U.S. patent application number 13/994510 was filed with the patent office on 2013-10-10 for exhaust heating device for internal combustion engine and control method therefor.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Naoki Takeuchi. Invention is credited to Naoki Takeuchi.
Application Number | 20130263579 13/994510 |
Document ID | / |
Family ID | 46244196 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130263579 |
Kind Code |
A1 |
Takeuchi; Naoki |
October 10, 2013 |
EXHAUST HEATING DEVICE FOR INTERNAL COMBUSTION ENGINE AND CONTROL
METHOD THEREFOR
Abstract
An exhaust heating device for heating an exhaust gas led to an
exhaust purifying device from an engine is disposed in a second
exhaust passage that is located upstream of a confluent portion of
a first exhaust passage connected through a turbine of a first
turbocharger to the purifying device and the second passage
connected to the purifying device through a turbine of a second
turbocharger used primarily in a lower speed range of the engine
than the first turbocharger in a state of bypassing the turbine of
the first turbocharger and downstream of the turbine of the second
turbocharger. A valve for regulating a flow of the exhaust gas in
the second passage is disposed in the second passage that is
located downstream of a branched portion of the first and second
passages and upstream of the turbine of the second
turbocharger.
Inventors: |
Takeuchi; Naoki;
(Susono-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Takeuchi; Naoki |
Susono-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
46244196 |
Appl. No.: |
13/994510 |
Filed: |
December 17, 2010 |
PCT Filed: |
December 17, 2010 |
PCT NO: |
PCT/JP2010/007331 |
371 Date: |
June 14, 2013 |
Current U.S.
Class: |
60/274 ;
60/320 |
Current CPC
Class: |
F02B 37/007 20130101;
F01N 3/2053 20130101; F01N 13/00 20130101; F01N 3/106 20130101;
F01N 3/36 20130101; Y02T 10/12 20130101; Y02T 10/144 20130101; Y02T
10/20 20130101 |
Class at
Publication: |
60/274 ;
60/320 |
International
Class: |
F01N 13/00 20060101
F01N013/00 |
Claims
1-7. (canceled)
8. An exhaust heating device for an internal combustion engine for
heating an exhaust gas introduced in an exhaust purifying device
from the internal combustion engine in which a first exhaust
turbocharger and a second exhaust turbocharger used primarily in a
lower-rotation region of the internal combustion engine than the
first exhaust turbocharger are incorporated, wherein the exhaust
heating device is provided in a second exhaust passage positioned
upstream of a confluent portion of a first exhaust passage
connected through an exhaust turbine of the first exhaust
turbocharger to the exhaust purifying device and the second exhaust
passage connected through an exhaust turbine of the second exhaust
turbocharger to the exhaust purifying device in a state of
bypassing the exhaust turbine of the first exhaust turbocharger and
downstream of the exhaust turbine of the second exhaust
turbocharger, and a valve for regulating a flow of an exhaust gas
in the second exhaust passage is provided in the second exhaust
passage downstream of a branched portion of the first exhaust
passage and the second exhaust passage and upstream of the exhaust
turbine of the second exhaust turbocharger.
9. The exhaust heating device for the internal combustion engine as
claimed in claim 8, wherein an opening/closing valve for
opening/closing the first exhaust passage is provided in the first
exhaust passage downstream of the branched portion of the first
exhaust passage and the second exhaust passage and upstream of the
exhaust turbine of the first exhaust turbocharger.
10. The exhaust heating device for the internal combustion engine
as claimed in claim 8, wherein the exhaust heating device includes
a fuel supply valve for supplying fuel to the second exhaust
passage, and an igniting unit for igniting and conflagrating the
fuel supplied from the fuel supply valve to the second exhaust
passage.
11. The exhaust heating device for the internal combustion engine
as claimed in claim 9, wherein the exhaust heating device includes
a fuel supply valve for supplying fuel to the second exhaust
passage, and an igniting unit for igniting and conflagrating the
fuel supplied from the fuel supply valve to the second exhaust
passage.
12. The exhaust heating device for the internal combustion engine
as claimed in claim 10, wherein an oxidation catalytic converter is
provided in the exhaust passage between the igniting unit and the
exhaust purifying device.
13. The exhaust heating device for the internal combustion engine
as claimed in claim 11, wherein an oxidation catalytic converter is
provided in the exhaust passage between the igniting unit and the
exhaust purifying device.
14. The exhaust heating device for the internal combustion engine
as claimed in claim 10, wherein in a case of igniting the fuel
using the igniting unit, an opening of the valve is regulated such
that a flow of the exhaust gas in the second exhaust passage is
less than a flow of the exhaust gas in the first exhaust
passage.
15. The exhaust heating device for the internal combustion engine
as claimed in claim 11, wherein in a case of igniting the fuel
using the igniting unit, an opening of the valve is regulated such
that a flow of the exhaust gas in the second exhaust passage is
less than a flow of the exhaust gas in the first exhaust
passage.
16. The exhaust heating device for the internal combustion engine
as claimed in claim 12, wherein in a case of igniting the fuel
using the igniting unit, an opening of the valve is regulated such
that a flow of the exhaust gas in the second exhaust passage is
less than a flow of the exhaust gas in the first exhaust
passage.
17. The exhaust heating device for the internal combustion engine
as claimed in claim 13, wherein in a case of igniting the fuel
using the igniting unit, an opening of the valve is regulated such
that a flow of the exhaust gas in the second exhaust passage is
less than a flow of the exhaust gas in the first exhaust
passage.
