JPH03190586A - Motor tool - Google Patents

Abstract

PURPOSE:To lengthen the service life of a motor by switching between a mode for performing control as a conventional brushless motor and a mode for performing control as a step motor, in the drive circuit section for the brushless motor in a motor tool. CONSTITUTION:Hall elements HU-HW detect position signals of a rotor (not shown) which is then provided to a distribution circuit 2, and signals (d)-(i) for driving a motor as a brushless motor are inputted to a switching circuit 17. A control circuit 11 gates outputs, having short and long periods, from oscillators 12, 13 and provides the outputs to a six unit counter 15. An address necessary for a ROM 16 storing an excitation pattern is prepared based on the output from the counter 15, and signals D-I for driving the motor as a step motor are inputted to the circuit 17. An external switch SW1 is operated to switch the signals (d)-(i) with the signals D-I in order to energize a drive circuit section 10. Consequently, continuous rotation and stepping rotation are selected thus realizing long service life of the motor. Such a system is preferably employed in drill or driver.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to power tools such as drills and screwdrivers that use a brushless motor and have a long life.

Conventional technology] Conventionally, DC motors with brushes have often been used in rechargeable power tools, and their lifespan largely depends on the lifespan of the DC motor's brushes, and many tools allow for the brushes themselves to be replaced. Be looked at.

In recent years, with regard to extending the life of motors, many robots, tools, etc. have been announced that generally use brushless motors, which reduce the only part that wears out to bearings, making it possible to have an extremely long life and be maintenance-free.

This type of charging tool has a general shape as shown in FIG. Inside the main body 21 is a brushless motor 22.
A reduction gear 23 is attached to the rotating shaft of the brushless motor 22, and a chuck 24 is provided to the output shaft of the reduction gear 23. Further, a rechargeable battery 26 is housed inside the handle 25, and a switch lever 27 for power supply is attached to the upper part of the handle 25.

Hereinafter, the prior art will be specifically explained based on FIGS. 5 to 8. In a brushless motor for a rechargeable power tool, the Hall elements HU, Hv, and HV are arranged at a mechanical angle of 60° as shown in Figs. A signal corresponding to the magnetic pole of the child 1 or the magnetic flux density of the position detection magnet is output. As shown in Fig. 8(a) to (c), each signal has a phase of 2π.
The voltage waveform becomes a sinusoidal voltage waveform shifted by /3, and from this signal, the six power M connected to each coil LU, Lv, Lw is transmitted through the distribution circuit 2 which creates the signal train necessary for the three-phase bipolar drive circuit. OS F E TTr+i~Trz+
6 as shown in FIGS. 8(d) to (i) for driving the
Outputs signal strings. Of the six signal train outputs shown in FIGS. 8(cl) to (i), FIGS. 8(e), (g), (
The output shown in i) is a transistor bridge 5. consisting of PNP and NPN type transistors. ~5. The lower power MOSFET Tr + of a pair of half bridges is
s ~ T r 21 gates in Fig. 8(k)(s)(o
).

Here, the output of the 5-way distribution circuit 2 (Fig. 8 (e) export) (i))
When is at H level, transistor bridge 5. The output at ~5° becomes H level, and the power MO8FET “1.~T
r2+ is turned on. Moreover, when the output of the 5-way distribution circuit 2 (Fig. 8(e), (g), and (i)) is at L level, the above is reversed, and the power MOSFETTr+s~Tr+
s will be turned off. Similarly, the output of the other signal train (Fig. 8(d), (f), and h) is also connected to the transistor T r
+ * ~ T r, and floating power supply 4. ~4
1. Transistor bridges 51-5. Therefore, the power MO8FET on the upper side of the half bridge Tr+s”-Tr+s
The gates of are driven as shown in FIGS. 8(j), (f), and (n). However, the upper power MOSFET Tr+s
The source of ~Tr+@ is the lower power MO3FET Tr
Since it is connected to the drain of +s~Trz+, the potential seen from the ground is lower power MO9FET TrIl.
~It differs depending on whether the Tr21 is on or off.

