DESC:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)

TITLE OF THE INVENTION
“SYSTEM AND METHOD FOR PRECISE DETERMINATION OF ENGINE SPEED IN VEHICLES”

APPLICANTS:

Name : Mahindra &Mahindra Ltd

Nationality : India

Address : Mahindra Research Valley, Mahindra World
City Plot No. 41/1, Anjur P.O. Chengalpattu
Kancheepuram Dist, Tamilnadu.- 603204

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
The embodiments herein relate to cluster panels in vehicles for displaying engine speed.

BACKGROUND
Generally, in vehicles, cluster panels are provided to display engine speed (typically in the form of Revolutions per Minute (RPM)) of the vehicle. In vehicles without engine speed sensor, the cluster receives input signal from an alternator to calculate the engine speed. The cluster includes a microcontroller/microprocessor/PLC with a pre-defined value of pulley-diameter ratio for engine speed calculation and based on the alternator input signal, indicates the engine speed (rpm) accordingly. This predefined/programmed pulley-diameter ratio value is based on theoretical calculation(s) considering the effective diameters of engine crank pulley and alternator pulley. However, due to pulley’s tolerance variation during manufacturing and due to wear and tear of the pulley and belt, there is a deviation between the actual and predefined pulley-diameter ratio, leading to incorrect display of engine speed (rpm) in the cluster.
For calculating the engine speed, the input is taken from the W terminal of the alternator. The W terminal of alternator can generate a frequency corresponding to the speed of alternator. Example for a 12 pole alternator, alternator frequency is given by,
Alternator frequency= (speed of alternator in RPM)/10
where,
RPM = Revolutions per minute.
This alternator frequency is converted into engine speed based on the relation,
engine speed in RPM= (alternator frequency*10)/(programmed pulley-diameter ratio)
where,
programmed pulley-diameter ratio= (diameter of engine crank pulley)/(diameter of alternator pulley)
The predefined/programmed pulley-diameter ratio value can be calculated based on theoretical calculation considering effective diameters of engine crank pulley and alternator pulley. However, the programmed/predefined pulley-diameter ratio value will not match with real or actual pulley-diameter ratio value due to tolerance variation, wear and tear of pulley and belt and belt slippage.
If the predefined pulley-diameter ratio is less than the actual pulley-diameter ratio, the cluster will show high engine speed (rpm) than actual engine speed (rpm). If the predefined pulley-diameter ratio is greater than the actual pulley-diameter ratio then the cluster will show low engine speed (rpm) than actual engine speed (rpm).
In vehicles like tractors, due to faulty display of engine speed (rpm) in the cluster, a user can set incorrect speed for an application resulting in either increased fuel consumption or reduced productivity.