18. A control method of the exhaust heating device as claimed in
claim 10, comprising the steps of: determining presence/absence of
activation of the exhaust purifying device; detecting a rotational
speed of the internal combustion engine; setting an opening of the
valve based upon the detected rotational speed of the internal
combustion engine; and in a case where it is determined that the
exhaust purifying device is not activated, driving the valve to
open in the set opening for flowing the exhaust gas of a
predetermined flow in the second exhaust passage, and operating the
exhaust heating device.
19. A control method of the exhaust heating device as claimed in
claim 11, comprising the steps of: determining presence/absence of
activation of the exhaust purifying device; detecting a rotational
speed of the internal combustion engine; setting an opening of the
valve based upon the detected rotational speed of the internal
combustion engine; and in a case where it is determined that the
exhaust purifying device is not activated, driving the valve to
open in the set opening for flowing the exhaust gas of a
predetermined flow in the second exhaust passage, and operating the
exhaust heating device.
20. The control method of the exhaust heating device as claimed in
claim 18, wherein in a case where it is determined that the exhaust
purifying device is not activated, the step of driving the valve to
open in the set opening for flowing the exhaust gas of a
predetermined flow in the second exhaust passage and operating the
exhaust heating device includes a step of driving the first
opening/closing valve such that the first exhaust passage is in a
fully opened state.
21. The control method of the exhaust heating device as claimed in
claim 19, wherein in a case where it is determined that the exhaust
purifying device is not activated, the step of driving the valve to
open in the set opening for flowing the exhaust gas of a
predetermined flow in the second exhaust passage and operating the
exhaust heating device includes a step of driving the first
opening/closing valve such that the first exhaust passage is in a
fully opened state.
Description
TECHNICAL FIELD
[0001] The present invention relates to an exhaust heating device
in an internal combustion engine provided with an exhaust purifying
device, which can increase a temperature of an exhaust gas for
activation of the exhaust purifying device and for maintaining an
active state thereof.
BACKGROUND ART
[0002] A turbocharger which can relatively easily realize an
increase in output of an internal combustion engine has a tendency
of bringing in degradation of fuel consumption at the same time.
Recently in response to a strong demand for the fuel consumption
improvement in an internal combustion engine in which such a
turbocharger is incorporated, an internal combustion engine having
incorporated therein two turbochargers having different
characteristics is proposed by Patent Literature 1 or Patent
Literature 2. Any of them includes a first turbocharger functioning
primarily in a low speed range of the internal combustion engine
and a second turbocharger functioning primarily in a speed other
than the low speed range, which are arranged in series to or in
parallel to intake and exhaust passages.
[0003] Now, for meeting strict exhaust emissions regulations for an
internal combustion engine, it is necessary to accelerate
activation of an exhaust purifying device at the starting-up of the
internal combustion engine or maintain the active state thereof
during the operation of the internal combustion engine. Therefore
an internal combustion in which an exhaust heating device is
incorporated in an exhaust passage upstream of the exhaust
purifying device is proposed by Patent Literature 3 or the like.
This exhaust heating device generates heated gases in the exhaust
gas, and supplies the generated heated gas to the downstream
exhaust purifying device, thus accelerating the activation of the
exhaust purifying device or maintaining the active state thereof.
Therefore the exhaust heating device generally includes a fuel
supply valve for supplying fuel into the exhaust passage, and an
igniting device such as a glow plug for heating the fuel for
ignition, thus generating heated gases. Further, for increasing a
temperature of the heated gas, it is known also a compact oxidation
catalytic converter disposed in the exhaust passage downstream of
the igniting device. This oxidation catalytic converter includes
itself a heat-generating function and a reforming function of fuel
to a low carbon component, but differs in the configuration from an
oxidation catalytic converter used as a part of the exhaust
purifying device.
CITATION LIST
Patent Literature
[0004] PTL 1: Japanese Patent Laid-Open No. 2008-255902 [0005] PTL
2: Japanese Patent Laid-Open No. 2009-270470 [0006] PTL 3: Japanese
Patent Laid-Open No. 2006-112401
SUMMARY OF INVENTION
Technical Problem
[0007] It is apparent that an internal combustion engine that is
excellent in all of output characteristics, fuel consumption, and
clean exhaust gases will become an important technology in the
future. From this point of view, it is considered to further
incorporate the exhaust heating device in the internal combustion
engine having incorporated the aforementioned exhaust turbochargers
of a two-stage type therein.
[0008] In the exhaust heating device disclosed in Patent Literature
3, in an operating condition of the internal combustion engine in
which an intake flow becomes large, a flow speed of an exhaust gas
in the exhaust passage also increases relatively. Therefore there
is a possibility that the fuel supplied to the exhaust passage from
the fuel supply valve of the exhaust heating device can not remain
in the periphery of the igniting device, and even if the fuel is
ignited, the flame thereof is blown out by the flow of the exhaust
gas, so that unburned fuel flows into the exhaust purifying
device.
[0009] Meanwhile, in the internal combustion engine in which the
exhaust turbochargers of a two-stage type are incorporated, there
is a tendency that the exhaust flow becomes basically increased.
Further, since the exhaust gas passes through each of exhaust
turbines of the two turbochargers, an exhaust temperature largely
reduces because of heat release to an outside or a heat capacity of
the exhaust turbine itself. As a result, since the aforementioned
problem more remarkably occurs, the exhaust heating device can be
operated only at the time the exhaust flow is small, such as at
deceleration of a vehicle.
[0010] An object of the present invention is to provide an exhaust
heating device that can stably continue ignition of fuel in an
internal combustion engine in which exhaust turbochargers of a
two-stage type are incorporated.
