JP2013119126A - Power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the workability and handleability of a disc grinder or the like by downsizing a power transmission part because there is a problem that, in a disc grinder where the rotation axis of a spindle intersects the motor axis of a power motor, a bevel gear is used for converting a power transmission direction while decelerating rotative power, however, the diameter of the bevel gear is relatively large, thereby the size of a gear head is increased, and workability is degraded.SOLUTION: A power transmission part 3 is downsized by using an outer rotor type electric motor 10 capable of outputting low-speed rotation and high torque as a drive source, and interposing universal joints 12, 13 instead of conventional bevel gears between its output shaft 10c and a spindle 14.

Description

  The present invention relates to a power tool that uses, for example, an electric motor as a drive source, such as a disc grinder or an angle drill.

  For example, a disk grinder used for stone grinding or the like has an electric motor built in a tool main body part that also serves as a grip part gripped by a user, and an axis line orthogonal to the rotation axis (motor axis line) of the output shaft of the electric motor It is equipped with a configuration in which a circular grindstone is attached to a spindle that is rotatably supported around it. At the front part of the tool body, the rotational output is reduced between the spindle and the electric motor, and the rotation axis is converted into an orthogonal direction. The gear head part (power transmission part) which accommodated the reduction gear train for this is provided. Usually, a so-called bevel gear (bevel gear) is used as a reduction gear train for rotation axis conversion. The following patent document discloses a disc grinder having such a general gear head portion.

JP 2011-104765 A

However, the conventional disc grinder has the following problems. As described above, in order to make the rotation axis of the spindle perpendicular to the motor axis, the gear head portion mainly including the bevel gear is provided at the front portion of the tool main body portion. This gear head portion has a structure in which a relatively large-diameter bevel gear is housed in the gear head case in order to reduce the rotation output of the electric motor to an appropriate reduction ratio. As a result, the gear head portion is greatly stretched forward of the tool body portion. It was provided in the state to put out. For this reason, in the conventional work especially in a narrow place, the gear head portion is obstructed, and the working range by the grindstone is likely to be restricted. In this respect, there is a problem that the workability and handling of the disc grinder are deteriorated. It was. Conventionally, efforts have been made to make the gear head portion compact by reducing the diameter of the bevel gear, reducing the thickness of the gear housing, and the like, but this has a limit.
An object of the present invention is to make the power transmission portion provided in the front portion of the tool main body portion compact and to greatly improve the workability and handleability of this type of electric tool.

The above problems are solved by the following invention.
1st invention WHEREIN: In the electric tool which the motor axis line of the electric motor as a drive source and the rotation axis line of the spindle which attached the tip tool cross | intersect, the structure which transmits the rotational power of an electric motor to a spindle via a universal joint This is an electric tool.
According to the first invention, a universal joint (universal joint, JIS B1454) is used instead of the conventional bevel gear between the output shaft of the electric motor and the spindle whose rotational axis intersects the output shaft. Rotational power is transmitted. Since the universal joint is housed in the gear head housing in place of the bevel gear, the power transmission unit can be made compact, thereby improving the workability and handling of the power tool.
A second invention is an electric tool using an outer rotor type electric motor as the electric motor in the first invention.
According to the second invention, by using an outer rotor type electric motor that can output higher torque at a lower speed than the inner rotor type motor as a drive source, the universal joint can be operated without being decelerated by interposing a bevel gear as in the prior art. Thus, an appropriate rotation speed and output torque of the spindle can be obtained.
A third invention is an electric tool in which a plurality of universal joints are interposed in the first or second invention.
According to the third aspect of the invention, the spindle can be rotationally supported at a position where the rotation axis is orthogonal to the motor axis.
A fourth invention is an electric tool according to any one of the first to third inventions, wherein the crossing angle of the spindle with respect to the motor axis can be changed via a universal joint.
According to the fourth aspect of the invention, the direction of the tip tool can be arbitrarily changed according to the work mode, so that efficient work can be easily performed.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the front portion of the tool main body portion in which the electric motor is housed in the head housing that accommodates the universal joint and rotatably supports the spindle via the bearing. The power tool is configured such that the projecting dimension of the head housing from the front portion of the tool body portion depends on the bearing.
According to the fifth invention, the projecting dimension of the head housing from the front portion of the tool main body depends on the presence of a bearing having a smaller diameter than the conventional bevel gear, so that the rotational power is converted to the spindle using the conventional bevel gear. Compared to the configuration that transmits to the head, the overhang dimension of the head housing can be greatly reduced, which makes the front part of the tool main body much smaller than before, making the power tool workable and easy to handle Can be increased.
A sixth invention is the disc grinder according to any one of the first to fifth inventions, wherein a spindle is provided with a circular grindstone as a tip tool.
According to the sixth invention, the above-described effects can be obtained by applying any one of the first to fifth inventions to the disc grinder.

