U.S. patent application number 11/808233 was filed with the patent office on 2007-12-13 for exhaust purifying apparatus of an internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Takuji Matsubara.
Application Number | 20070283684 11/808233 |
Document ID | / |
Family ID | 38820502 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070283684 |
Kind Code |
A1 |
Matsubara; Takuji |
December 13, 2007 |
Exhaust purifying apparatus of an internal combustion engine
Abstract
An exhaust purifying apparatus has an adsorbent capable of
adsorbing hydrocarbons in an exhaust passage of an internal
combustion engine, estimates the temperature of the adsorbent by
repeated processing to estimate the current value by adding an
added value to the previous estimated value, and changes the added
value in response to the intake air amount and the ignition timing
of the internal combustion engine.
Inventors: |
Matsubara; Takuji;
(Nagoya-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
TOYOTA-SHI
JP
|
Family ID: |
38820502 |
Appl. No.: |
11/808233 |
Filed: |
June 7, 2007 |
Current U.S.
Class: |
60/285 ; 60/274;
60/297; 60/324 |
Current CPC
Class: |
F01N 3/0835 20130101;
F01N 3/0814 20130101; F01N 13/017 20140601; F01N 3/0878
20130101 |
Class at
Publication: |
60/285 ; 60/274;
60/324; 60/297 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 7/00 20060101 F01N007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2006 |
JP |
2006-158288 |
Claims
1. An exhaust purifying apparatus of an internal combustion engine
comprising: an adsorbent that adsorbs a hydrocarbon in an exhaust
passage of the internal combustion engine; a temperature estimation
part that estimates a temperature of the adsorbent by repeating
processing wherein an added value is added to the previous
estimated value to obtain the current estimated value; and an added
value calculation part that calculates the added value to change
the added value based on an intake air amount and an ignition
timing of the internal combustion engine.
2. The exhaust purifying apparatus of the internal combustion
engine according to claim 1, further comprising: a valve mechanism,
provided in the exhaust passage, that changes an opening amount to
change the passage condition of exhaust toward the adsorbent,
wherein the added value calculation part calculates the added value
to change the added value based on the opening amount of the valve
mechanism.
3. The exhaust purifying apparatus of the internal combustion
engine according to claim 2, wherein the exhaust passage has a
multiple structure partitioned into a first passage disposed in the
central part and a second passage disposed to surround an outer
periphery of the first passage and to provide the adsorbent, and
wherein the valve mechanism provided upstream from the multiple
structure is structured to limit exhaust flowing into the first
passage, and is structured to change an opening amount between a
fully closed position that allows exhaust to flow into the second
passage and a fully open position that allows exhaust to flow into
both the first passage and the second passage.
4. The exhaust purifying apparatus of the internal combustion
engine according to claim 3, further comprising: a driving
apparatus that drives the valve mechanism to change the opening
amount of the valve mechanism, wherein the valve mechanism
maintains an arbitrary opening amount between the fully closed
position and the fully open position.
5. The exhaust purifying apparatus of the internal combustion
engine according to claim 2, wherein the added value calculation
part calculates the added value using a weighting coefficient based
on the opening amount of the valve mechanism.
6. The exhaust purifying apparatus of the internal combustion
engine according to claim 4, wherein the added value calculation
part calculates the added value using a weighting coefficient based
on the opening amount of the valve mechanism.
7. The exhaust purifying apparatus of the internal combustion
engine according to claim 1, wherein the internal combustion engine
is provided in a prescribed vehicle as one of a plurality of
driving power sources for running, and the vehicle is configured to
be runnable with only a driving power source for running other than
the internal combustion engine, and wherein the temperature
estimation part estimates the temperature of the adsorbent when the
internal combustion engine is in the stopped condition by
successive subtraction of the subtracted value from the estimated
temperature at the time the drive of internal combustion engine is
stopped, and includes a subtracted value calculation part wherein
the subtracted value is calculated considering a running condition
of the vehicle when the internal combustion engine is in the
stopped condition.
8. The exhaust purifying apparatus of the internal combustion
engine according to claim 1, further comprising: a time-keeping
apparatus that measures a stopped time up to a subsequent start
time of the internal combustion engine as the starting point of the
time during which the drive of the internal combustion engine is
stopped; and a starting time temperature estimation part that
estimates the temperature of the adsorbent at the starting time of
the internal combustion engine based on the measured by the
time-keeping apparatus, wherein the temperature estimation part
uses the estimation result from the starting time temperature
estimation part as an initial value before adding the added
valued.
9. The exhaust purifying apparatus of the internal combustion
engine according to claim 1, wherein the temperature estimation
part, in the case in which the temperature of the estimation result
by the starting time temperature estimation part is lower than that
of an intake air, the temperature of the intake air instead of the
estimation result is used as the initial value.
10. A method of controlling of an exhaust purifying apparatus for
an internal combustion engine comprising: calculating an initial
value as a temperature estimation base of an adsorbent that adsorbs
a hydrocarbon in an exhaust passage of the internal combustion
engine; acquiring an amount of intake air taken into the internal
combustion engine; acquiring an ignition timing of the internal
combustion engine; calculating an added value based on the intake
air amount and the ignition timing; estimating the temperature of
an adsorbent by adding the added value to the initial value; and
controlling an exhaust purifying apparatus based on the estimated
temperature of the adsorbent.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2006-158288 filed on Jun. 7, 2006 including the specification,
drawing, and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exhaust purifying
apparatus of an internal combustion engine providing an adsorbent
capable of adsorbing hydrocarbons in an exhaust passage.
