US3688516A

US3688516A - Air conditioning control system

Info

Publication number: US3688516A
Application number: US99807A
Authority: US
Inventors: Alwin B Newton
Original assignee: Borg Warner Corp
Current assignee: York International Corp
Priority date: 1970-12-21
Filing date: 1970-12-21
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05

Abstract

A control system for an air conditioning or refrigeration apparatus includes a constant pressure regulating valve (automatic expansion valve) between the condenser and the evaporator and a temperature responsive valve between the evaporator and the compressor. Both valves are capable of adjustment to establish: (1) a predetermined pressure (and corresponding temperature) in the evaporator; and (2) a predetermined temperature of the refrigerant in the suction line leading to the compressor. Means are provided for coordinating the setting for both such valves to maintain a certain minimum superheat in the suction gas.

Description

nited States atent Newton Sept. 5, 1972 Primary Examiner-Meyer Perlin AttrneyDonald W. Banner, John W. Butcher and William S. McCurry [72] Inventor: Alwin B. Newton, York, Pa.

[73] Assignee: Borg-Warner Corporation, [57] A S Chicago, 111.

A control system for an air conditioning or refrigera- Filedi 21, 1970 tion apparatus includes a constant pressure regulating [21] Appl. No.: 99,807 valve (automatic expansion valve) between the condenser and the evaporator and a temperature responsive valve between the evaporator and the compres- [52] US. Cl. ..62/205, 62/217, 62/225 SOL Both valves are capable of adjustment to lIIt. establish: a predetennined pressure CO[. [58] Field of Search ..62/205, 210, 217, 222, 225 responding temperature) in the evaporator; and (2) a predetermined temperature of the refrigerant in the [56] References Cited suction line leading to the compressor. Means are pro- UNITED STATES PATENTS vided for coordinating thesetting for both such valves to maintain a certain minimum superheat 1n the suc- 3,296,816 1/1967 We11ed ..62/210 tion 2,116,801 /1938 Shivers ..62/217 4 Claims, 1 Drawing Figure o 71 68 f o 2:

5 e4 60 52 44 E 4 Q Q 11 Q: 74 6 W ,r-dl

34 2O 56 L 30 I 12 PATENTEDsEr s an INVENTOR AZW/IV 5. NEWTQ/V BY ,ZvaQ/Z ATTOR N EV BACKGROUND OF THE INVENTION 1. Field of the Invention Automatic control of vapor cycle refrigeration or air conditioning systems in which an automatic expansion valve and a temperature responsive suction throttling valve are independently adjustable with means for maintaining a minimum superheat to prevent carryover ofliquid in the suction line.

2. Description of Prior Art US. Pat. No. 3,260,064, A. B. Newton, issued July 12, 1966, shows a system utilizing a constant pressure expansion device and a suction throttling valve sensing the temperature of refrigerant upstream from the throttling valve.

U.S. Pat. No. 3,119,559, J. W. I-leidorn, issued Jan. 28, 1964, describes an automotive air conditioning system provided with an evaporator pressure regulator downstream from the evaporator and a thermal expansion valve controlling flow of refrigerant from the high side to the low side of the system.

SUMMARY OF THE INVENTION This invention relates generally to a control for refrigeration systems and more particularly to air conditioning apparatus.

In US. Pat. No. 3,119,559, the evaporator pressure regulating valve effectively prevents the evaporator coil pressure from dropping below a predetermined, non-icing pressure condition, for example, 32 psig. Under low loads, the evaporator becomes partially flooded, sending slugs of liquid through to the compressor. This condition sometimes results in broken compressor valves and other damage.

In US. Pat. No. 3,260,064 (Newton), an improved system is described which includes an adjustable automatic expansion valve and means to control the capacity of the compressor by various techniques, for exam ple, by throttling the suction gas or by unloading one or more compressor cylinders. In the embodiment using suction gas throttling, the refrigerant temperature is sensed as the gas leaves the evaporator on the upstream side of the valve.

In the Newton system, if the setting on the automatic expansion valve is adjusted, it is necessary to reset the temperature responsive suction line valve to assure some minimum superheat in the gas entering the compressor. For example, assume that a system is using R- 12 refrigerant and that the evaporator pressure is set, by adjustment of the automatic expansion valve, to 30.07 psig (32F). If 6 of superheat is desired, the setting on the suction line valve would control the flow to the compressor so as to maintain 38F because the temperature responsive valve only reads the temperature component of superheat. If the automatic expansion valve is then adjusted to higher pressure, say 40.7 psig to produce an evaporator coil temperature of 44F the evaporator coil would be completely flooded and liquid would flow through the suction line into the compressor.

