JPH08226302A - Fixing mechanism for impeller of centrifugal compressor or centrifugal turbine - Google Patents

Abstract

PURPOSE: To provide a structure preventing the drift between the centers of an impeller and a shaft and capable of suppressing the shaft vibration small during rotation. CONSTITUTION: A circular coupling section 14 is provided on the axial contact face between an impeller 1 and a shaft 2, and the circular coupling section 14 is constituted of a circular projection 8 (or a circular groove 9) provided on the impeller 1 side coaxially with the shaft 2 and the circular groove section 9 (or the circular projection 8) provided on the shaft 2 side to be coupled with the circular projection 8 (or the circular groove section 9). The outer periphery of the circular projection 8 (or the inner periphery of the circular groove section 9) of the impeller 1 is positioned in the radial direction by the outer periphery of the circular groove section 9 (or the inner periphery of the circular projection 8) of the shaft 2 during rotation. A gap is provided between a through shaft and the through shaft hole of the impeller 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing mechanism for an impeller of a centrifugal compressor or a centrifugal turbine.

[0002]

2. Description of the Related Art An impeller of a centrifugal compressor or a centrifugal turbine is usually installed outside a bearing that supports a shaft because the flow of wind is bent at a right angle from an inlet to an outlet so that the flow must be smooth. The structure that can be mounted by overhanging is adopted. This typical structure is, for example, the document Ishikawajima Harima Technical Report, published in July 1986, Vol. 26, No. 4, P265.
"Development of high efficiency ball bearing turbocharger" F
ig. 2 is shown. This is an example of a turbocharger that recovers exhaust gas energy of an internal combustion engine and supplies compressed air. Each impeller of a turbine and a compressor is arranged outside a shaft supported by two bearings, and a central portion of the impeller is arranged. It is a structure in which the impeller is fixed in the axial direction by bolting at the end of the shaft that passes through.

Details of the fixing mechanism are shown in FIG.
In FIG. 5, reference numeral 1 denotes a compressor or turbine impeller,
Reference numeral 2 is a shaft connected to a drive source or a load, 3 is a bearing for supporting the shaft 2, and a ball bearing, an oil lubrication sleeve bearing or the like is applied. Reference numeral 4 is a through shaft that penetrates a through shaft hole provided at the center of the impeller 1 and is integrally or mechanically connected to the shaft 2. Reference numeral 5 denotes a screw formed on the end of the through shaft 4, and 6 denotes a nut incorporated in the screw 5, which are arranged for the purpose of fastening and fixing the impeller 1 to the shaft 2.
Reference numeral 7 is a contact surface where the shaft 2 and the impeller 1 come into axial contact with each other when the impeller 1 is tightened by the nut 6.

Next, the function of such an impeller fixing mechanism will be described. The centrifugal compressor or the centrifugal turbine must transmit the transmission torque generated in the shaft 2 to the impeller 1 or the torque generated in the impeller 1 to the shaft 2.
This requires that the shaft 2 and the impeller 1 be mechanically and firmly fixed so that the shaft 2 and the impeller 1 do not shift relative to each other in the rotational direction. Further, the impeller 1 must have a structure that can be detached from the shaft 2 for the convenience of assembly and disassembly. For this reason, FIG.
In the structure shown in (1), the inner diameter of the through shaft hole of the impeller 1 and the outer diameter of the through shaft 4 are finished so that the impeller 1 can be inserted into and withdrawn from the through shaft 4, and the impeller 1 is inserted into the through shaft 4 when assembling. , The nut 6 of the screw 5 at the end of the through shaft 4 is applied, and the nut 6 is tightened to fix the impeller 1 to the shaft 2. At this time, a surface pressure is generated on the contact surface 7 between the shaft 2 and the impeller 1 due to the tightening force of the nut 6, but the frictional force associated with this surface pressure causes mutual torque transmission between the impeller 1 and the shaft 2. It will be possible. In addition,
There is also a method of transmitting a torque by interposing a key between the impeller 1 and the penetrating shaft 4, but for a machine that rotates at high speed such as a turbocharger, there is a problem of balance of the rotating body or the strength of the impeller 1. Therefore, it is general to adopt the structure shown in FIG. 5 instead of the key system.

