Control valve and method for controlling such a control valve for a fluid circuit

Abstract

Control valve, which can be actuated for a bidirectional flow direction in a fluid circuit, with a housing (12) which has a first opening (14) and a second opening (16) which are connected to each other by a through-channel (17) which has a through-opening (18) and between the first opening (14) and the through-opening (18) a control chamber (19) is formed and with a needle valve (26) arranged in the control chamber (19), which has a valve element (31) with a through-bore (32) and a valve seat (34) and comprises a valve needle (33) which in a closed position rests in the valve seat (34) of the valve element (31) and closes the through-bore (32) and in an open position is lifted from the valve seat (34), with an actuating device (24) which actuates a stroke movement of the valve needle (33) of the needle valve (26),wherein the actuation of the valve needle (33) is provided depending on a flow direction of a fluid from the first opening (14) to the second opening (16) or from the second opening (16) to the first opening (14), characterized in that the valve element (31) with the valve needle (33) forms an expansion valve (40) in a flow direction from the first opening (14) to the second opening (16) and the valve element (31) with the valve needle (33) forms a two-stage valve with a first and second flow valve (66, 67) in a flow direction from the second opening (16) to the first opening (14), wherein the first flow valve (66) is formed by the valve element (31) and the valve needle (33), which opens during a first working stroke of the valve needle (33) and the second flow valve (67) is formed by the valve element (31) and a sealing element (41) which is attached to a flow valve seat (47) iswhich is located in the transition area between the flow channel (17) and the control chamber (18), wherein the second flow valve (67) opens on a second working stroke of the valve needle (33).

Description

[0001] The invention relates to a control valve which can be controlled for a bidirectional flow direction in a fluid circuit, as well as a method for controlling such a control valve so that both cooling operation and heat pump operation are possible.

[0002] US 2015 / 0114495 A1 discloses a control valve for a heat pump circuit that enables bidirectional operation of the heat pump circuit. This control valve comprises a housing with an inlet opening and an outlet opening that are connected to one another by a through-channel. A through-bore is provided in the through-channel, which includes a valve seat that can be opened and closed by an electrically controllable valve closing element. This valve seat is provided on a housing section fixedly arranged in the housing. For cooling operation, an opening position of the valve closing element is controlled via an electric drive, allowing expansion of the fluid in the through-bore. During cooling operation, only the through-bore is open in the flow direction.

[0003] When the control valve is used for heat pump operation, the flow direction of a fluid is reversed. Adjacent to the through-bore, which serves as a flow valve with the valve closure element in this operation, bypass bores are provided radially outside the through-bore. These bypass bores are closed in cooling mode by a disc-shaped valve closure element. In heat pump operation, the disc-shaped valve closure element opens due to the prevailing pressure, allowing a first passage with a constant flow volume. In addition, the valve closure element arranged next to the through-bore can be controlled to control a variably adjustable mass flow in addition to the constant mass flow.

[0004] Such a control valve as described above is also known from US 2010 / 0263397 A1.

[0005] This control valve has the disadvantage that, during heat pump operation, low-pressure flow is not possible due to the fixed flow cross-section of the bypass holes and the variable flow cross-section that can be applied. This adversely affects the efficiency of heat pump operation.

[0006] US 2013 / 0206851 A1 discloses a control valve that enables bidirectional operation of a fluid circuit. When the circuit is operated in one flow direction, the control valve acts as an expansion valve. When the control valve is operated in the opposite flow direction, the valve stroke can control the volume of the mass flow. Such a control valve with an analogous function is known from US 2013 / 0306176 A1.

[0007] The invention is based on the object of proposing a control valve and a method for controlling the control valve for a heat pump circuit, in which both a high control quality for an expansion process of the fluid in cooling operation and a low pressure loss within the control valve during heat pump operation, i.e. a low pressure loss characteristic, are possible.

[0008] This object is achieved by a control valve for a heat pump circuit, which comprises a housing with a first and a second opening, which are connected to one another by a through-channel which has a passage opening and a control chamber is formed between the first opening and the passage opening, wherein a valve element is arranged in the control chamber, which has a through-bore with a valve seat, which is closed with a valve needle in a closed position and in an open position the valve needle is lifted from the valve seat, and with a drive device which controls a lifting movement of the valve needle, wherein the control of the valve needle is provided depending on the flow direction from the first to the second opening or from the second to the first opening,wherein the valve element and the valve needle form an expansion valve in a flow direction of the fluid from the first to the second opening, and in a flow direction of the fluid from the second opening to the first opening of the valve element and the valve needle form a first flow valve, and furthermore the valve element forms a second flow valve with a sealing element that rests against a flow valve seat formed in the transition region between the through-channel and the regulating chamber.

