JP2022027892A - Electric tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric tool that can contribute to service-life elongation of a tip tool.

SOLUTION: An electric tool comprises a drilling function. The electric tool comprises: a trigger switch 40 that is retracted; a motor 21 that rotates an output shaft; a rotation rate changing part that is configured to set a limited rotation rate that is lower than a maximum rotation rate in a state where a limit is not put on a rotation rate, with respect to the maximum rotation rate which is a rotation rate of the output shaft corresponding to a maximum retraction amount of the trigger switch 40; and a control part 50 that when the limited rotation rate is set, controls the motor 21 in accordance with the retraction amount of the trigger switch 40 so that the maximum rotation rate is equal to the limited rotation rate. The control part 50 performs feed-back control so that the rotation rate of the output shaft at the time when the trigger switch 40 is retracted maximally is equal to a rotation rate selected by an operation part 41.

SELECTED DRAWING: Figure 5

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a power tool having a drill function.

Conventionally, a power tool having a drill function such as a drill driver is known (see, for example, Patent Document 1). Such a power tool can make a hole in an iron plate, a wooden plate, or the like by using a tip tool such as a drill or a hole saw.

In a power tool having a drill function, the rotation speed of the motor changes according to the pull-in amount (operation amount) of the trigger switch that can be operated by the user. Specifically, the more the trigger switch is pulled in, the higher the rotation speed of the motor. That is, the rotation speed of the tip tool that rotates by transmitting the driving force of the motor also increases as the trigger switch is pulled in.

Japanese Unexamined Patent Publication No. 2009-12153

By the way, in a power tool having a drill function, a hole saw or the like may be used to drill a hole in an iron plate or the like. In such a case, for example, if the trigger switch is pulled in more than necessary, the rotation speed of the tip tool will be higher than necessary, and if the drilling work is performed in that state, the tip tool will be excessively worn. There is a risk of doing so.

An object of the present invention is to provide a power tool that can contribute to extending the life of a tip tool.

In an example of the power tool according to the present invention, the power tool is a power tool having a drill function, and is a trigger switch to be pulled in, a motor for rotating an output shaft, and the output corresponding to the maximum pull-in amount of the trigger switch. The rotation speed changing unit configured to be able to set a lower limit rotation speed than the maximum rotation speed in the state where the rotation speed is not limited with respect to the maximum rotation speed which is the rotation speed of the shaft, and the limit rotation speed are set. If so, the motor is provided with a control unit that controls the motor according to the pull-in amount of the trigger switch so that the maximum rotation speed becomes the limit rotation speed.

According to the power tool of the present invention, it is possible to contribute to extending the life of the tip tool.

Perspective view of a power tool. The side view of the power tool which shows the state of the L gear of a reduction mechanism. The side view of the power tool which shows the state of the H gear of a reduction mechanism. The plan view explaining the operation part. A block diagram illustrating an electrical connection of a power tool. A graph showing the relationship between the pull-in amount of the trigger switch and the rotation speed of the output shaft.

Hereinafter, an embodiment of the power tool will be described with reference to the drawings.
As shown in FIG. 1, the power tool 10 of the present embodiment has a tool main body 11 and a battery pack 12 that can be attached to and detached from the tool main body 11. As an example, the battery pack 12 has a built-in secondary battery composed of a plurality of battery cells.

The tool body 11 of the power tool 10 is, for example, a drill driver having a drill function, and includes a substantially bottomed cylindrical body portion 14 and a grip portion 15 extending downward from the middle of the body portion 14 in the longitudinal direction. It has a main body case 13 composed of. In the present embodiment, the longitudinal direction of the body portion 14 is defined as the front-rear direction, the direction orthogonal to the front-rear direction in the substantially extending direction of the grip portion 15 is described as the vertical direction, and the direction orthogonal to the front-rear and vertical directions is described as the left-right direction. do.

