FORM 2
THE PATENTS ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE
“A SYSTEM FOR DIAGNOSING ENGINE RPM SENSOR FAULT OF AN ENGINE”
APPLICANT
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. Sashikant Tiwari; Mr. Chandrakant Dhanjibhai Parmar; and Mr. Sethuramalingam Tyagarajan
All are 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 Description
The following specification particularly describes the invention and the manner in which it is to be performed. 2

FIELD OF INVENTION
The present disclosure generally relates to field of diagnostic system. Particularly but not exclusively, the present disclosure relates to a system for diagnosing engine rpm sensor signal fault.
BACKGROUND OF INVENTION
Inputs from the Engine rpm sensor is used by the Engine management system to control engine parameters such as the fuel injection or the ignition system timing and for configuring Engine management system’s strategy. Engine rpm sensor provide important input for fuel injection and ignition/spark timing. If there is the fault in engine rpm/ crank sensor, the fuel injection and ignition will not take place and engine will not start. Further, the engine rpm detected by the engine rpm sensor is also displayed on the dashboard of the vehicle. Accordingly, Engine rpm sensor has to be properly functioning for ensuring proper functioning of the engine and the vehicle.
Generally, for a vehicle having engine rpm sensor and cam phase sensor, engine rpm sensor signal failure is detected using cam phase sensor synchronization method. But in cases of engine where cam phase sensor is not present in engine, engine rpm sensor fault detection is not possible by conventional method. In that case, the system and method for engine rpm sensor fault detection becomes complex, inaccurate and non-reliable. For such systems (engine without cam-phase sensor) and methods, engine rpm sensor fault detection require skilled technicians and require time for detecting the fault. If there is fault in engine speed/ crank sensor, then the engine will not start and there will not be any error logged. In such case the service engineer has to invest lot of time and energy to diagnose fuel system, ignition system and wiring harness issues. In case the service person is not able to detect the engine rpm sensor fault in time, then there is delay in the repair, servicing, thereby increasing in servicing and repair costs that adds to customer dis-satisfaction. 3

Accordingly, there is a need for a system and method for detecting engine rpm sensor fault that is simple, accurate, and reliable. Further, there is a need for a system and method for detecting engine rpm sensor fault that do not require skilled technicians. Furthermore, there is a need for a system and method for detecting faults that enables quick detection of the faults, faster servicing and repair. Furthermore, there is a need for a system for detecting engine rpm sensor fault that can be easily retrofitted in the present vehicles, without much modification.
OBJECTS OF INVENTION
One object of the present disclosure is to a system and method for detecting engine rpm sensor fault that overcomes the drawbacks associated with the systems (engine without cam-phase sensor).
Another object of the present disclosure is to a system and method for detecting engine rpm sensor fault that is simple in construction.
Yet another object of the present disclosure is to provide a system and a method for detecting engine rpm sensor fault that enables the technician to easily and quickly identify the source and exact cause of the fault in the Engine Management system.
Another object of the present disclosure is to provide a system and method for detecting engine rpm sensor fault that is accurate and reliable
Another object of the present disclosure is to provide a system and method for detecting engine rpm sensor fault that is inexpensive and efficient.
Still another object of the present disclosure is to provide a system and method for detecting engine rpm sensor fault that enables quick detection of the faults, faster servicing and repair. 4

Another object of the present disclosure is to provide a system for detecting engine rpm sensor fault that can be easily retrofitted in the present vehicles, without much modification.
SUMMARY OF INVENTION
The shortcomings of the prior art are overcome and additional advantages are provided through the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.
In an embodiment of the present disclosure a system (100) for diagnosing engine rpm sensor fault of an engine of is disclosed. The system (100) includes at least one manifold pressure sensor, an engine RPM sensor (30) and a controller. The manifold pressure sensor (10) detects and generate intake manifold pressure dip signal. The engine RPM sensor (30) senses speed of a crankshaft of the engine. The controller is communicably coupled to the at least one manifold pressure sensor (10) and the engine RPM sensor (30). The controller (20) receive signals from the manifold pressure sensor (10) and the engine RPM sensor (30). The controller (20) further processes the received signals to diagnose the engine rpm sensor fault.
Typically, the controller (20) is an engine Management System of the vehicle.
Generally, the controller (20) logs an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure dip signals.
The controller (20) also confirms engine rotation if intake manifold pressure dip signal is present but crank wheel teeth detection signal is absent. 5