[0004] 2. Description of the Related Art
[0005] In an internal combustion engine, at the time of a cold
start, for example, there are cases in which a catalytic converter
provided in an exhaust passage does not reach the activation
temperature, making it impossible to purify hydrocarbons in the
exhaust passage. For this reason, in a conventional method, a
hydrocarbon adsorbent (hereinafter referred to simply as an
adsorbent) capable of adsorbing hydrocarbons in a prescribed
temperature range is provided to suppress a worsening of exhaust
emissions before the catalytic converter reaches the activation
temperature. The adsorption performance of such an adsorbent
exhibits a temperature dependency, and when a prescribed upper
temperature limit is exceeded, adsorbed hydrocarbons are desorbed.
The adsorbent also exhibits a change in the amount of hydrocarbons
that can be adsorbed dependent on the temperature. For this reason,
the accurate determination of the temperature of the adsorbent is
important in efficiently adsorbing hydrocarbons.
[0006] For example, there is a conventional exhaust purifying
apparatus (Japanese Patent Application Publication No. 10-331625)
in which temperature sensors are provided in both the input port of
and on the inside of the adsorbent to detect the exhaust
temperature at the input port and the temperature inside the
adsorbent, the adsorbed heat occurring in the adsorbent being
calculated in accordance with the difference between the detection
results and a predicted temperature of the adsorbent to calculate
the amount of adsorbed hydrocarbons. There is also a conventional
apparatus (Japanese Patent Application Publication No. 2000-54829)
that predicts the temperature of the adsorbent by determining the
temperature of the exhaust gas based on a prescribed map, using the
internal combustion engine load and engine rpm as parameters, and
also successively determines an appropriately weighted moving
average of the exhaust gas temperature.
[0007] The apparatus of Japanese Patent Application Publication No.
10-331625 requires additional parts such as temperature sensors to
detect the temperature of the adsorbent, and the additional parts
require space and time, and incur costs. Because the apparatus of
Japanese Patent Application Publication No. JP-A-2000-54829
estimates the temperature of the adsorbent based on a moving
average of the exhaust temperature, the quantitative change in the
exhaust gas is not reflected in the estimated temperature
results.
SUMMARY OF THE INVENTION
[0008] The present invention has an object to provide an exhaust
purifying apparatus in an internal combustion engine that does not
require an additional part for detecting a temperature of an
adsorbent, resulting in reduction of space, time, and cost for
detecting the temperature, and that obtains estimated results of
the temperature in which the quantitative change of the exhaust gas
is reflected.
[0009] The exhaust purifying apparatus of the internal combustion
engine according to a first aspect of the present invention
provides an adsorbent adsorbing hydrocarbons in an exhaust passage
of the internal combustion engine; a temperature estimation part
estimating a temperature of the adsorbent by repeating processing
wherein an added value is added to the previous estimated value to
obtain the current estimated value; and an added value calculation
part calculating the added value to change the added value based on
an intake air amount and an ignition timing of the internal
combustion engine.
[0010] According to the present aspect of the exhaust purifying
apparatus, the added value is calculated based on the intake air
amount and the ignition timing, and the added value is added to the
previous estimated value, thereby estimating the temperature of the
adsorbent. It is therefore possible, without preparing additional
parts, such as a temperature sensor, to estimate the temperature of
the adsorbent and reduce space, time, and cost for detecting the
temperature. Furthermore, for a given span of temperature of the
exhaust gas, when the amount of exhaust gas varies, the span of the
temperature rise of the adsorbent also varies. According to the
exhaust purifying apparatus of this aspect, because the added value
is calculated based on the ignition timing and the intake air
amount, the quantitative change of the exhaust gas can be reflected
in the estimated results.
[0011] According to the first aspect of the present invention, the
exhaust purifying apparatus further has a valve mechanism that is
provided in the exhaust passage, changing an opening amount to
change the passage condition of exhaust gas toward the adsorbent.
The added value calculation part may calculate the added value to
change the added value based on the opening amount of the valve
mechanism. Since adsorption performance of the adsorbent depends on
a temperature, by changing the passage condition of the exhaust gas
using the valve mechanism responsive to the change of the adsorbent
performance, hydrocarbons can be efficiently adsorbed. In this
case, the passage condition of the exhaust gas changes by changing
the opening amount of the valve mechanism, thereby changing an
amount of heat which the adsorbent receives from the exhaust gas.
In this aspect, the added value based on the opening amount of the
valve mechanism changes, resulting in the further improvement in
the accuracy of estimating the temperature of the adsorbent.
[0012] In order to change the passage condition of the exhaust gas
toward the adsorbent using the valve mechanism, various aspects can
be adopted. For example, a bypass passage that bypasses the
adsorbent may be provided in the exhaust passage and the limitation
and the allowance of the exhaust gas flowing into the bypass
passage may be switchable by the change of the opening amount of
the valve mechanism. The exhaust passage may have a multiple
structure partitioned into a first passage disposed in the central
part and a second passage disposed to surround an outer periphery
of the first passage and to provide the adsorbent. In this case,
the valve mechanism provided upstream from the multiple structure
may be structured to limit exhaust gas flowing into the first
passage, and to change an opening amount between a fully closed
position that allows exhaust gas to flow into the second passage
and a fully open position that allows exhaust gas to flow into both
the first passage and the second passage.
[0013] In the latter case of the foregoing aspects, when the valve
mechanism is in the fully closed position, because the exhaust gas
flowing into the first passage is limited and the exhaust gas is
allowed to flow into the second passage, in which the adsorbent is
disposed, the adsorbent receives heat directly from the exhaust
gas. In contrast, when the valve mechanism is in the fully open
position, because the flow of exhaust gas into both the first
passage and the second passage is allowed, the adsorbent receives
less heat directly from the exhaust gas, resulting in receiving
most heat indirectly via the first passage. By calculating the
added value based on the change of the opening amount of the valve
mechanism, because the change of the amount of heat received by the
adsorbent according to the change of the opening amount of the
valve mechanism is considered, the accuracy of estimating the
temperature of the adsorbent is improved.
