JP5440753B2 - Engine exhaust purification system - Google Patents

Description

  The present invention relates to an engine exhaust purification device, and more particularly, to an engine exhaust purification device using an oxygen catalyst.

Conventionally, exhaust particulates contained in exhaust gas from an internal combustion engine such as a diesel engine have been captured by a filter to reduce the amount of particulates discharged to the outside.
Further, in order to reduce engine nitrogen oxides (NO _x ), an engine exhaust gas recirculation device (EGR device) is provided that recirculates part of the exhaust gas to the intake passage and slows combustion.

In Patent Document 1, an oxidation catalyst is provided upstream of the filter in the exhaust passage of the engine, and this oxidation catalyst oxidizes NO (nitrogen monoxide) in the exhaust gas to NO ₂ (nitrogen dioxide). An engine exhaust purification apparatus is described in which exhaust particulates captured by a downstream filter are oxidized with NO ₂ to CO ₂ (carbon dioxide) to remove the exhaust particulates.
In the engine exhaust gas purification apparatus of Patent Document 1, when the filter is clogged with exhaust particulates, fuel is injected into the cylinder or into the exhaust pipe, thereby increasing the exhaust temperature, and the filter. The exhaust particulate trapped in the combustion chamber is burned and removed to regenerate the filter.

  In the exhaust emission control device of the engine disclosed in Patent Document 1, when exhaust gas containing unburned fuel that is being regenerated is flowing in the exhaust passage, the EGR device is operated and a part of the exhaust gas is introduced to the intake side. When a certain EGR gas is flowed, unburned fuel contained in the exhaust gas flows into the EGR passage and the intake passage of the engine, and this unburned fuel recirculates, resulting in unstable combustion or clogging of the EGR passage. In order to cause a failure, the recirculation of EGR gas to the intake passage is stopped during filter regeneration.

JP 2005-282477 A

When the recirculation of the EGR gas to the intake passage is stopped during the regeneration of the filter as in the engine exhaust gas purification device described in Patent Document 1, the nitrogen oxide (NO) of the engine, which is the original purpose of the EGR device. _X ) cannot be reduced, which is a problem.
In order to solve this problem, the present inventors newly provide an exhaust fuel injection valve downstream of the EGR device in the exhaust passage, and regenerate the filter by injecting fuel from the exhaust fuel injection valve. Was devised (see FIG. 1). As a result, recirculation of unburned fuel to the intake passage is prevented, and even during filter regeneration, EGR gas can be recirculated to the intake passage to reduce engine nitrogen oxides (NO _x ). .

  However, when an exhaust fuel injection valve is provided in the exhaust passage, there is a difference between the injection valves, and there is a large variation in the injection amount due to the deterioration of the injection valve. A new problem (challenge) has occurred.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an engine exhaust gas purification device that can efficiently purify exhaust gas by eliminating the difference in solids and variation in the injection amount of the injection valve.

In order to achieve the above object, the present invention provides:
An engine exhaust gas purification device for purifying exhaust gas in an exhaust passage of an engine,
Purification means for purifying exhaust gas provided in the exhaust passage and exhausted from the engine;
An oxidation catalyst disposed upstream of the exhaust passage than said purifying means,
An exhaust fuel injection valve for injecting fuel is provided in the exhaust passage upstream of the oxidation catalyst,
And operating region detecting means for detecting a deceleration fuel cut operation region of the engine,
And parameter value detection means for detecting a parameter value associated with the temperature of the oxidation catalyst,
And oxygen consumption calculation means for calculating the oxygen consumption in the oxidation catalyst,
When the oxygen concentration of and the exhaust passage detected parameter value is at least a predetermined threshold value by the parameter value detection means is in the deceleration fuel cut operation region is the atmospheric acid concentration condition, the target injection amount corresponding to the injection command value Is injected from the exhaust fuel injection valve, the oxygen consumption calculation means calculates oxygen consumption in the oxidation catalyst, and the actual injection estimated from the oxygen consumption calculated by the oxygen consumption calculation means Learning means for learning the difference between the amount and the target injection amount ,
The purifying means is a filter that captures exhaust particulates entrained in the exhaust gas, and further includes filter regeneration means that burns and regenerates exhaust particulates captured by the filter, the filter regeneration means When performing the regeneration of the filter, the injection amount of the exhaust fuel injection valve is controlled by reflecting the deviation of the injection amount learned by the learning means.
This is an exhaust emission control device for an engine .
In the present invention configured as described above, an exhaust fuel injection valve for injecting fuel into the exhaust passage upstream of the oxidation catalyst is provided, and the parameter value related to the temperature of the oxidation catalyst is equal to or greater than a predetermined threshold value and the deceleration fuel cut operation is performed. When it is in the region, the fuel is injected from the exhaust fuel injection valve by the injection command value, and the learning means is actually estimated from the target injection amount corresponding to the injection command value and the oxygen consumption amount calculated by the oxygen consumption amount calculation unit. The deviation from the injection amount is learned. As a result, according to the present invention, it is possible to easily learn the injection amount of the exhaust fuel injection valve, and it is possible to eliminate individual differences and variations in the injection amount of the exhaust fuel injection valve. Furthermore, when regenerating the filter that captures the exhaust particulates, the amount of injection of the exhaust fuel injection valve is learned, so that filter regeneration can be performed efficiently.

