JP5262561B2 - Impeller fastening structure - Google Patents

Description

  The present invention relates to an impeller fastening structure for fastening an impeller and a rotating shaft.

  Conventionally, various fastening structures have been proposed as a structure for fastening the impeller and the rotating shaft.

  As shown in FIG. 4A, the structure described in Patent Document 1 is a structure in which the tip of the rotating shaft 30 is screwed into a bush 32 integrally fixed to the back surface of the impeller 31, and the both are coupled. It has become. FIG. 4B is an enlarged view of FIG. 4A, in which a male screw portion 33 is formed in the vicinity of the tip portion of the rotating shaft 30, and a female screw portion 34 is formed on the inner peripheral surface of the bush 32. The fitting surfaces 35 of the bush 32 and the rotary shaft 30 are set at positions before and after the male screw portion 33 and the female screw portion 34.

  In order to fasten the rotating shaft 30 and the impeller 31 in the structure of FIGS. 4A and 4B, the rotating shaft 30 and the impeller 31 are relatively rotated, and the fitting surface 35 is slid and rotated while being screwed. The direction of the screws of the male screw portion 33 and the female screw portion 34 is selected so as not to loosen from the rotation direction of the rotary shaft 30 and the impeller 31.

  As shown in FIG. 5, the structure described in Patent Document 2 is provided with a through hole 41 in the impeller 40, and a nut 43 is screwed into the through hole 41 through the rotation shaft 42 and the tip of the rotation shaft 42. The impeller 40 and the rotating shaft 42 are fastened. A washer 44 is disposed between the nut 43 and the impeller 40. In order to prevent the nut 43 from loosening, a spring washer or a plastic locking part is generally used as the washer 44.

  As shown in FIG. 6, the structure described in Patent Document 3 is provided with a tapered portion 51 at the tip portion of the rotating shaft 50, and the center hole of the impeller 52 is tapered so as to correspond to the tapered portion 51. In addition, the impeller 52 and the rotary shaft 50 are fastened by the nut 54. This structure aims to ensure the concentricity between the impeller 52 and the rotating shaft 50 even during high speed rotation by generating circumferential stress and surface pressure on the impeller 52 when the bolt 54 is tightened. .

JP 2005-532506 A JP-A-5-79346 JP 2001-173597 A

  In the case of the structure of Patent Document 1 described above, prevention of loosening of the screw portion is effective only in one direction. Further, since the fitting part 35 is slid and rotated, there is a problem that the fitting part 35 is damaged and the accuracy of the fitting part 35 is lowered every time it is assembled and assembled.

  In the case of the structure of Patent Document 2 described above, the weight of the nut 43 and the washer 44 increases, so that the overhang weight of the shaft increases, so that the critical speed of the rotating shaft 42 decreases. Further, it is difficult to match the washer 44 with the core of the rotating shaft 42, and the unbalance weight increases. Furthermore, the plastic locking parts cannot maintain their function at high or low temperatures.

  In the case of the structure of Patent Document 3 described above, high-precision taper machining is required to optimize the taper tightening allowance, and the cost is very high. In addition, when the rotation speed is higher than a certain level, the amount of deformation of the center hole of the impeller becomes too large due to centrifugal force, and the concentricity cannot be maintained.

  The present invention has been made in view of the above-described problems, can prevent loosening in both directions, can prevent deterioration of the accuracy of the fitting portion during assembly and assembly, can reduce the overhang weight, and is tapered. It is an object of the present invention to provide an impeller fastening structure that can ensure concentricity during high-speed rotation of the impeller without providing a portion.

  In order to solve the above problem, the impeller fastening structure of the present invention employs the following technical means.

(1) The impeller fastening structure of the present invention includes an impeller having a through-hole penetrating in the axial direction at the center, a rotating shaft having a tip inserted on the back side of the impeller, and the impeller having a function of preventing looseness. It is provided with the volt | bolt which fastens the said rotating shaft.

According to said structure, since an impeller and a rotating shaft are fastened by the volt | bolt which has an anti-rotation function, not only one direction but both directions can be prevented.
Further, since the shaft and the impeller can be fitted and separated by sliding in the axial direction without rotating the fitting portion, it is possible to prevent the accuracy of the fitting portion from being lowered during assembly and assembly.
Further, since the shaft does not protrude from the impeller, the overhang weight can be suppressed.

(2) Further, in the impeller fastening structure according to (1), the bolt is a spring bolt in which a slit is provided at a tip of a thread.

  According to the above configuration, it is possible to effectively prevent loosening by using the spring bolt.

