A cooling fan apparatus for an automobile

Abstract: A cooling fan apparatus has a cooling fan, a fan shroud and a protecting net. The protecting net comprises a bell mouth ring and a net portion. A bell mouth ring is disposed in front of the fan shroud through a predetermined clearance. The net portion comprises a plurality of rings and a radial grid which is disposed around the rings.

Description: The invention relates to a cooling fan apparatus for an automobile according to the preamble of claim 1. US - A - 4 476 820 discloses an engine compartment structure comprising a cooling fan which is disposed in front of a radiator in advance direction of the automobile. The engine compartment temperature is regulated by opening shutters and operating blowers as well as by a radiator cooling fan to provide air flow through the compartment to maintain a minimum temperature. Fig. 12 shows a conventional cooling fan apparatus. A cooling fan 2 is disposed in front of the condenser 1 in an advance direction of an automobile. The cooling fan has a boss 3 at a center portion thereof, wherein a electric motor 4 is disposed. A fan shroud 5 is disposed around the cooling fan 2. A protecting net 6 is connected to the fan shroud 5 at a front end thereof. A bracket 7, which is formed integrally with the fan shroud 5, is disposed at a center portion of the protecting net 6. The electric motor 4 has a hub 8 which is connected to the bracket 7 through a rivet 9, so that the electric motor 4 is fixed on the center axis of the protecting net 6. As shown in Fig. 13, the protecting net 6 has a plurality of rings 10 which are disposed concentrically with each other from an outer periphery through an inner periphery of the protecting net 6. It has been required that a noise of the cooling fan is reduced and a cooling efficiency of the cooling fan is improved. The inventors of the present invention researched on the noise reduction of the cooling fan and the improvement of cooling efficiency. The inventors noticed that a turbulence of air flow, which flows through the fan shroud 5, is one of causes of the noise. The air turbulence is supposed to be increased around the protecting net 6 when the automobile is stopped, namely an engine is under a condition of idling, because the air in the engine room is sucked by the cooling fan 2. As shown in Fig. 15, the inventors made a clearance X between the fan shroud 5 and the protecting net 6 in order to smooth the air flow, so that the noise was reduced 0.5dB. According to the result of the experiment described above, the inventors disposed a bell mouth ring 11 at the outer periphery of the protecting net 6, as shown in Fig. 16, in order to smooth the air flow which flows through the clearance X. The opening area of the bell mouth ring 11 is increased in the advance direction of the automobile. The noise of the cooling fan 2 shown in Fig. 16 is less 0.9dB than that of the cooling fan 2 shown in Fig. 15. The amount of air flowing through the cooling fan 2 shown in Fig. 16 is increased about 5 % rather than the cooling fan 2 shown in Fig. 15. Since the cooling fan shown in Fig. 13 has the rings 10 up to the outer periphery, the air turbulence is supposed to be increased especially at the vicinity of the outer periphery of the protecting net 6. As shown in Fig. 17, the air flow is disturbed behind the ring 10a and ring 10b which are disposed at the outer periphery of the protecting net 6. In order to prevent such an air turbulence, a radial grid 12 is disposed at the periphery portion of the protecting net 6 as shown in Fig. 18, so that the noise is reduced 0.6 dB as compared with the cooling fan 2 shown in Fig. 16. An object of the present invention is to reduce a noise due to a protecting net and to increase an amount of air which flows through a cooling fan. This object is achieved by the features in the characterizing part of claim 1. According to the present invention, a cooling fan apparatus has a fan shroud around a cooling fan and a protecting net in front of the fan shroud through a predetermined clearance. The protecting net has a bell mouth ring at the outer periphery. The opening area of the bell mouth ring is reduced gradually toward the fan shroud. The air flow is guided along the outer surface of the bell mouth ring without turbulence, so that the noise is reduced and the amount of air supplied by the cooling fan is increased. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially cross-sectional view showing a cooling fan apparatus; Fig. 2 is a front view of a protecting net; Fig. 3 is a side view of a protecting net, which is partially cross-sectional; Fig. 4 is a front view of a cooling fan apparatus; Fig. 5 is a exploded view of a cooling fan apparatus; Fig. 6 is a schematical view showing a cooling fan apparatus disposed in an engine room of an automobile; Fig. 7 is a front view showing a cooling fan apparatus disposed in an engine room of a automobile; Fig. 8 and Fig. 9 are diagrams showing effects of a cooling fan apparatus of the present invention; Fig. 10(a), (b) and (c) are front views of another embodiment of the present invention; Fig. 11 is a cross-sectional view of a conventional cooling fan apparatus; Fig. 12 is a cross-sectional view of a conventional cooling fan apparatus; Fig. 13 is a front view of the cooling fan apparatus shown in Fig. 12; Figs. 14 through 18 are schematic views for explaining the background of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 6 shows a cooling fan apparatus disposed in an engine room 15. A radiator 14 for cooling a engine coolant is disposed in front of an engine 13. A condenser 1 for condensing a refrigerant is disposed in front of the radiator 14 in an advance direction of an automobile. A cooling fan, a fan shroud 5 and a protecting net 6 are disposed in front of the condenser 1. A bumper 16 and a radiator grille 17 are provided at a front portion of the automobile. As shown in Fig 7, the protecting net 6 is connected to the fan shroud 5 through a stay, and the fan shroud 5 is connected to a body of the automobile through a stay 18 and to the condenser 1 through a stay 19. A detailed structure of the cooling fan apparatus is shown in Fig. 1. The cooling fan 2 has a boss 3 on the central axis thereof, the boss 3 in which an electric motor 4 is disposed. The fan shroud 5 is disposed around the cooling fan 2. The fan shroud 5 comprises a cylindrical portion 5a confronting the cooling fan 2, a intake duct 5b of which opening area is gradually increased in advance direction of the automobile and a skirt portion 5c of which opening area is gradually decreased in advance direction of the automobile. The cylindrical portion 5a, the intake duct 5b and the skirt portion 5c are integrally formed and made of fiber reinforced resin such as polypropylene. The protecting net 6 is disposed in front of the intake duct 5b through a clearance X, which is about 2 cm. The protecting net 6 has a bell mouth ring 11 at outer periphery. The opening area of the bell mouth ring 11 is increased in advance direction of the automobile. The outer and inner surfaces of the bell mouth ring 11 are smooth curved surfaces. A bracket 7, which is formed integrally with the fan shroud 5, is connected to the protecting net 6 at the center portion thereof. A hub 8 of the electric motor 4 is fixed to the bracket 7 through the rivet 9. Therefore, the electric motor 4 and the cooling fan 2 are connected to the protecting net 6 through the bracket 7. The protecting net is made of fiber reinforced resin such as polypropylene. Fig. 2 is a front view of the protecting net 6 and Fig. 3 is a side view of the protecting net 6. A radial grid 12, which comprises a plurality of radial ribs, is provided along the inner surface of the bell mouth ring 11. The radial ribs of the radial grid 12 stand radially side by side in constant interval. A plurality of rings 10(four rings in this embodiment) are provided at inner side of the radial grid 12. Both of the rings 10 and the radial grid 12 protect the cooling fan 2 from foreign objects. The protecting net 6 has four stays 20 integrally for being connected to the fan shroud 5. A holding ring 21 is provided at the center portion of the four stays 20, into which the bracket 7 is inserted firmly. The air flows toward the electric motor 4 through an opening space 22 of the holding ring 21. Fig. 4 shows the protecting net 6, the electric motor 4 and the fan shroud 5, which are assembled to each other. The protecting net 6 is connected to the fan shroud 5 through the stays 20 and bolts 23. The fan shroud 5 has stays 18 through which the fan shroud 5 is connected to the body of the automobile. The fan shroud 5 has another stays 19 through which the fan shroud 5 is connected to the condenser 1. Fig. 5 is a exploded view of the protecting net 6 and the fan shroud 5. The fan shroud 5 has a connecting portion 24 which has a through hole 25 for