Patent Description:
A centrifugal compressor is known as a device for compressing a fluid to produce a compressed fluid. As a kind of the centrifugal compressor, a geared compressor is known, in which the fluid is compressed step by step with a plurality of impellers via a plurality of gears. For example, Patent Document <NUM> discloses a geared compressor including a drive gear that is rotationally driven by a drive device, a first intermediate gear and a second intermediate gear that mesh with the drive gear, a first driven gear that meshes with the first intermediate gear, and a second driven gear that meshes with the second intermediate gear. The geared compressor of Patent Document <NUM> includes two first-stage compression sections connected to a first driven shaft of the first driven gear, and a second compression section and a third compression section that are connected to a second driven shaft of the second driven gear. Each compression section has an impeller. The fluid compressed by the two first-stage compression sections flows through the second compression section and the third compression section in that order and is gradually pressurized. Patent Document <NUM> discloses a geared compressor with one driving gear connected to two intermediate gears, which are respectively connected to two driven gears. On the first driven gear a first and a second compressor are connected, while on the second driven gear a third and a forth compressors are connected.

Incidentally, as in Patent Document <NUM>, when two intermediate gears mesh with the drive gear at positions separated from each other, one of the two intermediate gears receives both an upward load in a vertical direction and a pressure load in a horizontal direction from the drive gear and the driven gear. Then, due to the upward load in the vertical direction, a lifting force is applied to the intermediate gear. In a case where the upward load in the vertical direction and a weight of the intermediate gear are balanced, if the pressure load in the horizontal direction received from the drive gear and the pressure load in the horizontal direction received from the driven gear are balanced, the intermediate gear becomes unstable. In this state, the rotation of the intermediate gear at a high speed may cause destabilizing vibration in the intermediate gear. In particular, in a case where sizes of the impellers of the compression sections connected to the driven gears meshing with the intermediate gears are different for each end portion, the vibration of the intermediate gear becomes significant.

The present disclosure provides a geared compressor capable of suppressing vibration of an intermediate gear even if impellers connected to driven gears have different sizes.

A geared compressor according to the claimed invention includes a drive gear that configured to rotate about a drive axis by rotation of a drive device; a first intermediate gear that meshes with the drive gear and configured to rotate about a first intermediate axis parallel to the drive axis; a second intermediate gear that meshes with the drive gear at a position spaced apart from the first intermediate gear and configured to rotate about a second intermediate axis parallel to the drive axis; a first driven gear that meshes with the first intermediate gear at a position spaced apart from the drive gear and configured to rotate about a first driven axis parallel to the drive axis; a second driven gear that meshes with the second intermediate gear at a position spaced apart from the drive gear and configured to rotate about a second driven axis parallel to the drive axis; a first impeller and a second impeller that are connected to the first driven gear and configured to compress a working fluid supplied from an outside by rotation of the first driven gear; and a third impeller and a fourth impeller that are connected to the second driven gear and configured to compress a working fluid supplied from the outside by rotation of the second driven gear, in which, when viewed from an axial direction in which the drive axis extends, the drive axis is disposed below the first intermediate axis, the second intermediate axis, the first driven axis, and the second driven axis in a vertical direction, and in a case where the working fluid is compressed in order from the first impeller to the fourth impeller, the first impeller has a larger outer diameter than outer diameters of the second impeller, the third impeller, and the fourth impeller and when viewed from the axial direction, positions of the first intermediate axis, the second intermediate axis, the first driven axis, and the second driven axis (O5) in the vertical direction are the same.

According to the geared compressor of the claimed invention, vibration of a rotating shaft can be suppressed even if the impellers connected to the driven gears have different sizes.

Hereinafter, an embodiment for implementing a geared compressor <NUM> according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to only this embodiment.

As shown in <FIG> and <FIG>, the geared compressor <NUM> has a multi-axis and multistage configuration that drives a plurality of impellers <NUM>. The geared compressor <NUM> has a drive device <NUM>, a compression section drive mechanism <NUM>, and a plurality of compression sections <NUM>.

The drive device <NUM> generates power for driving the geared compressor <NUM>. For example, a steam turbine can be used as the drive device <NUM>. An output shaft <NUM> of the drive device <NUM> is disposed coaxially with a drive axis O1 of a drive gear <NUM> which will be described later. Therefore, the output shaft <NUM> of the drive device <NUM> is rotatable around the drive axis O1.

