JP5709451B2 - Diesel engine exhaust purification system - Google Patents

Description

  The present invention relates to an exhaust emission control device for a diesel engine, and in particular, regeneration of a diesel particulate filter (hereinafter abbreviated as DPF) that collects particulate matter (particulate matter, hereinafter abbreviated as PM) contained in exhaust gas. The present invention relates to a control device.

In the exhaust gas regulations for diesel engines, PM is as important as NOx reduction. As an effective technique for this, DPF is known.
The DPF is a PM collection device using a filter, and in an engine operating state where the exhaust gas temperature is low, PM continues to be stored in the DPF, so that forced regeneration is performed in which the temperature is forcibly increased to burn the PM.

  This forced regeneration is performed by supplying unburned fuel to the DOC by late post-injection after the pre-stage oxidation catalyst (diesel oxidation catalyst, hereinafter abbreviated as DOC) installed upstream of the DPF reaches the activation temperature. The oxidation is generated by heating and the DPF inlet temperature is raised to about 600 ° C. However, when the DOC is lower than the activation temperature, the temperature of the DOC is increased by changing the throttle of the intake throttle valve and the early post injection conditions. The change in the throttle valve throttle and the early post injection condition continues even when the DOC is normally higher than the activation temperature.

  On the other hand, part of the fuel from the late post injection adheres to the inner wall of the cylinder and is scraped off by the piston ring when the piston descends to reach the oil pan, so-called oil die that dilutes the engine oil in the oil pan. A solution. When such dilution progresses, the viscosity of the engine oil decreases and the lubricity decreases, and in addition, the amount of encin oil increases, resulting in problems such as ejection of engine oil.

  The dilution of engine oil increases as the amount of fuel by late post injection used during forced regeneration of the DPF increases. Therefore, it is necessary to perform efficient forced regeneration control by reducing the injection amount of late post injection.

  Patent Documents 1 (Japanese Patent Laid-Open No. 2009-62966) and Patent Document 2 (Japanese Patent Laid-Open No. 2009-138703) are known as prior arts for performing DPF regeneration control while avoiding oil dilution by post injection. Yes.

  Patent Document 1 discloses a technique for stopping post injection when the fuel injection amount of post injection within a predetermined period reaches a regulation value. Patent Document 2 discloses a technique in which only sub fuel injection is stopped when the rotational speed of an internal combustion engine is equal to or lower than a predetermined idle rotational speed during forced regeneration.

JP 2009-62966 A JP 2009-138703 A

  However, the techniques of Patent Documents 1 and 2 both reduce the oil dilution by stopping the post injection and stopping the fuel supply, and the environmental conditions such as atmospheric pressure and atmospheric temperature are reduced. It is not intended to reduce the oil dilution by controlling the post-injection amount suitable for the change in the exhaust gas temperature at the engine outlet due to the change, efficiently performing the forced regeneration and reducing the fuel consumption rate.

  On the other hand, the throttle valve throttle condition is set so that the minimum opening that cannot be throttled further is set in advance so that the exhaust gas concentration (HC concentration increase) and the engine condition (engine misfire) are not affected. It is set by a map determined by the load, etc., and in normal cases, the DOC inlet temperature is raised with the throttle opening reduced to this minimum opening. Then, with the map value set in advance, the amount of air decreases, causing an increase in HC concentration and misfire, and there is a concern about fuel consumption deterioration due to unstable combustion.

  Further, when the air flow rate decreases, the exhaust temperature at the engine outlet increases, so that the deviation from the late post-injection amount determined according to the engine speed and load in the base state in advance during the forced regeneration of the DPF increases, and the control of the DPF inlet temperature Sex is reduced. As a result, the PM inside the DPF is rapidly heated, which increases the risk of damage to the DPF and a decrease in the thermal performance of the supported catalyst, and the temperature is low and the regeneration does not proceed sufficiently. When the regeneration completion is managed, or when the soot regeneration amount is estimated and managed by the DPF temperature, the regeneration time is prolonged and the fuel consumption is deteriorated. In addition, if the regeneration time is prolonged, the risk that the amount of oil dilution increases will also increase.

  In late post-injection, the late post-injection amount corresponding to the engine operating conditions is set in advance using a map, etc., but if there is a change in atmospheric pressure such as high altitude, or a change in environmental conditions such as atmospheric temperature, etc. The engine outlet exhaust temperature changes, there is a risk that the deviation between the preset injection amount and the required injection amount becomes large and the fluctuation width of the DPF temperature may increase. As a result, the PM inside the DPF suddenly increases. This increases the temperature and increases the risk of damage to the DPF and a decrease in the thermal performance of the supported catalyst, and further, the regeneration time is not sufficiently advanced because the DPF temperature is low and the fuel consumption rate is deteriorated. In addition, if the regeneration time is prolonged, there is a concern that the amount of oil dilution increases.

  Accordingly, the present invention has been made in view of these problems, and corrects the minimum opening of the throttle valve and the post-injection amount with respect to changes in environmental conditions such as atmospheric temperature or atmospheric pressure during forced regeneration of the DPF. Thus, it is possible to provide a diesel engine exhaust purification system that can suppress DPF breakage due to an increase in HC concentration, engine misfire or excessive temperature rise, and reduce oil dilution by suppressing the fuel consumption rate during forced regeneration as much as possible. For the purpose.

