JPS6222332A - Switch for power tool - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of the Invention The present invention relates to a switch for a power tool such as that used in a six-weigh power tool such as an electric screwdriver, an electric drill, an electric saw, etc. This invention relates to a switch for a power tool with improved operability of the operating lever for driving the power tool.

(B) Background of the Invention Conventionally, a switch for a power tool of this scale is attached to a grip part of the main body of a power tool such as an electric screwdriver, and an operating lever of the switch is protruded from the front of the grip part so that it can be pressed down. The motor is provided to be turned on and off or controlled to change gears by switching between contact portions of an internal switch mechanism based on the depression of a protruding operating lever.

However, this operating lever normally moves back and forth in the forward and backward direction to control the switch mechanism of the inner NI, so it only slides when it is pressed down, which makes it difficult to obtain a sufficient stroke length. On the other hand, if the stroke is set well, the protrusion m of the operating lever protrudes more than the front surface of the grip, making it difficult to press down, resulting in poor operating performance.

(c) Purpose of the Invention Therefore, it is an object of the present invention to provide a switch for a power tool that allows a sufficiently long stroke length even if the protrusion of the operating lever is set small.

(d) Summary of the Invention This invention has the upper part of an operating lever for driving and controlling a motor engaged with a movable piece that switches and moves between contact parts of a switch-like structure, and the lower part of an operating lever that engages with a movable piece that switches and moves between contact parts of a switch-like structure, and the lower part of an operating lever that drives and controls a motor. It is characterized by being a switch for a power tool that is pivoted at the lower end.

(E) Effects of the Invention According to this invention, the lower part of the operating lever is pivotally connected to the lower end of the support piece vertically installed on the switch case, and the operating lever is tilted using this pivoting part as a fulcrum. The movement of the movable piece that engages the upper part of the slider is achieved by tilting a small operating lever using the lower end as a fulcrum, and a large sliding stroke can be obtained.

Therefore, when the switch is attached to the grip of a power tool,
This operating lever has a sufficiently long pressing stroke suitable for operating the lever while having a small protrusion against the front surface of the grip, and the operating performance is reliably improved.

(f) Examples of the invention An embodiment of the present invention will be described in detail below based on the drawings.

The drawings show a switch for a DC power tool, and in FIGS. 1 to 3, the switch for a DC power tool includes a control circuit section 11 for a DC motor, an operating lever 12 for driving and operating the motor, and a combination thereof. It is comprised of a supporting switch case 13, and is used, for example, by being incorporated into the grip of a power tool such as an electric screwdriver.

The above-mentioned control circuit section 11 includes a power transistor 14,
An upper heat dissipation cover 15 that covers this power transistor from above and below, a lower heat dissipation cover 16, a printed circuit board 17 on which a control circuit is mounted, a resistor board 18 provided as a part of the speed change control circuit, and a sliding contact with this resistor board 18. It is composed of a brush 19 that changes the resistance value correspondingly, a movable piece 23 having first to third movable contact pieces 20 to 22, and a return spring 24 for this movable piece.

The above-mentioned power transistor 14 has a rectangular shape, and the three terminals 25 protruding from the side surface thereof are bent downward and connected to a power supply terminal and a motor terminal, which will be described later. Controls the armature circuit ON/OFF.

By the way, this type of power transistor 14 generally generates heat easily, so the upper and lower heat dissipation covers 15 are made of a metal such as an aluminum alloy that has better heat absorption than the upper and lower sides.
16 to absorb the heat generated by the power transistor 14.

In this case, the upper and lower surfaces of the power transistor 14 are sandwiched between the horizontal surfaces of the upper and lower heat dissipation covers 15 and 16.
Due to the fastening effect of screws 26 passing through these parts, the upper and lower parts are brought closer to each other. These closely spaced horizontal surfaces promote efficient heat absorption to the power transistor 14, and the vertical walls of the covers 15, 16 are largely removed to provide a large heat dissipation area of the covers themselves. This prevents performance deterioration and life expectancy due to heat generation.