The compression section drive mechanism <NUM> rotates an impeller <NUM> of a compression section <NUM>, which is a device for compressing a working fluid supplied from the outside, by transmission of power (torque) generated by the drive device <NUM>. The compression section drive mechanism <NUM> of the present embodiment includes a gear case <NUM>, a drive gear <NUM>, a first intermediate gear <NUM>, a second intermediate gear <NUM>, a first driven gear <NUM>, a second driven gear <NUM>, a plurality of radial bearings <NUM>, and a plurality of thrust bearings <NUM>. The gear case <NUM> is a casing for accommodating a plurality of gears therein. The gear case <NUM> of the present embodiment accommodates the drive gear <NUM>, the first intermediate gear <NUM>, the second intermediate gear <NUM>, the first driven gear <NUM>, and the second driven gear <NUM> in an internal space thereof.

The drive gear <NUM> is accommodated in the gear case <NUM>. The drive gear <NUM> is rotated by the rotation of the steam turbine that is the drive device <NUM>. The drive gear <NUM> has a drive spindle <NUM> and a drive gear main body <NUM>. The drive spindle <NUM> is formed in a cylindrical shape extending around the drive axis O1 extending in a horizontal direction Dh.

One end portion of the drive spindle <NUM> in an axial direction Da in the present embodiment is integrally connected to the output shaft <NUM> of the drive device <NUM> via a coupling (not shown). Therefore, the drive spindle <NUM> is rotated around the drive axis O1 by the rotation of the drive device <NUM>.

In the present embodiment, a direction in which the drive axis O1 extends is simply referred to as the "axial direction Da". Further, of two sides in the axial direction Da, one side Da1 (first side) is simply referred to as "one side Da1", and the opposite side Da2 (second side) is simply referred to as "the other side Da2". The one side Da1 in the axial direction Da in the present embodiment is a side on which the drive device <NUM> is not disposed with respect to the drive spindle <NUM>. That is, the other side Da2 in the axial direction Da in the present embodiment is a side on which the drive device <NUM> is disposed with respect to the drive spindle <NUM>.

The drive spindle <NUM> is disposed so as to protrude from the drive gear main body <NUM> to both sides in the axial direction Da. An end portion of the drive spindle <NUM> on the other side Da2 in the axial direction Da protrudes outside the gear case. The drive spindle <NUM> is rotatably supported on the gear case by a pair of the radial bearings <NUM> at positions separated from the drive gear main body <NUM> to the one side Da1 and the other side Da2 in the axial direction Da.

The drive gear main body <NUM> is fixed to an outer periphery of the drive spindle <NUM>. The drive gear main body <NUM> is, for example, a helical gear that expands around the drive spindle <NUM>. The drive gear main body <NUM> expands so as to protrude in a vertical direction Dv and a horizontal direction Dh perpendicular to the drive axis O1.

The first intermediate gear <NUM> is accommodated in the gear case <NUM>. The first intermediate gear <NUM> rotates with the rotation of the drive gear <NUM>. The first intermediate gear <NUM> has a first intermediate spindle <NUM> and a first intermediate gear main body <NUM>.

The first intermediate spindle <NUM> is formed in a cylindrical shape extending around a first intermediate axis O2 parallel to the drive axis O1. The first intermediate spindle <NUM> rotates around the first intermediate axis O2 by the rotation of the drive gear <NUM>. The first intermediate spindle <NUM> is disposed so as to protrude from the first intermediate gear main body <NUM> to both sides in the axial direction Da. Both ends of the first intermediate spindle <NUM> are rotatably supported on the gear case by a pair of the radial bearings <NUM> at positions separated from the first intermediate gear main body <NUM> to the one side Da1 and the other side Da2 in the axial direction Da.

The first intermediate gear main body <NUM> meshes with the drive gear main body <NUM>. The first intermediate gear main body <NUM> is fixed to an outer periphery of the first intermediate spindle <NUM>. The first intermediate gear main body <NUM> is, for example, a helical gear that expands around the first intermediate spindle <NUM>. The first intermediate gear main body <NUM> expands so as to protrude in the vertical direction Dv and the horizontal direction Dh perpendicular to the first intermediate axis O2.

The second intermediate gear <NUM> is accommodated in the gear case <NUM>. The second intermediate gear <NUM> rotates with the rotation of the drive gear <NUM>. The second intermediate gear <NUM> is disposed at a position separated from the first intermediate gear <NUM>. The second intermediate gear <NUM> has a second intermediate spindle <NUM> and a second intermediate gear main body <NUM>.

