FIELD OF THE INVENTION
This invention is a system for radiator cooling fan of an engine that can be used in a two-wheeled vehicle.
BACKGROUND
Liquid cooled engines have a radiator for cooling a coolant fluid. A radiator 10 cooling system consists of channels inside the engine block and heads, a water pump to circulate the coolant, a thermostat to control the coolant temperature, a radiator to chill the coolant, a radiator cap for managing the pressure in the system, and some plumbing with interconnecting hoses to move the coolant from the engine to radiator.
15 The radiator cooling system works by sending a liquid coolant through passages in the engine block and heads. As the coolant flows through these passages, the heat from the engine is picked up by the coolant. The heated fluid then makes its way through a rubber hose to the radiator at a front side of the vehicle. As it flows through the thin tubes in the radiator, the hot liquid is cooled by an air
20 stream entering from fins in front of the vehicle. Once the fluid is cooled, it returns to the engine to absorb more heat. A water pump performs the function of keeping the coolant fluid moving through the system of plumbing and hidden passages.
The coolant follows in a path that takes it from the water pump through passages 25 inside the engine block where it collects the heat produced by the engine cylinder. The coolant then flows up to the cylinder head and collects more heat from the combustion chamber.
A thermostat is situated between the engine and the radiator to make sure that the coolant stays above a certain preset temperature. If the coolant temperature falls 30 below the pre-set temperature, the thermostat prevents the coolant flow to the radiator, forcing the fluid instead through a bypass directly back to the engine. The coolant will continue to flow as mentioned until it reaches the desired

5 temperature, at which point, the thermostat will open a valve and allow the coolant back through the radiator.
An electrically operated cooling fan is used to promote the heat transfer between the surrounding atmosphere and the radiator. When the engine coolant temperature exceeds a predetermined value, the coolant fan is turned ON to 10 increase the rate of heat transfer and cool the engine. The cooling fan will be turned OFF once the coolant temperature goes below a second predetermined value. The engine coolant temperature is maintained within the predetermined limits to ensure optimum engine operating temperature and thereby maximize engine efficiency.
15 The above-mentioned type of radiator cooling system is usually employed for vehicles with large engine capacity where a natural air drift is not sufficient to cool the engine efficiently.
Problems
During the radiator cooling fan operation, air flow direction is from the front side
20 of the vehicle towards the radiator and then to the engine. If the engine is
operating at a high load for a long duration such as when climbing a hill, the heat
generated will be immense. In such a case, the heat transferred to the coolant will
also be high which in turn will result in high temperature in the radiator. The
cooling fan operation will thus direct the hot air towards the engine. In a
25 motorcycle, the rider’s legs are positioned close to the engine and the hot air
directed from the radiator towards the engine will cause discomfort to the rider.
Particularly, when the vehicle is moving at low speeds, the natural air drift will be
insufficient to cool the rider’s body and the hot air blown by the cooling fan can
lead to skin irritation. The rider might choose to stop the vehicle and move away
30 to allow the engine to cool naturally before continuing the ride. The hot air
directed towards the rider’s body will also heat the vehicle body parts disposed
closer to the rider’s body like cowl and side panels.

5 Also, while riding in heavy traffic conditions inside a city, there is a possibility that the engine temperature shoots up rapidly, and frequent ON/OFF of the cooling fan is required to increase the cooling capacity which also increases the electrical power consumption. This high power demand might lead to a quick discharge of vehicle battery.
10 DISCUSSION OF THE PRIOR ART
Japanese Patent JP19990041997 discloses a radiator cooling system in which rider discomfort due to hot air directed by the coolant fan is avoided by adding a thermal insulation between the exhaust pipe and the cooling fan blade. But such a design reduces the air flow, increases the weight and cost of the system.
15 Japanese Patent JP20020342114 discloses a radiator cooling system in which deterioration of power supply voltage due to continuous operation of the cooling fan during the abnormal operation of coolant temperature sensor is avoided by intermittently driving the cooling fan for the engine speed lower than a threshold.
Japanese expired Patent JP19820153520 discloses an arrangement of radiator 20 cooling fan that will stream hot air in the same direction as the advancing direction of the motorcycle to avoid discomfort to the rider. Such an arrangement will avoid discomfort only for the high vehicle speeds. The above-mentioned problem of rider discomfort while riding at low speed and with high engine load still persists.
25 US 2013168039 titled “Air guide structure of radiator in straddle vehicle” discloses a radiator cooling system for a motorcycle wherein a shroud is used to prevent the hot air from being directed towards the rider’s legs. The shroud covers the lateral sides of the cooling fan and is only open towards the downward end of the radiator and therefore the hot air is directed towards the downward end of the
30 radiator. But the shroud increases the weight and cost of the system.
Indian Patent Publication 2648/MUM/2013 discloses a radiator cooling fan control system in which the cooling fan actuation, speed, and direction are controlled based on the engine speed, battery voltage, vehicle speed and coolant