[0009] This design of the valve element enables the valve element with the valve needle to function as an expansion valve during cooling operation. The valve element's stroke movement enables precise control of the expansion characteristic or the release of the throttle cross-section depending on the valve stroke. This allows for high control quality. For heat pump operation, the valve element with the valve needle acts as a first flow valve or pilot valve, so that when the valve needle lifts off the valve element, a first flow cross-section is released to create pressure equalization.Subsequently, at a small pressure difference, the valve element, which forms a second flow valve with the flow valve seat, is lifted off the flow valve seat, thereby releasing a large flow cross-section so that essentially the entire mass flow of the fluid can be transferred from the second opening directly to the first opening. At a larger pressure difference between the second opening and the first opening, the second flow valve is immediately opened during a working stroke of the valve needle of the first flow valve, i.e. the valve element lifts off the flow valve seat. In both cases, a low-pressure loss flow of the fluid in the heat pump circuit is achieved, so that a high level of efficiency of the heat pump circuit is achieved in consumption-critical heating operation at low temperatures.

[0010] Preferably, the flow cross-section of the second flow valve is larger than the flow cross-section of the first flow valve on the valve element. As a result, after the valve element opens, the mass flow of the fluid takes a direct path from the flow valve seat through the regulating chamber to the first opening, and possibly only a small portion of the mass flow flows via the first flow cross-section to the first opening. This enables a reduction in pressure loss.

[0011] Furthermore, a closing spring is preferably provided in the regulating chamber, which arranges the second flow valve provided on the valve element in a closed position. This enables the valve element to be arranged closed in a defined position within the regulating chamber during expansion operation. As a result, a throttle cross-section in the through-bore of the valve element is only released in accordance with the stroke movement of the valve needle, so that an exclusive expansion valve function is provided. During heat pump operation, however, it is possible for the valve element to delay or immediately open the second flow valve depending on the pressures or a corresponding control of the valve needle in order to release a large flow cross-section.

[0012] Furthermore, the valve needle is preferably conical and has a control surface that engages the through-bore. A valve closure element is preferably arranged at an end section of the control surface. The conical valve needle with a control surface arranged thereon allows a desired control characteristic to be selected and adjusted depending on the application by adjusting the control surface, thus achieving high control quality during cooling operation.

[0013] The drive device preferably controls a first working stroke of the valve needle, whereby the valve needle can be moved from a closed position relative to the through-bore to an open position that exposes the flow cross-section of the through-bore. An increasing stroke within the working stroke increases the flow cross-section, and finally, after the valve needle is removed from the through-bore, it can also be completely exposed.

[0014] The valve element preferably has a sleeve opposite the second flow valve, which is connected to the valve element. The valve element is guided by means of the sleeve on a guide section provided on the housing or a drive housing arranged thereon. This enables a simple axial displacement or lifting movement of the valve element within the regulating chamber.

[0015] Preferably, the guide section accommodates the closing spring on its outer circumference, which rests on the opposite side of the valve element. This enables a simple and compact design within the control chamber.

[0016] Furthermore, an end face is preferably provided at a front end of the guide section facing the valve element, which limit the stroke movement of the valve element. This limit for the valve element is set such that, on the one hand, a maximum mass flow of the fluid can flow from the second to the first opening, while, on the other hand, still providing a compact installation space.

[0017] The valve needle of the needle valve preferably has a stop at an end opposite a tip of the valve needle, which stop rests against a shoulder of the sleeve arranged on the valve element after a first working stroke of the valve needle has been activated. This limits the first working stroke with regard to a free lifting movement of the valve needle between the through-bore and the sleeve. Upon a further lifting movement of the valve needle, the valve element is forcibly lifted because the stop rests against the sleeve and the sleeve is connected to the valve element and lifts it against a further lifting movement of the valve needle. Alternatively, it can be provided that a driver is provided on the tip of the valve needle, which extends through the through-bore and engages behind it.In this alternative embodiment, after completing a first working stroke, the valve needle is released from the through-bore of the valve element with respect to its control surfaces, but is engaged behind by the driver attached to the tip of the valve needle. Upon a further stroke of the valve needle, the valve element can again be forcibly lifted. In this embodiment, the sleeve can be simplified to a tubular section, which is attached to the valve element on one side and guided in the guide section on the other.

