Method of manufacturing rotor assembly, rotor assembly, and turbo compressor

A method of manufacturing a rotor assembly in which a first impeller and a second impeller are fixed to a rotation shaft which is supported by a bearing so as to be rotatable, the method including: fixing the second impeller to the rotation shaft; fitting and fixing a sleeve to the rotation shaft after fixing the second impeller; fitting and fixing the bearing to the sleeve after fitting and fixing the sleeve; and fixing the first impeller after fitting and fixing the bearing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a rotor assembly, a rotor assembly, and a turbo compressor.

Priority is claimed on Japanese Patent Application No. 2010-074929, filed on Mar. 29, 2010, the content of which is incorporated herein by reference.

2. Description of Related Art

Typically, a turbo compressor that compresses and discharges a gas such as air or a refrigerant gas by rotating an impeller is known (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2007-177695). The impeller is fixed to a rotation shaft, and the rotation shaft is supported by a bearing so as to be rotatable. The rotation shaft and the impeller are rotated by the rotating power of a predetermined driving device (a motor or the like), and as the impeller is rotated, the gas is sent to a diffuser formed at the periphery of the impeller to be compressed.

The impeller, the rotation shaft, and the bearing may be assembled into a rotor assembly before being built in the turbo compressor. In a turbo compressor having two compression stages as disclosed in Japanese Patent Application No. 2007-177695, two impellers are provided on both sides with a predetermined bearing interposed therebetween. In addition, on the opposite side of a rotation shaft to the side to which an impeller is fixed, a pinion gear is molded integrally with a rotation shaft main body. Accordingly, the rotor assembly may be assembled in the order of fitting the bearing to a supporting portion after passing one impeller through the supporting portion of the rotation shaft supported by the bearing and fixing the impeller thereto at a predetermined position.

However, when a long bearing life span needs to be ensured, for example, using a large bearing is considered. In order to use the large bearing, the rotation shaft needs to be of a thickness corresponding to the inside diameter of the bearing. However, as described above, during assembly of the rotor assembly, the one impeller is first passed through the supporting portion of the rotation shaft. Accordingly, it is difficult to use a thick rotation shaft, and thus it is difficult to ensure a long bearing life span using the large bearing.

In order to solve the problems, an object of the invention is to provide a method of manufacturing a rotor assembly, a rotor assembly, and a turbo compressor having the same, capable of ensuring a long bearing life span with the use of a large bearing.

In order to accomplish the object, the invention employs the following apparatus.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method of manufacturing a rotor assembly in which a first impeller and a second impeller are fixed to a rotation shaft which is supported by a bearing so as to be rotatable, the method including: fixing the second impeller to the rotation shaft; fitting and fixing a sleeve to the rotation shaft after fixing the second impeller; fitting and fixing the bearing to the sleeve after fitting and fixing the sleeve; and fixing the first impeller after fitting and fixing the bearing.

In the method of manufacturing a rotor assembly according to the first aspect of the invention, after fixing the second impeller to the rotation shaft, the sleeve is fitted and fixed to the rotation shaft, and the bearing is fitted and fixed to the sleeve. That is, instead of thickening the rotation shaft, the sleeve is used, so that it becomes possible to use a large bearing.

In addition, the method of manufacturing a rotor assembly according to a second aspect of the invention includes, before fitting and fixing the sleeve, adjusting the sleeve to an outside diameter measurement corresponding to a change in an outside diameter of the sleeve which is going to be caused while fitting and fixing the sleeve.

In the method of manufacturing a rotor assembly according to the second aspect of the invention, in the sleeve adjusting step, the sleeve is adjusted to the outside diameter measurement corresponding to the change in the outside diameter caused in the sleeve fixing step. Accordingly, there is no need to perform machining work on the outer peripheral surface of the sleeve in order to ensure a suitable interference between the sleeve and the bearing after the sleeve fixing step.

