U.S. patent application number 15/645571 was filed with the patent office on 2017-10-26 for particulate collection system and particulate collection apparatus.
The applicant listed for this patent is NGK SPARK PLUG CO., LTD.. Invention is credited to Kentaro MORI, Hiroyuki SUZUKI, Takaya YOSHIKAWA.
Application Number | 20170306826 15/645571 |
Document ID | / |
Family ID | 56682746 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306826 |
Kind Code |
A1 |
YOSHIKAWA; Takaya ; et
al. |
October 26, 2017 |
PARTICULATE COLLECTION SYSTEM AND PARTICULATE COLLECTION
APPARATUS
Abstract
A particulate collection system collects particulates contained
in exhaust gas discharged from an internal combustion engine. The
particulate collection system includes a first particulate
collection filter; a second particulate collection filter capable
of storing or radiating heat; a heating member for heating the
second particulate collection filter; and a control section which
selectively executes collection of particulates by the first
particulate collection filter, collection of particulates by the
first particulate collection filter and the second particulate
collection filter, and heating of the second particulate collection
filter by the heating member.
Inventors: |
YOSHIKAWA; Takaya;
(Kasugai-shi, JP) ; SUZUKI; Hiroyuki;
(Kasugai-shi, JP) ; MORI; Kentaro; (Nagoya-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NGK SPARK PLUG CO., LTD. |
Nagoya-shi |
|
JP |
|
|
Family ID: |
56682746 |
Appl. No.: |
15/645571 |
Filed: |
July 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15047824 |
Feb 19, 2016 |
|
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15645571 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 9/002 20130101;
Y02T 10/40 20130101; F01N 2550/12 20130101; F01N 2900/1602
20130101; F01N 3/0275 20130101; F01N 3/031 20130101; Y02T 10/12
20130101; Y02T 10/47 20130101; F01N 3/101 20130101; F01N 2900/08
20130101; Y02T 10/22 20130101; F01N 2410/04 20130101 |
International
Class: |
F01N 9/00 20060101
F01N009/00; F01N 3/027 20060101 F01N003/027; F01N 3/031 20060101
F01N003/031 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2015 |
JP |
2015-036509 |
Mar 11, 2015 |
JP |
2015-048054 |
Claims
1. A particulate collection apparatus disposed in an exhaust pipe
passage of an internal combustion engine, the particulate
collection apparatus comprising: an introduction opening for
introducing exhaust gas from the internal combustion engine; a
discharge opening for discharging the introduced exhaust gas; a
first particulate collection filter disposed at the introduction
opening or the discharge opening; a first flow passage establishing
communication between the introduction opening and the discharge
opening; a second particulate collection filter disposed in the
first flow passage, the second particulate collection filter
capable of storing or radiating heat; a heating member disposed in
the first flow passage; a second flow passage which differs from
the first flow passage, the second flow passage establishing
communication between the introduction opening and the discharge
opening; and a changeover section configured to lead the exhaust
gas to either one of the first flow passage or the second flow
passage.
2. A particulate collection apparatus according to claim 1, wherein
the heating member and the second particulate collection filter are
integrally formed.
3. A particulate collection apparatus according to claim 1, further
comprising a second heating member disposed at the discharge
opening.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of prior U.S. patent
application Ser. No. 15/047,824, filed Feb. 19, 2016, which claims
priority to Japanese Patent Application No. 2015-036509, filed on
Feb. 26, 2015, and Japanese Patent Application No. 2015-048054,
filed Mar. 11, 2015, the disclosures of which are herein
incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a particulate collection
system and a particulate collection apparatus which are disposed in
an exhaust pipe passage of an internal combustion engine.
Description of Related Art
[0003] In order to cope with recent regulations on the components
of emission gas (exhaust gas) of an internal combustion engine,
various types of exhaust gas purification units are disposed in the
exhaust pipe passage of the internal combustion engine. These
exhaust gas purification units purify the exhaust gas components
such as NOx and PM (particulate matter) through chemical reaction
between a chemical substance such as catalyst or urea water and the
exhaust gas components, and the chemical substance exhibits an
optimum purification performance in a certain temperature range
(see, for example, Patent Document 1).
RELATED ART DOCUMENTS
[0004] Patent Document 1 is Japanese Patent Application Laid-Open
(kokai) No. 2010-261423.
BRIEF SUMMARY OF THE INVENTION
[0005] However, in the case of a diesel engine, the generation
amounts of NOx and PM tend to increase at the time of acceleration
and at the time of high load. Therefore, a PM purification unit,
for example, a diesel particulate filter (DPF), must be designed on
the basis of the amount of PM generated at the time of
acceleration, or a process of regenerating the DPF must be
performed frequently. In the case where the PM purification unit is
designed on the basis of the PM generation amount at the time of
acceleration, a problem arises in that the size of the PM
purification unit becomes large as compared with the frequency at
which the PM purification unit becomes necessary. Particularly, a
plasma DPF which removes PM using low-temperature plasma has
problems in that a circuit required to generate plasma becomes
larger and a larger amount of electric power is consumed. Also, the
DPF regeneration process raises a problem in that frequent DPF
regeneration increases the rate of fuel consumption because the
regeneration process consumes fuel.
[0006] Accordingly, efficient purification of exhaust gas has been
desired.
[0007] The present invention has been accomplished so as to solve
the above-described problem and can be realized as the following
modes.
[0008] A first mode provides a particulate collection system for
collecting particulates contained in exhaust gas discharged from an
internal combustion engine. The particulate collection system
according to the first mode comprises a first particulate
collection filter; a second particulate collection filter; a
heating member for heating the second particulate collection
filter; and a control section configured to selectively execute
collection of particulates by the first particulate collection
filter, collection of particulates by the first particulate
collection filter and the second particulate collection filter, and
heating of the second particulate collection filter by the heating
member.
[0009] The particulate collection system according to the first
mode can efficiently purify the exhaust gas.
[0010] In the particulate collection system according to the first
mode, the heating member may generate heat using electric power
obtained through regeneration and regenerate the second particulate
collection filter. In this case, it is possible to cause the
heating member to generate heat to thereby regenerate the second
particulate collection filter without lowering the overall energy
efficiency of the vehicle.
[0011] In the particulate collection system according to the first
mode, the particulate collection system may be disposed in a stage
before an exhaust gas purification unit disposed in an exhaust pipe
passage of the internal combustion engine. In this case, in the
case where heat is stored in the second particulate collection
filter, it is possible to heat the exhaust gas by the heat stored
in the second particulate collection filter, and adjust the
temperature of the exhaust gas purification unit to a proper
operating temperature range or assist the adjustment through use of
the heated exhaust gas.
[0012] In the particulate collection system according to the first
mode, the exhaust gas purification unit may be a selective
catalytic reduction unit, a three-way catalyst, or an oxidation
catalyst. In this case, in the case where heat is stored in the
second particulate collection filter, it is possible to heat the
exhaust gas by the heat stored in the second particulate collection
filter, and adjust the temperature of the selective catalytic
reduction unit, the three-way catalyst, or the oxidation catalyst
to a proper operating temperature range or assist the adjustment
through use of the heated exhaust gas.
