JPH0265630A - Power source circuit for ac/dc chargable electrically-driven tool - Google Patents

Abstract

PURPOSE:To improve work efficiency by providing a means for switching power supply between a load and battery and a means for switching the output current from a DC power source between high and low levels thereby producing sufficient motor drive force within a predetermined load torque range. CONSTITUTION:In AC drive mode, power switches SW1, SW2 are turned OFF and only a battery 7 is charged by the output current from a switching power source 16, while when the power switch SW1 or SW2 is turned ON the battery 7 is charged by the output current from the switching power source 16 and a mode 15 is driven. Since the residual amount of the battery and the load condition are different in AC drive mode, the magnitude of the output current from the switching power source 16 is switched through an output current control circuit 17 corresponding to whether the battery 7 is charged or a motor 15 is driven with AC power. By such arrangement, battery drive is available at all times and since the output current is low when the battery is charged, safety can be ensured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a dual-use charging/AC system that can supply charging current from an AC power source to a storage battery, and further supply power to a load with the current from the storage battery or the current from the AC power source. Related to power supply circuits for power tools.

[Conventional technology]

In conventional power supply circuits for charging and alternating-current power tools, the motor load varies greatly depending on the working conditions, so constant current control is performed taking into consideration the range from no-load to locked state. In other words, if the motor is locked for a long time when driven by an AC power source, the load on the output side will be short-circuited and a large current will flow through the power circuit, potentially causing thermal damage. . Also, when the battery is being charged,
When driving with no load or light load using an AC power source, the battery may be overcharged due to the large current. For this reason,
Conventional power supply circuits for charging and alternating current power tools are limited to a constant current value so that the output current does not increase beyond a certain value, regardless of the state of the load.

Problems to be solved by Invention C] As mentioned above, the conventional charging system that limits the output current to a constant value
In the power supply circuit of an AC power tool, for example, if the output current value of the power supply circuit is set according to the maximum load,
When the power switch for driving the motor is turned off and the storage battery is only charged from the power supply circuit, there is a risk that a large current exceeding the rated value will flow through the storage battery and the storage battery will be destroyed. In addition, if the output current value of the power supply circuit is set according to the charging current of the storage battery, when the power switch is turned on and the motor is driven, the output current of the power supply circuit will be small during heavy load work, resulting in insufficient power. However, it had the disadvantage that it did not function adequately as a power tool.

[Means to solve the problem]

In order to solve the above problems, a first invention provides a DC power source, a rechargeable storage battery connected in parallel to the DC power source, and a rechargeable storage battery connected in parallel to the storage battery, the current of the storage battery or the DC power source being In a power supply circuit for a charging/AC power tool comprising a load supplied with power by an output current, a power supply switching means for switching between power supply to the load and power supply to the storage battery; The output current is switched in conjunction with the power supply switching means so that a large current value is selected when power is supplied to the load. be.

Further, a second invention is such that in the power supply circuit of the power tool for both charging and alternating current use, the switching timing of the rFJ power supply switching means and the switching timing of the output current switching means are shifted from each other. .

[For production]

The power supply circuit of the charging/AC power tool with the above configuration is as follows:
When the power switch is turned on to drive a load, the output current of the power supply circuit is switched to a large constant current to charge the storage battery and drive the load, and when the power switch is turned off, the output current of the power supply circuit is switched to a small constant current. It switches to current and operates to charge only the storage battery.

In addition, since the power switch's on/off switching timing and the output current switching timing can be staggered, if the power switch is turned on earlier than the output current switching timing, the motor will be turned on after the motor is driven. The supplied current changes from a small current to a large current, and the driving force of the motor gradually increases. Also, if the power switch is turned on later than the output current switching timing,
Even when the battery capacity of the storage battery is low, a large current is supplied from the start of driving the motor, and a large driving force can be obtained.

〔Example〕

First, an embodiment of the overall configuration of a charging/AC dual-purpose electric device to which the present invention is applied will be described with reference to the block diagram shown in FIG.