Solution to Problem
[0011] A first aspect of the present invention is an exhaust
heating device for heating an exhaust gas fed to an exhaust
purifying device from an internal combustion engine in which a
first exhaust turbocharger and a second exhaust turbocharger used
primarily in a lower speed range of the engine than the first
turbocharger are incorporated. The exhaust heating device is
disposed in a second exhaust passage so that the exhaust heating
device is located upstream of a confluent portion of a first
exhaust passage connected through an exhaust turbine of the first
turbocharger to the purifying device and the second passage
connected through an exhaust turbine of the second turbocharger to
the purifying device in a state of bypassing the turbine of the
first turbocharger and downstream of the turbine of the second
turbocharger. A valve for regulating a flow of an exhaust gas in
the second passage is disposed in the second passage so that the
valve is located downstream of a branched portion of the first and
second exhaust passages and upstream of the turbine of the second
turbocharger.
[0012] In a case where it is necessary to operate the exhaust
heating device in the present invention, an opening of the valve is
adjusted to introduce a part of the exhaust gas to the second
passage. A heated gas generated by the operation of the exhaust
heating device mixes with an exhaust gas flowing in the first
passage at the confluent portion of the second and first passages,
which flows into the exhaust purifying device.
[0013] In the exhaust heating device for the engine according to
the first aspect of the present invention, an opening/closing valve
for opening/closing the first passage may be disposed in the first
passage so that the opening/closing valve is located downstream of
the branched portion of the first and second exhaust passages and
upstream of the turbine of the first turbocharger.
[0014] The exhaust heating device may include a fuel supply valve
for supplying fuel to the second passage, and an igniting unit for
igniting and conflagrating the fuel supplied from the fuel supply
valve to the second passage. In this case, an oxidation catalytic
converter may be further disposed in the exhaust passage between
the igniting unit and the exhaust purifying device.
[0015] In a case where the fuel is supplied from the fuel supply
valve to the second passage, an opening of the valve may be
adjusted such that a flow of the exhaust gas in the second passage
is less than a flow of the exhaust gas in the first passage.
[0016] A second aspect of the present invention is a control method
of the exhaust heating device according to the first aspect of the
present invention including the fuel supply valve for supplying
fuel to the second passage, and the igniting unit for igniting and
conflagrating the fuel supplied from the fuel supply valve to the
second passage. The control method comprises the steps of
determining presence/absence of activation of the exhaust purifying
device, detecting a rotational speed of the engine, setting an
opening of the valve based upon the detected rotational speed of
the engine, and in a case where it is determined that the exhaust
purifying device is not activated, driving the valve to open in the
set opening for flowing the exhaust gas of a predetermined flow
rate in the second passage, and operating the exhaust heating
device.
[0017] According to the present invention, in a case of an
operating condition in which the second passage can be closed, for
example, in a case where the engine is in a region other than a
low-rotation region, the opening of the valve is adjusted to
introduce the exhaust gas of a predetermined flow rate also to the
second passage, while operating the exhaust heating device. The
heated gas caused by the exhaust heating device interfluent with
the exhaust gas flowing in the first passage at the confluent
portion of the second and first passages, which flows into the
exhaust purifying device.
[0018] In the control method of the exhaust heating device
according to the second aspect of the present invention, in a case
where it is determined that the exhaust purifying device is not
activated, the step of driving the valve to open in the set opening
for flowing the exhaust gas of a predetermined flow rate in the
second passage, and operating the exhaust heating device may
include a step of driving a first opening/closing valve such that
the first passage is in a fully opened state.
Advantageous Effects of Invention
[0019] According to the present invention, also in the internal
combustion engine in which the exhaust turbocharger of the
two-stage type is incorporated, the exhaust heating device can be
stably operated by adjusting the opening of the valve. Further, the
heated gas can efficiently interfluent with the exhaust gas flowing
in the first passage at the confluent portion with the second
exhaust passage.
[0020] In a case where the opening/closing valve for
opening/closing the first passage is disposed in the first passage
downstream of the branched portion of the first and second exhaust
passages and upstream of the turbine of the first turbocharger,
efficient power boost can be performed according to the operating
condition of the engine.
[0021] In a case where the oxidation catalytic converter is
disposed in the exhaust passage between the igniting unit and the
exhaust purifying device, the heated gas can be highly increased in
temperature more efficiently.
[0022] In a case where the opening of the valve is adjusted such
that the flow of the exhaust gas in the first passage is less than
the flow of the exhaust gas in the second passage, the stable
heated gas can be more certainly generated.
[0023] In a case where the exhaust purifying device is not
activated, when the first opening/closing valve is driven such that
the first passage is in the fully opened state, the stable heated
gas can interfluent with the exhaust gas flowing in the first
passage at the confluent portion with the second exhaust
passage.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a concept diagram showing an embodiment of an
exhaust heating device in an internal combustion engine according
to the present invention;
[0025] FIG. 2 is a control block diagram of a primary part of the
embodiment shown in FIG. 1;
[0026] FIG. 3 is a graph representing a relation of an engine speed
and a turbine speed; and
[0027] FIG. 4 is a flow chart representing the control procedure of
the exhaust heating device shown in FIG. 1.
DESCRIPTION OF EMBODIMENTS
[0028] An embodiment in which the present invention is applied to
an internal combustion engine of a compression-ignition type will
be in detail explained with reference to FIG. 1 to FIG. 4. However,
the present invention is not limited to this embodiment, and the
configuration can be freely altered according to required
characteristics. The present invention is effective also for a
spark-ignition internal combustion engine in which, for example,
gasoline, alcohol or LNG (liquid natural gas) is used as fuel and
the fuel is ignited by a spark plug.
