DESC:[FIELD OF INVENTION]
[0001] The present subject matter relates to an engine of a vehicle. More particularly, the present invention relates to determining air temperature for an electronic fuel injection hereinafter called as EFI system of the engine.
[BACKGROUND OF THE INVENTION]
[0002] Fuel injection is a term used for injection of fuel into an engine. In general, a carburetor is used for mixing of air and fuel in an appropriate ratio for injection into the engine. However, with the advent of technology the electronic fuel injection (EFI) replaces the technology of carburetor, by electric controls for better results such as fuel efficiency. A control unit, hereinafter referred as an electronic control unit (ECU) is a generic term used for controlling of one or more electrical components. Similarly, an ECU is used for controlling the amount of fuel, duration of fuel injection, amount of air, and receiving temperature of engine, temperature of air intake etc. from various sensors. More specifically, an engine temperature sensor senses the temperature of engine, and an intake air sensor senses the temperature of ambient air. These parameters are used by ECU for the EFI system for functioning of the engine.
[BRIEF DESCRIPTION OF DRAWING]
[0003] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings with reference to the features and components.
[0004] Figure 1 and Figure 2 and Figure 3 represents a general assembly of sensors as per known art.
[0005] Figure 4 presents a flowchart of ambient temperature learning method as per current invention.
[0006] Figure 5 illustrates a graphical illustration.

[DETAILED DESCRIPTION OF THE INVENTION]
[0007] For efficient operation of an EFI system, an ECU controls the various parameters such as fuel injection amount, duration of fuel injection etc. However, the ECU performs all such function based upon inputs from various sensors such as engine temperature sensor which provides temperature of the engine or power generation unit, an intake air temperature sensor (IAT) which provides temperature of ambient air, etc. More the number of sensors, higher the amount of cost incorporated in the ECU. Therefore, eliminating even a single sensor from the engine management system will make significant difference in cost saving including material and manufacturing cost, elimination of hardware interface with ECU thereby less maintenance, elimination of diagnostic circuit for that sensor in ECU and cost of logic in ECU corresponding to sensor. Additionally, there will be elimination of special connector and associated wiring harness. If the eliminated sensor is near to power unit, hereinafter referred as engine, such an arrangement will also save corrugated tube and additional temperature protection features.
[0008] The primary function of IAT sensor is to retrieve the temperature of atmospheric air. The IAT sensor is a primary element for determining the amount of air entering the engine with air with aid of manifold air pressure sensor. This information is necessary for determining the amount of fuel to be injected in the engine for appropriate air fuel ratio. But when the engine starts and operates for certain time, the temperature of the air sensed by the IAT sensor is high since the IAT sensor is near to throttle body which is turn is close to engine thereby leading to increase in the temperature of the air in the vicinity of the IAT sensor. Therefore, only during the start of the engine, the IAT sensor provides accurate temperature of the ambient air. The engine temperature sensor and the IAT sensor both works on similar principals but for different purposes. As per known art, the IAT sensor can be eliminated by prediction made by a sensor which estimates the engine OFF time using soak timer. That means soak timer continuously operates even when the vehicle is OFF which lead to unnecessary battery drainage.
[0009] As per yet another known art, the IAT sensor is eliminated using plurality of thermistors which requires the ECU to be mounted near to the engine. However, such as arrangement of positioning the ECU mounted to the body of engine is not preferred as the ECU is susceptible to high amount of heat generated by the engine.
[00010] Usually in the engine, the major amount of temperature is transferred to the intake pipe and throttle body by means of conduction and convection. The heat transfer through conduction process depends on surface area, material coefficient, and temperature difference. In equation form:
Q conduction= KA (T Eng - TTHB)……………………………equation (1)
Q convection= hA (TTHB – TIAT) ……………………………equation (2)
Wherein TIAT is ambient temperature; TTHB throttle body temperature; T Eng is temperature of engine, A is surface area; K is conduction co-efficient which is material specific, and H is convection coefficient which is material specific.