The second intermediate spindle <NUM> is formed in a cylindrical shape extending around a second intermediate axis O3 parallel to the drive axis O1 and the first intermediate axis O2. The second intermediate spindle <NUM> rotates around the second intermediate axis O3 by the rotation of the drive gear <NUM>. The second intermediate spindle <NUM> is disposed so as to protrude from the second intermediate gear main body <NUM> to both sides in the axial direction Da. Both ends of the second intermediate spindle <NUM> are rotatably supported on the gear case by a pair of the radial bearings <NUM> at positions separated from the second intermediate gear main body <NUM> to the one side Da1 and the other side Da2 in the axial direction Da.

The second intermediate gear main body <NUM> meshes with the drive gear main body <NUM>. The second intermediate gear main body <NUM> does not mesh with the first intermediate gear main body <NUM>. The second intermediate gear main body <NUM> is fixed to an outer periphery of the second intermediate spindle <NUM>. The second intermediate gear main body <NUM> is, for example, a helical gear that expands around the second intermediate spindle <NUM>. The second intermediate gear main body <NUM> expands so as to protrude in the vertical direction Dv and the horizontal direction Dh perpendicular to the second intermediate axis O3.

The first driven gear <NUM> is accommodated in the gear case <NUM>. The first driven gear <NUM> rotates with the rotation of the first intermediate gear <NUM>. The first driven gear <NUM> is disposed at a position separated from the drive gear <NUM> and the second intermediate gear <NUM>. The first driven gear <NUM> has a first driven spindle <NUM> and a first driven gear main body <NUM>. The first driven spindle <NUM> is formed in a cylindrical shape extending around a first driven axis O4 parallel to the drive axis O1. The first driven spindle <NUM> rotates around the first driven axis O4 by the rotation of the first intermediate gear <NUM>. The first driven spindle <NUM> is disposed so as to protrude from the first driven gear main body <NUM> to both sides in the axial direction Da. Both ends of the first driven spindle <NUM> are disposed at positions protruding outside the gear case. The first driven spindle <NUM> is rotatably supported on the gear case by a pair of the radial bearings <NUM> at positions separated from the first driven gear main body <NUM> to the one side Da1 and the other side Da2 in the axial direction Da. Furthermore, the first driven spindle <NUM> is supported by the thrust bearings <NUM> inside the pair of radial bearings <NUM> in the axial direction Da. The thrust bearing <NUM> has, for example, a thrust collar (not shown) extending in a disc shape from an outer peripheral surface of the first driven spindle <NUM>. The thrust bearing <NUM> restricts movement of the first driven spindle <NUM> in the axial direction Da.

The first driven gear main body <NUM> meshes with the first intermediate gear main body <NUM>. The first driven gear main body <NUM> does not mesh with the drive gear main body <NUM> and the second intermediate gear main body <NUM>. The first driven gear main body <NUM> is fixed to an outer periphery of the first driven spindle <NUM>. The first driven gear main body <NUM> is, for example, a helical gear that expands around the first driven spindle <NUM>. The first driven gear main body <NUM> expands so as to protrude in the vertical direction Dv and the horizontal direction Dh perpendicular to the first driven axis O4.

The second driven gear <NUM> is accommodated in the gear case <NUM>. The second driven gear <NUM> rotates with the rotation of the second intermediate gear <NUM>. The second driven gear <NUM> is disposed at a position separated from the drive gear <NUM> and the first intermediate gear <NUM>. The second driven gear <NUM> has a second driven spindle <NUM> and a second driven gear main body <NUM>.

The second driven spindle <NUM> is formed in a cylindrical shape extending around a second driven axis O5 parallel to the drive axis O1. The second driven spindle <NUM> rotates around the second driven axis O5 by the rotation of the second intermediate gear <NUM>. The second driven spindle <NUM> is disposed so as to protrude from the second driven gear main body <NUM> to both sides in the axial direction Da. Both ends of the second driven spindle <NUM> are disposed at positions protruding outside the gear case. The second driven spindle <NUM> is rotatably supported on the gear case by a pair of the radial bearings <NUM> at positions separated from the second driven gear main body <NUM> to the one side Da1 and the other side Da2 in the axial direction Da. Further, the second driven spindle <NUM> is supported by the thrust bearings <NUM> inside the pair of radial bearings <NUM> in the axial direction Da. The thrust bearing <NUM> restricts movement of the second driven spindle <NUM> in the axial direction Da.

