Claims:CLAIMS
We claim,
1. A method for determining inertia of an engine in a vehicle using a chassis dynamometer, said method comprising:
mounting the vehicle on the chassis dynamometer;
setting the engine of the vehicle in a non-firing state;
setting a power transmission unit of the vehicle in a neutral position;
driving at least one wheel of the vehicle that is operatively connected to the engine through at least one roller of the chassis dynamometer;
setting the power transmission unit of the vehicle in a required gear position;
engaging the power transmission unit to the engine by engaging a clutch of the vehicle;
driving the roller of the chassis dynamometer on a predetermined inertia cycle, the inertia cycle includes an acceleration phase and a cruising phase;
measuring a torque required to drive the engine and the drive train of the vehicle during acceleration phase of the inertia cycle;
measuring a torque required to drive the engine and the drive train of the vehicle during cruising phase of the inertia cycle;
disengaging the power transmission unit from the engine by disengaging the clutch;
measuring a torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle;
measuring a torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle; and
determining the inertia of the engine based on the difference between, the difference of, torque required to drive the engine and drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the engine and drive train of the vehicle during cruising phase of the inertia cycle and the difference of, torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle.
2. The method as claimed in claim 1, wherein said step of setting the engine of the vehicle in the non-firing state includes switching off an ignition system of the engine.
3. The method as claimed in claim 1 further comprising a step of warming up the vehicle.
4. A method for determining inertia of a drive train in a vehicle using a chassis dynamometer, said method comprising:
mounting the vehicle on the chassis dynamometer;
disengaging a power transmission unit of the vehicle from an engine of the vehicle by disengaging a clutch of the vehicle;
setting the power transmission unit of the vehicle in a required gear position;
driving at least one wheel of the vehicle that is operatively connected to the drive train through at least one roller of the chassis dynamometer on a predetermined inertia cycle, the inertia cycle includes an acceleration phase and a cruising phase;
measuring a torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle;
measuring a torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle; and
determining the inertia of the drive train of the vehicle based on the difference between the torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle.
5. The method as claimed in claim 4, further comprising the step of setting the engine of the vehicle in a non-firing state.
6. The method as claimed in claim 5, wherein said step of setting the engine of the vehicle in the non-firing state includes switching off an ignition system of the engine.
7. The method as claimed in claim 4, further comprising a step of warming up the vehicle.
8. A chassis dynamometer comprising:
at least one roller adapted for driving at least one wheel of a vehicle;
an electric motor rotatably connected to said roller, said electric motor adapted for driving said roller;
at least one load sensor adapted for measuring a torque required for driving at least one of, an engine and a drive train of the vehicle; and
a control unit configured to drive said roller based on a predetermined inertia cycle and configured to communicate with said load sensor and to determine the inertia of at least one of engine and drive train,
wherein
the inertia of the engine is determined based on the difference between, the difference of, a torque required to drive the engine and drive train of the vehicle during an acceleration phase of the inertia cycle and a torque required to drive the engine and drive train of the vehicle during an cruising phase of the inertia cycle and the difference of, a torque required to drive the drive train of the vehicle during the acceleration phase of the inertia cycle and a torque required to drive the drive train of the vehicle during the cruising phase of the inertia cycle; and the inertia of the drive train is determined based on the difference between, the torque required to drive the drive train of the vehicle during the acceleration phase of the inertia cycle and the torque required to drive the drive train of the vehicle during the cruising phase of the inertia cycle.
, Description:TECHNICAL FIELD
The embodiments herein generally relate to engine testing in vehicles and more particularly but not exclusively to engine testing in vehicles using chassis dynamometer.

BACKGROUND
Generally, an engine of a vehicle is tested using an engine dynamometer for determining the emission values, durability, motoring loss, inertia of the engine etc. Testing a vehicle’s engine through an engine dynamometer is a time consuming process as the engine needs to be dismantled from the vehicle and mounted on to the test bed of engine dynamometer for testing the engine. Further, the testing involves the replication of wiring harness setup in test bed of the engine dyanamometer and emulation of requisite sensor signals necessary for proper operation of the electronic control unit (ECU) of the engine. Hence, the original setting of the engine invariably gets disturbed in the process and the vehicle is rendered unusable during the testing period.
Therefore, there exists a need for a simple method for determining the inertia of an engine in a vehicle through a chassis dynamometer. Furthermore, there exists a need for a method for determining the inertia of a drive train of a vehicle through a chassis dynamometer.

