Oil delivery device for a reciprocating piston pump, and method for operating such an oil delivery device

Abstract

The invention relates to an oil delivery device (20) for a reciprocating piston pump (1), in particular a reciprocating piston pump (1) which is designed as a refrigerant compressor, comprising: a hollow oil delivery cylinder (20) which extends along a longitudinal axis (B); and a reciprocating piston (24) which is arranged in the hollow oil delivery cylinder (20) so as to be movable along the longitudinal axis (B). The reciprocating piston (24) is in the form of a permanent magnet (25) or comprises at least one permanent magnet (25); and a magnetic field generator (30) is provided outside the oil delivery cylinder (20), the magnetic field generator being designed to generate a magnetic field which acts on the reciprocating piston (24) in order to hold the reciprocating piston (24) in an initial position and / or to move it into the initial position when the hollow oil delivery cylinder (20) moves along the longitudinal axis (B).

Description

[0001] R.415083

[0002] - 1 -

[0003] Description

[0004] Title and procedure for operating

[0005] The invention relates to an oil delivery device for a reciprocating pump. The invention further relates to a reciprocating pump with such an oil delivery device and a method for operating an oil delivery device according to the invention in a reciprocating pump.

[0006] State of the art

[0007] Compressors for compressing refrigerant in refrigeration circuits are often designed as reciprocating pumps, in which a piston moves back and forth in a linear motion within a cylinder. To reduce friction between the piston and the cylinder, an oil film can be created between them. The oil required for this is supplied to the area between the piston and the cylinder by an oil delivery device or oil pump. An oil delivery device for a reciprocating pump is known, for example, from US 2009 / 0317263 A1.

[0008] It is an object of the invention to provide an improved oil delivery device for a reciprocating pump, in particular an oil delivery device that is quieter in operation than the oil delivery devices known to date.

[0009] The invention comprises an oil delivery device for a reciprocating pump, in particular for a reciprocating pump designed as a refrigerant compressor, wherein the oil delivery device has: a hollow oil delivery cylinder extending along a longitudinal axis, and a reciprocating piston movably arranged along the longitudinal axis in the hollow oil delivery cylinder. The reciprocating piston of an oil delivery device according to the invention is a permanent magnet or with at least one R.415083

[0010] - 2 -

[0011] Permanent magnets are formed. Outside the oil delivery cylinder, a magnetic field generator is provided which generates a magnetic field that acts on the reciprocating piston to hold the reciprocating piston in a home position and / or to move the reciprocating piston to the home position when the hollow oil delivery cylinder moves along the longitudinal axis.

[0012] The invention also includes a reciprocating pump, in particular a reciprocating pump configured as a refrigerant compressor. A reciprocating pump according to the invention comprises a fluid delivery cylinder and a fluid delivery piston, which is movable along a longitudinal axis within the fluid delivery cylinder to compress and deliver a fluid, in particular a refrigerant. A reciprocating pump according to the invention further comprises an oil delivery device according to an embodiment of the invention, which is designed and configured to deliver a lubricant, in particular oil, when the reciprocating pump is operated, in order to reduce friction between the fluid delivery cylinder and the fluid delivery piston. The hollow oil delivery cylinder preferably also extends along the longitudinal axis, i.e., essentially parallel to the fluid delivery cylinder.The oil delivery cylinder is made of a non-magnetic material, such as aluminum or plastic.

[0013] During operation of a reciprocating piston pump according to the invention, the fluid delivery piston moves back and forth within the fluid delivery cylinder in an oscillating linear motion along the longitudinal axis. This oscillating movement of the fluid delivery piston in the fluid delivery cylinder generates vibrations along the longitudinal axis within the reciprocating piston pump, which also cause the oil delivery cylinder of the oil delivery device to vibrate along the longitudinal axis.

[0014] Since the piston of the oil delivery device is essentially held in a fixed position by the magnetic field generator, the vibrations of the oil delivery cylinder cause the oil delivery cylinder and the piston of the oil delivery device to move relative to each other along their longitudinal axis. This results in the piston performing pumping movements within the oil delivery cylinder, which draw oil from an oil reservoir or sump to the interface between the fluid delivery piston and the fluid delivery cylinder. R.415083

[0015] - 3 -

[0016] By mechanically decoupling the piston of an oil conveying device according to the invention from the oil conveying cylinder, the transmission of vibrations and thus also the generation of noise are reduced.

