DE102006057131B3 - Thermo-static expansion valve for controlling high pressure of transcritically and/or subcritically operable cooling and heating pump circuit, has control member controllable independent of pressure whose movement is coupled with area - Google Patents

Abstract

The valve (15) has a control member (46) thermally controllable, which is independent of high pressure. The positioning movement of the control member is movement-coupled with an effective area (37) of another control member (36), if a temperature-dependent positioning movement of the thermally controllable control member acts against the positioning movement of the effective area. A temperature usage value of the thermally controllable control member for the positioning movement is adjusted to a value as the maximum operation temperature of a control filling (41) of the control member.

Description

The The invention relates to a thermostatic expansion valve for a Cold- or heat pump cycle according to the generic term of claim 1.

In transcritical refrigeration or heat pump cycles, the high-pressure side heat release is usually above the critical pressure of the applied refrigerant. Due to the resulting sliding temperature gradient in the gas cooler, the pressure at the gas cooler outlet is a degree of freedom in the circulation process. Especially in cycles that use CO ₂ as a refrigerant, it is very important to regulate the high pressure as a function of the ambient or gas cooler outlet temperature in an optimal efficiency range. In CO ₂ air conditioners mostly only fixed throttles or externally controlled expansion elements are used in the regulation of the refrigeration cycle. The former do not allow adaptation of the high pressure to the process boundary conditions during operation.

Externally controlled Must have expansion organs therefor be controlled by electronic controls whose responsiveness especially for the automotive application is insufficient. Accordingly can they do not have sufficient operating safety Offer. Other disadvantages are high susceptibility to failure, high development and cost.

The DE 102 49 950 B4 discloses an expansion valve for high-pressure refrigeration systems with a valve seat and a valve element which cooperates with the valve seat, and a spring arrangement which acts on the valve element, and an adjusting device for the spring arrangement, wherein the spring arrangement at least a first spring and a second spring, which on the Valve element act, has. The first spring defines a working area and the second spring has a spring force variable by the adjusting device.

From the US 6,012,300 An expansion valve has become known which has a chamber in which refrigerant is trapped. The chamber is bounded by a membrane which acts indirectly on a valve element. However, the membrane is also exposed to the high-pressure side refrigerant. In particular, the active surfaces to which the refrigerant trapped in the chamber acts and the other effective surface to which the high-pressure side refrigerant coming from the gas cooler acts are identical. With the described expansion valve is no protection against high pressures above a max. permissible value (for example 120 bar) is possible. In addition, a safe starting behavior at inlet temperatures at the expansion valve above the critical temperature of the refrigerant is not possible. A reliable application can therefore not be realized with this expansion valve.

From the DE 10 2005 03 47 09.6 For example, a thermal expansion valve is known, which has a first and second active surface, which are coupled to a valve element for movement. The first active surface is part of a stretchable separation device, which comprises a chamber with a STEU fulfillment in the thermal head. As a result, the temperature of the high-pressure side refrigerant can be sensed. About this stretchable separating device of the thermal head of the temperature-dependent pressure of the control filling in the chamber is transferred to a temperature-independent spring element, which is in communication with the second effective surface, which also bears the high pressure. This refinement is intended to achieve a high-pressure-limiting function in the supercritical control range.

task Therefore, the present invention is an expansion valve to further develop the hypertension of a transcritical than also subcritically operable refrigeration or heat pump cycle Adjust within an optimal range and an exceeding a maximum allowable Value independently can prevent.

These The object is achieved by an expansion valve according to the features of the claim 1 solved. Through the use of a thermally controllable actuator whose Actuating movement with a first effective area of a first actuator is only motion coupled, if a temperature-dependent actuating movement the second, so the thermally controllable actuator against the Actuating movement of the first effective surface the first actuator acts, is that a pressure limiting function or given a safety function against excessive operating pressures is that does not require external control.

