Power tool

Abstract

To extend the operating time of a battery-powered power tool. [Solution] The power tool 1 according to the embodiment is an power tool having a battery 30, a first motor 41 that rotates using the power of the battery as a power source, and a workpiece 20 that is rotationally driven by the first motor. The power tool according to the embodiment has a second motor 51 that has a rotating shaft that rotates in conjunction with the rotation of the rotating shaft of the first motor, generates electricity as the rotating shaft rotates, and charges the battery.

Description

[Technical field]

[0001] FIELD OF THE PRESENT EMBODIMENTS The present invention relates to a power tool. [Background technology]

[0002] There are power tools, such as electric drills, that run on batteries rather than on commercial power. Battery-powered power tools are convenient for use outdoors.

[0003] In order to extend the operating time of battery-operated power tools, it is necessary to increase the capacity of the battery. However, the larger the capacity of the battery, the heavier it becomes, which leads to a problem of poor usability. Increasing the operating time of power tools is a major challenge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-273598 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to extend the operating time of a battery-powered power tool. [Means for solving the problem]

[0006] The electric power tool according to the embodiment for solving the above problem includes a battery, a first motor that uses the electric power of the battery as a power source to rotate, and a workpiece that is rotationally driven by the first motor. The electric power tool according to the embodiment includes a second motor that has a rotating shaft that rotates in conjunction with the rotation of the rotating shaft of the first motor, generates electric power in response to the rotation of the rotating shaft, and charges the battery. [Brief description of the drawings]

[0007] [Figure 1] 1 is a block diagram of an electric power tool according to an embodiment. [Diagram 2] 1 is a perspective view of a drive unit of a power tool according to an embodiment; [Diagram 3] FIG. 2 is a perspective view of a return portion of the power tool according to the embodiment. [Figure 4] 2 is a block diagram of a control unit of the power tool according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an electric power tool according to an embodiment will be described with reference to the drawings. Electric power tools operated by a battery include drilling tools such as an electric drill, fastening tools such as an electric screwdriver, electric grinding tools, and cutting tools such as a chainsaw. Here, an electric power drill will be used as an example. FIG. 1 is a block diagram of an electric power tool (electric power drill) according to an embodiment. The electric power drill 1 has a battery 30, a drive unit 40, a workpiece 20, a feedback unit 50, a connection unit 60, a control unit 70, a voltage monitor 90, and a control unit 80.

[0009] The battery 30 is, for example, a lithium ion battery. The output voltage of the battery 30 is a voltage suitable for driving the first motor 41 constituting the drive unit 40, and is, for example, a DC voltage of 24V.

[0010] The driving unit 40 is composed of a first motor 41. FIG. 2 is a perspective view of the first motor 41 constituting the driving unit 40. The first motor 41 rotates using the power of the battery 30 as a power source, and rotates and drives the workpiece 20. In this example, the power tool is an electric drill, so the workpiece 20 is a drill. The first motor 41 has a rotating shaft 42 whose axial direction is the X-axis direction. A three-pole type rotor is fixed to the rotating shaft 42, and a winding is wound around the rotor. One end of the winding wound around the rotor is connected to a terminal 43a, and the other end is connected to a terminal 43b. A direct current voltage is supplied from the battery 30 to the terminals 43a and 43b. The first motor 41 has a stator (magnet) arranged to cover the rotor. The rotor rotates around the rotating shaft 42 in a magnetic field formed by the stator.

[0011] 1, the connection part 60 transmits the rotation of the rotary shaft 42 of the first motor 41 to the rotary shaft 52 of the second motor 51. The connection part 60 is formed of, for example, a gear or the like.

[0012] The feedback unit 50 is composed of a second motor 51. FIG. 3 is a perspective view of the second motor 51 constituting the feedback unit 50. The second motor 51 has a rotating shaft 52 whose axis is in the X-axis direction and rotates in conjunction with the rotation of the rotating shaft 42 of the first motor 41. A three-pole type rotor is fixed to the rotating shaft 52, and a winding is wound around the rotor. One end of the winding wound around the rotor is connected to a terminal 53a, and the other end is connected to a terminal 53b. The second motor 51 is equipped with a stator (magnet) arranged to cover the rotor. The rotor rotates in a magnetic field formed by the stator with the rotating shaft 52 as its axis. The second motor 51 generates an AC current in the winding wound around the rotor by the rotor rotating in the magnetic field formed by the stator. The terminals 53a and 53b are connected to the control unit 70.

[0013] The control unit 70 converts the output voltage of the feedback unit 50 into a voltage suitable for the input of the battery 30. When the output voltage of the feedback unit 50 is a voltage suitable for the input of the battery 30, the control unit 70 can be omitted. FIG. 4 is a configuration diagram of the control unit 70. The control unit 70 has a rectifier unit 71 and a current driver 72.

[0014] The rectifier 71 converts the AC power output by the second motor 51 into DC power. The rectifier 71 is composed of, for example, a capacitor, a diode, etc. The rectifier 71 supplies the rectified DC voltage to the current driver 72. The current driver 72 is composed of, for example, a DC / DC converter. The current driver 72 converts the input DC voltage into a voltage suitable for charging the battery 30. The current driver 72 may be a constant current source that supplies a current suitable for charging the battery 30. Note that when the output voltage of the rectifier 71 is a voltage suitable for charging the battery 30, the current driver 72 may be omitted.

