FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
A METHOD OF MAXIMIZING THE FUEL EFFICIENCY IN AN
INTERNAL COMBUSTION ENGINE


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Babalal Sahebji Mulani, Narayan Dattatraya Jadhav, and
K. Gopalakrishna, all Indian national
of TATA MOTORS LIMITED an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

PREAMBLE OF THE DESCRIPTION The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF INVENTION
This invention relates to a method of maximizing the fuel efficiency in an internal combustion engine
BACKGROUND OF INVENTION
A vehicle engine converts the chemical energy of fuel into heat energy, which is partially utilized into the useful mechanical work. The heat energy available from the engine is distributed roughly 33% as mechanical work, 33% is rejected to the engine cooling system and remaining 33% heat is rejected to the atmosphere through exhaust system. The mechanical work existing through 33% heat of the engine needs to be utilized efficiently to drive the vehicle, which will result in better fuel economy. There are several subsystems mounted on the engine like viscous clutch fan, air compressor, water pump, alternator, and air conditioning compressor etc., which consumes part of mechanical work generated by engine. Hence it becomes essential to avoid the wastage of engine power because of improper selection, functioning or setting of engine subsystems. The most power consuming subsystem on the engine is viscous clutch fan, which consumes around 10 to 70 HP of engine in its peak running speed. The typical on-highway vehicle engine viscous clutch fan run time hits a year round average of 5-7%. The incorrect selection or setting of viscous clutch fan can take a big bite out of the vehicle fuel economy.
The viscous clutch fan is an essential component of engine cooling system, which is usually mounted behind the radiator. The viscous clutch fan is a device with silicone fluid coupled hydraulic turbine to transfer the rotational motion from driving element to the driven element. The engine is rejecting the heat from its casing to the coolant circulated around it. The hot coolant coming out from the engine will be at

the elevated temperature, which passes through the radiator. The viscous clutch fan rejects the heat to atmosphere by forced convection. The speed of viscous clutch fan is proportional to the engagement of its driving and driven member, which in turn depends on the amount of heat to be rejected from the radiator. A bimetallic sensor fitted at the front portion of viscous clutch fan senses the temperature of air passing through radiator and controls engagement and disengagement of driving and driven member. Improper setting of bimetallic sensor will have redundant higher speed of viscous clutch fan resulting in significant wastage of engine power. The viscous clutch fan selection parameters for particular vehicle application are diameter of fan, speed of fan, number of blades and the setting of bimetallic sensor fitted at the front portion of the viscous clutch fan body. Lesser the diameter and speed of viscous clutch fan lesser will be the power consumption; nevertheless it needs to be balanced with its capacity to reject the heat in engine peak heat generation phases. Hence correct selection of viscous clutch fan geometry (parameter) and its heat rejection capacity needs to be done to reduce the unnecessary wastage of engine power. The present invention provides such a method of maximizing the fuel efficiency in an internal combustion engine by selection of viscous clutch fan design parameters without deteriorating the performance of engine cooling system.
SUMMARY OF INVENTION
This invention is basically a method of maximizing the fuel efficiency in an internal combustion engine by choosing the viscous cooling fan-design parameter described with the help of block diagram modules in figure 2. A heavy commercial engine cooling packages consist of radiator, intercooler, viscous cooling fan, auxiliary coolant tank, air conditioner condenser etc. The base level engine-cooling package components available on the vehicle will have dimensions, which are derived from

