U.S. patent application number 13/643501 was filed with the patent office on 2013-02-14 for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Masahiro Fujiwara, Shunichi Hanada, Eiji Hashimoto, Chika Kanba, Taiichi Mori, Koki Uno. Invention is credited to Masahiro Fujiwara, Shunichi Hanada, Eiji Hashimoto, Chika Kanba, Taiichi Mori, Koki Uno.
Application Number | 20130036725 13/643501 |
Document ID | / |
Family ID | 44860962 |
Filed Date | 2013-02-14 |
United States Patent
Application |
20130036725 |
Kind Code |
A1 |
Uno; Koki ; et al. |
February 14, 2013 |
INTERNAL COMBUSTION ENGINE
Abstract
An internal combustion engine according to the present invention
includes an exhaust treatment apparatus provided in an exhaust
passage, and a burner apparatus provided upstream of the exhaust
treatment apparatus to raise exhaust temperature. A valve driving
state of at least one of an intake valve and an exhaust valve is
controlled so as to reduce a flow rate of exhaust gas passing
through the burner apparatus when the flow rate of the exhaust gas
is equal to or larger than a predetermined value. Possible flame
blow-out in the burner apparatus can be prevented or suppressed to
ensure sufficient ignition performance.
Inventors: |
Uno; Koki; (Susono-shi,
JP) ; Hashimoto; Eiji; (Susono-shi, JP) ;
Mori; Taiichi; (Susono-shi, JP) ; Fujiwara;
Masahiro; (Susono-shi, JP) ; Hanada; Shunichi;
(Mishima-shi, JP) ; Kanba; Chika; (Mishima-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Uno; Koki
Hashimoto; Eiji
Mori; Taiichi
Fujiwara; Masahiro
Hanada; Shunichi
Kanba; Chika |
Susono-shi
Susono-shi
Susono-shi
Susono-shi
Mishima-shi
Mishima-shi |
|
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
44860962 |
Appl. No.: |
13/643501 |
Filed: |
April 26, 2010 |
PCT Filed: |
April 26, 2010 |
PCT NO: |
PCT/JP2010/002984 |
371 Date: |
October 25, 2012 |
Current U.S.
Class: |
60/303 |
Current CPC
Class: |
F01N 2240/14 20130101;
F01N 3/204 20130101; Y02T 10/26 20130101; F01L 13/0005 20130101;
Y02T 10/18 20130101; F01N 3/2066 20130101; F01L 9/04 20130101; F01N
3/106 20130101; F01N 3/2033 20130101; F02D 13/0219 20130101; Y02T
10/12 20130101; F01N 3/103 20130101; Y02T 10/22 20130101; F01L
2013/001 20130101; F01N 2610/102 20130101; F01L 2001/0537 20130101;
F01N 3/0842 20130101; F01L 2800/00 20130101; F01L 9/02 20130101;
F02D 13/06 20130101; F01L 2001/34496 20130101; F01N 3/101 20130101;
F01N 2240/30 20130101 |
Class at
Publication: |
60/303 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Claims
1. An internal combustion engine comprising: an exhaust treatment
apparatus provided in an exhaust passage; a burner apparatus
provided upstream of the exhaust treatment apparatus to raise
exhaust temperature, and valve driving control unit for controlling
a valve driving state of at least one of an intake valve and an
exhaust valve so as to reduce a flow rate of exhaust gas passing
through the burner apparatus when the flow rate of the exhaust gas
is equal to or larger than a predetermined value.
2. The internal combustion engine according to claim 1, wherein the
valve driving control unit comprises: a valve timing varying
mechanism adapted to vary a valve timing for the exhaust valve, and
first control unit programmed to control the valve timing varying
mechanism in such a manner that the exhaust valve is kept open
until during a descent of a piston after end of an exhaust stroke,
when the flow rate of the exhaust gas is equal to or larger than
the predetermined value.
3. The internal combustion engine according to claim 1, wherein the
valve driving control unit comprises: a halting mechanism adapted
to halt operation of at least one of the intake valve and the
exhaust valve in a part of a plurality of cylinders; and second
control unit programmed to control the halting mechanism so as to
halt the operation of at least one of the intake valve and the
exhaust valve in the part of cylinders, when the flow rate of the
exhaust gas is equal to or larger than the predetermined value.