In order to solve the above problems, the present invention includes a diesel particulate filter (DPF) that collects a pre-stage oxidation catalyst (DOC) and exhaust particulates (PM) in an exhaust passage, and the PM collected in the DPF. In the exhaust gas purification apparatus for a diesel engine that regenerates the exhaust gas, the exhaust gas purification apparatus further comprises throttle valve control means for restricting the intake throttle valve so as to activate the DOC by increasing the exhaust gas temperature during forced regeneration of the DPF. A throttle valve minimum opening map in which the throttle valve minimum opening is set from the rotational speed and the engine load, and a throttle pressure correcting means for applying an atmospheric pressure correction to the opening value calculated by the throttle valve minimum opening map; At least one of the throttle temperature correction means for applying intake air temperature correction Provided by a throttle minimum opening correction means is,
Further, a fuel injection device is provided for controlling the fuel injection timing and the injection amount with respect to the fuel injection valve and injecting the fuel into the combustion chamber. The fuel injection device burns immediately after the main injection and the main injection when the DOC is active. Early post-injection, which is the first post-injection that injects a smaller amount of fuel than the main injection in a state where the indoor pressure is high, and after the DOC activation, the crank angle after the early post-injection further reaches near the bottom dead center Configure to perform late post injection, which is the second post injection that injects in the advanced state,
A late post injection amount control means for controlling an injection amount of the late post injection, the late post injection amount control means; a late post amount map in which a late post injection amount is set based on an engine speed and an engine load; A late post injection amount correcting means having at least one of a late post pressure correcting means for applying atmospheric pressure correction and a late post temperature correcting means for applying intake air temperature correction to the injection amount calculated by the post amount map ;
Correction interlocking means for performing correction by the minimum throttle opening correction means in preference to correction by the late post injection amount correction means is provided, and the correction interlocking means is configured to fully open the throttle valve opening by the throttle minimum opening correction means. When the throttle valve opening cannot be increased any more after reaching the state, a correction factor is calculated so that the post-injection amount is reduced by correcting the late post-injection amount as a correction that cannot be handled by the throttle valve opening. The correction coefficient from the correction map of the atmospheric pressure correction and the intake air temperature correction in the late post injection amount correction means is corrected .
The pressure used for atmospheric pressure correction is preferably an atmospheric pressure gauge value, but it may be the atmospheric pressure estimated from the static pressure in any part of the piping, or the static pressure itself in any part of the piping. Further, the intake air temperature sensor used for correcting the intake air temperature may be in any part from the air intake to the intake manifold.

  Here, in the exhaust gas purification apparatus having a DPF that collects DOC and PM in the exhaust passage, the fuel injection in the regeneration control apparatus for the DPF that regenerates the PM collected in the DPF includes main injection and early post injection. There is a late post injection, which will be described with reference to FIG. FIG. 6 shows changes in the DPF inlet temperature and the DOC inlet temperature during forced regeneration.

The main injection is an injection for causing the main combustion in the combustion chamber, and the early post injection means that the pressure in the cylinder immediately after the main injection is still high, and a smaller amount of fuel is injected than the main injection. By this early post-injection, the exhaust gas whose temperature has been increased by raising the exhaust gas temperature flows into the DOC, so that the DOC is activated and raised to about 250 ° C. necessary for activation. The active region of this DOC is the A region from t1 to t2 in FIG.
After that, the second post-injection is further performed with the crank angle after the early post-injection being advanced to the vicinity of the bottom dead center. This second post-injection is called late post-injection, and this late post-injection does not contribute to the combustion in the combustion chamber and is discharged from the combustion chamber to the exhaust passage by the exhaust stroke. The fuel discharged from the combustion chamber reacts in the already activated DOC and further raises the exhaust gas temperature by the generated oxidation heat to about 600 ° C. necessary for regeneration of the DPF to promote PM combustion. The PM combustion region in this DPF is the region B after t2 in FIG.

In the present invention, first, in the DOC activation region A, control is performed to throttle the intake throttle valve in order to minimize the amount of fuel to be injected. This control is normally continued even in the B region.
Throttle valve control means is provided to throttle the intake throttle valve so as to activate the DOC by increasing the exhaust gas temperature during forced regeneration of the DPF, and the throttle valve control means has a minimum throttle valve opening degree based on the engine speed and engine load. It has a set throttle valve minimum opening degree map. This throttle valve minimum opening map shows the minimum opening that cannot be further throttled so as not to affect the exhaust gas concentration increase (HC concentration increase) or the engine condition (engine misfire) in advance according to the engine operating conditions. The degree is set. During actual temperature rise, the temperature is raised in a state of being throttled to this minimum opening. Accordingly, it is possible to control the activity of the DOC while suppressing deterioration of exhaust gas concentration and engine misfire.

Further, the present invention provides a throttle minimum opening having at least one of a throttle pressure correcting means for applying atmospheric pressure correction to an opening value calculated by a throttle valve minimum opening map and a throttle temperature correcting means for applying intake air temperature correction. Degree correction means, the atmospheric pressure correction is performed by the throttle pressure correction means of the throttle minimum opening correction means, or the intake air temperature correction is applied by the throttle temperature correction means, and the intake throttle is adjusted by the throttle valve minimum opening after the correction. Since the minimum opening of the valve is limited, in an environment with low atmospheric pressure such as high altitudes, if the atmospheric pressure is not corrected, the intake air amount will decrease more than expected, exhaust gas concentration increase (HC concentration increase) and engine status ( Engine misfire) is a problem, but these problems are avoided by atmospheric pressure correction. Stabilization of combustion is made. Also, in an environment where the outside air temperature changes, the problem of combustibility due to the difference in the air density is avoided.
As a result, increase in HC concentration and engine misfire can be suppressed even when atmospheric pressure or intake air temperature changes. Furthermore, since the exhaust temperature at the DOC inlet can be kept constant in the base state, when the DPF inlet temperature is increased to about 600 ° C. by late post injection to promote PM combustion, the temperature increase width remains constant in the base state. Therefore, the temperature controllability of the DPF inlet can be maintained in a good state.

Preferably, in the present invention, the throttle pressure correction means has a throttle pressure correction map or a throttle pressure correction relational expression, and the throttle pressure correction map is a two-dimensional map in which a correction coefficient is set according to atmospheric pressure, or The throttle pressure correction relational expression may be a relational expression with atmospheric pressure as a function.
In this way, by using a throttle pressure correction map or a relational expression in which a correction coefficient corresponding to the atmospheric pressure is set in advance, the minimum throttle opening after the atmospheric pressure correction can be easily calculated, which complicates the apparatus. The atmospheric pressure can be corrected without any problems.
Similarly, the intake air temperature correction is sequentially performed by using a throttle temperature correction map or a throttle temperature correction relational expression.
Further, it may be a three-dimensional map in which a correction coefficient is determined according to the atmospheric pressure and the intake air temperature.

