JP7738468B2 - Grinding tools - Google Patents

Description

This disclosure relates to grinding tools such as grinders. Note that "grinding" in this disclosure is a concept that also includes "polishing."

In grinding tools such as grinders, measures are taken to reduce vibrations that occur during operation. For example, Patent Document 1 discloses an invention in which a handle, divided into two halves, is screwed to a motor housing that houses the motor, and a cylindrical vibration-damping member is interposed between a screw boss on the handle and a receiving portion on the motor housing.

EP 2251151

In the vibration-damping structure of Patent Document 1, the screw boss is fitted with an external vibration-damping member, which increases the radial size of the screw-fastening portion, potentially leading to an increase in product size.

The present disclosure therefore aims to provide a grinding tool that effectively reduces vibration while maintaining a compact product size.

In order to achieve the above object, a first configuration of the present disclosure includes a motor housing that accommodates a motor;
a pair of half housings that are screwed together with the motor housing sandwiched therebetween,
The half housings are fastened together by screws, with screw bosses provided on each half housing inserted into the motor housing, and elastic members interposed between the motor housing and each screw boss in the axial direction of the screw boss ,
Each of the screw bosses is a cylindrical member having a small diameter portion at the tip end thereof inserted into the motor housing and a large diameter portion at the base end thereof, and the elastic member is a rubber ring fitted around each of the small diameter portions.
When each of the small diameter portions is inserted into the motor housing and screwed in place, each of the rubber rings is positioned between the motor housing and each of the large diameter portions .
In order to achieve the above object, a second configuration of the present disclosure includes a motor housing that accommodates a motor;
a pair of half housings that are screwed together with the motor housing sandwiched therebetween,
The half housings are fastened together by inserting a shaft having threaded portions at both ends into the motor housing, and screwing a pair of nuts held by the pair of half housings onto the threaded portions at both ends,
A rubber ring is interposed between the motor housing and each of the half housings and is attached to an end of the shaft .
A rubber sleeve is interposed between the outer periphery of the shaft and the motor housing, and the rubber sleeve is provided over the entire length of the motor housing in the axial direction of the shaft, so that the motor housing and the shaft are not in contact with each other .

According to the present disclosure, an elastic member is interposed between the motor housing and the half housing in the axial direction of the screw boss or shaft that assembles the pair of half housings, so the screw-fastened portion of the half housing does not become larger in the radial direction. This enables effective vibration reduction while maintaining a compact product size.

FIG. 1 is a perspective view of a grinder according to a first embodiment. FIG. 1 is a side view of a grinder according to a first embodiment. 1 is a central vertical cross-sectional view of a grinder according to a first embodiment. FIG. 10 is an exploded perspective view of the screw fastening portion of the front grip portion. FIG. 3 is an enlarged cross-sectional view taken along line AA in FIG. 2. FIG. 3 is an enlarged cross-sectional view taken along line BB in FIG. 2. FIG. 10 is a side view of the grinder of the second embodiment. FIG. 10 is a partial central vertical cross-sectional view of a grinder according to a second embodiment. FIG. 10 is an exploded perspective view of the screw fastening portion of the front grip portion. FIG. 8 is an enlarged cross-sectional view taken along line CC of FIG. 7. FIG. 10 is a perspective view of a grinder according to a third embodiment. FIG. 10 is a side view of the grinder according to the third embodiment. FIG. 2 is an exploded perspective view of the front portion of the grip housing. 13 is an enlarged partial cross-sectional view taken along the line DD in FIG. 12. 13 is an enlarged cross-sectional view taken along line EE of FIG. 12. 13 is an enlarged cross-sectional view taken along the line FF in FIG. 12.

In one embodiment of the first configuration of the present disclosure, the motor housing may have an output shaft in front thereof, the half housings may be a pair of left and right half housings, and the axial direction of the screw boss may be the left-right direction of the motor housing.
According to this configuration, the elastic member can be clamped and fixed by utilizing the assembly of the left and right half housings.
In one embodiment of the first configuration of the present disclosure, the elastic members may be provided on the left and right sides of the motor housing.
This configuration provides a balanced vibration reduction effect on both the left and right sides.
In one embodiment of the first configuration of the present disclosure, the screw bosses may be provided at two locations on each half housing in the up-down direction of the motor housing.
This configuration provides a well-balanced vibration reduction effect both vertically and horizontally.
In one embodiment of the first configuration of the present disclosure, the motor housing may be cylindrical.
This configuration improves the unity between the motor housing and the housing halves.
In one embodiment of the first configuration of the present disclosure, second elastic members may be interposed between the housing halves on both the left and right sides of the motor housing.
This configuration provides a higher vibration reduction effect.
In one embodiment of the first configuration of the present disclosure, the motor housing and each half housing may be provided with a movement restricting portion that abuts against each other when the motor housing and each half housing move relative to each other by a predetermined amount.
This configuration reduces the risk of damage to the screw bosses and the like when an impact such as a drop is applied.