[0005]

By the way, in the conventional structure shown in FIG. 5, between the inner surface of the through shaft hole of the impeller 1 and the outer diameter of the through shaft 4 due to the influence of centrifugal force or thermal expansion during rotation. There is a possibility that the gap becomes large and the center of the shaft 2 and the center of the impeller 1 are deviated, resulting in a loss of balance and excessive vibration of the shaft 2. Therefore, at the time of assembly, the gap between the impeller 1 and the through shaft 4 is set as small as possible, or the impeller 1 is fixed to the through shaft 4 by shrinkage fitting. However, when the impeller 1 and the penetrating shaft 4 are made of similar materials, precisely, when both materials have similar thermal expansion coefficients, it becomes difficult to disassemble if a shrink fitting structure is used, and if a shrink fitting structure could be adopted. Also, since the expansion margin of the inner diameter of the impeller 1 due to the centrifugal force and heat during rotation is much larger than the expansion margin of the outer diameter of the penetrating shaft 4, the gap between the shaft 2 and the impeller 1 is inevitable during rotation. As a result, the position of the impeller 1 was misaligned, which often increased the shaft vibration. The centrifugal force and the spreading force of the impeller 1 due to heat are much larger than the frictional force of the contact surface 7 due to the surface pressure. Therefore, the center of the impeller 1 is within the above-mentioned gap generated during rotation.
Relative displacement easily occurs with respect to the center of the shaft 2.

As described above, in the conventional structure, in order to suppress the shaft vibration during rotation, it is desirable to make the inner diameter of the impeller a shrink fit, but the shrink fit structure makes it difficult to disassemble.
Alternatively, even with a shrinkage fitting structure, there is a problem that it is basically impossible to suppress the shaft vibration, such as generation of a gap during rotation and inevitable increase of shaft vibration. The present invention has been made for the purpose of solving the above problems, and an object of the present invention is to provide a structure capable of suppressing the shaft vibrations by eliminating the displacement of the centers of the impeller and the shaft even during rotation. And

[0007]

A compressor according to the present invention,
The turbine impeller fixing structure is provided with an annular engaging portion on an axial contact surface between the impeller and the shaft, and the annular engaging portion is provided with an annular protrusion or an annular groove portion concentric with the shaft on the impeller side. An annular groove portion or an annular protrusion portion provided on the shaft side so as to be combined with the annular protrusion portion or the annular groove portion, and the outer peripheral surface of the annular protrusion portion of the impeller during rotation is the outer peripheral surface of the annular groove portion of the shaft. Alternatively, the inner peripheral surface of the annular groove portion of the impeller is positioned in the radial direction by the inner peripheral surface of the annular protrusion portion of the shaft. Further, a gap is provided between the through shaft and the through shaft hole of the impeller.

[Operation] In the compressor / turbine impeller fixing structure according to the present invention, the outer peripheral surface of the annular groove portion on the shaft side or the inner peripheral surface of the annular protrusion portion on the annular protrusion portion or annular groove portion on the impeller side during rotation. On the other hand, it is positioned in the radial direction, and the concentricity of the impeller and the shaft is secured even during rotation,
As a result, the effect of suppressing the shaft vibration during rotation to be small is produced. Further, the gap between the through shaft and the through shaft hole of the impeller facilitates the assembly and disassembly of the impeller on the shaft.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
2 will be described. Figure 1 is a diagram showing the state at rest,
FIG. 2 is a diagram showing a state during rotation, and in the diagram, 1 to 7
Is the same as that shown in FIG. First, FIG. 1 when stationary will be described. In the figure, 8 is an annular projection provided on the surface of the impeller 1 facing the shaft 2, and 9 is an annular groove provided on the surface of the shaft 2 facing the impeller 1, which is a combination of the annular projection 8 and the annular groove 9. The annular engaging portion 14 is configured. A contact surface 7 for transmitting torque is formed on the outer shaft end surface of the annular engaging portion 14. When the annular engaging portion 14 is assembled, that is, at rest, the inner peripheral surface 10 of the annular protruding portion 8 of the impeller 1 and the inner peripheral surface 12 of the annular groove portion 9 of the shaft 2 serve as reference surfaces for positioning the two in the radial direction. Thus, that is, the inner peripheral surface 10 of the annular protruding portion 8 and the inner peripheral surface 12 of the annular groove portion 9 at rest during assembly.
Are configured so that the clearance between them is almost zero, for example, on the order of microns or less, or slightly tight. Further, the outer peripheral surface 13 of the annular groove portion 9 of the shaft 2 is such that the outer peripheral surface 11 of the annular protruding portion 8 of the impeller 1 fits during rotation, that is, the outer peripheral surface 13 of the annular groove portion 9 and the annular protruding portion during rotation. An outer peripheral surface 11 of 8 serves as a reference surface for radial positioning of the impeller 1 and the shaft 2. Therefore, the gap between the outer peripheral surface 13 of the annular groove portion 9 and the outer peripheral surface 11 of the annular protrusion portion 8 when stationary is relatively large with respect to the shaft 2 of the annular protrusion portion 8 of the impeller 1 due to centrifugal force or thermal expansion during rotation. It is set to be less than the spread amount.

