Electromagnetic Actuator

Abstract

To provide an electromagnetic actuator for operating a valve of a piston compressor, which is configured to be simple and compact as far as possible, and satisfies high requirements in efficiency, less maintenance, reliability, and a long life.SOLUTION: A power electronic device 6 of an actuator 1 is disposed between a coil 3 in an actuator casing 2 and an actuator end portion E in an axial direction of the actuator 1 provided with an operation opening portion 5a for an operation element 5. The power electronic device 6 is separated from the coil 3 by a casing wall 7 of the actuator casing 2, and a printed circuit board 8 of the power electronic device 6 is disposed on a fixed surface 9 provided on the casing wall 7. An electric coil contact 10 of the coil 3 is extended through the casing wall 7 and is connected to the printed circuit board 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to an electromagnetically operable actuator arranged on a piston compressor for operating a valve of the piston compressor, the actuator having an actuator casing in which a coil and a magnet armature are arranged, the magnet armature electromagnetically cooperating with the coil to move the magnet armature, the magnet armature being connected to an operating element for operating the valve, the actuator casing being provided at an axial actuator end with an operating opening for the operating element, the actuator being drivable and controllable by a power electronic device.The invention further relates to a piston compressor with at least one valve for controlling the medium flow of a compressed medium and an actuator for operating this valve, and also to a valve assembly arranged on the piston compressor, the valve being arranged on a housing casing and the actuator for operating the valve being fixed to the housing.

[0002] In piston compressors, mechanical or hydraulic valve controls have been used up to now to control the intake and discharge valves. However, such mechanical or hydraulic valve controls are relatively cumbersome, subject to wear and therefore expensive to manufacture and maintain. In order to make the valve control as simple, low-maintenance and particularly flexible as possible, electromagnetic actuators are increasingly being used in valve actuation. However, such actuators, the structure and manner of operation of which are basically known in the prior art, place very high demands on themselves when used for valve actuation. In particular, they should, on the one hand, enable short actuation times and a valve lift that is precisely adjustable and reproducible over the widest possible range, and, on the other hand, simultaneously ensure low energy consumption, high reliability, a long service life and a compact design.

[0003] However, particularly in large compressors, where relatively large objects have to be moved during valve control, the available electromagnetic actuators reach their limits. In order to meet the required boundary conditions, here in particular high-power coils are required, which generally require a relatively large construction space. The coils are loaded with high currents during operation, which results in the generation of a relatively large amount of heat. The temperatures in the area of ​​the coils of the actuator can, for example, be in the area of ​​more than 120° C. Since the power electronics which drive the coils of the actuator and are sensitive to temperature are not suitable for such high temperatures, the power electronics have been arranged up to now as far away from the coils as possible, for example in a separate casing, in order to reduce the ambient temperature of the power electronics to a tolerable level. This certainly protects sensitive electronic components from excessively high temperatures, but this makes the actuator as a whole even more complicated, for example because lines between the external casing and the actuator are required. Apart from this, the construction space required for the actuator is of course enlarged. However, this is disadvantageous, particularly in applications where the space available for arranging the actuator, including the lines, is limited.

[0004] The object of the present invention is therefore to provide an electromagnetic actuator for valve actuation of piston compressors which is designed as simply and compactly as possible and at the same time meets high requirements for efficiency, low maintenance, reliability and a long service life.

[0005] This object is achieved according to the invention by the fact that the power electronics are arranged in the actuator casing between the coil and the axial actuator end, where the operating opening is provided, the power electronics being separated from the coil by a casing wall of the actuator casing, the printed circuit board of the power electronics being arranged on a fixing surface provided on the casing wall, and the electrical coil contacts of the coil extending through the casing wall and connected to the printed circuit board, whereby the power electronics can be arranged thermally favorably between the coil and the axial actuator end, whereby the cooling of the heat generated by the coil is improved, whereby heat can be advantageously guided from the inside of the actuator through the casing wall to the actuator casing and through the axial actuator end, for example to the compressor casing of a piston compressor.

[0006] Advantageously, the actuator casing, at least in the region of the casing wall, is made of a heat-conducting material, for example metal, particularly preferably aluminum, which allows for improved heat dissipation through the casing wall.

