JP2771872B2 - Charging tool - Google Patents

Description

The present invention relates to a rechargeable drill provided with a brushless motor, a power MOSFET for driving the brushless motor, and a control circuit for controlling the gate of the power MOSFET. And a charging tool such as a driver.

[Prior Art] This type of charging tool has a general shape as shown in FIG. A brush type or brushless motor 2 is provided inside the main body 1, and a reduction gear box 3 is attached to a rotation shaft of the motor 2, and a gear box 3 is provided.
Is provided with a chuck 4. A rechargeable battery 6 is provided inside the handle 5, and a power switch lever 7 is attached to the upper portion of the handle 5.

Among motors, especially in the case of brushless motors, the control is of the bipolar drive type, in which the power MOSFET is used as the drive element (the drive method in which the current flowing through the coil is made to flow in both positive and negative directions by an electronic switch etc. to increase the torque) About the circuit,
This will be described in more detail with reference to FIGS.

First, FIG. 4 shows an example of the structure of a brushless motor, in which a rotor 11 is made of a multi-pole magnetized magnet, and this is a rotational force generated by a coil 13 wound around a stator core 12. And rotate. The switching timing of the current flowing through the coil 13 is determined by the signal distribution circuit 16 shown in FIG. 6 by the position distribution signal of the rotor 11 obtained from the position detection element 14 and the position detection magnet (or the magnetic field of the rotor 11 itself) 15. The gate signal turns on and off at a predetermined timing shown in FIG.

Next, the control circuit 10 for controlling the rotation of the brushless motor will be described. As shown in FIG. 5A, a position signal having the same shape as the magnetization distribution of the position detecting magnet 15 is obtained from the position detecting element 14 composed of a Hall element. Three position detecting elements 14 (Hall elements A, B, C) are installed, and their phases are shifted by an electrical angle of 120 °. Naturally, the output position signal is also shown in FIG. ) Has a phase difference of 120 °. This signal is inputted to the signal distribution circuit 16 to produce a signal d necessary for the gate of the power MOSFET Q ₁ to Q _6, as shown in FIG. 5 at a timing of each of the position signal (c).

Signal d in the conventional example shown in FIG. 6 is a power amplified by the transistor bridge B ₁ .about.B ₆ for driving the three sets of the gate of the power MOSFET Q ₁ to Q ₆ installed vertically, the power MOSFET Q ₁ ~ to drive the gate of Q _6. Here, in the upper and lower power MOSFET bridges (Q ₁ , Q ₂ ), (Q ₃ , Q ₄ ), and (Q ₅ , Q ₆ ), the upper power MOSFET Q ₁ , Generally, the floating method in which the ground is separated from the ground of the circuit is used for driving Q ₃ and Q ₅ .
That is, in order to turn on and off the output of the power MOSFET, the power MOSFET can be turned on and off by applying a predetermined voltage between its source and gate, and turned off by setting it to the same potential as the source.

However, in this conventional circuit configuration, the sources of the upper power MOSFETs Q ₁ , Q ₃ , Q ₅ are connected to the drains of the lower power MOSFETs Q ₂ , Q ₄ , Q ₆ .
By the on / off state of the lower power MOSFET TQ ₂ , Q ₄ , Q ₆ ,
The source potential of the upper power MOSFETs Q ₁ , Q ₃ , Q _{5 from} the ground varies. Therefore, in the circuit configuration as in the conventional example, the circuit for driving the gate of the power MOSFET located above must be separated from the entire circuit ground. The transistor bridges B ₁ , B ₃ , B ₅ for driving the gate of the power MOSFET shown in FIG. 6 are separated by ground separation resistors R ₁ , R ₂ , R _3, and the electric charge required for driving the gate is also ground. Capacitors C ₁ , C separated by separation resistors R ₁ , R ₂ , R _3
2, is supplied by the charge stored in C _3. Thus, the upper power MOSFETs Q ₁ , Q ₃ , Q ₅ are driven.