The second driven gear main body <NUM> meshes with the second intermediate gear main body <NUM>. The second driven gear main body <NUM> does not mesh with the drive gear main body <NUM> and the first intermediate gear main body <NUM>. The second driven gear main body <NUM> is fixed to an outer periphery of the second driven spindle <NUM>. The second driven gear main body <NUM> is, for example, a helical gear that expands around the second driven spindle <NUM>. The second driven gear main body <NUM> expands so as to protrude in the vertical direction Dv and the horizontal direction Dh perpendicular to the second driven axis O5.

In addition, as shown in <FIG>, an outer diameter of the drive gear main body <NUM> in the present embodiment is formed smaller than an outer diameter of each of the first intermediate gear main body <NUM> and the second intermediate gear main body <NUM>. Therefore, the number of teeth of the drive gear main body <NUM> is less than the number of teeth of the first intermediate gear main body <NUM>. For the "outer diameter" of the gear in the present embodiment, for example, a root circle diameter, a tip circle diameter, a pitch circle diameter, and the like, which can be measured as a distance (dimension) from a center axis in each gear, are adopted. The outer diameter of the drive gear main body <NUM> is formed larger than an outer diameter of each of the first driven gear main body <NUM> and the second driven gear main body <NUM>. Therefore, the number of teeth of the drive gear main body <NUM> is greater than the number of teeth of the first driven gear main body <NUM>. The outer diameter of the first intermediate gear main body <NUM> is formed larger than the outer diameter of the first driven gear main body <NUM>. Therefore, the number of teeth of the first intermediate gear main body <NUM> is greater than the number of teeth of the first driven gear main body <NUM>. The outer diameter of the first intermediate gear main body <NUM> is the same as the outer diameter of the second intermediate gear main body <NUM>. Therefore, the number of teeth of the first intermediate gear main body <NUM> is the same as the number of teeth of the second intermediate gear main body <NUM>.

Further, when viewed from the axial direction Da, the first intermediate axis O2, the second intermediate axis O3, the first driven axis O4, and the second driven axis O5 are disposed such that their positions in the vertical direction Dv are the same. That is, when viewed from the axial direction Da, the first driven axis O4 and the second driven axis O5 are disposed on an imaginary horizontal line VH connecting the first intermediate axis O2 and the second intermediate axis O3. The imaginary horizontal line VH is an imaginary straight line extending in the horizontal direction Dh orthogonal to the vertical direction Dv. Furthermore, when viewed from the axial direction Da, the first intermediate spindle <NUM>, the second intermediate spindle <NUM>, the first driven spindle <NUM>, and the second intermediate spindle <NUM> are arranged in parallel such that their positions in the vertical direction Dv overlap.

According to the claimed invention, when viewed from the axial direction Da, the first intermediate axis O2 and the second intermediate axis O3, and the first driven axis O4 and the second driven axis O5 are arranged at the same position in the vertical direction Dv, but the present disclosure is not limited to such an arrangement. That is, according to an embodiment not according to the claimed invention, when viewed from the axial direction Da, the first driven axis O4 and the second driven axis O5 may be displaced in the vertical direction Dv with respect to the first intermediate axis O2 and the second intermediate axis O3.

Further, when viewed from the axial direction Da, the drive axis O1 is disposed below the first intermediate axis O2, the second intermediate axis O3, the first driven axis O4, and the second driven axis O5 in the vertical direction Dv. Specifically, when viewed from the axial direction Da, the drive spindle <NUM> is disposed below the first intermediate spindle <NUM>, the second intermediate spindle <NUM>, the first driven spindle <NUM>, and the second driven spindle <NUM> such that their positions in the vertical direction Dv do not overlap. When viewed from the axial direction Da, the drive spindle <NUM> is disposed below the imaginary horizontal line VH in the vertical direction Dv so as not to overlap the imaginary horizontal line VH. When viewed from the axial direction Da, a distance between the drive spindle <NUM> and the first intermediate spindle <NUM> is the same as a distance between the drive spindle <NUM> and the second intermediate spindle <NUM>. Here, an imaginary line connecting the drive axis O1 and the first intermediate axis O2 is referred to as a first imaginary inclined line VC1. An offset angle formed by the first imaginary inclined line VC1 with respect to the imaginary horizontal line VH is preferably <NUM>° or more and <NUM>° or less. Further, the offset angle formed by the first imaginary inclined line VC1 with respect to the imaginary horizontal line VH is more preferably <NUM>° or more and <NUM>° or less. Similarly, an imaginary line connecting the drive axis O1 and the second intermediate axis O3 is referred to as a second imaginary inclined line VC2. An offset angle formed by the second imaginary inclined line VC2 with respect to the imaginary horizontal line VH is preferably <NUM>° or more and <NUM>° or less. Further, the offset angle formed by the second imaginary inclined line VC2 with respect to the imaginary horizontal line VH is more preferably <NUM>° or more and <NUM>° or less.