OBJECTS
The principal object of an embodiment of this invention is to provide a system and a method for calibrating a display cluster of a vehicle, such that the cluster will display the engine speed accurately.
The object of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
FIG. 1 depicts the cluster panel and associated components, according to embodiments as disclosed herein; and
FIG. 2 is a flowchart depicting the process of calibrating a display cluster of a vehicle, such that the cluster will display the engine speed accurately, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The embodiments herein achieve a system and a method for calibrating a display cluster of a vehicle, such that the cluster will display the engine speed accurately. Referring now to the drawings, and more particularly to FIGs. 1 and 2, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.
FIG. 1 depicts the cluster panel and associated components, according to embodiments as disclosed herein. The system (cluster panel) for determining and displaying engine speed of a vehicle comprises a device for processing signals, an actuator and a means for displaying engine speed of the vehicle. The vehicle can be at least one of a car, truck, bus, farm equipment, motorbike, scooter, or any other vehicle that does not use an engine speed sensor for determining the speed of the vehicle. The cluster can provide information such as display the engine speed, vehicle speed, turn indicators, warning indicators, and so on to the operator. In vehicles without engine speed sensor, the engine speed displayed by the cluster is based on an input signal from an alternator and a predefined pulley- diameter ratio value.
The cluster 100 as depicted comprises of a signal processor 101, a user interface 102, at least one connector 103, and a display 104. The user interface 102 can comprise of a means for enabling the user to perform an operation such as a button, a switch, a toggle, and so on. The connector 103 enables the cluster 100 to connect to at least one device and/or system in the vehicle. The cluster 100 can be further connected to the alternator in the vehicle using the connector 103. The display 104 can be used to display information to the user such as the engine speed, vehicle speed, turn indicators, warning indicators to a user of the vehicle. The signal processor 101 can be a microprocessor/microcontroller/PLC (Programmable Logic Controller) are any similar device that receives input signal from the alternator. The signal processor 101 can be programmed with at least one predefined value of pulley-diameter ratio for calculating and displaying the engine speed.
The signal processor 101 can initiate calibration, which comprises of determining the actual pulley-diameter ration, either automatically or manually. The signal processor 101 can initiate the calibration on detecting that the cluster 100 is not displaying the engine speed in a correct manner, wherein the error in engine speed is greater than a pre-defined threshold. The signal processor 101 can initiate the calibration on receiving an indication from a user. The user can provide the indication using the user interface 102. In an example, the indication can be the user pressing at least one button. In another example, the indication can be the user closing a calibration circuit in the cluster. The signal processor 101 can provide the user with an indication that the calibration process has started, using the user interface 102 (which can comprise of at least one light, icon, and so on).
The signal processor 101 can determine the actual pulley-diameter ratio using the formula,
pulley-diameter ratio= (speed (RPM)of alternator)/(speed (RPM) of engine)
To determine the speed of alternator (rpm), the engine is made to run at high idle for a predetermined amount of time. Now the alternator W terminal produces a signal with a frequency corresponding to the speed of the alternator. The signal processor 101 can determine the speed of the alternator from the signal produced by the W terminal of the alternator using the relation,
alternator frequency=(RPM of alternator)/10
(considering that the alternator is a 12 pole alternator)
The speed of the engine (rpm) is given by the rated speed of the engine, which is a predefined value.
Once the actual pulley-diameter ratio is calculated thereafter, the signal processor 101 can use the actual pulley-diameter ratio for calculating and displaying the engine speed at any time during the operation of the engine. The engine speed is calculated by the microprocessor of the cluster using the relation,
Engine speed in RPM = (Alternator Frequency*10)
Actual Pulley-diameter ratio
where,
Alternator Frequency = RPM of alternator (for 12 pole alternator)
10
Thereafter, the calculated engine speed in RPM is displayed using the display 104 in the cluster.
FIG. 2 is a flowchart depicting the process of calibrating a display cluster of a vehicle, such that the cluster will display the engine speed accurately. The cluster 100 initiates (201) calibration, which comprises of determining the actual pulley-diameter ration, either automatically or manually. The cluster 100 can initiate the calibration on detecting that the cluster 100 is not displaying the engine speed in a correct manner, wherein the error in engine speed is greater than a pre-defined threshold. The cluster 100 can initiate the calibration on receiving an indication from a user. The cluster 100 can provide the user of the vehicle with an indication that the calibration has started. The engine of the vehicle runs (202) at high idle for a pre-determined period of time. The cluster 100 can run the engine at high idle automatically. The cluster 100 can provide an indication to the user to run the engine at high idle for the pre-determined period of time. The cluster 100 determines (203) the speed of the alternator from the signal produced by the W terminal of the alternator using the relation,
alternator frequency= (RPM of alternator)/10
(considering that the alternator is a 12 pole alternator)
The cluster 100 then determines (204) the actual pulley-diameter ratio using the formula,
pulley-diameter ratio= (speed (RPM)of alternator)/(speed (RPM) of engine)
On determining the actual pulley-diameter ratio, the cluster 100 can provide an indication to the user that the calibration is complete and exit the calibration process. In an embodiment herein, the vehicle can be restarted to ensure that the cluster displays the engine RPM correctly.
Once the actual pulley-diameter ratio is calculated thereafter, the cluster 100 can use the actual pulley-diameter ratio for calculating and displaying the engine speed at any time during the operation of the engine. The engine speed is calculated by the microprocessor of the cluster using the relation,
Engine speed in RPM = (Alternator Frequency*10)
Actual Pulley-diameter ratio
where,
Alternator Frequency = RPM of alternator (for 12 pole alternator)
10
Thereafter, the calculated engine speed in RPM is displayed using the display 104 in the cluster. The various actions in method 200 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 2 may be omitted.
Embodiments herein disclose a cluster 100 with automatic pulley ratio calibration capability, which can self-calibrate and display engine RPM well within the acceptable tolerance limit.
Embodiments herein mitigate the error in the cluster displaying engine speed, with the cluster 100 displaying engine speed with an error of maximum up to ± 75 RPM.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

