WO2010134431A1

WO2010134431A1 - Electric tool

Info

Publication number: WO2010134431A1
Application number: PCT/JP2010/057803
Authority: WO
Inventors: 友幸近藤; 貴勇畔柳
Original assignee: 株式会社マキタ
Priority date: 2009-05-18
Filing date: 2010-05-07
Publication date: 2010-11-25
Also published as: JP2010264578A

Abstract

In a conventional electric tool incorporating an automatic transmission which is automatically shifted according to the external torque acting on the spindle, resetting the transmission to an initial state requires a switch lever to be set to the off position, and this has been an inconvenience for users. The electric tool of the invention is configured in such a manner that the transmission is automatically reset as soon as the external torque on the spindle becomes low, and this makes the electric tool more convenient to use. An internal gear of a planetary gear mechanism which constitutes a transmission (H) is supported by a bi-directional one-way clutch, and a rotation-prevented state and a rotation-permitted state of the internal gear are switched between each other by a switching motor (50) which is operated on the basis of increase and decrease of a load on an electric motor (10).

Description

Electric tool

This invention relates to an electric tool that mainly outputs rotational power, such as an electric drill for drilling and an electric screw tightening machine for screw tightening.

In general, this type of electric tool has a configuration in which the rotational power of an electric motor as a drive source is decelerated by a transmission to output a necessary rotational torque. In many cases, a planetary gear mechanism is used in the transmission.
For example, in a screw tightening machine, a small torque is sufficient at the beginning of tightening, and gradually a large rotational torque is required as the tightening progresses. Therefore, at the beginning of tightening, it is possible to reduce the speed reduction ratio of the transmission to output high speed and low torque, and to increase the speed reduction ratio of the transmission and increase low speed and high torque in the middle of tightening. This is a function required from the viewpoint of performing. In addition, the reduction ratio is automatically switched when the tightening resistance (load torque) applied to the spindle (output shaft) via the screw tightening bit reaches a certain value during the tightening stage. Required.
Patent Document 1 below discloses a screw tightening machine in which a transmission having a two-stage planetary gear mechanism is interposed between an output shaft of an electric motor and a spindle equipped with a screw tightening bit. According to this transmission, at the beginning of screw tightening, the output-side second planetary internal gear is directly connected to the carrier of the first-stage planetary gear for rotation. As a result, the reduction ratio is reduced and high-speed and low-torque is output. And fast screw tightening. When the screw tightening progresses and the user increases the pressing force of the screw tightening machine, the internal gear of the second stage planetary is relatively displaced in the axial direction and separated from the carrier of the first stage planet for rotation and fixed. As a result, the deceleration on the second stage planet is effective and added to the deceleration on the first stage planet. As a result, the speed reduction ratio of the transmission increases, and the low speed and high torque is output and the screws are securely tightened.
According to another prior art, this low-speed high-torque output state is locked by holding the internal gear of the second stage planet in a position separated from the carrier of the first stage planet. In this case, the transmission is reset to the high speed and low torque output state (initial state) by releasing the locked state of the internal gear and returning to the initial position directly connected to the rotation of the carrier of the first stage planet by the reset mechanism. Is done.
Patent Document 2 listed below discloses a reset mechanism for returning a low-speed high-torque output state switched by automatic gear shifting to an initial high-speed low-torque output state. According to this conventional reset mechanism, the transmission device is returned to the initial state (high-speed low-torque output state) by using the switch lever return operation (off operation) performed to stop the operation of the main body. Therefore, the transmission can be reset to the initial state without requiring a special operation of the user of the screw tightening machine.

Japanese Patent No. 3289958 Japanese Patent No. 3084138 Japanese Patent No. 3931932 JP-A-9-72393

However, the conventional automatic transmission is configured to be reset from the low speed high torque output state to the high speed low torque output state (initial state) by a reset mechanism that is operated by turning off the switch lever. For this reason, for example, when a screw loosening operation is performed, a large output torque is required at the beginning, and thus the electric tool shifts to a low-speed high-torque output state immediately after startup, but the screw is loosened. Even if the load torque of the spindle is small, the low-speed and high-torque output state remains as long as the switch lever is not turned off, so that the loosening operation cannot be performed quickly.
Also in screw tightening work, after completing one screw tightening, it is necessary to reset the transmission device by temporarily turning off the switch lever when performing the next screw tightening. Could not do the work.
Furthermore, when performing drilling work at a plurality of locations on a plate material of a constant thickness, the drill penetrated the plate material in a low speed and high torque output state, and after the drilling operation at one location was completed, the switch lever was turned on. When the next drilling operation is continued, the drilling is started in the low-speed and high-torque output state from the beginning, so that the quick drilling operation cannot be performed.
As described above, in the conventional transmission, once it is switched to the low-speed high-torque output state, this is maintained regardless of the load torque. To reset to the initial state, the switch lever is turned off, etc. As a result, it is necessary to operate the mechanism, and as a result, there is a problem that usability is impaired for the above-described work.
In this regard,

Patent Documents

3 and 4 disclose a transmission mechanism including a two-stage planetary gear mechanism and a bidirectional one-way clutch for each. However, this conventional transmission is configured to shift the speed by manually switching the rotation restriction direction of the one-way clutch, and is configured to automatically shift according to an external torque applied to the spindle during screw tightening work or the like. However, it was necessary to improve the usability.
The present invention has been made to solve the problems of the conventional transmission, and as the load torque increases, the high-speed low-torque output state automatically switches to the low-speed high-torque output state. The purpose is to improve the usability in various usage forms of the electric tool by automatically returning to the high speed and low torque output state without using the reset mechanism when it is reduced or no load is entered. .

