|Title of Invention||
A METHOD OF CONTROLLING FUEL INJECTION TO CYLINDERS BY AN ENGINE MANAGEMENT SYSTEM IN AN ENGINE
|Abstract||The invenmtion herein disclose a novel method of controlling fuel injection to cylinders in an engine. During highway driving the vehicle runs at a constant speed. This particular method will effectively enable fuel de-activation to at least one cylinder for every two revolution of the crankshaft (720. rotation of the crankshaft), said cylinder in which fuel is to be de-activated being determined by a table indexed with number of top dead centers (TDS) and number of cylinders to be cut along with the offset engine speed. The firing order of the cylinder also determines the cylinder in which fuel is to be cut during this mode of operation. This will result in a cuclic fuel cut in one culinder for every two revolutions thus leading to a significant fuel saving. A minimum of 15% fuel savings is achieved by this methodology.|
|Full Text||FORM 2
THE PATENTS ACT 1970
(39 of 1970)
THE PATENTS RULES, 2003
(See Section 10; rule 13)
TITLE OF THE INVENTION
A Method Of Controlling Fuel Injection To Cylinders In An Engine
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
Aniket Kulkarni, L Srinivasan and Nilesh Kankariya
all 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
PREAMBLE TO THE DESCRIPTION
The following complete specification particularly describes the invention and the manner in which
it is to be performed.
FIELD OF INVENTION
This invention relates to a method of controlling fuel injection to cylinders in an engine. This particular inventive methodology finds application in a typical Engine Management System (EMS) applied onto a vehicle.
BACKGROUND OF INVENTION
Rising fuel costs is one of the primary motive for the demand of increasing fuel efficiency. With the ever-increasing price of fuel, fuel-efficient vehicles are desired all around the world. The prerequisite is to develop a method to achieve increased fuel efficiency in comparison with a different EMS used on the same inertia class vehicle.
Cylinder de-activation, also called variable displacement, is one of the most prevalent technologies to achieve fuel economy with little to no compromise in performance. General Motors refers to its system as Displacement on Demand (DOD) (now known as Active Fuel Management™) on its midsize SUVs. A similar approach used by Chrysler in the Hemi V-8 is called Multiple Displacement System (MDS), which is available on the company's trucks, SUVs and some passenger cars. In its simplest terms this technology enables switching from eight to four cylinders under light load conditions and cruising speeds, thereby improving efficiency by reducing fuel consumption when the cylinders are de-activated. When full power is required, at acceleration or full load, the vehicle operates on all eight cylinders. The changeover process is seamless and imperceptible.
Cylinder de-activation technique used by Chrysler & GM consists of solenoids to activate special lifters that prevent the valves from opening. The key to the cylinder de-activation is a set of special two-stage hydraulic valve lifters, which allows the lifters of de-activated cylinders to operate without actuating valves. The lifters have inner and outer bodies, which normally operate as a single unit. When the engine controller determines cylinder deactivation conditions are optimal the outer body moves independently of the inner body on the disabled cylinders' lifters. The outer body moves in conjunction with camshaft
actuation, but the inner body does not move, holding the pushrod in place. This prevents the pushrod from actuating the valve, thereby halting the combustion process. Also, the fuel supply to the fuel injectors is halted while the cylinders are de-activated. The sophisticated engine controller is the "brain" behind the operation of this cylinder deactivation technique. In addition to standard engine housekeeping the engine controller must control cylinder activation/de-activation, electronic throttle control and noise abatement circuitry. Solenoid in the Lifter Oil Manifold Assembly (LOMA) operates to deliver high-pressure oil to the switching lifters, activating a release pin to separate the inner and outer bodies of the hydraulic lifters.
It is found that noise and vibration characteristics are different between, for example, a V-6 and the effective inline three-cylinder operation when the engine is in a fuel saving mode. Therefore, the engine and exhaust system are tuned to maintain consistent operational sound and feel.
The Civic Hybrid of Honda Motor Co. Inc. uses their i-VTEC technology for cylinder deactivation to idle three cylinders during deceleration. This friction by 50% and greatly increases the amount of energy recovered during deceleration. To deactivate the valves, hydraulic oil pressure, controlled by the computer with a solenoid, moves a synchronous pin that interlocks the rockers and cam follower. Now the cam follower is still free to move as the camshaft rotates but the rocker arms are no longer linked to it. This synchronous pin will move back and forth, linking or unlinking the rocker arms to control valve operation.
On the above-described cylinder de-activation techniques, the system has more components and complexity. The critical parts and pieces include two-stage switching lifters, lifter oil manifold assembly, redesigned lube circuit and oil pump, electronic throttle by-wire operation, pressure activated mufflers, etc. make the intricacy of the system and the vibration that results a disadvantage that needs to be overcome. Also cost increases with the increase of such intricately designed components.