4. The internal combustion engine according to claim 1, further
comprising detection unit for detecting an amount of intake air as
a substitute value for the flow rate of the exhaust gas, and
wherein the valve driving control unit controls the valve driving
state of at least one of the intake valve and the exhaust valve so
as to reduce the flow rate of the exhaust gas when the amount of
intake air detected by the detection unit is equal to or larger
than a predetermined value.
5. The internal combustion engine according to claim 1, wherein the
burner apparatus comprises a fuel addition valve, ignition unit,
and a pretreatment catalytic converter.
Description
TECHNICAL FIELD
[0001] The present invention relates to an internal combustion
engine, and in particular, to an internal combustion engine with a
burner apparatus provided in an exhaust passage and upstream of an
exhaust treatment apparatus to raise exhaust temperature.
BACKGROUND ART
[0002] In some internal combustion engines, a burner apparatus is
provided in an exhaust passage and upstream of an exhaust treatment
apparatus (catalyst). Heated gas generated by the burner apparatus
is utilized to raise exhaust temperature to heat the exhaust
treatment apparatus, thus facilitating warm-up of the exhaust
treatment apparatus.
[0003] PTL1 discloses a catalyst temperature rise apparatus
including an addition valve that allows fuel to be injected and
ignition means with a heating section that allows the injected fuel
to be ignited. The addition valve and the ignition means are
disposed at such positions that allow the fuel injected through the
addition valve to come into direct contact with the heating
section. Thus, typically, the burner apparatus uses the appropriate
ignition means to ignite and combust the fuel injected into the
exhaust passage.
[0004] The ignition performance of the burner apparatus tends to be
degraded when the flow rate of exhaust gas passing through the
burner apparatus increases to or beyond a predetermined value. This
is because at the increased flow rate, the exhaust gas may blow out
the flame, making the ignition difficult.
[0005] Thus, an object of the present invention is to provide an
internal combustion engine that allows sufficient ignition
performance to be ensured even when the flow rate of exhaust gas
passing through the burner apparatus increases.
CITATION LIST
Patent Literature
[0006] PTL1: Japanese Patent Laid-Open No. 2006-112401
SUMMARY OF THE INVENTION
[0007] An aspect of the present invention provides an internal
combustion engine characterized by including:
[0008] an exhaust treatment apparatus provided in an exhaust
passage;
[0009] a burner apparatus provided upstream of the exhaust
treatment apparatus to raise exhaust temperature, and
[0010] valve driving control means for controlling a valve driving
state of at least one of an intake valve and an exhaust valve so as
to reduce a flow rate of exhaust gas passing through the burner
apparatus when the flow rate of the exhaust gas is equal to or
larger than a predetermined value.
[0011] When the valve driving state is thus controlled so as to
reduce the flow rate of the exhaust gas, possible flame blow-out
can be prevented or suppressed to ensure sufficient ignition
performance.
[0012] Preferably, the valve driving control means includes:
[0013] a valve timing varying mechanism adapted to vary a valve
timing for the exhaust valve, and
[0014] first control means for controlling the valve timing varying
mechanism in such a manner that the exhaust valve is kept open
until during a descent of a piston after end of an exhaust stroke,
when the flow rate of the exhaust gas is equal to or larger than
the predetermined value.
[0015] When the exhaust valve is kept open until during the descent
of the piston after the end of the exhaust stroke, a negative
pressure generated during the descent of the piston can be utilized
to suck exhaust gas back into a combustion chamber. This enables a
reduction in the flow rate of exhaust gas fed to the burner
apparatus. Hence, sufficient ignition performance can be suitably
ensured.
[0016] Preferably, the valve driving control means includes a
halting mechanism adapted to halt operation of at least one of the
intake valve and the exhaust valve in a part of a plurality of
cylinders and second control means for controlling the halting
mechanism so as to halt the operation of at least one of the intake
valve and the exhaust valve in the part of cylinders, when the flow
rate of the exhaust gas is equal to or larger than the
predetermined value.
[0017] When the operation of the at least one of the intake valve
and the exhaust valve is halted in the certain number of cylinders,
exhaust gas is prevented from being passed from these cylinders
toward the burner apparatus, enabling a reduction in the total flow
rate of exhaust gas from all the cylinders. Hence, sufficient
ignition performance can be suitably ensured.
