U.S. patent application number 12/149333 was filed with the patent office on 2008-12-04 for exhaust gas purification device for internal combustion engine.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Tsukasa Kuboshima, Tsutomu Soga, Shigeto Yahata.
Application Number | 20080295491 12/149333 |
Document ID | / |
Family ID | 39917521 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080295491 |
Kind Code |
A1 |
Kuboshima; Tsukasa ; et
al. |
December 4, 2008 |
Exhaust gas purification device for internal combustion engine
Abstract
An exhaust gas purification device of a diesel engine having a
DPF (diesel particulate filter) for collecting particulate matters
such as soot and unburned components from exhaust gas of the diesel
engine calculates an oil dilution quantity as a quantity of fuel
diluting engine oil from a regeneration time of the DPF and an
operation state. The exhaust gas purification device alleviates an
increase in the oil dilution quantity by using a regeneration
device that causes the oil dilution quantity less than the oil
dilution quantity caused by another regeneration device when the
oil dilution quantity exceeds a predetermined value. Thus, both of
suppression of the oil dilution quantity and inhibition of
deterioration of fuel consumption due to post-injection can be
achieved.
Inventors: |
Kuboshima; Tsukasa;
(Okazaki-city, JP) ; Yahata; Shigeto; (Obu-city,
JP) ; Soga; Tsutomu; (Kariya-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
39917521 |
Appl. No.: |
12/149333 |
Filed: |
April 30, 2008 |
Current U.S.
Class: |
60/285 |
Current CPC
Class: |
F02D 41/402 20130101;
Y02T 10/47 20130101; F02D 41/405 20130101; F02D 2200/0812 20130101;
F02D 2250/11 20130101; F01N 2430/06 20130101; Y02T 10/40 20130101;
F01M 1/18 20130101; F01N 3/025 20130101; F01M 2001/165 20130101;
Y02T 10/44 20130101; F01N 9/002 20130101; F02D 41/029 20130101 |
Class at
Publication: |
60/285 |
International
Class: |
F01N 9/00 20060101
F01N009/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2007 |
JP |
2007-144844 |
Claims
1. An exhaust gas purification device of an internal combustion
engine having a diesel particulate filter for collecting
particulate matters contained in exhaust gas of the engine, the
exhaust gas purification device comprising: a controller that
controls operation of the exhaust gas purification device; a
particulate matter deposition quantity measurement section that
measures a deposition quantity of the particulate matters in the
diesel particulate filter; a particulate matter deposition quantity
determination device that determines whether the deposition
quantity of the particulate matters measured by the particulate
matter deposition quantity measurement section is greater than a
first predetermined value; an oil dilution related data measurement
device that measures oil dilution related data necessary for
deriving an oil dilution quantity as a quantity of fuel diluting
engine oil; an oil dilution related data determination device that
determines whether the oil dilution related data measured by the
oil dilution related data measurement device is greater than a
second predetermined value; and a regeneration device that combusts
the particulate matters to regenerate the diesel particulate
filter, the regeneration device including a first regeneration
device and a second regeneration device, which causes the oil
dilution quantity less than the oil dilution quantity cause by the
first regeneration device and causes a fuel consumption rate
greater than the fuel consumption rate caused by the first
regeneration device, wherein the controller has a selection device,
the selection device selects the first regeneration device from the
two regeneration devices when the particulate matter deposition
quantity determination device determines that the particulate
matters greater than the first predetermined value in quantity are
deposited in the diesel particulate filter and the oil dilution
related data determination device determines that the measured oil
dilution related data is lower than the second predetermined value,
and the selection device selects the second regeneration device
from the two regeneration devices when the particulate matter
deposition quantity determination device determines that the
particulate matters greater than the first predetermined value in
quantity are deposited in the diesel particulate filter and the oil
dilution related data determination device determines that the
measured oil dilution related data is higher than the second
predetermined value.
2. The exhaust gas purification device as in claim 1, wherein the
first regeneration device performs post-injection for injecting the
fuel in an expansion stroke, and the second regeneration device
performs the post-injection at injection timing advanced from
injection timing in the case of the first regeneration device in
the expansion stroke.
3. The exhaust gas purification device as in claim 1, wherein the
post-injection is performed as a plurality of injections performed
in a plurality of times during the expansion stroke.
