DE102006021327A1 - Control method for expansion valves in car air conditioning systems uses bellows filled with inert gas which pushes rods against spring attached to the valve stem so as to open valve when threshold pressure or temperature is exceeded - Google Patents

Abstract

The control method for expansion valves in car air conditioning systems with carbon dioxide as coolant uses a bellows (44) filled with inert gas which pushes rods (48) against a spring (39) attached to the valve stem so as to open the valve when a threshold pressure or temperature is exceeded. Alternatively a bypass channel is opened. An independent claim is included for expansion valves using the method,.

Description

The invention relates to a method for controlling an expansion valve and an expansion valve, in particular for operated with CO ₂ as a refrigerant vehicle air conditioning systems, according to the preamble of claim 1 and 2.

From the DE 10 2004 010 997 B3 An expansion valve and a method for the control thereof is known in which the opening and closing movement of a valve closing member is set as a function of the pressure difference which rests in a supply opening on the high pressure side and in a discharge opening of the expansion valve on the low pressure side. A return device holds the valve closing member in a closed position when the refrigerant circuit is stopped.

One Such expansion valve, which depends on the pressure difference between the high pressure side and the low pressure side, one must To meet a variety of operating conditions optimally. A fast response and good cooling performance were with such an expansion valve at low to medium Ambient temperatures, for example, up to about 40 ° C, achieved.

at Refrigerant plants is the achievement of a fast cooling after long downtimes of the vehicle desired, while during the downtime of the vehicle, the refrigerant pressure depends on the ambient temperature has risen to a high level. mostly Achieving the maximum cooling performance under high ambient temperatures too long.

Of the The invention is therefore based on the object, a method for Control of the expansion valve and an expansion valve of the aforementioned To develop further such that after long downtimes and given a fast response at high ambient temperatures is for a quick cooling to be cooled Room is achieved.

These The object is achieved by a Method according to the feature de claim 1 and an expansion valve according to the feature of the claim 2 solved. Further advantageous embodiments and further developments are in the further claims specified.

By the inventive method for controlling the expansion valve is achieved that an opening characteristic of the valve closure member the differential pressure controlled expansion valve to a lower opening pressure is shifted, causing the response of the refrigerant circuit elevated becomes. This is due to the effect that by shifting the Valve characteristic to lower values towards a premature opening of the Valve closure member takes place, whereby the achieved refrigerant mass flow between the very fast rising high pressure and the flatter decreasing low pressure increases becomes. When switching on the refrigerant circuit the compressor is switched on and within a few seconds high pressure side of the maximum permissible Pressure reaches over one Approximate start-up time is held. By an increase of the refrigerant mass flow under such conditions, there will be a rapid drop in low pressure achieved by the cooling of the Low-pressure side components of the cooling circuit.

The Achieving a larger pressure difference immediately after starting a stopped air conditioning is inventively by an expansion valve with a low-pressure side actuator allows which depending a rising low pressure side temperature or a rising Pressure over a predetermined threshold value a closing force of the valve closing member engaging Reset device reduces, leaving a refrigerant flow the passage opening flows through. This is done according to a first embodiment of the Control element at least one actuating element controlled, that at the restoring device of the valve closure member attacks. This is the response of the refrigerant circuit improved. Cooling is achieved after just a few seconds. Alternatively, to reduce the force acting on the valve closure member closing force the at least one actuating element is an embodiment provided, provided in parallel to the passage opening a passage is, with a low pressure side controllable actuator forms a bypass valve and is closed. When passing a predetermined threshold value of the low pressure or the low pressure side Temperature opens the bypass valve so that at high low pressure side pressures or temperatures, especially when starting under high ambient temperatures, a larger refrigerant flow expanded and already at an earlier date cooling occurs.

According to an advantageous embodiment of the expansion valve is provided that the controllable with low pressure actuator bellows bellows, in particular with an inert gas, is formed, which comprises plunger, which acts on a high-pressure side resetting device for reducing the closing force of the passage opening closing the valve closing member. When rising low pressure or evaporation pressure of the refrigerant in the expansion valve, for example, due to high ambient temperature or heating of the parts of the air conditioning is ent speaking the pressure reduces the free length of the bellows. Bellows arranged on the bellows project from the low-pressure side to the high-pressure side and engage an adjusting element for regulating the closing force. When reducing the stroke length of the bellows, the closing force, in particular the biasing force of a restoring device designed as a spring element is reduced, so that at an earlier time the valve closing member opens the passage opening and a refrigerant mass flow flows through the expansion valve.