In order to avoid this problem, the present invention provides a mechanical coordination between the setting of the automatic expansion value and the temperature responsive, suction line valve. Such means may take many forms, but in the preferred embodiment, it may simply be a pair of cables interconnecting an adjusting screw on each valve with a control dial. The two dials then are provided with interengaging stop means so that the respective settings on the automatic expansion valve and the suction line valve cannot be changed to positions which result in less than the desired minimum superheat.

DESCRIPTION OF THE DRAWING The FIGURE shows a refrigeration or air conditioning system, partly in schematic form, constructed in accordance with the principles of this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the FIGURE, there is shown a conventional vapor cycle refrigeration system including a compressor 10, condenser 12, and expansion device 14, evaporator 16, and a temperature responsive, suction line throttling valve 18.

Refrigerant gas is compressed in the compressor 10 and flows through line 20 to the condenser 12. Liquid refrigerant then flows through line 22 to the automatic expansion device 14 which is of a pressure responsive type, to be described in detail below, maintaining a relatively constant pressure in the evaporator. The low pressure liquid refrigerant then flows through line 24 to the evaporator, over which air is circulated by means of a blower 26. The refrigerant is evaporated from the inside of the coil and vaporized refrigerant gas flows through line 28 to the throttling valve 18, and then through line 29 to compressor 10.

The pressure responsive expansion device 14 is of the type that senses pressure on the downstream side of the valve to maintain a substantially constant pressure in the evaporator. On sensing a drop in pressure, the valve opens to permit more refrigerant to flow and will close upon a rise in pressure. Valve 14 comprises a housing 32 enclosing a diaphragm 34 attached to valve member 30, a first spring 36 biasing valve member 30 closed, and a second spring 38 biasing it open. The load on spring 38 is adjusted by a threaded plug 40 which determines the amount of force necessary to open the valve. Pressure on the downstream side of the valve is applied to diaphragm 34 through line 42, it being understood that the pressure could also be transmitted internally of the valve.

The suction line valve 18 comprises a housing 44 having an inlet chamber 46 communicating with the evaporator through line 28 and an outlet chamber 48 communicating with the suction line of the compressor through line 29. The housing is provided with a partition 50 separating

chambers

46 and 48, and having a valve seat 52 which cooperates with valve 54. At one end of the housing 44 is a valve operating mechanism comprising an operating bellows 56 connected with a remote thermal responsive bulb 58. The operating mechanism is sealed from chamber 48 by means of a bellows-type seal 60 which has a much smaller area than bellows 56. The stem 62 of valve 54 is attached to the operating bellows which expands and contracts in response to temperature sensed by bulb 58. Remote bulb 58 may be located either on the suction line 29 downstream from the valve, or in line 28 connecting the evaporator and the valve. In the FIGURE, the bulb is shown as being located in contact with line 28. The

force required to close the valve 54 i.e., the control point, is adjusted by the compression on spring 64, said spring being interposed between the operating bellows and an adjusting screw 66.

In accordance with the invention, the settings of the automatic expansion device 14 and the suction line valve 18 are mechanically coordinated to maintain some minimum degree of superheat. This may be accomplished in a relatively simple manner by interconnecting the adjustment screw 40 on valve 14 with an operating lever 68 via a torque transmitting cable 70; and adjusting screw 66 is connected to lever 72 by cable 74. For convenience, a common dial 7! may be used to correlate the position of

levers

68 and 72 with the evaporator temperature and superheat setting, respectively.

In order to assure that some minimum degree of superheat is present regardless of the settings on the respective levers, a lug 76 may be attached to one or the other of such levers, so that this provides interengaging stop means for preventing the position of lever 72 to be pushed beyond the setting of lever 68. For example, any attempt to move lever 72 counter clockwise (reducing superheat) will result in engagement of lever 68 to resposition it to a lower setting. Conversely, movement of lever 68 in a clockwise direction to obtain a higher evaporator pressure, will automatically move the suction line valve to a corresponding higher superheat setting.

