1. Field of the Invention
The present invention relates to a vacuum generating apparatus for a vacuum cleaner, and more particularly, to a vacuum generating apparatus for a vacuum cleaner in which an axial type coreless brushless direct-current (DC) motor is implemented in the form of a rotor-impeller integration structure, to thereby realize ultra-compactness, thinness, light-weight, low-noise, long lifetime, non-existence of carbon dust, and improved productivity.
2. Description of the Related Art
In accordance with development of electronics industry, a vacuum cleaner has become more compact, thinner and lighter. However, such reduction in size has confronted to a saturated state due to limitation of lengthy direction of a motor being an essential component in a vacuum cleaner.
In general, as the type of a vacuum cleaner, there are a traditional type as shown in FIG. 1, and an upright type and a canister type both of which are adopted in Europe. In all types of vacuum cleaners, compactness and lightness of the whole volume and weight are regarded as matters to be solved together with easiness of cleaning. In particular, in the case of an upright type of a vacuum cleaner, a big load is applied to hands during cleaning, to thereby cause much fatigue and inconvenience a user due to a large volume.
The structure of a conventional vacuum cleaner will be described below with reference to FIGS. 1 and 2.
In the conventional vacuum cleaner of FIG. 1, a motor 3 is incorporated in the inside of a housing 1 of a main body in which an impeller is fixed to a rotating shaft in order to generate a vacuum sucking force. Here, wheels 2 are rotatably installed on the lower portion of the main body. A dust bag 4 for accommodating dust is installed at the front stage of the motor 3. A dust sucking device 6 is detachably and attachably connected via a vacuum flexible hose tube 5 at the next end of the dust bag 4. A filter 7 is provided at the rear end of the housing 1.
In the conventional vacuum cleaner, the impeller is rotated due to driving of the motor 3, to thereby generate a sucking force. Accordingly, dust is absorbed into the dust bag 4 via the sucking device 6.
In a vacuum generating apparatus for a vacuum cleaner using a conventional alternating-current (AC) universal motor, as shown in a partially exploded sectional view of FIG. 2, both ends of a rotating shaft 8 of a rotor whose rotor coil 9 is wound around a core 9a are rotatably supported by bearings 10 and 20 fixed to a housing 16 of the motor 3. An electromagnet 11 for a stator is arranged with a predetermined gap along the external circumferential portion of th coil 9.
An impeller 12 is combined at the upper end of the rotating shaft 8 via an upper bearing 10 and a pair of washers 13 and fixed by a nut 14 and a fixing bolt 15.
Here, an electric power source for driving a motor is applied from a carbon brush 19 which is elastically supported on the housing 16 to the rotor coil 9 via a commutator 18 which is integrally formed on the lower side of the rotating shaft 8. Accordingly, a rotating magnetic field is generated to enable the rotor to rotate.
When the impeller 12 rotates, air is sucked via an upper-center hole 17 of the housing 16 and discharged via an outlet 16a which is located in the lower side of the housing 16 along the air stream in the direction of an arrow, to accordingly generate a vacuum sucking force in the inside of the housing 1 of the main body.
The conventional motor used for generating a vacuum sucking force increases air sucking noise generated during high-speed rotation according to an increase of an air output. The AC universal motor having the core type brush is limited in reduction of the axial length of the motor to accomplish compactness, thinness and light weight in view of the structure of the motor. Also, an air guide mechanism from sucking to discharging is formed by the impeller along the axial direction of the motor, which is not so simple that an output efficiency is lowered.
In case of the conventional structure, the impeller 12 and the rotor 9 are not integrated but separate, which require particular spacers, washers, nuts and bolts, etc., to combine them. Also, an air guide vane 21 is essentially required for guiding air from the impeller 12 to the discharging outlet 16a in order to increase an air pressure efficiently, which causes a complicated assembly to thus lower a productivity and increase a cost.
In the case of fabrication of the conventional impeller, a number of blades and upper and lower plates which are made of aluminium plate-type materials are combined up and down in order to maintain a mechanical strength and save a weight when the impeller rotates at high speed. Thus, an offset of a vacuum degree occurs according to a tightening degree between the combined upper and lower plates and the blades. As a result, during a press assembly, a tightening combination between the upper and lower plates and the blades is in pursuit of continuous improvement.
Furthermore, in the case of the structure adopting a carbon brush, carbon dust is scattered due to wear of the brush to thereby cause an environmental pollution. The worn-out brush should be replaced by a new one, to accordingly shorten a lifetime of the motor. Also, sparks are generated between the commutator and the brush and electromagnetic waves are radiated from the motor.
To solve the above problems in part, a twin impeller, an AC inverter motor, or a brushless type motor has been adopted, but those methods are not effective nor furthermore in progress due to limitation of the axial length (105.4 mm) in size of the motor and the weight (1.35 kg) thereof.