Compressor

This compressor is provided with a motor, a plurality of shafts each having a gear, a housing (30), and a plurality of impeller sections. The housing (30) includes a first housing element (31) and a second housing element (32) connectable to the first housing element from above and separable from the first housing element. A first upper end surface support section (41) is formed on an upper end surface of the first housing element (31). The housing (30) has at least one insertion support section (40A) having a shape that enables insertion of the gear and that supports the shaft, at a height position different from a height position of the first upper end surface support section (41).

TECHNICAL FIELD

The present invention relates to a compressor.

BACKGROUND ART

Centrifugal multistage compressors are conventionally known. For example, Patent Document 1 describes a three-stage compressor. The compressor includes a motor, an input shaft having an input gear, a first pinion shaft having a first-second stage pinion gear, a second pinion shaft having a three stage pinion gear, a first stage impeller, a second stage impeller, a third stage impeller, and a step-up gear housing. The number of teeth (pitch diameter) of the input gear is set to be larger than the number of teeth (pitch diameter) of each pinion gear. The motor is connected to the input shaft such that the input shaft is drivable and rotatable. In other words, the input gear and the pinion gears each serve as a step-up gear. The first stage impeller is connected to one end of the first pinion shaft. The second stage impeller is connected to the other end of the first pinion shaft. The third stage impeller is connected to one end of the second pinion shaft. The step-up gear housing places the input gear, the first-second stage pinion gear, and the third stage pinion gear, and has a shape that allows the opposite ends of the input shaft, the opposite ends of the first pinion shaft, and the opposite ends of the second pinion shaft to be exposed. The step-up gear housing supports the input shaft, the first pinion shaft, and the second pinion shaft such that each of the first-second stage pinion gear and the third stage pinion gear is engaged with the input gear. Specifically, the step-up gear housing includes a lower step-up gear housing and an upper step-up gear housing that are separable from and connectable to each other in an up and down direction. The shafts are arranged side-by-side along a division surface between the lower and upper step-up gear housings (on an upper end surface of the lower step-up gear housing). Accordingly, supporting portions for supporting the shafts are formed on the upper end surface of the lower step-up gear housing, thereby facilitating the installation of the shafts (in particular, the input shaft that has the input gear having the large pitch diameter) in the housing. Specifically, the shafts are first placed on the supporting portions formed on the upper end surface of the lower step-up gear housing. Then, the upper step-up gear housing is connected to the lower step-up gear housing from above. Accordingly, the installation of the shafts in the housing is completed.

In the compressor described above, when the motor is driven, the first pinion shaft is rotated through the input shaft, the input gear, and the first-second stage pinion gear, and at the same time, the second pinion shaft is rotated through the input shaft, the input gear, and the third pinion gear. Accordingly, the air compressed by the first stage impeller is further compressed by the second stage impeller, and the air compressed by the second stage impeller is subsequently further compressed by the third stage impeller.

The development of multistage compressors has been recently progressed. However, in the compressor described in Patent Document 1, it is difficult to increase the number of compression stages while preventing complicated installation of the shafts in the housing, a significant increase in size of the housing, and occurrence of poor engagement between the gears.

For example, in the compressor described in Patent Document 1, if the number of compression stages is increased while preventing the complicated installation of the shafts in the housing, an additional pinion shaft will be disposed on the upper end surface of the lower step-up gear housing. In this case, the size of the housing in a direction orthogonal to the shafts disposed on the upper end surface is increased. This becomes prominent as the number of additional pinion shafts (the number of additional compression stages) increases.

In addition, if the number of compression stages is increased while preventing the increase in size of the housing in the orthogonal direction, and the complicated installation of the shafts in the housing, for example, the upper step-up gear housing will be further divided in the up and down direction, and an additional pinion shaft will be placed along a division surface of the upper step-up gear housing. In this case, the number of divisions of the housing is increased. Therefore, tolerance generated in assembling the housing is accumulated, whereby the poor engagement between the gears may occur.

CITATION LIST

Patent Document

Patent Document 1: JP 2013-60882 A

SUMMARY OF INVENTION

An object of the present invention is to provide a compressor capable of increasing the number of compression stages while preventing complicated installation of shafts in a housing, a significant increase in size of the housing, and occurrence of poor engagement between gears.

