JP4265297B2 - Compression ignition internal combustion engine and fuel injection system for compression ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compression ignition type internal combustion engine, and more particularly to a compression ignition type internal combustion engine that injects fuel in at least one of an intake stroke, an expansion stroke, and an exhaust stroke for control and the like accompanying regeneration processing in an exhaust purification device. Is.
[0002]
[Prior art]
In recent years, for compression ignition internal combustion engines mounted on automobiles and the like, it is desired to suppress the release of particulates (PM) represented by soot and nitrogen oxides (NOx) into the atmosphere. ing.
[0003]
In response to such a requirement, conventionally, a technique is known in which an oxidation catalyst, a particulate filter, a NOx storage agent, and the like are arranged in an exhaust system of a compression ignition internal combustion engine (see, for example, Patent Document 1). .
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-53442
[Patent Document 2]
JP 2002-213229 A
[Patent Document 3]
JP 2000-18020 A
[Patent Document 4]
JP-A-11-166435
[Patent Document 5]
JP 2001-90539 A
[0005]
[Problems to be solved by the invention]
By the way, in the case of regenerating the PM collection capacity of the particulate filter or the NOx storage capacity of the NOx storage agent, in addition to the fuel injection (main injection) performed near the top dead center of the compression stroke, post injection and big rubber injection It is assumed that the sub-injection is performed.
[0006]
However, since the fuel injected by the above-mentioned big rubber injection or post injection is likely to be partially oxidized to carbon, carbon may deposit on the wall surface of the combustion chamber.
[0007]
An object of the present invention is to provide a technique capable of preventing carbon accumulation in a combustion chamber due to sub-injection such as big rubber injection and post injection in a compression ignition type internal combustion engine.
[0008]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems. That is, the compression ignition internal combustion engine according to the present invention includes a fuel injection unit that directly injects fuel into a combustion chamber, and the combustion chamber after the fuel injection unit performs fuel injection in an intake stroke, an expansion stroke, or an exhaust stroke. Wall surface temperature increasing means for increasing the temperature of the wall surface.
[0009]
The gist of the present invention is that in a compression ignition type internal combustion engine having a fuel injection means for directly injecting fuel into a combustion chamber, the fuel injection means injects fuel in an intake stroke, an expansion stroke or an exhaust stroke. By increasing the temperature of the wall surface, the carbon adhering to the wall surface of the combustion chamber and / or the carbon adhering to the wall surface of the combustion chamber is burned.
[0010]
When fuel is injected into the combustion chamber in the intake stroke, the expansion stroke, or the exhaust stroke, in other words, a secondary fuel at a time different from the normal fuel injection (hereinafter referred to as main injection) performed in the compression stroke. When injection (hereinafter referred to as sub-injection) is performed, carbon tends to adhere to the wall surface of the combustion chamber.
[0011]
On the other hand, when the wall surface temperature raising means raises the temperature of the wall surface of the combustion chamber after the sub-injection as described above is performed, it tends to adhere to the carbon attached to the wall surface of the combustion chamber or the wall surface of the combustion chamber. Carbon will be burned.
[0012]
As a result, the carbon is prevented from adhering to the combustion chamber wall surface, and further, the carbon adhering to the combustion chamber wall surface is removed, thereby preventing the carbon from accumulating on the combustion chamber wall surface due to the sub-injection.
[0013]
Therefore, a problem caused by the adhesion of carbon to the wall of the combustion chamber, specifically, carbon deposits on the fuel injection nozzle and changes the fuel spray characteristics. It is possible to prevent problems such as being discharged. Further, the wall surface temperature raising means raises the temperature of the wall surface of the combustion chamber, thereby promoting the evaporation of the fuel adhering to the inner wall surface of the cylinder. Therefore, in addition to the above effects, there is also a secondary effect that the oil on the cylinder inner wall surface is diluted by the fuel and the deterioration of the slidability of the engine can be suppressed.
[0014]
Note that if the wall surface temperature increasing means continues to increase the temperature of the wall surface of the combustion chamber, it is assumed that the temperature in the combustion chamber excessively increases and the internal combustion engine itself is overheated. However, the temperature of the wall surface of the combustion chamber may be raised only for a predetermined period from the time when the sub-injection is performed.
[0015]
The predetermined period described above may be a predetermined period obtained in advance, or may be a period changed according to the amount of carbon attached to the wall surface of the combustion chamber. The amount of carbon adhering to the wall surface of the combustion chamber has a correlation with the amount of fuel sub-injected into the combustion chamber from the fuel injection means. For example, the predetermined period is set longer as the amount of sub-injection fuel increases. The predetermined period may be set shorter as the amount of fuel injected becomes smaller.
[0016]
In the present invention, as a method for increasing the temperature of the wall surface of the combustion chamber, a method for increasing the pressure increase rate during combustion in the combustion chamber can be exemplified. Here, the rate of pressure increase during combustion is the ratio of the pressure in the combustion chamber when combustion occurs in the combustion chamber to the pressure in the combustion chamber before combustion occurs, or the change in pressure when combustion occurs in the combustion chamber Refers to the inclination of
[0017]
In this method, during normal operation, the temperature of the wall surface of the combustion chamber tends to be lower than the gas temperature in the combustion chamber, so a temperature boundary layer is formed in the vicinity of the wall surface of the combustion chamber. This is based on the knowledge that when the rate of pressure increase during combustion is increased, the temperature boundary layer disappears due to pressure waves generated during combustion of the fuel, and the temperature of the wall surface of the combustion chamber increases.
[0018]
As a method for increasing the rate of pressure increase during combustion in the combustion chamber, a method for generating knocking can be exemplified.
[0019]
That is, when knocking (diesel knock) occurs in a compression ignition type internal combustion engine, the combustion pressure rises more rapidly than during normal combustion. The layer can be lost.
[0020]
In a compression ignition type internal combustion engine, specific methods for generating the knocking include a method of advancing the fuel injection timing of the main injection, a method of retarding the fuel injection timing of the main injection, and before or after the main injection. A method of sub-injecting fuel from the fuel injection means into the combustion chamber at a predetermined time can be exemplified.
[0021]
When the fuel injection timing of the main injection is advanced, for example, the fuel injection timing after the advance is preferably in the range of 40 ° before compression top dead center to 10 ° before compression top dead center. This is because if the fuel injection timing of the main injection is advanced excessively, fuel may adhere to the cylinder wall surface and bore flushing may occur.
[0022]
When retarding the fuel injection timing of the main injection, for example, it is preferable that the fuel injection timing after the retard is not retarded by more than 20 ° after the compression top dead center. This is because if the fuel injection timing of the main injection is delayed too much, misfire of the main injected fuel may be induced.
[0023]
When sub-injection is performed before main injection, it is preferable that the injection timing of sub-injection is 30 ° before compression top dead center. This is because if the sub-injection is executed at a time later than 30 ° before the compression top dead center, the period from the sub-injection to the main injection is shortened and it is difficult to generate diesel knock. Here, the injection timing of the sub-injection may be about 360 ° before the compression top dead center, and so-called big rubber injection may be performed.
[0024]
The fuel injection amount in the sub-injection is preferably 0.5 or less with respect to the intake air amount. This is because if the fuel injection amount in the sub-injection is excessively increased, it is assumed that the rate of pressure increase during combustion is excessively increased.
[0025]
In the present invention, another method for increasing the temperature of the wall surface of the combustion chamber can be exemplified by a method for enhancing the air flow in the combustion chamber.
[0026]
In this method, when the air flow in the combustion chamber is strengthened, the temperature boundary layer formed in the vicinity of the combustion chamber wall surface becomes thin or disappears by the air flow. This is based on the knowledge that the heat transfer coefficient between the two increases, and as a result, the temperature of the wall surface of the combustion chamber increases.
