

Four control signals are sent from the microcomputer 1)0 via outputs 1)6.1)7.1)8 and 1)9. Therefore, two signals 1. and discharge pressure and suction pressure quadrant juicer 8
The two signals sent from 2 and 86 are sent to the microcomputer 1)0 via an analog input module,
It is processed here to give the appropriate outputs 1)6 to 1)9. Outputs 1) 6 and 1) 7 are respectively on line 12
2 and 123 to solenoids 120 and 121. Outputs 1)8 and 1)9 are each on line 127
and 128 to solenoids 125 and 126.

Solenoids 120 and 121, via control valve 130, control a hydraulic circuit that positions slide stop 33. Solenoids 125 and 126, via control valve 131, control a hydraulic circuit that positions slide valve 32.

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 7
2 and conduit 136 connects valve 130 to fluid port 68
Connect to. 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 1
38 connects valve 131 to fluid port 67 and conduit 13
9 connects valve 131 to fluid port 70.

In operation, when the solenoid 120 of the valve 130 is energized, fluid flows according to the diagram on the left side of the valve, i.e., fluid flows from "Po" to "B", thus causing hydraulic pressure to flow to the left side of the piston 60 via the conduit 136. simultaneously through conduit 135 and valve 130 from the opposite side of the piston.
The valve 130 is positioned to send oil from "A" to "T" and drain oil to the oil drain pipe. This results in
The piston and its associated slide stop are pushed to the right as viewed in the drawing.

When the solenoid 121 of valve 1.30 is energized, fluid flows according to the diagram shown on the right side of the valve 6, i.e. "Po
Fluid flows from "A" through conduit 135 to the right side of piston 60, pushing it to the left, and at the same time from the other side of the piston through conduit 136, and at the valve "B". Valve 130 is positioned to send oil from ``T'' to bleed oil to the bleed pipe.

Similarly, when the solenoid 125 of the valve 131 is energized, “
Fluid flows from Po to “B” applying pressure through fluid port 70, and from “A” to “T” through fluid port 67.
The valve 131 is positioned so that the oil is drained to "Po" and the slide valve is moved to the right in the drawing. When the solenoid 126 of the valve 131 is energized, fluid flows from "Po" to "A". Valve 131 is positioned to apply pressure through fluid port 67 and bleed from "B" to "T" through fluid port 70, moving the slide valve to the left.

When the compressor is used in a refrigeration system, it is usually desired to move the slide valve to maintain a 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 invention, the desired setpoint is entered into the microcomputer 1)0 by means of suitable switches connected to a control panel (not shown) associated with a display device 1)4. The control panel also includes structures for controlling the mode of operation, e.g. automatic or manual, and the operation of the slide stop, slide valve and compressor.

The readout device or display device 1)4 from the microcomputer 1)0 operates on the basis of the signals it receives. A control panel and a microcomputer 1)0 to perform the desired functions by means well known in the art.
The necessary electrical connections are made between.

A program associated with the microcomputer 1)0 selects the appropriate position of the slide stop 33 based on information received from the discharge pressure transducer 82 and suction pressure transducer 86, as well as the refrigerant and compressor characteristics. . This program is created to control the position of slide valve 32 based on suction pressure quadrangle reducer 86 or other suitable volume indications.

Therefore, the control system controls four variables: discharge pressure;
The suction pressure, the position of the slide stopper, and the position of the slide valve are constantly sensed, and as necessary, signals received and received by the microcomputer 1) 0 are sent to the program 1) 2.
Move the slide stop and slide valve in the appropriate direction until they are balanced with respect to the slide stop position and slide valve established in .

To avoid excessive current flowing through the motor that drives the compressor, systems using electric motors
A motor current transducer 140 for such a motor
is connected. This transducer 140 is connected to the microcomputer 1) by lines 141 and 142.
0 to an analog input module 98 connected to 0. The microcomputer 1)0 controls the slide valve 32 until the motor current exceeds a predetermined limit.
It is programmed to unload the compressor, but to reduce the load on the slide valve 32 if the motor current exceeds its upper limit.

The slide valve 32 operates as a floating type controller. Slide valve 32 is responsive to, for example, a volume control signal derived from suction pressure quadrangle reducer 86.
It is moved in the direction of loading or unloading, but is not placed in the correct position for any other signal or control.

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.

On the other hand, 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. used for. If a conflict condition exists, the slide valve is temporarily repositioned and the slide valve 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 arranging the slide valve and the slide stop relative to each other with respect to the rotor casing, the desired variation of the compression ratio is obtained, so that the compressor is "loaded" or "unloaded" as obtained by various parameters.
be made into

Although hydraulic means for moving the slide stop and slide valve are described, other means well known to those skilled in the art may also be used; for example, hydraulic means with an electric step motor or step motor drive, if desired. Can be used.

The description up to this point regarding the examples is from September 2, 1983.
1 illustrates a compressor environment in which the present invention is applied or used, as disclosed in US Pat.

Further, FIG. 5 will be explained. The compressor central rotor casing 1) has a pair of ports 150 and 151 in a sidewall spaced relationship from the end wall of the output casing 13. Port 150 is positioned such that it communicates with the threads of the interlobe volume before communicating with port 151. The interlobe volume is port 151
port 15 when first exposed to the interlobe volume.
It is understood that 0 is larger when first exposed to the interlobe volume. Therefore, when the internal volume ratio is relatively small, port 150 is closed and port 151 is open. Ports 15 at various locations on either side or end wall
Used for 0 and 151.