As shown in <FIG>, the compression section <NUM> compresses the working fluid by being rotated by either the first driven gear <NUM> or the second driven gear <NUM>. The compression section <NUM> has an impeller <NUM> which compresses the working fluid supplied from the outside by rotating. A plurality of compression sections <NUM> are disposed. In the present embodiment, the geared compressor <NUM> includes four compression sections <NUM> including a first-stage compression section <NUM>, a second-stage compression section <NUM>, a third-stage compression section <NUM>, and a fourth-stage compression section <NUM> as the plurality of compression sections <NUM>. The number of the compression sections <NUM> in the geared compressor <NUM> is not limited to four, and may be five or more or three or less.

The first-stage compression section <NUM> is connected to the first driven spindle <NUM>. The first-stage compression section <NUM> has a first impeller <NUM> and a scroll casing (not shown). The scroll casing covers the first impeller <NUM> and has a gas introduction portion and a gas outlet. The first impeller <NUM> is fixed to an end portion of the first driven spindle <NUM> on the one side Da1 in the axial direction Da. The first impeller <NUM> compresses the working fluid supplied from the outside by the rotation of the first driven gear <NUM>. The first impeller <NUM> is formed to be the largest among the plurality of impellers <NUM> in a case where the working fluid is compressed in order from the first impeller <NUM> to the fourth impeller <NUM> that will be described later.

The second-stage compression section <NUM> compresses the working fluid compressed by the first-stage compression section <NUM>. The second-stage compression section <NUM> is connected to the first driven spindle <NUM>. The second-stage compression section <NUM> has a second impeller <NUM> and a scroll casing (not shown). The scroll casing covers the second impeller <NUM> and has a gas introduction portion and a gas outlet. The second impeller <NUM> is fixed to an end portion of the first driven spindle <NUM> on the other side Da2 in the axial direction Da. The second impeller <NUM> compresses the working fluid supplied from the outside by the rotation of the first driven gear <NUM>. The second impeller <NUM> is formed to be the second largest among the plurality of impellers <NUM>.

The third-stage compression section <NUM> compresses the working fluid compressed by the second-stage compression section <NUM>. The third-stage compression section <NUM> is connected to the second driven spindle <NUM>. The third-stage compression section <NUM> has a third impeller <NUM> and a scroll casing (not shown). The scroll casing covers the third impeller <NUM> and has a gas introduction portion and a gas outlet. The third impeller <NUM> is fixed to an end portion of the second driven spindle <NUM> on the one side Da1 in the axial direction Da. The third impeller <NUM> compresses the working fluid supplied from the outside with the rotation of the second driven gear <NUM>. The third impeller <NUM> is formed to be the third largest among the plurality of impellers <NUM>.

The fourth-stage compression section <NUM> compresses the working fluid compressed by the third-stage compression section <NUM>. The fourth-stage compression section <NUM> is connected to the second driven spindle <NUM>. The fourth-stage compression section <NUM> has a fourth impeller <NUM> and a scroll casing (not shown). The scroll casing covers the fourth impeller <NUM> and has a gas introduction portion and a gas outlet. The fourth impeller <NUM> is fixed to an end portion of the second driven spindle <NUM> on the other side Da2 in the axial direction Da. The fourth impeller <NUM> compresses the working fluid supplied from the outside by the rotation of the second driven gear <NUM>. The fourth impeller <NUM> is formed to be the smallest among the plurality of impellers <NUM>.

Each of the first impeller <NUM>, the second impeller <NUM>, the third impeller <NUM>, and the fourth impeller <NUM> compresses the working fluid sucked into the scroll casing from the gas introduction portion while sending the working fluid to the outside of the impeller <NUM> in a radial direction via a flow path formed inside the scroll casing. The first-stage compression section <NUM>, the second-stage compression section <NUM>, the third-stage compression section <NUM>, and the fourth-stage compression section <NUM> are connected via a piping (not shown). As a result, in the geared compressor <NUM>, the working fluid flows through the first-stage compression section <NUM>, the second-stage compression section <NUM>, the third-stage compression section <NUM>, and the fourth-stage compression section <NUM> in that order so that the working fluid is gradually compressed. A heat exchanger (not shown) may be disposed in the middle of the piping connecting the first-stage compression section <NUM>, the second-stage compression section <NUM>, the third-stage compression section <NUM>, and the fourth-stage compression section <NUM>.

