U.S. patent application number 11/048790 was filed with the patent office on 2005-09-29 for method for sensing exhaust gas for obd.
This patent application is currently assigned to HINO MOTORS LTD.. Invention is credited to Funabashi, Hiroshi.
Application Number | 20050210868 11/048790 |
Document ID | / |
Family ID | 34858492 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050210868 |
Kind Code |
A1 |
Funabashi, Hiroshi |
September 29, 2005 |
Method for sensing exhaust gas for OBD
Abstract
All of NO.sub.x, PM, HC and CO concentrations necessary for
realization of OBD are determined by utilization of an in-vehicle
existing NO.sub.x sensor. A NO.sub.x sensor arranged in an exhaust
pipe detects the NO.sub.x concentration in the exhaust gas. On the
basis of O.sub.2 concentration detected in a course of detection of
the NO.sub.x concentration, PM, HC and CO concentrations are
determined in conversion through mutual correspondences of the
concentrations.
Inventors: |
Funabashi, Hiroshi;
(Hino-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
HINO MOTORS LTD.
Hino-shi
JP
|
Family ID: |
34858492 |
Appl. No.: |
11/048790 |
Filed: |
February 3, 2005 |
Current U.S.
Class: |
60/277 ;
60/274 |
Current CPC
Class: |
Y02T 10/47 20130101;
Y02A 50/20 20180101; F01N 2560/06 20130101; Y02A 50/2322 20180101;
F01N 2560/026 20130101; F01N 11/007 20130101; Y02T 10/40 20130101;
F01N 11/00 20130101; F01N 3/20 20130101 |
Class at
Publication: |
060/277 ;
060/274 |
International
Class: |
F01N 003/00; F01N
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2004 |
JP |
2004-091725 |
Claims
What is claimed is:
1. A method for sensing exhaust gas for OBD which comprises
detecting a NO.sub.x concentration in the exhaust gas by a NO.sub.x
sensor arranged in an exhaust pipe, PM, HC and CO concentrations
being determined in conversion, on the basis of an O.sub.2
concentration sensed in the course of detection of said NO.sub.x
concentration, from mutual correspondences of the
concentrations.
2. The method according to claim 1 wherein an oxidation catalyst is
arranged in the exhaust pipe and downstream of the NO.sub.x sensor,
a temperature sensor being arranged on an inlet side of said
oxidation catalyst to detect an exhaust temperature, purified
ratios of the PM, HC and CO concentrations being determined
depending upon catalytic activity of the oxidation catalyst at a
current exhaust temperature, the PM, HC and CO concentrations being
compensated on the basis of the purified ratios.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for sensing
exhaust gas for OBD.
[0003] 2. Description of the Related Art
[0004] It has been recently proposed to monitor controlled states
of exhaust gas from a vehicle by virtue of an in-vehicle computer.
It is generally called OBD (on-board diagnostic system); there is
an active trend towards future legal compulsion including
restrictions for OBD.
[0005] Detection of exhaust-gas temperature and NO.sub.x (nitrogen
oxides) concentration through sensors in a control system for an
exhaust purifying or aftertreatment apparatus has been disclosed
for example in JP 2002-161732 A.
[0006] However, most of conventionally known exhaust-gas sensors
are large-sized fixed devices in laboratory level so that, except a
NO.sub.x sensor which is compact in size and has been actually
mounted in a vehicle, sensors for PM (particulate matter), HC
(hydrocarbon) and CO (carbon monoxide) concentrations cannot be
mounted in a vehicle up to the present.
[0007] The invention was made in view of the above and has its
object to make it possible to detect or determine all of NO.sub.x,
PM, HC and CO concentrations necessary for realization of OBD by
virtue of an existing NO.sub.x sensor which can be mounted in a
vehicle.
BRIEF SUMMARY OF THE INVENTION
[0008] The invention is directed to a method for sensing exhaust
gas for OBD which comprises detecting a NO.sub.x concentration in
the exhaust gas by a NO.sub.x sensor arranged in an exhaust pipe,
PM, HC and CO concentrations being determined in conversion, on the
basis of an O.sub.2 concentration sensed in the course of detection
of said NO.sub.x concentration, from mutual correspondences of the
concentrations.
[0009] More specifically, the existing NO.sub.x sensor, which has
to utilize an O.sub.2 concentration in the course of detection of
the NO.sub.x concentration in an exhaust gas, inherently
accommodates an extensive O.sub.2 sensor which detects an O.sub.2
concentration in the exhaust gas.
[0010] Then, utilizing the feature of the NO.sub.x sensor that can
detect the O.sub.2 concentration, the PM, HC and CO concentrations
which have correspondences with the O.sub.2 concentration are
determined in conversion so that all of the PM, HC and CO
concentrations are obtained in alternative measurement in addition
to the NO.sub.x concentration directly sensed by the NO.sub.x
sensor.
[0011] The fact that the PM, HC and CO concentrations have
correspondences with the O.sub.2 concentration is the inventor's
knowledge. The PM, HC and CO concentrations greatly depend on
combustibility in an engine and tend to remarkably increase when
the combustibility becomes insufficient due to lowering of the
O.sub.2 concentration.
[0012] Thus, adoption of such sensing method makes it possible to
determine all of the NO.sub.x, PM, HC and CO concentrations
necessary for realization of OBD by virtue of an existing NO.sub.x
sensor which can be mounted in a vehicle.
[0013] If an oxidation catalyst is arranged in the exhaust pipe and
downstream of the NO.sub.x sensor in the invention, a temperature
sensor may be arranged on an inlet side of said oxidation catalyst
to detect an exhaust temperature, purified ratios of the PM, HC and
CO concentrations being determined depending upon catalytic
activity of said oxidation catalyst at a current exhaust
temperature, the PM, HC and CO concentrations being compensated on
the basis of the purified ratios.
[0014] More specifically, when the oxidation catalyst is arranged
in the exhaust pipe and downstream of the NO.sub.x sensor, the
NO.sub.x and O.sub.2 concentrations once detected by the NO.sub.x
sensor are lowered downstream since the exhaust gas passes through
the oxidation catalyst and is purified; therefore, compensation
must be done for the decrements to determine final values of the
PM, HC and CO concentrations.
[0015] The purified ratios of the PM, HC and CO concentrations
depend on catalytic activity of the oxidation catalyst which in
turn depends on an exhaust temperature on the inlet side of the
oxidation catalyst. Thus, the purified ratios of the PM, HC and CO
concentrations are determined depending upon the catalytic activity
of the oxidation catalyst at a current exhaust temperature and the
PM, HC and CO concentrations are compensated on the basis of the
purified ratios determined, so that the final values of the PM, HC
and CO concentrations in the exhaust gas purified through the
oxidation catalysts can be determined.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic view showing an embodiment of the
invention;
[0017] FIG. 2 is a graph showing correspondence of O.sub.2
concentration with PM concentration;
[0018] FIG. 3 is a graph showing correspondence of O.sub.2
concentration with HC concentration;
[0019] FIG. 4 is a graph showing correspondence of O.sub.2
concentration with CO concentration;
[0020] FIG. 5 is a graph showing correspondence of HC purified
ratio with exhaust temperature;
[0021] FIG. 6 is a graph showing correspondence of CO purified
ratio with exhaust temperature; and
[0022] FIG. 7 is a graph showing correspondence of PM purified
ratio with exhaust temperature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] Now, an embodiment of the invention will be described with
reference to the drawings.
[0024] FIGS. 1 to 7 show an embodiment of a method for sensing
exhaust gas for OBD according to the invention in which exhaust gas
3 is discharged via an exhaust manifold 2 from a diesel engine 1
and flows through an exhaust pipe 4. Arranged in the exhaust pipe 4
is a casing 6 which accommodates an oxidation catalyst 5 in the
form of a flow-through type honeycomb structure.
[0025] Arranged on a most upstream side in the exhaust pipe 4 is a
NO.sub.x sensor 8 which is positioned adjacent to a turbine outlet
of a turbocharger 7. Arranged on an inlet side of the casing 6 is a
temperature sensor 9 which detects temperature of the exhaust gas
3. Detection signals 8a and 9a from the sensors 8 and 9,
respectively, are inputted to an electronic control unit (ECU) 10
which is an engine controlling computer.
[0026] When NO.sub.x, PM, HC and CO concentrations grasped on the
basis of detection signals 8a and 9a from the sensors 8 and 9,
respectively, have something abnormal, then ECU 10 outputs a
lightening command signal 11a to light a caution-advisory indicator
11 on an instrument panel.
