JPH0911158A - Power tool - Google Patents

Abstract

PURPOSE: To effectively cool a bearing part on the load side on a speed reducer so as to improve durability of a bearing by providing a tool fixture on one side of a main body, and providing cooling passages around a bearing holding part in a speed reducer or in the vicinity of it. CONSTITUTION: When a switch of an electric drill 1 is put in so as to rotate a rotor 5, a chuck 15 is rotated through a gear 8 and a spindle 9 so as to perform drilling, because a gear cutting part 12 is provided on a load side end of the rotor 5 and the gear cutting part 12 meshes with the gear 8. A cooling fan 7 is press-fitted to the shaft of the rotor 5, open air is sucked from a suction port 13 by rotating the fan 7 together with the rotor 5, and respective parts of a stator 6 and the rotor 5 are cooled. Further the air is passed through a vent hole of a bracket 3 and introduced to the ventilation passage 18 of a gear case 2, this cooling wind 23 blows against a circumrference of a bearing holding member 17 on the load side so as to forcedly cool the holding part 17, and a wind after cooling is released outward from an exhaust port 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric tool having a function of cooling a load side bearing portion in a speed reducer.

[0002]

2. Description of the Related Art Electric tools include various electric tools such as electric drills, electric grinders, and electric circular saws. Here, the configuration of a conventional electric power tool will be described with reference to FIG. 3 by taking an electric drill as an example.

Electric drills use tools such as drills,
It is a tool that uses an electric motor as a drive source to punch a target object such as metal or wood with a certain diameter. An electric motor serving as a drive source is arranged inside the frame 4, and a load side shaft end of a rotor (armature) 5 of the electric motor is subjected to gear cutting. The gear cutting portion 12 and the gear 8 mesh with each other, and the gear 8 is fixed to the spindle 9.
The spindle 9 is held by the bearings 10 and 11 in the outer casing of the reduction gear (B gear case 20, B bracket 21), and a tool fixture (chuck 15, taper shank, etc.) is attached to the tip of the spindle 9. ing.

In such a structure, the rotor 5 is rotated by turning on the switch of the electric drill 1B, and the gear cutting portion 12 at the shaft end of the rotor 5 rotates at high speed.
This rotation is transmitted to the gear 8 and the number of rotations decreases. this,
Spindle 9 and chuck 1 at the same speed as the gear
5, and the drill is turned.

By applying a force in the thrust direction to the object such as metal or wood with the tip of the rotating drill, a hole having a constant diameter is opened by the rotational force and the load in the thrust direction.

A cooling fan 7 is provided on the shaft of the rotor 5, and the fan 7 is rotated by the rotation of the rotor 5. By this rotation, the outside air enters from the suction port (wind window) 13, passes between the stator 6 and the rotor 5, cools each, and is discharged from the B exhaust port 22.

Although not shown in the drawing when a large-diameter hole is formed in the object, one or two pinions are interposed between the gear cutting portion 12 and the gear 8 to reduce the speed in two or three stages. Drilling is performed by lowering the rotation speed of the drill.

[0008]

Generally, when performing this drilling work, a drilling work is often performed by applying a high load in the thrust direction in order to increase the work efficiency. As a result, the bearings of the spindle and pinion generate frictional heat due to overload and high-speed rotation, and this part overheats, which lowers the durability of the bearings.In particular, high load is applied to the bearings on the load side. There was a problem that the bearing would be shortened due to overheating. Further, as shown in FIG. 3, the load side bearing portion of the conventional electric power tool is cooled only by natural cooling by the outside air.

The present invention has been made in view of the above circumstances, and an air passage is provided around or near the bearing holding portion of the gear case, and the bearing holding portion is forced by blowing cooling air by a cooling fan. An object of the present invention is to provide an electric tool having a function of dissipating heat of a bearing portion by cooling.

[0010]

According to the present invention, a main body is provided with an intake port and an exhaust port, and further, an air passage is provided around or near a bearing holding portion inside the outer periphery of a speed reducer, and a rotation of an electric motor. The problem is solved by enhancing the effect of dissipating the frictional heat of the load side bearing portion by forcibly cooling the bearing holding portion by blowing cooling air by a cooling fan attached to the child.

[0011]

Operation: By turning on the switch of the electric drill, the rotor of the electric motor rotates at high speed.

By this rotation, the shaft end portion of the rotor on which gear cutting is performed is rotated at the same time. This rotation is transmitted to the gear and the number of rotations is reduced. The spindle, the chuck, and the drill rotate at the same rotation speed as this gear.

By applying a load in the thrust direction by applying the tip of the rotating drill to an object such as metal or wood, a hole having a constant diameter is made by the load and the rotating force. By continuing this drilling work, frictional resistance is applied to the bearing portion that receives the shaft such as the spindle, and the frictional heat generated thereby causes the bearing portion to gradually overheat.

A cooling fan is press-fitted into the shaft of the rotor, and the fan is simultaneously rotated by the rotation of the rotor. The rotation of the fan causes outside air to flow into the electric motor, and the cooling air passes through the stator and the rotor, and is then guided to the load-side bearing holding portion through the ventilation holes of the bracket and the ventilation passage of the gear case. The bearing holder is cooled by this cooling air. The heat released from the bearing holder moves the frictional heat of the bearing to the bearing holder, and the temperature of the bearing and the shaft on the load side decreases.

