Linear compressor

Abstract

The invention relates to a linear compressor (10), comprising: a piston; a cylinder (200) having a cylinder chamber (205) which at least partially receives the piston (100) to allow a reciprocating linear relative movement between the piston and the cylinder, wherein the relative movement defines a longitudinal direction (x); a coil arrangement (300) disposed on a circumference of the cylinder; at least one magnet (400) which is attached directly or indirectly to the cylinder and interacts electromagnetically with the coil arrangement; wherein the coil arrangement and the piston are disposed so as to be substantially immovable relative to each other in the longitudinal direction.

Description

[0001] Description

[0002] title

[0003] Linear compressor

[0004] The invention relates to a linear compressor. In particular, the invention relates to a linear compressor for use in cooling and refrigerant circuits, for example in a refrigerator or heat pump.

[0005] State of the art

[0006] Linear compressors comprise a cylinder with a cylinder chamber in which a piston can move back and forth. The piston defines a piston chamber on one side of the cylinder chamber, into which a fluid, such as a liquid or gaseous coolant or refrigerant, can be admitted via an inlet valve in a valve plate. During a compression stroke of the piston along a longitudinal direction of the linear compressor, the fluid admitted into the piston chamber is compressed and expelled via an outlet valve on the valve plate.

[0007] The piston's stroke is achieved through the interaction of an electrical coil arrangement with one or more permanent magnets, in the conventional manner of a linear drive. In the prior art, the coil arrangement is connected to the cylinder, while the permanent magnet is connected to the piston.

[0008] The cylinder and piston are longitudinally coupled via spring elements, while the cylinder is mounted within a housing via spring feet, allowing it to move to a certain extent. This arrangement causes the piston stroke to induce restoring forces in the spring elements, causing an oscillating movement of the linear compressor at the spring feet. By appropriately selecting the spring elements and the masses of the linear compressor's components, the desired vibration behavior can be achieved.

[0009] The inventors have determined that this design, known in the prior art, has several disadvantages. For example, the permanent magnet must be connected to the piston via a driver component. The force exerted by the coil on the magnet must be transmitted to the piston via the driver component to effect the piston stroke. On the one hand, this is not mechanically ideal, since wear and efficiency losses can occur whenever forces must be transmitted across different components and connections. On the other hand, the driver component and its assembly cause additional unit costs and assembly effort.

[0010] It is an object of the invention to provide an alternative or improved linear compressor.

[0011] Disclosure of the invention

[0012] The object of the invention is achieved by means of a linear compressor according to claim 1. Advantageous developments, additional features and / or advantages of the invention emerge from the dependent claims and the following description.

[0013] According to a first aspect, the present invention discloses:

[0014] A linear compressor comprising: a piston; a cylinder having a cylinder chamber that accommodates the piston at least in part for performing a reciprocating linear relative movement between the piston and the cylinder, wherein the relative movement defines a longitudinal direction; arranged adjacent to a circumference of the cylinder, a coil arrangement; at least one magnet attached directly or indirectly to the cylinder and electromagnetically interacting with the coil arrangement; wherein the coil arrangement and the piston are arranged substantially immovably relative to one another in the longitudinal direction. The coil arrangement and the piston can be attached to a common support structure.

[0015] The common support structure may be a first housing, and the coil assembly and the piston may be at least partially disposed within the first housing.

[0016] The cylinder may be arranged at least partially within the first housing.

[0017] The common support structure can be mounted so that it can be displaced at least in the longitudinal direction by means of spring-elastic bearing elements.

[0018] The cylinder can be coupled at least indirectly to the piston in the longitudinal direction via spring-elastic return elements.

[0019] The spring-elastic return elements may comprise a first cylinder spring which is arranged partially around the piston and between a first end of the cylinder and the common holding structure.

[0020] The spring-elastic return elements may comprise a second cylinder spring arranged between a second end of the cylinder opposite the first end of the cylinder and the common holding structure.

