JP2708916B2 - Electric tool - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power tool such as a drill and a driver that uses a brushless motor to achieve a long life.

[Prior art] Conventionally, in a rechargeable power tool, a DC motor with a brush is often used, and the life thereof largely depends on the life of the brush of the DC motor, and there are many tools that can replace the brush itself. Seen.

In recent years, in order to extend the life of a motor, a lot of robots, tools, and the like, which generally have a very long life and are maintenance-free when a brushless motor is used, have only wear parts, have been announced.

This type of charging tool has a general shape shown in FIG. A brushless motor 22 is provided inside the main body 21, a reduction gear 23 is attached to a rotation shaft of the brushless motor 22, and a chuck 24 is attached to an output shaft of the reduction gear 23.
Is provided. A rechargeable battery 26 is provided inside the handle 25, and a power switch lever 27 is attached to the upper portion of the handle 25.

Hereinafter, the prior art will be specifically described with reference to FIGS. In the brushless motor for a rechargeable power tool, the Hall elements H _U , H _V , and H _W are arranged at a mechanical angle of 60 ° as shown in FIGS. 5 and 6, and are opposed to each other via a gap. A signal corresponding to the magnetic pole of the permanent magnet rotor 1 or the magnetic flux density of the position detecting magnet is output. As shown in FIGS. 8 (a) to 8 (c), the signals are sinusoidal voltage waveforms whose phases are shifted by 2π / 3, and a signal train required for a three-phase bipolar drive circuit is created from these signals. Distribution circuit 2
Power MOSF connected to each coil L _U , L _V , L _W
It outputs six signal examples as shown in FIGS. 8 (d) to (i) for driving the ETTr _{16 to} Tr ₂₁ . Fig. 8 (d)-
8 (e) out of the six signal train outputs shown in FIG.
(G), the output shown in (i) is, PNP, Figure 8 a gate of the lower power MOSFETTr ₁₉ ~Tr ₂₁ of a pair of half-bridge from transistor bridge 5 _{4-5 6} consisting of NPN type transistors ( k) Drive as shown in (m) and (o).

Here, the output of the distribution circuit 2 (FIGS. 8 (e) and (g))
(I)) when the H level, transistor bridge 5 _{4-5 6}
The output of the H level, the power MOSFETTr ₁₉ ~Tr ₂₁ is turned on. The output of the distribution circuit 2 (FIG. 8 (e)
When (g) (i) is at the L level, it is contrary to the above, power MOSFETTr ₁₆ ~Tr ₁₈ will be turned off. And similarly the output of the other signal sequence (Figure 8 (d) (f) (h )) transistor Tr ₁₃ to Tr _15, the floating power supply 4 _{1-4 3,}
Gate eighth view of the transistor by a bridge 5 ₁ to 5 ₃ of the half-bridge upper power MOSFETTr ₁₆ ~Tr ₁₈ (j)
(L) Drive as shown in (n). However, the source of the upper power MOSFETTr ₁₆ ~Tr ₁₈ is lower power MOSFET
Since it is connected to the drains of Tr _{19 to} Tr ₂₁ , the potential as viewed from the ground turns on the lower power MOSFETs Tr _{19 to} Tr ₂₁ .
It is different when turned off.

However, usually, the power MOSFET, because it does not work unless a predetermined voltage is applied between the gate and the drain, the upper side of the power MOSFETTr ₁₆ ~Tr ₁₈ is below the power MOSFETTr ₁₉ ~
A power supply different from Tr ₂₁ is required, and therefore, a floating power supply 41 to ₁ composed of backflow prevention diodes D _{1 to} D ₃ , charge storage capacitors C _{1 to} C ₃ , and charging resistors R _{12 to} R _14.
4 ₃ was used, with the ground and a resistor R ₁₂ to R ₁₄ in the charge accumulated in the capacitor C ₁ -C ₃ separated, the top power MOSFETTr
The gates of _{16 to} Tr ₁₈ are driven. Here, FIG. 8 (d),
When the outputs shown in (f) and (h) are at the H level, as shown in FIGS. 8 (j), (l) and (n), the transistor Tr
_The L-level signal inverted by _{13 to} Tr ₁₅ is input to the gate, and the power MOSFETs Tr _{16 to} Tr ₁₉ are turned off. Also,
Figure 8 (d), (f), when the output is L-level as shown in (h), Figure 8 (j), (l), as shown in (n), inverted by the transistor Tr ₁₃ to Tr ₁₅ is input to the H level signal gates, power MOSFETTr ₁₆ ~Tr ₁₉ is turned on.