In the geared compressor <NUM> having the above configuration, as shown in <FIG>, the first intermediate gear <NUM> is interposed between the drive gear <NUM> and the first driven gear <NUM> when viewed from the axial direction Da. As a result, the first intermediate gear <NUM> receives the upward load in the vertical direction Dv and the pressure load in the horizontal direction Dh (force in the horizontal direction Dh) from the drive gear <NUM> and the first driven gear <NUM>. Due to the upward load in the vertical direction Dv, a lifting force is applied to the first intermediate gear <NUM>. In a case where the upward load in the vertical direction Dv and a weight of the first intermediate gear <NUM> are balanced, if the pressure load in the horizontal direction Dh received from the drive gear <NUM> and the pressure load in the horizontal direction Dh received from the first driven gear <NUM> are balanced, the first intermediate spindle <NUM> becomes unstable.

Here, the upward load in the vertical direction Dv and the pressure load in the horizontal direction Dh are loads that are generated by a tangential force when one gear is moved by an adjacent gear and a reaction force generated when moving the adjacent gear.

On the other hand, the inventors found that in a case where the upward load in the vertical direction Dv and the weight of the first intermediate gear <NUM> were balanced, when the pressure load in the horizontal direction Dh received from the drive gear <NUM> and the pressure load in the horizontal direction Dh received from the first driven gear <NUM> were balanced, eccentricity of the first intermediate gear <NUM> in the vertical direction Dv and the horizontal direction Dh with respect to the radial bearing <NUM> approached zero. As the eccentricity of the first intermediate gear <NUM> in the vertical direction Dv and the horizontal direction Dh approaches <NUM>, a gap between the radial bearing <NUM> that supports the first intermediate spindle <NUM> and the first intermediate spindle <NUM> becomes uniform over the entire circumference. In this state, when the loads in the vertical direction Dv and the horizontal direction Dh acting on the first intermediate spindle <NUM> are balanced so that the load acting on the first intermediate spindle <NUM> becomes small, the first intermediate spindle <NUM> is supported in an unstable state by the radial bearing <NUM>. This is because the rotation of the first intermediate spindle <NUM> at a high speed in this state causes unstable vibration in the first intermediate gear <NUM>.

Further, as shown in <FIG>, the first impeller <NUM> is formed to be the largest among the plurality of impellers <NUM>. That is, the first driven spindle <NUM> has one end portion connected to the first impeller <NUM> and the other end portion connected to the second impeller <NUM> smaller than the first impeller <NUM>. Therefore, in the first driven spindle <NUM>, weights of the impellers <NUM> supported at both ends are different. As a result, the vibration of the first driven spindle <NUM> tends to become unstable, which may destabilize the first intermediate spindle <NUM>.

However, as shown in <FIG>, in the geared compressor <NUM> of the claimed invention, the drive gear <NUM> is disposed such that the drive axis O1 is disposed below the first intermediate axis O2 and the first driven axis O4 in the vertical direction Dv. Therefore, even in a case where the load acting upward in the vertical direction Dv on the first intermediate gear <NUM> and the weight of the first intermediate gear <NUM> are balanced, the pressure load in the horizontal direction Dh received from the drive gear <NUM> and the pressure load in the horizontal direction Dh received from the first driven gear <NUM> cannot be balanced. As a result, the first intermediate spindle <NUM> can maintain a slightly eccentric state with respect to the radial bearing <NUM> in the horizontal direction Dh. Thus, the first intermediate spindle <NUM> can be continuously supported by the radial bearing <NUM> in a stable state. Furthermore, even if the sizes of the impellers <NUM> connected to the first driven gear <NUM> and the second driven gear <NUM> are different, unstable vibration in the first intermediate gear <NUM> can be suppressed.

Further, when viewed from the axial direction Da, the positions of the first intermediate axis O2, the second intermediate axis O3, the first driven axis O4, and the second driven axis O5 are the same in the vertical direction Dv. Therefore, positional relationships of the first intermediate gear <NUM> and the second intermediate gear <NUM> with respect to the first driven gear <NUM> and the second driven gear <NUM> can be made the same. Therefore, it is possible to reduce a transmission torque to the first intermediate gear <NUM> when the load in the vertical direction Dv acting on the first intermediate gear <NUM> is balanced. By reducing the transmission torque, a state in which the load in the vertical direction Dv acting on the first intermediate gear <NUM> is balanced can be passed at an early timing after the geared compressor <NUM> is started and the first intermediate gear <NUM> starts to rotate. Therefore, at a timing when the geared compressor <NUM> is operating at a rated speed, the load in the vertical direction Dv acting on the first intermediate gear <NUM> is no longer balanced, and the unstable vibration in the first intermediate gear <NUM> can be effectively suppressed.