[0018] Preferably, the internal combustion engine further includes
detection means for detecting an amount of intake air as a
substitute value for the flow rate of the exhaust gas, and
[0019] the valve driving control means controls the valve driving
state of at least one of the intake valve and the exhaust valve so
as to reduce the flow rate of the exhaust gas when the amount of
intake air detected by the detection means is equal to or larger
than a predetermined value.
[0020] Preferably, the burner apparatus includes a fuel addition
valve, ignition means, and a pretreatment catalytic converter.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a schematic diagram of an embodiment of the
present invention;
[0022] FIG. 2 is a side profile showing a burner apparatus;
[0023] FIG. 3 is a front profile of the burner apparatus as seen
from an upstream side;
[0024] FIG. 4 is a schematic diagram showing that an exhaust valve
is closed in a delayed manner; and
[0025] FIG. 5 is a schematic diagram showing that operations of an
intake valve and the exhaust valve are halted.
DESCRIPTION OF EMBODIMENTS
[0026] Preferred embodiments of the present invention will be
described below in detail. However, it should be noted that the
embodiments of the present invention are not limited to those which
are described below and that the present invention includes any
variations and applications embraced in the concepts of the present
invention defined by the claims. The dimensions, materials, shapes,
relative arrangements, and the like of components described in the
embodiments are not intended to limit the technical scope of the
present invention thereto unless otherwise specified.
[0027] FIG. 1 shows an engine main body 1 and an intake and exhaust
system thereof according to an embodiment. The engine main body 1
is an onboard four-stroke diesel engine. An intake pipe 2 and an
exhaust pipe 3 (exhaust passage) are connected to the engine main
body 1. An air flow meter 4 is provided in the middle of the intake
pipe 2 and outputs a signal corresponding to the flow rate of
intake air flowing through the intake pipe 2. The air flow meter 4
detects the amount of intake air flowing into the engine main body
1 per unit time (that is, the flow rate of intake air). The engine
main body 1 includes a plurality of cylinders each including an
intra-cylinder fuel injection valve 9. However, FIG. 1 shows only a
single intra-cylinder fuel injection valve 9.
[0028] The exhaust pipe 3 is connected to a muffler (not shown in
the drawings) at a terminal thereof and is open to the atmosphere
at an outlet of the muffler. In the middle of the exhaust pipe 3,
an oxidizing catalytic converter 6 and an NOx catalytic converter
26 are arranged in this order from the upstream side in series.
[0029] The oxidizing catalytic converter 6 allows an unchanged
component such as HC or CO to react with O.sub.2 to obtain CO,
CO.sub.2, H.sub.2O, or the like. A catalytic substance may be, for
example, Pt/CeO.sub.2, Mn/CeO.sub.2, Fe/CeO.sub.2, Ni/CeO.sub.2, or
Cu/CeO.sub.2.
[0030] An NOx catalytic converter 26 preferably includes an NOx
storage reduction (NSR) catalytic converter. The NOx catalytic
converter 26 has a function to absorb NOx in inflow exhaust when
the exhaust has a high oxygen concentration and to reduce the
absorbed NOx when the oxygen concentration of the exhaust decreases
and when a reduction component (for example, fuel) is present. The
NOx catalytic converter 26 includes a base material formed of an
oxide such as alumina Al.sub.2O.sub.3 and including rare metal such
as platinum Pt and an NOx absorbing component carried on a surface
of the base material; the rare metal serves as a catalytic
component. The NOx absorbing component contains at least one
selected from, for example, alkali metals such as potassium K,
sodium Na, lithium Li, and cesium Cs, alkali earths such as barium
Ba and calcium Ca, and rare earths such as lanthanum La and yttrium
Y. In addition, the NOx catalytic converter 26 may be a selective
catalytic reduction (SCR) NOx converter.
[0031] In addition to the oxidizing catalytic converter 6 and the
NOx converter 26, a particulate filter (DPF) may be provided which
collects particulates (PM) in the exhaust such as soot. Preferably,
the DPF is of continuous regeneration type that continuously
oxidizes and combusts collected particulates. Preferably, the DPF
is located at least downstream of the oxidizing catalytic converter
6 and upstream or downstream of the NOx catalytic converter 26. For
a spark ignition internal combustion engine, a three-way catalyst
is preferably provided in the exhaust passage. The oxidizing
catalytic converter 6, the NOx catalytic converter 26, the DPF, and
the three-way catalyst correspond to an exhaust treatment apparatus
according to the present invention.