[0007] To further improve the heat dissipation from the power electronics to the housing wall, it is advantageous if at least one heat conducting element is arranged between the fixing surface of the housing wall of the actuator casing and the printed circuit board.

[0008] The heat conducting element is preferably connected to the printed circuit board by means of a heat conducting adhesive or a heat conducting adhesive tape, so that good heat transfer from the printed circuit board to the heat conducting element can be achieved.

[0009] If a heat conducting element is provided, then preferably at least the heat-sensitive electronic components of the printed circuit board, in particular the MOSFETs, are arranged in the area of ​​the heat conducting element, which is advantageous for protecting at least the heat-sensitive components.

[0010] Furthermore, it is advantageous if the power electronics is at least partially covered with a thermally conductive potting compound, which makes it possible to further improve the removal of heat from the electronic components of the power electronics.

[0011] The electromagnetically operable actuator is preferably used in a piston compressor for operating a valve, preferably an intake valve, of the piston compressor by means of an operating element of the actuator. The invention at issue is explained below with reference to figures 1 to 2 which show an advantageous embodiment of the invention by way of example, schematic and non-limiting means. [Brief description of the drawings]

[0012] [Figure 1] FIG. 4 is an illustration of a cross section of an actuator in an advantageous embodiment; [Diagram 2] FIG. 2 is a cross-sectional view of the actuator as installed in the intake valve of a piston compressor.

[0013] In FIG. 1, an actuator 1 according to the invention is depicted in a longitudinal section. The actuator 1 shown has an actuator casing 2 in which at least one coil 3 and at least one magnet armature 4 cooperating therewith are arranged. For example, it is also possible to arrange several coils 3 evenly around the circumference, or the coil 3 may have several segments evenly arranged around the circumference. In this case, the magnet armature 4 may have several armature segments in the circumferential direction, which correspond to the coils 3 or coil segments. However, the specific constructional embodiment of the coils and the magnet armature 4 is not important for the invention. The invention is therefore described below on the basis of one coil 3 and one magnet armature 4 cooperating therewith. The coil 3 and the magnet armature 4 cooperate electromagnetically in order to move the magnet armature 4 in the axial direction. For this purpose, the coil 3 can be supplied with a voltage or a current in order to generate a magnetic field capable of generating a magnetic attraction force on the magnet armature 4. Due to the magnetic attraction force, the magnet armature 4 can be attracted in the direction of the coil 3. A return spring can be provided to return the magnet armature 4. Naturally, it is also possible to arrange several coils 3, but for the sake of clarity, only one coil 3 will be mentioned below.

[0014] The area in which the magnet armature 4 can move is called the armature stroke. The size of the armature stroke depends essentially on the concrete constructional embodiment of the actuator 1, which is itself adapted to the field of use of the actuator 1. The armature stroke can be in the range of several millimeters, for example. The coil 3 is preferably embedded in or surrounds an iron core 3a, which preferably has as high a magnetic permeability as possible. The iron core 3a is used to bundle and guide the magnetic flux generated by the coil 3 to the magnet armature 4. The structure and the way in which electromagnetic actuators work are basically known, so that no further details will be given here.

[0015] The magnet armature 4 is connected to an operating element 5, which here starts from the magnet armature 4 and runs essentially centrally in the axial direction through the actuator 1. At the axial actuator end E of the actuator casing 2 an operating opening 5a for the operating element 5 is provided.

[0016] The operating element 5 is axially movable in the operating opening 5a, i.e. the operating opening 5a is essentially used to guide the operating element 5. In the depicted embodiment, the end part 5E of the operating element 5 protrudes axially from the operating opening 5a of the actuator casing 2. However, this is not necessary and depends essentially on the concrete constructional embodiment of the actuator 1 and preferably of the valve cooperating therewith. For example, the end part 5E of the operating element 5 may be in the actuator casing 2, in which case the operating part of the valve cooperating therewith may extend partially axially inwards through the operating opening 5a. In both cases, however, the operating opening 5a is provided at the axial actuator end E. In the mounting state of the actuator 1 in the piston compressor 19 (not depicted in FIG. 1), the axial actuator end E of the actuator 1 faces towards the piston compressor 19 (see FIG. 2).