As shown in FIG. 2, a motor 21 is housed in the body portion 14 of the main body case 13 at a position on the rear side, and a driving force transmission unit including a deceleration mechanism 22 and a clutch mechanism (not shown) is in front of the motor 21. 23 is housed. A tip tool such as a hole saw can be attached to and detached from the chuck 25 provided at the front end of the tool body 11. The output of the driving force transmission unit 23 is transmitted to the chuck 25.

The reduction mechanism 22 of the driving force transmission unit 23 is a three-stage planetary gear mechanism, and the gear mechanism of each stage is meshed with the sun gear, the planetary gear arranged and meshed around the sun gear, and the planetary gear. It is equipped with a ring gear.

The rotating shaft 21a of the motor 21 is provided with a sun gear 31 of a first-stage gear mechanism so as to be integrally rotatable. The ring gear 32 of the second-stage gear mechanism is held in the main body case 13 so as to be movable within a predetermined range in the axial direction (front-back direction). A shift changeover switch 33 is provided on the upper surface of the main body case 13 for the user to switch the reduction ratio of the reduction mechanism 22. The shift changeover switch 33 is, for example, a slide switch, which is a switch that switches between high-speed low-torque drive (H gear) and low-speed high-torque drive (L gear) by sliding its position in the front-rear direction. The shift changeover switch 33 is drive-connected via a groove formed on the outer peripheral surface of the second-stage ring gear 32 and a connecting member 34.

As shown in FIG. 2, when the ring gear 32 moves forward (on the output shaft 38 side) by the sliding operation of the shift changeover switch 33, the ring gear 32 engages with the engaging portion 35 provided in the main body case 13. It becomes impossible to rotate. That is, the second-stage gear mechanism functions as a deceleration mechanism, and the rotational driving force of the motor 21 is decelerated by all the gear mechanisms of the first to third stages and transmitted to the output shaft 38 side. As a result, the tool body 11 can be operated by a low-speed high-torque drive (L gear) in which the second-stage gear mechanism functions.

As shown in FIG. 3, when the ring gear 32 moves to the rear (motor 21 side), the engagement state between the ring gear 32 and the engaging portion 35 is released, the ring gear 32 becomes rotatable, and the first stage Is meshed with the transmission gear 36 of. That is, the entire second-stage gear mechanism including the second-stage ring gear 32 rotates integrally and does not function as a reduction mechanism itself, and the rotational driving force of the motor 21 is the first-stage and third-stage gears. It is decelerated only by the mechanism and transmitted to the output shaft 38 side. As a result, the tool body 11 can be operated with a high-speed low torque drive (H gear) in which the second-stage gear mechanism does not function.

As shown in FIGS. 2 and 3, the main body case 13 is provided with an operation position detection switch 37 that outputs an on / off signal according to the operation position of the shift changeover switch 33. The operation position detection switch 37 outputs, for example, an on signal when operated by the L gear to drive at low speed and high torque, and an off signal when operated by the H gear to drive at high speed and low torque.

As shown in FIG. 2, the third-stage gear mechanism of the reduction mechanism 22 is drive-connected to the output shaft 38. The output shaft 38 is rotatably supported by a bearing (not shown) provided in the main body case 13, and is configured to transmit a driving force to a tip tool (for example, a hole saw) inserted in the chuck 25. There is. The clutch mechanism is provided between the deceleration mechanism 22 (third-stage gear mechanism) and the output shaft 38, and the deceleration mechanism 22 and the deceleration mechanism 22 are provided according to the load torque input via the output shaft 38. The output shaft 38 is switched between connected and unconnected.

As shown in FIGS. 1 and 2, a rotation direction changeover switch 39 for switching the rotation direction of the motor 21 is provided in the vicinity of the connection portion of the body portion 14 with the grip portion 15. The rotation direction changeover switch 39 is configured to be able to switch between three states of, for example, forward rotation, reverse rotation, and stop of the motor 21. A trigger switch 40 projects forward from the grip portion 15 in a state of being urged by, for example, a spring.