[0027]
As a specific method for enhancing the air flow in the combustion chamber, a method for generating a swirl in the combustion chamber and a method for strengthening the swirl generated in the combustion chamber can be exemplified.
[0028]
According to this, the air near the wall surface of the combustion chamber is agitated by the swirl generated in the combustion chamber or the swirl strengthened, and the temperature boundary layer formed near the wall surface of the combustion chamber becomes thin or disappears. . Thereby, the temperature of the combustion chamber wall surface can be raised.
[0029]
In the present invention, the wall surface temperature increasing means increases the temperature of the wall surface of the combustion chamber when the internal combustion engine is in a high load operation state, for example, when the load of the diesel engine 11 is 80% or more of the full load. It may not be allowed to. This is because when the diesel engine 11 is operated at a high load, the temperature of the wall surface of the combustion chamber tends to be high, and carbon is difficult to adhere to the wall surface of the combustion chamber. In this way, it is possible to more surely prevent the wall surface of the combustion chamber from overheating and causing seizure. In addition, it is possible to suppress the heat from escaping to the outside of the combustion chamber due to the temperature of the wall surface of the combustion chamber being increased, resulting in an increase in heat loss and consequently a deterioration in fuel consumption.
[0030]
In addition, the above-mentioned means for solving the problems can be used in combination as much as possible.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.
[0032]
(First embodiment)
First, a first embodiment of a compression ignition type internal combustion engine according to the present invention will be described with reference to FIGS.
[0033]
FIG. 1 is a cross-sectional view showing a schematic configuration of an entire compression ignition type internal combustion engine according to the present invention.
A compression ignition type internal combustion engine (hereinafter referred to as a diesel engine) 11 shown in FIG. 1 is an example of a four-stroke cycle water-cooled diesel engine having four cylinders, and includes a cylinder head 12 and four cylinders (cylinders) 13. And a cylinder block 14 having A piston 15 is accommodated in each cylinder 13 so as to reciprocate.
[0034]
Each piston 15 is connected via a connecting rod 20 to a crankshaft (not shown) that is an output shaft of the diesel engine 11. The reciprocating motion of each piston 15 is converted into rotational motion by the connecting rod 20 and transmitted to the crankshaft.
[0035]
An intake passage 16 is connected to the combustion chamber 54 of each cylinder 13, and air outside the diesel engine 11 is taken into the combustion chamber 54 through the intake passage 16. Further, the exhaust passage 17 is connected to the combustion chamber 54. The cylinder head 12 is provided with an intake valve 18 and an exhaust valve 19 for each cylinder 13.
[0036]
These intake / exhaust valves 18, 19 reciprocate in conjunction with the rotation of the crankshaft, thereby opening and closing the connection between the intake / exhaust passages 16, 17 and the combustion chamber 54. The combustion chamber 54 is provided with a glow plug 55 for improving the startability of the engine at a low temperature.
[0037]
The cylinder head 12 is provided with an injector 21 as fuel injection means for directly injecting fuel into the combustion chamber 54 of each cylinder 13. Fuel injection from each injector 21 to each combustion chamber 54 is controlled by a solenoid valve 22. The injector 21 is connected to a common rail 23 that is a pressure accumulation pipe common to the cylinders 13, and the fuel in the common rail 23 is injected from the injector 21 into the corresponding combustion chamber 54 while the electromagnetic valve 22 is open.
[0038]
A relatively high pressure corresponding to the fuel injection pressure is accumulated in the common rail 23. In order to realize this pressure accumulation, the common rail 23 is connected to a discharge port 26 of a supply pump 25 via a supply pipe 24. A check valve 27 is provided in the middle of the supply pipe 24 to allow fuel to be supplied from the supply pump 25 to the common rail 23 and to restrict the backflow of fuel from the common rail 23 to the supply pump 25. Yes.
[0039]
The suction port 28 of the supply pump 25 is connected to the fuel tank 31 via a filter 29, and the supply pump 25 sucks fuel from the fuel tank 31 via the filter 29. At the same time, the supply pump 25 reciprocates the plunger by a cam (not shown) synchronized with the rotation of the diesel engine 11 to increase the fuel to a predetermined pressure and supply the fuel to the common rail 23.
[0040]
In the vicinity of the discharge port 26 of the supply pump 25, a pressure control valve 32 is provided for controlling the fuel pressure discharged from the discharge port 26 toward the common rail 23 and thus the discharge amount. By opening the pressure control valve 32, surplus fuel that is not discharged from the discharge port 26 is returned from the return port 33 of the supply pump 25 to the fuel tank 31 via the return pipe 34.
[0041]
Then, the fuel is injected from the injector 21 into the high-temperature and high-pressure intake air introduced into the cylinder 13 through the intake passage 16 and compressed by the piston 15. This injected fuel self-ignites and burns. The piston 15 is reciprocated by the combustion gas generated at this time, the crankshaft is rotated, and the driving force (output torque) of the diesel engine 11 is obtained. The combustion gas is discharged to the outside of the diesel engine 11 through the exhaust passage 17.
[0042]
In the case of the four-cylinder engine in the present embodiment, the four exhaust passages 17 are connected to the four cylinders 13, respectively. The four exhaust passages 17 are connected to an exhaust branch pipe 47 formed so as to join one collecting pipe immediately downstream of the diesel engine 11.
[0043]
An exhaust purification catalyst 48 is provided on the most downstream side of the exhaust branch pipe 47. Examples of the exhaust purification catalyst 48 include hydrocarbons (HC) and carbon monoxide contained in the exhaust when the air-fuel ratio of the exhaust flowing into the exhaust purification catalyst 48 is a predetermined air-fuel ratio in the vicinity of the theoretical air-fuel ratio. (CO), a three-way catalyst for purifying nitrogen oxide (NOx), and when the air-fuel ratio of the exhaust gas flowing into the exhaust gas purification catalyst 48 is a lean air-fuel ratio, occludes nitrogen oxide (NOx) contained in the exhaust gas And a NOx storage reduction catalyst that reduces and purifies while releasing nitrogen oxide (NOx) stored when the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 48 is the stoichiometric air-fuel ratio or the rich air-fuel ratio, The selective reduction type NOx catalyst that reduces and purifies nitrogen oxide (NOx) in the exhaust when the air-fuel ratio of the exhaust flowing into the exhaust purification catalyst 48 is in an oxygen excess state and a predetermined reducing agent is present, or the above Each Catalyst such as is used comprising a combination of catalysts suitable.
[0044]
A downstream side of the exhaust purification catalyst 48 is connected to an exhaust pipe 49. In the middle of the exhaust pipe 49, a particulate filter 50 that collects exhaust particulate called PM (Particulate Matter) such as soot and SOF (Soluble Organic Fraction) contained in the exhaust is installed. Further, the exhaust pipe 49 is connected to a muffler (not shown) downstream of the particulate filter 50.
[0045]
As shown in FIG. 1, in the diesel engine 11 according to the present invention, various sensors are used to detect the operating state. An intake air temperature sensor 41 that detects an intake air temperature that is the temperature of the intake air is attached to the intake passage 16. An intake pressure sensor 42 that detects an intake pressure that is the pressure of intake air is attached to the intake passage 16 via a filter 35 and a vacuum switching valve (VSV) 36.
[0046]
A water temperature sensor 43 that detects the cooling water temperature, which is the temperature of the cooling water, is attached to the cylinder block 14. In the vicinity of the crankshaft, a rotational speed sensor 44 for detecting the engine rotational speed, which is the rotational speed, is disposed. Further, an accelerator sensor 45 that detects an accelerator opening degree that is a depression amount (depression opening degree) of the pedal 37 by the driver is disposed in the vicinity of the accelerator pedal 37 that is an accelerator operation member.