Start / stop of this kind of brushless motor is generally its function to the signal distribution circuit 16 and is incorporated, is carried out by a switch SW ₃ for setting is found start / stop to the outside. For example, by the L logic level signal IC, can the brushless motor to the stop state of the gate signal to the power MOSFET Q ₁ to Q ₆ all in the L level state, also, FIG. 5 at a H-level signal A gate signal train as shown in the time chart shown in FIG. In addition, with the same function, by setting a predetermined terminal to H level or L level via the switch SWb, the upper power MOSFETs Q ₁ , Q ₃ ,
Q ₅ is turned on all, by turning off all power MOSFETQ _2, Q _4, Q ₆ of the lower, full coil 13a of the brushless motor, 13b, 13
It has the function to make c short-circuited and stop the brake. The switch SWa is for switching the rotation direction.

When speed control is performed with this type of brushless motor, the phase of the position detection signal is sampled as a speed signal, compared with a voltage value set by an external potentiometer, and the difference is used as the gate of the power MOSFET. The signal is often fed back with a PWM signal.

In addition to the control circuit 10 described above, the conventional brushless motor or the motor with a brush that performs speed control using a power MOSFET usually includes a booster circuit 17. This is the voltage at which the normally used rechargeable battery voltage generally does not exceed the predetermined voltage required to drive the power MOSFET, or the voltage at which the power MOSFET can be driven sufficiently even if the battery voltage drops below the predetermined voltage. This is to ensure. The power MOSFET cannot be used in a completely switched state when the gate voltage falls below a predetermined voltage.
In the linear region, sufficient heat is not supplied to the motor, so that heat is generated and eventually the motor may be destroyed.

The reason why the brushless motor having the power MOSFET and the control circuit 10 for controlling the power MOSFET as described above is applied to a tool is that long life and low noise can be realized.
The installation is no different from the brushed motor, and as shown in FIG. 3, is composed of a chuck 4, a gear box 3, a motor 2, a rechargeable battery 6, and the like.

[Problem to be Solved by the Invention] In the charging tool having the power MOSFET and the control circuit 10 as described above, there are several methods for starting the brushless motor. For example, a voltage must not be applied between the drain and source while the power MOSFET is open.
Because, as shown in FIG. 7, when a voltage is applied between the drain and the source while the power MOSFET is in the open state (the state where the control power is not applied, the gate is neither at the H level nor at the L level), The power MOSFET turns on due to noise or the like. In FIG. 6, a pair of upper and lower power MOSFETs (Q ₁ ,
If any of Q ₂ ), (Q ₃ , Q ₄ ) and (Q ₅ , Q ₆ ) is turned on both up and down, the battery will be short-circuited and the battery and power MO
It leads to destruction of SFET.

For example, as shown in FIG. 8, the power supply of the control circuit 10 by closing the switch SW _2, (it is set from the beginning to the start state) without using the start / stop function previously described is activated in the method, or there is no main switch SW _1, comprising the above state when such the main switch SW ₁ is turned on first. Reference numeral 18 denotes a battery.

Also, when simultaneously starting the main switch and the control power supply switch as shown in FIG. 9 as one switch SW _2, the output voltage of the booster circuit 17 included in the control circuit 10 always control circuit power the voltage delayed after turning the switch SW ₂ is increased, while a sufficient gate voltage to fully turn on the power MOSFET is not obtained, the brushless motor 2 starts to rotate, sufficient on-resistance of power MOSFET Since the initial starting current at the time of starting the brushless motor 2 is not low, the power MOSFET may generate heat and may be damaged in some cases.

Alternatively, in order to extend the life of a brushless motor, it is necessary to extend not only the life of the motor, but also the life of the power-on switch. However, it is difficult to extend the life more than 10 times while opening and closing the current at the time of starting the motor and at the time of high output as in the conventional case.

The present invention has been made in view of the above points, and has as its object to provide a charging tool for the purpose of breaking a MOSFET and extending the life of each switch.

