JP2001170877A - Power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power tool in which noises produced by an air current from a runner is reduced. SOLUTION: In this power tool such as a grinder, a motor, and a runner installed on a rotary shaft of the motor are provided inside a casing, a tool body is connected to the rotary shaft of the motor, so the tool body is driven by the motor, and the runner is rotated by the motor, so a high speed air current is generated around the motor for cooling the motor. In this power tool, a flow passage forming member 20 is disposed to face the runner 4. In the flow passage forming member 20, four scrolls 21 are formed on a surface on the side of the runner 4, and discharge flow passages 23 communicated with the scrolls 21 are formed on a surface on the opposite side to the runner 4. The high speed air current from the runner 4 is speed-reduced by the scrolls 21, and then it is discharged out of the casing.

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 grinder, and more particularly to a power tool in which an impeller is mounted on a rotating shaft of a motor, and the impeller rotates to cool the motor.

[0002]

2. Description of the Related Art Generally, an electric tool such as a grinder is provided with a motor and a tool connected to a rotating shaft of the motor, and the motor is used to drive the tool to process a workpiece. Further, an impeller is attached to the rotating shaft of the motor, and the impeller is also rotated by the motor at the same time that the tool is driven to rotate, thereby generating a flow of air around the motor, thereby cooling the motor. . Usually, the motor and the impeller are housed in a box-shaped casing, and only the tools are exposed outside the casing, so that handling is convenient.

[0003]

However, according to the above-mentioned prior art, when the air accelerated by the impeller flows out of the casing to the outside, a loud noise is generated, and a person who operates the power tool and a surrounding area are operated. There is the problem of giving people discomfort. That is, in the conventional power tool, a plurality of holes are formed in the casing, and a high-speed airflow from the impeller is discharged to the outside through the holes.
When the air passes through the holes, it generates loud noises, such as jet noise.

[0004] It is an object of the present invention to provide a power tool that reduces noise generated by airflow from an impeller.

[0005]

In order to achieve the above object, the present invention provides a motor having a motor and an impeller mounted on a rotating shaft of the motor, wherein the rotating shaft of the motor is provided inside the casing. A tool body is connected, and the tool body is driven by the motor, and the impeller is rotated by the motor, thereby generating a high-speed airflow around the motor to cool the motor. In the power tool, a plurality of scrolls are provided on the outer periphery of the impeller,
A high-speed airflow from the impeller is guided to the outside of the casing via the plurality of scrolls.

According to the above configuration, the high-speed airflow from the impeller after the motor is cooled is reduced when passing through the scroll, so that the air flows out to the outside through the plurality of holes formed in the casing. Noise at the time of operation can be reduced.

According to the present invention, a flow path forming member is disposed to face the impeller, and the flow path forming member has the plurality of scrolls on a surface on the impeller side opposite to the impeller. A discharge channel communicating with the scroll is formed on the side surface. According to this structure, the high-speed airflow from the impeller is decelerated by the scroll and then rectified in the discharge passage, so that noise in the plurality of holes in the casing can be further reduced. In addition, since both surfaces of the flow path forming member can be effectively used, and since the discharge flow path does not hit the impeller, there is an advantage that the position of the discharge flow path can be freely set.

Further, in the present invention, the flow path forming member is provided with a partition wall for partitioning adjacent scrolls, and the leading end of the partition wall has an intermediate portion in a direction opposite to the air flow from the impeller. The scroll is characterized in that it protrudes in the shape of a chevron, and the vicinity including the protruding portion is bent outward in the radial direction of the scroll. According to this configuration, it is possible to reduce noise generated when the high-speed airflow from the impeller collides with the tip of the partition wall.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a grinder as an electric tool according to the present invention. In FIG. 1, a grinder 1 has a motor 2 and an impeller 4 attached to a rotating shaft 3 of the motor 2. The motor 2 and the impeller 4 are housed in a casing 5. A bevel gear 6 is attached to the tip of the rotating shaft 3 of the motor 2, and this bevel gear 6 meshes with a bevel gear 7 attached to a rotating shaft 8 of a grindstone 9. The casing 5 has a plurality of holes 10 for discharging the airflow from the impeller 4 to the outside.

