JP6906165B2 - Electric tool - Google Patents

Description

The present invention relates generally to power tools, and more specifically to power tools with triggers.

Conventionally, an electric tool that changes the rotation speed of a motor according to a displacement amount of a trigger has been disclosed (see, for example, Patent Document 1). The power tool of Patent Document 1 includes a speed change switch. The speed change switch includes a trigger that the user pulls with a fingertip and a load sensor. The load sensor outputs a voltage signal proportional to the pulling operation amount (pressing pressure) of the trigger. The control circuit unit adjusts the power supplied to the DC motor based on the output signal of the load sensor by PWM control.

Japanese Unexamined Patent Publication No. 2012-101326

The output of the load sensor (pressure sensitive unit) continuously changes with a change in the pulling operation amount (pulling amount) of the trigger. Therefore, for example, when working with an electric tool, if the pull-in amount of the trigger changes due to vibration accompanying the work, the rotation speed of the motor may become unstable.

The present invention has been made in view of the above reasons, and an object of the present invention is to provide an electric tool capable of stabilizing the rotation speed of a motor.

The power tool according to one aspect of the present invention includes a motor, a trigger, a pressure sensitive unit, and a control circuit. The motor rotates the tip tool by supplying electric power from a power source. The trigger is movably held by the tool body. The pressure-sensitive unit has a pressure-receiving unit that receives pressure according to the amount of pulling in the trigger, and detects the magnitude of the pressure received by the pressure-sensitive unit. The control circuit controls the rotation speed of the motor based on the detected pressure detected by the pressure sensitive unit. The control circuit determines whether the detected pressure is increasing or decreasing due to a change in time, and when the detected pressure changes from an increase to a decrease and a decrease to an increase, the rotation of the motor The rotation speed of the motor is controlled so as to maintain the speed.

The electric tool of the present invention has an effect that the rotation speed of the motor can be stabilized.

FIG. 1 is a block diagram of a power tool according to an embodiment of the present invention. FIG. 2 is an external perspective view of the same power tool. FIG. 3A is a schematic configuration diagram showing a state of the main switch and the pressure sensitive portion when the trigger in the power tool of the same is in the off position. FIG. 3B is a schematic configuration diagram showing a state of the main switch and the pressure sensitive portion when the trigger in the power tool of the same is in the on position. FIG. 4 is a graph showing the characteristics of the rotation speed of the motor with respect to the detected pressure in the same power tool.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely one of the various embodiments of the present invention. The following embodiments can be variously modified according to the design and the like as long as the object of the present invention can be achieved.

(Embodiment)
A block diagram of the power tool 1 of the present embodiment is shown in FIG. 1, and an external perspective view is shown in FIG. The power tool 1 of the present embodiment is, for example, an electric wrench used for tightening tightening parts such as bolts and nuts.

As shown in FIG. 2, the tool body 2 of the power tool 1 is detachably mounted with a tubular body portion 21, a grip 22 protruding radially from the peripheral surface of the body portion 21, and a battery pack 24. It has a mounting portion 23 and.

The motor 4 is housed in the body portion 21. The motor 4 is, for example, a DC motor, and is configured to rotate by supplying electric power from the battery 241 (power source) of the battery pack 24. The motor 4 is electrically connected to the battery 241 via a forward / reverse switching circuit 40, a main switch 6, and a drive switch 51 (see FIG. 1).

The forward / reverse switching circuit 40 has a bridge circuit composed of a plurality of switches, and a motor 4 is electrically connected between the output ends. The forward / reverse switching circuit 40 switches the rotation direction of the motor 4 between forward rotation and reverse rotation by switching the direction of the direct current supplied from the battery 241 to the motor 4. In the forward / reverse switching circuit 40, the positive electrode side input terminal T1 is electrically connected to the positive electrode terminal of the battery 241 via the main switch 6, and the negative electrode side input terminal T2 is electrically connected to the negative electrode terminal of the battery 241 via the drive switch 51. Is connected. Further, a regenerative diode 41 is electrically connected between the positive electrode side input terminal T1 and the negative electrode side input terminal T2 of the forward / reverse switching circuit 40. In the regenerative diode 41, the anode is electrically connected to the negative electrode side input terminal T2, and the cathode is electrically connected to the positive electrode side input terminal T1.