The present invention preferably further includes a deterioration degree estimating means for estimating the deterioration degree of the oxidation catalyst, and increases the threshold value of the parameter value as the deterioration degree of the oxidation catalyst estimated by the deterioration degree estimating means proceeds.
In the present invention configured as described above, even when the deterioration of the oxidation catalyst proceeds, learning of the injection amount of the exhaust fuel injection valve can be accurately executed.

  According to the engine exhaust gas purification apparatus of the present invention, exhaust gas purification can be performed efficiently by eliminating the difference in solids and the variation in the injection amount of the injection valve.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings. First, an engine exhaust gas purification apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram showing an engine exhaust gas purification apparatus according to a first embodiment of the present invention. The engine (internal combustion engine) to which the exhaust emission control device according to the first embodiment is applied is a diesel engine, but the present invention can also be applied to other types of engines.

As shown in FIG. 1, the code | symbol 1 shows the engine of a motor vehicle, This engine 1 is provided with the some cylinder. An intake port 2 and an exhaust port 4 are formed in the engine 1, and an intake passage 6 is connected to the intake port 2 and an exhaust passage 8 is connected to the exhaust port 4 through manifolds.
In the intake passage 6, an air cleaner 10, an intercooler 12, an intake control valve 14, a surge tank 16 and the like are provided from the upstream side.

The exhaust passage 8 is provided with an oxidation catalyst 18 and a filter 20 (also referred to as “particulate filter”) from the upstream side. The oxidation catalyst 18 oxidizes NO (nitrogen monoxide) in the exhaust gas to NO ₂ (nitrogen dioxide). The NO ₂ oxidizes the exhaust particulates captured by the downstream filter 20 to produce CO 2. ₂ (carbon dioxide) to remove exhaust particulates.
Here, in the present embodiment, the catalyst is not limited to the oxidation catalyst 18 and may be any oxidation catalyst catalyst such as a three-way catalyst.

  Further, a turbocharger 22 is provided in the intake passage 6 and the exhaust passage 8 so that the intake and exhaust gases are pressurized by the intake side turbine and the exhaust side turbine of the turbocharger 22. It has become.

Further, an EGR device 23 is provided between the intake passage 6 and the exhaust passage 8, and the EGR device 23 recirculates a part of the exhaust gas in the exhaust passage 8 to the intake passage 6, An EGR valve 26 that controls the amount of exhaust gas that recirculates and an EGR cooler 28 that cools the EGR gas are provided. By this EGR device 23, a part of the exhaust gas in the exhaust passage 8 is recirculated to the intake passage 6, thereby reducing engine nitrogen oxides (NO _x ).

  Next, the engine 1 is provided with an in-cylinder fuel injection valve 30 for injecting fuel into the combustion chamber, and further, on the downstream side of the EGR device 23 (EGR passage 24) in the exhaust passage 8 and on the upstream side of the oxidation catalyst 18. Is provided with an exhaust fuel injection valve 32 that injects fuel and promotes oxidation at the oxidation catalyst 18. The roles of the in-cylinder fuel injection valve 30 and the exhaust fuel injection valve 32 will be described later.

Further, an engine speed sensor 33 for detecting the rotational speed (Ne) of the engine 1, a vehicle speed sensor (not shown) for detecting the vehicle speed (Sv), and an accelerator opening for detecting the accelerator opening (θ). A degree sensor (not shown) is provided.
Further, an upstream exhaust pressure sensor 34 and a downstream exhaust pressure sensor 36 for detecting exhaust gas pressures (P1, P2) are provided on the upstream side and the downstream side of the filter 20 in the exhaust passage 8, respectively. As will be described in detail later, the amount of fine particles captured by the filter 20 is estimated from the differential pressure (P1-P2) of the exhaust gas obtained by these sensors 34, 36. In order to calculate the trapped amount of exhaust particulates by the filter 20, one differential pressure sensor may be provided.

