JPH05340386A - Centrifugal compressor - Google Patents

Abstract

(57) [Abstract] [Purpose] A motor (8) is disposed on the back side of the impeller (5), and the rotor (10) of this motor (8) is the shaft (12).
For the centrifugal compressor connected to the impeller (5) via the, the leakage of the compressed gas to the back side of the impeller (5) is effectively reduced to reduce the loss, and the compressor is easily assembled. Maintains high precision in balancing rotating parts. [Structure] The impeller (5) is connected to the rotor (1) of the motor (8).
At least the impeller (5) with the shaft (12) connecting to (0)
A thick shaft having the same diameter as that of and a gas bearing (16) are supported in the housing (1).

Description

Detailed Description of the Invention

[0001]

This invention relates to an impeller (impeller).
The present invention relates to a centrifugal compressor in which gas is discharged in the radial direction by centrifugal force to be compressed, and particularly to a technique for reducing leakage of high-pressure gas from the back side of an impeller.

[0002]

2. Description of the Related Art Centrifugal compressors have been well known as a type of compressor. This compressor has, for example, as shown in FIG. 3, a rotatable impeller (b) in a housing (a), and a gas inlet (c) is provided in the housing (a) on the rotation axis of the impeller (b). ) Is opened. Further, the space around the impeller (b) is a gas compression space (d).
This space (d) is communicated with a gas outlet (not shown) opening in the housing (a). A motor (e) that rotationally drives the impeller (b) is arranged on the back side of the impeller (b). The motor (e) includes a stator (f) fixed to a housing (a), a rotor (g) rotatably arranged in the stator (f) concentrically with the impeller (b), and the rotor (g). ) Supporting a rotor shaft (h), and a front end portion of the rotor shaft (h) has a bearing hole (i) penetratingly formed in the housing (a) and a bearing (j) such as a gas bearing or a bearing (illustrated example). Is rotatably supported via a gas bearing), and its front end is concentrically connected to the back surface of the impeller (b). On the other hand, the rear end of the rotor shaft (h) is supported in a bearing hole (k) formed through the housing (a) through a bearing (1) such as a gas bearing or a bearing. The impeller (b) driven by the motor (e)
The gas sucked into the housing (a) from the gas inlet (c) by the rotation of is discharged to the outside in the radial direction by centrifugal force, is compressed, and is discharged from the gas outlet.

By the way, in this type of centrifugal compressor, for example, "6. Centrifugal Blower" in the publication "Turbo / Blower and Compressor" (Takefumi Ikui, Masahiro Inoue / Corona Publishing / August 25, 1988)・ Theory and Design of Compressors ", 20th
As shown on pages 7 to 222, a part of the gas compressed by the impeller (b) and having a high pressure and high temperature is separated from the compression space (d) between the back surface of the impeller (b) and the housing (a). There is a problem in that leakage occurs and the loss of the compressor increases. Then, in the case where the motor (e) is provided on the rear side of the impeller (b) as described above, the leaked high temperature gas flows into the motor (e), so that the motor (e) rises in temperature and its efficiency is improved. It causes problems such as deterioration. Therefore, in order to reduce the leakage to the back side of the impeller (b), for example, a labyrinth structure is provided on the back surface of the impeller (b) and sealing is performed.

[0004]

However, in practice, it is difficult to increase the sealing length of the labyrinth structure on the back surface of the impeller (b), etc., and the sealing effect of the labyrinth structure is insufficient, and the impeller (b) is not effective. Leakage of compressed gas to the back side cannot be effectively reduced. In particular, it is remarkable when the compressor is small.

Also, the impeller (b) and the motor (e)
When assembling and, the front end of the rotor shaft (h) of the motor (e) is inserted into the bearing hole (i) of the housing (a), and the impeller (b) is fixed to the front end. In this case, although the rotational imbalance of the rotor (g) and the rotor shaft (h) on the motor (e) side and the rotational imbalance of the impeller (b) can be removed well, the impeller on the tip of the rotor shaft (h) can be removed. There is also a problem that it is difficult to take sufficient rotational imbalance due to the assembly of (b), and the accuracy of the overall rotational balancing after assembly is reduced.

