Electric blower

Abstract

To provide an electric blower capable of easily and firmly connecting an impeller and a rotating shaft, and difficult in easy disassembly of the impeller and the rotating shaft.SOLUTION: An electric blower 1 includes: a motor 3 having a stepped shaft 2 as an output shaft; and an impeller 6 having boss hole 5. An inner peripheral face 35 of the boss hole 5 and an outer peripheral face 25 of a small-diameter portion 21 of the stepped shaft 2 have a spiral recessed portion 26 and a spiral projecting portion 36 to be fitted to each other to move the impeller 6 toward a stepped portion 23 of the stepped shaft 2 in normal rotation of the impeller 6. A projecting end portion of the small-diameter portion 21 has a groove 27 extending in a radial direction of the stepped shaft 2, and the boss hole 5 has an open end portion 32 at one side of the boss hole arranged at a root end side of the small-diameter portion 21 and in contact with the stepped portion 23, and an open end portion 33 at the other side of the boss hole arranged at a projecting end side of the small-diameter portion 21. The impeller 6 is provided with a detent portion 39 disposed on the open end portion 33 at the other side of the boss hole 5 in a cantilever manner and fitted to the groove 27 to inhibit relative rotational displacement between the impeller 6 and the stepped shaft 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an electric blower. [Background technology]

[0002] A conventional fan includes an inner wall that bisects the boss hole of the fan boss, and a rotating shaft having an axial groove that is inserted into the inner wall. The inner wall of the fan boss inserted into the axial groove transmits driving force from the rotating shaft to the fan boss.

[0003] Furthermore, the conventional fan includes an annular groove provided on the outer circumferential surface of the rotating shaft, and a protrusion provided on the inner circumferential surface of the boss hole and fitted into the annular groove. The protrusion fitted into the annular groove prevents the rotating shaft from slipping out of the boss hole.

[0004] The fan boss of the conventional fan has a slot that allows the protrusion to elastically move in the radial direction of the rotating shaft. The slot allows the protrusion to easily fit into the annular groove and to easily remove the protrusion from the annular groove. By providing this slot in the fan boss, the conventional fan allows the fan boss to be easily connected to and disassembled from the rotating shaft without the need for a fastening member such as a nut. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 52-85874 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, for example, a propeller fan generates axial thrust through rotation.

[0007] Therefore, in conventional fans, there is a risk that the protrusion, which is elastically supported in the radial direction of the rotating shaft, may become unable to resist the axial thrust and may come out of the annular groove. If the protrusion comes out of the annular groove, the fan boss may unintentionally separate from the rotating shaft.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an electric blower in which the impeller and the rotating shaft can be easily and firmly connected and in which it is difficult to disassemble the impeller and the rotating shaft. [Means for solving the problem]

[0009] An electric blower according to an embodiment of the present invention comprises an electric motor having a stepped shaft as an output shaft, and an impeller having a boss hole, the stepped shaft having a small diameter portion disposed in the boss hole, and a large diameter portion having a diameter larger than that of the small diameter portion, the inner surface of the boss hole and the outer surface of the small diameter portion have spiral concave and convex portions which fit together to cause the impeller to move toward a step portion created by the diameter difference between the small diameter portion and the large diameter portion when the impeller is rotated in the forward direction, the protruding end of the small diameter portion has a groove extending radially of the stepped shaft, the boss hole has one open end which is disposed on the base end side of the small diameter portion and contacts the step portion, and the other open end which is disposed on the protruding end side of the small diameter portion, and the impeller has a rotation prevention portion which is fitted into the groove to inhibit relative rotational displacement between the impeller and the stepped shaft. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of an electric blower according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of the electric blower according to the embodiment of the present invention. [Diagram 3] FIG. 2 is a perspective view of a stepped shaft of the electric blower according to the embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a boss portion of the electric blower according to the embodiment of the present invention. [Diagram 5] FIG. 2 is a cross-sectional view of a boss portion of the electric blower according to the embodiment of the present invention. [Figure 6]FIG. 2 is a perspective view of the outlet side of a boss hole of the electric blower according to the embodiment of the present invention. [Figure 7] FIG. 2 is a front view of a boss hole of the electric blower according to the embodiment of the present invention. [Figure 8] FIG. 4 is a schematic cross-sectional view of a recess and a protrusion of the electric blower according to the embodiment. [Figure 9] FIG. 4 is a schematic cross-sectional view of a recess and a protrusion of the electric blower according to the embodiment. [Figure 10] FIG. 6 is a perspective view of another example of the boss portion of the electric blower according to the embodiment of the present invention. [Figure 11] FIG. 4 is an enlarged cross-sectional view of a portion of another example of an electric blower according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of an electric blower according to the present invention will be described with reference to Figures 1 to 11. Note that in the various drawings, the same or corresponding components are denoted by the same reference numerals.