OBJECTS
The principle object of an embodiment of this invention is to provide a method for determining the inertia of an engine in a vehicle through a chassis dynamometer.
Another object of an embodiment of this invention is to provide a method for determining the inertia of a drive train of a vehicle through a chassis dynamometer.
Yet, another object of an embodiment of this invention is to provide a chassis dynamometer for determining the inertia of an engine and a drive train of a vehicle.
These and other objects 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 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 DRAWINGS
The embodiments of the invention are 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 a schematic of the chassis dynamometer according to an embodiment of the invention as disclosed herein;
FIG. 2a depicts a vehicle mounted to the chassis dynamometer with the engine engaged to the power transmission unit of the vehicle according to an embodiment of the invention as disclosed herein;
FIG. 2b depicts a vehicle mounted to the chassis dynamometer with the engine disengaged from the power transmission unit of the vehicle according to an embodiment of the invention as disclosed herein;
FIG. 3 depicts a sample inertia cycle of the chassis dynamometer while driving the engine and drive train of the vehicle according to an embodiment of the invention as disclosed herein;
FIG. 4 depicts the flow chart of the method for determining the inertia of the engine in the vehicle according to an embodiment of the invention as disclosed herein;
FIG. 5 depicts the flow chart of the method for determining the inertia of the drive train in the vehicle according to an embodiment of the invention as disclosed herein; and
FIG. 6 depicts a graph showing the correlation between the test results of an engine dynamometer and the chassis dynamometer for two different vehicles according to an embodiment of the invention 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 simple a method for determining the inertia of an engine in a vehicle through a chassis dynamometer. Further, embodiments herein achieve a method for determining the inertia of a drive train of a vehicle through a chassis dynamometer. Referring now to the drawings, and more particularly to FIGS. 1 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
FIG. 1 depicts a schematic of the chassis dynamometer according to an embodiment of the invention as disclosed herein. The chassis dynamometer 100 includes, at least one roller 102, an electric motor/generator 104, at least one load sensor 106, a control unit 108, a power supply (not shown) and a frame (not shown).
In an embodiment a vehicle 200 to be tested includes at least one wheel 202, at least one engine 204, at least one clutch 206, at least one power transmission unit 208, and a wheel axle (not shown). In an embodiment the clutch 206, power transmission unit 208, and the wheel axle constitute the drive train (not shown) of the vehicle. However, it is also within the scope of the invention that drive train (not shown) of the vehicle 200 may include any other components or exclude any of the aforementioned components without otherwise deterring the intended function of the drive train (not shown) as can be deduced from the description. In an embodiment the drive train (not shown) is used for delivering the power from the engine 204 to the wheels 202 of the vehicle 200 for propulsion. In an embodiment the power transmission unit 208 includes a plurality of gears (not shown) actuated by a gear selecting lever (not shown) to offer different speed ratios. In an embodiment the vehicle 200 to be tested is a four wheeled vehicle. However, it is also within the scope of the invention to test two wheeled vehicles or vehicles with any number of wheels without otherwise deterring the intended function of the chassis dynamometer 100.
In an embodiment the roller 102 is used for driving the wheels 202 of a vehicle 200. The roller 102 is driven by the electric motor/generator 104 for driving the wheels 202 of the vehicle 200. In an embodiment the chassis dynamometer includes two rollers 102 (one for driving left wheel and one for driving right wheel). However, it is also within the scope of the invention to provide any number of rollers 102 without otherwise deterring the intended function of the roller 102 as can be deduced from the description. In an embodiment the load sensor 106 is connected with a housing (not shown) of the electric motor/generator 104 for measuring the torque required to drive the engine 204 and/or drive train of the vehicle. In an embodiment the load sensor 106 is a load cell. However, it is also within the scope of the invention to provide any other type of load sensor 106 without otherwise deterring the intended function of the load sensor 106 as can be deduced from the description.
In an embodiment the control unit 108 includes a display unit (not shown), at least one control switch (not shown) for setting the chassis dynamometer 100 in motoring/driving mode, at least one control switch (not shown) for setting the inertia cycle of the chassis dynamometer. In an embodiment the control unit 108 is provided in communication with the load sensor 106 for determining the inertia of the engine 204 and the drive train (not shown) of the vehicle 200. In an embodiment, the control unit 108 described herein can include for example, but not limited to, microprocessor, microcontroller, controller, smart phone, portable electronic device, communicator, tablet, laptop, computer, consumer electronic device, a combination thereof, or any other device capable of processing signals.