[0032] In the exhaust pipe 3, a burner apparatus 30 is located
upstream of the oxidizing catalytic converter 6. The burner
apparatus 30 includes a fuel addition valve 7, a glow plug 21
serving as ignition means, and a pretreatment catalytic converter
8. The burner apparatus 30 is located downstream of a collector
portion of an exhaust manifold (not shown in the drawings)
connected to the engine main body 1.
[0033] As shown in FIG. 2 and FIG. 3 in detail, the fuel addition
valve 7 allows a liquid fuel (light oil) to be added into the
exhaust. The fuel addition valve 7 includes a single nozzle 7a. The
central axis of the nozzle 7a contains a component traversing the
exhaust pipe 3 and is inclined obliquely downward toward the
downstream side of the exhaust pipe 3. Alternatively, a plurality
of nozzles maybe provided.
[0034] A pretreatment catalytic converter 8 that reforms fuel
injected through the fuel addition valve 7 is provided between the
fuel addition valve 7 and the oxidizing catalytic converter 6 in
the exhaust pipe 3. The pretreatment catalytic converter 8 can be
configured as an oxidizing catalytic converter including, for
example, a carrier made of zeolite and carrying rhodium or the
like.
[0035] When fuel is fed to the pretreatment catalytic converter 8,
if the pretreatment catalytic converter 8 has been activated, then
the fuel is oxidized in the pretreatment catalytic converter 8. The
resulting oxidizing reaction heat raises the temperature of the
pretreatment catalytic converter 8. This enables an increase in the
temperature of exhaust gas passing through the pretreatment
catalytic converter 8.
[0036] Furthermore, when the temperature of the pretreatment
catalytic converter 8 increases, hydrocarbons in the fuel which
have a large carbon number are decomposed into reactive
hydrocarbons with a smaller carbon number. This allows the fuel to
be reformed into reactive fuel.
[0037] In other words, the pretreatment catalytic converter 8, on
one hand, forms a rapid heater that generates heat rapidly, and on
the other hand, forms a reformed fuel discharger that discharges
the reformed fuel. Furthermore, a portion or all of the fuel fed
through the fuel addition valve 7 is ignited by the glow plug 21.
This also facilitates a rise in the temperature of exhaust gas.
[0038] The pretreatment catalytic converter 8 has an outer diameter
smaller than the inner diameter of the exhaust pipe 3. Thus, when
the pretreatment catalytic converter 8 is placed in the exhaust
pipe 3, exhaust can pass through a catalyst bypass circuit 3a that
is a gap between an outer peripheral surface f the pretreatment
catalytic converter 8 and an inner peripheral surface of the
exhaust pipe 3. The pretreatment catalytic converter 8 is of what
is called a straight flow type in which individual cells
communicate with one another from upstream side to the downstream
side. The pretreatment catalytic converter 8 is arranged in a
generally cylindrical outer frame 8a that is supported in the
exhaust pipe 3 by a plurality of generally radially arranged stays
8b. The pretreatment catalytic converter 8 is enclosed by the
catalyst bypass circuit 3a substantially all around the
circumference thereof except for portions thereof to which the
stays 8b are attached.
[0039] The exhaust pipe 3 is generally cylindrically formed. The
axis of the direction of an exhaust flow in the pretreatment
catalytic converter 8 is located lower, in FIG. 2 and FIG. 3, than
the axis of the direction of an exhaust flow in the exhaust pipe 3.
Thus, the catalyst bypass circuit 3a includes a wide-side bypass
circuit 3b shown in the upper part of FIG. 2 and FIG. 3 and a
narrow-side bypass circuit 3c shown in the lower part of FIG. 2 and
FIG. 3.
[0040] The glow plug 21 is installed such that a heating section
21a thereof is positioned downstream of the fuel addition valve 7
and upstream of the pretreatment catalytic converter 8. The glow
plug 21 is connected to an onboard DC power source via a booster
circuit (not shown in the drawings). The heating section 21a
generates heat when current is applied to the glow plug 21. The
heat generated by the heating section 21a enables the fuel fed
through the fuel addition valve 7 to be ignited to generate a flame
F. The glow plug 21 has an axis inclined toward the upstream side
of the exhaust pipe 3. However, the glow plug 21 may be arranged in
any orientation, for example, orthogonally to the direction of a
flow or parallel to a longitudinal direction of an impact plate 20
described below. The ignition means may be another apparatus such
as a ceramic heater or a spark plug, particularly an electrothermal
apparatus or a spark ignition apparatus.
