US3626979A

US3626979A - Fluit compression system control

Info

Publication number: US3626979A
Application number: US6621A
Authority: US
Inventors: Richard S Abell
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1970-01-28
Filing date: 1970-01-28
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

An unloading valve for controlling the capacity of a compressor comprising a housing defining a bore, an inlet to said housing connected to the discharge side of a compressor, a first outlet from said housing connected to the suction side of said compressor, and a second outlet from said housing connected to the discharge manifold of the compressor. Disposed in the bore is a piston assembly and poppet operable in response to changes of pressure in the bore. The piston and poppet move as a result of changes of pressure in the bore, created by the bore being selectively communicated with the side of the compressor and with the discharge side of the compressor. Movement of the piston assembly and poppet selectively communicates the inlet of said valve with either the suction side of the compressor when reduced capacity is required or with the discharge manifold when rated capacity is required.

Description

United States Patent [72] inventor Richard S. Abell Cazenovia, N.Y.

21 AppLNo. 6,621

[22] Filed Jan.28, 1970 Dec. 14, 1971 Carrier Corporation Syracuse, N.Y.

[45] Patented [73] Assignee [54] FLUID COMPRESSION SYSTEM CONTROL [56] References Cited UNITED STATES PATENTS 3,195,319 7/1965 Woltt 3,280,582 10/1966 Knachel 62/510 Primary Examiner-Meyer Perlin AnorneysHarry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: An unloading valve for controlling the capacity of a compressor comprising a housing defining a bore, an inlet to said housing connected to the discharge side of a compressor, a first outlet from said housing connected to the suction side of said compressor, and a second outlet from said housing connected to the discharge manifold of the compressor. Disposed in the bore is a piston assembly and poppet operable in response to changes of pressure in the bore. The piston and poppet move as a result of changes of pressure in the bore, created by the bore being selectively communicated with the side of the compressor and with the discharge side of the compressor. Movement of the piston assembly and poppet selectively communicates the inlet of said valve with either the suction side of the compressor when reduced capacity is required or with the discharge manifold when rated capacity is required.

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sum 2 0F 2 FIG 5 INVENTOR. RICHARD S. ABELL ATTORNEY FLUID COMPRESSION SYSTEM CONTROL BACKGROUND OF THE INVENTION This invention relates to fluid compressors, and in particular, to an unloading valve operable to control the capacity of such compressors.

In a compressor designed to operate at relatively constant speed, the load on the system in which the compressor is employed may sometimes vary, resulting in inefiicient operation of the compressor unless the capacity of the compressor may be varied to comply with the system variations. For example, constant speed compressors are generally employed in refrigeration systems wherein the load on such system may vary quite substantially.

One of the methods for varying the capacity of a compressor operating at constant speed is to provide means for bypassing some or all of the compressors output back to the suction side of the compressor from some point in the discharge manifold. One of the methods for obtaining the above-described reduction of capacity is to employ a valve that selectively communicates internal passages in the compressor cylinder that connects the discharge side of the compressor with the suction side thereof, to provide the desired control of the compressor capacity. Although such a method is efficient, the increased manufacturing costs are undesirable. Secondly, if maintenance is required, increased costs result due to the unloading device being located internally of the compressor cylinder. Another method of reducing capacity is to employ three-way valves externally of the compressor, in the discharge manifold. However, such valves are relatively expensive to manufacture and often require maintenance due to utilization springs which wear, due to their constant use in such applications.

Additionally, such valves generally create relatively large pressure drops therethrough and thus do not provide maximum capacity when the compressor is fully loaded.

The object of this invention is the provision of a three-way valve that is relatively inexpensive to manufacture, substantially maintenance free, a.nd one that does not create the excessive undesirable pressure drops so as to preclude delivery of rated capacity when such is required.

SUMMARY OF THE INVENTION This invention relates to fluid compressors, and in particular, to a method and apparatus for controlling the capacity of the compressor. More particularly, this invention relates to such a compressor employed in fluid compression systems including a refrigeration system.