In the figure, switching fL1a16 insulates and connects the noise filter circuit 2, the rectifier circuit 3 that rectifies the AC input of the AC power supply 1, the switching circuit 4 that switches on/off the output of the rectifier circuit 3, and the human output of the power supply circuit. It is composed of a transformer 5 for rectifying and smoothing the output waveform, and a rectifier circuit 6 for rectifying and smoothing the output waveform. Further, a rechargeable storage battery 7 is provided on the output side of the rectifier circuit 6, that is, on the output side of the switching power supply 16, and a fli source switch SWI of the motor drive 1u is provided.
, and a motor 15 as a load are connected in parallel via SW2. Note that when the switches SW1 and SW2 are turned on when connected to the al and a2 sides, respectively, the power is turned on and off by turning on and off the switch SWI or SW2. However, since the switch SW1 and the switch SW2 have a mechanism in which only one of them can be turned on independently, the switch SW1 and the switch SW2 are not turned on at the same time. When either the switch SWI or the switch SW2 is turned on, the motor 15 is driven in forward or reverse rotation, and when both the switch SW1 and the switch SW2 are turned off, the motor power is cut off. Note that in this embodiment, the switch SW1
When the switch SW2 is turned on, the motor is driven in the forward direction, and when the switch SW2 is turned on, the motor is driven in the reverse direction.

Next, the output current control circuit 17 determines whether the voltage of the storage battery 7 is higher or lower than the set value.The voltage detection circuit 8 determines whether the voltage of the storage battery 7 is higher or lower than the set value. The outputs of the temperature detection circuit 10, the voltage detection circuit 8, and the 7Ai degree detection circuit 10 are manually set and reset, and the output current of the rectification circuit 6 or the storage battery 7 is set manually.
a constant current circuit 12 for detecting the state of charge and constant current control of the output current, a constant voltage circuit 13 for detecting the output voltage of the rectifier circuit 6 and controlling the output current at a constant voltage, and the constant current circuit 12 or P that controls the pulse duty of the switching circuit 4 by a control signal of the constant voltage circuit 13.
It is composed of a WM control circuit 14.

By the way, the power tool for both charging and alternating current according to the present invention has the following features:
Alternating current? When the IS source is not connected, the motor 15 is driven by the discharge current of the storage battery 7, which is a battery drive mode, and when the AC power source is connected, the switching power source 16 and the output current control circuit 17 are activated, An AC drive mode is entered in which the motor 15 is driven by the output current of the switching power supply 16.

In the AC drive mode, when both the power switches SWI and SW2 are turned off, only the storage battery 7 is charged by the three output currents of the switching power supply 16, and when the power switch SW1 or SW2 is turned on, The output current of the switching power supply 16 charges the storage battery 7 and the motor 1.
5 is performed. In addition, in the AC drive mode, the remaining capacity of the storage battery 7 and the light/heavy state of the load are different, so the output current control circuit 17 drives the motor 15 when only charging the storage battery 7 (hereinafter referred to as "charging"). (hereinafter referred to as "AC driving"), the output current of the switching power supply 16 is switched between large and small. That is, when the power switch is turned on, a large output current of the switching power supply 16 is supplied to the storage battery and the load. Further, when the power switch is turned off, only a small charging current is supplied to the storage battery, and especially when the battery is fully charged, a very small charging current is supplied. By switching the output current in this way, the storage battery is always charged when the load is being driven, making it possible to use the battery at any time.When the storage battery is being charged, the output current is small, which improves safety. It gets expensive.

In the output current control circuit 17, a PWM control circuit]
4 controls the pulse duty of the switching circuit 4 so that the output current of the rectifier circuit 6 is constant (constant current) by the output signal from the constant current circuit 12, and also controls the pulse duty by the output signal from the constant voltage circuit 13. Constant voltage (constant voltage)
The pulse duty of the switching circuit 4 is controlled so that

The constant current circuit 12 receives a control signal of a circuit block composed of a voltage detection circuit 8, a temperature detection circuit 10, and an R-S flip-flop 11, and a power switch SWI or SW2.
A control signal corresponding to the load condition is output to the PWM control circuit 14 by switching on and off. and,
The constant current circuit 12 allows the output current of the switching power supply 16 to be divided into two: a large 7Ii current during AC drive and a small 71f current during charging.
It is controlled according to the classic method of constant current of various types and terminal current supplied when the storage battery 7 is fully charged.

The constant voltage circuit 13 is AC driven when the storage battery 7 has a large remaining capacity, and is controlled to prevent most of the large output current from flowing to the storage battery 7 and overcharging when driving with no load or light load. It is a circuit.

