JP2015166592A - Fuel reforming device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the calculation of the amount of reformed gas produced during executing reformation control without providing a special sensor.SOLUTION: When predetermined reformation control executing conditions are established, reformation control is executed so that a reformed fuel injection valve 35 injects reformed fuel and a fuel reforming catalyst 36 reforms the reformed fuel to produce reformed gas. During executing the reformation control, such characteristics are found that the pressure of gas on the downstream side of the fuel reforming catalyst 36 rises depending on the amount of the reformed gas produced by the fuel reforming catalyst 36 to increase a pressure difference between a pressure during executing the reformation control (an intake pressure detected by an intake pressure sensor 19 during executing the reformation control) and a pressure during stopping the reformation control (an intake pressure detected by the intake pressure sensor 19 during stopping the deformation control). Focusing on such characteristics, the amount of the reformed gas produced during executing the reformation control is calculated on the basis of the pressure difference between the pressure during executing the reformation control and the pressure during stopping the reformation control.

Description

  The present invention relates to a fuel reforming apparatus for an internal combustion engine provided with a fuel reforming catalyst for reforming the fuel of the internal combustion engine.

As a technique for improving the fuel consumption by reforming the fuel of the internal combustion engine, for example, there is one described in Patent Document 1 (Japanese Patent Laid-Open No. 2009-79548). This is a modification of the reforming fuel injection valve for injecting reforming fuel and the reforming fuel in the middle of the EGR passage for returning a part of the exhaust gas from the exhaust passage of the internal combustion engine to the intake passage as EGR gas. And a fuel reforming catalyst to be improved. The reforming fuel injected by the reforming fuel injection valve and the moisture (water vapor) in the EGR gas are reformed by the fuel reforming catalyst to generate hydrogen (H ₂ ) or carbon monoxide (CO). Thus, the reforming fuel is reformed to generate a reformed gas having high combustibility, and the reformed gas is supplied to the intake passage of the internal combustion engine. In Patent Document 1, an H ₂ sensor and a CO sensor are provided on the downstream side of the fuel reforming catalyst in the EGR passage, and the amount of reformed gas is detected by these sensors.

JP 2009-79548 A

However, in the technique of Patent Document 1, it is necessary to provide a special sensor (an expensive sensor that is not often used in a general engine control system) such as an H ₂ sensor or a CO sensor in order to detect the amount of reformed gas. For this reason, the request | requirement of cost reduction which is an important technical subject in recent years cannot be satisfied.

  Accordingly, an object of the present invention is to provide a fuel reformer for an internal combustion engine that can calculate the amount of reformed gas without providing a special sensor.

  In order to solve the above problems, the invention according to claim 1 is directed to a main fuel injection means (21) for injecting main fuel supplied to the internal combustion engine (11), and an exhaust passage (23) of the internal combustion engine (11). An EGR passage (32) that recirculates a part of the exhaust gas as EGR gas to the intake passage (12), reforming fuel injection means (35) that injects reforming fuel into the EGR passage (32), A fuel reformer for an internal combustion engine, comprising a fuel reforming catalyst (36) disposed in the EGR passage (32) and reforming the reforming fuel injected by the reforming fuel injection means (35). When a predetermined reforming control execution condition is satisfied, reforming fuel is injected by the reforming fuel injection means (35), and the reforming fuel is reformed by the fuel reforming catalyst (36), and reformed gas Reforming control means (37) for executing reforming control for generating a fuel reforming catalyst ( 6) Pressure information acquisition means (19, 37, 38) for detecting or estimating the pressure of the gas on the downstream side or information correlated therewith (hereinafter collectively referred to as “pressure information”), and reforming control Pressure information acquisition means (19, 37, 38) during execution of pressure information (hereinafter referred to as "reforming control execution pressure information") and pressure information acquisition means (19 , 37, 38), the amount of reformed gas generated during the execution of the reforming control is calculated based on the difference from the pressure information detected or estimated (hereinafter referred to as “reforming control stopping pressure information”). A reformed gas amount calculating means (37) is provided.