[Means for Solving the Problems] The present invention provides a control circuit power switch for supplying power to a control circuit that is operated first, and a main switch that is operated next to the control circuit power switch and supplies power to the MOSFET. , A start / stop switch operated next to the main switch and provided in the control circuit.

Further, the control circuit power switch, the main switch, and the start / stop switch are sequentially arranged so that the switch levers are turned on in the order of operation from off to on.

[Operation] First, the control circuit power switch is turned on, then the main switch is turned on, and then the start / stop switch is turned on. First, the control circuit power switch is turned on. If you start /
Since the stop switch stops the brushless motor, the gate of the MOSFET must be set to the L level to keep the gate open, and when the main switch is turned on, the start / stop switch is turned off. Still has the brushless motor stopped,
No current flows to the main switch, and when the start / stop switch is turned on, the brushless motor starts rotating.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. Figure 1 shows a block circuit diagram, constitute a MOSFET bridge six power MOSFET Q ₁ to Q ₆ shown in FIG. 6, the power MOSF
Main switch that supplies power from battery 18 to ETQ ₁ … side
The configurations of SW ₁ , switch SW ₂ for supplying power to control circuit 10, start / stop switch SW _3, and the like are the same as those in the related art. However, the present invention is characterized by the order of operation of the switches SW ₁ . Main switch SW ₁ is intended to flow a current through the power MOSFET Q ₁ ... to the brushless motor 2, the control circuit power switch SW ₂ opens and closes the power supply of the control circuit 10, also, the start / stop switch SW ₃ is , Provided at a start / stop terminal provided in the signal distribution circuit 16. Further, a volume 19 for speed control setting is provided.

Pre-boot is open all start / non-stop switch SW ₃ is. The start / stop switch SW ₃ is at a predetermined position where the brushless motor 2 is stopped. In the example of FIG.
Is stopped.

In Figure 2 shows the structure of the three switches SW ₁ to SW ₃ and Volume 19 for speed control setting. That is, the operation pieces 23, 21, 22 are vertically protruded from the rear surface of the switch lever 7, and the respective switches SW ₃ , 21 correspond to the operation pieces 23, 21, 22, respectively.
SW ₁ and SW ₂ are arranged in the vertical direction and on the back side of the switch lever 7 in order. An operation piece 24 is also provided at the upper portion on the rear surface of the switch lever 7 to adjust the volume 19. Thus, pressing the switch lever 7, first, the control circuit power switch SW ₂ is turned on, then the main switch S
W ₁ is turned on, then start / stop switch SW ₃ is turned on. Also, by further pressing the switch lever 7,
The slider 19a is slid by the operation piece 24 to change the resistance value and perform speed control setting. Thus, by pulling one switch lever 7 with a finger, each switch SW ₁ can be operated in a predetermined order.

The switches SW ₁ ... By the above-up sequence, when first applied to the control circuit power switch SW _2, since the start / stop switch is in the state of stopping the brushless motor 2, the power MOSFET without opening the gate with the gate in reliably state of L-level, then, when the main switch SW ₁ is turned on, a start / stop switch SW ₃ is also has a brushless motor 2 to the stop state Therefore, no current flows through the main switch SW _1, further, when charged with start / stop switch SW ₃ starts the rotation of the brushless motor 2.

Thus, the control circuit power switch SW ₂ to up procedure of the switch at startup, it was in the order of the main switch SW _1, the start / stop switch SW _3, when a voltage is applied between the drain and source in the power MOSFET, Before that, it is possible to reliably connect the gate of the power MOSFET to the ground to bring it into a stopped state, and to prevent malfunction due to power-on noise or the like. Accordingly, there is no upper and lower short circuit of the bridge of the power MOSFET. Moreover, until the rotation of the brushless motor 2 is a control circuit power switch SW ₂ is first turned on, then for performing in finally start / stop signal of the main switch SW ₁ after turning, turning on the start / stop switch SW ₃ The booster circuit 17, which generates a voltage necessary to drive the gate of the power MOSFET, completes the operation without fail. Therefore, with the configuration as in the present invention, the power MOSFET operates in a completely ON state, and there is no fear of destruction.

