JP5259980B2 - Method for controlling an expansion valve and in particular an expansion valve for a vehicle air-conditioning system operating with CO2 as coolant - Google Patents

Description

The invention relates to a method for controlling an expansion valve according to the front part of the features of claims 1 and 2, and in particular to an expansion valve for a vehicle air conditioning system operating with CO ₂ as coolant.

  DE 10 2004 010 997 B3 discloses an expansion valve and a method for controlling the expansion valve, in which the opening and closing movement of the valve closing member is a high-pressure supply opening and a low-pressure expansion valve removal opening. And is set as a function of the pressure difference. The resetting device maintains the valve closure member in the closed position when the coolant circuit is not operating.

  This type of expansion valve operating as a function of the pressure difference between the high pressure side and the low pressure side must optimally meet multiple operating conditions. Fast response characteristics and good cooling capacity were obtained with this type of expansion valve, for example, at low to average ambient temperatures up to about 40 ° C.

In the case of a coolant system, it is desirable to obtain rapid cooling after a long period of vehicle inactivity, where the coolant pressure has increased to a high value as a function of ambient temperature during the vehicle inactivity period. Under high ambient temperatures, it is common for the time taken to obtain maximum cooling capacity to be too long.
DE 10 2004 010 997 B3

  Therefore, the present invention is first of all intended to provide a method for controlling an expansion valve and a rapid response characteristic after a long period of inactivity and at high ambient temperatures, thereby providing a rapid cooling of the cooled space. Based on the purpose of developing an expansion valve of the stated type.

  This object is achieved according to the invention by a method according to the features of claim 1 and an expansion valve according to the features of claim 2. Other advantageous improvements and developments are given in the other claims.

  The effect obtained by the method according to the invention for controlling the expansion valve is that the opening feature of the valve closing member of the expansion valve controlled by the differential pressure is moved to a lower opening pressure, so that the coolant circuit The response characteristic is increased. This is achieved by moving the valve feature to a lower value, resulting in an early opening of the valve closure member, thereby obtaining between a high pressure that rises very quickly and a low pressure that drops rather than more rapidly. This is based on the effect of increasing the mass flow of the coolant produced. When the coolant circuit is switched on, the compressor is switched on and within a few seconds on the high pressure side, the maximum allowable pressure that is substantially maintained over the start period is reached. By increasing the coolant mass flow under such conditions, a rapid low pressure drop is achieved because cooling circuit components are cooled on the low pressure side.

  An adjustment that is relatively low pressure and that is activated on the low pressure side and activated via a predetermined threshold as a function of the rising temperature or pressure on the low pressure side, to obtain a relatively large pressure difference immediately after the inactive air conditioning system is started By means of an expansion valve for carrying out the method according to claim 1, in particular, the closing force of the resetting device acts on the bubble closure member so that a coolant flow flows through the passage opening. Will be possible. For this purpose, according to a first embodiment, the adjusting element is used to activate at least one actuating element acting on the resetting device of the valve closing member. This improves the response characteristics of the coolant circuit. Cooling is obtained even after a few seconds. As an alternative to reducing the closing force acting on the valve closing member by at least one actuating element, an embodiment is provided in which a passage parallel to the passage opening is provided, which passage can be activated on the low-pressure side Together with a bypass valve and closed by its adjusting element. When a predetermined threshold value of low pressure or temperature is exceeded on the low pressure side, the bypass valve is opened, thereby a relatively large amount of coolant when started at high pressure or high temperature on the low pressure side, especially under high ambient temperatures. The flow of water expands and cooling takes place earlier.

  According to an advantageous improvement of the expansion valve, the adjusting element is activated by low pressure, specifically designed as an expansion bellows with an inert gas filler, and to reduce the closing force of the valve closing member closing the passage opening It has a tappet that acts on the resetting device that acts on the high pressure side. When the low pressure or evaporating pressure of the coolant increases at the expansion valve, for example due to high ambient pressure or heating of a part of the air conditioning system, the free length of the expansion bellows is reduced by the pressure. The tappet arranged on the expansion bellows protrudes from the low pressure side to the high pressure side and acts on the setting valve so as to restrict the closing force. When the stroke length of the expansion bellows is shortened, the closing force, in particular the prestress of the resetting device designed as a spring element, is reduced, so that the valve closing member opens the passage opening earlier and the coolant Mass flow flows through the expansion valve.