However, since a power MO3FET normally does not operate unless a predetermined voltage is applied between the gate and drain, the upper power MOSFET
r, @ is the lower power MO9FETTr+s~
A power source different from Tr21 is required, so reverse current prevention diodes D1 to D5, charge storage capacitor C,
~C5, and a floating power supply 4 consisting of a charging resistor R+□~R1. ~4. using ground and resistor R2
With the charges accumulated in the capacitors C1 to C5 separated by 2 to RI4, the upper power MO8FE T
s~Tr 1. drive the gate. Here, the eighth
When the outputs shown in Figures (d), (f), and (h) are at H level, they are inverted by transistors Tr, , ~Tr, as shown in Figure 8 (j), (I), and (n). L that was done
The level signal is input to the gate, and the power MO8FET
Tr + 6 to Tr II are turned off. Also, FIGS. 8(d) and (f).

When the output shown in (h) is at L level, Fig. 8 (j),
As shown in (1) and (n), the transistor T r ,
The H level signal inverted by 3 to Tr and 5 is input to the gate, and the power MOSFET T
rB to Tr+s are turned on.

[Problems to be Solved by the Invention] In the conventional example described above, the brushless motor simply rotates, and for example, it is necessary to align the screw threads to a desired position or check the tightness of the screws. However, it was not possible to perform actions such as gradually tightening a certain amount. This is because, although the tool switch is opened to stop the rotation, the rotation speed of the electric motor cannot be controlled.

The present invention has been provided in view of the above points.7)
The 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 provides an electric tool using a brushless motor, which includes a drive circuit section that drives the brushless motor, and a drive circuit section that connects the brushless motor to the brushless motor during normal screw tightening operation. a first control circuit for controlling the brushless motor as a step motor; a second control circuit for controlling the drive circuit unit to operate the brushless motor in steps as a step motor; and a switching means for switching between the two control circuits at any time. It is something.

Also, the first oscillator that oscillates a basic clock pulse, the second oscillator that oscillates a clock pulse with a considerably longer period than the clock pulse of this first oscillator, and the output from the reoscillator are ANDed. A gate circuit, a counter that counts the output of this gate circuit, and a memory that uses the output of this counter as an address input and outputs pre-stored data corresponding to the address as an excitation signal that is the same as the excitation signal of the first control circuit. This is a configuration of the second control circuit described above.

[Function] Initially, the output of the first control circuit is input to the drive circuit section by the switching means to tighten the screw in the normal state, and the switching means is operated midway to input the output of the first control circuit to the drive circuit section. The output of the circuit is input to the drive circuit section, and the brushless motor is operated in steps.

Further, the memory outputs pre-stored data corresponding to the address by using the output of the counter as an address input as an excitation signal that is the same as the excitation signal of the first control circuit, and this excitation signal is sent to the first oscillator in the gate circuit. By repeating passing/stopping, the clock pulse from the motor is outputted in a stepwise manner, causing the brushless motor to operate in steps.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. As can be seen from the basic structure, a brushless motor has a structure equivalent to a step motor. Therefore, in addition to a normal brushless motor drive control circuit, the above problem can be solved by providing a control circuit for operating the brushless motor in steps as a step motor, and switching between the two using an external switch.

In other words, normal rotation is performed as a brushless motor, and at an appropriate point the brushless motor is operated in steps as a step motor, and intermittent operation is possible by repeating operation and stopping by a predetermined step feed amount. The screws can be tightened while checking the alignment and tightening amount. In addition, convenience can be improved by providing a switch for changing the operation on the body of the power tool, which 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 section 10 having the same configuration as the conventional one for driving a brushless motor, a distribution circuit 2 that is a control circuit for controlling the brushless motor as a brushless motor, and a step circuit for driving the brushless motor. It is divided into a control circuit 11 for step operation as a motor, and a distribution circuit 2.
The control circuit 11 is a switching circuit 17 consisting of a logic IC.
The brushless motor is switched between brushless motor operation and step motor operation.

Since the drive circuit section 10 and the distribution circuit 2 have the same configuration as the conventional one, the control circuit 11 that performs step operation will be explained. As shown in FIGS. 5 and 6, the structure of the brushless motor includes a permanent magnet rotor 1, and an excitation coil L on the outside.
, Lv, L, are arranged and have the same structure as that of a step motor.

The basic difference from a step motor is the method of generating the rotating magnetic field. In a brushless motor, three Hall elements are installed at positions where the current phase is always switched so that force is generated in the direction of rotation of the rotor, and the motor does this by itself.

