JP2000308268A - Charge system of electrical tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain large power when needed and give preference to the service life of a battery pack when it does not require large power, by enabling the connection from of plural batter packs to be switched over to series or parallel arrangement. SOLUTION: A motor drive circuit 30 is provided with a changeover switch 25 for switching the connection form over into the condition (series mode) where two battery packs 22 and 24 are connected in series or the condition (parallel mode) where they are connected in parallel. Consequently, when the user turns on a main switch 17 in series mode by turning off the changeover switch 25, an electric motor 12 start with the total voltage of the battery packs 22 and 24, so that this system cam perform heavy work. On the other hand, when he turns on the main switch 17 in parallel mode by turning on the changeover switch 25, it starts with the average voltage of the battery packs 22 and 24, so that the service life of the battery packs 22 and 24 extends sharply more than in the case of series mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power tool such as a table-top circular saw or an electric drill, which is powered by a battery pack (DC power supply).

[0002]

2. Description of the Related Art For example, in the case of a table-top circular saw board using an AC power supply as a power source, a power cord must be connected to a power outlet when used, so that the working position is limited to the vicinity of the power outlet. There was a bad usability.

[0003]

To solve this problem, a battery pack may be used as a power source.
In this case, the power (capacity) and life of the battery pack become problems. That is, depending on the usage mode of the power tool, heavy power may be required because of heavy work, and conversely, light power may not require much power because of light work. When large power is not required, it is desirable to give priority to the life of the battery pack. Therefore,
SUMMARY OF THE INVENTION It is an object of the present invention to provide a rechargeable power tool that can obtain a large amount of electric power when required and can prioritize the life of a battery pack when a large amount of electric power is not required.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a rechargeable power tool having the structure described in the above claims. According to the rechargeable power tool according to the first aspect, the connection mode of the plurality of battery packs can be switched in series or in parallel. Therefore, in the case of heavy work, the connection of the plurality of battery packs can be switched in series. While large power can be obtained, the life of the battery pack can be extended by switching the connection of a plurality of battery packs in parallel in the case of light work. As a power tool, the above-mentioned circular saw board,
The present invention can be applied to various electric tools using a battery pack as a power source, such as an electric drill and an electric screwdriver.

[0005] According to the rechargeable power tool of claim 2,
In addition to the above functions and effects, the connection mode (series or parallel) of the plurality of battery packs can be easily switched, so that the usability of the power tool can be further improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In the present embodiment, a tabletop saw blade 1 will be described as an example of a rechargeable power tool. FIG. 1 and FIG. 2 show the entire tabletop saw 1. In the figure, reference numeral 2 indicates a base. A table 3 for fixing the cutting material W on the upper surface of the base 2
Are rotatably supported. Auxiliary tables 2a, 2a are provided on both sides of the base 2, and the upper surfaces of the auxiliary tables 2a, 2a are flush with the upper surface of the table 3. Between the two auxiliary tables 2a, 2a, a fence 4 for positioning the cutting material W is attached across the table 3. A disk-shaped left and right tilting base 5 is integrally provided at a rear portion (right end portion in the figure) of the table 3. A left-right tilting arm 6 is supported by the left-right tilting base 5 so as to be tiltable left and right (in a direction perpendicular to the plane of FIG. 1). A circular saw body 10 is supported on the upper end of the left-right tilt arm 6 via a vertical tilt support shaft 7 so as to be tiltable up and down.

An electric motor 12 for rotating a saw blade 13 is provided on the side of the blade case 11 of the circular saw body 10.
Is attached. A saw blade 13 is attached to an output shaft of the electric motor 12. Almost the upper half of the saw blade 13 is housed in the blade case 11, and the lower half is housed in a blade cover 14 attached to the blade case 11 so as to be openable and closable. The blade cover 14 is provided to be openable and closable by rotating about the rotation axis of the saw blade 13.
Further, the link arm 15 is provided between the left-right tilting arm 6 and the blade case 11 so as to be opened and closed in conjunction with the vertical tilting operation of the circular saw body 10. That is, when the circular saw body 10 is pressed down, the blade cover 14 rotates in the opening direction (clockwise direction in FIG. 1) in conjunction with the downward movement, thereby exposing almost the lower half of the saw blade 13 to the table. The cutting material W fixed on 3 is now ready for cutting.

On the other hand, when the body 10 of the circular saw is returned upward,
In conjunction with this, the blade cover 14 rotates in the closing direction, whereby the lower half of the exposed blade 13 is accommodated in the blade case 14. Although not shown, a compression spring is interposed between the blade case 11 and the left / right tilting arm 6, thereby biasing the circular saw body 10 upward. During the cutting operation, the user pushes down the saw blade body 10 against the urging force of the compression spring.

Next, an operation handle 16 is provided on the side of the electric motor 12 so as to project sideways. The operation handle 16 is provided with a main switch 17 for turning on and off the electric motor 12 and a lock button 18 for locking the on state of the main switch 17. Two battery pack cases 21 and 23 are integrally provided side by side at the rear (right end in the figure) of the operation handle 16. The battery packs 22 and 24 are mounted on the battery pack cases 21 and 23, respectively, and the electric motor 12 rotates using the two battery packs 22 and 24 as power sources. The two battery packs 22 and 24 themselves are conventional rechargeable battery packs generally used for power tools, and need not be particularly changed in the present embodiment. Also, battery pack 2
The same battery pack 2 and battery pack 24 are used.