[0014] In these aspects, there is no particular limitation with
regard to the calculation of the added value based on the change of
opening amount of the valve mechanism. The added value calculation
part, for example, may calculate the added value using a weighting
coefficient based on the opening amount of the valve mechanism. If
the added value based on at least one opening amount is set in
advance, the added value of the other opening amounts can be
obtained by multiplying the added value by the weighting
coefficient. Because it is not necessary to set the added values
for every opening amount, the processing is simplified.
[0015] In the exhaust purifying apparatus of the internal
combustion engine according to the first aspect of the present
invention, the internal combustion engine may be provided in a
vehicle as one of a plurality of driving power sources for running,
and the vehicle may be configured to be runnable with only a
driving power source for running other than the internal combustion
engine. The temperature estimation part may estimate the
temperature of the adsorbent when the internal combustion engine is
in the stopped condition by successive subtraction of the
subtracted value from the estimated temperature at the time the
drive of internal combustion engine is stopped, and may further
include a subtracted value calculation part wherein the subtracted
value is calculated considering a running condition of the vehicle
when the internal combustion engine is in the stopped condition.
The vehicle that has a plurality of driving power sources for
running including the internal combustion engine, and that is
configured to be runnable with only a driving power source for
running other than the internal combustion engine includes a
so-called hybrid vehicle. This type of vehicle can run using
another driving power source even if the internal combustion engine
is stopped. In the case in which the internal combustion engine is
stopped, because the exhaust gas is not discharged the temperature
of the adsorbent is gradually decreased with the elapse of time. In
the case in which the internal combustion engine is stopped and the
vehicle is running, compared with the case in which the internal
combustion engine is stopped and the vehicle is stationary, the
temperature decrease of the adsorbent is accelerated by wind during
running. According to the present aspect, because the subtracted
value is calculated considering the running condition of the
vehicle, the adsorbent temperature can be accurately estimated.
[0016] According to the present aspect of the exhaust purifying
apparatus of the internal combustion engine may determine an
initial value as a base of estimation of a temperature using any
method, for example, by further providing a time-keeping apparatus
measuring a stopped time up to a subsequent start time of the
internal combustion engine as the starting point of the time during
which the drive of the internal combustion engine is stopped; and a
starting time temperature estimation part estimating the
temperature of the adsorbent at the starting time of the internal
combustion engine based on the stopped time measured by the
time-keeping apparatus, wherein the temperature estimation part may
use the estimation results from the starting time temperature
estimation part as the initial value before adding the added
valued. The longer the time in which the internal combustion engine
is stopped becomes, the lower the temperature of the adsorbent
becomes. According to this aspect, the temperature of the adsorbent
at the starting time of the internal combustion engine is estimated
considering a stopped time, a starting time temperature of the
estimated results is used as the initial value. The deviation
between the estimated temperature and the actual temperature can
therefore be reduced. In this case, in the case in which the
temperature of the estimated results by the starting time the
temperature estimation part becomes lower than that of an intake
air, the temperature estimation part may use the intake temperature
as the initial value in place of the estimated results. By
foregoing processing, it is possible to avoid the problem of using
the estimated temperature that is lower than the intake temperature
at the starting time as the initial value, resulting in a further
improvement in the accuracy of estimating the temperature of the
adsorbent after restarting.
[0017] As described in the above, according to the present
invention, the added value is calculated based on the intake air
amount and the ignition timing to be successively added to the
prescribed initial value, thereby estimating the temperature of the
adsorbent. Without preparing additional parts, such as a
temperature sensor, the temperature of the adsorbent can be
estimated and space, time, and cost for detecting a temperature can
be reduced. Because the added value is calculated based on the
ignition timing and the intake air amount, the quantitative change
of the exhaust gas can be reflected the estimated results.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and further objects, features, and advantages
of the invention will become apparent from the following
description of preferred embodiments with reference to the
accompanying drawings, wherein like numerals are used to represent
like elements, and wherein:
[0019] FIG. 1 is a drawing showing an internal combustion engine
provided with an exhaust purifying apparatus according to a first
embodiment of the present invention;
[0020] FIG. 2 is a drawing showing details of a rear purifying
apparatus of FIG. 1 in which a switching valve is a fully closed
position;
[0021] FIG. 3 is a drawing showing details of a rear purifying
apparatus of FIG. 1 in which a switching valve is a fully open
position;
[0022] FIG. 4 is a flowchart showing an example of temperature
estimation processing according to a first embodiment;
[0023] FIG. 5 is a drawing describing an example of a map giving an
additional value .DELTA.T (ads) with an intake air amount and
ignition timing as variables;
[0024] FIG. 6 is a flowchart showing another replaceable example
into a step S7 of FIG. 4;
[0025] FIG. 7 is a flowchart showing an example of processing
executed in preparation for a restart after stopping of an internal
combustion engine;
[0026] FIG. 8 is a flowchart showing an example of processing
calculating an initial value T0 (ads) as a base of an estimated
temperature in FIG. 4;
[0027] FIG. 9 is a drawing describing an example of a map giving a
temperature estimated value T (soak) with an estimation counter T
(ads) and a soak time as variables;
[0028] FIG. 10 is a flowchart showing another example of processing
calculating an initial value T0 (ads);
[0029] FIG. 11 is a drawing showing an internal combustion engine
provided with an exhaust purifying apparatus according to a second
embodiment of the present invention;
[0030] FIG. 12 is a flowchart showing an example of temperature
estimation processing according to the second embodiment;
[0031] FIG. 13 is a drawing describing an example of a map
associating a weighting efficient k with a switching valve opening
amount;
[0032] FIG. 14 is a flowchart showing an example of a temperature
estimation processing of an adsorbent according to a third
embodiment;
[0033] FIG. 15 is a drawing describing an example of a map giving a
subtracted value .DELTA.T (stop) with an estimation counter T (ads)
and a stop time as variables; and
[0034] FIG. 16 is a drawing describing an example of a map giving a
subtracted value .DELTA.T (run) with an estimation counter T (ads)
and a vehicle speed as variables.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] FIG. 1 shows a first embodiment of an internal combustion
engine provided with a purifying apparatus according to the present
invention. The internal combustion engine 1 in FIG. 1 mounted
aboard a vehicle as a drive power source for running provides an
engine body 3 having a plurality of cylinders 2 (four cylinders in
FIG. 1), an intake passage 4 and an exhaust passage 5 connected to
each cylinder 2, and an exhaust purifying apparatus 6. An air flow
meter 21 that outputs a signal based on an amount of intake air is
provided in the intake passage 4. The exhaust purifying apparatus 6
includes a front purifying apparatus 7 mounted in the exhaust
passage 5 and a rear purifying apparatus 8 mounted downstream from
the exhaust passage 5. The front purifying apparatus 7 is used for
preventing toxic substances from being exhausted before the rear
purifying apparatus 8 is activated, for example when the internal
combustion engine 1 is started, and is structured, for example, as
a three-way catalytic converter in which the volume is set to be
smaller than that of the rear purifying apparatus 8.