As shown in FIG. 1, a battery pack mounting portion 16 projecting forward is formed at the lower end of the grip portion 15, and the battery pack 12 is mounted on the battery pack mounting portion 16.
The upper surface 16a of the battery pack mounting unit 16 has an operation unit 41 as a switching unit and a display unit 42.

As shown in FIG. 4, the operation unit 41 is for the user to select the maximum rotation speed of the output shaft 38 (tip tool) when the trigger switch 40 is fully retracted.
As shown in FIG. 4, the display unit 42 is for notifying the user of the maximum rotation speed of the output shaft 38 (tip tool) selected by the operation unit 41. The display unit 42 is composed of, for example, a plurality of LEDs (Light Emitting Diodes) 42a to 42c, and the LEDs 42a to 42c corresponding to the maximum rotation speed selected by the operation of the operation unit 41 are turned on.

As shown in FIG. 1, a control unit 50 (see FIG. 5) that includes a motor 21 and controls the power tool 10 in an integrated manner is housed in the battery pack mounting unit 16.
Next, the electrical connection of the power tool 10 will be described.

As shown in FIG. 5, power is supplied from the battery pack 12 (omitted in FIG. 5) to the control unit 50 that controls the output of the tool body 11. Further, signals from various switches of the shift changeover switch 33 (operation position detection switch 37), the rotation direction changeover switch 39, and the trigger switch 40 are input to the control unit 50.

As shown in FIG. 5, the control unit 50 can grasp whether the shift changeover switch 33 is switched to the H gear or the L gear based on the signal from the operation position detection switch 37. .. Further, the control unit 50 switches and stops the rotation direction of the motor 21 based on the selection of forward rotation, reverse rotation, and stop of the motor 21 by the rotation direction changeover switch 39.

The trigger switch 40 outputs a signal according to the pull-in amount, and the control unit 50 performs output control according to the pull-in amount.
More specifically, as shown in FIG. 6, the motor 21 (see FIG. 5) is controlled so that the rotation speed of the output shaft 38 increases as the trigger switch 40 is pulled in. Incidentally, in FIG. 6, the straight line L1 shows the state of the H gear (high speed low torque drive), and the straight line L2 shows the state of the L gear (low speed high torque drive). As can be seen from FIG. 6, the rotation speed of the straight line L1 is higher than the rotation speed of the straight line L2 at the time of the pull-in amount Tm at which the pull-in amount of the trigger switch 40 is maximum. Further, when the pull-in amount of the trigger switch 40 is the same in each of the straight line L1 and the straight line L2, the state of the H gear indicated by the straight line L1 is always higher than the state of the L gear shown by the straight line L2.

As shown in FIG. 5, an operation unit 41 and a display unit 42 are connected to the control unit 50. Then, a signal to change to the maximum rotation speed of the output shaft 38 selected by the operation unit 41 is input to the control unit 50.

In the present embodiment, regardless of whether the shift changeover switch 33 is in the H gear or the L gear, each time the operation unit 41 is operated, the operation unit 41 is operated in four stages of 300 rpm (rotation per minute), 200 rpm, 100 rpm, and no rotation speed limit. It is possible to switch in stages. When there is no rotation speed limit, as described above, the output shaft 38 has the same pull-in amount of the trigger switch 40 between the H gear shown by the straight line L1 and the L gear shown by the straight line L2 in FIG. The number of rotations is different.

Here, the control unit 50 also functions as a rotation speed changing unit that changes the rotation speed to the rotation speed selected by the operation unit 41.
Specifically, when 300 rpm is selected by the operation unit 41, the rotation speed of the output shaft 38 of the control unit 50 is about the same as that of the trigger switch 40 at the time of the maximum pull-in amount Tm, as shown by the straight line L3 in FIG. The motor 21 (see FIG. 5) is controlled so as to have a speed of 300 rpm. This is a lower rotation speed than the state where the rotation speed is not limited as shown by the straight line L1 and the straight line L2.

