JP2014233811A - Rotary tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispose a groove part more efficiently when the groove part is disposed on a slide range of a spindle as a fretting wear resistance method, because when an impact relax mechanism for relaxing impact during starting up is disposed inside in a disk grinder, the spindle is supported with respect to a following gear by rotation support, so between the spindle and the following gear, fretting wear is easily generated.SOLUTION: A groove part 11a for fretting wear resistance is disposed in an overlap range T of an inner peripheral surface of a support hole of a following gear with respect to an outer peripheral surface of the spindle 11. A ratio of a non-slide contact area by the groove part 11a with respect to an area of the overlap range T is in a range of 20-40%.

Description

  The present invention relates to a rotary tool such as a disc grinder, for example.

Generally, this type of rotary tool has a configuration in which the rotational output of an electric motor built in a tool body is reduced through a reduction gear train and output to a spindle. In the case of a disc grinder, a spindle equipped with a reduction gear train in which a drive-side bevel gear meshes with a driven-side bevel gear, and a circular grindstone mounted around an axis perpendicular to the output shaft of the electric motor. Is configured to be rotatably supported.
In the reduction gear train, since an appropriate backlash is set, a start shock (impact) due to gear meshing (torque transmission) is likely to occur when the electric motor is started. For this reason, in this kind of rotary tool, various devices for eliminating or reducing the starting shock have been conventionally made.
For example, the following patent document discloses a technique related to an impact mitigation mechanism for reducing a shock at the time of startup. This shock mitigation mechanism is provided with a C-shaped torque transmission member elastically deformable in the radial direction between the driven gear (drive side) and the spindle (driven side) in the middle of the torque transmission path. The torque transmitting member is elastically deformed in the diameter increasing direction to transmit the driving torque from the driven gear to the spindle while absorbing the starting shock.

JP 2010-179436 A Japanese Patent Application Laid-Open No. 2002-264031

However, according to the above-described conventional impact mitigation mechanism, it is necessary to support the driven gear so that the driven torque can be relatively rotated with respect to the spindle, because the driving torque is transmitted through the C-shaped torque transmitting member. The spindle is supported by a support hole (inner peripheral hole) of the driven gear so as to be relatively rotatable with an appropriate clearance interposed therebetween. The clearance of the support hole of the driven gear with respect to the spindle is set to about 0.004 mm to 0.050 mm, for example, so that the assembling property can be ensured while suppressing the backlash (core runout) between the two as much as possible. Yes. Since the driven gear is supported so as to be relatively rotatable with respect to the spindle with a slight clearance in this way, wear is likely to occur between the support hole of the driven gear and the outer peripheral surface of the spindle, and the wear progresses. As a result, rattling occurs between the gear and the spindle, and the gears are disengaged and vibration is generated. As a result, the durability of the electric motor may be impaired.
An object of the present invention is to improve the durability of an electric motor by reducing wear between a driven gear and a spindle while reducing the impact at the time of starting the motor by a conventional impact reducing mechanism.

