JPH08177790A - Cooling fan for motor - Google Patents

Abstract

PURPOSE: To effectively relieve stress by vibration or the like, and restrain the occurrence of fatigue failure by forming bottom parts of slits in the shape of containing an almost U shape whose lower side is formed in a straight line shape in a cooling fan for a motor where plural blades are molded by arranging radial-shaped slits. CONSTITUTION: In this cooling fan 1, a steel plate is punched, and an installing hole 2 to a motor shaft is formed in the center, and radial-shaped slits 3a... are formed in on its periphery, and plural blades 3... are divided. In this case, in order to secure cooling efficiency, an interval on the outer peripheral side of the slits 3a is set narrower than the bottom part side. On the other hand, in bottom parts A of the respective slits 3a, side parts 4 of both side blades 3 are put in line symmetry, and are respectively continued with small circular arcs 5, and the small circular arcs 5 are continued with a large circular arc 6, and these are formed in an almost U shape. According to this, deformation of the bottom parts of the slits 3a is uniformized by the circular arcs 5 and 6, and is moderately changed in a large circular arc 6 part, and fatigue failure is restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling fan used for a motor such as an electric tool.

[0002]

2. Description of the Related Art The cooling fan is formed by radially punching a plurality of blades from a single steel plate or the like and twisting them by drawing. In particular, the bottom shape of the slit provided between the punched blades is, as shown in FIG. 5 (A), one in which the side portions 21 and 21 between the blades 20 and 20 are continuous with a semicircle 22, or the same figure ( B) as in B),
A mode in which a pinhole 25 is provided at the bottom of a notch 24 serving as a slit that divides the gap between 23 is adopted.

[0003]

With the rotation of the cooling fan, a load is applied by vibration due to air resistance and impact applied to the motor shaft, and the stress at this time is concentrated on the bottom of the slit. Therefore, if it is used for a long period of time, a fatigue fracture such as a crack 26 occurs at the bottom, and it becomes unusable. The semicircle 22 and the pinhole 25 have a shape provided for the purpose of relaxing the stress, but the stress concentration cannot be avoided due to the deformation of the bottom of the slit, that is, the root shape of the blade, which is applied by the twist of the blade. In the case of strong, the durability is not yet satisfactory.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention provides a cooling fan for a motor, which effectively relieves the stress at the bottom of the slit, which is the root of the blade, and has high durability. It is characterized in that the bottom of the slit has a shape including a substantially U-shape having a straight lower side. Incidentally, the straight line in the present invention means, of course, the straight line itself.
Also includes curves such as arcs that are close to straight lines.

[0005]

Since the bottom of the slit is formed in a shape including a substantially U-shape with the lower side being a straight line, the twisting of the blade is alleviated by the straight line portion, and the blade is continuously twisted and deformed to be continuous. Even if the blade vibrates due to the rotation, the stress there is less likely to concentrate on one part, and the fatigue fracture such as cracking can be delayed as much as possible.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a front view of the cooling fan, which is shown in a state before drawing. The cooling fan 1 punches a steel plate,
A plurality of blades 3, 3 ... Are formed by forming a mounting hole 2 for a motor shaft in the center and radial slits 3a, 3a.
In order to ensure the cooling efficiency, the gap on the outer peripheral side of the slit 3a is set to be narrower than that on the bottom side.
On the other hand, at the bottom of each slit 3a, as shown in FIG. 2, the side portions 4 and 4 of the vanes 3 and 3 on both sides are line-symmetrically continuous with the small circular arcs 5 and 5, respectively, and the small circular arcs 5 and 5 are large in the middle thereof. A bottom portion A having a substantially U shape on the lower side is formed continuously with the arc 6. The large arc 6 is obtained from a concentric circle 7 with the mounting hole 2 and has a length of 1.0 mm. Furthermore, the small arc 5, here
5 has a radius of 1.5 mm, the concentric circle 7 has a diameter of 53.0 mm, and the cooling fan 1 has a diameter of 92.0 mm. Even if the cooling fan 1 formed in this way is twisted as shown in FIG. 1 (B) by drawing, the deformation of the bottom of the slit 3a due to the twist is small arcs 5 and 5 and a large arc of the lower side. Since it is equalized with 6 and changes gradually in the large arc 6 part,
The small arcs 5 and 5 are smoothly continuous. The cooling fan 1 thus formed is integrated with the motor shaft 9 by press-fitting the bush 8 crimped and joined to the mounting hole 2 into the motor shaft 9, as shown in FIG. In the cooling fan 1 that rotates integrally with the motor shaft 9, even if each blade 3 vibrates or an impact is transmitted to the motor shaft 9, the bottom portion A has a large straight line with small arcs 5 and 5 as described above. Since it is smoothly continuous with the arc 6, the stress here is relieved, and fatigue failure such as cracking is less likely to occur. By the way, when compared to the cooling fan that adopts the semicircle and pinhole described in the above-mentioned prior art, it is about 3
~ 5 times longer life will be obtained.

Although the small arcs 5 and 5 are connected by the large arc 6 in the above embodiment, they may be connected by a straight line instead of such an arc, and the large arc 6 is a concentric circle of the mounting hole 2. 7
It does not matter even if it is an arc of a reverse curve instead of a blank.
On the other hand, the shape of the slit and its bottom portion is such that the notch 10 as shown in FIG. By forming it, it is possible to obtain the same effect as that of the above embodiment.

[0008]

As described above, according to the present invention, the bottom of the slit is formed in a shape including a substantially U-shape with the lower side being linear, so that the twist between the blades can be smoothly continued. Therefore, it becomes possible to effectively alleviate the stress caused by vibrations and the like, and to delay the occurrence of fatigue fracture as much as possible, which significantly extends the life of the cooling fan.

[Brief description of drawings]

FIG. 1A is a front view of a cooling fan. (B) It is sectional drawing of a cooling fan.

FIG. 2 is an explanatory diagram of a slit bottom portion.

FIG. 3 is an explanatory diagram showing a mounting state of a cooling fan on a motor shaft.

FIG. 4 is an explanatory diagram showing a modified example of a slit bottom portion.

FIG. 5A is an explanatory diagram showing a conventional cooling fan. (B) It is explanatory drawing which shows the conventional cooling fan.

[Explanation of symbols]

1 ... Cooling fan, 2 ... Mounting hole, 3 ... Blade, 4 ...
Side part, 5 ... Small arc, 6 ... Large arc, 7 ... Concentric circles, 8
..Bushings, 9 ... Motor shafts, 10 ...
..Straight line, 12..pinhole

Claims (1)

[Claims] 1. A cooling fan for a motor, wherein a plurality of blades are formed by providing a radial slit, wherein the bottom of the slit has a shape including a substantially U-shape having a straight lower side. Characteristic motor cooling fan.