Preferably, in the present invention, the feedback control calculated based on the deviation between the target temperature of the inlet temperature of the DOC and the actual temperature, with the opening value calculated by the throttle valve minimum opening map as the minimum opening. You should do it.
With such a configuration, the minimum opening calculated based on the throttle valve minimum opening map value is corrected by the throttle pressure correction means or the correction by the throttle temperature correction means, and the target temperature at the DOC inlet (200 By performing feedback control to (C to 400 ° C.), the DOC inlet temperature can be maintained at the target temperature, or even if it cannot be raised to the target temperature, it can be raised to the same temperature as the base state and stabilized. As a result, an increase in the HC concentration and engine misfire can be suppressed by reducing the throttle opening to the minimum as long as combustion does not deteriorate.

The present invention also includes a late post-injection amount control means for controlling the injection amount of late post-injection for injecting a timing that does not contribute directly to the combustion after the main injection after the DOC activation, the late post-injection quantity control means A late post injection map in which the late post injection amount is set from the engine speed and the engine load, a late post pressure correction means for applying atmospheric pressure correction to the injection amount calculated by the late post injection map, and intake air temperature correction And a late post injection amount correcting means having at least one of the late post temperature correcting means for multiplying the late post injection amount by the late post injection amount correcting means .

As described above, in the B region (see FIG. 6) after the activation of the DOC, the late post injection amount control means calculates the late post injection amount based on the late post injection amount from the engine speed and the engine load. The injection amount is corrected by a late post injection amount correcting means having at least one of atmospheric pressure and intake air temperature.
For this reason, if the engine outlet exhaust temperature changes when there is a change in high altitude, atmospheric pressure, or environmental conditions such as air temperature, the preset late post injection amount and the required late post injection amount The gap increases and the temperature fluctuation range of the DPF increases, and as a result, the problem of increasing the risk of the DPF breakage and the thermal performance degradation of the supported catalyst due to the rapid temperature rise of the PM inside the DPF is avoided. . Further, since the DPF temperature is low and the regeneration does not proceed sufficiently, the regeneration time is prolonged and the fuel consumption rate is deteriorated, and further, the problem of oil dilution is avoided.

Preferably, in the present invention, the late post pressure correction means has a late post pressure correction map or a late post pressure relational expression, and the late post pressure correction map is a two-dimensional model in which a correction coefficient is set according to the atmospheric pressure. The map or the late post pressure relational expression may be a relational expression with the atmospheric pressure as a function.
In this way, the late post injection amount after atmospheric pressure correction can be easily calculated by using a late post pressure correction map or a relational expression in which a correction coefficient corresponding to the atmospheric pressure is set in advance. The atmospheric pressure can be corrected without doing so. Similarly, the intake air temperature correction is sequentially performed by using a late post temperature correction map or a relational expression.

  In the present invention, it is preferable that both the late post pressure correcting unit and the late post temperature correcting unit are provided, and a three-dimensional map late post atmospheric correction in which a correction coefficient is determined according to the atmospheric pressure and the intake air temperature. It is preferable to have a coefficient map and correct the late post injection amount based on the correction coefficient determined by the late post atmospheric correction coefficient map. In this way, by using the late post atmospheric correction map in which the correction coefficient according to the atmospheric pressure and the intake air temperature is set in advance, it is possible to easily calculate the injection amount corrected by the atmospheric pressure and the intake air temperature. Correction to atmospheric pressure and intake air temperature is possible without complication.

Further, a feedback control command value calculated based on a deviation between the target temperature of the inlet temperature of the DPF and the actual temperature may be added to the injection amount calculated by the late post amount map.
With such a configuration, the feedforward control value calculated based on the late post amount map value is corrected by the late post pressure correcting means or the late post temperature correcting means, and in addition to the DPF inlet By adding the feedback control command value to the target temperature (for example, 600 ° C.), the DPF inlet temperature can be reliably maintained at the target temperature. As a result, the amount of fuel injected in late post injection is suppressed, efficient regeneration is performed, and oil dilution can be reduced.

Further, the present invention provides a correction interlocking means for performing the correction by the throttle minimum opening correction means in preference to the correction by the late post injection amount correction means, and the correction interlocking means is provided by the throttle minimum opening correction means. When the throttle valve opening reaches the fully open state and the throttle opening cannot be increased any more , the correction coefficient is set so that the post-injection amount is reduced by correcting the late post-injection amount as a correction that cannot be handled by the throttle valve opening. The correction coefficient is calculated, and the correction coefficient from the correction map of atmospheric pressure correction and intake air temperature correction in the late post injection amount correction means is corrected by the correction coefficient .

  In this way, the correction interlocking means is provided so that the priority of correction for environmental changes such as atmospheric pressure and atmospheric temperature is given priority over correction by the minimum throttle opening correction means over correction by the late post injection amount correction means. Controls the engine exhaust temperature to a constant temperature by controlling the throttle valve opening in response to environmental changes, and then targets the DPF inlet temperature by controlling the late post injection amount for a constant engine exhaust temperature. The control temperature can be controlled stably and reliably at about 600 ° C.

That is, the engine exhaust temperature is made constant by the throttle valve opening correction in conjunction with the late post-injection amount correcting means so that the minimum throttle opening correcting means is prioritized for correction to the environmental change, and then the late post-injection amount. When the correction is made by the correction means, and the minimum throttle opening correction means and the late post injection amount correction means are separately and independently corrected with respect to the environmental change, the correction is repeated and the predetermined DPF inlet temperature is changed. While stable control is difficult to obtain, DPF inlet temperature control is stably obtained.
As a result, it is possible to reduce fuel consumption deterioration and oil dilution due to abnormal temperature rise in the DPF and increase in regeneration time.