The above problems are solved by the following invention.
1st invention is a rotary tool which decelerates the rotation output of an electric motor through a reduction gear train, and outputs it to the spindle supported by rotation with the 1st and 2nd bearings. The driven gear of the reduction gear train is supported so as to be rotatable relative to the spindle. Further, a groove portion for fretting wear is provided in the overlapping range of the inner peripheral surface of the support hole of the driven gear with respect to the outer peripheral surface of the spindle. The ratio of the non-sliding contact area by the groove portion to the area of the overlap range is set within a range of 20% to 40%.
According to the first invention, since the driven gear is rotatably supported by the spindle via the third bearing, the surface pressure between the support hole of the driven gear and the spindle inserted through the support hole is reduced. As a result, the wear is reduced, and the durability of the reduction gear train can be increased.
In addition, a groove for preventing fretting (Fretting Corrosion) is provided in the overlapping range between the support hole of the driven gear and the spindle. By this groove portion, a range (non-sliding contact range) that is not slidable with each other is provided between the outer peripheral surface of the spindle and the inner peripheral surface of the support hole in the overlap range. The sliding contact area is reduced by the area of the non-sliding contact range, so that fretting and fretting wear can be reduced.
Furthermore, the wear powder generated by the sliding contact between the outer peripheral surface of the spindle and the inner peripheral surface of the support hole enters the groove portion to suppress the acceleration of wear, and the gear and the spindle are fixed (burned) by the wear powder. Can be prevented.
2nd invention is a rotary tool which used the groove part as the spiral groove in 1st invention.
According to the second invention, compared to a configuration in which a plurality of annular groove portions are provided at appropriate intervals, the occurrence of fretting can be suppressed evenly over the entire overlap range.
A third invention is the rotary tool according to the first or second invention, wherein the groove is provided in the spindle.
According to the third invention, the processing of the groove is facilitated as compared with the configuration provided on the inner peripheral surface of the support hole.
A fourth invention is a rotary tool according to any one of the first to third inventions, wherein the depth of the groove is set to at least 30 percent of the width of the groove.
According to the fourth aspect of the invention, it is possible to ensure a sufficient friction powder storage capacity for the groove.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the impact mitigation is achieved by interposing a torque transmission member that elastically deforms and transmits drive torque between the driven gear of the reduction gear train and the spindle. It is a rotary tool provided with a mechanism.
According to the fifth aspect of the invention, the impact mitigating mechanism mitigates the impact when the electric motor is started and meshed with the reduction gear train, and the durability of the reduction gear train is also enhanced in this respect.
In addition, even when impact torque is applied during use, the impact torque is absorbed by the impact mitigation mechanism, so that the impact applied to the meshing teeth of the reduction gear train is mitigated, resulting in the durability of the rotary tool. Can increase the sex.

It is a whole side view of the rotary tool which concerns on this embodiment. In this figure, the gear head portion is shown in a longitudinal section where it is broken. It is a longitudinal cross-sectional view of a gear head assembly. FIG. 3 is a cross-sectional view taken along line (III)-(III) in FIG. 2 and is a plan view of the gear head assembly. It is a side view of a single spindle. It is the (V) part enlarged view of FIG. 4, Comprising: It is an enlarged view of a groove part.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a rotary tool 1 according to this embodiment. As illustrated, in the present embodiment, a disc grinder is illustrated as an example of the rotary tool 1.
The rotary tool 1 includes a tool main body portion 3 in which an electric motor 2 is housed, and a gear head portion 10 coupled to a front portion of the tool main body portion 3. The tool body 3 has a cylindrical shape with a thickness that is easy for a user to grip with a hand, and is provided with a large switch lever 4 that is pulled by a hand gripped on the lower surface side thereof. When the switch lever 4 is pulled upward in the figure, the electric motor 2 is activated. When the pulling operation is stopped, the switch lever 4 is returned to the OFF position on the lower side in the figure, and the electric motor 2 is stopped. The switch lever 4 is provided with a lock lever 4a for holding the switch lever 4 in the on position and holding it in the off position.
The gear head unit 10 reduces the rotational output of the electric motor 2 through a reduction gear train and outputs it to the spindle 11. The gear head unit 10 is provided with an impact mitigation mechanism 30 which is a feature of this embodiment. Is incorporated. A gear head housing 12 that opens downward is attached to the front portion of the tool body 3. The output shaft 2 a of the electric motor 2 enters the gear head housing 12. A drive gear 13 is attached to the output shaft 2a. A bevel gear is used as the drive gear 13. A gear head assembly S is incorporated on the front side of the drive gear 13. The drive gear 13 is meshed with the driven gear 17 of the gear head assembly S. The rotational output of the electric motor 2 is decelerated and output to the spindle 11 by the decelerating gear train by the engagement of the drive gear 13 and the driven gear 17. Details of the gear head assembly S are shown in FIGS.
The gear head assembly S is obtained by assembling mainly a bearing holder 16, a driven gear 17, and an impact mitigating mechanism 30 on the spindle 11 in order from the lower side in FIG. Yes. As shown in FIG. 1, the bearing holder 16 is fixed to the lower surface of the gear head housing 12 by four fixing screws 16a to 16a.
The spindle 11 is supported so as to be rotatable about an axis via a first bearing 14 held by a bearing holder 16 and a second bearing 15 attached to the upper portion of the gear head housing 12. The rotation axis of the spindle 11 is substantially orthogonal to the rotation axis of the output shaft 2 a of the electric motor 2. In the present embodiment, ball bearings (ball bearings) are used as the first and second bearings 14 and 15.
A retainer 24 is fastened to the lower surface side of the bearing holder 16 on the lower surface side of the first bearing 14. The first bearing 14 is fixed to the bearing holder 16 in the axial direction by the retainer 24. An annular felt material 24 a is attached to the inner peripheral side of the retainer 24. The felt material 24a protects the first bearing 14 from dust.