[0036] As shown in FIG. 2 and FIG. 3, the rear purifying apparatus
8 has a casing 81 that forms a part of the exhaust passage 5, a
first passage 82 disposed in a central part of the casing 81, and a
second passage 83 disposed to surround an outer periphery of the
first passage 82. By doing this, a multiple structure 50 is
partitioned into the first passage 82 and the second passage 83 in
the exhaust passage 5. Both ends of the second passage 83 are
turned to open toward upstream from the exhaust passage 5,
specifically, toward an intake of the first passage 82. The
three-way catalytic converter 85 is provided in the first passage
82, and a hydrocarbon adsorbent 86 (hereinafter sometimes referred
to simply as an adsorbent) is disposed in the second passage 83.
The adsorbent 86 adsorbs hydrocarbons in a prescribed temperature
range and desorbs the hydrocarbons adsorbed at a high temperature
beyond the prescribed temperature range.
[0037] The rear purifying apparatus 8 is provided upstream from the
casing 81, that is, upstream from the multiple structure 50, and
further includes a switching valve 84 as the valve mechanism to
change the exhaust flow in the casing 81. The switching valve 84 is
structured to enable changing of the opening amount between a fully
closed position shown in FIG. 2 and a fully open position shown in
FIG. 3, thereby changing the state of the passage of exhaust gas
toward the adsorbent 86. Specifically, in the rear purifying
apparatus 8, when the switching valve 84 is fully closed, because
the exhaust gas flowing into the first passage 82 is limited, and
the flow of exhaust gas into the second passage 83 is allowed, the
exhaust gas passes through the second passage 83 and then the first
passage 82, as shown by the arrow in FIG. 2. On the other hand,
when the switching valve 84 is fully open, because exhaust gas is
allowed to flow into both the first passage 82 and the second
passage 83, exhaust gas passes through both the first passage 82
and the second passage 83, as shown by the arrow in FIG. 3. When
the switching valve 84 is in fully open position, however, the
direction of exhaust gas passing through the second passage 83 is
in the direction opposite from the case of the fully closed
position. Exhaust gas guided into the second passage 83 passes
through the first passage 82 after passing through the second
passage 83.
[0038] The rear purifying apparatus 8 has a diaphragm mechanism 87
for driving the switching valve 84 as shown in FIG. 1. The
diaphragm mechanism 87 is connected to the switching valve 84 via
the operating rod 88, and the inside of the diaphragm mechanism 87
is partitioned by a diaphragm 87a into a variable pressure chamber
87b and an atmospheric pressure chamber 87c, the internal pressure
of which is held at atmospheric pressure. The operating rod 88 is
linked to the diaphragm 87a. The diaphragm mechanism 87 places the
switching valve 84 in the fully closed position when the pressure
in the variable pressure chamber 87b is adjusted to be lower than
the atmospheric pressure, and places the switching valve 84 in the
fully open position when the pressure in the variable pressure
chamber 87b is adjusted to the atmospheric pressure. The variable
pressure chamber 87b and the intake passage 4 are connected by a
negative pressure passage 89, which is provided with a check valve
90 and a three-way valve 91. The check valve 90 is a unidirectional
valve that allows the flow of air from the variable pressure
chamber 87b toward the intake passage 4 in the case in which the
pressure in the intake passage 4 is lower than that in the variable
pressure chamber 87b. The three-way valve 91 provides communication
between the variable pressure chamber 87b and the intake passage 4,
and switches between the negative pressure introduction location a,
which guides the negative pressure of the intake passage 4 toward
the variable pressure chamber 87b, and the atmospheric open
position b introducing atmospheric pressure into the variable
pressure chamber 87b while blocking the communication between the
variable pressure chamber 87b and the intake passage 4. By doing
this, in the case in which the three-way valve 91 is switched to
the negative pressure introduction position a, the switching valve
84 is switched to the fully closed position, and in the case in
which the three-way valve 91 is switched to the atmospheric open
position b, the switching valve 84 is switched to the fully open
position. That is, in the embodiment shown in FIG. 1, the diaphragm
mechanism 87 switches the switching valve 84 selectively between
the fully closed position and the fully open position.