The upper heat dissipation cover 15 is provided in a box shape with an open bottom surface, and the above-mentioned power transistor 14 is placed inside the open bottom surface.
With the lower heat dissipation cover 16 housed and enclosed, the square holes 27 opened on both sides of the F section heat dissipation cover 15...
. . engages with side protrusions 28 . . . protruding from the outer surface of the switch case 13, which will be described later, and are integrally attached to the switch case 13. In this case, the heat dissipation cover 15
In order to improve heat dissipation, the switch is provided with a sufficiently large area not only on the horizontal side but also on the vertical side, and is also box-shaped so as to cover the entire switch, and is formed to improve dustproof performance at the same time. There is.

The lower heat dissipation cover 16 is provided in the shape of a mouth, and the square holes 29 opened on the side surfaces of both side hanging pieces of the mouth shape are engaged with side protrusions 30 protruding from the outer surface of the switch case 13, which will be described later. The switch case 13 is then fitted onto the switch case 13.

In this case, stepped portions 3 formed on both shoulders of the mouth shape.
1.31 presses down and supports the printed circuit board 17, which will be described later, at the time of mounting. Similarly, the heat radiation cover 16 is provided with a sufficiently large area not only on the horizontal surface side but also on the vertical surface side in order to improve heat radiation performance.

The printed circuit board 17 described above is fixedly supported on the switch case 13 by having both side edges pressed down by the step portions 31 and 31 of the lower heat dissipation cover 16.

Further, a terminal connection hole 32 is formed vertically through one end of the substrate 17, and a power terminal and a motor terminal, which will be described later, are connected to this hole.

Further, slide guide surfaces 33 are cut out on both side edges of the printed circuit board 17, and an upper slide protrusion 34 of the movable piece 23, which will be described later, is slidably guided by the slide guide surface 33, thereby regulating right and left steadying when the movable piece slides. On the other hand, this printed circuit board 1
The movable piece comes into contact with the lower surface of the movable piece 7, and the upward movement of the movable piece 23 is restricted.

Furthermore, a thin resistance board 18 on which a resistance element for a speed change control circuit for the motor is printed is attached to the lower surface of the printed circuit board 17.

The above-mentioned movable piece 23 is provided in a box shape that can be stored in the switch case 13, which will be described later. 20 is press-fitted from above, and a wide U-shaped second movable contact piece 21 is press-fitted from below into one of the raindrop pieces 36 and 37 that are vertically installed in parallel on the lower surface of the box shape in the front-rear direction. Attachment: The narrow U-shaped third movable contact piece 22 is similarly press-fitted from below to the other hanging piece 37.

Furthermore, a brush 1 formed in an L shape is provided in the brush mounting groove 39 on the inside side through the brush opening 38 on the front side of the upper surface.
9 is installed by inserting the proximal end side of the brush, and with the brush contact pieces 40.40 divided into left and right sides on the free end side of the brush being biased upward, these contact pieces 40.40 connect to the above-mentioned resistance board 1.
The brush 19 is biased against the lower surface of the movable piece 23.
By sliding together with the resistance board 18 and displacing the contact position with the resistance board 18, the resistance value for controlling the torque of the motor changes, thereby changing the torque of the motor.

Note that the brush 19 is normally positioned so as to be biased to one side together with the movable piece 23, and is set to have a maximum resistance value on this negative side and a minimum resistance value on the other side.

Furthermore, upper slide protrusions 34 corresponding to the above-mentioned slide guide surfaces 33 are provided at the four corners of the upper surface of the movable piece 23, and spring seat holes 41 are formed at the rear end of the lower surface. One end of the return spring 24 is inserted into this spring seat hole 41, and the other end is inserted and locked into a spring seat hole 42 formed on the rear end side of the switch case 13, which will be described later.
Normally, the movable piece 23 is biased forward by the biasing action of the return spring 24 stored in a compressed state.

Further, the lower front end side of the movable piece 23 is opened with an operating shaft engagement hole 43 into which the operating shaft of the operating lever described later is inserted, and the movable piece 23 is moved by the downward stroke of the operating lever via the operating shaft. , is operated by sliding in the front and rear directions.

