Reciprocating compressor

Abstract

A reciprocating compressor has an outer casing (2) having a base support (3); an actuation unit (4), which is arranged in the outer casing (2) and comprises a linear actuator (5) of annular shape extending around a central axis (A1), and a compression cylinder (6) extending along the central axis (A1) at least predominantly outside the linear actuator (5); a suspension system (7) comprising first elastic elements (8) arranged between the base support (3) of the outer casing (2) and the actuation unit (4); and a sliding unit (9), which comprises a compression piston (10) sliding inside the compression cylinder (6), the linear actuator (5) being configured to actuate a reciprocating sliding movement of the sliding unit (9) with respect to the compression cylinder (6) along the central axis (A1).

Description

[0001] Description

[0002] Title

[0003] Reciprocating compressor of the patent for an industrial invention entitled:

[0004] “RECIPROCATING COMPRESSOR” by ROBERT BOSCH GMBH of German nationality with registered address: POSTFAC H 30 02 20

[0005] 70442 STUTTGART (GERMANY)

[0006] Inventors: CECERE Martino, DIAFERIA Antonio, RANIERI Giuseppe, PINTO Valerio, MEDOLLA Ciro

[0007] *** ***** ***

[0008] Technical field

[0009] The present invention relates to a reciprocating compressor, in particular a piston compressor.

[0010] Prior art

[0011] Reciprocating compressors of known type generally comprise an outer casing, an oscillating unit arranged in the outer casing, and a suspension system, which includes elastic elements and vertically supports the oscillating unit in the outer casing.

[0012] Typically, the oscillating unit comprises a linear actuator of annular shape, a compression cylinder extending along a horizontal axis through the linear actuator, and a compression piston, which is engaged slidingly inside the compression cylinder and is actuated by the linear actuator.

[0013] In particular, the linear actuator is configured to actuate a reciprocating sliding movement of the compression piston along the horizontal axis with respect to the compression cylinder. Since the suspension system supports the oscillating unit elastically with respect to the outer casing, said reciprocating sliding movement of the compression piston causes a reciprocating oscillation of the oscillating unit along the horizontal axis and, consequently, the elastic elements of the suspension system are subjected to a bending moment

[0014] Typically, reciprocating compressors of known type have a mechanical configuration that influences the dynamics of the reciprocating compressor, limiting the efficiency thereof.

[0015] In particular, the bending moment to which the elastic elements of the suspension system are subjected applies a reciprocating torque to the oscillating unit, giving rise to a slight reciprocating rotation of the oscillating unit around a point of static equilibrium of the oscillating unit. Said reciprocating rotation generates transverse contact forces between the compression piston and the compression cylinder which increase the friction forces between the compression piston and the compression cylinder, raising the temperature inside the compression cylinder and having a detrimental effect on the efficiency of the reciprocating compressor.

[0016] Moreover, the efficiency of the compressor is further limited by the fact that, during the operation of the compressor, heat is generated inside the compression cylinder because of the electrical current which is supplied to the linear actuator, the friction caused by the sliding of the compression piston inside the compression cylinder, and the compression of the gas inside the compression cylinder.

[0017] Subject matter of the invention

[0018] It is an aim of the present invention to produce a reciprocating compressor which is capable of overcoming the drawbacks described above.

[0019] In accordance with the present invention, there is produced a reciprocating compressor comprising:

[0020] - an outer casing having a base support;

[0021] - an actuation unit, which is arranged in the outer casing and comprises a linear actuator of annular shape extending around a central axis, and a compression cylinder extending along the central axis at least predominantly outside the linear actuator;

[0022] - a suspension system comprising first elastic elements arranged between the base support of the outer casing and the actuation unit; and - a sliding unit, which comprises a compression piston sliding inside the compression cylinder, the linear actuator being configured to actuate a reciprocating sliding movement of the sliding unit with respect to the compression cylinder along the central axis.

[0023] By virtue of the present invention, it is possible to enhance the efficiency of the reciprocating compressor.

[0024] In practice, the fact that the compression cylinder extends predominantly outside the linear actuator prevents transmission of heat from the linear actuator to the compression cylinder, reducing the degree to which the gas entering the compression cylinder is heated up and, as a result, improving the volumetric efficiency of the compressor.

[0025] In particular, the suspension system is configured to support the actuation unit elastically in a direction substantially parallel to the central axis, the central axis preferably extending in a substantially vertical direction.

[0026] In other words, the suspension system supports the actuation unit in the direction of sliding of the compression piston inside the compression cylinder. In this way, it is possible prevent reciprocating torque being applied to the oscillating unit and, consequently, to limit the friction forces between the compression piston and the compression cylinder in such a way as to enhance the efficiency of the reciprocating compressor.

[0027] In more detail, the first elastic elements are configured to be compressed and extend in a direction substantially parallel to the central axis.

