[0001] The present disclosure, in general, relates to an internal combustion
engine for improving emissions performance, and in particular, to a method and a
5 system for controlling emissions and improving fuel efficiency by controlling
target voltage of secondary or rear oxygen sensor with respect to health of
catalytic converter.
BACKGROUND
[0002] Background description includes information that may be useful in
10 understanding the present invention.
[0003] Today, the automobile industry highly depends on catalyst-based aftertreatment technology to match with exhaust emission regulations. With the threeway converter, oxides of nitrogen (NOx) are reduced into simple nitrogen and
carbon-dioxide; and Hydrocarbons and carbon monoxide are oxidized to form
15 water and carbon-dioxide.
[0004] Catalyst operating efficiency is greatly affected by two factors:- 1.
Operating temperature; and Exhaust gas composition. In order for a catalyst to
best clean up NOx, the A/F ratio must be richer than 14.7:1. However, CO and
THC is generated when mixture is rich. For the catalyst to best clean up CO &
20 HC, the A/F ratio must be lean, but NOx is generated when mixture is lean. Three
way catalysts overcome this problem by using cerium for oxygen storage. If the
oxygen level is cycling slightly rich and slightly lean, cerium stores oxygen during
lean phase and uses the same oxygen in rich phase for oxidizing harmful gases. As
a result, HC, CO and NOx can be purified at the same time.
25 [0005] In order to ensure controlled oxygen cycling, oxygen sensor feedback
is used. Generally, two sensors are used where one is front or primary oxygen
sensor, which is positioned before the catalytic converter, and a rear or secondary
oxygen sensor positioned after the catalytic converter. The front oxygen sensor
provides fuel feedback to an Electronic Control Unit (ECU) to decide rich fuelling
3
or lean fuelling. Further, the rear oxygen sensor provides correction to primary
feedback of the front oxygen sensor to control fuelling.
[0006] Ideally, a catalytic converter should promote complete conversion of
harmful exhaust products into carbon-dioxide and water by using stored oxygen in
5 the catalyst. Therefore, a very less amount of oxygen should be available at the
rear oxygen sensor. In such conditions, the voltage output of rear oxygen sensor
under steady state conditions tend to stabilize with little fluctuations in its output
pattern. As the efficiency of the catalyst decreases, oxygen passes through the
converter without any reaction leading to high fluctuations in rear oxygen sensor
10 voltage. When the catalyst gets completely deteriorated the response pattern of the
front oxygen sensor and rear oxygen sensor becomes almost similar. The
difference in the voltage pattern of the two sensors between normal and
deteriorated catalyst as shown in Fig. 1.
[0007] Further, there are a number of methods for diagnosing catalyst health
15 using oxygen sensors, two of the most commonly used methods are-
[0008] Based on the feedback provided by the front oxygen sensor and rear
oxygen sensor, fuelling of the internal combustion engine is controlled by the
ECU. If base emissions are on leaner side, lean output signal is generated by front
oxygen sensor and rich side fueling gain signal is triggered by ECU. Similarly, if
20 base emissions are on richer side, output signal is generated by front oxygen
sensor & lean side fueling gain signal is triggered by the ECU. So depending upon
rich or lean emissions, either of these two maps should be calibrated. Therefore,
desired rich & lean mixture should be maintained as per the catalyst efficiency.
When the air-fuel ratio feedback is kept more towards the rich side, there will be
25 sudden increase in CO and THC formation; and rear oxygen sensor voltage may
not fluctuate. When the air-fuel ratio feedback is kept more towards the lean side,
there will be sudden increase in NOx formation; and rear oxygen sensor voltage
may fluctuate.
4
[0009] Currently, the rear oxygen sensor is provided to determine catalyst
health and provide indications to the driver when the catalytic converter or
catalyst is completely deteriorated which is called On Board Diagnostic (OBD).
[0010] Technical Problem: the existing system keeps changing feedback
5 value based on the total fuel feedback value provided by the front and rear oxygen
sensor. As fuel feedback value of the front oxygen sensor is independent of health
of catalytic converter; whereas the feedback correction value of the rear oxygen
sensor is dependent on the health of the catalytic converter. In existing system,
with non-deteriorated catalyst, deviation from static rear O2 target voltage is
10 reduced by rear O2 correction feedback & after target voltage is achieved,
feedback correction value approaches zero. However, due to catalytic convertor
ageing, it is unable to provide exhaust out gas corresponding to a particular rear
O2 target voltage even after fuel correction. The rear oxygen sensor keeps
providing fuel feedback correction value towards rich side based on the static
15 target operating voltage, continuously operating the system on richer side due to
which CO and THC emissions increases. The existing system with static target
operating voltage, which in general is slightly towards rich side to prevent NOx
generation keeps increasing fuelling to achieve target despite system capability
limitation to achieve such target due to catalyst ageing thereby impacting
20 emissions & fuel economy.