When the battery voltage of the storage battery 7 increases due to charging and exceeds a predetermined voltage value, the constant voltage circuit 13 detects this and outputs a control signal to the PWM control circuit 14 to suppress the output current.

Next, the voltage detection circuit 8, the temperature detection circuit 10 and the R-S
A circuit block constituted by a flip-flop 11 detects the charging capacity state of the battery 7. Then, a control signal is outputted to the constant current circuit 12 to switch the output current between a constant current for charging and a terminal current at the completion of charging. When the storage battery 7 has no battery capacity and the voltage of the battery 7 becomes lower than the set voltage in the voltage detection circuit 8, a high reset signal is input from the voltage detection circuit 8 to the reset input of the R-S flip-flop 11. At this time, the above-mentioned ? A Low signal is output to the IS flow circuit 12, and the yield current circuit 12 and the PWM control circuit 14
As a result, the output current of the switching power supply 16 is controlled to a small constant current for charging.

Further, when #battery 7 is charged by the constant 7 current, the battery voltage rises, and when it exceeds the set voltage value, the voltage detection circuit 8
The reset signal from becomes Low. Then, when the battery capacity exceeds 10096 as a result of further charging, the battery temperature rises. When the temperature exceeds the set temperature in the temperature detection circuit 10, a high set signal is input from the temperature detection circuit 10 to the set input of the R-S flip-flop 11.

At this time, the R-S flip-flop 11 outputs a high signal to the constant current circuit 12, and the constant current circuit 12 and the PWM control circuit 14 control the output current of the switching power supply 16 to the dawn current. .

Next, when the battery temperature is high and a high signal is being input from the temperature detection circuit 10 to the R-S flip-flop 11, if the battery capacity is exhausted and the battery voltage is decreasing, A high reset signal is output from the 7u pressure detection circuit 8 to the R-S flip-flop 11.
The output of the flip-flop 11 becomes Low. From this, the output current is constant 71. The current is switched to i-stream, and the storage battery 7 is charged.

Now, FIG. 2 shows a more specific circuit diagram of the power tool shown in FIG. 1. In the figure, the same components as those described above are given the same reference numerals. Further, the next power supply 18 and one secondary power supply represent the power supplies of each control circuit within the output current control circuit 17.

In this configuration, first of all, the configuration and operation of the constant current circuit 12 will be explained. The output current of the switching power supply 16 flows through the resistor R12 and is detected as a voltage between the terminals of the resistor R12. This voltage is input to and amplified by an amplifier circuit composed of an operational amplifier OPI, resistors R19 to R21, and a capacitor C6. Then, a current flows through the photocoupler PCI due to the output voltage of the operational amplifier OPI, and a control signal is manually input to the PWM control IC in the PWM control circuit 14. For PWM control IC, Photocabra P
The pulse duty of the on/off switch of the switching circuit 4 is determined in accordance with the current flowing through the CI, and the control signal thereof is output to the switching circuit 4.

With the above configuration, when the output current of the switching power supply 16 increases, the input voltage to the amplifier circuit increases and its output voltage also increases, so that the current flowing to the photocoupler PCI increases. Then, due to the increase in the current of the photocoupler PCI, the PWM control circuit 14 reduces the pulse duty of the switching circuit 4, and the output current decreases to be controlled by negative feedback to a constant current value.

By the way, the amplifier circuit has a resistor R2 between the inverting input terminal of the operational amplifier OP1 and the negative line Q of the rectifier circuit 6.
0 and a resistor R21 are connected in parallel via a switch SW3, and the amplification factor is switched by the switch SW3.

In addition, the switch SW3 is the power switch SWI or SW
When the motor 15 is driven by turning on the switch SW1 or SW2, the switch SW3 is connected to the b side, and the resistor R21 is disconnected from the resistor R20. Further, when the switch SWI or SW2 is turned off to charge the storage battery 7, the switch SW3 is connected to the a side, and the resistor R20 is connected in parallel with the resistor R2+. The switch SW3 switches the resistance between the inverting input terminal of the operational amplifier OPI and the minus line g of the rectifier circuit 6, so that the amplification factor of the amplifier circuit is switched as follows.