[0013] The particulate collection system according to the first
mode may further comprise a first flow passage for the exhaust gas
(i.e., the first flow passage serves as a flow passage for the
exhaust gas), the first flow passage containing the second
particulate filter; a second flow passage for the exhaust gas
(i.e., the second flow passage serves as a flow passage for the
exhaust gas) which differs from the first flow passage; and a
changeover section which leads the exhaust gas to either one of the
first flow passage or the second flow passage (i.e., the changeover
section switches the flow passage for the exhaust gas to either one
of the first flow passage or the second flow passage), wherein the
first particulate collection filter is disposed in a stage before
or after the first flow passage and the second flow passage, and
the control section selectively executes the collection of
particulates by the first particulate collection filter, the
collection of particulates by the first particulate collection
filter and the second particulate collection filter, and the
heating of the second particulate collection filter by the heating
member by controlling the changeover section. In this case, the
collection of particulates by the second particulate collection
filter can be selectively performed by switching the exhaust gas
flow passage between the flow passage in which the second
particulate collection filter is disposed and the flow passage in
which the second particulate collection filter is not disposed.
[0014] In the particulate collection system according to the first
mode, the control section may switch the changeover section to lead
the exhaust gas to the first flow passage when load of the internal
combustion engine is above a predetermined range, and the control
section switches the changeover section to lead the exhaust gas to
the second flow passage and causes the heating member to generate
heat when the load of the internal combustion engine is below the
predetermined range. In this case, particulates which are produced
greatly when the load of the internal combustion engine is greater
than the load within the predetermined range are collected by the
second particulate collection filter, and the second particulate
collection filter can be regenerated when the load of the internal
combustion engine is less than the load within the predetermined
range.
[0015] In the particulate collection system according to the first
mode, the control section may switch the changeover section to lead
the exhaust gas to the second flow passage when the load of the
internal combustion engine falls within the predetermined range. In
this case, particulates can be collected by the first particulate
collection filter.
[0016] A second mode provides a particulate collection apparatus
disposed in an exhaust pipe passage of an internal combustion
engine. The particulate collection apparatus according to the
second mode comprises an introduction opening for introducing
exhaust gas from the internal combustion engine; a discharge
opening for discharging the introduced exhaust gas; a first
particulate collection filter disposed at the introduction opening
or the discharge opening; a first flow passage establishing
communication between the introduction opening and the discharge
opening; a second particulate collection filter disposed in the
first flow passage, the second particulate collection filter
capable of storing or radiating heat; a heating member disposed in
the first flow passage; a second flow passage which differs from
the first flow passage, the second flow passage establishing
communication between the introduction opening and the discharge
opening; and a changeover section configured to lead the exhaust
gas to either one of the first flow passage or the second flow
passage (i.e., the changeover section switches a flow passage,
through which the exhaust gas flows, to either one of the first
flow passage or the second flow passage).
[0017] The particulate collection apparatus according to the second
mode can efficiently purify the exhaust gas.
[0018] In the particulate collection apparatus according to the
second mode, the heating member and the second particulate
collection filter may be integrally formed. In this case, the
efficiency of the operation of storing heat in the second
particulate collection filter through use of the heating member can
be improved.
[0019] The particulate collection apparatus according to the second
mode may further comprise a second heating member disposed at the
discharge opening. In this case, the shortage of heat which occurs
as a result of heating by the second particulate collection filter
only can be supplemented by the heat generated by the second
heating member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Illustrative aspects of the invention will be described in
detail with reference to the following figures wherein:
[0021] FIG. 1 is an explanatory view schematically showing a
vehicle including a particulate collection system used in a first
embodiment.
[0022] FIG. 2 is an external perspective view schematically showing
the structure of a particulate collection apparatus according to
the first embodiment.
[0023] FIG. 3 is a schematic transverse cross-sectional view of the
particulate collection apparatus according to the first embodiment
taken along line 3-3 shown in FIG. 2.
[0024] FIG. 4 is an explanatory view showing an operating state of
the particulate collection apparatus according to the first
embodiment at the time of steady operation.
[0025] FIG. 5 is an explanatory view showing an operating state of
the particulate collection apparatus according to the first
embodiment at the time of acceleration.
[0026] FIG. 6 is an explanatory view showing an operating state of
the particulate collection apparatus according to the first
embodiment at the time of deceleration.
[0027] FIG. 7 is an explanatory view showing an exhaust gas
purification system including a conventional DPF.
[0028] FIG. 8 is a block diagram schematically showing the
electrical connections among electrical components in the vehicle
having a heat reservoir according to the first embodiment.
[0029] FIG. 9 is a flowchart showing a processing routine for
controlling the operation of the particulate collection apparatus
in the first embodiment.
[0030] FIG. 10 is an explanatory view showing an operating state of
a particulate collection apparatus according to a second embodiment
in a steady state.
[0031] FIG. 11 is an explanatory view showing an operating state of
the particulate collection apparatus according to the second
embodiment at the time of acceleration.
[0032] FIG. 12 is an explanatory view showing an operating state of
the particulate collection apparatus according to the second
embodiment at the time of deceleration.
[0033] FIG. 13 is an explanatory view showing a modification of the
particulate collection apparatus according to the first
embodiment.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0034] One mode of a particulate collection system according to the
present invention will now be described by taking as an example a
vehicle including a diesel engine (internal combustion engine).
FIG. 1 is an explanatory view schematically showing a vehicle
having a particulate collection system used in a first
embodiment.
A. First Embodiment
[0035] A vehicle 500 includes a diesel engine (hereafter referred
to as the "engine") 510, four wheels 520, and a particulate
collection system 10. The engine 510 uses light oil as fuel and
outputs drive force by means of explosive combustion of the fuel.
Also, as a result of the explosive combustion, the engine 510
discharges exhaust gas containing NOx (nitrogen oxides) and PM
(particulate matter) to the atmosphere through the particulate
collection system 10 provided in the exhaust system of the vehicle
500. Notably, the configuration of the vehicle shown in FIG. 1 and
used in the first embodiment can be used similarly in other
embodiments.
[0036] The particulate collection system 10 includes various types
of exhaust gas purification units provided on an exhaust pipe 11
(exhaust pipe passage). The exhaust pipe 11 is connected to the
engine 510 through a manifold 11a on the side toward the engine 510
(on the upstream side with respect to the flow direction of the
exhaust gas), and has a muffler end pipe 11b on the furthest
downstream side with respect to the flow direction of the exhaust
gas. The particulate collection system 10 includes a diesel
oxidation catalyst (DOC) 12, a diesel particulate filter (DPF) 13,
a particulate collection apparatus 20, a selective catalytic
reduction (SCR) unit 14, and an ammonia slip diesel oxidation
catalyst (NH.sub.3 DOC) 15 which are provided on the exhaust pipe
11 in this order from the upstream side with respect to the flow
direction of the exhaust gas. A fuel injection unit 17 may be
disposed on the exhaust pipe 11 to be located upstream of the DOC
12, and a urea water injection unit 18 is disposed upstream of the
SCR unit 14. A first temperature sensor 191 is disposed on the
particulate collection apparatus 20, and a second temperature
sensor 192 is disposed upstream of the particulate collection
apparatus 20. The first temperature sensor 191 may be disposed on
the upstream side or downstream side of the particulate collection
apparatus 20. The second temperature sensor 192 may be disposed at
any location where it can detect the temperature of the exhaust gas
introduced into the particulate collection apparatus 20, for
example, on the downstream side (outlet side) of the DPF 13.
Notably, the expression "on the exhaust pipe" in the present
embodiment encompasses both the case where a relevant unit or the
like is provided inside the exhaust pipe and in the case where a
relevant unit or the like is provided in the midway of the exhaust
pipe (a relevant unit or the like constitutes a portion of the
exhaust pipe).