[00011] Hence, there is need to provide an improved engine management system that will eliminate an additional sensor component during the fuel injection process which overcomes all limitations and problems cited above as well as other problems of known art. The improve system should be capable of achieving a more accurate result, increased efficiency at a reduced cost without compromising in the battery power, and design change by mounting ECU on the body of the engine.
[00012] It is an objective of present invention to provide a vehicle having an engine management system which will eliminate the use of IAT sensor and yet reliably retrieve or determine the ambient temperature from already existing sensor which determines a first predetermined attribute of the power unit such as temperature using the engine temperature sensor. Therefore, the present invention reduces cost, maintenance cost, and man hour for overall vehicle manufacturing. Alternatively, as per an objective of the present invention, an improved engine management system is required which works without using an IAT sensor. Also, the value of ambient temperature achieved from the present invention is not merely accurate at the beginning of engine operation, instead accurate results are achieved throughout the process of vehicle operation, thereby increasing accuracy and reliability of the vehicle. Additionally, the present invention does not rely on the battery, or any other energy source, and does not involve any design change to the existing vehicle layout. Further, clearance around the various engine components are increased by eliminating the sensor.
[00013] As per an object of present invention, an improved engine management system is disclosed which is configured of being capable to provide a method of determining ambient air temperature using an already existing sensor i.e. engine temperature sensor using the concepts of thermodynamic of conduction and convection.
[00014] The present invention is configured with two pre-defined look up tables for conduction and convection. The conduction table is based on graph prepared by Q conduction= KA (T Eng - TTHB) (equation (1)) which is unique for each value of throttle body temperature with respect to each value of engine temperature. This assists in enhancing the accuracy of the whole system. Similarly, a predefined convection table is prepared based upon Q convection= hA (TTHB – TIAT) (equation (2)) which is unique for each value of ambient air temperature TIAT with respect to each value of throttle body temperature TTHB. When the vehicle is started by ignition, a first pre-determined attribute of the engine such as, the engine temperature is sensed by the engine temperature sensor. After sensing the predetermined temperature, it is important to detect any failure mode of the engine temperature sensor because the engine temperature sensor as per the present invention is used to determine two value i.e. engine temperature and ambient temperature. If there is no failure at the engine temperature sensor, the values of temperature of engine (Teng ) is obtained for a first predefined time interval. Based upon the values of first predefined time interval and calculated engine temperature, a slope is prepared in for engine temperature vs time. The slope is important to ascertain the rate of change of temperature of engine with respect to time for accuracy purpose. The values of engine temperature for a specific first predefined interval of time is important to get accurate ambient temperature during whole operation of the vehicle, such that accurate air fuel ratio is obtained for whole span of engine operation.
[00015] A standard deviation for the slope is determined for comparison with a threshold standard deviation. The comparison of the standard deviation with threshold standard deviation is crucial to eliminate any error in determining the ambient temperature value. A standard deviation of the slope indicates variation in between the consecutive values of engine temperature with respect to time values, thereby assisting in determining any error in the determined values if any. In general, a low standard deviation value indicates the value are close to the expected value and a high standard deviation indicates the values are spread across a wider range of values.
[00016] In case the standard deviation of the slope is less than threshold value , the value of temperature of the throttle body TTBH i.e. a second attribute for calculating ambient air temperature is determined by referring a predefined lookup conduction table. The conduction table is based on pre-calibrated graph prepared by equation Q conduction= KA (T Eng - TTHB) (equation (1)) which is unique for each throttle body temperature value and engine temperature value. Referring the pre-defined lookup conduction table with respect to calculated engine temperature slope, the corresponding throttle body temperature is retrieved. The throttle body temperature is retrieved for second predetermined time by the ECU from the conduction look up table. If the standard deviation of the slope is more than threshold value of, then system continues to monitor the same engine temperature with time because a higher standard deviation may not provide an accurate ambient temperature value. The standard deviation of the slope higher than the threshold value of indicates that there is some unexpected error, outliers or fault at the previous stages. Therefore, the present invention ensures accurate air ambient temperature value calculation at all stages of engine operation.
