JP2013188025A - Brushless motor and electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor in which locking strength of a cylindrical magnet for the shaft can be enhanced when compared with a case of fixing only with an adhesive, and to provide an electric tool using it as a drive source.SOLUTION: A first holder 34 has a protrusion 34a rising to the axial rear end side of a shaft 31 at the abutting part (outer edge of the rear end) against a cylindrical magnet 32. The cylindrical magnet 32 has a recess 32a (notch) at the abutting part (tip) against the first holder 34. The protrusion 34a of the first holder 34 and the recess 32a of the cylindrical magnet 32 form an uneven fitting structure, which serves as a mechanical locking part for preventing rotation of the cylindrical magnet 32 for the shaft 31.

Description

  The present invention relates to a brushless motor having a cylindrical magnet in a rotor and an electric tool using the brushless motor as a drive source.

  For example, in a factory line for flow work, the power tool is suspended from the ceiling with elastic rubber, etc., and the operator holds the power tool with a dominant hand and performs work such as screw tightening on the material to be tightened. Is going. In power tools used for such applications, it is required to make the brushless motor as a driving source small in order to make the gripping part of the housing easy to grip, and in order to make a brushless motor with a small diameter, Uses a cylindrical magnet. There is a gap between the inner surface of the cylindrical magnet and the outer periphery of the shaft, and the cylindrical magnet is bonded and fixed to the outer periphery of the shaft by an adhesive applied to the gap.

JP 2011-194484 A

  Adhesives deteriorate due to temperature changes and changes over time. For this reason, if it is configured to rely only on the adhesive to fix the cylindrical magnet and the shaft, the adhesive may be peeled off when the torque of the brushless motor is large, for example, while it is used for a long time even if there is no problem at first. is there. The same is true when checking the product life. When the adhesive is peeled off, the cylindrical magnet rotates with respect to the shaft, and the magnetization boundary line of the cylindrical magnet deviates from the design position, causing a problem in rotation control of the brushless motor.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a brushless motor capable of increasing the detent strength of the cylindrical magnet with respect to the shaft as compared with the case where only the adhesive is fixed. The object is to provide a power tool as a drive source.

One embodiment of the present invention is a brushless motor. This brushless motor
A shaft,
A rotor including a cylindrical magnet provided on the outer periphery of the shaft;
A stator including a magnetic flux generator facing the outer peripheral surface of the cylindrical magnet;
And a detent for restricting rotation of the cylindrical magnet with respect to the shaft.

Two holders that are integrated with the shaft by press fitting and sandwich the cylindrical magnet from both sides in the axial direction,
The butting portion between at least one of the holder and the cylindrical magnet may form the rotation preventing portion that is non-perpendicular to the axial direction of the shaft.

  The anti-rotation part may have an uneven fitting structure.

  The uneven fitting structure may be provided at a plurality of locations of the butting portion so as to be symmetric with respect to the axis of the shaft.

  The shaft and the holder may be made of metal.

  The cylindrical magnet may be a sintered magnet.

  The cylindrical magnet may be bonded to the shaft with an adhesive.

Another embodiment of the present invention is a brushless motor. This brushless motor
A shaft,
A rotor including a cylindrical magnet provided on the outer periphery of the shaft;
A stator including a magnetic flux generator facing the outer peripheral surface of the cylindrical magnet;
Two holders integrated with the shaft by press-fitting and sandwiching the cylindrical magnet from both axial sides;
At least one of the holders serves as a detent for the cylindrical magnet.

  Another aspect of the present invention is an electric tool using the brushless motor as a drive source.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, the holder integrated with the shaft by press-fitting forms a mechanical detent of the cylindrical magnet with respect to the shaft. The stopping strength can be increased.