  According to the present invention, by correcting the minimum opening of the throttle valve and the post injection amount with respect to changes in environmental conditions such as atmospheric temperature or atmospheric pressure during forced regeneration of the DPF, an increase in HC concentration and engine Oil dilution can be reduced by suppressing DPF breakage due to misfire or excessive temperature rise and performing efficient regeneration control while suppressing the fuel consumption rate during forced regeneration as much as possible.

1 is a schematic configuration diagram of an exhaust emission control device for a diesel engine according to an embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of throttle valve control means of basic configuration 1 ; FIG. 6 is a block diagram showing the configuration of late post injection amount control means of basic configuration 2 ; It is a block diagram showing another example of the correction map of the throttle valve control means and the late post injection amount control means. It is a flowchart which shows the forced regeneration control of DPF. It is explanatory drawing which shows the change state of the DOC inlet temperature and DPF inlet temperature in the forced regeneration control of DPF. It is a configuration block diagram of an embodiment . FIG. 8 is an enlarged explanatory diagram of a C part in FIG. 7. It is a curve which shows the relationship between the throttle valve minimum opening degree and a pressure loss coefficient.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

With reference to FIG. 1, the exhaust emission control device of the diesel engine which concerns on embodiment of this invention is demonstrated.
As shown in FIG. 1, in an exhaust passage 3 of a diesel engine (hereinafter referred to as an engine) 1, a DOC (pre-stage oxidation catalyst) 5 and a DPF (diesel particulate) that collects PM (particulate matter) on the downstream side of the DOC 5. An exhaust gas aftertreatment device 9 comprising a curate filter) 7 is provided.

  Further, in FIG. 1, the engine 1 is provided with an exhaust turbocharger 17 having an exhaust turbine 13 and a compressor 15 driven coaxially thereto, and air discharged from the compressor 15 of the exhaust turbocharger 17. Passes through the air supply passage 19 and enters the intercooler 21 to cool the intake air, and then the intake air flow rate is controlled by the intake throttle valve 23, and then the combustion chamber (not shown) of the engine 1 from the intake port 25 provided for each cylinder. 29 flows in.

  Further, the engine 1 is provided with a common rail fuel injection device 31 that controls the fuel injection timing and the injection amount and injects the fuel into the combustion chamber 29, and the common rail fuel injection device 31 supplies the fuel injection valve 33 with the common rail. On the other hand, a predetermined amount of fuel is supplied at a predetermined fuel injection timing, and a control signal is input to the common rail fuel injection device 31 from a regeneration control device 35 of the DPF 7 described later.

  Further, an EGR (exhaust gas recirculation) pipe (not shown) is branched from the middle of the exhaust passage 3 and is introduced into the downstream portion of the intake throttle valve 23 via the EGR valve.

  The combustion gas, that is, the exhaust gas 37 combusted in the combustion chamber 29 of the engine 1 passes through the exhaust manifold and the exhaust passage 3 in which exhaust ports provided for each cylinder are gathered, and passes through the exhaust turbine 13 of the exhaust turbo supercharger 17. After being driven and used as a power source for the compressor 15, it flows into the DOC 5 of the exhaust gas aftertreatment device 9 through the exhaust passage 3.

  In addition, a DPF 7 is disposed on the downstream side of the DOC 5, and the regeneration control device 35 of the DPF 7 includes an air flow rate sensor 55 that detects the flow rate of air flowing into the compressor 15, a DOC inlet temperature sensor 56, and a DPF inlet temperature sensor. 57, a signal from the differential pressure sensor 58 of the DPF 7, a signal from the intake air temperature sensor 59, an engine speed signal, an engine load (fuel injection amount) signal, and an atmospheric pressure signal are input.

  The regeneration control device 35 includes a throttle valve control means 60, an early post injection amount control means 62, and a late post injection amount control means 64. Further, the throttle valve control means 60 includes a throttle valve minimum opening map 66. A throttle pressure correction means 68 and a throttle temperature correction means 69 are provided. The throttle pressure correction means 68 and the throttle temperature correction means 69 constitute a throttle minimum opening correction means 75 for correcting the minimum opening of the intake throttle valve 23 with respect to environmental changes.

  The outline of the forced regeneration control by the regeneration control device 35 of the DPF 7 configured as described above will be described with reference to FIG. FIG. 5 is a flowchart showing forced regeneration control of the DPF 7, and FIG. 6 is an explanatory diagram showing a change state of the DOC inlet temperature and the DPF inlet temperature in the forced regeneration control of the DPF 7.

  In step S2, it is determined whether the forced regeneration control is started. That is, the determination is made based on the conditions for starting the forced regeneration, for example, in the case of a vehicle, the travel distance, the operating time of the engine, the total fuel consumption, and the like. When forced regeneration is started, DOC temperature raising control for activating DOC5 is executed in steps S3 to S5. This DOC temperature raising control is performed in the A region in FIG. 6 (may be continued up to the B region). In step S3, the opening of the intake throttle valve 23 is throttled by a signal from the throttle valve control means 60, the amount of air flowing into the combustion chamber is throttled, and the unburned fuel in the exhaust gas is increased. Further, in step S4, the DOC is activated by changing the early post injection conditions.

  This early post-injection is the first post-injection in which a small amount of fuel is injected immediately after main injection while the pressure in the cylinder is still higher than main injection. Increases the temperature of the exhaust gas without affecting the exhaust gas, and the heated exhaust gas flows into the DOC 5 to activate the DOC 5, and when the unburned fuel in the exhaust gas is oxidized as the DOC 5 is activated. The exhaust gas temperature is raised by the generated oxidation heat.

  In step S5, the signal from the DOC inlet temperature sensor 56 determines whether the DOC inlet temperature has reached 200 to 400 ° C. If it has exceeded, the inlet temperature of the DPF 7 is set by late post injection in step S6. Raise further.