The novel valve herein disclosed provides means to obtain the desired capacity control for such compressors. The valve includes a housing having an inlet in communication with the discharge side of the compressor. The valve includes first and second discharge lines extending therefrom, the first line being connected to the suction side of the compressor, and the second line being connected to the discharge manifold of the compressor. The valve functions to selectively communicate the discharge side of the compressor with either the suction side thereof or with the discharge manifold.

The housing of the valve defines a bore. Disposed in the bore is pressure-responsive means including a piston assembly and a poppet. Means associated with the valve selectively communicate the bore with either the suction side of the compressor when it is desired to operate the compressor at reduced capacity, or with the discharge side of the compressor when it is desired to operate the compressor at maximum capacity. When the bore is in communication with the suction side of the compressor, the piston and poppet move within the bore so as to communicate the inlet of the housing with the suction side of the compressor and to prevent communication between said inlet and the discharge manifold. The short circuiting of the refrigerant flow thus obtained effectively reduces the capacity of the compressor when maximum capacity is not needed, due to a decrease in the load on the system.

When maximum or rated capacity is desired, the bore of the valve is placed in communication with the discharge side of the compressor. The piston assembly and the poppet are thereby moved so as to communicate the inlet of the valve with the discharge manifold. When compressors of the type under discussion are employed in a refrigeration system, the discharge manifold is connected to the inlet of the condenser of such system.

Although the invention has been discussed as being employed with a reciprocating-type compressor, it should be understood that the invention can be also utilized with other types of fluid compressors, such as centrifugal types, employed in other applications besides refrigeration systems.

For example, in applications where a centrifugal compressor is employed to provide pressurized gas, it may be desirable to operate the machine even though no output therefrom is required, due to there being no load on the system. During such operation, the invention may be actuated so that gas discharged from the compressor is vented to the atmosphere or other relatively low-pressure area. Thus, it is apparent that the invention may readily be utilized with any type of compressor in any pressurized system where it is desirable to vary the output of the compressor, either totally, as with the centn'fugal compressor, or partially, as with the reciprocating compressor.

The attached drawings illustrate a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a refrigeration system illustrating the invention herein disclosed;

FIG. 2 is a cross-sectional view of the novel unloading valve utilized in the invention illustrating one operating position;

FIG. 3 is a cross-sectional view of the valve in its second operating position; and

FIG. 4 is a fragmentary sectional view taken along the line lVlV of FIG. 3..

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings there is shown the present invention employed in a refrigeration system. As noted above, the invention may be employed with compressors utilized in other applications wherein the load on the system may vary. ln referring to the drawings, like numerals shall refer to like parts.

Referring to FIG. 1 there is shown a refrigeration system including multicylinder compressor 10 comprising cylinders 11 and 12. Cylinders 11 and 12 have extending therefrom

discharge lines

13 and 14 respectively; discharge line 14 extends to discharge manifold 24 and line 13 communicates cylinder 11 with unloading valve 15. Valve 15 has extending therefrom a first discharge conduit 16 and a second discharge conduit 23. As will be apparent hereinafter, valve 15 functions to selectively communicate line 13 with either conduit 16 or conduit 23.

Conduit 16 communicates valve 15 with discharge manifold 24. Connected to the discharge manifold is condenser 17. Line 18 connects the outlet of the condenser to the inlet of thermal expansion valve 19, which functions as the refrigerant expansion device. It should be understood that other expansion devices, such as capillary tubes may be employed in lieu of expansion valve 19. The outlet of expansion valve 19 is connected to the inlet of evaporator coil 20 via conduit 18'.

The outlet from evaporator coil 20 is connected to suction manifold 22 via conduit 21. Additionally, conduit 23 communicates valve 15 with suction manifold 22. Suction lines 21' and 22' extend from the suction manifold to cylinders 11 and 12, respectively.

In operation, gaseous refrigerant is discharged from compressor cylinders 1 I and 12 via

lines

13 and 14. The high-pressure refrigerant gas flowing through line 14 passes to the condenser 17 via discharge manifold 24.

