Device for conveying lubricant

Abstract

The invention relates to a device for conveying lubricant in a pump or compressor, the pump or compressor comprising a piston-cylinder assembly configured to perform a reciprocating movement along a stroke direction during operation of the pump or compressor; the device comprising: a lubricant piston that is aligned along or parallel to the stroke direction and is connected directly or indirectly to the piston-cylinder assembly in such a way that it follows the reciprocating motion along the stroke direction during operation of the pump or compressor; a lubricant cylinder which is movably mounted on the lubricant piston along the stroke direction or parallel to the stroke direction, wherein the lubricant piston and the lubricant cylinder define a variable lubricant working space; a lubricant reservoir that communicates fluidically with the lubricant working chamber via a suction line; a lubricant line that fluidically connects the lubricant working chamber to a lubrication point.

Description

[0001] The invention relates to a device for conveying lubricant in a pump or compressor. In particular, the invention relates to a device for conveying lubricant in a compressor within a refrigerant circuit. The invention further relates to a compressor for compressing a fluid, in particular a compressor for use in refrigerant circuits, for example in a refrigerator or a heat pump, and to a refrigerant circuit. State of the art

[0002] Compressors for refrigerant circuits, which compress a refrigerant, are well-known and often designed with a reciprocating piston drive. This drive can be, for example, a crank mechanism or a linear drive. Both principles share the characteristic that friction occurs between a cylinder and a piston, resulting in heat generation and component wear. To reduce the coefficient of friction and minimize friction, a lubricating film, such as an oil film, is typically applied at lubrication points located between the cylinder and piston. The necessary lubricant is supplied by a lubricant pump, for example, from a lubrication sump.

[0003] Pumping lubricant to the lubrication points requires energy that reduces the overall efficiency of the compressor. Therefore, an object of the invention is to provide an alternative or improved device for conveying lubricant in a pump or compressor. A further object of the invention is to provide an alternative or improved compressor for compressing a fluid, in particular a compressor for use in a refrigerant circuit, for example in a refrigerator or heat pump. A further object of the invention is to provide a refrigerant circuit. Disclosure of the invention

[0004] The object of the invention is achieved by means of a device for conveying lubricant in a pump or a compressor according to claim 1. The object is further achieved by means of a compressor for compressing a fluid according to claim 13, and by means of a refrigerant circuit according to claim 16.

[0005] Advantageous further developments, additional features and / or benefits of the invention will become apparent from the dependent claims and the following description. According to a first aspect, the following is disclosed:

[0006] A device for conveying lubricant in a pump or compressor, the pump or compressor comprising a piston-cylinder assembly configured to perform a reciprocating motion along a stroke direction during operation of the pump or compressor; the device comprising: a lubricant piston that is aligned along or parallel to the stroke direction and is connected directly or indirectly to the piston-cylinder assembly in such a way that it follows the reciprocating motion along the stroke direction during operation of the pump or compressor; a lubricant cylinder which is movably mounted on the lubricant piston along the stroke direction or parallel to the stroke direction, wherein the lubricant piston and the lubricant cylinder define a variable lubricant working space; a lubricant reservoir that communicates fluidically with the lubricant working chamber via a suction line; a lubricant line that fluidically connects the lubricant working chamber to a lubrication point.

[0007] In this device, the lubricant cylinder is arranged around the lubricant piston and oscillates along the stationary lubricant piston. This is advantageous, among other reasons, because in this design the mass of the lubricant cylinder can be chosen essentially without regard to the rest of the device's design. For example, it may be desirable to increase the mass of the stroke-executing part of the device in order to keep the natural frequency of the lubricant oscillation system low and to maximize the stroke and thus the pumping efficiency during lubricant delivery. In the present design, this can be achieved simply by increasing the dimensions, such as the wall thickness, of the lubricant cylinder. This can be done without restricting the design freedom with regard to other components, such as the lubricant working chamber.

[0008] A first check valve may be arranged in the lubricant line, which is designed to prevent a backflow of lubricant from the lubrication point towards the lubricant working chamber.

[0009] A second check valve may be arranged in the suction line, which is designed to prevent a backflow of lubricant from the lubricant working chamber towards the lubricant reservoir.

[0010] The device may have a first return element which is configured to exert a first force on the lubricant cylinder, proportional to a deflection of the lubricant cylinder, along the stroke direction or parallel to the stroke direction.

