JP2014124745A - Electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric tool which has sufficient dust resistance and vibration proof properties in a bearing part.SOLUTION: An electric tool includes a motor 31 as a driving source, a housing 11 for housing the motor 31, a motor shaft 32 of the motor 31, a bearing for journaling the motor shaft 32, a labyrinth formation member 20 fitted to an outer ring of the bearing, a bearing storage hole 12b for supporting the bearing, and a dust-proof collar 40 which is disposed adjacent to the labyrinth formation member 20 and forms a labyrinth clearance in cooperation with the labyrinth formation member 20. The labyrinth formation member 20 has an elastic body fitting part which is formed on the outer periphery of the labyrinth formation member 20, an elastic body is fitted to the elastic body fitting part, and the bearing 20 to which the labyrinth formation member 20 is fitted, is supported in the bearing storage hole 12b via the elastic body.

Description

  The present invention relates to a dust-proof structure and a vibration-proof structure of a bearing portion that supports a motor shaft and the like in a power tool.

  Conventionally, in an electric tool that uses a motor as a drive source, a dustproof structure has been provided in order to prevent dust such as cutting powder from entering a bearing that supports a motor shaft. For example, in the electric power tool described in Patent Document 1 below, a labyrinth forming member (bearing cap) that is attached to the outer ring of the bearing, a dust-proof collar (dust-proof ring) installed adjacent to the bearing, and a bearing housing in the motor housing A labyrinth gap is formed by a ring-shaped protrusion formed around the opening of the hole (bearing insertion hole), thereby preventing dust from entering the bearing.

  In addition, the description of Patent Document 1 below discloses that the labyrinth forming member is formed of rubber or resin, and when rubber is selected, the bearing is a bearing receiving hole through the rubber labyrinth forming member. Therefore, the transmission of the vibration of the motor shaft to the motor housing is suppressed.

JP-A-8-182242

  However, as described above, when the labyrinth forming member is made of rubber, the shape accuracy is low, so it is difficult to set the labyrinth gap to the dimension as designed. Moreover, even if it can be manufactured in the shape as designed, there is a possibility that the shape may change due to insertion resistance or the like when it is inserted into the bearing housing hole during assembly. Further, the shape of the power tool may change due to the load during operation of the power tool or the use for many years, and the labyrinth gap may not be maintained at the designed dimensions. For example, if the labyrinth gap becomes zero and contact (sliding contact) occurs between the members that form the labyrinth gap, wear powder is generated, and the wear powder may break into the bearing and damage the bearing. I'm worried.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an electric tool that stably has sufficient dustproof properties and vibration-proofing properties in a bearing portion.

  An electric power tool according to the present invention includes a motor that is a drive source, a housing that houses the motor, a motor shaft of the motor, a bearing that supports the motor shaft, and a labyrinth that is attached to an outer ring of the bearing. A labyrinth forming member, a bearing housing hole in which the bearing is supported, and a dust-proof collar that is disposed adjacent to the labyrinth forming member and forms a labyrinth gap in cooperation with the labyrinth forming member. The member has an elastic body mounting portion formed on an outer peripheral portion, the elastic body mounting portion is mounted with an elastic body, and the bearing on which the labyrinth forming member is mounted is stored in the bearing via the elastic body. It is supported by a hole.

  In the electric tool according to the present invention, the outer surface of the elastic body is in contact with the inner peripheral surface of the bearing storage hole, and a gap is formed between the outer surface of the labyrinth forming member and the inner peripheral surface of the bearing storage hole. Can be formed.

  Moreover, in the electric tool which concerns on this invention, the said elastic body mounting part can be formed as a surrounding groove.

  Furthermore, in the electric tool according to the present invention, the elastic body can be formed in a ring shape.

  Furthermore, in the electric tool according to the present invention, a labyrinth gap can be formed between the outer peripheral surface of the dust-proof collar and the inner peripheral surface of the bearing housing hole.

  ADVANTAGE OF THE INVENTION According to this invention, in the bearing part, the electric tool which has sufficient dustproof property and vibration proof property stably can be provided.

It is a top view of the electric tool concerning this embodiment. It is a left view of the electric tool which concerns on this embodiment. It is a figure which shows the cross section AA in FIG. It is a principal part enlarged view of FIG. It is a figure explaining another embodiment.

  Hereinafter, a preferred embodiment for carrying out the present invention will be described with reference to FIGS. In the following embodiments, a case where the present invention is applied to a hand-held electric grinder will be described as an example. In addition, the following embodiments do not limit the invention according to each claim, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. .