In this case, a temperature input value of the thermally actuable actuator is selected for an actuating movement, which corresponds to a temperature value of the MOT of the control charge. The temperature usage value is the temperature at which the thermally controllable actuator generates an actuating or lifting movement. The operating characteristic of the thermally controlled actuator has the same gradient as the operating characteristics of the control charge in the superheated steam state, but in the opposite direction. This achieves the safety function. Furthermore, an absolute pressure limitation, ie the achievement of the MOP function (maximum operation pressure), is made possible at all temperature levels. While the first actuator with its first effective area preferably of a high-pressure side, coming from the inner heat exchanger refrigerant is pressurized and absorbs its temperature, the working behavior of the thermally actuable actuator is independent of the refrigerant pressure.

To a further advantageous embodiment of the invention is provided that between the first actuator and the second, thermally controllable Actuator a detachable mechanical coupling is provided and the second actuator a first effective area the first actuator or at one with the first actuator engaged valve element attacks. This mechanical Coupling, which occurs from a predeterminable temperature value, allows that in normal operation at a common temperature range the first actuator independent of the thermally actuatable actuator operates and the first Control member is only motion coupled to the valve element, when a further increase in temperature occurs, the use of the Safety function required.

The control charge the first actuator is preferably provided in a chamber, the membrane or bellows-like is formed and the temperature of the high-pressure side refrigerant receives. At the effective surface the first actuator is the temperature-dependent pressure of the control filling in the Chamber of the actuator and the high pressure. Out of himself resulting pressure difference results in an adjusting force, which sets the valve element in motion and in dependence the throttle properties of the associated valve seat a specific Flow area releases.

Prefers can be an additional, be provided in particular biased spring element, the Increased effect against the high pressure. This has the consequence that an opening movement the valve element then takes place when the temperature independent, on the effective area from the high pressure of the refrigerant system generated excess power sufficient to the bias of the particular preloaded spring element and overcome the force of the chamber, creating a passage released between the valve seat and the valve element, respectively the cross section of the passage opening is enlarged.

The control charge the chamber of the first actuator preferably has a filling density which is below its critical density. Preferred is the Further provided that about it addition, a mixture for the tax filling chosen which has a critical temperature which is above the critical temperature of the refrigerant to be controlled. This shows the tax filling a two-phase condition in most temperature ranges with high vapor content. Only when the of the tax filling absorbed Energy is enough to depend on the prevailing filling density existing liquid phase Completely to evaporate, goes the tax filling in the overheated Steam condition over. Developed under these circumstances a control pressure at a further temperature rise only with a lower gradient than in the previous two-phase State of taxation next, which is not equal to zero. The temperature value from which this physical effect occurs, referred to as MOT (Maximum Operating Temperature). The associated Pressure value for the control charge is called MOP (Maximum Operation Pressure). Furthermore is preferably provided that the temperature-dependent force of the thermally controlled and high pressure independent Actuator of the slope of the control filling of the first actuator in the overheated State corresponds. At a further temperature rise in the overheated Steam state, the pressure rises with only a significantly lower gradient as in the previous two-phase state. Due to the adaptation of the thermally controlled actuator to these gradients is the Safety function achieved by the thermally controlled and High pressure independent Actuator in the opposite direction with the same gradient acts, so that a maximum operating pressure is adjustable, the as desired horizontal pressure response at a MOP level.

Of the the aforesaid temperature value or temperature application value is preferred by the structural design of the thermally drivable Actuator determined. According to a first advantageous embodiment a thermally actuable actuator is provided that stacked bi-metal elements, in particular bi-metal discs, are provided. These stacked bi-metal discs are for example, bellows-shaped arranged. Dependent on lead from their default These bi-metal elements only from a certain temperature one Actuating movement.

A second alternative embodiment sees to the formation of a thermally actuable actuator in that a diaphragm, a bellows or a spring element, in particular a spiral spring or a spiral bellows made of a shape memory alloy is made. This in turn can be a temperature-dependent control allows be.