For this reason, this invention was set as the electric tool of the structure described in each claim of a claim.
According to the first aspect of the present invention, the external torque applied to the spindle is indirectly detected by the load of the electric motor, and based on this, the switching motor is activated and the one-way clutch of the first stage planetary gear mechanism is activated. By switching, the first stage planetary gear mechanism is switched between valid and invalid, and the transmission is automatically shifted from the initial high speed low torque output state to the low speed high torque output state or vice versa. For this reason, there is no need to reset the transmission by temporarily turning off the switch lever as in the prior art, and even if the switch lever is kept on, the initial state will be restored if the additional torque of the spindle decreases. Since it is automatically reset, for example, it is possible to quickly and efficiently perform an operation of continuously performing screw tightening or drilling.
According to the power tool of claim 2, for example, when screw tightening is performed and the electric motor is started in the forward rotation direction, the first stage and the second stage are interlocked with the switching operation of the forward / reverse switching lever. The planetary gear mechanism's internal gear rotation regulation direction is switched according to the rotation direction of the electric motor, and when the tightening of the electric motor increases the load of the electric motor, the switching motor is activated and the transmission is slowed down. The gear is shifted to a high torque output state. When the screw tightening is completed and the load of the electric motor is removed, the switching motor is activated to the reset side, and the transmission is reset to the high speed and low torque output state.
Thus, according to the electric tool of the second aspect, when the load of the electric motor increases due to the external torque of the spindle both when the electric motor is rotating forward and when the electric motor is rotating in reverse, the switching motor is decelerated on the deceleration side. When the transmission is automatically shifted to the low speed and high torque output state and the external torque of the spindle is reduced or removed, the load of the electric motor is reduced. And the transmission is automatically reset to the high speed low torque output state (initial state). From this, it is not necessary to operate the special reset mechanism by temporarily turning off the switch lever as in the prior art, and the transmission can be reset to the initial state while the electric motor is activated, In this respect, the power tool according to claim 2 can enhance the usability in various usage forms.
According to the third aspect of the invention, the rotation of the internal gear is restricted by the engagement member biting into the wedge-shaped gap between the clutch ring and the internal gear. In conjunction with the switching operation of the forward / reverse switching lever and by the operation of the switching motor, the clutch ring rotates to switch the direction in which the engaging member bites, thereby switching the rotation regulating direction of the internal gear and rotating free. Switch to state.
When the internal gear on the high-speed output side is rotationally locked and the internal gear on the low-speed output side is in a rotation-free state, the former planetary gear mechanism is activated and high-speed and low torque is output. Conversely, when the internal gear on the high-speed output side is in the rotation free state and the internal gear on the low-speed output side is rotationally locked, low-speed high torque is output.

It is the longitudinal cross-sectional view of the whole electric tool of this embodiment. In FIG. 1, it is an enlarged view of a main-body part. FIG. 3 is a cross-sectional view taken along the line (III)-(III) in FIG. This figure shows a state where the clockwise rotation of the first-stage internal gear during the forward rotation of the electric motor is restricted and a high-speed and low-torque output state of the transmission. FIG. 4 is a cross-sectional view taken along line (IV)-(IV) in FIG. 2, and is a view of a longitudinal section of the first stage one-way clutch as viewed from the front side. This figure shows a state in which the first stage clutch ring is switched to the initial position for restricting the clockwise rotation of the first stage internal gear during forward rotation of the electric motor. FIG. 3 is a sectional view taken along the line (V)-(V) in FIG. 2, and is a view of a longitudinal section of a second stage planetary gear mechanism on the output side and a second stage one-way clutch as viewed from the front side. This figure shows a state where the clockwise rotation of the second stage internal gear is restricted in accordance with the forward rotation of the electric motor. FIG. 3 is a cross-sectional view taken along line (VI)-(VI) in FIG. 2, and is a view of a longitudinal section of a second stage one-way clutch as viewed from the front side. This figure shows a state in which the second-stage clutch ring is switched to a position that restricts the clockwise rotation of the second-stage internal gear in accordance with the forward rotation of the electric motor. It is a figure which shows the operation condition of the transmission accompanying the change of an external torque. In this figure, (A) and (B) on the upper side show the operating status during forward rotation of the electric motor, and (C) and (D) on the lower side show the operating status during reverse rotation of the electric motor. ing. Further, (A) stage and (C) stage show a high speed and low torque output state, and (B) stage and (D) stage show a low speed and high torque output state. In this figure, the rotation direction of the common carrier 23 is shown in parentheses in order to clarify the planetary gear mechanism on the side that does not output torque because the internal gear rotates. It is a (VIII)-(VIII) arrow directional view in FIG. 1, Comprising: It is a top view of the mode switching operation part provided in the battery attachment part.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the entire power tool 1 according to the present embodiment. In this embodiment, a rechargeable electric driver drill is illustrated as an example of the electric tool 1. This electric tool 1 can be used as an electric screw tightener by attaching a driver bit as a tip tool, and can be used as an electric drill for drilling by attaching a drill bit.
The electric tool 1 includes a main body 2 and a handle 3. The main body portion 2 has a substantially cylindrical shape, and the handle portion 3 is provided in a state of projecting sideways from the middle in the longitudinal direction (axis direction, left-right direction in FIG. 1).
A trigger-type switch lever 4 is arranged on the front side of the base portion of the handle portion 3. When the user pulls the switch lever 4 with a fingertip (on operation), the main switch 4a is turned on. Based on the ON signal of the main switch 4a, the electric motor 10 built in the rear part of the main body 2 is started. A forward / reverse switching lever 7 is disposed above the switch lever 4. The forward / reverse switching lever 7 is disposed so as to penetrate the base portion of the handle portion 3 to the left and right. By pushing and moving the left end portion or the right end portion, the rotation direction of the electric motor 10 is forward or reverse. Can be switched to the side. The screw is tightened by rotating the electric motor 10 forward, and the screw is loosened by rotating the electric motor 10 in the reverse direction.
In addition, a battery mounting base portion 6 for mounting the battery pack 5 is provided at the tip of the handle portion 3. The electric motor 10 operates using the battery pack 5 as a power source.
The rotational power of the electric motor 10 is decelerated by the transmission H having three planetary gear mechanisms and output to the spindle 11. A chuck for mounting a tip tool such as a drill bit is attached to the tip of the spindle 11. In the drawing, the illustration of the tip tool and the chuck is omitted.
The three planetary gear mechanisms are interposed in a power transmission path from the electric motor 10 to the spindle 11. Hereinafter, from the drive side (electric motor 10 side) of the power transmission path, the first stage planet 20, the second stage planet 30, and the third stage planet 40 will be abbreviated. To distinguish. The details of the first to