When AC driving, [1+R19/R20] times when charging, [1+ R19/ (R20/R21) ] times. However, R
20/ R21-R20・R21/ (R20+R21
) As described above, since the amplification factor of the amplifier circuit during AC drive is switched to be smaller than the amplification factor during charging, the output current of the switching power supply 16 becomes larger during AC drive than during charging. Therefore, during AC drive, greater power is applied than when battery drive is performed, and the power tool can be used even when the battery capacity of #i battery 7 is low.

Next, the configuration and operation of the constant voltage circuit 13 will be explained. In the constant voltage circuit 13, the anode side of a plurality of series-connected diodes DIO to D13 is connected to the positive electrode of the storage battery 7, and the cathode side of the diode row is connected to the front side of the photocoupler P.
One of the anodes of the CI is connected to each of the two anodes. When the forward voltage of the diode is F and the number of diodes is N, the set voltage is determined by VFXN, and when the output voltage of the switching power supply 16 exceeds VFXN (4Vp in this case), the voltage is applied through the diodes DIO to D13. Current flows through the photocoupler PCI. Then, as mentioned above, PW
The M control circuit 14 operates to reduce the pulse duty of the switching circuit 4, thereby lowering the output voltage of the switching power supply 16, and performs negative feedback control to maintain a constant voltage value.

When the storage battery 7 is charged and has a large remaining capacity, if no-load operation is performed with AC drive, the output current is controlled to a large rated current by the constant 1u current circuit 12 during AC drive, so that no current flows to the motor 15. The remaining large current is all stored in storage battery 7.
, and the storage battery 7 may be overcharged with a large current. The constant voltage circuit 13 detects the battery voltage of the storage battery 7 that increases due to large current charging, limits the output current, and controls the output current to a constant voltage.

By the way, when the constant voltage circuit 13 operates during charging,
The battery voltage of storage battery 7 increases due to charging. , the charging current will be limited and the battery will not be fully charged or will not be fully charged. Therefore, so that the constant voltage circuit 13 operates during AC drive and sometimes does not operate, the set voltage during charging is switched higher than the set voltage during AC drive within a range that does not affect charging control. That's what I do. That is, when the selector switch SW3 is connected to the b side in conjunction with the power switch SW1 or SW2 during AC drive, the diode D8 between the cathode of the photocoupler PCI and the negative line ρ of the rectifier circuit 6
．． D9 is short-circuited so that the set voltage during AC drive is lower than during charging.

Next, in the voltage detection circuit 8, the battery voltage is held by an integrating circuit made up of a resistor R35 and a capacitor C9 to prevent the battery voltage from decreasing due to the starting current and malfunctioning. By increasing the time constant of this integrating circuit OCR, it does not respond to an instantaneous voltage drop, and the above-mentioned malfunction can be prevented.

Further, the voltage of the storage battery 7 is always applied manually to the No. 3 pin of the voltage detection IC in the voltage detection circuit 8 via the resistor 35. On the other hand, the reference voltage to be compared with the battery voltage is input from the second bin of the voltage detection IC when the AC power supply 1 is connected, the power supplies 18 and 19 are turned on, and each control circuit starts operating. Therefore, when AC power supply 1 is connected, the battery voltage at pin 3 is higher than the reference voltage at bin 2, and pin 8, where the comparator output in the voltage detection IC is sent, is always Low, and charging starts. It may not be done.

Therefore, in order to prevent the voltage detection circuit 8 from operating when the AC xi is turned on, the voltage of the storage battery 7 that is manually input to the voltage detection circuit 8 is made to rise later than the reference voltage. That is, the diodes D14 to D connected in series
The anode side of I7 is the 3rd bin where the battery voltage is input,
Further, the cathode side of the same diode array is connected to the power input (bin No. 9) of the voltage detection IC.

When the AC type I17.1 is turned off, the accumulated charge in the capacitor C9 is discharged through the diodes D14 to D17, and assuming that the forward voltage of the diode is VF, the voltage of the third bin becomes 4VF. When AC power supply 1 is turned on again, the voltage at pin 3 is slowly charged from 4VF by the time constant of resistor 35 and capacitor C9, and the voltage at pin 3 rises slowly, so the reference voltage rises first and normal operation occurs. can get.