The drive switch 51 is composed of, for example, an n-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor). In the drive switch 51, the drain terminal is electrically connected to the negative electrode side input terminal T2 of the forward / reverse switching circuit 40, and the source terminal is electrically connected to the negative electrode terminal of the battery 241. The drive switch 51 is controlled by the control circuit 5.

The control circuit 5 is composed of, for example, a microcomputer (microcomputer), and outputs a control signal for controlling the drive switch 51. The control signal is output to the gate terminal of the drive switch 51 directly or via the drive circuit, and the drive switch 51 is turned on / off. The control circuit 5 controls the rotation speed of the motor 4 by controlling the drive switch 51 based on the detection result of the pressure-sensitive unit 7, which will be described later. Specifically, the control circuit 5 controls the rotation speed of the motor 4 by controlling the drive switch 51 by, for example, a PWM (Pulse Width Modulation) method in which the duty ratio can be adjusted.

Further, the control circuit 5 controls the forward / reverse changeover circuit 40 based on the state of the forward / reverse changeover switch 222 provided on the grip 22 of the tool body 2. The control circuit 5 controls the forward / reverse switching circuit 40 so that the rotation direction of the motor 4 becomes the rotation direction set by the forward / reverse changeover switch 222.

Further, the control circuit 5 operates by the control power supplied from the power supply circuit 50. The power supply circuit 50 is electrically connected to the battery 241 via the main switch 6. The power supply circuit 50 converts the DC power supplied from the battery 241 into DC to generate control power, and supplies the control power to the control circuit 5.

As shown in FIG. 2, the output shaft 211 projects from one end side of the body portion 21 in the axial direction. The output shaft 211 is configured to rotate in conjunction with the rotational operation of the motor 4. A cylindrical socket 212 (tip tool) for tightening or loosening the tightening component is detachably attached to the output shaft 211. That is, the motor 4 is configured to rotate the socket 212 by supplying electric power from the battery 241. The size of the socket 212 attached to the output shaft 211 is appropriately selected by the operator according to the size of the tightening component. The power tool 1 can perform operations such as tightening or loosening the tightening parts by rotating the socket 212 by the rotational operation of the motor 4.

The grip 22 of the tool body 2 is a portion to be gripped by an operator when performing work, and a trigger 3 is provided. The trigger 3 is an operation unit for turning on / off the rotational operation of the motor 4 and adjusting the rotational speed of the motor 4, and is configured to be able to move forward and backward into the grip 22. The trigger 3 can move between an off position (see FIG. 3A) where the pull-in amount protrudes from the grip 22 and is zero, and an on position (see FIG. 3B) where the pull-in amount is pulled into the grip 22 and is the upper limit. It is held by the tool body 2 as described above. A force is applied to the trigger 3 by a spring in a direction protruding from the grip 22.

A switch box 221 is provided inside the grip 22. The main switch 6 and the pressure sensitive unit 7 are housed in the switch box 221.

The main switch 6 is a switch for turning on / off the power supply from the battery 241 to the motor 4 and the power supply circuit 50, and has a fixed contact 61 and a movable contact 62.

The fixed contact 61 is provided on the fixed contact plate 610. The fixed contact plate 610 is held in the switch box 221. The fixed contact plate 610 is electrically connected to the positive electrode terminal of the motor 4 via a conductive wire.

The movable contact 62 is provided on the movable contact plate 620. The movable contact plate 620 is held in the switch box 221 so that the other end can be moved with one end as a fulcrum, and the movable contact 62 is provided on the other end so as to face the fixed contact 61. The movable contact plate 620 is electrically connected to the positive electrode terminal of the battery 241 via a conductive wire. In the movable contact plate 620, a force is applied by a spring in a direction in which the movable contact 62 is separated from the fixed contact 61.