[0011] The first return element can include an axial spring.

[0012] The first return element can comprise at least one first permanent magnet arranged on the lubricant cylinder and at least one second permanent magnet arranged in a fixed position relative to the lubricant piston, wherein the second permanent magnet is arranged adjacent to the first permanent magnet in such a way that a magnetic attraction force acts between the first permanent magnet and the second permanent magnet.

[0013] The first return element can comprise a coil winding of an electromagnet arranged around the lubricant cylinder, and the lubricant cylinder can comprise a ferromagnetic component.

[0014] The device may include a second return element configured to exert a second axial force on the lubricant cylinder that is opposite to the first force and proportional to a deflection of the lubricant cylinder.

[0015] The reciprocating motion of the piston-cylinder assembly can have a first frequency, wherein a mass of the lubricant cylinder, as well as the first force and optionally the second force, are selected or matched such that a natural frequency of the motion of the lubricant cylinder along the stroke direction or parallel to the stroke direction lies in a range that corresponds to at least 1.2 times the first frequency, preferably at least 1.3 times the first frequency, and particularly preferably at least 1.4 times the first frequency.

[0016] The lubricant piston can essentially be designed as a hollow cylinder and define a lubricant piston interior.

[0017] The lubricant piston can be arranged on a frame connected to the piston-cylinder assembly, wherein the suction line and the lubricant line are at least partially formed in a first wall of the frame and communicate fluidically with each other via a pre-chamber.

[0018] The lubricant piston can be located on the first wall of the frame, with the piston interior communicating fluidically with the pre-chamber.

[0019] According to another aspect, the following is disclosed: A compressor for compressing a fluid, comprising: a piston-cylinder assembly designed to perform a reciprocating motion along a stroke direction during operation of the compressor; a lubricant piston aligned along or parallel to the stroke direction and connected directly or indirectly to the piston-cylinder assembly in such a way that it follows the reciprocating motion along the stroke direction during operation of the compressor; a lubricant cylinder movably mounted on the lubricant piston along or parallel to the stroke direction, wherein the lubricant piston and the lubricant cylinder define a variable lubricant working space; a lubricant reservoir that communicates fluidically with the lubricant working chamber via a suction line; a lubricant line that fluidically connects the lubricant working chamber to a lubrication point.

[0020] The piston-cylinder assembly may include: a piston; a cylinder with a cylinder chamber that accommodates the piston, at least in part, for the execution of a linear relative movement between the piston and the cylinder along a stroke direction; a coil arrangement arranged adjacent to the circumference of the cylinder; at least one magnet attached directly or indirectly to the cylinder and interacting electromagnetically with the coil arrangement; wherein the coil assembly and the piston are arranged in a substantially immovable manner relative to each other in the stroke direction; and wherein the coil assembly and the piston are attached to a common support structure, preferably a frame.

[0021] The lubrication point can include at least part of a contact area between the piston and the cylinder.

[0022] According to another aspect, the following is disclosed: A refrigerant circuit, including: a piping system for the circulation of a refrigerant; and fluidically connected through the piping system, a compressor as defined above, a condenser, an expansion valve, and an evaporator. Brief description of the characters

[0023] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying schematic drawing, which is not to scale. The figures (Fig.) in the drawing are merely examples and show: Fig. 1 schematically an embodiment of a compressor, comprising an embodiment of a device for conveying lubricant in the compressor; Fig. 2 schematically an embodiment of a compressor, comprising an embodiment of a device for conveying lubricant in the compressor; and Fig. 3 schematically an embodiment of a device for conveying lubricant.

[0024] Based on the Fig. 1, Fig. 2 to Fig. Figure 3 below schematically describes the structure and function of a device 10 for conveying lubricant, as it can be used in a pump or compressor 100. Corresponding reference numerals are used in the figures for corresponding features.

[0025] Fig. Figure 1 shows a sectional view of components of an embodiment of a compressor 100. The compressor 100 comprises a piston 109 which moves along a stroke direction that is shown in Fig. The piston 109, marked with H, extends between a first end 109a and a second end 109b. The piston 109 is mounted, at least partially, in a cylinder chamber 114 of a cylinder 110, such that the piston 109 and cylinder 110 can perform a reciprocating linear relative movement along the stroke direction H. During the stroke, the piston 109 fills the cylinder chamber 114 to varying degrees. A working space 105, defined at least partially by the piston 109 and the cylinder chamber 114, therefore changes in volume during the stroke and is cyclically subjected to overpressure and underpressure, which will be described in more detail later.