Next, since the temperature detection circuit 10 does not operate when the temperature of the storage battery 7 is low, the output current of the switching power supply 16 is a constant current while the temperature of the storage battery 7 is low. However, if the AC power supply 1 is repeatedly turned on and off while the temperature of the storage battery 7 does not rise due to charging, overcharging of the storage battery 7 will be repeated. To prevent this, the capacitor c8 is connected to the positive terminal of the operational amplifier OP2. It is inserted between the inverting input terminal and the minus line ρ. When the AC power supply 1 is turned on, the voltage applied to the normal input terminal of the operational amplifier OP2 rises slowly due to the capacitor c8, so the output of the temperature detection circuit 1o is directly connected to the R-S flip-flop 1.
The set input of 1 is Hlgh. During this time, the voltage detection circuit 8 disconnects the battery capacity and determines the output current.

Next, FIG. 3 shows another example of a specific circuit configuration. In the same figure, the constant voltage circuit 13' is different from that in FIG.
It is composed of 2 to 24. In this embodiment, the base r$ lightning voltage is determined by the diodes D22 to D24 and the volume R44, and the difference between the reference voltage and the output voltage of the switching power supply 16 is amplified by the differential amplifier circuit, and the output voltage is used to control the photocoupler PCI. A current flows to control the output voltage of the switching rb source 16.

According to this configuration, the set voltage can be arbitrarily set using the volume R44, and constant voltage control can be performed in accordance with the temperature characteristics of the pond 7.

The above two embodiments are powered by a power switch SWI or SW2.
At the same time, the switch SW3 changes the amplification factor of the amplifier circuit, thereby changing the constant current value of the output current. By the way, the output current is determined by the power switch SWI or sW.
Switching can also be performed by shifting the switching timing of switch SW2 and the switching timing of switch SW3.

Examples thereof will be described below. Figure 4 shows the output current, motor terminal voltage, and
It shows changes in each waveform of motor current. In the figure, point A indicates the time when AC power supply 1 is input, point B indicates the time when changeover switch SW3 is turned on, and point C indicates the time when power switch SW1 or SW2 is turned on.

Note that turning on the changeover switch SW3 here means that the second switch SW3 is turned on.
In the figure, the changeover switch SW3 is turned to the b side, which means that the output current is changed to a constant 'l8tTl, which has a large output current.

When AC power supply 1 is input at point A, switching power supply 1
6 and the output current control circuit 17 are activated, a constant current IB is output from the switching power supply 16, and the storage battery 7 is charged. Further, at this time, the battery voltage increases to the constant voltage VB during charging. After that, at point B, the output cuff 1S flow changeover switch SW
3, the output current changes to a large constant current ID, and the storage battery 7 is rapidly charged with a large current. Furthermore, due to rapid charging, the battery voltage gradually increases from the constant voltage VB during charging to the constant voltage VD when driving the motor. And C
When the power switch SWI or SW2 is turned on at this point, the motor 15 is supplied with a sufficient drive voltage vD and can immediately start driving. In other words, the power switch SW
By turning on the changeover switch SW3 before turning on SW1 or SW2 and making the output current a large constant current, for example, even when the storage 7U battery 7 has no capacity, rapid charging is performed and the motor 15 is turned on. Start-up can be made easier.

Next, FIG. 5 shows changes in the waveforms of the output current, motor terminal voltage, and motor current when the changeover switch SW3 is turned on after the power switch SWI is turned on. In the figure, point A indicates the time when AC power supply 1 is input, point B indicates the time when power switch SW1 or SW2 is turned on, and point C indicates the time when changeover switch SW3 is turned on. When AC power supply 1 is input at point A, switching power supply 16 and output current control circuit 17 are activated, constant current IB is output from switching power supply 16, and storage battery 7
is charged. Further, at this time, the battery voltage increases to the constant voltage VB during charging. Then, at point B, turn on the power switch SWI.
Alternatively, when SW2 is turned on, the motor 15 is started. At this time, depending on the load at the time of startup, the motor? if
The current flows rapidly and at 7, the cell voltage gradually drops from the constant voltage VB.

For this reason, sufficient rotational torque cannot be obtained at the time of startup, resulting in low speed rotation. Then, at point C, switch the changeover switch SW.
3 turns on, the output current changes from the constant current IB during charging to the large constant current ID during AC drive, and a large current is supplied to the motor 15. Then, the battery voltage, which had been falling, rapidly rises to the motor drive voltage VD, and the rotation is switched to high speed, allowing sufficient work to be performed. That is, when the changeover switch SW3 is turned on after the power switch SW1 or SW2 is turned on and the output current is set to a large constant current value, the rotation speed is initially low, so for example, when tightening a screw or drilling a hole, Center positioning can be easily done, making work easier.