5 temperature to ensure that the hot air is not directed to the rider’s legs. When the cooling fan direction is reversed, the hot air is sucked away from the engine, and the radiator is cooled at a lower rate.
A radiator cooling system that can be controlled to prevent the hot air from being directed to the rider’s legs, during low-speed operation of the vehicle without 10 deteriorating the engine efficiency and durability, will be advantageous.
SUMMARY OF THE INVENTION
The present invention is a radiator cooling fan control system for a motorcycle comprising an electronic control unit (ECU) for controlling electrical and electronic parts of an engine, a coolant temperature sensor fitted on the engine to
15 provide a signal indicative of a coolant temperature to the ECU, a cooling fan controlled by the ECU to force the atmospheric air to cool a radiator through which a coolant fluid is circulating after absorbing the heat from the engine, a vehicle speed sensor providing a signal indicative of the vehicle speed, an engine speed sensor providing a signal indicative of the engine speed wherein, when the
20 vehicle speed is higher than a predetermined first speed threshold for a predetermined first duration, the ECU turns ON the cooling fan if the coolant temperature is above a first temperature threshold and thereafter turns OFF the cooling fan if the coolant temperature reduces below a second temperature threshold. If the vehicle speed is lower than the predetermined first speed
25 threshold for the predetermined first duration, the ECU turns ON the cooling fan if the coolant temperature is above a third temperature threshold which is higher than the first temperature threshold. The ECU turns OFF the cooling fan if the coolant temperature reduces below a fourth temperature threshold which is higher than the second temperature threshold.
30 This invention is a control system for a radiator cooling fan of a vehicle for enhanced driver comfort having, a radiator, a mechanical fan, a motor, an electronic control unit (ECU), an electromechanical relay, a coolant temperature sensor, an engine speed sensor, a vehicle speed sensor, an intake air temperature

5 sensor, a battery, a fuse, coolant fluid and, coolant tubes. The mechanical fan is driven by the motor mounted at a rear side of the radiator, said coolant fluid is circulated along the coolant tubes inside the radiator, said motor is powered by said battery. The motor sucks natural air from the atmosphere and feeds it to the radiator through which the coolant fluid circulates after absorbing the heat from
10 the engine. The electronic control unit (ECU) controls the motor by switching ON or OFF the electromechanical relay based on inputs from the coolant temperature sensor, engine speed sensor, vehicle speed sensor, and intake air temperature sensor. The motor is an Electric Permanent Magnet Direct Current (PMDC) motor. The motor is a Brushless Direct Current (BLDC) motor. The motor is an
15 induction motor.
In the present invention, a method of a control system for a radiator cooling fan of a vehicle for enhanced driver comfort including, a radiator, a mechanical fan, a motor, an electronic control unit (ECU), an electromechanical relay, a coolant temperature sensor, an engine speed sensor, a vehicle speed sensor, an intake air
20 temperature sensor, a battery, a fuse, coolant fluid, and coolant tubes, comprising the steps of, checking vehicle speed by the ECU after receiving signal from the vehicle speed sensor immediately after starting engine when the ignition switch is ON, verifying coolant temperature based on a signal from the coolant temperature sensor, when the vehicle speed exceeds a predetermined threshold for a
25 predetermined duration, switching ON the mechanical fan by driving the electromechanical relay if the coolant temperature is greater than a first predetermined temperature threshold, monitoring the coolant temperature continuously, switching OFF the mechanical fan by de-energizing the electromechanical relay, if the coolant temperature decreases below a second
30 predetermined temperature threshold, switching ON the mechanical fan for the coolant temperature exceeding the first predetermined temperature threshold, wherein the heat from the radiator is transferred to the external environment at a faster rate and thus reducing the coolant temperature, turning ON the motor for a vehicle speed lesser than the predetermined threshold only when the coolant

