JP2013099842A - Speed reduction mechanism for power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the vibration and resultant noise of an intermediate shaft in a portable circular saw including a two-stage speed reduction mechanism using helical gears in order to solve a problem that, when the portable circular saw includes a speed reduction mechanism in which the output of an electric motor is reduced through two stages using the helical gears and outputted to a spindle, a thrust load is applied to the intermediate shaft by the engagement of the helical gears, thus causing the axial vibration of the intermediate shaft and the resultant noise.SOLUTION: The intermediate shaft 31 is so supported as to be axially moved. The torsional direction of two helical gears 34, 35 supported on the intermediate shaft 31 is aligned in the same direction, and only a forward thrust load is made to act on the intermediate shaft 31 and received by a damping member 40 disposed at the front to absorb the vibration.

Description

  The present invention relates to a reduction mechanism for reducing the output of an electric motor as a drive source and transmitting it to a spindle in an electric tool such as a portable circular saw.

For example, the following Patent Document 1 discloses a technique regarding a speed reduction mechanism in the portable circular saw described above. In this prior art, an intermediate shaft is interposed between an output shaft of an electric motor as a drive source and a spindle to which a saw blade is attached, and a helical gear as two intermediate gears is interposed on this intermediate shaft. Thus, in the configuration in which the output of the electric motor is decelerated in two stages, by setting the twist direction of the two intermediate gears to the same direction (right twist or left twist), one intermediate gear and the drive gear of the motor output shaft The thrust loads in two directions applied to the intermediate shaft are canceled by making the acting directions of the thrust loads generated by the meshing with the other intermediate gear and the output gear on the spindle side opposite to each other, Thereby, it is the structure which reduces the thrust load with respect to the bearing which carries out rotation support of the said intermediate shaft, and raises the durability.
Further, in Patent Document 1 below, in addition to the above-described configuration, by setting different twist angles for the two intermediate gears, the thrust load applied to the intermediate shaft is fixed in one direction. A technique is described in which the bearing is securely received by one of the bearings.

JP 2007-210063 A JP-A-11-333762 Japanese Utility Model Publication No. 55-74252

However, it is necessary to further improve the conventional reduction mechanism. As a phenomenon peculiar to circular saws in which a circular saw blade is cut into the cutting material, the teeth on the drive side where the teeth (chips) of the saw blade mesh with each other due to intermittent cutting resistance received from the cutting material. The helical gear and the driven helical gear vibrate within the range of backlash in the rotational direction (flapping), and this has a problem of causing noise (gear sound).
Conventionally, in a one-stage reduction mechanism in which the drive gear (helical gear) of the electric motor is directly meshed with the output gear (helical gear) of the spindle, the electric motor rotor can be slightly displaced in the axial direction. Technology in which the elastic body absorbs the vibration in the axial direction generated by the cutting resistance or the like by supporting the elastic body against one end of the rotor shaft (motor output shaft). Is disclosed in Patent Documents 1 and 2, for example.
An object of the present invention is to provide a technique for reducing vibration or noise peculiar to the case of cutting with a saw blade in a two-stage reduction mechanism using a helical gear.