[0011] In the view of the above-cited problem(s), there is a need for a method
and a system that can be implemented in the existing Engine Control Unit (ECU)
to prevent ineffective fuel correction feedback & keep emissions in control in the
aged vehicle specifically generation of CO and THC due to deteriorated health of
25 catalytic converter and false judgement by the rear oxygen sensor. Further, a
system is required that can solve the above mentioned technical problem without
additional cost in the existing system.
OBJECTS OF THE DISCLOSURE
[0012] Some of the objects of the present disclosure, which at least one
30 embodiment herein satisfy, are listed hereinbelow.
5
[0013] It is a general object of the present disclosure to provide a catalytic
health monitoring system to dynamically update target operating voltage of rear
oxygen sensor based on health of the catalytic converter.
[0014] It is another object of the present disclosure to provide a system that
5 restricts generation of more CO and THC when health of the catalytic converter is
deteriorated.
[0015] It is another object of the present disclosure to provide a method and a
system to negate the negative effect of static target operating voltage of the rear
oxygen sensor when the health of the catalytic converter is deteriorated.
10 [0016] It is another object of the present disclosure is to improve health of
catalytic converter by controlling fuel based on real time health of catalytic
converter. As the target voltage is always set to richer side (as the NOx target are
stringent, taking a lean output, which means more NOx generation, therefore to
meet the demand, the system will always pass signal to make the system more
15 richer to meet the target. As more rich mean more fuel and more fuel mean more
impurities.
[0017] These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following detailed
description taken in conjunction with the accompanying drawings in which a
20 preferred form of the present invention is illustrated.
SUMMARY
[0018] This summary is provided to introduce concepts related to a system to
improve emission performance and improve fuel economy by controlling target
operating voltage for rear oxygen sensor with respect to health of catalytic
25 converter. The concepts are further described below in the detailed description.
This summary is not intended to identify key features or essential features of the
claimed subject matter, nor is it intended to be used to limit the scope of the
claimed subject matter.
6
[0019] In an embodiment, the present disclosure relates to a catalytic health
monitoring system provided in an Engine Control Unit for reducing emissions and
improving fuel economy. The catalytic health monitoring system is coupled with a
plurality of fuel injectors and a catalytic converter provided in exhaust gas system
5 of the vehicle. The catalytic health monitoring system includes a feedback control
module coupled with a front oxygen sensor and a rear oxygen sensor to control
fuel injection in rich mode or in lean mode; a catalytic health monitoring module
determines health of the catalytic converter; and a target operating voltage update
module to update target operating voltage of the rear voltage sensor based on
10 determined health of the catalytic converter.
[0020] In an embodiment, the target operating voltage update module
compares the determined health of the catalytic converter with a pre-stored lookup
table having predetermined experimented values for the health of the catalytic
converter and corresponding target operating voltage of the rear voltage sensor;
15 selects the target operating voltage of the rear voltage sensor based on the
comparison between the determined health of the catalytic converter with the prestored lookup table; and updates and calibrates the target operating voltage of the
rear voltage sensor based on the selected target operating voltage from the prestored lookup table.
20 [0021] In an embodiment, the feedback control module adds updated amount
of fuel feedback based on the updated target operating voltage of the rear voltage
sensor to fuel feedback value of the front oxygen sensor to control fuel injection
in rich and lean mode.
[0022] In an embodiment, the catalytic health monitoring module determines
25 health of the catalytic converter based on Oxygen Storage Capability method or
Oxygen Storage time method.
[0023] In another embodiment of the present subject matter is to provide a
method for reducing emissions and improving fuel economy of an internal
combustion (IC) engine. The method comprising determining health of a catalytic
30 converter positioned in exhaust gas system; comparing the determined health of
7
the catalytic converter with a pre-stored lookup table having predetermined
experimented values for health of the catalytic converter and corresponding target
operating voltage of a rear voltage sensor; selecting the target operating voltage of
the rear voltage sensor from the pre-stored lookup table; and updating and
5 calibrating the target operating voltage of the rear voltage sensor based on the
selected target operating voltage from the pre-stored lookup table.
[0024] In an embodiment, the method includes adding update amount of fuel
feedback based on the update target operating voltage of the rear voltage sensor to
fuel feedback value of the front oxygen sensor to control fuel injection in rich and
10 lean mode.
[0025] In an embodiment, the method includes the health of the catalytic
converter is determined based on Oxygen Storage Capability or Oxygen Storage
time.
[0026] Various objects, features, aspects, and advantages of the inventive
15 subject matter will become more apparent from the following detailed description
of preferred embodiments, along with the accompanying drawing figures in which
like numerals represent like components.