  According to an alternative refinement of the invention, the activation of the valve closing element performed on the low pressure side is effected using a valve closing member, in which case the resetting device is arranged on the low pressure side. As a result, premature opening of the valve closure member, and thus displacement of the opening feature of the expansion valve to the premature opening time, is similarly obtained as a function of low pressure or when the low pressure rises.

  According to another advantageous refinement of the expansion valve according to the invention, the adjustment element can be activated when the temperature on the low-pressure side rises, the adjustment element comprising a temperature sensor arranged on the low-pressure side, and A reduction in the closing force of the expansion closing member of the expansion valve can likewise be obtained. For example, a wax expansion element is provided as a temperature sensor that produces an adjustment travel that is provided to open the valve closure member when the temperature rises. An alternative embodiment is provided by the spring element comprising a shape memory alloy which shortens the free length of the spring element as the temperature rises, so that again an early opening of the valve closing member takes place.

  According to an alternative improvement of the invention, a resetting device is provided on the low-pressure side for maintaining the valve closing member in the closed position. The adjusting element acting on the valve closing member and comprising a temperature sensor can be designed in the same way as the high-pressure resetting element.

  According to another advantageous refinement of the invention, it is provided that the temperature sensor of the adjustment element is also provided outside the housing of the expansion valve. As a result, ambient or adjacent temperature can be taken as a basis for the control variable.

According to another advantageous refinement of the invention, a bypass valve, which is arranged on the low pressure side and can be activated as a function of low pressure, is arranged on the membrane element or the expansion bellows and eliminates the supply opening. It is provided to have a closure member for closing the passage parallel to the passage opening between the openings. The membrane element or expanded bellows is preferably filled with an inert gas, which allows it to be activated as a function of low pressure to open the bypass. Alternatively, the bellows can be filled with a coolant, especially CO _2. In this case, the filling is designed so that the pressure of the filling material corresponds approximately to the evaporation pressure, for example at a temperature below 15 ° C. or 20 ° C.

  Alternative improvements to the bypass on the low pressure side of the expansion valve can activate the bypass valve as a function of the temperature on the low pressure side. In this case, the temperature of the coolant or ambient temperature and also the temperature of other parts of the air conditioning system can be used as control variables. A control medium is preferably provided on the bellows that produces a stroke movement as a function of the temperature of the coolant. As an alternative to bellows or expanding bellows, a wax expanding element or a spring element made of a shape memory alloy can be used.

  According to another advantageous improvement of the pressure-dependent bypass valve, it is provided that the valve closing member for closing the passage is arranged on the high-pressure side and has a closing element, in particular a spring element acting against the valve seat. The As a result, the closed position can be guaranteed when the vehicle is not operating.

  The invention and other advantageous embodiments and developments of the invention are described and explained in more detail below with reference to the examples shown in the drawings. The features collected from the description and drawings can be used individually by themselves, or some of them can be used in any desired combination according to the invention.

FIG. 1 shows a coolant circuit 11 that preferably operates on CO ₂ . This coolant circuit 11 is used, for example, as a vehicle air conditioning system. The compressor 12 supplies the high-pressure side compressed coolant to the external heat exchanger 14. The latter is connected to the surroundings and exhausts heat out. An internal heat exchanger 15 that supplies coolant to the expansion valve 16 via a supply line 17 is connected downstream of the latter. There is an input pressure upstream of the high-pressure side expansion valve 16, for example 120 bar in summer. The coolant flows through the expansion valve 16 and proceeds to the low pressure side. On the output side, the expansion valve 16 has a pressure between 35 and 45 bar under resting conditions. The coolant cooled by the pressure reduction proceeds to the internal heat exchanger 21 via the removal line 18 and removes heat from the surroundings, and as a result, cools the interior of the vehicle and the like. A collector 22 is connected downstream of the heat exchanger. The coolant in the form of steam flows through the internal heat exchanger 15 and proceeds to the compressor 12. In order to operate this coolant circuit 11, a differential pressure expansion valve 16 is provided, which is described in more detail and fully referenced in DE 10 2004 010 997 B3. Based on the operation described in this document for the expansion valve 16, FIG. 2 in which the cooling curve in the vehicle is depicted at high ambient temperatures is described in more detail below.