To an alternative embodiment of the invention, it is provided that the low-pressure side control of the valve closing member on a valve closure member is provided, wherein the restoring device on the low pressure side is arranged. This can also be dependent on the low pressure or with increasing low pressure, a premature opening of the Valve closure member and thus a shift of the opening characteristic of the expansion valve to be achieved at an early opening time.

To a further advantageous embodiment of the expansion valve according to the invention is provided that the actuator with increasing low pressure side Temperature is controllable, wherein the actuating element is a temperature sensor includes, which is arranged on the low pressure side and also a Clamping force reduction of the valve closure member achieved in the expansion valve. For example, as a temperature sensor a Wachsdehnelement provided, which increases in temperature generates a travel that for opening of the valve closure member is provided. An alternative embodiment is by a spring element from a shape memory alloy provided, which with increasing temperature a shortening of its free spring length causes, in turn, a premature opening of the valve closure member is effected.

To an alternative embodiment of the invention is the restoring device, which the valve closure member in a closed position stops, low pressure side intended. The valve closing member can attacking and a temperature sensor comprehensive actuator thereby also formed as in the high-pressure side return element be.

To a further advantageous embodiment of the invention is provided that the temperature sensor of the control element also outside of the housing provided by the expansion valve. This can change the ambient temperature or a part temperature of adjacent parts as the control quantity be placed.

According to a further advantageous embodiment of the invention, it is provided that the bypass valve arranged on the low pressure side and controllable in dependence on the low pressure has a closing element arranged on a membrane element or bellows which closes a parallel passage to the passage opening between the supply and discharge openings. The membrane element or the bellows is preferably filled with inert gas, so that a low-pressure-dependent control for opening the bypass is possible. Alternatively, the bellows can be filled with a refrigerant, in particular CO ₂ . In this case, the filling is designed such that the filler pressure at temperatures, for example below 15 ° C or 20 ° C corresponds approximately equal to the evaporation pressure.

A alternative embodiment of the low-pressure side bypass in the expansion valve provides that the bypass valve depends on the low-pressure side Temperature is controllable. Here, the temperature of the refrigerant or the ambient temperature as well as the temperature of others Parts of the air conditioner can be used as a control variable. Prefers a control medium is provided in a bellows, which depends on the refrigerant temperature causes a lifting movement. Alternatively to the bellows or bellows can a Wachsdehnelement or spring element made of a shape memory alloy be used.

To a further advantageous embodiment of the temperature-dependent bypass valve is provided that the passage closing valve closing member high pressure side is arranged and acting on the valve seat closing element, in particular spring element. This can be a closed position be ensured at standstill of the vehicle.

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 cycle process,

2 a diagram showing a cooling curve with a dp valve without "traction help" in a vehicle at high ambient temperature in various phases of operation,

3 FIG. 2 is a schematic sectional view of an expansion valve with a low-pressure-dependent displacement of the opening characteristic; FIG.

4 a schematic sectional view of an expansion valve with a low-pressure side, temperature-dependent displacement of the opening characteristic,

5 a schematic sectional view of an alternative embodiment to 3 .

6 a schematic sectional view of an alternative embodiment to 4 .

7 a schematic sectional view of an alternative embodiment of an expansion valve with a parallel to the differential pressure relief valve on the low pressure side controlled bypass valve and

8th a schematic sectional view of an alternative embodiment of an expansion valve with a temperature-controlled bypass valve parallel to the differential pressure valve.