[0027] It is to be understood that the aspects and embodiments of the
disclosure described above may be used in any combination with each other.
20 Several of the aspects and embodiments may be combined to form a further
embodiment of the disclosure.
[0028] The foregoing summary is illustrative only and is not intended to be in
any way limiting. In addition to the illustrative aspects, embodiments, and features
described above, further aspects, embodiments, and features will become apparent
25 by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are incorporated in and constitute
a part of this disclosure, illustrate exemplary embodiments and, together with the
description, serve to explain the disclosed principles. In the figures, the left-most
8
digit(s) of a reference number identifies the figure in which the reference number
first appears. The same numbers are used throughout the figures to reference like
features and components. Some embodiments of system and/or methods in
accordance with embodiments of the present subject matter are now described, by
5 way of example only, and with reference to the accompanying figures, in which:
[0030] Fig. 1 illustrates variation voltage of front oxygen sensor and rear
oxygen sensor at good catalyst health condition and at completely deteriorated
catalyst health condition;
[0031] Fig. 2 illustrates architecture of Internal Combustion Engine with
10 exhaust gas system and Engine Control Unit (ECU);
[0032] Fig. 3 illustrates architecture of ECU with front and rear oxygen
sensor;
[0033] Fig. 4 illustrates a system architect of Catalytic Health Monitoring
system provided in the Engine Control Unit (ECU), in accordance with an
15 embodiment of the present disclosure;
[0034] Fig. 5 illustrates a method for dynamically updating target operating
voltage of the rear oxygen sensor, in accordance with an embodiment of the
present disclosure; and
[0035] Fig. 6 illustrates graph between the health of the catalytic converter in
20 terms of kilometre running of the vehicle and dynamic the variation of the target
operating voltage of the rear oxygen sensor to control the emissions;
[0036] Fig. 7a illustrates target operating voltage of rear oxygen sensor in
new vehicle and vehicle after ageing, in view of existing technologies; and
[0037] Fig. 7b illustrates target operating voltage of rear oxygen sensor in
25 new vehicle and vehicle after ageing, in view of present subject matter.
[0038] It should be appreciated by those skilled in the art that any block
diagrams herein represent conceptual views of illustrative systems embodying the
principles of the present subject matter. Similarly, it will be appreciated that any
9
flow charts, flow diagrams, state transition diagrams, pseudo code, and the like
represent various processes which may be substantially represented in a computerreadable medium and executed by a computer or processor, whether or not such
computer or processor is explicitly shown.
5 DETAILED DESCRIPTION
[0039] The detailed description of various exemplary embodiments of the
disclosure is described herein with reference to the accompanying drawings. It
should be noted that the embodiments are described herein in such details as to
clearly communicate the disclosure. However, the amount of details provided
10 herein is not intended to limit the anticipated variations of embodiments; on the
contrary, the intention is to cover all modifications, equivalents, and alternatives
falling within the spirit and scope of the present disclosure as defined by the
appended claims.
[0040] It is also to be understood that various arrangements may be devised
15 that, although not explicitly described or shown herein, embody the principles of
the present disclosure. Moreover, all statements herein reciting principles, aspects,
and embodiments of the present disclosure, as well as specific examples, are
intended to encompass equivalents thereof.
[0041] The terminology used herein is for the purpose of describing particular
20 embodiments only and is not intended to be limiting of example embodiments. As
used herein, the singular forms “a", “an” and “the” are intended to include the
plural forms as well, unless the context clearly indicates otherwise. It will be
further understood that the terms “comprises,” “comprising,” “includes” and/or
“including,” when used herein, specify the presence of stated features, integers,
25 steps, operations, elements and/or components, but do not preclude the presence
or addition of one or more other features, integers, steps, operations, elements,
components and/or groups thereof.
[0042] In addition, the descriptions of "first", "second", “third”, and the like in
the present invention are used for the purpose of description only, and are not to
10
be construed as indicating or implying their relative importance or implicitly
indicating the number of technical features indicated. Thus, features defining
"first" and "second" may include at least one of the features, either explicitly or
implicitly.
5 [0043] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For example,
two figures shown in succession may, in fact, be executed concurrently or may
sometimes be executed in the reverse order, depending upon the functionality/acts
involved.
10 [0044] Unless otherwise defined, all terms (including technical and scientific
terms) used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which example embodiments belong. It will be further
understood that terms, e.g., those defined in commonly used dictionaries, should
be interpreted as having a meaning that is consistent with their meaning in the
15 context of the relevant art and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0045] Micro-Controller: It is a compact integrated circuit designed to
govern a specific operation in an embedded system. A typical microcontroller
includes a processor, memory and input/output (I/O) peripherals on a single chip.
20 Generally, microcontrollers are designed to be readily usable without additional
computing components because they are designed with sufficient on board
memory as well as offering pins for general I/O operations, so they can directly
interface with sensors and other components.
