JP3289958B2 - Transmission of rotary power tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission for automatically performing a shift operation in a rotary electric tool such as an electric screwdriver.

[0002]

2. Description of the Related Art It is most desirable for a rotary electric tool such as an electric screwdriver, an electric wrench, and an electric drill to be able to work at high speed and high torque, but the output is limited. For this reason, a low torque / high speed rotation state and a high torque / low speed rotation state are actually switched according to the load condition.

[0003]

For this purpose, there has been provided a device equipped with a speed reducer capable of changing the speed, but the conventional device changes the speed only by the switching operation of the user. Which reduction ratio (output characteristic) is selected by the operation is determined by the user. In order to make this switch, the work must be temporarily stopped. This means that, for example, when tightening a screw, high-speed, low-torque rotation is required until seating, and low-speed, high-torque rotation after seating is desired. Become.

[0004] The present invention has been made in view of such a point, and an object of the present invention is to perform a work in which it is desired to change the reduction ratio during the work without interrupting the work. Another object of the present invention is to provide a transmission for a rotary electric tool capable of obtaining high working efficiency.

[0005]

Means for Solving the Problems] Thus the present invention, Mo
Of the sun gear and gear case attached to the output shaft of the
Internal gear fixed to the surface, this sun gear and
A plurality of planetary gears and planetary gears meshing with the internal gear;
First stage planets composed of carriers that support
Mechanism and the carrier of the first stage planetary
Around the shaft with respect to the sun gear and gear case
The first stage is provided at the rear end in the axial direction.
The engagement part with the carrier in the planetary mechanism of the
Has an interface provided with an engagement portion with the gear case.
And a planetary gear connected to the output shaft.
With the second stage planetary mechanism formed, the output shaft in the axial direction
And can be moved back and forth in the axial direction.
Change the internal gear of the planetary
Movement of output shaft with respect to gear case in conjunction with axial movement
It is characterized in that it is formed so as to be movable in the direction opposite to the direction . At this time, the output shaft and gear case are
And move freely in the axial direction relative to the base.
The spring is urged in the axial direction by a spring,
Position of the internal gear in the body case
To be fixed, or if the output shaft is
The shaft is free to move in the axial direction with respect to
In the second direction, and
The gear rotates in conjunction with the axial movement of the output shaft.
Moves in the direction opposite to the direction of the output shaft
The gear case's axial position is
Can be configured to be fixed to the

[0006]

According to the present invention, the reduction ratio is automatically switched according to the magnitude of the force pressing the output shaft against the work surface.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. In the illustrated rotary electric tool, the rotation of the motor 8 is reduced by a speed reducer comprising a two-stage planetary mechanism, and a chuck 90 is provided. The output of the reduction gear is a sun gear 11 attached to the output shaft of the motor 8.
, An internal gear 12 fixed to the inner surface of the gear case 7, a plurality of planetary gears 13 meshing with the sun gear 11 and the internal gear 12, and a first stage planetary mechanism with a carrier 14 supporting these planetary gears 13. The sun gear 21 provided integrally with the carrier 14, the internal gear 22, and the planetary gear 23 constitute a second stage planetary mechanism. The planet gears 23 are gear case 7
The output shaft 9 is supported by a rear end of the output shaft 9 supported by a bearing 91.

The internal gear 22 in the second stage planetary mechanism is provided so as to be rotatable around an axis and movable in the axial direction, and has an axial rear end. An engagement portion with the carrier 14 in the first-stage planetary mechanism has a gear case 7 at the front end in the axial direction.
When the internal gear 22 is engaged with the carrier 14 as shown in FIG. 1, the carrier 14 and the second planet In order to directly connect with the output shaft 9 which is a carrier in the mechanism, the output shaft 9 is driven at low torque and high speed rotation, and the internal gear 22 moves forward to move the gear case 7.
Therefore, the output shaft 9 is driven at a high torque and a low speed because the second stage planetary mechanism is also decelerated.

An annular groove is formed on the outer peripheral surface of the internal gear 22, and the U-shaped transmission lever 51 having elasticity, which is held by the shafts 70, 70 on the outer surface of the gear case 7, is provided here. Both ends are engaged. As is apparent from FIG. 1, both ends of the speed change lever 51 are also engaged with engagement portions 52 provided on the inner surface of the main body case 1.