third stage planets

20, 30, 40 are shown in FIG. In the present embodiment, the first stage planet 20 functions for high-speed output, and the second stage planet 30 functions for low-speed output.
The first to

third stage planets

20, 30, 40 are incorporated in a cylindrical gear housing 15 and a front housing 16 fixed to the main body 2, and are arranged coaxially with the output shaft 10 a of the electric motor 10. It is arranged coaxially with the spindle 11. Hereinafter, the rotation axis of the spindle 11 (the rotation axis of the output shaft 10a of the electric motor 10) is also referred to as the machine axis J. On this axis J, the electric motor 10, the first to

third stage planets

20, 30, 40 and the spindle 11 are coaxially arranged. The direction along the machine axis J is the machine axis direction of the electric power tool 1, and the machine axis J direction is the longitudinal direction of the main body 2.

The first stage sun gear 21 of the first stage planet 20 is attached to the output shaft 10 a of the electric motor 10. Three first stage planetary gears 22 to 22 are meshed with the first stage sun gear 21. Since the number of teeth of the three first-stage planetary gears 22 to 22 with respect to the first-stage sun gear 21 is set to increase in speed, the first-stage planetary 20 functions for high-speed output.
The three first stage planetary gears 22 to 22 are rotatably supported by the common carrier 23 via a support shaft 22a. The common carrier 23 functions as a common carrier for the first stage planet 20 and the second stage planet 30. The three first stage planetary gears 22 to 22 are meshed with the first stage internal gear 24. The first stage internal gear 24 is attached along the inner surface of the gear housing 15 via the first stage one-way clutch 25. The first stage internal gear 24 is switched between a state in which the right rotation or left rotation around the axis J is restricted by the first stage one-way clutch 25 and a state in which the rotation is permitted. As the first stage one-way clutch 25, a conventionally known bidirectional one-way clutch is used. Details of the first stage one-way clutch 25 will be described later.
The first stage sun gear 21 is provided with a smaller-diameter second stage sun gear 31 coaxially and integrally. Three second stage planetary gears 32 to 32 are meshed with the second stage sun gear 31. Since the number of teeth of the three second-stage planetary gears 32 to 32 with respect to the second-stage sun gear 31 is set in a deceleration relationship, the second-stage planetary 30 functions for low-speed output.
The three second stage planetary gears 32 to 32 are rotatably supported by the common carrier 23 via a support shaft 32a.
The three second stage planetary gears 32 to 32 are meshed with the second stage internal gear 34. The second-stage internal gear 34 is attached along the inner surface of the gear housing 15 via a second-stage one-way clutch 35. A conventionally known bidirectional one-way clutch is also used for the second stage one-way clutch 35. The second stage internal gear 34 is switched between right rotation and left rotation in accordance with the rotation direction of the electric motor 10 in the direction in which the rotation around the axis J is regulated by the second stage one-way clutch 35. Details of the second stage one-way clutch 35 will also be described later.
A third stage sun gear 41 of the third stage planet 40 is integrally provided at the center of the front surface of the common carrier 23. Three third stage planetary gears 42 to 42 are meshed with the third stage sun gear 41. The three third stage planetary gears 42 to 42 are rotatably supported by the third stage carrier 43. The three third stage planetary gears 42 to 42 are meshed with the third stage internal gear 44. The third internal gear 44 is attached along the inner surface of the front housing 16. The third internal gear 44 is fixed with respect to rotation around the machine axis J and movement in the machine axis J direction.
The spindle 11 is coaxially coupled to the center of the front surface of the third stage carrier 43. The spindle 11 is supported by the front housing 16 through

bearings

13 and 14 so as to be rotatable around the machine axis J. A chuck is attached to the tip of the spindle.