The movable contact plate 620 is configured to be moved by a rod-shaped plunger 31 connected to the trigger 3. Specifically, the plunger 31 is provided so as to penetrate the hole formed in the switch box 221 and one end thereof is mechanically connected to the trigger 3. In FIGS. 3A and 3B, the trigger 3 moves to the left when pulled. Therefore, the amount of the plunger 31 inserted into the switch box 221 increases when the trigger 3 is pulled. A protrusion 32 is provided so as to project from the peripheral surface of the plunger 31. When the trigger 3 is pulled and the amount of the plunger 31 inserted into the switch box 221 is increased, the protrusion 32 moves the end of the movable contact plate 620 toward the fixed contact plate 610 against the force of the spring. Move to push. That is, the movable contact plate 620 moves toward the fixed contact plate 610 by being pushed by the protrusion 32 of the plunger 31 when the trigger 3 is pulled.

As shown in FIG. 3A, when the trigger 3 is in the off position, the protruding portion 32 is located near the fulcrum of the movable contact plate 620, so that the movable contact 62 is separated from the fixed contact 61. That is, when the trigger 3 is in the off position, the main switch 6 is turned off, and the power supply from the battery 241 to the motor 4 and the power supply circuit 50 is cut off. Further, as shown in FIG. 3B, when the trigger 3 is in the on position, the protrusion 32 moves the end portion of the movable contact plate 620 toward the fixed contact plate 610, and the movable contact 62 and the fixed contact 61 come into contact with each other. do. That is, when the trigger 3 is in the on position, the main switch 6 is turned on, and power is supplied from the battery 241 to the motor 4 and the power supply circuit 50.

The pressure sensitive unit 7 is a switch for adjusting the rotation speed of the motor 4, and has a pressure receiving unit 71 and a support 72 that supports the pressure receiving unit 71. The pressure-sensitive unit 7 is provided on the substrate 70 held by the switch box 221 and is configured to detect the magnitude of the pressure received by the pressure-sensitive unit 71. In the present embodiment, the pressure-sensitive unit 7 is, for example, an electrostatic pressure-sensitive sensor whose capacitance changes according to the magnitude of the pressure received by the pressure-sensitive unit 71. The pressure receiving portion 71 is configured to be deformed by receiving pressure, and the amount of deformation increases as the received pressure increases. The pressure sensitive portion 7 is configured so that the magnitude of the capacitance changes according to the amount of deformation of the pressure receiving portion 71, and the magnitude of the capacitance is the magnitude of the pressure received by the pressure receiving portion 71. Corresponds to the detection result (detection pressure). The pressure sensitive unit 7 converts the magnitude of the capacitance (the magnitude of the pressure received by the pressure receiving unit 71) into an electric signal and outputs the detection result (detected pressure) to the control circuit 5. Output to. The pressure-sensitive unit 7 is not limited to the electrostatic pressure-sensitive sensor, and may be, for example, a resistance-type pressure-sensitive sensor whose resistance value changes according to the magnitude of the pressure received.

The pressure sensitive portion 7 is arranged so as to face the movable pressure plate 8 housed in the switch box 221. The movable pressure plate 8 is provided with a pressure portion 81 so as to project from the surface on the pressure sensitive portion 7 side. The pressurizing portion 81 is made of, for example, hard rubber or the like, and is arranged so as to face the pressure receiving portion 71.