[0046] FIG. 2 illustrates an architecture 100 of an internal combustion engine
25 with Engine Control Unit (ECU) coupled with front and rear oxygen sensors to
control emissions based on fuelling feedback and monitoring of health of catalytic
converter. As shown in fig. 2 and 3, the ECU 300 controls fuelling in the internal
combustion (IC) engine 101 (herein after can be referred as engine 101 based on
fuel feedback value received from the front oxygen sensor 103 and the rear
30 oxygen sensor 104. After combustion, the engine 101 releases exhaust gases 106
11
that comprises carbon monoxide (CO), Total Hydrocarbons (THC), nitro oxide
(NOx) and other pollutants. A catalytic converter 107 is provided in exhaust gas
system to treat the emissions and convert the pollutants in acceptable form. The
front oxygen sensor 103 is positioned before the catalytic converter 107; and the
5 rear oxygen sensor 104 is positioned after the catalytic converter 107 in the
exhaust gas system. The front oxygen sensor 103 detects the oxygen content in the
exhaust gas 106 coming from the engine 101 and gives output signal 103a to the
ECU 300 to calculate fuel feedback. After treatment of the emissions, the rear
oxygen sensor 104 determines the oxygen content in the treated emissions after
10 the catalytic converter 107 and compares the determine oxygen content with the
threshold value of the oxygen content on which the rear oxygen sensor 104is
calibrated. Upon comparison, the rear oxygen sensor 104 signal provides fuel
feedback value 104a to the ECU 300.
[0047] The front oxygen sensor 103 and the rear oxygen sensors 104
15 determines the oxygen content in the exhaust gas and provides their output in term
of voltages. Further, working of the oxygen sensors is well known to a person
skilled in the art and well available in the existing arts.
[0048] The ECU 300 combines both the fuel feedback values 103a and 104a
and calculates a final fuel feedback value 105 to determine air-fuel mixture in the
20 engine 101. The ECU 300 controls fuel injectors 102 to maintain the air-fuel ratio
at desired level. Based on the final fuel feedback value 105, the ECU 300
determines whether emissions are on leaner side or on richer side. Based on the
determination, fueling is updated towards rich side or in lean side.
[0049] With the usage of the catalytic converter 107, health of the catalytic
25 converter 107 start deteriorating and its efficiency for converting the pollutants
also starts decreasing. Health of the catalytic converter decreases due to exposure
of catalyst to high temperature; presence of impurities such as lead compounds,
sulphur and phosphorous in fuel; physical damage by fracturing causing leaks to
the atmosphere; and thermal shocks.
12
[0050] The catalytic converter 107 with deteriorated health is not efficient to
convert the pollutants effectively.
[0051] Case I: When catalytic converter is 100% healthy and rear oxygen
sensor 104 has target operating voltage X volts.
5 [0052] The catalytic converter 107 complete converts the pollutants, such as
CO, THC, and NOx from the emissions into Carbon dioxide (CO2), Water (H2O),
and nitrogen oxides (NO2). The rear oxygen sensor 104 determines the oxygen
content in terms of voltage and compares with the predefined static target
operating voltage (Vopt). The rear oxygen sensor 104 provides the difference
10 between the target operating voltage (Vopt) and the determined voltage to a
catalytic health monitoring system 200 (explained in detail in figure 3).
For example:
Catalytic converter is 100% efficient
Target operating voltage (Vopt) = X volts
15 Determined voltage = X-.05 volts
Difference in the voltage as fuel feedback value = 0.05 Volts
[0053] The catalytic health monitoring system 200 adds difference in the
voltage as fuel feedback value to the fuel feedback value of the front oxygen
sensor to determine the air-fuel ratio.
20 [0054] Case II: When catalytic converter is 50 % healthy and rear oxygen
sensor 104 has target operating voltage X volts.
[0055] The catalytic converter 107 converts the pollutants, such as CO, THC,
and NOx from the emissions into Carbon dioxide (CO2), Water (H2O), and
nitrogen oxides (NO2) based on the efficiency. The rear oxygen sensor 104
25 determines the oxygen content in terms of voltage in the emissions coming from
the catalytic converter 107 having 50% efficiency and compares with the
predefined static target operating voltage (Vopt). The rear oxygen sensor 104
provides the difference between the target operating voltage (Vopt) and the
13
determined voltage to a catalytic health monitoring system 200 (explained in
detail in figure 3).