Next, a charging/AC electric screwdriver according to an embodiment of the present invention will be described. Figure 6 shows an external view of a dual-purpose electric screwdriver. Also, Figure 7 (
a) is the internal structure of the electric screwdriver for both charging and alternating current;
FIG. 7(b) is a view of the lock ring 28 seen from the bottom, and FIG. 8 is a view showing the state in which the shock bar 23 is opened in FIG.

To explain the structure of the electric screwdriver for both charging and AC, the electric screwdriver for charging and AC has two housings 21a.
, 21b form an exterior, inside which interior parts are built and fixed with screws 33a and 33b. A speed change handle 25 is provided at the top of a small diameter cylindrical portion at the front of the main body, and a speed change reducer block 37 operated by the motor 15 and the speed change handle 25 is housed within the cylinder. In addition, there is a storage battery 7 inside the large-diameter cylinder located behind the small-diameter cylinder.
is housed, and a source module 34 is housed in the groove at the bottom of the cylinder. The reason why the cylindrical part at the front of the cylinder is made small in diameter is to emphasize workability in narrow spaces.

At the rear end of the grip, an inlet 32 is connected to a housing 21a,
21b, and the inlet 32 is covered with a lock ring 28 for holding the socket portion 30a at the tip of the power cord 30. Further, two terminals 22 for supplying an AC 7d power source are insert-molded in the inlet 32, and the socket portion 30a is inserted and fitted into these terminals, and power is supplied through the AC power cord 30. The lock ring 28 is rotatable by 90 degrees with respect to the driver body, and the socket portion 30a and the insertion opening 28a of the lock ring 28 have an irregular oval shape. With this structure, the socket part 30a
After inserting the lock ring 28 into the inlet 32,
By rotating the socket part 30a by 0 degrees, the collar part 3 of the socket part 30a
0b is locked so as not to come off from the lock ring 28, and the power cord 30 is prevented from detaching from the main body.

The AC power supply terminal 22 of the inlet 32 is connected to the input end of a power supply module 34, and the output end of the module 34 is further connected to the motor 15 via the storage battery 7 and switches SWI, SW2. The rotational force of the motor 15 is transmitted to a speed reducer block 37, and further outputted via the block 37 to a driver bit 29 attached to a drive shaft 40. Furthermore, a rotary clutch handle 24 that can adjust the torque limit is provided at the tip of the speed reducer block 37.

Next, a driver bit storage section is provided on the upper surface of a portion of the cylinder. The driver bit storage section has a bit cover 23 for opening and closing the bit storage section, and slide rails are provided on the bit cover 23 and the housings 21a and 21b, respectively.
3 can be slid in the axial direction of the cylinder.

Further, an elastic hook 23a is provided at the tip of the bit cover 23.
is provided, and when the bit storage section is closed, the housing 2
Recesses 21 formed in 1a and 21b. c and 21d to be locked. Furthermore, when sliding, the inner surface of the bit cover 23 comes into contact with the outer surfaces of the cylinders of the housings 21a and 21b by the slide rail, so that the bit cover 23 is stably held at the 51-degree angle.
You can slide between rows. In addition, four parts for bit storage are formed inside the bit storage part, and driver bit 2
9 and 11-1 are accommodated in the recess.

Next, to explain charging and motor drive, when the switch handle 26 is not pulled in, the power cord 3
0 is connected to the main body and AC power is input, AC power is supplied to the power supply module 34 via the inlet 32, converted to DC power in the module 34, and then supplied to the storage battery 7. Then, the storage battery 7 is charged under the control of the power supply module 34, and when the battery capacity becomes full, charging is suppressed.

Next, when AC power is input, when the switch handle 26 is pulled in and the power switch SW1 or SW2 is turned on, the output current changeover switch SW3 disposed on the printed board of the power supply module 34 is switched on. It is turned on in conjunction with SWI or SW2, and DC power is supplied to the motor drive circuit and battery charging circuit by the operation of the power supply module 34. Note that the output voltage of the direct A7S source in the power supply module 16 is set higher than the output voltage of the storage battery 7, so that a larger rotational force can be obtained than when driven by the storage battery 7, and the power is also larger within a predetermined load torque range. It has become.