That is, by such a setting, the outer peripheral surface 11 of the annular projection 8 of the impeller 1 is rotated by the annular groove 9 of the shaft 2 during rotation.
With respect to the outer peripheral surface 13 of the above, since it spreads more than the set clearance value at rest, the clearance of this portion is clogged at the time of rotation, thereby positioning the impeller 1 and the shaft 2. Here, the inner peripheral surface 10 and the outer peripheral surface 1 of the annular protrusion 8 of the impeller 1
1, or the inner peripheral surface 12 and the outer peripheral surface 13 of the annular groove portion 9 of the shaft 2.
Need to be finished concentrically, so that the concentricity of the impeller 1 and the shaft 2 at the time of rotation can be secured at the same level as at rest.

FIG. 2 conceptually shows the positional relationship at the time of rotation of the annular engaging portion 14 constructed with the above intention. The function and function of such an impeller fixing structure will be described in more detail. In FIG. 1, at the time of assembly, the impeller 1 is first passed through the through shaft 4. In this invention,
Since the inner diameter of the through shaft hole of the impeller 1 and the outer diameter of the through shaft 4 do not play any role of positioning, it is not necessary to insert a shrink fit and there may be a gap therebetween. This produces an advantage that the impeller 1 can be easily disassembled and assembled as compared with the conventional configuration. After passing the impeller 1 through the penetrating shaft 4, the nut 6 is put on the threaded portion 5 to tighten the impeller 1 in the axial direction. Due to this tightening force, the impeller 1 and the shaft 2
A surface pressure is generated on the axial contact surface 7 and the resulting frictional force causes mutual torque transmission between the impeller 1 and the shaft 2.

FIG. 1 shows the state in which the impeller 1 is tightened in this way, and at this time, the annular projection 8 of the impeller 1 is shown.
The inner peripheral surface 10 and the inner peripheral surface 12 of the annular groove portion 9 of the shaft 2 are fitted, and in this state, the balance static balance and the dynamic balance of the rotating body are adjusted. When the rotation starts next, the radial expansion of the impeller 1 due to the influence of centrifugal force and heat is larger than that of the shaft 2, so that the outer peripheral surface 11 of the annular projection 8 and the outer peripheral surface 13 of the annular groove 9 are expanded. The gap between the two shrinks, and eventually the gap becomes 0 during the rise of rotation, and a fit is achieved on this side. FIG. 2 shows the state at this time. Since the inner peripheral surface 10 and the outer peripheral surface 11 of the annular protruding portion 8 and the inner peripheral surface 12 and the outer peripheral surface 13 of the annular groove portion 9 are concentric with each other, the impeller 1 is rotated even during rotation.
And the concentricity of axis 2 is not lost, so
The balance at the time of rotation is secured and the shaft vibration can be suppressed to be small.