  FIG. 1 is a plan view of the electric power tool according to the present embodiment. FIG. 2 is a left side surface of the electric power tool according to the present embodiment. FIG. 3 is a view showing a section AA in FIG. 4 is an enlarged view of a main part of FIG. Further, in this specification, “front and rear” are defined and described as shown in FIG.

  As shown in FIGS. 1 to 4, a hand-held electric grinder 10 that is an electric tool according to the present embodiment includes a housing 11 formed in a substantially cylindrical shape so that an operator can hold it, and a grinding operation. And a disk-shaped grindstone 21 which is a rotary tool for performing the above.

  The housing 11 is disposed in front of the motor case 12 as a casing that houses the main part of the motor 31 serving as a drive source, and is used to transmit the rotational driving force from the motor 31 to the grindstone 21. A gear case 13 that houses a driving force transmission means composed of a plurality of gear groups and the like, and a power supply device such as a power cord and a switch box that are arranged behind the motor case 12 and supplies power to the motor 31 are housed. The tail cover 14 as a cover member is formed as a main constituent member.

  The motor case 12 is formed in a cylindrical shape from a metal such as a resin or an aluminum alloy. The outer periphery of the motor housing portion of the motor case 12 is configured as a gripping portion that is gripped by an operator, and a switch 28 is disposed on the front side. The outer shape of the motor case 12 is formed in a substantially cylindrical shape so that the operator can easily hold it, and an uneven shape 12a for preventing slipping is formed on the surface thereof. In the present embodiment, the motor case 12 is formed in a cylindrical shape, but may be divided into two.

  The gear case 13 connected to the front side of the motor case 12 with the inner case 16 interposed therebetween is made of a metal member such as an aluminum alloy. And the grindstone 21 as a rotary tool which will perform grinding work is arrange | positioned at the lower part of this gear case 13, and a chip etc. are with respect to an operator on the back side (rear side) of the grindstone 21. A safety cover 22 is installed in order to prevent splashing.

  The tail cover 14 is formed in a cylindrical shape with resin. By removing the tail cover 14, maintenance of the power supply device installed inside can be performed. In the present embodiment, the tail cover 14 is formed in a cylindrical shape, but may be divided into two. In the case of the split structure, by removing one member, it is possible to perform maintenance of the power supply device installed inside.

  As shown in FIG. 3 depicting the internal structure of the hand-held electric grinder 10, a motor 31 serving as a drive source for driving the grindstone 21 is accommodated in the motor case 12. The motor 31 includes a stator 31a that is fixed in the motor case 12, and a rotor 31b that is rotatably disposed inside the stator 31a. The rotor 31 b includes a motor shaft 32 and a commutator 33, and a front end portion 32 a of the motor shaft 32 protrudes from the motor case 12 into the gear case 13, and a shaft is attached to the front bearing 17 attached to the gear case 13. It is supported. On the other hand, the rear end portion 32 b of the motor shaft 32 is pivotally supported by the rear bearing 18 at the rear portion of the motor case 12. The rear bearing 18 is supported by a bearing housing hole 12b having a bottom formed in the bearing support portion 12c at the rear portion of the motor case 12 via a bearing rubber 41 as an elastic body and a labyrinth forming member 20 described later ( (See FIG. 4). Therefore, the motor shaft 32 is configured to be able to rotate at high speed by pivotally supporting the both end portions 32a and 32b by the front and rear bearings 17 and 18. In the present embodiment, deep groove ball bearings with seals are employed as the front and rear bearings 17 and 18.

  On the side of the front end portion 32 a of the motor shaft 32, a substantially bowl-shaped fan casing 36 installed adjacent to the motor 31, and the cooling fan 19 installed adjacent to the fan casing 36 and fixed to the motor shaft 32. Is provided. The cooling fan 19 is arranged in the motor case 12 to play a role of passing cooling air through the motor case 12. That is, when the cooling fan 19 rotates together with the motor shaft 32, outside air is taken in from the opening of the tail cover 14, cools the motor 31 and the like through the gaps in the tail cover 14 and the motor case 12, and then exhausts the gear case 13. It will be discharged out of the machine from the exit.

  The rotor 31 b includes a commutator 33, and the commutator 33 is attached to the rear portion of the motor shaft 32. The commutator 33 is in contact with a brush 35 slidably guided by a brush boulder 38 installed in the motor case 12. The brush holder 38 is extended to a position close to the outer periphery of the commutator 33 in order to stably guide the brush 35 in the direction of the commutator 33. The commutator 33, the brush 35, and the brush holder 38 are also cooled by the cooling air introduced by the action of the cooling fan 19 described above.

  Next, the dust-proof structure and the vibration-proof structure formed in the rear bearing 18 part will be described.

  As shown in FIG. 4, the rear bearing 18 includes an outer ring 18 a, an inner ring 18 b, and a plurality of steel balls, and the inner ring 18 b is press-fitted and fixed to the rear end portion 32 b of the motor shaft 32. A labyrinth forming member 20 made of resin is attached to the outer ring 18 a of the rear bearing 18. The labyrinth forming member 20 is a member that forms a labyrinth gap as a dust-proof structure in cooperation with a dust-proof collar 40 described later. The inner diameter side of the labyrinth forming member 20 is formed on the rear side of the bearing insertion hole 20a with a bearing insertion hole 20a into which the outer ring 18a of the rear bearing 18 is inserted and an inner diameter smaller than the bearing insertion hole 20a. Is provided with a contact wall 20b. The axial length of the bearing insertion hole 20a is set to be larger than the axial length (width) of the rear bearing 18, and the rear bearing 18 is inserted into the bearing insertion hole 20a so as to be fitted to the contact wall 20b. The front portion of the labyrinth forming member 20 protrudes from the front side surface of the rear bearing 18 in the contact state. The outer diameter side of the labyrinth forming member 20 includes a large-diameter outer peripheral portion 20c having an outer diameter slightly smaller than the inner diameter of the bearing housing hole 12b, and a small-diameter outer peripheral portion 20d formed in front of the large-diameter outer peripheral portion 20c. . The arrangement position of the small-diameter outer peripheral portion 20d substantially coincides with the portion protruding from the front side surface of the rear bearing 18 in the axial direction. Further, a circumferential groove 20e as an elastic body mounting portion for mounting a bearing rubber 41 to be described later is formed in the central portion in the axial direction of the large-diameter outer peripheral portion 20c.

  A ring-shaped bearing rubber 41 as an elastic body is attached to the circumferential groove 20a formed in the central portion in the axial direction of the large-diameter outer peripheral portion 20c of the labyrinth forming member 20. In a state where the bearing rubber 41 is mounted on the labyrinth forming member 20, the diameter of the outer peripheral surface of the bearing rubber 41 is set to be slightly larger than the diameter of the large-diameter outer peripheral portion 20 c of the labyrinth forming member 20. . Therefore, the rear bearing 18 to which the labyrinth forming member 20 is attached is supported by the bearing housing hole 12b via the bearing rubber 41. Specifically, in a state where the bearing rubber 41 is attached to the labyrinth forming member 20, the diameter of the outer peripheral surface of the bearing rubber 41 is 0.1 mm to 0.9 mm larger than the diameter of the large-diameter outer peripheral portion 20 c of the labyrinth forming member 20. In this state, when inserted into the bearing storage hole 12b, the outer peripheral surface of the bearing rubber 41 and the inner peripheral surface of the bearing storage hole 12b come into contact with each other, and the large-diameter outer peripheral portion 20c of the labyrinth forming member 20 A slight gap is formed between the inner peripheral surface of the bearing housing hole 12b. In this embodiment, the bearing rubber 41 is molded from NBR with a rubber hardness of Hs50 ± 5, and the labyrinth forming member 20 is molded from polycarbonate (PC) or polyamide (PA) containing glass fiber. Yes. In the present embodiment, the front portion of the bearing housing hole 12b is formed with an enlarged diameter portion 12d whose inner diameter gradually increases toward the front opening, and the labyrinth forming member 20 and the bearing rubber 4 are mounted. The rear bearing 18 can be smoothly inserted into the bearing housing hole 12b.

  The dustproof collar 40 is a member that forms a labyrinth gap as a dustproof structure in cooperation with the labyrinth forming member 20. The dustproof collar 40 is fixed to the rear end portion 32b of the motor shaft 32 at a position adjacent to the labyrinth forming member 20, and the position is inside the bearing housing hole 12b. The dust-proof collar 40 is a substantially cylindrical resin member. By setting the outer diameter of the outer peripheral portion 40a to be smaller than the inner diameter of the bearing storage hole 12b, the dust-proof collar 40 has an inner diameter between the outer peripheral portion 40b and the bearing storage hole 12b. A labyrinth gap is formed between the peripheral surface. Further, the labyrinth gap is formed between the small-diameter outer peripheral portion 20d and the small-diameter outer peripheral portion 20d by inserting the small-diameter outer peripheral portion 20d of the labyrinth forming member 20 on the side surface of the dust bearing collar 40 on the rear bearing 18 side (rear side). An escape portion 40a formed as an annular groove is provided. As described above, in the present embodiment, the inner circumferential surface of the bearing housing hole 12b, the dust-proof collar 40, and the labyrinth forming member 20 form a labyrinth gap having a long dust entry path, thereby providing sufficient dust-proof performance. ing. In addition, since the elements constituting the labyrinth gap formed by the inner peripheral surface of the bearing storage hole 12b, the dust-proof collar 40, and the labyrinth forming member 20 are concentrated inside the bearing storage hole 12b, a compact labyrinth structure is provided. It has been realized. Furthermore, in this labyrinth structure, the inner peripheral surface of the bearing housing hole 12b is used as an element constituting the labyrinth gap, so that the labyrinth structure can also be used in an electric tool having a split housing.

  With the above-described configuration, in the hand-held electric grinder 10 of the present embodiment, the bearing rubber 41 is attached to the circumferential groove 20a of the large-diameter outer peripheral portion 20c of the resin labyrinth forming member 20, and the labyrinth forming member 20 is attached. Since the rear bearing 18 is supported by the bearing housing hole 12b via the bearing rubber 41, the elasticity of the bearing rubber 41 suppresses the transmission of vibration of the motor 31 to the housing 11. In addition, the labyrinth forming member 20 is formed of a resin having high shape accuracy and little change in shape due to load and aging, so that the labyrinth gap can be set and maintained at a dimension as designed, and dustproof performance can be maintained over a long period of time. Can be demonstrated. Further, by mounting the bearing rubber 41 in the circumferential groove 20a, it is possible to prevent the positional displacement of the bearing rubber 41 when being inserted into the bearing housing hole 12b.

  Further, the outer peripheral surface of the bearing rubber 41 and the inner peripheral surface of the bearing storage hole 12b are in contact with each other, and a slight gap is formed between the large-diameter outer peripheral portion 20c of the labyrinth forming member 20 and the inner peripheral surface of the bearing storage hole 12b. Therefore, when a large load is applied to the motor shaft 32 during the operation of the hand-held electric grinder 10 and the amount of elastic deformation of the bearing rubber 41 increases, the large-diameter outer peripheral portion 20c of the labyrinth forming member 20 and the bearing housing hole Since the amount of elastic deformation of the bearing rubber 41 can be regulated by contact with the inner peripheral surface of 12b, the positional deviation of the motor shaft 32 can be kept within an allowable value. Therefore, it is possible to prevent problems such as contact between the stator and the rotor caused by the displacement of the motor shaft 32. Further, it is possible to prevent deterioration due to an increase in the amount of elastic deformation of the bearing rubber 41.

  In addition, since the members constituting the labyrinth gap composed of the bearing housing hole 12b, the dust-proof collar 40, and the labyrinth forming member 20 are concentrated inside the bearing housing hole 12b, a compact labyrinth structure can be realized, Contributes to the downsizing of tools.

  Furthermore, due to the elastic deformation of the bearing rubber 41, it is possible to absorb misalignment of the motor shaft 32 due to component errors.

  As mentioned above, although preferred embodiment of this invention was described, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the embodiment.

  For example, in the above-described embodiment, the embodiment in which the present invention is applied to the hand-held electric grinder 10 has been described. However, the invention can be applied to an electric trimmer, an electric drill, or the like. In the above-described embodiment, the rear bearing 18 is a deep groove ball bearing, but may be a bearing such as an angular ball bearing. Furthermore, although the motor 31 is a commutator motor in the above-described embodiment, it may be a motor of another type.

  In the above-described embodiment, the bearing rubber 41 is molded from NBR having a rubber hardness of Hs50 ± 5. However, the bearing rubber 41 can be molded from an elastic material such as silicon rubber or fluororubber. Moreover, in the above-mentioned embodiment, although the labyrinth forming member 20 was shape | molded with the polycarbonate (PC) or polyamide (PA) containing glass fiber, it is also possible to form with a metal.