On the other hand, the step motor is excited externally at an arbitrary speed, and in extreme cases, the rotor may not be able to keep up with the excitation speed. Various excitation methods can be considered for this external excitation pattern, and it is implemented by driving a step motor, but since this brushless motor is directly driven as a step motor, in the present invention, the same excitation pattern ( (2-phase excitation) is created using a logic circuit, PROM, etc.

The present invention provides logic-level external excitation patterns (d), (e), (f), (h), (
i)), in which a drive circuit section 10 for driving a brushless motor is used as a circuit for power amplifying the signal of the external excitation pattern, and a switching circuit 17 switches the circuit.

Next, the specific configuration of the control circuit 11 will be explained. 1st
In the figure and FIG. 2, the oscillator 12 generates a relatively high frequency (but within the self-starting range of the brushless motor).
A basic pulse signal (clock 1) for step operation as a step motor is generated, and the next oscillator 13 generates a relatively long pulse (clock 2), and the gate circuit 14 generates a relatively long pulse (clock 2).
By repeating passing/stopping of clock 1 and clock 2, the brushless motor is intermittently driven as a step motor. This determines how many steps the shaft tip of the drill takes to drive one revolution.

This basic step is necessary for the following reasons. When this brushless motor is driven by a step motor with two-phase excitation,
One step is 30 degrees in mechanical angle. However, when incorporated into a tool, the speed must be reduced using a reduction gear. Therefore, one step of the step motor corresponds to the 1/' reduction ratio of the electric tool, so in order to move the tool axis at a fixed angle, the step motor must intermittently repeat operation/stop for a certain number of pulses. There is. The basic step set here corresponds to one step at the tip of the tool axis. Note that this does not apply if the reduction ratio is small, but since the reduction ratio is usually 1/10 or more, the speed of the tool shaft tip will become slow unless it is operated/stopped.

During the period set by the clock 2, the basic steps of the clock 1 are input to the hexadecimal counter 15, and a necessary address is created in the ROM 16, such as an EPROM, which stores the excitation pattern. The hexadecimal counter 15 has three output lines that count from 0 to 5 in binary in response to six input pulses, and since this brushless motor operates with excitation signals in six modes, it is possible to A hexadecimal counter 15 is used. The output signal of this hexadecimal counter 15 is K shown in FIG.

Input this to the address of the ROM 16 using L and M.

In the ROM 16, the glue shown in Fig. 2, E, F, G.

The excitation patterns shown in H and I when driving the brushless motor are stored as they are, and as the address signal increases by 1, the excitation patterns are read out in order. This excitation pattern D, E, F, G.

H and I are (in Fig. 8) in the conventional brushless motor.
d), (e), (f), (g), (h), (
i), and the signals of excitation patterns D, E, F, G, H, and I, which are the same signals as those from the distribution circuit 2 when driving a brushless motor, are input to the switching circuit 17. . The switching circuit 17 consisting of a logic IC switches the output using an external operation switch SW.
By operating this operation switch SWI, the signal from the distribution circuit 2 and the signal from the control circuit 11 are switched and output to the drive circuit section 10. In addition, the switching circuit 17
and the operation switch SW constitute a switching means.

When tightening normal screws, use the external operation switch SW.
1 to control the switching circuit 17 so that the signal from the distribution circuit 2 is input to the drive circuit section 10. Then, at an arbitrary time point, the operation switch SW is operated to switch the output from the switching circuit 17 so that it becomes a signal from the control circuit 11 that causes the brushless motor to operate in steps. Therefore, when the clock 2 signal is at H level, the condition shown in FIG.

Signals with excitation patterns shown in E, F, G, H, and T are input to the drive circuit section 10 to rotate the brushless motor,
Further, when the clock 2 signal is at L level, the excitation signal is not output, so the brushless motor stops. Therefore, the brushless motor rotates intermittently, so
The screws can be rotated gradually to align the threads. In addition, the necessary tightening can be done slowly to the maximum force.

FIG. 3 shows the addresses and data of the ROM 16, and the data is stored so as to form the excitation pattern shown in the figure in response to each address input that increases one step at a time. That is, the signals E, F, G, H, and I are recorded in bits 0, 1, 2, 3, and 4.5 of the ROM 16, respectively.