[0047]
Further, on the upstream side of the exhaust purification catalyst 48, at the portion where the four branch pipes merge into one collecting pipe, the exhaust flowing in the exhaust branch pipe 47, in other words, the exhaust flowing into the exhaust purification catalyst 48. An air-fuel ratio sensor 51 that outputs an electrical signal corresponding to the air-fuel ratio is attached.
[0048]
An engine control unit (hereinafter referred to as “ECU”) 46 is provided in the vehicle as means for controlling each part of the diesel engine 11 based on the detection values of the various sensors 41 to 45, 51, that is, the engine operating state.
[0049]
FIG. 2 is a block diagram showing an internal configuration of the ECU.
[0050]
The ECU 46 is connected to various sensors such as the intake air temperature sensor 41, the intake air pressure sensor 42, the water temperature sensor 43, the rotation speed sensor 44, the accelerator sensor 45, and the air-fuel ratio sensor 51 described above via electric wiring. Output signals from these various sensors are input to the ECU 46.
[0051]
The ECU 46 is connected to an electromagnetic valve drive circuit 52, a throttle actuator drive circuit 53, and other drive circuits via electrical wiring, and the ECU 46 uses the output signal values of the various sensors described above as parameters as parameters. The throttle actuator drive circuit 53 and other drive circuits can be controlled.
[0052]
The fuel injection device according to the present invention includes an electromagnetic valve drive circuit 52 (to be described later) in addition to the electromagnetic valve 22, the common rail 23, the supply pump 25, in addition to the injector 21 as the fuel injection means described above. .
[0053]
Here, as shown in FIG. 2, the ECU 46 includes a CPU 401, a ROM 402, a RAM 403, a backup RAM 404, an input port 405, and an output port 406 that are connected to each other via a bidirectional bus 400. A connected A / D converter (hereinafter referred to as A / D) 407 is provided.
[0054]
The A / D 407 is connected to sensors that output signals in the form of analog signals, such as an intake air temperature sensor 41, an intake air pressure sensor 42, a water temperature sensor 43, an accelerator sensor 45, an air-fuel ratio sensor 51, and the like through electrical wiring. ing. The A / D 407 converts the output signal of each sensor described above from an analog signal format to a digital signal format, and transmits the converted signal to the input port 405.
[0055]
The input port 405 is connected to the above-described sensor that outputs a signal in the analog signal format via the A / D 407 and is directly connected to a sensor that outputs a signal in the digital signal format including the rotation speed sensor 44. It is connected.
[0056]
The input port 405 inputs output signals from various sensors and transmits the output signals to the CPU 401 and the RAM 403 via the bidirectional bus 400.
[0057]
The output port 406 is connected to each drive circuit described above via electrical wiring. Then, the control signal output from the CPU 401 is input via the bidirectional bus 400, and the control signal is transmitted to each drive circuit.
[0058]
The ROM 402 includes a fuel injection amount control routine for determining a fuel injection amount, a fuel injection timing control routine for determining fuel injection timing, a throttle opening control routine for determining the opening of a throttle valve (not shown), In addition to application programs such as a particulate filter regeneration control routine for regenerating the particulate filter collection capability, carbon for removing carbon adhering to the wall surface of the combustion chamber 54 is a program according to the present invention. Remember the removal routine.
[0059]
The ROM 402 stores various control maps in addition to the application programs described above. The above-described control map is, for example, a fuel injection amount control map showing the relationship between the operation state of the diesel engine 11 and the fuel injection amount, a fuel injection timing control map showing the relationship between the operation state of the diesel engine 11 and the fuel injection timing, In addition to a throttle opening degree control map showing the relationship between the operating state of the diesel engine 11 and the opening degree of a throttle valve (not shown), the map is used in a particulate filter regeneration control routine.
[0060]
In the present invention, the ROM 402 performs an injection timing advance control map, an injection timing retard control map, and a sub injection timing control for switching from the fuel injection timing control map and the fuel injection amount control map in the carbon removal routine. A map, a sub injection amount control map, a main injection amount control map, and the like are also stored.
[0061]
The RAM 403 stores output signals of the sensors, calculation results of the CPU 401, and the like. The calculation result is, for example, the engine speed calculated based on the output signal of the rotation speed sensor 44. Various data stored in the RAM 403 is updated to the latest data every time the rotation speed sensor 44 outputs a signal.
[0062]
The backup RAM 404 is a non-volatile memory that retains data even after the operation of the diesel engine 11 is stopped. The backup RAM 404 stores learning values related to various controls, information for specifying a location where an abnormality has occurred, and the like.
[0063]
The CPU 401 operates in accordance with the application program stored in the ROM 402, and executes well-known controls such as fuel injection control, throttle control, and particulate filter regeneration control, as well as carbon removal control that is the gist of the present invention. To do.
[0064]
Hereinafter, the particulate filter regeneration control will be described.
[0065]
The particulate filter 50 collects particulate matter (PM) such as soot and SOF contained in the exhaust gas. However, since the collection capability is limited, the particulate filter 50 has a PM higher than the collection capability. If accumulated in the exhaust gas, the exhaust flow path in the particulate filter 50 may be clogged, and a problem such as excessive increase in the back pressure acting on the diesel engine 11 may occur.
[0066]
Here, since PM such as soot and SOF is burned (oxidized) at a high temperature of about 500 ° C. to 700 ° C., in a high load operation region where the exhaust temperature of the diesel engine 11 becomes high, the PM is in the high temperature exhaust. Although oxidized and hardly deposited on the particulate filter 50, PM is not easily oxidized and tends to be deposited on the particulate filter 50 in the low load operation region where the exhaust temperature of the diesel engine 11 is low.
[0067]
For this reason, when the diesel engine 11 is continuously operated at a low load, the PM collecting ability of the particulate filter 50 is saturated, and there is a possibility that the above-described problems may occur. Therefore, when the diesel engine 11 is continuously operated at low and medium loads, the temperature of the particulate filter 50 is raised to a high temperature range of 500 ° C. to 700 ° C. at an appropriate time, and the inside of the particulate filter 50 is oxidized. It needs to be an atmosphere.
[0068]
By the way, the diesel engine 11 is operated at a lean air-fuel ratio in most of the operation region, and the air-fuel ratio of the exhaust gas discharged from the diesel engine 11 becomes a lean air-fuel ratio in most of the operation region. It can be said that no special control for making the air-fuel ratio of the exhaust gas a lean air-fuel ratio is necessary for regenerating the PM trapping ability of the curate filter 50.
[0069]
However, for an internal combustion engine that is operated in stoichiometric air-fuel ratio (or rich air-fuel ratio operation), secondary air is added to the exhaust gas upstream of the particulate filter 50 when the PM trapping ability of the particulate filter 50 is regenerated. By using such means, the air-fuel ratio of the exhaust gas flowing into the particulate filter 50 needs to be a lean air-fuel ratio.
[0070]
As a method of raising the temperature of the particulate filter 50 to a temperature range of 500 ° C. to 700 ° C. when the diesel engine 11 is in a low / medium load operation state, an electric heater is attached to the particulate filter 50, and PM Although it is conceivable to heat the particulate filter 50 with the heater when regenerating the collection capacity, etc., this method requires the addition of hardware such as a heater to raise the temperature of the particulate filter 50. Further, there is a problem that a space for attaching the heater to the particulate filter 50 is required.
[0071]
Therefore, when actually regenerating PM collection capacity, control to perform additional fuel injection in the expansion stroke or exhaust process after the main injection of fuel (post-injection) or before the main injection to raise the exhaust temperature. Control is performed in which a small amount of fuel is sub-injected in the vicinity of the top dead center of the intake stroke, and then main injection is performed in the vicinity of the compression top dead center (bi-rubber injection). The case where post injection is performed among the above will be described in detail.