[0018] The sleeve on the valve element is preferably long enough to allow the valve needle arranged within the sleeve to undergo a first working stroke, during which the control surface can be moved from a closed position to a position completely exposing the cross-section of the through-bore at the end of the first working stroke, and a stop on the valve needle rests against a shoulder of the sleeve. Thus, by controlling a second working stroke, a forced opening of a second flow valve can be achieved, or the forced lifting of the valve element from a support surface surrounding a through-channel of the second opening of the housing can be enabled in order to expose an enlarged flow cross-section.

[0019] It is preferably provided that, when the valve needle is actuated with a second working stroke following the first working stroke, the valve element is forcibly moved by a stop or driver arranged on the valve needle into a position in which the second flow valve is open. This design of the sleeve has the advantage that a secure lifting of the valve element from the second flow valve seat is possible during heat pump operation, particularly with small pressure differences upstream and downstream of the second flow valve, in order to create a large flow cross-section.

[0020] According to a further preferred embodiment of the invention, the sealing element of the second flow valve provided on the valve element is molded onto the valve element or arranged in a form-fitting and / or force-fitting manner by means of a stop element. Preferably, the sealing element can be clamped between the valve element and the stop element, wherein, for example, the stop element can be mounted to the valve element by means of a screw connection or a press connection. The sealing element can preferably be designed as an annular elastomer seal that seals against a flow valve. This allows for a simple and structural design with a low leakage rate.

[0021] Furthermore, the valve element preferably has a stop surface adjacent to the sealing element, preferably radially surrounding it on the outside, which, in a closed position, rests against a support surface in the regulating chamber. This ensures a defined closing position of the valve element relative to the regulating chamber and enables a defined and consistent zero-point positioning of the valve needle relative to the valve seat on the valve element. This, in turn, can ensure control quality during expansion operation. At the same time, the defined closing position can close the second flow valve, preventing crushing, damage, or overloading of the sealing element, which rests against the raised flow valve seat.

[0022] Furthermore, the flow valve seat is preferably formed by a circumferential, preferably wedge-shaped, raised portion pointing toward the sealing element. This enables a secure seal with a long service life.

[0023] Furthermore, a filter element is preferably provided in the passageway, upstream and downstream of the control chamber, associated with the opening in the housing, or at least one filter element is provided in the control chamber. This protects the components arranged in the control chamber for achieving the individual control characteristics from possible contamination, regardless of the flow direction of the fluid in the heat pump circuit.

[0024] The drive device can be designed as an electric, electromagnetic, pneumatic, or a motor driven by at least one shape memory alloy actuator. All of these drives have the advantage that individual stroke movements can be adjusted and controlled to control the control valve accordingly in both cooling and heat pump mode.

[0025] The opening time of the second flow valve in heat pump operation, at which the fluid flows from the second opening to the first opening, depends on the pressure difference of the fluid between the second opening and the first opening as well as the closing force of a closing spring acting on the valve element. It is preferably provided that the opening time can be adjusted at a pressure difference between 0.05 bar and 10 bar using the closing force and the closing spring. Depending on whether, when the valve needle is lifted in heat pump operation, only pressure equalization and subsequent lifting of the valve element is desired, or whether immediate lifting of the valve element is desired as soon as the valve needle is lifted from the through-bore of the valve element, the closing spring can be adjusted accordingly, taking into account the prevailing pressure difference in heat pump operation.

[0026] The object underlying the invention is further achieved by a method for controlling a control valve for a heat pump circuit through which fluid flows, in which during cooling operation, in which the flow direction of the fluid flows from the first to the second opening, the valve needle is controlled as an expansion valve and the flow cross section of the through-bore in the valve element is determined by the size of a working stroke and during heat pump operation, in which the flow direction of the fluid flows from the second opening to the first opening, the valve needle is subjected to a first working stroke and at a small differential pressure between the second and first opening, the through-bore in the valve element is released and a first flow valve, which is formed between the valve needle and the through-bore, is opened and for opening a second,the valve needle is actuated with a second working stroke by means of the flow valve provided on the valve element, by means of which the valve element, which forms the second flow valve with a sealing element arranged between the through-bore and the regulating chamber and which bears against a flow valve seat, is lifted off the second flow valve seat against the closing spring or, in the case of a high pressure difference between the second and the first opening, the second flow valve is opened immediately as soon as the valve needle is lifted by the first working stroke.