4. The exhaust gas purification device as in claim 1, wherein the
oil dilution related data measurement device measures the oil
dilution related data from vehicle speed and a travel distance in a
period in which the first regeneration device or the second
regeneration device is operated or from the vehicle speed and a
travel time in a period in which the first regeneration device or
the second regeneration device is operated.
5. The exhaust gas purification device as in claim 1, wherein the
oil dilution related data measurement device measures the oil
dilution related data from a duration in which the first
regeneration device or the second regeneration device is
operated.
6. The exhaust gas purification device as in claim 1, wherein the
oil dilution related data measurement device derives the oil
dilution related data from a difference between the oil dilution
quantity and an oil evaporation quantity as a quantity of the fuel
evaporating from the oil.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2007-144844 filed on May
31, 2007.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exhaust gas purification
device of an internal combustion engine having a diesel particulate
filter (also referred to as a DPF) in an exhaust pipe for exhaust
purification.
[0004] 2. Description of Related Art
[0005] There is a conventional technology of a post-injection for
sending additional fuel directly into a DPF in order to effectively
combust particulate matters in the DPF by injecting the additional
fuel in an expansion stroke after a main injection of an engine
when a deposition quantity of the particulate matters in the DPF
exceeds a predetermined value, for example, as described in Patent
document 1 (Japanese Patent Application No. H08-42326) or Patent
document 2 (Japanese Patent Application No. 2005-307746). The
particulate matters are soot, unburned matters and the like
contained in exhaust gas of the engine.
[0006] However, since the post-injection is performed during the
expansion stroke, the injected fuel is hard to evaporate and tends
to adhere to a wall surface of a cylinder. The fuel adhering to the
wall surface of the cylinder descends through a gap between a
piston ring and the cylinder, causing a problem of engine oil
dilution.
[0007] Furthermore, if the post-injection is repeatedly performed
for a long time and the quantity of the fuel diluting the oil
(referred to as an oil dilution quantity, hereinafter) becomes
excessive, there is a possibility that lubrication of the piston is
deteriorated or vaporized fuel enters an air intake side, causing a
problem of increase in engine rotation speed.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide an
exhaust gas purification device of an internal combustion engine
capable of achieving both of inhibition of oil dilution and
inhibition of fuel consumption deterioration due to a
post-injection.
[0009] According to an aspect of the present invention, an exhaust
gas purification device of an internal combustion engine having a
diesel particulate filter for collecting particulate matters
contained in exhaust gas of the engine has a controller, a
particulate matter deposition quantity measurement section, a
particulate matter deposition quantity determination device, an oil
dilution related data measurement device, an oil dilution related
data determination device, and a regeneration device. The
controller controls operation of the exhaust gas purification
device. The particulate matter deposition quantity measurement
section measures a deposition quantity of the particulate matters
in the diesel particulate filter. The particulate matter deposition
quantity determination device determines whether the deposition
quantity of the particulate matters measured by the particulate
matter deposition quantity measurement section is greater than a
first predetermined value. The oil dilution related data
measurement device measures oil dilution related data necessary for
deriving an oil dilution quantity as a quantity of fuel diluting
engine oil. The oil dilution related data determination device
determines whether the oil dilution related data measured by the
oil dilution related data measurement device is greater than a
second predetermined value. The regeneration device combusts the
particulate matters to regenerate the diesel particulate filter.
The regeneration device includes a first regeneration device and a
second regeneration device. The second regeneration device causes
the oil dilution quantity less than the oil dilution quantity
caused by the first regeneration device and causes a fuel
consumption rate greater than the fuel consumption rate caused by
the first regeneration device.
[0010] The controller has a selection device. The selection device
selects the first regeneration device from the two regeneration
devices when the particulate matter deposition quantity
determination device determines that the particulate matters
greater than the first predetermined value in quantity are
deposited in the diesel particulate filter and the oil dilution
related data determination device determines that the measured oil
dilution related data is lower than the second predetermined value.
The selection device selects the second regeneration device from
the two regeneration devices when the particulate matter deposition
quantity determination device determines that the particulate
matters greater than the first predetermined value in quantity are
deposited in the diesel particulate filter and the oil dilution
related data determination device determines that the measured oil
dilution related data is higher than the second predetermined
value.
[0011] With the configuration, the exhaust gas purification device
can selectively use the first regeneration device, which causes the
large oil dilution but the small fuel consumption deterioration,
and the second regeneration device, which causes the small oil
dilution but the large fuel consumption deterioration, based on the
present oil dilution quantity in the engine. Thus, the exhaust
purification device can inhibit the fuel consumption deterioration
while controlling the oil dilution quantity to or under the
predetermined value. That is, the exhaust gas purification device
exerts an effect of achieving both of inhibition of the oil
dilution and inhibition of deterioration of the fuel consumption
during the DPF regeneration.
