U.S. patent application number 15/940294 was filed with the patent office on 2018-10-11 for catalyst apparatus for internal combustion engine.
This patent application is currently assigned to NGK Spark Plug Co., LTD.. The applicant listed for this patent is NGK Spark Plug Co., LTD.. Invention is credited to Yuki SAITO, Takaaki YAMADA, Takaya YOSHIKAWA.
Application Number | 20180291785 15/940294 |
Document ID | / |
Family ID | 63525516 |
Filed Date | 2018-10-11 |
United States Patent
Application |
20180291785 |
Kind Code |
A1 |
YOSHIKAWA; Takaya ; et
al. |
October 11, 2018 |
CATALYST APPARATUS FOR INTERNAL COMBUSTION ENGINE
Abstract
A catalyst apparatus is disposed in an exhaust passage for
exhaust gas discharged from an internal combustion engine and
includes a catalyst section for purifying the exhaust gas, and a
heater section disposed upstream of the catalyst section in the
exhaust passage and adapted to heat the exhaust gas. The pressure
loss of the catalyst section in the flow velocity direction of the
exhaust passage is smaller than the pressure loss of the catalyst
section in a direction orthogonal to the flow velocity direction,
and the heat capacity of the catalyst section is larger than the
heat capacity of the heater section.
Inventors: |
YOSHIKAWA; Takaya; (Kasugai,
JP) ; YAMADA; Takaaki; (Iwakura, JP) ; SAITO;
Yuki; (Inuyama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NGK Spark Plug Co., LTD. |
Nagoya |
|
JP |
|
|
Assignee: |
NGK Spark Plug Co., LTD.
Nagoya
JP
|
Family ID: |
63525516 |
Appl. No.: |
15/940294 |
Filed: |
March 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/12 20130101;
F01N 3/2026 20130101; F01N 3/28 20130101; F01N 2900/1411 20130101;
F01N 2900/1406 20130101; F01N 3/281 20130101; F01N 3/2013
20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 3/28 20060101 F01N003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2017 |
JP |
2017-070680 |
Feb 26, 2018 |
JP |
2018-031571 |
Claims
1. A catalyst apparatus for an internal combustion engine which is
disposed in an exhaust passage for exhaust gas discharged from an
internal combustion engine, comprising: a catalyst section that is
configured to purify the exhaust gas; and a heater section disposed
upstream of the catalyst section and adapted to heat the exhaust
gas, wherein a pressure loss of the catalyst section in a flow
velocity direction of the exhaust passage is smaller than a
pressure loss of the catalyst section in a direction orthogonal to
the flow velocity direction, and a heat capacity of the catalyst
section is larger than a heat capacity of the heater section.
2. The catalyst apparatus for the internal combustion engine
according to claim 1, further comprising a control section which is
configured to use regenerated energy of a vehicle including the
internal combustion engine as electric power for energizing the
heater section.
3. The catalyst apparatus for the internal combustion engine
according to claim 1, wherein the heater section and the catalyst
section are adjacently disposed in a common casing.
4. The catalyst apparatus for the internal combustion engine
according to claim 1, further comprising a retainer that is
disposed to contact an upstream side of the heater section, wherein
the heater section is in contact with the catalyst section, the
retainer has an insulating property and allows passage of the
exhaust gas therethrough, and the heater section is sandwiched
between the retainer and the catalyst section.
5. The catalyst apparatus for the internal combustion engine
according to claim 1, wherein the catalyst section includes at
least a reduction catalyst.
6. The catalyst apparatus for the internal combustion engine
according to claim 2, wherein the heater section and the catalyst
section are adjacently disposed in a common casing.
7. The catalyst apparatus for the internal combustion engine
according to claim 2, further comprising a retainer that is
disposed to contact an upstream side of the heater section, wherein
the heater section is in contact with the catalyst section, the
retainer has an insulating property and allows passage of the
exhaust gas therethrough, and the heater section is sandwiched
between the retainer and the catalyst section.