[0072]
FIG. 3 shows a flowchart of a particulate filter regeneration control routine executed by the ECU 46. This particulate filter regeneration control routine is a routine stored in the ROM 402 in advance, and is a routine that is repeatedly executed by the CPU 401 every predetermined time (for example, every time the rotation speed sensor 44 outputs a pulse signal).
[0073]
In the particulate filter regeneration control routine, first, in step S501, the CPU 401 determines whether the PM trapping capacity regeneration condition of the particulate filter 50 is satisfied.
[0074]
Here, when the PM trapping capacity regeneration condition is satisfied, (1) the diesel engine 11 is in a low load operation state, (2) the diesel engine 11 is continuously operated at a low load for a predetermined time or more, (3) The value obtained by subtracting the integrated value of the high load operation time from the integrated value of the low load operation time is equal to or greater than a predetermined value. (4) Integration of the amount of PM contained in the inflow exhaust gas of the particulate filter 50 Examples of the condition include that the value is a predetermined amount or more, or (5) the exhaust pressure in the exhaust passage (exhaust pipe 49) upstream from the particulate filter 50 is a predetermined pressure or more.
[0075]
If it is determined in S501 that the PM collection capability regeneration condition as described above is not satisfied, the CPU 401 proceeds to S504 and executes normal fuel injection timing control.
[0076]
On the other hand, if it is determined in S501 that the PM trapping capacity regeneration condition is satisfied, the CPU 401 proceeds to S502 and determines whether or not the operation state of the diesel engine 11 is in a high load operation state.
[0077]
When it is determined in S502 that the operation state of the diesel engine 11 is in the high load operation state, the CPU 401 considers that it is not necessary to execute the PM trapping capacity regeneration control, and proceeds to S504. In S504, the CPU 401 executes normal fuel injection timing control.
[0078]
This is because, when the diesel engine 11 is in a high-load operation state, as described above, relatively high-temperature exhaust is discharged from the diesel engine 11, and thus such high-temperature exhaust flows into the particulate filter 50. This is because the PM collected by the particulate filter 50 is oxidized.
[0079]
On the other hand, if it is determined in S502 that the operation state of the diesel engine 11 is not in the high load operation state, the CPU 401 discharges the exhaust gas at a relatively low temperature from the diesel engine 11, and therefore the PM trapping of the particulate filter 50 is performed. Considering that it is necessary to raise the exhaust temperature to regenerate the collecting ability, the process proceeds to S503.
[0080]
In step S503, in order to raise the exhaust gas temperature, post injection, which is additional fuel injection in the expansion stroke or the exhaust stroke, is performed after the main fuel injection. When performing post injection, a PM regeneration sub-injection timing control map that defines a target post-injection amount and a target post-injection time for raising the temperature of the particulate filter to a recyclable target exhaust temperature, and PM regeneration sub-injection The post-injection timing and injection amount are obtained from the amount control map and the PM regeneration main injection amount control map, and injected from the injector 21.
[0081]
Here, part of the fuel injected into the cylinder by the post-injection is burned in the cylinder, but does not affect the output of the engine. Further, most of the fuel that has not been combusted is vaporized in the cylinder and discharged together with the exhaust gas into the exhaust passage, combusted by the catalytic action of the exhaust purification catalyst 48, and the exhaust temperature rises due to the heat generated at that time. As a result, the temperature of the particulate filter 50 rises, and the PM collected by the particulate filter 50 is oxidized.
[0082]
Then, after continuing the post-injection for a predetermined period, the fuel injection is returned to the normal state, and then the CPU 401 ends this routine.
[0083]
Here, the period during which the post-injection is continued may be a predetermined period as described above, but is a period that is changed according to the degree of the PM collection capability regeneration condition established in S501. Also good.
[0084]
Further, for example, a flow in which the exhaust pressure in the exhaust passage (exhaust pipe 49) upstream of the particulate filter 50 is detected by a pressure sensor (not shown) and post injection is continued until the detected exhaust pressure becomes a predetermined value or less. It may be.
[0085]
As described above, the post injection has been described in detail. However, the particulate filter regeneration control by the big rubber injection also differs only in the sub injection timing, and the PM regeneration sub injection timing control map and PM regeneration sub injection amount read in S503. It is considered that only the contents of the control map and the PM regeneration main injection amount control map are different.
[0086]
In other words, the post injection or the big rubber injection means that the fuel injection means injects fuel in at least one of the intake stroke, the expansion stroke, and the exhaust stroke.
[0087]
Next, problems caused by performing the above-described post injection or big rubber injection will be described.
[0088]
As described above, when sub-injection such as big rubber injection or post injection is performed, the air-fuel ratio that is the ratio of the intake air amount and the fuel injection amount is in a rich state where the ratio of the fuel injection amount is higher than the stoichiometric air-fuel ratio, or Since the state is close, the amount of fuel adhering to the wall surface of the combustion chamber 54 increases.
[0089]
As a result, the amount of carbon adhering to and remaining on the wall surface of the combustion chamber 54 also increases.
[0090]
While this carbon adheres to the wall surface in the combustion chamber 54, it has the effect of improving the heat insulation efficiency of the wall surface of the combustion chamber 54 and improving the combustion efficiency. On the other hand, when the vehicle starts or accelerates, the deposited carbon is desorbed all at once. For example, there is a risk that the commercial value of the vehicle may be significantly reduced, such as being discharged as smoke from the tail pipe.
[0091]
In addition, carbon adheres to the tip of the fuel injection valve, so that carbon accumulates in the fuel injection nozzle provided at the tip of the fuel injection valve, and the fuel spray characteristics and the fuel injection direction change to change the engine. In addition to adversely affecting the combustion stability of the fuel, there is a possibility that the fuel injection amount is reduced by blocking the injection port of the fuel injection valve or that the fuel injection becomes impossible and the engine operation is hindered.
[0092]
As described above, the object of the present invention is that, in a compression ignition type internal combustion engine, carbon adheres or accumulates in the combustion chamber 54 by vigorous rubber injection, post-injection, etc. It is to prevent problems from occurring.
[0093]
In order to achieve the object of the present invention, in the present embodiment, the fuel injection timing is set in order to remove carbon adhering to the wall surface of the combustion chamber 54 after the secondary injection such as post injection or big rubber injection. Control to advance the angle.
[0094]
Hereinafter, the flow of the carbon removal control in the present embodiment will be described with reference to FIG.
[0095]
FIG. 4 shows a carbon removal routine for removing carbon adhering to the combustion chamber 54. This carbon removal routine is a routine stored in the ROM 402 in advance, and is executed by the CPU 401 immediately or after a predetermined time has elapsed after exiting the above-described particulate filter regeneration control routine.
[0096]
In the carbon removal routine, first, in S601, the CPU 401 switches the map for reading the fuel injection timing data in the fuel injection timing control routine from the fuel injection timing control map to the injection timing advance control map.
[0097]
Then, the CPU 401 transmits a control signal based on the data in the injection timing advance control map to the solenoid valve drive circuit 52. Accordingly, from this point, the injector 21 injects fuel at a timing advanced by a predetermined time from the normal time.
[0098]
Thereafter, in step S602, the CPU 401 starts a timer and sets a predetermined time t. ₀ This operation is continued until elapses. Therefore, the injector 21 ₀ Until the time elapses, fuel injection at the advanced timing is continued.
[0099]
And t ₀ In step S604, the CPU 401 returns the map for reading the fuel injection timing data in the fuel injection timing control routine from the injection timing advance control map to the fuel injection timing control map, and then ends this routine.
[0100]
During execution of this routine, as described above, the injector 21 injects fuel at a timing earlier than the normal time by a predetermined time. As a result, the time from fuel injection to ignition becomes relatively long, and the fuel injected during that time evaporates and mixes to form a combustible mixture. When they reach the ignition point, explosion combustion occurs at a time, so the rate of pressure increase during combustion increases. In other words, the combustion pressure wave that accompanies combustion will be greater than in normal operation.
