JPH04304975A - Speed change gear of motor-driven tool - Google Patents

Abstract

PURPOSE:To perform smooth gear shift action regardless of whether a tool is operated or stopped and to achieve good efficiency, miniaturization and weight reduction of a speed change gear. CONSTITUTION:A spring 13 is held by a gear shift lever 9 provided to an outer frame 14 and has both ends sandwiched between walls provided to a shift arm 15 and has one end engaged in a clutch 12: When a tool is stopped the gear shift lever is moved and then the shift arm is moved via a spring and the clutch is connected to an aimed gear; when the clutch is not fitted with the gear the spring is compressed and the clutch is pressed by the resiliency of the spring, so that when the tool starts to rotate the gear and the clutch are fitted with each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission for a power tool.

0002

2. Description of the Related Art FIG. 3 shows a conventional example of a transmission device for a power tool. In the figure, the rotation of motor shaft 1 passes through pinion 2, first gear 3, and second pinions 4 and 5.
transmitted to. The second pinions 4 and 5 mesh with integrally formed final gears 6 and 7, respectively. The final gears 6 and 7 are spline-fitted to a spindle 8 and are moved on the spindle 8 by a speed change lever 9. That is, when either the final gear 6 and the second pinion 4 or the final gear 7 and the second pinion 5 mesh with each other, the gear ratio changes and a speed change operation is performed.

FIG. 4 shows another example of a conventional transmission. As shown in the figure, the rotation of the motor shaft 1 is transmitted to second pinions 4 and 5 via a first gear 3. The second pinions 4 and 5 mesh with a high speed gear 10 and a low speed gear 11, which are rotatably fitted into the spindle 8, respectively, and the high speed gear 10
and the low-speed gear 11 is a clutch 12 which fits into the protrusion 9a of the speed change lever 9 at its outer periphery and is movable in the axial direction by fitting into a spline formed on the spindle 8.
are arranged. When the gear shift lever 9 is rotated, the clutch 12 moves on the spindle 8 and fits into the clutch boss 12a provided on the side of the clutch 12 and the clutch hole 12c provided in the high speed gear 10 or the low speed gear 11. In the figure, it is fitted with the low speed gear 11). On the other hand, the gear (high-speed gear 10 in the figure) that is not fitted into the clutch boss 12a and the clutch hole 12c is idle relative to the spindle 8, so the rotation of the motor shaft 1 is caused by the second pinion 5 and the low-speed gear 11. transmitted between. When the clutch 12 is moved rearward from this state, rotation is transmitted between the second pinion 4 and the high speed gear 10, and a speed change operation is performed. When performing a gear shifting operation, even if the clutch boss 12a and the clutch hole 12c do not match, the high speed gear 10 and the low speed gear 11 are each urged from the outside in the direction of the clutch 12 by the spring 13, so that the motor When the shaft 1 starts to rotate, the elasticity of the spring 13 naturally brings the clutch boss 12a and the clutch hole 12c into a fitted state.

[0004] Furthermore, although the configuration is different, as a transmission of the same type, there is the U.S. Publication No. 51-30232 or the U.S. Publication No. 58-1146.
It is disclosed in Publication No. 2. In Japanese Utility Model Publication No. 51-30232, a pair of final gears equipped with springs are opposed to each other and biased inwardly, similar to the example shown in Fig. 4, and the gear shift operation is performed by disengaging the clutch teeth arranged between them. It is something. Further, in Japanese Utility Model Publication No. 58-11462, a spring is incorporated in a clutch device disposed between a pair of opposing final gears. In any of these cases, even if the clutch is not engaged during the speed change operation, the clutch is configured to be engaged naturally by starting the tool.

[0005]

[Problems to be Solved by the Invention] The above-mentioned prior art has the following drawbacks. In the known example shown in FIG. 3, since the final gear is directly moved by the speed change lever, it is impossible to change the speed while the tool is in use, that is, while the motor is rotating, and if the speed change is forced, teeth will be lost. Furthermore, if the gear does not engage with the second pinion when the gear is changed while the tool is stopped, the spindle must be manually rotated to engage the second pinion. Further, due to its configuration, the final gear has to be thick, and a space is required to move the final gear back and forth, which is an obstacle to making the entire device smaller and lighter.