[0026] Bottom dead center of the relative motion between piston 109 and cylinder 110 is reached when the entire cylinder chamber 114 is filled by the piston 109, which occurs in Fig. Figure 1 shows the following. Starting from this position, the cylinder 110 can move relative to the piston 109 to a position in which the working chamber 105 reaches its maximum volume. This movement is also called the inlet stroke. The position in which the working chamber 105 reaches its maximum volume defines the top dead center of the relative movement. The movement from the top dead center to the bottom dead center is also called the compression stroke.

[0027] Various technical concepts can be used to drive the relative motion described above. Examples include the well-known crank mechanisms and linear drives. Fig. Figure 1 shows an embodiment in which a special design of a linear drive is used, which will be described in more detail later.

[0028] The non-continuous, cyclical movement of the cylinder 110 along the piston 109, which is also referred to simply as stroke movement or stroke cycle, is used in the compressor 100 to take in a fluid to be compressed, for example in a cooling or refrigerant circuit, from a fluid reservoir and convey or compress it, as will be briefly explained below.

[0029] As in Fig. As can be seen in Figure 1, an inlet damper 120 is arranged at a first cylinder end 110a, extending along the stroke direction H of the cylinder 110. In this embodiment, the inlet damper is movable with the cylinder 110 and thus follows its oscillatory movement along the stroke direction H. Such an inlet damper 120 is used to limit the noise generated by the compressor 100. The inlet damper 120 is connected to the working chamber 105 via a first opening 115 in a cylinder base 116 of the cylinder chamber 114, thus communicating fluidically with it. A third check valve 135 is arranged in the first opening 115 such that it closes the first opening 115 when the pressure in the working chamber 105 exceeds a defined overpressure, thereby preventing backflow of fluid from the working chamber 105 into the inlet damper 120.The inlet damper 120 communicates fluidically with a fluid reservoir (not shown) containing a fluid, for example refrigerant to be pumped or compressed, and directs this fluid to the first opening 115.

[0030] The piston 109 is at least partially hollow-cylindrical and has, at least partially, a piston cavity 118 between the first end 109a and the second end 109b, which is fluidically connected to the working chamber 105 via a piston opening 121 located in the first end 109a of the piston 100. A fourth check valve 136 is arranged in the piston opening 121 such that, at pressures in the working chamber 105 that are below a defined pressure, it closes the piston opening 121 and thus prevents a backflow of fluid from the piston cavity 118 into the working chamber 105.

[0031] When cylinder 110 moves away from piston 109 during the inlet stroke, i.e., in relation to the in Fig. In the coordinate system shown, opposite to the positive x-direction, the volume of the working chamber 105 increases between the cylinder base 116 and the second end 109a of the piston 109. This creates a vacuum in the working chamber 105, and the third check valve 135 is open. This vacuum draws the fluid to be compressed from the inlet damper 120 through the first opening 115 into the working chamber 105, where it is compressed during the compression stroke following the inlet stroke.

[0032] When the movement of cylinder 110 relative to piston 109 has passed top dead center and the volume of the working chamber 105 is reduced by the cylinder 110, which is now moving in the positive x-direction, during the compression stroke, an overpressure builds up in the working chamber 105. As a result, the third check valve 135 closes the first opening 115, while the fourth check valve 136 opens the piston opening 121, allowing the fluid to escape from the working chamber 105 into the piston cavity 118. The fluid then flows through the piston cavity 118 to an outlet opening 201 located at the second piston end 109b, through which it can exit the piston cavity 118 into a fluid channel 202. In the embodiment shown, the fluid conductor 202 represents the high-pressure side of the compressor 100 and in embodiments can, for example, be the high-pressure side of a refrigeration circuit.The fluid conductor 202 directs the now compressed fluid to, for example, a condenser of the refrigerant circuit in a manner known per se and not shown further.

[0033] Because the cylinder 110 has mass, the oscillating movement of the cylinder 110 along the stroke direction H results in restoring forces at the supports 180 of the compressor 100, as described in Fig. 1 are designed as spring or spring-damper bearings to reduce the stress on the supports 180 caused by the restoring forces and to reduce noise. As a result, vibrations occur throughout the entire assembly connected by the frame 200 along the stroke direction H.

