JP2012115958A - Power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power tool which keeps motor motion uninterrupted even when voltage of a secondary cell falls below the drive voltage of a microcomputer in the power tool for soft starting by the microcomputer the driving source of which is the secondary cell.SOLUTION: In the power tool having a motor 2b driven by a secondary cell 1, a microcomputer 2p for controlling the motor 2b, a first circuit part for driving the motor 2b from output of the microcomputer 2p, and a second circuit part for supplying the voltage to the first circuit part from the output of the microcomputer 2p, the first circuit part has an FET2f, driven by the soft start control signal output by the microcomputer 2p, and an FET2c operated by an inverted signal of the soft start control signal in opposite to the FET2f and driving the motor 2b. In addition, the second circuit part has an FET2h, driven by the soft start control signal output by the microcomputer 2p, and an FET2k turned on by on switching of the FET2h and supplying the voltage to the FET2c.

Description

  The present invention relates to a power tool technology, and more particularly to a power tool that can perform a soft start by using a secondary battery as a drive source and performing pulse control of an FET installed between the motor and the secondary battery. It is.

  For example, in a power tool that uses a secondary battery as a drive source, software that gradually increases the number of revolutions of the motor at the time of tool activation, for example, to reduce recoil at the time of tool activation and make it easier to perform accurate work. A tool for starting is developed (for example, see Patent Document 1).

JP 2003-159669 A

  One possible method of performing the soft start as described above is to provide an FET between the secondary battery and the motor and turn on the trigger switch provided between the motor and the secondary battery and simultaneously with the secondary switch. This is a method in which a microcomputer using a battery as a drive source is driven and the FET is pulse-controlled by this microcomputer.

  However, when soft start is performed in this way, the drive source of the microcomputer is a secondary battery, so if the tool is subjected to a heavy load momentarily, the voltage of the secondary battery may be However, there is a case where the voltage drops momentarily below the minimum drive voltage of the microcomputer and is reset.

  The soft start in this case is to gradually increase the current flowing through the motor by controlling the FET with a pulse only at the start, and the FET is in a full-on state after the soft start is completed. If the microcomputer is reset in this state, the FET is turned off, then the load of the secondary battery is released, and the microcomputer is restarted. The tool stops until the microcomputer restarts. After that, when the microcomputer is activated, the soft start may be repeated again, that is, the tool may be repeatedly turned on and off.

  Accordingly, an object of the present invention is to solve the above-described problem, in an electric tool that performs a soft start by a microcomputer using a secondary battery as a driving source, even if the voltage of the secondary battery becomes equal to or lower than the driving voltage of the microcomputer. It is to provide a power tool that maintains operation.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, in order to achieve the above object, the power tool of the present invention includes a motor driven by a battery (secondary battery), a control means (microcomputer) for controlling the motor, and a motor based on the output of the control means. A first circuit unit for driving and a second circuit unit for supplying a voltage to the first circuit unit based on an output of the control unit; the first circuit unit is connected to the control unit and controlled A first switch that is driven by a soft start control signal output from the means, and a second switch that is connected to the first switch and the motor, and that is operated by an inverted signal of the soft start control signal in reverse to the first switch. It is characterized by having.

  More preferably, the second circuit unit is connected to the control means, and is connected to the third switch driven by the soft start control signal output from the control means, the third switch and the second switch, and when the third switch is turned on. And a fourth switch that is turned on and supplies a voltage to the second switch.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  That is, according to the present invention, in an electric tool that performs a soft start by a microcomputer using a secondary battery as a drive source, an electric tool that maintains motor operation even when the voltage of the secondary battery falls below the microcomputer drive voltage is provided. can do.

