WO2004038310A1

WO2004038310A1 - Expansion valve for high-pressure refrigeration systems

Info

Publication number: WO2004038310A1
Application number: PCT/DK2003/000716
Authority: WO
Inventors: Jürgen Süss; Holger Nicolaisen
Original assignee: Danfoss A/S
Priority date: 2002-10-26
Filing date: 2003-10-22
Publication date: 2004-05-06
Also published as: DE10249950B4; AU2003273779A1; DE10249950A1

Abstract

The invention relates to an expansion valve (1) for high-pressure refrigeration systems with a valve seat (5), a valve element (9) cooperating with the valve seat (5), a spring arrangement, which acts upon the valve element (9), and an adjusting device (23) for the spring arrangement. It is endeavoured to provide an expansion valve, which can be driven by a relatively weak drive, also in connection with high pressures. For this purpose, the spring arrangement has at least a first spring (11) and a second spring (12), which act upon the valve element, the first spring (11) defining a operating area and the second spring (12) having a spring force, which can be changed by means of the adjusting device.

Description

Expansion valve for high-pressure refrigeration systems

The invention relates to an expansion valve for high- pressure refrigeration systems with a valve seat, a valve element cooperating with the valve seat, a spring arrangement, which acts upon the valve element, and an adjusting device for the spring arrangement .

The invention particularly relates to a motor-operated expansion valve for C0₂ refrigeration systems. In refrigeration systems using C0₂ as refrigerant, the pressure is typically relatively large. Pressures of 100 bar or more are usual . The large pressures are the result of the physical properties of the carbon dioxide.

In the expansion valve the pressure of the C0₂ acts in the opening direction. In the opposite direction acts the force of the spring arrangement . In order to be able to close the expansion valve properly, the force of the spring arrangement must be relatively large. In order to make a refrigeration system, using carbon dioxide as refrigerant, work optimally from an energetic point of view, the spring force, which determines the opening pressure of the valve, must be adjustable during operation. The energetically optimal pressure in the gas cooler of the refrigeration system will change, when the temperature, at which the carbon dioxide leaves the gas cooler, changes. Among other things, this temperature depends on the ambi- ent temperature of the gas cooler. The related pressure is controlled by the expansion valve. It is known to let the adjusting device change the spring force, that is, the force, with which the spring arrangement acts upon the valve element. The adjusting device can, for example, be in the form of a motor. As, however, the force of the spring arrangement is relatively large, either a relatively strong motor or a gear between motor and valve will be required. This increases the manufacturing costs.

The invention is based on the task of operating an expansion valve with a relatively weak drive, also in connection with high pressures.

With an expansion valve as mentioned in the introduction, this task is solved in that the spring arrangement has at least a first spring and a second spring, which act upon the valve element, the first spring defining a operating area and the second spring having a spring force, which can be changed by means of the adjusting device.

Thus, the force acting upon the valve element is produced by at least two springs. For this purpose, one spring is dimensioned so that it produces a fixed preload. This preload then defines a force level, that is, a operating area or a operating point. The second spring, however, determines the dynamic area during operation, that is, the moving possibility of the valve element in the operating area or in relation to the operating point. It is also possible to work only in one direction from the operating point. The upper limit of the operating area is determined by the maximum reaction force of the second spring. The adjusting device does not adjust the first spring. Thus, the adjusting device can be dimensioned weaker by at least the force that is provided by the first spring. It merely has to be dimensioned for the force, which is produced by the second spring. However, a safe closing of the expansion valve is still possible.

Preferably, the first spring is stronger than the second spring. Thus, the first spring has a larger spring constant than the second spring. Accordingly, the distribution of the forces produced by the springs is so that the adjusting device only has to produce a small share of the total force provided by the spring arrangement. Thus, the adjusting device can be dimensioned to be relatively weak, without having a negative influence on the dynamic behaviour of the expansion valve.

Preferably, the spring force of the first spring is adjustable. The first spring can be preloaded to adapt the operating point determined by said first spring to different conditions. This can take place during manufacturing of the expansion valve, but also later, when the unit is finished, for example by means of an adjusting screw. However, the spring force of the first spring is not adjustable during operation, that is, it is not dynamic. Thus, the adjusting device does not have to be dimensioned for adjusting the first spring.

Preferably, the second spring is supported on a spindle, movable by the adjusting device, the movement stroke of said spindle being limited by a stop, on which the first spring is supported. In this situation, the valve element should be able to lift off from the valve seat, when the pressure is large enough. In other words, the expansion valve can be opened in this position. As the first spring is supported on the same stop, an adjustment of this stop is a simple manner of fixing the operating point of the expansion valve .