[0029] FIG. 1 diametrically shows a primary part of an engine
system in the present embodiment, and FIG. 2 shows a control block
diagram thereof, wherein a valve-operating mechanism for intake and
exhaust valves, an EGR device and the like are omitted in
illustration for simplified purposes. An engine 10 in the present
embodiment is a multi-cylinder internal combustion engine (in the
illustrated example, four cylinders) of a compression-ignition type
that causes spontaneous ignition by directly injecting light oil as
fuel within a combustion chamber 12 in a compressed state from a
fuel injection valve 11. However, a single-cylinder internal
combustion engine may be adopted in view of the attribution of the
present invention. The quantity and the injection timing of the
fuel supplied in the combustion chamber 12 from the fuel injection
valve 11 are controlled based upon an opening of an accelerator
pedal 13 by a driver and an operating condition of a vehicle by an
ECU (Electric Control Unit) 14. The opening of the accelerator
pedal 13 is detected by an accelerator position sensor 15, and the
detection information is outputted to the ECU 14, which is used for
setting an injection quantity of the fuel from the fuel injection
valve 11 and so forth.
[0030] An intake pipe 17 connected through an intake manifold 16 to
the engine 10 defines an intake passage 18 together with the intake
manifold 16, and includes a branched portion 19d and a confluent
portion 19c to a branched intake pipe 19 at the upstream side and
the downstream side. That is, both the ends of the branched intake
pipe 19 are connected to the intake pipe 17 at the upstream
branched portion 19d and at the downstream confluent portion 19c in
the intake passage 18. In other words, a portion of the intake pipe
17 positioned between the upstream branched portion 19d and the
downstream confluent portion 19c in the intake passage 18 and the
branched intake pipe 19 are in a state of being arranged in
parallel. In the present embodiment, the portion defined by the
branched intake pipe 19 is called a first intake passage 18f for
convenience in writing, and the portion defined by the intake pipe
17 positioned between the upstream branched portion 19d and the
downstream confluent portion 19c in the intake passage 18 is called
a second intake passage 18s.
[0031] An airflow meter 20 and an intake temperature sensor 21 are
mounted to the intake pipe 17 upstream of the upstream branched
portion 19d in the intake passage 18, and information regarding an
intake flow rate and an intake temperature detected by these
sensors is outputted to the ECU 14. The ECU 14 makes correction of
the injection quantity of the fuel from the fuel injection valve 11
based upon the detection information from the airflow meter 20 and
the intake temperature sensor 21 and so forth.
[0032] The intake pipe 17 downstream of the downstream confluent
portion 19c in the intake passage 18 is provided with an
intercooler 22 cooling intake air for increasing a charge density
of the intake air flowing in the intake passage 18 and a throttle
valve 23 for adjusting an opening of the intake passage 18. The
throttle valve 23 in the present embodiment is mechanically linked
to an opening of the accelerator pedal 13 a depressing amount of
which is adjusted by a driver, but it is possible to adopt a
throttle valve an opening of which can be electrically corrected
according to an operating condition of a vehicle, without
mentioning.
[0033] An exhaust pipe 25 connected through an exhaust manifold 24
to the engine 10 defines an exhaust passage 26 together with the
exhaust manifold 24, and includes a branched portion 26d and a
confluent portion 26c in regard to a pair of branched exhaust pipes
27 and 28 arranged in parallel in the exhaust pipe 25. That is,
both the ends of the pair of the branched exhaust pipes 27 and 28
are connected to the exhaust pipe 25 at the upstream branched
portion 26d and the downstream confluent portion 26c in the exhaust
passage 26. In the present embodiment, a portion defined by the one
branched exhaust pipe 27 corresponds to a first exhaust passage 27f
in the present invention and a portion defined by the other
branched exhaust pipe 28 corresponds to a second exhaust passage
28s in the present invention.
[0034] A first exhaust turbocharger (hereinafter, described simply
as a first turbocharger) 29 is arranged across the first intake
passage 18f and the first exhaust passage 27f, and a compressor 29a
thereof is positioned in the first intake passage 18f, and an
exhaust turbine 29b is positioned in the first exhaust passage 27f.
In addition, a second turbocharger 30 used primarily in a lower
speed range of the engine 10 than the first turbocharger 29 is
arranged across the second intake passage 18s and the second
exhaust passage 28s. A compressor 30a of the second turbocharger 30
is positioned in the second intake passage 18s, and an exhaust
turbine 30b thereof is positioned in the second exhaust passage
28s. Therefore the second exhaust passage 28s branched from the
upstream branched portion 26d joins with the first exhaust passage
27f at the downstream confluent portion 26c through the exhaust
turbine 30b of the second turbocharger 30 in a state of bypassing
the exhaust turbine 29b of the first turbocharger 29. An exhaust
purifying device 31 is installed to the exhaust pipe 25 positioned
downstream of the downstream confluent portion 26c in the exhaust
passage 26.