[0037] The diesel oxidation catalyst 12 carries a noble metal such
as platinum (Pt), palladium (Pd), or the like as a catalyst. The
diesel oxidation catalyst 12 oxidizes carbon monoxide (CO) and
hydrocarbon (HC) which are unburned gas components contained in the
exhaust gas and convert them to carbon dioxide (CO.sub.2) and water
(H.sub.2O), and oxides nitrogen monoxide (NO) contained in the
exhaust gas and coverts it to nitrogen dioxide (NO.sub.2).
[0038] The diesel particulate filter 13 is a filter which collects
the particulates (PM) contained in the exhaust gas by a porous
ceramic or metallic member having fine pores or openings (holes).
Broadly speaking, the diesel particulate filter 13 is one mode of
the exhaust gas purification unit. However, in the present
invention, attention is paid to the PM collection function of the
diesel particulate filter 13, and the diesel particulate filter 13
is regarded as a first particulate collection filter. A metal
catalyst such as platinum or the like is applied to the surface of
the porous member. The diesel particulate filter 13 is naturally
regenerated as follows. In the presence of NOx produced by the
diesel oxidation catalyst 12, the particulate matter chemically
reacts with the catalyst in an atmosphere of 250 to 300.degree. C.
and is converted to carbon dioxide (CO.sub.2) and water (H.sub.2O),
whereby the diesel particulate filter 13 is regenerated. The diesel
particulate filter 13 can be regenerated by means of forced
regeneration as well. Specifically, fuel is supplied to the diesel
oxidation catalyst 12 directly through the fuel injection unit 17
or indirectly from the engine 510 in the exhaust stroke, and
hydrocarbon originating from the fuel is catalytically combusted so
as to increase the temperature of the exhaust gas to 450.degree. C.
or higher, whereby the collected particulate mater is oxidized.
Thus, the diesel particulate filter 13 is regenerated.
[0039] Notably, the DPF 13 may be a DPF of a type which physically
collects the particulate matter and oxidizes the particulate matter
by catalytic combustion of hydrocarbon or a plasma DPF which
includes a plasma generation unit for generating low-temperature
plasma to thereby generate active species (mainly O.sub.3) and
which supplies the generated active species to the PDF and converts
(oxidizes) the components of the particulate matter such as HC and
C to H.sub.2O and CO.sub.2. Since the plasma DPF can oxidize the
particulate matter without using fuel and does not collect the
particulate matter physically (by a physical shape), there has been
demanded to design the plasma generation unit such that it can
generate active species in an amount corresponding to the amount of
particulate matter to be processed in advance.
[0040] The selective catalytic reduction (SCR) unit 14 is an
apparatus which carries a zeolite-based catalyst or a
vanadium-based catalyst and selectively reduces NOx. In general,
the selective catalytic reduction unit 14 operates as follows. Urea
water is sprayed on the exhaust gas by the urea water injection
unit 18 at a location before the inlet of the selective catalytic
reduction unit 14. The selective catalytic reduction unit 14
produces ammonia (NH.sub.3) through thermal decomposition of the
urea water and hydrolysis reaction, and converts the NOx component
of the exhaust gas to nitrogen (N.sub.2) and water (H.sub.2O).
Accordingly, at the location before the inlet of the selective
catalytic reduction unit 14, the exhaust gas must have a proper
temperature (for example, 200.degree. C. or higher) in order to
obtain ammonia from the urea water.
[0041] The ammonia slip diesel oxidation catalyst 15 carries the
same catalyst as the diesel oxidation catalyst 12. The ammonia slip
diesel oxidation catalyst 15 oxidizes and decomposes ammonia not
used for the reaction at the selective catalytic reduction unit 14
to thereby produce nitrogen or NOx.
[0042] The particulate collection apparatus 20 used in the
particulate collection system 10 according to the first embodiment
will now be described in detail. FIG. 2 is an external perspective
view schematically showing the structure of the particulate
collection apparatus according to the first embodiment. FIG. 3 is a
schematic transverse cross-sectional view of the particulate
collection apparatus according to the first embodiment taken along
line 3-3 shown in FIG. 2.
[0043] The particulate collection apparatus 20 includes a casing
201 (housing), a first flow passage pipe 21, a second flow passage
pipe 22, a heat reservoir 30, a heating member 31, a heat
insulating material 23, and a flow passage changeover valve 25.
Notably, in the present embodiment, a particulate collection filter
which is high in heat storing and radiating performance is used and
is referred to as the heat reservoir 30. However, in the case where
a particulate collection filter which does not have heat storing
and radiating performance or is low in heat storing and radiating
performance is used, it may be simply referred to as a particulate
collection filter. The casing 201 is formed of stainless steel or
steel sheet with oxidation prevention treatment performed thereon.
The first flow passage pipe 21 defines a first flow passage 21a
through which the exhaust gas flows, and the second flow passage
pipe 22 defines a second flow passage 22a through which the exhaust
gas flows. The first flow passage pipe 21 and the second flow
passage pipe 22 are disposed in parallel to each other. The casing
201 has an introduction opening 20a for introducing the exhaust gas
into the inside of the casing 201 and a discharge opening 20b for
discharging the exhaust gas to the outside. The introduction
opening 20a communicates with the first flow passage pipe 21 and
the second flow passage pipe 22, and the discharge opening 20b
communicates with the first flow passage pipe 21 and the second
flow passage pipe 22. Although the first flow passage pipe 21 and
the second flow passage pipe 22 have the shape of a hollow
parallelepiped, they may have a cylindrical shape or any other
shape.
[0044] On one side of the casing 201 where the introduction opening
20a is provided, the flow passage changeover valve 25 is provided
so as to switch the flow passage pipe through which the exhaust gas
flows, between the first flow passage pipe 21 and the second flow
passage pipe 22. The flow passage changeover valve 25 may be a
changeover valve in which selective switching between the flow
passages is realized by swing motion of a plate-shaped valve body
about a shaft provided at one end of the valve body as shown in the
drawings, a changeover valve in which selective switching between
the flow passages is realized by rotation of a rotary valve body
about its axis, the rotary valve body having communication passages
formed therein, or a changeover valve in which selective switching
between the flow passages is realized by straight movement of a
plate-shaped valve body. Examples of an actuator for driving the
valve body include a motor such as a stepping motor, an
electromagnetic actuator, and an actuator using fluid such as air
or oil. Notably, as will be described later, there exist cases
where the switching between the flow passages is not required to be
selective; i.e., exclusive. In such a case, the flow passage
changeover valve 25 is required to introduce the exhaust gas,
introduced through the introduction opening 20a, to both of the
first and second flow passage pipes 21 and 22. The flow passage
changeover valve 25 may be provided for each of the flow passage
pipes 21 and 22. In this case, it is possible to close one flow
passage pipe and adjust the flow rate of the exhaust gas flowing
through the other flow passage pipe. Namely, the exhaust gas flow
rates at the two flow passage pipes can be controlled
independently.
[0045] The heat reservoir 30 is disposed inside the first flow
passage pipe 21 to partially occupy the interior of the flow
passage pipe 21. Although the heat reservoir 30 has a rectangular
parallelepipedic shape corresponding to the shape of the first flow
passage pipe 21, the heat reservoir 30 may have a circular columnar
shape or any other shape. The heat reservoir 30 may be any of a
ceramic member, a sintered body of metal powder, a metal honeycomb,
an expanded metal, and the like each of which has internal flow
passages through which the exhaust gas can flow. In the present
embodiment, the heat reservoir 30 also functions as a second
particulate collection filter for collecting the particulates (PM).