[0012] FIG. 1 is a schematic cross-sectional view of an electric blower according to an embodiment of the present invention.

[0013] FIG. 2 is an enlarged cross-sectional view of a portion of the electric blower according to the embodiment of the present invention.

[0014] 1 and 2, an electric blower 1 according to this embodiment includes an electric motor 3 having a stepped shaft 2 as an output shaft, and an impeller 6 having a boss hole 5. The stepped shaft 2 fixed to the boss hole 5 integrates the electric motor 3 and the impeller 6 together.

[0015] When electric blower 1 rotates impeller 6 counterclockwise in a front view indicated by solid arrow A, it causes fluid, primarily air, to flow toward the front indicated by solid arrow F. When electric blower 1 rotates impeller 6 clockwise in a front view indicated by solid arrow A, it causes fluid to flow toward the rear, which is the opposite direction of solid arrow F (the direction of solid arrow A).

[0016] Note that the rotation of the impeller 6 and the stepped shaft 2 that causes the fluid to flow toward the front as indicated by solid arrow F will be referred to as "forward rotation", and the rotation of the impeller 6 and the stepped shaft 2 that causes the fluid to flow toward the back, which is the opposite direction of solid arrow F (the direction of solid arrow A), will be referred to as "reverse rotation". In Fig. 1, the forward rotating impeller 6 rotates by moving the left side of the rotation center line C toward the front of the paper, and the right side of the rotation center line C toward the back of the paper. In Fig. 1, the reverse rotating impeller 6 rotates by moving the left side of the rotation center line C toward the back of the paper, and the right side of the rotation center line C toward the front of the paper.

[0017] Furthermore, when a fluid flowing from the rear side of the impeller 6 to the front side of the impeller 6, i.e., a fluid flowing in the direction of the solid line arrow F, is blown onto the rear side of the impeller 6, the impeller 6 and the stepped shaft 2 rotate in the forward direction. When a fluid flowing from the front side of the impeller 6 to the rear side of the impeller 6, i.e., a fluid flowing in the opposite direction of the solid line arrow F, is blown onto the front side of the impeller 6, the impeller 6 and the stepped shaft 2 rotate in the reverse direction.

[0018] The electric motor 3 rotates the impeller 6. The stepped shaft 2 transmits the rotational driving force of the electric motor 3 to the impeller 6, or transmits the rotational driving force of the impeller 6 to the electric motor 3. The stepped shaft 2 is the center of rotation of the impeller 6.

[0019] The impeller 6 is, for example, an axial flow impeller, or a so-called propeller. The impeller 6 includes a hub 11 having a boss hole 5, and a plurality of blades 12 that protrude radially outward from the outer circumferential surface of the hub 11 in the radial direction of the hub 11. The impeller 6 is, for example, a molded product made of resin. The impeller 6 may be an integrally molded product, or may be an assembly of a plurality of parts.

[0020] The hub 11 has a cylindrical boss portion 15 having a boss hole 5, a flange portion 16 that extends radially outward in a circular shape from the boss portion 15, and a cylindrical portion 17 that annularly surrounds the boss portion 15 and the flange portion 16. The center line of the boss portion 15, the center line of the flange portion 16, and the center line of the cylindrical portion 17 substantially coincide with the rotation center line C of the impeller 6.

[0021] The boss portion 15 supports the impeller 6 on the stepped shaft 2 .

[0022] The blades 12 are provided on the outer circumferential surface of the cylindrical portion 17 and are aligned at substantially equal intervals in the circumferential direction of the cylindrical portion 17 .

[0023] FIG. 3 is a perspective view of a stepped shaft of an electric blower according to an embodiment of the present invention.