The present invention has been made to solve such problems all at once, and its purpose is to devise a shaft for connecting the impeller and a rotor of a motor so that compressed gas to the rear side of the impeller can be prevented. While effectively reducing leakage,
The object is to facilitate the assembling of the compressor and maintain the balancing accuracy of the rotating parts with high accuracy.

[0007]

In order to achieve the above object, in the invention of claim 1, the shaft connecting the impeller and the motor rotor is a thick shaft having at least the same diameter as the impeller, and the peripheral speed during rotation thereof is By raising the pressure, the pressure of the gas film in the gas bearing formed between the shaft and the bearing hole is increased to seal the leakage of the compressed gas.

Specifically, in the present invention, as shown in FIG. 1, an impeller (5) connected in series to a motor (8) via a shaft (12) on a concentric line is provided in a housing (1). In the centrifugal compressor, which has a structure in which the gas sucked into the housing (1) is discharged to the outside in the radial direction by the rotation of the impeller (5) driven by the motor (8) and is compressed, At least the same diameter as the impeller (5) is connected to the impeller (5) with almost no space and is supported by the gas bearing (16) with respect to the housing (1).

According to a second aspect of the invention, the shaft (1
2) has the same diameter as the rotor (10) of the motor (8) and is connected to the rotor (10) without any gap, and the inner diameter of the stator (9) of the motor (8) is the bearing hole (14) of the gas bearing (16). ) And the same diameter.

According to a third aspect of the invention, as shown in FIG. 2, in the centrifugal compressor of the second aspect, the bearing hole (14) of the gas bearing (16) is formed in the inner peripheral surface of the stator (9) of the motor (8).
A sleeve (21) that is substantially flush with the inner peripheral surface is provided.

[0011]

With the above construction, in the first aspect of the invention, the shaft (12) connecting the impeller (5) and the rotor (10) of the motor (8) is a thick shaft having the same diameter as the impeller (5). Therefore, when the impeller (5) is rotated by driving the motor (8), the peripheral speed of the shaft (12) is higher than that of the conventional thin shaft. Since the shaft (12) is supported by the housing (1) by the gas bearing (16), the gas pressure in the gas bearing (16) rises as the peripheral speed increases, and the gas film having a high pressure increases. Is generated, and a large sealing effect using this gas film as a wall is obtained. Due to this sealing effect, it is possible to effectively reduce the leakage of the compressed gas to the back side of the impeller (5) and reduce the loss due to the leakage.

Further, since the shaft (12) and the impeller (5) are connected to each other with substantially no space therebetween, a large loss that increases in proportion to the cube of the rotational speed, that is, the back surface of the impeller (5) and the opposite surface thereof are opposed to each other. The disc friction loss with the housing (1) can be reduced.

Further, since the shaft (12) has the same diameter as the impeller (5), when the compressor is assembled, the impeller (5), the shaft (12) and the rotor (10) are integrated in advance outside the housing (1). And the assembly is inserted into the housing (1) from the motor (8) side, and the shaft (12) is arranged in the bearing hole (14) while inserting the impeller (5) into the bearing hole (14). Then assemble it. Therefore, unlike the conventional case, it is not necessary to assemble the impeller from the opposite side after inserting the shaft from the motor side into the bearing hole, and the assembling can be facilitated and the number of assembling steps can be reduced. .

In addition, since the impeller (5), the shaft (12) and the rotor (10) are integrally assembled before being assembled in the housing (1), the rotational imbalance is removed at that time so that the balancing accuracy is set with high accuracy. If you keep
Even if the high accuracy is assembled to the housing (1), it can be maintained as it is, and the balancing accuracy can be ensured with high accuracy.

According to the second aspect of the present invention, the shaft (12) has the same diameter as the rotor (10) and is connected to the rotor (10) without any gap, and the inner diameter of the stator (9) of the motor (8) is a gas bearing. Since the bearing hole (14) of (16) has substantially the same diameter, the impeller (5), the shaft (12) and the rotor (1
0) all have the same diameter, and the effect of further reducing the friction loss due to rotation is added.

