Centrifugal blower

Abstract

A centrifugal multi-blade fan has multiple blades about a rotational shaft and draws in air along the rotational shaft and then blows the air approximately perpendicular to the rotational shaft to reduce wind noise. A scroll casing encloses the multi-blade fan and defines a scroll-shaped airflow passage for directing the air blown from the multi-blade fan. The scroll casing has an intake opening and an outlet opening at a scroll end, in a downstream scroll casing portion. The scroll casing expands such that a flow passage cross-sectional area on the airflow downstream side is larger than that on an airflow upstream side. A ratio of a blade length to a diameter of the multi-blade fan is greater than or equal to 0.12, and an outer scroll casing radius, relative to the rotational axis, increases as a logarithmic spiral, its expansion angle being from 3.3° to 4.8°.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10 / 192,131 filed on Jul. 10, 2002. This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Applications No. 2001-215649 filed Jul. 16, 2001, and No. 2001-322201 filed Oct. 19, 2001.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a centrifugal blower having a centrifugal multiblade fan (abbreviated as a centrifugal fan hereafter) applied to a vehicular air-conditioning apparatus. [0004] 2. Description of the Related Art [0005] Generally, centrifugal fans use a centrifugal force to take in air in an axial direction, and to blow the air outward in a radial direction. The air blown out from the centrifugal fan has an airflow of an axial direction component directed from an intake side to a counter-intake side. [0006] In the invention disclosed...

AI Technical Summary

Benefits of technology

[0009] In view of the foregoing problems, an object of the present invention is to provide a centrifugal blower which can sufficiently reduce the wind noise even when the airflow quantity is small.

[0015] A dimension of the winding-end portion in the direction parallel with the rotational shaft is 1.1 times to 2.3 times a dimension of a nose in the scroll casing in the direction parallel with the rotational shaft in a third aspect of the invention. With this constitution, noise is sufficiently reduced even when the airflow quantity is small as shown in FIGS. 8 and 10 described below.

[0016] The dimension of the winding-end portion in the direction parallel with the rotational shaft is from 1.3 times to 2.1 times of the dimension of a nose in the scroll casing in the direction parallel with the rotational shaft in a fourth aspect of the invention. With this constitution, noise is sufficiently reduced even when the airflow quantity is small as shown in FIGS. 8 and 10 described below.

[0017] The airflow passage may be constituted so as to have an approximately rectangular cross-section in a fifth aspect of the invention. The airflow passage is constituted so as to have an approximately rectangular cross-section whose corners are formed as an arc (rounded internal corners) in a sixth aspect of the invention. With this constitution, since an unstable swirling flow is prevented from being generated at the corners in the airflow passage, and simultaneously, a generated swirling flow is circulated smoothly, the swirling flow is stabilized, and the noise is reduced.

[0019] When the protrusion is provided at a part with which air with the highest flow rate of the air blown out from the centrifugal multiblade fan collides, the air blown out from the centrifugal multiblade fan is easily split into the inlet opening side and the outlet opening side. As a result, generation of a swirling flow is promoted, and wind noise is reduced.

Problems solved by technology

As a result, the flow becomes unstable, the airflow tends to be disturbed, and wind noise becomes worse.

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