A further alternative embodiment of the actuator is given by a filled, bellows-like spring element, which is preferably filled with a medium above its vapor pressure or below its saturation temperature in the working area in the liquid Physical state exists.

suitable filling media are for example oils or generally hydrocarbons with a high boiling point. These temperature-Weggeberelemente are preferably hermetically sealed membrane, corrugated tube, Faltenbalgelemente or also cylinder piston designs, causing high thermal forces due to thermal expansion of their liquid filling. These elements can be designed so that their stroke-temperature characteristic only from a certain Temperature begins.

Prefers is provided that the thermally actuable actuators a pressure independent Have device to bias this. This will allow that the temperature value at which the thermal safety function of the valve is adjustable. Preferred is such Device manually from the outside adjustable. Alternatively, an electronic or motorized control be provided.

Of Furthermore, it is preferably provided that the chamber of the first actuator, in particular an inner contour of the chamber, through a sleeve or Footbridges led becomes. This allows that Deformations are prevented by the effect of tax filling.

In a rest position of the valve element of the thermostatic expansion valve is preferably provided that a minimum passage opening released is. This means that if the temperature and pressure dependent excess force not at the bottom of the thermally actuated actuator sufficient to overcome its bias, just a purposefully predefined Throttle cross section is released and the thermostatic expansion valve acts as a fixed throttle, causing the high pressure in the circuit self-adjusting.

In the scope of the present invention thus falls a transcritical or subcritical cold or heat pump cycle with an internal heat exchanger, a thermostatic expansion valve with a self-adjustable overflow function or safety function allows without, for example an additional Cable routing must occur at the evaporation inlet. simultaneously can the thermostatic control option of the COP-optimal High pressure is maintained.

The Invention and further advantageous embodiments and further developments The same will be described below with reference to the drawings Examples closer described and explained. The features to be taken from the description and the drawings can individually for applied to one or more in any combination according to the invention become. Show it:

1 a schematic representation of a refrigerant circuit,

2 a state diagram for illustrating the function of a refrigerant circuit with the aforementioned thermostatic expansion valve,

3 A first embodiment of a thermostatic expansion valve,

4a , b is a schematic representation of a control filling characteristic and the effect of the thermally actuable actuator on the valve opening characteristic,

5 a state diagram of valve lift characteristics at different operating pressures,

6 a second embodiment of a thermostatic expansion valve and

7 a third embodiment of a thermostatic expansion valve.

1 shows a refrigeration and / or heat pump cycle 11 an air conditioner. In a refrigerant compressor 12 is a gaseous refrigerant, in particular CO ₂ , compressed. The compressed refrigerant becomes a gas cooler 13 supplied, where a heat exchange between the compressed refrigerant and the environment takes place in order to cool the refrigerant. The gas cooler 13 leaving refrigerant reaches an internal heat exchanger 14 that with an expansion valve 15 communicates. The expansion valve 15 acts on the one hand to limit the pressure of the refrigerant and on the other to the pressure of the refrigerant at the outlet of the inner heat exchanger 14 to regulate. From the expansion valve 15 the refrigerant reaches an evaporator 16 , In the evaporator 16 the refrigerant absorbs heat from the environment. The evaporator 16 downstream is an accumulator 17 to separate gas phase and liquid phase refrigerant while collecting liquid CO ₂ . The accumulator 17 again stands with the inner heat exchanger 14 in connection.

Based on the state diagram of 2 , Where the pressure p is plotted against the specific enthalpy H, the operation of the air conditioner will now be explained. A refrigerant, for example CO ₂ , in the gas phase is in the refrigerant compressor 12 compacted (AB). Then the hot, high pressure transcritical refrigerant in the gas cooler becomes 13 and in the internal heat shear 14 cooled (BC or CD). The pressure is in the expansion valve 15 reduced (DE) to the now two-phase (gas and liquid phase) refrigerant in the evaporator 16 to vaporize (EF) and thereby deprive the environment of heat. The COP is determined by the ratio of the enthalpy change Δi in step EF and the enthalpy change ΔL in step AB, ie COP = Δi / ΔL.