For example:
Catalytic converter is 50% efficient
5 Target operating voltage (Vopt) = X volts
Determined voltage = X-.20 volts
Difference in the voltage as fuel feedback value = 0.20 Volts
[0056] The catalytic health monitoring system 200 adds difference in the
voltage as fuel feedback value to the fuel feedback value of the front oxygen
10 sensor to determine the air-fuel ratio. As health of the catalytic converter is
deteriorated to 50% and the catalytic converter 107 is not converting the complete
emissions efficiently. With the fixed or static target operating voltage (Vopt), the
oxygen sensor 104 determines less oxygen content in the emissions 106a and adds
the fuel feedback value to the fuel feedback value of the front oxygen sensor 103
15 to make the air-fuel ratio more towards richer side.
[0057] As the health of the catalytic converter is deteriorated, it will not
convert the emissions based on the updated air-fuel ratio, which is towards the
richer side, and further output result of the rear oxygen sensor 104 is same as
before updating the air-fuel ratio. The rear oxygen sensor 104 further provides a
20 fuel feedback value to make the air-fuel ratio richer. Resultantly, the air-fuel ratio
is continuously maintained towards richer side and untreated pollutants, such as
CO and THC keeps on increasing in the emissions.
[0058] Referring to fig. 2, 3, and 4, the present subject matter provides a
catalytic health monitoring system 200 that is implemented in the Electronic
25 Control Unit (ECU) 300 of the vehicle. In another embodiment, the catalytic
health monitoring system 200 may be embedded in the ECU 300 or installed in
the ECU 300. In another embodiment, the catalytic health monitoring system 200
may be provided as pre-configured micro-controller to dynamically update the
target operating voltage (Vopt) of the rear oxygen sensor 104. The catalytic health
14
monitoring system 200 monitors the health of the catalytic converter 107 and
dynamically update the target operating voltage (Vopt) of the rear oxygen sensor
104. The catalytic health monitoring system 200 includes a processor(s) 202, an
interface(s) 204, and a memory 206. In an embodiment, the processor(s) 202, the
5 interface(s) 204, and the memory 206 is same as of the ECU 300.
[0059] The processor(s) 202 may be implemented as one or more
microprocessors, microcomputers, microcontrollers, digital signal processors,
logic circuitries, and/or any devices that manipulate data based on operational
instructions.
10 [0060] Among other capabilities, the one or more processor(s) 202 are
configured to fetch and execute computer-readable instructions and one or more
routines stored in the memory 206. The memory 206 may store one or more
computer-readable instructions or routines, which may be fetched and executed to
implement updating target operating voltage of the oxygen sensor 104. The
15 memory 206 may include any non-transitory storage device including, for
example, volatile memory such as RAM, or non-volatile memory such as
EPROM, flash memory, and the like.
[0061] The interface(s) 204 may include a variety of interfaces, for example,
interfaces for data input and output devices referred to as I/O devices, storage
20 devices, various sensors, such as front oxygen sensor 103 and rear oxygen sensor
104, and the like. The interface(s) 204 may facilitate communication of the
catalytic health monitoring system 200 with various devices, such as fuel
injectors, oxygen sensors coupled to the catalytic health monitoring system 200.
The interface(s) 204 may also provide a communication pathway for one or more
25 components of the catalytic health monitoring system 200. Examples of such
components include, but are not limited to, processing modules(s) 208 and data
210.
[0062] The processing module(s) 208 may be implemented as a combination
of hardware and programming (for example, programmable instructions) to
30 implement one or more functionalities of the processing module(s) 208. In
15
examples described herein, such combinations of hardware and programming may
be implemented in several different ways. For example, the programming for the
processing modules(s) 208 may be processor-executable instructions stored on a
non-transitory machine-readable storage medium and the hardware for the
5 processing modules(s) 208 may include a processing resource (for example, one
or more processors), to execute such instructions. In the present examples, the
machine-readable storage medium may store instructions that, when executed by
the processing resource, implement the processing module(s) 208. In such
examples, the catalytic health monitoring system 200 may include the machine10 readable storage medium storing the instructions and the processing resource to
execute the instructions or the machine-readable storage medium may be separate
but accessible to the catalytic health monitoring system 200 and the processing
resource. In other examples, the processing modules(s) 208 may be implemented
by electronic circuitry.
15 [0063] In an aspect, the processing module(s) 208 may include a feedback
control module 212, a catalytic health monitoring module 214, and target
operating voltage update module 216. The processing modules(s) 208 may include
other unit(s) which may implement functionalities that supplement applications or
functions performed by the catalytic health monitoring system 200 or the
20 processing modules(s) 208.
[0064] Further, the data 210 may include data that is either stored or generated
as a result of functionalities implemented by any of the components of the
processing modules(s) 208. In some aspects, the data 210 may be stored in the
memory 206 in the form of various data structures. In the present subject matter, a
25 lookup table having health values of the catalytic converter and corresponding
target operating voltage of the rear oxygen sensor. The lookup table is stored in
the data 210 or in the memory 206. Additionally, data 210 can be organized using
data models, such as relational or hierarchical data models. The data 210 may
store data, including temporary data and temporary files, generated by the
16
processing modules(s) 208 for performing the various functions of the catalytic
health monitoring system 200.