In an embodiment the power supply (not shown) is used for powering the electric motor/generator 104 and the control unit 108. In an embodiment the frame (not shown) is used for mounting the vehicle 200 over the chassis dynamometer 100 for testing the engine 204.
In an embodiment the control unit 108 determines the inertia of the engine 204 (Ieng) based on the following equation,
Ieng= I/(OGR*OGR)
where,
Ieng = Inertia of the engine in ‘kg-m2’
I = Inertia of the engine reflected at wheels in ‘kg-m2’
OGR = Overall gear ratio in the power transmission unit (no unit)
The control unit 108 determines the inertia of the engine 204 (I) reflected at wheels based on the following equation,
I= ((T1-T2)-(T1^'-T2^')*r)/a
where,
I = Inertia of the engine reflected at the wheels in ‘kg-m2’
T1 = Torque required to drive the engine and drive train of the vehicle (acceleration phase) in ‘Nm’
T2 = Torque required to drive the engine and drive train of the vehicle (cruising phase, V = constant) in ‘Nm’
T1’ = Torque required to drive the drive train of the vehicle (acceleration phase) in ‘Nm’
T2’ = Torque required to drive the drive train of the vehicle (cruising phase, V = constant) in ‘Nm’
r = Dynamic rolling radius of wheel tyre in ‘m’
a = Dynamometer roller acceleration (equivalent to vehicle acceleration) in ‘m/s2’
V = Vehicle velocity in ‘kmph’

In an embodiment the control unit 108 determines the inertia of the drive train (I’) based on the following equation,

I'= ((T1^'-T2^')*r)/a
where,
I’ = Inertia of the drive train in ‘kg-m2’

T1’ = Torque required to drive the drive train of the vehicle (acceleration phase) in ‘Nm’
T2’ = Torque required to drive the drive train of the vehicle (cruising phase, V = constant) in ‘Nm’
r = Dynamic rolling radius of wheel tyre in ‘m’
a = Dynamometer roller acceleration (equivalent to vehicle acceleration) in ‘m/s2’
V = Vehicle velocity in ‘kmph’

FIG. 3 depicts a graph showing a sample inertia cycle of the chassis dynamometer while driving the engine and drive train of the vehicle according to an embodiment of the invention as disclosed herein. The inertia cycle is a predetermined cycle set in the chassis dynamometer based on which the roller 102 is accelerated and driven. The inertia cycle is predetermined based on the low idle governing speed or creep speed and the maximum speed of the gear position selected in the power transmission unit 208 of the vehicle 200. The path of the inertia cycle is shown in the fig. 3 where,
V1 = Inertia cycle minimum velocity in ‘kmph’
V2 = Inertia cycle cruising phase velocity (i.e V = Constant) in ‘kmph’
V3 = Inertia cycle maximum velocity in ‘kmph’
?t = Delta time in ‘sec’
By driving the roller 102 of the chassis dynamometer 100 based on the inertia cycle, T1 and T2 are determined when driving the engine 204 and the drive train of the vehicle 200 at a required gear position. Similarly, by driving the roller 102 of the chassis dynamometer 100 based on the inertia cycle, T1’ and T2’ are determined when driving the drive train of the vehicle 200 at the same gear position used for determining T1 and T2. The inertia cycle includes an acceleration phase and a cruising phase. During the acceleration phase of the inertia cycle, the roller 102 accelerates the wheels 202 of the vehicle 200 at a predetermined acceleration for determining T1 and T1’ and during the cruising phase of the inertia cycle, the roller 102 drives the wheels 202 of the vehicle 200 at a predetermined constant speed for determining T2 and T2’. The load sensor 106 of the chassis dynamometer 100 measures the T1, T2, T1’ and T2’ and provides input to the control unit 108 for determining the inertia of the engine 204 and the drive train of the vehicle 200.