The movable pressure plate 8 is held in the switch box 221 so that the other end side can be moved with one end side as a fulcrum. In the movable pressure plate 8, a force is applied by a spring in a direction in which the pressure portion 81 is separated from the pressure receiving portion 71. The movable pressure plate 8 is configured to move toward the pressure sensitive portion 7 by being pushed by the plunger 31. Specifically, the movable pressure plate 8 has a trapezoidal cross section, and the thickness on the other end side is larger than the thickness on the one end side. In other words, in the movable pressure plate 8, the second surface 802 opposite to the first surface 801 is inclined with respect to the first surface 801 provided with the pressurizing portion 81. In the movable pressure plate 8, when the trigger 3 is pulled and the amount of insertion of the plunger 31 into the switch box 221 increases, the tip end portion of the plunger 31 comes into contact with the second surface 802. That is, the tip end portion of the plunger 31 comes into contact with the slope (second surface 802) of the movable pressure plate 8. Therefore, when the insertion amount of the plunger 31 is further increased, the tip portion of the plunger 31 pushes the movable pressure plate 8 while moving along the second surface 802, so that the movable pressure plate 8 moves toward the pressure sensitive portion 7. do. As a result, the pressure receiving portion 81 comes into contact with the pressure receiving portion 71 and applies pressure, so that the pressure receiving portion 71 is deformed. Since the second surface 802 of the movable pressure plate 8 is inclined with respect to the first surface 801, the pressure applied by the pressurizing portion 81 to the pressure receiving portion 71 increases as the insertion amount of the plunger 31 increases. That is, when the trigger 3 is pulled, the movable pressurizing plate 8 is pushed by the tip of the plunger 31 and moves toward the pressure sensitive portion 7, and as the pulling amount of the trigger 3 increases, the pressurizing portion 81 moves to the pressure receiving portion 71. The pressure applied to is increased. The tip of the plunger 31 may be an inclined surface, and the pressure applied to the pressure receiving portion 71 by the pressurizing portion 81 may increase as the insertion amount of the plunger 31 increases.

Here, when the trigger 3 is pulled in from the off position and the pull-in amount reaches the first pull-in amount, the movable contact 62 contacts the fixed contact 61 and the main switch 6 is turned on. When the pull-in amount of the trigger 3 becomes the second pull-in amount larger than the first pull-in amount, the pressurizing portion 81 of the movable pressure plate 8 comes into contact with the pressure receiving portion 71 of the pressure-sensitive portion 7. Then, as the pull-in amount of the trigger 3 becomes larger than the second pull-in amount, the pressure applied by the pressurizing section 81 to the pressure receiving section 71 becomes stronger. That is, when the trigger 3 is pulled in from the off position, the main switch 6 is first turned on, and then pressure is applied to the pressure sensitive unit 7.

As shown in FIG. 2, the mounting portion 23 of the tool body 2 is formed in a flat rectangular shape, and the battery pack 24 is detachably mounted on one surface opposite to the grip 22. The battery pack 24 has a resin case 240 (see FIG. 2) formed in a rectangular shape, and a battery 241 (for example, a lithium ion battery) is housed inside the case 240.

The control circuit 5 is housed in the mounting portion 23. Further, the mounting portion 23 is provided with an operation panel 231. The operation panel 231 is provided with, for example, a plurality of pushbutton switches 232 and a plurality of LEDs 233 (Light Emitting Diodes), and can perform various settings, status confirmation, and the like of the power tool 1. The operator can check the remaining capacity of the battery 241 by operating the operation panel 231 (push button switch 232), for example. Further, the mounting portion 23 is provided with a light emitting portion 234. The light emitting unit 234 is composed of, for example, an LED. The light emitting unit 234 is arranged so as to irradiate light toward the work portion during work. The light emitting unit 234 is configured to light up when the main switch 6 is turned on.

Next, the control of the rotation speed of the motor 4 by the control circuit 5 will be described with reference to FIG. The control circuit 5 controls the drive switch 51 so that the rotation speed of the motor 4 increases as the detected pressure (pressure received by the pressure receiving unit 71) detected by the pressure sensitive unit 7 increases.

Specifically, the control circuit 5 samples the detected pressure at a predetermined cycle, and determines whether the detected pressure is increasing or decreasing due to a change in time. That is, the control circuit 5 determines whether the trigger 3 is pulled toward the on position or returned toward the off position.

