U.S. patent application number 13/637098 was filed with the patent office on 2013-12-26 for particulate matter processing apparatus (as amended).
The applicant listed for this patent is Shinichi Mitani, Eiji Murase, Hiroshi Nomura. Invention is credited to Shinichi Mitani, Eiji Murase, Hiroshi Nomura.
Application Number | 20130340415 13/637098 |
Document ID | / |
Family ID | 46830216 |
Filed Date | 2013-12-26 |
United States Patent
Application |
20130340415 |
Kind Code |
A1 |
Mitani; Shinichi ; et
al. |
December 26, 2013 |
PARTICULATE MATTER PROCESSING APPARATUS (AS AMENDED)
Abstract
An excessively large electric current is suppressed from flowing
to an electrode. A particulate matter processing apparatus in which
a processing part with an electrode installed therein is arranged
in an exhaust passage of an internal combustion engine, wherein
particulate matter is caused to aggregate by generating a potential
difference between the electrode and the processing part, is
provided with a power supply that is connected to the electrode and
applies a voltage thereto, a current detection device that detects
an electric current which passes through the electrode, an air fuel
ratio detection device that detects or estimates an air fuel ratio
of an exhaust gas which flows through the exhaust passage, and a
voltage control device that makes the voltage applied to the
electrode from the power supply smaller in cases where the air fuel
ratio detected by the air fuel ratio detection device is a rich air
fuel ratio, than in cases where it is a stoichiometric air fuel
ratio or a lean air fuel ratio.
Inventors: |
Mitani; Shinichi;
(Susono-shi, JP) ; Nomura; Hiroshi; (Gotenba-shi,
JP) ; Murase; Eiji; (Gotenba-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitani; Shinichi
Nomura; Hiroshi
Murase; Eiji |
Susono-shi
Gotenba-shi
Gotenba-shi |
|
JP
JP
JP |
|
|
Family ID: |
46830216 |
Appl. No.: |
13/637098 |
Filed: |
March 16, 2011 |
PCT Filed: |
March 16, 2011 |
PCT NO: |
PCT/JP2011/056295 |
371 Date: |
September 25, 2012 |
Current U.S.
Class: |
60/311 |
Current CPC
Class: |
B03C 3/41 20130101; F01N
2560/025 20130101; Y02T 10/20 20130101; B03C 3/68 20130101; B03C
2201/32 20130101; F01N 9/00 20130101; F01N 3/01 20130101; B03C 3/49
20130101; B03C 2201/08 20130101; Y02T 10/40 20130101; F01N 2900/08
20130101; Y02T 10/47 20130101; B03C 2201/30 20130101; F01N 11/00
20130101; Y02T 10/12 20130101; B03C 2201/24 20130101 |
Class at
Publication: |
60/311 |
International
Class: |
F01N 11/00 20060101
F01N011/00 |
Claims
1. A particulate matter processing apparatus in which a processing
part with an electrode installed therein is arranged in an exhaust
passage of an internal combustion engine, wherein particulate
matter is caused to aggregate by generating a potential difference
between the electrode and the processing part, said apparatus
comprising: a power supply that is connected to said electrode and
applies a voltage thereto; a current detection device that detects
an electric current which passes through said electrode; an air
fuel ratio detection device that detects or estimates an air fuel
ratio of an exhaust gas which flows through said exhaust passage;
and a voltage control device that makes the voltage applied to said
electrode from said power supply smaller in cases where the air
fuel ratio detected or estimated by said air fuel ratio detection
device is a rich air fuel ratio, than in cases where it is a
stoichiometric air fuel ratio or a lean air fuel ratio.
2. The particulate matter processing apparatus as set forth in
claim 1, further comprising: an insulation part that insulates
electricity between said processing part and said exhaust passage;
and a ground part that grounds said processing part; wherein said
current detection device detects the electric current in said
ground part.
3. The particulate matter processing apparatus as set forth in
claim 1, wherein the lower the air fuel ratio detected or estimated
by said air fuel ratio detection device, the smaller said voltage
control device makes the voltage applied to said electrode from
said power supply.
4. The particulate matter processing apparatus as set forth in
claim 1, further comprising: an exhaust gas amount detection device
that detects or estimates an amount of exhaust gas of the internal
combustion engine; wherein the more the amount of exhaust gas
detected or estimated by said exhaust gas amount detection device,
the smaller said voltage control device makes the voltage applied
to said electrode from said power supply.
5. The particulate matter processing apparatus as set forth in
claim 2, wherein the lower the air fuel ratio detected or estimated
by said air fuel ratio detection device, the smaller said voltage
control device makes the voltage applied to said electrode from
said power supply.
6. The particulate matter processing apparatus as set forth in
claim 2, further comprising: an exhaust gas amount detection device
that detects or estimates an amount of exhaust gas of the internal
combustion engine; wherein the more the amount of exhaust gas
detected or estimated by said exhaust gas amount detection device,
the smaller said voltage control device makes the voltage applied
to said electrode from said power supply.
7. The particulate matter processing apparatus as set forth in
claim 3, further comprising: an exhaust gas amount detection device
that detects or estimates an amount of exhaust gas of the internal
combustion engine; wherein the more the amount of exhaust gas
detected or estimated by said exhaust gas amount detection device,
the smaller said voltage control device makes the voltage applied
to said electrode from said power supply.
Description
TECHNICAL FIELD
[0001] The present invention relates to a particulate matter
processing apparatus.
BACKGROUND ART
[0002] There has been known a technique in which a discharge
electrode is arranged in an exhaust passage of an internal
combustion engine, and a corona discharge is caused to occur from
the discharge electrode, whereby particulate matter (hereinafter
also referred to as PM) is charged and condensed or aggregated
(see, for example, a first patent document). By the condensation or
aggregation of the particulate matter, the number of particles in
the particulate matter can be decreased. Moreover, the sizes of
particles in the particulate matter become large, so when a filter
is arranged at a downstream side, it becomes easy to trap the
particulate matter with the filter.
[0003] However, no consideration has been given to the fact that
electricity flows to the electrode through unburnt fuel such as HC,
CO, etc., contained in an exhaust gas. Then, when a lot of unburnt
fuel is contained in the exhaust gas, an electric current passing
through the electrode may become large, thus giving rise to a fear
that a power supply, the electrode, or other circuits may be
deteriorated or failed. In addition, if the apparatus is
constructed so as to withstand a large electric current, it will
result in an increase in the cost of production. Moreover, when the
electric current increases, electric power consumption will become
large, so there will also be a fear that fuel economy may get
worse.
PRIOR ART REFERENCES
Patent Documents
[0004] First Patent Document: Japanese patent application laid-open
No. 2006-194116
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0005] The present invention has been made in view of the problems
as referred to above, and has for its object to suppress an
excessively large electric current from passing to an
electrode.
Means for Solving the Problems
[0006] In order to achieve the above-mentioned object, a
particulate matter processing apparatus according to the present
invention in which a processing part with an electrode installed
therein is arranged in an exhaust passage of an internal combustion
engine, wherein particulate matter is caused to aggregate by
generating a potential difference between the electrode and the
processing part, is provided with:
[0007] a power supply that is connected to said electrode and
applies a voltage thereto;
[0008] a current detection device that detects an electric current
which passes through said electrode;
[0009] an air fuel ratio detection device that detects or estimates
an air fuel ratio of an exhaust gas which flows through said
exhaust passage; and
[0010] a voltage control device that makes the voltage applied to
said electrode from said power supply smaller in cases where the
air fuel ratio detected or estimated by said air fuel ratio
detection device is a rich air fuel ratio, than in cases where it
is a stoichiometric air fuel ratio or a lean air fuel ratio.
[0011] Here, when a voltage is applied to the electrode, the
particulate matter can be electrified or charged. The charged
particulate matter is caused to move toward an inner wall of the
exhaust passage by means of a Coulomb force or a flow of the
exhaust gas. The particulate matter, which has reached the inner
wall of the exhaust passage, releases electrons to the exhaust
passage, so electricity flows to a ground side rather than to the
electrode. Then, the particulate matter, which has released the
electrons, aggregates with other particulate matter which exists
nearby, so it is possible to decrease the number of particles.
[0012] In addition, when HC, CO, or the like, which is unburnt
fuel, is contained in the exhaust gas, the unburnt fuel serves as a
carrier, so when a voltage is applied to the electrode, an electric
current passes to the electrode through the unburnt fuel. This
electric current is detected in the current detection device. Then,
in cases where the air fuel ratio of the exhaust gas is a rich air
fuel ratio, a lot of unburnt fuel is contained in the exhaust gas,
so the electric current passing through the electrode becomes very
large.