  When reforming fuel and moisture (steam) in EGR gas are reformed with a fuel reforming catalyst to generate reformed gas containing hydrogen, carbon monoxide, etc., the number of moles increases. The pressure of the gas (EGR gas including reformed gas) on the downstream side of the fuel reforming catalyst increases. For this reason, the pressure of the gas on the downstream side of the fuel reforming catalyst increases in accordance with the amount of reformed gas generated by the fuel reforming catalyst during the reforming control, and the reforming control in-process pressure is changed. There is a characteristic that the pressure difference (= pressure during reforming control execution-pressure during reforming control stop) with the pressure during quality control stop increases.

Focusing on such characteristics, the present invention is based on the difference between the pressure information during reforming control execution and the pressure information during reforming control stop, and the amount of reformed gas generated during the reforming control ( For example, since the flow rate of the reformed gas is calculated, the reformed gas amount can be obtained with high accuracy. In this case, it is not necessary to provide a special sensor (an expensive sensor that is rarely used in a general engine control system) such as an H ₂ sensor or a CO sensor in order to detect the amount of reformed gas. Further, there is no need to provide pressure sensors or temperature sensors on both the upstream side and the downstream side of the fuel reforming catalyst.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in Embodiment 1 of the present invention. FIG. 2 is a time chart for explaining a method for calculating the reformed gas amount when the reforming control is shifted from stop to execution. FIG. 3 is a time chart for explaining a method for calculating the reformed gas amount when the reforming control is shifted from execution to stop. FIG. 4 is a flowchart showing the flow of processing of the reforming control routine. FIG. 5 is a flowchart showing the flow of processing of the deterioration determination routine. FIG. 6 is a diagram for explaining the second embodiment.

  Hereinafter, some embodiments embodying the mode for carrying out the present invention will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 (intake passage) of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pressure sensor 19 (pressure information acquisition means) for detecting intake pressure (gas pressure in the intake pipe 12) is provided in the surge tank 18. It has been. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and main fuel is injected into the intake port at or near the intake port connected to the intake manifold 20 of each cylinder. A main fuel injection valve 21 (main fuel injection means) is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in each cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

  On the other hand, the exhaust pipe 23 (exhaust passage) of the engine 11 is provided with a catalyst 24 such as a three-way catalyst for purifying exhaust gas, and the exhaust gas air-fuel ratio or rich gas is respectively provided upstream and downstream of the catalyst 24. / Exhaust gas sensors 25 and 26 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean etc. are provided.

  A cooling water temperature sensor 27 that detects the cooling water temperature and a knock sensor 28 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 30 that outputs a pulse signal every time the crankshaft 29 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 29. Based on the output signal of the crank angle sensor 30, the crank angle and engine The rotation speed is detected.

  The engine 11 is equipped with an EGR device 31 that recirculates a part of the exhaust gas from the exhaust pipe 23 to the intake pipe 12 as EGR gas. The EGR device 31 has an EGR pipe 32 (EGR passage) connected between the upstream side (or downstream side) of the catalyst 24 in the exhaust pipe 23 and the downstream side of the throttle valve 16 in the intake pipe 12. The EGR pipe 32 is provided with an EGR cooler 33 for cooling the EGR gas and an EGR valve 34 for adjusting the flow rate of the EGR gas. By opening the EGR valve 34, the EGR gas is recirculated from the exhaust pipe 23 to the intake pipe 12 through the EGR pipe 32.

A reforming fuel injection valve 35 (reforming fuel injection means) for injecting reforming fuel into the EGR pipe 32 is provided on the upstream side of the EGR cooler 33 in the EGR pipe 32. The main fuel injection valve 21 and the reforming fuel injection valve 35 are supplied with fuel from a common fuel tank (not shown). Further, a fuel reforming catalyst 36 for reforming the reforming fuel injected by the reforming fuel injection valve 35 is disposed on the downstream side of the reforming fuel injection valve 35 in the EGR pipe 32. . The fuel reforming catalyst 36 is configured to exchange heat with the exhaust gas flowing in the exhaust pipe 23, and reforms the reforming fuel and moisture (water vapor) in the EGR gas by using the heat of the exhaust gas. By reacting to generate hydrogen (H ₂ ) and carbon monoxide (CO), the reforming fuel is reformed to generate a reformed gas having high combustibility.

  Outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 37. The ECU 37 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  At that time, the ECU 37 calculates a target EGR rate (target value of the EGR rate) based on the engine operating state when a predetermined EGR control execution condition is satisfied, and an EGR gas flow rate (target value) corresponding to the target EGR rate. EGR control for controlling the opening degree of the EGR valve 34 so as to realize (EGR gas flow rate) is executed. Here, the EGR rate is a ratio of the in-cylinder inflow EGR gas flow rate to the in-cylinder inflow total gas flow rate (= in-cylinder inflow EGR gas flow rate / in-cylinder inflow total gas flow rate).

  In the first embodiment, the target EGR rate is changed between execution and stop of reforming control described later. Specifically, during the execution of the reforming control, the reforming component concentration (for example, the concentration of hydrogen or carbon monoxide) in the EGR gas is increased and the combustibility of the engine 11 is improved (that is, the EGR limit is increased). Therefore, the target EGR rate is made larger than when the reforming control is stopped. On the other hand, when the reforming control is stopped, the reforming component concentration in the EGR gas becomes low and the combustibility of the engine 11 decreases (that is, the EGR limit becomes low). Reduce the rate.

  In the first embodiment, the ECU 37 executes a routine shown in FIG. 4 described later to execute reforming control when a predetermined reforming control execution condition is satisfied. In this reforming control, reforming fuel is injected into the EGR pipe 32 by the reforming fuel injection valve 35, and the reforming fuel and moisture (water vapor) in the EGR gas are reformed by the fuel reforming catalyst 36. The reforming fuel is reformed to generate a reformed gas having high combustibility by generating hydrogen and carbon monoxide through a quality reaction, and the reformed gas is supplied to the intake pipe 12.

  Further, in the first embodiment, the routine of FIGS. 4 and 5 described later is executed by the ECU 37 so that the intake pressure detected by the intake pressure sensor 19 during the reforming control and the reforming control are stopped. Based on the pressure difference from the intake pressure detected by the intake pressure sensor 19, the amount of reformed gas (for example, the flow rate of the reformed gas) generated during the reforming control is calculated. Hereinafter, the intake pressure detected by the intake pressure sensor 19 during execution of reforming control is referred to as “reforming control executing pressure”. The intake pressure detected by the intake pressure sensor 19 while the reforming control is stopped is referred to as “reforming control stopping pressure”.

When the reforming fuel and moisture (water vapor) in the EGR gas are reformed by the fuel reforming catalyst 36 to generate reformed gas containing hydrogen, carbon monoxide, etc., the number of moles increases. The pressure of the gas (EGR gas including the reformed gas) on the downstream side of the fuel reforming catalyst 36 increases. For this reason, the pressure of the gas on the downstream side of the fuel reforming catalyst 36 increases according to the amount of reformed gas generated by the fuel reforming catalyst 36 during the reforming control, and is detected by the intake pressure sensor 19. As a result, the pressure difference between the reforming control execution pressure and the reforming control stop pressure (= reforming control execution pressure-reforming control stop pressure) increases. Therefore, the amount of reformed gas is accurately calculated by calculating the amount of reformed gas generated during execution of reforming control based on the pressure difference between the pressure during reforming control execution and the pressure during reforming control stoppage. Can be sought.
In the first embodiment, the reforming gas amount is calculated by detecting (or estimating) the reforming control stop pressure and the reforming control execution pressure by the following three methods (1) to (3).

  (1) When the reforming control execution condition is satisfied while the reforming control is stopped, after the reforming control stop pressure is detected by the intake pressure sensor 19, the reforming control is executed and the intake pressure sensor 19 Detect pressure during quality control.