The spindle 11 protrudes further downward from the bearing holder 16, and a circular grindstone 20 and a grindstone cover 21 that covers a substantially half-circumferential range mainly on the rear side of the grindstone 20 are attached to the protruding portion. The grindstone 20 is firmly attached while being sandwiched between a receiving flange 22 and a fixing nut 23 attached to the tip of the spindle 11.
A bevel gear is also used for the driven gear 17 supported on the spindle 11. In the case of this embodiment, the driven gear 17 is supported by the spindle 11 via the gear holder 18 so as to be relatively rotatable. The gear holder 18 is fixed integrally with the driven gear 17 and substantially forms a part of the driven gear 17. The spindle 11 is inserted into the support hole 18 a of the gear holder 18. A support boss portion 18 b is provided on the lower surface side of the gear holder 18. The support boss portion 18 b enters the inner peripheral side of the bearing holder 16. The support boss portion 18 b is rotatably supported on the inner peripheral side of the bearing holder 16 via the third bearing 19. In the present embodiment, a ball bearing (ball bearing) is used for the third bearing 19 as well as the first and second bearings 14 and 15. In the case of this embodiment, the clearance between the support hole 18a of the gear holder 18 and the spindle 11 is set to about 0.004 mm to 0.050 mm as in the prior art, and the driven gear 17 (gear holder 18) of the spindle 11 is set. Assemblability is ensured, and rattling (core wobbling) is suppressed.
In this way, the driven gear 17 is indirectly supported so as to be relatively rotatable with respect to the spindle 11 via the third bearing 19, so that the runout between the two rotation axes is reduced, and as a result, when torque is transmitted. The surface pressure of the support hole 18a of the gear holder 18 with respect to the outer peripheral surface of the spindle is reduced to reduce wear.
A receiving boss portion 18c having a diameter larger than that of the support boss portion 18b is provided on the upper portion of the gear holder 18. The receiving boss portion 18c and the support boss portion 18b are provided coaxially. In this embodiment, the driven gear 17 is press-fitted and integrated in the outer peripheral side of the receiving boss portion 18c.

