FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION THERMOSTAT DIAGNOSTIC DEVICE


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
Mr. D. R. Katkar, Mr. D. S. Kulkarni both Indian nationals
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 TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF THE INVENTION
The present invention relates to the fields of thermostat of automotive vehicles. The present invention specifically relates to an arrangement for detecting proper functioning of the thermostat and providing an indication to the driver in case of thermostat malfunction. The present invention also relates to a arrangement through which the corrective action can be taken in case of therrnostat malfunction.
BACKGROUND OF THE INVENTION
Automotive engines are fitted with thermostat as a thermal switch. The thermostat regulates circulation of cooling water between the engine and a radiator. The thermostat is used to achieve engine operating temperature faster and maintain the desired operating temperature during engine operation. Thermostat is a two-way valve, which receives coolant from the engine. When tfre coolant temperature is low, the engine coolant is circulated back to the engine When the engine cooling temperature exceeds the normal operating temperature, the by pass path is closed and the thermostat starts opening and thus allowing the coolant to flow through the radiator, which cools the engine coolant. During short vehicle trips the recirculation mode is in operation for a considerable time whereas during long trips the thermostat open mode is in operation for significantly long period.
Thermostat malfunction occurs in following two ways, i.e. thermostat stuck open and thermostat stuck close. In the first case, the thermostat causes a continuous flow of the engine coolant to the radiator even when the coolant temperature is low. This result in prolonged warm up period of the engine, which leads to higher cold phase emissions and lower fuel economy. This kind of thermostat failure is difficult to
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detect. In the second case, the thermostat fails to open even after the engine coolant temperature exceeds thermostat opening temperature due to mechanical failure. Hence, it continuously increases the engine coolant temperature, which leads to engine overheating and the consequential failure, since no bypass is provided for the thermostat to address this failure.
Both these thermostat failure conditions are severe for vehicle operation. Similarly there is no positive indication to the vehicle driver when these failures are occurred. Typically, the cost of the automotive engine is 200 - 400 times the cost of the thermostat. Thus, it is necessary to provide diagnostic device for the thermostat and an arrangement to take corrective action in case of thermostat malfunction.
However, the conventional method of patent US0210361 describes that thermostat failure is diagnosed and determined by comparing the stored cooling water temperature with the corrected target temperature with regard to influence of intake air. Similarly, the US patent 6752 011 explains about an apparatus for an internal combustion engine in which a failure can be effectively made. In this prior art, after starting of the engine, the thermostat failure is judged on the basis of time in which the cooling water temperature rises to a predetermined temperature. Such failure diagnosis of the thermostat can be rationally made only when the engine generating heat quantity is large to some degree to prevent erroneous diagnosis. The above two prior arts utilize the engine airflow as a primary measure of detecting the thermostat failure when the engine operates the desired water temperature.
Moreover, the US patent 7299993 explains about an apparatus for detecting a failure of a thermostat. The apparatus comprises a controller that detects the thermostat failure based on the output of the radiator water temperature sensor when the engine
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has reached the desired warm condition. This prior art determines the thermostat malfunction based on pre and post thermostat coolant temperatures, a vehicle related process or an estimated engine water temperature.
With respect to the conventional arts, none of the arrangments and/or methods provides a corrective means after diagnosing the thermostat failure. However, the prior art does not determine both the thermostat failure conditions, i.e. thermostat stuck open and thermostat stuck close. Therefore, it is desirable to provide an arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and compensating said malfunction, which provides an indication to the driver in case of thermostat malfunction.
OBJECT OF THE INVENTION
An object of the present invention is to provide an arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and compensating said malfunction, which checks the proper functioning of the thermostat during vehicle operation.
Another object of the present invention is to provide an arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and compensating said malfunction, which enables the driver to take necessary corrective action in case of thermostat malfunction.
Yet another object of the present invention is to provide an arrangement that detects all the thermostat malfunction conditions.
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Yet another object of the present invention is to provide an arrangement that can be retrofitted on in-use vehicles without any modifications.
SUMMARY OF THE INVENTION
According to one aspect, the present invention, which achieves the objectives, relates to an arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and compensating said malfunction comprises a magnetic flow detection device that detects proper functioning of a thermostat on a vehicle during vehicle operation by checking flow of engine coolant between the thermostat and a radiator as a function of engine coolant temperature. An electronic controller provides an indication on a dashboard regarding thermostat malfunction based on the output of the flow detection device. Two butterfly valves can respectively be located at a bypass path to the thermostat and downstream of the thermostat and the flow detection device. The butterfly valves are electrically operated through knobs by the electronic controller in order to regulate the engine coolant flow in case of thermostat malfunction, which enables diagnosis and compensation for the thermostat malfunction in an easy and rapid manner.
STATEMENT OF INVENTION
This invention relates to an arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and for compensating said malfunction, comprising: a magnetic flow detection device mounted downstream of a thermostat for measuring flow velocity of engine coolant between said thermostat and a radiator; an engine coolant temperature sensor; an electronic controller for indicating the thermostat malfunction based on the inputs from said magnetic flow detection and said
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temperature sensor; a bypass path with first butterfly valve to bypass flow through said thermostat; a second butterfly valve located at downstream of said thermostat; and said first and second butterfly valves controlled manually.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be discussed in greater detail with reference to the accompanying Figures.
FIG. 1 shows a constructional detail of an arrangement of components in a conventional cooling system of a vehicle, in accordance with a prior art.
FIG. 2 illustrates an overall arrangement of components in a cooling system of a vehicle, in accordance with principles of the present invention.
FIG. 3 illustrates a schematic view of a magnetic flow detection device, in accordance with an exemplary embodiment of the present invention.
FIG. 4 illustrates a schematic view of an electronic controller for thermostat diagnostic, in accordance with an exemplary embodiment of the present invention.
FIG. 5 illustrates a flow chart for detecting thermostat failures conditions, in accordance with an exemplary embodiment of the present invention.
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DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a constructional detail of an arrangement of components in a conventional cooling system of a vehicle is illustrated. The conventional cooling system of an internal combustion engine comprises an engine (1) that includes an upper water cooling line (2) on which a temperature sensor (3) is mounted. The upper water cooling line (2) carries the coolant from the engine (1) to a radiator (4). A thermostat (5) can be placed between the engine (1) and the radiator (4). A bypass line (6) can be carried from the thermostat (5) to a water pump (7), where the water pump (7) circulates the engine coolant through the engine (1) when the engine (1) is started.
Initially when the engine coolant temperature is low, the thermostat (5) remains closed and blocks the engine coolant flow through the radiator (4). Then, the coolant is re-circulated into the engine (1) via the bypass line (6), which helps in faster engine warm up. When the engine coolant temperature rises further, the thermostat (5) opens and the by pass line (6) is closed, which results in coolant flow through the radiator (4) to cool the engine coolant. The functioning of the conventional engine cooling system primarily depends on proper operation of the thermostat.
Referring to FIG. 2, an overall arrangement of components in a cooling system of a vehicle is illustrated, in accordance with principles of the present invention. In addition to the basic cooling system and components, a thermostat malfunction diagnostic and compensation arrangement is included, which is primarily of add on type. Such arrangement comprises a magnetic flow detection device (18) that is mounted downstream of a thermostat (15), where the output of the magnetic flow detection device (18) is provided to an electronic controller (19).
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Based on an engine coolant temperature sensor signal from a temperature sensor (13), the electronic controller (19) determines whether the coolant flow to the radiator should occur or not. The electronic controller (19) compares the engine coolant temperature sensor signal with the output of the magnetic flow detection device (18). If there is a mismatch, the electronic controller (19) provides an indication to a vehicle driver by using a thermostat malfunction lamp provided on a dashboard.
Two butterfly valves (20) and (21) can be provided in the cooling system of the vehicle. The butterfly valve (20) is located at a bypass path of the thermostat (15), which is kept normally in a closed condition. Similarly, the butterfly valve (21) is located downstream of the thermostat (15) and the magnetic flow detection device (18), which is kept normally in an open condition. The butterfly valve (20) and (21) can be operated by a cable through knobs (22) and (23), respectively, where the knobs (22) and (23) are provided on the dashboard and operated electrically through the electronic controller (19).
FIG. 3 illustrates a schematic view of the magnetic flow detection device (18), in accordance with an exemplary embodiment of the present invention. The magnetic flow detection device (18) can be fitted downstream of the thermostat (14). Basically, it is a non-contact type electromagnetic flow detection device that measures flow velocity by measuring the change in induced voltage of the conductive fluid passing across a controlled magnetic field. The flow detection device (18) comprises a set of permanent magnets (31) and (32) that provides the magnetic field. A voltage output (34) proportional to the flow velocity of the coolant is generated when the coolant flows (33) through the magnetic flow detection device (18).
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FIG. 4 shows a schematic view of the electronic controller (19) for thermostat diagnostic, in accordance with an exemplary embodiment of the present invention. The electronic controller (19) is microprocessor based and is capable of receiving multiple inputs from various components of the cooling system. The electronic controller (19) can be programmed with multiple input parameters (41) and receives multiple input signals (42) from the engine (11) and the flow detection device (18), where the input signals are engine coolant temperature signal, engine start signal, vehicle speed signal and output signal (43) from the magnetic flow detection device (18).
In addition, the electronic controller (19) is also programmed with the thermostat opening temperature, which represents the upper limit of complete opening of the thermostat (15). The electronic controller (19) primarily depends on the engine coolant temperature sensor signal from the temperature sensor (13). The controller (19) provides an output signal by comparing the output voltage signal from the magnetic flow detection device (18) with the engine coolant temperature sensor signal. During normal operation, when the engine coolant temperature exceeds the thermostat opening temperature, the thermostat (15) is expected to open and allow the engine coolant to flow to the radiator (14). In such case, the controller (19) looks for a corresponding step in output current for the magnetic flow detection device (18). Similarly, when the engine coolant temperature is less, the controller expects no voltage output signal from the magnetic flow detection device (18).
Referring to FIG. 5, a flow chart for detecting thermostat failures conditions is illustrated, in accordance with an exemplary embodiment of the present invention. During normal operation, the controller checks for the engine coolant temperature (Tw) after receiving the engine start signal, as depicted at steps 502 and 504. At step
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506, the engine coolant temperature (Tw) can be compared with the thermostat opening temperature (SOT). If the coolant temperature is lower than the thermostat opening temperature, the output of the magnetic flow detection device (18) is checked that there is no flow of coolant to the radiator (14) and correspondingly no output from the magnetic flow detection device (18), as depicted at step 508. Similarly, when the coolant temperature is higher than the thermostat opening temperature, the coolant can flow to the radiator (14) and a positive output is received by the electronic controller (19) from the magnetic flow detection device (18). as shown at step 510. Thus, the controller (19) checks the functioning of the thermostat (15) as a function of engine coolant temperature using the output signal from the magnetic flow detection device (18).
As illustrated at step 512, the electronic controller (19) compares the actual flow detection device output with logical correct output from the temperature sensor (13). Therefore, the electronic controller (19) determines whether the thermostat stuck open failure or closed failure based on the comparison output, as depicted at steps 514 and 516. When the thermostat (15) is stuck open, then the coolant is continuous flowed to the radiator (14) even when the engine coolant temperature is less, which results in continuous output voltage signal to the electronic controller (19). In such case, the electronic controller (19) gives thermostat stuck open signal on the dashboard, which enables the driver to take necessary corrective action. Thus, the failure gets detected easily and quickly. To counter the thermostat stuck open failure, the butterfly valve (21) is closed by pulling a knob (23), as shown at step 518. Once the engine coolant temperature reaches thermostat opening temperature, the controller (22) provides an indication to open the butterfly valve (21).
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When the thermostat (15) remains stuck closed, the engine temperature rises continuously beyond the thermostat open temperatures, since there is no coolant flow to the radiator (14), which results in no output voltage signal to the controller (19). In such case, the controller (19) provides thermostat stuck close signal on the dashboard, which enables the driver to take necessary corrective action. To counter the thermostat stuck closed failure, the butterfly valve (20) in the thermostat bypass path is opened by pulling a knob (22), as illustrated at step 520. Once the engine coolant temperature drops below the thermostat opening temperature, the controller (19) gives an indication to close the butterfly valve (20).
When the engine coolant temperature sensor (13) fails or when it indicates an abnormal reading, the controller (19) goes into the limp home or fail safe mode. In such case, the controller (19) estimates the engine coolant temperature based on two parameters, i.e. time since engine start and a distance traveled since engine start calculated using integrating function of the controller (19). Then, the controller (19) provides a signal to open the bypass valve (20) after a predetermined time since engine start or a predetermined distance traveled.
When such a unit is an OE fitment, these input parameters are programmed at the vehicle assembly stage as an end of the line programming. Similarly, when it is a retro-fitment, the input parameters are programmed by the installer of the equipment.
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WE CLAIM
1. An arrangement for diagnosing thermostat malfunction in a vehicular engine
cooling system and for compensating said malfunction, comprising:
a magnetic flow detection device mounted downstream of a thermostat for measuring flow velocity of engine coolant between said thermostat and a radiator;
an engine coolant temperature sensor;
an electronic controller for indicating the thermostat malfunction based on the inputs from said magnetic flow detection and said temperature sensor;
a bypass path with first butterfly valve to bypass flow through said thermostat;
a second butterfly valve located at downstream of said thermostat; and
said first and second butterfly valves controlled manually.
2. The arrangement as claimed in claim 1, wherein said electronic controller is configured to determine whether the flow of engine coolant to said radiator should occur or not, based on an engine coolant temperature sensor signal from a temperature sensor.
3. The arrangement as claimed in claim 1, wherein said electronic controller is configured to compare the coolant flow determination result with the output of the magnetic flow detection device.
4. The arrangement as claimed in claim 1, wherein said electronic controller is microprocessor based and programmed with multiple input signals such as engine cooling temperature, time elapsed since engine stop, magnetic flow detection device
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input, vehicle speed input and multiple outputs such as indication for thermostat malfunction.
5. The arrangement as claimed in claim 1, wherein said electronic controller is programmed with back up strategy to estimate the engine coolant temperature.
6. The arrangement as claimed in claim 1, wherein said magnetic flow detection device is configured to generate a voltage output proportional to the flow velocity of the engine coolant.
7. The arrangement as claimed in claim 8, wherein said magnetic flow detection device is a non-contact type electromagnetic flow detection device.
8. The system as claimed in claim 1, wherein said one or more knobs are provided on the said dashboard and connected to the said one or more butterfly valves.
9. A vehicular engine cooling system, comprising:
a radiator;
an engine including an upper water cooling line, which carries engine coolant from the said engine to the said radiator;
a temperature sensor mounted on the upper water cooling line of said engine;
a thermostat placed between said engine and said radiator for re-circulating the engine coolant flow through said engine and said radiator;
a bypass line carried from said thermostat to a water pump, which circulates the engine coolant through said engine; wherein
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an arrangement for diagnosing thermostat malfunction in the vehicular engine cooling system and compensating said malfunction includes:
a magnetic flow detection device mounted downstream of a thermostat for measuring flow velocity of engine coolant between said thermostat and a radiator;
an electronic controller for indicating the thermostat malfunction using one or more thermostat malfunction indication lamps based on the output of the magnetic flow detection device; and
one or more butterfly valves located at a bypass path to the thermostat and downstream of the thermostat and the flow detection device, wherein said one or more butterfly valves controlled through one or more knobs.
10. The vehicular engine cooling system and the arrangement for diagnosing thermostat malfunction in a vehicular engine cooling system and compensating said malfunction as claimed in claims 1-11 largely as described in specifications and as illustrated in accompanying figures.
Dated this 13th day of February 2009
TATA MOTORS LIMITED By their Agent & Attorney

(Karuna Goleria) of DePENNING & DePENNING
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