[0021] The linear compressor may comprise a fluid pump arranged on the common support structure for circulation, i.e. for conveying a fluid, in particular a lubricant.

[0022] The piston may have at least one cavity for circulation, i.e., for guiding the fluid, wherein the piston may be connected to the fluid pump via a fluid supply line. The fluid pump may comprise a cavity and a pump piston mounted in the cavity for movement in the longitudinal direction.

[0023] The piston can have, with respect to the longitudinal direction, a first end facing away from the cylinder and a second end facing the cylinder. During the relative movement between the piston and the cylinder chamber, the first end is always outside the cylinder chamber, and the second end is always inside the cylinder chamber. The piston can have, at least in sections, a piston cavity between the first end and the second end, with at least one piston opening arranged in the second end, through which a fluid to be compressed can pass from the cylinder chamber into the piston cavity.

[0024] At least one outlet opening can be arranged in the first end of the piston, through which fluid to be compressed can pass from the piston cavity into a fluid conductor.

[0025] The cylinder may extend along the longitudinal direction from a first cylinder end facing the piston to a second cylinder end opposite the first cylinder end, wherein a cylinder pre-chamber may be arranged at the second cylinder end, which is connected to a reservoir of fluid to be compressed.

[0026] The cylinder chamber may form a cylinder bottom at the second cylinder end, wherein the cylinder chamber may be fluidically connected to the cylinder pre-chamber via an opening in the cylinder bottom.

[0027] Short description of the characters

[0028] The invention is explained in more detail below using exemplary embodiments with reference to the attached schematic drawings, which are not to scale. The figures (Fig.) of the drawings, which are merely exemplary, show:

[0029] Fig. 1 shows schematically an embodiment of a linear compressor.

[0030] The structure and function of a linear compressor are described schematically below using Figure 1.

[0031] Figure 1 shows a sectional view of an embodiment of a linear compressor 10. The linear compressor 10 comprises a piston 100 which extends along a longitudinal direction, which is marked with x in Figure 1, between a first end 110 and a second end 120. The piston 100 is mounted at least partially in a cylinder chamber 205 of a cylinder 200, such that the piston 100 and cylinder 200 can perform a reciprocating linear relative movement along the longitudinal direction x, during which the piston 100 fills the cylinder chamber 205 to varying degrees.

[0032] As will be explained in more detail later, the relative movement between the piston 100 and the cylinder 200 is limited by suitable stops such that the first end 110 always remains outside the cylinder chamber 205 and the second end always remains inside the cylinder chamber 205.

[0033] A bottom dead center of the relative movement between piston 100 and cylinder 200 is reached when the entire cylinder chamber 205 is filled by the piston 100. This situation is illustrated in Figure 1. Starting from this position, the cylinder 200 can move relative to the piston 100 in a direction indicated by the arrow Z in Figure 1. A position of the piston 100 in the cylinder 200 in which a volume of the cylinder chamber 205 not filled by the piston 100 reaches its maximum defines a top dead center of the relative movement.

[0034] To drive this relative movement, an electrical coil arrangement 300 is arranged adjacent to a circumference of the cylinder 200. As can be seen in Figure 1, in the embodiment shown, the coil arrangement 300 is arranged in a cylindrical ring shape around a cylinder axis of the cylinder 200 that coincides with the longitudinal direction x, wherein the coil arrangement 300 is at a certain distance from the cylinder 200 in a radial direction R indicated by an arrow in Figure 1.

[0035] In the embodiment of Figure 1, the coil assembly 300 comprises a winding support 305, a coil winding 310 wound concentrically along a circumferential direction of the cylinder 200, which in turn is connected to an electrical power unit (not shown), and an external stator 315.