According to the third aspect of the invention, the bearing hole (14) of the gas bearing (16) is formed in the inner peripheral surface of the stator (9) of the motor (8).
Since the sleeve (21) which is substantially flush with the inner peripheral surface is arranged, the gas pressure between the rotor (10) and the stator (9) of the motor (8) is also increased to form a kind of gas bearing. Can be formed and the gas bearing (1) on the shaft (12) is also formed in the motor (8) part.
The same sealing effect as 6) is obtained, and the gas leakage to the back side of the impeller (5) can be further effectively reduced by the synergistic effect of these two sealing effects.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a centrifugal compressor (C) according to Embodiment 1 of the present invention. This compressor (C) is an ultra-compact and ultra-high speed type, and is large due to high-speed rotation. It is set to obtain the same performance as a compressor. In Figure 1,
(1) is a housing, which has a partition wall (2) near the front end (the left side is the front side in the figure), and the partition (2) causes the internal space of the housing (1) to be a front side impeller chamber (3). It is partitioned into a motor chamber (4) on the rear side. The impeller chamber (3) is a substantially frustoconical space whose inner diameter increases rearward, and inside the impeller chamber (3), a plurality of substantially triangular plate-shaped blades (5b), (5b), around the shaft portion (5a), An impeller (5) having an outer diameter of about 30 to 50 mm, which is radially attached, is rotatably accommodated. A gas inlet (6) is opened at the front end of the housing (1) on the axis of rotation of the impeller (5), while the space around the impeller (5) in the impeller chamber (3) is centrifuged from the impeller (5). It is used as a compression space (7) for the gas released by force, and this compression space (7)
Are connected to a gas outlet (not shown) that opens into the housing (1). Then, the gas is sucked into the housing (1) from the gas inlet (6) by the super-high speed rotation of the impeller (5) driven by the motor (8) described later, and the sucked gas is discharged radially outward by the centrifugal force. It is then compressed and discharged from the gas outlet.

On the other hand, in the motor chamber (4), a motor (8) for rotationally driving the impeller (5) at an ultrahigh speed of, for example, 10,000 rpm or more is housed concentrically with the impeller (5). The motor (8) includes a substantially cylindrical stator (9) fixed to the housing (1), which is a peripheral wall of the motor chamber (4), with its front end closely attached to the back surface of the partition wall (2).
A rotor (10) rotatably arranged in the stator (9) concentrically with the impeller (5); and a rotor shaft (11) penetrating the center of the rotor (10) concentrically. A magnetic field is generated by supplying power to a coil (not shown) in (9) to rotate the rotor (10) around the rotor shaft (11). The outer diameter of the rotor (10) is the same as that of the impeller (5).

Further, a front bearing hole (14) having the same diameter as the stator (9) of the motor (8) is formed in the partition wall (2) of the housing (1) concentrically with the stator (9). A rear bearing hole (15) is opened in the housing (1) at the rear side of the motor chamber (4) concentrically with the stator (9) and the front bearing hole (14). In the rotor shaft (11), the front shaft (12) protruding toward the front of the rotor (10) is supported in the front bearing hole (14), and its entire length is the same as that of the bearing hole (14). Further, the front shaft (12) has the same outer diameter as the impeller (5) and the rotor (10), and the back surface thereof is in close contact with the front end surface of the rotor (10) without a gap, while the front end surface is impeller (5). Are concentrically connected to the back surface of the rotor so that they are in close contact with each other without any gap. With this structure, the impeller (5) and the rotor shaft (11)
The front shaft (12) and the rotor (10) are connected to each other in series so that their outer peripheral surfaces are flush with each other in series without a gap.
Further, the front shaft (12) generates a gas film due to gas pressure in a gap between the front bearing hole (14) and the inner peripheral surface of the bearing hole (14) by rotation of the front shaft (12) to generate the gas. It is rotatably supported by a gas bearing (16) which floats the front shaft (12) with a membrane. (17), (17), ... Are helical groove portions formed on the outer surface of the front shaft (12) for generating a gas film.

On the other hand, the rear shaft (13) of the rotor shaft (11) protruding rearward of the rotor (10) is rotatably supported by the gas bearing (18) in the rear bearing hole (15). The gas bearing (18) is composed of inner and outer races (19) and (20) arranged concentrically with a gap,
The inner race (19) has the rear shaft (13) fixed therethrough, while the outer race (20) is fitted and fixed in the bearing hole (15) so as to be integral with the rear shaft (13). Due to the rotation of the race (19), a gas film due to gas pressure is generated in the gap between the inner surface of the outer race (20) and the rear shaft (13) is levitated by the gas film.

Therefore, in the above embodiment, when the compressor (C) is operated, the rotor (10) is rotated around the rotor shaft (11) at an extremely high speed by the operation of the motor (8), and this rotation causes the front side to rotate. A gap between the front bearing hole (14) in the gas bearing (16) and the front shaft (12) of the rotor shaft (11), and between the inner and outer races (19) and (20) in the rear gas bearing (18). A gas film having a pressure is generated in each of the gaps, and the gas film causes the rotor shaft (11) to rotate while floating. Then, as the rotor (10) rotates at an extremely high speed, the impeller (5) that is integrally connected to the rotor shaft (11) also rotates at an extremely high speed, and the impeller (5) rotates at an extremely high speed to generate gas. Is sucked into the housing (1) from the gas inlet (6), and the sucked gas is blown outward in the radial direction by the centrifugal force accompanying the rotation and is compressed to a high pressure in the compression space (7). Is discharged from the gas outlet to the outside of the housing (1).

At this time, of the rotor shaft (11) of the motor (8), the front shaft (12) whose front end is connected to the impeller (5) has the same diameter as the impeller (5) and the outer peripheral surface. Since the shaft is made thick so as to be flush with the surface, the peripheral speed is higher even if the rotation speed is the same, as compared with the case where the front shaft (12) is a thin shaft. Therefore, in the gas bearing (16) on the front side, the pressure of the gas forming the gas film rises, and a large sealing effect can be obtained with the gas film having a high pressure as a wall. As a result, the impeller (5) above
The gas compressed in the compression space (7) leaks from the compression space (7) to the back side of the impeller (5) by the motor (8).
Between the rotor (10) and the stator (9) of the motor can be effectively reduced by the above-mentioned sealing effect, the loss due to leakage of compressed gas can be reduced, and the efficiency due to the temperature rise of the motor (8) can be reduced. It is possible to prevent the decrease.

Moreover, since the front shaft (12), the impeller (5), and the rotor (10) are closely connected to each other with the same outer diameter without any clearance, the housing is disposed opposite to the back surface of the impeller as in the conventional case. It is possible to surely reduce the disc friction loss that occurs in the case of the above.

Further, since the impeller (5), the front shaft (12) and the rotor (10) having the same diameter are concentrically connected and connected in series, when the compressor (C) is assembled, the impeller is previously prepared. (5), the rotor shaft (11) of the motor (8) and the rotor (10) are integrally assembled outside the housing (1), and the assembly is a motor chamber (4) or an impeller chamber inside the housing (1). It is possible to insert the impeller (5) into the front bearing hole (14) while inserting the impeller (5) into the front bearing hole (14) while inserting the impeller (5) into the front bearing hole (14). Therefore, as in the past,
After the rotor shaft front end portion is inserted from the motor side into the front side bearing hole, the trouble of assembling the impeller from the front side to the front end of this shaft is not required, and the assembling can be performed easily and the number of assembling steps can be reduced.

Moreover, since the impeller (5), the rotor shaft (11) of the motor (8) and the rotor (10) are integrally assembled before being assembled in the housing (1) in this way,
At that time, if the rotational imbalance is removed with high accuracy, the high balancing accuracy can be maintained as it is even when it is assembled to the housing (1), and high accuracy of balancing can be secured.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention (note that the same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted). A sleeve (21) having an inner peripheral surface that is substantially flush with the front bearing hole (14) is fitted and inserted in (9). The sleeve (21) may be a rotor (1) of the stator (9).
A thin member or a magnetically permeable material is preferable so as not to have a great influence on the magnetic flux for 0).