Furthermore, the main switch SW ₁ is to be connected after turning of the control circuit power switch SW ₂ as described above, yet not rotating brushless motor 2 at this time, the coil current does not flow. Therefore, the main switch SW ₁ also not the turned off of the current, just simply because only passing a current, no depletion of the contact by the arc. Main switch SW
When _one cutting has expired start / stop switch SW ₃ before that, because the current brushless motor 2 by the power MOSFET is off, contact erosion also by the arc in this case is not. Also in other switches, the control circuit power switch SW ₂ are the power supply for the control circuit 10, electric power off / on is small, also,
Start / stop switch SW _3, because the level of the logic IC, since there is no life problems, each switch SW ₁ ... becomes longer life, the life of the drill becomes equal to the brushless motor 2 by the configuration of the present invention .

[Effects of the Invention] As described above, the present invention provides a control circuit power switch that is operated first to supply power to the control circuit, a main switch that is operated next to the control circuit power switch to supply power to the MOSFET, A start / stop switch which is operated next to the main switch and provided in the control circuit is provided. First, the control circuit power switch is turned on, then the main switch is turned on, and then the start / stop switch is turned on. Is turned on, and when the control circuit power switch is turned on first,
The start / stop switch stops the brushless motor.
It does not malfunction due to power-on noise, etc.
Next, when the main switch is turned on, the start / stop switch still stops the brushless motor, so that no current flows through the main switch.
In addition, when the start / stop switch is turned on, the brushless motor starts rotating, so that the MOSFET operates completely in the ON state, and therefore, there is no danger of destruction. It is.
Further, since the main switch is turned on before the start / stop switch is turned on, the brushless motor is not rotating at this time, and no current flows through the coil. However, the contact is not consumed by the arc because the current is merely supplied, and the power to be turned on and off is small because the control circuit power switch is for supplying power to the control circuit.
In addition, the start / stop switch opens and closes a low-level signal in the control circuit, so there is no problem with the life. Therefore, the life of each switch is extended, and the life as a charging tool such as a drill is longer than that of a brushless motor. This has the effect of being equivalent.

Further, the control circuit power switch, the main switch, and the start / stop switch are arranged in order so that the switch lever is turned on in the order of operation from off to on, so that the switch lever is special. The effect described above can be obtained by simply operating the switch lever in one direction from OFF to ON without performing any operation.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of the switch, FIG. 3 is a cutaway side view of a rechargeable tool, and FIGS. 4 (a) and 4 (b) are brushless. FIG. 5 is a time chart showing a pulse train required for driving the brushless motor, FIG. 6 is a specific circuit diagram of a control circuit of the brushless motor, and FIG. 7 is a MOSFET.
FIG. 8 is a block circuit diagram of a conventional example, and FIG. 9 is a block circuit diagram of another conventional example. 2 brushless motor, the switch lever 7, the control circuit 10, Q ₁ to Q ₆ is a power MOSFET, SW ₁ is a main switch, S
W ₂ the control circuit power switch, SW ₃ is a start / stop switch.

Continuation of the front page (72) Inventor Toshiharu Ohashi 1048 Odakadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (56) References JP-A-55-101303 (JP, A) JP-A-49-15915 (JP, A) JP-A-1-2466083 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B25F 5/00 H02P 7/28 B25B 21/00

Claims (2)

(57) [Claims] 1. A charging tool comprising a brushless motor, a MOSFET for driving the brushless motor, a control circuit for controlling the driving of the brushless motor by turning on and off the MOSFET, and a battery for supplying power to each part. A control circuit power switch that is operated to supply power to the control circuit, and the MOSF that is operated next to the control circuit power switch
A main switch for supplying power to the ET, and a start / start switch provided in the control circuit operated next to the main switch.
A charging tool comprising a stop switch. 2. The control circuit power switch, the main switch, and the start / stop switch are sequentially arranged so that the switch levers are turned on in the order of operation from off to on. The charging tool according to 1.