JPH0763193A - Impeller installation structure for centrifugal type low temperature compressor - Google Patents

Abstract

PURPOSE:To provide an impeller installing structure, which is prevented from levitation due to centrifugal force because of high speed rotation from a rotary shaft and is easily installed/removed, for a centrifugal type low temperature compressor. CONSTITUTION:A bush 13 with the same coefficient of thermal expansion as a rotary shaft 11 is fitted in an impeller 14, and a fastening margin S1, which does not float by centrifugal force, is provided around the outer circumference of the bush 13 for a purpose of shrinkage-fitting of the impeller 14. The impeller 14 is fitted in the rotary shaft 11 via the bush 13 without any clearance between them, and a nut 15 is fastened in a screw part 12 in the tip so as to regulate the movement in the axial direction. In this way, no clearance is made between the bush 13 and the rotary shaft 11 even at low temperature, and installation/removal of them can be carried out without any heating or cooling. In addition, a back face ring 16 consisting of a material with the same or larger coefficient of thermal expansion as that of the impeller 14 is shrinkage-fitted in the back face of the impeller 14 via a fastening margin S2 regulating the deformation, which is caused by centrifugal force generated in the impeller 14, of the inside diameter of the impeller back face, so that the impeller 14 is more surely prevented from floating due to centrifugal force and can be rotated stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impeller mounting structure for a centrifugal low-temperature compressor, which prevents the centrifugal shaft from being lifted by a centrifugal force due to high-speed rotation or ultra-high-speed rotation, and facilitates mounting and removal. It is the one.

[0002]

2. Description of the Related Art In a centrifugal low-temperature compressor used for compressing low-temperature gas, it is necessary to attach an impeller to a rotary shaft that is driven by being connected to a drive source. For example, the material of the impeller is thermally expanded from the rotary shaft. It is made of a material with a high rate, and when the impeller is in a low temperature state during operation, the amount of heat shrinkage is larger than that of the rotating shaft, so that the tightening force is automatically applied (self-tightening).

When the impeller is operated at high speed or ultra-high speed, centrifugal force deforms the part of the impeller that is attached to the rotary shaft, and the impeller tends to float up from the rotary shaft. As shown in the front and rear states, the diameter of the mounting portion of the impeller 2 is set to be small with respect to the rotary shaft 1,
The interference S that exceeds the amount of deformation of the inner circumference of the impeller 2 due to centrifugal force
Then, the impeller 2 is shrink-fitted to the rotary shaft 1.

In such a centrifugal low-temperature compressor, when the compressor is disassembled for inspection or repair, it is necessary to remove the impeller 2 from the rotary shaft 1.
In the state where the impeller 2 is shrink-fitted to the rotary shaft 1, only the rotary shaft 1 cannot be cooled, and the impeller 2 must be heated and removed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the case of heating, since the rotary shaft 1 is also warmed at the same time, it is necessary to heat the rotary shaft 1 only, and to heat the impeller 2 to a significantly higher temperature than when assembled.

However, when the heating temperature is increased, the impeller 2 and other parts of the compressor are thermally affected, so that the heating temperature naturally has a limit, and as a result, the burn-off between the rotary shaft 1 and the impeller 2 is limited. The tightening margin S at the time of tightening also has a limit, deformation due to centrifugal force caused by high-speed rotation cannot be suppressed, and the impeller 2 floats up with respect to the rotary shaft 1 and cannot be operated in a stable state. I have a problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to prevent the centrifugal shaft from being lifted up by a centrifugal force due to high-speed rotation and to easily mount and remove the impeller of a centrifugal low-temperature compressor. It is intended to provide a mounting structure.

[0008]

In order to solve the problems of the above-mentioned prior art, the impeller mounting structure for a centrifugal low-temperature compressor according to claim 1 of the present invention has a bush fitted between the impeller and the rotary shaft. It is made of a material that has the same coefficient of thermal expansion as the rotating shaft, and its inner diameter can be mounted at room temperature without any gap between it and the rotating shaft. While giving a tightening margin that offsets the deformation due to
This impeller is mounted on a rotary shaft having a threaded portion at its tip through the bush and is tightened with a nut to restrict movement in the axial direction.

According to a second aspect of the present invention, in addition to the structure of the first aspect, the impeller mounting structure for a centrifugal low-temperature compressor is formed on an annular protrusion provided on the back surface of the impeller during operation of the impeller. The back ring made of a material having a coefficient of thermal expansion equal to or higher than that of the impeller is shrink-fitted by giving a tightening margin for restricting deformation of the inner diameter of the back surface of the impeller due to centrifugal force.