The control circuit 5 Hysteresis controls the rotation speed of the motor 4 so that the rotation speed of the motor 4 with respect to the detection pressure is different between the case where the detection pressure increases and the case where the detection pressure decreases due to the time change. FIG. 4 is a graph of a characteristic curve showing the rotation speed of the motor 4 with respect to the detected pressure. Y1 in FIG. 4 is a pressurizing characteristic curve showing the rotation speed of the motor 4 with respect to the detected pressure when the detected pressure increases with time. Y2 in FIG. 4 is a decompression characteristic curve showing the rotation speed of the motor 4 with respect to the detected pressure when the detected pressure decreases with time.

As shown by the pressurizing characteristic curve Y1, when the detected pressure is increased from the lower limit value Pmin to the upper limit value Pmax, the rotation speed of the motor 4 continuously increases from the speed S1. When the detected pressure reaches the pressure value P1, the rotational speed of the motor 4 reaches the upper limit value Smax, and the rotational speed of the motor 4 is maintained at the upper limit value Smax while the detected pressure is from the pressure value P1 to the upper limit value Pmax.

As shown by the decompression characteristic curve Y2, when the detected pressure is reduced from the upper limit value Pmax to the lower limit value Pmin, the rotation speed is maintained at the upper limit value Smax while the detected pressure is from the upper limit value Pmax to the pressure value P2. The pressure value P2 is a value smaller than the pressure value P1. When the detected pressure decreases from the pressure value P2, the rotation speed of the motor 4 continuously decreases from the upper limit value Smax to the speed S2, and when the detected pressure reaches the lower limit value Pmin, the rotation speed of the motor 4 becomes zero, that is, the motor 4 stops. do. The speed S2 is a speed higher than the speed S1.

The lower limit value Pmin of the detected pressure is zero. That is, when the detected pressure is the lower limit value Pmin, it indicates that the pull-in amount of the trigger 3 is between zero (off position) and the second pull-in amount. Further, when the detected pressure is the upper limit value Pmax, it indicates that the position of the trigger 3 is the on position.

As shown in FIG. 4, comparing the case where the detected pressure increases and the case where the detected pressure decreases due to the time change, the detected pressure ranges from the lower limit value Pmin to the pressure value P1 when the detected pressure decreases due to the time change. Then, the rotation speed of the motor 4 with respect to the detected pressure is always large. As a result, hysteresis control of the rotation speed of the motor 4 is performed.

The control circuit 5 controls the rotation speed of the motor 4 along the pressurization characteristic curve Y1 or the decompression characteristic curve Y2 according to the time change of the detected pressure.

Further, the control circuit 5 maintains the rotational speed of the motor 4 constant even when the detected pressure increases and decreases within a predetermined range. For example, it is assumed that the detected pressure increases from the lower limit value Pmin to the pressure value P10 (<pressure value P1). In this case, the control circuit 5 increases the rotational speed of the motor 4 to the speed S10 along the pressurizing characteristic curve Y1. Here, in the decompression characteristic curve Y2, it is assumed that the detected pressure when the rotation speed of the motor 4 is the speed S10 is the pressure value P20 (<pressure value P10). The control circuit 5 maintains the rotational speed of the motor 4 at the speed S10 while the detected pressure decreases to the pressure value P20 on the decompression characteristic curve Y2. Further, the control circuit 5 maintains the rotation speed of the motor 4 at the speed S10 even when the detected voltage increases between the pressure value P20 and the pressure value P10. That is, the control circuit 5 maintains the rotational speed of the motor 4 at the speed S10 when the detected pressure increases and decreases within the range ΔP between the pressure value P20 and the pressure value P10. Therefore, even if the pull-in amount of the trigger 3 changes due to the vibration caused by the work of the electric tool 1, the rotation speed of the motor 4 is within the range ΔP if the change in the detected pressure due to the change in the pull-in amount of the trigger 3 is within the range ΔP. Is kept constant.