A first exhaust gas temperature sensor 37 for detecting an oxidation catalyst upstream exhaust temperature (Tu) is provided on the upstream side of the oxidation catalyst 18 in the exhaust passage 8, and further, the oxidation catalyst 18 and the filter in the exhaust passage 8 are provided. 20 is provided with a second exhaust gas temperature sensor 38 for detecting the temperature of the exhaust gas for determining an abnormality of the exhaust fuel injection valve 32.
Further, an acidity concentration sensor 39 for detecting the oxidation catalyst downstream oxygen concentration (Do) is provided immediately downstream of the filter 20 in the exhaust passage 8.
Further, the opening degree of the EGR valve 26, the timing and amount of fuel injection by the in-cylinder fuel injection valve 30, the timing and amount of fuel injection by the exhaust fuel injection valve 32 are controlled, and the exhaust fuel injection to be described in detail later. A controller 40 for learning the difference between the target injection amount of the valve 32 and the actual injection amount is provided.

  Next, the contents of control for filter regeneration according to the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing the control content of filter regeneration by the engine exhaust gas purification apparatus according to the embodiment of the present invention. S in the flowchart of FIG. 2 indicates each step.

  First, in S1, the filter upstream exhaust pressure (P1) detected by the upstream exhaust pressure sensor 34 and the filter downstream exhaust pressure (P2) detected by the downstream exhaust pressure sensor 36 are input.

  Next, in S2, the trapped amount (M) of the exhaust particulates in the filter 20 is calculated from the differential pressure (P1-P2) between the filter upstream exhaust pressure (P1) and the filter downstream exhaust pressure (P2). The larger the differential pressure (P1-P2), the larger the trapped amount (M) of exhaust particulates, and the relationship between the two is calculated in advance.

Next, in S3, it is determined whether or not the trapped amount (M) of exhaust particulates is equal to or less than a first predetermined value (Y), and the trapped amount (M) of exhaust particulates is greater than a first predetermined value (Y). In this case, the process proceeds to S4, where it is determined whether or not the trapped amount (M) of the exhaust particulates is equal to or greater than a second predetermined value (X) that is a value greater than the first predetermined value (Y). If (M) is equal to or greater than the second predetermined value (X), the process proceeds to S5, and the regeneration execution flag is set to “1”.
On the other hand, if it is determined in S3 that the trapped amount (M) of the exhaust particulates is equal to or smaller than the first predetermined value (Y), the process proceeds to S6 and the regeneration execution flag is set to “0”.
Further, when it is determined in S4 that the trapped amount (M) of the exhaust particulates is smaller than the second predetermined value (X), the process proceeds to S7, and it is determined whether or not the regeneration execution flag is “1”.

  In other words, in S3 to S7, regeneration of the filter is started when the trapped amount (M) of the exhaust particulates by the filter is equal to or greater than the second predetermined value (X), and the trapped amount (M) of the exhaust particulates is the first. The filter regeneration is terminated when the value is equal to or less than a predetermined value (Y) (where X> Y).

    Next, proceeding to S8, filter regeneration is executed. Specifically, after the main injection is performed by the in-cylinder fuel injection valve 30, the first post-injection is performed by the in-cylinder fuel injection valve 30, and the second post-injection is performed by the exhaust fuel injection valve 32. As a result, filter regeneration is executed.

This filter regeneration will be described more specifically. As shown in FIG. 3, after the main injection is performed by the in-cylinder fuel injection valve 30 near the top dead center of the compression stroke of the engine 1, the in-cylinder fuel injection valve 30 The first post-injection is executed in the expansion stroke, and then the second post-injection is executed in the exhaust stroke by the exhaust fuel injection valve 32.
Here, the injection timing of the second post-injection by the exhaust fuel injection valve 32 is controlled so that the exhaust gas discharged in the exhaust stroke of each cylinder of the engine 1 passes through the exhaust fuel injection valve 32. Is preferred. As a result, the second post-injection by the exhaust fuel injection valve 32 is mixed with the exhaust gas discharged from the engine 1, and a good oxidation reaction is enabled in the oxidation catalyst 18.

  According to the present embodiment, the first post-injection following the main injection is executed by the in-cylinder fuel injection valve 30, thereby increasing the temperature of the exhaust gas discharged from the engine 1 and increasing the temperature of the oxidation catalyst 18 ( Activation). Further, by executing the second post-injection by the exhaust fuel injection valve 32, the unburnt fuel is supplied to the activated oxidation catalyst 18 and oxidized, thereby rapidly increasing the temperature of the exhaust gas flowing into the filter 20. The exhaust particulates captured by the filter 20 are burned.