[0024] 1 to 3, the stepped shaft 2 of the electric blower 1 according to this embodiment has a small diameter portion 21 that is placed in the boss hole 5 of the impeller 6, and a large diameter portion 22 that has a larger diameter than the small diameter portion 21. The stepped shaft 2 also has a step portion 23 due to the diameter difference between the small diameter portion 21 and the large diameter portion 22.

[0025] The small diameter portion 21 has a substantially uniform diameter. The outer peripheral surface 25 of the small diameter portion 21 has a spiral recess 26. The recess 26 extends from the base end of the small diameter portion 21 to the protruding end of the small diameter portion 21. When viewed in the direction of the solid arrow A, the recess 26 winds counterclockwise from the base end of the small diameter portion 21 to the protruding end of the small diameter portion 21. In other words, the recess 26 has a spiral shape that winds in the same direction as a right-handed screw.

[0026] The stepped shaft 2 of the present embodiment has one recess 26, but may have two recesses 26. The two recesses 26 are preferably arranged at equal intervals in the circumferential direction of the small diameter portion 21, that is, at intervals of 180 degrees.

[0027] In addition, the protruding end of the small diameter portion 21 has a groove 27 extending radially of the stepped shaft 2, and a chamfered portion 28 that brings the outer peripheral edge of the protruding end closer to the step portion 23 than the central portion of the protruding end.

[0028] Groove 27 extends in a straight line through the center line of small diameter portion 21, the center line of stepped shaft 2, and the rotation center line C of electric blower 1. Groove 27 has a rectangular shape that is open in the extension direction of small diameter portion 21. It is preferable that groove 27 does not overlap with the end of recess 26 that appears at the protruding end of small diameter portion 21. In this embodiment, the end of recess 26 that appears at the protruding end of small diameter portion 21 is located at the point farthest from groove 27, that is, at a point 90 degrees away from the center line of groove 27 in the circumferential direction of small diameter portion 21.

[0029] The chamfered portions 28 are provided at all corners of the projecting end portion of the small diameter portion 21 except for the edges (corners) of the grooves 27 .

[0030] The chamfered portion 28 may be a C-chamfer (chamfer) in which the corner of the protruding end of the small diameter portion 21 is cut into a flat surface (Figure 3), or it may be an R-chamfer (round) in which the corner of the protruding end of the small diameter portion 21 is cut into a round shape.

[0031] In addition, chamfered portion 28 may be formed by simply removing the corners of the protruding end of small diameter portion 21, or by making a convex portion 31, which has a diameter slightly smaller than that of small diameter portion 21, protrude from the protruding end of small diameter portion 21 and removing the corners of convex portion 31 (FIG. 3).

[0032] In the vicinity of the end of the recess 26 appearing at the protruding end of the small diameter portion 21, the chamfered portion 28 is preferably disposed toward the center of the small diameter portion 21, avoiding the recess 26. Therefore, most of the chamfered portion 28 extends in an arc shape when viewed in the axial direction, while the chamfered portion 28 has an avoidance portion 28a that extends in a straight line like a chord of the arc, avoiding the recess 26, in the vicinity of the end of the recess 26. In addition, the avoidance portion 28a of the chamfered portion 28 extends parallel to the groove 27, reliably avoiding the recess 26, since the end of the recess 26 appearing at the protruding end of the small diameter portion 21 is disposed at a position 90 degrees away from the center line of the groove 27 in the circumferential direction of the small diameter portion 21. In other words, the avoidance portion 28a is closer to the center line of the small diameter portion 21 than other parts of the chamfered portion 28.

[0033] Step portion 23 is an annular surface facing the protruding end of stepped shaft 2, and has a normal line substantially parallel to rotation center line C of stepped shaft 2. Step portion 23 contacts open end 32 of boss hole 5 of impeller 6 closer to electric motor 3. Step portion 23 determines the position of impeller 6 in the direction in which impeller 6 approaches electric motor 3, and supports a force (thrust) that moves impeller 6 closer to electric motor 3.

[0034] 4 and 5 are cross-sectional views of a boss portion of an electric blower according to an embodiment of the present invention.

[0035] Fig. 4 is a cross-sectional view taken at the same cross-sectional position as Fig. 1 and Fig. 2. Fig. 5 is a cross-sectional view taken at a cross-sectional position passing through the rotation center line C of the stepped shaft 2 and perpendicular to the cross section of Fig. 4.