Further, when viewed from the axial direction Da, if the first driven axis O4 and the second driven axis O5 are disposed above the first intermediate axis O2 and the second intermediate axis O3 in the vertical direction Dv, the transmission torque to the first intermediate gear <NUM> when the load in the vertical direction Dv acting on the first intermediate gear <NUM> is balanced becomes large. Therefore, the load in the vertical direction Dv acting on the first intermediate gear <NUM> is more likely to be balanced in a state close to a timing when the geared compressor <NUM> is operating at a rated speed. As a result, there is a possibility that unstable vibration in the first intermediate gear <NUM> cannot be effectively suppressed.

Furthermore, when viewed from the axial direction Da, if the first driven axis O4 and the second driven axis O5 are disposed below the first intermediate axis O2 and the second intermediate axis O3 in the vertical direction Dv, the first driven axis O4 and the second driven axis O5 approach the drive axis O1. Therefore, the pressure loads in the horizontal direction Dh received by the first intermediate gear <NUM> and the second intermediate gear <NUM> from the first driven gear <NUM> when the loads in the vertical direction Dv acting on the first intermediate gear <NUM> and the second intermediate gear <NUM> are balanced become small. Thus, an amount of eccentricity in the horizontal direction Dh of the drive spindle <NUM> with respect to the radial bearing <NUM> may become small. As a result, there is a possibility that unstable vibration in the first intermediate gear <NUM> cannot be effectively suppressed.

Therefore, when viewed from the axial direction Da, a state in which the first intermediate axis O2, the second intermediate axis O3, the first driven axis O4, and the second driven axis O5 have the same position in the vertical direction Dv can most effectively suppress unstable vibration in the first intermediate gear <NUM>.

In addition, there are only two positions of the respective axes in the vertical direction Dv, that is, the position of the drive axis O1 and the position of the first intermediate axis O2. As a result, the structure of the gear case <NUM> covering each gear can be simplified.

Furthermore, as shown in <FIG>, when the offset angle becomes small, the pressure load in the horizontal direction Dh received by the first intermediate gear <NUM> from the drive gear <NUM> when the load in the vertical direction Dv acting on the first intermediate gear <NUM> is balanced becomes small. Thus, an amount of eccentricity in the horizontal direction Dh of the drive spindle <NUM> with respect to the radial bearing <NUM> may become small. As a result, there is a possibility that unstable vibration in the first intermediate gear <NUM> cannot be effectively suppressed.

Further, when the offset angle becomes large, the pressure load in the horizontal direction Dh received by the first intermediate gear <NUM> from the drive gear <NUM> when the load in the vertical direction Dv acting on the first intermediate gear <NUM> is balanced can become large. However, the position of the drive spindle <NUM> in the horizontal direction Dh becomes close to the first intermediate gear <NUM> and the second intermediate gear <NUM>. As a result, the positions of the first driven spindle <NUM> and the second driven spindle <NUM> in the horizontal direction Dh also become close to each other. This limits the size of the impeller <NUM> that can be disposed on the first driven spindle <NUM> and the second driven spindle <NUM>. Further, if an attempt is made to dispose a large impeller <NUM>, the first intermediate gear <NUM> and the second intermediate gear <NUM> must be made large. As a result, a weight of a machine and a moment of inertia increase, making it impossible to optimize the compression section drive mechanism <NUM>.

On the other hand, since the offset angle is <NUM>° or more and <NUM>° or less, the position of the drive spindle <NUM> in the horizontal direction Dh can be sufficiently separated from the first intermediate gear <NUM> and the second intermediate gear <NUM> while the pressure loads in the horizontal direction Dh received by the first intermediate gear <NUM> and the second intermediate gear <NUM> from the drive gear <NUM> are ensured. Thus, unstable vibration in the first intermediate gear <NUM> can be effectively suppressed without limiting the size of the impeller <NUM> that can be disposed.

Furthermore, since the offset angle is <NUM>° or more and <NUM>° or less, the unstable vibration in the first intermediate gear <NUM> can be more effectively suppressed without limiting the size of the impeller <NUM> that can be disposed.