Therefore, the heat reservoir 30 has pores, perforations, openings,
protrusions, etc. which function as a particulate collection
portion for collecting particulates. Notably, the internal flow
passages may be intentionally formed flow passages (for example,
straight flow passages) or flow passages (for example, meandering
flow passages) formed by openings formed due to the property of the
material. Also, depending on the required heat capacity or PM
collection amount, the heat reservoir 30 may be disposed in the
first flow passage pipe 21 such that the heat reservoir 30 occupies
the entire internal space of the first flow passage pipe 21.
[0046] The heating member (heater) 31 is embedded in the heat
reservoir 30. In the example shown in FIGS. 2 and 3, since the
first flow passage pipe 21 has a rectangular parallelepipedic shape
and the heat reservoir 30 also has a parallelepipedic shape
corresponding thereto, the heating member 31 has a shape having a
rectangular spiral cross section. However, the heating member 31
may have a shape having a circular spiral cross section. Since the
heating member 31 is used to store heat in the heat reservoir 30 or
combust the particulates (PM) collected by the heat reservoir 30,
the heating member 31 may be partially or entirely embedded in the
heat reservoir 30, or may be disposed near or joined to a portion
or the entirety of the outer peripheral surface of the heat
reservoir 30. The heating member 31 may be a heating member which
is formed by stacking a plurality of flat or corrugated metal
plates, or flat and corrugated metal plates, in such a manner that
they are spaced from one another and in which the plates themselves
generate heat upon energization. In this case, it is desired that
holes be formed in the metal plates or irregularities be formed on
the metal plates in order to increase their heat generation surface
areas. A plurality of heating members each of which has a rod-like
shape and which are inserted into the internal flow passages of the
heat reservoir 30 to extend along the flow direction of the exhaust
gas may be used as the heating member 31. Notably, the heating
member in the present embodiment may be a resistance heating
element (heat generation member) whose periphery is not covered
with an insulating material and which itself generates heat when
electricity is supplied thereto. For example, the heating member
may be a wire-shaped heating member such as Nichrome wire, copper
wire, or tungsten wire. Alternatively, the heating member 31 may be
a plate-shaped bare metallic member formed of, for example,
stainless steel, cupper, or aluminum. Alternatively, the heating
member 31 may be formed of non-metallic material (e.g., silicon
carbide, carbon, etc.) which is small in heat capacity and does not
function well as a heat reservoir. Alternatively, the heating
member 31 may be a heating member which includes a resistance
heating element disposed within a casing and covered with powder of
an inorganic insulating material such as magnesia; i.e., the
heating member 31 may be a heating member generally called
"heater."
[0047] Notably, the heating member 31 may be used as a heat
reservoir without separately providing the heat reservoir 30. For
example, in the case where the heating member 31 has a form having
a spiral cross section as a result of stacking of plates or has a
rectangular three-dimensional shape as a result of stacking of
plates, since each metal plate can function as a sensible heat
storage member, the heating member 31 functions as a heat reservoir
30 having a predetermined heat capacity. In addition, as a result
of hole formation processing or irregularity formation processing
on each plate, the heating member 31 also functions as a
particulate collection filter. Therefore, the heating member 31 can
realize PM collection by the heat reservoir. The separating spaces
between the stacked plates can function as internal flow passages
and also function as a particulate collection portion.
[0048] Further, the heating member 31 is not required to be
embedded in the heat reservoir 30 and may be disposed at least on
the upstream side (the engine side) or the downstream side of the
heat reservoir 30 to be located near the heat reservoir 30. Namely,
no limitation is imposed on the position of the heating member 31
so long as the heating member 31 can heat the heat reservoir 30 and
causes the heat reservoir 30 to store heat.
[0049] The heat insulating material 23 is disposed or charged in
the space between the casing 201 and the first flow passage pipe 21
and the second flow passage pipe 22. For example, a sheet material
formed of ceramic, a cylindrical hard ceramic material, or a
foamable ceramic material is used as the heat insulating material
23. As a result of provision of the heat insulating material 23,
the amount of heat conducted to the metallic casing 201 can be
reduced, and the heat insulating efficiency of the particulate
collection apparatus 20 can be maintained at a desired level.
Notably, in order to further improve the heat insulation property,
the casing 201 may have a double wall structure in which a layer of
air is provided between the two walls.
[0050] The switching of the flow passage changeover valve 25 in
accordance with the operation state of the vehicle and the heating
of the heat reservoir 30 by the heating member 31; namely, the
operation of the particulate collection apparatus 20 according to
the first embodiment, will be described with reference to FIGS. 4
to 6. FIG. 4 is an explanatory view showing an operating state of
the particulate collection apparatus according to the first
embodiment at the time of steady operation. FIG. 5 is an
explanatory view showing an operating state of the particulate
collection apparatus according to the first embodiment at the time
of acceleration. FIG. 6 is an explanatory view showing an operating
state of the particulate collection apparatus according to the
first embodiment at the time of deceleration.
[0051] In the particulate collection system 10 according to the
first embodiment, the DPF 13 is disposed in a stage before the
particulate collection apparatus 20; i.e., on the introduction
opening 20a side thereof. A filter having a large hole (opening)
diameter may be used as the DPF 13. In this case, relatively large
particulates (PM) are collected by the filter, and smaller
particulates (PM) are collected by the heat reservoir 30 having a
smaller hole (opening) diameter. Alternatively, a plasma DPF may be
used as the DPF 13. In the case where a filter having a large hole
(opening) diameter or a plasma DPF is used as the DPF 13, the
amount of particulates (PM) generated at the time of acceleration
exceeds the amount of particulates (PM) which can be collected by
the DPF 13. Therefore, in the first embodiment, the PM collection
at the time of acceleration is assisted by the heat reservoir 30.
Notably, in the present specification, the phrase "load within a
predetermined range" means load in the case where the operation
state of the vehicle is a steady operation state, the phrase "load
above the predetermined range" means load in the case where the
operation state of the vehicle is an acceleration state, and the
phrase "load below the predetermined range" means load in the case
where the operation state of the vehicle is a deceleration
state.
[0052] In the case where the operation state of the vehicle is a
steady operation state, as shown in FIG. 4, the flow passage
changeover valve 25 is switched so as to close the first flow
passage pipe 21 and lead the exhaust gas from the engine 510 to the
second flow passage pipe 22; i.e., the second flow passage 22a.
Namely, the particulates (PM) are collected by the DPF 13. At the
time of steady operation, the amount of the generated particulates
(PM) is smaller than that at the time of acceleration, and the
generated particulates (PM) can be collected sufficiently by the
PDF 13 on the upstream side. Notably, the flow passage changeover
valve 25 may be switched to establish communication between the
introduction opening 20a and both of the first and second flow
passage pipes 21 and 22 to thereby lead the exhaust gas from the
engine 510 to the first and second flow passage pipes 21 and 22;
i.e., the first and second flow passages 21a and 22a. In this case,
it is possible to heat the heat reservoir 30, by exposing the heat
reservoir 30 to the exhaust gas introduced into the particulate
collection apparatus 20, to thereby cause the heat reservoir 30 to
store heat. The heat stored in the heat reservoir 30 allows the
heating member 31 to quickly burn the particulates (PM) at the time
of acceleration.