  Next, the contents of learning control for learning the difference between the target injection amount and the actual injection amount of the exhaust fuel injection valve according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the contents of learning control for learning the difference between the target injection amount of the exhaust fuel-injected flight and the actual injection amount by the engine exhaust gas purification apparatus according to the embodiment of the present invention. S in the flowchart of FIG. 4 indicates each step.

  First, in S11, the oxidation catalyst upstream exhaust temperature (Tu) detected by the first exhaust gas temperature sensor 37, the oxidation catalyst downstream acidity concentration (Do) detected by the acidity concentration sensor 39, and the vehicle detected by the vehicle speed sensor. The speed (Sv), the accelerator opening (θ) detected by the accelerator opening sensor, and the engine rotation speed (Ne) detected by the engine speed sensor 33 are input.

  Next, proceeding to S12, the oxidation catalyst upstream exhaust temperature (Tu) is integrated, and the deterioration degree of the oxidation catalyst 18 is calculated based on this Tu integrated value. In S12, the degree of deterioration of the oxidation catalyst 18 is estimated from the heat history. Therefore, the degree of deterioration of the oxidation catalyst 18 is not limited to the oxidation catalyst upstream exhaust temperature (Tu), but may be estimated based on the oxidation catalyst downstream exhaust temperature or the exhaust temperature on both the upstream and downstream sides of the oxidation catalyst.

Next, the process proceeds to S13, and a threshold value for the oxidation catalyst upstream exhaust temperature (Tu), which is a condition for learning the difference between the target injection amount of the exhaust fuel injection valve 32 and the actual injection amount, which will be described later, is calculated. The threshold value of the oxidation catalyst upstream exhaust temperature (Tu) increases as the degree of deterioration of the oxidation catalyst 18 increases. Since the oxidation catalyst becomes difficult to oxidize fuel as the degree of deterioration progresses, the oxidation catalyst upstream exhaust temperature (Tu), which is a learning execution threshold value, is increased in order to facilitate oxidation as the deterioration progresses. For this reason, even if the deterioration of the oxidation catalyst 18 progresses, the learning of the injection amount of the exhaust fuel injection valve 32 described later can be accurately executed.
As a condition for learning the difference between the target injection amount of the exhaust fuel injection injection valve 32 and the actual injection amount, oxidation that is a parameter related to the temperature of the oxidation catalyst other than the oxidation catalyst upstream exhaust temperature (Tu) is used. You may make it calculate the catalyst downstream exhaust temperature and the threshold value of the exhaust temperature of both the upstream and downstream of an oxidation catalyst.

  Next, proceeding to S14, it is determined whether or not the learning completion flag is “1”. Since the learning of the injection amount deviation is not executed after the engine is started, “0” is set. Here, learning is executed only once after the engine is started, and learning is not executed until the next engine is started.

Next, in S15, it is determined whether or not the vehicle speed (Sv) is zero. If it is not zero (that is, if the vehicle is traveling), the process proceeds to S16, where the accelerator opening (θ) is fully closed. If it is fully closed (that is, if the accelerator is not operated), the process proceeds to S17, where it is determined whether or not the engine speed (Ne) is equal to or lower than the return speed. If so, the process proceeds to S18. Here, the return rotational speed is a threshold value for preventing engine stall, and fuel is automatically injected when the engine rotational speed becomes lower than the threshold value.
These S15, S16, and S17 are steps for determining whether or not the engine is in the “deceleration fuel cut operation region”. In other words, it is necessary to keep the oxygen concentration state of the exhaust passage 8 during the learning execution to the atmospheric oxygen concentration state.

  If it is the “decelerated fuel cut operation region”, the process proceeds to S18 to determine whether or not the oxidation catalyst upstream exhaust temperature (Tu) is equal to or higher than a threshold value. That is, when the fuel is supplied to the oxidation catalyst 18, it is determined whether or not the oxidation catalyst 18 is in a temperature state that can oxidize the fuel. This threshold value is changed according to the degree of deterioration of the oxidation catalyst 18 (see S13).

  When the oxidation catalyst upstream exhaust temperature (Tu) is equal to or higher than the threshold value shown in S13, the process proceeds to S19. In S14 to S18 described above, since the learning control execution condition is satisfied, an injection command value corresponding to the target injection amount is sent to the exhaust fuel injection valve 32, and fuel is injected from the exhaust fuel injection valve 32.