The critical temperature of CO ₂ is about 31 ° C, which is lower than the critical temperature (often> 100 ° C) of fluorocarbons that are currently used in air conditioning systems. This causes the temperature of CO ₂ at the exit of the internal heat exchanger 14 can be higher than the critical temperature of CO ₂ . In this state, the CO ₂ condenses itself at the exit of the inner heat exchanger 14 Not. Therefore, the pressure at the outlet of the internal heat exchanger must be 14 be managed. So if the external temperature, for example in summer, is high, it becomes necessary at the exit of the internal heat exchanger 14 to set a high pressure in order to obtain a sufficient cooling capacity. The outlet temperature at the inner heat exchanger 14 depends among other things on the refrigerant side temperature at the gas cooler outlet, which in turn depends on the ambient temperature. This means that the temperature of the CO ₂ at the outlet of the internal heat exchanger 14 can also be used for the regulation of the otherwise dependent on the refrigerant side gas cooler outlet temperature COP-optimized high pressure.

In the diagram according to 2 is through the characteristics 21 ' and 21 '' the COP-optimized control range is displayed. The double arrow in between 22 indicates a valve lift range from 0 to about 75% of the valve lift. Between the characteristic 21 '' and the characteristic 21 ''' the overpressure control range is shown. By further opening the valve stroke over approximately 75%, an excess pressure can be reduced. The characteristic 21 '''' provides an adjustable high pressure limit for the refrigerant circuit to be controlled 11 This can be made variable.

In 3 is a first embodiment of a thermostatic expansion valve according to the invention 15 which illustrates an operation of a refrigerant system according to a state diagram in FIG 2 allows. The expansion valve 15 includes a valve housing 26 , which is a high-pressure side feed opening 27 that is in a high pressure room 28 leads. The high pressure room 28 is via a passage opening 29 with a low-pressure discharge opening 31 connected. The passage opening 29 has a valve seat 32 in which a valve element 33 is provided in a closed position and the feed opening 27 to the discharge opening 31 separates.

In the high pressure room 28 is a first actuator 36 provided, which has a first effective area 37 comprises, on which the valve element 33 is provided. At this first effective area 37 grab a chamber 38 in the closing direction of the valve element 33 which is membrane-shaped or bellows-like.

Furthermore, a spring element 39 provided, which, for example, the chamber 38 surrounds and preferably biased and in the same direction of force as the chamber 38 at the effective surface 37 attacks. In coordination of the size of the valve element 33 or the length of the shaft or one in the high-pressure chamber 28 provided stop element is a bias of the spring element 39 and / or the chamber 38 allows.

The chamber 38 is preferably formed of a good thermal conductivity material. In the chamber 38 is a tax filling 41 provided, the pressure in the chamber 38 is temperature dependent. As soon as a high pressure is applied to the high pressure side, it acts against the effective surface 37 and opens the passage opening 29 , provided that the applied high pressure an excess of force relative to the prestressed spring element 39 and the pressure of the tax filling 41 in the chamber 38 having. The opening and closing movement in the COP-optimized control range is independent of a thermally actuable actuator 46 , which is also in the high pressure room 28 is provided.

In the embodiment according to 3 engages the thermally actuable actuator 46 at the first effective area 37 opposite to the chamber 38 and the optionally existing spring element 39 at. Alternatively, the actuator 46 also on the valve element 33 or in addition to the valve element 33 attack. The thermally controlled actuator 46 is formed of bi-metal discs, which are stacked in a bellows-shaped superimposed. The bi-metal discs can be biased by a pressure-independent device, not shown, so that they perform an adjusting movement or a lifting movement only when the safety function is required. This is the case when the temperature of the refrigerant rises above the MOT. Consequently, the bias of the bi-metal discs or their material design is adapted to such a temperature usage value.

