Abstract: A blower fan including an impeller easily mounted on the rotational shaft of a motor generates less noise. The impeller is mounted on the rotational shaft of the motor using a fastener with an elastic vibration isolator and a washer in between. The washer has a predetermined shape including radial projections from a circumference about a central receiving hole. The vibration isolator has the predetermined shape larger than the predetermined shape of the washer, and has a first recess having the predetermined shape on its top surface to receive the washer fittingly. The impeller has a second recess having the predetermined shape on its top surface to receive the vibration isolator fittingly. The vibration isolator thus separates the impeller mounted on the rotational shaft from the washer in both the axial and rotational directions of the motor to reduce vibrations in both directions propagating to the impeller, generating less noise.

Abstract: A centrifugal fan with an increased shutoff pressure maintains a negative pressure between a casing and a rotatable disk. The centrifugal fan includes an impeller including a rotatable disk and blades extending vertically from the rotatable disk and arranged radially about an axis of rotation of the rotatable disk toward a rim of the disk, a casing accommodating the impeller and including a base plate at its end face nearer the rotatable disk, and a motor mounted on the base plate externally and including a shaft fixed at a center of the rotatable disk to rotate the impeller. The rotatable disk has reflux holes at positions between inner rims and outer rims of the blades in its radial direction. The reflux holes allow a gas to reflux from between the rotating disk and the base plate inside the impeller as the impeller rotates.

Abstract: A blower fan including an impeller easily mounted on the rotational shaft of a motor generates less noise. The impeller is mounted on the rotational shaft of the motor using a fastener with an elastic vibration isolator and a washer in between. The washer has a predetermined shape including radial projections from a circumference about a central receiving hole. The vibration isolator has the predetermined shape larger than the predetermined shape of the washer, and has a first recess having the predetermined shape on its top surface to receive the washer fittingly. The impeller has a second recess having the predetermined shape on its top surface to receive the vibration isolator fittingly. The vibration isolator thus separates the impeller mounted on the rotational shaft from the washer in both the axial and rotational directions of the motor to reduce vibrations in both directions propagating to the impeller, generating less noise.

Abstract: A centrifugal fan with an increased shutoff pressure maintains a negative pressure between a casing and a rotatable disk. The centrifugal fan includes an impeller including a rotatable disk and blades extending vertically from the rotatable disk and arranged radially about an axis of rotation of the rotatable disk toward a rim of the disk, a casing accommodating the impeller and including a base plate at its end face nearer the rotatable disk, and a motor mounted on the base plate externally and including a shaft fixed at a center of the rotatable disk to rotate the impeller. The rotatable disk has reflux holes at positions between inner rims and outer rims of the blades in its radial direction. The reflux holes allow a gas to reflux from between the rotating disk and the base plate inside the impeller as the impeller rotates.

Abstract: A premixing apparatus for mixing a fuel gas with air has an air resistance changeover device for changing over a flow resistance in the air feed passage and a gas resistance changeover device for changing over a flow resistance in the gas feed passage. The air resistance changeover device includes a venturi portion provided in that part of the air feed passage which is on a downstream side of the butterfly valve. A gas chamber is provided in that part of the gas feed passage which is on a downstream side of the gas resistance changeover device. A gas suction portion is configured such that the fuel gas is sucked from the gas chamber into an entire circumference of that part of the air feed passage which is adjacent to a downstream side of the venturi portion.

Abstract: A premixing apparatus for mixing a fuel gas with air has an air resistance changeover device for changing over a flow resistance in the air feed passage and a gas resistance changeover device for changing over a flow resistance in the gas feed passage. The air resistance changeover device includes a venturi portion provided in that part of the air feed passage which is on a downstream side of the butterfly valve. A gas chamber is provided in that part of the gas feed passage which is on a downstream side of the gas resistance changeover device. A gas suction portion is configured such that the fuel gas is sucked from the gas chamber into an entire circumference of that part of the air feed passage which is adjacent to a downstream side of the venturi portion.

Abstract: A fluid dynamic bearing mechanism includes a stationary shaft, a sleeve portion arranged to rotate with respect to the shaft, and a thrust portion including an upper end surface arranged oppose to a lower end surface of the sleeve portion. An inside surface of the thrust portion includes an inside surface contact portion arranged in contact with an outside surface of the shaft, and an inside surface lower non-contact portion spaced away from the outside surface of the shaft, and arranged to extend downward from a lower end of the inside surface contact portion. An outside surface of the thrust portion includes an outside surface inclined portion arranged in contact with an interface of a lubricating oil. The lower end of the inside surface contact portion is arranged at a level axially higher than that of a lower end of the outside surface inclined portion.

Abstract: A fluid dynamic bearing mechanism includes a stationary shaft, a sleeve portion arranged to rotate with respect to the shaft, and a thrust portion including an upper end surface arranged oppose to a lower end surface of the sleeve portion. An inside surface of the thrust portion includes an inside surface contact portion arranged in contact with an outside surface of the shaft, and an inside surface lower non-contact portion spaced away from the outside surface of the shaft, and arranged to extend downward from a lower end of the inside surface contact portion. An outside surface of the thrust portion includes an outside surface inclined portion arranged in contact with an interface of a lubricating oil. The lower end of the inside surface contact portion is arranged at a level axially higher than that of a lower end of the outside surface inclined portion.