The above-mentioned switch case 13 is provided in a box shape with an open top surface, and the above-mentioned movable piece 23 is accommodated within this top surface opening 44 while being allowed to slide in the front and back direction, and the printed circuit board 17 and the power transistor 14 are placed above the movable piece 23 . are placed through the heat dissipation covers 15, 16, and the respective square holes 27, 29, . 3
0... and are integrally attached.

Further, several terminal mounting grooves 46 are formed in the rear side wall 45 of the top opening 44, and the terminal mounting grooves 46 on both outer sides have a first power terminal 47 and a second terminal mounting groove. 'Fi
The source terminal 48 is inserted, and the terminal mounting groove 46 between them...
- includes a first motor terminal 49 and a second motor terminal 50;
The circuit connection terminals 51 are respectively inserted and installed.

As a result, the first IT source terminal 47 and the first motor terminal 49 are opposed to each other, and the second power source terminal 48 and the second
A pair of motor terminals 50 face each other, and the above-mentioned vertical pieces 36 and 37 of the movable piece are slidably sandwiched between the circular arc-shaped contact portions 52 and 52 of the opposing tips. The first motor terminal 46 and the second motor terminal 50 are connected to the first motor terminal 46 and the second motor terminal 50.
The movable contact pieces 20 are in contact with each other, and as the movable piece 23 is slid, the second and third movable contact pieces 21
．． 22.

Furthermore, the rear ends of these terminals are located outside the switch case 13, and are provided with appropriate transistor terminal insertion holes 53, and protrusions 54 for connecting printed circuit boards.
and a connection hole 55 for connecting a lead wire are formed, of which the terminal 25 of the power transistor described above is directly soldered and connected to the transistor terminal insertion hole 53. Since this connection is made outside the switch case 13, soldering is easy and the connection can be made easily. Further, the protrusion 54 for connecting the printed circuit board is fitted into the terminal connection hole 32 of the printed circuit board and then soldered. On the other hand, the first
- The second Ti source terminals 47 and 48 are connected to the electrodes of the battery, and the first and second motor terminals 49 and 50 are connected to the normal direction changeover switch of the motor.

Note that the circuit connection terminal 51 connects the control circuits of the power transistor 14 and the printed circuit board 17 to each other.

A spacer 56 is provided opposite to the upper surface side of these terminals 47 to 51, and this spacer 56 is inserted and fixed to the upper center of the rear side wall 45 of the switch case. While being pressed down by the mounting action, each terminal 4 is
7 to 51 are pressed down to prevent the terminal from coming out.Furthermore, a hanging piece 57 is provided hanging down at the center of the lower surface as a part of the spring seat hole 42 on the rear side of the switch case, and this spacer 56 is also provided. This effectively seals the rear end of the switch case and improves dust resistance.

In addition, a pair of long grooves 58 and 58 for guiding the movable piece slide are carved on both sides of the bottom surface of the top opening 44, and furthermore, in the center of the bottom surface, an operation shaft insertion hole 59 opened along the front and rear direction. is provided, and an operating shaft of an operating lever, which will be described later, is inserted through this operating shaft insertion hole 59.

Furthermore, a support piece 60 is vertically provided on the lower surface of the switch case 13, and this support piece 60 has a communication groove 61 that communicates with the operation shaft insertion hole 59 in the front-rear direction on the upper side, and A pivot pin 62.62 is provided protruding from the outer surface, and an operating lever, which will be described later, is pivotally attached to this pivot pin 62.62.

The above-mentioned operating lever 12 is provided in a half-cylindrical shape, and this cylindrical surface is set as a push-down operation surface 63 on the front side, and pivot holes 64, 64 protruding from the peripheral outer surface of the lower part of this lever are provided. By being pivotally connected to the above-mentioned pivot pins 62, 62, the operating lever 12 can be tilted forward and backward using the pivot point at the lower end as a fulcrum. The upper end of the communication groove 61 and the operating shaft insertion hole 59
The movable piece 23 is engaged with the operating shaft engagement hole 43 of the movable piece through the .