Said subject is solved by each following invention.
A first aspect of the present invention is a reduction mechanism for decelerating the rotational output of the electric motor and transmitting it to a spindle with a tip tool attached thereto in an electric tool using an electric motor as a drive source, the output shaft of the electric motor and the spindle An intermediate shaft is provided between the motor and the output shaft of the electric motor and the intermediate shaft, and between the intermediate shaft and the spindle. The intermediate shaft is supported so as to be displaceable in the axial direction, and a buffer for absorbing a thrust load generated by the meshing of the helical gear at at least one end thereof. A speed reduction mechanism with a member interposed therebetween.
According to the first aspect of the invention, the rotational output of the electric motor is decelerated via the two-stage helical gear meshing and transmitted to the spindle. With the configuration that decelerates and outputs the rotational output of the electric motor in two stages, a helical gear with a small diameter can be used by the spindle as compared with the configuration that decelerates in one stage. The adjustment range of the cutting depth of the saw blade can be set large by setting the spindle core height small.
In such a two-stage reduction mechanism, the axial direction component of the cutting resistance is caused by the engagement of the drive gear of the electric motor with one of the intermediate gears on the intermediate shaft and the engagement of the other intermediate gear with the output gear of the spindle, respectively. As a thrust load, the intermediate shaft vibrates in the axial direction due to the thrust load. However, according to the first invention, the vibration is absorbed by the buffer member, and the conventional noise generation is suppressed.
A second invention is the speed reduction mechanism according to the first invention, wherein a buffer member for absorbing a thrust load is interposed on the rotor shaft of the electric motor in addition to the intermediate shaft.
According to the second invention, it is possible to absorb not only the vibration of the intermediate shaft but also the vibration of the motor shaft, thereby more reliably suppressing the vibration of the electric tool and the noise caused thereby. it can.
According to a third invention, in the first or second invention, the intermediate shaft is rotatably supported by the gear case via the bearing, and the intermediate shaft is moved to the shaft by the axial displacement of the bearing with respect to the gear case. A speed reduction mechanism that is supported so as to be displaceable in a direction and has a buffer member interposed between a bearing and a gear case.
According to the third aspect of the invention, it is possible to absorb the vibration due to the thrust load of the intermediate shaft and the bearing that rotatably supports the intermediate shaft, thereby suppressing noise and increasing the durability of the bearing.
According to a fourth aspect of the present invention, in any one of the first to third aspects, a buffer member is interposed between the bearing and the gear case that supports the distal end side that is the distal end tool side of the axial end portions of the intermediate shaft. This is a reduced speed mechanism.
According to the fourth aspect of the invention, vibration to the axial front end side (tip tool side) of the intermediate shaft can be absorbed by the buffer member, and vibration can be suppressed only by inserting the buffer member on one side.
According to a fifth invention, in any one of the first to fourth inventions, the intermediate shaft includes a second gear that meshes with the first gear of the output shaft of the electric motor and a third gear that meshes with the fourth gear of the spindle. Is a reduction mechanism in which the twisting directions of the second gear and the third gear are the same.
According to the fifth invention, the twisting directions of the second gear and the third gear supported by the intermediate shaft are the same. Therefore, the first gear, the second gear, the third gear and the fourth gear are included in the intermediate shaft. Since each thrust load due to the combination of gears acts in the direction of canceling out, the thrust load applied to the intermediate shaft can be reduced as a result. Also, in this case, the thrust load in both directions is not set to the same magnitude, but by setting either one to be superior (different magnitude), as a result, a thrust load in only one direction is added. Can be arranged only on the side of the intermediate shaft to which the thrust load is applied to effectively absorb the vibration.
In the fifth invention, the drive gear of the motor output shaft corresponds to the first gear, and the output gear of the spindle corresponds to the fourth gear. The second gear and the third gear are fixed coaxially on the intermediate shaft and rotate together.
According to a sixth invention, in the fifth invention, the torsion angle of the second gear is made larger than that of the third gear to generate an axial force toward the distal end relative to the intermediate shaft, and the axial force is generated at the distal end of the intermediate shaft. This is a speed reduction mechanism configured to absorb by a buffer member interposed on the side.
According to the sixth invention, by setting the torsion angle of the third gear larger than that of the second gear, it is possible to apply only the thrust load to the axial front end side (tip tool side) to the intermediate shaft. Therefore, by disposing the buffer member at the tip of the intermediate shaft, it is possible to effectively absorb the forward vibration generated in the intermediate shaft, and to effectively reduce the vibration as the reaction. it can.

It is a top view of the portable circular saw provided with the deceleration mechanism which concerns on embodiment of this invention. FIG. 2 is a sectional view taken along line (2)-(2) in FIG. 1 and is a longitudinal sectional view of a speed reduction mechanism. It is the figure which looked at schematic structure of the speed-reduction mechanism based on this embodiment from the arrow (3) direction in FIG.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the entire cutting machine 1 provided with a speed reduction mechanism according to the present embodiment. In this embodiment, a portable circular saw is illustrated as an example of a cutting machine. The cutting machine 1 has a configuration in which a cutting machine main body 20 is supported on a top surface side (front side in FIG. 1) of a flat plate-like base 10 placed on a cutting material so as to be tiltable up and down via a support shaft 13. Yes.
The cutting machine body 20 is provided with a blade case 22 that covers a range of the upper half of the upper side of the circular saw blade 21. The front end portion of the blade case 22 in the cutting direction is supported via the support shaft 13 so as to be tiltable up and down. A gear case 23 is attached to the rear side (the upper side in FIG. 1) of the blade case 22. A reduction mechanism 30 according to the present embodiment is incorporated in the gear case 23. A motor case 24 in which an electric motor 25 is housed is coupled to the gear case 23. The rotation output of the electric motor 25 is transmitted to the spindle 11 through the speed reduction mechanism 30 of the present embodiment described below. A saw blade 21 is attached to the tip of the spindle 11. The lower side of the saw blade 21 protrudes from the lower surface of the base 10, and the protruding portion is cut into the cutting material, and the cutting material is cut. When the cutting machine main body 20 is tilted up and down around the support shaft 13, the projecting dimension of the saw blade 21 from the lower surface of the base 10 changes, whereby the depth of cut with respect to the cutting material can be adjusted.

Details of the speed reduction mechanism 30 according to the present embodiment incorporated in the gear case 23 are shown in FIG. An output shaft 25 a of the electric motor 25 is rotatably supported by the gear case 23 via a bearing 26. The rotation axis of the output shaft 25a is denoted by reference numeral C1 in FIGS. A helical gear 27 is formed at the tip of the output shaft 25a. This helical gear 27 is a drive gear, and is also referred to as a first gear 27 hereinafter. The first gear 27 protrudes into the gear case 23.
An intermediate shaft 31 is supported in the gear case 23 via bearings 32 and 33 so as to be rotatable around the shaft. The rotation axis of the intermediate shaft 31 is indicated by reference numeral C2 in FIGS. As shown in FIG. 2, a ball bearing is used for the bearing 32 on the front end side (left side in FIG. 2), and a needle bearing is used for the bearing 33 on the rear end side (right side in FIG. 2). In this specification, the saw blade 21 side (tip tool side) in the axial direction is referred to as the tip side or the front side, and the opposite end side is referred to as the rear end side or the rear side.
Two helical gears 34 and 35 are attached to the intermediate shaft 31. Both helical gears 34 and 35 are fixed to the intermediate shaft 31 and rotate integrally with the intermediate shaft 31 (coaxial rotation axis C2). Of the two helical gears 34, 35 on the intermediate shaft 31, the helical gear 34 on the rear side is meshed with the first gear 27, and the helical gear fixed to the spindle 11 by the helical gear 35 on the front side. The gear 36 is engaged. Hereinafter, the helical gears 34, 35, and 36 are also referred to as a second gear 34, a third gear 35, and a fourth gear 36, respectively. The second gear 24 and the third gear 35 correspond to the helical gear (intermediate gear) supported on the intermediate shaft in the first invention. As described above, the rotational output of the electric motor 25 is transmitted to the spindle 11 after being decelerated in two stages through the meshing of the first gear 27 and the second gear 34 and the meshing of the third gear 35 and the fourth gear 36.
As described above, since the rotational output of the electric motor 25 is decelerated in two steps and transmitted to the spindle 11, the gear diameter of the fourth gear 36 can be set small, thereby ensuring a sufficient reduction ratio. However, the distance (the core height of the axis C3) of the spindle 11 with respect to the lower surface of the base 10 (the contact surface with the cutting material) can be reduced, and thus the adjustment range of the cutting depth of the saw blade 21 can be increased. it can.

Next, the intermediate shaft 31 that supports the second gear 34 and the third gear 35 is supported in a state in which movement is allowed with a slight stroke (about 1 mm) in the axial direction. In the case of the present embodiment, the front bearing 32 is supported so as to be movable in the axial direction in a holding hole 23 a provided in the gear case 23, and the intermediate shaft 31 is supported so as to be movable in the axial direction. A buffer member 40 is sandwiched between the bottom of the holding hole 23 a and the bearing 32. An annular rubber ring having a thickness of about 3 mm is used for the buffer member 40. The shock absorbing member 40 absorbs the thrust load applied to the bearing 32 and the intermediate shaft 31. In addition, the elastic coefficient (elastic performance) as a material of the buffer member 40 is also appropriate so that sufficient shock absorption capacity can be ensured (so as not to be crushed) with respect to the assumed thrust load (axial displacement). In addition, the durability of the buffer member 40 is ensured.
Since the rear side of the intermediate shaft 31 is received by a needle bearing (bearing 33), slight movement of the intermediate shaft 31 in the axial direction relative to the bearing 33 is allowed.
The spindle 11 is supported by the gear case 23 via bearings 37 and 38 so as to be rotatable about its axis. The axis of rotation of the spindle 11 is denoted by reference numeral C3 in FIGS. As shown in the drawing, in the present embodiment, a ball bearing is used for the front bearing 37 and a needle bearing is used for the rear bearing 38, as with the intermediate shaft 31. The tip of the spindle 11 protrudes from the gear case 23 into the blade case 22, and a saw blade 21 is attached to the protruding portion.
The front bearing 37 is accommodated in the holding hole 23b of the gear case 23 and is fixed by the fixing nut 28 so as not to move in the axial direction. The spindle 11 is supported through the bearings 37 so as not to move in the axial direction. On the spindle 11, a distance collar 39 is mounted between the fourth gear 36 and the front bearing 37. The fourth gear 36 is fixed between the flange portion 11a provided on the spindle 11 and the distance collar 39 so as not to move in the axial direction.

