JP2006315119A - Trigger switch and motor driving circuit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a trigger switch which is long in service life and high in extendability. <P>SOLUTION: According to the structure of the trigger switch, a trigger portion 38 is arranged so as to be slidable away from a switch main body 36. The trigger portion 38 has a movable member 40 which has a magnet 42 at an end thereof, and two Hall elements are staggeredly arranged in the switch main body 36 in a sliding direction of the moving member 40. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a trigger switch used in an electric tool and a motor drive circuit using the same.

A brushless DC motor is used as a driving source for electric tools such as impact drivers and grinders. In order to drive the brushless DC motor, an inverter circuit, a control circuit for controlling the inverter circuit, and the like are built in the electric power tool. And the rotation speed of a tool is made variable by operating the trigger switch provided in the housing of the electric tool with an operator's finger (for example, refer to patent documents 1).
JP 2004-23823 A

  As the trigger switch of the electric tool as described above, a voltage changeover switch, a slide resistance, or the like is used. Such a mechanically contacted switch has a problem that the mechanical contact portion deteriorates over time and has a short life, and when the configuration is changed, it is built into the electric tool. Therefore, there is a problem in that the wiring board that is used is required to be changed and there is no scalability.

  In view of the above problems, the present invention provides a trigger switch having a long life and high expandability, and a motor drive circuit using the same.

  The invention according to claim 1 is the trigger switch in which the trigger portion is slidably arranged from the switch body, and the moving member protrudes from the trigger portion toward the inside of the switch body, and the moving member is provided with a magnet. In the switch body, n (where n> 1) hall elements are arranged along the direction in which the moving member slides, and adjacent to the n hall elements. A trigger switch characterized in that a part of the hall elements to be arranged are arranged so as to overlap each other in the sliding direction.

  The invention according to claim 2 is the trigger switch according to claim 1, wherein n = 2.

  The invention according to claim 3 is the trigger switch according to claim 1, wherein the n hall elements are arranged in a staggered manner.

  According to a fourth aspect of the invention, the trigger switch according to the first aspect, a control circuit for controlling the rotational speed of the motor, and the control of the speed command signal based on Hall signals from n Hall elements in the trigger switch. A motor driving circuit having a speed control circuit for outputting to the circuit, wherein the speed control circuit corresponds to the kth Hall element (where k> = 1) when the trigger portion is pressed. When a hall signal is input only from the kth hall element, a speed command signal for rotating the motor at a rotational speed Vm (Vm> 0) is output, and the trigger portion is pressed. Stroke to the position corresponding to the kth Hall element and the (k + 1) th Hall element, and the Hall signal is transmitted only from the kth Hall element and the (k + 1) th Hall element. Is input, a speed command signal for rotating the motor at a rotational speed V (m + 1) (where V (m + 1)> Vm) is output, and the trigger unit is pressed to (k + 1) th. When the stroke signal is stroked to the position corresponding to the hall element and the hall signal is input only from the (k + 1) th hall element, the motor is rotated at a rotational speed V (m + 2) (where V (m + 2)> V (m + 1). The motor drive circuit is characterized by outputting a speed command signal for rotation at (1) and outputting (2n-1) speed command signals for n Hall elements.

  The invention according to claim 5 is characterized in that the speed control circuit outputs a speed command signal for stopping the motor when no hall signal from the n number of hall elements is inputted. 5. A motor drive circuit according to item 4.

  The invention according to claim 6 is the motor drive circuit according to claim 4, wherein the motor is a brushless DC motor.

  In the present invention, since it is composed of a magnet provided on the moving member protruding from the trigger portion and the Hall element, they are not in contact with each other, and do not deteriorate over time due to mechanical contact. Therefore, the life of the trigger switch can be extended.

[First Embodiment]
Hereinafter, the cordless electric tool 10 of the 1st Embodiment of this invention is demonstrated based on FIGS. 1-4.

(1) Structure of Cordless Electric Tool 10 The structure of the cordless electric tool 10 will be described based on FIG.

  As shown in FIG. 1, the cordless electric tool 10 is an impact driver, and includes a screw-type housing 12, and the housing 12 includes a cylindrical main body 14 and a gripping portion 16 that protrudes from the rear lower surface of the main body 14. And have. The main body 14 has a brushless DC motor (hereinafter simply referred to as a motor) 18 and a gear box 20 connected to the output shaft of the motor 18, and the output shaft of the gear box 20 is connected to a chuck 22. A driver 24 is attached.

  Below the motor 18, a wiring board 28 provided with a drive circuit 50 for driving the motor 18 is attached.

  A trigger switch 30, which will be described in detail later, is provided at the boundary between the main body 14 and the grip 16. A rechargeable battery 32 made of a lithium ion battery is detachably provided at the lower end of the grip portion 16.

(2) Structure of trigger switch 30 Next, the structure of the trigger switch 30 will be described with reference to FIG.