In addition, in the method of manufacturing a rotor assembly according to a third aspect of the invention, in adjusting the sleeve, the sleeve is adjusted to the outside diameter measurement obtained by subtracting the expansion amount of the outside diameter of the sleeve which is going to be caused while fitting and fixing the sleeve, from a predetermined outside diameter measurement.

According to a fourth aspect of the invention, there is provided a rotor assembly including: a rotation shaft supported by a bearing so as to be rotatable; two impellers fixed to the rotation shaft; and a sleeve which is fitted and fixed to the rotation shaft and is provided inside the bearing.

In the rotor assembly according to the fourth aspect of the invention, since the bearing is provided on the rotation shaft with the sleeve interposed therebetween, it becomes possible to use a large bearing without thickening the rotation shaft.

According to a fifth aspect of the invention, there is provided a turbo compressor which compresses a gas introduced from the outside so as to be discharged by rotating a rotor assembly including two impellers, and as the rotor assembly, the rotor assembly according to the fourth aspect is included.

According to the invention, the sleeve is provided on the rotation shaft, so that a large bearing can be used. Therefore, a long bearing life span can be ensured.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the invention will be described with reference toFIGS. 1 to 4. In addition, in the drawings used for the following description, in order to allow each member to have a recognizable size, the scale of each member is appropriately changed.

FIG. 1is a horizontal cross-sectional view of a turbo compressor1according to this embodiment. In addition,FIG. 2is a plan view of a rotor assembly23according to this embodiment. In addition,FIG. 3Ais a plan view of a schematic diagram of a sleeve24according to this embodiment.FIG. 3Bis a front view of the schematic diagram of the sleeve24according to this embodiment. In addition,FIG. 4is a horizontal enlarged cross-sectional view of a compressor unit20and a gear unit30included in the turbo compressor1according to this embodiment.

The turbo compressor1according to this embodiment is used in a turbo refrigerator (not shown) provided in a building, a factory, or the like to generate air-conditioning cooling water, and compresses and discharges a refrigerant gas introduced from an evaporator (not shown) of the turbo refrigerator. As shown inFIG. 1, the turbo compressor1includes a motor unit10, a compressor unit20, and a gear unit30.

The motor unit10has an output shaft11and includes a motor12which generates rotating power to drive the compressor unit20and a motor casing13which encloses the motor12and in which the motor12is provided. In addition, a driving unit that drives the compressor unit20is not limited to the motor12, and for example, may also be an internal combustion engine.

The output shaft11of the motor12is supported so as to be rotatable by a first bearing14and a second bearing15which are fixed to the motor casing13.

The compressor unit20includes a first compression stage21that intakes and compresses the refrigerant gas and a second compression stage22that further compresses the refrigerant gas compressed by the first compression stage21to be discharged as a compressed refrigerant gas. In addition, inside the compressor unit20, a rotor assembly23that is provided in both the first and second compression stages21and22is provided.

The configuration of the rotor assembly23which is a feature of the turbo compressor1will be described. As shown inFIG. 2, in the rotor assembly23, a first impeller23aand a second impeller (impeller)23bare fixed to a rotation shaft23cextending in a predetermined direction (a direction in which the first and second compression stages21and22are opposed, seeFIG. 1).

The first and second impellers23aand23beach have a configuration in which a plurality of blades are lined up in a peripheral direction on a peripheral surface of a substantially conical hub, and are fixed to the rotation shaft23cso that their rear surface sides (bottom surface sides of the conical hubs) are in a posture opposed to each other. The first impeller23ais fixed to one end side of the rotation shaft23cusing a nut23d. The second impeller23bis fixed to the substantially center portion of the rotation shaft23cby shrink-fitting, press-fitting, or the like.