A compressor according to an aspect of the present invention includes: a motor having an output shaft; a plurality of shafts each having a gear; a housing placing the gears and supporting the shafts such that opposite ends of each of the shafts are exposed; and a plurality of impeller portions each fixed to at least one end of the opposite ends of each of the shafts. The housing includes a first housing element and a second housing element connectable to the first housing element from above and separable from the first housing element. A first upper end surface supporting section is formed on an upper end surface of the first housing element, the first upper end surface supporting section supporting some of the shafts. The housing has at least one insertion support portion at a position in height different from a position in height of the first upper end surface supporting section, the at least one insertion support portion having a shape that enables the gear to be inserted into the at least one insertion support portion and enables the shaft to be supported by the at least one insertion support portion.

DESCRIPTION OF EMBODIMENTS

A compressor according to an embodiment of the present invention will be described with reference toFIGS. 1 to 7.

As shown inFIG. 1, the compressor includes a motor10having an output shaft12, a plurality of shafts20each having a gear21, a housing30, and a plurality of impeller portions50. In the embodiment, carbon dioxide gas is compressed by the impeller portions50.

The shafts20includes five shafts (a first shaft20A to a fifth shaft20E) and an input shaft20F, shown inFIG. 7.

The first shaft20A has a first pinion gear21A as the gear21. The second shaft20B has a second pinion gear21B as the gear21. The third shaft20C has a third pinion gear21C as the gear21. The fourth shaft20D has a fourth pinion gear21D as the gear21. The fifth shaft20E has a fifth pinion gear21E as the gear21.

The input shaft20F has a bull gear21F as the gear21. The number of teeth (pitch diameter) of the bull gear21F is set to be larger than the number of teeth (pitch diameter) of each of the pinion gears21A to21E. The output shaft12of the motor10is connected to the input shaft20F via a coupling14. The output shaft12may be, however, connected to one of the other shafts instead of the input shaft20F.

The housing30places the gears21and supports the shafts20such that at least one ends of each of the shafts20are exposed. As shown inFIG. 2, the housing30includes a first housing element31, a second housing element32, and a third housing element33. InFIG. 2, the shafts20are not shown.

The first housing element31includes a square tubular side wall31A and a bottom wall31B covering an opening at a bottom of the side wall31A. A first upper end surface supporting section41is formed on an upper end surface of the first housing element31so as to support some of the shafts20. Specifically, the first upper end surface supporting section41includes a second shaft supporting portion41B supporting the second shaft20B, a third shaft supporting portion41C supporting the third shaft20C, and an input shaft supporting portion41F supporting the input shaft20F. The second shaft supporting portion41B, the input shaft supporting portion41F, and the third shaft supporting portion41C are arranged side-by-side in this order. As shown inFIGS. 6 and 7, the second shaft supporting portion41B is formed in such a position that allows the second shaft20B to be supported by the second shaft supporting portion41B such that the second pinion gear21B is engaged with the bull gear21F. The third shaft supporting portion41C is formed in such a position that allows the third shaft20C to be supported by the third shaft supporting portion41C such that the third pinion gear21C is engaged with the bull gear21F. The supporting portions41B,41C, and41F are formed to be recessed downwardly from the upper end surface of the side wall31A other than the supporting portions41B,41C, and41F. In the embodiment, the supporting portions41B,41C, and41F are formed into a semicircular are.

The first housing element31has an insertion support portion40A supporting the first shaft20A. As shown inFIG. 2, the insertion support portion40A is provided in a portion of the first housing element31, and the portion is located below a position in height of the first upper end surface supporting section41. Specifically, as shown inFIGS. 6 and 7, the insertion support portion40A is formed in such a position that allows the first shaft20A to be supported by the insertion support portion40A such that the first pinion gear21A is engaged with the bull gear21F. The insertion support portion40A has a shape that enables the first pinion gear21A to be inserted into the insertion support portion40A and enables the first shaft20A to be supported by the insertion support portion40A.