5 temperature exceeds a third predetermined temperature threshold higher than the first predetermined temperature threshold, to cool the engine to an optimum temperature, and monitoring the coolant temperature continuously, such that if the coolant temperature reduces below a fourth predetermined temperature threshold being higher than the second predetermined threshold then the motor is switched 10 OFF, and the ECU performs checking of the vehicle speed again.
This invention can be applied in a two wheeler radiator cooling system. Modifications like indirect methods of vehicle speed sensing such as by using engine speed and throttle position can be applied to this system.
BRIEF DESCRIPTION OF THE DRAWINGS 15 Figure 1 shows the circuit diagram for the radiator cooling fan control system. Figure 2 shows the flowchart for the radiator cooling fan control system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 is a typical electrically operated radiator cooling fan system which comprises a radiator made up of aluminium, coolant fluid which circulates along
20 coolant tubes inside the radiator, a mechanical fan driven by an Electric Permanent Magnet Direct Current (PMDC) or Brushless Direct Current (BLDC) motor 10 mounted at the rear side of the radiator to suck natural air from atmosphere and provide to the radiator, an electronic control unit (ECU) 20 controls the motor 10 by switching ON/OFF an electromechanical relay 30 based
25 on inputs from a coolant temperature sensor 40, engine speed sensor 50, vehicle speed sensor 60 and intake air temperature sensor 70, a battery 80 supplies electrical power for operation of the vehicle electrical loads including the motor 10 and a fuse 90 protects wiring against short circuit conditions.
Figure 2 shows the process of the invention. The ECU 20 checks the vehicle
30 speed 120 based on signal from the vehicle speed sensor 60 immediately after
start of the engine 110 when the ignition switch is on 100, to understand if it is in
a highway riding condition with speed greater than a predetermined threshold for

5 a predetermined duration (80 kmph for 30 seconds in the preferred embodiment). If the vehicle is judged to be at speeds exceeding 80 kmph for 30 seconds 130, then the coolant temperature is checked 140 based on a signal from the coolant temperature sensor 40. If the coolant temperature is greater than a first predetermined temperature threshold 150 (101°C in the preferred embodiment)
10 then the motor 10 is switched ON 160 by driving the relay 30 coil. Thereafter, the coolant temperature is continuously monitored 170 and when the coolant temperature decreases below a second predetermined temperature threshold 180 (85°C in the preferred embodiment) then the motor 10 is switched OFF 190 by de-energizing the relay 30 coil. By switching ON the motor 10 for coolant
15 temperature exceeding the first predetermined temperature threshold, the heat from the radiator is transferred to the external environment at a faster rate thereby reducing the coolant temperature.
If the vehicle speed is lower than the predetermined threshold, the motor 10 is turned ON 220 only when the coolant temperature exceeds a third predetermined
20 temperature threshold 200, 210 (105°C in the preferred embodiment) that is higher than the first predetermined temperature threshold (101°C in the preferred embodiment). This ensures engine cooling to the optimum temperature. Thereafter the coolant temperature is continuously monitored 230 and if it reduces below a fourth predetermined temperature threshold 240 (95°C in the preferred
25 embodiment) which is higher than the second predetermined threshold (85°C in the preferred embodiment) then the motor 10 is switched OFF 250 and the ECU 20 checks the vehicle speed again.
Since the motor 10 is turned ON / OFF at lower temperature thresholds when the vehicle is driven at high speed, the engine coolant temperature is maintained at a 30 lower level. After, driving at high speed if the vehicle speed is decreased such as when entering city traffic, the coolant temperature does not immediately increase beyond the third temperature threshold. The motor 10 does not immediately get turned ON 160 at low vehicle speeds, and therefore hot air is not directed to the rider’s legs. Maintaining a lower turn ON / turn OFF temperature thresholds when