(3) Further, in the impeller fastening structure according to the above (1) or (2), a metal washer having a sleeve portion fitted concentrically with the impeller is disposed between the impeller and the bolt. Has been.

  According to said structure, an unbalance weight is not increased by using a washer with a fitting part with an impeller. Further, by using a metal washer instead of a plastic material, the function can be maintained even when the temperature condition is low or high.

(4) Moreover, in the impeller fastening structure according to any one of (1) to (3), the impeller has a first hollow cylindrical portion having the through hole as a hollow portion on the back side, and the rotating shaft Has a second hollow cylindrical portion surrounding the first hollow cylindrical portion at the tip, and an outer peripheral surface of the first hollow cylindrical portion and an inner peripheral surface of the second hollow cylindrical portion are connected to the impeller and the rotation. It is a fitting part with the shaft.

  According to the above configuration, the rotation shaft (second hollow cylindrical portion) is disposed outside the fitting portion between the impeller and the shaft, and the impeller (first hollow cylindrical portion) is disposed inside the fitting portion. Even if a large centrifugal force acts on the impeller during rotation, the first hollow cylindrical portion of the impeller is firmly supported by the second hollow cylindrical portion outside the impeller, so that concentricity can be maintained. Therefore, the concentricity at the time of high-speed rotation can be ensured without going through a highly accurate and difficult taper processing.

  According to the present invention, it is possible to prevent loosening in both directions, to prevent deterioration of the accuracy of the fitting portion during assembly and assembly, to reduce the overhang weight, and at the time of high speed rotation of the impeller without providing a taper portion The concentricity can be secured.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram showing an impeller fastening structure 1A according to a first embodiment of the present invention. In this embodiment, the rotational speed is relatively low, such as a low-temperature compressor or a low-temperature liquid circulation pump using an aluminum impeller, and the through hole 4 in the fitting portion 11 is in a planned operation state (rotation speed, temperature). This is suitable when the inner diameter is not much larger than or slightly smaller than the outer diameter of the rotary shaft 5.

  In the impeller fastening structure 1 </ b> A of FIG. 1, the impeller 3 and the rotating shaft 5 are fastened by a bolt 7. The impeller 3 is, for example, a compressor impeller, a turbine impeller, or the like. In FIG. 1, the left side is the front side and the right side is the back side. Reference symbol a denotes the axis of the impeller 3 and the rotating shaft 5.

  The impeller 3 has a through hole 4 penetrating in the axial direction at the center thereof. The through hole 4 is a circular hole, and is formed near the back surface of the impeller 3 and has a large diameter portion 4a into which the rotating shaft 5 is inserted. The large diameter portion 4a is adjacent to the front surface side of the impeller 3 and has a large diameter portion 4a. And a small diameter portion 4b having a smaller diameter.

  The rotating shaft 5 has a tip portion inserted on the back side of the impeller 3. Specifically, the distal end portion of the rotating shaft 5 is inserted into the large diameter portion 4 a of the through hole 4 of the impeller 3. In FIG. 1, reference numeral 11 denotes a fitting portion 11 between the rotating shaft 5 and the impeller 3. In the present embodiment, the end surface of the distal end portion of the rotating shaft 5 is in contact with a wall formed by a step between the large diameter portion 4a and the small diameter portion 4b. A hole extending in the axial direction is formed at the tip of the rotating shaft 5, and a female screw portion 6 a is formed on the inner surface of this hole.

  Considering that the inner diameter of the through-hole 4 of the impeller 3 is expanded by centrifugal force during operation, the impeller 3 and the rotary shaft 5 are fitted to each other so that the inner diameter of the large-diameter portion 4a of the impeller 3 is larger than the outer diameter of the rotary shaft 5. It should be set slightly smaller and have an interference fit. In this case, when the rotating shaft 5 and the impeller 3 are assembled, the rotating shaft 5 is fitted by enlarging the inner diameter by slightly warming the impeller 3 or the like, thereby causing friction between the rotating shaft 5 and the impeller 3 in the fitting portion 11. Damage can be prevented. Also, when disassembling, the impeller 3 can be warmed to enlarge the inner diameter and the rotary shaft 5 can be easily pulled out, thereby preventing the fitting portion 11 from being damaged.

  The bolt 7 is a component that fastens the impeller 3 and the rotating shaft 5. The bolt 7 is formed with a male screw portion 6 b that is screwed with the female screw portion 6 a of the rotating shaft 5. In the present invention, the bolt 7 has a loosening prevention function. As the bolt 7 having such a loosening prevention function, for example, a spring bolt in which a slit is provided at the tip of a thread can be applied. This slit is a groove extending spirally along the tip of the screw thread, and by having such a slit, an elastic stress is generated in the flank of the male screw and the female screw, and the effect of preventing loosening is exhibited.