[0065] The health values of the catalytic converter 107 and corresponding
target operating voltage (Vopt) of the rear oxygen sensor is stored in the lookup
5 table are experimented values. Example of Look-up table is given below:
Table 1
Cata Health
Value Ch
>8000
>=6000 &
<8000
>=5000 &
<6000
>=4500
& <5000
<4500
Target
Operating
Voltage
(Vopt)
X X-a X-b X-c
Y
Disable
feedback
[0066] The above mentioned values are given for reference only actual values
may differ from the given values.
10 [0067] Above-mentioned values are given for reference these are not actual
values. Further, the actual values of the lookup table may depend on the type of
vehicle, type of fuel, type of catalytic converter. Fig. 6 illustrates graph between
the health of the catalytic converter in terms of kilometre running of the vehicle
and dynamic the variation of the target operating voltage of the rear oxygen sensor
15 104 to control the emissions.
[0068] In operation, when the catalytic converter 107 is deteriorating in health
due to various factors, such as ageing. The catalytic health monitoring module 214
determines health of the catalytic converter 107 by means of existing health
monitoring techniques. The existing health monitoring techniques may be Oxygen
20 Storage Capacity (OSC) and Oxygen Storage Time (OST). In the Oxygen Storage
Capacity method, oxygen storage capacity (OSC) of the catalyst is measured
during transition from rich to lean mixture. The oxygen sensor helps in precise
measurement of the air-fuel mixture. Although the methodology followed by
different manufacturers for oxygen storage calculation may vary, the basic
25 concept remains the same. In Oxygen Storage Time (OST) method, the catalyst
17
uses the delay time between front and rear oxygen sensor signal to calculate its
oxygen storage time in milliseconds. Larger delay time indicates good condition
of catalytic converter (high oxygen storage capacity) and small delay time
indicates vice versa. During catalyst diagnosis, a feedback period adjustment
5 delay is introduced to increase the target feedback period calculated from front
oxygen sensor response.
[0069] With the help of the existing health monitoring techniques, the
catalytic health monitoring module 214 determines health of the catalytic
converter. The target operating voltage update module 216 compares the
10 determined health of the catalytic converter with the pre-stored health values in
the lookup table. Upon comparison, the target operating voltage update module
216 selects the target operating voltage (Vopt) corresponding to determined health
of the catalytic converter 107. The target operating voltage update module 216
update the target operating voltage (Vopt) of the rear oxygen sensor 104 for
15 further operation of the rear oxygen sensor 104 based on the health of the catalytic
converter 107.
[0070] Case III: When catalytic converter is 50% healthy and rear
oxygen sensor 104 has been updated to target operating voltage X-b volts
based on the health of the catalytic converter.
20 [0071] The catalytic health monitoring module 214 determines the health of
the catalytic converter 107. Upon determination, the target operating voltage
update module 216 compares the determined health of the catalytic converter 107
with the pre-stored experimented values in the lookup table. Based on the
comparison, the target operating voltage update module 216 selects the target
25 operating voltage (Vopt) X-b volts for the rear oxygen sensor 104 and calibrates
the rear oxygen sensor 104 with the selected target operating voltage (Vopt) for
operation. The rear oxygen sensor 104 determines the oxygen content in terms of
voltage in the emissions coming from the catalytic converter 107 having 50%
efficiency and compares with the updated target operating voltage (Vopt) X-b
30 volts. The rear oxygen sensor 104 provides the difference between the target
18
operating voltage (Vopt) and the determined voltage as fuel feedback value to the
feedback control module 212 of the catalytic health monitoring system 200 to
correct the air-fuel ratio either towards richer side or leaner side.
For example:
5 Catalytic converter is 50% efficient
Target operating voltage (Vopt) = X-b volts, where b is .20 V
Determined voltage = X-.15 volts
Difference in the voltage as fuel feedback value = 0.05 Volts
[0072] The catalytic health monitoring system 200 adds difference in the
10 voltage as fuel feedback value to the fuel feedback value of the front oxygen
sensor to determine the air-fuel ratio. With the updated target operating voltage
(Vopt), the rear oxygen sensor 104 determines oxygen content in the emissions
106a and compares the same with the reduced target voltage which is based on the
health of the catalytic converter. Further, addition of the fuel feedback value by
15 the rear oxygen sensor 104 on the basis of updated target operating voltage, the
fuel feedback control module 212 adds actual fuel feedback value based on actual
content of oxygen in the emissions and health of the catalytic converter to control
the air-fuel ratio to avoid generation of more CO and THC in the emissions due to
static target operating voltage of the rear oxygen sensor 104. Resultantly, the air20 fuel ratio is maintained to work according to health of the catalytic converter and
the rear oxygen sensor 104 provides fuel feedback value based on updated target
operating voltage.