As described above, the speed reduction mechanism 30 according to this embodiment reduces the rotational output of the electric motor 25 in two stages through the meshing of the first gear 27 and the second gear 34 and the meshing of the third gear 35 and the fourth gear 36. Thus, a configuration for transmitting to the spindle 11 is provided. The first to fourth gears 27, 34, 35, and 36 are all helical gears.
The twist direction and the twist angle of the four helical gears 27, 34, 35, and 36 are set appropriately. In the present embodiment, the second gear 34 and the third gear 35 on the intermediate shaft 31 are set in the same twist direction. For this reason, the acting direction of the thrust load applied to the intermediate shaft 31 by the engagement of the first gear 27 and the second gear 34 and the thrust applied to the intermediate shaft 31 by the engagement of the third gear 35 and the fourth gear 36 The acting directions of the loads are opposite to each other. In the present embodiment, the former is set in the forward direction (leftward in FIG. 2), and the latter is set in the rearward direction (rightward in FIG. 2). For this reason, the former thrust load and the latter thrust load are offset.
Moreover, in the present embodiment, the twist angle of the second gear 34 on the driving side is set larger than the twist angle of the third gear 35 for the two intermediate gears. For this reason, the forward thrust load generated by the meshing of the first gear 27 and the second gear 34 is larger than the backward thrust load generated by the meshing of the third gear 35 and the fourth gear 36. As a result, the thrust loads in both directions are offset and the intermediate shaft 31 is set so that a forward thrust load acts on the intermediate shaft 31. The thrust load acting direction with respect to the intermediate shaft 31 is held forward because the rotation direction of the saw blade 21 (rotation direction of the electric motor 25) is constant. As described above, this forward thrust load with respect to the intermediate shaft 31 is added to the intermediate shaft 31 as an intermittent (intermittent) cutting resistance that each cutting edge of the saw blade 21 receives from the cutting material, and this is applied by the buffer member 40 described above. Absorbed.
Further, as a result of a forward thrust load acting on the intermediate shaft 31, a backward thrust load acts on the output shaft 25 a of the electric motor 25 through meshing of the first gear 27 and the second gear 34. The backward thrust load with respect to the motor output shaft (rotor shaft) is absorbed by a buffer member interposed on the rear side of the output shaft 25a as in the prior art, though not shown.

According to the speed reduction mechanism 30 of the present embodiment configured as described above, the cutting resistance that the saw blade 21 receives from the cutting material is intermittently applied to the intermediate shaft 31 in the mechanism that reduces the rotational output of the electric motor 25 in two stages. Even when applied as a thrust load (vibration), the vibration (thrust load) of the intermediate shaft 31 is received by the buffer member 40 and can absorb the vibration in the axial direction of the spindle 11. Noise can be reduced.
In this way, the cutting machine performs using the circular saw blade 21, and the vibration unique to the cutting machine that decelerates the output of the electric motor 25 in two stages by meshing the toothed gear and outputs it to the spindle 11. Alternatively, the noise generated due to this can be significantly reduced by the buffer member 40 as compared with the prior art, and the noise can be reduced.
In the case of the present embodiment, since the rotation direction of the saw blade 21 is always constant, the shock absorbing member 40 disposed only on the front side (tip tool 21 side) with a forward thrust load applied to the intermediate shaft 31. Therefore, the above-described effects can be obtained with a simpler configuration than the configuration in which similar buffer members are arranged not only on the front side but also on the rear side.