The vehicle is not operated at a high ambient temperature for a long time, for example, and a high ambient temperature exceeding 40 ° C. is prevalent. When the vehicle is not operating (II) , there is typically a pressure balance of about 80 bar on the high and low pressure sides of the coolant circuit 11. Immediately after the start of the coolant circuit 11 (II-1), the pressure of the high-pressure side coolant rises within a few seconds due to the compressor power, for example, up to a maximum allowable value of 133 bar on the high-pressure side. In contrast, on the low pressure side, the pressure drops very slowly (lower curve). During other operations of the start phase (II-1), the low pressure drops only with a small slope. As a result, a very small pressure change is provided, whereby slow cooling of the interior of the vehicle takes place in the start phase (II-1). The response characteristic of the air conditioning system is delayed. During the driving mode (II-2), a stationary state is created which is essentially drawn by the horizontal part of the upper and lower curves. The third stage (III) shows the high pressure upstream of the expansion valve 16 in the idling mode (upper curve) and the lower pressure downstream of the expansion valve 16 (lower curve).

In order to obtain an improved response characteristic in the start phase (II-1) and to reduce the duration of the start phase, according to the present invention, while the pressure difference is still relatively average, It is proposed to enhance the opening of the valve under these conditions to provide a large mass flow. To this end, it is proposed that this is done by means of displacing the opening characteristics of the expansion component controlled by the differential pressure to a lower opening pressure. Reduction takes place via the increasing low pressure side or the evaporating temperature at which the coolant or ambient temperature increases. As an alternative to displacing the opening characteristic of the valve closing member of the expansion valve, it is proposed to provide a bypass valve that is reduced on the low pressure side and opened as a function of temperature or pressure. The exemplary embodiment described above is based on the evaporation temperature and evaporation pressure of the coolant. These activating means according to the invention are shown in more detail in FIGS.

  FIG. 3 shows a schematic cross-sectional view of the first expansion valve 16 according to the invention. A supply opening 32 connected to the removal opening 36 via the passage opening 34 is provided in the valve housing 31. A valve closing member 37 is provided in the passage opening 34. When pressure balance is present, the valve closing member 37 is held on the high pressure side of the valve seat 41 via a resetting device 39 which is preferably designed as a spring element. An adjustment element 42 comprising an expansion bellows or bellows 44 filled with an inert gas 46 is provided in the removal opening 36. At one end, the bellows 44 is supported on the wall 47 of the housing. On the opposite side, the bellows 44 activates at least one actuating element 48, in particular a tappet extending into the supply opening 32 as a function of low pressure. These tappets 48 engage displacement elements 49 that act to set the prestress of the resetting device 39. In order to limit the stroke movement of the adjustment element 42, a stop 43 is provided to determine the end position of the adjustment element 42.

As soon as the pressure on the low pressure side of the removal opening 36 increases, the bellows 44 is compressed due to the increasing pressure and performs a stroke movement. At the same time, a one-way stroke movement of the tappet 48 is performed to reduce the pre-stress of the resetting device 39, whereby the valve closing member 37 is opened even when the pressure differential is relatively small, and the coolant starts. It proceeds from the high pressure side to the low pressure side earlier in the stage. As a result, a pressure dependent displacement of the operating feature can be obtained for the expansion valve 16.

  FIG. 4 shows an alternative embodiment to FIG. The structure of the expansion valve 16 corresponds to the structure of FIG. Apart from this, a temperature-dependent adjusting element 42 is provided instead of the adjusting element 42 depending on the low pressure or the evaporation pressure. The temperature-dependent adjusting element 42 includes a spring 52 made of, for example, a shape memory alloy. At least one actuating element 48 is provided on the adjusting element 42 and acts on the resetting device 39 to reduce the closing force. As soon as the low-pressure side temperature exceeds a desired value, the spring 52 made from the shape memory alloy is shortened. As a result, the pressure acting on the resetting device 39 is reduced, thereby allowing the passage opening 34 to be opened. Further, a wax expansion element, bimetal, or other two material elements can be provided as a temperature sensor to activate the adjustment element 42. Alternatively, the adjustment element 42 can also act directly on the valve closure element.

