DESC:FIELD OF INVENTION
[0001] The present invention relates to a protection system for an internal combustion engine and more particularly to a temperature based engine stop system.
BACKGROUND OF INVENTION
[0002] In an internal combustion engine, combustion of fuel inside cylinder powers transmission system along with production of a large amount of heat energy. This heat energy is mainly concentrated near cylinder block and cylinder head of the internal combustion engine. Furthermore, it is very necessary to maintain engine temperature at an optimum level to improve combustion process inside the internal combustion engine. Thus, the heat generated in the cylinder block, which may be transmitted to the cylinder head and other parts of the engine, shall be removed by using an external cooling mechanism.
[0003] In such a vehicle with swinging engine, a coolant circulated through cylinder block and cylinder head is used to extract the heat and thus cool down the engine. Different cooling system for extraction of heat from the internal combustion is possible. In such a two-wheeler, firstly the placing, locating and orientation of radiator and the coolant reservoir becomes a great challenge due to space constraints. Secondly, a system is desired which checks the healthiness of the radiator functioning and cylinder block and cylinder head temperature. If the engine operates with cylinder head and cylinder block temperature above a threshold value due to vehicle abuse or during an uphill wherein a vehicle operates at wide-open throttle for a longer period, the engine may cease and become irreparable and unusable.
SUMMARY OF THE INVENTION
[0004] Hence, to obviate the problem of overheating of the cylinder head and cylinder block, in case of a malfunctioning of the cooling mechanism (specifically, the radiator), the current invention proposes a cooling system which is capable of switching off the engine on attaining a pre-determined temperature values of the cylinder head and cylinder block temperature. The current invention uses output of a thermostat (a temperature measuring device) to actuate a switch. The switch further connects to the engine ignition path either to “make” or “break” the path. In case, the temperature at the cylinder head and cylinder block is within the normal operating range, the switch does not interrupt the ignition path. Once the temperature at the cylinder head and cylinder block are out of the operating range, the switch interrupts the ignition path, which eventually stops the ignition.
[0005] The coolant temperature in a liquid cooled engine is a parameter that has a significant effect on the engine performance. An over-hot coolant means that the engine is overheated and needs to cool down to avoid unpredictable catastrophic failures. Similarly, an over-cooled coolant indicates overcooling of the engine, which will reduce the engine thermal efficiency.
[0006] The customer needs to be warned of the coolant temperature in both the above cases (esp. in the hotter case). The temperature in the cylinder head region according to the current invention is sensed via a thermal sensor. Either this thermal sensor is a resistance type RTD or a thermocouple or any other temperature-sensing device capable of generating a signal proportionate to the temperature and is installed on the cylinder head. The resultant voltage from the temperature sensor is fed to a logic controller that indicates coolant temperature to the vehicle driver through a digital display on the speedometer. An advantage of obtaining temperature of coolant by thermal sensor installed on cylinder head and generating signal to be fed to a TCI unit (a controller) which controls the ignition is that the engine protective system isolates the ignition control path even in case of the thermostat failure. Hence, since the sensing of temperature is by thermal sensor so that any failure of thermostat can also be managed by the thermal sensor to cut off the engine.
[0007] The liquid cooled system and hence the engine’s temperature is heavily dependent on the coolant temperature. If the coolant temperature gets very high, the engine will overheat and this can lead to catastrophic failures, including engine seizure. Thus, it is very important to allow the engine to cool down if coolant overheats. This invention also describes a logic path that turns off the engine in case of overheating of coolant. In yet another embodiment, it is an aim of the current invention to indicate the coolant temperature on the vehicle dashboard.
BRIEF DESCRIPTION OF DRAWINGS
[0008] Figure 1illustrates a typical two-wheeler.
[0009] Figure 2 illustrates the cooling mechanism in side view of said vehicle.
[00010] Figure 3 illustrates the radiator mounting.
[00011] Figure 4 illustrates the cooling path through cylinder block from radiator.
[00012] Figure 5 illustrates coolant flow path.
[00013] Figure 6 illustrates the integration of thermostat for ignition control in normal operating condition when temperature is within the operating range.
[00014] Figure 7 illustrates the integration of thermostat for ignition control in normal operating condition when temperature is within the operating range.
[00015] Figure 8 illustrates the method of ignition control based on the cylinder head and cylinder block temperature.
[00016] Figure 9 illustrates the dashboard display of coolant temperature measured by thermal sensor.