4 and Japanese Utility Model Publication No. 51-30232 both cover the shortcomings of the known example shown in FIG. 3, but both final gears are biased from the outside by springs. , friction occurs at various places. For example, friction loss is particularly large between the spring and the final gear, and between both final gears (in Utility Model Publication No. 51-30232, the final gears are not involved in gear shifting) and the gear shift lever, resulting in reduced work efficiency and parts wear. This was the main cause. In particular, cordless tools, which have recently become the mainstream of portable power tools, use a limited amount of energy in the form of storage batteries, so friction loss immediately reduces the amount of work, and frequent charging of the storage battery is required, which significantly reduces work efficiency. This was the main cause of the decline.

[0007]Although the Japanese Utility Model Publication No. 11462/1988 compensates for the drawbacks of the above-mentioned conventional example, it has a complicated structure, is difficult to assemble, and has restrictions on the shape of parts, so its usable range is extremely narrow.

The present invention has been developed in view of the above points, and allows the gear change to be carried out smoothly and without tooth loss whether the tool is in use or stopped, and the motor It is an object of the present invention to provide a transmission device for a power tool that minimizes friction loss in rotation to achieve high efficiency, has a simple component configuration, and can be applied to a wide range of applications.

[0009]

[Means for Solving the Problems] The above object is to provide a transmission with a transmission lever provided on an outer frame of the transmission and movable in the axial direction of a shaft, a spring held on the transmission lever, and a spring held on the transmission lever. This is achieved by holding both ends of a spring so that it operates in response to the movement of the gear shift lever, and by constructing a shift arm that is partially engaged with a clutch.

0010

[Operation] Since the above means is provided, when the gear shift lever is moved while the tool is stopped, the shift arm moves via the spring, and the clutch and the target gear are engaged. If the clutch and gear do not engage, the spring will be compressed,
The restoring force of the spring presses the clutch, and as soon as the tool begins to rotate, the gear and clutch become engaged.

[0011]

[Examples] Next, the present invention will be explained in detail with reference to Examples.

[Embodiment 1] An embodiment of the present invention is shown in FIGS. 1 and 2. Note that parts that are the same as those in the conventional model are given the same reference numerals, and therefore their explanations will be omitted. In this embodiment, the transmission is provided in the outer frame 14 of the transmission, and the shaft (
a speed change lever 9 movable in the axial direction of the spindle) 8;
A spring 13 held by the gear shift lever 9 and a shift arm 15 which pinches both ends of the spring 13 and operates in response to the movement of the gear shift lever 9, and a portion of which is engaged with the clutch 12. I had it and composed it. By doing this, when the shift lever 9 is moved while the tool is stopped, the shift arm 15 is moved via the spring 13, and the clutch 12 is connected to the target gear (high speed gear 10 or low speed gear 11). If the clutch 12 and the gear (high-speed gear 10 or low-speed gear 11) are not engaged, the spring 13 is compressed, and the restoring force of the spring 13 presses the clutch 12, and the tool When the tool starts to rotate, the gear 10 or gear 11 and the clutch 12 are quickly engaged, so that the gear shift is smooth whether the tool is in use or stopped, and no tooth loss occurs. Therefore, it is possible to obtain a transmission device for a power tool, which is capable of rotating the motor without friction, minimizes friction loss, increases the efficiency of motor rotation, has a simple component configuration, and can be used in a wide range of applications.

That is, the rotation of the motor shaft 1 is caused by the pinion 2,
It is transmitted to second pinions 4 and 5 via first gear 3. The second pinions 4 and 5 are rotatably fitted into the spindle 8 and mesh with a high speed gear 10 and a low speed gear 11, which are prevented from moving on the shaft by a retaining ring 16 and a key 17, respectively. There is a key 1 between high speed gear 10 and low speed gear 11.
7, a clutch 12 is arranged so as to be able to rotate together with the spindle 8 and move back and forth. clutch 12
Clutch bosses 12a and 12b that fit into clutch holes 12c and 12d formed in the high-speed gear 10 and low-speed gear 11, respectively, are provided on the side surfaces of the gear. A spring 1 is held in a spring chamber 9b of a gear shift lever 9 which is held between an outer frame 14 of an electric screwdriver so as to move back and forth.
Both ends of the gear shift lever 3 are held by protrusions 15a formed on the shift arm 15 that fit into the grooves of the clutch 12, and the protrusions 15a fit into a slit 9c provided in the gear shift lever 9. The shift arm 15 and clutch 12 move back and forth in response to the movement.