It is a circuit diagram which shows an example of a structure of the electric tool which concerns on Embodiment 1 of this invention. In the electric power tool according to Embodiment 1 of the present invention, (a) and (b) are characteristic diagrams showing an example of an on-duty ratio by a pulse signal output from a microcomputer, and a waveform diagram showing an example of this pulse signal. c) and (d) are a characteristic diagram showing an example of an on-duty ratio by a pulse signal input to an FET for driving a motor, and a waveform diagram showing an example of this pulse signal. It is a circuit diagram which shows an example of a structure of the electric tool which concerns on Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

[Embodiment 1]
A first embodiment of the present invention will be described with reference to FIGS.

  The electric power tool of Embodiment 1 drives a motor based on a motor (motor 2b) driven by a battery (secondary battery 1), a control means (microcomputer 2p) for controlling the motor, and an output of the control means. And a second circuit unit (FETs 2h, 2k, diodes 2n, etc.) for supplying a voltage to the first circuit unit based on the output of the control means. The first circuit unit is connected to the control means, and is connected to the first switch (FET 2f) driven by the soft start control signal output from the control means, the first switch and the motor, and the first switch is softer than the first switch. And a second switch (FET 2c) that operates by an inverted signal of the start control signal to drive the motor.

  More preferably, the second circuit unit is connected to the control means, and is connected to the third switch (FET2h) driven by the soft start control signal output from the control means, and to the third switch and the second switch. And a fourth switch (FET 2 k) that is turned on by turning on and supplies a voltage to the second switch.

  The power tool of the first embodiment having the above characteristics will be specifically described below. In the first embodiment and the subsequent embodiments, an FET is described as an example of the switch, but the present invention is not limited to this. For example, it can be applied to a transistor or the like.

<Configuration of power tool>
FIG. 1 is a circuit diagram showing an example of the configuration of the electric power tool according to Embodiment 1 of the present invention.

  The electric power tool according to the first embodiment includes a secondary battery (battery pack) 1 and an electric tool main body 2 that uses the secondary battery 1 as a drive source. In this electric power tool, when the secondary battery 1 is mounted on the electric power tool body 2, the positive terminal (+) of the secondary battery 1 is electrically connected to the positive terminal (+) of the electric tool body 2, and The negative electrode terminal (−) of the secondary battery 1 is electrically connected to the negative electrode terminal (−) of the electric power tool body 2.

  The secondary battery 1 has a plurality of battery cells 1a connected in series. For example, a lithium ion battery, a nickel cadmium battery, a nickel metal hydride battery, or the like is used as the secondary battery 1. Moreover, you may connect the battery cell 1a in parallel.

  The electric tool body 2 includes a trigger switch 2a, a motor 2b, an Nch (N-channel type) FET 2c for performing soft start by pulse control, an Nch FET 2f, 2h, a Pch (P channel type) FET 2k, and resistors 2d, 2e. , 2g, 2i, 2j, 2l, 2m, a diode 2n, a constant voltage circuit 2o serving as a microcomputer drive source, and a microcomputer 2p.

  Next, circuit connection of the electric power tool 2 will be described.

  First, in the secondary battery 1, a plurality of positive terminals (+) of the secondary battery 1 are connected to the high potential side of the battery cells 1 a connected in series, and the negative terminal (−) is connected to the low potential side. Yes.

  On the other hand, in the electric tool main body 2, the positive terminal (+) of the electric power tool main body 2 is connected to one end of the trigger switch 2a. The other end of the trigger switch 2a is connected to the positive terminal of the motor 2b and to the input side of the constant voltage circuit 2o. The output side of the constant voltage circuit 2o is connected to the power supply terminal of the microcomputer 2p. Further, the negative terminal (−) of the electric power tool body 2 is connected to the GND terminal of the microcomputer 2p.

  When the secondary battery 1 is attached to the electric tool body 2, the positive terminal (+) of the secondary battery 1 is connected to the positive terminal (+) of the electric tool body 2 and the negative electrode of the secondary battery 1. The terminal (−) is connected to the negative terminal (−) of the electric power tool body 2.

  The output port of the microcomputer 2p is connected to the gate of the Nch FET 2f. A resistor 2g is provided between the gate and the source of the FET 2f to ensure the off operation of the FET 2f.