[0017] A reciprocating pump equipped with an oil conveying device according to the invention can therefore be operated with significantly less noise than a reciprocating pump equipped with a conventional oil conveying device.

[0018] In one embodiment, the magnetic field generator is mounted in the reciprocating pump in such a way that it does not move together with the oil delivery cylinder during operation of the pump. Such an embodiment is particularly advantageous when the reciprocating piston has a large mass or inertia and / or when the vibration frequencies are low.

[0019] In one embodiment, the magnetic field generator is mounted in the reciprocating pump such that, during operation of the pump, it moves along the longitudinal axis of the oil delivery cylinder together with the cylinder. Due to the inertia of the piston, the piston also moves relative to the magnetic field generator in this case when the oil delivery cylinder oscillates in the direction of its longitudinal axis B during operation of the pump. This embodiment is particularly advantageous with a smaller mass or inertia of the piston and / or at higher oscillation frequencies.

[0020] In one embodiment, the oil delivery cylinder of the oil delivery device has a length ranging from 40 mm to 80 mm. In another embodiment, the stroke length of the piston is between 1 mm and 5 mm. In yet another embodiment, the oil delivery cylinder of the oil delivery device has a diameter ranging from 4 mm to 12 mm.

[0021] The dimensions mentioned depend on the desired delivery rate of the oil pump and may, if necessary, fall outside the specified ranges. R.415083

[0022] - 4 -

[0023] Oil delivery cylinders of such dimensions have proven to be well suited to delivering a quantity of oil sufficient to adequately lubricate the interface between the fluid delivery piston and the fluid delivery cylinder.

[0024] In one embodiment, the magnetic field generator has at least one permanent magnet which is designed and configured to generate the magnetic field that acts on the piston in order to hold the piston in a starting position and / or to move it into the starting position.

[0025] Permanent magnets make it possible to equip an oil conveying device according to the invention with a simple, reliable, maintenance-free and cost-effective magnetic field generator.

[0026] In one embodiment, the magnetic field generator and / or the piston have several permanent magnets arranged such that their magnetic fields reinforce each other. In this way, the restoring force acting on the piston can be further increased.

[0027] In one embodiment, the magnetic field generator has at least one ring magnet. The at least one ring magnet can, in particular, be designed such that it encloses the oil delivery cylinder in a ring shape along its outer circumference.

[0028] A ring magnet that encircles the oil delivery cylinder along its outer circumference is particularly efficient in generating a strong magnetic field in the oil delivery cylinder, which acts on the piston to hold the piston in a starting position and / or move it to the starting position.

[0029] In order to further increase the magnetic field in the oil delivery cylinder, several ring magnets can be arranged next to each other along the circumference of the oil delivery cylinder in one embodiment.

[0030] In one embodiment, the magnetic field generator has at least one electromagnet equipped with at least one electrical coil. The at least one electromagnet can furthermore be equipped with at least one iron core. By energizing the at least one coil R.415083

[0031] - 5 - a magnetic field can be generated that acts on the piston to hold the piston in a starting position and / or to move it to the starting position.

[0032] At least one electromagnet can be mounted in the piston pump in such a way that it does not move together with the oil delivery cylinder during operation. Alternatively, at least one electromagnet can be mounted in the piston pump in such a way that it moves together with the oil delivery cylinder during operation.

[0033] In one embodiment, the magnetic field generator has at least one electrical coil that surrounds the oil delivery cylinder in a ring shape along its outer circumference, so that by energizing the at least one coil a magnetic field can be generated in the oil delivery cylinder which acts on the piston to hold the piston in a starting position and / or to move it into the starting position.

[0034] At least one electrical coil can be mounted in the piston pump in such a way that it does not move together with the oil delivery cylinder during operation. Alternatively, at least one electrical coil can be mounted in the piston pump in such a way that it moves together with the oil delivery cylinder during operation.

[0035] In one embodiment, a magnetic field generator has several coils and / or several electromagnets in order to generate an even stronger magnetic field.

[0036] Magnetic field generators equipped with at least one electrical coil make it possible to switch the magnetic field generated by the magnetic field generator on and off selectively.

[0037] Furthermore, with such a magnetic field generator, the strength of the magnetic field produced by the generator can be varied by varying the electric current flowing through the at least one electrical coil. In this way, the amount of oil delivered by the oil delivery device can be adapted to the current operating condition of the reciprocating pump. This ensures that the R.415083

[0038] - 6 - The amount of oil delivered is sufficient to adequately lubricate the interface between the fluid delivery piston and the fluid delivery cylinder without delivering too much oil. An excessive amount of oil could, due to the oil's viscosity, lead to an undesirable increase in the resistance to the movement of the fluid delivery piston within the fluid delivery cylinder.