[0010]

According to the impeller mounting structure of the centrifugal low-temperature compressor of claim 1, the bush fitted in the impeller is made of a material having the same coefficient of thermal expansion as that of the rotating shaft, and the bush is floated even if a centrifugal force is applied to the outer circumference of the bush. The impeller is shrink-fitted with no interference, so that the bush and the impeller can be installed without any hindrance during operation.

Further, an impeller is attached to the rotary shaft via a bush without a gap, and a nut is fastened to a threaded portion at the tip of the rotary shaft to restrict axial movement. Due to the expansion coefficient, it can be operated without gaps even at low temperatures, and can be installed or removed without the need for heating or cooling.

Further, according to the impeller mounting structure of the centrifugal low-temperature compressor of claim 2, in addition to the above-mentioned structure, a back ring made of a material having a coefficient of thermal expansion equal to or higher than that of the impeller is used, which is used during operation of the impeller. The shrinkage is applied to the back surface of the impeller by restricting the deformation of the inner diameter of the back surface of the impeller due to the generated centrifugal force, and the shrinkage at the low temperature is used to more reliably lift the impeller due to the centrifugal force. It prevents it so that it can be operated in a stable rotation state.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. 1 is a cross-sectional view of an impeller mounting structure for a centrifugal low-temperature compressor according to an embodiment of the present invention before and after assembly. In this impeller mounting structure 10 for a centrifugal low-temperature compressor, a step 11a is formed on a rotating shaft 11 that is driven and rotated.
Is formed to form a small diameter impeller mounting portion 11b, and a threaded portion 12 having a smaller diameter than the impeller mounting portion 11b is formed at the tip end portion.

An impeller 14 is attached to the impeller mounting portion 11b of the rotary shaft 11 via a bush 13.

The bush 13 is made of a material having a coefficient of thermal expansion β2 (= β1) which is the same as the coefficient of thermal expansion β1 of the rotating shaft 11, and is formed into a substantially cylindrical shape. It is machined so that it can be installed without a gap with the outer diameter, and the impeller 14 is attached to the axial rear end.
A large-diameter portion 13a is formed to secure the predetermined wall thickness.

The inner diameter of the mounting portion of the impeller 14 mounted on the outer diameter portion of the bush 13 is smaller than the outer diameter of the bush 13, and the difference in this diameter when the bush 13 is shrink fitted into the impeller 14. The tightening margin S1 is set so as to regulate the deformation due to the centrifugal force generated during the operation.

Then, the impeller 14 shrunk to the bush 13 is mounted on the impeller mounting portion 11b of the rotary shaft 11 so as to tighten the axial movement with the step 11a of the rotary shaft 11, so that the threaded portion 12 of the rotary shaft 11 is secured. A nut 15 for screwing is prepared.

Further, in the case of an impeller that operates at a high rotational speed, in order to restrict the rise of the inner diameter due to the deformation of the back surface 14a of the impeller 14 due to the centrifugal force generated during operation, the outer circumference of the back surface 14a of the impeller 14 is restricted. A back ring 16 to be shrink-fitted is prepared, and the tightening margin S2 due to shrink-fitting prevents the inner diameter from rising, and the back ring 16 itself is fitted with a coefficient of thermal expansion β3 of the impeller 16.
It is made of a material with a coefficient of thermal expansion β4 (≧ β3) that is equal to or higher than.

Impeller 1 of such a centrifugal low-temperature compressor
4 is attached to the rotary shaft 11 as follows.

In advance, the impeller 14 is shrink-fitted to the outer diameter portion of the bush 13, and in the case of the impeller 14 used at high speed rotation, the back ring 16 is further shrink-fitted to the back surface 14a of the impeller 14 and these Keep together.

With the impeller 14, the bush 13 and the back ring 16 integrated, the inner diameter portion of the bush 13 is fitted into the impeller mounting portion 11b of the rotary shaft 11.

At this time, since the impeller mounting portion 11b of the rotary shaft 11 and the inner diameter portion of the bush 14 having the same coefficient of thermal expansion are machined so that no gap can be formed at room temperature during assembly, they can be easily mounted.

The threaded portion 12 at the tip of the rotary shaft 11
A nut 15 is used to press the bush 13 against the step 11a of the rotating shaft 11, and the bushing 13 is tightened with a tightening torque such that relative displacement does not occur on the contact surface even during operation.

By mounting the impeller 14 on the rotary shaft 11 via the bush 13 in this manner, the impeller 14 can be reliably supported.

According to the impeller mounting structure 10 for such a centrifugal low-temperature compressor, even when the temperature of the low temperature fluid contacting the impeller 14 becomes lower than the temperature of the rotating shaft 11, the rotating shaft 11 and the bush 13 have the same heat. Since the material has an expansion coefficient (β1 = β2), the relative displacement in the axial direction is small,
By increasing the tightening torque by the nut 15 in advance, the impeller 14 can be securely attached to the rotating shaft 11 via the bush 13.