[0012] According to another aspect of the present invention, the
first regeneration device performs post-injection for injecting the
fuel in an expansion stroke, and the second regeneration device
performs the post-injection at injection timing advanced from
injection timing in the case of the first regeneration device in
the expansion stroke.
[0013] With the configuration, the exhaust gas purification device
can have the two regeneration devices of the first regeneration
device, which causes the large oil dilution but the small fuel
consumption deterioration, and the second regeneration device,
which causes the small oil dilution but the large fuel consumption
deterioration, even without providing any specific external device.
That is, the two kinds of the regeneration devices can be provided
without necessitating an extra cost.
[0014] According to another aspect of the present invention, the
post-injection is performed as a plurality of injections performed
in a plurality of times during the expansion stroke.
[0015] With the configuration, a quantity of the post-injection per
one injection can be reduced even if the total post-injection
quantity is the same. Thus, the quantity of the fuel adhering to
the cylinder can be reduced and the oil dilution quantity can be
reduced.
[0016] According to another aspect of the present invention, the
oil dilution related data measurement device measures the oil
dilution related data from vehicle speed and a travel distance in a
period in which the first regeneration device or the second
regeneration device is operated or from the vehicle speed and a
travel time in a period in which the first regeneration device or
the second regeneration device is operated.
[0017] The DPF regeneration time lengthens and the oil dilution
quantity increases when the vehicle speed is low and exhaust
temperature is low. With the above configuration, the oil dilution
quantity can be calculated from the relationship.
[0018] According to another aspect of the present invention, the
oil dilution related data measurement device measures the oil
dilution related data from a duration in which the first
regeneration device or the second regeneration device is
operated.
[0019] Generally, the oil dilution quantity increases if the DPF
regeneration time lengthens. With the above configuration, the
exhaust purification device can derive the oil dilution quantity
from the DPF regeneration time.
[0020] According to yet another aspect of the present invention,
the oil dilution related data measurement device derives the oil
dilution related data from a difference between the oil dilution
quantity and an oil evaporation quantity as a quantity of the fuel
evaporating from the oil.
[0021] With the configuration, the oil dilution quantity can be
derived accurately from the difference between the oil dilution
quantity and the oil evaporation quantity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Features and advantages of embodiments will be appreciated,
as well as methods of operation and the function of the related
parts, from a study of the following detailed description, the
appended claims, and the drawings, all of which form a part of this
application. In the drawings:
[0023] FIG. 1 is a system diagram showing an exhaust gas
purification device of an internal combustion engine according to a
first embodiment of the present invention;
[0024] FIG. 2 is a schematic diagram showing a construction example
of an ECU according to the first embodiment;
[0025] FIG. 3 is a flowchart showing regeneration processing of a
DPF according to the first embodiment;
[0026] FIG. 4A is a diagram showing a relationship between a crank
angle and an opening degree of an injector in the case of a first
regeneration device according to the first embodiment;
[0027] FIG. 4B is a diagram showing a relationship between the
crank angle and the opening degree of the injector in the case of a
second regeneration device according to the first embodiment;
[0028] FIG. 5A is a diagram showing a comparison example of
temperature in a cylinder between the case of the first
regeneration device and the case of the second regeneration device
according to the first embodiment;
[0029] FIG. 5B is a diagram showing a comparison example of an oil
dilution quantity between the case of the first regeneration device
and the case of the second regeneration device according to the
first embodiment;
[0030] FIG. 5C is a diagram showing a comparison example of fuel
consumption deterioration between the case of the first
regeneration device and the case of the second regeneration device
according to the first embodiment;
[0031] FIG. 6 is a flowchart showing regeneration processing of a
DPF according to a second embodiment of the present invention;
[0032] FIG. 7A is a diagram showing a change in an oil evaporation
quantity due to engine coolant temperature and an oil dilution
quantity according to the second embodiment;
[0033] FIG. 7B is a diagram showing a change in the oil dilution
quantity due to engine output torque and engine rotation speed
according to the second embodiment; and
[0034] FIG. 8 is a diagram showing a relationship between a
difference between the oil evaporation quantity and the oil
dilution quantity and a travel time or a travel distance according
to the second embodiment.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0035] Now, a first embodiment of the present invention will be
described with reference to drawings. FIG. 1 is a system diagram
showing an exhaust gas purification device of an internal
combustion engine 1 according to the present embodiment. A diesel
engine 2 shown in FIG. 1 serves as a motor. An airflow meter 3 for
measuring a flow rate of an air on an intake side of the diesel
engine 2, an engine rotation sensor 4 for measuring rotation speed
NE of the diesel engine 2, and an accelerator position sensor 5 for
measuring a position ACC of an accelerator achieved by a driver are
provided as sensors for determining a state of the diesel engine 2.