[0036] 1, 2, 4, and 5, boss hole 5 of electric blower 1 according to this embodiment has one open end 32 disposed on the base end side of small diameter portion 21 of stepped shaft 2 and facing stepped portion 23, and the other open end 33 disposed on the protruding end side of small diameter portion 21. One open end 32 is closer to motor 3 than the other open end 33. One open end 32 is in contact with stepped portion 23 of stepped shaft 2. For ease of explanation, the opening on the side of one open end 32 is called inlet 32a of boss hole 5, and the opening on the side of the other open end 33 is called outlet 33a of boss hole 5.

[0037] The boss hole 5 has a substantially uniform inner diameter. An inner peripheral surface 35 of the boss hole 5 has a spiral convex portion 36. The convex portion 36 extends from one open end 32 toward the other open end 33, but does not reach the other open end 33. The convex portion 36 is wound counterclockwise from one open end 32 toward the other open end 33 when viewed in the direction of the solid arrow A. In other words, the convex portion 36 has a spiral shape that winds in the same direction as a right-handed screw.

[0038] The boss hole 5 in this embodiment has one protrusion 36, but may have two protrusions 36. The two protrusions 36 are preferably arranged at equal intervals in the circumferential direction of the boss hole 5. The boss hole 5 preferably has the same number of protrusions 36 as the recesses 26 of the small diameter portion 21, but may have fewer protrusions 36 than the recesses 26 of the small diameter portion 21.

[0039] 1, the recess 26 of the small diameter portion 21 is tightly fitted into the protrusion 36 of the boss hole 5 the more the stepped shaft 2 is rotated counterclockwise relative to the impeller 6. Therefore, the recess 26 of the small diameter portion 21 and the protrusion 36 of the boss hole 5 are fitted together so that the impeller 6 moves toward the stepped portion 23 when the impeller 6 is rotated forward by the electric motor 3. The recess 26 of the small diameter portion 21 and the protrusion 36 of the boss hole 5 are also fitted together so that the impeller 6 moves toward the stepped portion 23 when a fluid flowing in the direction of the solid arrow F is sprayed against the back surface of the impeller 6.

[0040] FIG. 6 is a perspective view of the outlet side of the boss hole of the electric blower according to the embodiment of the present invention.

[0041] Fig. 7 is a front view of a boss hole of an electric blower according to an embodiment of the present invention. That is, Fig. 7 is a view of the boss hole viewed in the direction of solid arrow A in Fig. 1. As described above, impeller 6 rotates forward in the counterclockwise direction (solid arrow X) and reversely rotates clockwise (solid arrow Y).

[0042] As shown in FIGS. 1, 2, and 4 to 7, the impeller 6 is provided with a rotation prevention portion 39 provided in a cantilever shape at the other open end portion 33 of the boss hole 5.

[0043] The anti-rotation portion 39 is integrally molded with the boss portion 15. The anti-rotation portion 39 is a so-called anti-rotation portion that is fitted into the groove 27 at the protruding end of the stepped shaft 2 during the process of inserting the stepped shaft 2 into the boss hole 5, and inhibits relative rotational displacement between the impeller 6 and the stepped shaft 2. The anti-rotation portion 39 is provided so as to protrude from the inner circumferential surface 35 of the boss hole 5. Therefore, it elastically deforms so as to bend (flex) with the end connected to the inner circumferential surface 35 of the boss hole 5 as the fixed end.

[0044] The anti-rotation portion 39 has a pair of opposing cantilever-shaped fixed pieces 41. The pair of fixed pieces 41 are separated by a gap on the center line of the boss hole 5. The anti-rotation portion 39 has a rectangular cross section that fits into the rectangular groove 27 of the stepped shaft 2.

[0045] When the protruding end of the stepped shaft 2 is aligned with the entrance 32a of the boss hole 5 and the protruding portion 36 of the boss hole 5 is fitted into the recessed portion 26 of the stepped shaft 2, the stepped shaft 2 is rotated counterclockwise relative to the impeller 6 as viewed in the direction of the solid arrow A in FIG. 1 (this is equivalent to rotating the impeller 6 clockwise relative to the stepped shaft 2 and rotating in the direction to tighten the right-handed screw), the protruding portion 36 of the boss hole 5 advances through the recessed portion 26 of the stepped shaft 2 and the stepped shaft 2 is screwed into the boss hole 5. Then, before the entrance 32a of the boss hole 5 reaches the stepped portion 23 of the stepped shaft 2, the anti-rotation portion 39 provided at the exit 33a of the boss hole 5 comes into contact with the protruding end of the small diameter portion 21 of the stepped shaft 2. When the stepped shaft 2 is further screwed into the boss hole 5, the anti-rotation portion 39 in contact with the protruding end of the small diameter portion 21 is pushed by the small diameter portion 21 and begins to bend elastically.