The rotation shaft23cis, for example, a bar-shaped member molded of chrome molybdenum steel having high rigidity. A pinion gear23eis molded on the opposite side of the rotation shaft23cto a side to which the first impeller23ais fixed. The pinion gear23eis a gear for transmitting the rotating power of the motor12(seeFIG. 1) to the first and second impellers23aand23band is molded integrally with the rotation shaft23cwhen the rotation shaft23cis molded. Between the pinion gear23eof the rotation shaft23cand the second impeller23b, a labyrinth seal23ffor preventing leakage of the refrigerant gas from the second compression stage22toward the gear unit30is provided. The labyrinth seal23fsurrounds the rotation shaft23cand is fixed thereto by shrink-fitting, press-fitting, or the like. Moreover, similarly to the pinion gear23e, the labyrinth seal23fmay also be molded integrally with the rotation shaft23cwhen the rotation shaft23cis molded.

In addition, the rotation shaft23cis provided with a third bearing (bearing)23gand a fourth bearing23h. Both the third and fourth bearings23gand23hare rolling-element bearings and support the rotation shaft23cso as to be rotatable.

The third bearing23gis a bearing (a so-called angular bearing) capable of supporting loads in both the radial and thrust directions. The third bearing23gis fixed to the rotation shaft23cvia a sleeve24between the first and second impellers23aand23b. The sleeve24is a member molded in a substantially cylindrical shape (seeFIGS. 3A and 3B) and is fitted and fixed to a supporting portion23iof the rotation shaft23cbetween the first and second impellers23aand23bby shrink-fitting, press-fitting, or the like. Similarly, the third bearing23gis fitted and fixed to the sleeve24by shrink-fitting, press-fitting, or the like. Since the sleeve24is provided between the rotation shaft23cand the third bearing23g, a large bearing can be used as the third bearing23gwithout the use of a rotation shaft23chaving a large diameter. Moreover, in order to regulate movement of the third bearing23gfitted to the sleeve24in an axial line direction of the rotation shaft23c, the sleeve24is provided with a first snap ring23jhaving an annular shape from the first impeller23aside.

As shown inFIG. 3A, the sleeve24has a configuration in which a flange portion24bis molded to widen from one end side of a cylindrical sleeve main body24ain the diameter direction, and a male threaded portion24cis formed on the other side. In addition, the sleeve24is molded using general carbon steel (ordinary steel). The flange portion24bis a regulating portion for preventing the third bearing23gfitted to the sleeve24from moving toward the second impeller23b. The male threaded portion24cis a portion to which the first snap ring23jis mounted. To an inner peripheral surface24dof the sleeve main body24a, the supporting portion23iof the rotation shaft23cis fitted with a predetermined interference, and to the outer peripheral surface24eof the sleeve main body24a, the third bearing23gis fitted with a predetermined interference (seeFIG. 2).

As shown inFIG. 2, the fourth bearing23his fitted and fixed to the rotation shaft23con the opposite side to the labyrinth seal23fwith the pinion gear23einterposed therebetween by shrink-fitting, press-fitting, or the like. Moreover, in order to regulate the movement of the fourth bearing23hfitted to the rotation shaft23cin the axial line direction of the rotation shaft23c, a second snap ring23khaving an annular shape is provided in the rotation shaft23c. The second snap ring23kis mounted to a male threaded portion (not shown) formed on an end portion of the rotation shaft23c.

Subsequently, the configurations of the first compression stage21, the second compression stage22, and the gear unit30are described.

As shown inFIG. 4, the first compression stage21includes a first diffuser21athat compresses the refrigerant gas by converting the velocity energy of the refrigerant gas applied by the rotating first impeller23ainto pressure energy, a first scroll chamber21bthat leads the refrigerant gas compressed by the first diffuser21ato the outside of the first compression stage21, and an intake21cthat intakes the refrigerant gas to be supplied to the first impeller23a.

Moreover, some portions of the first diffuser21a, the first scroll chamber21b, and the intake21care formed by a first impeller casing21ethat encloses the first impeller23a.

In the intake21cof the first compression stage21, a plurality of inlet guide vanes21gfor controlling the intake capacity of the first compression stage21is installed.