  FIG. 5 shows an alternative embodiment of FIG. This embodiment is different in that the resetting device 39 and the valve closing member 37 are arranged on the low pressure side. In order to guide the valve closing member 37 on the low pressure side, a holding and guiding element 55 is provided for guiding the bubble closing element 37 to be displaced therein. Furthermore, the holding and guiding element 55 receives the valve closing member 37 on the low pressure side and closes the bellows 44. As a result, the holding and guiding element 55 has more than one function. In addition, this acts as an actuating element 48, in particular as a tappet, to join the stop 43 in order to obtain a limitation of the closing force of the valve closing member 37 in which the closing force acts on the passage opening 34. As the low pressure increases, according to the exemplary embodiment, the bellows 44 is pressurized and moves to the right. Thereby, the prestress of the resetting device 39 is reduced, whereby an early opening of the passage opening 34 takes place. Thereby, the response characteristic of the coolant circuit 11 is improved. Otherwise, the function is the same as in the embodiment according to FIG.

  FIG. 6 shows an alternative embodiment to FIG. In this embodiment, the resetting device 39 and the valve closing member 37 are similarly configured on the low pressure side. Instead of the actuating element 48 according to the embodiment of FIG. 4, the actuating element 48 is provided in a functionally identical manner and is designed as a tubular element and as a function of the progressive change of the spring 52 made from a shape memory alloy. Increase or decrease the prestress of the resetting device 39 to the closure member 37. The tubular element moves between two end positions or stops 43 that constrain the displacement of the feature.

  FIG. 7 shows a schematic diagram of another alternative embodiment of the expansion valve 16. This embodiment has a basic structure with a differential pressure expansion valve described in DE 10 2004 010 997 B3. Furthermore, in parallel with the passage opening 34, there is a parallel passage 61 which is arranged on the low pressure side and which is closed by an adjustment element 42 which forms a bypass valve 62 with the passage 61. According to the embodiment of FIG. 7, this bypass valve 62 is activated on the low pressure side as a function of the evaporation pressure. For this purpose, for example, a bellows 44 is provided which is filled with an inert gas or whose interior is connected to the atmosphere while the closing force is implemented by a compression spring. At the end of the bellows 44 facing the passage 61 there is a closing member 63 which closes the passage 61 when a low pressure value is present in the coolant system 11 corresponding to normal operation, for example less than 45 bar.

  FIG. 8 shows an alternative embodiment of FIG. Instead of a bypass valve 62 that can be activated as a function of the evaporation pressure, a bypass valve 62 is provided that can be activated as a function of temperature. A control medium 66 is provided in the adjustment element 62, which is designed as a bellows and undergoes a change in volume as a function of temperature. The closing member 63 is actuated by an actuating element 48, for example in the form of a tappet, which is arranged on the bellows and is preferably provided on the high pressure side of the passage 61, and is closed via a closing member 68, in particular a spring element. Retained.

The filler enclosed inside the bellows has pressure and temperature characteristics such that when the temperature of the CO ₂ coolant rises on the low pressure side, the pressure rises higher than the outside of the bellows. As a result, opening of the bypass can be achieved when the temperature rises on the low pressure side.

  All of the features described above are themselves essential to the invention and can be combined with one another as desired.

It is the schematic which shows a coolant circulation process. FIG. 5 shows the cooling curves of the various operating stages at high ambient temperatures with a differential pressure valve without “start assistance” in the vehicle. FIG. 6 is a schematic cross-sectional view of an expansion valve with an open feature displacement performed as a function of low pressure. FIG. 6 is a schematic cross-sectional view of an expansion valve with an open feature displacement performed on the low pressure side as a function of temperature. FIG. 4 is a schematic cross-sectional view of the alternative embodiment of FIG. 3. FIG. 5 is a schematic cross-sectional view of the alternative embodiment of FIG. FIG. 6 is a schematic cross-sectional view of an alternative embodiment of an expansion valve having a bypass valve controlled on the low pressure side parallel to the differential pressure valve. FIG. 6 is a schematic cross-sectional view of an alternative embodiment of an expansion valve having a temperature controlled bypass valve parallel to the differential pressure valve.