In steps S6 to S8 after the late post injection, PM combustion control of the DPF 7 is executed. This combustion control is performed in region B of FIG.
Late post-injection refers to the second post-injection in which the crank angle after the early post-injection is advanced to the vicinity of the bottom dead center. By this late post-injection, the combustion chamber is opened when the exhaust valve is open. The fuel flows out from the exhaust passage 3 to the exhaust passage 3 and the discharged fuel reacts in the already activated DOC 5, and the exhaust gas temperature is further increased by the generated oxidation heat to generate a temperature necessary for regeneration of the DPF 7, for example, 600 Accelerate PM combustion at ℃.

In step S7, a signal from the DPF inlet temperature sensor 48 determines whether the DPF inlet temperature has reached 600.degree. C., and if it has exceeded, in step S8, the intake throttle valve 23 set in step S3 is determined. The throttle amount, the early post injection condition set in step S4, and the late post injection amount set in step S6 are controlled to continue the combustion of the PM collected in the DPF 7.
In step S9, a determination is made based on a predetermined condition, for example, an elapsed time from the start of forced regeneration, a deposition amount estimation calculation formula, a deposition amount calculated based on the differential pressure sensor 58, and the like. End forced regeneration.

( Basic configuration 1 )
In the forced regeneration control of the DPF 7 as described above, a method for setting the throttle amount of the intake throttle valve 23 in step S3 will be described next with reference to the block diagram of FIG.

  The throttle amount of the intake throttle valve 23 is controlled by the throttle valve control means 60. The basic minimum throttle valve opening is set in a throttle valve minimum opening map 66, which is set in a three-dimensional map based on the engine speed and engine load (fuel injection amount).

Then, the minimum opening value of the throttle valve determined by the throttle valve minimum opening map 66 is corrected by the throttle pressure correction means 68 based on the atmospheric pressure signal from the atmospheric pressure sensor and the signal from the intake air temperature sensor 59. Based on the above, correction by the throttle temperature correction means 69 is performed.
The correction by the throttle pressure correction means 68 and the correction by the throttle temperature correction means 69 may be performed either or both. The case where both are performed will be described below.

  The correction by the throttle pressure correction means 68 is calculated from a two-dimensional throttle pressure correction map 70 in which a pressure correction coefficient is set for the atmospheric pressure, and the correction by the throttle temperature correction means 69 is a temperature correction coefficient for the intake air temperature. Is calculated from a two-dimensional throttle temperature correction map 71 in which is set, and the pressure correction coefficient is multiplied by a temperature correction coefficient by a multiplier 72, and the multiplied correction coefficient is multiplied by a multiplier 73 to the minimum throttle valve. The corrected minimum opening of the throttle valve is calculated by multiplying the minimum opening value of the throttle valve determined by the opening map 66.

  As shown in FIG. 2, the correction coefficient of the throttle pressure correction map 70 increases the correction coefficient to increase the limit of the minimum opening value as the atmospheric pressure decreases (does not throttle), and increases the HC concentration. The engine misfire is not affected. Further, as shown in FIG. 2, the correction coefficient of the throttle temperature correction map 71 increases the correction coefficient to increase the limit of the minimum opening value as the intake air temperature increases (the amount of air is not reduced but is reduced). To avoid problems with density differences).

  Further, the opening value calculated by the throttle valve minimum opening map 66 and the minimum opening after the pressure correction and temperature correction are set as the minimum value (limit), and the target temperature of the inlet temperature of the DOC 5 (constant 200 to 400 ° C.). A throttle valve minimum opening feedback control unit (F / B control unit) 74 that performs a feedback control command calculated based on a deviation between the value) and the actual temperature. Control is performed using the feedback control command value calculated by the feedback control unit 74.

In this way, the minimum opening calculated based on the throttle valve minimum opening map 66 is corrected by the throttle pressure correcting means 68 and the throttle temperature correcting means 69 to perform the throttle valve opening feedback control unit 74. By performing feedback control to the target temperature at the DOC inlet by means of, the DOC inlet temperature can be reliably maintained at the target temperature even if the atmospheric pressure changes.
As a result, since the exhaust temperature at the DOC inlet is constant with respect to environmental changes, when the DPF inlet temperature is increased to about 600 ° C. by late post-injection to promote PM combustion, the temperature rise is constant in the base state. Therefore, the temperature controllability at the DPF inlet can be maintained in a good state. As a result, the problem of increasing the risk of DPF breakage and the risk of lowering the thermal performance of the supported catalyst due to sudden temperature rise of the PM inside the DPF is avoided, and in addition, the regeneration time is low because the regeneration is not sufficiently advanced. Deterioration of the fuel consumption rate due to the prolongation of the oil and the problem of oil dilution are avoided.

  In order to perform the correction by the throttle pressure correction means 68 and the correction by the throttle temperature correction means 69, the two two-dimensional maps of the throttle pressure correction map 70 and the throttle temperature correction map 71 are not provided. As shown, a three-dimensional map throttle atmospheric correction coefficient map 77 in which correction coefficients are set according to the atmospheric pressure and the intake air temperature may be provided.

  Further, the throttle pressure correction means 68 may be calculated by providing a throttle pressure correction relational expression that is a relational expression using the atmospheric pressure as a function instead of the throttle pressure correction map 70. In this way, by using a throttle pressure correction map or a relational expression in which a correction coefficient corresponding to the atmospheric pressure is set in advance, the minimum throttle opening after the atmospheric pressure correction can be easily calculated, which complicates the apparatus. The atmospheric pressure can be corrected without any problems. Similarly, the intake air temperature correction has the same effect by using a throttle temperature correction map or a relational expression.

( Basic configuration 2 )
Next, in the forced regeneration control of the DPF 7, the DPF inlet temperature increase control by late post injection in step S6 will be described with reference to the configuration block diagram of FIG.
The late post-injection amount is set in the late post amount map 78 as a basic injection amount, and is set in a three-dimensional map based on the engine speed and the engine load (fuel injection amount).