Various modifications can be made to the embodiment described above. For example, although the configuration in which the buffer member 40 is interposed only on the front side of the intermediate shaft 13 is illustrated, the buffer material may be interposed on the rear side in addition to the front side.
In addition, the configuration in which the twist directions of the two intermediate gears (the second and third gears 35 and 36) are made the same and the acting direction of the thrust load applied to the intermediate shaft 13 is set in the opposite directions, The twisting directions of both intermediate gears may be opposite to each other, and a forward thrust load may be applied to the intermediate shaft 13 so as to be received by the buffer member 40.
Furthermore, although the structure which receives the thrust load added to the intermediate shaft 31 via the bearing 32 is illustrated, the buffer member may be brought into direct contact with the front end portion of the intermediate shaft to absorb the thrust load (vibration). Good. Accordingly, a configuration using a needle bearing for the bearing 32 or a configuration using a ball bearing for the rear bearing 33 may be used.
In addition, although a rubber ring is exemplified as the buffer member, a configuration using a buffer member made of an industrial sponge may be used, or a configuration such as a spring such as a compression coil spring or a leaf spring, or an air damper may be used. .
Further, the buffer member on the motor shaft 25a side (the buffer member that receives the thrust load directed rearward of the motor shaft 25a) may be omitted.
Moreover, although the portable circular saw was illustrated as an electric tool, it is the same also about electric tools used for other operations, such as a drilling machine and a screw tightening machine, without being limited to other cutting machines or cutting machines such as a tabletop circular sawing machine. By adopting the configuration, it is possible to obtain an equivalent effect.

1 ... Portable circular saw (cutting machine)
DESCRIPTION OF SYMBOLS 10 ... Base 11 ... Spindle 13 ... Spindle 20 ... Cutting machine main body 21 ... Saw blade 22 ... Blade case 23 ... Gear case, 23a, 23b ... Holding hole 24 ... Motor case 25 ... Electric motor, 25a ... Output shaft (rotor shaft) )
26 ... Bearing 27 ... No. 1 gear (drive gear)
28 ... Fixing nut 30 ... Deceleration mechanism 31 ... Intermediate shafts 32, 33 ... Bearing 34 ... Second gear (intermediate gear)
35 ... No. 3 gear (intermediate gear)
36 ... 4th gear (output gear)
37, 38 ... Bearing 39 ... Distance collar 40 ... Buffer member (rubber ring)

Claims (6)

In an electric tool using an electric motor as a drive source, a reduction mechanism that decelerates the rotational output of the electric motor and transmits it to a spindle with a tip tool attached thereto,
An intermediate shaft is provided between the output shaft of the electric motor and the spindle, and a helical gear is provided between the output shaft of the electric motor and the intermediate shaft and between the intermediate shaft and the spindle. Comprising a configuration in which the rotational output of the electric motor is decelerated in two stages through meshing and transmitted to the spindle;
The intermediate shaft is supported so as to be displaceable in the axial direction thereof, and a speed reduction mechanism in which a buffer member for absorbing a thrust load generated by meshing of the helical gear is interposed at at least one end thereof. 2. The speed reduction mechanism according to claim 1, wherein a buffer member for absorbing the thrust load is interposed on the rotor shaft of the electric motor in addition to the intermediate shaft. The reduction mechanism according to claim 1 or 2, wherein the intermediate shaft is rotatably supported by a gear case via a bearing, and the intermediate shaft is displaced by the axial displacement of the bearing with respect to the gear case. A speed reduction mechanism that is supported so as to be displaceable in the axial direction, and wherein the buffer member is interposed between the bearing and the gear case. The speed reduction mechanism according to any one of claims 1 to 3, wherein a buffer is provided between the bearing and the gear case that supports the tip side that is the tip tool side of the axial end portions of the intermediate shaft. A speed reduction mechanism with a member interposed. 5. The speed reduction mechanism according to claim 1, wherein the intermediate shaft meshes with a second gear that meshes with a first gear of an output shaft of the electric motor, and a fourth gear of the spindle. A reduction mechanism in which a third gear is supported, and the twisting directions of the second gear and the third gear are the same. 6. The reduction mechanism according to claim 5, wherein a torsion angle of the second gear is made larger than that of the third gear to generate an axial force toward the tip side with respect to the intermediate shaft, and the axial force is A speed reduction mechanism configured to absorb by a buffer member interposed on the tip side of the intermediate shaft.

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