In 1 is a refrigerant circuit 11 shown, which is preferably operated with CO ₂ . This refrigerant circuit 11 is used for example as a vehicle air conditioning system. A compressor 12 leads the compressed refrigerant high pressure side of an outdoor heat exchanger 14 to. This communicates with the environment and gives off heat to the outside. Downstream of this is an internal heat exchanger 15 containing the refrigerant an expansion valve 16 via a supply line 17 supplies. In front of the expansion valve 16 is on the high pressure side to an inlet pressure, which may be 120 bar, for example, in summer. The refrigerant flows through the expansion valve 16 and gets to the low pressure side. On the output side, the expansion valve 16 under steady state conditions pressures between 35 and 45 bar. About a discharge line 18 enters the cooled by the pressure release refrigerant into the indoor heat exchanger 21 and deprives the environment of heat, whereby the cooling, such as a vehicle interior, is achieved. In the heat exchanger 21 is a collector 22 connected downstream. The vaporous refrigerant flows through the inner heat exchanger 15 and gets to the compressor 12 , To operate this refrigerant circuit 11 is a pressure difference expansion valve 16 provided, which in the DE 10 2004 010 997 B3 is described in more detail and is fully incorporated by reference. Based on the described operation of the expansion valve 16 will be the following 2 described in more detail, in which a cooling curve in the vehicle is shown at a high ambient temperature.

For example, the vehicle was not put into operation for a long time at high ambient temperatures, and there are high ambient temperatures of more than 40 ° C. At standstill (I) of the vehicle is a balance of pressure at about 80 bar on the high pressure and low pressure side of the refrigerant circuit 11 usually given. Immediately after the start (II-1) of the refrigerant circuit 11 The high-pressure-side refrigerant pressure rises within a few seconds due to the compressor capacity on the high pressure side to the maximum allowable value, for example 133 bar. On the low pressure side, on the other hand, the pressure drops only slowly (lower curve). During further operation in the starting phase (II-1), the low pressure drops only with a slight increase. As a result, only a slight change in pressure is given, which causes slow cooling to take place in the vehicle interior in the starting phase (II-1). The response of the air conditioning is delayed. During driving (II-2), a steady state occurs, which is represented substantially by the horizontal portions of the upper and lower curves. The third phase (III) sets the high pressure in front of the expansion valve 16 (upper curve) and low pressure after the expansion valve 16 (lower curve) in idle mode.

So that in the starting phase (II-1) an improved response is given or the duration of the starting phase is shortened, the invention proposes to increase the valve opening under these conditions in order to increase a larger refrigerant mass flow at still relatively moderate pressure differences. For this purpose, it is proposed that this takes place by a shift of the opening characteristic of a differential pressure controlled expansion device to a low opening pressure, wherein the control takes place via the rising low pressure or the rising evaporation temperature of the refrigerant or the ambient temperature. As an alternative to the displacement of the opening characteristic of the valve closing member in the expansion valve, it is proposed that a bypass valve actuated on the low-pressure side be provided, which in turn opens depending on the temperature or the pressure. The aforementioned embodiments are based on the evaporation temperature of the refrigerant and the evaporation pressure. These controls according to the invention are in the 3 to 8th shown in more detail.

In 3 is a schematic sectional view of a first expansion valve according to the invention 16 shown. In a valve housing 31 is a feed opening 32 provided, which has a passage opening 34 with a discharge opening 36 connected is. In the passage opening 34 is a valve closure member 37 intended. This valve closure member 37 is high pressure side via a return device 39 , which is preferably designed as a spring element with pressure equalization, in a closed position in a valve seat 41 held. In the discharge opening 36 is an actuator 42 provided, which is a bellows or bellows 44 with an inert gas filling 46 includes. At one end supports the bellows 44 on a housing wall 47 from. Opposite controls the bellows 44 depending on the low pressure, at least one actuating element 48 , in particular tappets which extend into the feed opening 32 extend. These pestles 48 grab an adjusting element 49 which is used to adjust the biasing force of the return device 39 serves. To limit the lifting movement of the control element 42 is a stop 43 provided so that the end position of the actuating element 42 is defined.

Once the low pressure in the discharge opening 36 rises, the bellows 44 compressed due to the increasing pressure and performs a lifting movement. At the same time a rectified lifting movement of the plunger takes place 48 to reduce the biasing force of the return device 39 , so that the valve closing member 37 already opens at a lower pressure difference and a refrigerant passes earlier in the start-up phase from the high pressure side to the low pressure side. This allows a pressure-dependent shift of the operating characteristic for the expansion valve 16 be achieved.