Then, with respect to the basic injection amount value of the late post injection determined by the late post amount map 78, the correction by the late post pressure correction means 88 based on the atmospheric pressure signal from the atmospheric pressure sensor, and the signal from the intake air temperature sensor 59 Based on the above, correction by the late post temperature correction means 89 is performed. The late post pressure correction means 88 and the late post temperature correction means 89 constitute a late post injection amount correction 95 that corrects the late post injection amount with respect to environmental changes.
The correction by the late post pressure correction means 88 and the correction by the late post temperature correction means 89 may be performed either or both. The case where both are performed will be described below.

  The correction by the late post pressure correction means 88 is calculated from a two-dimensional late post pressure correction map 90 in which a pressure correction coefficient is set for the atmospheric pressure, and the correction by the late post temperature correction means 89 is for the intake air temperature. The temperature correction coefficient is calculated from a two-dimensional late post temperature correction map 91 in which a temperature correction coefficient is set. The pressure correction coefficient is multiplied by a temperature correction coefficient by a multiplier 92, and the multiplied correction coefficient is multiplied by a multiplier 93. Is multiplied by the late post injection amount determined by the late post amount map 78 to calculate the corrected late post injection amount.

  As shown in FIG. 3, the correction coefficient of the late post pressure correction map 90 decreases the correction coefficient to reduce the late post injection amount as the atmospheric pressure decreases, thereby reducing the deviation from the required injection amount. The fluctuation width of the DPF inlet temperature is reduced. As a result, the temperature controllability at the DPF inlet is improved, the risk of damage to the DPF and the thermal performance of the supported catalyst is avoided, and deterioration of the fuel consumption rate and increase in oil dilution due to prolonged regeneration time are suppressed. Further, the correction coefficient of the late post temperature correction map 91 is reduced as the intake air temperature increases to reduce the late post injection amount.

  Further, based on the late post amount calculated by the late post amount map 78, and the late post amount after pressure correction and temperature correction, based on the deviation between the target temperature (for example, 600 ° C.) of the inlet temperature of the DPF 7 and the actual temperature. A late post injection amount feedback control unit (F / B control unit) 94 that adds the calculated feedback control command value. The feedback control command value calculated by the feedback control unit 94 is added by an adder 96 to calculate a late post injection amount command value.

As described above, the late post injection amount calculated based on the late post amount map 78 is corrected by the late post pressure correcting means 88 and the late post temperature correcting means 89, and in addition to this, the late post injection amount is further corrected. By adding the feedback control command value to the target temperature at the DOC inlet by the amount feedback control unit 94, the DOC inlet temperature can be reliably maintained at the target temperature even if the atmospheric pressure or the intake air temperature changes.
As a result, the amount of fuel injected in late post injection is suppressed, efficient regeneration is performed, and oil dilution can be reduced.

  In order to perform the correction by the late post pressure correction unit 88 and the correction by the late post temperature correction unit 89, two two-dimensional maps of the late post pressure correction map 90 and the late post temperature correction map 91 are not provided. As shown in (b), it may have a three-dimensional late post atmospheric correction map 97 in which correction coefficients are set in accordance with the atmospheric pressure and the intake air temperature.

Further, the late post pressure correction means 88 may be a late post pressure correction relational expression instead of the late post pressure correction map 90, or may be provided with a late post pressure correction relational expression that is a relational expression as a function of the atmospheric pressure. Good.
In this way, by using a late post pressure correction map or a relational expression in which a correction coefficient corresponding to atmospheric pressure is set in advance, the minimum throttle opening after atmospheric pressure correction can be easily calculated, thus complicating the device. The atmospheric pressure can be corrected without doing so. Similarly, the intake air temperature correction has the same effect by using a throttle temperature correction map or a relational expression.

According to the basic configuration 1 and the basic configuration 2 described above, in the PM combustion region (B region after t2 in FIG. 6) in the DPF 7, the throttle valve minimum opening and the late post injection amount are set based on the atmospheric pressure and the intake air temperature. By controlling the DPF damage due to the increase in HC concentration and engine misfire or overheating, the fuel consumption rate during forced regeneration due to prolonged regeneration time because the DPF temperature is low and regeneration does not proceed sufficiently The oil dilution can be reduced as much as possible.

( Embodiment )
In the basic configuration 1 , the throttle valve minimum opening value determined by the throttle valve minimum opening map 66 is corrected by the throttle pressure correcting means 68 based on the atmospheric pressure signal from the atmospheric pressure sensor, and the intake air temperature sensor. Based on the signal from 59, correction by the throttle temperature correction means 69 is performed.
In the basic configuration 2 , the late post injection basic injection amount value determined by the late post amount map 78 is corrected by the late post pressure correcting means 88 based on the atmospheric pressure signal from the atmospheric pressure sensor, and the intake air temperature. Based on the signal from the sensor 59, correction by the late post temperature correction means 89 is performed.

As described above, in the basic configuration 1 and the basic configuration 2 , the correction for the environmental change of the minimum opening value of the throttle valve and the correction for the environmental change of the late post injection amount are independently performed.
On the other hand, in the embodiment , as shown in FIG. 7, the throttle valve minimum opening degree is linked with the correction of the throttle valve minimum opening degree and the correction of the late post injection amount with respect to the environmental change such as the atmospheric pressure and the atmospheric temperature. The correction interlocking means 108 is provided so that this correction is prioritized over the correction of the late post injection amount.

In FIG. 7, the minimum opening of the intake throttle valve 23 is a three-dimensional map throttle valve minimum opening map in which the minimum opening of the throttle valve is set based on the engine speed and the engine load (fuel injection amount). 66. Then, the minimum opening value of the throttle valve 23 obtained from the throttle valve minimum opening map 66 is obtained from the throttle atmospheric correction coefficient map 77 of a three-dimensional map in which correction coefficients are set according to the atmospheric pressure and the intake air temperature. The correction coefficient is multiplied by the multiplier 100 to correct the environmental change.
The corrected throttle valve minimum opening is set to the minimum opening, and the signal from the feedback control unit (F / B control unit) 74 is limited to be output as a throttle valve opening command value.
FIG. 8 shows details of the correction coefficient integration portion C by the multiplier 100 and a case where the pressure loss coefficient correction map 106 is used as an example of the throttle valve opening atmospheric correction map 77.