[0013] The electric current passing through the unburnt fuel such
as HC, CO, etc., at the time when the air fuel ratio of the exhaust
gas is a rich air fuel ratio becomes larger than an electric
current passing through the particulate matter. Then, an
excessively large electric current passes to various kinds of
devices, so there is a fear that these devices may be deteriorated.
On the other hand, in the case of a rich air fuel ratio, the
voltage control device makes the voltage to be applied small. When
the voltage to be applied is made small, an amount of electron
emission will decrease and the electric current passing through the
electrode will decrease. That is, it is possible to suppress an
excessively large current from flowing to the electrode, the power
supply, and so on.
[0014] In the present invention, provision is further made for:
[0015] an insulation part that insulates electricity between said
processing part and said exhaust passage; and
[0016] a ground part that grounds said processing part;
[0017] wherein said current detection device can detect the
electric current in said ground part.
[0018] The current detection device detects the electric current at
an electric potential reference point side from the electrode. In
general, wiring is made often longer or thicker at a power supply
side from the electrode than at a ground side from the electrode.
In addition, electric charges may be stored at the power supply
side from the electrode. Then, in cases where an electric current
is detected at the power supply side from the electrode, even if a
strong discharge is generated in the electrode, the rising and
falling of the electric current detected by the current detection
device at that time become slow. On the other hand, at the ground
side from the electrode, wiring can be made relatively short and
thin. For this reason, it is possible to detect the electric
current in a more accurate manner. In addition, due to the
provision of the insulation part, it is possible to suppress
electricity from flowing to other than the ground part. For this
reason, it is possible to detect the electric current in a more
accurate manner.
[0019] Moreover, in the present invention, the lower the air fuel
ratio detected or estimated by said air fuel ratio detection
device, the smaller said voltage control device can make the
voltage applied to said electrode from said power supply.
[0020] That is, the lower the air fuel ratio, the higher the
concentration of the unburnt fuel in the exhaust gas becomes, so
the larger electric current passes therethrough. In contrast to
this, by making the voltage to be applied smaller, it is possible
to suppress an excessively large current from flowing to the
electrode and the power supply.
[0021] Further, in the present invention, provision is further made
for an exhaust gas amount detection device that detects or
estimates an amount of exhaust gas of the internal combustion
engine,
[0022] wherein the more the amount of exhaust gas detected or
estimated by said exhaust gas amount detection device, the smaller
said voltage control device can make the voltage applied to said
electrode from said power supply.
[0023] The amount of exhaust gas may be the mass of the exhaust gas
flowing through the exhaust passage per unit time. The more the
amount of exhaust gas, the more unburnt fuel passes through the
surroundings of the electrode, so the larger electric current can
pass therethrough. In contrast to this, by making the voltage to be
applied smaller, it is possible to suppress an excessively large
current from flowing to the electrode and the power supply.
Effect of the Invention
[0024] According to the present invention, it is possible to
suppress an excessively large electric current from flowing to the
electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a view showing the schematic construction of a
particulate matter processing apparatus according to an embodiment
of the present invention.
[0026] FIG. 2 is a flow chart showing a flow for controlling a
voltage to be applied according to the embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0027] Hereinafter, reference will be made to a specific embodiment
of a particulate matter processing apparatus according to the
present invention based on the attached drawings.
First Embodiment
[0028] FIG. 1 is a view showing the schematic construction of a
particulate matter processing apparatus 1 according to this
embodiment of the present invention. The particulate matter
processing apparatus 1 is arranged in an exhaust passage 2 of a
gasoline engine.
[0029] The particulate matter processing apparatus 1 is constructed
to include a housing 3 which is connected at its opposite ends with
the exhaust passage 2. As a material for the housing 3, there is
used a stainless steel material. The housing 3 is formed into a
hollow cylindrical shape with its diameter being larger than that
of the exhaust passage 2. The opposite end portions of the housing
3 are each formed into a tapered shape of which the cross-sectional
area becomes smaller as they become closer to their ends,
respectively. Here, note that in FIG. 1, an exhaust gas flows
through the exhaust passage 2 in the direction of an arrow, and
flows into the interior of the housing 3. For this reason, the
housing 3 may also be a part of the exhaust passage 2.