[0035] An intake opening/closing valve 32 for opening/closing the
first intake passage 18f is disposed in the first intake passage
18f downstream of the compressor 29a in the first turbocharger 29
and upstream of the branched portion 19d. An opening/closing valve
driving motor 33 is connected to the intake opening/closing valve
32, and the ECU 14 controls an operation of the opening/closing
valve driving motor 33 according to an operating condition of a
vehicle to switch an opening/closing operation of the intake
opening/closing valve 32. Basically in a case where an engine
speed, that is, an engine rotation number N.sub.n per unit time is
equal or more than a rotation number N.sub.R in which the first
turbocharger 29 starts to achieve a turbocharging capability
(hereinafter, described as a turbocharged state determining speed),
the intake opening/closing valve 32 becomes in a fully opened
state. In reverse, in a case where the engine speed N.sub.n is less
than the turbocharged state determining speed N.sub.R, the intake
opening/closing valve 32 is controlled to be in a substantially
closed state. Therefore a crank angle position of the engine 10 is
detected by a crank angle sensor 34, and the detection information
is outputted to the ECU 14. The ECU 14 calculates an engine speed
N.sub.n based upon the information from the crank angle sensor
34.
[0036] Similarly, an exhaust opening/closing valve 35 for
opening/closing the first exhaust passage 27f is disposed in the
first exhaust passage 27f upstream of the exhaust turbine 29b of
the first turbocharger 29 and downstream of the branched portion
26d. The aforementioned opening/closing valve driving motor 33 is
connected to the exhaust opening/closing valve 35 in the present
embodiment together with the intake opening/closing valve 32, and
the exhaust opening/closing valve 35 is configured to open/close
the first exhaust passage 27f to be substantially linked to the
opening/closing operation of the intake opening/closing valve 32.
However, an actuator may be independently connected to the exhaust
opening/closing valve 35 to open/close the first exhaust passage
27f independently of the opening/closing operation of the intake
opening/closing valve 32.
[0037] A flow regulating valve 36 for regulating a flow of an
exhaust gas in the second exhaust passage 28s is disposed in the
second exhaust passage 28s upstream of the exhaust turbine 29b of
the first turbocharger 29 and downstream of the branched portion
26d. In addition, a valve opening sensor 37 is attached to the flow
regulating valve 36 for detecting an opening thereof, and the
detection information is outputted to the ECU 14. A regulation
valve driving motor 38 which an operation thereof is controlled by
the ECU 14 is also connected to the flow regulating valve 36, and
the opening is adjusted based upon an operating condition of a
vehicle and the detection information from the valve opening sensor
37.
[0038] Characteristics of the first and second turbochargers 29 and
30 in the present embodiment are shown in FIG. 3. The first
turbocharger 29 having a relatively large inertia mass does not
almost have the turbocharging capability in a region in which the
engine speed N.sub.n is less than the turbocharged state
determining speed N.sub.R. In contrast, the second turbocharger 30
having a relatively small inertia mass is configured to achieve the
turbocharging capability from a region of a low engine speed in
which the first turbocharger 29 does not work.
[0039] Therefore the ECU 14, in a case where the engine speed
N.sub.n is less than the supercharging-state determination rotation
number N.sub.R, holds the intake opening/closing valve 32 and the
exhaust opening/closing valve 35 in a fully closed state and
basically holds the flow regulating valve 36 in a substantially
fully opened state. Accordingly the intake and exhaust gases flow
in the second intake passage 18s and the second exhaust passage
28s. In reverse, in a case where the engine speed N.sub.n is equal
to or more than the turbocharged state determining speed N.sub.R,
the ECU 14 holds the intake opening/closing valve 32 and the
exhaust opening/closing valve 35 in a fully opened state and
basically holds the flow regulating valve 36 in a fully closed
state. Accordingly the intake and exhaust gases flow in the first
intake passage 18f and the first exhaust passage 27f.
[0040] An exhaust heating device 39 is disposed in the second
exhaust passage 28s upstream of the confluent portion 26c of the
first exhaust passage 27f and the second exhaust passage 28s and
downstream of the exhaust turbine 30b of the second turbocharger
30. The exhaust heating device 39 generates heated gases and
supplies the heated gas to the exhaust purifying device 31 disposed
in the downstream side to maintain the activation and the active
state. The exhaust heating device 39 in the present embodiment is
provided with a fuel supply valve 40, a glow plug 41 as an igniting
unit in the present invention and an auxiliary oxidation catalytic
converter 42 in that order from the upstream side.
[0041] The fuel supply valve 40 supplies fuel in the second exhaust
passage 28s, and the supply timing and the supply quantity of the
fuel are controlled by the ECU 14 based upon presence/absence of
the active state of the exhaust purifying device 31 and the
operating condition of the vehicle. The supply operation of the
fuel from the fuel supply valve 40 into the second exhaust passage
28s is performed in a case where the exhaust purifying device 31 is
in an inactive state. Accordingly even in an operating condition
where it is not necessary to introduce an exhaust gas in the second
exhaust passage 28s, that is, in an operating condition where it is
not necessary to cause the second turbocharger 30 to function, the
exhaust heating device 39 is operated as needed. In addition, even
in a case where an exhaust gas is introduced to the second exhaust
passage 28s to cause the second turbocharger 29 to function, the
exhaust heating device 39 is operated as needed.
[0042] The glow plug 41, in a case where the fuel supplied in the
second exhaust passage 28s from the fuel supply valve 40 does not
cause spontaneous ignition, is provided for igniting the fuel. The
glow plug 41 is connected to a direct current source (not shown)
for supplying power thereto and a booster circuit, and a surface
temperature thereof is controlled by the ECU 14. It should be noted
that a ceramic heater may be used as the igniting unit in the
present invention instead of the glow plug 41.