[0101]
In this way, in the compression ignition type internal combustion engine, when the fuel in the combustion chamber 54 reaches the ignition point in the compression stroke, the rate of increase in pressure during combustion increases due to explosion combustion at a time, resulting in an increase in pressure waves. This phenomenon is called knocking (diesel knock).
[0102]
On the other hand, in the internal combustion engine including the compression ignition type internal combustion engine 11, the temperature of the inner surface of the cylinder 13 is usually lower than the temperature at the center of the combustion chamber 54. This is because the heat capacity of the cylinder 13 is larger than that of the combustion gas in the combustion chamber 54 and the cylinder block 14 is cooled.
[0103]
A gas layer in the combustion chamber 54 called a temperature boundary layer is formed between the central portion of the high temperature combustion chamber 54 and the inner surface of the low temperature cylinder 13. The inside of this temperature boundary layer has a high temperature equivalent to the central portion of the combustion chamber 54, and the outside has a low temperature equivalent to the inner surface of the cylinder, and a temperature gradient is generated in the thickness direction of the temperature boundary layer. is there.
[0104]
In the present embodiment, knocking (diesel knock) is generated as described above, and the temperature boundary layer formed in the vicinity of the wall surface of the combustion chamber 54 is lost by a large pressure wave generated at that time. it can.
[0105]
When the temperature boundary layer in contact with the wall surface of the combustion chamber 54 disappears, the hot gas at the center of the combustion chamber contacts the wall surface of the combustion chamber 54. As a result, the temperature of the wall surface of the combustion chamber 54 rises, and the carbon layer attached to the wall surface of the combustion chamber 54 can be burned and removed. For the same reason, the adhesion of carbon can be prevented.
[0106]
Here, the wall surface temperature increasing means in the present invention includes the ECU 46 in which the injection timing advance control map and the carbon removal routine program are stored in the ROM 402.
[0107]
According to the present embodiment, the temperature of the wall surface of the combustion chamber 54 can be increased only by advancing the fuel injection timing without adding a heating member such as a heater. That is, the carbon adhering to or depositing on the wall surface of the combustion chamber 54 can be removed with a simple structure without increasing the cost and space of the entire engine. Further, it is possible to prevent carbon from adhering to the wall surface of the combustion chamber 54.
[0108]
As a result, defects due to carbon adhering to the wall surface of the combustion chamber, specifically, carbon deposits on the fuel injection nozzle and changes the fuel spray characteristics. It is possible to prevent problems such as being discharged separately.
[0109]
In the above, t is the time for continuing the advance of the injection timing ₀ May be a predetermined period determined in advance, but the amount of carbon adhering to the wall surface of the combustion chamber 54 is the amount of fuel sub-injected into the combustion chamber 54 from the injector 21 during sub-injection such as post-injection. Therefore, for example, a period in which the post-injection fuel amount performed in the particulate filter regeneration control routine is set to be longer as the post-injection fuel amount is increased, and the post-injection fuel amount is set to be shorter may be set.
[0110]
However, the longer knocking (diesel knock) generation time may affect the durability of the engine. ₀ Is desirably 30 minutes or less.
[0111]
The advance amount of the fuel injection timing should be determined individually according to engine characteristics, but is preferably in the range of 10 ° to 40 ° before compression top dead center.
[0112]
If the compression top dead center is 10 ° or less, the effect of the injection timing advance is not significant. If the compression top dead center is 40 ° or more, the residence time of the fuel before combustion in the combustion chamber 54 is too long. This is because there is a risk that a fuel may adhere to the cylinder liner (not shown) mounted on the cylinder block 14 or the cylinder wall surface, resulting in the occurrence of bore flushing.
[0113]
(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.
[0114]
In the first embodiment described above, the example in which the fuel injection timing is advanced in the carbon removal routine has been described. However, in the present embodiment, the fuel injection timing is retarded in the carbon removal routine. Further, an example will be described in which the amount of carbon attached to the wall surface of the combustion chamber 54 is actually detected, and the period during which the temperature of the wall surface of the combustion chamber 54 is raised is determined based on the detected amount.
[0115]
FIG. 5 is a cross-sectional view showing the vicinity of the exhaust valve 19 of the diesel engine 11 according to the second embodiment.
[0116]
Here, since the mechanism for driving the exhaust valve 19 is known, the description thereof is omitted.
[0117]
The difference from the same part in FIG. 1 is that the cylinder head 12 is provided with a crystal resonator 70 as carbon adhesion amount detection means.
[0118]
An input / output cable 71 is connected to the crystal unit 70, and the other end of the input / output cable 71 is connected to the vibration frequency detection circuit 56 and the crystal unit drive circuit 57.
[0119]
FIG. 6 is a block diagram showing an internal configuration of the ECU according to the second embodiment.
[0120]
In FIG. 6, the vibration frequency detection circuit 56 is connected to an A / D 407 of the ECU. An electric signal that oscillates at the natural frequency is generated from the crystal unit 70 and transmitted to the vibration frequency detection circuit 56.
[0121]
Thereafter, the vibration frequency detection circuit 56 converts the electric signal into a detection signal corresponding to the vibration frequency and inputs the detection signal to the A / D 407. The detection signal corresponding to the vibration frequency is converted into a digital signal and stored in the ROM 402.
[0122]
On the other hand, the crystal oscillator driving circuit 57 is connected to the output port 406 of the ECU 46, and receives a command from the CPU 401 to transmit a signal of the natural frequency to the crystal oscillator 70, whereby the crystal oscillator 70. Is driven to oscillate.
[0123]
The natural frequency of the crystal unit 70 changes due to carbon adhering to the surface thereof. In general, if the amount of carbon attached is large, the vibration frequency changes to the low frequency side.
[0124]
Therefore, when post injection or big rubber injection is performed in the particulate filter regeneration routine, if carbon adheres to the above-described crystal resonator 70, the detection signal input from the vibration frequency detection circuit 56 to the ECU 46 changes. .
[0125]
The amount of carbon adhesion can be detected from the amount of change.
[0126]
FIG. 7 shows a carbon removal routine in the second embodiment. As in the first embodiment, this routine is executed immediately after the particulate filter regeneration control routine ends or after a predetermined time has elapsed.
[0127]
In FIG. 7, first, in step S <b> 801, the CPU 401 takes in a signal indicating the carbon adhesion amount detected by the crystal resonator 70 serving as the carbon adhesion amount detection unit, and is preset as a threshold value for determining whether or not carbon removal is necessary. Carbon adhesion m ₁ Compare with
[0128]
Carbon adhesion amount is m ₁ If it is less, the routine is exited without removing the carbon. Carbon adhesion amount is m ₁ If YES in step S802, the flow advances to step S802, and the map for reading the fuel injection timing data in the fuel injection timing control routine is switched from the fuel injection timing control map to the injection timing retardation control map.
[0129]
Then, the CPU 401 transmits a control signal based on the data in the injection timing retardation control map to the solenoid valve drive circuit 52. Therefore, from this time, the injector 21 injects fuel at a timing delayed by a predetermined time from the normal time.
[0130]
Thereafter, in step S803, the CPU 401 starts a timer and sets a predetermined time t. ₁ This operation is continued until elapses. Therefore, the injector 21 ₁ Until the time elapses, fuel injection is continued at the retarded timing.
[0131]
And t ₁ After the elapse of time, in step S805, the CPU 401 again captures a signal indicating the carbon adhesion amount detected at that time by the crystal resonator 70 serving as the carbon adhesion amount detection unit, and the m ₁ Compare with
[0132]
Carbon adhesion amount is m ₁ If it is smaller, the map for reading the fuel injection timing data in the fuel injection timing control routine in S806 is returned from the injection timing retardation control map to the fuel injection timing control map, and then this routine is terminated.