In this way, by providing the annular engaging portion 14 on the axial contact surface between the impeller 1 and the shaft 2, the assembly and
It is possible to realize a structure that can be easily disassembled and that suppresses shaft vibration during rotation. In addition, the annular engaging portion 1 at rest
The clearance on the outer peripheral side in 4 may be 0, but in that case the stress around the annular engaging portion 14 during rotation becomes high, so it is desirable to set the clearance to such an extent that it does not occur. In the above embodiment, the example in which the annular protrusion 8 is arranged on the impeller 1 side and the annular groove 9 is arranged on the shaft 2 side has been shown.
On the contrary, the annular projection 8 is on the shaft 2 side and the annular groove 9 is on the impeller 1 side.
You may arrange | position on the side, and the same effect as the said Example is produced. In this case, it is necessary to provide a fit on the outer peripheral surface side of the annular projection portion 8 and the annular groove portion 9 when stationary, and a fit on the inner peripheral surface side of the annular projection portion 8 and the annular groove portion 9 when rotating. At the time of stationary, at the time of rotation, the annular engaging portion 14
The positional relationship of is shown in FIG. 3 and FIG. The thinking action in this case is the same as that of the example of FIGS.

In each of the embodiments shown in FIGS. 1 to 4, the axial contact surface 7 between the impeller 1 and the shaft 2 is formed on the outer peripheral side of the annular engaging portion 14, but the position is not always required. It is not necessary to form the contact surface with, and the axial contact surface may be formed within the annular engaging portion 14 or on the inner peripheral side of the annular engaging portion 14. However, in order to obtain a large torque transmission force, it is better to form the axial contact surface on the outer peripheral side of the annular engaging portion 14 as in the above embodiment.

[0015]

As described above, according to the present invention, the annular engaging portion including the annular protrusion or the annular groove provided on the impeller side and the annular groove or the annular protrusion provided on the shaft side is arranged, The outer peripheral surface of the annular groove portion on the shaft side or the inner peripheral surface of the annular protrusion portion is relative to the annular protrusion portion or the annular groove portion on the impeller side,
Since the structure is designed to be concentric with each other due to the positioning in the radial direction, a gap can be provided between the penetrating shaft and the penetrating shaft hole, making it easy to assemble / disassemble and to rotate the shaft. It is possible to realize a fixing mechanism of the impeller, which can suppress the vibration to be small and can accurately determine the axial fitting position of the impeller.

[Brief description of drawings]

FIG. 1 is a sectional view showing a stationary state of a fixing mechanism for an impeller according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state during rotation of the impeller fixing mechanism according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a stationary state of a fixing mechanism of an impeller showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a state during rotation of a fixing mechanism of an impeller showing another embodiment of the present invention.

FIG. 5 is a sectional view showing a conventional fixing mechanism of an impeller.

[Explanation of symbols]

1 Impeller 2 Shaft 4 Through shaft 7
Contact surface 8 Annular protrusion 9 Annular groove 14 Annular engagement

Claims (4)

[Claims] 1. An impeller having a through shaft hole, a shaft having an end surface in contact with the impeller, and a shaft integrally or mechanically connected to the shaft and penetrating through the through shaft hole of the impeller, and at the end portion of the impeller. A fixing mechanism for an impeller of a centrifugal compressor or a centrifugal turbine configured with a through shaft having a tightening mechanism, wherein an annular engaging portion is provided at a portion where the impeller and the shaft end surface are in contact with each other. The annular engaging portion is composed of an annular projection portion provided on the end surface of the shaft concentrically with the shaft, and an annular groove portion provided on a contact surface of the impeller in contact with the shaft end surface and engaging with the annular projection portion. Is
While stationary, a gap is formed between the outer peripheral surface of the annular projection of the shaft end surface and the outer peripheral surface of the annular groove of the impeller, and during rotation, the outer peripheral surface of the annular groove of the impeller is the annular projection of the shaft end surface. An impeller fixing mechanism for a centrifugal compressor or a centrifugal turbine, characterized in that radial positioning is performed by the outer peripheral surface of the. 2. The inner peripheral surface of the annular groove portion of the impeller is positioned in the radial direction by the inner peripheral surface of the annular projection portion of the shaft end surface while stationary. Fixing mechanism for impeller of centrifugal compressor or centrifugal turbine. 3. The contact between the impeller and the shaft end surface is
The centrifugal compressor or the centrifugal turbine impeller according to claim 1 or 2, wherein the shaft end surface is formed outside the annular protrusion or the annular groove. Fixing mechanism. 4. The centrifugal type according to claim 1 or 2, wherein a gap is provided between an outer peripheral surface of the through shaft and an inner peripheral surface of a through shaft hole of the impeller. Fixing mechanism for compressor or centrifugal turbine impeller.