Radiator-Shroud Structure

Abstract

A shroud 15 attached to an air discharge side of a radiator 13 narrows toward a centrifugal-flow-type rotary fan 11 and forms a cylindrical shape. A surrounding portion 17 is provided so as to surround the rotary fan 11, and a guide portion 19 extending in the centrifugal direction of the rotary fan 11 is provided at the end of the surrounding portion 17. The length of the guide portion 19 is about 6% the diameter of the rotary fan 11. Since this mitigates turbulence of centrifugally flowing air 21 flowing out of the rotary fan 11 and suppress a drop in the amount of air passing through the radiator 13, the cooling capacity of the radiator 13 can be enhanced.

Description

TECHNICAL FIELD

The present invention relates to a radiator-shroud structure which is provided between a radiator and a fan of a vehicle so as to guide air, and more particularly, to a radiator-shroud structure capable of preventing reverse flow of centrifugal flow produced by means of a rotary fan.

BACKGROUND ART

As shown in FIG. 5, in a vehicle such as a cab-over-type vehicle 1, an engine section 5 including a radiator 13 and a rotary fan 11 is disposed under a cab 3, and air (wind) is taken from the outside via an air intake opening provided in an unillustrated front panel in the direction of arrow B, whereby the cooling capacity of the radiator 13 is enhanced. A shroud 15 is provided between the radiator 13 and the rotary fan 11, and guides air discharged from the radiator 13 to the rotary fan 11.

In order to improve cooling capacity, increasing the amount of air passing through the radiator 13 is important. For such a purpose, there has been proposed a shroud having a devised shape (see Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2002-38952

As shown in FIGS. 6 and 7, in general, the shroud 15 is attached to the radiator 13, and assumes a shape which surrounds the outer circumference of the rotary fan 11. That is, as shown in FIG. 6, the radiator 13 typically has a rectangular structure, and therefore, the shroud 15 assumes a rectangular shape at a connection portion at which the shroud 15 is connected to the radiator 13. Further, since the radiator 13 is disposed at an inclined orientation so as to efficiently use a space, a lower side of the shroud 15 assumes a shape narrowing toward the rotary fan 11. At a position corresponding to the outer circumference of the rotary fan 11, the shroud 15 has a cylindrical surrounding portion 17 which surrounds the rotary fan 11. Meanwhile, in the cab-over-type vehicle 1, the rotary fan 11 is connected to the engine section 5, because, in general, the rotary fan 11 rotates as a result of transmission of rotation of a crankshaft of the engine section 5 thereto.

Air having passed through the radiator 13 passes through the shroud 15 and the rotary fan 11, and is discharged. In some cases, the clearance between the end of the fan and the shroud must be increased from the viewpoint of design of the vehicle. In such a case, if an axial flow fan is employed, an air flow leaks through the clearance between the end of the fan and the shroud, and the amount of air passing through the radiator 13 decreases. Such a leak, which causes a reduction in the amount of air, can be prevented through employment of a fan which produces a centrifugal flow.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, when a rotary fan 11 which produces a centrifugal flow is provided, air flows not only in the direction of arrow A but also in the directions of arrows A′ and A″ in FIG. 7, and there arises a problem in that air flow turbulence occurs at the end of the surrounding portion 17 of the shroud 15.

FIG. 8 shows the results of a simulation performed on turbulence of flow of air flowing through the radiator 13, the shroud 15, and the rotary fan 11 for the case where the shroud 15 is a conventional one. A portion colored in black corresponds to a region where a large turbulence occurs. As can be seen from FIG. 8, the flow of air flowing out of the blade ends of the rotary fan 11 changes to the direction of arrow A′ or A″, and turbulence occurs.

If air flow turbulence occurs at the end of the surrounding portion 17 of the shroud 15, it becomes difficult for the air discharged from the radiator 13 to pass the vicinity of the surrounding portion 17, so that the amount of air decreases. This causes a drop in the cooling capacity of the radiator.

FIG. 8 also shows a flow of air which reversely flows from the end of the rotary fan 11 toward the radiator 13. This reverse flow also hinders the flow of air discharged from the radiator 13, and lowers the cooling capacity of the radiator. However, this problem is not related to the present invention, and will not be described here.

The present invention has been accomplished in light of the above problems, and an object of the present invention is to provide a radiator-shroud structure which mitigates turbulence of centrifugally flowing air 21 discharged from the rotary fan 11 so as to suppress a decrease in the amount of air passing through the radiator 13, to thereby enhance the cooling capacity of the radiator 13.

MEANS FOR SOLVING THE PROBLEMS

The present invention, which solves the above-described problem, is a radiator-shroud structure including a rotary fan which produces a centrifugal flow of air, a radiator provided in the vicinity of the rotary fan, and a shroud for forming an air guide passage extending from the radiator toward the rotary fan, the radiator-shroud structure being characterized by comprising a surrounding portion which surrounds the outer circumference of the rotary fan at one end of the shroud, and a guide portion extending from a circumferential edge of the surrounding portion in a radially outward direction.

Since the guide portion extending outward in the radial direction of the fan is provided at the circumferential edge of the surrounding portion of the shroud, the centrifugally flowing air discharged from the rotary fan flows along the guide portion. Therefore, the air flow turbulence at the end of the surrounding portion can be mitigated. Thus, a sufficient amount of air passing through the radiator is secured, and the cooling capacity of the radiator can be enhanced.

The width of the guide portion is desirably set to about 6% the diameter of the rotary fan. That is, when the rotary fan has a diameter of 500 mm, the width of the guide portion is about 30 mm. Further, the guide portion is desired to assume an annular shape and extend over the entire circumference. However, the guide portion may be partially removed so as to prevent interference with other parts such as a radiator hose.

EFFECTS OF THE INVENTION

By virtue of the radiator-shroud structure according to the present invention, the air flow turbulence at the end of the surrounding portion of the shroud can be mitigated, and the amount of air passing through the radiator is increased. Thus, the cooling capacity of the radiator can be enhanced. Moreover, since the rigidity of the surrounding portion increases, the clearance between the fan and the surrounding portion can be designed to be small so as to effectively prevent air leakage, and noise radiated from the shroud can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a radiator-shroud structure according an embodiment of the present invention.

FIG. 2 is a perspective view of the radiator-shroud structure.

FIG. 3 shows results of flow simulation.

FIG. 4 is a graph showing the relation between length of a guide portion and air-amount change ratio.

FIG. 5 is an explanatory view of a cab-over-type vehicle.

FIG. 6 is a perspective view of a conventional radiator-shroud structure.

FIG. 7 is a sectional view of the conventional radiator-shroud structure.

FIG. 8 shows the results of simulation of turbulent flow for the case of the conventional radiator-shroud structure.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will next be described in detail with reference to the drawings. FIG. 1 is a sectional view of a radiator-shroud structure according an embodiment of the present invention; FIG. 2 is a perspective view of the radiator-shroud structure; FIG. 3 shows results of a simulation in which air flow is simulated for the case where the shroud has a guide portion; and FIG. 4 is a graph showing the relation between length of the guide portion and air-amount change ratio.

As shown in FIG. 1, a radiator 13 is attached to a frame extending under a cab 3 of a cab-over-type vehicle 1. In FIG. 1, the left side of the radiator 13 corresponds to the front direction of the vehicle 1. In many cases, the radiator 13 is obliquely disposed as shown in the drawing in order to increase surface efficiency.

Meanwhile, in the case of a truck, rotation is transmitted from a pulley provided on a crankshaft of an engine to a pulley provided on a rotary shaft of a rotary fan 11. Therefore, the rotary fan 11 is attached to an engine section 5 present on the right side of the rotary fan 11 in FIG. 1.

The rotary fan 11 can be of an axial flow type or a centrifugal flow type. When the rotary fan 11 is of an axial flow type, an air flow leaks at the clearance between the end of the fan and the shroud, and the amount of air passing through the radiator 13 decreases. Therefore, in the present embodiment, the rotary fan 11 is of a centrifugal flow type. The centrifugal-flow-type rotary fan 11 can be obtained by determining the shape of the rotary fan 11 in consideration of the coarseness of the grid of the radiator 13.

When the centrifugal-flow-type rotary fan 11 is used, most of air flowing out of the radiator 13 and through the rotary fan 11 flows in the centrifugal direction of the rotary fan 11. Therefore, the air can be caused to flow to the rear of the engine while avoiding the engine section 5.

A shroud 15 is provided in order to guide to the rotary fan 11 air having passed through the radiator 13.

The shroud 15 is formed of, for example, a metal or a resin, and is attached to the radiator 13. As shown in FIG. 2, at a portion where the shroud 15 is attached to the radiator 13, the shroud 15 assumes a rectangular shape to match the shape of the radiator 13. The shroud 15 narrows toward the rotary fan 11, and in the vicinity of the rotary fan 11, the shroud 15 is formed into a cylindrical shape so as to surround the rotary fan 11. Further, in order to efficiently guide air to the rotary fan 11, a tubular surrounding portion 17 is provided on the shroud 15. Further, in order to eliminate turbulence of the centrifugally flowing air, a guide portion 19, which preferably has an annular shape, is provided at an end portion of the surrounding portion 17. The surrounding portion 17 and the guide portion 19 of the shroud 15 may be formed as a single member or as separate members, which are then fixed together by use of rivets or the like.

Ideally, the clearance between the shroud 15 and the rotary fan 11 is set to zero, from the viewpoint of efficient guiding of air. However, since the shroud 15 is attached to the radiator 13 and the rotary fan 11 is attached to the engine section 5, the shroud 15 is designed and disposed in such a manner that a small space is provided between the shroud 15 and the rotary fan 11 in consideration of deformation and vibration during travel.

Since the guide portion 19 as shown in FIGS. 1 and 2 is provided on the shroud 15, air from the rotary fan 11 flows in the centrifugal direction along the guide portion 19, whereby turbulence can be prevented.

FIG. 3 shows the results of simulation of turbulent flow for the case where the guide portion 19 is provided. As can be seen from FIG. 3, the turbulence is mitigated as compared with the case of FIG. 8.

FIG. 4 shows the relation between the length of the guide portion 19 and the change ratio of amount of air passing through the radiator 13. The amount of air starts to increase when the length of the guide portion 19 is set to a or greater, and the increase in the amount of air saturates when the length becomes β or greater. Therefore, the length of the guide portion 19 is desired to be set to a value near β.

The results of this experiment show that a good result is attained when the length of the guide portion 19 is set to about 6% the diameter of the rotary fan 11. That is, in the case where the rotary fan 11 has a diameter of 500 mm, a good result is attained when the length of the guide portion 19 is set to about 30 mm.

The present invention is not limited to the above-described embodiment, and may be modified in various manners, and these modifications fall within the technical scope of the present invention. For example, in the present embodiment, the length of the guide portion 19 is set to about 6% the diameter of the rotary fan 11. However, the length of the guide portion 19 is not limited thereto, and may change depending on the type of the rotary fan 11, the shape of the shroud 15, and the like. Further, the shroud may be fixed to the engine or the frame, rather than the radiator. Moreover, the vehicle is not limited to the cab-over-type vehicle, and the present invention can be applied to a hood-type vehicle.

INDUSTRIAL APPLICABILITY

By virtue of the radiator-shroud structure according to the present invention, the turbulence of air flowing out of the rotary fan 11 in the centrifugal direction can be mitigated, and the amount of air passing through the radiator 13 can be increased so as to enhance the cooling capacity of the radiator 13.

Claims

1. A radiator-shroud structure comprising:

a rotary fan which produces a centrifugal flow of air;

a radiator provided in the vicinity of the rotary fan; and

a shroud for forming an air guide passage extending from the radiator toward the rotary fan, the radiator-shroud structure being characterized by comprising:

a surrounding portion which surrounds the outer circumference of the rotary fan at one end of the shroud; and

a guide portion extending from a circumferential edge of the surrounding portion in a radially outward direction.

2. A radiator-shroud structure according to claim 1, wherein the guide portion has a width about 6% the diameter of the rotary fan.