The second housing element32is connectable to the first housing element31from above and is separable from the first housing element31. The second housing element32is formed into a square tube. A portion of a lower end surface of the second housing element32, which is opposite the first upper end surface supporting section41in the up and down direction, is formed into a semicircular are that is recessed upwardly from the remaining portion of the lower end surface of the second housing element32.

A second upper end surface supporting section42is formed on an upper end surface of the second housing element32so as to support some of the shafts20. Specifically, the second upper end surface supporting section42includes a fourth shaft supporting portion42D supporting the fourth shaft20D, and a fifth shaft supporting portion42E supporting the fifth shaft20E. As shown inFIG. 7, the fourth shaft supporting portion42D is formed in such a position that allows the fourth shaft20D to be supported by the fourth shaft supporting portion42D such that the fourth pinion gear21D is engaged with the bull gear21F. The fifth shaft supporting portion42E is formed in such a position that allows the fifth shaft20E to be supported by the fifth shaft supporting portion42E such that the fifth pinion gear21E is engaged with the bull gear21F. The supporting portions42D,42E are formed to be recessed downwardly from the upper surface of the second housing element32other than the supporting portions42D,42E. In the embodiment, the supporting portions42D,42E are formed into a semicircular arc.

The third housing element33is connectable to the second housing element32from above and separable from the second housing element32. The third housing element33is formed into a square tube. A portion of a lower end surface of the housing element33, which is opposite the second upper end surface supporting section42in the up and down direction, is formed into a semicircular are recessed upwardly from the remaining portion of the lower end surface of the third housing element33.

The impeller portions50each are fixed to at least one end of the opposite ends of each of the first shaft20A to the fifth shaft20E. Accordingly, when the respective impeller portions50are fixed to the opposite ends of each of the shafts20A to20E, ten-stage compression becomes possible. The impeller portions50are covered by a casing (not shown), and the impeller portions50compress gas (in the embodiment, carbon dioxide) within the casing. For example, as shown inFIG. 1, the gas compressed by an impeller portion50B fixed to one end of the second shaft20B is cooled by a cooler15, and is subsequently further compressed by an impeller portion50B fixed to the other end of the second shaft20B. After that, the gas compressed by an impeller portion50C fixed to one end of the third shaft20C is cooled by a cooler16, and is subsequently further compressed by an impeller portion50C fixed to the other end of the third shaft20C. The gas is also compressed by the impeller portions50fixed to each of the first shaft20A, the fourth shaft20D, and the fifth shaft20E, and is appropriately cooled by a cooler provided along a flow passage between the impeller portions.

In the embodiment, each of the shafts20A to20F are received by a bearing portion70provided in a bearing housing60. InFIG. 1, the bearing housings60and the bearing portions70are not shown.FIG. 2shows only the bearing housing60that holds the bearing portion70receiving the first shaft20A. The bearing housings60and the bearing portions70will be described below with reference to theFIGS. 3 and 4.FIG. 3shows the bearing portion70receiving the first shaft20A, and the bearing housing60holding this bearing portion70.

The bearing housing60is formed into a ring. As shown inFIG. 3, the bearing housing60is fixed to the first housing element31by fixing tools62such as bolts. Specifically, the first housing element31has a circular through hole (insertion support portion40A) in which the bearing housing60is fitted. The bearing housing60is fixed to a side surface of the first housing element31by the fixing tools62with the bearing housing60fitted in the through hole. The through hole is set to have a diameter larger than a tip diameter of the first pinion gear21A.

The bearing portion70includes an inner ring81, rolling elements (not shown), an outer ring82, and a preventing portion83. In the embodiment, the bearing portion70is an eccentric bearing. The bearing portion70is, however, limited to the eccentric bearing. InFIG. 4, the inner ring81and the outer ring82are not shown.