DETAILED DESCRIPTION OF THE INVENTION
[00017] The current invention discloses a cooling system 40 for a two wheeled vehicle with an inbuilt auto cutoff mechanism which cut offs the engine ignition based on pre-determined temperature of the cylinder head and cylinder block. This engine auto cutoff mechanism is implemented through a thermostat located in the cylinder head coolant jacket path. In yet another embodiment of the present invention, apart from a thermostat, any other temperature sensor can also be used. The thermal sensor (here, a thermostat) senses the temperature at the cylinder head water jacket and generates a corresponding signal. The signal generated is fed to the output of the thermostat is fed to an intelligent ignition control system (TCI) which, based upon the predetermined values, gives a “make” or a “break” signal to the ignition coil. A “make” signal continues providing electric supply to the ignition coil so that engine doesn’t get switched off and a “break” signal cuts off the electric supply to the ignition coil and engine is switched off. This engine shut off could be achieved by a system of relay and a fuel shutoff control valve. The relay being operated by signal from a thermostat and output of relay controlling the fuel shut off to stop the ignition.
[00018] Figure 1 illustrates a typical two-wheeled vehicle. Figure 1 shows a rider seat 1, floorboard 5, and step through two wheeled vehicle 10, side cover 11, radiator 12 and front cover 13. The vehicle 10 shown as illustration is a step through vehicle. The scope of the current invention is limited not only to a step through vehicle but is also applicable to all the two-wheeled vehicles including the motorcycles.
[00019] Figure 2 illustrates the cooling mechanism for the engine in side view of said vehicle. Figure 2 shows the rider seat 1, step through two wheeled vehicle 10, radiator 12, front cover 13, and coolant reservoir 14, cross member 15, vehicle left Lt, vehicle right Rt, vehicle rear R and vehicle front F. The coolant reservoir 14 stores the coolant which travels from the radiator to the cylinder head of the engine. The radiator 12 is further equipped with ducts which is open to atmosphere from outside and carries the coolant within it.
[00020] Proper functioning of the radiator 12 and sufficient amount of coolant inside the coolant reservoir 14 is very critical to keep the cylinder head and cylinder block temperature within the required operating range. The fan inside radiator 12 according to the present invention could be propelled directly through the crankshaft or could be electrically operated. Furthermore, in case the fan of the radiator 12 is electrically operated, its speed can be related to the engine speed so that at higher rpm revolutions of engine, wherein more fuel combustion takes place and more heat energy is generated, the fan rotates at much higher speed to take away or radiate the excess heat energy.
[00021] Figure 3 illustrates the radiator mounting. Figure 3 shows rider seat 1, radiator 12, radiator top 31, exhaust muffler 32, a thermostat 35 and a thermal sensor 36. The thermal sensor is a means and includes any device to detect temperature and generate a signal proportional to said temperature. Figure 3 shows the radiator has a top end portion profiled to accommodate the nearby automotive parts. In liquid cooled engines, it is common practice to cool the engine by pumping hot coolant through a radiator, which dissipates heat to ambient air. Such radiators have efficient metallic tube and fin structures for transmitting heat to the air. The coolant reservoir functions as to transfer the coolant between the radiator hoses and the tubes. The coolant reservoir may be of metallic or of plastic. The top portion raised above the radiator duct avoids air entrapment in the liquid cooling system 40 (Figure 4) and at the same time helps in muffler mounting accessibility. This shape of radiator top, also avoids the unnecessary volume of the coolant. Moreover, due to protruding top portion, the radiator cap is not easily accessible, thereby preventing the user from touching it when hot during maintenance activities.
[00022] Figure 4 illustrates the cooling path from radiator to cylinder head and back to radiator. Figure 4 shows radiator top 31, coolant flow radiator top to bottom 41, coolant flow path 42 from radiator outlet 33 to cylinder block, coolant flow path 44 from cylinder block to cylinder head, coolant flow path 45 from cylinder head to thermostat 35 and coolant flow path 46 from thermostat to radiator. The coolant inside the coolant reservoir 14 is pumped to the cylinder head and cylinder block region. Upon reaching the cylinder block and cylinder head region (48), the coolant exchanges heat and become hot. The same coolant while coming back to the coolant reservoir passes through an open to atmosphere coolant duct on radiator where the coolant further gets cooled thus thereby extracting heat from the cylinder head and the cylinder block region (48). According to one embodiment of the present invention, the cylinder region (48) comprising of cylinder head and cylinder block comprises of a cooling path (42, 43) for extracting heat from the cylinder region (48) and thus bring down the temperature of the cylinder region (48).
[00023] A closed cooling path (41, 42, 43, 44, 45, 46) is formed which comprises of a pump and an air-cooled radiator (12). The closed cooling path (41, 42, 43, 44, 45, 46) starts from radiator outlet (33), cylinder block cooling path (42), portion of cylinder head cooling path (43) and then back to a radiator inlet (34). The thermostat (35) allows the flow of coolant from the cylinder head to the radiator once the coolant temperature reaches a set temperature. While the hot coolant is allowed to flow from cylinder head to radiator, a cooler coolant enters the cooling path (41, 42, 43, 44, 45, and 46) through the radiator outlet (33). Thus, the temperature at the cylinder region (48) is maintained within a pre-determined range.