When 200 rpm is selected by the operation unit 41, the control unit 50 causes the rotation speed of the output shaft 38 to be about 200 rpm at the time of the maximum pull-in amount Tm of the trigger switch 40, as shown by the straight line L4 in FIG. Controls the motor 21 (see FIG. 5). This is a lower rotation than the state with no rotation speed limitation shown by the straight line L1 and the straight line L2, and further lower than the state shown by the straight line L3.

When 100 rpm is selected by the operation unit 41, the control unit 50 causes the rotation speed of the output shaft 38 to be about 100 rpm at the time of the maximum pull-in amount Tm of the trigger switch 40, as shown by the straight line L5 in FIG. Controls the motor 21 (see FIG. 5). This is a lower rotation speed than the state without rotation speed limitation shown by the straight line L1 and the straight line L2, and further lower than the state shown by the straight line L3 and the straight line L4.

As shown in FIG. 5, a detection signal corresponding to the drive current supplied from the current detection unit 60 as the load detection unit to the motor 21 is input to the control unit 50. The control unit 50 detects the load torque applied to the output shaft 38 based on the detection signal from the current detection unit 60. Based on the detected load torque, the control unit 50 performs feedback control so that the rotation speed of the output shaft 38 when the trigger switch 40 is pulled in to the maximum becomes the rotation speed selected by the operation unit 41.

Next, one operation example (action) of the power tool 10 of the present embodiment will be described.
In the power tool 10 of the present embodiment, the motor 21 is driven by the control unit 50 when the trigger switch 40 is pulled in. As a result, the output shaft 38 is rotated via the driving force transmission unit 23, and the tip tool that rotates integrally with the output shaft 38 is rotated, so that work such as drilling is possible.

At this time, the control unit 50 of the power tool 10 drives the motor 21 so that the operation unit 41 is operated by the user to limit the rotation speed of the output shaft 38 to any of 100 rpm, 200 rpm, and 300 rpm. It is designed to be controlled.

Next, the effect of this embodiment will be described.
(1) The rotation speed of the output shaft 38 when the trigger switch 40 is fully retracted is changed to a lower rotation speed than in the unrestricted state, and the rotation speed of the trigger switch 40 is adjusted to that rotation speed. It has a control unit 50 that controls the rotation speed of the motor 21 based on the above. By changing the rotation speed of the output shaft 38 when the trigger switch 40 is fully retracted in this way, for example, the rotation speed of the output shaft 38 can be set to a low rotation speed (low speed) such as 100 rpm, 200 rpm, or 300 rpm. Can be done. As a result, wear of the tip tool such as a hole saw mounted on the chuck 25 can be suppressed, and the life of the tip tool can be extended.

(2) It has an operation unit 41 that outputs a signal for stepwise switching the rotation speed of the output shaft 38 to the control unit 50 when the trigger switch 40 is pulled in to the maximum based on the operation by the user. As a result, the user can easily reduce the rotation speed of the output shaft 38 to a low rotation speed (low speed) by operating the operation unit 41.

(3) A battery pack mounting portion 16 as an extending portion extending forward is formed at the lower end of the grip portion 15 that can be gripped by the user. Then, by operating the operation unit 41 provided on the battery pack mounting unit 16, the rotation speed of the output shaft 38 can be easily set to a low rotation speed (low speed).

(4) The driving force transmission unit 23 is configured so that the reduction ratio can be mechanically switched in at least two stages. The control unit 50 changes the rotation speed of the output shaft 38 regardless of the reduction ratio (H gear / L gear) of the driving force transmission unit 23. Thereby, the rotation speed of the output shaft 38 can be maintained regardless of the two reduction ratios.

(5) The drive current of the motor 21 is detected by the current detection unit 60, and the load (load torque) acting on the output shaft 38 is detected (estimated) by the control unit 50 from the detected drive current. Then, the control unit 50 performs feedback control based on the detected load torque so that the rotation speed is selected by the operation unit 41. With such a configuration, the rotation speed selected by the operation unit 41 can be maintained as much as possible even when the load fluctuates.