Each of the inlet guide vanes21gis rotated by a drive mechanism21hfixed to the first impeller casing21eso as to change the apparent area of the refrigerant gas from the upstream side of a flow direction. In addition, outside the first impeller casing21e, a vane driving unit25(seeFIG. 1) that rotates and drives each of the inlet guide vanes21gconnected to the drive mechanism21his installed.

The second compression stage22includes a second diffuser22athat compresses the refrigerant gas by converting the velocity energy of the refrigerant gas applied by the rotating second impeller23binto pressure energy so as to be discharged as the compressed refrigerant gas, a second scroll chamber22bthat leads the compressed refrigerant gas discharged from the second diffuser22ato the outside of the second compression stage22, and an introduction scroll chamber22cthat guides the refrigerant gas compressed by the first compression stage21to the second impeller23b.

Moreover, the second diffuser22a, the second scroll chamber22b, and the introduction scroll chamber22care formed by a second impeller casing22ethat encloses the second impeller23b.

The first scroll chamber21bof the first compression stage21and the introduction scroll chamber22cof the second compression stage22are connected via an external pipe (not shown) which is provided separately from the first and second compression stages21and22such that the refrigerant gas compressed by the first compression stage21is supplied to the second compression stage22via the external pipe.

The third bearing23gof the rotor assembly23is fixed to the second impeller casing22ein a space26between the first and second compression stages21and22, and the fourth bearing23his fixed to the second impeller casing22eon the gear unit30side. That is, the rotation shaft23cof the rotor assembly23is supported inside the compressor unit20so as to be rotatable via the third and fourth bearings23gand23h.

The gear unit30includes a flat gear31which transmits the rotating power of the motor12to the rotation shaft23cfrom the output shaft11, and is fixed to the output shaft11of the motor12and is engaged with the pinion gear23eof the rotation shaft23c, and a gear casing32which accommodates the flat gear31and the pinion gear23e.

The flat gear31has an outside diameter greater than that of the pinion gear23e. As the flat gear31and the pinion gear23ecooperate with each other, the rotating power of the motor12is transmitted to the rotation shaft23cso that the number of rotation of the rotation shaft23cbecomes greater than that of the output shaft11. Moreover, a transmission method is not limited to the above method, and the diameters of a plurality of gears may be set so that the number of the rotation shaft23cis the same as or smaller than that of the output shaft11. In order to ensure proper rotation of the flat gear31and the pinion gear23eengaged with each other, the spacing therebetween is set to an appropriate value.

The gear casing32accommodates the flat gear31and the pinion gear23ein an internal space32aformed therein and are molded as a separate member from the motor casing13and the second impeller casing22eso as to connect the motor casing13and the second impeller casing22e. In addition, an oil tank33(seeFIG. 1) that recovers and stores a lubricating oil supplied to sliding parts of the turbo compressor1is connected to the gear casing32.

The gear casing32is connected to the second impeller casing22eat a first connection portion C1, and is connected to the motor casing13at a second connection portion C2.

Next, a method of manufacturing the rotor assembly23according to this embodiment will be described. The description will be provided appropriately referring toFIGS. 2,3A,3B.

First, each of the first impeller23a, the second impeller23b, the rotation shaft23c, the labyrinth seal23f, and the sleeve24is manufactured by casting, machining work, or the like. Here, manufacturing of the sleeve24which is a feature of this embodiment will be described in detail.

As described above, the sleeve24is fitted and fixed to the supporting portion23iof the rotation shaft23cwith a predetermined interference. Accordingly, when the sleeve24is fitted to the rotation shaft23c, the sleeve main body24ais biased outward from the rotation shaft23cin the diameter direction, and the outer peripheral surface24ethereof is swollen, so that the outside diameter D of the sleeve main body24aexpands. In addition, although the third bearing23gis fitted and fixed to the outer peripheral surface24eof the sleeve main body24a, in order to prevent seizing or the like and ensure a long bearing life span of the third bearing23g, the interference between the sleeve main body24aand the third bearing23gneeds to be adjusted to a suitable value. That is, at the time of fitting the third bearing23gto the sleeve main body24a, the outside diameter D needs to be set to a suitable outside diameter measurement corresponding to the inside diameter of the third bearing23g.

