Reciprocating compressor with dual oil pump

1 . A reciprocating compressor comprising:

a case containing an oil reservoir;

a motor including a stator disposed inside the case and a rotor that rotates with respect to the stator;

a drive shaft that rotates integrally with the rotor and includes a cavity formed at a lower portion thereof;

a primary oil pump inserted into the cavity of the drive shaft and disposed in the case, the primary oil pump including a coupling protrusion protruding from a lower end thereof;

a secondary oil pump into which a lower end portion of the drive shaft is inserted and coupled to the primary oil pump, the secondary oil pump including a coupling hole, formed on a bottom thereof, into which the coupling protrusion of the primary oil pump is inserted;

a primary oil passage formed between an inner circumferential surface of the cavity of the drive shaft and the primary oil pump; and

a secondary oil passage formed around the primary oil pump between an outer circumferential surface of the lower end portion of the drive shaft and the secondary oil pump,

wherein, when the drive shaft rotates, oil contained in the oil reservoir moves to an upper portion of the cavity of the drive shaft along the primary oil passage and the secondary oil passage.

2 . The reciprocating compressor of claim 1 ,

wherein the drive shaft includes a helical shaped first oil supply passage formed on an outer circumferential surface of an upper portion of the drive shaft, and

wherein the secondary oil pump is formed in a shape of a cylindrical container with a bottom.

3 . The reciprocating compressor of claim 2 ,

wherein the drive shaft includes a communication hole formed adjacent to an upper end of the cavity,

wherein the oil contained in the oil reservoir flows into the secondary oil pump through a lower portion of the secondary oil pump, and

wherein some of the oil that flows into the secondary oil pump moves upward along the primary oil passage, and the remaining oil moves upward along the secondary oil passage, flows into the cavity through the communication hole, and moves to the upper portion of the cavity along with the some of the oil moving along the primary oil pump.

4 . The reciprocating compressor of claim 3 ,

wherein the secondary oil passage is formed as a helical groove formed on the outer circumferential surface of the lower portion of the drive shaft inserted into the secondary oil pump, and

wherein a helical direction of the helical groove of the secondary oil passage is identical to a helical direction of the helical shaped first oil supply passage.

5 . The reciprocating compressor of claim 3 ,

wherein the secondary oil passage is formed as a helical groove formed on the inner circumferential surface of the secondary oil pump, and

wherein a helical direction of the helical groove of the secondary oil passage is opposite to a helical direction of the helical shaped first oil supply passage.

6 . The reciprocating compressor of claim 3 , wherein the secondary oil pump includes a plurality of oil inlets formed in at least one of a bottom or a lower portion of the outer circumferential surface adjacent to the bottom.

7 . The reciprocating compressor of claim 3 , wherein an upper end of the secondary oil passage is formed below an upper end of the secondary oil pump.

8 . The reciprocating compressor of claim 7 , wherein the upper end of the secondary oil passage is formed to correspond to the communication hole.

9 . The reciprocating compressor of claim 3 , wherein an upper end of the secondary oil pump is adjacent to a lower surface of the rotor and is located above a surface of the oil contained in the oil reservoir.

10 . The reciprocating compressor of claim 2 ,

wherein the oil contained in the oil reservoir flows into the secondary oil pump through an upper portion of the secondary oil pump, and

wherein the oil flowing into the secondary oil pump moves to a lower end of the drive shaft along the secondary oil passage, and then moves to the upper portion of the cavity of the drive shaft along the primary oil passage.

11 . The reciprocating compressor of claim 10 ,

wherein the secondary oil passage is formed as a helical groove formed on the outer circumferential surface of the lower portion of the drive shaft inserted into the secondary oil pump, and

wherein a helical direction of the helical groove of the secondary oil passage is opposite to a helical direction of the helical shaped first oil supply passage.

12 . The reciprocating compressor of claim 10 ,

wherein the secondary oil passage is formed as a helical groove formed on the inner circumferential surface of the secondary oil pump, and

wherein a helical direction of the helical groove of the secondary oil passage is identical to a helical direction of the helical shaped first oil supply passage.

13 . The reciprocating compressor of claim 10 , wherein the secondary oil pump includes at least one oil inlet formed on the outer circumferential surface adjacent to an upper end of the secondary oil pump.

14 . The reciprocating compressor of claim 10 , wherein an upper end of the secondary oil passage is formed at the upper end of the secondary oil pump.

15 . The reciprocating compressor of claim 10 , wherein an upper end of the secondary oil pump is adjacent to a lower surface of the rotor and is located below a surface of the oil contained in the oil reservoir.

16 . The reciprocating compressor of claim 2 , wherein a gap between an inner circumferential surface of the secondary oil pump and an outer circumferential surface of a lower portion of the drive shaft is 0.1 millimeters (mm) to 0.15 mm.

17 . The reciprocating compressor of claim 1 , wherein the coupling hole is formed in one of a circular, polygonal, or oval shape.

18 . The reciprocating compressor of claim 1 , wherein the primary oil pump and the secondary oil pump are coupled by screw coupling or press-fit coupling.