In this case, the motor 8 and the gear case 7 to which the motor 8 is fixed are housed so as to be movable in the axial direction of the output shaft 9 with respect to the main body case 1. It is urged in the axial direction by a spring 3 abutting on the end face. Accordingly, the output shaft 9 is also movable in the axial direction while being biased by the spring 3, and is attached to the tip end of the gear case 7 so as to be rotatable around the axis. Handle 6
Are also movable in the axial direction.

A rear end of the spring 3 is connected to a nut 3 screwed to a male screw 30 provided in a rear end of the main body case 1.
1 is received by the nut 31
And a disk 32 for engaging with the disk 3
2 and 4, the lever portion 33 is exposed to the outside through a long hole 36 provided in the main body case 1 and extending in the circumferential direction. In FIG. 2, reference numeral 19 denotes a battery pack removably housed in the grip portion of the main body case 1, and reference numeral 18 denotes a changeover switch for changing the rotation direction of the motor 8.

Thus, in this rotary electric tool,
Normally, the motor 8, the gear case 7, and the output shaft 9 are at positions advanced in the main body case 1 due to the urging by the spring 3, and the shift lever is provided on an engagement portion 52 provided on the inner surface of the main body case 1. The internal gear 22 connected via 51 is at a relatively retracted position. Accordingly, if the motor 8 is operated by pulling the trigger switch 40 shown in FIG. 2 in this state, the output shaft 9 is rotated at high speed and low torque as described above because the reduction gear is in the small reduction ratio setting state. Driven in state.

However, when the force for pressing the rotary power tool against the work surface is increased, such as after the screw is seated in the screw tightening operation, the output shaft 9, the gear case 7, and the motor 8 are moved relative to the body case 1 by a spring. 3, and at this time, as shown in FIG.
2 relatively moves forward and switches to a large reduction ratio in a low-speed rotation / high-torque state. If you reduce the force pressing on the work surface,
Since the motor 8, the gear case 7 and the output shaft 9 return by the bias of the spring 3, the motor 8 returns to the high-speed rotation / low-torque state. The pressing load value at which the speed change operation is performed can be adjusted by operating the lever portion 33 to rotate the disk 32 and screw the nut 31 receiving one end of the spring 3 forward and backward.

Further, in this rotary electric tool, by rotating the handle 6, the automatic shifting can be canceled to fix the high-speed rotation / low-torque state or the low-speed rotation / high-torque state. Has become. That is, as shown in FIG. 3, a pin 61 is provided on the outer peripheral surface of the handle 6 which is axially movable together with the gear case 7 by being attached to the gear case 7.
An engagement recess 62 into which the pin 61 fits is provided on the inner surface of the distal end portion of the main body case 1. This engagement recess 62 is provided in FIG.
As shown in the figure, the front-rear width is long at the center in the circumferential direction, the groove width is narrowed toward the front at one end, and narrow toward the rear at the other end, and the pin 61 is located at the center of the engagement recess 62. when doing,
Although the automatic shifting operation is permitted, if the handle 61 is rotated to position the pin 61 in a narrow groove width near the front of the engaging concave portion 62, the retreat of the handle 6 is not allowed. Since the retraction of the gear 7 and the reduction gear is not allowed, the lock is locked in the high-speed rotation / low-torque state. By rotating the handle 6 in the reverse direction, the pin 61 is shifted toward the rear of the engagement recess 62. When the steering wheel 6 and the gear case 7 are positioned in a narrow position, the steering wheel 6 and the gear case 7 are fixed at the retracted position, and the reduction ratio is locked in a large reduction ratio state of low-speed rotation and high torque.

FIGS. 7 and 8 show another embodiment. Although the motor 8 and the gear case 7 are fixed inside the main body case 1 here, the output shaft 9, the support 95 supporting the output shaft 9 and the handle 6 can be freely moved in the axial direction with respect to the main body case 1. In addition, the spring 3 is disposed between the gear case 7 and the support 95 to urge the output shaft 9 forward. Then, as shown in FIG.
1 is connected to a central portion by a connection bar 55. The output shaft 9 and the carrier 24 that supports the planetary gear 23 of the second stage planetary mechanism in the reduction gear are spline-coupled.