[0036] The coil arrangement 300 interacts electromagnetically with at least one magnet 400 attached to the cylinder 200. The magnet 400 can be a cylindrical ring-shaped permanent magnet, as shown in Figure 1. The coil arrangement 300 and the magnet 400 are separated from each other in the radial direction R by an air gap. In the embodiment of Figure 1, a magnetic yoke 405 is arranged between the magnet 400 and the cylinder 200. This yoke serves to close the magnetic circuit, thereby amplifying a magnetic flux of the magnetic field of the magnet 400. In the embodiment shown, the magnet 400 is therefore connected to the cylinder 200 via the magnetic yoke 405. In other embodiments, the magnet 400 is connected directly to the cylinder 200.

[0037] In contrast to prior art solutions in which the piston and magnet are connected to each other via driver structures, in the present case, the coil assembly 300 and the piston 100 are essentially immovable relative to each other in the longitudinal direction x. This is achieved in embodiments of the linear compressor 10 by attaching the coil assembly 300 and the piston 100 to a common support structure, for example, to a common frame or a common yoke.

[0038] This design is mechanically advantageous because the forces acting between the coil assembly 300 and the magnet 400 can be transmitted directly to the piston 100 and the cylinder 200, without the need for additional driver components as in the prior art. The force flow between the components is therefore shorter and the design is stiffer, enabling more precise control and reducing wear. The number of components to be assembled is smaller than in prior art solutions with driver components, resulting in cost savings.

[0039] In the embodiment shown in Figure 1, the common holding structure is designed as a first housing 500, which accommodates the coil arrangement 300 and a part of the piston 100 and is essentially closed except for a housing opening 530, the function of which will be explained later. The connection between the first housing 500 and the coil arrangement 300 or the piston 100 can be non-positively and / or positively locking and can optionally include known joining methods. In the embodiment of Figure 1, the first housing 500 is pot-shaped in the region of the coil arrangement 300 such that it accommodates the coil arrangement 300 in a positively locking manner and prevents movement of the coil arrangement 300 relative to the first housing 500.A recess 505 on an inner side 515 of the first housing 500 is shaped such that it positively and / or non-positively receives a complementarily shaped end region of the first end 110 of the piston 100. In this way, the piston 100 is held immovably relative to the first housing 500. In embodiments, the piston 100 is connected to the housing 500 by a welded joint.

[0040] In the embodiment shown in Figure 1, a silencer 112 is also arranged in the region of the first end 110 of the piston 100. The silencer 112 rests against an outer side 512 of the first housing 500 and is fluidly connected to the cylinder cavity 150. The silencer 112 can have additional components arranged in the piston cavity 150, not shown in Figure 1, and serves to dampen the sound emanating from the linear compressor 10.

[0041] Furthermore, it can be seen in Figure 1 that the cylinder 200 is also arranged within the first housing 500 and is indirectly coupled to the piston 100 in the longitudinal direction x via spring-elastic return elements, specifically via the first housing 500. The spring-elastic return elements comprise a first cylinder spring 610, which is arranged partially around the piston 100 and between the first end 210 of the cylinder 200 and a first inner wall 510 of the first housing 500, and a second cylinder spring 620, which is arranged between a second end 220 of the cylinder 200 opposite the first end of the cylinder 200 and a second inner wall 520 of the first housing 500 opposite the first inner wall 510 of the first housing 500.As can be easily understood from Figure 1, a displacement of the cylinder 200 in a first direction R1 shown in Figure 1 relative to the first housing 500 causes a restoring force in a second direction R2 by compressing the first cylinder spring 610, while a displacement of the cylinder 200 in the second direction R2 relative to the first housing 500 causes a corresponding restoring force in the second cylinder spring 620 in the first direction R1.

[0042] When an electrical voltage is applied to the coil arrangement 300, the current flowing through the coil winding 310 creates a magnetic flux in the outer stator 315. This magnetic flux generates an electromagnetic force that acts on the magnet 400. Depending on the direction of the electrical current, the electromagnetic force can be directed in the first direction R1, whereupon the cylinder 200 moves to bottom dead center during a compression stroke, or in the second direction R2, whereupon the cylinder 200 moves to top dead center during an intake stroke. During this process, the piston 100 and the coil arrangement 300 remain at rest relative to one another due to their immovable mounting, while the cylinder 200 executes the reciprocating linear relative movement between bottom and top dead center along the piston 100 as the polarity of the coil winding 310 successively changes.With respect to the first housing 500, it can be said that the cylinder 200 oscillates within the first housing 500 during this relative movement, while the piston 100 remains at rest relative to the first housing 500.