[0030] The exhaust passage 2 and the housing 3 are connected to
each other through insulation parts 4. The insulation parts 4 are
each made of an electrically insulating material. The insulation
parts 4 are each sandwiched between a flange 21, which is formed at
an end of the exhaust passage 2, and a flange 31, which is formed
at one adjacent end of the housing 3. The exhaust passage 2 and the
housing 3 are fastened to each other, for example, by means of
bolts and nuts. Then, these bolts and nuts are also subjected to
insulation processing so as to prevent electricity from flowing
through these bolts and nuts. In this manner, electricity is
prevented from flowing between the exhaust passage 2 and the
housing 3.
[0031] An electrode 5 is mounted on the housing 3. The electrode 5
penetrates through a side surface of the housing 3, extend from the
side surface of the housing 3 in the direction of a central axis
thereof, are then bent to an upstream side of the flow of the
exhaust gas in the vicinity of the central axis, and extend toward
the upstream side of the flow of the exhaust gas in parallel to the
central axis. Then, the electrode 5 further bends to a side surface
side of the housing 3 at its upstream side, and leads to the
outside while penetrating through the side surface of the housing
3.
[0032] In addition, the electrode 5 is provided with insulator
parts 51, 55 each made of an electrically insulating material,
which serve to prevent electricity from flowing between the
electrode 5 and the housing 3. These insulator parts 51, 55 are
located between the electrode 5 and the housing 3, and have a
function of insulating electricity and at the same time fixedly
securing the electrode 5 to the housing 3.
[0033] Then, the electrode 5 has its one end connected to a power
supply 6 through a power supply side electric wire 52. The power
supply 6 can supply electricity to the electrode 5 and at the same
time change a voltage to be applied thereto. This power supply 6 is
connected to a control device 7 and a battery 8 through electric
wires, respectively. The control device 7 controls the voltage
which is applied to the electrode 5 by the power supply 6. In
addition, a ground electric wire 54 for connecting the power supply
6 to a reference point of electric potential is connected to the
power supply 6. The power supply 6 is connected to ground through
this ground electric wire 54.
[0034] Moreover, the electrode 5 has its other end connected to the
ground electric wire 54 through a short circuit electric wire 56.
To the middle of the short circuit electric wire 56, a switch 57
for opening and closing an electric circuit is provided or
connected. An electric current flows through the short circuit
electric wire 56 by turning on the switch 57 during the application
of the voltage by the power supply 6. At this time, the electrode 5
is placed in a short-circuited state, so the temperature of the
electrode 5 goes up. Here, note that in this embodiment, the power
supply side electric wire 52 is connected to the downstream side
insulator part 51 and the short circuit electric wire 56 is
connected to the upstream side insulator part 55, but instead of
this, the short circuit electric wire 56 may be connected to the
downstream side insulator part 51, and the power supply side
electric wire 52 may be connected to the upstream side insulator
part 55.
[0035] Also, a ground side electric wire 53 is connected to the
housing 3, so that the housing 3 is connected to ground through the
ground side electric wire 53. A detection device 9, which serves to
detect the electric current passing through the ground side
electric wire 53, is provided or connected to the ground side
electric wire 53. The detection device 9 detects the electric
current, for example, by measuring a potential difference between
opposite ends of a resistance which is provided or inserted in the
middle of the ground side electric wire 53. This detection device 9
is connected to the control device 7 through an electric wire.
Then, the electric current detected by the detection device 9 is
inputted to the control device 7. Here, note that the ground side
electric wire 53 is smaller in electric capacity than the power
supply side electric wire 52, so a response at the time of
detecting an electric current is higher when the detection device 9
is provided or connected to the ground side electric wire 53 than
when the detection device 9 is provided or connected to the power
supply side electric wire 52. Also, note that in this embodiment,
the detection device 9 corresponds to a current detection device in
the present invention.
[0036] In addition, an accelerator opening sensor 71, a crank
position sensor 72, a temperature sensor 73, an air flow meter 74,
and an air fuel ratio sensor 75 are connected to the control device
7. The accelerator opening sensor 71 detects an engine load by
outputting an electric signal corresponding to an amount of
depression of an accelerator pedal at which the driver of a vehicle
with the internal combustion engine installed thereon has depressed
or stepped down the accelerator pedal. The crank position sensor 72
detects the number of engine revolutions per unit time. The
temperature sensor 73 detects the temperature of the internal
combustion engine by detecting the temperature of cooling water or
the temperature of lubricating oil in the internal combustion
engine. The air flow meter 74 detects an amount of intake air
sucked into the internal combustion engine. The air fuel ratio
sensor 75 is mounted on the exhaust passage 2 at a location
upstream of the housing 3, and detects the air fuel ratio of the
exhaust gas which flows through the exhaust passage 2. Here, note
that in this embodiment, the air fuel ratio sensor 75 corresponds
to an air fuel ratio detection device in the present invention. In
addition, the air fuel ratio of the exhaust gas may be estimated
from an operating state of the internal combustion engine.