Sectional drawing of the electric tool 1 which concerns on embodiment of this invention. The side view of the motor 3 of the electric tool 1 shown in FIG. Sectional drawing of the motor 3 of the electric tool 1 shown in FIG. The side view which made a part of rotor set of the motor 3 shown in FIG.2 and FIG.3 the cross section. The assembly explanatory drawing of the shaft 31, the cylindrical magnet 32, and the 1st holder 34 which are shown in FIG. (A) is an A arrow view of FIG. 5, (B) is a B arrow view of FIG. The side view which made a section of a rotor set which has a detent structure in another embodiment of the present invention a section. Assembly explanatory drawing of the shaft 31, the cylindrical magnet 32, and the 1st holder 34 which are shown in FIG. (A) is an A arrow view of FIG. 8, (B) is a B arrow view of FIG. It is the side view which made a section of a rotor set which has a rotation stopping structure in another embodiment of the present invention a section. Assembly explanatory drawing of the shaft 31, the cylindrical magnet 32, and the 1st holder 34 which are shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a cross-sectional view of a power tool 1 according to an embodiment of the present invention. FIG. 2 is a side view of the motor 3 of the electric power tool 1 shown in FIG. FIG. 3 is a sectional view of the same. FIG. 4 is a side view in which a part of the rotor set of the motor 3 shown in FIGS. FIG. 5 is an assembly explanatory diagram of the shaft 31, the cylindrical magnet 32, and the first holder 34 shown in FIG. 6A is a view as seen from an arrow A in FIG. 5, and FIG. 6B is a view as seen from an arrow B in FIG.

  As shown in FIG. 1, the electric tool 1 includes a motor 3 (brushless motor), a rotation transmission mechanism 4, and a control unit 5 inside a housing 2. A tip tool holding portion 6 is provided at the tip of the housing 2, and a switch 7 projects from the side surface of the housing 2. A power cord (not shown) is connected to the rear end of the housing 2, and power is supplied to the control unit 5 from an AC power source such as a commercial power source. On / off of energization to the control unit 5 is performed by an operator operating the switch 7. The control unit 5 is realized by hardware, software, and a combination thereof. The control unit 5 drives the motor 3, the rotation of the motor 3 is transmitted to the tip tool holding unit 6 by the rotation transmission mechanism 4, and a tip tool such as a bit (not shown) held by the tip tool holding unit 6 is driven to rotate. Work such as screw tightening is performed. The rotation control of the motor 3 by the control unit 5 is known per se and will not be described in detail. The rotation transmission mechanism 4 has a speed reduction mechanism and a clutch mechanism as shown in Patent Document 1, and the clutch mechanism is operated when a predetermined torque is reached, and the rotation transmission mechanism 4 is interposed between the speed reduction mechanism and the tip tool holding portion 6. Release rotation transmission.

  As shown in FIGS. 2 and 3, the motor 3 is a so-called inner rotor type brushless DC motor, and includes a shaft 31, a cylindrical magnet 32 that forms a rotor, a magnetic flux generator 33 that forms a stator, and first and first motors. 2 holders 34 and 35. For example, as shown in FIG. 3, the shaft 31 made of metal (steel or the like) includes, in order from the tip, a tip-side small diameter portion 31 a, a tip-side medium diameter portion 31 b, a large-diameter portion 31 c, and a rear-end side medium diameter portion 31 d. And integrally. The front end side medium diameter part 31b and the rear end side medium diameter part 31d of the shaft 31 are rotatably supported by bearings 36 and 37 fixed to the housing 2 side. The cylindrical magnet 32 is, for example, a sintered magnet, and is provided on the outer periphery of the shaft 31 (specifically, is provided to face the outer peripheral surface of the large-diameter portion 31c (surrounds the outer peripheral surface), for example, an adhesive. Glued). The cylindrical magnet 32 is magnetized after the shaft 31 is inserted. The magnetic flux generation unit 33 is an electromagnet whose magnetic pole faces the outer peripheral surface of the cylindrical magnet 32, and is formed by, for example, star-connected three-phase stator windings on the stator core. Since the configuration of the magnetic flux generator 33 is well known, detailed description thereof is omitted.

  The first and second holders 34 and 35 are made of a metal such as brass and are formed in a cylindrical shape. The first holder 34 is integrated with the distal end side middle diameter portion 31b of the shaft 31 by press-fitting, and the second holder 35 is a shaft. The first and second holders 34 and 35 sandwich the cylindrical magnet 32 from both sides in the axial direction of the shaft 31. The first and second holders 34 and 35 function as balance weights, and the outer circumferential surfaces of the first and second holders 34 and 35 are provided with concave grooves 341 and 351, respectively, around the axis of the shaft 31. It is done. The concave grooves 341 and 351 serve as guides when holes are provided for balancing.