The preventing portion83is fixed to an outer periphery of the outer ring82and prevents the rotation of the outer ring82relative to the bearing housing60. Specifically, the bearing housing60includes a receiving portion60areceiving the preventing portion83, and the preventing portion83is disposed within the receiving portion60a. More specifically, the receiving portion60aincludes a contact portion60bthat is in contact with the preventing portion83in a circumferential direction of the outer ring82. The preventing portion83is in contact with the contact portion60b, thereby preventing the rotation of the outer ring82relative to the bearing housing60or the first housing element31. The receiving portion60ahas a shape recessed radially outward of the bearing housing60from an inner periphery of the bearing housing60. The receiving portion60aalso has a shape that is open in a direction parallel to the central axis of the first shaft20A (in a thickness direction of the bearing housing60). The contact portion60bis formed into a plane that is parallel to the first housing element31other than the first upper end surface supporting section41. In the embodiment, the preventing portion83includes a protruded portion84and an adjusting portion85.

The protruded portion84has a shape protruded outwardly of the outer ring82from the outer periphery of the outer ring82. The protruded portion84has a female screw portion.

The adjusting portion85is a member that allows the position of the protruded portion84relative to the contact portion60bto be adjusted with the adjusting portion85in contact with the contact portion60b. The adjusting portion85has a male screw portion that is in engagement with the female screw portion with the adjusting portion85in contact with the contact portion60b. The male screw portion is configured such that the male screw portion is rotated relative to the female screw portion, thereby displacing the protruded portion84between a first position and a second position. The first position is a position where a dimension between the protruded portion84and the contact portion60bis a first dimension. The second position is a position where a dimension between the protruded portion84and the contact portion60bis a second dimension larger than the first dimension. The male screw portion is rotated relative to the female screw portion, thereby displacing the position of the protruded portion84relative to the contact portion60b. As a result, the position of the outer ring82relative to the first housing element31is displaced. In other words, the male screw portion is rotated relative to the female screw portion, thereby displacing the position of a central axis O of the first shaft20A, as shown inFIG. 6. Accordingly, the engagement between the first pinion gear21A and the bull gear21F is adjusted.

In the embodiment, the preventing portions83of the bearing portions70receiving the second shaft20B to the fifth shaft20E have the same configuration (adjusting function) as the preventing portion83of the bearing portion70receiving the first shaft20A. Meanwhile, the preventing portion83of the bearing portion70receiving the input shaft20F has no adjusting function. The bearing portions70receiving the second shaft20B to the fifth shaft20E and the input shaft20F, and the bearing housings60holding these bearing portions70each are formed divisible into two in the up and down direction.

A process for assembling the compressor according to the embodiment will be described next with reference toFIGS. 6 and 7.

First, the first shaft20A is inserted into the insertion support portion40A of the first housing element33, and then, the bearing portion70and the bearing housing60are installed. Specifically, one end of the first shaft20A is inserted into the insertion support portion40A such that the first pinion gear21A reaches the inside of the first housing element31through the insertion support portion40A from the outside of the first housing element31. Then, the bearing housing60is fixed to the first housing element31with the bearing portion70and the bearing housing60located around the other end of the first shaft20A.

Next, three shafts, that is, the input shaft20F, the second shaft20B, and the third shaft20C, are placed on the first upper end surface supporting section41. At this time, respective lower parts (not shown) of the bearing housings60and respective lower parts (not shown) of the bearing portions70are first placed on the second shaft supporting portion41B, the third shaft supporting portion41C, and the input shaft supporting portion41F. Then, the shafts20B,20C, and20F are, respectively, placed on the supporting portions41B,41C, and41F. Subsequently, upper parts (not shown) of the bearing housings60and upper parts of (not shown) the bearing portions70are, respectively, connected to the lower parts from above the second shaft supporting portion41B, the third shaft supporting portion41C, and the input shaft supporting portion41F. After that, the second housing element32is connected to the first housing element31from above. The upper parts and the second housing element32may be simultaneously connected to the first housing element31.

Subsequently, as shown inFIG. 7, the two shafts, that is, the fourth shaft20D and the fifth shaft20E, are placed on the second upper end surface supporting section42. The process for placing theses shafts is the same as that for placing three shafts20B,20C, and20F on the first upper end surface supporting section41. Lastly, the upper parts of the bearing housing60, those of the bearing portions70, and the third housing element33are connected to the second housing element32from above.