[0034] The relative movement between the piston 109 and the cylinder 110 is subject to friction, and without suitable lubrication between an outer surface 130 of the piston 109 and the cylinder 110, both efficiency losses of the compressor 100 and damage can occur. Therefore, compressors typically incorporate lubricant reservoirs and lubricant delivery systems.

[0035] In the in the Fig. 1 and Fig. In the embodiments shown in Figure 2, a circular lubrication point 108 is schematically arranged on the outer surface 130 of the piston 109, at which lubricant, for example a suitable oil, is supplied. For this purpose, the lubrication point 108 is connected to a device 10 for conveying lubricant.

[0036] It is proposed to design the device 10 such that the energy for conveying the lubricant is at least partially derived from the vibrations of the compressor 100 assembly connected by the frame 200 along the stroke direction H, as described above. While the Fig. 1 embodiment of compressor 100 shown from the one in Fig. Although the compressor 100 shown in section 2 differs in some details, the respective embodiments of the device 10 for conveying lubricant are largely identical or similar, so that the following descriptions of this device 10 apply to both Fig. 1 as well as on Fig. 2, unless it is expressly stated that this is not the case.

[0037] For this purpose, the device 10 comprises a lubricant piston 12, which, in the embodiment shown, is aligned parallel to the stroke direction H and connected to the piston-cylinder assembly 140 via the frame 200. Due to this design, it follows the reciprocating movement along the stroke direction H during operation of the compressor 100. A lubricant cylinder 13 is mounted coaxially and movably relative to the lubricant piston 12 along the stroke direction H, such that the lubricant piston 12 variably fills an interior space 11 of the lubricant cylinder 13. The lubricant piston 12 and the lubricant cylinder 13 thus define a variable lubricant working space 14, which increases as the lubricant cylinder 13 moves away from the lubricant piston 12 along the stroke direction. Fig. 1 also in the direction of the negative x-axis, and smaller when the lubricant cylinder 13 moves along the stroke direction towards the lubricant piston 12, in Fig. 1 also in the direction of the positive x-axis. During this cyclical movement, the fluid-tight seal between the lubricant cylinder 13 and the lubricant piston 12 alternately generates an overpressure and an underpressure in the lubricant working chamber 14, which is used to pump lubricant from a lubricant reservoir 15 and transport it to the lubrication point 108.

[0038] The movement of the lubricant cylinder 13 relative to the lubricant piston 12 is caused by the inertia of the lubricant cylinder 13, which can be briefly explained using the following: Fig. The configuration shown in point 1 will be explained.

[0039] When the lubricant piston 12 is accelerated from its position shown by a corresponding deflection of the frame 200 in the direction of the positive x-axis (to the right in the figure), the lubricant cylinder 13 is also accelerated in this direction by forces acting between the lubricant piston 12 and the lubricant cylinder 13. These forces result partly from the fluid film between the components and partly from the inertia of the fluid contained in the lubricant working chamber 14. This acceleration is counteracted by an inertial force acting in the negative x-direction, which is proportional to the mass of the lubricant cylinder 13 and causes the movement of the lubricant cylinder 13 to follow the movement of the lubricant piston 12 with a time and amplitude offset.If the direction of movement of the lubricant piston 12 is reversed by the frame, the reversal of the direction of movement of the lubricant cylinder 13 also occurs with a time delay.

[0040] In the illustrated embodiment, the characteristic of the vibration of the lubricant cylinder 13 on the lubricant piston 12 is further influenced by a first restoring element 31 and a second restoring element 32, each of which exert forces on the lubricant cylinder 13 parallel to the stroke direction H.

[0041] In the illustrated embodiment, the first return element 31 is designed as an axial spring and is arranged between an end of the lubricant cylinder 13 facing the lubricant piston 12 and a retaining structure 33 attached to the frame 200. The second return element 32 is also designed as an axial spring and is arranged within the working chamber 14 between opposing end faces of the lubricant piston 12 and the lubricant cylinder 13.