8. The catalyst apparatus for the internal combustion engine
according to claim 3, further comprising a retainer that is
disposed to contact an upstream side of the heater section, wherein
the heater section is in contact with the catalyst section, the
retainer has an insulating property and allows passage of the
exhaust gas therethrough, and the heater section is sandwiched
between the retainer and the catalyst section.
9. The catalyst apparatus for the internal combustion engine
according to claim 2, wherein the catalyst section includes at
least a reduction catalyst.
10. The catalyst apparatus for the internal combustion engine
according to claim 3, wherein the catalyst section includes at
least a reduction catalyst.
11. The catalyst apparatus for the internal combustion engine
according to claim 4, wherein the catalyst section includes at
least a reduction catalyst.
Description
[0001] This application claims the benefit of Japanese Patent
Applications No. JP 2017-070680 filed Mar. 31, 2017 and No.
2018-031571, filed Feb. 26, 2018, which are incorporated herein by
reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to a catalyst apparatus for an
internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] A conventionally known catalytic converter is disposed in an
exhaust passage of an internal combustion engine and adapted to
clean HC, CO, NOx, etc. in exhaust gas (see Japanese Unexamined
Publication No. H05-184938). This catalytic converter is configured
to cause only a central portion of a honeycomb catalytic carrier
formed of metal to generate heat, and the heat capacity of the
central portion is smaller than that of an outer circumferential
side thereof. Thus, upon energization, the central portion generate
heat quickly, whereby exhaust gas at low temperature can be heated
in an early stage, and catalytic reaction can be promoted.
Problem to be Solved by the Invention
[0004] Incidentally, the honeycomb carrier is configured such that
the pressure loss in the flow velocity direction (axial direction)
of the exhaust passage is smaller than that in the radial
direction. As will be described later, the actual evidence provided
by the present inventors reveals that heat conduction in the radial
direction is considerably low. Namely, when the central portion of
the catalytic carrier is heated as in the technique described in
Japanese Unexamined Publication No. H05-184938, the heat is not
transferred sufficiently to the outer circumferential side thereof.
Therefore, activation of a catalyst at low temperature is
difficult.
[0005] Thus, an object of the present invention is to provide a
catalyst apparatus for an internal combustion engine which can
activate a catalyst in an early stage when the temperature of
exhaust gas is low.
SUMMARY OF THE INVENTION
Means for Solving the Problem
[0006] In order to solve the above problem, a catalyst apparatus
for an internal combustion engine of the present invention is a
catalyst apparatus which is disposed in an exhaust passage for
exhaust gas discharged from an internal combustion engine,
comprising a catalyst section that is configured to purify the
exhaust gas and a heater section disposed upstream of the catalyst
section in the exhaust passage and adapted to heat the exhaust gas,
wherein a pressure loss of the catalyst section in a flow velocity
direction of the exhaust passage is smaller than a pressure loss of
the catalyst section in a direction orthogonal to the flow velocity
direction, and a heat capacity of the catalyst section is larger
than a heat capacity of the heater section.
[0007] According to the present catalyst apparatus for the internal
combustion engine, the heat capacity of the catalyst section is
larger than the heat capacity of the heater section. Therefore, the
heater section can generate heat quickly so as to heat exhaust gas
at low temperature more early, thereby reliably promoting a
catalytic reaction at the catalyst section.
[0008] Since the pressure loss of the catalyst section in the flow
velocity direction of the exhaust passage is smaller than the
pressure loss of the catalyst section in the direction orthogonal
to the flow velocity direction, heat is not transferred
sufficiently in the radial direction of the catalyst section. In
view of this, the heater section is disposed on the upstream side
of the catalyst section. In this case, since exhaust gas heated by
the heater section flows through the entire catalyst section within
the exhaust passage, it is possible to reliably heat the catalyst
section, to thereby promote the catalytic reaction.
[0009] Also, since the heat capacity of the catalyst section is
large, the catalyst section having become warm as a result of heat
generation by the heater section cools slowly even after
interruption of the energization of the heater section. Thus, the
time during which the energization of the heater section is
interrupted can be extended accordingly, whereby electric power can
be saved.