[0027] By controlling the control valve in this way, two fundamentally contradictory requirements are met, namely that in one flow direction - i.e. from the first to the second opening in cooling mode - the valve needle opens and closes and has a high control characteristic and in the other flow direction - i.e. from the second opening to the first opening in heat pump mode - a servo function is provided, which supports a low pressure loss characteristic.

[0028] Preferably, the opening start of the second flow valve is determined as a function of the differential pressure between the second and first openings and the closing force of the closing spring acting on the valve element, which, in an initial position, holds the second flow valve in a closed position. This allows for further control of the heat pump operation.

[0029] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The features shown in the description and the drawings can be used individually or in any combination according to the invention. They show: Fig. 1 a schematic partial section of a control valve according to the invention, Fig. 2 a schematic sectional view of the control valve during a cooling operation with a valve needle in a closed position, Fig. 3 a schematic sectional view according to Fig. 2 with the valve needle in a control position, Fig. 4 a schematic sectional view of the control valve in a heat pump operation with a valve needle which is subjected to a first working stroke, Fig. 5 a schematic sectional view according to Fig. 4, in which the valve needle is subjected to a second subsequent working stroke following the first working stroke, Fig. 6 a schematic sectional view of an alternative embodiment of the control valve to the Fig. 1 to 5, Fig. 7 a schematic diagram showing the change in the flow cross sections of the control valve when operating as an expansion valve and Fig. 8 a schematic diagram showing the change in flow cross-sections depending on the working strokes during operation as a flow valve.

[0030] In Fig. Figure 1 shows a schematic partial section of a control valve 11 according to the invention. This control valve 11 comprises a housing 12 with a first inlet or first opening 14 and a second inlet or second opening 16, which are connected to one another by a through-channel 17. A regulating chamber 19 assigned to the first opening 14 is provided in the through-channel 17. A guide section 21 is inserted or screwed into this regulating chamber 19 and, via a seal 22, seals the regulating chamber 19 from this housing-open side. This guide section 21 can be designed as a separate component to which a drive device 24 can be fastened.

[0031] Likewise, this guide section 21 can be part of this drive device 24.

[0032] This drive device 24 can be constructed in different ways. For example, an electric drive, in particular a stepper motor, can be provided. Alternatively, an electromagnetic drive, a pneumatic drive, or a drive by means of an SMA (shape memory alloy) actuator can be provided. This drive device 24 controls a needle valve 26 by a lifting movement of a valve needle 33 relative to the valve element 31. In doing so, this valve needle 33 dips to a greater or lesser extent into a through-bore 32 of the valve element 31. Sensors can be provided to detect the position of the valve needle 33. For example, a Hall sensor can be used.

[0033] Furthermore, a filter element 28 is inserted into the regulating chamber 19. This filter element 28 is, for example, ring-shaped and can be fixed to the housing by means of the guide section 21. The filter element 28 thus acts upon the supply of fluid via the opening 14. Furthermore, a filter element 29 can be assigned to the second opening 16, so that when the fluid is supplied via the second opening 16, dirt particles are also retained before entering the regulating chamber 19.

[0034] Fig. 2 shows a schematic enlargement of the structure of the control valve 11, which is described below.

[0035] The valve element 31 comprises the through-bore 32, into which the valve needle 33 of the needle valve 26 engages. This through-bore 32 comprises a valve seat 34 on its outer circumference. The valve needle 33 is preferably conical and comprises a control surface 36, which increases in cross-section from a tip 37 of the valve needle 33, whereby various contours can be provided. Opposite the tip 37 of the valve needle 33 is a valve closing member 38, which can be integrated into the control surface 36. The valve needle 33 has a stop 39 directly adjacent to the valve closing member 38 or further spaced from the tip 37 of the valve needle 33, which extends further outward in the radial direction than the valve closing member 38.

[0036] The valve element 31 is, for example, pot-shaped or cup-shaped, with the through-bore 32 provided in the bottom of the pot. A sealing element 41 is provided at a distance from the edge of the pot, which is received and positioned relative to the valve element 31 by means of an annular stop element 42. This stop element 42 can be pressed, welded, soldered, or screwed on. The stop element 42 has a stop surface 43, which rests oppositely on a support surface 45 on the housing 12. This support surface 45 surrounds the through-channel 17 and delimits the regulating chamber 19.