Typically both fuel supply and air supply is cut to achieve a cylinder de-activation.
SUMMARY OF THE INVENTION
The method to achieve cylinder de-activation according to this invention comprises a progressive fuel cut which increases the number of cylinders cut, following an increase in the engine speed above a threshold value. This particular technique would only be cutting fuel to the cylinders. The primary difference between the proposed invention and the prior art technique would be the manner in which the cylinders are de-activated. In the prior art technique a progressive fuel cut takes place, while in our proposed invention fuel cut takes place alternately in the sequence of an engine's firing order, or in an order to achieve the desired noise and vibration performance as intended by the designer. This particular method is called rolling cut. A rolling air cut is not feasible due to the inability of having a mechanical hardware to implement the same for other reasons including cost.
During a highway or a steady state driving we observe that the fuelling is consistent for a constant speed drive. Thus during this particular driving if we are able to cut at least one cylinder then we would be able to achieve considerable saving on fuel consumption.
According to this invention, a steady state driving condition is identified using the inputs from sensors. Following a steady state driving, the cylinders are cut utilizing a cylinder cut table, which induces a cyclic fuel cut. This will result in a loss of power that the driver has to correct by manually controlling the throttle, since our present application utilizes a mechanical throttle. This controlling action by the driver will result in the engine operating at a higher brake mean effective pressure (BMEP) point. At this point the specific fuel consumption (SFC) is lower thus leading to a further increase in the fuel efficiency. Activation of this particular feature can also be controlled either by hardware or a software switch. A Light emitting diode (LED) is provided on the dashboard to indicate if the cylinder is de-activated.
This particular method has been modeled in Matlab/Simulink. After modeling the methodology has been tested in Software in loop simulation (SIL), for the validation of the concept. Following the verification subsequent Hardware in loop simulation (HIL) testing has been completed to validate the functionality on a real time environment. In addition the
methodology has been integrated with rapid control prototyping hardware and validated on
a real vehicle. This particular methodology is cost effective i.e. no additional hardware costs involved, along with about 15% increase in fuel efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: The method of Fuel Injection Management for Cylinder De-activation according to the invention.
Figure 2: A snapshot of a cylinder cut table and map in Matlab/Simulink and Excel respectively.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 illustrates the invention. The pre-requisite for the cylinder de-activation is the detection of steady state operation of the engine. The outputs from various sensors such as engine speed, engine load, throttle position (TPS) & manifold air pressure (MAP) sensor provide the necessary inputs to identify a steady state operation. The criteria can be stated as, say for example, engine speed variation between ± 50rpm, TPS variation in between ± 2% & MAP variations in between ± lOKPa. If the said criteria are satisfied then the engine is declared to be in a steady state operation condition. The operating range for cylinder deactivation would be in a range of vehicle speed, say for example - between 50 and 80 km/h and a minimum engine speed of say 1300rpm. Also this particular method will be subject to a gear input, say for example - 4th gear, along with no transients taking place during the driving. If for some reason the said criteria are not satisfied for a calibratable delay then the vehicle runs in normal running mode, otherwise it enters the fuel cut mode.
A table indexed with number of top dead center's (TDC) & number of cylinders to be cut along with the offset engine speed is used as illustrated in Figure 2. Thus a cyclic fuel cut is applied resulting in non-fuelling in one cylinder after every 2 revolutions of the crankshaft (720° rotation of the crankshaft). The cylinder to be cut is determined by the cylinder firing order. Using a crank angle sensor the cylinder that is in power stroke is detected due to the mechanical arrangement of the crank wheel. Also, this is cross-
referenced by the cam sensor, which can give us the position of the valve opening. Thus when a particular engine is assembled, it is done such that initially cylinder 1 is in firing. Thus a firing order for a particular engine, particularly in a 4 cylinder case it is 1-3-4-2. This information is converted to crank angle degrees for each firing cylinder and then fed to the engine management system. The crank angle sensor input gives input about the crank angle degrees. The cylinder firing order determines the cylinder that needs to be deactivated for every 2 revolutions of the crankshaft.
As seen in Figure 2, the x-axis represents the offset engine speed while the z-axis denotes the number of cylinder to be cut. The offset engine speed is calculated by using the formula mentioned below:
Offset engine speed = Engine speed - Activation threshold speed
Thus for example, if the engine speed is 1900rpm and activation threshold speed is 1500 rpm, then the offset engine speed in 400 rpm. This value is then looked up into this map and it is noted that a single cylinder has to be cut, which in effect is cut.