The diesel engine 2 has an injector including a fuel injection
valve for injecting fuel. The injector is electrically connected to
an ECU 10 (engine control unit) as a control unit. The ECU 10
manages an opening degree and timing of the fuel injection valve of
the injector for injecting the fuel. The airflow meter 3, the
engine rotation sensor 4 and the accelerator position sensor 5 are
also electrically connected to the ECU 10 as the control unit and
transmit measurement values to the ECU 10. The ECU 10 grasps and
manages the engine state based on the measurement values.
[0036] Exhaust temperature sensors 6 for measuring exhaust
temperature TE, an oxygen concentration sensor 7 for measuring an
oxygen concentration of the exhaust gas between the diesel engine 2
and a DPF 9 for removing particulate matters, and a differential
pressure sensor 8 (a particulate matter deposition quantity
measurement section) for measuring pressure difference .DELTA.P of
the exhaust gas across the DPF 9 are provided as sensors for
acquiring information about exhaust gas from the engine. The
exhaust temperature sensors 6, the oxygen concentration sensor 7,
and the differential pressure sensor 8 are also electrically
connected to the ECU 10 as the control unit like the engine
rotation sensor 4 and the accelerator position sensor 5 and
transmit measurement values to the ECU 10. The transmitted
measurement values are used for grasping the state of the engine.
The differential pressure .DELTA.P measured by the differential
pressure sensor 8 is used for determining a particulate matter
deposition quantity PM of the DPF 9.
[0037] FIG. 2 is a schematic diagram showing a construction example
of the ECU 10 according to the present embodiment. The ECU 10
consists of CPU 20 for controlling respective components, ROM 21
for storing control programs, various data and the like, RAM 22
serving as a workspace for the computation performed by the CPU 20,
and EEPROM 23 as a nonvolatile memory for saving various settings.
The components of the ECU 10 exchange the data through a bus 50.
Electric connection with exteriors such as the sensors is made
through the bus 50 and an I/O 51.
[0038] The ROM 21 stores a particulate matter deposition quantity
calculation program 31 (a particulate matter deposition quantity
determination device) that calculates a quantity of the particulate
matters deposited on the DPF 9 (i.e., the particulate matter
deposition quantity PM) from the differential pressure .DELTA.P
measured with the differential pressure sensor 8, a DPF temperature
control program 32 that controls temperature of the DPF 9 through
the post-injection during the regeneration of the DPF 9, an
operation state measurement program 34 (an oil dilution related
data measurement device) that measures vehicle speed, travel
distance and travel time as data for calculating an oil dilution
quantity Qd, an oil evaporation quantity calculation program 35
(the oil dilution related data measurement device) that calculates
a quantity of the fuel evaporating form the oil (i.e., an oil
evaporation quantity Qv) based on engine coolant temperature Teng
and the oil dilution quantity Qd, an oil dilution quantity
calculation program 36 (the oil dilution related data measurement
device) that calculates the oil dilution quantity Qd from the
engine rotation speed NE and engine output torque TOR, and a DPF
regeneration time measurement program 37 (the oil dilution related
data measurement device) that measures a regeneration time TRdpf of
the DPF 9.
[0039] The CPU 20 executes various types of processing by deploying
the contents of the ROM 21 to the RAM 22. The CPU 20 executes
various types of processing by deploying the values of the various
settings necessary for the processing from the EEPROM 23 to the RAM
22. When there is change to the settings, the CPU 20 saves the
settings by writing the changed values in the EEPROM 23.
[0040] Next, control of the post-injection during the regeneration
of the DPF 9 according to the present embodiment will be explained
with reference to a flowchart. The regeneration processing of the
DPF 9 according to the present embodiment is processing for
combusting and removing the particulate matters in the DPF 9 when
the particulate matter deposition quantity PM collected by the DPF
9 exceeds a predetermined value. In the present embodiment, the
post-injection is performed after a main injection and the
particulate matters deposited on the DPF 9 is removed by combustion
such as the combustion of the fuel of the post-injection. Thus, the
DPF 9 is regenerated.