An impact relaxation mechanism 30 is incorporated on the inner peripheral side of the receiving boss portion 18c. The rotational torque of the driven gear 17 is transmitted to the spindle 11 through the impact relaxation mechanism 30. The shock relaxation mechanism 30 has a basic configuration in common with a conventionally known one. On the inner peripheral side of the receiving boss portion 18c, a joint sleeve 31 is integrated with the spindle 11 by press fitting. The joint sleeve 31 is provided with one driven convex portion 31a projecting outward in the radial direction. Opposing to the driven convex portion 31a, one driving convex portion 18d is provided on the inner peripheral side of the receiving boss portion 18c so as to project inward in the radial direction.
A C-shaped torque transmission member 32 is interposed around the joint sleeve 31 and on the inner peripheral side of the receiving boss portion 18c. The driving convex portion 18d and the driven convex portion 31a are located between both end portions 32a and 32b of the torque transmitting member 32. As shown in FIG. 2, the displacement of the torque transmission member 32 in the spindle axis direction is regulated by the stopper flange 33. The stopper flange 33 is restricted in displacement in the spindle axis direction by a retaining ring 34.
When the rotational torque in the direction of the white arrow in FIG. 3 is transmitted to the driven gear 17 through meshing with the drive gear 13, the one end portion 32a of the torque transmission member 32 is the same by the drive convex portion 18d provided integrally therewith. Pushed in the direction. When one end portion 32a of the torque transmitting member 32 is pushed in the direction of the white arrow in FIG. 3, the other end portion 32b is abutted against the driven convex portion 31a on the spindle 11 side. Thus, the one end portion 32a is pushed by the drive convex portion 18d on the driven gear 17 side and the other end portion 32b is abutted against the driven convex portion 31a on the spindle 11 side, whereby the torque transmitting member 32 is elastically deformed in the diameter increasing direction. Thus, it is pressed along the inner peripheral surface of the receiving boss portion 18c, whereby the driven gear 17 and the spindle 11 are integrated for rotation.
In this way, the driven gear 17 and the spindle 11 are integrated with respect to the rotation via the impact mitigating mechanism 30, so that the rotational torque in the direction of the white arrow in FIG. 3 is transmitted to the spindle 11 via the driven gear 17, and therefore to the grindstone 20. Output a large rotational torque. Further, when the electric motor 2 is started, the torque transmission member 32 is elastically deformed in the diameter increasing direction, so that an impact when the drive gear 13 and the driven gear 17 are engaged is absorbed or alleviated.

As described above, the inner peripheral surface of the support hole 18 a of the gear holder 18 is always in sliding contact with the outer peripheral surface of the spindle 11. For this reason, fretting (Fretting Corrosion) is likely to occur on the sliding surface. Abrasion powder is generated by the occurrence of fretting, and the generated abrasion powder adheres to the phenomenon of further promoting the wear. As wear progresses, there is a risk that trouble (burn-in) may occur in which the spindle 11 and the gear holder 18 and thus the driven gear 17 are integrated with respect to rotation.
As a countermeasure against this fretting, in the impact mitigation mechanism of the present embodiment, a groove 11a for fretting wear is provided in a range where the spindle 11 and the support hole 18a of the gear holder 18 overlap in the axial direction (overlap range). ing. In the present embodiment, one groove portion 11 a is spirally provided on the outer peripheral surface of the spindle 11. The groove 11a functions as a non-sliding contact range where the groove 11a is not slidably contacted (contacted) with the inner peripheral surface of the support hole 18a. Therefore, the sliding contact area between the outer peripheral surface of the spindle 11 and the inner peripheral surface of the support hole 18a of the gear holder 18 is larger than the area of the overlap range (overlap area) (the area of the non-sliding contact range by the groove 11a ( The fretting wear (abrasion caused by fretting) is reduced by the amount of non-sliding contact area) (sliding contact area = overlap area−non-sliding contact area).
Further, the wear powder generated by fretting wear between the outer peripheral surface of the spindle 11 and the inner peripheral surface of the support hole 18a also enters the groove portion 11a. Thus, the driven gear 17 and the spindle are prevented from sticking (burn-in).
Thus, by appropriately adjusting (reducing) the sliding contact area between the outer peripheral surface of the spindle 11 and the inner peripheral surface of the support hole 18a of the gear holder 18 by the groove portion 11a, the fretting wear is reduced and the shock mitigation mechanism is ensured. Can function. Therefore, as a result of testing various cases with respect to the width, pitch, and the like of the groove portion 11a, the present applicant has determined that the ratio R of the non-sliding contact area by the groove portion 11a in the overlap range of the support hole 18a is, for example, about 22%. It has been confirmed that fretting wear can be effectively suppressed.