[0028] In practice, the oscillation of the oscillating unit along the central axis causes each elastic element to deform only in a direction substantially parallel to the central axis between a compressed position and an extended position. In this way, is possible prevent the elastic elements from being subjected to a bending moment.

[0029] Brief description of the figure

[0030] Further features and advantages of the present invention will become clear from the following description of non-limiting example embodiments thereof, provided with reference to the Figure of the attached drawings, in which the Figure is a view in cross section, with parts removed for the sake of clarity, of a reciprocating compressor produced in accordance with the present invention.

[0031] Preferred embodiment of the invention With reference to the Figure, a reciprocating compressor is generally designated by the reference numeral 1 , which reciprocating compressor may, in particular, be used in an electrical appliance such as a refrigerator, an air conditioning unit or a heat pump.

[0032] The reciprocating compressor 1 comprises an outer casing 2 having a base support 3; an actuation unit 4, which is arranged in the outer casing 2 and comprises a linear actuator 5 of annular shape extending around a central axis A1 and a compression cylinder 6 extending along the central axis A1 , predominantly outside the linear actuator 5; a suspension system 7 comprising elastic elements 8 arranged between the base support 3 of the outer casing 2 and the actuation unit 4; and a sliding unit 9, which comprises a compression piston 10 engaged slidingly inside the compression cylinder 6.

[0033] In particular, the linear actuator 5 is configured to actuate a reciprocating sliding movement of the sliding unit 9 with respect to the compression cylinder 6 along the central axis A1 .

[0034] In more detail, the linear actuator 5 is configured to control the reciprocating sliding movement of the compression piston 10 inside the compression cylinder 6 in such a way as to selectively take in gas into the compression cylinder 6 and compress said gas inside the compression cylinder 6. In practice, said reciprocating sliding movement of the compression piston 10 comprises an intake stroke, in which the gas is taken into the compression cylinder 6, and a compression stroke, in which the compression piston 10 compresses the gas taken into the compression cylinder 6.

[0035] In particular, the outer casing 2 delimits a closed chamber 11 , inside which are arranged the actuation unit 4, the suspension system 7 and the sliding unit 9. In more detail, the suspension system 7 is configured to support the actuation unit 4 elastically in a direction substantially parallel to the central axis A1 .

[0036] In practice, the elastic elements 8 are configured to be compressed and extend in a direction substantially parallel to the central axis A1 , which, in particular, extends in a substantially vertical direction.

[0037] In the case described and illustrated here, which is not limiting on the present invention, each elastic element 8 comprises a helical spring and is configured to selectively be compressed and extend when the distance between the base support 3 of the outer casing 2 and the actuation unit 4 varies. In particular, each elastic element 8 extends along a respective longitudinal axis A2 substantially parallel to the central axis A1.

[0038] In particular, the linear actuator 5 is of electric type and comprises a stator portion 12 and a movable portion 13, which is provided with permanent magnets and is coupled to the stator portion 12 slidingly along the central axis A1 .

[0039] In more detail, the stator portion 12 is integrally coupled to the compression cylinder 6, is of annular shape and extends around the central axis A1. Furthermore, the stator portion 12 is provided with an annular sliding seat 14 formed at one circumferential end of the stator portion 12.

[0040] The movable portion 13 is of tubular shape and is engaged inside the sliding seat 14 slidingly along the central axis A1 .

[0041] In accordance with the present invention, the compression cylinder 6 comprises a delivery valve 15 arranged at a distance D1 from the base support 3 measured along the central axis A1 , and a free end 16 arranged at a distance D2 from the base support 3, which is measured along the central axis A1 and is greater than the distance D1 .

[0042] In other words, the compression cylinder 6 extends along the central axis A1 between the delivery valve 15 and the free end 16.

[0043] The stator portion 12 of the linear actuator 5 extends between a distance D3 from the base support 3 measured along the central axis A1 and a distance D4 from the base support 3, which is measured along the central axis A1 and is smaller than the distance D3. The distance D1 is greater than the distance D4 and, in particular, is between the distance D3 and the distance D4.

[0044] In practice, the linear actuator 5 delimits a cylindrical space 17 inside the stator portion 12. The compression cylinder 6 extends predominantly outside the cylindrical space 17 and, in particular, the free end 16 is arranged at a distance from said cylindrical space 17.

[0045] The reciprocating compressor 1 further comprises elastic elements 18, which connect the sliding unit 9 elastically to the actuation unit 4 in such a way as to provide a return force to the sliding of the compression piston 10 in the compression cylinder 6.

[0046] In the case described and illustrated here, the actuation unit 9 comprises a support element 19, which is integrally coupled to the stator portion 12 of the linear actuator 5 and is interposed between the linear actuator 5 and the suspension system 7; and a connection frame 20, which integrally connects the stator portion 12 of the linear actuator 5 and the compression cylinder 6.