  Further, in the above-described embodiment, the ring-shaped bearing rubber 41 as the elastic body is mounted on the circumferential groove 20a as the elastic body mounting portion formed in the central portion in the axial direction of the large-diameter outer peripheral portion 20c of the labyrinth forming member 20. However, other embodiments may be employed in the present invention. Therefore, another embodiment that can be adopted by the present invention will be described with reference to FIG. In the following description, the description of the same configuration as that of the above-described embodiment may be omitted. As shown in FIG. 5, in another embodiment that can be adopted by the present invention, the bearing housing hole 52 has an enlarged diameter portion 12d and an enlarged diameter portion 52a in which the inner diameter gradually increases from the opening side toward the front opening. And a small-diameter portion 52b, and a wall 52c is formed at the connecting portion between the large-diameter portion 52a and the small-diameter portion 52b. The labyrinth forming member 60 includes a protruding portion 60b on the outer peripheral portion 60a. The bearing rubber 71, which is an elastic body, is formed in a ring shape, and is mounted adjacent to the rear side surface of the protruding portion 60b on the outer peripheral portion 60a of the labyrinth forming member 60. The bearing rubber 71 is disposed between the protruding portion 60b and the wall 52c in a state where the bearing 18 to which the labyrinth forming member 60 is attached is inserted into the bearing housing hole 52, and the outer peripheral surface thereof is large. It is in contact with the inner peripheral surface of the diameter portion 52a. Further, a slight gap is formed between the outer surface of the projecting portion 60b and the inner peripheral surface of the large diameter portion 52a. By adopting such a configuration, it is possible to obtain the same effect as that of the above-described embodiment.

  Further, in the above-described embodiment, the ring-shaped bearing rubber 41 as the elastic body is mounted on the circumferential groove 20a formed as the elastic body mounting portion in the central portion in the axial direction of the large-diameter outer peripheral portion 20c of the labyrinth forming member 20. However, it is also possible to form a plurality of holes as elastic body mounting portions on the outer peripheral portion of the labyrinth forming member 20 and mount a cylindrical bearing rubber in the plurality of holes.

  It is apparent from the scope of the claims that the embodiments added with such changes or improvements are also included in the technical scope of the present invention.

  10 Handheld Electric Grinder, 11 Housing, 12 Motor Case, 12a Uneven Shape, 12b Bearing Housing Hole, 12c Bearing Support Part, 12d Expanded Diameter Part, 13 Gear Case, 14 Tail Cover, 16 Inner Case, 17 Front Bearing, 18 Rear bearing, 18a outer ring, 18b inner ring, 19 cooling fan, 20 labyrinth forming member, 20a bearing insertion hole, 20b abutting wall, 20c large diameter outer peripheral part, 20d small diameter outer peripheral part, 20e peripheral groove, 21 grindstone, 22 safety cover , 28 switch, 31 motor, 31a stator, 31b rotor, 32 motor shaft, 32a front end, 32b rear end, 33 commutator, 35 brush, 36 fan casing, 38 brush holder, 40 dustproof collar, 40a relief 40b, outer periphery, 1 bearing rubber, 52 bearing receiving hole, 52a large diameter portion, 52b small-diameter portion, 52c wall, 60 labyrinth forming member, 60a outer peripheral portion, 60b protruding portion, 71 a bearing rubber

Claims (5)

A motor that is a drive source, a housing that houses the motor, a motor shaft of the motor, a bearing that supports the motor shaft, a labyrinth forming member that is attached to an outer ring of the bearing, and the bearing are supported. An electric power tool comprising a bearing housing hole and a dustproof collar disposed adjacent to the labyrinth forming member and forming a labyrinth gap in cooperation with the labyrinth forming member,
The labyrinth forming member has an elastic body mounting portion formed on an outer peripheral portion, the elastic body mounting portion is mounted with an elastic body, and the bearing on which the labyrinth forming member is mounted is interposed via the elastic body. An electric tool supported by the bearing housing hole.   The outer surface of the elastic body is in contact with the inner peripheral surface of the bearing storage hole, and a gap is formed between the outer surface of the labyrinth forming member and the inner peripheral surface of the bearing storage hole. The electric tool according to claim 1.   The electric tool according to claim 1, wherein the elastic body mounting portion is formed as a circumferential groove.   The electric tool according to any one of claims 1 to 3, wherein the elastic body is formed in a ring shape.   The power tool according to any one of claims 1 to 4, wherein a labyrinth gap is formed between an outer peripheral surface of the dust-proof collar and an inner peripheral surface of the bearing housing hole.

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