In one embodiment of the second configuration of the present disclosure, the elastic member may be interposed between the outer periphery of the shaft and the motor housing.
According to this configuration, vibrations transmitted to the half housings via the shaft are reduced, and the vibration reduction effect is enhanced.
In one embodiment of the second configuration of the present disclosure, the motor housing has an output shaft on the front side, the half housings are a pair on the left and right, the shaft passes through the motor housing in the left-right direction, and a second elastic member is interposed between each half housing on the left and right sides of the motor housing in the axial direction of the shaft, and the second elastic member may overlap the elastic member in the radial direction of the shaft.
According to this configuration, a vibration reduction effect can be obtained that is well balanced on the left and right sides, and a high vibration reduction effect can be obtained due to the overlapping of the elastic member and the second elastic member.
In one embodiment of the second configuration of the present disclosure, third elastic members may be interposed between the housing halves on both the left and right sides of the motor housing.
This configuration provides a higher vibration reduction effect.

In one embodiment of the present disclosure, an elastic body is provided on the outer surface of either the motor housing or the pair of half housings, covering the outer surface, and the elastic body may be provided with a sealing portion that protrudes toward the other housing and abuts against the other housing, sealing between the two housings.
This configuration effectively prevents dust and other foreign matter from entering even if there is a gap between the motor housing and the housing halves for vibration isolation. In particular, the seal is formed using an elastic material that covers the outer surface of the housing, making it easy to obtain the seal at low cost.
In one embodiment of the present disclosure, the elastic body and the seal portion may be provided on the pair of half housings.
According to this configuration, the seal portion can be integrally formed when the half housing is manufactured.
In one embodiment of the present disclosure, the seal portion may extend toward the motor housing and abut against the motor housing.
This configuration allows for an appropriate seal for the motor housing where vibrations occur.

Hereinafter, an embodiment according to the first configuration of the present disclosure will be described with reference to the drawings.
Fig. 1 is a perspective view of a grinder, which is an example of a grinding tool, Fig. 2 is a side view, and Fig. 3 is a central longitudinal cross-sectional view.
The grinder 1 has a motor housing 2 that extends in the front-to-rear direction. An intermediate housing 3 that is rectangular in front view is attached to the front side of the motor housing 2. A gear housing 4 is attached to the front side of the intermediate housing 3. A grip housing 5 that extends in the front-to-rear direction is attached to the rear of the motor housing 2.
The motor housing 2 has a cylindrical rear housing portion 6 and a square front housing portion 7 when viewed from the front. A motor 8 is housed in the rear housing portion 6. The front housing portion 7 is connected to the gear housing 4 via the intermediate housing 3 by screws (not shown) that are screwed into the gear housing 4 from the front.

The motor 8 is an inner rotor brushless motor having a cylindrical stator 9 and a rotor 10 that penetrates the stator 9. The stator 9 is housed in the rear housing portion 6. The rotor 10 has a rotating shaft 11 at its axis. The rotating shaft 11 extends in the front-to-rear direction, and its rear end is supported by a rear portion of the rear housing portion 6 via a bearing 12. A bearing holder 13 that is circular in rear view and holds the bearing 12 is protruded from the center of the rear surface of the rear housing portion 6. The front portion of the rotating shaft 11 penetrates the front housing portion 7 and the intermediate housing 3 and protrudes into the gear housing 4. A fan 14 is fixed to the rotating shaft 11 within the intermediate housing 3. A first bevel gear 15 is fixed to the front end of the rotating shaft 11 within the gear housing 4.
A downwardly protruding spindle 16 is journaled within the gear housing 4. A second bevel gear 17 that meshes with the first bevel gear 15 is fixed to the spindle 16.
A disk-shaped tool bit (e.g., a grinding wheel) 18 is attached perpendicularly to the lower end of the spindle 16. A wheel cover 19, which is semicircular in plan view and covers the rear part of the tool bit 18 from above and behind, is attached to the lower part of the gear housing 4.

The grip housing 5 has a front grip portion 20, a middle grip portion 21, and a rear grip portion 22. The front grip portion 20 expands forward and is attached to the outside of the rear housing portion 6 of the motor housing 2. The middle grip portion 21 has a smaller diameter than the front grip portion 20 and houses a switch 23 therein. The rear grip portion 22 expands rearward and houses a controller 24 and a terminal block 25 therein. A battery pack 26, which serves as a power source, is attached to the rear grip portion 22.
A switch lever 27 is provided below the motor housing 2 and the grip housing 5. The front end of the switch lever 27 is rotatably connected to the underside of the rear housing portion 6 and extends rearward to the underside of the middle grip portion 21. When the switch lever 27 is pushed upward, the switch 23 is turned ON.

The grip housing 5 is made up of left and right half housings 5a and 5b. The half housings 5a and 5b are connected to each other by screwing multiple screws 30, 30... from the right side of the right half housing 5b into the left half housing 5a. The screws are fastened at two locations, one at the top and bottom, on the front grip portion 20, one at the middle grip portion 21, and two at the top and bottom, on the rear grip portion 22.
4 and 5, a pair of upper and lower guide tubes 31, 31 are integrally formed on the rear surface of the rear housing part 6 at the screw fastening location of the front grip part 20. The guide tubes 31 have the same diameter and extend in the left-right direction. The guide tubes 31, 31 are disposed above and below the bearing holder 13 and overlap the bearing 12 and the bearing holder 13 in the up-down direction.

In the front grip portion 20, a pair of upper and lower left screw bosses 32, 32 that protrude to the right and are coaxial with the guide tube portions 31, 31 are integrally formed on the inner surface of the left half-housing 5a. Each left screw boss 32 is a two-stage cylindrical shape with a left large diameter portion 33 on the left side, which is the base, and a left small diameter portion 34 on the right side. The left large diameter portion 33 has the same diameter as the guide tube portion 31. The left small diameter portion 34 has an outer diameter that allows it to be loosely inserted into the guide tube portion 31, and is internally threaded with a female thread 35. The left small diameter portion 34 is formed longer to the right than the center in the left-right direction.
A pair of upper and lower right screw bosses 36, 36 are formed on the inner surface of the right half housing 5b, coaxially with the guide tube portions 31, 31 and protruding to the left. Each right screw boss 36 is a two-stage cylindrical shape with a right large diameter portion 37 on the right side, which is the base, and a right small diameter portion 38 on the left side. The right large diameter portion 37 has the same diameter as the guide tube portion 31 and opens onto the right side surface of the half housing 5b. The right small diameter portion 38 has an outer diameter that allows it to be loosely inserted into the guide tube portion 31 and is shorter than the left small diameter portion 34.

In the front grip portion 20, the left and right half housings 5a, 5b are assembled by inserting the left small diameter portions 34, 34 of the upper and lower left screw bosses 32, 32 and the right small diameter portions 38, 38 of the upper and lower right screw bosses 36, 36 into the guide tube portions 31, 31 from the left and right, respectively. In this state, the end faces of the left small diameter portions 34, 34 and the right small diameter portions 38, 38 are close to or abut against each other within the guide tube portions 31, 31. At this time, the left large diameter portions 33, 33 and the right large diameter portions 37, 37 do not abut against the end faces of the guide tube portions 31, 31, but are spaced apart in the left-right direction.
Rubber rings 40, 40... are respectively fitted to the left small diameter portion 34 of each left screw boss 32 and the right small diameter portion 38 of each right screw boss 36. Each rubber ring 40 has the same outer diameter as the guide tube portion 31, and its axial length is slightly longer than the left-right distance between the guide tube portion 31 and the left large diameter portion 33 and right large diameter portion 37 in the assembled state.

When screwing the front grip portion 20, the screws 30 are inserted from the right side into the openings of the right large diameter portions 37 of the right screw bosses 36. The screws 30 are then screwed into the female threads 35 of the left small diameter portions 34 of the left screw bosses 32. As a result, the left and right rubber rings 40 of the guide tube portions 31 are compressed in the axial direction between the left large diameter portion 33 and the right large diameter portion 37. In this way, the left screw bosses 32 and the right screw bosses 36 are screwed together with the rubber rings 40 interposed between the guide tube portions 31.
In addition, screw fastening locations other than the front grip portion 20 are similarly fastened by the left screw boss 32 and the right screw boss 36, except that the guide tube portion 31 and the rubber ring 40 are not present.

As shown in FIG. 6 , a pair of left and right rubber sheets 41 are interposed between the rear housing portion 6 and the front grip portion 20, forward of the screw fastening point of the front grip portion 20. The rubber sheets 41 are strip-shaped and extend in the circumferential direction of the rear housing portion 6. A pair of inner recesses 42 are formed on the left and right outer peripheral surfaces of the rear housing portion 6, extending in the circumferential direction to match the outer shape of the rubber sheets 41. A pair of outer recesses 43 are formed on the left and right inner peripheral surfaces of the front grip portion 20, extending in the circumferential direction to match the outer shape of the rubber sheets 41. Each rubber sheet 41 is fitted across the inner recesses 42 and outer recesses 43 to be positioned between the rear housing portion 6 and the front grip portion 20. When the front grip portion 20 is assembled, each rubber sheet 41 is compressed radially between the inner recesses 42 and outer recesses 43.
Therefore, the rear housing portion 6 and the front grip portion 20 are assembled with the rubber rings 40 and the rubber sheets 41 interposed therebetween.

In the grinder 1 configured as described above, the switch lever 27 is pressed with the hand holding the middle grip portion 21 of the grip housing 5 to turn on the switch 23. This causes the controller 24 to supply a drive current to the stator 9 of the motor 8, causing the rotor 10 to rotate. Thus, the rotation of the rotating shaft 11 is transmitted to the spindle 16 via the first and second bevel gears 15 and 17, causing the tool bit 18 to rotate. The rotating tool bit 18 can then be used to grind the workpiece.
During this operation, vibrations may occur due to the tool bit 18 and the motor 8. However, the rubber ring 40 and rubber sheet 41 are interposed between the motor housing 2 and the grip housing 5, so the vibrations transmitted to the grip housing 5 are reduced. This reduces the likelihood of discomfort to the operator's hands due to the vibrations.
In particular, the rubber ring 40 is arranged in the axial direction of the left and right screw bosses 32, 36 between the guide tube portion 31 on the motor housing 2 side and the left and right screw bosses 32, 36 on the grip housing 5 side, so even if the rubber ring 40 is provided, the screw-fastened portion does not become larger in the radial direction.