[0053] In the case where the operation state of the vehicle is an
acceleration, as shown in FIG. 5, the flow passage changeover valve
25 is switched to close the second flow passage pipe 22 and lead
the exhaust gas from the engine 510 to the first flow passage pipe
21; i.e., the first flow passage 21a. Namely, the particulates (PM)
are collected by the DPF 13 and the heat reservoir 30. At the time
of acceleration, the engine load increases, whereby the amounts of
emitted NOx and particulates (PM) increase and the flow rate of the
exhaust gas itself increases. Accordingly, all of the particulates
(PM) cannot be collected by the DPF 13 on the upstream side, and
uncollected particulates (PM) are collected by the heat reservoir
30. Notably, since the hole (opening) diameter of the heat
reservoir 30 is smaller than the filter hole (opening) diameter of
the DPF 13 as having been already described, particulates (PM)
which are small in diameter and have not been collected by the DPF
13 are collected by the heat reservoir 30.
[0054] In the case where the operation state of the vehicle is a
deceleration, as shown in FIG. 6, the flow passage changeover valve
25 is switched to close the first flow passage pipe 21 and lead the
exhaust gas from the engine 510 to the second flow passage pipe 22;
i.e., the second flow passage 22a. Namely, the heat reservoir 30 is
heated by the heating member 31. As will be described later, at the
time of deceleration, the vehicle according to the present
embodiment can collect the kinetic energy at the time of
deceleration as electrical energy through use of an alternator to
thereby obtain regenerative electric power. In view of this, at the
time of deceleration, the heating member 31 generates heat through
use of the regenerative electric power to thereby heat the heat
reservoir 30. It is desired that the heating member 31 generate an
amount of heat required to convert (oxidize) the collected
particulate maters. Since the heat reservoir 30 holds the
particulates (PM) collected at the time acceleration, as a result
of heat generation of the heating member 31, the collected
particulates (PM) are converted (oxidized) to H.sub.2O and
CO.sub.2. As a result, the heat reservoir 30 is generated and heat
is stored in the heat reservoir 30.
[0055] FIG. 7 is an explanatory view showing an exhaust gas
purification system including a conventional DPF. In the case of a
conventional DPF 13P shown in FIG. 7, small-diameter particulates
(PM) are required to be collected by the DPF 13P only, and its hole
(opening) diameter is small. Therefore, the DPF 13P easily reaches
the PM collection capacity due to the particulates (PM) generated
at the time of acceleration. Also, in the case where a plasma DPF
is employed, a plasma generation unit must be designed on the basis
of the amount of the particulates (PM) generated at the time of
acceleration. Therefore, the conventional DPF has a large size and
consumes a large amount of electric power.
[0056] FIG. 8 is a block diagram schematically showing the
electrical connections among electrical components in the vehicle
having the heat reservoir according to the first embodiment. The
vehicle 500 includes an alternator (generator) 40 which is driven
by the drive force of the engine 510. The engine 510 has an
engine-side pulley 511 for providing to the alternator 40 the drive
force (output) taken out from a crankshaft (not shown). The
alternator 40 has an alternator-side pulley 401 for receiving the
drive force provided from the engine 510. The engine-side pulley
511 and the alternator-side pulley 401 are mechanically connected
by a belt 512, whereby the drive force of the engine 510 is
transmitted to the alternator 40 through the belt 512.
[0057] The vehicle 500 includes the flow passage changeover valve
25, a vehicle accessory 41, the battery 42, a control unit 60, a
first relay 61, a second relay 62, the first temperature sensor
191, and the second temperature sensor 192. The flow passage
changeover valve 25, which has the above-described structure, is
connected to the control unit 60 through a control signal line. The
valve body of the flow passage changeover valve 25 is driven by its
actuator in accordance with the control signal from the control
unit 60, whereby the flow passage of the exhaust gas is switched to
the first flow passage pipe 21, to the second flow passage pipe 22,
or to the first and second flow passage pipes 21 and 22. The
control unit 60 functions as a control section for controlling
(performing and stopping) the collection of particulates (PM) at
the particulate collection apparatus 20.
[0058] The control unit 60 properly and selectively performs,
through switching, the collection of particulates (PM) by the DPF
13, the collection of particulates (PM) by the DPF 13 and the heat
reservoir 30, and the heating of the heat reservoir 30 by the
heating member 31. Notably, in the present specification, a
combination of the particulate correction apparatus 20 and the
control unit 60 will be referred to as the particulate collection
system 10, and the apparatus itself will be referred to as the
particulate correction apparatus 20. However, the term "particulate
collection system 10" and the term "particulate correction
apparatus 20" may be used in the same meaning.
[0059] The vehicle accessary 41 is an accessary which is used when
the vehicle travels and which is driven by (consumes) the electric
power output from the alternator 40 or the electric power stored in
the battery 42. Examples of the vehicle accessary 41 include head
lamps, an audio system, a navigation system, and an electric
heater.
[0060] The output terminal of the alternator 40 is electrically
connected to the heating member 31 through the first relay 61.
Also, the output terminal of the alternator 40 is electrically
connected to the vehicle accessary 41 through the second relay 62
and is electrically connected to the positive terminal (+) of the
battery 42 through an ammeter 64. Notably, a DC/DC converter for
voltage step up or voltage step down may be disposed in a wiring
path extending from the alternator 40 to the vehicle accessary 41
and the battery 42. The ground-side terminals of the alternator 40,
the vehicle accessary 41, and the heating member 31 are
electrically connected to the negative terminal (-) of the battery
42 through the body ground.
[0061] The first relay 61 is a switch which turns the heating
member 31 on and off; namely, allows and stops the supply of
electric power to the heating member 31. The second relay 62 is a
switch which allows and stops the supply of electric power
generated by the alternator 40 to the accessary 41 and the battery
42. The first and second relays 61 and 62 are connected to the
control unit 60 through control signal lines and are turned on
(closed) and turned off (opened) by the control signals from the
control unit 60. The ammeter 64 detects the output current of the
battery 42 and provides the detected output current to the control
unit 60 through a signal line. The first temperature sensor 191,
which is used to detect the temperature of the particulate
collection apparatus 20 (the heat reservoir 30), and the second
temperature sensor 192, which is used to detect the temperature of
the exhaust gas introduced into the particulate collection
apparatus 20, are both connected to the control unit 60 through
signal lines.
[0062] In the present embodiment, the electric power generated by
the alternator 40 can be supplied to the heating member 31
directly, namely, without storing the electric power in the battery
42, by turning the first relay 61 on and turning the second relay
62 off. For example, under the condition that the battery 42 is in
a prescribed fully charged state at the time of deceleration of the
vehicle and the electric power output from the alternator 40
becomes excessive power, it is possible to operate the alternator
40 so as to supply electric power to the heating member 31 for heat
generation. Accordingly, in the case where electric power is
charged into the battery 42, the output voltage of the alternator
40 is limited to 12 V or 24 V. However, in the case where electric
power is supplied directly to the heating member 31, electric power
can be supplied at a voltage of 12 V to 100 V. The thermal energy
generated by the heating member 31 is used to heat the heat
reservoir 30, whereby the conversion (oxidation) of the
particulates (PM) collected by the heat reservoir 30 is realized,
and heat is stored in the heat reservoir 30. As a result, it is
possible to convert the kinetic energy of the vehicle to electrical
energy and then to thermal energy, without wasting the kinetic
energy, to thereby execute the process of regenerating the heat
reservoir 30 by oxidizing the particulates (PM) collected by the
heat reservoir 30. Also, the heat stored in the heat reservoir 30
is used to increase the temperature of the exhaust gas in
accordance with the operation state of the vehicle.