In this embodiment, the shift lever 51 supported by the shaft 70 on the outer surface of the gear case 7 also advances at its central portion, and the internal Since both end portions connected to the gear 22 are at the retracted position, they are in a high-speed rotation / low-torque state. When the output shaft 3 and the support 95 are retracted against the spring 3 by increasing the pressing load, the transmission lever 5
Since the central portion of the motor 1 is retracted and both ends connected to the internal gear 22 advance, the state is switched to the low-speed rotation / high torque state.

As shown in FIG. 9, the value of a load current flowing through the motor 8 is monitored by a current detection circuit 80, and when the load current exceeds a reference current value preset in a comparison circuit 81, an alarm means such as a buzzer is provided. Is provided, the user can confirm the shift timing.

[0018]

As described above, in the present invention, the second stage
Gears in the planetary gear mechanism of the car engage with the carrier
The first stage planetary mechanism
Output to directly connect the carrier and the output shaft.
The power shaft is driven with low torque and high speed rotation.
Rotating screws, as after a screw has been seated during
When the force that presses the power tool against the work surface is increased,
The output shaft retreats with respect to the case,
Internal gear in the star mechanism against the gear case
By moving forward in the axial direction, it engages with the gear case,
Since the second stage planetary mechanism is also decelerated,
The power shaft is driven with high torque and low speed rotation, and the reduction ratio is automatically switched according to the magnitude of the force pressing the output shaft against the work surface. When the torque is small, the pressing load can be small, and when the load torque is large, the pressing load is usually large.Therefore, it is possible to switch the reduction ratio in the middle of the work without interrupting the work. It can be performed and high working efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment.

FIG. 2 is a side view showing the entire rotary electric tool according to the first embodiment;

FIG. 3 is a cutaway side view of the same.

FIG. 4 is a transverse sectional view of the same.

FIG. 5 is a front view of a locking engagement recess.

FIG. 6 is a cross-sectional view showing a state at the time of shifting according to the first embodiment.

FIG. 7 is a sectional view of another embodiment.

FIG. 8 is a cutaway side view of the same.

FIG. 9 is a block circuit diagram of another example.

[Description of Signs] 1 Body case 7 Gear case 8 Motor 9 Output shaft 11 Sun gear 12 Internal gear 13 Planetary gear 14 Carrier 21 Sun gear 22 Internal gear 23 Planetary gear 51 Shift lever

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-34275 (JP, A) JP-A-64-34678 (JP, A) JP-A-62-224584 (JP, A) JP-A-4- 262151 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B25B 21/00 B25B 21/00 520

Claims (6)

(57) [Claims] A sun gear attached to an output shaft of a motor.
A, internal gear fixed to the inner surface of the gear case,
The sun gear and the internal gear
Consists of a planetary gear and a carrier that supports the planetary gear
First stage planetary mechanism and the first stage planetary
A shaft for the sun gear and gear case provided integrally with
It is provided so that it can rotate freely and is movable in the axial direction.
At the rear end in the direction, the engagement with the carrier in the first stage planetary mechanism
At the front end in the axial direction, there is an engagement part with the gear case.
Connected to the provided internal gear and output shaft
Equipped with a second stage planetary mechanism consisting of
The output shaft is urged in the axial direction and moves back and forth in the axial direction.
Movably formed internal gear in the second stage planetary mechanism
Gear in the gear case in conjunction with the axial movement of the output shaft.
On the other hand, it is formed to be movable in the direction opposite to the direction of movement of the output shaft.
A transmission for a rotary electric tool, comprising: 2. An output shaft and a gear case are attached to a main body case.
To move freely in the axial direction
It is biased in the axial direction.
The axial position of the internal gear is fixed to the body case
Transmission of the rotary power tool according to claim 1, characterized in that it is. 3. The output shaft is shifted in the axial direction with respect to the gear case.
It is movable and is urged in the axial direction by a spring.
The internal gear of the second stage planetary gear is output
In conjunction with the axial movement of the shaft, the output shaft
It is free to move in conjunction with the direction of movement,
The axial position of the gear case is fixed with respect to the body case.
It is transmission of rotational power tool of claim 1, wherein. 4. The transmission for a rotary electric tool according to claim 1, further comprising a lock means for inhibiting a shifting operation. 5. The transmission of a rotary electric tool according to claim 2, further comprising adjusting means for changing a spring load of the spring. 6. The transmission of a rotary electric tool according to claim 1, further comprising a notifying means for detecting a shift timing and notifying the shift timing.