  A cooling fan 38 is rotatably provided integrally with the shaft 31 at the small-diameter portion 31 a on the front end side of the shaft 31, and a sensor magnet 39 for position detection is integrally formed with the shaft 31 at the rear-end-side intermediate diameter portion 31 d of the shaft 31. It is provided so as to be rotatable. Three hall elements (not shown) are provided at 60 ° intervals around the axis of the shaft 31 at positions facing the sensor magnet 39. The rotational position of the motor 3 is detected by the output signals of these Hall elements.

  4-6, the 1st holder 34 has the convex part 34a which stands | starts up at the axial direction rear end side of the shaft 31 in the butting | matching part (outer edge part of a rear end) with the cylindrical magnet 32. As shown in FIG. The cylindrical magnet 32 has a recess 32 a (notch) at the abutting portion (tip) with the first holder 34. The convex portion 34 a of the first holder 34 and the concave portion 32 a of the cylindrical magnet 32 form a concave-convex fitting structure, and serve as a mechanical detent portion that prevents the cylindrical magnet 32 from rotating relative to the shaft 31. On the other hand, the abutting portion between the cylindrical magnet 32 and the second holder 35 (the rear end of the cylindrical magnet 32 and the front end of the second holder 35) is in the same plane perpendicular to the axis of the shaft 31 to form a detent structure. Not done. As shown in FIGS. 6A and 6B, two protrusions 34 a of the first holder 34 and two recesses 32 a of the cylindrical magnet 32 are symmetric with respect to the axis of the shaft 31. Each is formed in the same shape.

  According to the present embodiment, the following effects can be achieved.

(1) The concave / convex fitting structure of the convex portion 34a of the first holder 34 and the concave portion 32a of the cylindrical magnet 32 integrated with the shaft 31 by press-fitting serves as a mechanical detent for the cylindrical magnet 32 with respect to the shaft 31. Therefore, a greater anti-rotation strength can be obtained as compared with the case of fixing with an adhesive that is greatly deteriorated due to a change in temperature or a change with time. For this reason, it can prevent that the magnetization boundary line of the cylindrical magnet 32 shifts | deviates from a design position, a malfunction arises in rotation control of the motor 3, and it becomes possible to improve the reliability of a product.

(2) When the cylindrical magnet 32 is fixed to the shaft 31 by press-fitting, the strength at the time of press-fitting or thermal expansion after press-fitting tends to be insufficient, but in this embodiment, the inner surface of the cylindrical magnet 32 and the shaft 31 Even if there is a gap between the large-diameter portion 31c and the outer peripheral surface of the large-diameter portion 31c, the problem of insufficient strength of the cylindrical magnet 32 need not be considered, and a sintered magnet can be used. Further, an adhesive is interposed in the gap, so that the cylindrical magnet 32 can be more reliably fixed to the shaft 31 in addition to the mechanical detent described above.

(3) Since the convex portion 34a of the first holder 34 and the concave portion 32a of the cylindrical magnet 32 are formed so as to be symmetrical with respect to the axis of the shaft 31, the balance of the motor 3 by adopting a detent structure is adopted. Can reduce or eliminate adverse effects on

(4) Since the holders 34 and 35 that function as balance weights are used as rotation stoppers, it is not necessary to provide a rotation stopper separately, and the size of the motor 3 can be prevented from being increased. In addition, you may provide an anti-rotation part separately, for example, what is necessary is just to press-fit another anti-rotation part between a holder and a rotor, but the dimension of the axial direction of the motor 3 may become large, It takes time for assembly. Therefore, by constructing the rotation preventing portion integrally with the holder, it is possible to prevent the motor 3 from becoming large and reduce the number of assembly steps.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

  The first holder 34 is provided with a concave portion instead of the convex portion 34a, the cylindrical magnet 32 is provided with a convex portion instead of the concave portion 32a, and the concave-convex fitting structure between the concave portion of the first holder 34 and the convex portion of the cylindrical magnet 32 The anti-rotation part may be formed.

  The number of concave-convex fitting structures forming the rotation stopper is not limited to two described in the above embodiment, and may be one or three or more. In the case where the number is three or more, it is preferable in terms of balance to have the same angular spacing and the same shape so as to be symmetrical with respect to the axis of the shaft 31 as in the embodiment.

  In addition to the first holder 34, the same convex portion is provided at the tip of the second holder 35, and the same concave portion is provided at the rear end in addition to the tip of the cylindrical magnet 32, so that the cylindrical magnet 32 and the second holder An anti-rotation portion may also be formed at the abutting portion with 35.

  The adhesive between the shaft 31 and the cylindrical magnet 32 may not be provided, and the rotation of the cylindrical magnet 32 with respect to the shaft 31 may be prevented only by a mechanical detent structure.

  FIG. 7 is a side view, partly in section, of a rotor set having a detent structure according to another embodiment of the present invention. FIG. 8 is an assembly explanatory diagram of the shaft 31, the cylindrical magnet 32, and the first holder 34 shown in FIG. 9A is a view as seen from an arrow A in FIG. 8, and FIG. 9B is a view as seen from an arrow B in FIG. As shown in these drawings, the shape of the convex portion 34a of the first holder 34 and the concave portion 32a of the cylindrical magnet 32 is not limited to the quadrangle (for example, a rectangle) shown in FIGS. ). Alternatively, it may be semicircular or semielliptical. In other words, as long as the concave / convex fitting structure is formed that prevents rotation of the cylindrical magnet 32 with respect to the shaft 31, the shape of the concave portion and the convex portion is not limited.

  FIG. 10 is a side view of a part of a rotor set having a detent structure according to still another embodiment of the present invention. FIG. 11 is an assembly explanatory diagram of the shaft 31, the cylindrical magnet 32, and the first holder 34 shown in FIG. As shown in these drawings, the rotation prevention of the cylindrical magnet 32 with respect to the shaft 31 is not limited to the concave / convex fitting structure between the cylindrical magnet 32 and the first holder 34, and for example, the cylindrical magnet 32 and the first holder 34. May be realized by forming inclined end portions 32b and 34b that are planarly cut non-perpendicularly with the axis of the shaft 31. That is, as long as it functions as a mechanical detent that prevents rotation of the cylindrical magnet 32 relative to the shaft 31, the shape of the detent portion is not limited.

  The electric tool is not limited to the type that is suspended from the ceiling, for example, the type in which the motor 3 and the tip tool (tip tool holding portion 6) are arranged in a straight line and the housing 2 near the outer diameter of the motor 3 is gripped and used. Pistol or other types may be used.

  The brushless motor is not limited to a power tool, but may be used for other applications having a cylindrical magnet in the rotor.

1 Electric Tool 2 Housing 3 Motor (Brushless Motor)
4 Rotation transmission mechanism 5 Control unit 6 Tip tool holding unit 7 Switch 31 Shaft 32 Cylindrical magnet 32a Concave portion 33 Magnetic flux generating unit 34 First holder 34a Convex portion 35 Second holder 36, 37 Bearing 39 Sensor magnet

Claims (9)

A shaft,
A rotor including a cylindrical magnet provided on the outer periphery of the shaft;
A stator including a magnetic flux generator facing the outer peripheral surface of the cylindrical magnet;
A brushless motor, comprising: a rotation preventing portion that restricts rotation of the cylindrical magnet with respect to the shaft. Two holders that are integrated with the shaft by press fitting and sandwich the cylindrical magnet from both sides in the axial direction,
2. The brushless motor according to claim 1, wherein a butting portion between at least one of the holder and the cylindrical magnet forms the rotation preventing portion that is not perpendicular to the axial direction of the shaft.   The brushless motor according to claim 1, wherein the rotation preventing portion has an uneven fitting structure.   4. The brushless motor according to claim 3, wherein the concave-convex fitting structure is provided at a plurality of locations of the butting portion so as to be symmetric with respect to the axis of the shaft.   The brushless motor according to any one of claims 1 to 4, wherein the shaft and the holder are made of metal.   The brushless motor according to any one of claims 1 to 5, wherein the cylindrical magnet is a sintered magnet.   The brushless motor according to any one of claims 1 to 6, wherein the cylindrical magnet is bonded to the shaft with an adhesive. A shaft,
A rotor including a cylindrical magnet provided on the outer periphery of the shaft;
A stator including a magnetic flux generator facing the outer peripheral surface of the cylindrical magnet;
Two holders integrated with the shaft by press-fitting and sandwiching the cylindrical magnet from both axial sides;
A brushless motor in which at least one of the holders serves as a detent for the cylindrical magnet.   The electric tool which uses the brushless motor as described in any one of Claim 1 to 8 as a drive source.

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