[0037] In the transition area between the support surface 45 and the through-channel 17, a flow valve seat 47 is provided by an elevation pointing in the direction into the receiving space 19, which at least partially engages or engages in the sealing element 41, provided that the valve element 31 is arranged in a first working position 30.

[0038] A closing spring 49 is provided between the guide section 21 and the valve element 31, which positions the valve element 31 in a starting position 30 or first working position through its closing force. The closing spring 49 is preferably guided on the outer circumference of the guide section 31. Opposite, the closing spring 49 is also preferably received and guided on an edge region of the valve element 31 and the stop element 42.

[0039] A sleeve 51 is provided within the guide section 21 and is preferably permanently attached to the valve element 31. This sleeve encompasses the cup-shaped section of the valve element 31. The sleeve 51 is preferably welded, soldered, screwed, or pressed onto it. Recesses 52 are provided on a peripheral wall of the sleeve 51 so that the fluid in the regulating chamber 19 can also reach an interior of the sleeve 51. An opening 54 is provided at one end of the sleeve 51, through which a shaft 56 of the valve needle 33 extends, so that the valve needle 33 is arranged with the stop 39 within the sleeve 51. The stop 39 of the valve needle 33 is larger in its outer circumference than the diameter of the opening 54 of the sleeve 51, so that the stop 39 can bear against an inner end face of the sleeve 51 after the valve needle 33 has completed a first working stroke.

[0040] In Fig. 2, the valve needle 33 is shown in a closed position 61. The valve element 31 rests fluid-tight against the flow valve seat 47 above the sealing element 41.

[0041] For cooling operation of a heat pump circuit in which the control valve 11 is used, the fluid flows through the housing 12 of the control valve 11 according to the arrows shown. The fluid is supplied via the first opening 14 and discharged via the second opening 16. Fig. With the arrangement of the valve needle 33 and the valve element 31 in the control chamber 13 shown in Figure 2, the passage channel 17 is blocked. The control valve 11 is closed.

[0042] In a cooling operation, the valve needle 33 is controlled by means of the drive device 24, wherein the control 62 determines a lifting movement of the valve needle 33 in order to transfer this valve needle 33 from a closed position to an open position, as shown in Fig. 3 is shown.

[0043] The Fig. 3 shows that the needle valve 26 is open. In the Fig. 2, the needle valve 26 operates as an expansion valve. The change in the released cross-section in the through-bore 32 through the valve needle 33 can be determined by the stroke position of the valve needle 33 relative to the through-bore 32. In this mode of operation, the valve element 31 is held in a sealing position relative to the through-channel 17 by the closing spring 49, with the stop surface 43, which rests on the support surface 45, preventing overloading of the sealing element 41. At the same time, the valve element 31 assumes a defined position within the working chamber. In addition, the pressure present in the regulating chamber 19 on the inlet side at the first opening 14, which is greater than the outlet side pressure at the second opening 16, acts on the valve element 31 to arrange it in this closed position.

[0044] By controlling the valve needle 33 with the drive device 34 with a first working stroke to open the first through hole 32, in which the valve needle is moved from a closed position according to Fig. 2 into an open position according to Fig. 4, in particular the valve needle 33 has been led out of the through-bore 32, it is also achieved that a pressure equalization of the prevailing differential pressure between the first opening 14 and the second opening 16 takes place. This reduces the opening force for the valve element 31, which is required by the drive device 24 via the valve needle 33 to lift the valve element 31 from the valve seat 34. By controlling a lifting movement of the valve needle 33, an expansion cross-section in the throttle bore 32 can be controlled by the first working stroke 58. Likewise, by controlling the second working stroke, an opening and closing movement of the valve element 31 with respect to the flow valve seat 47 can take place to open the through-bore 18, so that a forced control of different opening cross-sections is possible.If the valve element 31 is lifted from the flow valve seat 47 in expansion operation, the pressure difference between the first opening 14 and the second opening 16 is reduced to a minimum.

[0045] In the Fig. 4 and Fig. Figure 5 shows the operating positions of the control valve 11 during heat pump operation. During heat pump operation, the fluid flows through the housing 12 of the control valve 11, entering the control chamber 19 via the opening 16 and from there being guided to the first opening 14.