Further, as shown in <FIG>, the outer diameter of the drive gear <NUM> is made smaller than that of the first intermediate gear <NUM> and the second intermediate gear <NUM>. Furthermore, the outer diameters of the first driven gear <NUM> and the second driven gear <NUM> are made smaller than that of the drive gear <NUM>. Thus, regarding the first intermediate gear <NUM> and the second intermediate gear <NUM>, the pressure load in the horizontal direction Dh received from the drive gear <NUM> can be larger than the pressure load in the horizontal direction Dh received from the first driven gear <NUM> and the second driven gear <NUM>. As a result, the pressure load in the horizontal direction Dh received from the drive gear <NUM> and the pressure load in the horizontal direction Dh received from the first driven gear <NUM> and the second driven gear <NUM> can be reliably shifted. Thus, the drive spindle <NUM> can be reliably maintained in a slightly eccentric state with respect to the radial bearing <NUM> in the horizontal direction Dh. Therefore, the unstable vibration in the first intermediate gear <NUM> can be reliably suppressed.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims.

In addition, the outer diameter of each gear is not limited to the shape of the embodiment. For example, the outer diameter of the first intermediate gear main body <NUM> is not limited to being the same as the outer diameter of the second intermediate gear main body <NUM>. The outer diameter of the first intermediate gear main body <NUM> may be larger or smaller than the outer diameter of the second intermediate gear main body <NUM>. Further, the outer diameter of the first driven gear main body <NUM> is not limited to being the same as the outer diameter of the second driven gear main body <NUM>. Therefore, the outer diameter of the first driven gear main body <NUM> may be larger or smaller than the outer diameter of the second driven gear main body <NUM>.

According to the claimed invention, the outer diameters of the second impeller <NUM>, the third impeller <NUM>, and the fourth impeller <NUM> are smaller than the outer diameter of the first impeller <NUM>. According to embodiments not according to the claimed invention, a size relationship between the respective impellers <NUM> is not limited to the shape in the embodiment. The outer diameters of the second impeller <NUM>, the third impeller <NUM>, and the fourth impeller <NUM> may be the same, and only some of the second impeller <NUM>, the third impeller <NUM>, and the fourth impeller <NUM> may have the same outer diameter.

Claim 1:
A geared compressor (<NUM>) comprising:
a drive gear (<NUM>) that configured to rotate about a drive axis (O1) by rotation of a drive device;
a first intermediate gear (<NUM>) that meshes with the drive gear (<NUM>) and configured to rotate about a first intermediate axis (<NUM>) parallel to the drive axis (O1);
a second intermediate gear (<NUM>) that meshes with the drive gear (<NUM>) at a position spaced apart from the first intermediate gear (<NUM>) and configured to rotate about a second intermediate axis (<NUM>) parallel to the drive axis (O1);
a first driven gear (<NUM>) that meshes with the first intermediate gear (<NUM>) at a position spaced apart from the drive gear (<NUM>) and configured to rotate about a first driven axis (<NUM>) parallel to the drive axis (O1);
a second driven gear (<NUM>) that meshes with the second intermediate gear (<NUM>) at a position spaced apart from the drive gear (<NUM>) and configured to rotate about a second driven axis (<NUM>) parallel to the drive axis (O1);
a first impeller (<NUM>) and a second impeller (<NUM>) that are connected to the first driven gear (<NUM>) and configured to compress a working fluid supplied from an outside by rotation of the first driven gear (<NUM>); and
a third impeller (<NUM>) and a fourth impeller (<NUM>) that are connected to the second driven gear (<NUM>) and configured to compress a working fluid supplied from the outside by rotation of the second driven gear (<NUM>),
characterized in that,
when viewed from an axial direction (Da) in which the drive axis (O1) extends, the drive axis is disposed below the first intermediate axis (<NUM>), the second intermediate axis (<NUM>), the first driven axis (<NUM>), and the second driven axis (<NUM>) in a vertical direction, and in that in a case where the working fluid is compressed in order from the first impeller (<NUM>) to the fourth impeller (<NUM>), the first impeller (<NUM>) has a larger outer diameter than outer diameters of the second impeller (<NUM>), the third impeller (<NUM>), and the fourth impeller (<NUM>), and in that when viewed from the axial direction (Da), positions of the first intermediate axis (<NUM>), the second intermediate axis (<NUM>), the first driven axis (<NUM>), and the second driven axis (<NUM>) in the vertical direction are the same.