5 the vehicle is driven at high speed ensures rider comfort when the vehicle speed is reduced. Because of ram air at high vehicle speeds, the motor 10 operation at high vehicle speed does not cause rider discomfort. As the high vehicle speed is also associated with high engine speed, the electricity generation from a generator connected with the engine crankshaft will also be high. Thus, long duration of 10 cooling fan operation can be supported by the vehicle electrical system without deteriorating vehicle performance. The duration of cooling fan operation at low vehicle speed is reduced which helps the vehicle electrical system because the electricity generation at low vehicle speed will also be less.
Further, the motor 10 operation can also be controlled based on the engine speed 15 signal obtained from the engine speed sensor 50. This can further improve riding comfort when the rider is moving in slow traffic conditions wherein the hot air directed towards the rider is not cooled due to air from the environment. While the preferred embodiment has ON/OFF control of the cooling fan based on predetermined values of coolant temperature and vehicle speed, the motor 10 20 operation can be a function of coolant temperature, engine speed, and vehicle speed. Further, the motor 10 speed can also be a function of the above-mentioned variables to allow greater control of hot air directed towards the rider. The motor 10 could be a PMDC motor or a BLDC motor or an induction motor. The vehicle could be a scooter or a motorcycle wherein the rider’s legs will be positioned 25 close to the engine. The radiator cooling fan control system is also applicable to a hybrid vehicle wherein in addition to the engine, an electric motor powered by a battery also drives a wheel. These and other modifications are possible without departing from the spirit and scope of the invention.

WE CLAIM:
1. A control system for a radiator cooling fan of a vehicle for enhanced
driver comfort having, a radiator, a mechanical fan, a motor (10), an
electronic control unit (ECU) (20), an electromechanical relay (30), a
coolant temperature sensor (40), an engine speed sensor (50), a vehicle
speed sensor (60), an intake air temperature sensor (70), a battery (80), a
fuse (90), coolant fluid and, coolant tubes,
wherein,
the mechanical fan is driven by the motor (10) mounted at a rear side of the radiator, said coolant fluid is circulated along the coolant tubes inside the radiator, said motor (10) is powered by said battery (80).
2. The control system for a radiator cooling fan of claim 1, wherein the motor (10) sucks natural air from the atmosphere and feeds it to the radiator through which the coolant fluid circulates after absorbing the heat from the engine.
3. The control system for a radiator cooling fan of claim 1, wherein the electronic control unit (ECU) (20) controls the motor (10) by switching ON or OFF the electromechanical relay (30) based on inputs from the coolant temperature sensor (40), engine speed sensor (50), vehicle speed sensor (60), and intake air temperature sensor (70).

4. The control system for a radiator cooling fan of claim 1, wherein the motor (10) is an Electric Permanent Magnet Direct Current (PMDC) motor.
5. The control system for a radiator cooling fan of claim 1, wherein the motor (10) is a Brushless Direct Current (BLDC) motor.
6. The control system for a radiator cooling fan of claim 1, wherein the motor (10) is an induction motor.
7. A method of a control system for a radiator cooling fan of a vehicle for enhanced driver comfort including, a radiator, a mechanical fan, a motor (10), an electronic control unit (ECU) (20), an electromechanical relay (30), a coolant temperature sensor (40), an engine speed sensor (50), a vehicle speed sensor (60), an intake air temperature sensor (70), a battery (80), a fuse (90), coolant fluid, and coolant tubes, comprising the steps of:
checking vehicle speed (120) by the ECU (20) after receiving a signal from the vehicle speed sensor (60) immediately after starting the engine (110) when the ignition switch is ON (100);
verifying coolant temperature (140) based on a signal from the coolant temperature sensor (40), when the vehicle speed exceeds a predetermined threshold for a predetermined duration (130);
switching ON (160) the mechanical fan (60) by driving the electromechanical relay (30) if the coolant temperature is greater than a first predetermined temperature threshold (150);
monitoring the coolant temperature continuously (170);
switching OFF (190) the mechanical fan (60) by de-energizing the electromechanical relay (30), if the coolant temperature decreases below a second predetermined temperature threshold (180);

switching ON the mechanical fan (60) for the coolant temperature exceeding the first predetermined temperature threshold, wherein the heat from the radiator is transferred to the external environment at a faster rate and thus reducing the coolant temperature;
turning ON (220) the motor (10) for a vehicle speed lesser than the predetermined threshold only when the coolant temperature exceeds a third predetermined temperature threshold (210, 200) higher than the first predetermined temperature threshold (150), to cool the engine to an optimum temperature; and
monitoring the coolant temperature continuously (230), such that if the coolant temperature reduces below a fourth predetermined temperature threshold (240) being higher than the second predetermined threshold (180) then the motor (10) is switched OFF (250), and the ECU (20) performs checking of the vehicle speed again.