In 4 is an alternative embodiment to 3 shown. The construction of the expansion valve 16 corresponds to the in 3 , Deviating from this is that instead of a low-pressure or evaporation pressure-dependent actuator 42 a temperature-dependent actuator 42 is provided. This temperature-dependent actuator 42 for example, consists of a spring 52 which is made of a shape memory alloy. On the actuator 42 is at least one actuator 48 provided, which at the return device 39 attacks and reduces the closing force. As soon as the low-pressure-side temperature has exceeded a certain set value, the spring is shortened 52 from a shape memory alloy. This will affect the reset device 39 acting force is lowered, whereby an opening of the through hole 34 is possible. For controlling the control element 42 may be provided as temperature sensors further Wachsdehnelemente, bimetals or other binary elements. Alternatively, the actuator 42 also attack directly on the valve closure member.

In 5 is an alternative embodiment to 3 shown. This embodiment differs in that the restoring device 39 and the valve closing member 37 are arranged on the low pressure side. To guide the low-pressure side valve closure member 37 is a holding and guiding element 55 provided, which is a valve closure member 37 in it displaceably leads. Furthermore, the holding and guiding element takes 55 the valve closure member 37 low pressure side and closes the bellows 44 from. This shows the holding and guiding element 55 a multiple function. In addition, this serves as an actuator 48 , in particular as a ram, which on a stop 43 connects to a boundary of the opening 34 acting closing force of the valve closure member 37 to achieve. When the low pressure is increased, the bellows are pressurized 44 which moves to the right according to the embodiment. Thereby, the biasing force of the return device 39 reduces, allowing premature opening of the passage opening 34 he follows. This is the response of the refrigerant circuit 11 improved. Incidentally, the functions are the same as in the embodiment according to FIG 3 ,

In 6 is an alternative embodiment to 4 shown. In this embodiment is also the return device 39 and the valve closing member 37 arranged on the low pressure side. Instead of the actuating element 48 according to the embodiment in 4 is functionally identical designed as a ring element actuator 48 provided, which depends on the change in the travel of the spring 52 from a shape memory alloy, the biasing force of the return device 39 on the valve closure member 37 increased or reduced. The ring element moves between two end positions or attacks 43 that limit the characteristic shift.

In 7 is a schematic representation of another alternative embodiment of an expansion valve 16 shown. This embodiment has a basic structure according to that in the DE 10 2004 010 997 B3 described differential pressure expansion valve on. In addition, it is parallel to the passage opening 34 a parallel passage 61 provided by a low pressure side arranged actuator 42 which together with the passage 61 a bypass valve 62 forms, is closed. This bypass valve 62 is according to the embodiment in 7 triggered depending on the evaporation pressure on the low pressure side. For this example, the bellows 44 provided, which is filled with an inert gas or the inside of which communicates with the atmosphere, while the closing force is carried out by means of a compression spring. At one to the passage 61 pointing end of the bellows 44 is a closing element 63 provided, which the passage 61 at low pressure values in the refrigerant system 11 closes that correspond to normal operation and, for example, below 45 bar.

In 8th is an alternative embodiment to 7 shown. Instead of a controllable depending on the evaporation pressure bypass valve 62 is a bypass valve 62 provided, which is temperature-dependent controllable. Im as Bellows trained actuator 42 is a control medium 66 provided, which assumes a volume change as a function of the temperature. The closing element 63 is by an actuator disposed on the bellows 48 , For example, as a plunger, actuated and is preferred high-pressure side to the passage 61 provided and via a closing member 68 , In particular a spring element, held in a closed position.

The enclosed in the Balginneren filling has such a pressure-temperature behavior that with increasing low-pressure side temperature of the CO ₂ -Kältemittels a higher pressure increase than on the bellows outside takes place. As a result, a bypass opening can be achieved with increasing low-pressure side temperature.

All above-described features are essential to the invention in each case and can be combined with each other as desired.