The above embodiment may be modified as follows.
-In the above embodiment, the position of the operation unit 41 is set to the battery pack mounting unit 16, but the present invention is not limited to this.

-In the above embodiment, the battery pack 12 is adopted as a power source, but the present invention is not limited to this, and a commercial power source may be adopted as a power source.
-In the above embodiment, the shift changeover switch 33 enables two-step switching between high-speed low-torque drive (H gear) and low-speed high-torque drive (L gear), but the present invention is not limited to this. It may be configured to switch between three or more reduction ratios. Further, a configuration in which a plurality of reduction ratios cannot be selected may be adopted. Further, a configuration may be adopted in which the speed is automatically changed (the reduction ratio is switched) based on the fluctuation of the load torque acting on the output shaft 38.

-In the above embodiment, the load of the output shaft 38 is detected (estimated) from the drive current of the motor 21, but the configuration is not limited to this, and a configuration of directly detecting the load (load torque) of the output shaft 38 is adopted. You may.

-The above embodiment and each modification may be combined as appropriate.
Next, the technical idea that can be grasped from the above embodiment and another example will be added below.
(Appendix 1) A motor, a driving force transmission unit that decelerates the driving force of the motor and transmits it to the output shaft, a trigger switch that can be pulled in by the user, and a trigger switch when the trigger switch is pulled in to the maximum. The rotation speed change unit that can change the rotation speed of the output shaft to a lower rotation speed than the unrestricted state, and the rotation speed changed by the rotation speed change unit, based on the pull-in amount of the trigger switch. An electric tool characterized by being equipped with a control unit that controls the rotation speed of the motor.

(Appendix 2) In the power tool according to the appendix 1, a signal for stepwise switching the rotation speed of the output shaft when the trigger switch is fully pulled in based on the operation by the user is a rotation speed changing unit. A power tool characterized by having a switching unit that outputs to.

(Appendix 3) In the power tool according to the appendix 2, an extension portion extending forward is provided at the lower end of the grip portion that can be gripped by the user, and the switching portion is provided in the extension portion. A power tool featuring.

(Appendix 4) In the power tool according to any one of the items 1 to 3, the power transmission unit is configured to be mechanically capable of switching the reduction ratio to at least two stages or more, and the rotation thereof. The number changing unit is an electric tool characterized by changing the rotation speed of the output shaft regardless of any of the reduction ratios of the power transmission unit.

(Appendix 5) In the power tool according to any one of the appendices 1 to 4, the power tool has a load detecting unit for detecting a load acting on the output shaft, and the control unit is detected by the load detecting unit. A power tool characterized in that feedback control is performed so that the rotation speed is changed by the rotation speed changing unit based on a load.

10 ... Power tool, 15 ... Grip part, 16 ... Battery pack mounting part that constitutes the extension part, 21 ... Motor, 23 ... Driving force transmission part, 38 ... Output shaft, 40 ... Trigger switch, 41 ... Switching part Operation unit, 50 ... Control unit that constitutes the rotation speed change unit and load detection unit, 60 ... Current detection unit that constitutes the load detection unit.

Claims (2)

A power tool with a drill function
A trigger switch that is pulled in and
A motor that rotates the output shaft and
It is configured so that a limit rotation speed lower than the maximum rotation speed in a state where there is no rotation speed limit can be set for the maximum rotation speed which is the rotation speed of the output shaft corresponding to the maximum pull-in amount of the trigger switch. Rotation speed change part and
When the limit rotation speed is set, the motor is provided with a control unit that controls the motor according to the pull-in amount of the trigger switch so that the maximum rotation speed becomes the limit rotation speed.
The control unit is an electric tool that performs feedback control so that the rotation speed of the output shaft when the trigger switch is fully retracted becomes the rotation speed selected by the operation unit. Further equipped with a load detection unit for detecting a load acting on the output shaft,
The power tool according to claim 1, wherein the control unit performs the feedback control based on the load detected by the load detection unit.

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