By the way, the three switches SWa, SWb, and SWe shown in FIG. 1 and provided on the distribution circuit 2 side have the following functions. That is, the switch SWa is a switch that supplies power to the drive circuit section 10, and the switch swb
is the power MOSFETTr, 6...
It is a switch that supplies power to the switch S.
Wc is a switch with a start/stop function. The order of turning on each switch is S W a-*
The configuration is such that S W b-+ S W c.

By following the above procedure for turning on the switch at startup, if voltage is applied between the drain and source of the power MO8FET, the gate of the power MO8FET can be connected to ground beforehand. It can be put into a stopped state and will not malfunction due to noise when the power is turned on.

Therefore, there is no short circuit between the upper and lower bridges of the power MO9FET, and the rotation of the brushless motor 22 is controlled by the switch SW.
A is first turned on, then switch Swb is turned on, and finally the start/stop signal is used, so switch SW
By the time c is turned on, power is reliably supplied to the power MOSFET, and the power MOSFET operates in a completely on state, eliminating the possibility of destruction.

FIG. 4 shows the switches S W a , S W b ,
The configuration of S W e is shown. That is, operating pieces 28, 29.30 are provided to protrude in the vertical direction from the back surface of the switch lever 27, and corresponding to these operating pieces 28, 29.30, the respective switches S W a , S W b , S
W c are arranged in the vertical direction and in order on the back side of the switch lever 27 . Further, an operating piece 31 is also provided protruding from the upper part of the back surface of the switch lever 27 in order to adjust the speed setting volume 32. Therefore, switch lever 2
When 7 is pressed, the power supply switch SWa of the drive 02 circuit section 1-0 is turned on, and then the power MO3FET is turned on.
The switches SW and the like for supplying the t source are turned on, and then the start/stop switch SWc is turned on. Further, by further pushing the switch/y lever 27, the slider 33 is slid by the operation piece 31, and the resistance value can be varied and speed control settings can be performed. In this way, one switch l/bar 2
By pulling 7 with your finger, each switch SWa・
...can be operated.

[Effects of the Invention] As described above, the present invention provides a power tool using a brushless motor, which includes a drive circuit section that drives the brushless motor, and a drive circuit section that connects the brushless motor to the brushless motor during normal screw tightening operation. As IIl
lltM! A second control circuit that controls the drive circuit section to operate the brushless motor in steps as a step motor, and a switching means that switches between the two control circuits at any time. Therefore, at first, the output of the first control circuit is input to the drive circuit section using the switching means to tighten the screw in the normal state, and the switching means is operated in the middle to drive the output of the second control circuit. The brushless motor can be inputted to the circuit section to make the brushless motor move in steps. Therefore, the brushless motor can be switched to step action at a predetermined position and gradually rotated to align the screw threads. This has the effect of making it possible to tighten slowly to a maximum force.

Further, a first oscillator that oscillates a basic clock pulse, a second oscillator that oscillates a clock pulse whose period is considerably longer than the clock pulse of this first oscillator,
A gate circuit that takes the AND of the outputs from both oscillators, a counter that counts the output of this gate circuit, and an excitation signal for the first control circuit that uses the output of this counter as an address input and stores data corresponding to the address in advance. Since the second control circuit is configured with a memory that outputs the same m magnetic signal, the memory uses the output of the counter as an address input and stores the data stored in advance corresponding to the address in the first control circuit. The same excitation signal as the excitation signal of It is possible.

[Brief explanation of drawings]

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

Claims (2)

[Claims] (1) In power tools using brushless motors,
A drive circuit unit that drives the brushless motor, a first control circuit that controls the brushless motor as a brushless motor during normal screw tightening operation, and a first control circuit that controls the drive circuit unit to operate the brushless motor. A power tool comprising: a second control circuit that operates stepwise as a step motor; and switching means that switches between the two control circuits at any given time. (2) A first oscillator that oscillates a basic clock pulse, a second oscillator that oscillates a clock pulse with a considerably longer period than the clock pulse of this first oscillator, and the AND of the outputs from both oscillators. a counter that counts the output of the gate circuit; and a memory that uses the output of the counter as an address input and outputs pre-stored data corresponding to the address as an excitation signal that is the same as the excitation signal of the first control circuit. 2. The power tool according to claim 1, wherein the second control circuit is comprised of: