FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"INNOVATIVE CUT FAN FOR ENGINE COOLING OF AN AUTOMOTIVE
VEHICLE"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89, M.I.D.C, SATPUR,
NASHIK-422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION DESCRIBES THE NATURE OF THE INVENTION AND MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION:
The present invention relates to the engine cooling fan of an automotive vehicle. More particularly it relates to engine cooling fan with specially fashioned cut out at the trailing edge of the fan blade that reduces the incab noise and improves the sound quality of an automotive vehicle.
BACKGROUND OF THE PRESENT INVENTION:
Prior art discloses variety of noiseless fans with variety of cut architecture. US patent Nos. US5165846 and US5192182 describes noiseless fan for cooling motors having a group of parallel and thin closely spaced disks rotatable at relatively high speed. When the fan is running, a body of air between each pair of facing disks is rotated about the disk axes by virtue of boundary layers of the air on the facing sides of the disks. This air body tends to shear radially outwards due to centrifugal force and thus move in a spiral path towards the outer peripheries of the disks with very lower amplitude of oscillations reduces the noise drastically. The major disadvantage of this concept is complexity in manufacturing and huge cost involved in its production.
In vehicles, generally viscous on/off or modulating fans are used for engine cooling, it is observed that in engaged or on condition, fan is suddenly inducing higher noise levels inside as well as exterior of the vehicle. Fan noise is unacceptable to customer due to higher noise, loudness, sharpness and roughness levels (sound quality). Fan generally induces two types of noise namely discrete tones related to blade passing frequency and broad band noise due to vortex / turbulence generation at leading as well as trailing edge. Hence to improve the sound quality perception, reduce noise levels and to improve cooling efficiency, the present invention is targeted.
OBJECTIVES OF THE PRESENT INVENTION:
The main object of the present invention is to provide a fan with specific cuts for engine cooling and to improve the NVH performance of an automotive vehicle.

Accordingly the invention provides an innovative cut fan for engine cooling of an automotive vehicle comprising a rotating spindle having two or more number fan blades provided with one or more cut slots at distant on trailing end of said fan blade and one cut slot at tip of the blade.
DESCRIPTION OF THE FIGURES:
Figure 1 shows the innovative fan with square cut outs on the fan blade in accordance with the present invention.
Figure 2 shows the design parameters of notches on the fan blade with different ratios.
Figure 3 shows the comparative noise performance of the conventional fan and the fan with square cut outs of this invention.
Figure 4 shows comparative sound quality of the conventional fan and the fan with square cut outs of this invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION:
Innovative fan is provided with blades having specific cuts. The cut slots on the fan blade are of specific shapes and sizes and experimentally assessed on the test rig level to optimize the shape, size of the slot and functional requirements like flow capacity of the fan. The assessment results revealed that the square cut slot on trailing side and tip of the fan blade is the optimized cut design to achieve improved NVH (Noise, Vibration, and Harshness) character of the vehicle. By these improvements, fan noise energy distribution is altered and distributed in different band with different intensity of sound. Due to this the Psycho-Acoustics sound quality parameters has been improved due spread of spectral content.

Due to cut out designs at trailing edge creation of broad band noise due to random force fluctuation is eliminated. The fluctuations are generated by the interaction of the blade surfaces with the turbulent ffow. These random force fluctuations create turbulence at trailing edge. To reduce the air turbulence innovative cut outs at the trailing edge of the blade is provided. This feature leads to the simplicity in manufacture of fan for automotive applications. It is a low cost and low weight solution for reducing the fan noise. Due to these even pitched slots on the trailing edges of fan turbulence and discrete tones vortex shedding phenomenon is reduced and lower fan noise is induced. Due to this noise level inside the cab are reduced by 1 to 2 dBA throughout the rpm range as well as exterior noise is reduced by 0.5 to 1 dBA. Sound quality of fan noise is substantially improved by 20%.
Referring to figure 1 automobile engine cooling fan having number of blades mounted over a spindle. Each of the said fan blade having two number of square cut on trailing end of blade at distant and square cut slot on the tip end of blade. The location of the said cut slot/slots on trailing end of blade on each of the blade is/are at equidistant from the centre.
This modification to the fan blades of engine cooling fan shown improvement of NVH performance.
Figure 3 shows the comparative noise performance of the conventional fan and the fan with square cut outs of this invention.
Figure 4 shows comparative sound quality of the conventional fan and the fan with square cut outs of this invention.
From the study of these graphs of figures 3 & 4, It is observed that the there is improvement in the invented cut fan over the traditional fan.
The fan mass of the cut out fan is reduced when compared to viscous fan This reduction in fan mass is inversely related to operating life of other operationally

related engine fan drive components such as bearings. It reduces the fan noise as well as to improve the sound quality of the vehicle.
Referring to Figure 2,
Rw=Ratio of slot width to total blade width (W) = 0.19 to 0.21
Rl= Ratio of slot length to total blade length (L) =0.09 to 0.11
Rp= Ratio of pitch to total length=0.21 to 0.24
Rmt= Ratio of top margin length to total blade length=0.36 to 0.38
Rmb=Ratio of bottom margin to total blade length = 0.25 to 0.28
Rtw= Ratio of slot width to total blade width= 0.22 to 0.24
Rtl= Ratio of slot height to total blade length =0.08 to 0.12
N= Vertical slot density =No. of slots divided by length =0.016 to 0.020

WE CLAIM:-
1. An innovative cut fan for engine cooling of an automotive vehicle comprising a rotating spindle having two or more number fan blades provided with one or more cut slots at distant on trailing edge of said fan blade and one cut slot at top edge of the blade.
2. An innovative cut fan as claimed in claim 1 wherein the location of the said cut slot/slots on trailing edge of blade on each of the blade is/are at equidistant from the centre.
3. An innovative cut fan as claimed in claim 1 wherein the ratio of pitch of the square cut on the trailing edge of the fan to the total length of the blade (Rp) is 0.21 to 0.24; the ratio of top margin of the trailing edge to the total blade length (Rmt) is 0.36 to 0.38; the ratio of width of the slot on the trailing edge to the total blade length (Rl) is 09 to 0.11.
4. An innovative cut fan as claimed in claim 1 wherein the ratio of slot width of the slot on the top edge of the blade to the total blade width (Rtw) is 0.22 to 0.24 and the ratio of depth of the cut on the top edge of the blade to blade length (Rtl) is 0.08 to 0.12.
5. An innovative cut fan as claimed in claim 1 wherein the said cut slots optimized are square shape.