[0017] The operating element 5 is surrounded by the coil 3 in a substantially annular manner in the depicted embodiment. The operating element 5 is used to operate the valve (not shown) in order to open and / or close the valve. For this purpose, an armature stroke is transmitted to the valve via the operating element 5, which results in a so-called valve lift VH, as shown in FIG. 1. The valve lift VH can in the simplest case correspond to the armature stroke. In some cases, however, it is also possible to provide a transmission element between the magnet armature 4 and the operating element 5, for example, in order to generate a certain conversion ratio between the armature stroke and the valve lift VH. This allows, for example, to increase the valve lift VH relative to the armature stroke and at the same time to reduce the force available for operating the valve (and vice versa). When operating the actuator 1, a relative movement between the magnet armature 4 and the operating element 5 and the actuator casing 2 thus occurs.

[0018] To operate the actuator 1, the coil 3 can be electrically controlled by a power electronics 6. The power electronics 6 are components provided in a suitable form for the energy supply of the coil 3. This includes, for example, converters and / or amplifiers of electrical quantities such as current, voltage, frequency, etc., in order to control the coil 3 in the desired manner. The power electronics 6 has for this purpose at least one printed circuit board 8 on which certain electronic components 12 (resistors, capacitors, MOSFETs, etc.) are arranged, which are connected to the printed circuit board 8 in a suitable manner, for example soldered, glued, mounted, etc. As mentioned at the beginning, the power electronics 6 has hitherto been arranged outside the actuator casing 2, for example in a separate casing, and has been connected via suitable lines to the actuator casing 2, in particular to the coil 3 arranged therein.

[0019] This is due in particular to the fact that the electronic components 12 arranged on the printed circuit board 8 are generally very sensitive to temperature. On the one hand, this can mean that many electronic components and / or solder connections are damaged above a certain temperature, which limits their function completely or at least partially. However, this also generally means that the losses in many electronic components, for example MOSFETs, increase more than proportionally with increasing temperature, which is likewise detrimental to the energy-efficient operation of the actuator 1. In particular, the temperatures in the actuator casing 2 have hitherto become unacceptably high due to the heat released by the coil 3, which leads to damage and / or a reduced performance of the power electronics 6 and thus of the actuator 1 as a whole. Particularly in safety-relevant applications, for example when operating valves of gas compressors, such limitations are not acceptable, since here there are high demands on the long-term durability and availability of the actuators (for example standardized according to a certain safety integrity level SIL). For this reason, arranging the power electronics 6 inside the actuator casing 2 has been avoided up to now.

[0020] In order to be able to meet the above-mentioned requirements, however, the invention provides that the power electronics 6 are arranged in the actuator casing 2 between the coil 3 and the axial actuator end E and are separated from the coil 3 by a casing wall 7 of the actuator casing 2. A printed circuit board 8 of the power electronics 6 is arranged on a fixing surface 9 provided on the casing wall 7. Electrical coil contacts 10 of the coil 3, as can be seen in FIG. 1, extend through the casing wall 7 and are connected to the printed circuit board 8. For this purpose, suitable openings, for example holes, are provided in the casing wall 7. The separation by means of the casing wall 7 protects on the one hand the power electronics 6, in particular the electronic components 12 arranged thereon, from the coil 3. Furthermore, the thermally favorable arrangement of the power electronics 6 between the coil 3 and the axial actuator end E improves the removal of heat generated by the coil 3. This heat can thereby advantageously be guided from the inside of the actuator 1 through the casing wall 7 to the actuator casing 2 and through the axial actuator end E to the compressor casing 20 of the piston compressor 19 (see FIG. 2).

[0021] The energy supply of the power electronics 6 and the transmission of the control commands can take place, for example, via suitable electric lines 15, which can be guided, for example, through an opening 17 provided on the side of the actuator 1. If necessary, an actuator control unit 16 can be provided in the actuator 1, which receives control commands from a higher-level control unit 18, for example from a compressor control unit, processes them and transmits them to the power electronics 6. It is also possible, however, for the power electronics 6 to be directly controlled by the higher-level control unit 18. Depending on a predefined control program, the control units 16, 18 can control the actuator 1 with control commands in order to move the magnet armature 4 or the operating element 5, for example to open / close a valve of the compressor. This allows, for example, a very flexible quantity control of the compressor.