[0037] Moreover, the switch 57 is connected to the control device 7
through an electric wire, so that the control device 7 performs an
ON-OFF operation of the switch 57. Here, by turning the switch into
an ON state during the time when a voltage is applied to the
electrode 5 from the power supply 6, an electric current passes
through the short circuit electric wire 56. On the other hand, by
turning the switch into an OFF state, the electric current passing
through the short circuit electric wire 56 is put into a stopped
state.
[0038] In the particulate matter processing apparatus 1 as
constructed in this manner, electrons are released from the
electrode 5 by applying a negative high direct current voltage from
the power supply 6 to the electrode 5 when the switch 57 is in the
OFF state. That is, electrons are caused to be released from the
electrode 5 by making the electric potential of the electrode 5
lower than that of the housing 3. Then, particulate matter in the
exhaust gas can be charged to negative polarity by means of these
electrons. The particulate matter thus charged to negative polarity
is caused to move by means of a Coulomb force and a gas stream of
the exhaust gas. Thereafter, when the particulate matter reaches
the housing 3, the electrons, which have charged the particulate
matter to negative polarity, will be released to the housing 3. The
particulate matter, which has released the electrons to the housing
3, aggregates, thereby making larger the particle diameter or size
of each particle. In addition, the number of particles in the
particulate matter is reduced due to the aggregation of particulate
matter. That is, by applying the voltage to the electrode 5, the
diameters or sizes of particles in the particulate matter can be
made larger, thus making it possible to reduce the number of
particles in the particulate matter.
[0039] In addition, when a voltage is applied from the power supply
6 to the electrode 5 by turning on the switch 57, the electrode 5
is placed in a short-circuited state, whereby the temperature of
the electrode 5 goes up. As a result of this, substances such as
particulate matter, water, and the like, adhered to the electrode
5, can be removed by being oxidized or evaporated.
[0040] Incidentally, if unburnt fuel such as HC, CO, etc., is
contained in the exhaust gas, upon application of a voltage to the
electrode 5, the unburnt fuel will serve as a carrier for
electrons, so that an ionic current will flow. Then, when the air
fuel ratio of the exhaust gas becomes a rich air fuel ratio, the
amount of the unburnt fuel in the exhaust gas will increase, and
the ionic current will increase. As a result, the electric current
to be detected will become larger. Then, the ionic current due to
the unburnt fuel is by far larger than the electric current which
passes through particulate matter when the particulate matter is
aggregated.
[0041] Here, there is a fear that when an excessively large
electric current due to the ionic current passes through the power
supply 6, the electrode 5, and other circuits, these devices or
elements may be deteriorated or failed. In addition, if the
apparatus is constructed so as to withstand an excessively large
electric current, it will result in an increase in the cost of
production.
[0042] Accordingly, in this embodiment, the voltage applied to the
electrode 5 from the power supply 6 is made smaller in cases where
the air fuel ratio of the exhaust gas is a rich air fuel ratio than
in cases where it is a stoichiometric air fuel ratio or a lean air
fuel ratio. Thus, by making the voltage to be applied small in this
manner, the electric current can be made smaller, so the
above-mentioned devices or elements can be protected.
[0043] Here, note that when the air fuel ratio of the exhaust gas
is a rich air fuel ratio, an amount of electric current to be made
smaller can be set to a predetermined value which has beforehand
been calculated through experiments, etc. In addition, the lower
the air fuel ratio of the exhaust gas, the higher the concentration
of the unburnt fuel becomes, so the larger the electric current
becomes. As a result, the lower the air fuel ratio of the exhaust
gas, the smaller the voltage to be applied may be made.
[0044] Moreover, the more an amount of exhaust gas (which may also
be a flow rate of exhaust gas) in the internal combustion engine,
the more the unburnt fuel which passes through the housing 3
increases, so the more electric current can pass. Accordingly, the
more the amount of exhaust gas, the smaller the voltage to be
applied may be made.
[0045] Here, note that in this embodiment, due to the provision of
the insulation parts 4, it is suppressed that electricity passes to
the exhaust passage 2. Accordingly, the electric current, which
passes to the housing 3 through a deposit on the electrode 5,
particulate matter afloat in the exhaust gas, and unburnt fuel, is
detected by the detection device 9. In addition, the detection
accuracy of the electric current can be enhanced by detecting the
electric current in the ground side electric wire 53. In general,
the power supply side electric wire 52 is often longer in wiring
length or thicker in wiring diameter than the ground side electric
wire 53. Then, if an electric current is detected in the power
supply side electric wire 52, the rising and falling of the
detected electric current become slower than an actual change of
the electric current. For this reason, there is a fear that the
detection accuracy of the electric current may become low.
[0046] On the other hand, in the ground side electric wire 53,
wiring can be made relatively short and thin. For this reason, the
response to an actual change of electric current is higher when the
electric current is detected in the ground side electric wire 53.
Accordingly, by detecting the electric current in the ground side
electric wire 53, it is possible to detect the electric current in
a more accurate manner.
[0047] Here, note that in this embodiment, a catalyst for oxidizing
unburnt fuel may be provided at the upstream side of the housing 3.
Then, when the catalyst is in an activated state, an amount of
unburnt fuel which flows into the housing 3 can be decreased.
According to this, it is possible to suppress an excessively large
current from flowing to the electrode 5.
[0048] Next, FIG. 2 is a flow chart showing a flow or routine for
controlling the voltage to be applied according to this embodiment.
This routine is carried out by means of the control device 7 in a
repeated manner at each predetermined time interval.
[0049] In step S101, the operating state of the internal combustion
engine is obtained. For example, the values to be needed for
hereafter processing, such as the number of engine revolutions per
unit time, the engine load, the air fuel ratio of the exhaust gas,
and so on, are read in. The number of engine revolutions per unit
time is detected by the crank position sensor 72, and the engine
load is detected by the accelerator opening sensor 71. In addition,
the air fuel ratio of the exhaust gas is detected by the air fuel
ratio sensor 75. Here, note that the air fuel ratio of the exhaust
gas can also be estimated from the number of engine revolutions per
unit time, the engine load, the temperature of the internal
combustion engine, and so on. Also, the temperature of the internal
combustion engine (e.g., the temperature of lubricating oil or the
temperature of cooling water) is detected by the temperature sensor
73.
[0050] In step S102, the voltage to be applied to the electrode 5
is calculated. The voltage to be applied is set according to the
number of particles in the particulate matter (pieces/cm.sup.3)
estimated. This number of particles in the particulate matter is
the number of particles in the particulate matter which are emitted
by the internal combustion engine, and is the number of particles
in the particulate matter before the particulate matter flows into
the housing 3. The number of particles in the particulate matter
has a correlation with the number of engine revolutions per unit
time, the engine load, and the temperature of the internal
combustion engine (e.g., the temperature of lubricating oil or
temperature of cooling water), and hence is calculated based on
these values. A plurality of maps according to the temperature of
the internal combustion engine may be stored which are used for
calculating the number of particles in the particulate matter from
the number of engine revolutions per unit time and the engine load,
and the number of particles in the particulate matter may be
calculated based on these maps.
[0051] Here, note that a sensor for detecting the number of
particles in the particulate matter may be mounted on the exhaust
passage 2 at a location upstream of the housing 3, so that the
number of particles in the particulate matter is detected by this
sensor.
[0052] Then, the voltage to be applied is calculated based on the
number of particles in the particulate matter and the amount of
exhaust gas (g/sec) in the internal combustion engine. Such a
relation may have beforehand been obtained through experiments,
etc., and made into a map. The amount of exhaust gas in the
internal combustion engine has a correlation with the amount of
intake air in the internal combustion engine, and hence, can be
obtained based on the amount of intake air detected by the air flow
meter 74. In addition, the amount of exhaust gas may be estimated
from the number of engine revolutions per unit time and the engine
load. A sensor for detecting the amount of exhaust gas may also be
arranged in the exhaust passage 2. Thus, the control device 7,
which calculates the amount of exhaust gas in the internal
combustion engine, corresponds to an exhaust gas amount detection
device in the present invention.
[0053] Here, the smaller the amount of exhaust gas, the smaller the
inertia force of the particulate matter becomes, and hence, the
influence of an electrostatic action becomes relatively larger. For
this reason, it becomes easy for the particulate matter to
aggregate. Accordingly, the smaller the amount of exhaust gas, with
the smaller voltage to be applied, the particulate matter
aggregates. For this reason, the smaller the amount of exhaust gas,
the smaller the voltage to be applied is made. In addition, the
more the number of particles in the particulate matter, the shorter
become the distances between adjacent particles in the particulate
matter, and hence, the influence of the electrostatic action
becomes relatively larger. For this reason, the more the number of
particles in the particulate matter, with the smaller voltage to be
applied, the particulate matter aggregates. As a result, the more
the number of particles in the particulate matter, the smaller the
voltage to be applied is made.
[0054] In addition, the voltage to be applied may also be, for
example, such a value that the reduction or decrease rate of the
number of particles in the particulate matter becomes a
predetermined value (e.g., 40%). Also, the voltage to be applied
may also be a specified value which has been set beforehand.
[0055] Then, after the voltage to be applied has been calculated,
this voltage is applied, and the routine goes to step S103, in
which an electric current is detected. This electric current is a
value detected by the detection device 9.
[0056] In step S104, it is determined whether the air fuel ratio of
the exhaust gas obtained in step S101 is a rich air fuel ratio. In
this step, it is determined whether a lot of unburnt fuel is
contained in the exhaust gas.
[0057] Then, in cases where an affirmative determination is made in
step S104, the routine advances to step S105. On the other hand, in
cases where a negative determination is made, this routine is
terminated, and thereafter, various kinds of control are carried
out based on the detected electric current. For example, when water
or particulate matter adheres to the electrode 5, the detected
electric current will become large, and hence, a determination may
be made based on the detected electric current as to whether there
exists a deposit on the electrode 5. Then, in cases where it is
determined that a deposit exists on the electrode 5, by applying a
voltage thereto while turning on the switch 57, the temperature of
the electrode 5 is raised, thereby making it possible to remove the
deposit. In addition, the detected electric current becomes larger
in accordance with the increasing amount of aggregation of the
particulate matter, so the amount of aggregation of the particulate
matter may be estimated based on the detected electric current.
[0058] In step S105, the voltage to be applied is decreased from
the value thereof calculated in step S102. That is, the voltage to
be applied is made smaller in the case of a rich air fuel ratio
than in the case of a stoichiometric air fuel ratio or a lean air
fuel ratio.
[0059] Here, note that the smaller the air fuel ratio of the
exhaust gas, the smaller the voltage to be applied is made. In
addition, the larger the amount of exhaust gas in the internal
combustion engine, the smaller the voltage to be applied is made.
The relation between the extent to which the voltage to be applied
is made smaller and the air fuel ratio of the exhaust gas, and the
relation between the extent to which the voltage to be applied is
made smaller, and the amount of exhaust gas of the internal
combustion engine have beforehand been obtained through
experiments, etc., and made into a map. Here, note that in this
embodiment, the control device 7, which carries out the processing
of step S105, corresponds to a voltage control device in the
present invention.
[0060] In this manner, the voltage to be applied is made smaller at
the time of a rich air fuel ratio, so it is possible to suppress an
excessively large current from flowing to the power supply 6, the
electrode 5, and the other circuits. As a result, these devices or
elements can be protected. In addition, an increase in the power
consumption by the passage of a large electric current can be
suppressed. As a result, deterioration in fuel economy can be
suppressed.
EXPLANATION OF REFERENCE NUMERALS AND CHARACTERS
[0061] 1 particulate matter processing apparatus [0062] 2 exhaust
passage [0063] 3 housing [0064] 4 insulation parts [0065] 5
electrode [0066] 6 power supply [0067] 7 control device [0068] 8
battery [0069] 9 detection device [0070] 21 flange [0071] 31 flange
[0072] 51 insulator part [0073] 52 power supply side electric wire
[0074] 53 ground side electric wire [0075] 54 ground electric wire
[0076] 55 insulator part [0077] 56 short circuit electric wire
[0078] 57 switch [0079] 71 accelerator opening sensor [0080] 72
crank position sensor [0081] 73 temperature sensor [0082] 74 air
flow meter [0083] 75 air fuel ratio sensor
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