[0041] FIG. 3 is a flowchart showing the regeneration processing of
the DPF 9 according to the present embodiment. First, in S100 of
the flowchart, the ECU 10 determines whether the particulate matter
deposition quantity PM of the DPF 9 is greater than a first
predetermined value a requiring the regeneration of the DPF 9. The
determination is performed with the use of a publicly known
technology. The publicly-known technology is, for example, a method
of measuring the pressure difference .DELTA.P between the inlet and
the outlet of the DPF 9 with the differential pressure sensor 8 and
by estimating the particulate matter deposition quantity PM. The
differential pressure .DELTA.P measured by the differential
pressure sensor is large when the particulate matter deposition
quantity PM is large. It is determined that the particulate matter
deposition quantity PM of the DPF 9 is greater than the first
predetermined value a when the pressure difference .DELTA.P exceeds
a prescribed value. If it is determined that the particulate matter
deposition quantity PM is equal to or less than the first
predetermined value a in S100 (S100: NO), the ECU 10 enters a
waiting state until the determination of whether the particulate
matter deposition quantity PM is greater than the first
predetermined value a requiring the regeneration of the DPF 9 is
performed next time.
[0042] If it is determined that the particulate matter deposition
quantity PM is greater than the first predetermined value a
requiring the regeneration of the DPF 9 in S100 (S100: YES), the
ECU 10 starts the regeneration of the DPF 9 in S110. When the
regeneration of the DPF 9 is performed, the post-injection is
performed to send unburned fuel to the DPF 9 with the exhaust gas,
and the particulate matters in the DPF 9 are combusted with
oxidization heat of an oxidation catalyst supported by the DPF 9.
Thus, the quantity of the particulate matters deposited on the DPF
9 decreases. The deposition of a large quantity of the particulate
matters hinders the stream of the exhaust gas, lowering an engine
output. Therefore, the regeneration is indispensable for the DPF 9.
The particulate matters begin to combust at approximately 550
degrees C.
[0043] Performing the post-injection during the regeneration means
that the fuel is injected into the cylinder in a state where the
piston has descended after passing a top dead center and that the
fuel adheres to a cylinder wall. The fuel adhering to the cylinder
wall causes the oil dilution as mentioned above. In such the case,
there is a possibility that the adhering fuel causes defective
lubrication of the piston or a phenomenon that the vaporized fuel
enters the air intake side and the engine rotation speed rises.
[0044] In order to avoid the above-mentioned phenomena, the ECU 10
determines whether the oil dilution quantity Qd as the quantity of
the fuel diluting the engine oil is greater than a predetermined
quantity in S120. Since it is difficult to directly measure the oil
dilution quantity Qd, it is determined whether the oil dilution
quantity Qd is greater than the predetermined quantity based on the
operation condition. For example, emission of low-temperature
exhaust gas is continued when low-speed operation is continued for
a predetermined time or over. This causes a large quantity of the
unburned fuel to adhere to the cylinder wall, advancing the oil
dilution. Therefore, when the low-speed operation is continued for
the predetermined time or over, it is determined that the oil
dilution quantity Qd is greater than the predetermined quantity in
S120 (S120: YES). For example, in the present embodiment, it is
determined that the oil dilution quantity Qd is greater than the
predetermined quantity on a condition that operation at the vehicle
speed of 20 km/h or lower continues for 60 minutes or over. The
condition for determining whether the oil dilution quantity Qd is
greater than the predetermined quantity is not limited to this
condition.
[0045] For example, it may be determined that the oil dilution
quantity Qd is greater than the predetermined quantity on a
condition that the low-speed operation is continued for a
predetermined distance or over. In the present embodiment, for
example, a condition that the operation at the vehicle speed of 20
km/h or lower continues for a distance of 20 km or over may be used
for the determination. The condition for determining whether the
oil dilution quantity Qd is greater than the predetermined quantity
is not limited to this condition.