In this case, the operating lever 12 tilts around the pivot point at the lower end as a fulcrum, so even if the amount of tilting of this lever is relatively small, the upper part is thicker (tilting and can take a large stroke, so it is useful for power tools). When installed, the protrusion of the operating lever 12 is not too thick (it is in a state where it is easy to press down without protruding).

Further, in the operation shaft insertion hole 59, a first seal cover 66 having a hollow rectangular shape is arranged such that the upper part faces the first seal cover in the same shape and the lower part surrounds the operation shaft 65.
A bellows-shaped second seal cover 67 is provided, which is engaged with the lower part of the operating shaft. It is crimped and fixed in place to prevent dust from entering from below the switch case.

The DC 112 power tool switch configured in this way is
The operating lever 12 is disposed in a grip of a power tool, and is normally in a state in which it is biased and can be pressed down so that it projects obliquely forward from the front surface of the grip with its lower end as a fulcrum.

By pressing down this operation lever 12, the movable piece 23 interlocked with this lever slides rearward, and in this sliding process, the first and second motor terminals 49.
The arc-shaped contact portions 52, 52 of 0 are separated from the first movable contact piece 20 and become non-contact, and at the same time, the first power terminal 47 and the first motor terminal 49 come into contact with the second movable contact piece 21.

As a result, the power is turned on and the motor starts.

At this time, by adjusting the stroke based on the pressing stroke of the operating lever 12, the contact position between the brush 19 and the resistance board 18 via the speed change control circuit of the power transistor 14 is displaced, so that the torque of the motor can be varied. controlled and adjusted to the desired output torque suitable for the usage situation of the power tool.

Then, when the operating lever 12 is pressed down to one full stroke, the movable piece 23 slides to the rear end position, and the second power terminal 48 and the second motor terminal 50 come into contact with the third movable contact piece 22 .

As a result, the power transistor 14 of the speed change control circuit is short-circuited, the motor torque is fully opened, and high output is achieved.

Next, when the pressing operation of the operating lever 12 is released, the movable piece 23 slides toward the front end side under the return action of the return spring 24, and the operating lever also returns to its original tilted state.
And the first and second power supply terminals 47.48 connected to this
Then, the second and third movable contact pieces 21 and 22 come out of contact, and the power is turned off.

In this case, at the same time as the power is turned off, the first and second motor terminals 49 and 50 respectively contact the original first movable contact piece 20, and this contact action causes the power to be turned off.
After this occurs, a back electromotive force is generated on the motor side that rotates due to inertia, and this back electromotive force applies a braking effect to the motor, instantly stopping the rotation of the motor and performing OFF control suitable for operating the power tool. can get.

As mentioned above, the motor is turned on/off and the speed is controlled based on the pressing operation of the operation lever. However, since the lever to be pressed is tilted with its lower part as a fulcrum, the upper side of the lever is Due to the structure in which the switch tilts significantly and the internal movable piece slides significantly, a large slide stroke can be obtained in relation to the amount of push operation, making it a switch with good operating performance suitable for a control lever for a power tool.

Regarding the correspondence between the structure of this invention and the above-described embodiments, the operating lever of this invention corresponds to the operating lever 12 of the embodiment, the switch case corresponds to the switch case 13, and the movable piece corresponds to the operating lever 12 of the embodiment. , corresponds to the movable piece 23, and the support piece corresponds to the support piece 60. However, the present invention is not limited to the configuration of the above-described embodiment.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, FIG. 1 is an exploded perspective view of a switch for a DC power tool, FIG. 2 is a cross-sectional plan view of a main part of the switch for a DC power tool, and FIG. 3 is a switch for a DC power tool. FIG. 12... Operating lever 13... Switch case 23... Movable piece 60... Supporting piece A^6 --N(lO

Claims (1)

[Claims] 1. A switch for a power tool that controls driving of a motor based on a pressing operation of an operating lever, the operating lever comprising:
A switch for a power tool, in which the upper part is engaged with a movable piece that switches between contact parts of a switch mechanism, and the lower part is pivotally connected to the lower end of a support piece hanging vertically from a switch case.