FIGS. 9(a) and 9(b) show the above-mentioned power switch S.
This figure shows an external view of a power supply module 34 in which a power switch block in which W1 and SW2 are divided into blocks and a changeover switch SW3 are arranged on the same printed board. In the figure, power switches SWI, SW2 and changeover switch S
The position of W3 is determined to match the position of the lever 42 and the operator 26a of the switch handle 26, respectively, when stored in the main body grip. By arranging the power switches SWI, SW2 and the changeover switch SW3 at predetermined positions on the same printed board in this manner, the assembly of the power tool can be facilitated.

Power switch SW1. SW2 and changeover switch SW3 can be operated in conjunction with each other by operating the switch handle 26. It is also possible to operate each switch by shifting the on/off timing. In this way, the power switch SW1. Switching between SW2 and the output current changeover switch SW3 can be performed only by the switch handle 26, which makes the operation easier and improves safety.

Next, the structure of the power switches SWI and SW2 will be explained. Figure 10 shows the blocked power switch SWI
, shows a structural diagram of SW2.

The power switch SWI, SW2 block has two 3-terminal 2-circuit microswitches with a lock plate 4 between them.
1 is sandwiched and stacked on top of each other. The lock plate 41 is provided with protrusions that are press-fitted into the holes of the power switches SWI and SW2.

SW2 is made into a block. Also, lock plate 4
], when the forward/reverse handle 27 that switches the rotation direction of the motor 15 between the forward and reverse directions is in the neutral position, the power switch S is turned on.
A protrusion 41a is provided to form a wall that locks WI and SW2 and prevents them from being turned on. In addition,
As already explained, two microswitches SWI, S
Each W2 operates independently, and a mechanism is adopted in which only one of them can be turned on.

Next, the operation parts of the power switch and the rotation direction changeover switch will be explained. The operation parts are composed of a switch handle 26, a forward/reverse handle 27, a lever 42, and a return spring 43. FIG. 11 shows a structural diagram of the forward/reverse handle 27.

In FIG. 7, the forward/reverse handle 27 and the lever 42 are coupled to each other so as to restrain each other in the lateral direction and swing in the rotational direction. Further, both are rotatably supported by a fulcrum 27a relative to the housings 21a and 21b. In addition, the forward/reverse handle 27 and the lever 42 are arranged in the direction in which the microswitches SWI and SW2 are stacked (perpendicular to the drawing).
You can slide to. And power switch SW1
Alternatively, when SW2 is off, the forward/reverse handle 27 is in a neutral state, and equal amounts of knobs protrude from both sides of the housings 21a, 21b.

Then, by pushing the knob toward the housing and sliding the forward/reverse handle 27 to either side of the housing 21a or 21b, the rotation direction of the motor 15 is switched. Further, the switch handle 26 is pivotally supported by the housings 21a and 21b at a fulcrum 26b, so that it can be pulled into the grip.

In the above configuration, for example, when the switch handle 26 is pulled into the grip while the forward/reverse handle 27 is slid toward the housing 21b (in the pushing direction relative to the drawing), the lever comes into contact with the rib 26c of the switch handle 26. 42 is pressed, and the operator 28a of the lower switch SW1 is further pressed to turn on the switch SWI, and the motor 15 is driven in normal rotation. Conversely, when the switch handle 26 is pulled into the grip while the forward/reverse handle 27 is slid toward the housing 21a (in the direction of drawing in the drawing), the operator 28b of the switch SW2 is pressed in the same manner as described above, and the switch is closed. SW2 is turned on and the motor 15 is driven in reverse. Further, when the forward/reverse handle 27 is in the neutral position, the lever 42 hits the protrusion 41a of the lock plate 41, and the 2
The switches SWI and SW2 are both turned off, resulting in a switch lock (power off) state.

The switch handle 26 and the forward/reverse handle 27 have different pivot positions relative to the housings 21a, 21b. Further, the switch handle 26 and the A portion of the forward/reverse handle 27 are provided with recesses and recesses for clicking, and the switch handle 26 utilizes the springiness of the return spring 43 to perform a click for switching the slide of the forward/reverse handle 27. It's out.