[0015] The voltage monitor 90 measures the output voltage of the battery 30 and notifies the control unit 80 of the measured value.

[0016] The control unit 80 controls the rotation speed of the first motor 41 of the drive unit 40 based on the settings of the switches etc. The control unit 80 also controls the charging of the battery 30 by the control unit 70 based on the measurement value of the voltage monitor 90.

[0017] Next, the operation of the electric drill 1 will be described. The rotating shaft 42 of the first motor 41 constituting the drive unit 40 is rotated by receiving power from the battery 30. In detail, the rotating shaft 42 of the first motor 41 is rotated by a force that the current-carrying winding wound on the rotor constituting the first motor 41 receives from the magnetic field generated by the stator (permanent magnet) constituting the first motor 41, based on Fleming's rule.

[0018] The second motor 51 has a rotating shaft 52 that rotates in conjunction with the rotation of the rotating shaft 42 of the first motor 41, and generates power with the rotation of the rotating shaft 52. The rotating shaft 52 of the second motor 51 rotates at a rotation speed according to the ratio N of the number of teeth of the first gear of the connection part 60 to the rotation speed of the rotating shaft 42 of the first motor 41. A winding wound on a rotor fixed to the rotating shaft 52 rotates in a magnetic field formed by a stator (permanent magnet) constituting the second motor 51, and a current proportional to the rotation speed of the rotating shaft 52 is generated in the winding wound on the rotor of the second motor 51 based on Fleming's law. The second motor 51 charges the battery 30 via the control unit 70. The control unit 70 converts the output of the feedback part 50 into a current and voltage suitable for charging the battery 30, and charges the battery 30.

[0019] The control unit 80 judges whether the remaining capacity of the battery 30 is less than a threshold value. If the remaining capacity of the battery 30 is equal to or greater than the threshold value, the control unit 80 controls the control unit 70 to stop charging the battery 30. This threshold value is set so that the remaining capacity of the battery 30 becomes a predetermined remaining capacity (e.g., 90% or 95%) with respect to the fully charged state. This control makes it possible to prevent overcharging of the battery 30 and reduce accidents caused by damage to the battery 30.

[0020] On the other hand, when the remaining capacity of the battery 30 is less than the threshold value, the control unit 80 controls the control unit 70 to charge the battery 30.

[0021] As described above, the electric drill 1 (electric tool) according to the embodiment is provided with the feedback section 50, thereby effectively utilizing the thermal energy lost by the first motor 41. The energy supplied from the battery 30 to the first motor 41 of the drive section 40 is used to drive the workpiece 20. However, a part of the energy supplied to the first motor 41 is lost as thermal energy by the first motor 41. The electric drill 1 according to the embodiment returns a part of the rotational energy of the first motor 41 to the battery 30 via the second motor 51, thereby effectively utilizing the thermal energy lost by the first motor 41, thereby making it possible to extend the operating time of the electric drill 1 (electric tool) operated by the battery power. In other words, for example, when the continuous operating time is set to one hour, the battery 30 can be made smaller. Therefore, the electric drill 1 (electric tool) can be made smaller and lighter, making it easier to use.

[0022] (Variation 1) When the power tool is a fastening tool such as an electric screwdriver, the workpiece 20 is a screwdriver or wrench that is rotationally driven by the first motor 41 .

[0023] (Variation 2) When the power tool is an electric grinding tool, the workpiece 20 is a grinder (grinding tool) that is driven to rotate by a first motor 41 .

[0024] (Variation 3) Where the power tool is a cutting tool such as a chain saw, the work piece 20 is a saw blade operated by a chain which is driven in rotation by a first motor 41 .

[0025] (Variation 4) In the above description, the control unit 80 determines the charging state of the battery and controls charging of the battery. However, the control of charging of the battery 30 by the voltage monitor 90 and the control unit 80 may be omitted.

[0026] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the invention and its equivalents described in the scope of the utility model registration claims. [Explanation of symbols]

[0027] 1...Power tools 20...Working materials 30…Battery 40…Drive unit 41…First motor 42...rotation shaft of first motor 50…Return section 51...Second motor 52...rotation shaft of second motor 60…Connection 70…Control unit 80...Control unit 90…Voltage monitor

Claims

1. Battery and a first motor that rotates using the power of the battery as a power source; a workpiece rotated by the first motor; A power tool having An electric power tool having a second motor having a rotating shaft that rotates in conjunction with rotation of the rotating shaft of the first motor, generating electric power in conjunction with the rotation of the rotating shaft and charging the battery.

2. a voltage monitor for monitoring an output voltage of the battery; a control unit that controls charging of the battery based on a measurement result by the voltage monitor; The power tool of claim 1 .

3. The control unit controls the battery not to be charged when a measurement value by the voltage monitor indicates that the battery is fully charged. The power tool according to claim 2.

4. 3. The power tool according to claim 1, wherein when the power tool is a drilling tool, the workpiece is a drill that is rotationally driven by the first motor.

5. 3. The power tool according to claim 1, wherein when the power tool is an abrasive tool, the workpiece is a grinder that is rotationally driven by the first motor.

6. 3. The power tool according to claim 1, wherein when the power tool is a fastening tool, the working member is a screwdriver or a wrench that is rotationally driven by the first motor.

7. 3. A power tool according to claim 1 or 2, wherein when the power tool is a cutting tool, the work piece is a saw operated by a chain driven in rotation by the first motor.

Images