[0046] To achieve a large flow volume during heat pump operation, the needle valve 26 is opened. The valve needle 33 undergoes a first working stroke, which can be such that the stop 39 rests against an inner end face of the sleeve 51. In this operating state, the valve element 31 and the valve needle 33 form a first flow valve, for example to achieve pressure equalization between the inlet side in the second opening 16 and the outlet side in the first opening 14. To increase the flow cross-section, a second working stroke of the valve needle 33 is activated to open a second flow valve 67. This second flow valve 67 is formed by the sealing element 41 of the valve element 31 and the flow valve seat 47.

[0047] To open the second flow valve 67, at a lower pressure difference between the second opening 16 and the opening 14, the valve element 31 can be opened by a second working stroke of the valve needle 33, by means of the stop 39, the sleeve 51 and thus the valve element 31 are forcibly lifted from the second flow valve seat 47. This is shown in Fig. 5. The valve element 31 undergoes a stroke 71, releasing a large flow volume so that the fluid can flow directly from the passage 17 into the regulating chamber 19 and from there flow out again via the first opening 14.

[0048] The design of the stop 39 on the valve needle 33 ensures that the second flow valve 67 can be lifted and opened safely during heat pump operation.

[0049] If the pressure difference between the second opening 16 and the first opening 14 is sufficiently large, for example three bar or more, the valve element 31 will simultaneously lift off from the flow valve seat 47 upon initiation of the first working stroke of the valve needle 33, so that the first flow valve 66 will not open at all, but the second flow valve 67 will open immediately.

[0050] The closing force of the closing spring 49 can influence the opening time of the second flow valve 67.

[0051] In Fig. 6 is a schematic sectional view of an alternative embodiment of the control valve 11. This alternative embodiment of the control valve 11 differs only from the Fig. 1 to 5 in that, instead of a stop 39, a driver 73 is provided at an end opposite the tip 37 of the valve needle 33. The stop 39 has been omitted. The driver 73 extends from the tip 37 of the valve needle 33 through the through-bore 32 and has holding elements or gripping sections or the like which engage behind the through-bore 32. As soon as the valve needle 33 has completed the first working stroke 58, the driver 73 engages behind the through-bore 32. Upon initiation of the second working stroke 59, the valve element 31 is forcibly lifted off the flow valve 47 and can be moved with a stroke 71 according to Fig. 5 may be applied.

[0052] In such an embodiment, the design of the sleeve 51 is simplified since it need only be designed as a piece of pipe, so that this sleeve 51 is fixed on the valve element 31 on the one hand and forms the introduction for the valve element 31 within the guide section 21 on the other hand.

[0053] In all other respects, the analogous statements apply to the Fig. 1 to 5 also for this embodiment.

[0054] In Fig. Figure 7 shows a schematic diagram illustrating the change in flow cross-sections when the control valve 11 is actuated as an expansion valve. In cooling mode, the fluid flows from the first opening 14 to the second opening 16. The diagram plots the distance or stroke of the working strokes 58, 59 along the X-axis. The Y-axis represents the opening cross-sections of the through-bore 32 and the passage opening 18 in the through-channel 17.

[0055] By controlling the valve needle 33 within a first working stroke 58 in expansion mode, the through-bore 32 can be completely closed or partially or completely opened with respect to its cross-section. If an increased mass flow of fluid is now to pass from the first opening 14 to the second opening, the valve element 31 can be forcibly lifted by subjecting the valve needle 33 to a second working stroke 59 by the drive device 24. Due to the stop 39 or the driver 73, the valve element 31 is lifted from the flow valve 47, and a complete opening of the maximum flow cross-section occurs. The characteristic curve 75 results from the above.

[0056] In Fig. Figure 8 shows a schematic diagram for controlling the flow cross-sections of the control valve 11 during heat pump operation. In heat pump operation, the fluid flows from the second opening 16 to the first opening 14.

[0057] If the pressure difference between the first opening 14 and the second opening 16 is small, for example in a pressure difference range of 0.05 bar to 10 bar, and the closing force of the closing spring 36 is adjusted so that it applies such a closing force within this pressure difference range, the second flow valve 67 remains closed when a first working stroke 58 of the valve needle 33 is activated. A controlled flow of fluid occurs via the through-bore 32 of the first flow valve 66 from the second opening 16 to the first opening 14. If a further release of a flow cross-section is now desired, a second stroke movement 59 of the valve needle 33 can be activated with the drive device 24, so that the passage opening 18 of the through-channel 17 is released. This mode of operation is represented by the characteristic curve 76.