With sufficient excess force of the high pressure is compared to the pressure force of the chamber 38 and the possibly existing spring element 39 Released via a predefined stroke characteristic of the optimal opening cross-section and thus the optimum high pressure (COP-optimized range) depending on the high-pressure side outlet temperature of the refrigerant set on the inner heat exchanger.

By the expansion valve according to the invention 15 is a self-adjustable overpressure and safety feature allows, so that the refrigerant circuit can work with COP optimal high pressure. Out 4a is a schematic representation of a characteristic 19 for a tax filling in a chamber 38 of the first actuator 36 where the pressure is above the temperature up to the critical point. Since the two-phase present tax filling above the MOT value 20 for the circulation 11 In the single-phase, overheated gas state, the pressure of the tax filling increases only with a much weaker gradient on. However, the safety function can only by a horizontal pressure curve from the MOT value 20 be achieved. This further disadvantageous increase is achieved in an expedient design of the present invention by the use of the thermally actuable actuator 46 compensated whose characteristic with 46 ' in 4a is shown. This will create a valve opening characteristic 22 is achieved, which in 4b is shown. This valve opening characteristic 22 This valve characteristic 22 with the horizontal pressure curve at MOP level leads to a maximum mass flow development when the high pressure of the circuit 11 is above, so that there is a self-inhibiting high-pressure development, because in the closing direction of the valve element 33 acting, temperature-related pressure force of the chamber 38 is compensated. The thermally controlled actuator 46 can also prematurely on the opening cross-section of the passage opening 29 act, so that an increase in the high pressure on the MOP value is prevented.

It should also be noted that although the refrigerant side gas cooler exit temperature is the preferred control temperature in terms of COP optimization, the high pressure side exit temperature at the inner heat exchanger 14 can also be applied for the purpose of regulating the high pressure in a COP-optimal range. For this purpose, either simulation or experimental technology for the circulation, in which the thermostatic expansion valve described by this invention 15 Use is made of the exit states at the inner heat exchanger that correspond to each COP-optimal gas cooler exit state 14 determined. About the high-pressure side outlet temperature at the inner heat exchanger 14 This results in a COP-optimized pressure curve, on the optimal valve stroke characteristic 22 in accordance with the state diagram in 5 is aligned, in which the mass flow is plotted against the temperature. This COP-optimal valve lift characteristic 22 is limited to a part of the total valve stroke range to be determined in terms of the application, for example between 0 and 75%. This is in 2 through the characteristics 21 ' and 21 '' shown. The double arrow 22 shows the COP-optimized control range. Beyond its upper limit, the overflow function starts. If a mass flow characteristic 23 the throttle point above the above limit, that is until reaching 100% of the total valve lift, is designed sufficiently steep that so much mass flow from the high to the low pressure side flow and thus a further rise in the high pressure of the system can be avoided achieved one claimed by the present invention safety function against excessive system pressures.

By the arrangement of such a thermostatic expansion valve 15 At the evaporator inlet one avoids complex piping arrangements as for example when using a thermostatic expansion valve according to patent US 6,012,300 are necessary because the valve described there must absorb the refrigerant side outlet temperature on the gas cooler - either by a local arrangement on the gas cooler or by the passage of a capillary between valve and gas cooler outlet.

In 6 is an alternative embodiment to 3 shown. Deviating from this is the thermally actuable actuator 46 made as a spring element of a shape memory alloy. This actuator 46 can be adjusted so that the lifting movement takes place only from a predetermined temperature entry value. In addition, the effective force practicing cross section of the spring element can also be determined. In addition, could also be an electrical control of this thermally drivable actuator 46 be possible from the shape memory alloy. The others too 3 described functions and variants also apply to this embodiment.