Explanation of symbols

  11 Coolant circuit, 12 Compressor, 14 External heat exchanger, 15 Internal heat exchanger, 16 Expansion valve, 17 Supply line, 18 Removal line, 21 Internal heat exchanger, 22 Collector, 31 Valve housing, 32 Supply opening , 34 passage opening, 36 removal opening, 37 bubble closure member, 39 resetting device, 41 valve seat, 42 adjustment element, 43 stop, 44 expansion bellows, 46 inert gas filler, 48 actuating element tappet, 49 displacement element , 52 Spring, 55 Holding and guiding element, 61 Passage, 62 Bypass valve, 63 Closing member, 66 Control medium

Claims (9)

A valve housing (31) having a supply opening (32) and a removal opening (36), and a valve seat (41) of a passage opening (34) disposed between the supply opening and the removal opening (32, 36) An expansion valve of a vehicle air conditioning system, in particular operating with CO2 as coolant, having a valve closing member (37) for closing) and a resetting device (39) acting in the closing direction of said valve closing member (37) A method of controlling,
The low pressure side of the regulatory elements to be allocated to the valve closure member (37) (42), when the pressure of the low-pressure side is increased, or when the temperature of the low-pressure side is increased, activated through a predetermined threshold value in the low-pressure side Actuating at least one actuating element (48), which actuating element (48) reduces the closing force of the resetting device (39) acting on the valve closing member (37), thereby providing a passage The opening (34) is enlarged and the adjusting element (42) is reduced by a function of the low pressure or by the temperature on the low pressure side, so that the opening characteristic of the valve closing member (37) controlled by the differential pressure is increased. A method characterized by being moved to a lower opening pressure . A valve housing (31) having a supply opening (32) and a removal opening (36), and a valve seat (41) of a passage opening (34) disposed between the supply opening and the removal opening (32, 36) An expansion valve comprising: a valve closing member (37) for closing) and a resetting device (39) acting in the closing direction of said valve closing member (37),
In order to reduce the closing force of the valve closure member (37), adjusting elements (42) disposed on the low pressure side, the comparatively abuts the valve closure member (37), provided on the valve closure member (37) at least one actuating element expansion valve characterized that you connect to (48) acting on the resetting device (39) was. The adjustment element (42) activated by low pressure is formed by a membrane element or an expansion bellows (44) to reduce the closing force of the valve closing member (37) closing the passage opening (34). 3. An expansion valve according to claim 2, characterized in that the tappet (48) acting on the high pressure side resetting device (39) is actuated. The adjustment element (42) activated by low pressure is formed by a membrane element or an expansion bellows (44) to reduce the closing force of the valve closing member (37) closing the passage opening (34). 3. An expansion valve according to claim 2, characterized in that it operates a tappet (48) acting on the resetting device (39) on the low-pressure side.   3. An expansion valve according to claim 2, wherein the regulating element (42) actuated by low pressure comprises an inert gas filler (46).   The adjusting element (42) activated when the low-pressure side temperature rises reduces the closing force acting on the low-pressure side against the valve closing member (37) or the resetting device (39) A temperature sensor acting on the valve closing member (37) with a spring force acting in the opening direction parallel to the valve closing member (37) is held in the closed position by the high pressure side resetting device (39) The expansion valve according to claim 2.   The adjusting element (42) activated when the temperature on the low-pressure side rises reduces the closing force acting on the low-pressure side against the valve closing member (37) or the resetting device (39) A temperature sensor acting on the valve closing member (37) with a spring force acting in the opening direction parallel to the valve closing member (37) is held in the closed position by the resetting device (39) on the low pressure side The expansion valve according to claim 2.   3. An expansion valve according to claim 2, characterized in that the adjustment element (42) which is activated when the low-pressure side temperature rises is in the form of a shape memory alloy or a wax expansion element.   The expansion valve according to claim 6 or 7, wherein the temperature sensor is provided outside the housing (31) and includes an ambient temperature or a temperature of a vehicle part.

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