The installation of the first shaft20A in the first housing element31may be performed after the connection of the third housing element33to the second housing element32. Furthermore, at any time after the input shaft20F is supported by the input shaft supporting portion41F, the output shaft12of the motor10is connected to the input shaft20F.

As needed, the engagement between the bull gear21F and each of the pinion gears21A to21E is adjusted by the corresponding adjusting portion85.

As described above, in the compressor according to the embodiment, the housing30has the insertion support portion40A at the position in height different from the position in height of the first upper end surface supporting section41, and the insertion support portion40A allows the first pinion gear21A to be inserted thereinto. Therefore, it is possible to increase the number of compression stages while preventing the significant increase in size of the housing30in the direction orthogonal to the central axes of the shafts20B,20C, and20F which are supported by the first upper end surface supporting section41, the complicated installation of the shafts in the housing30, and the occurrence of the poor engagement between the gears. Specifically, the insertion support portion40A has a shape that enables the first pinion gear21A to be inserted into the insertion support portion40A and enables the first shaft20A to be supported by the insertion support portion40A. Accordingly, the first shaft20A is inserted into the insertion support portion40A such that the first pinion gear21A reaches the inside of the housing30through the insertion support portion40A from the outside of the housing30. Thus, the first shaft20A is installed in the housing30. Therefore, it is possible to easily install an additional shaft in the housing30(increase the number of compression stages) without increasing the number of divisions of the housing30, in other words, while preventing the occurrence of the poor engagement between the gears21F,21A due to accumulation of the tolerance generated in assembling the housing30.

In addition, in the embodiment, the first upper end surface supporting section41includes the input shaft supporting portion41F that supports the input shaft20F having the bull gear21F. The output shaft12of the motor10is connected to the input shaft20F. Therefore, the gears can serve as step-up gears, and the complicated installation of the input shaft20F, which has the bull gear21F having the large number of teeth (pitch diameter) in the housing30, can be prevented.

Furthermore, in the embodiment, the housing30includes the third housing element33. The second upper end surface supporting section42is formed on the upper end surface of the second housing element32. The insertion support portion40A is formed a portion of the first housing element31, and the portion is located below the first upper end surface supporting section41. Therefore, it is possible to effectively increase the number of compression stages (the number of shafts) while preventing the significant increase in size of the housing30. Specifically, the shafts20B to20F are supported by the first upper end surface supporting section41and the second upper end surface supporting section42located above the first upper end surface supporting section41, and thus, the insertion support portion40A is formed below the first upper end surface supporting section41. Therefore, the gears21A to21F can be effectively disposed in a space within the housing30.

In the embodiment, the housing30also can support the five shafts20A to20E. Therefore, when the opposite ends of each of the five shafts are fixed to the respective impeller portions50, up to ten-stage compression becomes possible.

In addition, in the embodiment, the preventing portion83includes the protruded portion84and the adjusting portion85. In other words, the preventing portion83has both a function of preventing the rotation of the outer ring82relative to the bearing housing60and a function of adjusting the positions of the central axes of the shafts (the engagement between the bull gear21F and each of the pinion gears21A to21E), thereby simplifying the configuration. Specifically, the adjusting portion85is in contact with the contact portion60b, thereby preventing the rotation of the outer ring82relative to the bearing housing60. In addition, the position of the protruded portion84relative to the contact portion60bis displaced, thereby displacing the positions of the bearing portion70and the central axis of the shaft supported by this bearing portion70relative to the bearing housing60(housing30). Therefore, the engagement between the gears is adjusted.

Specifically, in the embodiment, the protruded portion84has the female screw portion, and the adjusting portion85has the male screw portion that is in engagement with the female screw portion with the adjusting portion85in contact with the contact portion60b. Therefore, only rotating the adjusting portion85, which has the male screw portion, relative to the protruded portion84, which has the female screw portion, enables adjustment of the engagement between the gears.

Furthermore, in the embodiment, the receiving portion60ahas a shape that is open in the direction parallel to the central axes of the shafts20A to20E. Accordingly, the adjusting portion85provided within the receiving portion60acan be adjusted from the side of the bearing housing60, thereby facilitating adjustment of the central positions of the shafts20A to20E.