Even when the temperature of the gas in contact with the impeller 14 becomes lower than the temperature at the time of assembling the impeller 14, the rear ring 16 has a coefficient of thermal expansion (β that is equal to or higher than that of the impeller 14).
Since it is a material having 4 ≧ β 3), the tightening margin is increased, and it is possible to prevent the inner diameter of the rear surface 14a of the impeller 14 during operation from rising.

On the other hand, when the assembled impeller 14 is removed from the rotary shaft 11, the nut 15 at the tip of the rotary shaft 11 is loosened and the impeller 14 is pulled out together with the bush 13 so that heating and cooling are not necessary. Can be easily removed.

Therefore, it is possible to raise the design limit of the centrifugal low-temperature compressor that rotates at an extremely high speed, which has conventionally been caused by an assembly problem, and the degree of freedom in designing the impeller 14 is increased, which is highly efficient and compact. A centrifugal low temperature compressor can be designed.

Further, in the conventional structure, when the impeller is attached to the rotary shaft, shrink fitting is necessary, but in the mounting structure 10, the impeller 14 can be shrink fitted to the bush 13 in advance. Therefore, the final assembly can be easily performed, and the assemblability is improved.

Further, when disassembling the compressor or replacing the impeller 14, it has conventionally been necessary to remove the impeller by applying high heat, but this mounting structure 10 does not require heating or cooling and is simple. Further, the impeller 14 together with the bush 13 can be removed, and there is little risk of damage at the time of removal, and the bush can be used repeatedly.

The present invention is not limited to the above-mentioned embodiments, and each constituent element may be modified within the scope of the invention.

[0032]

As described above in detail with reference to the embodiment, according to the impeller mounting structure of the centrifugal low-temperature compressor according to claim 1 of the present invention, the bush fitted in the impeller has the same heat as the rotating shaft. As the material has a coefficient of expansion and the bush is fitted around the outer circumference of the bush by a shrinkage fit that does not float even if centrifugal force is applied, there is no obstacle such as lifting during operation of the bush and impeller. You can

Further, since the impeller is attached to the rotary shaft through the bush without a gap and the nut is fastened to the screw portion at the tip of the rotary shaft to restrict the axial movement, the heat of the bush and the rotary shaft are equal. Due to the expansion coefficient, it can be operated without gaps even at low temperatures, and can be installed and removed easily without the need for heating or cooling.

Further, according to the impeller mounting structure for a centrifugal low-temperature compressor of claim 2 of the present invention, in addition to the above-mentioned constitution, a back ring made of a material having a coefficient of thermal expansion equal to or higher than that of the impeller is used, and this is used for the impeller. The shrinkage of the inner diameter of the impeller back face due to the centrifugal force generated during the operation of the impeller is given to the back face of the impeller so that it is shrink-fitted. It is possible to operate in a stable rotating state by preventing the floating due to.

Therefore, there is an advantage that the degree of freedom in designing the impeller is increased as compared with the conventional structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view before and after assembly according to an embodiment of an impeller mounting structure for a centrifugal low-temperature compressor of the present invention.

FIG. 2 is a cross-sectional view of an impeller mounting structure for a conventional centrifugal low-temperature compressor before and after assembly.

[Explanation of symbols]

 10 Centrifugal compressor impeller mounting structure 11 Rotating shaft 12 Threaded portion 13 Bushing 14 Impeller 15 Nut 16 Rear ring S1 Shrinkage interference of bush and impeller S2 Impeller and interference shrinkage of rear ring

Front page continuation (72) Inventor Kei Asakura 3-21-16 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Toyosu General Office (72) Inventor Shunji Nagai 3-2-1-16 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Co., Ltd.Toyosu General Office

Claims (2)

[Claims] 1. The bush fitted between the impeller and the rotary shaft is made of a material having the same coefficient of thermal expansion as the rotary shaft, and the inner diameter of the bush can be mounted at room temperature without any gap between the bush and the rotary shaft. The bush is formed on the outer diameter portion of the bush, and the impeller is shrink-fitted by giving a tightening margin to offset the deformation caused by centrifugal force generated during the operation of the impeller, while the impeller is screwed to the tip portion through the bush. An impeller mounting structure for a centrifugal low-temperature compressor, which is mounted on a rotating shaft provided and regulated in axial movement to be tightened with a nut. 2. A tightening allowance for restricting deformation of the inner diameter of the impeller, which is formed on a ring-shaped projection provided on the back surface of the impeller and has a coefficient of thermal expansion equal to or higher than that of the impeller, due to centrifugal force generated during operation of the impeller. The impeller mounting structure for a centrifugal compressor according to claim 1, wherein the back ring is shrink-fitted by applying the above.