In accordance with an embodiment, the controller further receives crank wheel teeth detection signal at the time of cranking the engine “E”.
A method for diagnosing engine rpm sensor fault of an engine is disclosed in accordance with an embodiment of the present disclosure. The method includes the steps of detecting and generating intake manifold pressure dip signal by at least one manifold pressure sensor (10). Thereafter, receiving signals from the manifold pressure sensor (10) and an engine RPM sensor (30), and processing the received signals to diagnose the engine rpm sensor fault by a controller.
Typically, the method further includes the step of crank wheel teeth detection signal at the time of cranking the engine “E” by the controller.
In accordance with an embodiment, the method includes the step of logging an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure dip signals received by the controller.
The method further includes the step of confirming engine rotation if intake manifold pressure dip signal is received but crank wheel teeth detection signal is not received by the controller.
BRIEF DESCRIPTION OF DRAWINGS
The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which: 6

FIG. 1 illustrates the schematic representation of a system (100) without cam-phase sensor, in accordance with an embodiment of the present disclosure;
FIG. 2 illustrates a graphical representation depicting manifold pressure dip signal as detected by a manifold pressure sensor, with removed crank sensor connector, in accordance with an embodiment of the present disclosure; and
FIG. 3 illustrates a flow chart depicting the logic used by the system and method for detecting engine rpm sensor fault in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF INVENTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
The present disclosure generally relates to a system and method for detecting engine rpm sensor fault for ensuring error free operation of the engine rpm sensor, that in turn 7

ensures proper function of the Engine Management System and the engine vehicle. Particularly, the present invention relates to EMS ECU systems and methods of engine rpm sensor diagnosis for engine without cam phase sensor. When starter engages and engine starts rotating, manifold pressure in the manifold changes or reduced during suction. This dip of manifold pressure is used for diagnosis. The system utilizes sensor for detecting pressure drop (dip) in intake manifold during suction stroke for interpreting engine rpm sensor fault. When engine rotates and engine speed sensor signal is not received or detected but pressure dip is detected, this condition confirms that engine is rotating as pressure dip is only possible when engine is rotating during suction stroke. When the crank/engine speed sensor signal is not received / detected, this condition confirms that the engine speed sensor signal is faulty/engine speed sensor is not working.
FIG. 1 illustrates the schematic representation of a system (100) without cam-phase sensor, in accordance with an embodiment of the present disclosure, depicting the various elements thereof along with inter connection and interaction between the various elements thereof such as the intake manifold pressure sensor (10), the controller (20), the engine (E) and the engine rpm sensor (30). FIG. 2 illustrates a graphical representation depicting manifold pressure dip signal as detected by a manifold pressure sensor (10), with removed engine rpm sensor connector, in accordance with an embodiment of the present disclosure. In absence of the cam phase sensor in the engine, the system and method for engine rpm sensor fault detection becomes complex, inaccurate and non-reliable. Referring to FIG. 2, the graphical representation that depicts the variation of the intake manifold pressure “P” (in mbar) plotted along the Z axis w.r.t. Engine rpm “E rpm” plotted along the Y axis and time “t” along the X axis. Specifically, the “1” represents “0 engine rpm as crank sensor connector is removed”, whereas “2” represents “intake manifold pressure dips during cranking”. In an embodiment of the present disclosure a system (100) for diagnosing engine rpm sensor fault of an engine is disclosed that facilitates accurate engine rpm sensor fault detection even without the cam phase sensor in the engine. The system (100) includes at least one manifold pressure sensor (10), an engine RPM sensor (30) and a controller (20). The manifold pressure sensor (10) detects and generate intake manifold pressure dip signal. The engine RPM sensor (30) senses 8

speed of a crankshaft of the engine. The controller (20) is communicably coupled to the at least one manifold pressure sensor (10) and the engine RPM sensor (30). The controller (20) receive signals from the manifold pressure sensor (10) and the engine RPM sensor (30). The controller (20) further processes the received signals to diagnose the engine rpm sensor fault. The controller (20) is an engine Management System of the vehicle. The controller (20) logs an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure dip signals.
The controller also confirms engine rotation if intake manifold pressure dip signal is present but crank wheel teeth detection signal is absent.
FIG. 3 illustrates a flow chart depicting the logic/ strategy used by the system (100) and method for detecting engine rpm sensor fault in accordance with an embodiment of the present disclosure. At the time of cranking, the strategy continuously monitors the crank wheel teeth. During cranking if crank wheel teeth are detected and calibrated numbers of crank wheel teeth are captured, it confirms there is no fault in engine RPM sensor (30). In case of failure/ fault in engine speed/ crank sensor signal, there will be no crank wheel teeth detected but if there is the dip in manifold pressure sensor (10), it confirms that the engine is rotating. When calibrated number of intake manifold pressure sensor signal dips are observed but there are no crank wheel teeth captured, such condition confirms that there is fault in engine rpm/ crank speed signal.
Specifically, the intake manifold pressure signal dips are checked w.r.t to threshold when engine is cranked. If engine rpm sensor signal is faulty then the Engine Management System (EMS) will not detect correct number of crank teeth within consecutive intake manifold pressure signal dips. And if this repeats for predetermined maximum number of times specified in EMS then EMS will log engine rpm sensor error. 9