[0046] At this time, the anti-rotation portion 39 bends by moving the tip portion of the fixed piece 41 outward from the boss hole 5 like a cantilever beam whose root connected to the inner peripheral surface 35 of the boss hole 5 is a fixed end. In other words, the pair of fixed pieces 41 are deformed into a mountain shape. The amount of bending (magnitude of bending displacement) of each fixed piece 41 is controlled by the chamfered portion 28 of the protruding end of the small diameter portion 21, and is kept small within a range in which elastic deformation is possible without bending. The chamfered portion 28 makes the protruding end of the small diameter portion 21 have a tapered shape, that is, a tapered shape. Therefore, the chamfered portion 28 moves the contact point between the small diameter portion 21 and the anti-rotation portion 39 closer to the center line side of the small diameter portion 21 than a protruding end that is not chamfered and is angular, in other words, farther from the fixed end of the anti-rotation portion 39. Therefore, the amount of bending of the anti-rotation portion 39 that is pushed and bent by the small diameter portion 21 is suppressed compared to when it is pushed and bent by a protruding end that is not chamfered and is angular. The range of the chamfered portion 28 is determined so that the bending of the anti-rotation portion 39 falls within the range of the elastic deformation of the anti-rotation portion 39 .

[0047] When the stepped shaft 2 is further screwed into the boss hole 5 while the anti-rotation portion 39 is being pressed and bent by the small diameter portion 21, the entrance 32a of the boss hole 5 reaches and comes into contact with the stepped portion 23 of the stepped shaft 2. Furthermore, essentially at the same time that the entrance 32a of the boss hole 5 comes into contact with the stepped portion 23 of the stepped shaft 2, the anti-rotation portion 39 fits into the groove 27 at the protruding end of the stepped shaft 2, and the elastic deformation (flexure, bending) of the anti-rotation portion 39 is restored.

[0048] As a result, the movement of the impeller 6 in the direction toward the electric motor 3 is restricted by contact with the step portion 23 of the stepped shaft 2, and the rotation of the impeller 6 relative to the stepped shaft 2 is restricted by the anti-rotation portion 39 fitted into the groove 27 of the stepped shaft 2, and the movement of the impeller 6 in the direction away from the electric motor 3 is restricted.

[0049] The anti-rotation portion 39 fitted into the groove 27 is pressed strongly against the side surface of the groove 27, and is not pressed strongly against the bottom surface of the groove 27, regardless of whether the impeller 6 rotates forward or backward. In other words, the anti-rotation portion 39 fitted into the groove 27 does not undergo bending deformation that would cause it to come out of the groove 27 due to the load or weight caused by the rotation of the impeller 6. If the impeller 6 is to be separated from the stepped shaft 2, the anti-rotation portion 39 must be intentionally bent significantly to come out of the groove 27, and then while maintaining that state, the impeller 6 and the stepped shaft 2 must be rotated in the direction that removes the right-handed threads.

[0050] When the electric motor 3 is driven to rotate the impeller 6 in the forward direction, a thrust is generated in the impeller 6 in a direction approaching the electric motor 3 (the direction of the solid arrow A in FIG. 1), and this thrust is supported by the stepped portion 23 of the stepped shaft 2. Also, when a fluid flowing from the front side of the impeller 6 to the rear side of the impeller 6 (the opposite direction of the solid arrow F in FIG. 1) is sprayed onto the front side of the impeller 6, the impeller 6 is pushed in a direction approaching the electric motor 3 while rotating in the reverse direction, and the force of this fluid is supported by the stepped portion 23 of the stepped shaft 2.

[0051] On the other hand, when the electric motor 3 is driven to rotate the impeller 6 in the reverse direction, a thrust is generated in the impeller 6 in a direction away from the electric motor 3 (the opposite direction of the solid arrow A in FIG. 1), but the rotational displacement of this thrust is limited by the anti-rotation portion 39, and the thrust is supported by the restricted recess 26 of the stepped shaft 2 and the protrusion 36 of the impeller 6. Also, when a fluid flowing from the rear side of the impeller 6 to the front side of the impeller 6 (in the direction of the solid arrow F in FIG. 1) is sprayed onto the rear side of the impeller 6, the impeller 6 is pushed in a direction away from the electric motor 3 while rotating forward, but the force of this fluid is supported by the restricted recess 26 of the stepped shaft 2 and the protrusion 36 of the impeller 6, and the rotational displacement of this thrust is limited by the anti-rotation portion 39.

[0052] The protrusion 36 that has not reached the other open end 33 of the boss hole 5 is closer to the center of the boss hole 5 than the anti-rotation portion 39 in the direction of the center line of the boss hole 5. In other words, in a cross-sectional view perpendicular to the center line of the boss hole 5, the cross section of the anti-rotation portion 39 and the cross section of the protrusion 36 do not appear at the same time. The boss portion 15 and the impeller 6 having such a cross-sectional structure can easily have the protrusion 36 and the anti-rotation portion 39 molded integrally with resin inside the boss hole 5.

[0053] Next, the fit between the recess 26 of the stepped shaft 2 and the protrusion 36 of the boss hole 5 will be described.

[0054] 8 and 9 are schematic cross-sectional views of the recessed and protruding portions of the electric blower according to this embodiment.

[0055] As shown in Figure 8, when the protruding height dimension H of the convex portion 36 of the boss hole 5 is larger than the depth dimension d of the recessed portion 26 of the stepped shaft 2, it is preferable that the depth dimension d of the recessed portion 26 is 0.8 times or more the protruding height dimension H of the convex portion 36. [Number 1] (depth dimension d of recess 26) ≧ (projection height dimension H of protrusion 36) × 0.8

[0056] Furthermore, as shown in FIG. 8, when the depth dimension d of the recess 26 of the stepped shaft 2 is greater than the protruding height dimension H of the protruding portion 36 of the boss hole 5, it is preferable that the protruding height dimension H of the protruding portion 36 is 0.8 times or more the depth dimension d of the recess 26 of the stepped shaft 2. [Number 2] (Protruding height dimension H of convex portion 36) ≧ (Depth dimension d of concave portion 26) × 0.8

[0057] In other words, it is preferable that at least 80% or more of the height (depth) of the convex portion 36 and the concave portion 26 are fitted together. Therefore, it is preferable that the relationship of [Equation 3] be satisfied between the protruding height dimension H of the convex portion 36 and the depth dimension d of the concave portion 26. [Number 3] 0.8≦(protruding height dimension H of convex portion 36)÷(depth dimension d of concave portion 26)≦1.25

[0058] Furthermore, it is preferable that the gap between the convex portion 36 and the concave portion 26 in the direction parallel to the rotation center line C of the stepped shaft 2, that is, the play, is smaller than the overlap between the groove 27 of the stepped shaft 2 and the anti-rotation portion 39 in the direction parallel to the rotation center line C of the stepped shaft 2. Such a gap reliably prevents the anti-rotation portion 39 from slipping out of the groove 27 even when a force acts on the impeller 6 in a direction approaching the electric motor 3, and reliably maintains the anti-rotation function between the stepped shaft 2 and the impeller 6.

[0059] Note that the recess 26 may be provided in the boss hole 5, and the protrusion 36 may be provided in the stepped shaft 2. In other words, it is sufficient that the inner circumferential surface 35 of the boss hole 5 and the outer circumferential surface 25 of the small diameter portion 21 have the spiral recess 26 and protrusion 36 that fit together to move the impeller 6 toward the stepped portion 23 when the impeller 6 is rotated in the forward direction.

[0060] Furthermore, when the recess 26 is provided in the boss hole 5 and the protrusion 36 is provided in the stepped shaft 2, the recess 26 does not reach the other open end 33 and is closer to the center of the boss hole 5 than the anti-rotation portion 39 in the center line direction of the boss hole 5. The boss portion 15 and the impeller 6 having such a cross-sectional structure can easily have the recess 26 and the anti-rotation portion 39 integrally molded with resin within the boss hole 5. In other words, it is sufficient that either the protrusion 36 or the recess 26 is provided on the inner circumferential surface 35 of the boss hole 5, does not reach the other open end 33 of the boss hole 5, and is closer to the center of the boss hole 5 than the anti-rotation portion 39 in the center line direction of the boss hole 5.