[0043] This oscillation is supported by the first cylinder spring 610 and the second cylinder spring 620, which, as already described, are each compressed by a movement of the cylinder in the first direction R1 or in the second direction R2, respectively, and partially transfer the stored energy back to the cylinder 200 during the movement of the cylinder 200 in the opposite direction. By appropriately adjusting the spring stiffness and mass of this oscillation system, as well as the frequency of the polarity change of the coil winding 310, the frequency and amplitude of the cylinder stroke of the linear compressor 10 can be adjusted.

[0044] The movement of the cylinder 200 along the piston 100 is used to compress a fluid to be compressed, for example in a cooling or refrigerant circuit, as will be explained in more detail below.

[0045] Figure 1 shows a cylinder pre-chamber 700, which is arranged at the second cylinder end 220 in the extension of the cylinder 200 along the longitudinal direction x, within a space that is spirally circumscribed by the second cylinder spring 620. The cylinder pre-chamber is fluidically connected to the cylinder chamber 205 via an opening 245 in a cylinder base 240 of the cylinder chamber 205. When the cylinder 200 moves in the direction of arrow Z during the induction stroke, starting from the bottom dead center position shown in Figure 1, and the volume of the cylinder chamber 200 between the cylinder base 240 and the second end 120 of the piston 100 increases, a negative pressure is generated in the cylinder chamber 205. As a result of this negative pressure, fluid to be compressed located in the cylinder pre-chamber 700 is sucked through the opening 235 into the cylinder chamber 205. The cylinder pre-chamber 700 is in turn connected to a reservoir of fluid to be compressed.In the embodiment shown in Figure 1, the cylinder pre-chamber 700 is connected via an opening 730 to an environment of the cylinder pre-chamber 700 within the first housing 500, so that fluid to be compressed can enter the cylinder chamber 205 from this area.

[0046] The fluid to be compressed can be located in the first housing 500 and / or enter the first housing 500 through a housing opening 530 of the first housing 500. The first housing opening is in turn, as shown in Figure 1, fluidically connected to a further volume, which in this embodiment is defined by a second housing 800 in which the first housing 500 is completely accommodated. In a manner not shown in Figure 1, the second housing 800 can have a penetration in a wall 810 of the first housing, through which fluid to be compressed can enter the second housing 800. This side of the linear compressor is its low-pressure side.

[0047] As shown, an outer circumference of the cylinder pre-chamber 700 can serve to define a position of the second spring element 620 in the radial direction R.

[0048] The piston 100 has, at least in sections, a piston cavity 150 between the first end 110 and the second end 120, which is fluidically connected to a piston opening 130 arranged in the second end 120 of the piston 100. When the movement of the cylinder 200 relative to the piston 100 has exceeded top dead center and the volume of the cylinder chamber 205 is reduced by the incoming cylinder 100, a valve (not shown in Figure 1) closes the opening 245 so that the fluid to be compressed cannot flow back into the cylinder pre-chamber 700.

[0049] When a certain pressure has built up in the cylinder chamber 205, a valve 140 arranged in the second end of the piston 100 opens the piston opening 130, allowing the compressed fluid to escape from the cylinder chamber 205 into the piston cavity 150. As the free volume of the cylinder chamber 205 is further reduced, the fluid is finally conveyed through the piston cavity 150, which, as shown in Figure 1, can be constructed in several parts for fluid mechanics reasons, to an outlet opening 160 located in the silencer 150, through which it can pass from the piston cavity 150 into a fluid conductor 170. In the embodiment shown, the fluid conductor 170 represents the high-pressure side of the linear compressor 10 and, in practice, can be, for example, the high-pressure side of a refrigeration circuit. The fluid conductor 170 guides the now compressed fluid out of the second housing 800 in a manner not further shown.In embodiments in which no silencer 112 is arranged in the region of the first end 110, the fluid conductor 170 is fluidly connected to the piston cavity 150 in another suitable manner, for example via an opening in the first housing 500.