the theoretical design calculations. When these cooling packages fits on the vehicle, their performance changes due to influencing factors like vehicle cab interruption and other components in the vicinity of cooling package. During the design stage itself the cooling packages are considered for their maximum heat rejection capacity but most of the time these packages will be running in part load condition only, leading to higher engine power consumption by viscous cooling fan.
By referring to figure 2 the base level cooling package (1) is first tested for its ability to meet the norm set by engine manufacturer by carrying out the cooling trial testing (2) on the vehicle. The base level cooling package (1) is a cooling package (i.e. combination of radiator, intercooler, viscous fan etc), which comes on the vehicle built as a prototype for the first time. The sizes (geometry) of the base level cooling package (1) will be available on the vehicle as per the theoretical calculations done by the designer with some excessive margin. The vehicle, which comes with this base level cooling package (1) needs to be tested in the worst-case heat generation phase of the engine to verify its correct operation i.e. to cool the engine coolant to acceptable values. The name of the test in which the cooling package is tested is called as 'cooling trial' (module 2). In the cooling trial testing the vehicle will be running in such a way that the engine will be producing the maximum heat. The 'cooling margin' (module 2) is the safeguard temperature available for the engine coolant not to boil and to meet the cooling testing norm. The cooling margin is calculated by subtracting the maximum coolant temperature observed in cooling trial from the maximum coolant temperature allowed by engine manufacturer. The cooling margin should be positive in order to have good performance of the engine. The criterion for meeting the cooling norm is derived in terms of cooling margin. The best cooling package will have appositive cooling margin between 1.5 Deg C to 4 Deg C (module 5). If the cooling package is not meeting the cooling norm because of negative cooling margin (module 4) then the engine damage may happen due to it's

overheating. To increase the cooling margin the radiator size or the fan sizes or fan speed can be increased (module 7). If the calculated cooling margin is much greater than expected positive margin i.e. greater than 4 Deg C then the cooling package needs to be considered for the reducing the sizes of its components (module 6), as it will unnecessarily waste the engine power by overcooling the engine coolant. The cooling margin calculated after cooling trial testing with changed sizes components will be checked again whether it is more than 1.5 Deg C and less than 4 Deg C (module 5). In some designs the change in size of radiator and/or intercooler will not be possible due to assembly issues with vehicle cab in such cases the reduction or increase in the diameter and/or speed of fan will be possible. Once the best possible cooling package is derived after cooling trial testing, it needs to be tested for the viscous fan bimetallic strip test (module 8). In this test the temperature of the air flowing over the fan is measured along with the engine coolant temperature and fan speed. This test will give the information about the air-on temperature at which the fan is running at its full speed. The viscous fan should run at its full speed only when the engine will be generating the maximum heat. A thermostat is a device, which is fitted in the engine acts as a gate between engine and radiator. It will fully open if the coolant temperature reaches a value suitable to its full-opening. If the coolant temperature is not high enough to open the thermostat then the coolant is not allowed to flow through the radiator. If the coolant temperature value is in between the full-open and close state of the thermostat then the thermostat is at the partially open state. The measurement of coolant temperature defines the position of the thermostat in the engine. If fan starts to rotate at high speed before the situation of thermostat fully open then it will be huge wastage of engine power. At high speed running of the viscous fan its power consumption is directly proportional to the third power of its diameter and fifth power of its speed. To avoid wastage of power, the bimetallic strip setting of the viscous fan needs to be done which will delay the full speed running of

Further, said sensor is a bi-metallic strip, which is configured to fully engage said cooling fan under said coolant temperature and said thermostat condition.
Further, if said cooling fan is running at its full speed in the thermostat partially open situation then the bimetallic strip is rotated clockwise to delay the full speed running of the viscous fan.
Further, if said cooling fan is not running at full speed when the thermostat is fully open and coolant temperature is lesser than maximum allowed coolant temperature by 5°C then the bimetallic strip is rotated anticlockwise to advance the full speed running of the viscous fan
Further, the dimensions of said radiator, said intercooler and said cooling fan are optimized to obtain said coolant temperature range under peak heat generation phase of said engine.
OBJECT OF INVENTION
The main object of this invention is to provide a method of maximizing the fuel efficiency in an internal combustion engine having a cooling package including at least a radiator, a cooling fan, and an intercooler.
Yet another object of this invention is to provide an optimization technique for optimizing the dimensions of the radiator, intercooler and cooling fan to obtain said coolant temperature range under peak heat generation phase of said engine.
BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the cooling package of a heavy commercial vehicle Figure 2 shows the method of maximizing the fuel efficiency and optimizing of the dimensions of the cooling package components according to the present invention Figure 3 shows the bimetallic strip sensor according to this invention
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same,
By referring to figure 1 a cooling package of a heavy commercial vehicle consists of radiator (1), intercooler (2), viscous fan (3) etc. which are mounted in front of the engine (5). The coolant available in the engine casing will take the heat generated during the combustion of fuel. A coolant supply hose (6) is fitted from the engine (5) to radiator (1). A thermostat (7) acts as a gate in between the engine to radiator coolant supply. The thermostat (7) will be fully open when the coolant temperature reaches a defined value as the actuation of thermostat gate is dependent on the coolant temperature. If the coolant temperature is below the defined value then the thermostat (7) will be in closed condition and it will not allow the coolant to flow to the radiator (1). Radiator (1) is a device which cools the coolant of the engine to a value which will not damage or deteriorate the engine performance and returns the coolant to the engine by coolant return line (8). An intercooler (2) is a device which is used to reject the heat available in the compressed air to be used for the engine. The radiator (1) and intercooler (2) acts as a heat load to the cooling package of the engine. A viscous fan (3) acts as a device to reject the heat from radiator (1) and intercooler (2) which is mounted on the engine (5) and is driven by the belt drive provided from the engine pulley. The viscous fan (3) consumes the power of engine