FIG. 4 shows the spindle 11 as a single unit. One groove portion 11a is provided in an axial range (overlap range T = axial range of the support hole 18a) on the outer peripheral surface of the spindle 11 where the inner peripheral surface of the support hole 18a of the gear holder 18 is slidably contacted. It is provided in a spiral. The applicant has tested the occurrence of fretting wear when the diameter D and the axial length L of the sliding contact range T of the spindle 11 and the groove width W, groove depth H, and groove pitch P of the groove portion 11a are variously changed. went. Some of the results are shown in Table 1 below. In the test illustrated in Table 1 below, two cases are shown in which the groove width W, the groove depth H, and the groove pitch P are not changed, but the diameter D and the axial length L of the overlap range T are changed. In the illustrated two cases, the ratio of the groove depth H to the groove width W is set to 50%. Further, the groove pitch P is set to 3.5 mm in both cases.

In the upper and lower cases, the ratio R of the non-sliding contact area is 21.9% and 32%, and no significant fretting has been confirmed in either case. In the lower case, no fretting wear has been confirmed.
In the case where the ratio R of the non-sliding contact area was set to 13.7% and 20.6%, the occurrence of fretting and fretting wear was confirmed, and the sufficient effect of providing grooves as a countermeasure against fretting was confirmed. I couldn't.
On the contrary, when the ratio R of the non-sliding contact area is set to exceed 40%, for example, fretting does not occur, but it is confirmed that the wear increases as the surface pressure increases.
From the above test results, the ratio of the area of the groove portion 11a in the overlap range T between the spindle 11 and the support hole 18a (ratio R of the non-sliding contact area) is over 20% to 40%. By appropriately setting the diameter D, the axial length L, or the width W, the depth H, and the pitch P of the groove portion 11a, the occurrence of fretting and fretting wear can be effectively suppressed.
Next, by setting the depth H of the groove 11a to about 50% of the groove width W, the groove 11a has a sufficient capacity for holding the wear powder while ensuring the strength and durability of the spindle 11. You can have it.

According to the rotary tool 1 of the present embodiment configured as described above, the gear holder 18 (the driven gear 17) is supported so as to be relatively rotatable with respect to the spindle 11 because it is necessary to provide the impact relaxation mechanism 30. In order to eliminate the problem of friction between the spindle 11 and the support hole 18a caused by this, a configuration in which a third bearing 19 is interposed between the driven gear 17 (gear holder 18) and the spindle 11 is provided. In such a configuration, the occurrence of fretting or fretting wear becomes a problem with respect to the overlap range T of the spindle 11, but in this embodiment, the outer peripheral surface of the spindle 11 and the spiral groove portion 11a in the overlap range T are present. By appropriately setting the ratio R of the non-sliding contact area to the overlap area by the groove 11a within a range of 20% to 40%, it is possible to effectively suppress or reduce defects such as fretting. Thus, the impact mitigating mechanism 30 can function efficiently and the durability of the electric motor 2 can be enhanced.
In addition, since the groove portion 11a for fretting measures is provided in a spiral shape, the entire range in the axial direction of the overlap range is more uniform than the configuration in which a plurality of annular groove portions are provided at appropriate intervals. The occurrence of fretting can be suppressed.
Furthermore, since the driven gear 17 is rotatably supported by the spindle 11 via the third bearing 19, the support hole 18a of the gear holder 18 to which the driven gear 17 is integrally attached, and the spindle 11 inserted through the support hole 18a. As a result of the reduction of the surface pressure between the two, wear of both 18a and 11 is reduced. By reducing the wear between the driven gear 17 and the spindle 11 that supports the driven gear 17, it is possible to reduce vibrations of the driven gear 17 due to torque transmission, thereby improving the durability of the electric motor 2. it can.
Also in the illustrated rotary tool 1, an impact mitigation mechanism 30 for mitigating a starting shock due to meshing of the reduction gear train at the time of starting the electric motor 2 is interposed between the driven gear 17 (gear holder 18) and the spindle 11. Therefore, the durability of the electric motor 2 is also improved in this respect.