[0047] In particular, the actuation unit 4 comprises a dissipation chamber 21 , which is arranged inside the linear actuator 5 and is configured to contain compressed gas exiting the compression cylinder 6 in such a way as to dissipate pressure waves generated by the phases of intake and compression of the gas inside the compression cylinder 6.

[0048] In practice, the dissipation chamber 21 is in fluidic communication with the compression cylinder 6 and faces the delivery valve 15 of the compression cylinder 6.

[0049] In particular, the dissipation chamber 21 is arranged inside the stator portion 12 of the linear actuator 5, in particular inside the cylindrical space 17. In more detail, the dissipation chamber 21 is arranged between the delivery valve 15 of the compression cylinder 6 and the support element 19.

[0050] In the case described and illustrated here, the sliding unit 9 comprises a connection element 22, which connects the compression piston 10 to the movable portion 13 of the linear actuator 5; and a dissipation chamber 23, which is in fluidic communication with the compression piston 10 and the compression cylinder 6, and is configured to contain the gas entering the compression cylinder 6 in such a way as to dissipate pressure waves generated by the phases of intake and compression of the gas inside the compression cylinder 6.

[0051] In accordance with the present invention, the reciprocating compressor 1 comprises a cooling circuit 24, which is formed inside the actuation unit 4 and is configured to allow the passage of a cooling fluid inside the actuation unit 4; and a pumping assembly 25 provided with at least one supply pump 26, which is arranged between the base support 3 of the outer casing 2 and the actuation unit 4 and is configured to supply the cooling fluid to the cooling circuit 24.

[0052] In particular, the cooling circuit 24 extends through the compression cylinder 6 and the linear actuator 5.

[0053] In the case described and illustrated here, the cooling circuit 24 comprises a plurality of ducts formed inside the actuation unit 4.

[0054] In particular, the cooling circuit 24 comprises a delivery duct 27, which is formed in the support element 19 and is in fluidic communication with the supply pump 26; a delivery duct 28, which is formed in the stator portion 12 of the linear actuator 5 and is in fluidic communication with the delivery duct 27; a delivery duct 29, which is formed in the connection frame 20 and is in fluidic communication with the delivery duct 28; an annular duct 30, which is formed in the compression cylinder 6 and is in fluidic communication with the delivery duct 29; a return duct 31 , which is formed in the connection frame 20 and is in fluidic communication with the annular duct 30; a return duct 32, which is formed in the stator portion 12 of the linear actuator 5 and is in fluidic communication with the return duct 31 ; and a return duct 33, which is formed in the support element 19 and is in fluidic communication with the return duct 32.

[0055] The pumping assembly 25 is immersed in the cooling liquid, which is contained inside the outer casing 2, in particular between the base support 3 and the support element 19, and is in fluidic communication with an inlet of the supply pump 26 and with an outlet of the return duct 33.

[0056] In more detail, the delivery duct 28 and the return duct 32 are arranged inside the stator portion 12 of the linear actuator 5 in such a way that the passage of the cooling fluid in the delivery duct 28 and in the return duct 32 allows cooling of the stator portion 12.

[0057] In the case described and illustrated here, which is not limiting on the present invention, the pumping assembly 25 comprises a plurality of supply pumps 26 arranged parallel to one another between the base support 3 of the outer casing 2 and the stator portion 12 of the linear actuator 5. In particular, the pumping assembly 25 comprises one or more supply pumps 26 in parallel.

[0058] In the case described and illustrated here, which is not limiting on the present invention, each supply pump 26 extends along a respective longitudinal axis A2 substantially parallel to the central axis A1 . In particular, each supply pump 26 is coupled to the actuation unit 4 and to the base support 3 of the outer casing 2 in parallel with the elastic elements 8. In this way, the elastic elements 8 and the supply pump 26 form a suspension system of the spring-damper type.

[0059] In accordance with an embodiment, each supply pump 26 is integrated in a respective elastic element 8. In practice, each supply pump 26 is arranged inside the helical spring of the respective elastic element 8.

[0060] Note that the supply pumps 26 may take up any other position in the space between the outer casing 2 and the stator portion 12 of the linear actuator 5, without the need to be integrated in respective elastic elements 8.

[0061] In more detail, each supply pump 26 is of reciprocating type, comprises a pumping cylinder 34 and a pumping piston 35 engaged slidingly in the pumping cylinder 34, and is configured to dampen the oscillations of the actuation unit 4 with respect to the base support 3 of the outer casing 2 and supply the cooling fluid to the cooling circuit 24.

[0062] In practice, each supply pump 26 is coupled to the stator portion 12 of the linear actuator 5 and to the outer casing 2 in such a way as to be actuated by the oscillations of the stator portion 12 with respect to the outer casing 2.