proportional to its speed and its diameter. The power consumed by the viscous fan (3) is directly proportional to the third power of its diameter and fifth power of its speed hence the viscous fan design parameters should be selected in such a way that the power consumption should be as less as possible. The principle of viscous fan operation works on the viscous clutch, in which the speed of the viscous fan (3) is controlled by the bimetallic strip sensor (4). The amount of engagement and disengagement of viscous fan (3), which will in turn defines the speed, is controlled by the bimetallic strip sensor (4) fitted at the front portion of the viscous fan (3). The bimetallic strip (4) is a metal coil which expands or contracts with respect to the temperature of air passing through the radiator (1) and intercooler (2) and will rotate a shaft inside the viscous fan (3) housing resulting in increasing or decreasing the speed of viscous fan (3). In the situation when the thermostat (7) is closed or partially open the viscous fan (3) should not rotate at its high speed because the coolant is not be available in the radiator (1) and cooling the radiator in the absence of coolant is a complete wastage of the engine power. To avoid this the setting of bimetallic strip (4) is very important which will allow the full speed running of viscous fan (3) when the thermostat is fully open and the coolant temperature is lesser by 5 Deg C than the allowed maximum coolant temperature by the engine manufacturer. In the situation other than this the viscous fan (3) will be rotating at the minimum speed i.e. idle speed consuming minimum power from the engine.
It is utmost important to design the cooling package components to the suitable sizes to have lesser engine power consumption and better fuel economy. The designers usually design the radiator (1), intercooler (2) and viscous fan (3) with the excessive cooling margin in order to safeguard the engine in its worst case operation where the maximum heat will be generated by the engine (5). With this scientific methodology of testing it can be concluded whether the sizes of cooling package components are

over-designed or under-designed. If it is over-designed then the reduction in the sizes of the components is possible which will enhance the fuel economy of the engine (5). By referring figure 2, which is the scientific testing methodology, it will lead to arrive at the best suitable cooling package for the better fuel economy of the engine. When a new vehicle (proto) is built for the first time it comes with the cooling package components sizes derived from the theoretical calculations which can be called as 'base level cooling package' (module 1). These sizes needs to be confirmed for the correct functionality of the cooling package by following the scientific testing procedure defined in figure 2. The base level cooling package (module 1) is tested for the cooling trial (module 2) first to verify the correct functionality of cooling package and the engine. In the cooling trial (module 2), the vehicle is driven in such a way that the engine is producing the maximum amount of heat continuously for considerable amount of time. In this trial the test data for the coolant temperature, engine speed, fan speed and air-on temperature is logged on the real time basis. The air-on temperature is the temperature of the air passing through the radiator and intercooler and comes in contact with the viscous fan bimetallic strip. With this worst case operation of the cooling package, the maximum coolant temperature is verified so that it will not cross the maximum coolant temperature allowed by the engine manufacturer. The cooling margin is calculated after the cooling trial by subtracting the maximum coolant temperature value observed in the cooling trial from the maximum coolant temperature allowed by the engine manufacturer. There are three following possibilities, in which the cooling margin may appear.
Module 3- If the cooling margin is positive and it is greater than 4deg C (module 3) then it is necessary to reduce the size of the cooling package components (module 6) as the cooling package is overcooling the engine and wasting the power of engine which is not required. After reducing the size of intercooler and/or radiator and/or