Claims (10)

Method for controlling an expansion valve, in particular for vehicle air conditioners operated with CO ₂ as refrigerant, with a valve housing ( 31 ), which has a feed opening ( 32 ) and a discharge opening ( 36 ), with a valve closure member ( 37 ), which has a valve seat ( 41 ) a passage opening ( 34 ) between the feed and discharge openings ( 32 . 36 ) and closes with a resetting device ( 39 ), in the closing direction of the valve closure member ( 37 ), characterized in that a valve closure member ( 37 ) associated actuating element ( 42 ) is controlled on the low pressure side with increasing low pressure or with increasing low pressure side temperature above a predetermined threshold, which comprises at least one actuating element ( 48 ) actuated by a closing force of the valve closing member ( 37 ) resetting device ( 39 ) is reduced so that a passage opening ( 34 ) or, parallel to the passage opening ( 34 ) arranged passage ( 61 ) of a low pressure side arranged bypass valve ( 62 ) is opened. Expansion valve, in particular for carrying out the method according to claim 1, with a valve housing ( 31 ), which has a feed opening ( 32 ) and a discharge opening ( 36 ), with a valve closure member ( 37 ), which has a valve seat ( 41 ) a passage opening ( 34 ) between the feed and discharge openings ( 32 . 36 ) is arranged, closes and with a closing direction of the valve closing member ( 37 ) resetting device ( 49 , characterized in that a low pressure side an actuator ( 42 ) is provided, which the valve closing member ( 37 ) and with at least one actuating element ( 48 ) connected to one of the valve closure member ( 37 ) resetting device ( 39 ) or that a low pressure side an actuator ( 42 ) is provided, which with a parallel to the passage opening ( 34 ) arranged passage ( 61 ) a low pressure side arranged bypass valve ( 62 ). Expansion valve according to claim 2, characterized in that the controllable with low pressure actuator ( 42 ) as a membrane element or bellows ( 44 ), in particular with an inert gas filling ( 46 ), which plunger ( 48 ) actuated at a high pressure side resetting device ( 39 ) for reducing the closing force of the passage opening ( 34 ) closing valve closure member ( 37 attack). Expansion valve according to claim 2, characterized in that the controllable with low pressure actuator ( 42 ) as a membrane element or bellows ( 44 ), in particular with an inert gas filling ( 46 ), which plunger ( 48 ) actuated at a low-pressure resetting device ( 39 ) for reducing the closing force of the passage opening ( 34 ) closing valve closure member ( 37 ) attacks. Expansion valve according to claim 2, characterized in that the controllable with increasing low-pressure side temperature control element ( 42 ) comprises a temperature sensor, in particular as a shape memory alloy or Wachsdehnelement comprising a low pressure side of the valve closure member ( 37 ) acting closing force or with an opening parallel to the restoring device ( 39 ) acting spring force on the valve closure member ( 37 ), wherein the valve closure member ( 37 ) with a high pressure side reset device ( 39 ) is held at a closed position. Expansion valve according to claim 2, characterized in that the controllable with increasing low-pressure side temperature control element ( 42 ) comprises a temperature sensor, in particular as a shape memory alloy or Wachsdehnelement comprising a low pressure side of the valve closure member ( 37 ) acting closing force or with an opening parallel to the restoring device ( 39 ) acting spring force on the valve closure member ( 37 ), wherein the valve closure member ( 37 ) with a low pressure side reset device ( 39 ) is held at a closed position. Expansion valve according to claim 5 or 6, characterized in that the temperature sensor outside the housing ( 31 ) and the ambient temperature or the temperature of Vehicle parts includes. Expansion valve according to claim 2, characterized in that the bypass valve arranged on the low pressure side and controllable in dependence on the low pressure ( 62 ) on a bellow ( 44 ) or membrane element arranged closing member ( 63 ), wherein the bellows ( 44 ), in particular with inert gas. Expansion valve according to claim 2, characterized in that the bypass valve arranged on the low pressure side and controllable in dependence on the temperature ( 62 ) comprises a temperature sensor, which in particular as with a control medium ( 66 ) filled bellows ( 44 ) is formed as a wax expansion element or as a spring element made of a shape memory alloy, the one at the passage ( 61 ) provided closing member ( 63 ). Expansion valve according to claim 9, characterized in that the passage ( 61 ) closing closure member ( 63 ) is arranged on the high pressure side and a passage ( 61 ) acting closing element, in particular spring element ( 68 ), having.