[0063] In use and with reference to Figure 1 , the actuation of the stator portion 12 of the linear actuator 5 causes the movable portion 13 to slide in the sliding seat 14 along the central axis A1. Since the movable portion 13 is rigidly secured to the connection element 22 and to the compression piston 10, the sliding of the movable portion 13 in the sliding seat 14 causes the sliding of the compression piston 10 inside the compression cylinder 6.

[0064] The elastic elements 18 generate a return force between the connection frame 20 and the connection element 22 which causes the reciprocating sliding movement of the compression piston 10 inside the compression cylinder 6 in such a way as to selectively take in and compress the gas in the compression cylinder 6.

[0065] The reciprocating sliding movement of the sliding unit 9 with respect to the actuation unit 4 along the central axis A1 causes oscillations of the actuation unit 4 with respect to the base support 3 of the outer casing 2. In other words, the distance between the base support 3 of the outer casing 2 and the actuation unit 4 measured along the central axis A1 varies intermittently.

[0066] By virtue of the fact that the oscillations of the actuation unit 4 are directed only along the central axis A1 , each elastic element 8 applies an elastic force to the actuation unit 4 along the respective longitudinal axis A2, substantially parallel to the central axis A1. In this way, the suspension system 7 does not apply any reciprocating torque to the actuation unit 4.

[0067] Furthermore, since the compression cylinder 6 extends predominantly outside the linear actuator 5, it is possible to limit the degree to which the gas entering the compression cylinder 6 heats up, improving the volumetric efficiency of the reciprocating compressor 1.

[0068] Lastly, it is clear that the present invention covers other alternatives of the embodiments described that fall within the scope of protection of the attached claims.

Claims

Claims1 . Reciprocating compressor comprising:- an outer casing (2) having a base support (3);- an actuation unit (4), which is arranged in the outer casing (2) and comprises a linear actuator (5) of annular shape extending around a central axis (A1), and a compression cylinder (6) extending along the central axis (A1) at least predominantly outside the linear actuator (5);- a suspension system (7) comprising first elastic elements (8) arranged between the base support (3) of the outer casing (2) and the actuation unit (4); and- a sliding unit (9), which comprises a compression piston (10) sliding inside the compression cylinder (6), the linear actuator (5) being configured to actuate a reciprocating sliding movement of the sliding unit (9) with respect to the compression cylinder (6) along the central axis (A1).

2. Reciprocating compressor according to Claim 1 , in which the suspension system (7) is configured to support the actuation unit (4) elastically in a direction substantially parallel to the central axis (A1), the central axis (A1) preferably extending in a substantially vertical direction.

3. Reciprocating compressor according to Claim 1 or 2, in which the first elastic elements (8) are configured to be compressed and extend in a direction substantially parallel to the central axis (A1).

4. Reciprocating compressor according to any of the preceding claims, in which the compression cylinder (6) comprises a delivery valve (15) arranged at a first distance (D1) from the base support (3) measured along the central axis (A1), and a free end (16) arranged at a second distance (D2) from the base support (3), which is measured along the central axis (A1) and is greater than the first distance (D1); the linear actuator (5) comprising a stator portion (12)extending between a third distance (D3) from the base support (3) measured along the central axis (A1) and a fourth distance (D4) from the base support (3), which is measured along the central axis (A1) and is smaller than the third distance (D3); the first distance (D1) being greater than the fourth distance (D4) and, preferably, being between the third distance (D3) and the fourth distance (D4).

5. Reciprocating compressor according to Claim 4, in which the linear actuator (5) comprises a movable portion (13) of tubular shape, which is coupled slidingly to the stator portion (12) at one circumferential end of the stator portion (12).

6. Reciprocating compressor according to any of the preceding claims, in which the actuation unit (4) comprises a dissipation chamber (21), which is configured to contain compressed gas exiting the compression cylinder (6) and is arranged inside the linear actuator (5).

7. Reciprocating compressor according to any of the preceding claims, and comprising at least one second elastic element (18), which connects the sliding unit (9) elastically to the actuation unit (4).

8. Reciprocating compressor according to any of the preceding claims, and comprising a cooling circuit (24), which is formed inside the actuation unit (4) and is configured to allow the passage of a cooling fluid inside the actuation unit (4).

9. Reciprocating compressor according to Claim 8, and comprising a pumping assembly (25) provided with at least one supply pump (26), which is arranged between the base support (3) of the outer casing (2) and the actuation unit (4) and is configured to dampen the oscillations of the actuation unit (4) with respect to the base support (3) and supply the cooling fluid to the cooling circuit (24).

10. Reciprocating compressor according to Claim 9, in which the at least one supply pump (26) extends along a respective longitudinal axis (A2)substantially parallel to the central axis (A1); preferably, the at least one supply pump (26) is coupled to the actuation unit (4) and to the base support

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