[00017] The whole calculation of the engine temperature Teng with respect to time for plotting a slope and calculating standard deviation for calculation of throttle body temperature is a cyclic process. The throttle body temperature is obtained for a predefined second time interval. A second slope (throttle body temperature vs. time) for the throttle body temperature TTHB and second time interval is calculated by the ECU. A standard deviation is calculated for comparison with threshold standard deviation of. In case the standard deviation is less than threshold value of, the value of temperature of intake air TIAT is determined by referring a predefined look up convection table. The lookup convection table is based on pre-calibrated graph prepared by equation Q convection= hA (TTHB – TIAT) (equation (2)). The ambient air temperature can be determined by a convection look up table with corresponding slope of throttle body temperature vs second time interval. If the standard deviation of the slope is more than threshold value of, then system continues to monitor the throttle body temperature in loop.
[00018] Therefore, the present invention ensures that the ambient air temperature is calculated efficiently and accurately over entire duration of the vehicle operation without compromise on additional cost, maintenance.
[00019] Figure 1 and Figure 2 illustrates general assembly of engine temperature sensor (101) and throttle body (100) in an engine assembly 102. The throttle body (100) is the part of air intake system that controls the amount of air flowing into the engine. A controller or an ECU (not shown) with the help of various sensors such as intake air temperature sensor, the engine temperature sensor etc. monitors the air fuel ratio for the combustion of the engine (102).
[00020] Figure 3 illustrates the position of IAT sensor (301) as per known art. The primary function of IAT sensor is to retrieve the temperature of atmospheric air. The IAT sensor (301) is a primary element for determining the amount of air entering the engine (102) with aid of manifold air pressure sensor. This information is necessary for determining the amount of fuel to be injected in the engine (102) for appropriate air fuel ratio.
[00021] Fig. 3A illustrates a simple block diagram showing a vehicle (10) comprising an engine management system (103) as per present invention. The engine management system (103) includes the controller (104) and engine temperature sensor (101). The ECU (104) is configured to retrieve accurate ambient air temperature based on pre-defined look up tables. The detailed explanation of the present invention is explained below.
[00022] Figure 4 illustrates flowchart of ambient temperature learning or retrieving method as per present invention. The present invention is configured with two look up tables based on conduction and convection. The conduction table is based on graph prepared by Q conduction= KA (T Eng - TTHB) (equation (1)) which is unique for each value of throttle body temperature TTHB and value of engine temperature TEng , thereby enhancing the accuracy of the whole system. Similarly, a convection table is prepared based up Q convection= hA (TTHB – TIAT) (equation (2)) which is unique for each value of ambient air temperature TIAT and corresponding value of each throttle body temperature TTHB. As per figure 4, the vehicle (10) is started at step (300) by ignition (301). If the vehicle is started, reading of pre-determined attribute of the engine such as, the engine temperature reading is done at step (302) by the sensor or more specifically engine temperature sensor (101). Once the engine temperature at step (302) is read, it is important to detect any failure mode of the engine temperature sensor at step (303) because the engine temperature sensor (101) as per the present invention is used to determine two value i.e. engine temperature T Eng and ambient temperature TIAT. If there is no failure detected in the engine temperature sensor (101), the values of temperature of engine (Teng ) is obtained for a predefined time interval TIM_1. Based upon the time interval TIM_1 and TEng , a slope S_TEng is obtained in step (305) by the ECU (104). The slope represents value of engine temperature TEng vs time TIM_1 in a graphical manner. The slope S¬¬_Teng important to ascertain the rate of change of temperature of engine with respect to time. The values of engine temperature TEng for a specific predetermined interval of time is important to get accurate ambient temperature TIAT during whole operation of the vehicle. This will ensure accurate air fuel ratio for whole span of engine operation.