Input part port) 150 is a tube! 152 to a valve 153 which is operated by a solenoid 154. Similarly, the input valve 151
55 to valve 153. The valve 153 is
A liquid coolant line 156 connects through a thermal expansion valve 157 to a line 158 that 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 Figure 4 includes a cross section of a screw type compressor with dual slides for volume ratio and volume control. Used to introduce liquid refrigerant into the compression zone of a screw compressor.

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, which Controlled by output 160.

Output 160 serves to energize or deenergize solenoid 154 and directs refrigerant to input port 150 or input port 1.
51 to the compressor housing. 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.

Thus, for example, U.S. Patent No. 3 by Moody et al.
, 885,402, the internal port locations and sizes are selected to provide the best specific performance at the operating internal volume ratio of the compressor.

For example, for a compressor with a low internal volume ratio, the port is located closer to the beginning of compression than for a machine designed to operate with a built-in high internal volume ratio. As a result, the power required to compress this refrigerant can be reduced, increasing the overall efficiency of the compressor.

For screw-type compressor compressors with variable volume ratios, the optimum position of the ports is given to obtain 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
A situation-responsive operating valve changes from one internal port to another.

Thus, when the internal volume ratio is small, injection occurs 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 drawings]

・FIG. 1 is a cross-sectional view of a screw compressor as disclosed in U.S. Patent Application No. 416.769 filed September 10, 1983; FIG. 2 is a cross-sectional view of L1 of FIG.
2-2 is a sectional view showing a part of the compressor; FIG. 3 is a view similar to FIG. 1 but showing the slide valve and slide stopper in a different position from FIG. 1; FIG. 4 1 is a schematic diagram including a control circuit according to the invention as used in the compressor shown in FIG. 1; FIG. FIG.

Claims (7)

[Claims] (1) Intermeshing helical rotors are mounted on mutually parallel axes in a housing with intersecting cylindrical bores, the rotors and housing providing an interlobe volume that varies with rotation of the rotor. , the housing has a high-pressure end wall at one end of the housing and a low-pressure end wall at the other end, the low-pressure end wall having an input opening as an input to the compressor, and the high-pressure end wall having a A screw compressor having a discharge opening as the output of the compressor, comprising means for varying the internal volume ratio of the compressor, and a first port and a second port provided in the housing. and wherein the two ports are provided in the housing for exposing the interlobe volume at selected locations of the rotor, the first port being such that the interlobe volume is initially exposed to the first port. The inter-lobe volume is relatively large when the
The second port is provided such that the interlobe volume is relatively small when the rotor is first exposed to the second port, and the interlobe volume is such that the interlobe volume is relatively small when the rotor is exposed to the port. A screw compressor, characterized in that the screw compressor is configured to change when first communicating with either of the two ports, and further comprising means for selectively introducing liquid refrigerant into one or the other of the two ports. (2) The compressor according to claim 1, wherein the means for changing the internal volume ratio operates automatically in response to one or more operating environments 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 ports. (4) The means for selectively introducing the liquid refrigerant into one or the other of the two ports is a valve means, and the electric means operates the valve means. ) Compressor described in section. (5) interdigitating helical rotors are mounted on mutually parallel axes in a housing with intersecting cylindrical bores, said rotors and housing providing an interlobe volume that varies with rotation of said rotor; , the housing has a high-pressure end wall at one end of the housing and a low-pressure end wall at the other end, the low-pressure end wall having an input opening as an input to the compressor, and the high-pressure end wall having a the output of the compressor having a discharge opening, axially extending recess means being provided in the housing in open communication with bore means for varying the internal volume ratio of the compressor; a slide valve member mounted for axial movement within the means, said slide valve member having an inner surface in sealing relationship with said rotor, said slide valve member adjacent said high pressure end wall; a discharge surface at one end thereof and a rearward surface at the other end; and a slide stop member is mounted for axial movement within the recess means; an inner surface in sealing relationship with the rotor, the slide stop member having a front surface selectively adapted to close the axially extending recess means relative to the input opening; the slide valve member and the slide stopper having an aperture of various sizes and axial positions therebetween that engages the rear surface of the slide valve member to form a continuous composite member that is actuated to In a screw compressor that can be separated from each other to form an opening communicating with the input opening, a first port and a second port are provided in the housing, and the two ports are connected to the rotor. the first port is provided in the housing for exposure to an interlobe volume at a selected location, the first port being configured such that the interlobe volume is relatively large when the interlobe volume is initially exposed to the first port; The second
ports are provided such that the interlobe volume is relatively small when the rotor is first exposed to the second port, and the interlobe volume is such that the interlobe volume is relatively small when the rotor is first exposed to either of the ports. A screw compressor, characterized in that it has: means for selectively introducing liquid refrigerant into one or the other of the two ports, the screw compressor being configured to change when communicating with the two ports. (6) Intermeshing helical rotors are mounted on mutually parallel axes in a housing having intersecting cylindrical bores, and the cylindrical bores allow the volume between the lobes to be released from the input position by rotation of the rotors. The position of the part changes,
a screw comprising means for varying the internal volume ratio and means for injecting oil into the interlobe volume at selected locations to seal and lubricate said rotor and to cool the working gas in the compressor; type compressor, injecting liquid refrigerant into the interlobe volume at one of two or more predetermined locations where the interlobe volume varies and before the interlobe volume moves to the discharge location. A method for cooling oil, comprising the steps of: selecting the position in response to the prevailing internal volume ratio. (7) When the internal volume ratio is relatively small, the selected position for injection is far from the ejection part position, and when the internal volume ratio is relatively large, the position selected for injection is far from the ejection part position. A method according to nearby claim (6).