On both sides of the battery packs 22, 24,
Push buttons 22a, 22a, 24a, 24a are provided, respectively, and each push button 22a, 22a, 24
Engagement claws 22b, 24b are formed at the tips of a, 24a, respectively. In each of the battery packs 22 and 24, the engaging claws 22 b, 22 b, 24 b and 24 b of the two push buttons 22 a, 22 a, 24 a and 24 a are provided with engaging portions (not shown) provided on the inner surfaces of the openings of the battery pack cases 21 and 23. ), And thereby the battery packs 22, 24
Are fixed to the battery pack cases 21 and 23, respectively. Conversely, double push buttons 22a, 22a, 24a, 24
The battery packs 22 and 24 are pulled out while being pushed in, respectively.
3 can be removed.

[0011] DC power supply terminals 21a, 21a, 23a, 23a connected to battery packs 22, 24 are connected to the bottoms of both battery pack cases 21, 23, respectively.
Terminal, the other is a negative terminal, only one side is shown in the figure). Power terminals 21a, 21
a, 23a, and 23a are connected to the motor drive circuit 30, respectively. This motor drive circuit 30 is shown in FIG.

The motor drive circuit 30 can switch between a state in which the two battery packs 22 and 24 are connected in series (series mode) and a state in which they are connected in parallel (parallel mode). Double battery pack 2
A changeover switch 25 for switching between the connection modes 2 and 24 is provided on the side of the blade case 11 as shown in FIG. FIG. 3 shows the changeover switch 2
5 shows a state in which the drive circuit 30 is turned off to switch the drive circuit 30 to the serial mode. Note that the main switch 17 is off. In this series mode, since the changeover switch 25 is turned off and the coil C is not excited,
As shown, the common contacts c1 and c2 of the relays R1 and R2 are connected to the normally closed contacts b1 and b2, respectively. In this state, the battery packs 22 and 24 are connected in series via the contact b2 of the relay R2. Is done. On the other hand, when the changeover switch 25 is turned on, the coil C is excited by using the battery pack 24 as a power source, so that the common contacts c1 and c2 of both relays R1 and R2 are switched to the normally open side, thereby the common contact c1 , C2 are connected to the a1 contact and the a2 contact, respectively. In this state, battery packs 22 and 24 are connected to relays R1 and R1, respectively.
It is connected in parallel via the normally open side of R2.

As described above, by switching the changeover switch 25, the connection form of the two battery packs 22 and 24 is switched in series or in parallel, whereby the motor drive circuit 30 is switched in series mode or parallel mode.
Therefore, if the main switch 17 is turned on while the changeover switch 25 is turned off and the motor drive circuit 30 is switched to the serial mode, the electric motor 12 starts with the total voltage of the battery pack 22 and the battery pack 24. The saw blade 13 rotates with a high torque, thereby performing heavy work (for example, work for cutting hard material).

On the other hand, when the changeover switch 25 is turned on and the motor drive circuit 30 is switched to the parallel mode, and the main switch 17 is turned on in the parallel mode, the electric motor 12 is started with the average voltage of the battery packs 22 and 24. Therefore, the saw blade 13 rotates with lower torque than in the case of the serial mode. In this case, the life of the battery packs 22 and 24 is greatly extended as compared with the case of the serial mode. Note that diodes D1 and D2 are arranged at two places in the motor drive circuit 30, so that the flow of current is regulated in a certain direction.

According to the rechargeable power tool of the present embodiment configured as described above, heavy work can be performed by connecting the two battery packs 22 and 24 in series and setting the motor drive circuit 30 to the serial mode. Alternatively, in the case of light work, the two battery packs 22 and 24 are connected in parallel, and the motor drive circuit 30 is switched to the parallel mode, thereby giving priority to extending the life of the battery packs 22 and 24. be able to. By switching the connection mode of the two battery packs 22 and 24 in accordance with the work mode in this way, the capabilities of the battery packs 22 and 24 can be used more effectively. In particular, in the case of an electric tool such as the exemplified saw blade 1, which performs relatively heavy work, a large amount of electric power can be obtained when necessary while considering the life of the battery packs 22 and 24. Is maximized.

The embodiment described above can be implemented with various modifications. For example, although a circular saw has been exemplified as an example of a rechargeable power tool, the present invention can be widely applied to other rechargeable power tools such as an electric drill and an electric screwdriver. Also, two battery packs 2
Although the configuration for switching between 2 and 24 has been illustrated, a configuration may be adopted in which three or more battery packs are mounted as necessary, and the connection mode for some or all of them is switched in series or in parallel.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, and is a side view of a tabletop saw blade.

FIG. 2 is a plan view of a tabletop saw blade.

FIG. 3 is a circuit diagram of a motor drive circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Table saw blade 3 ... Table 10 ... Star blade body 11 ... Blade case 12 ... Electric motor 13 ... Saw blade 16 ... Operating handle 17 ... Main switch 18 ... Lock button 21, 23 ... Battery pack cases 22, 24 ... Battery pack 25 ... Changeover switch 30 ... Motor drive circuit R1, R2 ... Relay

Claims (2)

[Claims] 1. A rechargeable power tool using a plurality of battery packs as a power source, the connection of the plurality of battery packs being switched in series or parallel. 2. The electric tool according to claim 1, wherein a battery pack switch is provided in the power supply circuit, and the connection of the plurality of battery packs is switched in series or in parallel by switching the battery pack switch. Power tool.