[00024] In yet another embodiment of the present invention, a thermal sensor (36) capable of sending an electrical/electronic/digital signal corresponding to any temperature at its location of placement is mounted between said portion of cylinder head cooling path (43) and said radiator inlet (34). This electrical signal generated by thermal sensor (36) based on detected temperature is fed to control system to control the ignition inside the internal combustion engine.
[00025] The coolant temperature in a liquid cooled engine is a parameter that has a significant effect on the engine performance. An over-hot coolant means that the engine overheated and needs to cool down to avoid unpredictable catastrophic failures. Similarly, an over-cool coolant indicates overcooling of the engine, which will reduce the engine thermal efficiency.
[00026] The customer needs to be warned of the coolant temperature in both the cases (esp. in the hotter case). The temperature in the cylinder head region according to the current invention is sensed via a thermal sensor. This thermal sensor is either a resistance type RTD or a thermocouple or any other temperature sensing device capable of generating a signal proportionate to the temperature and is mounted either on the cylinder head or cylinder block. The resultant voltage from the temperature sensor is fed to a logic path that indicates coolant temperature to the vehicle driver through a digital display.
[00027] The liquid cooled system and hence the engine’s temperature is heavily dependent on the coolant temperature. In cases of malfunctioning of cooling system, the coolant temperature increases and the engine will overheat which can lead to catastrophic failures, including engine seizure. Thus, it is very important to allow the engine to cool down if coolant overheats. This invention also describes a logic path that turns off the engine in case of coolant overheating. In yet another embodiment, it is an aim of the current invention to indicate the coolant temperature on the vehicle dashboard.
[00028] Furthermore, yet in another embodiment of the current invention, the current invention extends to an engine kill path that ensures that the engine gets switched off before a catastrophic failure results from overheating. A thermal sensor, mounted in the engine cylinder head, before the thermostat, senses the coolant temperature. The resultant voltage from the sensed coolant temperature is converted & shown in the analog / digital gauge on the vehicle dashboard. Another logic path enables the glowing of a light on the vehicle dashboard if the coolant temperature (and hence the resultant voltage from the thermal sensor) crosses a certain value (Threshold 1). If the coolant temperature exceeds beyond another, higher value (Threshold 2), then the kill switch path cuts off ignition supply to the engine thus immobilizing the engine/vehicle until the coolant temperature drops back to a safe level (Threshold 2”).
[00029] Figure 5 illustrates a block diagram to show the flow of colder coolant going to the cylinder head and the hot coolant coming back to the coolant reservoir 14 of the radiator. From the coolant reservoir, the coolant travels to the radiator from where it is pumped to cylinder block water jacket and further to the cylinder head water jacket. The water jackets mentioned in the invention pertains to the path traversed by the coolant. A thermal sensor (36) is installed in the coolant path between the cylinder head and the radiator inlet. Cylinder head water jacket has the thermal sensor (36) inserted which gives signal corresponding to the temperature. From cylinder head water jacket, the coolant further travels back to the radiator and then to the coolant reservoir.
[00030] Figure 6 shows the “make” signal reaching the ignition coil while the temperature parameters being within a pre-determined normal operating range. In this condition, the ignition coil continues to receive the signal corresponding to the temperature and spark plug operates to generate spark. Figure 7 shows the “break” signal reaching the ignition coil under the temperature parameters being outside a pre-determined normal operating range. In this condition, the ignition coil and hence the spark plug does not receive the signal corresponding to the temperature and engine is switched OFF.
[00031] Figure 8 shows the process of controlling the operation of an engine by switching OFF of the engine in case of temperature parameters going outside a normal pre-determined operating range. The thermal sensor (36) (installed between the cylinder head and the radiator inlet) senses the coolant temperature at the cylinder head water jacket region (48). According to the present invention, the temperature range in between the first pre-determined value and the second pre-determined value is the first predetermined range. In addition, the temperature range above the second pre-determined range is the second pre-determined range.
[00032] According to one embodiment of the present invention, the thermal sensor (36) is installed on the cylinder head. When the coolant temperature sensed by the thermal sensor (36) is below a first pre-determined value, the coolant temperature LED is switched OFF which indicates a normal process. During operation of the engine, when the coolant temperature is greater than the first predetermined threshold value (72), a coolant temperature LED (79) is switched ON as a warning signal to indicate the coolant temperature above a first predetermined value (72). When the coolant temperature reaches above a second pre-determined threshold value (74), an ignition cut off signal (82) is sent to the ignition coil through the TCI (shown in Figure 7) to disable the ignition and switch OFF the engine. In this condition, an “Engine OFF” LED (83) is ON and glows on the speedometer.
[00033] Under the engine OFF condition, simultaneously a hazard lamp (TSL) (81) starts blinking on the vehicle to communicate to other road users about the “Engine OFF” state (83) of the vehicle. Once engine is switched OFF and the coolant temperature comes down to a temperature which is less than the second threshold temperature, the ignition cut off switch is disabled and ignition signal is communicated to the ignition coil through TCI to allow the ignition and restart the engine. In this condition, the Hazard (TSL) light is switched OFF, “Engine OFF” LED (83) is OFF and coolant LED (79) is ON until the coolant temperature further decreases below the first pre-determined value (72). Once switched OFF, the engine is capable of restarting only once the coolant temperature is lower than or equal to a temperature in the first pre-determined range (72).
[00034] Figure 9 shows a vehicle dashboard 90 with engine RPM display 91, vehicle speed display 92 and radiator coolant temperature display 93. The radiant coolant temperature display 93 has a lower end temperature denoted by “C” and a higher end temperature denoted by “H”. The temperature between “C” and first threshold is the normal range of coolant temperature. The temperature between the first threshold value and the second threshold value is the warning range of coolant temperature. The temperature above the second threshold value is the engine cut off range wherein the ignition circuit cuts off the elements required for the engine operation such as fuel and spark.
[00035] The engine protection method and system as described in the present invention, provides a warning signal to an user about the coolant temperature during a first range of temperature of the coolant temperature and once the vehicle is used beyond a second threshold value, the engine is switched OFF thereby saving the engine from ceasing and irreparable damages.
,CLAIMS:We Claim:
1. A cooling system (40) for protection of an internal combustion engine comprising:
a cooling path (42, 43) for extraction of heat energy from a cylinder region (48);
a means (36) capable of sending an electrical signal corresponding to temperature;
an ignition system controller (61) capable of processing signals received from the means (36);
a closed cooling path (41, 42, 43, 44, 45, 46) comprising a pump and an air-cooled radiator (12), the closed cooling path (41, 42, 43, 44, 45, 46) passing through radiator outlet (33), cylinder block cooling path (42), portion of cylinder head cooling path (43) and then back to a radiator inlet (34);
characterized in that:
the means (36) capable of sending an electrical signal corresponding to a temperature at its location of placement to said ignition controller (61) is installed between said radiator inlet (34) and cylinder head cooling path (43).
2. An engine protection method for an internal combustion engine of a two-wheeled vehicle, said method comprising steps of:
a means (36) for sensing and generating a signal proportional to temperature at a pre-determined location between a cylinder head cooling path (43) and a radiator inlet (34);
an ignition system controller (61) categorizing said temperature to lie in a first pre-determined range (72) or a second pre-determined range (74);
the ignition system controller (61) providing signal to a coolant temperature LED (79) to glow when the temperature signal generated by thermal sensor (36) lies in the first pre-determined range (72); and
the ignition system controller (61) to cut off supply to ignition coil (62) when the temperature signal generated by said thermal sensor (36) lies in the second pre-determined range (74).
3. The engine protection method for an internal combustion engine of a two-wheeled vehicle as claimed in claim 2 wherein after supply cut off to ignition coil (62), the engine is switched off and the engine is capable of being restarted once the temperature signal generated by said thermal sensor (36) corresponds to a temperature either lower or equal to a temperature in the first pre-determined range (72).
4. The cooling system (40) for the internal combustion engine as claimed in claim 1 or claim 2 wherein a controller processes signal generated by said thermal sensor (36).
5. The cooling system (40) for the internal combustion engine as claimed in claim 1 or claim 2 wherein the engine is switched off once the temperature transducer (35) detects and sends a signal corresponding to a second pre-determined range (74).
6. The cooling system (40) for the internal combustion engine as claimed in claim 1 wherein the radiator top (12) is projected upwards to avoid air entrapment in the liquid cooling system.
7. The cooling system (40) for the internal combustion engine as claimed in claim 1 or claim 2 wherein signal generated by said thermal sensor (36) corresponding to temperature between said portion of cylinder head cooling path (43) and said radiator inlet (34) is used to display current engine temperature on a vehicle dashboard (90).
8. The cooling system (40) for the internal combustion engine as claimed in Claim 1 or claim 2 wherein a hazard lamp (81) is switched ON when the temperature signal generated by said thermal sensor (36) lies in the second pre-determined range (74).
9. The cooling system (40) for the internal combustion engine as claimed in Claim 1 or claim 2 wherein said engine is capable to be restarted only when the temperature signal generated by said thermal sensor (36) is lower than the first pre-determined range (72).
10. The cooling system (40) for the internal combustion engine as claimed in claim 1 or claim 2 or claim 7 wherein said dashboard display (90) is added with an audio signal for a pre-determined range of temperature (72, 74).