[0046] If the ECU 10 determines that the low-speed operation is not
continued, i.e., if the ECU 10 determines that the oil dilution
quantity Qd is not greater than the predetermined quantity in S120
(S120: NO), then, the ECU 10 determines whether the regeneration
duration TRdpf is greater than a second predetermined value .beta.
in S130 as another determination of whether the oil dilution
quantity Qd is greater than the predetermined quantity. During the
regeneration of the DPF 9, the post-injection is performed
continuously and there is a state where the oil dilution quantity
Qd continues increasing. Therefore, the determination of the
regeneration duration TRdpf can be used as a reference for
determining whether the oil dilution quantity Qd reaches the
predetermined value. When the regeneration duration TRdpf is long,
there is a possibility that the oil dilution quantity Qd has
increased significantly. Therefore, in such the case, the
regeneration device is switched to inhibit the increase of the oil
dilution quantity Qd.
[0047] If it is determined that the regeneration duration TRdpf is
not greater than the second predetermined value .beta. in S130
(S130: NO), the ECU 10 determines that the oil dilution quantity Qd
is not greater than the predetermined quantity and operates a first
regeneration device (REGENERATION I, in FIG. 3) in S140 to
efficiently proceed the combustion of the particulate matters in
the DPF 9.
[0048] FIG. 4A shows a relationship between a crank angle (CA) and
an opening degree (i.e., a lift amount L) of the injector in the
case of the first regeneration device. Points where the injector is
open (i.e., points where the lift amount L is not zero) represent a
pilot injection 61 for mixing an air and the fuel before ignition
to suppress an engine operation sound, a main injection 62 for
obtaining motive energy, a post-injection A 63 and a post-injection
B 64 from the left side in FIG. 4A. The post-injection A 63 and the
post-injection B 64 are performed to send unburned fuel into the
DPF 9 as the fuel for combusting the particulate matters deposited
on the DPF 9 after explosion. If the post-injection of a large fuel
quantity is performed at once in the state where the piston has
descended after passing the top dead center, the unburned fuel of
the quantity larger than a predetermined quantity will adhere to
the cylinder wall, causing the increase in the oil dilution
quantity Qd. As contrasted thereto, by dividing the post-injection,
the post-injection quantity per injection can be reduced and the
cylinder volume with respect to the fuel can be increased. This
leads to reduction of the unburned fuel adhering to the cylinder
wall and reduction of the oil dilution quantity Qd. TDC (Top Dead
Center) In FIG. 4A represents the top dead center of the piston. In
the present embodiment, FIG. 4A shows that the main injection 62
starts immediately after the top dead center.
[0049] In FIG. 4A, the post-injection A and the post-injection B
are performed at timings considerably later than the main injection
62. Since the fuel reaching the DPF 9 without being combusted can
be increased by delaying the injection timing, the particulate
matters in the DPF 9 can be efficiently combusted with the
comparatively small quantity of the post-injection. However, since
the injection is performed in a state where the temperature in the
cylinder is comparatively low, the unburned fuel reaching the
cylinder wall increases and causes the increase of the oil dilution
quantity Qd.
[0050] If the unburned fuel reaching the DPF 9 increases, the
injection quantity or the time number of the post-injection until
the fuel of a predetermined quantity reaches the DPF 9 reduces,
alleviating the deterioration of the fuel consumption.
[0051] Then, the ECU 10 determines whether the particulate matter
deposition quantity PM has sufficiently decreased through the
regeneration of the DPF 9 in S160. The determination is performed
using the publicly-known technology like S100. When it is
determined that the particulate matter deposition quantity PM
decreases sufficiently in S160 (S160: YES), the ECU 10 ends the
regeneration of the DPF 9. When it is determined that the
particulate matter deposition quantity PM has not decreased yet in
S160 (S160: NO), the ECU 10 returns to S120 to perform the
regeneration of the DPF 9.
[0052] If it is determined that the oil dilution quantity Qd is
greater than the predetermined quantity in S120 (S120: YES), the
ECU 10 operates a second regeneration device (REGENERATION II in
FIG. 3) to alleviate the increase in the oil dilution quantity Qd
in S150.
[0053] FIG. 4B shows a relationship between the crank angle (CA)
and the opening degree (i.e., the lift amount L) of the injector in
the case of the second regeneration device. It is shown that the
timing of the post-injection is earlier in the case of FIG. 4B than
in the case of FIG. 4A. Since the timing of the post-injection is
advanced, the post-injection is performed while the pressure in the
cylinder is high as compared to the case of the first regeneration
device. Accordingly, the fuel reaching the cylinder wall reduces in
quantity and the increase in the oil dilution quantity Qd is
alleviated.