  In this case, with the EGR gas flow rate controlled to the target EGR gas flow rate while the reforming control is stopped (the EGR gas flow rate corresponding to the target EGR rate when the reforming control is stopped), the reforming control stop pressure and the reforming control are controlled. After the execution pressure is detected and the reforming control execution pressure is detected, the target EGR rate during the reforming control stop is switched to the target EGR rate during the reforming control execution.

  Specifically, as shown by a solid line in FIG. 2, when the reforming control execution condition is satisfied while the reforming control is stopped, the EGR gas flow rate is controlled to the target EGR gas flow rate when the reforming control is stopped. Thus, the reforming control stop pressure is detected by the intake pressure sensor 19 while the reforming control is stopped.

  Thereafter, the reforming control is executed in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate when the reforming control is stopped, and the reforming control execution pressure is set by the intake pressure sensor 19 during the reforming control. To detect.

  In this way, when the reforming control is shifted from stop to execution, after the reforming control stop pressure and reforming control execution pressure are detected by the intake pressure sensor 19, the reforming control execution pressure and reforming are detected. The reformed gas amount is calculated by a map or the like based on the pressure difference from the control stop pressure.

  Thereafter, the target EGR rate when the reforming control is stopped is switched to the target EGR rate during the reforming control, and the EGR gas flow rate is changed to the target EGR gas flow rate during the reforming control execution (the target EGR rate during the reforming control execution). To EGR gas flow rate).

  (2) After a predetermined condition is satisfied during the execution of reforming control (for example, when the reforming control execution period exceeds a predetermined value), after the pressure during reforming control is detected by the intake pressure sensor 19 Then, the reforming control is stopped, and the pressure during the reforming control stop is detected by the intake pressure sensor 19.

  In this case, before detecting the pressure during reforming control, the target EGR rate during reforming control is switched from the target EGR rate during reforming control stop, and the EGR gas flow rate is changed to the target EGR while reforming control is stopped. While controlling the gas flow rate (the EGR gas flow rate corresponding to the target EGR rate when the reforming control is stopped), the reforming control execution pressure and the reforming control stop pressure are detected.

  Specifically, as shown by a solid line in FIG. 3, when a predetermined condition is satisfied during the reforming control, the target EGR rate during the reforming control is switched to the target EGR rate during the reforming control stop. Then, the EGR gas flow rate is controlled to the target EGR gas flow rate while the reforming control is stopped.

Thereafter, with the EGR gas flow rate controlled to the target EGR gas flow rate while the reforming control is stopped, the pressure during reforming control is detected by the intake pressure sensor 19 during the reforming control.
Thereafter, the reforming control is stopped in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate during which the reforming control is stopped, and the reforming control stopping pressure is set by the intake pressure sensor 19 while the reforming control is stopped. To detect.

  In this way, when the reforming control is shifted from the execution to the stop, after the reforming control executing pressure and the reforming control stopping pressure are detected by the intake pressure sensor 19, the reforming control executing pressure and the reforming are detected. The reformed gas amount is calculated by a map or the like based on the pressure difference from the control stop pressure.

(3) While the reforming control is being executed, the reforming control executing pressure is detected by the intake pressure sensor 19 and the reforming control stopping pressure under the current operating conditions is estimated.
In this case, the reforming control stop pressure is detected by the intake pressure sensor 19 while the reforming control is stopped, the reforming control stopping pressure is learned for each operation condition, and the reforming control is stopped during the reforming control. When the reforming control execution pressure is detected by the sensor 19, the reforming control stop pressure under the current operating conditions is estimated based on the learned value of the reforming control stop pressure.

  Alternatively, a map that prescribes the relationship between the operating conditions and the reforming control stop pressure is stored in advance, and when the reforming control executing pressure is detected by the intake pressure sensor 19 during the reforming control, The pressure during the reforming control stop under the current operating conditions is estimated using the map.

  In this way, while reforming control is being executed, the pressure during reforming control is detected by the intake pressure sensor 19, and after the reforming control stopping pressure is estimated based on the learned value, the reforming control executing pressure is And the reformed gas amount is calculated by a map or the like based on the pressure difference between the reforming control stoppage pressure and the stoppage pressure.