The embodiment according to the present invention is described above. It should be considered that the embodiment disclosed herein is exemplary in all respects, and are not limitative. The scope of the present invention is not represented by the above description but by the scope of claims, and it is intended that connotation equivalent to the scope of claims, and all changes within the scope are included.

For example, the insertion support portion40A may be formed in the second housing element32or the third housing element33. In addition, the number of insertion support portions40A is not limited to one. For example, inFIG. 2, an additional insertion support portion may be formed in a portion of the first housing element31, and the portion is located leftward of the portion where the insertion support portion40A is formed.

The number of shafts each having a pinion gear is limited to five.

The second housing element32and the third housing element33may be not formed divisible but formed integrally. In this case, the fourth shaft supporting portion42D and the fifth shaft supporting portion42E each may have the same configuration as the insertion support portion40A.

The bearing housings60and the bearing portions70which are placed on the first upper end surface supporting section41are each limited to be formed divisible in the up and down direction. In addition, the bearing housings60and the bearing portions70which are placed on the second upper end surface supporting section42are each limited to be formed divisible in the up and down direction.

The impeller portions50fixed to the first shaft20A may be used as expanding portions, and the impeller portions50connected to the second shaft20B to the fifth shaft20E may be used as compressing portions.

The compressor according to the above embodiment will be outlined now.

The compressor according to the embodiment includes: a motor having an output shaft; a plurality of shafts each having a gear; a housing placing the gears and supporting the shafts such that opposite ends of each of the shafts are exposed; and a plurality of impeller portions each fixed to at least one end of the opposite ends of each of the shafts. The housing includes a first housing element and a second housing element connectable to the first housing element from above and separable from the first housing element. A first upper end surface supporting section is formed on an upper end surface of the first housing element, the first upper end surface supporting section supporting some of the shafts. The housing has at least one insertion support portion at a position in height different from a position in height of the first upper end surface supporting section, the at least one insertion support portion having a shape that enables the gear to be inserted into the at least one insertion support portion and enables the shaft to be supported by the at least one insertion support portion.

In the compressor according to the embodiment, the housing has the insertion support portion at the position in height different from the position in height of the first upper end surface supporting section, and the insertion support portion allows the gear to be inserted thereinto. Therefore, it is possible to increase the number of compression stages while preventing the significant increase in size of the housing in the direction orthogonal to the central axes of the shafts supported by the first upper end surface supporting section, the complicated installation of the shafts in the housing, and the occurrence of the poor engagement between the gears. Specifically, the insertion support portion has a shape that enables the gear to be inserted into the insertion support portion and enables the shaft to be supported by the insertion support portion. Accordingly, the shaft is inserted into the insertion support portion such that the gear reaches the inside of the housing through the insertion support portion from the outside of the housing. Thus, the shaft is installed in the housing. Therefore, it is possible to easily install an additional shaft in the housing (increase the number of compression stages) without increasing the number of divisions of the housing, in other words, while preventing the occurrence of the poor engagement between the gears due to accumulation of the tolerance generated in assembling the housing.

In the above compressor, the shafts may include an input shaft having a bull gear as the gear, the bull gear having the number of teeth that is larger than the number of teeth of each of the other gears. The first upper end surface supporting section may include an input shaft supporting portion that supports the input shaft such that the bull gear is engaged with each of the gears other than the bull gear. The output shaft of the motor may be connected to the input shaft.

Accordingly, the gears can serve as step-up gears, and the complicated installation of the input shaft, which has the bull gear having the large number of teeth (pitch diameter), in the housing can be prevented.

In the above compressor, the housing may further include a third housing element connectable to the second housing element from above and separable from the second housing element. A second upper end surface supporting section may be formed on an upper end surface of the second housing element, the second upper end surface supporting section supporting some of the shafts other than the input shaft. The at least one insertion support portion may be formed in a portion of the first housing element, the portion located below the first upper end surface supporting section.

Accordingly, it is possible to effectively increase the number of compression stages (shafts) while preventing the significant increase in size of the housing. Specifically, the shafts are supported by the first upper end surface supporting section and the second upper end surface supporting section located above the first upper end surface supporting section, and thus, the insertion support portion is formed below the first upper end surface supporting section. Therefore, the gears can be effectively disposed in a space within the housing.