  The distance L from the rear surface of the head 7a of the bolt 7 (the contact surface between the head 7a of the bolt 7 and the washer 9 in FIG. 1) to the contact surface between the impeller 3 and the tip of the rotary shaft 5 is the bolt 7 due to the difference in thermal expansion. To prevent loosening, it is better not to make it too long.

  According to the impeller fastening structure 1A configured as described above, since the impeller 3 and the rotating shaft 5 are fastened by the bolt 7 having a rotation prevention function, it is possible to prevent loosening in both directions as well as in one direction. In addition, since the fitting portion 11 can be slid in the axial direction without turning, and the rotating shaft 5 and the impeller 3 can be fitted and separated, the accuracy of the fitting portion 11 is lowered during assembly and assembly. Can be prevented. Moreover, since the rotating shaft 5 does not protrude from the impeller 3, the overhang weight can be suppressed.

  When the impeller 3 is made of a low-hardness material such as an aluminum alloy, a washer 9 is preferably disposed between the impeller 3 and the bolt 7 as in the configuration example of FIG. The washer 9 is made of metal and has a hollow cylindrical sleeve portion 9 a that is concentrically fitted to the impeller 3, and has a circular opening through which the bolt 7 penetrates, between the bolt head 7 a and the impeller 3. It consists of the flat plate part 9b pinched | interposed.

  Since the washer 9 having such a configuration is fitted concentrically with the impeller 3, an increase in unbalanced weight due to the addition of the washer 9 does not occur. Further, by using a metal washer 9 instead of a plastic material, the function can be maintained even when the temperature condition is low or high.

  FIG. 2 is a diagram illustrating an impeller fastening structure 1B according to a second embodiment of the present invention. In the present embodiment, the inner diameter of the fitting portion 11 on the side of the impeller 3 becomes large during operation because the rotational speed is fast, and in the configuration of FIG. 1, the deformation due to the centrifugal force becomes too large, and the impeller 3 and the rotating shaft 5 This is suitable when a situation where the concentricity of the lens cannot be properly maintained is expected.

  In FIG. 2, the impeller 3 has a through hole 4 at the center, but unlike the first embodiment, the large diameter portion 4 a for inserting the rotating shaft 5 is not provided. In this embodiment, the impeller 3 has the 1st hollow cylindrical part 3a which makes the through-hole 4 a hollow part on the back side. The rotating shaft 5 has the 2nd hollow cylindrical part 5a surrounding the 1st hollow cylindrical part 3a in a front-end | tip part. The outer peripheral surface of the first hollow cylindrical portion 3 a and the inner peripheral surface of the second hollow cylindrical portion 5 a form a fitting portion 11 between the impeller 3 and the rotating shaft 5.

  In the configuration example of FIG. 2, an annular groove 12 extending in the axial direction and the circumferential direction is formed so as to surround the first hollow cylindrical portion 3 a in the impeller 3. The annular groove 12 goes around the axis. The inner diameter of the radially outer wall of the annular groove 12 is larger than the diameter of the outer peripheral surface of the second hollow cylindrical portion 5a, and the tip end portion (second hollow cylindrical portion 5a) of the rotating shaft 5 is inserted into the annular groove 12. Has been. The end surface of the second hollow cylindrical portion 5 a is in contact with the innermost wall in the axial direction of the annular groove 12.

  In the rotating shaft 5, the female screw portion 6 a is formed on the back side (right side in FIG. 2) in the axial direction of the rotating shaft 5 with respect to the second hollow cylindrical portion 5 a. Therefore, the bolt 7 in the second embodiment is longer than the bolt 7 in the first embodiment.

  The impeller 3 and the rotary shaft 5 are fitted with an intermediate fit by setting the outer diameter of the first hollow cylindrical portion 3a to be substantially the same as the diameter of the inner peripheral surface of the second hollow cylindrical portion 5a. It is good to set it slightly larger than the diameter of the internal peripheral surface of 2 hollow cylindrical parts 5a, and to set it as an interference fit. In this case, when the rotating shaft 5 and the impeller 3 are assembled, the impeller 3 is cooled with a low-temperature liquefied gas such as liquid nitrogen to reduce the outer diameter of the first hollow cylindrical portion 3a, thereby rotating the rotating shaft in the fitting portion 11. It is possible to prevent damage caused by rubbing between the impeller 3 and the impeller 3. Further, when disassembling, the impeller 3 is cooled with a low-temperature liquefied gas such as liquid nitrogen so that the rotating shaft 5 can be easily pulled out, whereby the fitting portion 11 can be prevented from being damaged.