Therefore, in this embodiment, the sleeve (21) which is substantially flush with the inner peripheral surface of the bearing hole (14) of the gas bearing (16) is fitted in the stator (9) of the motor (8). Therefore, the gap between the rotor (10) and the stator (9) of the motor (8) is kept uniform over the entire circumference by the sleeve (21), and gas is generated in the gap as the rotor (10) rotates at an extremely high speed. A gas film is formed in the bearing, and the same sealing effect as that of the front gas bearing (16) is obtained even in the motor (8) part. As a result, another gas bearing is formed on the rear side of the gas bearing (16) on the front side shaft (12) of the rotor shaft (11), and the sealing effect of the two gas bearings acts synergistically. The gas leakage to the back side of the impeller (5) can be reduced more effectively.

Although the present invention is particularly effective for the small-sized centrifugal compressor (C) that rotates at a very high speed as in the above embodiment, the gas bearing (16) can be formed and the circumference of the front shaft (12) can be improved. It can be applied to a relatively large compressor as long as a rotation speed that can be expected to increase rapidly can be obtained.

[0030]

As described above, according to the first aspect of the present invention, the centrifugal compressor in which the motor is arranged on the back side of the impeller, and the rotor of the motor is connected to the impeller through the shaft, By making the shaft a thick shaft having at least the same diameter as the impeller and supporting it with the gas bearing in the housing, the peripheral speed during rotation of the shaft is increased, and the gas film in the gas bearing between the shaft and the bearing hole is increased. It is possible to increase the pressure of the generated gas to enhance the sealing effect and effectively prevent the compressed gas from leaking to the back side of the impeller, and reduce the disk friction loss on the back side of the impeller. The loss of the machine can be reduced. Further, since the impeller, the shaft and the motor rotor are integrally assembled in advance and then assembled into the housing, the compressor can be easily assembled and the number of assembling steps can be reduced, and when the impeller, the shaft and the motor rotor are integrally assembled. It is possible to maintain the rotation balancing accuracy obtained in the above as it is at the time of assembling to the housing, and to secure high accuracy of balancing.

According to the second aspect of the present invention, the shaft has the same diameter as the motor rotor and is connected to the rotor without any gap, and the stator inner diameter of the motor has substantially the same diameter as the bearing hole of the gas bearing. It is possible to further reduce friction loss due to rotation by making the shaft and the rotor all have the same diameter.

According to the third aspect of the invention, by disposing the sleeve substantially flush with the inner peripheral surface of the bearing hole of the gas bearing on the inner peripheral surface of the stator of the motor, the motor portion is similar to the gas bearing in the shaft. The gas bearing can be formed to obtain the sealing effect, and the synergistic effect of the two sealing effects can further effectively reduce the gas leakage to the back side of the impeller.

[Brief description of drawings]

FIG. 1 is a sectional view of a centrifugal compressor according to a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment.

FIG. 3 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

 (C) Centrifugal compressor (1) Housing (5) Impeller (8) Motor (9) Stator (10) Rotor (11) Rotor shaft (12) Front shaft (shaft) (14) Front bearing hole (16) Gas bearing (21) Sleeve

Claims (3)

[Claims] 1. A motor (8) having an impeller (5) concentrically connected in series via a shaft (12) in a housing (1), the impeller (5) driven by the motor (8). In the centrifugal compressor configured to discharge the gas sucked into the housing (1) by the rotation of the nozzle to the outside in the radial direction to compress the gas, the shaft (12) has at least the same diameter as the impeller (5) and has a substantially clearance. A centrifugal compressor characterized in that the centrifugal compressor is connected to the housing (1) by a gas bearing (16). 2. The centrifugal compressor according to claim 1, wherein the shaft (12) has the same diameter as the rotor (10) of the motor (8) and is connected with substantially no gap, while the stator of the motor (8) is connected. The inner diameter of (9) is the gas bearing (1
A centrifugal compressor having the same diameter as the bearing hole (14) of 6). 3. The centrifugal compressor according to claim 2, wherein the gas bearing (1) is provided on the inner peripheral surface of the stator (9) of the motor (8).
6) The sleeve (2) which is substantially flush with the inner peripheral surface of the bearing hole (14)
Centrifugal compressor characterized in that 1) is provided.