  Further, the drain of the FET 2 f is connected to the gate of an Nch FET 2 c provided between the negative terminal of the motor 2 b and the secondary battery 1 in order to perform soft start by pulse control. A resistor 2e is provided between the gate and the source of the FET 2c in order to ensure the off operation of the FET 2c.

  The output port of the microcomputer 2p is connected to the gate of the FET 2f as described above, and is also connected to the gate of the Nch FET 2h through the diode 2n. A resistor 2j is provided between the gate and the source of the FET 2h to ensure the off operation of the FET 2h.

  The gate of the FET 2h is connected to the drain of the Pch FET 2k via the resistor 2i. The drain of the FET 2h is connected to the gate of the FET 2k via the resistor 2m. A resistor 21 is provided between the gate and the source of the FET 2k in order to ensure the off operation of the FET 2k. The drain of the FET 2k is connected to the gate of the FET 2c via the resistor 2d.

  The source of the FET 2c, the source of the FET 2f, the source of the FET 2h, and the GND terminal of the microcomputer 2p are connected to the negative terminal (−) of the electric power tool body 2 and are at the ground potential.

<Operation of the power tool>
Next, with reference to FIG. 2, the operation when starting the microcomputer 2 p and the operation after starting the microcomputer 2 p in the above-described electric tool of FIG. 1 will be described. 2, (a) and (b) are characteristic diagrams showing an example of an on-duty ratio by a pulse signal output from the microcomputer 2p, and waveform diagrams showing an example of the pulse signal, (c) and (d). These are the characteristic view which shows an example of the on-duty ratio by the pulse signal input into FET for driving a motor, and the wave form diagram which shows an example of this pulse signal.

  First, when starting the microcomputer 2p, the trigger switch 2a is turned on. When the trigger switch 2a is turned on, power is supplied from the secondary battery 1 to the input of the constant voltage circuit 2o, the output (for example, 5V) of the constant voltage circuit 2o is input to the microcomputer 2p, and the microcomputer 2p is activated.

  Then, a pulse signal as a soft start control signal is output from the output port of the activated microcomputer 2p to the gate of the FET 2f and the diode 2n connected to the output port. As shown in FIG. 2A, the pulse signal as the soft start control signal is obtained by gradually changing the on-duty ratio from 100% to 0% for a predetermined time, that is, until the soft start time. It is going. As shown in FIG. 2B, the on-duty ratio characteristic as shown in FIG. 2A is such that the pulse width of the ON period in each cycle is gradually decreased with respect to the pulse width of the OFF period. This is possible by outputting a pulse signal.

  When this pulse signal is output, a signal is input to the gate of the FET 2f, and at the same time, a voltage is input in a pulse to the gate of the FET 2h via the diode 2n. When a voltage is input to the gate of the FET 2h even with one pulse, the FET 2h is turned on. When the FET 2h is turned on, the Pch FET 2k is also turned on. The on state of the FET 2h and the on state of the FET 2k are continued after the first pulse of the pulse signal output from the output port of the microcomputer 2p is input.

  At this time, the voltage of the secondary battery 1 is input to the gate of the FET 2c via the FET 2k and the resistor 2d. On the other hand, as described above, the pulse signal is input to the gate of the FET 2f while gradually decreasing the on-duty ratio from 100% to 0% during the predetermined time, that is, until the soft start time. Is done. When the FET 2f is turned on, the gate of the FET 2c becomes the ground potential, so that the FET 2c is not turned on. Conversely, when the FET 2f is turned off, the voltage of the secondary battery 1 is input to the gate of the FET 2c via the FET 2k and the resistor 2d as described above, and thus the FET 2c is turned on. That is, when the FET 2f is turned on, the FET 2c is turned off. Conversely, when the FET 2f is turned off, the FET 2c is turned on.