[0039] The invention also includes a method for operating an oil conveying device according to the invention, which is equipped with at least one coil. The method comprises allowing an electric current to flow through the at least one electric coil in order to generate the magnetic field.

[0040] In one embodiment, the method comprises adjusting the quantity of oil delivered by the oil delivery device to a desired value by varying the electric current flowing through the electric coil.

[0041] The method can, in particular, include adjusting the amount of oil delivered by the oil delivery device to the current operating state of the reciprocating pump by varying the electrical current. In this way, the oil delivery device can be operated with particular efficiency.

[0042] Exemplary embodiments of the invention are described below with reference to the accompanying figures.

[0043] Brief description of the characters

[0044] Figure 1 shows a section of a cross-sectional view of a reciprocating piston pump according to the invention, which is equipped with an oil conveying device according to an embodiment of the invention.

[0045] Figure 2 shows an enlarged cross-sectional view of an oil conveying device designed according to another embodiment of the invention.

[0046] Figure 3 shows an enlarged cross-sectional view of an oil conveying device designed according to a further embodiment of the invention.

[0047] Figure 4 shows an enlarged cross-sectional view of an oil conveying device designed according to yet another embodiment of the invention. R.415083

[0048] - 7 -

[0049] Figure 1 shows a section of a cross-sectional view of a reciprocating piston pump 1 according to the invention, which is equipped with an oil conveying device according to the invention.

[0050] A piston pump 1, as shown in part in Figure 1, can in particular be used as a refrigerant compressor in a refrigeration circuit, for example in a refrigerator or freezer.

[0051] The reciprocating pump 1 has a frame 3 which supports a fluid delivery cylinder 2. A fluid delivery piston 4 is located in the fluid delivery cylinder 2 and can be moved back and forth along the longitudinal axis A of the fluid delivery cylinder 2 by a drive (not shown in Figure 1).

[0052] The drive not shown in Figure 1 could, for example, be a crank drive or a linear drive.

[0053] At the right end of the fluid delivery piston 4, as shown in Figure 1, a suction valve 6 is provided for drawing in a fluid to be delivered, in particular a refrigerant. An outlet valve 8a for releasing the compressed fluid / refrigerant is elastically mounted and held elastically closed by an outlet valve spring 8c. The outlet valve spring 8c is arranged in an outlet cap 8b, which is attached to one end of the fluid delivery cylinder 2.

[0054] When the fluid delivery piston 4 is moved linearly back and forth along an axis A of the fluid delivery cylinder 2 in the fluid delivery cylinder 2, it alternately performs a suction stroke and a compression and delivery stroke.

[0055] During the suction stroke, the fluid / refrigerant is drawn into a compression chamber 5, which is formed between the fluid delivery piston 4 and the fluid delivery cylinder 2.

[0056] During the compression and delivery stroke, the fluid / refrigerant is initially in the compression chamber 5 R.415083 with the outlet valve 8a closed.

[0057] - 8 - compressed and then, after the exhaust valve 8a has opened against the elastic force of the exhaust valve spring 8c, pushed out of the compression chamber 5.

[0058] Within frame 3, an oil supply channel 12 and an oil recovery channel 14 are formed. The oil supply channel 12 and the oil recovery channel 14 are in fluid communication with an oil circulation channel 10, which is formed at the interface between the fluid delivery cylinder 2 and the fluid delivery piston 4, in order to supply oil to the oil circulation channel 10 and to recover oil from the oil circulation channel 10.

[0059] The oil circulation channel 10 is formed by an annular fluid delivery cylinder groove 10a, which is formed on the inner circumference of the fluid delivery cylinder 2, and an annular piston groove 10b, which is formed on the outer circumference of the fluid delivery piston 4. The fluid delivery cylinder groove 10a and the annular piston groove 10b overlap each other, as shown in Figure 1.

[0060] In a lower area of ​​Figure 1, an oil conveying device 20 is shown, which is designed and configured to convey oil through the oil supply channel 12, the oil circulation channel 10 and the oil recovery channel 14.

[0061] The oil delivery device 20 comprises a hollow oil delivery cylinder 22 with a longitudinal axis B that extends substantially parallel to the longitudinal axis A of the fluid delivery cylinder 2. The end of the oil delivery cylinder 22 shown on the right side in Figure 1 is in fluid communication with the oil supply channel 12 via an oil supply valve arrangement 28.