[0041] A lower part of a front end of the outer frame 8a with the
pretreatment catalytic converter 8 accommodated therein forms a
gutter-like projecting portion 8c that projects toward the upstream
side. The impact plate 20, which is formed of a flat plate, is
fixed to a leading end (upstream end) and upper end of the
projecting portion 8c. The impact plate 20 is slightly inclined so
as to lie below the axis of the exhaust pipe 3 and so that a
downstream end of the impact plate 20 is positioned below the
upstream end thereof.
[0042] The impact plate 20 can be formed of a material such s SUS
which has high heat resistance and high impact resistance. The fuel
addition valve 7 allows fuel to be injected obliquely backward and
downward toward the impact plate 20. The central axis of the nozzle
7a of the fuel addition valve 7 lies toward the center 20a of top
surface of the impact plate 20. The trajectory of the fuel fed
through the fuel addition valve 7 contains a component acting in a
direction traversing the exhaust pipe 3. Upon impacting the impact
plate 20, the fuel is more smoothly atomized and more appropriately
dispersed and diffused. The fuel having impacted the impact plate
20 is directed toward the downstream side by an exhaust flow. The
fuel having impacted the impact plate 20 is fed to the pretreatment
catalytic converter 8 and the heating section 21a of the glow plug
21.
[0043] The heating section 21a of the glow plug 21 is located in
the vicinity of the pretreatment catalytic converter 8 and slightly
upstream of and above a front end surface of the pretreatment
catalytic converter 8 so as to be capable of exchanging heat with
pretreatment catalytic converter 8. That is, the glow plug 21 is
positioned such that when the temperature of the pretreatment
catalytic converter 8 rises, the resulting heat radiation and
convection serves to raise the temperature of vicinity of the
heating section 21a of the glow plug 21, thus facilitating the
ignition of the fuel fed through the fuel addition valve 7.
However, the position of the heating section 21a of the glow plug
21 in the flow direction may be the same as the position of the
front end surface of the pretreatment catalytic converter 8 or a
position located downstream of the front end surface.
[0044] As shown in FIG. 1, the engine main body 1 includes an
electronic control unit (hereinafter referred to as an ECU) 10 that
controls various devices according to the operating status of the
engine main body 1, a driver's request, or the like. The ECU 10
includes a CPU that carries out various arithmetic processes for
engine control, a ROM that stores programs and data required for
the control, a RAM that temporarily stores the results of
calculations carried out by the CPU, and an input/output port
through which the ECT 10 outputs and receives signals to and from
an external apparatus.
[0045] The ECU 10 connects, via electric wires, not only to the
above-described air flow meter 4 but also to various sensors
including a crank angle sensor 24 that detects the crank angle of
the engine main body 1 and an accelerator opening sensor 25 that
outputs electric signals depending on the opening of the
accelerator. Output signals from the sensors are input to the ECU
10. Furthermore, the ECU 10 further connects, via electric wires,
to various devices including the intra-cylinder injection valve 9,
the fuel addition valve 7, and the glow plug 21. The devices are
controlled by the ECU 10. The ECU 10 can detect the amount of
intake air based on the output value from the air flow meter 4,
detect the number of engine rotations based on the output value
from the crank angle sensor 24, and detect a demand load on the
engine main body 1 based on the output value from the output value
from the accelerator opening sensor 25.
[0046] The engine main body 1 further includes an intake side valve
timing varying mechanism 41 and an exhaust side valve timing
varying mechanism 42 which vary valve timings for the intake valve
and exhaust valve, respectively, of each cylinder. The varying
mechanisms 41 and 42 vary the relative phases of an intake cam
shaft 43 and an exhaust camshaft 44, respectively, with respect to
a crank shaft to vary the opening and closing timings for the
intake valve and the exhaust valve with the same working angle
maintained. These varying mechanisms 41 and 42 are included in the
various devices and controlled by the ECU 10.