As described above, the grinder 1 of the first embodiment includes the motor housing 2 that houses the motor 8, and a pair of half housings 5a, 5b that are screwed together with the motor housing 2 sandwiched therebetween. The half housings 5a, 5b are screwed together by inserting the left screw boss 32 and the right screw boss 36 (screw bosses) provided on each half housing 5a, 5b, respectively, into the guide tube portion 31 of the motor housing 2, and by interposing a rubber ring 40 (the elastic member in the first configuration) between the guide tube portion 31 and the left and right screw bosses 32, 36 in the axial direction of the left and right screw bosses 32, 36.
This configuration makes it possible to effectively reduce vibration while maintaining a compact product size.

In particular, the grinder 1 has a spindle 16 (output shaft) in front of the motor housing 2, the half housings 5a, 5b are a pair of left and right half housings, and the axial direction of the left and right screw bosses 32, 36 is the left and right direction of the motor housing 2.
Therefore, the rubber ring 40 can be clamped and fixed by utilizing the assembly of the left and right half housings 5a, 5b.
The rubber rings 40 are provided on the left and right sides of the guide tube portion 31 .
Therefore, a balanced vibration reduction effect can be obtained on both sides.
The left and right screw bosses 32, 36 are provided at two locations on each of the half housings 5a, 5b in the vertical direction of the motor housing 2.
Therefore, a well-balanced vibration reduction effect can be obtained in both the vertical and horizontal directions.
The motor housing 2 is cylindrical.
This improves the unity between the motor housing 2 and the housing halves 5a and 5b.
Rubber sheets 41 (second elastic members in the first configuration) are interposed between the housing halves 5a and 5b on both the left and right sides of the motor housing 2.
Therefore, a higher vibration reduction effect can be obtained.

In the first embodiment, the number of screw fastening locations on the front grip portion is not limited to two, at the top and bottom. There may be one screw fastening location, or three or more screw fastening locations. The screw fastening locations are not limited to the rear surface of the motor housing, but may also be on the top or bottom surface of the motor housing. The screw fastening direction may be reversed left and right. The length of the screw boss may also be reversed left and right, or the length of the screw boss may be the same left and right.
The length and diameter of the rubber rings between the guide tube portion and the left and right screw bosses can be changed as needed depending on the distance between the guide tube portion and the left and right screw bosses. Multiple rubber rings may be stacked in the axial direction. Materials other than rubber may also be used as the elastic member.
In the above example, the rubber ring is provided only at the screw fastening point of the front grip portion, but elastic members for the rubber ring may also be provided at other screw fastening points such as the middle grip portion.
The rubber sheets may be arranged above and below instead of left and right, or may be arranged above, below, left and right. The second elastic member may be made of a material other than rubber. However, the second elastic member may be omitted.

Next, an example according to a second configuration of the present disclosure will be described, where the same components as those in the first example will be assigned the same reference numerals and overlapping descriptions will be omitted.
7 is a side view of the grinder, FIG. 8 is a partial vertical cross-sectional view, and FIG. 9 is an exploded perspective view of the screw fastening portion of the front grip.
In the grinder 1A, the front grip 20 is also fastened with screws at two locations, top and bottom. Instead of using screw bosses and screws, shafts 50, 50 inserted into the guide tubes 31, 31 and nuts 51, 51 held by the left and right half housings 5a, 5b, respectively, are used.

The shaft 50 is made of metal and has threaded portions 52, 52 on both the left and right ends. As shown in Figure 10, the left and right inner sides of each threaded portion 52 are formed with a medium-diameter portion 53 and a flange portion 54, whose diameter gradually increases toward the left and right center. The left-side medium-diameter portion 53 is formed with chamfered portions 55, 55. Between the left and right flange portions 54, 54, is a small-diameter portion 56 with the same diameter as the threaded portion 52. A rubber sleeve 57 is fitted around the small-diameter portion 56. The outer diameter of the rubber sleeve 57 is the same as the flange portion 54. The shafts 50, 50 together with the rubber sleeve 57 are inserted into the guide tube portions 31, 31. In this state, the tip portions of each shaft 50 protrude to the left and right from both the left and right ends of the rubber sleeve 57 beyond the guide tube portion 31.

The half housings 5a, 5b each have a receiving portion 60, 60 formed coaxially with the shaft 50, 50. Each receiving portion 60 is cylindrical, with open left and right outer sides and protruding toward the inner surface, and the outer diameter on the inner surface is the same as that of the guide tube portion 31. A bottomed hole 61 is formed on the inner surface of each receiving portion 60, into which the medium diameter portion 53 of the shaft 50 fits. The left bottomed hole 61 has chamfered portions 62, 62 formed to match the chamfered portions 55, 55 of the left medium diameter portion 53. A through hole 63 is formed in the center of the bottom of the bottomed hole 61, through which the threaded portion 52 passes.
When assembling the left and right half housings 5a, 5b, the left chamfered portions 55, 55 of each shaft 50 are fitted into the chamfered portions 62, 62 of the receiving portion 60. Then, the left and right threaded portions 52, 52 of each shaft 50 are prevented from rotating and protrude into the receiving portions 60, 60. At this time, the left and right receiving portions 60, 60 do not abut against either end of the guide tube portion 31, but are spaced apart in the left-right direction.
The rubber rings 40 here are fitted on the left and right sides of the shaft 50 between the guide tube portion 31 and the left and right receiving portions 60, 60. The axial length of each rubber ring 40 is slightly longer than the left-right distance between the guide tube portion 31 and the receiving portion 60 when assembled.

The nuts 51 are inserted from the outside into the left and right receiving portions 60. Each nut 51 is screwed onto a threaded portion 52 protruding into the receiving portion 60. The left and right half housings 5a and 5b are then pressed against the left and right medium diameter portions 53 of the shaft 50 and fixed in place. In this state, the left and right rubber rings 40 of the guide tube portion 31 are compressed in the axial direction between the left and right receiving portions 60. The rubber rings 40 are fitted over and radially overlap the rubber sleeve 57 and flange portion 54 of the shaft 50.
In this way, the left and right half housings 5 a and 5 b are fixed by the shaft 50 and the nut 51 with the rubber rings 40 interposed between the receiving portions 60 and the guide tube portion 31 .
On the front side of the shaft 50 , rubber sheets 41 , 41 are also interposed on the left and right between the rear housing portion 6 and the front grip portion 20 .

In the grinder 1A configured as described above, vibrations may occur during operation due to the tool bit 18 and the motor 8. However, the rubber ring 40 and rubber sheet 41 are interposed between the motor housing 2 and the grip housing 5, so the vibrations transmitted to the grip housing 5 are reduced. This reduces the likelihood of the operator's hands feeling uncomfortable due to the vibrations.
In particular, the rubber ring 40 is arranged in the axial direction of the shaft 50 between the guide tube portion 31 on the motor housing 2 side and the left and right receiving portions 60, 60 on the grip housing 5 side, so even if the rubber ring 40 is provided, the screw-fastening portion does not become larger in the radial direction.
In addition, a rubber sleeve 57 is interposed between the guide tube portion 31 of the rear housing portion 6 and the shaft 50, so vibrations transmitted from the rear housing portion 6 side to the grip housing 5 via the shaft 50 are also reduced.

As described above, the grinder 1A of the second embodiment includes the motor housing 2 that houses the motor 8, and a pair of half housings 5a, 5b that are screwed together and sandwich the motor housing 2. The half housings 5a, 5b are screwed together by inserting a shaft 50, which has threads 52 on both ends, through a guide tube 31 of the motor housing 2, and by screwing a pair of nuts 51, 51 held by the pair of half housings 5a, 5b onto the threads 52 on both ends. A rubber sleeve 57 (elastic member in the second configuration) is interposed between the guide tube 31 and each half housing 5a, 5b.
This configuration makes it possible to effectively reduce vibration while maintaining a compact product size.

In particular, the rubber sleeve 57 is interposed between the outer periphery of the shaft 50 and the guide tube portion 31 .
Therefore, the vibration transmitted to the grip housing 5 via the shaft 50 is reduced, and the vibration reduction effect is enhanced.
The motor housing 2 has a spindle 16 (output shaft) on the front side, the half housings 5a, 5b are a pair on the left and right, and the shaft 50 passes through the guide tube portion 31 in the left-right direction. Rubber rings 40, 40 (second elastic members) are interposed between the half housings 5a, 5b on the left and right sides of the guide tube portion 31 in the axial direction of the shaft 50, and a rubber sleeve 57 overlaps with the rubber ring 40 in the radial direction of the shaft 50.
Therefore, a balanced vibration reduction effect can be obtained on both sides, and a high vibration reduction effect can be obtained due to the overlap of the rubber ring 40 and the rubber sleeve 57.
Rubber sheets 41, 41 (third elastic members in the second configuration) are interposed between the half housings 5a, 5b on both the left and right sides of the motor housing 2.
Therefore, a higher vibration reduction effect can be obtained.

In the second embodiment, the number of shafts is not limited to a pair, one above the other. Only one shaft may be provided, or conversely, three or more shafts may be provided. The installation position of the shafts is also not limited to the rear surface of the motor housing, and they may be provided on the top or bottom surface of the motor housing.
The shaft does not have to be prevented from rotating between the receiving portion and the motor housing, but may be prevented from rotating between the motor housing and the guide tube by providing a chamfered portion in the through hole of the guide tube.
The rubber sleeve may not overlap the rubber ring in the radial direction of the shaft, and may be divided in the axial direction.
In the above example, the shaft, nut, and rubber ring are screwed only at the front grip portion, but similar screw fastening may also be performed at other screw fastening locations such as the middle grip portion.
The elastic member such as a rubber sleeve, the second elastic member such as a rubber ring, and the third elastic member such as a rubber sheet may be made of a material other than rubber. The second elastic member and the third elastic member may be omitted.

11 is a perspective view of the grinder from the rear, FIG. 12 is a side view of the grinder, and FIG. 13 is an exploded perspective view of the front portion of the grip housing.
The grinder 1B shown here also has the same vibration-reducing structure as the grinder 1 of Example 1. That is, as shown in Fig. 16, the half housings 5a, 5b in the front grip portion 20 are fastened together with screws such that the left screw boss 32 and the right screw boss 36 provided on each half housing 5a, 5b are inserted into the guide tube portion 31 of the motor housing 2, and a rubber ring 40 is interposed between the guide tube portion 31 and the left and right screw bosses 32, 36 in the axial direction of the left and right screw bosses 32, 36.
Further, rubber sheets 41 are interposed between the half housings 5a and 5b on both the left and right sides of the motor housing 2, respectively.

This embodiment differs from the first embodiment in that a seal structure is provided to seal the gap formed between the motor housing 2 and the grip housing 5 .
In the half housings 5a and 5b, the front end portion 65, which is semicircular in front view, is covered over its entire periphery with elastomer 80. As shown in Figures 14 and 15, the elastomer 80 includes an outer surface portion 81 that covers the outer surface of the front end portion 65, an inner surface portion 82 that covers the inner surface of the front end portion 65, and a front surface portion 83 that covers the front surface of the front end portion 65.
The front end portion 65 has notches 66, 66 formed at both circumferential ends. A through-hole 67 is formed in the radial direction in a circumferentially intermediate portion of the front end portion 65. The outer surface portion 81 and the inner surface portion 82 are connected to each other at both circumferential ends via connecting portions 84 made of elastomer that fill the notches 66, 66. Furthermore, the outer surface portion 81 and the inner surface portion 82 are connected to each other at the circumferentially intermediate portion via connecting portions 85 made of elastomer that fill the through-hole 67.
A seal portion 86 is provided on the front surface portion 83. The seal portion 86 protrudes forward from a position closer to the radial inside of the front surface portion 83 and is formed in a band shape over the entire circumferential length of the front surface portion 83.

An outer stopper 70 consisting of a circumferentially extending protrusion is formed on the inner surface of the half housing 5a between the left-hand screw bosses 32, 32. Similarly, an outer stopper 70 extending in the circumferential direction is also formed on the inner surface of the half housing 5b between the right-hand screw bosses 36, 36.
The rear housing portion 6 of the motor housing 2 has a front half portion 71 that connects to the front housing portion 7, and a rear half portion 72 to which the grip housing 5 is attached. The rear half portion 72 has a smaller diameter than the front half portion 71. A ring-shaped opposing surface 73 that faces the front end of the grip housing 5 is formed on the rear surface of the front half portion 71.
A pair of rearward-protruding restricting pieces 74, 74 are provided on both the left and right sides of the rear surface of the rear housing portion 6. Each restricting piece 74 is located radially inward of the outer stopper 70 of the half housing 5a, 5b, corresponding to the outer stopper 70. An inner stopper 75 consisting of a circumferentially extending protrusion is formed at the rear end of each restricting piece 74. The inner stopper 75 protrudes radially outward rearward of the outer stopper 70 and overlaps with the outer stopper 70 in the front-to-rear direction. Step portions 76, 76 are formed on the left and right sides of the rear surface of the rear housing portion 6 in front of the outer stoppers 70, 70, and positioned radially outward of the restricting pieces 74, 74. The step portions 76, 76 also overlap with the outer stoppers 70 in the front-to-rear direction. A pair of upper and lower ribs 77, 77 connecting the bearing holder 13 and the restricting pieces 74, 74 are formed symmetrically on the rear surface of the rear housing portion 6.

In the grinder 1B, the front grip portion 20 is screwed to the rear half portion 72 of the rear housing portion 6, as in Example 1, to assemble the housing halves 5a and 5b. The front end portions 65 and elastomers 80 of the housing halves 5a and 5b then abut against each other at their upper ends. The front end portions 65 and elastomers 80 are adjacent to the sides of the switch lever 27, respectively. The forward protrusion length of the seal portion 86 is greater than the front-to-rear gap S1 (Figure 14) between the opposing surface 73 of the front half portion 71 and the front surface 83 of the elastomer 80. Therefore, when the front end of the seal portion 86 abuts against the opposing surface 73, it bends outward and contracts in the front-to-rear direction. Therefore, the gap S1 between the front surface 83 and the opposing surface 73 is sealed by the seal portion 86. In this assembled state, a radial gap S2 is formed between the rear half 72 and the inner surface 82 of the seal portion 86.

The outer stoppers 70, 70 provided on the housing halves 5a, 5b are located in the front-to-rear direction between the step portions 76, 76 on the rear surface of the rear housing portion 6 and the inner stoppers 75, 75 of the restricting pieces 74, 74. Therefore, the motor housing 2 and the grip housing 5 are able to move relative to each other within the range in which the outer stopper 70 abuts the inner stopper 75 and the step portion 76 in the front-to-rear direction. In the assembled state, the clearance C1 between the outer stopper 70 and the inner stopper 75 in the front-to-rear direction is smaller than the clearance C2 between the outer stopper 70 and the step portion 76 in the front-to-rear direction. Clearance C2 is smaller than gap S1.

In the grinder 1B configured as described above, the rubber ring 40 and the rubber sheet 41 are interposed between the motor housing 2 and the grip housing 5, reducing vibrations transmitted to the grip housing 5. This reduces the likelihood of discomfort to the operator's hands due to vibrations.
In particular, each elastomer 80 of the grip housing 5 is provided with a seal portion 86 that abuts against the motor housing 2 to seal the gap S1, making it difficult for dust and other particles to enter through the gap S1. Even if the motor housing 2 vibrates and moves back and forth relative to the grip housing 5, the seal portion 86 elastically deforms to follow and maintain its sealing performance. Furthermore, because the inner surface 82 of the elastomer 80 is not in contact with the motor housing 2 due to the gap S2, vibrations of the motor housing 2 are not transmitted to the grip housing 5 via the elastomer 80.

When the grip housing 5 moves rearward relative to the motor housing 2, and the amount of movement reaches a clearance C1 between the outer stopper 70 and the inner stopper 75, the outer stopper 70 and the inner stopper 75 come into contact with each other, restricting relative movement beyond the clearance C1. On the other hand, when the grip housing 5 moves forward relative to the motor housing 2, and the amount of movement reaches a clearance C2 between the outer stopper 70 and the step 76, the outer stopper 70 and the step 76 come into contact with each other, restricting relative movement beyond the clearance C2. However, since the seal portion 86 is compressed within the gap S1 during forward relative movement of the grip housing 5, depending on the length, thickness, etc. of the seal portion 86, elastic deformation of the seal portion 86 may restrict relative movement before the amount of movement reaches the clearance C2.
Therefore, even if a high load is applied due to an impact such as a drop, the load is not concentrated on the left and right screw bosses 32, 36, but is dispersed from both stoppers 70, 75 to the motor housing 2 and the grip housing 5. As a result, damage to the left and right screw bosses 32, 36 can be effectively prevented.

In this way, the grinder 1B of the third embodiment also provides the same effects as those of the first embodiment, such as effective vibration reduction while maintaining a compact product size.
In particular, an elastomer 80 (an example of an elastic body) is provided on each of the outer surfaces of the half housings 5a and 5b to cover the outer surfaces, and each elastomer 80 is provided with a sealing portion 86 that protrudes toward the motor housing 2 and abuts against the motor housing 2, sealing between the motor housing 2 and the grip housing 5.
Therefore, even if a gap S1 for vibration prevention is present between the motor housing 2 and the grip housing 5, it is possible to effectively prevent the intrusion of dust and other foreign matter. In particular, since the seal portion 86 is formed using the elastomer 80 that covers the outer surfaces of the housing halves 5a and 5b, the seal portion 86 can be obtained easily and at low cost.

Since the seal portions 86 are provided on the half housings 5a and 5b, the seal portions 86 can be integrally formed when the half housings 5a and 5b are manufactured.
The seal portion 86 extends toward the motor housing 2 and abuts against the motor housing 2, thereby enabling an appropriate seal to be provided for the motor housing 2 where vibrations occur.
The motor housing 2 and the half housings 5a, 5b are each provided with an outer stopper 70, an inner stopper 75, and a step portion 76 (an example of a movement restricting portion) that abut against each other when the motor housing 2 and the half housings 5a, 5b move relative to each other by a predetermined amount.
Therefore, the risk of damage to the left and right screw bosses 32, 36, etc. when an impact such as a drop is applied is reduced.

In the third embodiment, the joining of the elastomer on the front and back of the half housing is not limited to the above example. For example, the number of through holes may be increased, or one of the notches and the through holes may be omitted.
The elastomer may be formed so that the outer surface extends toward the rear of the half housing. The inner surface and/or the front surface may be omitted. In this case, the sealing portion may be formed continuously from the outer surface.
The seal portion may be formed in multiple locations (for example, double) in the radial direction and may be brought into contact with the motor housing.
In the above example, the elastomer and the seal are provided on the half housing, but they may also be provided on the motor housing, with the seal abutting against the front end of the half housing.
The elastic body forming the seal portion is not limited to an elastomer.

The structure relating to the sealing portion is not limited to the vibration reduction structure of the first embodiment, but can also be applied to the vibration reduction structure of the second embodiment.
The structure relating to the seal portion can also be applied to a power tool having a first housing and a second housing assembled to be movable relative to the second housing, where a gap is formed between the first and second housings when assembled, and where an elastic body is provided on the outer surface of one of the first or second housing to cover the outer surface of the one housing. That is, if the elastic body is provided with a seal portion that protrudes toward the other housing and abuts against the other housing to seal between the two housings, the seal portion can be easily formed using the elastic body, and it is possible to effectively prevent foreign matter from entering between the housings.
In this case, the elastic body may also be formed on the inner surface of the housing, and may penetrate the housing in the thickness direction and be connected to the front and back of the housing.