[0073] Fig. 7a illustrates target operating voltage of rear oxygen sensor 104 in
new vehicle and vehicle after ageing, in view of existing technologies. In the new
25 vehicle, the target operating voltage is X voltages and actual voltage is also X
volts. However, in the vehicle after ageing, target operating voltage is X volts and
actual voltage is X-a volts. Therefore, the rear oxygen sensor 104 provides high
fuel feedback value because there is high difference in target operating voltage
(Vopt) and the actual voltage of the rear oxygen sensor 104.
19
[0074] Fig. 7b illustrates target operating voltage of rear oxygen sensor 104 in
new vehicle and vehicle after ageing, in view of present subject matter. In the new
vehicle, the target operating voltage is X voltages and actual voltage is also X
volts. Therefore, the rear oxygen sensor 104 does not provide any false or un5 necessary high fuel feedback value. In the vehicle after ageing, updated target
operating voltage is X-a volts and actual voltage is also X-a volts. Therefore, the
rear oxygen sensor 104 does not provides high fuel feedback value as there is no
difference of voltage between the actual and the target operating voltage of the
rear oxygen sensor.
10 [0075] The fuel feedback control module 212 receives fuel feedback value of
the front oxygen sensor 103 and the rear oxygen sensor 104 to control the air-fuel
ratio. With implementation of the present subject matter, the fuel feedback control
module 212 receives correct fuel feedback value or correction from the rear
oxygen sensor 104 based on the updated target operating voltage (Vopt) to
15 improve emission performance with respect to health of the catalytic converter
107.
[0076] Based on real time health of the catalytic converter, the feedback value
improves the health of catalytic converter by controlling fuelling to more richer
side (which means less impurities as more rich mean more fuel And as fuel
20 contain impurities, which can contaminate the catalytic converter. FIG. 5
illustrates a method 500 for improving emissions by controlling target operating
voltage (Vopt) of the rear oxygen sensor with respect to health or ageing of the
catalytic converter. The order in which the method 500 is described is not
intended to be construed as a limitation, and any number of the described method
25 blocks can be combined in any appropriate order to carry out the method 500 or
an alternative method. Additionally, individual blocks may be deleted from the
method 500 without departing from the scope of the subject matter described
herein.
[0077] At block 502, the method includes determining health of the catalytic
30 converter by the catalytic health monitoring module using existing health
20
monitoring techniques, such as Oxygen Storage Capacity (OSC) and Oxygen
Storage Time (OST). The health monitoring techniques are not limited to OSC or
OST, it may include other existing techniques that determines health of the
catalytic converter.
5 [0078] At block 504, the method includes comparing the determine health of
the catalytic converter (CC) with a pre-stored lookup table having experimented
health values and its corresponding target operating voltages (Vopt).
[0079] At block 506, the method includes selecting a target operating voltage
(Vopt) corresponding to determined health of the catalytic converter based on the
10 comparison from the pre-stored lookup table in the memory of the ECU.
[0080] At block 508, the method includes updating and calibrating the
selected target operating voltage (Vopt) of the rear oxygen sensor based on the
determined health of the catalytic converter.
[0081] In an aspect, adding update amount of fuel feedback based on the
15 updated target operating voltage of the rear voltage sensor 104 to fuel feedback
value of the front oxygen sensor 103 to control air-fuel mixture in rich and lean
mode.
[0082] Upon updating and calibrating the target operating voltage (Vopt) the
rear oxygen sensor 104 does not provide high corrections of high fuel feedback
20 value to the feedback control module 212 to update the air-fuel ratio.
[0083] With feedback value based on real time health of the catalytic
converter, the feedback value improves the health of catalytic converter by
controlling fuel in rich mode which means less impurities as more rich mean more
fuel and more fuel mean more impurities. (please change based on above inputs)
25 Technical advantages:
[0084] With the present system implemented in the Engine Control Unit
(ECU) a controlled air-fuel mixture is maintained to improve emission
performance by controlling target operating voltage (Vopt) of the rear oxygen
sensor with respect to the health of the catalytic converter.
21
[0085] With the present ECU, the controlled air-fuel mixture is obtained
which improves fuel economy of the vehicle.
[0086] With the present disclosure, there is no need to add any extra
component in the system to improve the emission performance.
5 [0087] With the present system, there is no requirement of any other new
hardware, existing hardware can be optimized to obtain technical advanced
results.
[0088] With the present system, the existing hardware works in more efficient
and technically advance way to reduce the emissions.