In FIG. 8, the throttle valve minimum opening determined by the throttle valve minimum opening map 66 is converted into a pressure loss coefficient by a pressure loss coefficient curve 104 showing the relationship between the throttle valve opening (%) and the pressure loss coefficient (ζ). Convert to
Then, this pressure loss coefficient is multiplied by a correction coefficient calculated by a pressure loss coefficient correction map 106 as an example of the throttle atmospheric correction coefficient map 77 by the multiplier 100, and the corrected pressure loss coefficient is multiplied by the pressure loss coefficient again. The throttle valve opening is returned to the throttle valve minimum opening by the loss coefficient curve 104.
As shown in FIG. 9, the pressure loss coefficient curve 104 is experimentally obtained in advance by taking the throttle valve opening (%) on the vertical axis and the pressure loss coefficient (ζ) of the throttle valve portion on the horizontal axis. There is a characteristic that the pressure loss coefficient becomes the smallest when the opening degree is 100% and the pressure loss coefficient becomes larger as the opening degree is reduced from 100%.
The throttle atmospheric correction coefficient map 77 and the integration portion C constitute a throttle minimum opening correction means 99.

In this way, the throttle valve minimum opening degree is once converted into a pressure loss coefficient using the pressure loss coefficient curve 104, and the pressure loss coefficient is corrected by multiplying the pressure loss coefficient by the correction coefficient, and then the throttle is again adjusted. In order to return to the minimum valve opening, the correction due to environmental changes needs to be corrected so that the intake mass flow through the throttle valve is almost the same. This is because the relationship between the amount of change and the amount of change in flow rate is different, so that the corrected opening cannot be determined by the same coefficient multiplication for various opening degrees that can be taken depending on the operating state.
If the pressure loss coefficient is determined from the differential pressure and the flow rate, it is possible to correct the same flow rate by multiplying the corresponding pressure loss coefficient by the same correction coefficient even for various opening degrees. That is, even with the same atmospheric correction, the amount of change in the opening is small in the region where the throttle valve opening is small, and the amount of change in the opening can be large in the region where the throttle valve opening is large.

  The correction interlocking unit 108 gives priority to the correction of the throttle valve minimum opening degree for the correction to the environmental change. When the corrected minimum throttle valve opening degree reaches 100%, the throttle valve opening is performed. Since the ratio cannot be dealt with in the degree, the ratio of the shortage correction is calculated, and the shortage ratio is calculated as a correction value of the late post injection amount and input to the multiplier 110.

  On the other hand, regarding the late post injection amount, the late post injection amount is set as a basic injection amount in the late post amount map 78, and is represented in a three-dimensional map by engine speed and engine load (fuel injection amount). Is set.

Then, the correction coefficient from the late post atmospheric correction map 97 of the three-dimensional map in which the correction coefficient is set according to the atmospheric pressure and the intake air temperature with respect to the basic injection amount value of the late post injection determined by the late post amount map 78. Is corrected by the multiplier 110 with the correction coefficient from the correction interlocking means 108, and the correction coefficient corrected by the multiplier 110 is multiplied by the multiplier 112 to correct the environmental change.
Then, the adder 114 adds the signal from the feedback control unit (F / B control unit) 94 to the corrected late post injection amount in the multiplier 112 and outputs it as a late post injection command value.

A multiplier 110 is provided between the late post atmospheric correction map 97 and the multiplier 112, and a correction coefficient from the correction interlocking means 108 is input. The correction coefficient input to the multiplier 110 is a coefficient of the ratio of insufficient correction that cannot be handled by the throttle valve opening when the corrected minimum throttle valve opening reaches 100%.
That is, for example, when the corrected pressure loss coefficient is smaller than the pressure loss coefficient of the throttle valve opening 100% in FIG. The correction coefficient is calculated so as to reduce the late post injection amount by using the minute as the post post injection amount correction, and is input to the multiplier 110.
The late post injection correction unit 113 includes the late post atmospheric correction map 97, the multiplier 110, and the multiplier 112.

According to the embodiment , the correction interlocking unit 108 is provided, the priority of correction for environmental changes such as atmospheric pressure and atmospheric temperature, the correction by the throttle minimum opening correction unit 99 is corrected by the correction by the late post injection amount correction unit 113. Therefore, the engine exhaust temperature is controlled to be a constant temperature by controlling the throttle valve opening, and the late post injection amount is controlled for the constant engine exhaust temperature. The inlet temperature of the DPF can be stably and reliably controlled to the target control temperature of about 600 ° C.

  That is, the engine exhaust temperature is made constant by correcting the opening of the throttle valve 23 in conjunction with the late post injection amount correcting means 113 so that the correction for the environmental change is given priority to the minimum throttle opening correcting means 99. Then, after that, the minimum post-injection amount correcting means 99 and the late post-injection amount correcting means 113 with respect to the environmental change Are independently corrected, it is difficult to obtain a stable control of a predetermined DPF inlet temperature because the corrections are duplicated, whereas the DPF inlet temperature control is stably obtained. As a result, it is possible to reduce fuel consumption deterioration and oil dilution due to abnormal temperature rise in the DPF and increase in regeneration time.

  According to the present invention, by correcting the minimum opening of the throttle valve and the post injection amount with respect to changes in environmental conditions such as atmospheric temperature or atmospheric pressure during forced regeneration of the DPF, an increase in HC concentration and engine Diesel capable of reducing oil dilution by suppressing DPF breakage due to misfire and overheating, and reducing the fuel consumption rate during forced regeneration as much as possible and performing efficient regeneration control within a predetermined time Suitable for use in engine exhaust purification systems.