[0133]
Carbon adhesion amount is m ₁ If it is above, the process returns to S803, the timer starts again, and the time t ₁ Until the time elapses, fuel injection is repeated at the retarded timing.
[0134]
In step S805, the carbon adhesion amount detected by the crystal unit 70 is m. ₁ The fuel injection at the retard timing is continued until a smaller value is indicated.
[0135]
After that, in S805, the carbon adhesion amount detected by the crystal unit 70 is m. ₁ When the value is smaller, the map for reading the fuel injection timing data in the fuel injection timing control routine is returned to the fuel injection timing control map from the injection timing retardation control map in 806, and this routine is terminated.
[0136]
During execution of this routine, as described above, the injector 21 injects fuel at a timing later than the normal time by a predetermined time.
[0137]
Also in the present embodiment, as in the first embodiment, the wall surface temperature raising means includes the ECU 46 that stores the above-described injection timing retardation control map and carbon removal routine program in the ROM 402.
[0138]
According to the present embodiment, since the fuel injection timing is delayed with respect to the normal injection timing, the fuel in the combustion chamber 54 is harder to ignite than in the normal state. As a result, the ignition timing is delayed, and the fuel injected during that time evaporates and mixes to form a combustible mixture. When they reach the ignition point, explosion combustion occurs at a time, so the rate of increase in pressure during combustion increases, and as a result, knocking (diesel knock) occurs.
[0139]
As a result of the increase in the pressure increase rate during combustion, the temperature boundary layer formed in the vicinity of the wall surface of the combustion chamber 54 by the increased pressure wave can be eliminated.
[0140]
As a result, as in the first embodiment, the wall surface temperature of the combustion chamber 54 rises, and the carbon layer attached to the wall surface of the combustion chamber 54 can be burned and removed. Also, carbon adhesion can be prevented.
[0141]
Further, it is possible to prevent problems such as carbon depositing on the fuel injection nozzle and changing the fuel spray characteristics, and a large amount of accumulated carbon being desorbed and discharged at the time of starting. .
[0142]
Further, according to the present embodiment, the amount of carbon adhering to the wall surface of the combustion chamber 54 is detected by the crystal resonator 70 which is a carbon adhering amount detection means, and the detected carbon adhering amount is a predetermined amount m. ₁ Since the fuel injection at the timing delayed until it becomes smaller is continued, the carbon adhering to the combustion chamber 54 can be reliably removed.
[0143]
Further, according to the present embodiment, the amount of carbon attached to the wall surface of the combustion chamber 54 is m. ₁ When it becomes less, the fuel injection at the retarded timing is terminated. Accordingly, since the injection angle delay timing operation time can be minimized, it is possible to prevent waste of energy without unnecessarily prolonging the state where the pressure wave in the combustion chamber 54 is large. At the same time, the influence on the durability of the diesel engine 11 can be minimized.
[0144]
In the above routine, the carbon adhesion amount is detected again by the crystal unit 70 in S805, but the step of S805 is omitted, and the fuel injection at the retard timing is performed according to the value of the carbon adhesion amount detected in S801. T is the duration ₁ This value may be stored in advance in the map of the ROM 403, and fuel injection at the retarded angle timing may be continued only during the period corresponding to the detected value of the carbon adhesion amount.
[0145]
By adopting such a configuration, carbon adhering to the combustion chamber 54 can be reliably removed.
[0146]
Further, in the above routine, the carbon adhesion amount detected by the crystal unit 70 in S805 is the predetermined amount m. ₁ If this is the case, t ₁ During this period, the fuel injection at the retard timing is to be continued. ₁ T is a shorter time ₂ It may be configured to extend the time only and detect the carbon adhesion amount again.
[0147]
By adopting such a configuration, it is possible to continue the fuel injection at the retarded angle only for the time really necessary to remove the attached carbon.
[0148]
The retard amount of the fuel injection timing should be determined individually according to engine characteristics, but is desirably in the range of 20 ° or less after the compression top dead center. This is because if it is 20 ° or more after the compression top dead center, the pressure in the combustion chamber 54 decreases, and it may become impossible to reach the ignition condition, resulting in a misfire.
[0149]
In the present embodiment, the carbon adhering amount detecting means using the change in the vibration frequency of the crystal oscillator 70 shown in FIG. 5 is used. Using the change in electrical characteristics such as capacitance or electrical resistance, and that the eddy current generated on the metal surface facing the piston 15 changes depending on the amount of carbon deposited on the piston 15. The strength of the ionic current generated during combustion by applying a constant voltage between the electrode and the body of the glow plug 55 for improving engine startability at low temperatures is used on the glow plug 55. Those that use changes in the thickness of carbon deposited on the surface, and those that measure changes in reflectivity due to the amount of carbon attached to the metal surface. There.
[0150]
Also, the carbon adhesion amount m determined as a threshold value for determining whether or not carbon removal is necessary. ₁ As described above, carbon that causes defects such as carbon depositing at the injection nozzle of the injector 21 to change the fuel spray characteristics, a large amount of accumulated carbon being desorbed and discharged at the time of starting, etc. The adhesion amount may be obtained experimentally, and may be a constant value obtained by multiplying this by a safety factor, or may be changed depending on conditions such as the total operation time of the diesel engine 11.
[0151]
In the present embodiment, the predetermined amount used in S801 and S805 to be compared with the detected carbon adhesion amount is the same value m. ₁ For example, m in S805 ₁ , M ₁ Smaller m ₂ By doing so, more reliable carbon removal can be realized.
[0152]
(Third embodiment)
A third embodiment will be described with reference to FIG.
[0153]
Also here, the configuration different from the first and second embodiments will be described, and the description of the same configuration will be omitted.
[0154]
In the present embodiment, in the carbon removal routine, in order to increase the temperature of the wall surface of the combustion chamber 54, a small amount of fuel is injected as a secondary injection before the compression top dead center, and then the main fuel is near the compression top dead center. Injection is performed.
[0155]
Further, in the present embodiment, when proceeding to the carbon removal routine, it is determined whether or not the diesel engine 11 is in a high load operation. If the engine is in a high load operation, the carbon removal operation is not performed and is continued. This routine is to be terminated.
[0156]
This is because during high-load operation, the in-cylinder temperature is high, so that carbon adhesion is less likely to occur, and there is no need to remove carbon, and when the combustion pressure wave is further increased at high temperatures ( This is because when the engine is knocked, the engine may be adversely affected.
[0157]
FIG. 8 is a carbon removal routine according to the present embodiment.
[0158]
The CPU 401 enters this routine immediately after the end of the particulate filter regeneration control routine or after a predetermined time has elapsed.
[0159]
First, in step S901, the CPU 401 determines whether the current engine operation is a high load operation. Here, whether or not the operation is a high load operation is determined from the accelerator opening degree detected by the accelerator sensor 45 or the like.
[0160]
If it is determined in S901 that the operation is a high load operation, this routine is directly exited. On the other hand, if it is determined that the operation is not a high load operation, the process proceeds to S902, and a map for reading the fuel injection amount data in the fuel injection amount control routine is changed from the fuel injection amount control map to the sub injection amount control map and the main injection amount control map. Switch to.
[0161]
Further, the map for reading the fuel injection timing data in the fuel injection timing control routine is switched from the fuel injection timing control map to the sub injection timing control map and the main injection timing control map.
[0162]
Then, the CPU 401 transmits a control signal based on the data in the sub injection amount control map, the sub injection timing control map, the main injection amount control map, and the main injection timing control map to the electromagnetic valve drive circuit 52. Therefore, from this point of time, the injector 21 starts sub injection of a small amount of fuel before compression top dead center, and then performs main injection at compression top dead center.
[0163]
Thereafter, in step S903, the CPU 401 starts a timer and sets a predetermined time t. ₃ This operation is continued until elapses. Therefore, the injector 21 ₃ Until the time elapses, the sub-injection and the main injection are continued.
[0164]
Then, after the timer is started in S903, t ₃ In step S905, the CPU 401 returns a map for reading the fuel injection amount data in the fuel injection amount control routine to the fuel injection amount control map, and a map for reading the fuel injection timing data in the fuel injection timing control routine. After returning to the control map, this routine ends.
[0165]
According to the present embodiment, the fuel by the sub-injection evaporates and mixes to form a combustible air-fuel mixture and combines with the fuel by the main injection to increase the relative fuel amount, so that these reach the ignition point. When this occurs, explosion combustion occurs at a time, and the rate of pressure increase during combustion increases. As a result, knocking (diesel knock) occurs.
[0166]
Depending on the amount of sub-injection, ignition and combustion may occur before the main injection is started. In this case as well, the sub-injected fuel forms a combustible mixture sufficient to increase the rate of pressure increase during combustion. Therefore, the same effect can be obtained.
[0167]
A large combustion pressure wave generated by knocking (diesel knock) causes the temperature boundary layer in the vicinity of the wall surface of the combustion chamber 54 to disappear and raises the wall surface temperature of the combustion chamber 54, thereby removing attached carbon. In addition, adhesion of carbon can be prevented.
[0168]
In this case, the total amount of fuel in one injection is larger than that in normal fuel injection, but has less influence on the engine output than in the case where the amount of fuel in main injection is increased.
[0169]
Further, according to the present embodiment, as described above, since the temperature of the combustion chamber 54 is already high during high load operation, normal fuel injection is performed without performing sub-injection during high load operation. I am going to do that.
[0170]
Therefore, it is possible to prevent the fuel efficiency from being deteriorated by performing unnecessary sub-injection, and the combustion chamber 54 from being excessively heated to adversely affect the engine.
[0171]
In the present embodiment, the wall surface temperature increasing means includes an ECU 46 that stores the main injection amount control map, the sub injection amount control map, the main injection timing control map, the sub injection timing control map, and the carbon removal routine program in the ROM 402. Consists of including.
[0172]
In this embodiment, the threshold value for determining whether or not the engine is operating at a high load may be determined individually depending on the physical properties of the engine and the operating state. It may be determined that the operation is high load.
[0173]
When operating at a torque of 80% or more of the full load torque, the temperature in the combustion chamber is sufficiently high, and it is possible to burn carbon adhering to the wall surface of the combustion chamber 54 without performing sub-injection. This is because it is considered.
[0174]
In addition, the injection amount at the time of sub-injection in the present embodiment may be determined individually depending on the physical properties of the engine and the operating state, but it is desirable that the equivalent ratio is 0.5 or less. This is because if the fuel injection amount is excessive, the pressure wave at the time of combustion described above becomes too large and may adversely affect the engine.
[0175]
Further, the lower limit of the sub-injection timing should be determined individually, but it is desirable to set it to 30 ° or more before the compression top dead center. This is because if the sub-injection timing is 30 ° or less before the compression top dead center, the effect of performing the sub-injection is not significant.
[0176]
The upper limit of the sub-injection timing may be determined individually from the range up to around 360 ° before compression top dead center according to the physical properties of the engine, and the intake top dead center at 360 ° before compression top dead center. You may implement big rubber injection performed near.
[0177]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from the first embodiment will be described. Since other configurations and operations are the same as those of the first embodiment, description of the same components will be omitted.
[0178]
In the present embodiment, a swirl control device 65 that generates a swirl in the combustion chamber 54 and further changes the strength of the swirl is provided. When performing the carbon removal routine, the swirl control device 65 is provided. An example in which the temperature of the wall surface of the combustion chamber 54 is increased by strengthening the swirl in the combustion chamber 54 will be described. It is assumed that the cylinder head 12 in the present embodiment is provided with the crystal resonator 70 as the carbon adhesion amount detecting means shown in FIG. 5 as in the second embodiment.
[0179]
FIG. 9 is a bottom view of the cylinder head 12 in the present embodiment. In the present embodiment, the diesel engine 11 is an intake and exhaust two-valve type, so that two intake passages 16 a and 16 b are connected to the combustion chamber 54 via two intake valves 18, and two exhaust valves 19 are connected. The two exhaust passages 17 are connected to the inside of the combustion chamber 54 via.
[0180]
Here, one of the two intake passages 16 a is swung in the intake air so as to generate an air flow that swirls laterally in the cylinder 13 when the intake air is introduced into the cylinder 13, that is, a swirl is generated. It is a helical port that gives velocity components. Further, the other 16b of the two intake passages 16 is a straight port that does not particularly give a swirl speed component to the intake air. The straight port 16b is provided with a swirl control valve 60 that allows the straight port 16b to be opened and closed.
[0181]
The swirl control valve 60 is driven by a drive device such as a step motor. When the straight port 16b is closed by the swirl control valve 60, the intake air is introduced into the cylinder 13 only by the helical port 16a. Since it turns in the horizontal direction, a strong swirl is generated in the cylinder 13.
[0182]
On the other hand, when the straight port 16b is opened by the swirl control valve 60, the intake air is introduced into the cylinder 13 from both the helical port 16a and the straight port 16b. In this case, the intake air introduced from the helical port 16a is given the above-described swirl speed component, but in order to swirl within the cylinder 13, the intake air introduced from the straight port 16b must be swung together. In other words, it becomes a resistance and cannot generate a strong swirl.
[0183]
Therefore, the strength of the swirl formed in the cylinder 13 can be controlled by changing the opening degree of the swirl control valve 60 as described above. In other words, the strength of the swirl generated in the combustion chamber 54 can be estimated from the opening of the swirl control valve 60. The strength of the swirl can also be expressed as a swirl ratio. The swirl ratio is a value obtained by dividing the rotational speed of the swirl generated in the combustion chamber by the engine rotational speed at that time. Moreover, in this Embodiment, the swirl control apparatus 65 is comprised including said helical port 16a and the swirl control valve 60. FIG.
[0184]
FIG. 10 shows a carbon removal routine in the present embodiment. As in the first embodiment, this routine is executed immediately after the end of the filter regeneration control routine or after a predetermined time has elapsed.
[0185]
When this routine is executed, first, in S1001, the carbon adhesion amount detected by the crystal unit 70 as the carbon adhesion amount detection means is a predetermined amount m. ₁ It is judged whether it is less, and the carbon adhesion amount is a predetermined amount m. ₁ If it is determined that the number is smaller, this routine is temporarily terminated as it is. On the other hand, the carbon adhesion amount is a predetermined amount m. ₁ If it is determined that the above is true, the process proceeds to S1002. Since the content of the process of S1001 is the same as the process of S801 shown in FIG. 7, detailed description is abbreviate | omitted.
[0186]
Next, in S1002, it is determined at that time whether the diesel engine 11 is operating at a high load. If it is determined that the high load operation is being performed, the routine is temporarily terminated. On the other hand, if it is determined that the high load operation is not being performed, the process proceeds to S1003. The contents of the process of S1002 are also the same as the contents of the process of S901 shown in FIG.
[0187]
Next, the routine proceeds to S1003, where the opening degree θ of the swirl control valve 60, which is the target in this routine, is determined. ₁ And the swirl strengthening duration t, which is the time during which the swirl strengthening of the combustion chamber 54 is continued ₄ Determine the value of. Here, swirl reinforcement duration t ₄ The value of the swirl control valve 60 opens the opening θ ₁ The amount of carbon detected in S1001 is reduced to m by squeezing up to a point and strengthening the swirl in the combustion chamber 54. ₁ It is determined as a sufficient time necessary to remove until the following.