[0061] Furthermore, the protrusions 36 and the recesses 26 have an arcuate cross-sectional shape that allows them to fit together, but they may have a polygonal cross-sectional shape such as a triangular or rectangular shape.

[0062] FIG. 10 is a perspective view of another example of the boss portion of the electric blower according to the embodiment of the present invention.

[0063] FIG. 11 is a partially enlarged cross-sectional view of another example of an electric blower according to an embodiment of the present invention.

[0064] 10 and 11, impeller 6A of electric blower 1 according to this embodiment includes anti-rotation portion 39A disposed outside boss hole 5A. In other words, anti-rotation portion 39A is provided outside outlet 33a of boss hole 5A. When stepped shaft 2 is tightened into boss hole 5A, the protruding end of small diameter portion 21 protrudes from outlet 33a of boss hole 5A to the outside of boss hole 5A within the range of overlapping dimension between groove 27 and anti-rotation portion 39A in the direction of rotation center line C.

[0065] In impeller 6A, protrusion 36 may extend from inlet 32a to outlet 33a of boss hole 5A. Since anti-rotation portion 39A is disposed outside boss hole 5A, a cross section of anti-rotation portion 39A and a cross section of protrusion 36 do not appear at the same time in a cross section perpendicular to the center line of boss hole 5A. Therefore, boss portion 15A and impeller 6A can easily be integrally molded with recess 26 inside boss hole 5 and anti-rotation portion 39 outside boss hole 5 using resin.

[0066] As described above, the electric blower 1 according to this embodiment includes the spiral recess 26 and protrusion 36 that are provided on the inner peripheral surface 35 of the boss hole 5, 5A and the outer peripheral surface 25 of the small diameter portion 21 and that fit together to move the impeller 6, 6A toward the step portion 23 caused by the diameter difference between the small diameter portion 21 and the large diameter portion 22 when the impeller 6, 6A is rotated forward, and the anti-rotation portions 39, 39A that are provided in a cantilever shape on the other open end 33 of the boss hole 5, 5A and are fitted into the groove 27 at the protruding end of the small diameter portion 21 to inhibit the relative rotational displacement between the impeller 6, 6A and the stepped shaft 2. Therefore, the electric blower 1 can easily and firmly connect the impeller 6, 6A and the stepped shaft 2, but the impeller 6, 6A and the stepped shaft 2 cannot be easily disassembled. That is, unlike conventional propeller fans, the impellers 6, 6A will not unintentionally come off the stepped shaft 2. Note that a fixing structure between the stepped shaft and the impeller similar to that of the electric blower 1 according to this embodiment can be easily applied to sirocco fans, cross flow fans, and turbo fans, which are not prone to coming apart by reversing the direction of rotation like a propeller fan.

[0067] Furthermore, electric blower 1 according to this embodiment has chamfered portion 28 that brings the outer circumferential edge of the protruding end of small diameter portion 21 closer to stepped portion 23 than the center of the protruding end of small diameter portion 21. Therefore, when fixing impellers 6, 6A to stepped shaft 2, electric blower 1 can smoothly insert stepped shaft 2 into boss hole 5, and when anti-rotation portions 39, 39A come into contact with the protruding end of small diameter portion 21 just before fitting into groove 27 of small diameter portion 21, anti-rotation portions 39, 39A can bend gently and the amount of bending can be suppressed.

[0068] Furthermore, electric blower 1 according to this embodiment includes anti-rotation portions 39, 39A having a pair of opposing cantilever-shaped fixed pieces 41. Therefore, electric blower 1 can reduce stress generated at the fixed ends of fixed pieces 41 due to the rotation load of impellers 6, 6A.

[0069] Moreover, electric blower 1 according to this embodiment has spiral recessed portion 26 and protruding portion 36 that fit together with a relationship of 0.8≦(projection height dimension H of protruding portion 36)÷(depth dimension d of recessed portion 26)≦1.25. Therefore, electric blower 1 can suppress slippage and gaps (play) between impellers 6, 6A and stepped shaft 2, and can improve assembly ease.

[0070] Furthermore, electric blower 1 according to this embodiment has recessed portion 26 and protruding portion 36 that have a gap in the direction of rotation center line C that is smaller than the overlap between groove 27 and anti-rotation portions 39, 39A. Therefore, electric blower 1 can reliably prevent impellers 6, 6A and stepped shaft 2 from being unintentionally disassembled.

[0071] Furthermore, electric blower 1 according to this embodiment includes protrusion 36 or recess 26 that is provided on inner circumferential surface 35 of boss hole 5, does not reach the other open end 33 of boss hole 5, and is closer to the center of boss hole 5 than anti-rotation portion 39 in the direction of the center line of boss hole 5. Therefore, electric blower 1 can easily be integrally molded with resin impeller 6.

[0072] Furthermore, electric blower 1 according to this embodiment includes protruding portion 36 and recessed portion 26 having an arc-shaped or polygonal cross-sectional shape that can fit together. In other words, electric blower 1 allows for easy assembly and precise fit between recessed portion 26 and protruding portion 36.

[0073] Therefore, according to electric blower 1 of this embodiment, impellers 6, 6A and stepped shaft 2 can be easily and firmly connected, and impellers 6, 6A and stepped shaft 2 are difficult to disassemble easily.

[0074] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0075] 1...electric blower, 2...stepped shaft, 3...electric motor, 5, 5A...boss hole, 6, 6A...impeller, 11...hub, 12...blade, 15, 15A...boss portion, 16...flange portion, 17...cylindrical portion, 21...small diameter portion, 22...large diameter portion, 23...step portion, 25...outer peripheral surface of small diameter portion, 26...recess, 27...groove, 28...chamfered portion, 28a...avoidance portion, 31...convex portion, 32...one opening end, 32a...inlet, 33...the other opening end, 33a...outlet, 35...inner peripheral surface of boss hole, 36...convex portion, 39, 39A...anti-rotation portion, 41...fixing piece.

Claims

1. an electric motor having a stepped shaft as an output shaft; an impeller having a boss hole; the stepped shaft has a small diameter portion disposed in the boss hole and a large diameter portion having a diameter larger than that of the small diameter portion, an inner peripheral surface of the boss hole and an outer peripheral surface of the small diameter portion have a spiral recess and a spiral protrusion that fit together to move the impeller toward a step portion caused by a diameter difference between the small diameter portion and the large diameter portion when the impeller is rotated in the forward direction; the protruding end of the small diameter portion has a groove extending in a radial direction of the stepped shaft, the boss hole has one opening end portion disposed on a base end side of the small diameter portion and in contact with the step portion, and the other opening end portion disposed on a protruding end side of the small diameter portion, The impeller of the electric blower has a rotation prevention portion that is fitted into the groove and prevents relative rotational displacement between the impeller and the stepped shaft.

2. 2. The electric blower according to claim 1, wherein the protruding end has a chamfered portion that brings an outer circumferential edge portion of the protruding end, which is closer to the outer circumferential surface of the small diameter portion, closer to the stepped portion than a central portion of the protruding end, which is closer to a center line of the stepped shaft.

3. 3. The electric blower according to claim 1, wherein the anti-rotation portion has a pair of cantilever-shaped fixing pieces facing each other.

4. When the protruding height of the convex portion is H and the depth of the concave portion is d, the relationship between the protruding height H of the convex portion and the depth d of the concave portion is expressed as follows: 0.8≦(H÷d)≦1.25 4. The electric blower according to claim 1, wherein

5. In the direction of the rotation centerline, The electric blower according to claim 1 , wherein a gap between the protrusion and the recess is smaller than an overlap between the groove and the anti-rotation portion.

6. 6. The electric blower according to claim 1, wherein one of the convex portion and the concave portion is provided on an inner circumferential surface of the boss hole, does not reach the other open end of the boss hole, and is closer to a center of the boss hole in a center line direction of the boss hole than the anti-rotation portion.

7. The electric blower according to claim 1 , wherein the protruding portion and the recessed portion have a cross-sectional shape that is an arc or a polygon so as to be able to fit into each other.

8. The electric blower according to claim 1 , wherein an outer circumferential surface of the small diameter portion has a plurality of recesses, and an inner circumferential surface of the boss hole has fewer protrusions than recesses.

9. An electric blower as described in any one of claims 1 to 7, wherein the inner surface of the boss hole has a recess consisting of multiple rows, and the outer surface of the small diameter portion has a protrusion with fewer rows than the recess.

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