In 7 is another alternative embodiment of a thermally actuable actuator 46 to 3 shown. In this embodiment, a hydraulically filled, bellows-like spring element is provided which allows the overflow function or safety function. The fillings of the thermally actuable actuator 46 include, for example, various oils and hydrocarbons.

All The aforementioned features are each essential to the invention and can be arbitrary be combined with each other.

Claims (14)

Thermostatic expansion valve for regulating a high pressure of a transcritical as well as subcritically operable refrigeration or heat pump cycle ( 11 ) with a valve housing ( 26 ), in which the input side, a high pressure in a feed opening ( 27 ) and on the output side a low pressure at a discharge opening ( 31 ) is applied, with a valve element ( 33 ), which has a valve seat ( 32 ) a passage opening ( 29 ) located between the feed opening ( 27 ) and the discharge opening ( 31 ) is arranged, for flowing through the refrigerant closes and moves in the opening direction and a first actuator ( 36 ), wherein the first actuator ( 36 ) one with a first effective area ( 37 ) limited chamber ( 38 ), which contains a tax 41 ), characterized in that a thermally actuatable actuator ( 46 ) is provided whose adjusting movement with the first active surface ( 37 ) of the first actuator ( 36 ) is motion-coupled, if a temperature-dependent actuating movement of the thermally actuable actuator ( 46 ) against the adjusting movement of the first effective surface ( 37 ) of the first actuator ( 36 ), wherein a temperature application value of the thermally actuable actuator ( 46 ) for an actuating movement to the same value as the MOT (maximum operation temperature) of the control filling ( 41 ) of the first actuator ( 36 ), which has a bulk density that is below its critical density. Valve according to claim 1, characterized in that between the first actuator ( 36 ) and the thermally actuable actuator ( 46 ) a releasable mechanical coupling is provided and the thermally actuable actuator ( 46 ) at the first effective area ( 37 ) of the first actuator ( 36 ) or at one with the first actuator ( 36 ) associated valve element ( 33 ) attacks. Valve according to claim 1, characterized in that the chamber ( 38 ) is formed membrane-like or bellows-like and thermally conductive to receive the temperature of the high-pressure side refrigerant. Valve according to claim 1, characterized in that the critical temperature of the control filling ( 41 ) of the first actuator ( 36 ) is above the critical temperature of the refrigerant. Valve according to claim 1, characterized in that the temperature-dependent force of the thermally actuable actuator ( 46 ) the slope of the tax inflow ( 41 ) of the first actuator ( 36 ) in the overheated state. Valve according to one of the preceding claims, characterized in that the thermally actuable actuator ( 46 ) in the form of stacked bi-metal elements, in particular bi-metal discs, is formed. Valve according to one of claims 1 to 6, characterized in that the thermally actuable actuator ( 46 ) is formed in the form of a shape memory alloy consisting of a spring element. Valve according to one of claims 1 to 6, characterized in that the thermally actuable actuator ( 46 ) in the form of a filled bellows-like spring element, in particular of a hydraulically filled bellows-like spring element is formed. Valve according to claim 7 or 8, characterized in that the thermally actuable actuator ( 46 ) is biased by a pressure independent device. Valve according to claim 9, characterized in that the bias of the thermally actuable actuator ( 46 ) is adjustable by the pressure-independent device to a temperature usage value, which uses the thermal safety function. Valve according to claim 9 or 10, characterized that the pressure independent Device adjustable, in particular adjustable from the outside. Valve according to claim 1, characterized in that the chamber ( 38 ), in particular an inner contour of the chamber ( 38 ), is guided by a sleeve or webs. Valve according to one of the preceding claims, characterized in that in a rest position of the valve element ( 33 ) a predetermined minimum passage opening ( 29 ) between the valve element ( 33 ) and the valve seat ( 32 ) is released, which is adjustable from the outside during assembly. Transcritical or subcritical refrigeration or heat pump cycle ( 11 ) with an internal heat exchanger ( 14 ), characterized in that an expansion valve ( 15 ) is provided according to one of the preceding claims.