[0050] The first housing 500, and in alternative embodiments, the common support structure of the piston 100 and the coil assembly 300, is mounted displaceably at least in the longitudinal direction x via spring-elastic spring feet or bearing elements 910, 920, and in the embodiment of Figure 1 also perpendicular to this direction. It was described above that the electromagnetic force acting between the coil assembly 300 and the magnet 400 causes a displacement of the magnet 400 and thus of the cylinder 200. Due to the well-known mechanical principle that a force always causes a reaction force, this electromagnetic force also acts on the first housing 500, which in turn experiences a displacement counter to the direction of displacement of the cylinder 200 due to the displaceable mounting of the first housing 500.This occurs oscillatory and depends on the frequency determined by the variable polarity of the coil winding 310, the mass of the components of the linear motor 10, and the stiffness of the spring-elastic return elements 610, 620.

[0051] In embodiments of the linear compressor, this movement of the first housing 500 is used to pump a fluid, in particular a lubricant, located in a pump sump 1000 of the second housing 800. For this purpose, a fluid pump 1100 for circulating, i.e., pumping, the lubricant is arranged on the first housing 500 and is attached to it by a suitable joining method, so that the oscillatory movement performed by the housing 500 is transferred to the fluid pump 1100.

[0052] In embodiments, the fluid pump 1100 comprises a housing 1110 that encloses a cavity 1120 in which a pump piston 1140 is located. The pump piston 1140 has a cross-section that fills a cross-section of the cavity 1120 perpendicular to the longitudinal direction x to such an extent that a first region 1122 of the cavity 1120, which is located on a first side of the pump piston 1140, is separated from a second region 1124 of the cavity 1120 to such an extent that fluid located in the cavity can only reach the first region 1122 to the second region 1124 via a connecting channel 1150 along a circumference of the pump piston 1140 that is small compared to the height of the pump piston 1140.

[0053] The pump piston 1140 can have a cylindrical shape, as shown in Figure 1. In other embodiments, the pump piston has a different shape, for example, spherical. The pump piston 1140 is mounted in the cavity 1120 so as to be movable with respect to the longitudinal direction x and can perform a reciprocating movement in this direction, which is stimulated by the movement of the first housing 500 connected to the fluid pump 1100 and causes an opposing enlargement or reduction of the first region 1122 and the second region 1124 of the cavity 1120 in cycles.

[0054] In the first region 1122, an opening (not shown) is arranged in the housing 1110, through which lubricant from the pump sump 1000 can enter the cavity 1120. A valve arranged in the opening ensures that lubricant can enter the cavity 1120 through the opening, but cannot escape from the cavity 1120 through the opening.

[0055] As can be seen in Figure 1, the cavity 1120 in the second region 1124 is connected via a fluid supply line 1300 to a cavity 190 arranged in the piston 100, which cavity can be formed in the piston 100, for example, as a channel system. The cavity 190 serves to convey the lubricant into a boundary region 180 between an outer wall of the piston 100 and an inner wall of the cylinder chamber 205, where it reduces the friction between these components. During its reciprocating movement in the cavity 1120, the pump piston 1140 can thus pump lubricant from the

[0056] Suction from pump sump 1000 into the first region 1122, convey it via the connecting channel 1150 into the second region 1124, and convey it via the fluid conductor 1300 into the cavity 190 of the piston 100. The invention is not limited to the described and illustrated embodiments. Rather, it also encompasses all expert developments within the scope of the invention defined by the patent claims. In addition to the described and illustrated embodiments, further embodiments are conceivable, which may include further modifications and combinations of features.