[0058] If a large pressure difference exists between the second opening 16 and the first opening 14, which is higher than the closing force of the closing spring 39, the valve element 31 is immediately lifted from the flow valve seat 47 when a first working stroke 58 of the valve needle 33 is triggered by the drive device 24 due to the pressure difference, and the second flow valve 67 immediately begins to open. In such a case, the maximum stroke 71 of the valve element 31 to the flow valve seat 47 can be triggered by triggering the first and second working strokes 58, 59. A corresponding characteristic curve is indicated by the reference number 77 in Fig. 8 shown.

Claims

[1] Control valve which can be controlled for a bidirectional flow direction in a fluid circuit, comprising a housing (12) which has a first opening (14) and a second opening (16) which are connected to one another by a through-channel (17) which has a passage opening (18) and a regulating chamber (19) is formed between the first opening (14) and the passage opening (18), and comprising a needle valve (26) arranged in the regulating chamber (19), which has a valve element (31) with a through-bore (32) and a valve seat (34) and comprises a valve needle (33) which, in a closed position, rests in the valve seat (34) of the valve element (31) and closes the through-bore (32) and, in an open position, is lifted off the valve seat (34), comprising a drive device (24) which causes a lifting movement of the valve needle (33) of the needle valve (26). targets,wherein the control of the valve needle (33) is provided as a function of a flow direction of a fluid from the first opening (14) to the second opening (16) or from the second opening (16) to the first opening (14), , characterized bythat the valve element (31) with the valve needle (33) forms an expansion valve (40) in a flow direction from the first opening (14) to the second opening (16), and the valve element (31) with the valve needle (33) forms a two-stage valve with a first and a second flow valve (66, 67) in a flow direction from the second opening (16) to the first opening (14), wherein the first flow valve (66) is formed by the valve element (31) and the valve needle (33), which opens during a first working stroke of the valve needle (33), and the second flow valve (67) is formed by the valve element (31) and a sealing element (41) which bears against a flow valve seat (47) which is arranged in the transition region between the through-channel (17) and the regulating chamber (18), wherein the second flow valve (67) during a second working stroke of the valve needle (33) opens. [2] Control valve according to claim 1, characterized bythat a flow cross-section of the second flow valve (67) is larger than the flow cross-section of the first flow valve (66). [3] Control valve according to claim 1 or 2, characterized by that a closing spring (49) is provided in the regulating chamber (19), which arranges the second flow valve (67) provided on the valve element (31) in a closed position. [4] Control valve according to one of the preceding claims, characterized by that the valve needle (33) of the needle valve (26) is conical and has a control surface (36) which engages in the through-bore (32) and preferably limits an immersion movement of the control surface (36) by means of a valve closing member (38). [5] Control valve according to one of the preceding claims, characterized bythat the drive device (24) controls a first working stroke (58) within which the valve needle (33) can be transferred from a closed position to the through-bore (32) into an opening position releasing a flow cross-section of the through-bore (32). [6] Control valve according to one of the preceding claims, characterized by in that the valve element (31) receives a sleeve (51) opposite the sealing element (41), which sleeve is firmly connected to the valve element (31), wherein the valve element (31) is guided by means of the sleeve (51) in a guide section (21), in particular a cylindrical guide section, which is provided on the housing (12) or a drive housing. [7] Control valve according to claim 6, characterized by that the guide section (21) receives and guides a closing spring (49) on its outer circumference, which is supported oppositely on the valve element (31). [8] Control valve according to claim 6 or 7, characterized by that at a front end of the guide section (21) facing the valve element (31), an end face is provided which limits a lifting movement of the valve element (31). [9] Control valve according to one of claims 6 to 8, characterized by that the valve needle (33) has a stop (39) at an end opposite a tip (37) of the valve needle (33), which stop rests against a shoulder of the sleeve (51) after a first working stroke of the valve needle (33), or that a driver (73) is provided at the tip of the valve needle (33), which driver extends through the through-bore (32) and engages behind it. [10] Control valve according to one of claims 6 to 9, characterized bythat the sleeve (51) arranged on the valve element (31) with a shoulder arranged thereon has a length such that the valve needle (33) arranged inside the sleeve (51) undergoes a first working stroke, in which the valve needle (33) can be transferred into a closed position relative to the valve seat (34) and into a position completely exposing the cross section of the through-bore (32) at the end of the first working stroke. [11] Control valve according to claim 9, characterized by that the valve element (31) can be controlled with a second working stroke which follows the first working stroke and the valve element (31) is forcibly