[0062] The oil delivery cylinder 22 is made of a non-magnetic material, for example aluminum or plastic.

[0063] The oil supply valve assembly 28 comprises a plate-shaped valve blade 28a, which is installed on one side of the frame 3 and communicates with the oil cylinder 22 and the oil supply passage 12, an oil suction valve (not shown) for drawing in the oil, and an oil drain valve (not shown) for draining the oil, which are installed on the valve blade 28a and can be opened and closed. R.415083

[0064] - 9 -

[0065] The oil supply valve arrangement 28 further comprises a blade cover 28b, which is installed outside the valve blade 28a and overlaps with the valve blade 28a, as well as a suction storage chamber 29a and a drain storage chamber 29b for temporarily storing the oil.

[0066] To prevent unwanted leakage of oil from the oil supply valve assembly 28, various additional sealing components / seals may be present between the valve blade 28a and the blade cover 28b, which are not explicitly shown in Figure 1.

[0067] An oil supply line 21 opens into one end of the oil supply channel 12 shown below in Figure 1, the other end of which, not shown in Figure 1, is arranged in an oil reservoir or oil sump not shown in Figure 1.

[0068] In the cavity formed inside the oil delivery cylinder 22 there is a piston 24 which divides the cavity inside the oil delivery cylinder 22 into an oil delivery chamber 22a shown on the right in Figure 1 and a compensation chamber 22b shown on the left in Figure 1.

[0069] The outer end of the compensation chamber 22b is closed by a plug 27. A ventilation opening 26 is formed in the plug 27, which allows pressure equalization between the interior of the compensation chamber 22b and the environment of the oil delivery cylinder 22.

[0070] The piston 24 is movable along the longitudinal axis B of the oil delivery cylinder 22 within the cavity.

[0071] By moving the piston 24 back and forth in the oil delivery cylinder 22, the volumes of the oil delivery chamber 22a and the compensation chamber 22b can be varied. The volume of the oil delivery chamber 22a increases when the volume of the compensation chamber 22 decreases. Conversely, the volume of the oil delivery chamber 22a decreases when the volume of the compensation chamber 22 increases.

[0072] By moving the piston 24 in the oil delivery cylinder 22, oil can be drawn into the oil delivery chamber 22a through the oil supply line 21 in an oil suction stroke R.415083

[0073] - 10 - By moving the piston 24 in the opposite direction, the oil drawn into the oil delivery chamber 22a during the suction stroke can be forced out through the oil supply valve assembly 28 into the oil supply channel 12 and the oil circulation channel 10 during an oil delivery stroke. In a conventional oil delivery device 20, the piston 24 is elastically supported on the two inner end faces of the oil delivery cylinder 22 by springs (not shown in Figure 1). As a result, during rapid movements of the oil delivery cylinder 22 along the longitudinal axis A, such as those occurring during operation of the reciprocating pump 1 due to the oscillating movements of the fluid delivery piston 4, the piston 24 oscillates back and forth within the oil delivery cylinder 22.In this process, oil is drawn in through the oil supply line 21 into the oil delivery chamber 22a of the oil delivery cylinder 22 in an oil suction stroke and expelled in a subsequent oil delivery stroke through the oil supply valve arrangement 28 into the oil supply channel 12 and into the oil circulation channel 10.

[0074] In an oil conveying device 20 designed according to the invention, as shown in Figure 1, no springs are provided in the oil conveying cylinder 22 to elastically support the piston 24 on the two inner end faces of the oil conveying cylinder 22.

[0075] Instead, the piston 24 of the oil conveying device 20 is designed as a permanent magnet or with at least one permanent magnet 25. This allows the piston 24 to be fixed and / or moved within the oil conveying cylinder 22 by magnetic forces acting externally on the oil conveying device 20.

[0076] Outside the oil delivery cylinder 22, a magnetic field generator 30 is provided, which is designed to generate a magnetic field that acts on the reciprocating piston 24 or on the at least one permanent magnet 25 of the reciprocating piston 24 in order to hold the reciprocating piston 24 in its starting position or to move the reciprocating piston 24 back to its starting position when the hollow oil delivery cylinder 22 moves along its longitudinal axis B.