FIG. 4 depicts the flow chart of the method for determining the inertia of the engine in the vehicle according to an embodiment of the invention as disclosed herein. The method 300 for determining the inertia of the engine in the vehicle using a chassis dynamometer includes, mounting the vehicle on the chassis dynamometer step 301, warming up the vehicle step 302, setting the engine of the vehicle in a non-firing state step 303, setting a power transmission unit of the vehicle in a neutral position step 304, driving at least one wheel of the vehicle that is operatively connected to the engine through at least one roller of the chassis dynamometer step 305, setting the power transmission unit of the vehicle in a required gear position step 306, engaging the power transmission unit to the engine by engaging a clutch of the vehicle step 307, driving the roller of the chassis dynamometer on a predetermined inertia cycle step 308, the inertia cycle includes an acceleration phase and a cruising phase, measuring a torque required to drive the engine and the drive train of the vehicle during acceleration phase of the inertia cycle step 309, measuring a torque required to drive the engine and the drive train of the vehicle during cruising phase of the inertia cycle step 310, disengaging the power transmission unit from the engine by disengaging the clutch step 311, measuring a torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle step 312, measuring a torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle step 313, determining the inertia of the engine based on the difference between, the difference of, torque required to drive the engine and drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the engine and drive train of the vehicle during cruising phase of the inertia cycle and the difference of, torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle step 314.
The working of the chassis dynamometer 100 in conjunction with the method 300 for determining the inertia of the engine in a vehicle is as follows. FIG. 2a depicts a vehicle mounted to the chassis dynamometer with the engine engaged to the power transmission unit of the vehicle according to an embodiment of the invention as disclosed herein. FIG. 2b depicts a vehicle mounted to the chassis dynamometer with the engine disengaged from the power transmission unit of the vehicle according to an embodiment of the invention as disclosed herein.
First the vehicle 200 is mounted on the chassis dynamometer 100 and the vehicle 200 is warmed up. Then the engine 204 is set in non-firing state by switching off an ignition system (not shown) of the engine 204. Based on the type of vehicle 200 the appropriate wheels 202 of the vehicle 200 are provided in contact with the rollers 102. For example if the vehicle 200 to be tested is a rear wheel drive vehicle the rear wheels of the vehicle 200 are provided in contact with the rollers 102. The vehicle’s power transmission unit 208 is set to neutral position and the chassis dynamometer 100 is set to motoring/driving mode through the control unit 108. Thereafter, the rollers 102 of the chassis dynamometer 100 starts driving the appropriate wheels 202 of the vehicle 200 at a minimum speed. Thereafter the power transmission unit 208 is set to any required gear position using the gear shift selector (not shown). Then the power transmission unit 208 is engaged to the engine 204 as shown in Fig. 2a. In an embodiment engaging the power transmission unit 208 to the engine 204 is done using the clutch 206. In an embodiment the clutch 206 is disengaged by depressing the clutch pedal (not shown) and the required gear position in the power transmission unit 208 is selected and the clutch 206 is engaged by gradually releasing the clutch pedal (not shown) for engaging the power transmission unit 208 to the engine. However it is also within the scope of the invention to engage and disengage the clutch 206 without using clutch pedal (not shown). As the wheels 202 of the vehicle 200 are driven by the rollers 102 of the chassis dynamometer 100, the drive train (wheel axle, the power transmission unit 208, the clutch 206) and the components of the engine 204 such as crankshaft (not shown), camshaft (not shown), pistons (not shown), etc., are driven as the power transmission unit 208 is engaged to the engine 204. Thereafter the rollers 102 of the chassis dynamometer 100 are driven based on the predetermined inertia cycle using the control unit 108. The inertia cycle is predetermined based on the low idle governing speed or creep speed and the maximum speed of the gear position selected in the power transmission unit 208 of the vehicle 200 during testing. Now the rollers 102 of the chassis dynamometer 100 is driven based on the inertia cycle and the torque required to drive the engine 204 and the drive train of the vehicle 200 (T1 and T2) during acceleration phase and cruising phase of the inertia cycle is measured using the load sensor 106. Thereafter the clutch 206 is disengaged and the power transmission unit 208 is disengaged from the engine 204 as shown in Fig. 2b. As the power transmission unit 208 is disengaged from the engine 204 only the drive train of the vehicle 200 is driven by the rollers 102 of the chassis dynamometer 100 based on the inertia cycle and the torque required to drive the drive train (not shown) of the vehicle 200 (T1’ and T2’) during acceleration phase and cruising phase of the inertia cycle is measured using the load sensor 106. Based on the input provided by the load sensor 106, the control unit 108 determines the inertia of the engine 204 of the vehicle 200. Based on the difference between, the difference of torque required to drive the engine and drive train of the vehicle during acceleration phase and cruising phase of the inertia cycle and the difference of torque required to drive the drive train of the vehicle during acceleration phase and cruising phase of the inertia cycle, the control unit 108 of the chassis dynamometer 100 determines the inertia of the engine 204.