[0047] According to the present embodiment, when temperature rise
control is performed using the burner apparatus 30, the ECU 10
controls the fuel addition valve 7 and the glow plug 21. That is,
fuel is injected through the fuel injection valve 7, and current is
applied to the glow plug 21 as necessary to heat the glow plug 21
to a sufficiently high temperature. The injected fuel is ignited
and combusted by the glow plug 21 to generate a flame F and thus
hot heated gas. The heated gas is fed to the oxidizing catalytic
converter 6 and the NOx catalytic converter 26. Furthermore, the
flame F or heated gas can be utilized to combust reformed fuel
discharged through an outlet of the pretreatment catalytic
converter 8.
[0048] The amount of fuel injected through the fuel addition valve
7 is set based on parameters indicative of the operating status of
the engine (the parameters include the number of engine rotations,
the accelerator opening, and the amount of intake air) in
accordance with a map pre-stored in the ROM of the ECU 10.
[0049] As described above, the ignition performance of the burner
apparatus 30 tends to be degraded when the flow rate of exhaust gas
passing through the burner apparatus 30 increases to or beyond a
predetermined value. This is because at the increased flow rate,
the exhaust gas may blow out the flame, making the ignition
difficult.
[0050] Such a flame blow-out phenomenon may occur, for example,
when the flow rate of the exhaust gas increases to or beyond 12
g/s.
[0051] Thus, to deal with this, the present embodiment controls the
valve driving state of at least one of the intake valve and the
exhaust valve so as to reduce the flow rate of exhaust gas passing
through the burner apparatus 30 when the flow rate of the exhaust
gas is equal to or larger than a predetermined value. When the
valve driving state is thus controlled so as to reduce the flow
rate of the exhaust gas passing through the burner apparatus 30,
possible flame blow-out can be prevented or suppressed to ensure
sufficient ignition performance.
[0052] More specifically, the exhaust-side valve timing varying
mechanism 42 is controlled such that the exhaust valve is kept open
until during a descent of the piston after the end of an exhaust
stroke, when the flow rate of the exhaust gas passing through the
burner apparatus 30 is equal to or larger than the predetermined
value.
[0053] As shown in FIG. 4, when the exhaust valve 13 is kept open
until during the descent of the piston 12 after the end of the
exhaust stroke (that is, the exhaust valve 13 is closed in a
delayed manner), a negative pressure generated during the descent
of the piston can be utilized to suck the exhaust gas back into the
combustion chamber 14 (that is, to carry out internal EGR). This
enables a reduction in the flow rate of exhaust gas fed to the
exhaust pipe 3 and thus the burner apparatus 30. Hence, even when
the flow rate of the exhaust gas increases to or beyond the
predetermined value, the increased flow rate of the exhaust gas can
be reduced to prevent or suppress possible flame blow-out. As a
result, appropriate and sufficient ignition performance can be
ensured. In FIG. 4, the intake valve is shown by reference numeral
15. An intake port that is in communication with the intake pipe 2
is shown by reference numeral 16. An exhaust port that is in
communication with the exhaust pipe 3 is shown by reference numeral
17.
[0054] The flow rate of the exhaust gas can be detected directly by
the sensor, but the amount of intake air Ga is preferably used as a
substitute value for the flow rate of the exhaust gas and detected
by the air flow meter 4 and the ECU 10. The ECU 10 controls the
exhaust-side valve timing varying mechanism 42 so as to close the
exhaust valve 13 (specifically, to end closing the exhaust valve
13) at a predetermined first timing during the descent of the
piston after the end of the exhaust stroke, when the amount of
intake air Ga detected using the air flow meter 4 is equal to or
larger than a predetermined value (for example, 12 g/s). This keeps
the exhaust valve 13 open from before an exhaust top dead center to
the first timing after the exhaust top dead center. On the other
hand, when the amount of intake air Ga detected using the air flow
meter 4 is smaller than the predetermined value, the ECU 10
controls the exhaust-side valve timing varying mechanism 42 so as
to close the exhaust valve 13 at a predetermined second timing that
is earlier than the first timing.
[0055] Now, another embodiment will be described. This embodiment
is substantially the same as the above-described embodiment, and
mainly differences from the above-described embodiment will be
described.