viscous fan the cooling package needs to be tested again for the cooling trial (module 2) to check the cooling margin.
Module 4- If the cooling margin is negative then the cooling trial requirement is not met by the base level cooling package and it is required to increase the size of intercooler and/or radiator and/or viscous fan (module 7).
Module 5- If the cooling margin is between 1.5 Deg C and 4deg C (module 5) then it is the correct cooling package which can be used on the vehicle. The cooling package with correct sizes of radiator, intercooler and viscous fan needs to be tested for the viscous fan bimetallic strip test (module 8). This test ensures the correct functioning of the viscous fan at different air-on temperature at different heat generation situations of the engine. In this test, the real time data acquisition of fan speed, engine speed, air on temperature, coolant temperature is taken, while the engine is generating maximum amount of heat. The data evaluation will show at what air-on temperature and coolant temperature the viscous fan is rotating at its full speed. There are three following possibilities, in which the results may appear.
Module 9- If the fan is running at its full speed in the thermostat partially open situation then the setting of bimetallic strip is not correct. The complete bimetallic strip needs to be rotated clockwise (module 12) to delay the full speed running of the viscous fan. Refer figure 3 for the procedure of rotating the complete bimetallic strip. The step of 3 degrees needs to be selected for the first change in delaying the full speed engagement. The cooling package needs to be tested again for the viscous fan bimetallic test (module 8) for the correct functioning of the fan.

Module 10- If the fan full speed is not observed at the situation of thermostat fully open and coolant temperature is lesser than maximum allowed coolant temperature by 5 Deg C (module 10) then the bimetallic strip needs to be rotated anticlockwise (module 13) to advance the full speed running of the viscous fan. The step of 3 degrees needs to be selected for the first change in advancing the full speed engagement. The cooling package needs to be tested again for the viscous fan bimetallic test (module 8) for the correct functioning of the fan.
Module 11- If the viscous fan full speed is observed at the situation of thermostat fully open and coolant temperature is lesser than maximum allowed coolant temperature by 5 Deg C (module 11) then the setting of bimetallic strip on the viscous fan is correct.
By following the detailed scientific procedure the final cooling package with better fuel efficient operation of engine can be obtained.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. A method of maximizing the fuel efficiency in an internal combustion engine
having a cooling package including at least a radiator, a cooling fan, and an
intercooler, said method comprising the steps of:
maintaining the engine coolant temperature within 1.5 to 4°C lesser than the maximum allowable coolant temperature;
fully engaging the cooling fan with the engine when the temperature is 4 to 6°C lesser than the maximum allowable coolant temperature and thermostat of said engine is in fully open condition.
2. The method as claimed in claim 1, wherein a sensor assembly is provided to sense the temperature of air passing through the radiator to the cooling fan.
3. The method as claimed in claim 2, wherein said sensor is a bi-metallic strip, which is configured to fully engage said cooling fan under said coolant temperature and said thermostat condition.
4. The method as claimed in claim 3, wherein if said cooling fan is running at its full speed in the thermostat partially open situation then the bimetallic strip is rotated clockwise to delay the full speed running of the viscous fan.
5. The method as claimed in claim 3, wherein if said cooling fan is not running at full speed when the thermostat is fully open and coolant temperature is lesser than maximum allowed coolant temperature by 5°C then the bimetallic strip is rotated anticlockwise to advance the full speed running of the viscous fan.

6. The method as claimed in claim 1, wherein the dimensions of said radiator, said intercooler and said cooling fan are optimized to obtain said coolant temperature range under peak heat generation phase of said engine.
7. An internal combustion engine wherein fuel efficiency is maximized by a method as claimed in claim 1 to 4.
Dated this 29th day of December 2008