[00023] A standard deviation SD_STEng of the slope S_TEng is calculated for comparison with a threshold standard deviation SD_TH_Teng at step (306). The comparison of the standard deviation (SD_STEng ) with threshold standard deviation (SD_TH_Teng ) is crucial to eliminate or determine any error in calculation of engine temperature TEng by the sensor (101). This is important for determining the error free ambient temperature value TIAT . A standard deviation (SD_STeng ) of the slope indicates variation in between the consecutive engine temperature values over a time period. In general, a low standard deviation value indicates the value are close to the expected value and a high standard deviation indicates the values are spread across a wider range of values.
[00024] In case the SD_STeng is less than threshold value of SD_TH_Teng, , the value of temperature of the throttle body TTBH i.e. a first attribute for calculating ambient air temperature is determined at step 307. The ECU retrieves the values of throttle body temperature TTBH by referring a predefined look up conduction table. Said conduction table is based on pre-calibrated graph prepared by equation Q conduction= KA (T Eng - TTHB) (equation (1)) which is unique for each throttle body temperature value and engine temperature value. Based on the slope STeng and calculated engine temperature T Eng, the corresponding throttle body temperature TTHB value from the conduction table is retrieved. More certainly, the throttle body temperature TTHB is retrieved (step 307, 308) for second predetermined time TIM_2 from the conduction look up table defined in the ECU (104). If the standard deviation SD_STeng of the slope S Teng is more than threshold value of SD_TH_Teng, then system continues to monitor the same in a loop at step 306, because a higher standard deviation SD_STeng may not provide an accurate ambient temperature value TIAT . The standard deviation SD_STeng of the slope S_Teng higher than the threshold value of SD_TH_Teng indicates that there is some unexpected error, outliers, or fault at the previous stages, therefore a fresh calculation of the standard deviation SD_STeng of a new slope of engine temperature Teng is performed as part of the loop. Therefore, the present invention ensures accurate air ambient temperature value calculation at all stages of engine operation.
[00025] The whole calculation of the engine temperature Teng with respect to time TIM_1 for plotting a slope S_Teng and calculating standard deviation SD_STeng for calculation of throttle body temperature TTHB is a cyclic process done by the ECU (104). The throttle body temperature TTHB is retrieved by the ECU (104) from the pre-defined conduction look up table for a time interval of TIM_2 at step (308). A slope STTHB is obtained between the TTHB and time interval of TIM_2 at step (309) which defines a slope of the temperature of the throttle body vs. time. A standard deviation SD_ STTHB is calculated for comparison with threshold standard deviation of SD_ TH_TTHB at step 310.
[00026] In case the SD_ STTHB is less than threshold value of SD_ TH_TTHB, the value of temperature of intake air TIAT, that is the second attribute is determined at step 311 by referring a predefine convection look up table. The convection lookup table is based on pre-calibrated graph prepared by equation Q convection= hA (TTHB – TIAT) (equation (2)). The temperature of intake air TIAT is retrieved by the ECU (104) based on the slope STTHB and the corresponding ambient air temperature value in the convection look up table (step 311). If the standard deviation SD_ STTHB of the slope STTHB is more than threshold value of SD_ TH_TTHB, then system continues to monitor the same in a loop at step 310.
[00027] Figure 5 illustrates an exemplary comparison of efficiency in calculating ambient air temperature as per present invention in contrast to prior arts. Assuming the ambient air temperature in a controlled environment, the value of ambient air temperature as per present invention is same as the real intake air temperature (ambient). However, intake air temperature sensor as per prior art increases with increase in engine temperature value. The graph clearly lays out the efficiency of the present invention for calculating ambient air temperature over known state of art.
[00028] The above invention provides a simple method based upon thermodynamic concepts for retrieving ambient air temperature without use of any special sensor. The present invention is counter intuitive as without using a special sensor, the present invention achieves more accurate, precise results thereby assisting in appropriate air fuel ratio for the vehicle in accost effective manner. Furthermore, additional material cost, manufacturing cost, hardware interfacing components in ECU is eliminated. Additionally, diagnostic circuit for checking of a sensor, special hardware and associated wirings, and cost of logics have been removed.
[00029] Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention.