[Problems to be Solved by the Invention] In the above-mentioned conventional example, the brushless motor merely rotates, and for example, the position of the screw thread is adjusted to an arbitrary position, or the tightening state of the screw is confirmed. However, it was not possible to perform the operation of gradually tightening by a fixed amount. Because to stop the rotation,
The switch of the tool is opened because the rotation speed of the electric motor cannot be controlled.

The present invention has been provided in view of the above points,
An object of the present invention is to provide a power tool that can switch to step drive during screw tightening and gradually rotate to align the screw threads.

[Means for Solving the Problems] The present invention relates to a power tool using a brushless motor, wherein a drive circuit unit for driving the brushless motor;
A first control circuit for controlling the brushless motor as a brushless motor during a normal screw tightening operation of the drive circuit unit, and a second control circuit for controlling the drive circuit unit to perform step operation of the brushless motor as a step motor And a switching means for switching between the two control circuits at an arbitrary time. The second control circuit includes a first oscillator that oscillates a basic clock pulse, and a period considerably longer than the clock pulse of the first oscillator. A second oscillator that oscillates a long clock pulse, a gate circuit that takes the logical product of the outputs from both oscillators, a counter that counts the output of the gate circuit, and the output of this counter as an address input that corresponds to the address in advance. A memory for outputting the stored data as the same excitation signal as the excitation signal of the first control circuit. That.

[Operation] First, the output of the first control circuit is input to the drive circuit section by the switching means so that the screw is tightened in a normal state, and the switching means is operated on the way to perform the second control. The output of the circuit is input to the drive circuit, and the brushless motor is operated in a step operation.

The output of the counter is used as an address input by the memory, and data stored in advance corresponding to the address is output as the same excitation signal as the excitation signal of the first control circuit, and the excitation signal is supplied to the first oscillator by the gate circuit. The clock pulse is output stepwise by repeating passing / stopping, so that the brushless motor is operated stepwise.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. As can be seen from the basic structure, the brushless motor has the same structure as the step motor. Therefore, in addition to a drive control circuit for a normal brushless motor, a control circuit for performing a step operation using the brushless motor as a step motor is provided, and the two can be switched by an external switch to solve the above problem.

That is, normal rotation is performed as a brushless motor, and the brushless motor is stepped as a step motor at an appropriate point in time. The screw can be tightened while aligning and checking the tightening amount. Note that the convenience of the switch can be improved by providing the switch for switching the operation on the body of the power tool that is near the thumb when held.

FIG. 1 shows a specific circuit diagram. The configuration of the present invention can be roughly divided into a drive circuit unit 10 for driving a brushless motor and a distribution circuit 2 which is a control circuit for controlling the brushless motor as a brushless motor.
And a control circuit 11 for operating the brushless motor as a step motor in a step operation.
The control circuit 11 switches a brushless motor between a brushless motor operation and a step motor operation by a switching circuit 17 composed of a logic IC.

Since the drive circuit 10 and the distribution circuit 2 have the same configuration as the conventional one,
The control circuit 11 for performing the step operation will be described. The structure of the brushless motor has a permanent magnet rotor 1 as shown in FIGS. 5 and 6, and the excitation coils L _U , L _V ,
_LW is arranged, and has the same structure as that of the step motor.

The difference from the step motor is basically the method of generating the rotating magnetic field. The brushless motor is provided at a position where three installed Hall elements switch the current phase so that the rotor always generates a force in the rotation direction, and this is performed by itself.

On the other hand, the excitation of the step motor is performed at an arbitrary speed from the outside, and in an extreme case, the rotor may not come to the excitation speed in some cases. Various excitation methods can be considered for this external excitation pattern, and the excitation is performed by stepping motor driving. However, since the present brushless motor is driven as a stepping motor as it is, in the present invention, the same excitation pattern as when the brushless motor operates is used. (Two-phase excitation) is created using a logic circuit and PROM.