[0077] The magnetic field generator 30 can be mounted independently of the frame 3 in the piston pump 1, so that it does not occur together with the R.415083

[0078] - 11 -

[0079] Frame 3 and the oil delivery cylinder 22 attached to frame 3 are moved.

[0080] In an alternative embodiment, the magnetic field generator 30 can be mounted on the frame 3 or on the oil delivery cylinder 22, so that it moves together with the frame 3 and the oil delivery cylinder 22 when the reciprocating pump 1 is operated.

[0081] Due to the mechanical inertia of the reciprocating piston 24, the reciprocating piston 24 also moves in this case relative to the oil delivery cylinder 22 and the magnetic field generator 30 when the frame 3 and the oil delivery cylinder 22 oscillate in the direction of the longitudinal axis B of the oil delivery cylinder 22 during operation of the reciprocating piston pump 1.

[0082] In the case of a large mass or inertia of the reciprocating piston 24 and low vibration frequencies, it is generally advantageous to mount the magnetic field generator 30 independently of the frame 3 in the reciprocating piston pump 1, so that it does not move together with the frame 3 and the oil delivery cylinder 22 attached to the frame 3.

[0083] With a small mass or inertia of the piston 24 and higher vibration frequencies, it is generally advantageous to attach the magnetic field generator 30 to the frame 3 in the piston pump 1, so that during operation of the piston pump 1 it moves together with the frame 3 and the oil delivery cylinder 22 attached to the frame 3 along the longitudinal axis B of the oil delivery cylinder 22.

[0084] The oil delivery cylinder 22 can, for example, have a length L in the range of 40 mm to 80 mm and / or a diameter D in the range of 4 mm to 12 mm. The stroke length of the piston 24 can be between 1 mm and 5 mm.

[0085] The dimensions of the oil delivery cylinder 22 and the stroke length of the piston 24 depend on the desired delivery rate of the oil delivery device 20 and may, if necessary, also lie outside the specified ranges. R.415083

[0086] - 12 -

[0087] The magnetic field generator 30 can comprise at least one permanent magnet 32, which is arranged on the outer circumference of the oil delivery cylinder 22, as shown in Figure 1.

[0088] To increase the magnetic force of the magnetic field generator 30, two or more permanent magnets 32 can also be arranged along the outer circumference of the oil delivery cylinder 22 in such a way that the magnetic forces exerted by the permanent magnets 32 on the piston 24 reinforce each other.

[0089] The magnetic field generator 30 can also have at least one ring magnet 34 that encircles the outer circumference of the oil delivery cylinder 22 in a ring shape, as shown schematically in Figure 2. Such a ring magnet 34 is particularly efficient in generating the strongest possible magnetic force, which acts on the piston 24 or on the at least one permanent magnet 25 of the piston 24.

[0090] Figure 3 shows another possible embodiment of an oil conveying device according to the invention. In the embodiment shown in Figure 3, the magnetic field generator 30 has at least one electromagnet 36, which is arranged on the outer circumference of the oil conveying cylinder 22.

[0091] The at least one electromagnet 36 can be configured as a bar magnet with a coil 38 and an iron core 40, as shown in Figure 3. Alternatively, the at least one electromagnet 36 can also be configured as a ring magnet 34, as shown in Figure 2 for a permanent magnet.

[0092] The at least one electromagnet 36 can be mounted independently of the frame 3 in the piston pump 1, so that it does not move together with the frame 3 and the oil delivery cylinder 22 attached to the frame 3.

[0093] In an alternative embodiment, the at least one electromagnet 36 can be mounted on the frame 3 of the piston pump 1, so that it moves together with the frame 3 and the oil delivery cylinder 22 attached to the frame 3. R.415083

[0094] - 13 -

[0095] Figure 4 shows another embodiment in which an electrical coil 38 is wound around the oil delivery cylinder 22 such that the oil delivery cylinder 22 is movable within the electrical coil 38 along the longitudinal axis A.

[0096] When an electric current flows through the coil 38, the electromagnet 36 shown in Figure 3 and the coil 38 shown in Figure 4 each generate a magnetic field that acts on the piston 24 and on the at least one permanent magnet 25 of the piston 24, respectively.

[0097] When the oil delivery cylinder 22 oscillates along the longitudinal axis B during operation of the reciprocating pump 1, as previously described, the reciprocating piston 24 is held in the stationary coordinate system of the electromagnet 36 or the coil 38 by the magnetic fields generated by the electromagnet 36 or the coil 38 during operation.