receiving the bolt 23. A clip 26 made of spring steel is provided on the connecting portion 27 which is confronted with the through hole 25. The bolt 23 is screwed to the washer portion 27 of the clip 26 through a through hole 28 of the stay 20 and a through holes 25 of the connecting portion 24. The fan shroud 5 has radial stays 29 integrally which are fitted into the inside of the stays 20 of the protecting net 6, so that the protecting net 6 and the fan shroud 5 are connected to each other. The bracket 7 is provided on the stays 29. The comparison of noise reduction between the cooling fan shown in Fig. 4 and the cooling fan shown in Fig. 13 is described hereinafter. Fig. 8 shows a relation between noise level and noise frequency, wherein the consumed energy of the electric motor 4 is 80 watt and the cooling fan rotates at the speed of 2000 r.p.m. A line y represent cooling fan apparatus according to the present invention and a broken line 2 represents the conventional apparatus shown in Fig. 13. It is apparent from Fig. 8 that the noise reduction is achieved whole range of noise frequency. Fig. 9 is a diagram corresponding to Fig. 8, wherein the consumed energy of the electric motor 4 is 120 watt and the cooling fan rotates at the speed of 2000 r.p.m. The effect of noise reduction is remarkable in Fig. 9 rather than in Fig. 8. It is admitted that the noise is reduced about 2 dB and the amount of the air is increased about 5% according to the experiment shown in Fig. 8. According to the another experiment shown in Fig. 9, the noise is reduced about 2.3dB and the amount of the air is increased about 5%. In the embodiment described above, the protecting net 6 and the fan shroud 5 are connected to each other with using the clip 26 as shown in Fig. 5. In another embodiment, the fan shroud 5 is connected to the protecting net 6 directly with utilizing an elasticity of resin material as shown in Fig. 10(a), (b) and (c). The fan shroud 5 integrally has tongue portions 30 each of which includes nail portion 31. The protecting net 6 has receiving holes 32 for receiving the nail portion 30 therein. The tangue portion 30 is inserted into the inside of the protecting net 30 and the nail portion 31 is inserted into the receiving hole 32 formed on a fixing portion 33 with utilizing an elasticity of resin material. A hydraulic motor can be used to drive the cooling fan instead of the electric motor 4.

Claims: A cooling fan apparatus for an automobile, which is disposed in front of a radiator (14) in advance direction of the automobile, comprising: a cooling fan (2) for introducing cooling air toward said radiator (14), characterized by a fan shroud (5) disposed around said cooling fan (2) for guiding the cooling air; and a protecting net (6) disposed in front of said fan shroud (5) for protecting the cooling fan; said protecting net (6) having a bell mouth ring (11) of which opening area is gradually increased in the advance direction of the automobile and a net portion (10,12) disposed inside of said bell mouth ring for preventing foreign objects passing through the bell mouth ring. A cooling fan apparatus for an automobile claimed in claim 1, wherein said net portion comprises a plurality of rings (10) disposed concentrically with each other and a radial grid (12) disposed around said rings. A cooling fan apparatus for an automobile claimed in claim 1 or claim 2, wherein said bell mouth ring (11) is disposed in front of said fan shroud (5) through a predetermined clearance (X). A cooling fan apparatus for an automobile claimed in claim 3, wherein said predetermined clearance (X) is approximately 2cm. A cooling fan apparatus for an automobile claimed in one of claim 1 through claim 4, wherein said protecting net (6) integrally has stays (20) which protrude from the outer surface of said bell mouth ring (11) toward said fan shroud (5), and said protecting net and the fan shroud are connected to each other through said stays (20). A cooling for apparatus for an automobile claimed in one of claim 1 through claim 5, wherein said cooling fan (2) is driven by an electric motor (4) which is disposed on a center axis thereof and is fixed to a center portion of said protecting net (6).

Inventors: HASEBE YASUAKI, HOSHINO YOSHITAKE, SAKANE TAKAAKI, HASEBE, YASUAKI, HOSHINO, YOSHITAKE, SAKANE, TAKAAKI
Applicants: NIPPON DENSO CO, NIPPONDENSO CO., LTD.
Application year: 1991
Main classification: F01P5
IPC codes: F01P5, F04D29, F01P11