[0063] Operation control for the particulate collection apparatus
20 in the first embodiment will be described with reference to FIG.
9. FIG. 9 is a flowchart showing a processing routine for
controlling the operation of the particulate collection apparatus
in the first embodiment. The present processing routine is executed
by the control unit 60. Notably, the control unit 60 includes at
least a central processing unit (CPU), memories, and an
input/output interface for exchanging control signals and detection
signals with external devices. The CPU, the memories, and the
input/output interface are not shown in the drawings.
[0064] The control unit 60 starts the present processing routine
when the vehicle is started, and detects the operation state of the
vehicle using various sensors provided on the vehicle. For example,
the control unit 60 can judge the operation state of the vehicle
(i.e., an acceleration state, a deceleration state, or a steady
operation state) on the basis of an input signal input from an
accelerator pedal opening sensor and an input signal input from the
temperature sensor 192 disposed on the upstream side of the
particulate collection apparatus 20.
[0065] The control unit 60 judges whether or not the operation
state of the vehicle is a deceleration state (step S100). In the
case where the control unit 60 judges that the operation state of
the vehicle is a deceleration state (step S100: Yes), the control
unit 60 sends a control signal to the flow passage changeover valve
25 so as to close the first flow passage pipe 21 (the first flow
passage 21a) (step S102) and establish communication between the
introduction opening 20a and the second flow passage pipe 22 (the
second flow passage 22a) to thereby lead the exhaust gas to the
second flow passage 22a as shown in FIG. 6. Namely, the control
unit 60 prevents the heat reservoir 30 from being exposed to the
flow of the exhaust gas to thereby efficiently execute the process
of regenerating the heat reservoir 30 by oxidizing the particulates
(PM) collected by the heat reservoir 30, through use of the heating
member 31 which will be described later. In the case where the
input signal from the accelerator pedal opening sensor indicates
that the accelerator pedal is not operated (the opening (the amount
of operation of the pedal) is zero), the control unit 60 judges
that the operation state of the vehicle is a deceleration state
(coasting state). The control unit 60 turns off the second relay 62
(step S104), turns on the first relay 61 (step S106), and returns
to the detection of the operation state. As a result of switching
of the second relay 62 to the off position, the connection between
the battery 42 and the alternator 40 is broken. Meanwhile, as a
result of the first relay 61 being turned on, the regenerative
electric power generated by the alternator 40 as a result of
deceleration is supplied to the heating member 31, whereby the
heating member 31 generates heat and the heat reservoir 30 is
heated. The particulates (PM) collected by the heat reservoir 30
are converted (oxidized) to H.sub.2O and CO.sub.2 as a result of
heating by the heating member 31. As a result, the heat reservoir
30 is regenerated, and heat is stored in the heat reservoir 30.
[0066] Notably, the control unit 60 may judge whether or not the
second relay 62 is in the on position before sending an off signal
(opening signal) to the second relay 62 and send the off signal to
the second relay 62 only when the second relay 62 is in the on
position, or the control unit 60 may send the off signal to the
second relay 62 irrespective of the present position of the second
relay 62. This procedure is the same in the valve position
switching control for the flow passage changeover valve 25 and in
the on-off control for the first relay 61.
[0067] In the case where the control unit 60 judges that the
operation state of the vehicle is not a deceleration state (step
S100: No), the control unit 60 judges whether or not the operation
state of the vehicle is an acceleration state (step S108). In the
case where the control unit 60 judges that the operation state of
the vehicle is an acceleration state (step S108: Yes), the control
unit 60 sends a control signal to the flow passage changeover valve
25 so as to close the second flow passage pipe 22 (the second flow
passage 22a) (step S110) and establish communication between the
introduction opening 20a and the first flow passage pipe 21 (the
first flow passage 21a) to thereby lead the exhaust gas to the
first flow passage 21a as shown in FIG. 5. The control unit 60
judges that the operation state of the vehicle is an acceleration
state, for example, when the opening of the accelerator pedal is
equal to or greater than a predetermined angle and a change in
vehicle speed per unit time is equal to or greater than a
predetermined value. The control unit 60 turns off the first and
second relays 61 and 62 (step S112) and returns to the detection of
the operation state. As a result of switching of the first and
second relays 61 and 62 to the off position, the heating member 31
is turned off (disconnected from the electric power circuit), and
the connection between the battery 42 and the alternator 40 is
broken. Notably, at least the second relay 62 is not required to be
turned off. Also, a control of stopping the power generation by the
alternator 40 at the time of acceleration may be performed. Since
at the time of acceleration the flow rate of the exhaust gas
increases and the amounts of PM and NOx also increase, the heat
reservoir 30 is exposed to the exhaust gas so as to collect the
particulates (PM) by the heat reservoir 30. Also, by the thermal
energy stored in the heat reservoir 30 or the heat generated by the
heating member 31 or a different heating member provided at the
discharge opening 20b through use of the electric power from the
battery 42, the exhaust gas is heated so as to raise the
temperature of the exhaust gas discharged from the particulate
collection apparatus 20 to a desired temperature. Notably, the
desired temperature is, for example, a temperature within a
temperature range within which the SCR unit 14 can operate properly
and convert NOx to nitrogen (N.sub.2) and water (H.sub.2O).
[0068] In the case where the control unit 60 judges that the
operation state of the vehicle is not an acceleration state (step
S118: No), the control unit 60 judges that the operation state of
the vehicle is a steady state and sends a control signal to the
flow passage changeover valve 25 so as to close the first flow
passage pipe 21 (the first flow passage 21a) (step S118) and
establish communication between the introduction opening 20a and
the second flow passage pipe (the second flow passage 22a) to
thereby lead the exhaust gas to the second flow passage 22a as
shown in FIG. 4. In the present specification, the steady state
means that the operation state of the vehicle is neither a
deceleration state nor an acceleration state. Notably, the steady
state may be defined to exclude a cold start state and a low load
state in which the load of the engine 510 is low (for example, the
case where the opening of the accelerator pedal is less than a
predetermined opening and the vehicle speed is approximately
constant). The control unit 60 turns off the first relay 61 (step
S120) and returns to the detection of the operation state. As a
result of switching of the first relay 61 to the off position, the
heating member 31 is turned off (disconnected from the electric
power circuit). The second relay 62 may be turned on or off
depending on the charging state of the battery 42. In the steady
state, the flow rate of the exhaust gas is smaller than that at the
time of acceleration, and the particulates (PM) can be collected
sufficiently by the DPF 13.
[0069] According to the above-described particulate collection
system 10 according to the first embodiment, the particulates (PM)
the amount of which increases at the time of acceleration can be
collected by the heat reservoir 30, which serves as a second
particulate collection filter. Therefore, it is possible to reduce
the amount of the particulates (PM) collected by the DPF 13, which
serves as a first particulate collection filter, to thereby
decrease the number of times of regeneration which is performed at
the DPF 13 and which consumes fuel independently of travel. As a
result, the fuel efficiency of the vehicle can be improved.