Preferably, the first spring and the second spring act upon the valve element in parallel to one another. Thus, the forces of the two springs are added. Through the mutual overlaying of the two spring forces, the increase of the force of a spring ensures a relatively simple setting of the correct closing or opening force of the valve element .

It is particularly preferred that the first spring and the second spring are in the form of helical springs arranged concentrically in relation to one another. This saves space. The second spring can be arranged inside the first spring, without causing that the two springs impede the operating possibilities of one another.

Preferably, the spring arrangement acts upon the valve element via a joint connection, which has a ball element between the valve element and the spring arrangement . Particularly when using helical springs, it is difficult to direct the spring effect of the spring arrangement exactly axially, that is, in the movement direction of the valve element, on the valve element. By means of the ball between the valve element and the spring arrangement, slightly slanted positions of the spring arrangement are balanced, without causing a simultaneous slanting of the valve element. The orientation of the valve element in relation to the valve seat can thus be maintained with a high reliability. It is particularly preferred that the ball element is arranged between a pressure plate, on which the spring arrangement is supported, and a surface of the valve element. This makes it easier to perform a reliable transfer of the forces from the spring arrangement to the valve element .

Preferably, the pressure plate and/or the surface . of the valve element have a ball socket, in which the ball ele- ment is arranged. Thus, the ball element is retained in the pressure plate and/or in the valve plate. Additionally, the ball element can also be retained laterally in a housing part, so that the use of a ball element, which is arranged to be a separate component between the pressure plate and the valve element plate, will cause no disturbances of the operation.

Preferably, a diaphragm is arranged between the valve element and the valve seat, said diaphragm forming a wall of a pressure chamber. This is a simple way of making the pressure at the inlet act upon the valve element. As the diaphragm is resilient and has a certain flexibility, this at the same time provides a good closing behaviour of the valve, that is, at the same time the diaphragm produces a sealing surface, with which the valve element acts upon the valve seat .

It is preferred that the diaphragm is suspended between a valve housing and an actuator housing. Thus, the valve housing gets tight, and it is ensured that the pressure does not propagate to the actuator housing. No further sealings are required in the operation part. At the same time, the diaphragm is reliably fixed. It is particularly preferred that the actuator housing has a bearing surface for the diaphragm, on which the diaphragm bears in the open state of the valve . As the expan- sion valve is activated at high pressures of the refrigerant, the bearing surface is a good aid in preventing a too heavy dilatation of the diaphragm. As soon as the valve is opened, the diaphragm bears on the bearing surface.

In the following, the invention is described in detail on the basis of a preferred embodiment in connection with the only figure, showing:

a schematic section through an expansion valve of a C0₂ refrigeration system.

The figure shows an expansion valve 1 of a C0₂ refrigeration system with an inlet 2 and an outlet 3, which are arranged in a valve housing 4. In the valve housing 4 is provided a valve seat 5. The valve seat 5 can be arranged on an orifice insert 6, which is inserted in the housing 4.

An actuator housing 7 is screwed into the valve housing 4. Between the valve housing 4 and the actuator housing 7 is suspended a diaphragm 8 , which can be brought to bear on the valve seat 5 by means of a valve element 9. Together with the valve housing 4, the diaphragm 8 surrounds a pressure chamber 10, which is connected with the inlet 2. Thus, the pressure at the inlet 2 acts upon the diaphragm

8. The actuator housing 7 has the form of a hollow cylinder.

In the hollow cylinder is arranged a first spring 11 in the form of a helical pressure spring. Concentrically to and inside the first spring 11 is arranged a second spring 12. Together, the two springs 11, 12 form a spring arrangement, which is supported on a pressure plate 13, that is, the pressure plate 13 forms a movable counter flange for the two springs 11, 12.

The pressure plate 13 is part of a joint connection 14, which has a ball element 15. Also a surface of the valve element 9 belongs to the joint connection 14. The ball element 15 is guided laterally, that is, in the radial direction, in a bore 16 at the foot of the actuator housing 7. In the opening direction of the valve element 9 the ball element 15 is movable.

Both the pressure plate 13 and the valve element 9 have ball sockets 17, 18, in which the ball element 15 is sup- ported. Thus, within certain limits, the pressure plate 13 is able to perform tilting movements in relation to the valve element 9.