Next, the battery block will be explained. FIG. 12 is a structural diagram of the 7-hike block. Two nickel cadmium storage batteries 7 are welded in series by connecting lugs 46,
A battery temperature detection thermistor 48 is disposed between the two batteries. An elastic rubber cushion 47 is inserted onto the thermistor 48 for detecting battery temperature, and the thermistor 4
8 is fixed to the storage battery 7 with a heat-shrinkable tube 45 so as to be in close contact with the storage battery 7. The positive and negative electrodes of the battery are provided with absorbing plates 44 made of non-woven material 6i or open cell foam. Further, a thin film 50 is provided on the surface thereof, which has pores of several microns which have air permeability but are difficult for liquid to pass through. The absorbing plate 44 and the thin film 50 are fixed to the storage battery 7 by the heat shrink tube 45. The absorbing plate 44 is for absorbing the electrolyte that flows out from the positive electrode side of the storage battery when the battery is damaged.

〔Effect of the invention〕

As explained above, according to the invention as set forth in claim 1, when the power switch is turned on and the load is driven, the output current of the DC power source is switched to a large constant current in conjunction with the power switch. Therefore, sufficient motor driving force can be obtained within a predetermined load torque range, and work efficiency is improved. Furthermore, when the power switch is turned off and the storage battery is charged, the output current of the DC power source is switched to a small constant current in conjunction with the YTI source switch.
The storage battery is not overcharged and destroyed by large current, and is always properly charged.

Next, according to the invention as claimed in claim 2, since the switching timing of the power switch and the timing for switching the output current are shifted, for example, if the power switch is turned on earlier than the timing for switching the output current After the motor is driven, the rotational force of the motor gradually increases, making it easier to center screw tightening and hole drilling operations. Furthermore, if the power switch is turned on later than the output current switching timing, a large RC current is supplied from the start of driving the motor, making it easy to start up and use even when there are no batteries.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the overall configuration of a charging/AC power tool to which the present invention is applied. FIG. 2 is a more specific circuit diagram of the power tool shown in FIG. 1. FIG. 3 is a specific circuit diagram showing another embodiment of the present invention. FIGS. 4 and 5 are waveform diagrams of the output current, motor terminal voltage, and motor current with respect to the switching timing of the power switch and the output current changeover switch. FIG. 6 is an external view of the charging/AC electric screwdriver according to the present invention. FIG. 7(a) is a diagram showing the internal structure of a charging/AC electric screwdriver. FIG. 7(b) is a bottom view of the lock ring portion of the electric screwdriver for both charging and AC use. FIG. 8 is a diagram showing a state in which the pit cover in FIG. 7 is opened. FIGS. 9(a) and 9(b) are external views of the power supply module '34. FIG. 10 is a structural diagram of power switches SWI and SW2. FIG. 11 is a 414-dimensional drawing of the forward/reverse handle 27. 1st
Figure 2 is a structural diagram of the battery block. 4... Switching circuit, 7... Storage battery, 12...
・Constant current circuit, 14...PWM control circuit, 15...
Motor, 16... Switching power supply, 17... Output current control circuit, 26... Switch handle, SWI,
SW2゜SW3...Switch, R20, R21...
Resistance, op1~OP3...Operational amplifier, PCI.
··Photo coupler. Patent applicant Matsushita Electric Works Co., Ltd. Representative Patent attorney Etsushi Kotani
Patent Attorney Long 11 Seiyo Patent Attorney Takao Ito Figure (b) Figure Figure Figure Figure

Claims (1)

[Claims] 1. A DC power source, a rechargeable storage battery connected in parallel to the DC power source, and a rechargeable storage battery connected in parallel to the storage battery and supplied with power by the current of the storage battery or the output current of the DC power source. A power supply circuit for a charging/AC power tool comprising a load, comprising a power supply switching means for switching between supplying power to the load and supplying power to the storage battery, and a switching means for switching the output current of the DC power supply from large to small. , and the output current is switched in conjunction with the power supply switching means so that a large current value is selected when power is supplied to the load. circuit. 2. The charging device according to claim 1, wherein the switching timing of the power supply switching means and the switching timing of the output current switching means are shifted from each other.
Power supply circuit for AC power tools.