CLAIMS
We claim,
A method for calibrating a cluster of a vehicle for displaying engine speed of the vehicle, the method comprising:
operating the engine of the vehicle at high idle for a predetermined amount of time, on initiating calibration;
determining a speed of an alternator when the engine of the vehicle is operated at high idle; and
determining an actual pulley-diameter ratio based on the determined speed of the alternator and a predefined engine speed value.
The method, as claimed in claim 1, wherein the calibration is initiated in at least one of a manual manner; and an automatic manner.
The method, as claimed in claim 1, wherein the method further comprises of determining engine speed of the vehicle using the actual pulley-diamter ratio.
The method, as claimed in claim 1, wherein the method further comprises of providing an indication to a user, when the calibration process is ongoing.
A cluster in a vehicle configured for:
determining a speed of an alternator when an engine of the vehicle is operated at high idle, on initiating calibration; and
determining an actual pulley-diameter ratio based on the detemined speed of the alternator and a predefined engine speed value.
The cluster, as claimed in claim 5, wherein the cluster is configured to intiatiate calibration in at least one of a manual manner; and an automatic manner.
The cluster, as claimed in claim 5, wherein the cluster is configured to determine engine speed of the vehicle using the actual pulley-diamter ratio.
The cluster, as claimed in claim 5, wherein the cluster is configured to provide an indication to a user, when the calibration process is ongoing.
The cluster, as claimed in claim 5, wherein the cluster further comprises an actuator for providing signals to the device for processing signals for calibrating the pulley-diameter ratio value.

Dated this 29th September 2015

Signature:
Name: Kalyan Chakravarthy

ABSTRACT
System and method for precise determination of engine speed in vehicles. The embodiments herein relate to cluster panels in vehicles for displaying engine speed. Embodiments herein disclose a system and a method for calibrating a display cluster of a vehicle, such that the cluster will display the engine speed accurately.
FIG. 2

,CLAIMS:CLAIMS
We claim,
1. A method for calibrating a cluster of a vehicle for displaying engine speed of the vehicle, the method comprising:
operating the engine of the vehicle at high idle for a predetermined amount of time, on initiating calibration;
determining a speed of an alternator when the engine of the vehicle is operated at high idle; and
determining an actual pulley-diameter ratio based on the determined speed of the alternator and a predefined engine speed value.
2. The method, as claimed in claim 1, wherein the calibration is initiated in at least one of a manual manner; and an automatic manner.
3. The method, as claimed in claim 1, wherein the method further comprises of determining engine speed of the vehicle using the actual pulley-diamter ratio.
4. The method, as claimed in claim 1, wherein the method further comprises of providing an indication to a user, when the calibration process is ongoing.
5. A cluster in a vehicle configured for:
determining a speed of an alternator when an engine of the vehicle is operated at high idle, on initiating calibration; and
determining an actual pulley-diameter ratio based on the detemined speed of the alternator and a predefined engine speed value.
6. The cluster, as claimed in claim 5, wherein the cluster is configured to intiatiate calibration in at least one of a manual manner; and an automatic manner.
7. The cluster, as claimed in claim 5, wherein the cluster is configured to determine engine speed of the vehicle using the actual pulley-diamter ratio.
8. The cluster, as claimed in claim 5, wherein the cluster is configured to provide an indication to a user, when the calibration process is ongoing.
9. The cluster, as claimed in claim 5, wherein the cluster further comprises an actuator for providing signals to the device for processing signals for calibrating the pulley-diameter ratio value.

Dated this 29th September 2015

Signature:
Name: Kalyan Chakravarthy