moved by the stop (39) or the driver (73) into a position in which the second flow valve (67) is open. [12] Control valve according to one of the preceding claims, characterized bythat the sealing element (41) is injection-molded onto the valve element (31) or is arranged in a form-fitting and / or force-fitting manner to the valve element (31) by means of a stop element (42) and is preferably designed as an annular elastomer seal which bears against the flow valve seat (47) between the through-channel (17) and the regulating chamber (19). [13] Control valve according to one of the preceding claims, characterized by that the valve element (31) has a stop surface (43) adjacent to the sealing element (41), preferably lying radially outside, which in an initial position rests on a support surface (45) in the regulating chamber (19). [14] Control valve according to one of the preceding claims, characterized by that an elevation forms the flow valve seat (47) for the second flow valve (67). [15] Control valve according to one of the preceding claims, characterized bythat at least one filter element (28, 29) is provided in the through-channel (17) before and after the regulating chamber (19) or a filter element (28, 29) is provided between the first opening (14) and the regulating chamber (19) and the second opening (16) and the regulating chamber (19). [16] Control valve according to one of the preceding claims, characterized by that the drive device (24) is designed as an electrically, electromagnetically or pneumatically driven motor or as an actuator made of at least one shape memory alloy, which is controlled by a controller (62). [17] Control valve according to one of the preceding claims, characterized bythat an opening time of the second flow valve (67) depends on the pressure difference of the fluid between the second opening (16) and the first opening (14) in heat pump operation and a closing force of the closing spring (49), and preferably the opening time is adjustable at a pressure difference between 0.05 bar and 10 bar by the closing force of the closing spring (49). [18] Method for controlling a control valve for a heat pump circuit through which fluid flows, which is controlled bidirectionally in heat pump operation and cooling operation, in which a housing (12) with a first opening (14) and a second opening (16) is connected in the heat pump circuit, wherein the first and second openings (14, 16) are connected to one another by a through-channel (17) which has a through-opening (18) and a regulating chamber (19) is formed between the first opening (14) and the through-opening (18), and with a needle valve (26) arranged in the regulating chamber (19), which has a valve element (31) with a through-bore (32) and a valve seat (34) and comprises a valve needle (33), which in a closed position rests in the valve seat (34) of the valve element (31) and the through-bore (32) is closed, and in an open position by the valve seat (34) is lifted,and wherein a lifting movement of the valve needle (33) is controlled by a drive device (34), , characterized by , - that, in cooling operation, in which the fluid flows from the first opening (14) to the second opening (16), the valve needle (33) to the valve element (31) is controlled as an expansion valve (40) and the flow cross-section of the through-bore (32) in the valve element (31) is determined by the size of a first working stroke (58) of the valve needle (33), - that in heat pump operation, in which the flow direction of the fluid flows from the second opening (16) to the first opening (14) and - when there is a slight pressure difference between the second opening (16) and the first opening (14), a first flow valve (66) is opened, which is formed by the through-bore (32) with the valve seat (34) in the valve element (31) and the valve needle (33), and a first working stroke of the valve needle (33) is activated, and to open a second flow valve (67) provided on the valve element (31), which is formed by a flow valve seat (47) and a sealing element (41) of the valve element (31) lying thereon, a second working stroke of the valve needle (26) is activated, by means of which the valve element (31) is lifted off the second flow valve seat (47) against the closing spring (49), - or in the case of a higher pressure difference between the second opening (16) and the first opening (14), the second flow valve (67) is opened simultaneously with the first working stroke of the valve needle (26). [19] Method according to claim 18, characterized by that the start of opening of the second flow valve (67) is determined as a function of the pressure difference between the second opening (16) and the first opening (14) and the closing force of the closing spring (49). [20] Method according to claim 18 or 19, characterized by in that in the cooling operation, in which the fluid flows from the first opening (14) to the second opening (16), the valve needle (33) is controlled with a second working stroke (59) after being controlled with the first working stroke (58) and the valve element (31) is lifted off the flow valve seat (47). [21] Method according to one of claims 18 to 20, characterized bythat both in cooling operation, when the fluid flows from the first opening (14) to the second opening (16), and in heat pump operation, when the fluid flows from the second opening (16) to the first opening (14), at least one two-stage positively controlled expansion or throttling of the fluid is controlled by at least two successive working strokes (58, 59) of the valve needle (33) by means of the drive device (14).

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