  Next, it progresses to S20 and the oxygen consumption in the oxidation catalyst 18 is calculated. Here, the oxygen consumption amount is obtained as a value (= atmospheric oxygen concentration−Do) obtained by subtracting the oxidation catalyst downstream acidity concentration (Do) detected by the oxygen concentration sensor 39 from the atmospheric oxygen concentration.

Next, the process proceeds to S21, and the deviation of the actual injection amount calculated from the target injection amount and the oxygen consumption amount based on the injection command value of the exhaust fuel injection valve 32 is learned.
Thereafter, the process proceeds to S22, and the learning completion flag is set to “1”.

  According to this embodiment, the exhaust fuel injection valve 32 that injects fuel into the exhaust passage 8 upstream of the oxidation catalyst 18 is provided, and the parameter value related to the temperature of the oxidation catalyst 18 (oxidation catalyst upstream exhaust temperature (Tu)). Is equal to or greater than a predetermined threshold value and is in the deceleration fuel cut operation region, fuel is injected from the exhaust fuel injection valve 32 according to the injection command value, and is estimated from the target injection amount corresponding to the injection command value and the calculated oxygen consumption amount. The deviation from the actual injection amount is learned. As a result, according to the present embodiment, it is possible to easily learn the injection amount of the exhaust fuel injection valve 32, and it is possible to eliminate the difference in solids and the variation in the injection amount of the exhaust fuel injection valve 32.

  In the present embodiment, an injection command value reflecting a difference between the target injection amount of the exhaust fuel injection valve and the actual injection amount obtained by the learning control shown in FIG. 4 is supplied to the exhaust fuel injection valve 32, and the filter Playback is to be executed. As a result, according to the present embodiment, when the filter 20 that captures the exhaust particulates is regenerated, the injection amount of the exhaust fuel injection valve 32 is learned, so that the filter regeneration can be performed efficiently.

1 is an overall configuration diagram illustrating an engine exhaust gas purification apparatus according to a first embodiment of the present invention. It is a flowchart which shows the control content of the filter reproduction | regeneration by the engine exhaust gas purification apparatus by embodiment of this invention. It is a time chart which shows fuel injection when performing filter reproduction | regeneration in S8 of FIG. It is a flowchart which shows the shift | offset | difference learning control content of the injection amount of the exhaust fuel injection flight by the engine exhaust purification apparatus by embodiment of this invention.

Explanation of symbols

1 Engine 6 Intake passage 8 Exhaust passage 18 Oxidation catalyst 20 Filter 23 EGR device 24 EGR passage 26 EGR valve 30 In-cylinder fuel injection valve 32 Exhaust fuel injection valve 33 Engine speed sensor 34 Upstream exhaust pressure sensor 36 Downstream exhaust pressure sensor 37 First exhaust gas temperature sensor 38 Second exhaust gas temperature sensor 39 Oxygen concentration sensor 40 Controller

Claims (2)

An engine exhaust gas purification device for purifying exhaust gas in an exhaust passage of an engine,
Purification means for purifying exhaust gas provided in the exhaust passage and exhausted from the engine;
An oxidation catalyst disposed upstream of the exhaust passage than said purifying means,
An exhaust fuel injection valve for injecting fuel is provided in the exhaust passage upstream of the oxidation catalyst,
And operating region detecting means for detecting a deceleration fuel cut operation region of the engine,
And parameter value detection means for detecting a parameter value associated with the temperature of the oxidation catalyst,
And oxygen consumption calculation means for calculating the oxygen consumption in the oxidation catalyst,
When the oxygen concentration of and the exhaust passage detected parameter value is at least a predetermined threshold value by the parameter value detection means is in the deceleration fuel cut operation region is the atmospheric acid concentration condition, the target injection amount corresponding to the injection command value Is injected from the exhaust fuel injection valve, the oxygen consumption calculation means calculates oxygen consumption in the oxidation catalyst, and the actual injection estimated from the oxygen consumption calculated by the oxygen consumption calculation means and learning means for learning a deviation of the amount and the target injection quantity, the possess,
The purifying means is a filter that captures exhaust particulates entrained in the exhaust gas, and further includes filter regeneration means that burns and regenerates exhaust particulates captured by the filter, the filter regeneration means When performing the regeneration of the filter, the injection amount of the exhaust fuel injection valve is controlled by reflecting the deviation of the injection amount learned by the learning means.
An exhaust emission control device for an engine. Further, the deterioration degree of the oxidation catalyst to have a degradation degree estimation means for estimating, increase the threshold value of the parameter values as the degree of deterioration of the oxidation catalyst estimated by the deterioration degree estimation means advances,
The exhaust emission control device for an engine according to claim 1.

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