Specifically, the shafts may include: a first shaft having a first pinion gear as the gear, the first pinion gear having the number of teeth that is smaller than the number of teeth of the bull gear; a second shaft having a second pinion gear as the gear, the second pinion gear having the number of teeth that is smaller than the number of teeth of the bull gear; a third shaft having a third pinion gear as the gear, the third pinion gear having the number of teeth that is smaller than the number of teeth of the bull gear; a fourth shaft having a fourth pinion gear as the gear, the fourth pinion gear having the number of teeth that is smaller than the number of teeth of the bull gear; and a fifth shaft having a fifth pinion gear as the gear, the fifth pinion gear having the number of teeth that is smaller than the number of teeth of the bull gear. The at least one insertion support portion may be formed in such a position that allows the first shaft to be supported by the at least one insertion support portion such that the first pinion gear is engaged with the bull gear. The first upper end surface supporting section may further include a second shaft supporting portion that supports the second shaft such that the second pinion gear is engaged with the bull gear, and a third shaft supporting portion that supports the third shaft such that the third pinion gear is engaged with the bull gear. The second upper end surface supporting section may include a fourth shaft supporting portion that supports the fourth shaft such that the fourth pinion gear is engaged with the bull gear, and a fifth shaft supporting portion that supports the fifth shaft such that the fifth pinion gear is engaged with the bull gear.

Accordingly, when the opposite ends of each of the five shafts, that is, the first shaft to the fifth shaft are fixed to the respective impeller portions, up to ten-stage compression becomes possible.

The compressor may further include a bearing housing fixed in the at least one insertion support portion, and a bearing portion receiving the shaft within the bearing housing. The bearing portion may be an eccentric bearing. The bearing portion may include an inner ring, an outer ring, and a preventing portion fixed to an outer periphery of the outer ring, the preventing portion preventing rotation of the outer ring relative to the bearing housing. The bearing housing may include a contact portion being in contact with the preventing portion in a circumferential direction of the outer ring, and a receiving portion that receives at least a portion of the preventing portion. The preventing portion may have a protruded portion that is protruded outwardly of the outer ring from the outer periphery of the outer ring, and an adjusting portion that enables a position of the protruded portion relative to the contact portion to be adjusted with the adjusting portion in contact with the contact portion.

Accordingly, the preventing portion has both a function of preventing the rotation of the outer ring relative to the bearing housing and a function of adjusting the positions of the central axes of the shafts (the engagement between the gears), thereby simplifying the configuration. Specifically, the adjusting portion is in contact with the contact portion, thereby preventing the rotation of the outer ring relative to the bearing housing. In addition, the position of the protruded portion relative to the contact portion is displaced, thereby displacing the positions of the bearing portion and the central axis of the shaft supported by this bearing portion relative to the bearing housing (housing). Thus, the engagement between the gears is adjusted.

Specifically, the protruded portion may have a female screw portion. The adjusting portion may have a male screw portion that is in engagement with the female screw portion with the adjusting portion in contact with the contact portion. The male screw portion may be configured such that the male screw portion is rotated relative to the female screw portion to displace the protruded portion between a first position where a dimension between the protruded portion and the contact portion is a first dimension and a second position where the dimension between the protruded portion and the contact portion is a second dimension larger than the first dimension.

Accordingly, only rotating the adjusting portion, which has the male screw portion, relative to the protruded portion, which has the female screw portion, enables adjustment of the engagement between the gears.

In the compressor, the receiving portion may have a shape that is open in a direction parallel to central axes of the shafts.

Accordingly, the adjusting portion provided within the receiving portion can be adjusted from the side of the bearing housing, thereby facilitating the adjustment of the central position of the shaft.

In the compressor, the impeller portions may be used as compression portions that compress gas, or some of the impeller portions that are fixed to the shafts supported by the first upper end surface supporting section may be used as compressing portions, and at least one of the impeller portions that is fixed to the shaft supported by the at least one insertion support portion may be used as an expanding portion that expands gas.