On the other hand, the structure of the movement restricting portion can also be modified as appropriate.
For example, the outer stopper may be shortened in the circumferential direction or formed with multiple protrusions aligned in the circumferential direction. The inner stopper may also be elongated in the circumferential direction or formed with multiple protrusions aligned in the circumferential direction. Instead of the step, a circumferential protrusion or protrusion may be provided on the outer surface of the restricting piece.
The restricting piece may be eliminated, and a pair of inner stoppers may be provided on the outer surface of the motor housing, positioned before and after the outer stopper.
The movement restricting portion is not limited to a structure consisting of an outer stopper, an inner stopper, and a step. For example, a circumferential groove may be provided on the inner surface of the housing half, and a circumferential rib may be provided on the outer surface of the motor housing and positioned within the groove. In this case, the rib can also be abutted against the inner surface of the groove at the front and rear of the groove to restrict the relative movement range of the two housings.

In addition, as is common to all the embodiments, the grinder may be an AC tool that uses a commercial power source instead of a DC tool that uses a battery pack.
The motor is not limited to a brushless motor.
The grinding tool is not limited to a grinder, but may be other grinding tools such as a sander or a polisher.
The screw fastening direction between the half housings is not limited to the left-right direction. For example, the present disclosure is also applicable to half housings that are divided into upper and lower halves.
The half housing may be symmetrical or asymmetrical.

1, 1A, 1B... Grinder, 2... Motor housing, 4... Gear housing, 5... Grip housing, 5a, 5b... Half housing, 6... Rear housing section, 7... Front housing section, 8... Motor, 11... Rotating shaft, 16... Spindle, 18... Tip tool, 20... Front grip section, 30... Screw, 31... Guide tube section, 32... Left screw boss, 33... Left large diameter section, 34... Left small diameter section, 36... Right screw boss, 37... Right large diameter section Diameter portion, 38: Right small diameter portion, 40: Rubber ring, 41: Rubber sheet, 50: Shaft, 51: Nut, 52: Threaded portion, 57: Rubber sleeve, 60: Receiving portion, 65: Front end portion, 66: Notch, 67: Through hole, 70: Outer stopper, 73: Opposing surface, 74: Restricting piece, 75: Inner stopper, 76: Step portion, 80: Elastomer, 81: Outer surface portion, 86: Sealing portion, S1, S2: Gap, C1, C2: Clearance.

Claims (13)

a motor housing that accommodates a motor;
a pair of half housings that are screwed together with the motor housing sandwiched therebetween,
The half housings are fastened together by screws, with screw bosses provided on each half housing inserted into the motor housing, and elastic members interposed between the motor housing and each screw boss in the axial direction of the screw boss ,
Each of the screw bosses is a cylindrical member having a small diameter portion at the tip end thereof inserted into the motor housing and a large diameter portion at the base end thereof, and the elastic member is a rubber ring fitted around each of the small diameter portions.
A grinding tool characterized in that, when each of the small diameter portions is inserted into the motor housing and screwed in place, each of the rubber rings is positioned between the motor housing and each of the large diameter portions . The grinding tool described in claim 1, characterized in that an output shaft is provided in front of the motor housing, the half housings are a pair of left and right half housings, and the axial direction of the screw boss is the left-right direction of the motor housing. 3. The grinding tool according to claim 2, wherein the rubber rings are provided on the left and right sides of the motor housing. A grinding tool as described in claim 2 or 3, characterized in that the screw bosses are provided in two locations on each half housing in the vertical direction of the motor housing. A grinding tool according to any one of claims 2 to 4, characterized in that the motor housing is cylindrical. A grinding tool as described in any one of claims 2 to 5, characterized in that a second elastic member is interposed between each of the half housings on both the left and right sides of the motor housing. A grinding tool as described in any one of claims 1 to 6, characterized in that the motor housing and each half housing are each provided with a movement restriction portion that abuts against each other when the motor housing and each half housing move relative to each other by a predetermined amount. a motor housing that accommodates a motor;
a pair of half housings that are screwed together with the motor housing sandwiched therebetween,
The half housings are fastened together by inserting a shaft having threaded portions at both ends into the motor housing, and screwing a pair of nuts held by the pair of half housings onto the threaded portions at both ends,
A rubber ring is interposed between the motor housing and each of the half housings and is attached to an end of the shaft .
A grinding tool characterized in that a rubber sleeve is interposed between the outer periphery of the shaft and the motor housing, and the rubber sleeve is provided over the entire length of the motor housing in the axial direction of the shaft, so that the motor housing and the shaft are not in contact with each other . the motor housing has an output shaft on a front side, the half housings are a pair of left and right half housings, and the shaft penetrates the motor housing in the left-right direction;
9. The grinding tool according to claim 8, wherein the rubber rings are interposed between the half housings on the left and right sides of the motor housing in the axial direction of the shaft, and the rubber rings overlap the rubber sleeves in the radial direction of the shaft. 10. The grinding tool according to claim 9 , wherein third elastic members are interposed between the motor housing and each of the half housings on both the left and right sides of the motor housing. 11. The grinding tool according to claim 1, wherein an elastic body is provided on an outer surface of one of the motor housing and the pair of half housings, covering the outer surface, and the elastic body is provided with a sealing portion that protrudes toward the other housing and abuts against the other housing, thereby sealing between the two housings. 12. The grinding tool according to claim 11 , wherein the elastic body and the seal portion are provided on the pair of half housings. 13. The grinding tool according to claim 12 , wherein the seal portion extends toward the motor housing and abuts against the motor housing.