[0015]

The present invention will be described based on an embodiment shown in FIG. 1 by taking an electric drill as an example. In FIG. 1, the outer casing of the speed reducer is composed of an A gear case 2 and an A bracket 3, and the inside of the A gear case 2 is divided into a gear storage portion and an air passage 18 by an air passage cover 16. A load side bearing holding portion 17 is provided in the gear housing portion, and a bearing 10 such as a roller bearing, a ball bearing or a sleeve metal is inserted in this portion to support a shaft such as a spindle 9. A gear 8 is press-fitted into the spindle 9 and is locked by a key or the like. The ventilation passage lid may be fixed by fitting, screwing or caulking.

Although a large-diameter hole is opened at low speed, it is not shown in this figure, but one or two pinions are inserted between the gear cutting portion 12 and the gear 8 to form two or three stages. It slows down and drills. Also, A bracket 3
Is provided with a bearing holding portion that holds one of the other end of the spindle 9 and the pinion in the A gear case 2 and one of the rotors 5,
Further, ventilation holes are provided so that the cooling air 23 can pass from the frame 4 to the ventilation passage 18 in the A gear case 2.

FIG. 2 is a perspective view of a gear case in one embodiment of the present invention. This drawing shows an embodiment of the shape of the exhaust port of the gear case 2.

In such a structure, turning on the switch of the electric drill 1 causes the rotor 5 to rotate. There is a gear cutting portion 12 at the load side end of the shaft of the rotor 5, and since the gear cutting portion 12 meshes with the gear 8, the gear 8 is rotated. Further, the gear 8 is press-fitted into the spindle 9,
Since the rotation is stopped by a key or the like, the spindle 9 rotates. A chuck 15 is attached to the spindle 9, and a drill is fastened to the chuck 15. Therefore, the rotation of the spindle 9 rotates the drill.

By applying a load in the thrust direction by applying a rotating drill to the object, a hole having a constant diameter is made by the load and the rotating force. By continuing this drilling work, frictional resistance is applied to the bearing portion that holds the shaft such as the spindle, and the frictional heat generated thereby causes the bearing portion to gradually overheat. Particularly, the temperature of the load side bearing 10 is remarkably increased. The heat of each bearing portion is transferred to each bearing holding portion by heat conduction and the holding portion is heated.

An object of the present invention is to prevent seizure of the load side bearing 10 by forcibly cooling the load side bearing holding portion 17 as a measure against temperature rise of the load side bearing 10.

A method of cooling the bearing holder 17 will be described with reference to FIG. A cooling fan 7 is press-fitted into the shaft of the rotor 5, and the fan 7 is simultaneously rotated by the rotation of the rotor 5. By the rotation of the fan 7, the outside air enters through the suction port 13, cools each part of the stator 6 and the rotor 5, and is further guided to the ventilation passage 18 of the A gear case 2 through the ventilation holes of the A bracket 3. The cooling air 23 hits the periphery of the load-side bearing holder 17 and forcibly cools the holder 17.
Due to this cooling, the heat of the load side bearing 10 is changed to the bearing holding portion 17
And the load side bearing 10 is cooled. The wind that has absorbed heat from the bearing portion is discharged from the A exhaust port 14 to the outside.

Although not shown in this drawing when a large-diameter hole is formed, between the gear cutting portion 12 and the gear 8,
Furthermore, one to two pinions are inserted to perform deceleration of two to three steps. In this case, cooling can be performed simultaneously with the load side bearing portion 17 of the spindle 9 by providing the ventilation passage so that the load side bearing portion of the pinion also passes through.

Further, since the gear case is divided into two parts, a ventilation passage cover can be provided and molded when the gear case is molded, so that it is not necessary to newly attach a partition cover at the time of assembly. The two gear cases are integrated by tightening with screws when assembling.

If the exhaust port is small, the overall cooling effect including cooling of the stator 6 and the rotor 5 of the electric drill may be reduced, but in that case, the exhaust port 22 as shown in FIG. Then, a smaller exhaust port than this may be provided as the second exhaust port.

In this way, the load side bearing 10 is cooled by providing the ventilation passage in the gear case and applying the cooling air 23 to the bearing holding portion 17.

[0026]

According to the present invention, since the bearing portion on the load side is forcibly cooled, the temperature of the bearing portion is lowered, overheating can be prevented even if overload occurs, and the durability of the bearing is improved. Can be provided. It is also possible to use bearings with a smaller diameter than before.

[0027]

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electric drill according to an embodiment of the present invention.

FIG. 2 is a perspective view of a gear case according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of an electric drill in one example of a conventional product.

[Explanation of symbols]

 1 ... ・ Electric drill 2 ・ ・ ・ ・ A gear case 3 ・ ・ ・ ・ A bracket 4 ・ ・ ・ ・ Frame 5 ・ ・ ・ ・ Rotor 7 ・ ・ ・ ・ Cooling fan 8 ・ ・ ・ ・ ・ ・ Gear 9 ・ ・・ ・ Spindle 10 ・ ・ ・ ・ Load side bearing 11 ・ ・ ・ ・ ・ ・ Anti-load side bearing 12 ・ ・ ・ ・ Gear cutting part 13 ・ ・ ・ ・ Suction port 14 ・ ・ ・ ・ Exhaust port 16 ・ ・ ・ ・ Ventilation path Cover 17 ・ ・ ・ ・ Load side bearing holder 18 ・ ・ ・ Ventilation passage 23 ・ ・ ・ ・ Cooling air

Claims (1)

[Claims] 1. A power tool in which an electric motor, a speed reducer and a cooling fan are installed, an intake port and an exhaust port are provided, and a tool fixture is provided on one side of the main body, around a bearing holding portion in the speed reducer, or An electric tool characterized by having a ventilation path nearby.