[0070] In the case where a plasma DPF is used as the DPF 13, since
the amount of particulates (PM) to be collected by the DPF 13 is
decreased, the size of the plasma generation unit can be reduced
even when the plasma generation unit is designed in consideration
of collection of the particulates (PM) which increase in amount at
the time of acceleration. Also, since the amount of electric power
required for plasma generation can be reduced, the energy required
for the DPF processing can be reduced.
[0071] Further, regenerative electric power obtained during
deceleration of the vehicle is used as electric power which is
supplied to the heating member 31 when the processing of converting
the particulates (PM) collected by the heat reservoir 30; i.e., the
process of regenerating the heat reservoir 30, is performed.
Therefore, it is unnecessary to additionally operate the internal
combustion engine 510 (consume fuel) so as to obtain electric power
for causing the heating member 31 to generate heat for regeneration
of the heat reservoir 30. As a result, extra energy which does not
relate to travel is not needed. Also, the heat reservoir 30
functions as a particulate collection filter. Therefore, in the
case where heat has been stored in the heat reservoir 30 by exhaust
gas which is discharged at the time of acceleration and is
relatively high in temperature, the heat reservoir 30 can be heated
to a required temperature within a shorter period of time as
compared with the case where only an electrical heating member is
used. Therefore, the time required for the regeneration processing
can be shortened, and the electric power required for the
regeneration processing for the heat reservoir 30 can be
reduced.
[0072] As described above, the particulate collection system 10
according to the first embodiment includes the DPF 13 serving as
the first particulate collection filter and the heat reservoir 30
serving as the second particulate collection filter. Therefore, the
particulate collection system 10 can purify the exhaust gas
efficiently. As a result, the particulate collection system 10 can
purify the exhaust gas to a desired purification level without
lowing the overall energy efficiency of the vehicle.
B. Second Embodiment
[0073] A particulate collection apparatus 20 in a particulate
collection system 10A according to a second embodiment will be
described with reference to FIGS. 10 to 12. FIG. 10 is an
explanatory view showing an operating state of the particulate
collection apparatus according to the second embodiment in a steady
state. FIG. 11 is an explanatory view showing an operating state of
the particulate collection apparatus according to the second
embodiment at the time of acceleration. FIG. 12 is an explanatory
view showing an operating state of the particulate collection
apparatus according to the second embodiment at the time of
deceleration.
[0074] The particulate collection system 10A according to the
second embodiment differs from the first particulate collection
system 10 in the point that the DPF 13 is provided on the
downstream side of (in a stage following) the particulate
collection apparatus 20; namely, on the discharge opening 20b side
thereof. In the second embodiment, the DPF 13 has a hole (opening)
diameter equal to or smaller than that of the heat reservoir 30.
Also, a plasma DPF may be used as the DPF 13. In the second
embodiment, the heat reservoir 30 (the particulate collection
apparatus 20) which can collect particulates (PM) is provided in a
stage before the DPF 13. Therefore, even at the time of
acceleration, the amount of particulates (PM) to be collected by
the DPF 13 is not large. Therefore, the amount of particulates (PM)
to be collected at the time of acceleration is not required to be
taken into consideration when the DPF 13 is designed.
[0075] In the case where the vehicle is in a steady state shown in
FIG. 10, the flow passage changeover valve 25 is switched so as to
close the first flow passage pipe 21 and lead the exhaust gas from
the engine 510 to the second flow passage 22a. Namely, the
particulates (PM) are collected by the DPF 13. At the time of
steady operation, the amount of the generated particulates (PM) is
smaller than that at the time of acceleration, and the generated
particulates (PM) can be collected sufficiently by the DPF 13 on
the downstream side. Notably, at the time of steady operation, the
flow passage changeover valve 25 may be switched to establish
communication between the introduction opening 20a and the first
and second flow passage pipes 21 and 22 to thereby lead the exhaust
gas from the engine 510 to the first and second flow passages 21a
and 22a.
[0076] In the case where the vehicle is in an acceleration state
shown in FIG. 11, the flow passage changeover valve 25 is switched
so as to close the second flow passage pipe 22 and lead the exhaust
gas from the engine 510 to the first flow passage pipe 21; i.e.,
the first flow passage 21a. Namely, the particulates (PM) are
collected by the DPF 13 and the heat reservoir 30. At the time of
acceleration, the engine load increases, whereby the amounts of
emitted NOx and particulates (PM) increase, and the flow rate of
the exhaust gas itself increases. Accordingly, the heat reservoir
30 collects an amount of particulates (PM) corresponding to the
amount of particulates (PM) which will not be collected by the DPF
13 on the downstream side. Notably, since the filter hole (opening)
diameter of the DPF 13 is equal to or smaller than the hole
(opening) diameter of the heat reservoir 30 as having been
described already, the particulates (PM) which were not collected
by the heat reservoir 30 are collected by the DPF 13.
[0077] In the case where the vehicle is in a deceleration state
shown in FIG. 12, the flow passage changeover valve 25 is switched
so as to close the first flow passage pipe 21 and lead the exhaust
gas from the engine 510 to the second flow passage 22a. Namely, the
heat reservoir 30 is heated by the heating member 31. At the time
of deceleration, the heating member 31 generates heat using the
regenerative electric power obtained as a result of deceleration
and heat the heat reservoir 30. The particulates (PM) collected by
the heat reservoir 30 during acceleration are converted (oxidized)
to H.sub.2O and CO.sub.2 by the heat generated by the heating
member 31. As a result, the heat reservoir 30 is regenerated and
heat is stored in the heat reservoir 30.
[0078] The above-described particulate collection system 10A
according to the second embodiment has the following advantage in
addition to the advantage of the first embodiment because the
particulate collection apparatus 20 is disposed in a stage before
the DPF 13. Specifically, it is possibly to additionally apply the
particulate collection apparatus 20 to a conventional DPF to
thereby decrease the number of times of regeneration of the DPF.
Namely, exhaust gas is supplied directly to the heat reservoir 30,
which serves as the second particulate collection filter, without
through the DPF 13. Therefore, it is possible to collect
particulates (PM) at the heat reservoir 30 without adjusting the
hole (opening) diameter of the DPF 13.
[0079] Also, in the particulate collection system 10A according to
the second embodiment, the particulate collection apparatus 20 is
disposed in a stage before the DPF 13. Therefore, the temperature
of the exhaust gas introduced into the DPF 13 can be maintained at
a high temperature, and it is expected that spontaneous
regeneration is performed periodically without performance of
forced regeneration involving fuel injection. As a result, no fuel
is consumed for the regeneration process, whereby the fuel
efficiency of the vehicle can be improved.
C. Modifications:
[0080] (1) Although the particulate collection apparatus 20
according to the first embodiment shown in FIGS. 2 and 3 has the
first flow passage pipe 21 and the second flow passage pipe 22
which are arranged in parallel in the horizontal direction, the
particulate collection apparatus 20 may have a first flow passage
pipe 21 and a second flow passage pipe 22 which are arranged in
parallel in the vertical direction as shown in FIG. 13. FIG. 13 is
an explanatory view showing a modification of the particulate
collection apparatus according to the first embodiment. For
example, in the case where a mounting space extending in the
horizontal direction does not exist and a mounting space extending
in the vertical direction can be found, the particulate collection
apparatus 20 according to the first embodiment can be mounted on
the vehicle (in the mounting space extending in the vertical
direction).