Here, in this embodiment, the sleeve24is manufactured according to the expansion of the outside diameter D of the sleeve main body24a, which is going to be caused by fitting the sleeve24to the rotation shaft23c. More specifically, so as to cause the outside diameter D to be the suitable outside diameter measurement corresponding to the inside diameter of the third bearing23gby the expansion, during the manufacturing of the sleeve24, the outside diameter D is set to a measurement obtained by subtracting the expansion amount of the outside diameter D from the suitable outside diameter measurement.

As a method of calculating the expansion amount of the outside diameter D when the sleeve24is fitted to the rotation shaft23c, first, a first pressure P1exerted on the inner peripheral surface24dof the sleeve main body24aby the rotation shaft23cwhen the sleeve24is fitted to the rotation shaft23cwith an interference δ in the radial direction is calculated, and the expansion amount of the outside diameter D of the sleeve main body24ais calculated on the basis of the calculated first pressure P1.

When the sleeve24is fitted to the rotation shaft23cwith the interference8in the radial direction, the first pressure P1exerted on the inner peripheral surface24dby the rotation shaft23cis generally given by the following expression (1).

Here, E1is modulus of longitudinal elasticity of the rotation shaft23c, ν1is Poisson's ratio of the rotation shaft23c, E2is modulus of longitudinal elasticity of the sleeve24, ν2is Poisson's ratio of the sleeve24, r1is radius of the sleeve main body24aon the inner peripheral surface24dside, and r2is radius of the sleeve main body24aon the outer peripheral surface24eside.
P1=(δ/r1){1/[(r22+r12)/E2(r22−r12)+ν2/E2−(ν1−1)/E1]}  (1)

Next, on the basis of the calculated first pressure P1and a second pressure P2(in general, atmospheric pressure) exerted inward from the outer peripheral surface24eof the sleeve main body24a, a displacement u of the outer peripheral surface24eof the sleeve main body24ain the radial direction when the sleeve24is fitted to the rotation shaft23cis calculated. The displacement u is generally given by the following expression (2).

Since the displacement u is a displacement in the radial direction, the expansion amount of the outside diameter D of the sleeve main body24abecomes 2u. Therefore, the sleeve24is manufactured to have an outside diameter measurement obtained by subtracting the expansion amount 2u from the suitable outside diameter measurement corresponding to the inside diameter of the third bearing23g. Moreover, after purchasing a sleeve molded substantially in a cylindrical shape in advance, only the outer peripheral surface of the sleeve may be adjusted to the outside diameter according to the expansion.

Subsequently, the rotor assembly23is assembled using the components each manufactured. First, after the labyrinth seal23fis fixed to the rotation shaft23c, the second impeller23bis fitted and fixed to the rotation shaft23cby shrink-fitting, press-fitting, or the like. The second impeller23bis inserted from the opposite side to the side where the pinion gear23eof the rotation shaft23cis provided, is passed through the supporting portion23i, and is fixed to a predetermined position.

Next, the sleeve24is fitted and fixed to the supporting portion23iof the rotation shaft23cby shrink-fitting, press-fitting, or the like.