The gaseous refrigerant flowing through line 13 is either passed to suction manifold 22 or to discharge manifold 24, depending upon the operation of valve 15, as will be apparent hereinafter. If rated or maximum capacity is desired, valve 15 will function to pass'the refrigerant gas to discharge manifold 24 and thence to condenser 17. However, if less than maximum capacity is desired, valve 15 will operate to communicate line 13 with discharge conduit 23 and thence to suction manifold 22.

The gaseous refrigerant flowing through condenser 17 is passed in heat transfer relation with a relatively cold medium by means not shown whereby the cold medium extracts heat from the gaseous refrigerant to condense same.

The liquid refrigerant thus formed in condenser 17 flows via line 18 to expansion valve 19 and thence to evaporator 20. The refrigerant flowing through evaporator coil 20 passes in heat transfer relation with the medium to be cooled, such as room air, passed thereover by means not shown, whereby the refrigerant extracts heat from the medium to be cooled and is vaporized thereby.

The vaporous refrigerant formed in evaporator coil 20 flows to suction manifold 22 via conduit 21 and thence to the suction side of cylinders l l and 12 of compressor 10.

In referring now to FIGS. 2 and 3, there is shown a crosssectional view of the novel valve 15 shown in a loaded position and an unloaded position, respectively. The novel valve 15 includes a housing 25, which defines a cylindrical bore 29. Disposed in bore 29 is piston assembly 30, the piston assembly being operable to reciprocally move in the bore. The piston assembly includes stem section 31, which threadably engages the upper portion of the piston assembly at 31'.

-Additionally disposed in bore 29 is poppet 32, which also moves in a reciprocal manner in the bore. C-ring 28 limits the upward movement of the poppet in the bore. Piston assembly includes seal rings 26 and 27, such as O-rings or piston rings, mounted thereon for sealing purposes.

As noted hereinbefore, discharge line 13 communicates the inlet of the valve with the discharge side of cylinder 11. The gaseous refrigerant thus introduced into bore 29 will be directed by the operation of piston assembly 30 and poppet 32, as will be apparent hereinafter, to either discharge conduit 16 or discharge conduit 23.

A relatively small bleed line extends from discharge conduit 16 to orifice 39 provided in cap 36. Threadably engaging the lower portion of cap 36 is end piece 37, which functions to close off the upper portion of bore 29. Orifice 38 in end piece 37 is selectively communicated with orifice 39 in cap 36 and with orifice in cap 36. Orifice 40 is in communication with discharge conduit 23 via bleed line 34.

Acting to control the communication of orifice 38 with

orifices

39 and 40 is solenoid-actuated valve 33. As shown in FIG. 2, when full capacity is desired, valve 33 will operate to communicate orifice 39 with orifice 38.

As shown in FIG. 3 wherein valve 15 is shown in its unloaded position, solenoid 33 functions to communicate orifice 38 with orifice 40. FIG. 2 illustrates solenoid valve 33 in its deenergized position, whereas FIG. 3 illustrates solenoid valve 33 in its energized position. A source of power represented by lines L and L, controls the energization of solenoid valve 33. A switch, not shown, controls the supply of power to solenoid valve 33. It should be understood that other means may be employed to selectively communicate the orifices in lieu of solenoid valve 33.

Referring now to FIG. 3 wherein the novel valve is shown in its unloaded position, the manner in which the valve operates will hereinafter be described. As noted hereinabove, in the position illustrated by FIG. 3, orifice 38 is in communication with orifice 40. The piston assembly 30 is at the highest position within bore 29. Poppet 32 is seated on seat 41, thereby preventing flow from line 13 to conduit 16 and communicating line 13 with conduit 23. Conduit 23, as noted before, communicates with suction manifold 22 and is, therefore, at suction pressure. Similarly, line 13 is at suction pressure when in communication with conduit 23. Cylinder 11 is thereby prevented from reaching discharge pressure and the compressor is operated at reduced capacity as desired. The cost of operating the compressor at reduced capacity is substantially decreased since less power is required by the machine.