  Therefore, when the on-duty ratio of the voltage input to the gate of the FET 2f is gradually decreased from 100% to 0%, the gate voltage input to the FET 2c is reversed as shown in FIG. The on-duty ratio gradually increases from 0% to 100%, and soft start can be performed. The on-duty ratio characteristic as shown in FIG. 2 (c) is such that, as shown in FIG. 2 (d), the pulse width of the on period in each cycle is gradually increased with respect to the pulse width of the off period. This can be achieved by inputting a pulse signal to the FET 2c.

  Here, for comparison with the circuit configuration of the first embodiment, (1) first comparative example: when a pulse signal output from the output port of the microcomputer 2p is directly input to the gate of the FET 2c, (2) second Comparative example: When the FET 2c is operated via the FET 2f to reverse the logic of the pulse signal output from the output port of the microcomputer 2p. (3) Third comparative example: The battery voltage is directly input to the gate of the FET 2c. The case where it does is demonstrated.

(1) First Comparative Example Simply increasing the on-duty ratio of the pulse signal output from the output port of the microcomputer 2p directly from 0% to 100% directly on the gate of the FET 2c, a high load is applied. In this case, the voltage of the secondary battery 1 drops below the input voltage of the microcomputer 2p, and the microcomputer 2p is reset. When the microcomputer 2p is reset, the FET 2c cannot be turned on unless a signal is output from the microcomputer 2p, so that the FET 2c is turned off. When the FET 2c is turned off, the secondary battery 1 is released from the load, the voltage of the secondary battery 1 rises again, the microcomputer 2p is restarted and the FET 2c is turned on again, but the high load is still applied. If so, the voltage drops again. In this way, simply by directly inputting the pulse signal from the output port of the microcomputer 2p directly to the gate of the FET 2c, there is a possibility of repeated on / off.

(2) Second Comparative Example When the FET 2c is operated via the FET 2f in order to simply reverse the logic of the pulse signal output from the output port of the microcomputer 2p, the microcomputer 2p is turned off. Even if the pulse signal is not output, the FET 2c can maintain the on state. However, a certain period of time is required until the microcomputer 2p is started after the trigger switch 2a is pulled. During that time, the FET 2c is completely turned on, and the soft start cannot be performed.

(3) Third Comparative Example When the voltage of the secondary battery 1 is directly input to the gate of the FET 2c, when the trigger switch 2a is turned on, the FET 2c is in a full-on state with an on-duty ratio of 100% regardless of the signal from the microcomputer 2p. It becomes, and the soft start cannot be performed.

  Therefore, in the first embodiment, (2) in addition to the configuration of the second comparative example (FET 2c, FET 2f), as described above, the FET 2h, FET 2k, diode 2n, resistors 2i, 2j, 2l, 2m are used, and the FET 2c The voltage input to the gate can be supplied by inputting one pulse of the signal from the microcomputer 2p.

<Effect of Embodiment 1>
According to the electric tool of the first embodiment described above, the FET 2f is driven by the soft start control signal output from the microcomputer 2p, and on the contrary to the FET 2f, the motor 2b is driven by operating by the inverted signal of the soft start control signal. FET 2c that is driven by a soft start control signal output from the microcomputer 2p, and FET 2k that is turned on when the FET 2h is turned on to supply a voltage to the FET 2c. In the electric tool that performs soft start, the operation of the motor 2b can be maintained (not stopped) even when the voltage of the secondary battery 1 becomes equal to or lower than the driving voltage of the microcomputer 2p. In other words, soft start can be enabled without being affected by the battery voltage of the secondary battery 1. Further, the power supply from the secondary battery 1 is supplied to the microcomputer 2p when the trigger switch 2a is turned on, and further, the battery voltage is applied to the FET 2c when the FET 2k is turned on and the FET 2f is turned off, which contributes to energy saving. Can do.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG.