[0042] The massed lubricant cylinder 13, together with the restoring elements 31, 32, forms an oscillating system parallel to the stroke direction H, which, to distinguish it from the piston-cylinder assembly 140, is referred to here as the lubricant oscillation system. The natural frequency of the lubricant oscillation system can be adjusted by selecting the mass of the lubricant cylinder 13 and the stiffnesses of the restoring elements 31, 32, and thus the restoring forces mobilized by them. In one embodiment, this natural frequency is set such that it has a specific offset from the frequency at which the oscillation is excited by the reciprocating movement of the piston-cylinder assembly 140 of the compressor 100. The frequency of the movement of the piston-cylinder assembly 140 is hereinafter also referred to as the excitation frequency with regard to the lubricant oscillation system.

[0043] In some embodiments, the natural frequency of the lubricant oscillation system is greater than or equal to 1.2 times the excitation frequency. It is particularly advantageous if the natural frequency of the lubricant oscillation system is greater than or equal to 1.3 times the excitation frequency, or greater than or equal to 1.4 times the excitation frequency.

[0044] This ensures that the excitation frequency does not lead to resonance of the lubricant oscillation system, which would mean that the lubricant cylinder 13 would execute such large amplitudes on the lubricant piston 12 that damage to the components could occur. Because the natural frequency of the lubricant oscillation system is above the excitation frequency, it can be ruled out that the natural frequency will be encountered when traversing a specific frequency band during compressor 100 startup.

[0045] The lubricant working chamber 40 communicates fluidically with the lubricant reservoir 15 via a suction line 16 and with the lubrication point 108 via a lubricant line 17. In the Fig. 1, Fig. 2 to Fig. In the embodiment shown in Figure 3, both the suction of the lubricant from the lubricant reservoir 15 and the delivery of the lubricant to the lubrication point 108 are carried out via a lubricant piston interior 40, which forms the interior of the lubricant piston 12, designed as a hollow cylinder. The piston interior 40 is fluidically connected to the lubricant working chamber 14 and is arranged in extension to it.

[0046] In other configurations, the lubricant can also be transported into and out of the lubricant working chamber 14 in other ways, for example by connecting the suction line 16 and / or the lubricant line 17 to the lubricant cylinder 13. For this purpose, the suction line 16 and / or the lubricant line 17 can, for example, be designed to be flexible in order to allow the oscillatory movement of the lubricant cylinder 13. The [details of the configuration are missing from the original text.] Fig. 1, Fig. 2 to Fig. The embodiments shown in 3 have the advantage that the lubricant cylinder 13 is free of these connections and therefore no energy has to be expended for the deformation of these lines.

[0047] How the Fig. 1, Fig. 2 to Fig. The suction line 16 and the lubricant line 17, which can be removed from the frame 200, are sectionally formed or integrated into a first wall 51 and communicate fluidically with each other via a pre-chamber 52. The lubricant piston 12 is arranged on the first wall 51 such that the piston interior 40 also communicates fluidically with the pre-chamber 52. This can be achieved, for example, by forming a bore 41 in the first wall 51. Lubricant can thus flow from the lubricant reservoir 14 into the lubricant working chamber 14 and from the working chamber 14 to the lubrication point 108.

[0048] During periods of negative pressure in the lubricant working chamber 14, lubricant is drawn from the lubricant reservoir 15 through the piston interior 40 into the lubricant working chamber 14 via the suction line 16. A first check valve 21 located in the lubricant line 17 prevents lubricant from flowing back from the lubrication point 108 towards the lubricant working chamber 14. During periods of positive pressure in the lubricant working chamber 14, lubricant is forced from the lubricant working chamber 14 through the piston interior and into the lubricant line 17, from where it reaches the lubrication point 108. The first check valve 21 is open during this time. To prevent lubricant from being forced into the lubricant reservoir 15, a second check valve 22 is located in the suction line 16, preventing lubricant from flowing towards the lubricant reservoir 15.

[0049] In the Fig. In the embodiment shown in Figure 1, the piston 109 is partially double-walled and forms a cavity 117 which communicates fluidically with the lubricant line 17 at the second piston end 109b. Lubricant is transported through the cavity 117 to the lubrication point 108, which in the illustrated embodiment is located near the first piston end 109a.