[0081] (2) In the above-described embodiments, the temperature of
the heat reservoir 30 and the temperature of the exhaust gas are
obtained by the first temperature sensor 191 provided on the heat
reservoir 30 and the second temperature sensor 192 provided
upstream of the heat reservoir 30. However, these temperatures may
be equally obtained on the basis of the time elapsed after the
startup of the engine 510 or on the basis of the record of
energization of the heating member 31.
[0082] (3) Since the particulate collection apparatus 20 according
to the above-described embodiments is provided upstream of the SCR
unit 14, exhaust gas having a temperature suitable for NOx
purification can be steadily supplied to the SCR unit 14. As a
result, at the SCR unit 14, NOx purification can be performed under
a condition under which NOx purification cannot be conventionally
performed due to a decrease in the temperature of the exhaust gas,
whereby the amount of NOx emitted to the atmosphere can be reduced
further. Also, the processing of raising the exhaust gas
temperature by fuel combustion, which has been conventionally
performed at the DOC 12 or the DPF 13 in order to raise the exhaust
gas temperature, becomes unnecessary, whereby the amount of fuel
consumed independently of travel can be reduced.
[0083] (4) The term "purification unit" used in the present
specification encompasses not only a so-called
chemical-reaction-type purification catalyst which converts a
particular component (substance) contained in exhaust gas to a
harmless component (substance) using a catalyst, but also a
filter-type purification unit which traps the particular component
contained in exhaust gas. Even a filter-type purification unit may
have a proper temperature range for properly performing its
regeneration operation. Since the particulate collection apparatus
20 according to the above-described embodiments can maintain the
temperature of the exhaust gas introduced into the filter-type
purification unit to fall within the proper temperature range, the
filter-type purification unit can exhibit expected performance
under a wide range of conditions irrespective of the operation
state of the engine 510. Accordingly, the particulate collection
apparatus 20 according to the above-described embodiments may be
disposed upstream of any purification unit so long as the
purification unit exhibits expected performance as a result of
introduction of exhaust gas within a predetermined temperature
range, and as a result of being disposed upstream of such a
purification unit, the particulate collection apparatus 20 allows
the purification unit to exhibit its performance under a wide range
of conditions.
[0084] (5) In the above-described embodiments, a single heat
reservoir 30 is used. However, the heat reservoir 30 may be
composed of a plurality of independent heat reservoirs. In this
case, it is expected that the temperature distribution of exhaust
gas within the heat reservoir 30 becomes uniform as a result of
dispersion and mixing of exhaust gas temperatures among the heat
reservoirs 30. Also, in the above-described embodiments, the
particulate collection apparatus 20 uses the heat reservoir 30 as
the second particulate collection filter. However, a particulate
collection filter of a certain structure and/or a certain material
which does not have heat storage/radiation performance or is low in
the heat storage/radiation performance and which is generally not
used as a heat reservoir may be used in place of the heat reservoir
30.
[0085] (6) In the above-described embodiments, the particulate
collection apparatus 20 has the shape of a rectangular box.
However, the particulate collection apparatus 20 may have a
redundant shape which has a plurality of folds between the
introduction opening 20a and the discharge opening 20b, or may have
a cylindrical shape. Also, in the above-described embodiments, the
particulate collection apparatus 20 extends straight. However, the
particulate collection apparatus 20 may be applied to a
purification system in which a portion of the structure or pipe is
disposed to extend in a direction intersecting with the remaining
portion of the structure or pipe and which is formed into a folded
shape. For example, the particulate collection apparatus 20 may be
applied to a purification system which has a folded shape and which
includes a parallel portion which becomes parallel to the ground
surface when the system is mounted on a vehicle and an intersecting
portion which intersects with the parallel portion, whereby the
length in the flow direction of exhaust gas is shortened. Notably,
the purification system may be a purification system in which the
intersecting portion is a vertical portion perpendicular to the
ground surface and which has a larger size in the vertical
direction. In this case, the particulate collection apparatus 20
may be disposed in the parallel portion or the intersecting
portion.
[0086] (7) In the above-described embodiments, as shown in FIG. 12,
a second heating member 35 may be provided at the discharge opening
20b of the particulate collection apparatus 20. In the first
embodiment, the temperature of the SCR unit 14 provided in the
stage after the particulate collection apparatus 20 can be raised
to and maintained at a proper operating temperature by raising the
temperature of the discharged exhaust gas by the second heating
member. In the second embodiment, it becomes possible to supply
exhaust gas of higher temperature to the DPF 13, and further, it is
expected that spontaneous regeneration is performed periodically
without performance of forced regeneration involving fuel
injection.
[0087] (8) In the above-described embodiments, descriptions have
been given by taking the diesel engine 510 as an example. However,
the particulate collection apparatus 20 according to the
above-described embodiments may be disposed in an exhaust gas
passage of a gasoline engine and constitute an exhaust gas
purification system for the gasoline engine. A
direct-injection-type gasoline engine which injects fuel directly
into each combustion chamber may generate particulates (PM). Such
particulates (PM) can be removed by disposing the particulate
collection apparatus 20 in a stage before a three-way catalyst.
Also, quick warming up of the three-way catalyst can be realized by
heating exhaust gas through use of heat stored in the heat
reservoir 30. Accordingly, in the case where the particulate
collection apparatus 20 according to the above-described
embodiments is applied, the quick warming up can be realized
irrespective of the position of the three-way catalyst, and the
degree of freedom of vehicle design can be increased.
[0088] Although the present invention has been described on the
basis of embodiments and modifications thereof, the above-described
embodiments of the invention are provided so as to facilitate
understanding of the present invention and do not limit the present
invention. The present invention can be modified or improved
without departing from the spirit of the invention and the scopes
of the claims, and the present invention encompasses equivalents
thereof. For example, in order to solve, partially or entirely, the
above-mentioned problem or yield, partially or entirely, the
above-mentioned effects, technical features of the embodiments and
modifications corresponding to technical features of the modes
described in the section "Summary of the Invention" can be replaced
or combined as appropriate. Also, the technical feature(s) may be
eliminated as appropriate unless the present specification mentions
that the technical feature(s) is essential.
DESCRIPTION OF REFERENCE NUMERALS
[0089] 10: particulate collection system [0090] 10A: particulate
collection system [0091] 11: exhaust pipe [0092] 11a: manifold
[0093] 11b: muffler end pipe [0094] 12: diesel oxidation catalyst
[0095] 13: diesel particulate filter [0096] 14: selective catalytic
reduction unit [0097] 15: diesel oxidation catalyst [0098] 17: fuel
injection unit [0099] 18: urea water injection unit [0100] 191:
first temperature sensor [0101] 192: second temperature sensor
[0102] 20: particulate collection apparatus [0103] 20a:
introduction opening [0104] 20b: discharge opening [0105] 201:
casing [0106] 21: first flow passage pipe [0107] 21a: first flow
passage [0108] 22: second flow passage pipe [0109] 22a: second flow
passage [0110] 23: heat insulating material [0111] 25: flow passage
changeover valve [0112] 30: heat reservoir [0113] 31: heating
member [0114] 35: second heating member [0115] 40: alternator
[0116] 401: alternator-side pulley [0117] 41: accessary [0118] 42:
battery [0119] 500: vehicle [0120] 510: diesel engine [0121] 511:
engine-side pulley [0122] 512: belt [0123] 520: wheel [0124] 60:
control unit [0125] 61: first relay [0126] 62: second relay [0127]
64: ammeter
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