10 [0089] The above description does not provide specific details of the
manufacture or design of the various components. Those of skill in the art are
familiar with such details, and unless departures from those techniques are set out,
techniques, known, related art or later developed designs and materials should be
employed. Those in the art can choose suitable manufacturing and design details.
15 [0090] It should be understood, however, that all of these and similar terms
are to be associated with the appropriate physical quantities and are merely
convenient labels applied to these quantities. Unless specifically stated otherwise,
as apparent from the discussion herein, it is appreciated that throughout the
description, discussions utilizing terms such as “receiving,” or “determining,” or
20 “retrieving,” or “controlling,” or “comparing,” or the like, refer to the action and
processes of an electronic control unit, or similar electronic device, that
manipulates and transforms data represented as physical (electronic) quantities
within the control unit’s registers and memories into other data similarly
represented as physical quantities within the control unit memories or registers or
25 other such information storage, transmission or display devices.
[0091] Further, the terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the disclosure. It
will be appreciated that several of the above-disclosed and other features and
functions, or alternatives thereof, may be combined into other systems or
22
applications. Various presently unforeseen or unanticipated alternatives,
modifications, variations, or improvements therein may subsequently be made by
those skilled in the art without departing from the scope of the present disclosure
as encompassed by the following claims.
5 [0092] It will be appreciated that variants of the above-disclosed and other
features and functions, or alternatives thereof, may be combined into many other
different systems or applications. Various presently unforeseen or unanticipated
alternatives, modifications, variations, or improvements therein may be
subsequently made by those skilled in the art which are also intended to be
10 encompassed by the following claims.
[0093] The claims, as originally presented and as they may be amended,
encompass variations, alternatives, modifications, improvements, equivalents, and
substantial equivalents of the embodiments and teachings disclosed herein,
including those that are presently unforeseen or unappreciated, and that, for
15 example, may arise from applicants/patentees and others.

We claim:

1. A catalytic health monitoring system (200) provided in an Engine Control
Unit (200) for improving emission performance and improving fuel
economy, the catalytic health monitoring system (200) coupled with a
plurality of fuel injectors (102) and a catalytic converter (107), the catalytic
health monitoring system (200) comprising:
a feedback control module (212) coupled with a front voltage
sensor (103) and a rear voltage sensor (104) to control air-fuel
mixture;
a catalytic health monitoring module (214) to determine health
of the catalytic converter (107); and
characterized in that
a target operating voltage update module (216) to update target
operating voltage (Vopt) of the rear voltage sensor (104) dynamically
based on determined health of the catalytic converter (107).
2. The catalytic health monitoring system (200) as claimed in claim 1, wherein
the target operating voltage update module (216):
compares the determined health of the catalytic converter (107)
with a pre-stored lookup table having predetermined experimented values
for the health of the catalytic converter (107) and corresponding target
operating voltage of the rear voltage sensor (104);
selects the target operating voltage (Vopt) of the rear voltage
sensor (104) based on the comparison between the determined health of
the catalytic converter (107) with the pre-stored lookup table; and
updates and calibrates the target operating voltage (Vopt) of the
rear voltage sensor (104) based on the selected target operating voltage
(Vopt) from the pre-stored lookup table.
3. The catalytic health monitoring system (200) as claimed in claim 1, wherein
the feedback control module (212) adds updated amount of fuel feedback
based on the updated target operating voltage (Vopt) of the rear voltage
24
sensor (104) to fuel feedback value (103a) of the front oxygen sensor (103)
to control air-fuel mixture in rich and lean mode.
4. The catalytic health monitoring system (200) as claimed in claim 1, wherein
the catalytic health monitoring module (214) determines health of the
catalytic converter (107) based on Oxygen Storage Capability method or
Oxygen Storage Time.
5. A method (500) for reducing emissions and improving fuel economy of an
internal combustion (IC) engine (101), the method (500) comprising:
determining (502) health of a catalytic converter (107);
comparing (504) the determined health of the catalytic converter
(107) with a pre-stored lookup table having predetermined experimented
values for health of the catalytic converter (107) and corresponding target
operating voltage (Vopt) of a rear voltage sensor (104);
selecting (506) the target operating voltage (Vopt) of the rear
voltage sensor (104) from the pre-stored lookup table; and
updating and calibrating (508) the target operating voltage (Vopt)
of the rear voltage sensor (104) dynamically based on the selected target
operating voltage from the pre-stored lookup table.
6. The method (500) as claimed in claim 5, wherein the method (500) comprises:
adding update amount of fuel feedback based on the update target operating
voltage of the rear voltage sensor (104) to fuel feedback value of the front
oxygen sensor (103) to control air-fuel mixture in rich and lean mode.
7. The method (500) as claimed in claim 5, wherein the health of the catalytic
converter (107) is determined based on Oxygen Storage Capability or Oxygen
Storage time.