[0022] The actuator casing 2 is preferably made, at least in the region of the casing wall 7, from a material with the highest possible thermal conductivity in order to achieve the best possible heat dissipation. Advantageous materials are suitable metals, such as, for example, aluminum or aluminum alloys, but of course other materials are also conceivable. The printed circuit board 8 is fixed to the fixing surface 9 of the casing wall 7 by suitable fastening means 13. In the depicted embodiment, a number of screws are provided as fastening means 13, which are distributed around the periphery of the printed circuit board 8 at suitable intervals and are screwed to the actuator casing 2, in particular to the casing wall 7. However, of course, other forms of fastening are also conceivable, such as, for example, suitable plug connections or adhesive connections. However, screwing is preferred in order to allow easier installation and exchangeability of the power electronics 6.

[0023] As can be seen in Fig. 1, the coil contacts 10 of the coil 3 run, here axially, through the casing wall 7 and are connected to the printed circuit board 8 on the side of the casing wall 7 facing away from the coil, on which the fastening surface 9 is provided. In order to create an electrically conductive connection between the coil contacts 10 and the printed circuit board 8, suitable holding elements 14 are preferably provided on the printed circuit board 8. The holding elements 14 can be implemented, for example, by form-locking or friction-locking, for example by plug or crimp connections as are known in the prior art.

[0024] To further improve the heat dissipation of the actuator 1, it is advantageous if at least one heat conducting element 11 is arranged between the fastening surface 9 of the casing wall 7 of the actuator casing 2 and the printed circuit board 8. As the heat conducting element 11, for example, a die plate made of aluminum or another suitable material with good heat transfer properties can be provided. This heat conducting element 11 improves the heat transfer between the printed circuit board 8 and the casing wall 7. It is particularly advantageous if the heat conducting element 11 is connected to the printed circuit board 8. In this way, the entire power electronics 6 can be used as an already pre-mounted component in the actuator casing 2, which also reduces the installation and especially the maintenance effort of the actuator 1. The fastening of the heat conducting element 11 to the printed circuit board 8 is preferably carried out with the aid of a heat-conducting adhesive or adhesive tape in order to ensure good heat transfer between the printed circuit board 8 and the heat conducting element 11. In the illustrated embodiment, the fastening surface 9 is implemented in a stepped manner in the casing wall 7 in order to obtain sufficient space for the heat conducting element 11.

[0025] It is furthermore advantageous if at least the temperature-sensitive electronic components 12 of the printed circuit board 8 are arranged in the area of ​​the heat-conducting element 11, particularly if only limited space is available for arranging the heat-conducting element 11. In this case, it is advantageous to arrange at least the particularly temperature-sensitive components 12, such as MOSFETs, in the area of ​​the heat-conducting element 11. In order to utilize the improved heat conduction of the heat-conducting element 11 as well as possible, it is of course advisable to arrange as many, and preferably all, electronic components 12 as possible in the area of ​​the heat-conducting element 11.

[0026] In the exemplary embodiment shown in FIG. 1, the heat conducting element 11 does not extend completely to the radially outer edge of the printed circuit board 8 for the sake of clarity. Here, the heat conducting element 11 is thus radially separated from the step of the fastening surface 9 by a gap. This means that the electronic components arranged on the printed circuit board 8, which are (here) below this gap, do not benefit from the improved thermal conductivity of the heat conducting element 11. It is therefore advantageous to ensure that the heat conducting element 11 covers as large an area of ​​the printed circuit board 8 as possible. It is further particularly advantageous if the power electronics 6 are at least partially covered by a thermally conductive potting compound (not shown). This results in improved heat transfer from the electronic components 12 (covered by the potting compound) via the printed circuit board 8 to the housing wall 7, possibly via the heat conducting element 11.

