EP-4524494-B1 - OIL LUBRICATION-TYPE COMPRESSOR FOR CRYOCOOLER

Inventors

• SUZUKI, SHO

Dates

Publication Date

20260506

Application Date

20230417

Claims (9)

1. An oil lubrication-type compressor for a cryocooler (10) comprising: an air-cooled heat exchanger (26) that includes a cooling fan (50) and a first oil line (46) disposed to be forcibly cooled by the cooling fan (50); and a second oil line (48) that bypasses the first oil line (46) and that is disposed to be forcibly cooled by the cooling fan (50), characterized in that the air-cooled heat exchanger (26) further includes an orifice (56) provided in at least one of the first oil line (46) and the second oil line (48) so that a difference between a flow rate of an oil of the first oil line (46) and a flow rate of an oil of the second oil line (48) is reduced.
2. The oil lubrication-type compressor for a cryocooler (10) according to claim 1, wherein a length (L2) of the second oil line (48) is shorter than a length (L1) of the first oil line (46), and the orifice (56) is provided in the second oil line (48).
3. The oil lubrication-type compressor for a cryocooler (10) according to claim 1, further comprising: a compressor casing (28) that accommodates the air-cooled heat exchanger (26), wherein the compressor casing (28) includes two air intakes (52) at a portion surrounding the air-cooled heat exchanger (26), and air is taken into the air-cooled heat exchanger (26) through the air intakes (52).
4. The oil lubrication-type compressor for a cryocooler (10) according to claim 1, wherein the second oil line (48) bypasses the air-cooled heat exchanger (26).
5. The oil lubrication-type compressor for a cryocooler (10) according to claim 4, wherein the second oil line (48) includes an on-off valve (58) that operates to be closed when the cooling fan (50) is operated and to be opened when the cooling fan (50) is stopped.
6. The oil lubrication-type compressor for a cryocooler (10) according to claim 1, wherein the air-cooled heat exchanger (26) cools a refrigerant gas line (18).
7. The oil lubrication-type compressor for a cryocooler (10) according to any one of claims 1 to 6, further comprising: a liquid-cooled heat exchanger (24) that is connected in series upstream of the air-cooled heat exchanger (26).
8. The oil lubrication-type compressor for a cryocooler (10) according to claim 7, further comprising: an oil temperature sensor that is provided upstream or downstream of the liquid-cooled heat exchanger (24) or that is provided downstream of the air-cooled heat exchanger (26), wherein the cooling fan (50) operates based on an oil temperature measured by the oil temperature sensor.
9. The oil lubrication-type compressor for a cryocooler (10) according to claim 7, wherein the liquid-cooled heat exchanger (24) includes a refrigerant gas temperature sensor that is provided upstream or downstream of the liquid-cooled heat exchanger (24) on a refrigerant gas line (18), and the cooling fan (50) operates based on a refrigerant gas temperature measured by the refrigerant gas temperature sensor.

Description

Technical Field The present invention relates to an oil lubrication-type compressor for a cryocooler. Background Art An oil-lubricated helium compressor with a dual aftercooler is proposed (for example, see PTL 1). Two aftercoolers that cool helium and an oil, that is, a water-cooled aftercooler and an air-cooled aftercooler, are incorporated in the compressor. The air-cooled aftercooler is disposed in series or in parallel with the water-cooled aftercooler. By operating a fan of the air-cooled aftercooler, redundancy in a case where a cooling water circuit of the water-cooled aftercooler is blocked is provided. PTL 2 discloses an oil-lubricated helium compressor system comprising an indoor compressor unit including an oil separator and an oil absorber, and an outdoor air-cooled heat exchanger connected via an oil circulation line. PTL 3 discloses a compressor unit that includes a compressor, an aftercooler, an oil separator and absorber, pressure gauges, and suction/discharge couplings, with a cooling jacket connected in series with a water side of the aftercooler, and hose couplings for connection to an external water cooling system with a pump and fan. Citation List Patent Literature [PTL 1] Japanese Unexamined Patent Publication No. 2019-505751[PTL 2] United States Patent Publication No. 2011/107790[PTL 3] German Patent Publication No. 3023925 Summary of Invention Technical Problem The present inventor has studied the helium compressor described above and has recognized the following problems. Since the two heat exchangers including a water-cooled type and an air-cooled type are mounted on the compressor, the total length of an oil line to be cooled tends to be long, and the pressure loss of an oil flow can increase accordingly. A subsequent decrease in the flow rate of an oil can decrease the cooling capacity and can cause overheating of the compressor or a decrease in the life caused by a high-temperature operation. In particular, in a case where the temperature of cooling water supplied to the water-cooled heat exchanger is too low, the problem is likely to be manifested since oil viscosity can be nonlinearly increased at such a low temperature. As a possible measure, for example, it is conceivable to recover the flow rate of the oil by increasing input energy, such as driving an oil pump at high power. However, this is undesirable because power consumption is increased. An exemplary object of one embodiment of the present invention is to reduce a pressure loss of an oil line in an oil lubrication-type compressor for a cryocooler. Solution to Problem According to an aspect of the present invention, there is provided an oil lubrication-type compressor for a cryocooler. The compressor for a cryocooler includes an air-cooled heat exchanger that includes a cooling fan and a first oil line disposed to be forcibly cooled by the cooling fan, and a second oil line that bypasses the first oil line and that is disposed to be forcibly cooled by the cooling fan, in which the air-cooled heat exchanger further includes an orifice provided in at least one of the first oil line and the second oil line so that a difference between a flow rate of an oil of the first oil line and a flow rate of an oil of the second oil line is reduced. Advantageous Effects of Invention With the present invention, the pressure loss of the oil line in the oil lubrication-type compressor for a cryocooler can be reduced. Brief Description of Drawings Fig. 1 is a diagram schematically showing a cryocooler according to an embodiment.Fig. 2 is a diagram schematically showing an example of an oil circulation line of a compressor according to the embodiment.Fig. 3 is a diagram schematically showing another example of the oil circulation line of the compressor according to the embodiment. Description of Embodiments Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processing will be assigned with the same reference symbols, and redundant description thereof will be omitted as appropriate. The scales and shapes of shown parts are set for convenience in order to make the description easy to understand and are not to be understood as limiting unless stated otherwise. The embodiment is merely an example and does not limit the scope of the present invention. All characteristics and combinations to be described in the embodiment are not necessarily essential to the invention. Fig. 1 is a diagram schematically showing a cryocooler according to an embodiment. A cryocooler 10 includes an oil lubrication-type compressor for a cryocooler (hereinafter, also simply referred to as a compressor) 12 and a cold head 14. The compressor 12 is configured to collect a refrigerant gas of the cryocooler 10 from the cold head 14, to pressurize the collected refrigerant gas, and to supply the refrigerant gas to the