  The trigger switch 30 includes a box-shaped switch body 36 and a trigger portion 38 that is slidable with respect to the switch body 36. A rod-shaped moving member 40 protrudes from the trigger portion 38 toward the switch body 36. A magnet 42 is attached to the distal end portion of the moving member 40, and the distal end portion of the moving member 40 having the magnet 42 is inserted into the switch body 36. The trigger portion 38 is always urged outward by a coiled spring 44.

  Two Hall ICs 46 and 48 are provided in a staggered manner in the switch body 36 along the sliding direction of the moving member 40. The first Hall IC 46 is provided below the moving member 40 and near the trigger portion 38. The second Hall IC 48 is attached to a position above the moving member 40 and away from the trigger portion 38, and the first Hall IC 46 and the second Hall IC 48 overlap with each other with respect to the sliding direction of the moving member 40. There is a part.

  A main switch 34 made of a micro switch is disposed in front of the first Hall IC 46. The main switch 34 detects an initial position, which is a position of the moving member 40 in a state where the trigger portion 38 is not pressed at all. When the trigger member 38 is pressed even a little, the moving member 40 moves to an OFF state. To ON state.

  The main switch 34, the first Hall IC 46, and the second Hall IC 48 are provided on a wiring board (not shown), and the wiring board is accommodated in the switch body 36.

  In a state where the trigger portion 38 of the trigger switch 30 is not pressed at all, it is held at the initial position of FIG. Then, by pressing the trigger portion 38 with a finger, the moving member 40 moves and moves to the initial position, range A, range B, range C, range D in FIG.

  When the magnet 42 is in the range A, the trigger part 38 is pressed from the initial position and the moving member 40 is moving, so the main switch 34 is turned from the OFF state to the ON state. Further, as shown in FIG. 4, the Hall signals from the first Hall IC 46 and the second Hall IC 48 are both OFF.

  When the magnet 42 is in the range of B, only the first Hall IC 46 is supported, so that the Hall signal is turned on only from the first Hall IC 46, and the Hall signal from the second Hall IC 48 is turned off. It becomes a state.

  When the magnet 42 is in the range C, both Hall signals from the first Hall IC 46 and the second Hall IC 48 are turned on in order to correspond to the overlapping position of the first Hall IC 46 and the second Hall IC 48. It becomes a state.

  When the magnet 42 is in the range D, the Hall signal is output only from the second Hall IC 48 because it is separated from the first Hall IC 46 and only supports the second Hall IC 48.

  Therefore, the two Hall ICs 46 and 48 can realize four states of stop, low speed, medium speed, and high speed as shown in FIG.

(3) Configuration of Drive Circuit 50 Next, the configuration of the drive circuit 50 will be described with reference to FIG.

  As shown in FIG. 3, the drive circuit 50 includes an inverter circuit 52, a control circuit 54 that controls the inverter circuit 52, the main switch circuit 33 described above, a speed control circuit 56, and the trigger switch 30 described above. It is composed of

  The inverter circuit 52 is a full bridge circuit composed of six FETs 1 to 6 and three sets of circuits in which two FETs are connected in series attached in parallel. Then, a drive current is supplied to the stator winding of the motor 18 from the midpoint between the FETs 1 to 6 connected in series. The six FETs 1 to 6 can be turned on / off by a gate signal from a logic circuit built in the control circuit 54. The inverter circuit 52 is supplied with a voltage from the rechargeable battery 32 made of a lithium ion battery.

  In addition to the logic circuit described above, the control circuit 54 is based on a rotation speed detection circuit that detects the rotation speed of the motor 18, a rotation signal from the rotation detection circuit, and a speed command signal input from the speed control circuit 56. The feedback control is performed, and the motor 18 is subjected to PWM control of the rotational speed based on the speed command signal via the logic circuit.

  The control circuit 54 is supplied with power for driving from the rechargeable battery 32, and a main switch circuit 33 is provided between the rechargeable battery 32 and the control circuit 54. The main switch circuit 33 includes a main switch 34 and a switching transistor 35. When the main switch 34 is turned on, the switching transistor 35 is also turned on, and direct current power is supplied from the rechargeable battery 32 so that the control circuit 54 To drive.

  In addition to the speed command signal, a brake signal is input from the speed control circuit 56. When the brake signal is being input, among the six FETs 1 to 6 in the inverter circuit 52, the upper FET1, FET3, and FET5 are all turned on, and the other lower FETs 2, 4, and 6 are turned off. Then, the rotation of the motor 18 is stopped. In this case, all the upper FETs 1, 3, and 5 may be turned off, and the lower FETs 2, 4, and 6 may be turned on. Even in this case, the rotation of the motor 18 can be stopped.

(4) Operating State of Cordless Electric Tool 10 Next, the operating state of the cordless electric tool 10 will be described with reference to FIG.

  When the main switch 34 is in the OFF state, since the power is not supplied to the control circuit 54, the motor 18 is in a stopped state. However, even in this case, a voltage is applied from the rechargeable battery 32 to the inverter circuit 52.