In the present embodiment, the flow path forming block 20 is disposed so as to face the impeller 4. The details of the flow path forming block 20 will be described with reference to FIGS. FIG. 2 is an arrow view along the line AA in FIG.
0 and the impeller 4 are shown. FIG. 3 is also a view taken along the line AA, but with the impeller removed, and is a perspective view showing only the flow path forming block 20. FIG. 4 is an arrow view along the line BB in FIG.
Only shown. FIG. 5 is also a view taken along line BB, and is a perspective view of the flow path forming block 20.

As shown in FIGS. 2 and 3, four scrolls 21 are formed on the surface of the flow path forming block 20 on the side of the impeller 4 so as to face the outer periphery of the impeller 4. The scroll 21 has a flow path cross-sectional area of the air flow (the impeller 4).
Along with the high-speed air flow a) at a rate of about 4 degrees. A partition wall 22 is provided to partition adjacent scrolls 21 from each other. The number of scrolls 21 is not limited to four,
It may be two, three or five or more. Further, in the drawing, reference numeral 4A indicates the blade of the impeller 4, and arrow b indicates the rotation direction of the impeller 4. Further, as shown in FIGS. The scroll 21 is connected to the scroll 21 on the opposite side of the car 4.
A, and a discharge channel 23 is provided in communication with the scroll 21A. Similarly to the scroll 21, the scroll 21A is formed such that its flow path cross-sectional area gradually increases at a rate of about 4 degrees along the air flow a. The cross-sectional area of the discharge channel 23 does not increase along the air flow direction a, and is substantially the same at any position. Further, a discharge port 24 is formed at the tip of the discharge channel 23. The discharge ports 24 are provided at four corners of the flow path forming block 20. In addition, the discharge port 24 can be provided at a position facing the hole 10 of the casing 5.

When the motor 2 is rotated in the electric tool having the above configuration, the grindstone 9 is driven to rotate via the rotating shaft 3, bevel gears 6 and 7, and the rotating shaft 8. At the same time, the impeller 4 is rotationally driven, and external air is sucked into the casing 5 as shown by arrows c and d in FIG. 1 and flows through the casing 5 as shown by arrow e, whereby the motor 2 is cooled. You. The air after cooling the motor 2 passes through the impeller 4 as indicated by an arrow f.
Thereafter, as shown by the arrow g, it flows through the scrolls 21 and 21A of the flow path forming block 20 and the discharge flow path 23, and is further discharged from the hole 10 to the outside of the casing 5 through the discharge port 24 as shown by the arrow h.

Although the air flow flowing from the impeller 4 into the scroll 21 is as high as 80 m / s, it flows in because the flow path cross-sectional area of the scroll 21 is gradually increased in the direction of the air flow a. The airflow is decelerated when passing through the scroll 21. The scroll 21A is separated from the impeller 4 by the partition wall 22, but since the flow path is an extension of the scroll 21, the airflow is further decelerated when passing through the scroll 21A. Then, in the scrolls 21 and 21A, the velocity energy of the air flow is converted into pressure (static pressure) energy, and at the outlet of the scroll 21A, the air flow becomes low at about 25 m / s. further,
The low-velocity airflow is rectified when passing through the discharge flow path 23, and thereafter is discharged to the outside through the hole 10 of the casing 5 through the discharge port 24.

As described above, the airflow flowing out of the impeller 4 at a high speed of 80 m / s is
At 1 A, the speed is gradually reduced to about 25 m / s, which is reduced to about 1/3 as compared with the flow velocity at the exit of the impeller 4, so that the noise when passing through the hole 10 of the casing 5 is reduced. be able to. In the present embodiment, the noise can be reduced by about 6 dB as compared with a conventional jet sound in which a high-speed airflow flows out of the hole 10 of the casing 5 as it is conventionally.

As a whole, between the inlet of the scroll 21 and the outlet of the scroll 21A, the static pressure of the air flow increases each time the air flow decelerates, so that the static pressure of the turbo fan increases. , The intersection (operating point) between the turbo fan and the power tool ventilation system shifts to the large air volume range,
The motor cooling air volume is also increased, and the reliability of the motor of the power tool is greatly improved.

FIG. 7 shows a flow path forming block 20 'according to a modification of the present embodiment. The leading end of the partition wall 22 that separates the adjacent scrolls 21 from each other has an intermediate portion projecting in a chevron shape in a direction opposite to the air flow a from the impeller 4, and the vicinity including the projecting portion has a scroll 2.
1 is bent outward in the radial direction. Near the tip of the partition wall 22, the blade 4A of the impeller 4 (FIG. 2)
Each time the air passes through the front end of the partition wall 22, the air is compressed, so that the air flow is disturbed and causes noise.

In this modification, the intermediate portion at the front end of the partition wall 22 projects in a chevron shape, and the vicinity including the projecting portion is bent radially outward of the scroll 21 so as to have a V shape. Even when the blade 4A passes through, the air is not compressed, so that the flow of the air flow becomes smooth and the generation of noise can be suppressed.

Although the above embodiment has been described with respect to a grinder, the present invention is not limited to a grinder, but can be applied to an electric saw or the like.

[0019]

As described above, according to the present invention,
Since a plurality of scrolls are provided on the outer circumference of the impeller, the airflow from the impeller can be reduced by passing through the scroll, thereby suppressing the generation of noise due to the high-speed airflow from the impeller. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a power tool according to the present invention.

FIG. 2 is an arrow view of a flow path forming block viewed along the line AA in FIG. 1;

FIG. 3 is a perspective view of a flow path forming block shown in FIG.

FIG. 4 is an arrow view of the flow path forming block as viewed along the line BB in FIG. 1;

FIG. 5 is a perspective view of the flow path forming block shown in FIG.

FIG. 6 is a diagram illustrating a positional relationship between flow paths formed in a flow path forming block.

FIG. 7 is a perspective view of a flow path forming block according to a modification of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Grinder 2 Motor 3,8 Rotating shaft 4 Impeller 5 Casing 6,7 Bevel gear 9 Grindstone (tool main body) 10 Hole formed in casing 20,20 'Flow path forming block (flow path forming member) 21,21A Scroll 22 Partition wall 23 Discharge channel 24 Discharge port

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mitsuyuki Ishikawa 6-2, Otemachi 2-chome, Chiyoda-ku, Tokyo Inside Nippon Koki Co., Ltd. No. 2 F-term in Hitachi Koki Co., Ltd. (reference) 3C047 FF07 JJ16 3C058 AA02 AA14 BC02 CB06 5H609 BB12 BB18 PP01 PP02 PP05 PP06 QQ02 QQ12 QQ13 QQ15 RR07 RR16 RR24 RR27 RR33 RR36 RR40 RR42 RR43 RR42 RR43

Claims (3)

[Claims] A motor and an impeller mounted on a rotating shaft of the motor are provided inside a casing, and a tool body is connected to the rotating shaft of the motor, and the tool body is driven by the motor. On the other hand, by rotating the impeller with the motor, to generate a high-speed airflow around the motor to cool the motor, an electric tool having a configuration in which a plurality of scrolls are provided on the outer periphery of the impeller, A power tool for guiding a high-speed airflow from the impeller to the outside of the casing via the plurality of scrolls. 2. The power tool according to claim 1, wherein a flow path forming member is disposed to face the impeller, and the flow path forming member has the plurality of scrolls on a surface on the impeller side. A power tool, wherein a discharge channel communicating with the scroll is formed on a surface opposite to the impeller. 3. The power tool according to claim 2, wherein the flow path forming member is provided with a partition wall for partitioning adjacent scrolls, and a tip of the partition wall has an intermediate portion in which air from the impeller is formed. A power tool characterized in that it protrudes in a chevron shape in the direction opposite to the flow, and that its vicinity including the protruding portion is bent radially outward in a scroll shape.