1 Diesel engine 3 Exhaust passage 5 DOC (Pre-stage oxidation catalyst)
7 DPF (diesel particulate filter)
9 Exhaust gas aftertreatment device 17 Exhaust turbocharger 23 Intake throttle valve 31 Common rail fuel injection device 33 Fuel injection valve 35 Regeneration control device 55 Air flow sensor 56 DOC inlet temperature sensor 57 DPF inlet temperature sensor 59 Intake temperature sensor 60 Throttle valve control Means 62 Early post injection amount control means 64 Late post injection amount control means 66 Throttle valve minimum opening map 68 Throttle pressure correction means 69 Throttle temperature correction means 70 Throttle pressure correction map 71 Throttle temperature correction map 74 Feedback of throttle valve minimum opening Control unit 75, 99 Throttle minimum opening correction means 77 Throttle atmospheric correction map 78 Late post amount map 88 Late post pressure correction means 89 Late post temperature correction means 90 Late post pressure correction map 91 Late post temperature correction map 94 Late post injection amount feedback control unit 95, 113 Late post injection amount correction means 97 Late post atmospheric correction map 104 Loss coefficient map 106 Loss coefficient correction map 108 Correction interlock means

Claims (9)

In an exhaust emission control device for a diesel engine, which includes a diesel particulate filter (DPF) that collects a pre-stage oxidation catalyst (DOC) and exhaust particulates (PM) in an exhaust passage, and regenerates the PM collected in the DPF.
Throttle valve control means for restricting the intake throttle valve so as to activate the DOC by raising the exhaust gas temperature during forced regeneration of the DPF, the throttle valve control means has a minimum throttle valve opening degree from the engine speed and engine load. At least one of a set throttle valve minimum opening map, throttle pressure correcting means for applying atmospheric pressure correction to the opening value calculated by the throttle valve minimum opening map, and throttle temperature correcting means for applying intake air temperature correction And a throttle minimum opening correction means having
Further, a fuel injection device is provided for controlling the fuel injection timing and the injection amount with respect to the fuel injection valve and injecting the fuel into the combustion chamber. The fuel injection device burns immediately after the main injection and the main injection when the DOC is active. Early post-injection, which is the first post-injection that injects a smaller amount of fuel than the main injection in a state where the indoor pressure is high, and after the DOC activation, the crank angle after the early post-injection further reaches near the bottom dead center Configure to perform late post injection, which is the second post injection that injects in the advanced state,
A late post injection amount control means for controlling an injection amount of the late post injection, the late post injection amount control means; a late post amount map in which a late post injection amount is set based on an engine speed and an engine load; A late post injection amount correcting means having at least one of a late post pressure correcting means for applying atmospheric pressure correction and a late post temperature correcting means for applying intake air temperature correction to the injection amount calculated by the post amount map ;
Correction interlocking means for performing correction by the minimum throttle opening correction means in preference to correction by the late post injection amount correction means is provided, and the correction interlocking means is configured to fully open the throttle valve opening by the throttle minimum opening correction means. When the throttle valve opening cannot be increased any more after reaching the state, a correction factor is calculated so that the post-injection amount is reduced by correcting the late post-injection amount as a correction that cannot be handled by the throttle valve opening. An exhaust emission control device for a diesel engine, which corrects a correction coefficient from a correction map of atmospheric pressure correction and intake air temperature correction in the late post injection amount correction means .   The throttle pressure correction means has a throttle pressure correction map or a throttle pressure correction relational expression. The throttle pressure correction map is a two-dimensional map in which a correction coefficient is set according to atmospheric pressure, or the throttle pressure correction relational expression is atmospheric pressure. 2. An exhaust emission control device for a diesel engine according to claim 1, wherein the exhaust gas purification device is a relational expression with pressure as a function.   The throttle temperature correction means has a throttle temperature correction map or a throttle temperature correction relational expression. The throttle temperature correction map is a two-dimensional map in which a correction coefficient is set according to the intake air temperature, or the throttle temperature correction relational expression is an intake air. The exhaust gas purification apparatus for a diesel engine according to claim 1, wherein the relational expression is a function of temperature as a function.   A throttle atmosphere correction coefficient map of a three-dimensional map having both of the throttle pressure correction means and the throttle temperature correction means and having a correction coefficient determined in accordance with the atmospheric pressure and the intake air temperature; 2. The exhaust emission control device for a diesel engine according to claim 1, wherein the minimum opening of the intake throttle valve is corrected based on a correction coefficient determined by a map.   The feedback control calculated based on the deviation between the target temperature and the actual temperature of the inlet temperature of the DOC is performed by setting the opening value calculated by the throttle valve minimum opening map as the minimum opening. 1. An exhaust emission control device for a diesel engine according to 1.   The late post pressure correction means has a late post pressure correction map or a late post pressure relational expression, and the late post pressure correction map is a two-dimensional map in which a correction coefficient is set according to atmospheric pressure, or the late post pressure relation. 2. An exhaust emission control device for a diesel engine according to claim 1, wherein the expression is a relational expression having a function of atmospheric pressure.   The late post temperature correction means has a late post temperature correction map or a late post temperature relational expression, and the late post temperature correction map is a two-dimensional map in which a correction coefficient is set according to the intake air temperature, or the late post temperature relation. 2. The exhaust emission control device for a diesel engine according to claim 1, wherein the expression is a relational expression having a function of the intake air temperature.   A rate post atmospheric correction coefficient map of a three-dimensional map having both the late post pressure correction means and the late post temperature correction means, and a correction coefficient determined according to the atmospheric pressure and the intake air temperature; 2. The exhaust emission control device for a diesel engine according to claim 1, wherein the late post-injection amount is corrected based on a correction coefficient determined by a post atmospheric correction coefficient map.   The feedback control command value calculated based on the deviation between the target temperature of the inlet temperature of the DPF and the actual temperature is added to the injection amount calculated by the late post amount map. Diesel engine exhaust purification system.

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