  When the operator of the cordless power tool 10 presses the trigger portion 38 even a little from the initial position to turn on the main switch 34, that is, when it is within the range A, the control circuit 54 is powered on. However, when the magnet 42 is in the range A in FIG. 2, a brake signal is output from the speed control circuit 56 as shown in FIG. 4, and the control circuit 54 stops the motor 18 as described above. . Here, when the main switch 34 is turned on, the current flowing through the main switch 34 is a very small current, and since only the switching transistor 35 operates, no arc is generated.

  When the operator presses the trigger portion 38 and the magnet 42 is in the range B, a low speed command signal is output from the speed control circuit 56 as described above. Also, the brake signal is turned off. The control circuit 54 rotates the motor 18 at a low speed in accordance with the low speed command signal.

  When the operator further presses the trigger portion 38 and the magnet 42 is in the range C, a medium speed command signal is output from the speed control circuit 56.

  When the operator further presses the trigger portion 38 and the magnet 42 is in the range D, a high speed command signal is output from the speed control circuit 56.

  When the operator finishes the work and releases his / her hand from the trigger portion 38, the trigger portion 38 is further returned to the initial position from the range A by the urging force of the spring 44, and a brake signal is output from the speed control circuit 56. 18 stops.

  Thus, since only the power supply to the control circuit 54 is turned ON / OFF, it is possible to prevent the deterioration over time due to the arc.

  Further, since the trigger switch 30 is composed of the two Hall ICs 46 and 48 and the non-contact magnet 42, there is no mechanical contact and a long life can be achieved.

  Furthermore, it is possible to issue a four-step speed command of stop, low speed, medium speed, and high speed from the two Hall ICs 46 and 48.

[Second Embodiment]
In the above embodiment, the trigger switch 30 is provided with the two Hall ICs 46 and 48. However, the invention is not limited to this, and three or more Hall ICs are staggered along the moving direction of the moving member 40 of the trigger portion 38. It may be provided. In this case, the Hall ICs are arranged so as to overlap each other little by little. Thus, for example, when n Hall ICs are arranged, (2n-1) speed command signals can be output.

[Example of change]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist thereof.

  Although the cordless power tool 10 of the above-described embodiment has been described with respect to the impact driver, other cordless power tools such as a grinder may be used instead.

It is a side view of the cordless electric tool of a 1st embodiment of the present invention. It is a partial longitudinal cross-sectional view of a trigger switch. It is a circuit diagram of a drive circuit. It is a figure of the table | surface which shows the relationship between the stroke state of a trigger switch, a speed command signal, and a brake signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cordless electric tool 12 Housing 18 Motor 28 Wiring board 30 Trigger switch 32 Rechargeable battery 34 Main switch 36 Switch body 38 Trigger part 40 Moving member 42 Magnet 46 Hall IC
48 Hall IC
50 drive circuit 52 inverter circuit 54 control circuit 56 speed control circuit

Claims (6)

In the trigger switch where the trigger part is slidably arranged from the switch body,
A moving member projects from the trigger part toward the inside of the switch body,
The moving member is provided with a magnet,
Inside the switch body, n Hall elements (where n> 1) are arranged along the direction in which the moving member slides, and are adjacent to each other among the n Hall elements. A trigger switch characterized in that a part of Hall elements are arranged so as to overlap each other in the sliding direction. The trigger switch according to claim 1, wherein n = 2. The trigger switch according to claim 1, wherein the n hall elements are arranged in a staggered pattern. 2. A trigger switch according to claim 1, a control circuit for controlling the rotational speed of the motor, and a speed control circuit for outputting a speed command signal to the control circuit based on Hall signals from n Hall elements in the trigger switch; A motor drive circuit having
The speed control circuit includes:
When the trigger portion is pressed and strokes to a position corresponding to the kth hall element (where k> = 1), and a hall signal is input only from the kth hall element, the motor is turned on. A speed command signal for rotating at a rotational speed Vm (Vm> 0) is output,
The trigger portion is pressed and strokes to positions corresponding to the k-th hall element and the (k + 1) -th hall element, and the hall signal is transmitted only from the k-th hall element and the (k + 1) -th hall element. When input, a speed command signal for rotating the motor at a rotational speed V (m + 1) (where V (m + 1)> Vm) is output,
When the trigger portion is pressed and strokes to a position corresponding to the (k + 1) th Hall element, and a Hall signal is input only from the (k + 1) th Hall element, the motor is rotated at a rotational speed V (m + 2). (Note that V (m + 2)> V (m + 1)), and output a speed command signal for rotation.
A motor drive circuit, wherein (2n-1) speed command signals are output to n Hall elements. 5. The motor drive circuit according to claim 4, wherein the speed control circuit outputs a speed command signal for stopping the motor when no hall signal is input from the n number of hall elements. 6. . The motor drive circuit according to claim 4, wherein the motor is a brushless DC motor.

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