Engine rpm sensor diagnosis using intake manifold pressure sensor (10) in accordance with an embodiment of the present disclosure is divided in four stages.
• Intake manifold pressure sensor signal evaluation: The intake manifold pressure sensor signal is processed, checked and compared with minimum and maximum threshold. It should be within the limit to confirm its plausibility.
• Intake manifold pressure sensor signal dip detection: When engine is cranked then there is low intake manifold pressure during suction stroke, called dip. The magnitude of dip is used to define engine rpm sensor signal fault
• (Diagnosis of engine rpm sensor signal error: The EMS controller (20) checks whether crank teeth are detected or not within consecutive intake manifold pressure signal dips. EMS controller (20) will consider unsuccessful cranking attempt if calibrated numbers of dip are detected without correct number of crank teeth signals. And if unsuccessful cranking attempts repeats for predetermined maximum number of times specified in EMS controller (20) then EMS controller (20) will log engine rpm sensor error.
• Healing of error: Once the error is logged, EMS controller (20) will check for fault detection in next driving cycle for specified number of intake manifold pressure dip before confirming the healing. Error will be healed if engine rpm sensor signal error is not detected.

A method for diagnosing engine rpm sensor fault of an engine is disclosed in accordance with an embodiment of the present disclosure. The method includes the steps of detecting and generating intake manifold pressure dip signal from at least one manifold pressure sensor (10). Thereafter, receiving signals from the manifold pressure sensor and an engine RPM sensor, and processing the received signals to diagnose the engine rpm sensor fault.
Typically, the method further includes the step of crank wheel teeth detection signal at the time of cranking the engine “E”. 10

In accordance with an embodiment, the method includes the step of logging an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure dip signals.
The method further includes the step of confirming engine rotation if intake manifold pressure dip signal is present but crank wheel teeth detection signal is absent.
Although the system (100) for diagnosing engine rpm sensor fault of the present invention is explained with respect to the engine of a vehicle, however, the system (100) is not limited to engine of a vehicle only but is also applicable to other engines such as generator.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
Advantages:
The present disclosure provides a system and method for detecting engine rpm sensor fault that:
• overcomes the drawbacks associated with the conventional systems for detecting engine rpm sensor fault;
• is simple in construction;
• is accurate and reliable;
• is inexpensive and efficient;
• enables the technician to easily and quickly identify the source and exact cause of the fault in the Engine Management system;
• enables quick detection of the faults, faster servicing and repair;
• can be easily retrofitted in the present vehicles, without much modification; and

• is convenient to use and configure.

Referral Numerals: Reference Number Description
(100) A system for diagnosing engine rpm sensor fault of an engine
(10) manifold pressure sensor;
(20) Controller/ Engine Management System;
(30) Engine rpm sensor; and
“E” Engine
We Claim:
1. A system (100) for diagnosing an engine rpm sensor fault of an engine, said system (100) comprising:
• at least one manifold pressure sensor (10) adapted to detect intake manifold pressure dip signal;
• an engine RPM sensor (30) adapted to sense speed of a crankshaft of the engine;
• a controller (20) communicably coupled to said at least one manifold pressure sensor (10) and said engine RPM sensor, said controller (20) adapted to receive signals from said manifold pressure sensor and said engine RPM sensor, said controller (20) further adapted to process received signals to diagnose said engine rpm sensor fault.
2. The system (100) as claimed in claim 1, wherein said controller is an engine Management System of said vehicle.
3. The system (100) as claimed in claim 1, wherein said controller (20) adapted to log an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure-dip signals.
4. The system (100) as claimed in claim 1, wherein said controller (20) further adapted to confirm engine rotation if intake manifold pressure dip signal is present but crank wheel teeth detection signal is absent.
5. The system (100) as claimed in claim 1, wherein said controller (20) further adapted to receive crank wheel teeth detection signal at the time of cranking the engine “E”.
6. A method for diagnosing engine rpm sensor fault of an engine, said method comprising the steps of:
• detecting and generating intake manifold pressure dip signal by at least one manifold pressure sensor (10); and

•receiving signals from said manifold pressure sensor (10) and an engine RPM sensor, and processing the received signals to diagnose said engine rpm sensor fault by a controller.
7. The method as claimed in claim 1, further comprising the step of crank wheel teeth detection signal at the time of cranking the engine “E” by the controller.
8. The method as claimed in claim 1, comprising the step of logging an engine rpm sensor error when unsuccessful cranking attempts are repeated for a predetermined number of times, wherein one unsuccessful cranking attempt is considered, when the crank wheel teeth detection signals do not correspond to particular number of intake manifold pressure dip signals received by the controller.
9. The method as claimed in claim 1, further comprising the step of confirming engine rotation if intake manifold pressure dip signal is received but crank wheel teeth detection signal is not received by the controller.