The fuel cut in one cylinder for every 2 revolutions will result in a loss of power that the driver has to correct by manually controlling the throttle, if the application utilizes a mechanical throttle. This controlling action by the driver will result in the engine operating at a higher brake mean effective pressure (BMEP) point. At this point the specific fuel consumption (SFC) is lower thus leading to a further increase in the fuel efficiency. In vehicles having electronic throttle control (ETC) the foot maintains the same pressure on the throttle pedal because the ETC has internally opened (or closed) the throttle and therefore the driver does not experience a sudden drop or surge in power due to the cyclic fuel cut.
In order to comply with emissions, lambda feedback is maintained within ± 3%. Due to the cyclic fuel cut, there will be an imbalance in the oxygen sensor feedback owing to nonavailability of fuel in one cylinder resulting in an increase in the oxygen content at the exhaust. The solution for this lies in tuning the gains of the lambda controller to have a rich bias to achieve lambda = 1 (stoichiometric air/fuel ratio), which will result in satisfying the
emission criteria, achieving emission norms along with an increase in fuel efficiency. This cyclic de-activation primarily prevents any vibrations from occurring due to a fixed cylinder de-activation.
If the driver is not keen on utilizing the cylinder de-activation he can either use a hardware or software switch to choose the normal running mode of the vehicle. This output can be made visible on the dashboard through suitable instrument cluster arrangement utilizing LEDs.
The following tabulated remits show validation of the functionality
SrNo Enginespeed(rpm) Vehicle speed Gear Transients (Boolean) Rollingcut active (Boolean) Number Ofcylinders cut Lambda
1 1000 0 0 0 0 0 0JS
2 1700 35 3 1 o 0 QM
3 2200 53 4 0 1 1 0.96-1.27
4 2800 SO 5 0 1 1 1,14-1.4
Where values indicate following-
0-Boolean value indicating false
1-Boolean value indicating true.
(Note: The value indicated in this table are for an illustrative purpose)
1. A method of controlling fuel injection to cylinders in an engine comprising the
detecting steady state operation of the engine by obtaining values of certain predetermined factors through a plurality of sensor outputs;
enabling fuel de-activation to at least one cylinder for every two revolution of the crankshaft (720° rotation of the crankshaft), said cylinder in which fuel is to be de-activated being determined by a table indexed with number of top dead centers (TDC) and number of cylinders to be cut along with the offset engine speed.
2. The method as claimed in claim 1, wherein the cylinder in which fuel is to be deactivated is determined also by the cylinder firing order.
3. The method as claimed in claim 1, comprising the step of manually controlling the throttle to correct the loss of power occurring due to the cylinder de-activation.
4. The method as claimed in claim 1, wherein the pre-determined factors required to detect the steady state operation of the engine includes at least the engine speed and/or engine load and/or throttle position (TPS) and/or manifold air pressure (MAP).
5. The method as claimed in any one of the preceding claims, wherein the lambda feedback is maintained within ± 3% to satisfy emission norms.
6. The method as claimed in claim 5, comprising the step of tuning the gains of lambda controller to have a rich bias to achieve lambda = 1 to overcome the imbalance in the oxygen sensor feedback due to non-availability of fuel in at least one cylinder resulting in an increase in the oxygen content at the exhaust.
7. A method of controlling fuel injection to cylinders in an engine substantially as
herein described with reference to the accompanying drawings.
Dated this 7th day of September 2006.
TATA MOTORS LIMITED By their Agent & Attorney
of DePENNING & DePENNING
“Title: A method of controlling fuel injection to cylinders in an engine”
The invention herein discloses a novel method of controlling fuel injection to cylinders in an engine. During highway driving the vehicle runs at a constant speed. This particular method will effectively enable fuel de-activation to at least one cylinder for every two revolution of the crankshaft (720" rotation of the crankshaft), said cylinder in which fuel is to be de-activated being determined by a table indexed with number of top dead centers (TDC) and number of cylinders to be cut along with the offset engine speed. The firing-order of the cylinder also determines the cylinder in which fuel is to be cut during this mode of operation. This will result in a cyclic fuel cut in one cylinder for every two revolutions thus leading to a significant fuel saving. A minimum of 15% fuel savings is achieved by this methodology.
|Indian Patent Application Number||1430/MUM/2006|
|PG Journal Number||13/2009|
|Date of Filing||07-Sep-2006|
|Name of Patentee||TATA MOTORS LIMITED|
|Applicant Address||BOMBAY HOUSE, 24 HOMI MODY STREET, HUTATMA CHOWK, MUMBAI-400 001|
|PCT International Classification Number||F02M 41/16, F02M 45/08|
|PCT International Application Number||N/A|
|PCT International Filing date|