[0027] More specifically, the existing NO.sub.x sensor 8 has to
utilize an O.sub.2 concentration in the course of detection of the
NO.sub.x concentration, therefore the sensor 8 inherently
accommodates an extensive O.sub.2 sensor which senses the O.sub.2
concentration in the exhaust gas 3.
[0028] Thus, utilizing the feature of the NO.sub.x sensor 8 that
can detect the O.sub.2 concentration, the PM, HC and CO
concentrations which have correspondences with the O.sub.2
concentration are determined in conversion by the ECU 10, so that
all of the PM, HC and CO concentrations are obtained in alternative
measurement in addition to the NO.sub.x concentration directly
sensed by the NO.sub.x sensor 8.
[0029] The fact that the PM, HC and CO concentrations have
correspondences with the O.sub.2 concentration is the inventor's
knowledge; FIG. 2 shows correspondence of O.sub.2 concentration
with PM concentration; FIG. 3, of O.sub.2 concentration with HC
concentration; and FIG. 4, of O.sub.2 concentration with CO
concentration. CO concentration greatly depends upon combustibility
in the diesel engine 1 and tends to remarkably increase when the
combustibility becomes insufficient due to lowering of the O.sub.2
concentration.
[0030] In a case where, as in the embodiment, an oxidation catalyst
5 is arranged in the exhaust pipe 4 and downstream of the NO.sub.x
sensor 8, after the NO.sub.x and O.sub.2 concentrations are sensed
by the NO.sub.x sensor 8, the PM, HC and CO concentrations are
lowered since the exhaust gas 3 passes through the oxidation
catalyst 5 and is purified; therefore, the compensation must be
done for the decrements to determined the last values of the PM, HC
and CO concentrations.
[0031] As shown in FIGS. 5 to 7, these purified ratios of the PM,
HC and CO concentrations are determined depending on the catalytic
activity which in turn depends upon the exhaust temperature on the
inlet side of the oxidation catalyst 5; therefore, the purified
ratios of the PM, HC and CO concentrations are determined depending
upon the catalytic activity of the oxidation catalyst 5 at the
current exhaust temperature. On the basis of such determined
purified ratios, the determined PM, HC and CO concentrations as to
the exhaust gas 3 adjacent to the turbine outlet of said
turbocharger 7 are compensated to obtain final values of PM, HC and
CO concentrations in the exhaust gas 3 which has passed through the
oxidation catalyst 5 and is purified.
[0032] In the embodiment, the flow-through type oxidation catalyst
5 is singly arranged with no combination with another catalyst. In
a case where the oxidation catalyst 5 is carried by a particulate
filter or is followed by a separate particulate filter, then as
shown in two-dot-chain lines in the graph of FIG. 7, almost all of
PM are captured in the particulate filter with no connection with
the purified ratios by the oxidation catalyst 5, so that it can be
regarded with no specific determination that the final PM
concentration has been lowered to a substantially constant
concentration.
[0033] Whether the thus obtained NO.sub.x, PM, HC and CO
concentrations are within rate values of them, respectively, is
judged in the ECU 10; when judgment is made to be negative, the
lightening command signal 11a is outputted to the caution-advisory
indicator 11 on the instrument panel so that the caution-advisory
indicator 11 is lighted on to announce occurrence of abnormality to
a driver.
[0034] Shown in FIG. 1 is the single caution-advisory indicator 11;
however, the caution-advisory indicator 11 may be arranged for each
of the NO.sub.x, PM, HC and CO concentrations. Upon detection of
abnormality, preferably, such occurrence of abnormality is recorded
in a memory in the ECU 10 and/or a suitable correction operation is
made to the diesel engine 1.
[0035] As is clear from the foregoing, in a method for sensing
exhaust gas for OBD according to the invention, all of NO.sub.x,
PM, HC and CO concentrations can be determined by utilization of an
existing NO.sub.x sensor 8 which is mountable in a vehicle. Even if
the oxidation catalyst 5 is arranged in the exhaust pipe 4, the PM,
HC and CO concentrations can be suitably compensated on the basis
of an exhaust temperature detected by the temperature sensor 9 on
the inlet side of the oxidation catalyst 5; as a result, the OBD
can be realized readily and at a lower cost.
[0036] It is to be understood that a method for sensing exhaust gas
for OBD according to the invention is not limited to the above
embodiment and that various changes and modifications may be
effected within the gist of the invention. For example, it may be
applicable to a vehicle with an exhaust pipe 4 having no oxidation
catalyst 5.
* * * * *