Here, as the sleeve24is fitted to the rotation shaft23cwith the interference δ in the radial direction, the outside diameter D of the sleeve main body24aexpands after fixing the sleeve24. Above all, as described above, during the manufacturing of the sleeve24, the sleeve24is manufactured in advance to have the outside diameter obtained by subtracting the expansion amount 2u during fitting from the suitable outside diameter measurement corresponding to the inside diameter of the third bearing23g. Accordingly, the outside diameter D of the sleeve main body24aafter fixing the sleeve24has the suitable outside diameter measurement corresponding to the inside diameter of the third bearing23g. That is, after the sleeve24is fitted and fixed to the rotation shaft23c, there is no need to adjust the outside diameter D of the sleeve main body24ato the suitable outside diameter measurement by machining the outer peripheral surface24eof the sleeve main body24a. Therefore, there is no need to perform machining work again during assembly of the rotor assembly23, and laboriousness and costs in manufacturing the rotor assembly23can be reduced.

Thereafter, the third bearing23gis fitted and fixed to the sleeve24by shrink-fitting, press-fitting, or the like. Since the sleeve main body24ahas the suitable outside diameter measurement corresponding to the inside diameter of the third bearing23g, the third bearing23gcan be used under a suitable use condition. As a result, the third bearing23gcan be used for a long time. In addition, since the rotor assembly23according to this embodiment has the configuration in which the sleeve24is interposed between the rotation shaft23cand the third bearing23g, a large bearing can be used as the third bearing23gwithout the use of a rotation shaft23chaving a large diameter. Therefore, a long bearing life span can be ensured for the rotor assembly23.

Moreover, the third bearing23gis fixed to the sleeve24, and the fourth bearing23his fitted and fixed to the rotation shaft23c. Lastly, the first impeller23ais fixed to the rotation shaft23cusing the nut23dafter the rotation shaft23cis provided inside the compressor unit20.

Here, the second impeller23bmay be fixed to the rotation shaft23cbefore fitting the sleeve24to the rotation shaft23c.

As such, the manufacturing operation of the rotor assembly23is ended.

Subsequently, operations of the turbo compressor1according to this embodiment will be described.

First, the rotating power of the motor12is transmitted to the rotation shaft23cvia the flat gear31and the pinion gear23e, and thus the first and second impellers23aand23bof the compressor unit20are driven to rotate.

When the first impeller23ais driven to rotate, the intake21cof the first compression stage21is in a negative pressure state, so that the refrigerant gas flows into the first compression stage21via the intake21c. The refrigerant gas flowing into the first compression stage21flows to the first impeller23ain the thrust direction and is given velocity energy by the first impeller23aso as to be discharged in the radial direction.

The refrigerant gas discharged from the first impeller23ais compressed as its velocity energy is converted into pressure energy by the first diffuser21a.

The refrigerant gas discharged from the first diffuser21ais led to the outside of the first compression stage21via the first scroll chamber21b.

In addition, the refrigerant gas led to the outside of the first compression stage21is supplied to the second compression stage22via the external pipe (not shown).

The refrigerant gas supplied to the second compression stage22flows into the second impeller23bin the thrust direction via the introduction scroll chamber22cand is discharged in the radial direction in which velocity energy is applied thereto by the second impeller23b.

The refrigerant gas discharged from the second impeller23bis further compressed as its velocity energy is converted into pressure energy by the second diffuser22bto become the compressed refrigerant gas.

The compressed refrigerant gas discharged from the second diffuser22bis led to the outside of the second compression stage22via the second scroll chamber22b.

As such, the operations of the turbo compressor1are ended.

Therefore, according to this embodiment, the following advantages can be obtained.

According to this embodiment, since the sleeve24is provided between the rotation shaft23cand the third bearing23g, a large bearing can be used as the third bearing23g. Therefore, there is an advantage that a long bearing life span can be ensured for the rotor assembly2.

While the exemplary embodiments related to the invention have been described with reference to the accompanying drawings, it is needless to say that the invention is not limited to the embodiments. The shapes and combinations of the constituent members described in the above embodiments are only examples and can be modified in various manners depending on design requirements without departing from the scope of the invention.

For example, in this embodiment, the turbo compressor1is used in the turbo refrigerator (not shown). However, the invention is not limited thereto, and the turbo compressor1may also be used as a supercharger that supplies compressed air to an internal combustion engine.