When it is desired to deliver rated capacity due to an increase in the load on the refrigeration system, solenoid valve 33 is deenergized so that communication between

orifices

38 and 40 is prevented and orifice 38 is placed in communication with orifice 39.

Refrigerant gas at discharge pressure flows from conduit 16 having communication with manifold 24, through line 35 to orifice 39 and thence to orifice 38 in communication therewith. The lower surface of the stem 31 of piston assembly 30 has suction pressure acting thereon. The refrigerant gas at discharge pressure acting on the top surface of piston assembly 30 thus causes the piston assembly to move downwardly in bore 29 so as to prevent communication between line 13 and conduit 23, the poppet 32 and the stem 31 having a sliding fit enabling such action to obtain.

The refrigerant gas flowing from line 13 through valve 15 fills the space defined by the upper surface of the stem portion and the lower surface of the poppet. The pressure therein increases rapidly and very quickly reaches a magnitude to supply a force to move the poppet in an upward direction in bore 29. The upward movement of poppet 32 is limited by C- ring 28. When poppet 32 has reached its upper limit of movement, line 13 and discharge conduit 16 are in communication, thus placing line 13 at discharge pressure, the parts assuming the position indicated in FIG. 2. Cylinder l 1 thereby operates in its loaded position and discharges refrigerant gas therefrom at rated discharge pressure.

Assume now that the compressor is operating at rated capacity with the piston assembly and poppet positioned as shown in FIG. 2. If the load on the system decreases, it becomes desirable to reduce the capacity of the compressor to reduce the operating cost thereof and to prevent compressor flooding. To obtain the desired reduced capacity, solenoid valve 33 is energized so as to communicate orifice 38 with orifice 40. Communication of these orifices causes the refrigerant gas acting on the top surface of piston 30 to flow from orifice 38 through orifice 40 and bleed line 34 to conduit 23, which is at suction pressure as noted hereinbefore. The refrigerant gas trapped between piston 30 and poppet 32, which is substantially at discharge pressure, causes the piston assembly to begin moving in an upward direction in the bore as the pressure on the upper surface thereof is reduced. It should be noted that refrigerant gas at discharge pressure is able to pass into the space between the lower surface of the piston assembly and the upper surface of the poppet when the valve is in its loaded position as shown in FIG. 2 by leakage around the poppet and through the space of the C-n'ng, as clearly shown in FIG. 4 This space is thus maintained at substantially discharge pressure as is desired. The upward movement of piston assembly 30 in bore 29 starts to communicate line 13 with conduit 23 thereby diverting a portion of the flow of refrigerant gas through conduit 23 to the suction manifold and, additionally, reducing the pressure acting on the lower surface of poppet 32.

The reduced pressure lessens the force acting on the lower surface of poppet 32, and thereby creates a force acting on the poppet, which causes the poppet to move downwardly in the bore and to thus sit on seat 41. Poppet 32, when seated, prevents any flow of refrigerant gas from line 13 to conduit 16 and diverts all of the flow of refrigerant gas to conduit 23. Additionally, discharge pressure is maintained in bore 29, via the small passageway 42 shown in FIG. 3, provided between the top portion of the poppet and the housing. The passageway permits leakage of refrigerant gas from discharge conduit 16 back into the bore. The discharge pressure acts on the lower portion of the piston assembly and causes the piston assembly to move upward in bore 29 to its maximum position as shown in FIG. 3.

it is, therefore, readily apparent that the novel valve herein disclosed readily permits rapid and efficient reduction in compressor capacity when desired, and in addition, obviates the repair and manufacturing cost problems of the prior art. Additionally, the relatively large diameter conduits extending from valve and the absence of restrictions in the bore thereof, reduce the pressure drops therethrough as is desired to obtain rated capacity when required.