[0188]
That is, the amount of carbon adhering to be detected in S1001, the opening degree of the swirl control valve 60, and the adhering carbon at least m by swirl strengthening. ₁ The relationship with the time required to be removed until the following adhesion amount is experimentally obtained in advance and mapped, and in S1003, the swirl control valve opening θ ₁ And swirl reinforcement duration t ₄ Is determined by reading from the map.
[0189]
And in S1004, the process which actually strengthens the swirl in the combustion chamber 54 is performed. Specifically, the opening degree θ of the swirl control valve 60 determined by S1003. ₁ Squeeze until. As a result, the amount of intake air flowing into the combustion chamber 54 from the straight port 16b is reduced, and the proportion of intake air flowing into the combustion chamber 54 from the helical port 16a in the entire intake air is increased. The swirl in the combustion chamber 54 is strengthened.
[0190]
By this treatment, the air flow in the combustion chamber 54 is strengthened, and the temperature boundary layer formed in the vicinity of the wall surface of the combustion chamber 54 becomes thin or disappears. Thereby, the wall surface temperature of the combustion chamber 54 can be raised, and it can be brought close to the gas temperature at the center of the combustion chamber 54. As a result, carbon adhering to the wall surface of the combustion chamber 54 can be removed.
[0191]
Next, it progresses to S1005. Here, a timer is started. Then, the process proceeds to S1006, and the time from the start of the timer is t ₄ Whether it is smaller is determined. Where t ₄ The value of is the swirl strengthening duration determined in S1003.
[0192]
In S1006, the time from the start of the timer is t ₄ If it is smaller, the swirl strengthening duration has not yet elapsed, so the process returns to S1006 and the time from the start of the timer is again t12 in S1006. ₄ Whether it is smaller is determined. In S1006, the time from the start of the timer is t. ₄ This process is repeated until it is determined that the number is greater than or equal to.
[0193]
As described above, in the carbon removal routine in the present embodiment, in S1003, the optimum opening degree θ of the swirl control valve 60 with respect to the carbon adhesion amount detected in S1001. ₁ And swirl reinforcement duration t ₄ In S1004, the opening of the swirl control valve 60 is θ ₁ In step S1006, the swirl reinforcement duration t ₄ During this time, the swirl strengthening state in the combustion chamber 54 is continued. From this, after the processing of S1006, the carbon adhesion amount is m. ₁ Since it is presumed that it has been removed to the following, in this routine, the process of detecting the carbon adhesion amount is not performed again as in the process of S805 shown in FIG.
[0194]
Therefore, in S1006, the elapsed time from the timer start is t. ₄ If it is determined as above, the process proceeds to S1007, the opening degree of the swirl control valve 60 is returned to the original, the swirl in the combustion chamber 54 is weakened, and this routine is finished.
[0195]
As described above, in the present embodiment, the valve opening degree of the swirl control valve 60 is controlled, and the swirl in the combustion chamber 54 is strengthened to be in the high swirl state. As a result, the temperature boundary layer in the combustion chamber 54 is thinned or eliminated, thereby raising the wall surface temperature of the combustion chamber 54 and removing carbon adhering to the combustion chamber 54.
[0196]
Therefore, the temperature boundary layer in the combustion chamber 54 can be thinned or eliminated by simple control of strengthening the swirl in the combustion chamber 54 without affecting the fuel consumption, vibration, and noise of the diesel engine 11. The carbon adhering to the combustion chamber 54 can be removed.
[0197]
【The invention's effect】
According to the present invention, the temperature of the wall surface of the combustion chamber is increased by the wall surface temperature increasing means after the sub-injection such as the big rubber injection and the post injection is performed in the control associated with the regeneration process of the exhaust purification device, for example. By performing the sub-injection, it is possible to prevent the carbon from adhering to the wall surface of the combustion chamber or to remove the adhering carbon.
[0198]
That is, carbon adheres to and accumulates on the wall surface of the combustion chamber, so that when the vehicle starts or accelerates, the deposited carbon is released at a stretch and discharged as smoke from the tail pipe, reducing the commercial value of the vehicle, By adhering carbon to the tip of the fuel injection valve, carbon accumulates at the fuel injection nozzle provided at the tip of the fuel injection valve, and the fuel spray characteristics and fuel injection direction change, causing engine combustion. Not only does it adversely affect the stability, but it can also prevent problems such as the fuel injection amount being reduced by blocking the injection port of the fuel injection valve, or the operation of the engine being hindered because the fuel injection is disabled. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a compression ignition type internal combustion engine according to the present invention.
FIG. 2 is a block diagram showing an internal configuration of the ECU.
FIG. 3 is a diagram showing a particulate filter regeneration control routine.
FIG. 4 is a diagram showing a carbon removal routine in the first embodiment.
FIG. 5 is a cross-sectional view showing a schematic configuration in the vicinity of a crystal resonator that is carbon adhesion amount detection means in the second embodiment.
FIG. 6 is a block diagram showing an internal configuration of an ECU according to the second embodiment.
FIG. 7 is a diagram showing a carbon removal routine in the second embodiment.
FIG. 8 is a diagram showing a carbon removal routine in the third embodiment.
FIG. 9 is a bottom view of a cylinder head 12 according to a fourth embodiment of the present invention.
FIG. 10 is a diagram showing a carbon removal routine in a fourth embodiment of the present invention.
[Explanation of symbols]
11 .... Compression ignition type internal combustion engine (diesel engine)
16 .... Intake passage
16a Helical port
16b ... Straight port
17 ... Exhaust passage
18 .... Intake valve
19 ... Exhaust valve
21 ... Injector
22 ... Solenoid valve
46 .... ECU
50 ... Particulate filter
52... Solenoid valve drive circuit
60... Swirl control valve
65... Swirl control device
70 ・ ・ ・ ・ Quartz crystal unit
401 ... CPU
402 ... ROM

Claims (8)

Fuel injection means for directly injecting fuel into the combustion chamber;
Wall temperature raising means for raising the temperature of the wall surface of the combustion chamber immediately after execution of control in which the fuel injection means performs post injection separately from main injection for regeneration processing in the exhaust purification device ;
A compression ignition type internal combustion engine comprising: Carbon adhesion amount detection means for detecting the carbon adhesion amount on the wall surface of the combustion chamber is further provided, and the wall surface temperature increasing means is configured to detect the amount of carbon adhesion on the combustion chamber based on the carbon adhesion amount detected by the carbon adhesion amount detection means. 2. The compression ignition internal combustion engine according to claim 1, wherein a period during which the temperature of the wall surface is to be increased is determined. The compression ignition internal combustion engine according to claim 1 or 2, wherein the wall surface temperature increasing means increases a rate of pressure increase during combustion in the combustion chamber. The compression ignition type internal combustion engine according to claim 3, wherein the wall surface temperature raising means generates knocking in the combustion chamber. The compression ignition type internal combustion engine according to claim 1 or 2, wherein the wall surface temperature increasing means increases the temperature of the wall surface of the combustion chamber by strengthening air flow in the combustion chamber. A swirl control device capable of generating a swirl in the combustion chamber and controlling the strength of the swirl;
The compression ignition type internal combustion engine according to claim 5, wherein the wall surface temperature increasing means enhances air flow in the combustion chamber by generating or strengthening the swirl by the swirl control device. The compression ignition internal combustion engine according to any one of claims 1 to 6, wherein the wall surface temperature increasing means does not increase the temperature of the wall surface of the combustion chamber when the internal combustion engine is in a high load operation state. A fuel injection device that directly injects fuel into the combustion chamber; and a control unit that controls a fuel injection timing and a fuel injection amount of the fuel injection device, the control unit for the regeneration processing in the exhaust gas purification device. Immediately after execution of post injection control separately from main injection from the injection means, the fuel injection device is controlled to raise the temperature of the wall surface of the combustion chamber. Fuel injection system.

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