[0043] The auxiliary oxidation catalytic converter 42 is disposed
in the exhaust passage 26 between the glow plug 41 and the exhaust
purifying device 31. In the present embodiment, the auxiliary
oxidation catalytic converter 42 is disposed in the second exhaust
passage 28s upstream of the confluent portion 26c, but may be
disposed in the exhaust passage 26 downstream of the confluent
portion 26c. The auxiliary oxidation catalytic converter 42 has a
cross-section area smaller than that of the second exhaust passage
28s, which therefore enables apart of the exhaust gas to pass
without flowing in the auxiliary oxidation catalytic converter 42.
That is, a flow speed of the exhaust gas passing through the
auxiliary oxidation catalytic converter 42 is lower than that of
the exhaust gas not passing through that, making it possible to
further increase a temperature of the exhaust gas passing through
the auxiliary oxidation catalytic converter 42. In a case where the
auxiliary oxidation catalytic converter 42 is sufficiently
increased in temperature, that is, is activated, it is possible to
cut the power supply to the glow plug 41 for directly burning a
mixture in the auxiliary oxidation catalytic converter 42. However,
in a case where the auxiliary oxidation catalytic converter 42 is
not activated, such as at a cold start of the engine 10, it is
necessary to supply power to the glow plug 41. It should be noted
that as the auxiliary oxidation catalytic converter 42 becomes high
in temperature, a hydrocarbon having a large carbon number in the
unburned mixture is decomposed to be reformed to a hydrocarbon
having a small carbon number and high reactivity. In other words,
the auxiliary oxidation catalytic converter 42 is, on the one hand,
functions as a rapid heat generator itself rapidly generating heat,
and on the other hand, functions also as a fuel reform catalyst
generating the reformed fuel. In the present embodiment, there is
provided an auxiliary temperature sensor 43 which detects a
temperature of the auxiliary oxidation catalytic converter 42 and
outputs the detected temperature to the ECU 14, wherein
presence/absence of the power supply to the glow plug 41 is
determined based upon the detection information from the auxiliary
temperature sensor 43 by the ECU 14.
[0044] In this way, the heated gas is generated in the second
exhaust passage 28s, the high-temperature exhaust gas passes
through the auxiliary oxidation catalytic converter 42 to be
increased further in temperature, and the unburned gas is also
burned by the auxiliary oxidation catalytic converter 42 or
reformed to a hydrocarbon having high activity. Then theses gases
mix with the exhaust gas flowing in the first exhaust passage 27f
at the confluent portion 26c, which are supplied to the exhaust
purifying device 31. As a result, it is possible to quickly perform
the activation of the exhaust purifying device 31 and perform
maintenance of the active state thereof even at the time when a
vehicle is travelling.
[0045] It should be noted that for increasing ignitability of the
fuel injected in the second exhaust passage 28s from the fuel
supply valve 40, it is effective to provide a plate-shaped
vaporization promoting member to oppose the fuel supply valve 40
and the glow plug 41. The vaporization promoting member has a
function that the fuel injected from the fuel supply valve 42
collides therewith to spread out, thus promoting atomization of the
fuel, that is, vaporization thereof.
[0046] The exhaust purifying device 31 serves to make harmful
substances generated by combustion of the mixture in the combustion
chamber 12 harmless. The exhaust purifying device 31 in the present
embodiment is provided with an oxidation catalytic converter 44, a
three-way catalytic converter and a NO.sub.x catalytic converter in
that order from the upstream side of the exhaust passage 26, but
only the oxidation catalytic converter 44 disposed at the most
upstream side end is illustrated for the sake of clarity. A
catalyst temperature sensor 45 is incorporated in the oxidation
catalytic converter 44 for detecting a temperature thereof and
outputting the detected temperature to the ECU 14.
[0047] The ECU 14 controls the intake opening/closing valve 32 and
the exhaust opening/closing valve 35, and the flow regulating valve
36 or the exhaust heating device 39, that is, operations of the
fuel supply valve 40 and the glow plug 41, based upon an operating
condition of a vehicle and detection signals from the auxiliary
temperature sensor 43 and the catalyst temperature sensor 45. The
control to these components is performed according to preset
programs as follows. That is, in a case where a temperature T.sub.n
of the oxidation catalytic converter 44 (hereinafter described as a
catalyst temperature) is less than a temperature T.sub.R as an
index of activation of the oxidation catalytic converter 44
(hereinafter described as an activation index temperature), based
upon the detection signal from the catalyst temperature sensor 45,
it is determined that the exhaust purifying device 31 is not
activated, thereby operating the exhaust heating device 39. In
reverse, in a case where the catalyst temperature T.sub.n is equal
to or more than the activation index temperature T.sub.R, it is
determined that the exhaust purifying device 31 is activated,
thereby stopping the operation of the exhaust heating device 39. In
addition, in a case where a temperature T.sub.Sn of the auxiliary
oxidation catalytic converter 42 (hereinafter described as an
auxiliary catalyst temperature) is less than a temperature T.sub.SR
as an index of activation of the auxiliary oxidation catalytic
converter 42 (hereinafter described as an activation index
temperature), it is determined that the auxiliary oxidation
catalytic converter 42 is not activated, thereby supplying power to
the glow plug 41. In reverse, in a case where the auxiliary
catalyst temperature T.sub.Sn is equal to or more than the
activation index temperature T.sub.SR, it is determined that the
auxiliary oxidation catalytic converter 42 is activated, thereby
stopping the power supply to the glow plug 41. On the other hand,
in a case of operating the exhaust heating device 39 in a state
where the engine speed N.sub.n is equal to or more than the
turbocharged state determining speed N.sub.R, for achieving the
supercharging pressure required, the flow regulating valve 36 is
held in a slightly opened state while holding the opening/closing
valve 32 in a fully opened state, and also an opening of the
opening/closing valve 35 is controlled. In this way, the
introduction of a part of the exhaust gas to the second exhaust
passage 28s enables the fuel to be ignited and prevents the
misfiring (as an example, characteristics are shown as an arrow
view A in FIG. 3). In reverse, in a state where the engine speed
N.sub.n is less than the turbocharged state determining speed
N.sub.R, there is a possibility that in a state where the flow
controlling valve 36 is held in a fully opened state, the fuel
supplied to the second exhaust passage 28s and ignited therein is
misfired. Accordingly in this case, the opening/closing valve 32 is
switched from the fully closed state to the fully opened state, the
flow regulating valve 36 is held in a slightly opened state from
the fully opened state, and the opening of the opening/closing
valve 35 is controlled, thus introducing the required quantity of
the exhaust gas to the second exhaust passage 27s. Thereby a large
part of the exhaust gas is introduced to the first exhaust passage
27f to prevent occurrence of the misfiring of the fuel supplied to
the second exhaust passage 28s (as an example, characteristics are
shown as an arrow view B in FIG. 3).
[0048] In this way, the opening of the aforementioned flow
regulating valve 36 is regulated such that the fuel supplied from
the fuel supply valve 40 in the aforementioned exhaust heating
device 39 to the second exhaust passage 28s is not misfired. That
is, the flow of the exhaust gas introduced to the second exhaust
passage 28s is made less than the flow of the exhaust gas in the
first exhaust passage 27f. More specifically the opening of the
flow regulating valve 36 is set through a regulation valve driving
motor 38 by the ECU 14 such that the exhaust gas having the flow
speed to the extent that the flame caused by ignition of the fuel
in the second exhaust passage 28s is not misfired flows in the
second exhaust passage 28s. Thereby a predetermined flow rate of
the exhaust gas to the extent that the misfiring does not occur can
be made to flow in the second exhaust passage 28s, and the heated
gas obtained by the exhaust heating device 39 can be fed to the
exhaust purifying device 31.
[0049] The control procedure of such an exhaust heating device 39
is shown in a flow chart of FIG. 4. That is, in a step of S11, it
is determined whether or not the temperature T.sub.n of the
oxidation catalytic converter 44 detected by the catalyst
temperature sensor 45 is less than the activation determination
reference temperature T.sub.R. Here, in a case where it is
determined that since the temperature T.sub.n of the oxidation
catalytic converter 44 is equal to or more than the activation
determination reference temperature T.sub.R, that is, since the
exhaust purifying device 31 is activated, it is not necessary to
operate the exhaust heating device 39, the determining process in a
step of S11 continues to be performed without any processing. In
addition, in a case where it is determined in a step of S11 that
since the temperature T.sub.n of the oxidation catalytic converter
44 is less than the activation determination reference temperature
T.sub.R, that is, since the exhaust purifying device 31 is in an
inactive state, it is necessary to operate the exhaust heating
device 39, the process goes to a step of S12. In a step of S12, it
is determined whether or not the temperature T.sub.Sn of the
auxiliary oxidation catalytic converter 42 detected by the
auxiliary temperature sensor 43 is less than the activation
determination reference temperature T.sub.SR. Here, in a case where
it is determined that since the temperature T.sub.Sn of the
auxiliary oxidation catalytic converter is less than the activation
determination reference temperature T.sub.SR, that is, since the
auxiliary oxidation catalytic converter 42 is in an inactive state,
it is necessary to supply power to the glow plug 41, the process
goes to a step of S13. In a step of S13, it is determined whether
or not a flag for supplying the power to the glow plug 41 is set.
Since at first this flag is not set, the process goes to a step of
S14, wherein the flag is set and in a step S15, the power supply to
the glow plug 41 is performed, and in a step of S15, the opening of
the flow regulating valve 36 is set based upon the engine speed
N.sub.n.
[0050] For example, in a state where the engine speed N.sub.n is
less than the turbocharged state determining speed N.sub.R, the
flow regulating valve 36 is in a fully opened state and the
opening/closing valves 32 and 35 are in a fully closed state.
Therefore in a case where the fuel supplied to the second exhaust
passage 28s is ignited by the glow plug 41, the flow regulating
valve 36 is throttled from the fully opened state such that the
flow speed of the exhaust gas becomes a flow speed to the extent
that the ignited fuel is not misfired, and the opening/closing
valves 32 and 35 are switched to a fully opened state. Thereby the
flow of the exhaust gas in the second exhaust passage 28s is
throttled and the remaining exhaust gas is introduced to the first
exhaust passage 27f. In addition, in a state where the engine speed
N.sub.n is equal to or more than the turbocharged state determining
speed N.sub.R, the flow regulating valve 36 is in a fully closed
state, and the opening/closing valves 32 and 35 are in a fully
opened state. Therefore in order that the fuel supplied to the
second exhaust passage 28s can be ignited, the flow regulating
valve 36 is slightly opened from the fully closed state, and the
opening of the opening/closing valve 35 is controlled, thus
introducing the required quantity of the exhaust gas also to the
second exhaust passage 27s.
