Automotive Fan Shroud

Abstract

A shroud enclosing an automotive type fan has ridges projecting from the internal surface equally spaced circumferentially to provide a circumferentially undulating pattern to the axial flow of air forced through the space between the shroud and the fan to reduce the noise level of the shroud-fan combination.

Description

This invention relates, in general, to an automotive type fan shroud. More particularly, it relates to a construction to reduce the noise level of a fan shroud combination.

The use of a shroud to surround an automotive type fan to increase the efficiency of airflow through the engine compartment invariably also increases the noise level of the combination. Devices have been suggested for reducing the noise level, such as, for example, changing the curvature in an axial direction of the shroud. Such is shown, for example, in U.S. Pat. No. 3,334,807, Fan, K. D. McMahan. Another suggestion is to decrease the turbulence of flow through the shroud to decrease noise level, as shown, for example, in U.S. Pat. No. 3,433,403, Fan Inlet Shroud, Gerlitz. It will be noted, however, that, in both of the above instances, the circumferential pattern of air as it flows axially through the shroud is the same as other constructions, the airflow pattern in an axial direction being changed but not circumferentially.

The invention provides a construction to reduce noise level in which the circumferential pattern to the flow of air past the shroud and fan blades is undulating and provided by ridges located on the internal surface of the shroud equally spaced circumferentially around the shroud.

It is a primary object of the invention, therefore, to provide an automotive type fan shroud construction with a reduced noise level.

It is a further object of the invention to provide a fan shroud with internal ridges equally spaced circumferentially and projecting into the path of axial flow of air through the shroud so as to provide an overall circumferential undulating flow pattern to the air to reduce the noise level of the fan-shroud combination.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating a preferred embodiment thereof, wherein;

FIG. 1 is an end elevational view of a fan shroud embodying the invention;

FIG. 2 is a side elevational view of the fan shroud of FIG. 1, with parts broken away and in section, and,

FIG. 3 shows a modification.

As stated previously, the fan shroud of the invention is adapted to cooperate with a fan of the automotive type, such as, for example, that indicated at 10 in phantom in FIGS. 1 and 2. The fan would be mounted in a conventional manner on the engine, and would generally be of a stamped steel or similar design having a number (4 in this case) of circumferentially spaced fan blades 12. It will be understood of course that the number and spacing and construction of the fan play no part in the present invention and is optional insofar as the fan shroud construction is concerned.

The fan shroud in this case consists of a narrow section 14 of a thin cylinder that circumferentially surrounds and axially encloses the fan blades. It has a generally smooth exterior surface 16 that is welded or otherwise suitably secured to a generally rectangular supporting structure 18. The latter would be secured in a known manner adjacent the radiator of the motor vehicle for cooperation of the fan therewith to pull airflow through the radiator into the engine compartment.

As best seen in FIG. 2, the upper portion of the leading edge of the fan shroud 16 is formed with a cover for control purposes, for example, to control the total flow of air and provide proper restriction, as is common in an automotive fan shroud installation.

Attached to the inner surface 22 of shroud 14 are a plurality of ridges or projections 24 that extend axially for approximately an inch, for example, and are oriented with an axis parallel to the axis of the shroud. The ridges have a finger-like appearance, and are equally spaced circumferentially around the shroud inner surface, for example, in this case, approximately four inches apart. The ridges have a generally hat-shaped or square-like cross-section, although FIG. 3 indicates that the ridges 24' could have a half-round cross-section with a radius of approximately 0.25 inches. The radial projection of the ridges defines an annular clearance space between the ridges and fan blades, as shown. It will be obvious, of course, that other cross-sectional configurations could be used without departing from the scope of the invention. As best seen in FIG. 2, each of the ridges 24 is tapered axially at its leading edge for a nonturbulent entrance of the air past the ridges.

From the above, it will be seen that the airflow past the interior of the shroud as a whole will have a smoothly undulating pattern in a circumferential direction, but that otherwise the axial flow of air is essentially in parallel streamlines except for that portion of air blocked by the cover or baffle 20.

The above construction provides for the smooth entrance of air into the shroud, with the circumferentially undulating pattern reducing the shroud fan combination noise level.

While the invention has been described and illustrated in its preferred embodiments in the drawings, it will be clear to those skilled in the arts to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

Claims

We claim:

1. An automotive type fan shroud including a generally cylindrical section adapted to surround and axially enclose a fan and having circumferentially spaced projections from the internal surface to provide a circumferentially undulating pattern to the axial flow of air past the shroud thereby reducing fan-shroud combination noise level the fan having blades enclosed by the shroud, a radial clearance space being provided between the inner extremities of the projections and the outer radial extent of the fan blades.

2. A fan shroud as in claim 1, the projections each having a finger like appearance oriented parallel to the shroud axis and the projections together being equally spaced circumferentially around the shroud internal surface.

3. A fan shroud as in claim 2, the projections having an axially extending taper at the air entrance end.