The present invention provides a logic level external excitation pattern (eighth
(D), (e), (f), (g), (h),
The circuit for amplifying the signal of the external excitation pattern is switched by the switching circuit 17 using the driving circuit unit 10 for driving the brushless motor.

Next, a specific configuration of the control circuit 11 will be described. First
In FIG. 2 and FIG. 2, an oscillator 12 generates a basic pulse signal (clock 1) for a step operation as a step motor having a relatively high frequency (but within the self-starting range of the brushless motor). Generates a relatively long pulse (clock 2), and the gate circuit 14 intermittently drives the brushless motor as a step motor by repeatedly passing / stopping clock 1 with clock 2. This determines how many steps the drill tip drives per revolution.

This basic step is required for the following reasons. When the brushless motor is driven by a stepping motor with two-layer excitation, one step has a mechanical angle of 30 °. However, when it is incorporated in a tool, it is naturally used after being reduced by a reduction gear. Therefore, since one step of the step motor is 1 / reduction ratio of the power tool, the step motor needs to intermittently repeat the operation / stop for a certain number of pulses in order to operate at a fixed angle at the tool axis. is there. The basic step set here corresponds to one step ahead of the tool axis. Note that this is not always the case when the reduction ratio is small, but since the reduction ratio is usually 1/10 or more, the speed of the tool tip becomes slow unless the operation / stop is performed.

During the period set by the clock 2, the basic steps of the clock 1 are input to the hexadecimal counter 15, and necessary addresses are created in the ROM 16 such as an EPROM in which the excitation pattern is stored. The hexadecimal counter 15 has three output lines counting from 0 to 5 in binary with respect to six input pulses, and the brushless motor operates with a 6-mode excitation signal. Hexadecimal counter 15 is used. The output signals of the hexadecimal counter 15 are K, L, and M shown in FIG.
Enter the address.

The excitation pattern at the time of driving the brushless motor shown in D, E, F, G, H, and I in FIG.
The excitation pattern is read out in order as the address signal increases by one. This excitation pattern D, E, F, G, H, I
Fig. 8 (d) and Fig. 8 show a conventional brushless motor.
(E), (f), (g), (h), and (i) are equivalent signals, and are used to drive the brushless motor.
From the excitation signals D, E, F, G, H, I
Is input to the switching circuit 17. Switching circuit 17 consisting of logic IC is intended for switching the output by an external operation switch SW _1, the operation of the operation switch SW _1,
The signal from the distribution circuit 2 and the signal from the control circuit 11 are switched and output to the drive circuit unit 10. Incidentally, constitute a switching circuit means and the switching circuit 17 and the operation switch SW _1.

To tighten a normal screw, use the external operation switch SW.
By operating ₁ , the switching circuit 17 is controlled so that a signal from the distribution circuit 2 is input to the drive circuit unit 10. Then, it switches to a signal from the control circuit 11 outputs to the step operating the brushless motor from the switching circuit 17 by operating the operation switch SW ₁ at any time. Therefore, when the signal of the clock 2 is at the H level, the signals of the excitation patterns shown as D, E, F, G, H, and I in FIG.
When the brushless motor is rotated and the signal of the clock 2 is at the L level, no excitation signal is output, and the brushless motor stops. Therefore, the brushless motor rotates intermittently, so that the screw can be gradually rotated to make the screw thread uniform. Further, it is possible to slowly tighten up to the required tightening force.

FIG. 3 shows the address and data of the ROM 16, and the data is stored so as to form the illustrated excitation pattern corresponding to each address input which is sequentially increased by one step. That is, the signals D, E, F, G, H, and I are recorded in bits 0, 1, 2, 3, 4, and 5 of the ROM 16, respectively.

By the way, the three switches SWa, SWb, SWc provided on the distribution circuit 2 side shown in FIG. 1 have the following functions. That is, the switch SWa is a switch for supplying power to the drive circuit unit 10, and the switch SWb is a power MOSFET Tr.
_The switch SWc is a switch having a start / stop function. The order of turning on each switch is SWa → SWb → SW
It is configured to be c.

As described above, when a voltage is applied between the drain and the source of the power MOSFET by performing the above-described procedure for turning on the switch at the time of startup, the power MOSFET is surely provided earlier than that.
The gate of the ET can be stopped by connecting it to the ground, and does not 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. In addition, since the rotation of the brushless motor 22 is performed by turning on the switch SWa first and then finally turning on the start / stop signal after turning on the switch SWb, power is reliably supplied to the power MOSFET until the switch SWc is turned on. As a result, the power MOSFET operates in a completely on state, eliminating the risk of destruction.

FIG. 4 shows the configuration of the switches SWa, SWb, and SWc. That is, the operation pieces 28 and 2 are
9, 30 are protruded in the vertical direction.
Each switch SWa, SWb, SWc is in the vertical direction and
The switch lever 27 is arranged in the back side in order. Further, an operation piece 31 is also protrudingly provided at an upper portion on the back surface of the switch lever 27 in order to adjust the speed setting volume 32. Therefore, when the switch lever 27 is pressed, first, the power supply switch SWa of the drive circuit unit 10 is turned on, and then the power MOSFE
T Power supply switch SWb is turned on, then start /
The stop switch SWc is turned on. Further, when the switch lever 27 is further pressed, the slider 33 is slid by the operation piece 31, so that the resistance value can be varied and the speed control can be set. In this way, by pulling one switch lever 27 with a finger, each switch SWa can be operated in a predetermined order.

[Effects of the Invention] As described above, the present invention relates to a power tool using a brushless motor, a drive circuit unit for driving the brushless motor, and a brushless motor for driving the brushless motor during a normal screw tightening operation. A first control circuit that controls the drive circuit unit, a second control circuit that controls the drive circuit unit to perform a step operation using the brushless motor as a step motor, and a switching unit that switches between the two control circuits at an arbitrary time. First, the output of the first control circuit is input to the drive circuit unit by the switching means so that the screw is tightened in a normal state, and the output of the second control circuit is operated by operating the switching means on the way. Is input to the drive circuit, and the brushless motor can be operated in a step operation. , And gradually rotate to align the screw threads, and achieve an effect that the tightening can be slowly performed to a required tightening force.

In addition, the second control circuit includes a first oscillator that oscillates a basic clock pulse, a second oscillator that oscillates a clock pulse whose cycle is considerably longer than the clock pulse of the first oscillator, and both oscillators. A gate circuit for calculating the logical product of the outputs of the gate circuit, a counter for counting the output of the gate circuit, and using the output of this counter as an address input to store the data stored in advance corresponding to the address in the same manner as the excitation signal of the first control circuit. Since the memory is configured to output as a signal, the memory outputs the data stored in advance corresponding to the address as an excitation signal of the first control circuit as an excitation signal, This excitation signal is output in a step-like manner by the clock circuit from the first oscillator repeatedly passing / stopping at the gate circuit. Te, in which can be stepping a brushless motor.

[Brief description of the drawings]

1 is a specific circuit diagram of an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the above embodiment, FIG. 3 is an operation explanatory diagram of the above embodiment, FIG. 4 is a configuration diagram of a switch portion of the embodiment, and FIG. FIG. 6 is a longitudinal sectional view of the same, FIG. 7 is a specific circuit diagram of a conventional example, FIG. 8 is an operation waveform diagram of the same, and FIG. 9 is a cutaway side view of the power tool. . 2 is a distribution circuit, 10 is a drive circuit unit, 11 is a control circuit, 12 is a first oscillator, 13 is a second oscillator, 14 is a gate circuit, 15 is a hexadecimal counter, 16 is a ROM, and 22 is a brushless motor. is there.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshiharu Ohashi 1048 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References JP-A-61-177198 (JP, A) JP-A-59-59097 (JP, A)

Claims (1)

(57) [Claims] An electric tool using a brushless motor, a driving circuit for driving the brushless motor,
A first control circuit for controlling the brushless motor as a brushless motor during a normal screw tightening operation of the drive circuit unit, and a second control circuit for controlling the drive circuit unit to perform step operation of the brushless motor as a step motor And a switching means for switching between the two control circuits at an arbitrary time. The second control circuit includes a first oscillator that oscillates a basic clock pulse, and a period considerably longer than the clock pulse of the first oscillator. A second oscillator that oscillates a long clock pulse, a gate circuit that takes the logical product of the outputs from both oscillators, a counter that counts the output of the gate circuit, and the output of this counter as an address input that corresponds to the address in advance. A memory that outputs the stored data as the same excitation signal as the excitation signal of the first control circuit. Power tool and butterflies.