  The distance L from the back surface of the head 7a of the bolt 7 (the contact surface between the head 7a of the bolt 7 and the washer 9 in FIG. 2) to the contact surface between the impeller 3 and the tip of the rotary shaft 5 is the bolt 7 due to the difference in thermal expansion. To prevent loosening, it is better not to make it too long. Although it is possible to configure the contact surface in the axial direction between the impeller 3 and the rotary shaft 5 to be the tip surface of the first hollow cylindrical portion 3a, from the above viewpoint, the second hollow cylindrical portion 5a It is good to comprise so that a front end surface may turn into the contact surface of the impeller 3 and the rotating shaft 5 of the axial direction.

  According to the configuration of the present embodiment, the rotating shaft 5 (second hollow cylindrical portion 5a) is disposed outside the fitting portion 11 between the impeller 3 and the rotating shaft 5, and the impeller 3 (first hollow portion) is disposed inside the fitting portion 11. By arranging the cylindrical portion 3a), the first hollow cylindrical portion 3a of the impeller 3 is firmly supported by the outer second hollow cylindrical portion 5a even when a large centrifugal force acts on the impeller 3 during high-speed rotation. Therefore, the concentricity can be maintained. Therefore, the concentricity at the time of high-speed rotation can be ensured without going through a highly accurate and difficult taper processing.

  FIG. 3 is an enlarged view of a portion A in FIG. As shown in FIG. 3, an inner ring groove 14 that is recessed radially inward and extending in the circumferential direction is formed on the radially inner side of the innermost portion of the annular groove 12. The inner ring groove 14 makes a round around the axis. When this groove is not provided, the chamfering of the front end portion of the second hollow cylindrical portion 5a is made sufficiently large in order to reliably apply the front end surface of the second hollow cylindrical portion 5a to the innermost wall of the annular groove 12. As a result, it becomes difficult to secure a sufficient area of the contact surface 13 as a result. On the other hand, when the inner ring groove 14 is provided as in the configuration example of FIG. 3, the chamfering of the distal end portion of the second hollow cylindrical portion 5 a can be made as small as possible, so that the area of the contact surface 13 is easily secured.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. . The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

It is a figure which shows the impeller fastening structure which concerns on 1st Embodiment of this invention. It is a figure which shows the impeller fastening structure which concerns on 2nd Embodiment of this invention. It is the A section enlarged view of FIG. It is a figure which shows the prior art described in patent document 1. FIG. It is a figure which shows the prior art described in patent document 2. FIG. It is a figure which shows the prior art described in patent document 3. FIG.

Explanation of symbols

1A, 1B Impeller fastening structure 3 Impeller
3a 1st hollow cylindrical part 4 Through-hole 4a Large diameter part 4b Small diameter part 5 Rotating shaft 5a 2nd hollow cylindrical part 6a Female thread part 6b Male thread part 7 Bolt 7a Bolt head 9 Washer 9a Sleeve part 9b Flat part 11 Fitting part 12 Ring groove 13 Contact surface 14 Inner ring groove

Claims (4)

An impeller having a through hole in the center in the axial direction;
A rotating shaft having a tip inserted on the back side of the impeller;
A bolt having a loosening prevention function and fastening the impeller and the rotating shaft;
The impeller has a first hollow cylindrical portion having the through hole as a hollow portion on the back side,
The rotating shaft has a second hollow cylindrical portion surrounding the first hollow cylindrical portion at the front end portion of the impeller.
The head of the bolt is located on the front side of the impeller,
In the rotating shaft, the internal thread portion that is screwed into the bolt is formed on the opposite side of the front surface of the impeller from the second hollow cylindrical portion,
In the impeller, an annular groove extending in the axial direction and the circumferential direction is formed on the back side so as to surround the first hollow cylindrical portion, and the second hollow cylindrical portion is located in the annular groove,
Of the front end surface of the first hollow cylindrical portion opposite to the front surface of the impeller and the bottom surface of the annular groove, the bottom surface hits the rotating shaft, and the bottom surface is in the second hollow cylindrical portion, An impeller fastening structure characterized by being in contact with a front end surface of the impeller. 2. The impeller fastening structure according to claim 1 , wherein an inner ring groove that is recessed radially inward and extending in the circumferential direction is formed radially inward of the innermost portion of the annular groove. The impeller fastening structure according to claim 1 or 2 , wherein the bolt is a spring bolt in which a slit is provided at a tip of a screw thread. The impeller fastening according to any one of claims 1 to 3 , wherein a metal washer having a sleeve portion that is concentrically fitted to the impeller is disposed between the impeller and the bolt. Construction.

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