As described above, the rotation of the

internal gears

24 and 34 of the first stage planet 20 and the second stage planet 30 about the axis J is electrically driven by the bidirectional first stage one-way clutch 25 and second stage one-way clutch 35, respectively. The rotation regulation direction is switched in accordance with the normal rotation or reverse rotation of the motor 10. 3 and 5, the arrows attached to the gears of the first stage planet 20 and the second stage planet 30 indicate the rotation direction when the electric motor 10 rotates forward (counterclockwise). However, for the first and second stage

internal gears

24 and 34, the rotational directions to be regulated are shown. Due to the nature of the planetary gear mechanism, the rotation directions of the sun gears 21 and 31 and the common carrier 23 are the same and coincide with the rotation direction of the electric motor 10. Further, the rotation direction of the

planetary gears

24 and 34 coincides with the rotation direction of the

internal gears

24 and 34 or the addition direction of the rotation torque.
Details of the first stage one-way clutch 25 are shown in FIGS. The first stage one-way clutch 25 includes a clutch ring 26 and a plurality of engagement members (engagement pins) 27 to 27. The clutch ring 26 is supported on the inner peripheral side of the gear housing 15 in a state in which the clutch ring 26 can rotate around the machine axis J within a certain angular range on the outer peripheral side of the first stage internal gear 24. The clutch ring 26 is integrally provided with engagement convex portions 26a to 26a at the circumferentially divided position. On the inner peripheral side of the gear housing 15, partition wall portions 15 a to 15 a are provided in a state of protruding into the inner peripheral side at three circumferential positions. Each engaging convex part 26a has entered between the adjacent two

partition wall parts

15a, 15a. One engaging member 27 is arranged between each engaging convex portion 26a and the partition wall portion 15a. The radial widths of the three circumferential arc-shaped space portions 28 to 28 formed by the adjacent two

partition wall portions

15a and 15a of the gear housing 15 are narrowed by the flat surface 15b formed at the circumferential center portion thereof. It has become. When the engaging projection 26a is displaced with respect to the flat surface 15b, the engaging member 27 that bites into the narrow wedge-shaped gap is switched, and thereby the rotation of the first-stage internal gear 24 is restricted. The direction is switched. By engaging the clutch ring 26 with a certain angle in accordance with the rotation direction of the first-stage internal gear 24 that changes according to the forward rotation and reverse rotation of the electric motor 10, the engagement member 27 that bites into the wedge-shaped gap is engaged with the engagement convex portion 26a. The left and right can be switched.
As shown in FIG. 4, on the outer periphery of the clutch ring 26, operating recesses 26b are provided corresponding to the respective engaging projections 26a. One end side of the first stage switching lever 52 enters the upper operation recess 26b. The first stage switching lever 52 is supported by the gear housing 15 via a support shaft 53 so as to be tiltable left and right. The drive lever 51 is coupled to the other end side of the first stage switching lever 52 so as to be rotatable relative to each other. The drive lever 51 is attached to the output shaft 50 a of the switching motor 50. The switching motor 50 is attached to the upper part of the main body 2. The switching motor 50 is also driven by using the battery pack 5 as a power source.

The switching motor 50 is activated on the forward rotation side or activated on the reverse rotation side when the load of the electric motor 10 reaches a certain condition. The starting condition of the switching motor 50 is determined in advance based on various factors (load state) such as the voltage, current, and rotation speed of the electric motor 10 that are constantly detected. The switching motor 50 rotates forward at a predetermined angle or reverses at a predetermined angle based on the load state of the electric motor 10, whereby the drive lever 51 tilts left and right within a range of the fixed angle. As the drive lever 51 tilts to the left and right, the first stage switching lever 52 tilts in the opposite direction by substantially the same angle. As the first stage switching lever 52 tilts left and right, the first stage clutch ring 26 rotates about the machine axis J by a certain angle. When the first-stage clutch ring 26 rotates to the left and right by a certain angle, the respective engaging projections 26 a are forward or rearward with respect to the flat surface 15 b of the gear housing 15 in the rotational direction of the first-stage internal gear 24. The engagement member 27 that is displaced to the front (hereinafter simply referred to as the front side or the rear side) and thereby bites into the wedge-shaped gap is switched on the front side or the rear side of the engagement convex portion 26a. When the engaging member 27 that bites into the wedge-shaped gap is switched on the front side or the rear side of the engaging convex portion 26a, the rotation regulating direction of the first stage internal gear 24 is switched, and accordingly, the first stage internal gear is concerned. The state where the rotation of 24 is restricted and the state where the rotation is allowed are switched. With respect to the rotation direction of the first-stage internal gear 24, when the engagement convex portion 26a is displaced forward of the flat surface 15b, the biting direction of the engagement member 27 and the rotation direction of the first-stage internal gear 24 coincide. The rear engaging member 27 is bitten into the wedge-shaped gap, and the rotation of the first-stage internal gear 24 is restricted. With respect to the rotation direction of the first-stage internal gear 24, when the engagement convex portion 26a is displaced rearward from the flat surface 15b, the biting direction of the front-side engagement member 27 and the rotation direction of the first-stage internal gear 24 are changed. Since they do not coincide with each other, neither of the front and rear engaging