[0039] The opening amount control of the switching valve 84 is
performed by an electric control unit (ECU) 20 that controls the
operating condition of the internal combustion engine 1. The ECU 20
is a computer, which includes a microprocessor and peripheral
devices such as RAM and ROM necessary for the operation thereof.
The ECU 20 performs various control based on input information from
various sensors. In the control related to the exhaust purifying
apparatus according to this embodiment of the present invention,
when for example the temperature of the three-way catalytic
converter 85 provided in rear purifying apparatus 8 is lower than
the activation temperature, the ECU 20 switches the three-way valve
91 to the negative pressure introduction position a so that the
switching valve 84 is switched to the fully closed position. By
doing this, because the exhaust gas is guided into the three-way
catalytic converter 85 after the hydrocarbons of the exhaust gas
are adsorbed by the adsorbent, flow of hydrocarbons into an
inactivated three-way catalytic converter 85 is prevented, thereby
enabling prevention of a worsening of exhaust emissions.
[0040] The hydrocarbon adsorbing performing of the adsorbent 86
exhibits temperature dependency. For this reason, if the upper
limit of a prescribed temperature range in which the adsorbent 86
can adsorb is exceeded, adsorbed hydrocarbons are desorbed. In
order to efficiently adsorb hydrocarbons, therefore, it is
necessary to accurately determine the performance of the adsorbent
86, that is, the temperature of the adsorbent 86. For this reason,
the ECU 20 executes the temperature estimation processing described
below.
[0041] FIG. 4 is a flowchart showing an example of temperature
estimation processing executed by the ECU 20. The processing
program is stored in a ROM of the ECU 20, which reads out the
program when appropriate and repeats execution of the program at a
prescribed time interval. First, at step S1, the ECU 20 determines
whether there is a starting operation. The time of the start of
operation is, for example, the time of an operation by an operator
turning an ignition switch from off to on to indicate an intention
to start, at which point the ECU 20 determines the existence or
non-existence of such operation. In the case in which a starting
operation has occurred, processing proceeds to step S2, and if
there was no starting operation, steps S2 and S3 are skipped, and
processing proceeds to step S4.
[0042] At step S2, the value to serve as the base for temperature
estimation of the adsorbent 86, that is, the previous initial value
T0 (ads) before adding the added value, to be described below, is
calculated. The initial value T0 (ads) can be a physical quantity
correlated to the temperature of the adsorbent 86. For example,
this can be calculated by estimation from the cooling water
temperature of the internal combustion engine 1, and can also be
calculated by the initial value calculation processing to be
described later. Next, at step S3, the initial value T0 (ads)
calculated at step S2 is substituted into an estimation counter T
(ads) provided as a variable for storing the estimated temperature
value of the adsorbent 86.
[0043] At step S4, determination is performed of whether the
internal combustion engine 1 is operating. For example, if there is
a starting operation but the internal combustion engine 1 has not
yet started, or there is no starting operation and the internal
combustion engine 1 is stopped, the subsequent processing is
skipped and the current processing is ended. In the case in which
the internal combustion engine 1 is operating, processing proceeds
to step S5, at which the intake air amount is obtained based on a
signal from an air flow meter 21, and then step S6, at which the
ignition timing is acquired. The ECU 20 executes an ignition timing
control routine in parallel with this processing to set the
ignition timing in response to the operating condition of the
internal combustion engine 1. At step S6 the timing set by this
ignition timing control is acquired.
[0044] Next, at step S7, an added value .DELTA.T (ads)
corresponding to the span of temperature rise of the adsorbent 86
responsive to the processing execution period is calculated. The
added value .DELTA.T (ads) is calculated considering the intake air
amount acquired at step S5 and the ignition timing acquired at step
S6. Because the greater the intake air amount is, the greater is
the amount (more precisely, the flow amount) of exhaust gas, the
greater is the thermal energy of the exhaust gas. For this reason,
compared to the case in which the intake air amount is small, when
the intake air amount is large there is an increase in the amount
of heat received by the adsorbent 86 from the exhaust gas, and the
span of temperature rise per unit time becomes large. Also, because
the more the ignition timing is retarded, that is, the more it
approaches the retard angle side, the more non-combusted fuel there
is, combustion of the non-combusted fuel being promoted within the
exhaust passage, the higher is the exhaust gas temperature. For
this reason, compared to the case in which the ignition timing is
advanced, when the ignition timing is retarded the amount of heat
received by the adsorbent 86 from the exhaust gas increases,
resulting in an increase in the span of temperature rise per unit
time.
[0045] The calculation of the added value .DELTA.T (ads) reflecting
the above points can be implemented by an appropriate method. For
example, the ECU 20 can store beforehand a map such as shown in
FIG. 5, which gives the added value .DELTA.T (ads) with the intake
air amount and the ignition timing as variables, and can reference
the map to calculate an appropriate added value .DELTA.T (ads). The
map shown in FIG. 5 is constituted so that, the greater is the
intake air amount and the more retarded is the ignition timing, the
larger is the added value .DELTA.T (ads) that is given.
[0046] Next, at step S8 the added value .DELTA.T (ads) is added to
the current estimation counter T (ads) to update the estimation
counter T (ads), at which point the current processing is ended. By
repeating the foregoing processing, the added value .DELTA.T (ads)
is added to the previous estimated value to obtain the current
estimated value. By doing this, it is possible to accurately
estimate the temperature of the adsorbent 86 and, in this
embodiment in particular, the temperature of the adsorbent 86
during the process of a temperature rise.