[0010] The catalyst apparatus for the internal combustion engine of
the present invention may further comprises a control section which
is configured to use regenerated energy of a vehicle including the
internal combustion engine as electric power for energizing the
heater section.
[0011] According to the present catalyst apparatus for the internal
combustion engine, regenerated energy is utilized for energization
of the heater section, whereby electric power is saved.
[0012] In the catalyst apparatus for the internal combustion engine
of the present invention, the heater section and the catalyst
section may be adjacently disposed in a common casing.
[0013] According to the present catalyst apparatus for the internal
combustion engine, it is possible to dispose the heater section and
the catalyst section in a common casing while saving the space for
installation and decreasing heat loss.
[0014] The catalyst apparatus for the internal combustion engine of
the present invention may further comprise a retainer that is
disposed to contact an upstream side of the heater section. In the
catalyst apparatus, the heater section may be in contact with the
catalyst section, the retainer has an insulating property and
allows passage of the exhaust gas therethrough, and the heater
section may be sandwiched between the retainer and the catalyst
section.
[0015] According to the present catalyst apparatus for the internal
combustion engine, these members can be reliably fixed within the
exhaust passage.
[0016] In the catalyst apparatus for the internal combustion engine
of the present invention, the catalyst section may include at least
a reduction catalyst.
[0017] The reduction catalyst is small in amount of heat generation
as compared with an oxidation catalyst. Therefore, the present
invention is particularly effective. Examples of the reduction
catalyst include an SCR (reduction), a three-way catalyst
(reduction/oxidation), and ab NOx storage and reduction catalyst
(storage/reduction).
Effect of the Invention
[0018] According to the present invention, a catalyst apparatus for
an internal combustion engine which can activate a catalyst in an
early stage when the temperature of exhaust gas is low can be
obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other features and advantages of the present
invention will become more readily appreciated when considered in
connection with the following detailed description and appended
drawings, wherein like designations denote like elements in the
various views, and wherein:
[0020] FIG. 1 is a schematic view showing the configuration of a
catalyst apparatus for an internal combustion engine according to
an embodiment of the present invention.
[0021] FIG. 2 is schematic view showing the structure of a catalyst
section.
[0022] FIG. 3 is a plan view showing the structure of a heater
section.
[0023] FIG. 4 is a perspective view showing the structure of a
metal thin plate of the heater section.
[0024] FIG. 5 is a schematic view showing a state in which the
heater section is sandwiched between a retainer and the catalyst
section.
[0025] FIG. 6 is schematic view showing a measurement portion of
the heater section used for measurement of heat capacity.
[0026] FIG. 7 is a view showing conditions under which the
temperature distribution of a catalyst section having a reduced
pressure loss in a flow velocity direction is simulated.
[0027] FIG. 8 is an illustration showing results of the simulation
of FIG. 7.
DETAILED DESCRIPTION OF THE INVENTION
[0028] An embodiment of the present invention will next be
described with reference to the drawings.
[0029] FIG. 1 is a schematic view showing the configuration of a
catalyst apparatus 10 for an internal combustion engine according
to an embodiment of the present invention, FIG. 2 is a schematic
view showing the structure of a catalyst section 6, FIG. 3 is a
plan view showing the structure of a heater section 4, and FIG. 5
is a schematic view showing a state in which the heater section 4
is sandwiched between a retainer 2 and the catalyst section 6.
[0030] As shown in FIG. 1, a vehicle 100 is a diesel vehicle
including an internal combustion engine (e.g., a diesel engine) 102
and a motor 104. The internal combustion engine 102 and the motor
104 drive tires 106.
[0031] The catalyst apparatus 10 is disposed in an exhaust passage
108 for exhaust gas discharged from the internal combustion engine
102. The catalyst apparatus 10 has a canning structure in which the
catalyst section 6, the heater section 4 disposed upstream of the
catalyst section 6, and the retainer 2 disposed upstream of the
heater section 4 are press-fitted in a casing 8. The catalyst
apparatus 10 has a control section 9 (microcomputer) for
controlling energization of the heater section 4, and the control
section 9 is connected to a vehicle-side ECU 110.
[0032] The catalyst section 6 purifies exhaust gas and has an SCR
catalyst shown in FIG. 2 in the present embodiment. The SCR
catalyst 6a is formed of a cylindrical ceramic porous member having
a large number of holes 6h extending in a flow velocity direction
(axial direction) F. A catalyst such as vanadium is carried by this
ceramic carrier. Also, the catalyst section 6 also has a urea water
injector 6b and a DPF (Diesel Particulate Filter) 6c disposed
upstream of the SCR catalyst 6a as shown in FIG. 5.
[0033] The pressure loss of the SCR catalyst 6a in the flow
velocity direction F is smaller than the pressure loss in the
radial direction, which is the direction orthogonal to the flow
velocity direction F. Thus, a catalytic reaction occurs in a state
in which the exhaust gas smoothly flows in the exhaust passage 108
while passing through the holes 6h.
[0034] As shown in FIG. 3, the heater section 4 has a honeycomb
structure in which a single metal thin plate 4a having an
insulation sheet 4b stacked on one side thereof is wound spirally.
A positive electrode 4d and a negative electrode 4e are connected
to the center side and the outer circumferential side of the metal
thin plate 4a. When electricity is supplied to lead wires 4L1 and
4L2 connected to the two electrodes 4d and 4e, the metal thin plate
4a generates heat.
[0035] Also, as shown in FIG. 4, the metal thin plate 4a is
corrugated along the longitudinal direction such that as a result
of winding, a large number of gaps extending along the flow
velocity direction (axial direction) F are formed, thereby securing
passage of gas.
[0036] Thus, the heater section 4 heats the exhaust gas, whereby
the exhaust gas at low temperature is heated in an early stage, and
the catalytic reaction at the catalyst section 6 on the downstream
side is promoted.
[0037] Notably, the metal thin plate 4a can be formed of, for
example, Fe--Cr--Al alloy, and the insulation sheet 4b can be
formed of, for example, fabric woven from alumina wire.
[0038] Further, as shown in FIG. 5, the retainer 2 is a cylindrical
ceramic porous member having a center opening 2c and a large number
of holes 2h extending along the flow velocity direction (axial
direction) F. The lead wires 4L1 and 4L2 of the heater section 4
extend outward from the center opening 2c of the retainer 2.
[0039] The heater section 4 is axially retained between the
retainer 2 and the catalyst section 6, whereby these members are
fixed within the casing 8.
[0040] The control section 9 performs such control as to use energy
(electric power) regenerated by the motor 104 in the course of
deceleration of the vehicle 100 as power for energizing the heater
section 4 for heating. This control can be performed, for example,
by connecting, by means of switching, the lead wires 4L1 and 4L2 of
the heater section 4 to a battery which is charged with the
regenerated energy (electric power).
[0041] Also, the control section 9 shuts off electricity supplied
to the heater section 4 for saving electricity if energization is
unnecessary (e.g., when exhaust gas is sufficiently warm).
[0042] In the present embodiment, the heat capacity of the catalyst
section 6 is larger than the heat capacity of the heater section 4.
Therefore, the heater section 4 can generate heat quickly so as to
heat exhaust gas at low temperature more early, thereby reliably
promoting the catalytic reaction at the catalyst section 6.
[0043] Since the pressure loss of the catalyst section 6 in the
flow velocity direction F of the exhaust passage 108 is smaller
than the pressure loss of the catalyst section 6 in the direction
orthogonal to the flow velocity direction F, if the heater section
4 is disposed at the center of the catalyst section 6, heat is not
transferred sufficiently in the radial direction of the catalyst
section 6. In view of this, the heater section 4 is disposed on the
upstream side of the catalyst section 6. In this case, since
exhaust gas heated by the heater section 4 flows through the entire
catalyst section 6 within the exhaust passage 108, it is possible
to reliably heat the catalyst section 6, to thereby promote the
catalytic reaction.
[0044] Also, since the heat capacity of the catalyst section 6 is
large, the catalyst section 6 having become warm as a result of
heat generation by the heater section 4 cools slowly even after
interruption of the energization of the heater section 4. Thus, the
time during which the energization of the heater section 4 is
interrupted can be extended accordingly, whereby electric power can
be saved.
[0045] FIGS. 7 and 8 show the results of a simulation for
determining a temperature distribution in a catalyst section
(porous member) having a reduced pressure loss in the flow velocity
direction and temperature distributions on upstream and downstream
sides of the catalyst section (porous member) in the gas flow
velocity direction.
[0046] As shown in FIG. 7, the simulation was performed under the
conditions that an upstream space and a downstream space are
present on the upstream and downstream sides, respectively, of the
catalyst section (porous member) in the gas flow velocity
direction. Notably, the catalyst section (porous member) is
configured such that a heat generation section is present at a
center portion and a non-heat generation section is present on the
outer circumferential side thereof.
[0047] FIG. 8 shows the temperature distributions; i.e., the
results of the simulation. As shown in FIG. 8, the space on the
downstream side of the catalyst section (porous member);
specifically, the space on the downstream side of the center
portion where the heat generation section is present, is high in
temperature (a gray region of FIG. 8). Of the catalyst section
(porous member), the heat generation section (center portion) has a
high temperature (a white region of FIG. 8), and a portion on the
outer circumferential side of the heat generation section has a low
temperature approximately the same as the temperature before
introduction of gas (a black region of FIG. 8). As described above,
in the catalyst section having a reduced pressure loss in the flow
velocity direction, even when the heat generation section (center
portion) generates heat, the heat is not transferred sufficiently
to the outer circumferential side. It was found from this that the
heat conduction in the radial direction is considerably low.
[0048] Notably, this simulation was performed on the assumption
that the flow of the gas is a uniform flow along the exhaust
passage. However, even in the case where the gas does not flow
along the exhaust passage and its flow has components in different
directions, it is presumed that similar temperature distributions
are obtained, because the pressure loss of the catalyst section in
the flow velocity direction (axial direction) of the exhaust
passage is smaller than the pressure loss in the radial
direction.
[0049] The heat capacities of the catalyst section 6 and the heater
section 4 are obtained as follows. The catalyst section 6 and the
heater section 4 are individually placed in a thermostatic chamber
filled with the atmosphere of 300.degree. C. The temperatures of
the catalyst section 6 and the heater section 4 are monitored, and
their time constants are obtained from changes in their
temperatures with time. The heat capacities of the catalyst section
6 and the heater section 4 are calculated from the time
constants.
[0050] Also, as shown in FIG. 6, in the case of a heater section 40
which is composed of a portion located in the interior 108i of the
exhaust passage 108, a portion screwed to the side wall of the
exhaust passage 108, and a portion located outside the exhaust
passage 108, only the portion 40i located in the interior 108i of
the exhaust passage 108 is cut and taken out, and is used for
measurement of the heat capacity.
[0051] The same also applies to the catalyst section 6.
[0052] The present invention is not limited to the above
embodiment, but extends into various modifications and equivalents
encompassed by the ideas and scope of the invention. For example,
no particular limitation is imposed on the structures and shapes of
the retainer, the heater section, and the catalyst section. Also,
the material of the catalyst section 6 is not limited to the
ceramic porous member so long as the pressure loss in the flow
velocity direction is smaller than the pressure loss in the
direction orthogonal to the flow velocity direction. For example,
the catalyst section 6 may be formed by winding a metal thin plate
4a coated with an insulating film which is formed of alumina or the
like and which carries thereon a catalytic metal or the like.
DESCRIPTION OF REFERENCE NUMERALS
[0053] 2: retainer [0054] 4: heater section [0055] 6: catalyst
section [0056] 8: casing [0057] 9: control section [0058] 10:
catalyst apparatus for internal combustion engine [0059] 100:
internal combustion engine [0060] 108: exhaust passage
* * * * *