FIG. 5 depicts the flow chart of the method for determining the inertia of the drive train in the vehicle according to an embodiment of the invention as disclosed herein. The method 400 for determining the inertia of the drive train in a vehicle using a chassis dynamometer includes, mounting the vehicle on the chassis dynamometer step 401, warming up the vehicle step 402, setting an engine of the vehicle in a non-firing state step 403, disengaging a power transmission unit from the engine by disengaging a clutch of the vehicle step 404, setting the power transmission unit of the vehicle in a required gear position step 405, driving at least one wheel of the vehicle that is operatively connected to the drive train through at least one roller of the chassis dynamometer on a predetermined inertia cycle step 406, the inertia cycle includes an acceleration phase and a cruising phase, measuring a torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle step 407, measuring a torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle step 408, determining the inertia of the drive train of the vehicle based on the difference between the torque required to drive the drive train of the vehicle during acceleration phase of the inertia cycle and the torque required to drive the drive train of the vehicle during cruising phase of the inertia cycle step 409.
The working of the chassis dynamometer 100 in conjunction with the method 400 for determining the inertia of the drive train of the vehicle is as follows. FIG. 2b depicts a vehicle mounted to the chassis dynamometer with the engine disengaged from the power transmission unit of the vehicle according to an embodiment of the invention as disclosed herein. First the vehicle 200 is mounted on the chassis dynamometer 100 and the vehicle 200 is warmed up. Then the engine 204 is set in non-firing state by switching off an ignition system (not shown) of the engine 204. Based on the type of vehicle the appropriate wheels 202 of the vehicle 200 are provided in contact with the rollers 102. For example if the vehicle to be tested is a rear wheel drive vehicle the rear wheels of the vehicle 200 are provided in contact with the rollers 102. Thereafter the power transmission unit 208 is disengaged from the engine 204 by disengaging the clutch 206 as shown in Fig. 2b. In an embodiment, the clutch 206 is disengaged by depressing the clutch pedal (not shown). However, it is also within the scope of the invention to disengage the clutch 206 without using the clutch pedal (not shown). Thereafter, any required gear position is set in the power transmission unit 208 using the gear shift selector (not shown). Thereafter the rollers 102 of the chassis dynamometer 100 are driven based on the predetermined inertia cycle using the control unit 108. The inertia cycle is predetermined based on the low idle governing speed or creep speed and the maximum speed of the gear position selected in the power transmission unit 208 of the vehicle 200 during testing. As the wheels 202 of the vehicle 200 are driven by the rollers 102 of the chassis dynamometer 100, the drive train (wheel axle, the power transmission unit 208, the clutch 206) is driven. As the power transmission unit 208 is disengaged from the engine 204 only the drive train of the vehicle 200 is driven by the rollers 102 of the chassis dynamometer 100 based on the inertia cycle and the torque required to drive the drive train (not shown) of the vehicle 200 (T1’ and T2’) during acceleration phase and cruising phase of the inertia cycle is measured using the load sensor 106. Based on the input provided by the load sensor 106, the control unit 108 determines the inertia of the drive train of the vehicle 200. Based on the difference between, the torque required to drive the drive train of the vehicle during acceleration phase and the torque required to drive the drive train of the vehicle during cruising phase, the control unit 108 of the chassis dynamometer 100 determines the inertia of the drive train.
FIG. 6 depicts a graph showing the correlation between the test results of an engine dynamometer and the chassis dynamometer for two different vehicles according to an embodiment of the invention as disclosed herein. The graph depicts the engine inertia measured using the chassis dynamometer 100 and the engine inertia measured using an engine dynamometer (not shown) for two different vehicles (vehicle 1 & vehicle 2). The engine inertia measured using the chassis dynamometer 100 correlates with the engine inertia measured using the engine dynamometer by 96%.
The various actions, units, steps, blocks, or acts described in the method 300 and 400 can be performed in the order presented, in a different order, simultaneously, or a combination thereof. Further, in some embodiments, some of the actions, units, steps, blocks, or acts listed in the FIG. 4 and FIG. 5 may be omitted, added, skipped, or modified without departing from the scope of the invention.
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 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.