[0047] FIG. 6 is a flowchart showing another example of the
calculation processing (step S7) for calculating the added value
.DELTA.T (ads) of FIG. 4. In this example, the opening amount of
the switching valve 84 is considered when calculating the added
value .DELTA.T (ads). In this case, in order to calculate the added
value .DELTA.T (ads) a fully closed position map and a fully open
position map are prepared, and a map is selected that is
appropriate to the opening amount of the switching valve 84. That
is, as shown in FIG. 6, at step S71 the ECU 20 determines whether
the opening amount of the switching valve 84 is the fully closed
position and, in the case of the fully closed position, processing
proceeds to step S72, at which the fully closed position map is
selected. In the case of a position other than the fully closed
position, that is, in the case of the fully open position,
processing proceeds to step S73, at which the fully open position
map is selected. Then, at step S74, the added value .DELTA.T (ads)
is calculated by referencing the selected map.
[0048] Although the foregoing maps are not illustrated, they are
constituted to show the same trend as shown by the map shown in
FIG. 5. That is, the maps are constituted to give a larger added
value .DELTA.T (ads), the larger is the intake air amount and the
more retarded is the ignition timing. If these maps are compared,
it is seen that, for the same intake air amount and ignition timing
conditions, the added value .DELTA.T (ads) given by the fully
closed position map is larger than the added value .DELTA.T (ads)
given by the fully open position map. In the case in which the
switching valve 84 is in the fully closed position, the adsorbent
86 receives heat directly from the exhaust gas. In contrast, in the
case of the fully open position, the heat directly received from
the exhaust gas decreases, and the heat indirectly received via the
first passage 82 increases. As a result, for the same intake air
amount and ignition timing conditions, compared to the case of the
fully open position, in the case of the fully closed position the
span of temperature rise of the adsorbent 86 is greater.
[0049] Other processing executed by the ECU 20 is now described,
with reference being made to FIG. 7 through FIG. 10. FIG. 7 shows
the processing executed to prepare for restarting after stopping of
the internal combustion engine 1. The processing program of FIG. 7
is stored in the ROM of the ECU 20, which reads out the program
when appropriate and repeats execution of the program at a
prescribed time interval. First, at step S11, the ECU 20 determines
whether the internal combustion engine 1 is stopped. For example,
it is possible to determine whether the internal combustion engine
1 is stopped by detecting the operation of an operator turning an
ignition switch from on to off to indicate an intention to stop, or
by detecting that the rpm speed of the internal combustion engine 1
is zero based on a signal from a crank angle sensor (not
illustrated). When it is determined that the internal combustion
engine 1 is stopped, processing proceeds to step S12, and when the
determination of stopping is not made subsequent processing is
skipped and the current processing is ended.
[0050] At step S12, the estimation counter T (ads) at the current
point in processing is stored. The estimation counter T (ads) is
used in the processing of FIG. 4. By doing this, the estimated
temperature value of the adsorbent 86 at the point in processing at
step S12 is stored. Next, at step S13, a soak timer provided within
the ECU 20 for measuring the stopped time (soak time) until the
next time the internal combustion engine 1 is started with the
point at which the internal combustion engine 1 was stopped as the
starting point, is caused to operate. By doing this, the soak time
measurement starts and the processing of FIG. 7 ends. After the
soak timer has started operating, the measurement of the soak time
continues until a prescribed operation stopping condition is
satisfied.
[0051] FIG. 8 shows the processing of calculating the initial value
T0 (ads) that serves as the base for the temperature estimation of
FIG. 4, in which the processing results from FIG. 7, that is, the
estimation counter T (ads) at the time of stopping and the soak
timer measured value (soak time) are used. The program for the
processing of FIG. 8 is also stored in the ROM of the ECU 20, which
reads out the program when appropriate and repeats execution of the
program at a prescribed time interval. First, at step S21 the ECU
20 determines the existence of a starting operation and, if there
is a starting operation, processing proceeds to step S22, but if
there is not starting operation subsequent processing is skipped
and the current processing is ended.
[0052] At step S22, the estimation counter T (ads) stored at step
S12 is acquired. At the following step S23, the measured value of
the soak timer, that is, the soak time, is acquired. Next, at step
S24 the estimated temperature value T (soak) at the time of
restarting is calculated, based on the estimation counter T (ads)
acquired at step S22, that is, the estimated temperature value of
the adsorbent 86 at the previous time of stopping of the internal
combustion engine 1, and based on the soak time acquired at step
S23. The calculation of the estimated value T (soak) can be
implemented, for example, as shown in FIG. 9, by referencing a map
that gives the estimated temperature value T (soak) with the
estimation counter T (ads) and the soak time as variables. The map
of FIG. 9 gives an estimated temperature value (soak) so that the
span of decrease in the estimated value of temperature at the time
of stopping is larger, the longer is the soak time, and also so
that the span of decrease for a given soak time is larger, the
higher is the estimated temperature at the previous time of
stopping. Next, at step S25, the estimated temperature value T
(soak) calculated at step S24 is set as the initial value T0 (ads),
and the processing of FIG. 8 ends.
[0053] By the foregoing processing, when estimating the temperature
of the adsorbent 86 by the processing of FIG. 4, it is possible to
use the initial value T0 (ads) obtained by the processing of FIG.
8. Because the initial value T0 (ads) takes the soak time into
consideration, the deviation between the actual temperature and the
estimation results in the processing of FIG. 4 can be reduced.
[0054] Next, another example of the processing to calculate the
initial value T0 (ads) is described, with reference made to FIG.