  The electric power tool according to the second embodiment is different from the first embodiment in the third circuit unit (FET 2q, latch circuit 2s, etc.) for stopping the driving of the motor when the battery (secondary battery 1) is overdischarged / overcurrent. ) Is added. The third circuit unit is driven by an overdischarge / overcurrent signal output from the battery overdischarge / overcurrent protection IC, and a fifth switch (FET2q) for stopping the supply of voltage to the second switch (FET2c). It is characterized by having.

  The electric power tool of the second embodiment having the above characteristics will be specifically described below mainly with this characteristic part.

<Configuration of power tool>
FIG. 3 is a circuit diagram showing an example of the configuration of the power tool according to the second embodiment of the present invention.

  The electric power tool according to the second embodiment includes a secondary battery (battery pack) 1 and an electric tool body 2 that uses the secondary battery 1 as a drive source. In this electric power tool, when the secondary battery 1 is mounted on the electric power tool body 2, the positive terminal (+) of the secondary battery 1 is electrically connected to the positive terminal (+) of the electric tool body 2, and In addition to the negative electrode terminal (−) of the secondary battery 1 being electrically connected to the negative electrode terminal (−) of the electric power tool body 2, the signal terminal (E) of the secondary battery 1 is further connected to the electric power tool body. 2 signal terminals (E).

  In addition to a plurality of battery cells 1a connected in series, the secondary battery 1 further has an overdischarge / overcurrent protection that outputs an overdischarge / overcurrent signal when the battery cell 1a is overdischarged / overcurrent. IC1b is provided. In the secondary battery 1, the signal terminal (E) of the secondary battery 1 is connected to the output side of the overdischarge / overcurrent protection IC 1b. The input side of the overdischarge / overcurrent protection IC 1b is connected to the battery cell 1a in order to monitor overdischarge / overcurrent. Here, the protection IC 1b constantly monitors each cell voltage of the battery cell 1a and the current flowing through the cell, and when each cell voltage becomes equal to or lower than a predetermined overdischarge voltage, or the cell current exceeds a predetermined overcurrent current. In this case, an abnormal signal is output from the signal terminal (E). When the secondary battery 1 is connected to the charging device and charged, the overdischarge / overcurrent protection IC 1b outputs an overcharge signal from the signal terminal (E) when each cell voltage becomes equal to or higher than a predetermined overcharge voltage. Operates to output and stop charging.

  The power tool body 2 includes a trigger switch 2a, a motor 2b, an Nch FET 2c for performing soft start by pulse control, an Nch FET 2f, 2h, a Pch FET 2k, resistors 2d, 2e, 2g, 2i, 2j, 2l, 2m In addition to the diode 2n, the constant voltage circuit 2o as a driving source of the microcomputer, and the microcomputer 2p, it further includes an Nch FET 2q, a resistor 2r, and a latch circuit 2s.

  In the electric power tool main body 2, the signal terminal (E) of the electric power tool main body 2 is connected to the input side of the latch circuit 2s. The output side of the latch circuit 2s is connected to the gate of the FET 2q. The drain of the FET 2q is connected to the gate of the FET 2h. A resistor 2r is provided between the gate and the source of the FET 2q to ensure the FET 2q is turned off. The source of the FET 2q is a ground potential.

<Operation of the power tool>
Next, the operation at the time of overdischarge / overcurrent of the secondary battery 1 in the above-described electric tool of FIG. 3 will be described.

  At the time of overdischarge or overcurrent, an overdischarge / overcurrent signal is output from the overdischarge / overcurrent protection IC 1b of the secondary battery 1. In response to the output of the overdischarge / overcurrent signal, a high signal is input from the latch circuit 2s to the gate of the FET 2q, and the FET 2q is turned on. When the FET 2q is turned on, the FET 2h and the FET 2k are turned off, so that no voltage is supplied to the gate of the FET 2c, and the driving of the motor 2b is stopped.