Claims

Claims 1. A linear compressor (10), comprising: a piston (100); a cylinder (200) with a cylinder chamber (205) which accommodates the piston (100) at least in regions for performing a reciprocating linear relative movement between the piston (100) and the cylinder (200), wherein the relative movement defines a longitudinal direction (x); a coil arrangement (300) arranged adjacent to a circumference of the cylinder (200); at least one magnet (400) fastened directly or indirectly to the cylinder (200) and electromagnetically interacting with the coil arrangement (300); wherein the coil arrangement (300) and the piston (100) are arranged substantially immovably relative to one another in the longitudinal direction (x).

2. Linear compressor (10) according to claim 1, characterized in that the coil arrangement (300) and the piston (100) are attached to a common support structure.

3. Linear compressor (10) according to claim 2, characterized in that the common support structure is a first housing (500), and that the coil arrangement (300) and the piston (100) are arranged at least partially within the first housing (500).

4. Linear compressor (10) according to claim 3, characterized in that the cylinder (200) is arranged at least partially within the first housing (500).

5. Linear compressor (10) according to one of claims 2 to 4, characterized in that the common holding structure is displaceably mounted at least in the longitudinal direction (x) via spring-elastic bearing elements (910, 920).

6. Linear compressor (10) according to one of claims 1 to 5, characterized in that the cylinder (200) is coupled at least indirectly to the piston (100) via spring-elastic return elements in the longitudinal direction (x).

7. Linear compressor (10) according to claim 6, characterized in that the spring-elastic return elements comprise a first cylinder spring (610) which is arranged in regions around the piston (100) and between a first end (210) of the cylinder (200) and the common holding structure.

8. Linear compressor (10) according to one of claims 6 and 7, characterized in that the spring-elastic return elements comprise a second cylinder spring (620) which is arranged between a second end (220) of the cylinder (200) opposite the first end (210) of the cylinder (200) and the common holding structure.

9. Linear compressor (10) according to one of claims 2 to 8, comprising a fluid pump (1100) arranged on the common support structure for conveying a fluid, in particular a lubricant.

10. Linear compressor (10) according to claim 9, characterized in that the piston (100) has at least one cavity (190) for guiding the fluid, wherein the piston (100) is connected to the fluid pump (1100) via a fluid supply line (170).

11. Linear compressor (10) according to claim 10, characterized in that the fluid pump (1100) has a cavity (1120) and a pump piston (1140) movably mounted in the cavity (1120) in the longitudinal direction (x).

12. Linear compressor (10) according to one of the preceding claims, characterized in that the piston (100) has a first end (110) and a second end (120) with respect to the longitudinal direction (x), wherein the first end (110) is always outside the cylinder chamber (205) during the relative movement between the piston (100) and the cylinder (200) and the second end (120) is always inside the cylinder chamber (205); and that the piston (100) has, at least in sections, a piston cavity (150) between the first end (110) and the second end (120), wherein at least one piston opening (130) is arranged in the second end (120), through which a fluid to be compressed can pass from the cylinder chamber (205) into the piston cavity (150).

13. Linear compressor (10) according to claim 12, characterized in that at least one outlet opening (160) is arranged in the first end (110) of the piston (100), through which fluid to be compressed can pass from the piston cavity (150) into a fluid conductor (170).

14. Linear compressor (10) according to one of the preceding claims, characterized in that the cylinder (200) extends along the longitudinal direction (x) from a first cylinder end (210) facing the piston (100) to a second cylinder end (220) opposite the first cylinder end (210), and in that a cylinder pre-chamber (700) is arranged at the second cylinder end (220) and is connected to a reservoir of fluid to be compressed.

15. Linear compressor (10) according to claim 14, characterized in that the cylinder chamber (205) forms a cylinder bottom (240) at the second cylinder end (220), wherein the cylinder chamber (205) is fluidically connected to the cylinder pre-chamber (700) via an opening (245) in the cylinder bottom (240).

16. Linear compressor (10) according to one of claims 1 to 15, characterized in that the magnet (400) is connected to the cylinder (200) via a magnetic yoke (405).

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