While I have described and illustrated a preferred embodiment of my invention, it will be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

I claim:

1. An unloading valve for controlling the capacity of a fluid compressor comprising:

A. a housing;

B. inlet means to said housing;

C. first discharge means from said housing;

D. second discharge means from said housing;

E. pressure-responsive means disposed in said housing having a first operating position when the fluid compressor is functioning at rated capacity and having a second operating position when said fluid compressor is functioning at reduced capacity, said pressure-responsive means communicating said inlet means and said first discharge means when in its first operating position, and communicating said inlet means with said second discharge means when in its second operating position, said pressure-responsive means including:

1. piston means reciprocally disposed in said valve housing; and

2. poppet means reciprocally disposed in said valve housing, the movement thereof being in an opposite direction to the movement of said piston; and

F. means operable to vary the pressure acting on said pressure-responsive means, said pressure being of a first magnitude when it is desired to have said pressure-responsive means in its first operating position, and being of a second magnitude when it is desired to have said pressureresponsive means in its second operating position.

2. The unloading valve in accordance with claim 1 wherein said piston assembly includes a piston portion and a stern portion and wherein said poppet means is mounted about said stem portion to move relative thereto.

3. A method of operating an unloading valve for controlling the capacity of a compression mechanism comprising the steps of:

A. selectively communicating the bore of said unloading valve with the discharge side of said compression mechanism when it is desired to operate at rated capacity, and with the suction side of said compression mechanism when it is desired to operate below rated capacity;

B. moving a piston reciprocally disposed in the bore of said valve in an upward direction in said bore when said bore is in communication with the suction side of said compression mechanism and moving said piston in a downward direction in said bore when said bore is in communication with the discharge side of said compression mechanism; and

C. moving a poppet disposed in said bore in an opposite direction to the movement of said piston, said poppet and piston acting in conjunction with each other to communicate the inlet of said valve with the inlet of said compression mechanism when said bore is in communication with the suction side of said compression mechanism, and communicating the inlet of said valve to the discharge side of said compression mechanism when said bore is in communication with the discharge side of said compression mechanism.

Claims

1. An unloading valve for controlling the capacity of a fluid compressor comprising: A. a housing; B. inlet means to said housing; C. first discharge means from said housing; D. second discharge means from said housing; E. pressure-responsive means disposed in said housing having a first operating position when the fluid compressor is functioning at rated capacity and having a second operating position when said fluid compressor is functioning at reduced capacity, said pressure-responsive means communicating said inlet means and said first discharge means when in its first operating position, and communicating said inlet means with said second discharge means when in its second operating position, said pressure-responsive means including: 1. piston means reciprocally disposed in said valve housing; and 2. poppet means reciprocally disposed in said valve housing, the movement thereof being in an opposite direction to the movement of said piston; and F. means operable to vary the pressure acting on said pressureresponsive means, said pressure being of a first magnitude when it is desired to have said pressure-responsive means in its first operating position, and being of a second magnitude when it is desired to have said pressure-responsive means in its second operating position.

2. poppet means reciprocally disposed in said valve housing, the movement thereof being in an opposite direction to the movement of said piston; and F. means operable to vary the pressure acting on said pressure-responsive means, said pressure being of a first magnitude when it is desired to have said pressure-responsive means in its first operating position, and being of a second magnitude when it is desired to have said pressure-responsive means in its second operating position.

2. The unloading valve in accordance with claim 1 wherein said piston assembly includes a piston portion and a stem portion and wherein said poppet means is mounted about said stem portion to move relative thereto.

3. A method of operating an unloading vAlve for controlling the capacity of a compression mechanism comprising the steps of: A. selectively communicating the bore of said unloading valve with the discharge side of said compression mechanism when it is desired to operate at rated capacity, and with the suction side of said compression mechanism when it is desired to operate below rated capacity; B. moving a piston reciprocally disposed in the bore of said valve in an upward direction in said bore when said bore is in communication with the suction side of said compression mechanism and moving said piston in a downward direction in said bore when said bore is in communication with the discharge side of said compression mechanism; and C. moving a poppet disposed in said bore in an opposite direction to the movement of said piston, said poppet and piston acting in conjunction with each other to communicate the inlet of said valve with the inlet of said compression mechanism when said bore is in communication with the suction side of said compression mechanism, and communicating the inlet of said valve to the discharge side of said compression mechanism when said bore is in communication with the discharge side of said compression mechanism.