members

27, 27 is digged in, so that the first stage internal gear 24 is allowed to rotate.
A shift sensor 54 for detecting the shift state of the transmission H is attached to the other end side of the drive lever 51. The shift sensor 54 is a magnetic sensor. The shift sensor 54 detects the tilting direction of the drive lever 51. When the tilt direction of the drive lever 51 is detected by the magnetic sensor 54, the rotational position of the crunch ring 26 is detected, whereby the rotation regulation direction of the first stage internal gear 26 is distinguished or the rotation is regulated in both directions. It is detected that the rotation is not performed.

Next, FIG. 5 and FIG. 6 show details of the second stage one-way clutch 35. Similar to the first stage one-way clutch 25, the second stage one-way clutch 35 includes one second-stage clutch ring 36 and a plurality of engagement members (engagement pins) 37-37. The second-stage clutch ring 36 is supported on the inner peripheral side of the gear housing 15 so as to be rotatable about the machine axis J within a certain angular range on the outer peripheral side of the second-stage internal gear 34. The second-stage clutch ring 36 is also integrally provided with engaging convex portions 36a to 36a at the circumferentially equally divided position. Corresponding to the respective engaging projections 36a to 36a, partition wall portions 15d to 15d are provided on the inner peripheral side of the gear housing 15 in a state of being equally divided into three in the circumferential direction so as to protrude toward the inner peripheral side. Yes. Each engaging convex part 36a has entered between the adjacent two

partition wall parts

15d and 15d. One engaging member 37 is arranged between each engaging convex portion 36a and the partition wall portion 15d. The radial widths of the three circumferential arc-shaped space portions 28 to 28 formed by the adjacent two

partition wall portions

15d and 15d of the gear housing 15 are narrowed by the flat surface 15e formed at the circumferential center portion thereof. It has become. When the engaging projection 36a is displaced with respect to the flat surface 15e, the engaging member 37 that bites into the narrow wedge-shaped gap is switched. By engaging the clutch ring 36 with a certain angle in accordance with the rotation direction of the second-stage internal gear 34 that changes depending on the forward rotation and reverse rotation of the electric motor 10, the engagement member 37 that bites into the wedge-shaped gap is engaged with the engagement protrusion 36a. The left and right can be switched.

As shown in FIG. 6, on the outer periphery of the clutch ring 36, there are provided operating recesses 36b corresponding to the respective engaging projections 36a. One end of the second stage switching lever 55 enters the lower operation recess 36b. The second stage switching lever 55 is supported by the gear housing 15 via a support shaft 56 so as to be tiltable left and right. A forward / reverse switching lever 7 is disposed below the second stage switching lever 55. An engagement block body 8 is integrally provided at the center in the longitudinal direction of the forward / reverse switching lever 7. The engaging block body 8 is provided with an operating recess 8a that opens upward. The other end of the second stage switching lever 55 enters the operating recess 8a. For this reason, when the forward / reverse switching lever 7 is pushed in to the forward rotation side or the reverse rotation side, the second step switching lever 55 is tilted to the right and left around the support shaft 56 in conjunction with this operation. The ring 36 rotates around the machine axis J by a certain angle. When the second-stage clutch ring 36 rotates by a certain angle, the respective engaging projections 36a are displaced forward or rearward with respect to the flat surface 15e of the gear housing 15 and thereby engage into the wedge-shaped gap. The member 37 is switched to the front side or the rear side of the engagement convex portion 36a. The engagement member 37 that bites into the wedge-shaped gap is switched on the front side or the rear side of the engagement convex portion 36a, whereby the rotation restricting direction of the second stage internal gear 34 is switched, and accordingly, the second stage internal gear is concerned. The rotation of the motor 34 is switched to a state in which the electric motor 10 is restricted during both forward rotation and reverse rotation. When the electric motor 10 is switched to forward rotation or reverse rotation, the rotation restriction direction of the second stage one-way clutch 35 is automatically switched in accordance with this, and the second stage internal gear 34 is always maintained in the rotation restriction state. .
A forward / reverse sensor 9 for detecting the rotation direction of the electric motor 10 is attached to the engagement block body 8. A magnetic sensor is also used for the forward / reverse sensor 9. When the forward / reverse switching lever 7 is pushed into the forward rotation side or the reverse rotation side, the forward / reverse sensor 9 is turned on / off, whereby the rotational direction of the electric motor 10 is indirectly detected.

According to the transmission H configured as described above, when the external torque (load) applied to the spindle 11 increases above a certain value, the high speed / low torque output state (initial state) is automatically changed to the low speed / high torque output state. When the torque is switched and the external torque decreases thereafter, it is automatically reset to the initial state. FIG. 7 shows an operation state of the transmission H according to a change in the external torque when the electric motor 10 rotates forward and backward. Hereinafter, the operation state of the transmission H will be described with reference to FIG. In FIG. 7, the upper side shows the forward rotation of the electric motor 10, and the lower side shows the reverse rotation of the electric motor 10. A description will be given from the forward rotation of the electric motor 10.
When the forward / reverse switching lever 7 is switched to the forward rotation side (right side in FIG. 6) and the switch lever 4 is pulled, the electric motor 10 is activated to the forward rotation side (counterclockwise). Also, as shown in FIGS. 5 and 6, when the forward / reverse switching lever 7 is switched to the forward rotation side, the second stage switching lever 55 is tilted accordingly, and the clutch ring 36 of the second stage one-way clutch 35 is shown. As shown in FIG. 6, it rotates clockwise by a certain angle. For this reason, in FIG. 5, the engagement member 37 on the rear side of each engagement convex portion 36a in the internal torque application direction (addition direction of rotational torque applied to the

internal gears

24, 34, the same applies hereinafter) is wedge-shaped. By biting into the gap, the clockwise rotation of the second stage internal gear 34 is locked (restricted).
In addition, about the rotation direction of each gear, a clutch ring, etc., it shall say the direction seen from the spindle 11 side. Accordingly, in FIGS. 3 to 7, clockwise rotation is simply referred to as right rotation or clockwise rotation, and counterclockwise rotation is simply referred to as left rotation or counterclockwise rotation.

Since the external torque applied to the spindle 11 is low at the start of the electric motor 10, the load on the electric motor 10 is small. Therefore, the switching motor 50 includes the drive lever 51 and the first stage switching lever 52 in FIGS. 3 and 4. It is stopped in the initial state where it is located at the high speed position during forward rotation. The operation state of the transmission H at the beginning of the normal rotation is shown in FIG.
In the initial state of the switching motor 50 and in the state where the first stage switching lever 52 is positioned at the high speed position during normal rotation, the clutch ring 26 is held at the right rotation restricting position shown in FIG. In a state where the clutch ring 26 is positioned at the right rotation restriction position, as shown in FIG. 3, the engagement member 27 on the rear side in the internal rotation direction with respect to each engagement convex portion 26 a enters a wedge-shaped gap, As a result, the right rotation of the first stage internal gear 24 is locked. For this reason, in the first stage planet 20, the sun gear 21 rotates counterclockwise and each planetary gear 22 rotates clockwise at high speed, whereby the common carrier 23 rotates around the axis J at high speed counterclockwise. At this time, in the second stage planetary 30, the sun gear 31 rotates to the left integrally with the sun gear 21 and each planetary gear 32 rotates to the right at a low speed, but the supply carrier 23 rotates counterclockwise at a high speed. The two-stage internal gear 34 rotates counterclockwise. As a result, the reduction ratio of the first stage planet 20 in which the internal gear 24 does not rotate becomes effective and is input from the common carrier 23 to the third stage planet 40, whereby the spindle 11 rotates counterclockwise at high speed. As the spindle 11 rotates counterclockwise at high speed, screw tightening is performed quickly (stage (A): high-speed output state during normal rotation).

When the screw tightening progresses and the external torque applied to the spindle 11 increases and the load of the electric motor 10 satisfies a predetermined condition, the switching motor 50 is started based on this. When the switching motor 50 is activated, the drive lever 51 rotates from the position shown in FIG. 4 by a predetermined angle in the counterclockwise direction to move to an almost upright position. As a result, the first stage switching lever 52 is rotated during the forward rotation shown in FIG. From the high-speed position, it rotates by a certain angle around the support shaft 53 and moves to a low-speed position that is almost upright. The operating state of the transmission H at this time is shown in the (B) stage in FIG.
When the first stage switching lever 52 moves to the upright low speed position, the clutch ring 26 of the first stage one-way clutch 25 rotates counterclockwise from the position shown in FIG. When the clutch ring 26 rotates counterclockwise by a certain amount from the position shown in FIG. 4, each engagement protrusion 26a reaches a neutral position that coincides with the flat surface 15b with respect to the circumferential position. None of the engagement members 27 on the rear side will bite into the wedge-shaped gap, so that the first stage internal gear 24 is allowed to rotate clockwise and counterclockwise. In this internal free state, the sun gear 21 rotates counterclockwise and the planetary gear 22 rotates clockwise at a high speed but the internal gear 24 rotates clockwise as in the (A) stage. Rotational torque is not transmitted to 23. In this case, since the second-stage internal gear 34 is locked in the clockwise direction, the sun gear 31 of the second-stage planetary 30 rotates counterclockwise integrally with the sun gear 21, and each planetary gear 32 is at a low speed. , The common carrier 23 rotates counterclockwise at a low speed, and this is output to the spindle 11 via the third stage planet 40. In this way, the reduction ratio of the second stage planetary 30 becomes effective and the low speed and high torque is output to the spindle 11, so that the screw tightening is continued with a large torque (step (B): low speed during normal rotation). Output state).
When the screw tightening is completed and the screw tightening bit attached to the spindle 11 is removed from the screw, the spindle 11 becomes unloaded, so that the load of the electric motor 10 is removed. When the load of the electric motor 10 is reduced or removed, the switching motor 50 reverses and the drive lever 51 and the first stage switching lever 52 are returned to the high speed position during forward rotation shown in FIGS. Since the right rotation of the internal gear 24 is restricted, the first stage planetary 20 becomes effective, and therefore the transmission H is automatically reset to the initial state (high speed low torque output state) of the (A) stage. . For this reason, when another screw tightening operation is continued immediately after that, the screw tightening is quickly started in the initial state of the transmission H while the switch lever 4 is turned on without being turned off once as in the prior art. And can proceed.
Thus, during forward rotation of the electric motor 10, the position of the clutch ring 26 of the first one-way clutch 25 is switched to change the first stage internal 24 from the right rotation locked state to the rotation free state or vice versa. By switching, the first stage planet 20 for high speed and the second stage planet 30 for low speed are switched, whereby the output state of the spindle 11 is automatically changed between the high speed low torque output state and the low speed high torque output state. And it can be switched in both directions.

Next, when performing the work of loosening the screw that has already been tightened, the forward / reverse switching lever 7 is moved to the reverse side (pushing leftward in FIG. 6), and the electric motor 10 is rotated in the reverse direction. Switch. The operation state of the transmission H when the electric motor 10 is reversely rotated (clockwise) is shown in the (C) and (D) stages in FIG.
When the forward / reverse switching lever 7 is moved to the reverse side, the clutch ring 36 of the second stage one-way clutch 35 rotates counterclockwise from the position shown in FIG. Then, in FIG. 5, the engaging convex portion 36a is displaced to the front side in the internal torque addition direction with respect to the flat surface 15b, and the torque addition direction of the second-stage internal gear 34 to which the counterclockwise rotation torque is added at the time of reverse rotation. The engagement member 37 on the rear side bites into the wedge-shaped gap, and also in this case, the reverse rotation (left rotation) of the second internal gear 34 accompanying the reverse rotation of the electric motor 10 is locked.
Further, it is detected by the forward / reverse sensor 9 that the forward / reverse switching lever 7 has been switched to the reverse side, and based on this, the switching motor 50 is activated and the first stage switching lever 52 is at the high speed position during reverse rotation shown in FIG. Move to (initial position when reversing). When the first stage switching lever 52 moves to the high speed position during reverse rotation, the first stage clutch ring 26 rotates counterclockwise by a certain angle from the position shown in FIG. Displaces forward in the direction of internal torque application. For this reason, the engagement member 27 on the rear side in the internal torque addition direction is bitten into the wedge-shaped gap and the left rotation of the first stage internal gear 24 is locked, and the first stage planet for high speed is locked. As a result of 20 being effective, the transmission H is in the initial state of high speed and low torque output.
If the load on the spindle 11 is small at the start of reverse rotation, the common carrier 23 rotates clockwise at a high speed because the internal gear 24 of the first planetary 20 is locked counterclockwise as shown in stage (C). As a result, the first stage planet 20 becomes valid, and as a result, the internal gear 34 of the second stage planet 30 turns clockwise, the second stage planet 30 becomes invalid, and the spindle 11 rotates rightward at high speed (reverse rotation). High speed and low torque output state).

However, when the switch lever 4 is turned on with the screw tightening bit set on the screw to start the electric motor 10 in the reverse rotation direction, a larger torque is required from the start, so the load on the electric motor 10 is loosened. It becomes high from the beginning. Therefore, immediately after the electric motor 10 is activated, this is detected, the switching motor 50 is activated, and the first stage switching lever 52 is returned to the upright low-speed position. The operation status at this time is shown in the (D) stage.
When the first stage switching lever 52 moves to the low speed position, the first stage one-way clutch 25 switches to the neutral position, and the first stage internal gear 24 enters a rotation free state. For this reason, the sun gear 21 rotates clockwise, and each planetary gear 22 rotates counterclockwise at high speed, but the first stage internal gear 24 rotates counterclockwise and the reduction ratio of the first stage planet 20 is reached. Becomes invalid. In this case, in the low-speed second stage planetary 30 where the left rotation of the internal gear 34 is locked, the sun gear 31 rotates clockwise with the sun gear 21, and each planetary gear 32 rotates to the left at low speed. By rotating, the common carrier 23 rotates clockwise at a low speed, and this is effectively output to the spindle 11 via the third planetary 40 and the screw can be reliably loosened (low-speed high torque output state during reverse rotation).
When the screw loosening progresses and the load of the electric motor 10 decreases, this is detected and the switching motor 50 reverses. As a result, the first stage switching lever 52 rotates at a high speed during the reverse rotation shown in FIG. It moves to the position and is reset to the initial state where the left rotation of the first stage internal gear 24 is locked. For this reason, when the screw loosening progresses and the load on the electric motor 10 decreases, the transmission H automatically switches to the high speed low torque output state (initial position at the time of reverse rotation), and the subsequent screw loosening is performed quickly. .
As described above, even when the electric motor 10 rotates in the reverse direction, the position of the clutch ring 26 of the first one-way clutch 25 is switched according to the increase or decrease of the load of the spindle 11 to rotate the first-stage internal gear 24 from the left rotation locked state. By switching to the free state or vice versa, the first stage planet 20 for high speed and the second stage planet 30 for low speed are switched between valid and invalid, thereby changing the output state of the spindle 11 to the high speed low torque output state ( (C)) and a low-speed, high-torque output state ((D)) can be switched automatically and bidirectionally.

The electric power tool 1 of this embodiment has an output fixing function in addition to the automatic transmission function described above. In the present embodiment, the automatic transmission mode, the high speed fixed mode, and the low speed fixed mode can be switched. FIG. 8 shows a mode switching operation unit 60 for switching the modes. The mode switching operation unit 60 is provided on the upper surface of the battery attachment unit 6. The mode switching operation unit 60 includes a high-speed fixed button 61 that displays “Hi”, an automatic transmission button 62 that displays “Auto”, and a low-speed fixed button 63 that displays “Lo”. Has been placed.
When the high speed fixing button 61 is pressed, the high speed fixing mode is activated, and the transmission H is fixed in the high speed and low torque output state. For this reason, even if the external torque of the spindle 11 increases and the load of the electric motor 10 increases, the switching motor 50 does not operate, and the first stage switching lever 52 is fixed at the high speed position for forward rotation or the high speed position for reverse rotation. Thus, the transmission H is maintained in the high speed and low torque output state.
When the automatic speed change button 62 is pressed, the automatic speed change mode is activated, and the speed change device H automatically performs both forward rotation and reverse rotation of the electric motor 10 based on the external torque of the spindle 11 as described above. Thus, the speed is automatically changed from the high speed / low torque output state to the low speed / high torque output state or vice versa.
When the low speed fixing button 63 is pressed, the low speed fixing mode is activated, and the transmission H is fixed in the low speed high torque output state. In this low speed fixed mode, the switching motor 50 is locked in a state where the first stage switching lever 52 is positioned at the low speed position in the upright state. For this reason, irrespective of the external torque of the spindle 11, the electric tool 1 can be used while being fixed to the low-speed high-torque output state.
The output signal of the mode switching operation unit 60 is input to the control unit C. The control unit C incorporates a motor drive unit for controlling the start and stop of the electric motor 10 and the switching motor 50. Further, the control unit C receives the output signals of the forward / reverse sensor 9 and the shift sensor 54 and the ON signal of the main switch 4 a by the operation of the switch lever 4.

As described above, according to the transmission H of the present embodiment, the internal gear 24 of the first stage planet 20 is supported by the one-way clutch 25, and its rotation restricted state (high-speed low-torque output state) and rotation allowance. The state (low-speed high-torque output state) is automatically switched based on the magnitude of the external torque applied to the spindle 11, and the switch lever 4 can be turned on without turning the switch lever 4 off as in the prior art. Even if the on-operation state remains, the transmission H is automatically reset to the initial state when the external torque is removed or reduced. For this reason, continuous screw tightening work, screw loosening work or drilling work can be performed quickly and reliably, and in this respect, the convenience of the electric power tool 1 can be improved.
The embodiment described above can be implemented with various modifications. For example, the third planetary gear mechanism 40 can be omitted.
In addition, the forward / reverse switching type electric tool 1 has been exemplified in consideration of the screw loosening operation, but it can also be applied to a forward-only electric tool exclusively for screw tightening or drilling. In the case of forward rotation only, a mechanism for switching the rotation restricting direction of the second stage one-way clutch 35 can be omitted. Specifically, the second stage switching lever 55 and the engagement block body 8 are omitted, and the second stage clutch ring 36 is fixed at a fixed position (for example, the position shown in FIGS. 5 and 6). Can do. In such a configuration, only the operations (A) and (B) shown in FIG. 7 (or operations (C) and (D) only) are performed, and high-speed and low-speed automatic transmission is performed for one-way output. Made.
Furthermore, although the drilling and screw tightening combined machine was illustrated as an electric tool, it can also be applied to any one single-function machine.

Claims

An electric tool that incorporates an electric motor that is activated by turning on a switch lever, and a transmission that decelerates the rotational power of the electric motor and outputs it to the spindle,
The transmission includes a first-stage planetary gear mechanism for high-speed output and a second-stage planetary gear mechanism for low-speed output, and the internal gears of both planetary gear mechanisms are respectively set in a rotation restricted state via a one-way clutch. It is possible to switch between the high speed output state and the low speed output state by switching to the rotation free state and enabling one of the planetary gear mechanisms and disabling the other, and switching the internal gear to the load of the electric motor An electric tool configured to switch the position of the clutch ring of the one-way clutch by a switching motor that operates based on the above.
2. The electric tool according to claim 1, wherein the electric motor can be rotated forward or backward by a forward / reverse switching lever, and the one-way clutch can regulate rotation of the internal gear for both right rotation and left rotation. Is an interactive one-way clutch,
The rotation restriction direction of the one-way clutch on the first stage planetary gear mechanism side and the rotation restriction direction of the one-way clutch on the second stage planetary gear mechanism side are switched in conjunction with the forward / reverse switching lever, so An electric tool having a configuration in which the transmission can be shifted both during rotation and during reverse rotation.
3. The electric tool according to claim 2, wherein each of the one-way clutches includes a clutch ring that houses the internal gear on an inner peripheral side, and an engagement interposed between the clutch ring and the internal gear. A wedge-shaped gap formed between the member and the clutch ring and the internal gear, the width of which varies, and the engagement member is bitten into the gap to restrict the rotation of the internal gear, The internal gear is configured to release the biting state and allow the internal gear to rotate, and the rotational direction of the internal gear is switched by switching the biting direction of the engagement member by displacing the clutch ring in the rotational direction. A power tool with a configuration.