  Note that the latch circuit 2s is configured such that once the overdischarge / overcurrent signal is input, the output of the high signal continues while the trigger switch 2a is turned on. With such a configuration, the FET 2q is kept on and the FET 2h and FET 2k are kept off, so that the state where no voltage is supplied to the gate of the FET 2c continues, and the driving of the motor 2b is stopped. When the trigger switch 2a is turned off in this state, the output of the high signal of the latch circuit 2s is canceled (reset).

<Effect of Embodiment 2>
According to the electric tool of the second embodiment described above, in addition to the configuration of the first embodiment, the power tool is driven by the overdischarge / overcurrent signal output from the overdischarge / overcurrent protection IC 1b of the secondary battery 1. In addition to the same effects as those of the first embodiment, the driving of the motor 2b can be stopped when the secondary battery 1 is overdischarged / overcurrent by including the FET2q that stops the supply of voltage to the FET2c. . In addition, by having the latch circuit 2s, it is possible to continue to stop driving the motor 2b until the trigger switch 2a is turned off.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The electric power tool of the present invention can be used particularly for an electric power tool capable of performing a soft start by using a secondary battery as a drive source and performing pulse control of an FET installed between the motor and the secondary battery. .

DESCRIPTION OF SYMBOLS 1 ... Secondary battery, 1a ... Battery cell, 1b ... Overdischarge / overcurrent protection IC,
2 ... Electric tool body, 2a ... Trigger switch, 2b ... Motor, 2c ... FET (Nch), 2d, 2e ... Resistance, 2f ... FET (Nch), 2g ... Resistance, 2h ... FET (Nch), 2i, 2j ... Resistance, 2k ... FET (Pch), 2l, 2m ... Resistance, 2n ... Diode, 2o ... Constant voltage circuit, 2p ... Microcomputer, 2q ... FET (Nch), 2r ... Resistance, 2s ... Latch circuit.

Claims (8)

A motor driven by a battery;
Control means for controlling the motor;
A first circuit unit for driving the motor based on the output of the control means;
A second circuit unit for supplying a voltage to the first circuit unit based on the output of the control means;
The first circuit unit includes:
A first switch connected to the control means and driven by a soft start control signal output from the control means;
An electric tool comprising: a first switch connected to the motor; and a second switch that is driven by an inverted signal of the soft start control signal to drive the motor in reverse to the first switch. The electric tool according to claim 1,
The second circuit unit includes:
A third switch connected to the control means and driven by a soft start control signal output from the control means;
An electric tool comprising: a fourth switch connected to the third switch and the second switch, turned on when the third switch is turned on, and supplies a voltage to the second switch. In the electric tool according to claim 2,
When the fourth switch is turned on and the first switch is turned off, the voltage of the battery is applied to the second switch. In the electric tool according to claim 2,
The electric power tool, wherein the second switch is connected in series with the motor and the battery. In the electric tool according to claim 2,
A trigger switch connected in series with the motor and the battery;
The power tool is supplied to the control means when the trigger switch is turned on. In the electric tool according to claim 2,
The control means outputs a pulse signal that gradually decreases the on-duty ratio from 100% to 0% as the soft start control signal,
The second switch for driving the motor is driven by a pulse signal that gradually increases the on-duty ratio from 0% to 100% as an inverted signal of the soft start control signal. tool. In the electric tool according to claim 2,
A third circuit part for stopping driving of the motor at the time of overdischarge / overcurrent of the battery;
The third circuit unit has a fifth switch that is driven by an overdischarge / overcurrent signal output from the overdischarge / overcurrent protection IC of the battery and stops the supply of voltage to the second switch;
The motor is driven by stopping the supply of voltage to the second switch by the fifth switch. In the electric tool according to claim 7,
The third circuit unit includes a latch circuit;
When an overdischarge / overcurrent signal is output from the overdischarge / overcurrent protection IC, the latch circuit maintains the fifth switch in an ON state, and the supply of the voltage to the second switch stops the supply. An electric tool characterized by continuing to stop driving the motor.

Images