That is, in the control circuit 5, when the detection pressure is within the range from the lower limit value Pmin to the pressure value P1 and the rotation speed of the motor 4 is the speed Sx, the rotation speed of the motor 4 is changed even if the detection pressure changes within the range ΔPx. Is maintained at the speed Sx. The range ΔPx is a range between the pressure value Px1 in which the rotation speed of the motor 4 is the speed Sx on the pressurization characteristic curve Y1 and the pressure value Px2 in which the rotation speed of the motor 4 is the speed Sx on the decompression characteristic curve Y2. Is.

Further, when the detected pressure falls below the pressure value P20, the control circuit 5 reduces the rotational speed of the motor 4 from the speed S10 along the decompression characteristic curve Y2. Further, when the detected pressure exceeds the pressure value P10, the control circuit 5 increases the rotational speed of the motor 4 from the speed S10 along the pressurizing characteristic curve Y1.

In the above-mentioned example, the case where the electric tool 1 is an electric wrench has been described, but the electric tool 1 is not limited to the electric wrench, and may be another electric tool including a motor 4 such as an electric screwdriver and an electric drill.

As described above, the power tool 1 according to the first aspect includes a motor 4, a trigger 3, a pressure sensitive unit 7, and a control circuit 5. The motor 4 rotates the socket 212 (tip tool) by supplying electric power from the battery 241 (power source). The trigger 3 is movably held by the tool body 2. The pressure sensitive unit 7 has a pressure receiving unit 71 that receives pressure according to the amount of pulling in of the trigger 3, and detects the magnitude of the pressure received by the pressure receiving unit 71. The control circuit 5 controls the rotation speed of the motor 4 based on the detected pressure detected by the pressure sensitive unit 7. Further, the control circuit 5 Hysteresis controls the rotation speed of the motor 4 so that the rotation speed of the motor 4 with respect to the detection pressure is different between the case where the detection pressure increases and the case where the detection pressure decreases due to the time change.

With this configuration, the electric tool 1 suppresses the change in the rotation speed of the motor 4 even when the pull-in amount of the trigger 3 changes due to the vibration accompanying the work of the electric tool 1 or the pulsation of the finger pulling the trigger 3. It is possible to achieve stabilization.

In the power tool 1 according to the second aspect, in the first aspect, when the detected pressure decreases due to the time change, the control circuit 5 rotates the motor 4 with respect to the detected pressure as compared with the case where the detected pressure increases due to the time change. It is preferable to control the rotational speed of the motor 4 by hysteresis so that the speed increases.

With this configuration, the power tool 1 has a change amount of the pull-in amount of the trigger 3 within a predetermined range even when the change of the pull-in amount of the trigger 3 changes from an increase to a decrease and a change from a decrease to an increase. If so, the rotation speed of the motor 4 can be maintained.

1 Power tool 2 Tool body 212 socket (tip tool)
241 Battery (power supply)
3 Trigger 4 Motor 5 Control circuit 7 Pressure sensitive unit 71 Pressure receiving unit

Claims (2)

A motor that rotates the tip tool by supplying power from the power supply,
A trigger that is movably held in the tool body,
A pressure-sensitive unit that has a pressure-receiving unit that receives pressure according to the amount of pulling in the trigger and detects the magnitude of the pressure received by the pressure-receiving unit.
A control circuit for controlling the rotation speed of the motor based on the detected pressure detected by the pressure sensitive unit is provided.
The control circuit determines whether the detected pressure is increasing or decreasing due to a change in time, and when the detected pressure changes from an increase to a decrease and a decrease to an increase, the rotation of the motor An electric tool characterized in that the rotation speed of the motor is controlled so as to maintain the speed. The control circuit maintains the rotational speed of the motor when the detected pressure changes from an increase to a decrease and when the detected pressure changes from a decrease to an increase and the amount of change in the detected pressure is within a predetermined range. The power tool according to claim 1.

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