[0050] The first reset element 31 and the second reset element 32 are in the embodiments of the Fig. 1 and Fig. 2 designed as axial springs. In the Fig. In the schematically illustrated embodiment of the device 10, the first return element 31` is designed as a combination of a first permanent magnet 34 and a second permanent magnet 35. As the Fig. As can be seen from the first permanent magnet 34, it is arranged at a first end 13a of the lubricant cylinder 13, located away from the lubricant piston 12, and is immovably connected to it. The first permanent magnet 34 can, for example, be formed as part of a surface of the lubricant cylinder 13. The first permanent magnet 34 has a first magnetic pole 34a and a second magnetic pole 34b, both oriented towards the second permanent magnet 35.The second permanent magnet 35 is arranged on a suitable holding structure 33, which may be connected to the frame 200, so adjacent to the first permanent magnet 34 that a magnetic attraction force acting between the first permanent magnet 34 and the second permanent magnet 35 forces the lubricant cylinder 13 along the stroke direction H between the lubricant cylinder 13 and the lubricant piston 12 into a position corresponding to half the stroke of the lubricant cylinder 13 along the lubricant piston 12.

[0051] In other words, this position corresponds to the position from which the lubricant piston 13 moves along the lubricant piston 109 by the same distance in the direction of the lubricant piston 12 and in the opposite direction to the lubricant piston 12 during its oscillation. This position of the lubricant cylinder 13 can also be referred to as the neutral position.

[0052] The magnetic attraction force is dimensioned by suitable selection of the permanent magnets 34, 35 such that the lubricant cylinder 13 can perform oscillations along the lubricant piston in both directions from the neutral position as described above, but a magnetic restoring force always acts on the lubricant cylinder 13, which pulls it in the direction of the neutral position and thus limits the amplitude of the oscillation.

[0053] For the sake of completeness, it should be mentioned that in the Fig. In the embodiment shown in Figure 3, a second magnetic pole 35b of the second permanent magnet 35 is oriented in the direction of the first permanent magnet 34 and is magnetically polarized in the opposite direction to the first magnetic pole 34a of the first permanent magnet 34.

[0054] While in the with regard to Fig. In the embodiment of the device 10 described in Figure 3, permanent magnets 34, 35 are used. It should be noted that one or more electromagnets can also be used in the first return element 31', the magnetic attraction of which can be varied depending on certain parameters. Such parameters include, for example, the amplitude and / or frequency of the vibrations of the piston-cylinder assembly 140, and / or the level of lubricant requirement at the lubricant point 108. In embodiments, the electromagnet comprises a coil winding arranged around the lubricant cylinder 13, and the lubricant cylinder 13 comprises a ferromagnetic component with which the coil winding interacts as described above such that the lubricant cylinder 13 is forced into the neutral position.

[0055] The following will describe the in the Fig. The linear drive of the compressor 100, as shown in Figure 1, is described in more detail below. The linear drive comprises an electrical coil arrangement 111, which is arranged adjacent to one circumference of the cylinder 110. As shown in Figure 1, the linear drive comprises an electrical coil arrangement 111, which is arranged adjacent to one circumference of the cylinder 110. Fig. As can be seen in the embodiment shown, the coil arrangement 111 is arranged in a cylindrical ring shape around a cylinder axis of the cylinder 110 which coincides with the stroke direction H, wherein the coil arrangement 111 has a certain distance in a radial direction R from the cylinder 110, which is indicated in the figures by an arrow.

[0056] The coil arrangement 111 interacts electromagnetically with at least one magnet 112 attached to the cylinder 110 in the manner of a linear actuator. The magnet 112 can be a cylindrical permanent magnet, as shown in the figures. The coil arrangement 111 and the magnet 112 are separated from each other in the radial direction R by an air gap. In the embodiment shown, the magnet 112 is directly connected to the cylinder 110. In other embodiments, the magnet 112 can also be connected to the cylinder 110 via a yoke.

[0057] In contrast to prior art solutions in which the piston and magnet are connected to each other via drive structures, in the present case the coil assembly 111 and the piston 109 are essentially immovable relative to each other in the stroke direction H. This is achieved in embodiments of the compressor 100 by attaching the coil assembly 111 and the piston 109 to a common support structure, for example, a common frame or a common yoke.

[0058] This design offers mechanical advantages because the forces acting between the coil assembly 111 and the magnet 109 can be transmitted directly to the piston 109 and the cylinder 110, without the need for additional drive components as in the prior art. The force transmission path between the components is therefore shorter, and the design is more rigid, enabling more precise control and reducing wear. The number of components required is smaller than in prior art solutions with drive components, resulting in cost savings.