[0054] However, since the injection timing is early and the fuel is
injected while the cylinder internal temperature as of the
post-injection is high, part of the fuel of the post-injection
combusts. Although this combustion produces the engine output, the
combustion efficiency lowers and the fuel consumption deteriorates
because the combustion occurs at the timing largely delayed from
the top dead center. The amount corresponding to the combustion
efficiency lowering is discharged as heat energy from the engine to
the exhaust gas but part of the heat escapes from the exhaust pipe
to the ambient air before the heat reaches the DPF 9. Therefore,
the ratio of the fuel effectively used in raising the temperature
of the DPF 9 out of the fuel of the post-injection decreases as
compared to the case of the first regeneration device,
deteriorating the fuel consumption.
[0055] An example of comparison of the cylinder internal
temperature Tcyl as of the post-injection between the first
regeneration device and the second regeneration device is shown in
FIG. 5A. An example of comparison of the oil dilution quantity Qd
between the first regeneration device and the second regeneration
device is shown in FIG. 5B. An example of comparison of the fuel
consumption F between the first regeneration device and the second
regeneration device is shown in FIG. 5C. In each of FIGS. 5A to 5C,
I corresponds to the first regeneration device and II corresponds
to the second regeneration device. As shown in FIGS. 5A to 5C, the
cylinder internal temperature Tcyl and the fuel consumption F are
higher in the case of the second regeneration device than in the
case of the first regeneration device but the oil dilution quantity
Qd is higher in the case of the first regeneration device than in
the case of the second regeneration device.
[0056] After the ECU 10 performs the regeneration, the ECU 10 moves
to S160 to determine whether the particulate matter deposition
quantity PM has decreased sufficiently. If the ECU 10 determines
that the particulate matter deposition quantity PM has decreased
sufficiently in S160 (S160: YES), the ECU 10 ends the regeneration
of the DPF 9. If the ECU 10 determines that the particulate matter
deposition quantity PM has not decreased sufficiently yet in S160
(S160: NO), the ECU 10 returns to S120 to select the regeneration
device based on the oil dilution quantity Qd.
[0057] If it is determined that the regeneration duration TRdpf is
greater than the second predetermined value .beta. in S130 (S130:
YES), the ECU 10 determines that the oil dilution quantity Qd has
increased and operates the second regeneration device to alleviate
the increase in the oil dilution quantity Qd in S150.
[0058] Next, a second embodiment of the present invention will be
described. FIG. 6 is a flowchart showing regeneration processing of
the DPF 9 according to the second embodiment. First, the ECU 10
calculates an oil evaporation quantity Qv in S200. The oil
evaporation quantity Qv changes with an engine warming state (which
is known from the engine coolant temperature Teng or the like) and
the present oil dilution quantity Qd. The relationship among the
oil evaporation quantity Qv, the engine warming state and the oil
dilution quantity Qd is experimentally obtained beforehand and is
stored in the ECU 10.
[0059] The increase of the engine coolant temperature Teng means
increase of the temperature inside the engine. In such the case,
the fuel in the oil evaporates easily, increasing the oil
evaporation quantity Qv. If the oil dilution quantity Qd increases,
the fuel evaporating from the oil also increases, so the oil
evaporation quantity Qv also increases. FIG. 7A shows an increase
in the oil evaporation quantity Qv due to the engine coolant
temperature Teng and the oil dilution quantity Qd. In FIG. 7A,
equal oil evaporation quantity lines are drawn. The oil evaporation
quantity Qv is the same on each equal oil evaporation quantity
line. The oil evaporation quantity Qv increases if at least one of
the engine coolant temperature Teng and the oil dilution quantity
Qd increases.
[0060] Then, in S210 of the flowchart, the ECU 10 determines
whether the particulate matter deposition quantity PM of the DPF 9
is greater than a first predetermined value a requiring the
regeneration of the DPF 9 as in the first embodiment. If it is
determined that the particulate matter deposition quantity PM is
greater than the first predetermined value a requiring the
regeneration of the DPF 9 in S210 (S210: YES), the ECU 10 performs
the post-injection to start the regeneration of the DPF 9 in S220.
If it is determined that the particulate matter deposition quantity
PM is equal to or less than the first predetermined value a in S210
(S210: NO), the ECU 10 enters a waiting state until the
determination of whether the particulate matter deposition quantity
PM is greater than the first predetermined value a requiring the
regeneration of the DPF 9 is performed next time. The particulate
matter deposition quantity PM is measured with a publicly-known
technology, for example, as described in the description of the
first embodiment.