It is a whole perspective view of the electric tool concerning this embodiment. In this figure, a disk grinder is illustrated as an example of the electric tool. It is a longitudinal cross-sectional perspective view of the electric tool which concerns on this embodiment. FIG. 3 is a partially enlarged view of FIG. 2 and a perspective view of a power transmission unit. It is the whole electric tool perspective view concerning a 2nd embodiment of the present invention. It is the whole electric tool perspective view concerning a 2nd embodiment of the present invention. It is a longitudinal cross-sectional view of a direct drive type die grinder.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3 show a power tool 1 according to the first embodiment. In the first embodiment, a disc grinder is illustrated as an example of the electric tool 1. The electric tool 1 according to the first embodiment is a direct drive type disc grinder, and includes a tool main body 2 that includes an electric motor 10 as a drive source, and a power transmission unit 3 provided at the front of the tool main body 2. ing.
The tool main body 2 also has a function as a grip portion gripped by a user, and includes a configuration in which an electric motor 10 is housed in a cylindrical main body housing 4. A slide-type switch 5 is provided on the side of the tool body 2. The electric motor 10 can be started and stopped by sliding the switch 5 with the fingertip of the hand holding the tool body 2.
In the present embodiment, as the electric motor 10, a so-called outer rotor type electric motor capable of outputting low rotation and high torque is used. The outer rotor type electric motor 10 is known, and as shown in FIG. 2, a cylindrical stator 10a, a similarly cylindrical rotor 10b rotatably supported on the outer peripheral side thereof, and the rotor 10b. The output shaft 10c is fixed along the central axis. The output shaft 10c is fixed to the center of the rear end of the rotor 10b and extends forward. The output shaft 10c protrudes forward through the inner peripheral hole of the stator 10a. The front portion of the output shaft 10 c is rotatably supported by a bearing 6 attached to the front portion of the main body housing 4. The front part of the output shaft 10 c protrudes further from the bearing 6 to the front part and reaches the power transmission part 3.
When the switch 5 is turned on, the outer rotor 10b rotates around the stator 10a, and the output shaft 10c rotates about its axis (motor axis) integrally therewith. The outer rotor type electric motor 10 outputs a lower speed and higher torque than the inner rotor type electric motor.

Details of the power transmission unit 3 are shown in FIG. The power transmission unit 3 includes a head housing 11 attached to the front part of the tool body 2, two universal joints 12 and 13, and a spindle 14. A bifurcated first connecting portion 10 d is provided at the tip of the output shaft 10 c of the electric motor 10. The first connecting piece 12a of the first universal joint 12 is rotatably connected to the first connecting portion 10d via a first connecting shaft 10e. A bifurcated second connecting portion 12b is rotatably connected to the first connecting piece 12a via a second connecting shaft 12c. The first connecting portion 10d, the first connecting piece 12a, the second connecting portion 12b, and the first and second connecting shafts 10e and 12c constitute the first universal joint 12.
The second connecting portion 12 b of the first universal joint 12 is integrally provided with the third connecting portion 13 a of the second universal joint 13. One end side of the third connecting piece 13b is rotatably connected to the third connecting portion 13a having a bifurcated shape via a third connecting shaft 13c. The other end side of the third connecting piece 13b is rotatably connected to the fourth connecting portion 14a via the fourth connecting shaft 14b. The fourth connecting portion 14 a is integrally provided at the upper end of the spindle 14.
The spindle 14 is rotatably supported by the head housing 11 via a bearing 15. A known ball bearing (ball bearing) is used for the bearing 15. An outer ring 15a of the bearing 15 is fixed to the head housing 11 side.
The output shaft 10c of the electric motor 10 and the spindle 14 are connected via two universal joints 12 and 13, so that the spindle 14 intersects the output shaft 10c of the electric motor 10 at approximately 90 °. It is supported by. Therefore, the rotation axis J14 of the spindle 14 is orthogonal to the rotation axis (motor axis J10) of the output shaft 10c of the electric motor 10.
The spindle 14 protrudes below the head housing 11. A disc-shaped grindstone T is attached to the lower part of the spindle 14 protruding from the head housing 11 while being sandwiched between the receiving flange 16 and the fixing nut 17. The grinding wheel cover 18 is covered in the range of approximately half the rear of the grinding wheel T, and scattering of cutting powder and the like to the user side is prevented.

According to the electric tool 1 of the first embodiment configured as described above, the outer rotor type electric motor 10 is used as a drive source. For this reason, low-speed and high-torque rotational power is directly output from the output shaft 10 c of the electric motor 10. For this reason, in the electric power tool 1 of the first embodiment, the reduction gear train including the conventional bevel gear is omitted. The outer rotor-type electric motor 10 directly outputs low-speed and high-torque rotational power equivalent to that of the conventional motor to the spindle 14 via the first and second universal joints 12 and 13 without passing through the conventional reduction gear train. .
Further, the output shaft 10c of the electric motor 10 and the spindle 14 are connected to each other through two universal joints 12 and 13 so as to intersect each other at approximately 90 °. Therefore, in the first embodiment, the power transmission unit 3 including the two universal joints 12 and 13 is provided instead of the conventional reduction gear train, and the conventional bevel gear is not provided. Since a relatively large-diameter bevel gear is not provided, the overhanging dimension L of the head housing 11 depends on the size (outer diameter) of the outer ring 15a of the bearing 15 having a smaller diameter. Therefore, the projecting dimension L and the height dimension of the head housing 11 of the power transmission part 3 from the front part of the tool main body part 2 and its height dimension are greatly reduced in size as compared with the conventional gear head housing.
As described above, since the forward projecting dimension L and the height dimension of the power transmission unit 3 provided at the front part of the tool main body unit 2 are greatly reduced as compared with the conventional one, the grindstone T is displaced in various directions. In the grinding work to be performed, the work can be performed efficiently while avoiding the interference of the power transmission unit 3, and the workability and the handleability of the electric power tool 1 can be greatly improved in this respect.
Moreover, since it is the structure which does not use the conventional bevel gear (deceleration gear train) as the power transmission part 3, a gear sound does not generate | occur | produce but the noise reduction of the said electric tool 1 can be achieved.

Various modifications can be made to the first embodiment described above. For example, the configuration in which the rotation axis J14 of the spindle 14 is substantially orthogonal to the motor axis J10 with the first and second universal joints 12 and 13 interposed is illustrated, but the spindle is interposed with one universal joint interposed. For example, the motor axis may be crossed at an angle of about 45 ° or 60 °.
In addition, although the configuration in which the angle of the spindle 14 with respect to the motor axis J10 is fixed at a right angle is exemplified, the configuration can be arbitrarily changed. An example of such a swing-type electric tool 20 is shown in FIGS. The electric power tool 20 of the second embodiment is also exemplified by a disc grinder. Therefore, the same members and configurations as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the electric power tool 20 of the second embodiment, three universal joints 21 to 23 are interposed between the output shaft 10 c of the electric motor 10 and the spindle 14 in the head housing 11 of the power transmission unit 3. Angle adjustment mechanisms 24 and 24 are provided on both sides of the three universal joints 21 to 23. The left and right angle adjusting mechanisms 24, 24 are configured symmetrically.
Drive-side pedestal portions 25 and 25 are provided on the front surface of the tool main body 2 so as to protrude forward in parallel with each other. The rear sides of the connecting plates 27 and 27 are supported on the drive side pedestals 25 and 25 via the support shafts 26 so as to be tiltable up and down. On the other hand, on the left and right sides of the head pedestal portion 28 of the power transmission unit 3, driven side pedestal portions 29 and 29 are provided in a state of projecting rearward (upward) in parallel to each other. The head pedestal portion 28 constitutes a lower portion of the head housing 11 and is attached with a bearing 15 that rotatably supports the spindle 14. The front side of the connecting plate 27 is coupled to the left and right driven side pedestals 29 and 29 via a support shaft 30 so as to be tiltable up and down.

Each of the drive side pedestals 25 and 25 is provided with one lock pin 31 so that it can be inserted and removed left and right. In addition, a single lock pin 32 is also provided on each of the driven side pedestals 29 and 29 so as to be inserted and removed from the left and right. The lock pins 31 and 32 are protruded to the left and right sides, and knobs 31a and 32a are provided on the protruding head for the convenience of the user when inserting and removing. Two lock holes 27a and 27b, into which the drive-side lock pins 31 are inserted, are provided on the rear side of the connecting plates 27 and 27, respectively. In addition, two lock holes 27c and 27d into which the driven lock pins 31 are inserted are provided on the front side of the connecting plates 27 and 27, respectively.
Each of the lock pins 31 and 32 is biased by a coil spring in a direction (lock side) in which the tip end side is inserted into the lock holes 27a to 27d. If the left and right lock pins 31 and 31 on the drive side are pulled out to the unlock side, the left and right connecting plates 27 and 27 can be tilted up and down around the support shafts 26 and 26, whereby the power transmission unit 3 is moved to the tool body. 2, the rotation axis J14 of the spindle 14 can be changed with respect to the motor axis J10. By inserting the left and right lock pins 31, 31 on the drive side into either of the lock holes 27a, 27a and the lock holes 27b, 27b, the crossing angle θ of the spindle 14 with respect to the motor axis J10 can be changed at two positions. .
Further, if the left and right lock pins 32, 32 on the driven side are pulled out to the unlock side, the head pedestal 28 can be tilted up and down around the support shafts 30, 30 with respect to the left and right connecting plates 27, 27. Thus, the spindle 14 can be swung up and down with respect to the power transmission unit 3 and the tool main body 2, and therefore the rotation axis J14 of the spindle 14 can be changed up and down with respect to the motor axis J10. By inserting the left and right lock pins 32, 32 on the driven side into either of the lock holes 27c, 27d, the crossing angle θ of the spindle 14 with respect to the motor axis J10 can be changed at two positions.

FIG. 4 shows a state where the rotation axis J14 of the spindle 14 is locked at a position orthogonal to the motor axis J10 at approximately 90 °. On the other hand, FIG. 5 shows a state in which the rotation axis J14 of the spindle 14 is locked substantially coaxially with the motor axis J10.
In each of the left and right angle adjusting mechanisms 24, 24, by changing the lock holes 27a to 27d into which the drive-side and driven-side lock pins 31, 32 are inserted, four crossing angles θ with respect to the motor axis J10 of the spindle 14 are changed to four. The position can be changed arbitrarily. The user can change the swing angle of the spindle 14 (intersection angle θ with respect to the motor axis J10) by inserting / removing the lock pins 31, 31, 32, 32 according to the work content or work posture, etc. This makes it possible to perform an efficient grinding operation.
As shown in FIG. 5, a side grip 33 held by the user is attached to the left driven pedestal 29. Regardless of the swing angle (crossing angle θ) of the spindle 14, the side grip 33 is always disposed in the vicinity of the grindstone T, so that the user can perform the grinding work more easily.

According to the electric power tool 20 of the second embodiment configured as described above, rotational power is transmitted in a state where the rotational axis J14 of the spindle 14 intersects the motor axis J10 without using a conventional bevel gear. be able to. For this reason, as in the first embodiment, the projecting dimension L and the height dimension of the power transmission part 3 mainly from the front surface of the tool main body part 2 can be configured more compactly than conventional, whereby the power tool 20 Workability and handleability can be improved.
Further, according to the electric power tool 20 of the second embodiment, the power transmission unit 3 includes the three universal joints 21 to 23 and the left and right angle adjusting mechanisms 24 and 24, so that the spindle 14 can be moved with respect to the motor axis J10. Since the crossing angle θ can be changed up and down (can be swung), the workability and handling of the power tool 20 can be improved by changing the crossing angle θ to an arbitrary crossing angle θ according to the work mode. It can be further increased.

FIG. 6 shows a direct drive type die grinder 40 as an example of the electric tool. The die grinder 40 has a configuration in which an outer rotor type electric motor 42 is incorporated as a drive source in a tool main body portion 41 having a function as a grip portion to be gripped by a user.
The electric motor 42 includes a cylindrical stator 44 fixed to the main body housing 43 side of the tool main body 41 and a similarly cylindrical rotor 45 supported rotatably on the outer peripheral side of the stator 44. ing. An output shaft 46 is fixed to the front portion of the rotor 45. The output shaft 46 is inserted through the inner peripheral hole of the stator 44. The output shaft 46 is supported so as to be rotatable about its axis through bearings 47 and 48 in the axial direction. A cooling fan 49 is attached to the front portion of the output shaft 46. When the switch lever 50 provided on the side of the hand holding the tool body 41 is pulled, the electric motor 42 is activated.
The distal end side of the output shaft 46 of the electric motor 42 is directly connected to the spindle 51. The spindle 51 is rotatably supported coaxially with the output shaft 46 of the electric motor 42 via bearings 53 and 54 provided on the front case 52. The tip of the spindle 51 protrudes from the front end of the front case 52, and a grindstone 55 is attached to the protruding portion.

According to the direct drive type die grinder 40 configured as described above, since the outer rotor type electric motor 42 is incorporated as a drive source, it is possible to rotate at a low speed and output a high torque, such as a planetary gear train or the like. A sufficient grinding torque can be applied to the spindle 51 and thus the grindstone 55 at an appropriate rotational speed without using a speed reduction mechanism.
Since the rotational power of the electric motor 42 can be directly output to the spindle 51 without interposing a speed reduction mechanism, the die grinder 40 can be made particularly compact in the machine length direction (motor axial direction). Further, since it is not necessary to incorporate a speed reduction mechanism such as a planetary gear train near the front portion of the tool main body 41, the die grinder 40 can be made compact in the thickness direction (radial direction).
Furthermore, by using the outer rotor type electric motor 42 as a drive source, low-speed and high-torque can be output, so that the die grinder 40 that is difficult to fall off even under a large work load (grinding resistance) can be obtained. it can.

1 ... Electric tool (first embodiment)
2 ... Tool body 3 ... Power transmission part L ... Projection dimension 4 forward of power transmission part 3 ... Body housing 5 ... Switch 6 ... Bearing 10 ... Electric motor (outer rotor type motor)
J10 Motor axis (Rotation axis of electric motor 10)
DESCRIPTION OF SYMBOLS 11 ... Head housing 12 ... 1st universal joint 13 ... 2nd universal joint 14 ... Spindle 14a ... 4th connection part, 14b ... 4th connection axis J14 ... The rotational axis 15 of the spindle 14 ... Bearing (ball bearing)
16 ... Reception flange 17 ... Fixing nut T ... Grinding wheel 18 ... Grinding wheel cover θ ... Intersection angle 20 between the motor axis J10 and the rotation axis J14 of the spindle 14 ... Electric tool (second embodiment)
21 to 23 ... Universal joint (second embodiment)
24 ... Angle adjustment mechanism 25 ... Drive side pedestal portion 26 ... Support shaft 27 ... Connecting plate 28 ... Head base portion 29 ... Drive side pedestal portion 30 ... Support shafts 31, 32 ... Lock pins, 31a, 32a ... Knob portion 33 ... Side Grip 40 ... Die grinder (Direct drive type)
41 ... Tool body 42 ... Electric motor (outer rotor type)
43 ... Main body housing 44 ... Stator 45 ... Rotor (outer rotor)
46 ... Output shaft 51 ... Spindle

Claims (6)

An electric tool configured such that the rotational power of the electric motor is transmitted to the spindle via a universal joint in an electric tool in which a motor axis of an electric motor as a drive source intersects with a rotation axis of a spindle to which a tip tool is attached . The electric tool according to claim 1, wherein an outer rotor type electric motor is used as the electric motor. The electric tool according to claim 1 or 2, wherein a plurality of the universal joints are interposed. The electric tool according to any one of claims 1 to 3, wherein a crossing angle of the spindle with respect to the motor axis can be changed via the universal joint. 5. The electric power tool according to claim 1, wherein a head housing that accommodates the universal joint and rotatably supports the spindle via a bearing is provided in a tool main body including the electric motor. An electric tool provided at a front portion, wherein a projecting dimension of the head housing from the front portion of the tool body depends on the bearing. The electric power tool according to any one of claims 1 to 5, wherein the spindle is provided with a circular grindstone as a tip tool.

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