The first spring 11 is supported on an adjusting screw 19, which is screwed into the actuator housing 7. The adjusting screw 19 has surfaces 20 shaped for the application of torque, for example two bores, so that it can be adjusted inside the actuator housing 7. A turning of the adjusting screw 19 changes the distance between the adjusting screw 19 and the pressure plate 13, so that the preload of the first spring 11, which is suspended between the adjusting screw 19 and the pressure plate 13, can be changed. The second spring 12 bears on a projection 21 of a spindle

22, which is displaced in the longitudinal direction by a drive 23. An actuation of the drive 23 will thus change the preload of the second spring 12 during operation.

A movement of the spindle 22, which leads to a release of the second spring 12, is limited by the projection 21, which will rest on the adjusting screw 19 at the end of a movement .

The expansion valve 1 works as follows :

In the pressure chamber 10 acts the pressure of the refrigerant. Thus, the pressure acts upon the diaphragm 8, and the pressure in the pressure chamber 10 acts upon the valve element 9 in the opening direction.

In the opposite direction firstly acts the pressure of the first spring 11, which is fixedly preset, after that the adjusting screw 19 has been brought to a predetermined position. This setting is usually made during manufacturing or mounting of the expansion valve 1. The force of the spring 11 is sufficient to close the expansion valve 1 completely at a pressure in the lower end of the applica- tion area. Expediently, the setting of the adjusting screw 19 is therefore done, when the spindle 22 bears with its projection 21 on the adjusting screw 19.

During operation, the "fine tuning" of the valve element 9 is made via the spindle 22 and the second spring 12 acted upon by the spindle 22. The drive 23 thus controls the preload of the second, weaker spring 12. The preloads of the first spring 11 and the second spring 12 are added and together produce the spring force, which acts against the pressure in the pressure chamber 10.

Thus, it is possible, during operation, to adjust the de- sired opening pressure, which is present in the carbon dioxide gas .

The expansion valve is described in connection with a refrigeration system operating with carbon dioxide (C0₂) . In principle, however, the expansion valve 1 can also be used with other refrigerants, which are operated at a higher pressure, so that the preloads of the spring arrangement must be high.

The expansion valve is pressure-controlled. At the same time, it performs a safety function, as it opens at too high pressures. The opening pressure is adjustable, so that too high pressures in a connected system can be avoided.

Claims

Patent Claims

1. Expansion valve for high-pressure refrigeration systems with a valve seat, a valve element cooperating with the valve seat, a spring arrangement, which acts upon the valve element, and an adjusting device for the spring arrangement, characterised in that the spring arrangement has at least a first spring (11) and a second spring (12) , which act upon the valve element, the first spring (11) defining a operating area and the second spring (12) having a spring force, which can be changed by means of the adjusting device.

2. Valve according to claim 1, characterised in that the first spring (11) is stronger than the second spring (12) .

3. Valve according to claim 1 or 2 , characterised in that the spring force of the first spring (11) is adjustable .

4. Valve according to one of the claims 1 to 3, characterised in that the second spring (12) is supported on a spindle (22) , movable by the adjusting device (23) , the movement stroke of said spindle being limited by a stop (19) , on which the first spring (11) is supported.

5. Valve according to one of the claims 1 to 4, characterised in that the first spring (n) and the second spring (12) act upon the valve element (9) in parallel to one another.

6. Valve according to claim 5, characterised in that the first spring (11) and the second spring (12) are in the form of helical springs arranged concentrically in relation to one another.

7. Valve according to one of the claims 1 to 6, charac- terised in that the spring arrangement acts upon the valve element (9) via a joint connection (14) , which has a ball element (15) between the valve element (9) and the spring arrangement .

8. Valve according to claim 7, characterised in that he ball element (15) is arranged between a pressure plate (13) , on which the spring arrangement is supported, and a surface of the valve element.

9. Valve according to claim 8, characterised in that the pressure plate (13) and/or the surface of the valve element have a ball socket (17, 18), in which the ball element (15) is arranged.

10. Valve according to one of the claims 1 to 9, characterised in that a diaphragm (8) is arranged between the valve element (9) and the valve seat (15) , said diaphragm forming a wall of a pressure chamber (10) .

11. Valve according to claim 10, characterised in that the diaphragm (8) is suspended between a valve housing (4) and an actuator housing (7) .

2. Valve according to claim 11, characterised in that the actuator housing (7) has a bearing surface for the diaphragm (8) , on which the diaphragm (8) bears in the open state of the valve.