Various modifications can be made to the embodiment described above. For example, the configuration in which the groove portion 11a for fretting wear countermeasures is spirally arranged on the outer peripheral surface of the spindle 11 is exemplified, but a plurality of annular groove portions may be arranged in parallel, and further, the groove portion is supported. It is good also as a structure provided in the hole 18a side, or a structure provided in both.
In addition, by appropriately changing one or more of the width W, depth H, and pitch P of the groove 11a, the ratio R of the non-sliding contact area of the groove to the sliding contact area can be appropriately set. For example, two cases in which the ratio of the groove depth H to the groove width W is set to 50% have been illustrated, but by setting such a ratio to at least about 30%, a sufficient capacity for holding the friction powder in the groove portion can be obtained. Can be secured.
Further, the third bearing 19 is interposed between the outer peripheral side of the support boss portion 18b and the inner peripheral side of the bearing holder 16, and the driven gear 17 is indirectly rotated and supported by the spindle 11. A configuration may be adopted in which the third bearing is interposed on the inner peripheral side of the support boss portion 18b so as to directly rotate and support the spindle 11.
Moreover, although the ball bearing (ball bearing) was illustrated as a 3rd bearing, it is good also as a structure which uses not only a needle bearing, a taper roller bearing, or a rolling bearing but a sliding bearing.
Furthermore, the gear holder 18 separately prepared in advance is integrated with the driven gear 17 and the driven gear 17 is rotationally supported on the spindle 11. However, both the components 17 and 18 may be manufactured as a single unit from the beginning. Good.
Furthermore, although the disk grinder is illustrated as the rotary tool 1, it can be similarly applied to other types of rotary tools such as a cutting tool such as a disk sander, a polisher, and a circular saw, a brush cutter, and a portable band saw, Further, the present invention can be applied not only to electric tools but also to pneumatic tools.

1 ... Rotary tool (disc grinder)
2 ... Electric motor 3 ... Tool body 4 ... Switch lever, 4a ... Lock lever S ... Gear head assembly 10 ... Gear head 11 ... Spindle, 11a ... Groove (for fretting wear countermeasures)
DESCRIPTION OF SYMBOLS 12 ... Gear head housing 13 ... Drive gear 14 ... 1st bearing 15 ... 2nd bearing 16 ... Bearing holder 17 ... Driven gear 18 ... Gear holder 18a ... Support hole, 18b ... Support boss part, 18c ... Reception boss part, 18d ... Driving convex portion 19 ... third bearing 20 ... grinding stone 21 ... grinding stone cover 30 ... impact mitigating mechanism 31 ... joint sleeve, 31a ... driven convex portion 32 ... torque transmission member, 32a ... one end, 32b ... other end 33 ... stopper Flange 34 ... Retaining ring T ... Overlap range D ... Overlapping range diameter L ... Overlapping range axial length W ... Groove width H ... Groove depth P ... Groove pitch R ... Non-sliding contact area of groove with respect to overlap area Percentage of

Claims (5)

A rotary tool that decelerates the rotational output of the electric motor through a reduction gear train and outputs it to a spindle that is rotatably supported by the first and second bearings, and the driven gear of the reduction gear train is relative to the spindle. A rotary tool supported rotatably,
A groove for fretting wear is provided in the overlapping range of the inner peripheral surface of the support hole of the driven gear with respect to the outer peripheral surface of the spindle,
The rotary tool which set the ratio with respect to the area of the said overlap range of the non-sliding contact area by this groove part in the range of 20 to 40 percent. The rotary tool according to claim 1, wherein the groove portion is a spiral groove. The rotary tool according to claim 1 or 2, wherein the groove is provided on the spindle. The rotary tool according to any one of claims 1 to 3, wherein the depth of the groove is set to at least 30 percent of the width of the groove. 5. The rotary tool according to claim 1, wherein a torque transmission member that elastically deforms and transmits drive torque is interposed between the driven gear of the reduction gear train and the spindle. A rotary tool with an impact relief mechanism.