[0098] This results in the piston 24 moving back and forth relative to the oil delivery cylinder 22 along the longitudinal axis B of the oil delivery cylinder 22, thereby performing a pumping motion by which oil is pumped from the oil reservoir (not shown in the figures) into the oil supply channel 12 and from there into the oil circulation channel 10 to lubricate the interface between the fluid delivery piston 4 and the fluid delivery cylinder 2.

[0099] By varying the electric current flowing through the coil 38, the magnetic restoring force exerted on the piston 24 by the electromagnets 36 or by the coil 38 can be adjusted over a wide range.

[0100] By varying the electric current flowing through the coil 38, the amount of oil supplied by an oil supply device 20 according to the invention can be adapted to a current operating state of the reciprocating pump 1, so that neither too little nor too much oil flows through the oil channels 10, 12, 14.

[0101] The coil 38 can be mounted independently of the frame 3 and the oil delivery cylinder 22 in the piston pump 1, so that the coil 38 does not occur together with the frame 3 and the R.415083 attached to the frame 3.

[0102] - 14 -

[0103] The oil delivery cylinder 22 moves. This results in the oil delivery cylinder 22 moving relative to the coil 38 during operation of the reciprocating piston pump 1.

[0104] In an alternative embodiment, the coil 38 can also be attached directly to the oil delivery cylinder 22 or wound onto the oil delivery cylinder 22, so that the coil 38 moves together with the oil delivery cylinder 22 when the oil delivery cylinder 22 oscillates along its longitudinal axis B during operation of the reciprocating pump 1.

Claims

R.415083 - 15 - 1. Oil conveying device (20) for a reciprocating pump (1), in particular for a reciprocating pump (1) designed as a refrigerant compressor, wherein the oil conveying device (20) comprises: a hollow oil conveying cylinder (20) extending along a longitudinal axis (B), and a reciprocating piston (24) movably arranged in the hollow oil conveying cylinder (20) in the direction of the longitudinal axis (B); wherein the reciprocating piston (24) is designed as a permanent magnet (25) or with at least one permanent magnet (25); and wherein a magnetic field generator (30) is provided outside the oil conveying cylinder (20) which is configured to generate a magnetic field acting on the reciprocating piston (24) in order to hold the reciprocating piston (24) in a starting position and / or to move it to the starting position when the hollow oil conveying cylinder (20) moves in the direction of the longitudinal axis (B).

2. Oil conveying device (20) according to claim 1, wherein the oil conveying cylinder (20) has a length (L) in the range of 40 mm to 80 mm and / or wherein the oil conveying cylinder (20) has a diameter (D) in the range of 4 mm to 12 mm, and / or wherein the stroke length of the piston (24) is between 1 mm and 5 mm.

3. Oil conveying device (20) according to claim 1 or 2, wherein the magnetic field generator (30) is mounted in such a way that it does not move together with the oil conveying cylinder (22). R.415083 - 16 - 4. Oil conveying device (20) according to claim 1 or 2, wherein the magnetic field generator (30) is mounted such that it moves together with the oil conveying cylinder (22).

5. Oil conveying device (20) according to one of the preceding claims, wherein the magnetic field generator (30) has at least one permanent magnet (32).

6. Oil conveying device (20) according to one of the preceding claims, wherein the magnetic field generator (30) has at least one ring magnet (34), wherein the at least one ring magnet (34) surrounds the oil conveying cylinder (20) in a ring shape, in particular along its outer circumference.

7. Oil conveying device (20) according to one of the preceding claims, wherein the magnetic field generator (30) has at least one electromagnet (36) with an electrical coil (38).

8. Oil conveying device (20) according to one of the preceding claims, wherein the magnetic field generator (30) has an electrical coil (28) which surrounds the oil conveying cylinder (20) in a ring shape along its outer circumference.

9. Reciprocating piston pump (1), in particular a reciprocating piston pump (1) designed as a refrigerant compressor, wherein the reciprocating piston pump (1) has at least one fluid delivery cylinder (2), at least one fluid delivery piston (4) arranged to be linearly movable in the fluid delivery cylinder (2), and at least one oil delivery device (20) according to one of the preceding claims. R.415083 - 17 - 10. Method of operating an oil conveying device (20) according to claim 7 or 8, wherein the method comprises allowing an electric current to flow through the electric coil (28) in order to generate a magnetic field; wherein the method particularly comprises adjusting the quantity of oil conveyed by the oil conveying device (20) to a desired value by varying the electric current flowing through the electric coil (28).

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