[0059] In the embodiment shown in the figures, the common holding structure is designed as a first housing 200, which accommodates the coil assembly 111 and part of the piston 100. The connection between the first housing 200 and the coil assembly 110 or the piston 109 can be force-fit and / or form-fit and may optionally include known joining methods.

[0060] When an electrical voltage is applied to the coil assembly 111, the current flowing through the coil winding generates a magnetic flux, which produces an electromagnetic force acting on the magnet 112. Depending on the direction of the electric current, the electromagnetic force can be directed such that the cylinder 110 moves towards bottom dead center, i.e., towards the piston 109, which is also called the compression stroke, or such that the cylinder 110 moves towards top dead center, which is also called the lead-in stroke.

[0061] During this process, the piston 109 and the coil assembly 111 remain at rest relative to each other due to their fixed mounting, while the piston 109 and the cylinder 110 perform a reciprocating linear relative motion between bottom dead center and top dead center as the polarity of the coil winding 111 successively changes. With respect to the first housing 200, it can be said that the cylinder 110 oscillates within the first housing 200 during this relative motion, while the piston 109 remains at rest relative to the first housing 200.

[0062] The linear drive configuration of the piston-cylinder assembly 140 described above is particularly well-suited for use with the device 10 disclosed herein for conveying lubricant in the compressor 100, as it enables large stroke amplitudes at low frequencies. This is because the natural frequency of the oscillation of the lubricant cylinder 13 on the lubricant piston 12 also has relatively low frequencies, thus allowing for a larger cylinder mass. This makes it easier to achieve powerful conveying strokes for the lubricant. As already mentioned, the design of the device 10 disclosed herein makes it particularly easy to increase the mass of the oscillating component, namely the mass of the lubricant cylinder 13, without compromising the design freedom of the other components of the device 10.

[0063] The in Fig. The compressor shown in section 2, 100, 100`, differs from the one above in terms of Fig. The embodiment described in Section 1 is modified by the fact that it comprises a cylinder 110' that is stationary in a manner known per se and a piston 109' that is movable within the cylinder 110'. The operation of the device 10 for conveying lubricant is also determined in this embodiment by the vibrations along the stroke direction H caused by the frame 200' to which the piston-cylinder assembly 140 is attached, by the fact that the lubricant piston 109 is attached to the frame 200'. The above statements regarding the device 10 therefore apply accordingly.

[0064] The invention is not limited to the described and illustrated embodiments. Rather, it also encompasses all further developments by skilled craftsmen within the scope of the invention defined by the claims. In addition to the described and illustrated embodiments, further embodiments are conceivable, which may include further modifications and combinations of features.