10. In FIG. 10, processing parts that are the same as in FIG. 8 is
assigned the same numerals and are described explicitly herein. The
processing program is stored in the ROM of the ECU 20, which reads
out the program when appropriate and repeats execution of the
program at a prescribed time interval. The processing of FIG. 10 is
the processing of FIG. 8 with the processing of steps S26 to S28
added. That is, when the temperature estimated value T (soak) is
calculated at step S24, at the following step S26 the intake
temperature tha is acquired. The intake temperature tha is acquired
based on a signal from an intake temperature sensor (not
illustrated). Next, at step S27 determination is made of whether
the temperature estimated value T (soak) is higher than the intake
temperature tha. If the temperature estimated value T (soak) is
higher than the intake temperature tha, processing proceeds to step
S25, at which temperature estimated value T (soak) is set as the
initial value T0 (ads), whereupon processing ends. However, if the
temperature estimated value T (soak) is not higher than the intake
temperature tha, that is, if the temperature estimated value (soak)
is lower than the intake temperature tha, processing proceeds to
step S28, at which the intake temperature tha is set as the initial
value T0 (ads), whereupon processing ends.
[0055] By the foregoing processing, when estimating the temperature
of the adsorbent 86 by the processing of FIG. 4, it is possible to
use the initial value T0 (ads) obtained by the processing of FIG.
10. That is, in the case in which the temperature estimated value T
(soak) is lower than the intake temperature tha, it is possible to
use the intake temperature tha as the initial value in place of the
temperature estimated value T (soak). Therefore, even in the case
in which the temperature estimated value T (soak) of the adsorbent
86 has decreases to lower than the intake temperature, because it
is possible to avoid the problem of using the estimated value T
(soak) as the initial value in the processing of FIG. 4, resulting
in a further improvement in the accuracy of estimating the
temperature of the adsorbent 86 after restarting.
[0056] Next, the second embodiment of an exhaust purifying
apparatus according to the present invention will be described.
FIG. 11 shows an internal combustion engine 1 in which the exhaust
purifying apparatus according to the second embodiment has been
provided. The second embodiment, with the exception of a mechanism
that performs switching of the switching valve 84, has the same
constitution as the embodiment shown in FIG. 1. In the following,
elements that are the same as in the first embodiment as assigned
the same numerals and are not repeatedly described herein. As shown
in FIG. 11, the switching valve 84 is driven by a rotary actuator
287 serving as a driving apparatus. The rotary actuator 287 is
structured to enabling holding of the switching valve 84 at any
position between the fully closed position and the fully open
position. The rotary actuator 287 incorporates therewithin a
rotational position sensor 287a such as a resolver, capable of
detecting the rotational position, that is, the opening amount of
the switching valve 84.
[0057] In this embodiment, because the opening amount of the
switching valve 84 can be freely set, compared to the embodiment in
which the exhaust gas condition of passing to the adsorbent 86 is
switched between the fully open position and the fully closed
position, as in the first embodiment, it is possible to establish a
various conditions responsive to particular situations. The ECU 20
controls the operation of the rotary actuator 287, and the signal
from the rotational position sensor 287a is input to the ECU
20.
[0058] FIG. 12 is a flowchart showing the processing in the second
embodiment. The program for this processing is stored in the ROM of
the ECU 20, which reads out the program when appropriate and
repeats execution of the program at a prescribed time interval. The
only difference between the processing shown in FIG. 12 and the
processing in the first embodiment is the method of calculating the
added value .DELTA.T (ads). Specifically, step S7 of FIG. 4 is
replaced by steps S31 through S35 in the processing of FIG. 12.
Processing parts that are the same as in FIG. 4 is assigned the
same numerals and are not repeated described herein.
[0059] As shown in FIG. 12, after acquiring the ignition timing at
step S6, the opening amount of the switching valve is acquired at
step S31. The acquisition of the opening amount is performed based
on a signal from the rotational position sensor 287a within the
rotary actuator 287. Next, at step S32, the added value .DELTA.T
(close) corresponding to the fully closed position is calculated
and, at step S33, the added value .DELTA.T (open) corresponding to
the fully open position is calculated. The calculations of the
added values .DELTA.T (close) and .DELTA.T (open) can be
implemented by using maps that are the same as the maps used at
step S72 and step S73 in FIG. 6.
[0060] Next, at step S34, the weighting coefficient k corresponding
to the opening amount of the switching valve 84 is calculated. The
characteristic of the weighting coefficient k is set with
consideration given to the temperature change of the adsorbent 86
with respect to the opening amount of the switching valve 84. For
example, as shown in FIG. 13, it is possible to create a map that
associates the weighting coefficient k with the opening amount of
the switching valve 84, and to reference the map to calculate the
weighting coefficient k corresponding to the opening amount. Next,
at step S35, the calculated weighting coefficient k is used to
calculate the added value .DELTA.T (ads) corresponding to the
opening amount of the switching valve 84. In this embodiment,
because the weighting coefficient k is set in the range from 0 to
1, with the fully closed position as a reference, the added value
.DELTA.T (ads) is calculated by the following equation.
T(ads).rarw..DELTA.T(close).times.k+.DELTA.T(open).times.(1-k)
[0061] In the processing of FIG. 12, if a map that associates the
added value .DELTA.T (ads) with the intake air amount and the
ignition timing is prepared for at least one opening amount, and if
the weighting coefficient is set with that opening amount as a
reference, it is possible to calculate the added value .DELTA.T
(ads) corresponding to an opening amount without preparing maps for
each opening amount. It is possible, therefore, to reduce the
amount of storage capacity needed in the ECU 20.
[0062] Next, the third embodiment of an exhaust purifying apparatus
of the present invention will be described. In this embodiment, the
internal combustion engine 1 shown in FIG. 1 and FIG. 11 is mounted
aboard a so-called hybrid vehicle. In the hybrid vehicle, in
addition to an internal combustion engine, another driving power
source for running, such as a motor-generator, is installed, and
the structure enables appropriate distribution of the driving power
for running between the driving power of the internal combustion
engine and the other driving power source. This distribution is set
in response to various conditions, and there are cases in which,
under specific conditions, the internal combustion engine is
stopped and running is done with a different power source or
running is done with only the internal combustion engine.
[0063] In a conventional vehicle aboard which an internal
combustion engine is mounted, with the exception of unusual
operation, for example, when the engine is stopped but the vehicle
is running on momentum, when the internal combustion engine is
stopped, the vehicle is also stationary. For this reason, the major
cause of a drop in temperature of the adsorbent provided in the
exhaust system is natural heat radiation. In a hybrid vehicle,
however, because running is possible even with the internal
combustion engine stopped, added to natural heat radiation is the
amount of cooling caused by running wind. Given this, in the third
embodiment the accuracy of estimating the temperature decrease of
the adsorbent 86 is increased by considering the running condition
of the vehicle. Also, unless otherwise noted, the processing in the
foregoing embodiments may be executed in the third embodiment as
well.
[0064] FIG. 14 is a flowchart showing the processing to estimate
the temperature of the adsorbent 86 according to the third
embodiment. First, at step S81, the ECU 20 acquires the estimation
counter T (ads). The estimation counter T (ads) is the same as used
in the processing of FIG. 4. Next, processing proceeds to step S82,
at which a determination is made of whether the internal combustion
engine 1 is stopped. If the internal combustion engine 1 is
stopped, processing proceeds to step S83, at which the stopped time
of the internal combustion engine 1 is calculated. The stopped time
is calculated based on the count value of the stopped time counter
provided as a variable to manage the stopped time in the ECU
20.
[0065] Next, at step S84, the subtracted time .DELTA.T (stop) in
the stopped time of the internal combustion engine 1 is calculated.
The subtracted time .DELTA.T (stop) corresponds to the span of
temperature decrease of the adsorbent 86 by natural radiation
during a processing time period. The calculation can be performed,
for example, as shown in FIG. 15, by referencing a map that gives
the subtracted value .DELTA.T (stop) with the estimation counter T
(ads) and the stopped time as variables. The map shown in FIG. 15
is structured to give values of the subtraction value .DELTA.T
(stop) that are larger the longer is the stopped time and the
higher is the value of the estimation counter T (ads).
[0066] However, if the internal combustion engine 1 is not stopped
at step S82, that is, if the internal combustion engine 1 is
operating, processing proceeds to step S89, at which the stopped
time counter is cleared, after which, at step S90, zero is
substituted into the subtraction value .DELTA.T (stop) and
processing proceeds to step S85. This is done because in the case
in which the internal combustion engine 1 is operating there is no
decrease in temperature caused by natural heat radiation.
[0067] At step S85 a determination is made of whether the vehicle
is running. If it is running, processing proceeds to step S86, at
which the vehicle speed is acquired. The determination of whether
the vehicle is running and the acquisition of the vehicle speed are
performed based on a signal from a vehicle speed sensor (not
illustrated) provided in the vehicle. Next, at step S87, the
subtracted value .DELTA.T (run) when the vehicle is running is
calculated. The subtracted value .DELTA.T (run) corresponds to the
span of temperature decrease of the adsorbent 86 by running wind,
responsive to the time period of processing. This calculation can
be implemented, for example as shown in FIG. 16, by referencing a
map giving the subtracted value .DELTA.T (run) with the estimation
counter T (ads) and the vehicle speed as variables. The map shown
in FIG. 16 gives values of the subtraction value .DELTA.T (run)
that are larger the faster is the vehicle speed and the higher is
the value of the estimation counter T (ads).
[0068] However, if vehicle is not running at step S85, because
there is no need to consider the running wind, processing proceeds
to step S91, at which point zero is substituted into the subtracted
value .DELTA.T (run) and processing proceeds to step S88.
[0069] At step S88, the subtracted values .DELTA.T (stop) and
.DELTA.T (run) are each added to the current estimation counter
value T (ads) to update the estimation counter T (ads), this ending
the current processing. By the processing of FIG. 14, even in the
case in which the internal combustion engine 1 is stopped and the
vehicle is running, it is possible to accurately estimate the
temperature of the adsorbent 86.
[0070] In the foregoing embodiments, the switching valve 84 and the
diaphragm mechanism 87 or rotary actuator 287 may serve as the
valve mechanism of the present invention. Also, the soak timer
provided in the ECU 20 may serve as the time-keeping apparatus of
the present invention.
[0071] The ECU 20 may repeatedly execute the processing of FIG. 4
and FIG. 12 or repeatedly execute these processing parts in
parallel with executing the processing of FIG. 14, or may execute
the processing of step S25 in FIG. 8 or the processing of steps S25
and S28 in FIG. 10 to implement the function of the temperature
estimation part of the present invention. The ECU 20 may execute
step S7 of FIG. 4, the processing of FIG. 6 and steps S31 to S35 of
FIG. 12 to implement the function of the added value calculation
part of the present invention. Also, the ECU 20 may execute step
S87 of FIG. 14 to implement the function of the subtracted value
calculation part of the present invention. The ECU 20 may execute
step S24 of FIG. 8 or FIG. 10 to implement the function of the
starting time temperature estimation part of the present
invention.
[0072] It will be noted, however, that the present invention is not
restricted to the foregoing embodiment, and can be embodied in a
variety of forms. The constitution of the exhaust purifying
apparatus of the present invention is not restricted to the
embodiments shown in FIG. 1 and FIG. 11. For example, in addition
to providing a bypass passage that bypasses the adsorbent in the
exhaust passage, an embodiment may be structured so that the
limitation or allowing of the exhaust gas to flow into the bypass
passage is switched by changing the opening amount of the valve
mechanism.
[0073] While the invention has been described with reference to
example embodiments thereof, it is to be understood that the
invention is not limited to the example embodiments and
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the example embodiment are shown in
various combinations and configurations, which are exemplary, other
combinations and configurations, including more, fewer, or only a
single element, are also within the sprit and scope of the
invention.
* * * * *