[0056] The another embodiment includes a halting mechanism adapted
to halt operation of at least one of the intake valve 15 and the
exhaust valve 13 in a part (certain number) of the plurality of
cylinders as shown in FIG. 5. According to the present embodiment,
the halting mechanism includes an intake-side halting mechanism 18
provided for the intake valve 15 in each of halt-enabled cylinders
corresponding to the part of cylinders and an exhaust-side halting
mechanism 19 provided for the exhaust valve 13 in each halt-enabled
cylinder. The intake-side halting mechanism 18 and the exhaust-side
halting mechanism 19 are provided in each of the halt-enabled
cylinders and individually controlled by the ECU 10.
[0057] Various well-known mechanisms maybe adopted as the halting
mechanisms 18 and 19. For example, the following may be adopted: a
mechanism that selectively makes a cam on a camshaft free by
hydraulic control or the like or a mechanism that selectively
precludes, by hydraulic control or the like, a driving force from
being transmitted from the camshaft to the valve. Alternatively, an
electromagnetic driving valve may be used which can be electrically
inactivated. The present embodiment includes the valve timing
varying mechanisms 41 and 42 in addition to the halting mechanisms
18 and 19. However, the valve timing varying mechanisms 41 and 42
may be omitted. Any number of halt-enabled cylinders may be placed
at any positions. In each halt-enabled cylinder, one of the
intake-side halting mechanism 18 and the exhaust-side halting
mechanism 19 may be exclusively provided.
[0058] The present embodiment controls the intake-side halting
mechanism 18 and the exhaust-side halting mechanism 19 so as to
halt operations of both the intake valve 15 and the exhaust valve
13 in each halt-enabled cylinder as shown in FIG. 5 when the flow
rate of exhaust gas passing through the burner apparatus 30 is
equal to or larger than a predetermined value. In the halt state,
the intake valve 15 and the exhaust valve 13 are kept closed. Of
course, during a halt, no fuel is injected through the
intra-cylinder fuel injection valve 9 (omitted from FIG. 5). During
a halt, either the intake valve 15 or the exhaust valve 13 may be
exclusively halted. In short, the communication between the intake
port 16 or the intake pipe 2 and the exhaust port 17 or the exhaust
pipe 3 may be disrupted.
[0059] When the operation of the at least one of the intake valve
15 and the exhaust valve 13 in each halt-enabled cylinder is halted
as described above, no exhaust gas is fed from the halt-enabled
cylinder toward the exhaust pipe or the burner apparatus 30. This
enables a reduction in the total flow rate of exhaust gas from all
the cylinders. Even when the flow rate of the exhaust gas increases
to or beyond the predetermined value, the increased flow rate can
be reduced. Hence, possible flame blow-out can be prevented or
suppressed to ensure appropriate and sufficient ignition
performance.
[0060] As described above, the flow rate of the exhaust gas can be
detected directly by the sensor, but the amount of intake air Ga is
preferably used as a substitute value for the flow rate of the
exhaust gas and detected by the air flow meter 4 and the ECU 10.
The ECU 10 controls the intake-side halting mechanism 18 and the
exhaust-side halting mechanism 19 so as to halt the operations of
both the intake valve 15 and the exhaust valve 13 in each
halt-enabled cylinder when the amount of intake air Ga detected
using the air flow meter 4 is equal to or larger than a
predetermined value (for example, 12 g/s). This sets the
halt-enabled cylinders to a halt state, while setting the other
cylinders (normal cylinders) to an operative state. On the other
hand, the ECU 10 controls the intake-side halting mechanism 18 and
the exhaust-side halting mechanism 19 so as to operate both the
intake valve 15 and the exhaust valve 13 in each halt-enabled
cylinder, when the amount of intake air Ga detected using the air
flow meter 4 is smaller than a predetermined value. This makes both
the halt-enabled cylinders and the normal cylinders operative.
[0061] The present invention has been somewhat specifically
described. However, it should be noted various alterations and
changes may be made to the claimed invention without departing from
the spirit and scope of the invention. The embodiments of the
present invention are not limited to those which are described
above. The present invention includes any variations and
applications embraced in the concepts of the present invention
defined by the claims. Thus, the present invention should not be
interpreted in a limited manner but is applicable to any other
techniques included within the scope of the concepts of the present
invention. Means for solving the problems according to the present
invention may be combined together wherever possible.
[0062] At least one of the pretreatment catalytic converter and the
exhaust pipe may have a noncircular cross section such as a
rectangular cross section or an oblong cross section. The types and
arrangement sequence of the components of the exhaust treatment
apparatus which are present downstream of the pretreatment
catalytic converter are optional.
* * * * *