[0061] Then, the ECU 10 starts the regeneration of the DPF 9 in
S220. The processing in S220 is the same as S110 of the first
embodiment.
[0062] Then, the ECU 10 calculates the oil dilution quantity Qd in
S230. The oil dilution quantity Qd is related to the engine
rotation speed NE and the output torque TOR. Also, the oil dilution
quantity Qd is greatly influenced by the quantity of the
post-injection. FIG. 7B shows an increase in the oil dilution
quantity Qd due to the engine output torque TOR and the engine
rotation speed NE. In FIG. 7B, equal oil dilution quantity lines
are drawn. The oil dilution quantity Qd is the same on each equal
oil dilution quantity line. The oil dilution quantity decreases if
at least one of the engine output torque TOR and the engine
rotation speed NE increases. When the engine rotation speed NE or
the engine output torque TOR is low, the exhaust gas temperature TE
is low. Therefore, in such the case, it is necessary to send a
large quantity of the fuel into the DPF 9 for regenerating the DPF
9 through the post-injection. This causes a large quantity of the
fuel to adhere to the cylinder wall, increasing the oil dilution
quantity Qd.
[0063] Then, the ECU 10 calculates the quantity of the fuel
presently diluting the engine oil from the oil dilution quantity Qd
and the oil evaporation quantity Qv. The oil dilution quantity Qd
represents the quantity of the fuel diluting the engine oil before
evaporation. Therefore, the oil dilution quantity Qd also includes
the quantity of the fuel evaporating after the dilution (i.e., the
oil evaporation quantity Qv). The quantity of the fuel presently
diluting the engine oil can be calculated by subtracting the
quantity of the fuel evaporating after the dilution from the oil
dilution quantity Qd. The ECU 10 determines whether the thus
calculated quantity of the fuel diluting the engine oil is greater
than a third predetermined value y in S240. In this way, as
compared to the first embodiment, the quantity of the fuel diluting
the engine oil can be calculated more accurately and the ECU 10 can
select the regeneration device more suitably.
[0064] FIG. 8 shows a transition of the quantity of the fuel
diluting the engine oil (i.e., the difference between the oil
dilution quantity Qd and the oil evaporation quantity Qv) with
respect to the travel distance (or travel time). Since the
post-injection is performed during the regeneration period (R in
FIG. 8), the quantity of the fuel diluting the engine oil
increases. During a non-regeneration period (NR in FIG. 8), in
which the regeneration is not performed, the post-injection is not
performed. Therefore, the fuel diluting the engine oil only
evaporates and the quantity of the fuel diluting the engine oil
decreases. The ECU 10 switches the regeneration device from the
first regeneration device I to the second regeneration device II
when the quantity of the fuel diluting the engine oil exceeds a
threshold value A. Thus, the increase in the quantity of the fuel
diluting the engine oil is alleviated.
[0065] If it is determined that the quantity of the fuel diluting
the engine oil is not greater than the third predetermined value y
in S240 (S240: NO), the ECU 10 operates the first regeneration
device in S250 to prioritize the inhibition of the fuel consumption
deterioration and to proceed the combustion of the particulate
matters in the DPF 9 efficiently. The processing performed by the
first regeneration device is the same as the first embodiment.
[0066] Then, the ECU 10 determines whether the particulate matter
deposition quantity PM has sufficiently decreased through the
regeneration of the DPF 9 in S270. The determination is performed
in the publicly-known method as in the first embodiment. If it is
determined that the particulate matter deposition quantity PM has
decreased sufficiently in S270 (S270: YES), the ECU 10 ends the
regeneration of the DPF 9. If it is determined that the particulate
matter deposition quantity PM has not decreased yet in S270 (S270:
NO), the ECU 10 returns to S230 to perform the regeneration of the
DPF 9.
[0067] If it is determined that the quantity of the fuel diluting
the engine oil is greater than the third predetermined value y in
S240 (S240: YES), the ECU 10 determines that the oil dilution
quantity Qd is increasing and operates the second regeneration
device in S260 in order to alleviate the increase in the oil
dilution quantity Qd. The processing performed by the second
regeneration device is the same as the first embodiment.
[0068] The above embodiments may be modified, for example, such
that the oil dilution quantity Qd is calculated directly from
viscosity of the engine oil by using an oil level sensor, a
viscosity sensor or the like.
[0069] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *