JP2000117634A - Chip dust treatment structure for power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a reduction in the durability of a contact part or the like between a commutator and a carbon brush caused by damage given by chip dusts entering the inside of a case by being mixed in external air, for example a power grinder. SOLUTION: By this tool, a centrifugal fan 20 is attached to the other end of a motor shaft 4, and chip dusts of larger particle sizes entering from external air introducing ports 16 to 16 by the rotation of the centrifugal fan 20 are separated toward the outside of the diameter direction of the motor shaft 4. These chip dusts are caused to flow to chip dust separation windows L and A in separated states, and large-particle chip dusts are prevented from flowing to the periphery of a contact part between a commutator and a carbon brush.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing structure for reducing the influence of dust on an electric motor in an electric tool having a built-in electric motor.

[0002]

2. Description of the Related Art Normally, in this type of electric tool, a fan is attached to a motor shaft of an electric motor, the fan is rotated by starting the electric motor, and outside air is introduced from a rear portion of a case containing the electric motor. A structure for cooling the electric motor by the outside air is adopted.

[0003]

For this reason, it is easy to inhale dust from the outside air inlet at the rear of the case. Particularly in the case of an electric grinder, a large amount of dust containing relatively large particles is generated. When this enters the outside air inlet and passes through the inside of the case, for example, it enters the contact portion between the commutator of the electric motor and the carbon brush, damaging the contact portion or accelerating wear of the carbon brush (shortening of life). ). On the other hand, if you attach a filter to the outside air inlet of the case, for example,
Dust intrusion can be prevented to some extent, but this reduces the cooling efficiency. Conventionally, no effective countermeasure has been taken against this problem, so that priority has been given to cooling efficiency, so that the durability of the electric motor has to be sacrificed. SUMMARY OF THE INVENTION The present invention has been made in view of the above problem, and has as its object to provide a dust treatment structure capable of achieving both improvement in cooling efficiency and life of an electric motor.

[0004]

According to a first aspect of the present invention, there is provided a dust processing structure for an electric tool having a built-in electric motor, wherein a cooling fan attached to one end of a motor shaft of the electric motor has an outside air inlet of a case. A structure for treating dust entering the case mixed with the outside air introduced from the outside, wherein a centrifugal fan is attached to the other end of the motor shaft, and the centrifugal fan rotates to enter from the outside air inlet. The structure was such that the larger the particles, the more the dust was separated radially outward of the motor shaft. According to this dust treatment structure, the dust that has entered from the outside air introduction port is blown outward by a centrifugal fan in the radial direction of the motor shaft (on the wall surface side of the case) because the larger the dust, the larger the weight. On the other hand, the contact portion between the commutator and the carbon brush, the bearing for supporting the motor shaft, and the like are located relatively inside (the center of the case) in the radial direction of the motor shaft. From this, the relatively large dust blown radially outward by the centrifugal fan flows along the case wall while bypassing the center of the case, so that the contact point between the commutator and carbon brush located in the center of the case In addition, since it does not flow around a bearing or the like that supports the motor shaft (hereinafter, also referred to as “part concerned”), damage to such part can be prevented beforehand, and the durability of the power tool can be enhanced. In addition, since the configuration does not use the filter, the flow of the outside air is not hindered, and therefore, both high cooling efficiency and durability can be achieved.

[0005] The dust treatment structure according to the second aspect is the first aspect.
The dust processing structure according to the above, wherein a plurality of dust separation windows are formed in a radial direction of the motor shaft around the contact portion between the carbon brush and the commutator of the electric motor and downstream of the centrifugal fan. did. According to this dust treatment structure, in the contact portion between the carbon brush and the commutator and on the upstream side of the bearing supporting the motor shaft, the larger the dust, the more the dust flows through the outer dust separation window, so that the separation of the dust by the size of the particles Is performed more reliably.

[0006]

FIG. 1 shows an embodiment of the present invention.
A description will be given based on FIG. FIG. 1 shows a portable electric grinder 1 to which the dust treatment structure of the present embodiment is applied. The grinder 1 has a built-in electric motor 3 in a substantially cylindrical case 2 also serving as a handle. The motor shaft 4 of the electric motor 3 is connected to the case 2 by bearings 5 and 6.
It is rotatably supported at the approximate center. The output of the electric motor 3 is transmitted to the output shaft 10 through meshing between a bevel gear 8 attached to one end (left end in the figure) of the motor shaft 4 and a bevel gear 9 attached to the output shaft 10. Output shaft 10
Are rotatably supported by bearings 11 and 12 and rotate around an axis perpendicular to the motor shaft 4. A circular grindstone 13 is attached to the tip of the output shaft 10. The basic configuration of the grinder does not require any particular change compared to the prior art, and will not be described in detail.

A cooling fan 1 is provided at one end of the motor shaft 4.
5 is attached. When the motor shaft 4 rotates, the cooling fan 15 also rotates, whereby outside air is introduced from outside air introduction ports 16 to 16 provided at the rear part of the case 2, and the motor 3 is cooled by the outside air. After cooling the motor 3, the introduced outside air is blown out of the case 2 through a blowout port 17 provided in a front part of the case 2. That is, the rotation of the cooling fan 15 generates a flow of outside air (a flow of outside air from right to left in the figure) from the outside air inlet 16 to the outlet 17 inside the case 2. This is the same as the conventional case, and no particular change is required.

The other end of the motor shaft 4 has a centrifugal fan 2
0 is attached. By attaching the centrifugal fan 20 to the other end of the motor shaft 4, the contact portion between the commutator 3 a of the electric motor 3 and the carbon brush 18 and the bearing 6 supporting the motor shaft 4 are on the upstream side (right side in the figure). And is located downstream (left side in the figure) of the outside air introduction ports 16 to 16. Further, two layers of dust separation windows L and S are formed in the radial direction of the motor shaft 4 around the contact portion between the commutator 3a and the carbon brush 18 and downstream of the centrifugal fan 20. The dust separating windows L and S are defined by providing a substantially cylindrical inner wall 2a for dividing the inside of the case 2 into two layers in the radial direction of the motor shaft 4 inside the case 2 as shown in FIG. Is formed. The inner peripheral side of the inner wall 2a is a separation window S for small particles through which relatively small particles pass, and the space between the inner wall 2a and the case 2 becomes a separation window L for large particles through which relatively large particles pass. ing.

According to the dust treatment structure constructed as described above, when the motor 3 is started, the cooling fan 15 rotates, whereby the outside air inlets 16 to 16 are formed inside the case 2.
A flow of outside air from the air to the outlet 17 is generated. On the other hand, when the motor 3 is started, the grindstone 13 rotates and the workpiece can be ground. A large amount of dust generated by the grinding process is blown to the surroundings, mixed with the outside air, and enters the inside of the case 2 from the outside air introduction ports 16 to 16.

However, according to this embodiment, since the centrifugal fan 20 is attached to the rear end of the motor shaft 4,
Dust that has entered from the outside air inlets 16 to 16 is heavier due to the action of the centrifugal fan 20,
It is blown radially outward of the motor shaft 4. On the other hand, around the contact portion between the commutator 3a and the carbon brush 18 and downstream of the centrifugal fan 20, a separation window S for small particles on the inner peripheral side in the radial direction of the motor shaft 4 and a large particle separation window S on the outer peripheral side. A separation window L is formed. Therefore, the centrifugal fan 20
The large dust blown radially outward from the motor shaft 4 by the motor enters the large grain separation window L on the outer peripheral side. On the other hand, the small dust particles which are not blown off to the outer peripheral side by the centrifugal fan 20 and pass through the centrifugal fan 20 as they are in the flow of the outside air enter the small particle separating window S on the inner peripheral side.

As described above, the centrifugal fan 20 separates the dust into relatively large dust and relatively small dust, and the separated two types of dust are separated into the large-particle separation window L and the small-particle separation window S. Separated and flowing. The large dust and the small dust flowing in the separated state pass through the contact portion between the commutator 3a and the carbon brush 17 and the periphery of the bearing 6 in the axial direction of the motor shaft 4, and then the dust separation windows L, S Are merged, and then flow on the outside air in the merged state, and are finally blown out through the outlet 17.

As described above, according to the dust treatment structure of the present embodiment, in the contact portion between the commutator 3a and the carbon brush 18 and around the bearing 6, large dust is separated into the large grain separating window L on the outer peripheral side. As a result, the relevant portion is covered by the inner wall 2a, so that large particles are greatly prevented from entering the relevant portion, thereby preventing the carbon brush 17 and the commutator 3a from being worn or damaged. In addition, the bearing 6 can be prevented from being damaged, and the durability of the electric grinder 1 can be improved. And centrifugal fan 2
Since the structure is such that large particles are separated by 0 and not by a filter, the flow of outside air is not hindered, and thus the cooling efficiency is not sacrificed.

Various modifications can be made to the embodiment described above. For example, the dust separation windows L and S may be eliminated, and the dust may be separated only by the centrifugal fan 20. With such a configuration, the large dust is blown off toward the inner wall surface side of the case 2 and along the inner wall surface as it is. Therefore, the same effect as described above can be obtained. Therefore, the dust separation windows L and S may be provided as needed.

The dust separating window is exemplified by a configuration in which it is divided into two layers, a large particle separating window L and a small particle separating window S. However, even if the dust separating window is finely divided into three or more layers as long as the flow of outside air is not hindered. Good. Further, if there is sufficient space, the dust separating window may be formed longer in the axial direction of the motor shaft 4.

Finally, in the illustrated embodiment, the electric grinder 1 is illustrated as an example of the electric tool, but the present invention can be applied to other electric tools such as an electric drill, an electric circular saw, and the like.
The present invention can be widely applied to electric tools in which intrusion of dust is not a problem as in the electric grinder 1.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, and is an internal side view of an electric grinder.

FIG. 2 is a sectional view taken along line (2)-(2) of FIG. 1 and is a view of the dust separating window as viewed from an upstream side of a flow of outside air.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electric grinder 2 ... Case, 2a ... Inner wall 3 ... Electric motor, 3a ... Commutator 4 ... Motor shaft 6 ... Bearing (motor shaft rear end side) 10 ... Output shaft 13 ... Whetstone 15 ... Cooling fan 16 ... External air inlet 17 ... Blow-out port 18 ... Carbon brush 20 ... Centrifugal fan L ... Separation window for large grains S ... Separation window for small grains

Claims (2)

[Claims] In a power tool having a built-in electric motor, a cooling fan attached to one end of a motor shaft of the electric motor treats dust entering the case mixed with outside air introduced from an outside air introduction port of the case. A centrifugal fan is attached to the other end of the motor shaft, and dust that has entered from the outside air introduction port due to the rotation of the centrifugal fan,
A dust treatment structure for a power tool, wherein a larger particle is separated radially outward of the motor shaft. 2. The dust treatment structure according to claim 1, wherein
A dust treatment structure for an electric tool, wherein a plurality of dust separation windows are formed in a radial direction of a motor shaft around a contact portion between a carbon brush of an electric motor and a commutator and downstream of a centrifugal fan.