While the invention has been described in connection with a certain specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation; and the scope of the appended claims should be construed as broadly as the prior art will permit.

What is claimed is:

l. Refrigeration apparatus comprising: a compressor, a condenser, and an evaporator connected in a closed circuit, vapor cycle system through which a refrigerant is circulated; a constant pressure expansion device operatively connected between said condenser and said evaporator to maintain a predetermined pressure (and corresponding temperature) of refrigerant in said evaporator; temperature responsive valve means operatively connected between said evaporator and said compressor to control the flow of refrigerant therebetween, and maintain a predetermined superheat of the refrigerant leaving said evaporator; first adjusting means for adjusting the control point of said constant pressure expansion device; second adjusting means for independently adjusting the control point of said valve means; and means for mechanically interconnecting said first and second adjusting means to maintain a predetermined minimum temperature differential between the control point of said expansion device and the control point of said temperature responsive valve means.

2. Apparatus as defined in claim 1 wherein said first adjusting means includes a remotely located lever for changing the control point of said constant pressure expansion device, and said second adjusting means insion device is adju ted to a setting which would result in a temperature d1 ferential lower than said predetermined minimum.

3. In a refrigeration apparatus of the type including a compressor, a condenser, and an evaporator connnected in a closed circuit, vapor cycle system through which a refrigerant is circulated; a constant pressure expansion device operatively connected between said condenser and said evaporator to maintain a predetermined pressure (and corresponding temperature) of refrigerant in said evaporator; temperature responsive valve means operatively connected between said evaporator and said compressor to control the flow of refrigerant therebetween and maintain a predetermined superheat of the refrigerant leaving said evaporator; the improvement comprising first adjusting means for adjusting the control point of said constant pressure expansion device; second adjusting means for independently adjusting the control point of said valve means; and means for mechanically interconnecting said first and second adjusting means to maintain a predetermined minimum temperature differential between the control point of said expansion device and said temperature responsive valve means.

4. Refrigeration apparatus comprising: a compressor, a condenser, and an evaporator connected in a closed circuit, vapor cycle system through which a refrigerant is circulated; a constant pressure expansion device operatively connected between said condenser and said evaporator to maintain a predetermined pressure (and corresponding temperature) of refrigerant in said evaporator, said expansion device including a pressure responsive element actuating a valve, said valve closing upon a rise in evaporator pressure; temperature responsive valve means operatively connected between said evaporator and said compressor to control the flow of refrigerant therebetween and maintain a predetermined superheat of the refrigerant entering said compressor, said temperature responsive valve means having a temperature responsive element opening said valve means upon a temperature rise; first resilient means opposing the valve opening force of said temperature responsive element, first adjusting means for adjusting the compressive force on said first resilient means; second resilient means opposing the closing force of said pressure responsive element, and second adjusting means for adjusting the compressive force on said second resilient means; first and second remotely located levers operatively connected respectively to said first and second adjusting means; a lug attached to one of said levers adapted to engage the other of said levers after a predetermined rotation in a direction toward the same, the interengaging of said lug with said lever being adapted to prevent the setting of the constant pressure expansion device to produce a temperature lower than a predetermined temperature difference between the refrigerant in said evaporator and the refrigerant passing through said valve means.

Claims

1. Refrigeration apparatus comprising: a compressor, a condenser, and an evaporator connected in a closed circuit, vapor cycle system through which a refrigerant is circulated; a constant pressure expansion device operatively connected between said condenser and said evaporator to maintain a predetermined pressure (and corresponding temperature) of refrigerant in said evaporator; temperature responsive valve means operatively connected between said evaporator and said compressor to control the flow of refrigerant therebetween, and maintain a predetermined superheat of the refrigerant leaving said evaporator; first adjusting means for adjusting the control point of said constant pressure expansion device; second adjusting means for independently adjusting the control point of said valve means; and means for mechanically interconnecting said first and second adjusting means to maintain a predetermined minimum temperature differential between the control point of said expansion device and the control point of said temperature responsive valve means.

2. Apparatus as defined in claim 1 wherein said first adjusting means includes a remotely located lever for changing the control point of said constant pressure expansion device, and said second adjusting means includes an adjacent lever, and interengaging stop means on one of said levers adapted to reset the control point of said temperature responsive valve when said expansion device is adjusted to a setting which would result in a temperature differential lower than said predetermined minimum.