When the shift lever 9 is moved forward in the transmission device configured as described above, the shift arm 15 and the clutch 12 are moved forward via the spring 13. Further, when the clutch boss 12b is fitted into the clutch hole 12d, the low speed gear 11 is coupled to the spindle 8, and the rotation of the second pinion 5 is transmitted to the spindle 8. On the other hand, if the clutch boss 12b does not fit into the clutch hole 12d, only the gear shift lever 9 moves forward and the clutch boss 12b does not fit into the clutch hole 12d.
b comes into contact with the side surface of the low speed gear 11, and the shift arm 15 cannot move forward. But spring 1
3 is held in the spring chamber 9b, so the shift arm 1
5 continues to be biased by the spring 13, and when the motor shaft 1 starts rotating, the low speed gear 11 rotates via the second pinion 5, and the clutch hole 12d matches the position of the clutch boss 12b, and at the same time the clutch 12 is pushed forward, the clutch boss 12b and the clutch hole 12d are fitted, and the spindle 8 starts rotating. When the gear shift lever 9 is moved rearward from this state, the clutch boss 12b and the clutch hole 12d are disengaged, and
Both the low speed gear 11 and the high speed gear 10 become free with respect to the spindle 8, and the rotation of the motor shaft 1 is no longer transmitted to the spindle 8. When the gear shift lever 9 is further moved rearward, the clutch boss 12a and the clutch hole 1
2c are fitted, and the spindle 8 and high speed gear 10
are combined. Clutch boss 12a and clutch hole 12
If c does not fit, it is the same as moving the shift lever 9 forward, and the explanation will be omitted.

The above is an explanation when the tool is in a stopped state, but even if the tool is switched during operation, the shift arm 15 is continuously pressed by the spring 13, so the clutch boss 12a is quickly fitted into the clutch hole 12c. The gears are shifted.

As described above, according to this embodiment, a pair of high-speed gears and low-speed gears are loosely fitted on the spindle at a constant interval, and are arranged so that they can rotate together with the spindle and move in the axial direction of the spindle. The shift arm engaged with the gear shift lever uses a spring to constantly apply elastic force to the gear to be engaged and move the clutch, and the clutch, high-speed gear, and low-speed gear. Since the coupling with the gear is performed at a portion other than the teeth, the following effects can be achieved.

(1) Even when the tool is in operation, switching can be performed without causing problems such as chipping of tooth tips.

(2) Even if the clutch is not engaged due to switching while the tool is stopped, the clutch will be engaged naturally when the tool starts operating.

(3) A space for moving the thick final gear is no longer required, making it possible to reduce the size and weight of the transmission and, by extension, the entire tool.

(4) The spring does not come into contact with rotating parts, so friction loss is extremely small, and high efficiency of the tool can be achieved.

(5) The shape of the parts that hold the spring and the shape of the clutch are not limited to each other, and the transmission according to the present invention has a wide range of applications.

[0022]

[Effects of the Invention] As mentioned above, the present invention provides the following advantages:
Even when stopped, gear changes are performed smoothly and without tooth loss, and the motor rotation is highly efficient by minimizing friction loss, and the component configuration is simple and easy to use. This makes it possible to widen the range, allowing smooth gear changes and no tooth loss whether the tool is in use or stopped, as well as reducing friction loss in the rotation of the motor. It is possible to obtain a transmission device for a power tool that is minimized and highly efficient, has a simple component configuration, and can be applied to a wide range of applications.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of an embodiment of a transmission device for a power tool according to the present invention.

FIG. 2 is an exploded perspective view of the transmission shown in FIG. 1;

FIG. 3 is a longitudinal side view of a conventional power tool transmission.

FIG. 4 is a longitudinal side view of another example of a conventional power tool transmission.

[Explanation of symbols]

8...Spindle, 9...Shift lever, 10...High speed gear, 11...Low speed gear, 12...Clutch, 13
...Spring, 14...Outer frame, 15...Shift arm.

Claims (1)

[Claims] 1. A transmission for a power tool in which a clutch meshing with a plurality of gears is moved in the axial direction of a shaft supporting the gears to change the gear ratio, the transmission being provided in an outer frame of the transmission. a gear lever that is movable in the axial direction of the shaft; a spring held by the gear lever; and a spring held at both ends of the spring that operates in response to the movement of the gear lever; A transmission device for a power tool, characterized in that the transmission device includes a shift arm that is engaged with the clutch.