[0027] The electromagnetically operable actuator 1 is intended to operate the valves of a piston compressor 19, in particular the intake valve 21 of the piston compressor 19, as will be explained below with reference to FIG. 2. FIG. 2 shows an axial section of the actuator 1 as mounted on the piston compressor 19. The actuator 1 is in the illustrated embodiment part of a valve assembly, which can be arranged as an integral unit in a specially provided opening in a compressor casing 20 of the piston compressor 19. The valve assembly comprises a receiving casing 22 (which is part of the compressor casing 20), the actuator 1 and a valve, here the intake valve 21. The actuator 1 is arranged in the receiving casing 22, for example screwed thereto or fixed thereto in another suitable manner. The receiving casing 22 is arranged in a specially provided opening in the compressor casing 20 of the piston compressor 19 and is screwed thereto as shown diagrammatically. The valve is arranged in a receiving casing 22. In the illustrated embodiment, to operate the intake valve 21, an unloader 23 is operated by means of an operating element 5 of the actuator 1, which is arranged axially displaceable in the receiving casing 22 of the intake valve 21. To enable the unloader 23 to be operated by the operating element 5, an opening 22a is provided in the receiving casing 22. If necessary, it is also possible to provide an intermediately connected force transmission member, such as a push rod. Since the structure and operation of the intake valve 21 with the unloader 23 are basically known, for example from AU 509 878 C2, the manner of operation will only be described on the basis of the essential components.

[0028] The intake valve 21 generally consists of a valve seat 24 and a valve catcher 25. A valve element 26 is arranged between them, which can move back and forth between the valve seat 24 and the valve catcher 25. The valve element 26 can be a well-known valve plate in the simplest case. The valve element 26 cooperates with the valve seat 24 to perform a sealing function by closing and opening an annular passage channel 27 in the valve seat 24. For this purpose, the valve element 26 can be spring-loaded by a spring element 28 arranged in the valve catcher 25. The spring element 28 thereby presses the valve element 26 against the valve seat 24. The unloader 23 has an unloader finger 23a which extends through the passage channel 27 of the valve seat 24 and abuts against the valve element 26 in order to operate the valve element 26. The unloader 23 is used, for example, to start the compressor unloaded or to switch the compressor 19 into unloading operation or for quantity control of the compressor 19 .

[0029] If the actuator 1 is arranged in a piston compressor 19 as shown in FIG. 2, the heat generated by the coil 3 of the actuator 1 is guided from the actuator casing 2 to the compressor casing 20, as indicated by the arrows in FIG. 2. In the illustrated embodiment, the valve is configured as an intake valve 21 and is arranged in a valve assembly. The valve assembly includes the intake valve 21, including the above-mentioned components of the intake valve 21, a receiving casing 22 in which the valve 21 is arranged, and the actuator 1, which is fixed to the receiving casing 22. In the illustrated embodiment, the heat flows in particular from the actuator casing 2 through the receiving casing 22 of the valve assembly to the compressor casing 20. In general, the compressor casing 20 of the compressor 19 is cooled in the region of the intake valve 21 by a cooling medium flowing through the compressor casing 20. The cooling medium can in the simplest case be the intake compressed medium KM (e.g. a gaseous medium such as air or a process gas) itself, as indicated by the arrows in the intake channel 29 in FIG. 2. However, it is additionally possible to provide a separate cooling circuit with its own cooling medium, as shown, for example, in the case of water cooling, by the water jacket 30 .

[0030] The coil 3 reaches a maximum temperature during operation, which can typically be between 120° C. and 130° C. The power electronics 6, on the other hand, are a secondary heat source and reach a maximum temperature of 100° C. and 110° C. during operation, especially in the case of semiconductor switches such as MOSFETs which are typically installed. The components of the power electronics 6 have a maximum permissible temperature of, for example, 125° C. for high-temperature electronic components. For this reason alone, it was not possible up to now to arrange the power electronics 6 close to the coil 3, since there was a risk that the electronic components would be overheated and damaged or destroyed by the temperature of the adjacent coil 3. However, due to the inventive arrangement of the power electronics 6, the piston compressor 19 itself can be used as a heat sink for the actuator 1.

[0031] Due to the cooling of the compressor casing 20, temperatures of up to 70° C. generally occur in the compressor casing 20, or in this embodiment particularly in the accommodation casing 22 of the valve assembly. Due to this low temperature and the thermal coupling of the actuator 1 at the compressor 19, a temperature gradient occurs between the coil 3 and the compressor 19. This causes heat to be discharged from the actuator 1 in the direction of the cooler compressor 19, thereby cooling the power electronics 6. This makes it possible for the first time to arrange the power electronics 6 close to the coil 3 and in the actuator casing 2 of the actuator 1. Cooling by convection on the surface of the actuator casing 2 of the actuator 1 may not be sufficient for this. Measurements at the actuator 1 have shown that the inventive arrangement of the power electronics 6 allows the maximum temperature in the area of ​​the power electronics 6 to be kept below 110° C., so that the electronic components of the power electronics 6 are protected from overheating.

[0032] Arranging the power electronics 6 in the actuator casing 2 in the casing wall 7 between the coil 3 and the axial actuator end E of the actuator 1 therefore results in sufficient cooling of the power electronics 6, since the heat generated in the actuator 1 is guided via the casing wall 7 and the axial actuator end E of the actuator casing 2 to the compressor casing 20. The cooling of the compressor 19 can thus advantageously be used to improve the heat rejection from the actuator 1.

Claims

1. 1. An electromagnetically operable actuator (1) arranged on a piston compressor (19) for operating a valve, preferably an intake valve (21) of said piston compressor (19), said actuator (1) having an actuator casing (2) in which a coil (3) and a magnet armature (4) are arranged, said magnet armature (4) electromagnetically cooperating with said coil (3) for moving said magnet armature (4), said magnet armature (4) being connected to an operating element (5) for operating said valve, said actuator casing (2) having an axial actuator end (E) provided with an operating opening (5a) for said operating element (5), said actuator (1) being controllably operable by means of power electronics (6), 1. An electromagnetically operable actuator (1), characterized in that the power electronics (6) is arranged in the actuator casing (2) between the coil (3) and the axial actuator end (E) at which the operating opening is provided, the power electronics (6) is separated from the coil (3) by a casing wall (7) of the actuator casing (2), a printed circuit board (8) of the power electronics (6) is arranged on a fixing surface (9) provided on the casing wall (7), electrical coil contacts (10) of the coil (3) extend through the casing wall (7) and are connected to the printed circuit board (8), the coil contacts (10) being connected to the printed circuit board (8) on a side of the casing wall (7) opposite the coil (3) and on which the fixing surface (9) is provided.

2. 2. An electromagnetically operable actuator according to claim 1, characterized in that the actuator casing (2) is made of a thermally conductive material, preferably metal, particularly preferably aluminum, at least in the region of the casing wall (7).

3. 3. An electromagnetically operable actuator according to claim 1 or 2, characterized in that at least one heat conducting element (11) is arranged between the fixing surface (9) of the casing wall (7) of the actuator casing (2) and the printed circuit board (8).

4. 4. An electromagnetically operable actuator according to claim 3, characterized in that the heat conducting element (11) is connected to the printed circuit board (8), preferably by means of a heat conducting glue or a heat conducting adhesive tape.

5. 5. An electromagnetically operable actuator according to claim 3 or 4, characterized in that at least temperature-sensitive electronic components (12) of the printed circuit board (8), in particular MOSFETs, are arranged in the region of the heat conducting element (11).

6. 6. An electromagnetically operable actuator according to claim 1, characterized in that the power electronics (6) is at least partially covered with a thermally conductive potting compound.

7. A piston compressor (19) with at least one valve, in particular an intake valve (21), for controlling a medium flow of a compressed medium and an actuator for operating said valve, said actuator being embodied as an electromagnetically operable actuator (1) according to any one of claims 1 to 6, said operating element (5) of said actuator (1) being configured to cooperate with said valve for operating said valve.

8. 8. The piston compressor (19) according to claim 7, characterized in that a compressor casing (20) of the piston compressor (19) is cooled by a cooling medium in the region of the valve, preferably an intake valve (21), and the actuator (1) is arranged in the compressor casing (20) in such a way that heat generated by the coil (3) can be guided to the compressor casing (20) via the casing wall (7) of the actuator casing (2) and via the axial actuator end (E) of the actuator (1) in order to cool the actuator (1) in the region of the power electronics (6).

9. 1. A valve assembly for a piston compressor (19), comprising a receiving casing (22) in which a valve, in particular an intake valve (21), is arranged, and an actuator for operating the valve, which is fixed to the receiving casing (22), the actuator being embodied as an electromagnetically operable actuator (1) according to any one of claims 1 to 6, the operating element (5) of the actuator (1) being configured to cooperate with the valve through an opening (22a) arranged in the receiving casing (22) in order to operate the valve.

Images