Claims

[1] Device (10) for conveying lubricant in a pump or compressor (100, 100'), the pump or compressor (100, 100') comprising a piston-cylinder assembly (140, 140') configured to perform a reciprocating motion along a stroke direction (H) during operation of the pump or compressor (100, 100'); the device (10) comprising: a lubricant piston (12) which is aligned along the stroke direction (H) or parallel to the stroke direction (H) and is connected indirectly or directly to the piston-cylinder assembly (140, 140`) in such a way that it follows the reciprocating movement along the stroke direction (H) during operation of the pump or compressor (100, 100`); a lubricant cylinder (13) which is movably mounted on the lubricant piston (12) along the stroke direction (H) or parallel to the stroke direction (H), wherein the lubricant piston (12) and the lubricant cylinder (13) define a variable lubricant working chamber (14); a lubricant reservoir (15) which communicates fluidically with the lubricant working chamber (14) via a suction line (16); a lubricant line (17) which fluidically connects the lubricant working chamber (14) to a lubrication point (108, 108`). [2] Device (10) according to claim 1, wherein a first check valve (21) is arranged in the lubricant line (17) which is designed to prevent a backflow of lubricant from the lubrication point (18) towards the lubricant working chamber (14). [3] Device (10) according to one of claims 1 and 2, wherein a second check valve (22) is arranged in the suction line (16), which is designed to prevent a backflow of lubricant from the lubricant working chamber (14) towards the lubricant reservoir (15). [4] Device (10) according to one of claims 1 to 3, comprising a first return element (31, 31`) which is configured to exert a first force on the lubricant cylinder (13) proportional to a deflection of the lubricant cylinder (13) along the stroke direction (H) or parallel to the stroke direction (H). [5] Device (10) according to claim 4, wherein the first return element (31) comprises an axial spring. [6] Device (10) according to one of claims 4 and 5, wherein the first return element (31`) comprises at least one first permanent magnet (34) arranged on the lubricant cylinder (13) and at least one second permanent magnet (35) arranged in a fixed position relative to the lubricant piston (12), wherein the second permanent magnet (35) is arranged adjacent to the first permanent magnet (34) in such a way that a magnetic attraction force acts between the first permanent magnet (34) and the second permanent magnet (35). [7] Device (10) according to one of claims 4 to 6, wherein the first return element (31`) comprises a coil winding of an electromagnet arranged around the lubricant cylinder (13) and the lubricant cylinder (13) comprises a ferromagnetic component. [8] Device (10) according to one of claims 4 to 7, comprising a second return element (32) which is configured to exert a second axial force on the lubricant cylinder (13) that is opposite to the first force and proportional to a deflection of the lubricant cylinder (13). [9] Device (10) according to any one of claims 4 to 8, wherein the reciprocating motion of the piston-cylinder assembly (140, 140') has a first frequency, and wherein a mass of the lubricant cylinder (13) as well as the first force and optionally the second force are selected or matched such that a natural frequency of the motion of the lubricant cylinder (13) along the stroke direction (H) or parallel to the stroke direction (H) lies in a range which corresponds to at least 1.2 times the first frequency, preferably at least 1.3 times the first frequency, and particularly preferably at least 1.4 times the first frequency. [10] Device (10) according to any one of claims 1 to 9, wherein the lubricant piston (12) is essentially designed as a hollow cylinder and defines a lubricant piston interior (40). [11] Device (10) according to claim 10, wherein the lubricant piston (12) is arranged on a frame (200, 200`) connected to the piston-cylinder assembly (140, 140`) and the suction line (16) and the lubricant line (17) are formed at least partially in a first wall (51) of the frame (200, 200`) and communicate fluidically with each other via a pre-chamber (52). [12] Device (10) according to claim 11, wherein the lubricant piston (12) is arranged on the first wall (51) of the frame (200, 200`) and the piston interior (40) communicates fluidically with the prechamber (52). [13] Compressor (100, 100`) for compressing a fluid, comprising: a piston-cylinder assembly (140, 140`) designed to perform a reciprocating motion along a stroke direction (H) during operation of the compressor (100, 100`); a lubricant piston (12) which is aligned along the stroke direction (H) or parallel to the stroke direction (H) and is connected indirectly or directly to the piston-cylinder assembly (140, 140`) in such a way that it follows the reciprocating motion along the stroke direction (H) during operation of the compressor (100, 100`); a lubricant cylinder (13) which is movably mounted on the lubricant piston (12) along the stroke direction (H) or parallel to the stroke direction (H), wherein the lubricant piston (12) and the lubricant cylinder (13) define a variable lubricant working chamber (14); a lubricant reservoir (15) which communicates fluidically with the lubricant working chamber (14) via a suction line (16); a lubricant line (17) which fluidically connects the lubricant working chamber (14) to a lubrication point (108, 108`). [14] Compressor (100) according to claim 13, wherein the piston-cylinder assembly (140) comprises: a piston (109); a cylinder (110) with a cylinder chamber (114) which accommodates the piston (109) at least in part for the execution of a linear relative movement back and forth along a stroke direction between the piston (19) and the cylinder (110); arranged adjacent to a circumference of the cylinder (110), a coil arrangement (111); at least one magnet (112) attached directly or indirectly to the cylinder (110) and electromagnetically cooperating with the coil arrangement (111); wherein the coil arrangement (111) and the piston (109) are arranged in a substantially immovable manner relative to each other in the stroke direction; and wherein the coil assembly (111) and the piston (109) are attached to a common support structure, preferably to a frame (200). [15] Compressor (100, 100`) according to one of claims 13 and 14, wherein the lubrication point (108 108`) comprises at least part of a contact area between the piston (109, 109`) and the cylinder (110, 110`). [16] Refrigerant circuit, comprising: a piping system for circulating a refrigerant; and a compressor (100, 100`) according to one of claims 13 to 15, a condenser, an expansion valve, and an evaporator, connected fluidically through the piping system.

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