List of references:
10: Vehicle
100: Throttle body
101: Engine temperature sensor
102: Engine
103: Engine Management System (EMS)
104: Electronic Control Unit (ECU)
300-311- Steps of flowchart as per present invention
,CLAIMS:We claim:
1. A electronic Control Unit ECU (104) for a vehicle (10), said vehicle (10) comprising :
a ECU (104);
a power generation unit (102), said power generation unit (102) including:
a throttle body (100);
a sensor (101), said sensor (101) being configured to sense a pre- determined attribute of said power generation unit (102);
characterized in that said ECU (104) being configured to receive a signal from said sensor (101), and retrieve a first attribute and second attribute of said power generation unit (102) from said signal and one or more lookup table, and defined in said control unit (104).
2. The electronic Control Unit ECU (104) for the vehicle (10), wherein the first attribute of said power generation unit being temperature of said throttle body TTHB= and second attribute of said power generation unit being temperature of ambient air TIAT.
3. A method of retrieving ambient temperature TIAT by an electronic Control Unit ECU (104) of a vehicle (10), said vehicle (10) including a power generation unit (102) for powering said vehicle (10), said method comprising the steps of:
starting the vehicle (10) at step 300;
receiving from a sensor (101) value of a pre determined attribute Teng of said power generation unit (102) for a predetermined first time interval TIM_1,
calculating at step (305), by said ECU (104), a rate of change STeng of said pre- determined attribute with respect to time ;
retrieving at step (307, 308), by said ECU (104) value of a first attribute TTHB from one or more conduction look up table using rate of change of pre- determined attribute with respect to time STeng, and pre determined attribute Teng, wherein first attribute TTHB being retrieved for a predetermined interval second time TIM_2,
said conduction look up table being defined in said ECU (104);
retrieving at step (311), by said ECU (104), a value of a second attribute TIAT using rate of change of first attribute STTHB and said first attribute from one or more convection look up table , said convection look up table being defined in said ECU (104) .
4. The method as claimed in claim 2, wherein said power generation unit (102) includes a sensor (102) for sensing said value of said pre determined attribute, wherein retrieving value of first attribute TTHB comprises the steps of:
determining success of said sensor at step 303;
calculating at step 305, a value of standard deviation of said predetermined attribute (SD_ STeng) ;
determining as a first determination at step 306, whether said standard deviation SD_STeng being less than a threshold standard deviation SD_TH_Teng;
retrieving by said ECU (104) at step 307, a value of said first attribute TTHB from a one or more conduction look up table, said conduction look up table being defined in said ECU (104) ; else
repeating step 306 for calculating fresh standard deviation SD_STeng.
5. The method as claimed in claim 3 , wherein retrieving a value of ambient temperature TIAT from a convection look up table by said ECU (104) comprises the steps of:
retrieving at step 308, said first attribute TTHB from one or more conduction look up table for a second predetermined time TIM_2 at step 308;
calculating by said ECU (104) at step 309, a rate of change of first attribute STTHB and calculating a standard deviation SD_STTHB ;
determining as a second determination at step 310, whether said standard deviation SD_ STTHB being less than a threshold standard deviation SD_TH_ TTHB;
retrieving by said ECU (104) at step 311, a value of said ambient temperature TIAT from a one or more convection look up table, said convection look up table being defined in said ECU (104);
else
repeating step 310 of calculating fresh standard deviation
SD_ STTHB .
6. The method as claimed in claim 2, wherein said conduction look up table being based on said predetermined attribute Teng of said power generation unit (102), said predetermined attribute Teng being detected by said sensor (101); and a first attribute, said second attribute being a temperature of said throttle body TTHB.
7. The method as claimed in claim 3 or claim 4, wherein said convection look up table being based on said first attribute TTHB and said second attribute TIAT .
8. The method as claimed in claim 3 or claim 4, wherein the ECU (104) us configured with said conduction look up table being based on Q conduction= KA (T Eng – TTHB); and the convention look up table being based on Q convection= hA (TTHB – TIAT), wherein TIAT is second attribute; TTHB first attribute; T Eng is predetermined attribute, A is surface area; K is conduction co-efficient which is material specific, and H is convection coefficient which is material specific.