[0051] Next, in a step of S17 the fuel is injected to the second
exhaust passage 28s from the fuel supply valve 40. Thereby the fuel
is ignited in the second exhaust passage 28s in which the exhaust
gas slightly flows, and the obtained heated gas is further
increased in temperature by the auxiliary oxidation catalytic
converter 42. In addition, the heated gas interfluent with the
exhaust gas flowing from the confluent portion 26c with the first
exhaust passage 27f at the confluent portion 26c, which is led to
the exhaust purifying device 31 to increase a temperature of the
exhaust purifying device 31. Next, in a step of S18 it is
determined whether or not the temperature T.sub.n of the oxidation
catalytic converter 44 detected by the catalyst temperature sensor
45 is equal to or more than the activation determination reference
temperature T.sub.R. Here, in a case where it is determined that
since the temperature T.sub.n of the oxidation catalytic converter
44 is less than the activation determination reference temperature
T.sub.R, that is, since the oxidation catalytic converter 44 is in
an inactive state, it is necessary to continue the operation of the
exhaust heating device 39, the process goes back to a step of S12,
wherein the previous process is repeated. In addition, in a case
where it is determined that since the temperature T.sub.n of the
oxidation catalytic converter 44 is equal to or more than the
activation determination reference temperature T.sub.R, that is,
since the oxidation catalytic converter 44 becomes in an active
state, it is necessary to stop the operation of the exhaust heating
device 39, the process goes to a step of S19. In a step of S19 it
is determined whether or not the flag is set. In a case where it is
determined that the flag is set, in a step of S20 the power supply
to the glow plug 41 is stopped, and next, in a step of S21 the flag
is reset. After that, in a step of S22 supply of the fuel from the
fuel supply valve 40 is stopped and the valve opening control in a
step of S16 is finished, and the process again returns to the
determination step of S11. As a result, the opening/closing state
of each of the opening/closing valves 32 and 35 and the flow
regulating valve 36 is controlled such that the first and second
turbochargers 29 and 30 operate the most efficiently in response to
the engine speed N.sub.n.
[0052] On the other hand, in a case where it is determined that the
flag is set in the previous step of S13, that is, in a case where
it is determined that the glow plug 41 is in a power-supplied
state, the process goes to a step of S16 as it is, wherein the
operation of the exhaust heating device 39 continues.
[0053] In a case where in the previous step of S12 it is determined
that since the temperature T.sub.Sn of the auxiliary oxidation
catalytic converter 42 is equal to or more than the activation
determination reference temperature T.sub.SR, that is, since the
auxiliary oxidation catalytic converter 42 is in an active state,
it is not necessary to perform the power supply to the glow plug
41, the process goes to a step of S23. In a step of S23 it is
determined whether or not the flag is set. In a case where it is
determined that the flag is set, that is, in a case where it is
determined that the power supply to the glow plug 41 is performed,
the process goes to a step of S24, wherein the power supply to the
glow plug 41 is stopped, and next, in a step of S21 the flag is
reset. After that, the process goes to the previous step of S16,
wherein the operation of the exhaust heating device 39 continues.
On the other hand, in a case where it is determined that the flag
is not set in a step of S23, that is, in a case where it is
determined that the glow plug 41 is in a non-power supply state,
the process goes to a step of S16 as it is, wherein the operation
of the exhaust heating device 39 continues.
[0054] It should be noted that the present invention should be
interpreted only by the matters described in claims, and in the
above-described embodiment, it is possible to perform all changes
and modifications contained in the concept of the present invention
other than the described matters. That is, all the matters in the
above-described embodiment should not be the limitation to the
present invention, and, including all configurations not related
directly to the present invention, can be arbitrarily changed
according to its application and purpose.
REFERENCE SIGNS LIST
[0055] 10 Engine [0056] 11 Fuel injection valve [0057] 12
Combustion chamber [0058] 13 Accelerator pedal [0059] 14 ECU [0060]
15 Accelerator position sensor [0061] 16 Intake manifold [0062] 17
Intake pipe [0063] 18 Intake passage [0064] 18f First intake
passage [0065] 18s Second intake passage [0066] 19 Intake bypass
passage [0067] 20 Intake bypass pipe [0068] 20d Branched portion
[0069] 20c confluent portion [0070] 21 Airflow meter [0071] 22
Intake temperature sensor [0072] 23 Intercooler [0073] 24 Throttle
valve [0074] 25 Intake bypass valve [0075] 26 Bypass valve driving
motor [0076] 27 Exhaust passage [0077] 27f First exhaust passage
[0078] 27s Second exhaust passage [0079] 28 Exhaust pipe [0080] 29
First exhaust bypass passage [0081] 30 First exhaust bypass pipe
[0082] 30d Branched portion [0083] 30c Confluent portion [0084] 31
First exhaust bypass valve [0085] 32 Second exhaust bypass passage
[0086] 33 Second exhaust bypass pipe [0087] 33d Branched portion
[0088] 33c Confluent portion [0089] 34 Second exhaust bypass valve
[0090] 35 Second bypass valve driving motor [0091] 36 First
turbocharger [0092] 36a Compressor [0093] 36b Exhaust turbine
[0094] 37 Second turbocharger [0095] 37a Compressor [0096] 37b
Exhaust turbine [0097] 38 Exhaust purifying device [0098] 39
Oxidation catalytic converter [0099] 40 Catalyst temperature sensor
[0100] 41 Flow regulating valve [0101] 42 Valve opening sensor
[0102] 43 Regulation valve driving motor [0103] 44 Exhaust heating
device [0104] 45 Fuel supply valve [0105] 46 Glow plug [0106] 47
Auxiliary oxidation catalytic converter [0107] 48 Auxiliary
temperature sensor [0108] 49 Crank angle sensor [0109] N.sub.n
Engine speed [0110] N.sub.R Turbocharged state determining speed
[0111] T.sub.R Catalyst temperature [0112] T.sub.R Activation index
temperature [0113] T.sub.Sn Auxiliary catalyst temperature [0114]
T.sub.SR Activation index temperature
* * * * *