Further, in the first embodiment, the deterioration state of the fuel reforming catalyst 36 is determined by comparing the calculated reformed gas amount with the reference reformed gas amount under the operation condition for which the reformed gas amount is calculated. Further, in the first embodiment, the target EGR rate during the reforming control and the injection amount of the reforming fuel are corrected based on the calculated reformed gas amount.
Hereinafter, the processing content of each routine of FIG.4 and FIG.5 which ECU37 performs by a present Example is demonstrated.

[Reform control routine]
The reforming control routine shown in FIG. 4 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 37, and serves as reforming control means, reformed gas amount calculation means, and correction means in the claims. .

When this routine is started, first, at step 101, it is determined whether or not the reforming control execution condition is satisfied. For example, the execution condition of EGR control is satisfied (that is, the EGR control is being executed). That is, the determination is made based on whether all the conditions such as the temperature of the fuel reforming catalyst 36 being equal to or higher than the activation temperature are satisfied.
If it is determined in step 101 that the reforming control execution condition is not satisfied, this routine is terminated without executing the processing from step 102 onward.

  On the other hand, if it is determined in step 101 that the reforming control execution condition is satisfied, the process proceeds to step 102, where the EGR gas flow rate is controlled to the target EGR gas flow rate when the reforming control is stopped. While the reforming control is stopped, the pressure during the reforming control stop is detected by the intake pressure sensor 19, and the reforming control stopping pressure is learned (for example, stored in the backup RAM of the ECU 37). When the learning value of the reforming control stop pressure is used in step 207 of FIG. 5 (processing for estimating the reforming control stop pressure during execution of reforming control) to be described later, the detected reforming control stop is detected. The intermediate pressure is learned for each operation condition (for example, EGR gas flow rate).

  Thereafter, the process proceeds to step 103, and with the EGR gas flow rate controlled to the target EGR gas flow rate while the reforming control is stopped, the reforming fuel injection valve 35 starts the injection of the reforming fuel and performs the reforming control. Run. In this reforming control, reforming fuel is injected into the EGR pipe 32 by the reforming fuel injection valve 35, and the reforming fuel and moisture (water vapor) in the EGR gas are reformed by the fuel reforming catalyst 36. The reforming fuel is reformed to produce reformed gas with high combustibility by producing hydrogen and carbon monoxide through a quality reaction. At this time, the injection amount of the reforming fuel is determined by a map or the like based on at least one of the temperature and the deterioration state of the fuel reforming catalyst 36 and the EGR gas flow rate (for example, the EGR gas flow rate estimated from the target EGR rate). calculate.

  Thereafter, the process proceeds to step 104, and the reforming control execution pressure is detected by the intake pressure sensor 19 while the reforming control is being executed in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate during which the reforming control is stopped.

  In this way, when the reforming control is shifted from being stopped to being executed, the reforming control stopping pressure and the reforming control executing pressure are detected by the intake pressure sensor 19, and then the routine proceeds to step 105, where reforming control is executed. Based on the pressure difference between the intermediate pressure and the reforming control stop pressure (= reforming control executing pressure-reforming control stop pressure), the reformed gas amount is calculated by a map or the like. The map for calculating the reformed gas amount is created in advance based on design data, test data, and the like, and is stored in the ROM of the ECU 37.

  Thereafter, the process proceeds to step 106 where the map of the target EGR rate during the reforming control stop is switched to the map of the target EGR rate during the reforming control execution, and the map of the target EGR rate during the reforming control execution is used. A target EGR rate during execution of reforming control according to the current engine operating state is calculated. Furthermore, the actual EGR gas flow rate is calculated by a map or the like based on the reformed gas amount, and the target EGR rate during the reforming control is corrected based on the actual EGR gas flow rate. As a result, the target EGR rate during the reforming control stop is switched to the target EGR rate during the reforming control, and the target EGR rate during the reforming control is corrected based on the reformed gas amount. Further, the reforming fuel is corrected based on the reformed gas amount by correcting the injection amount of the reforming fuel based on at least one of the temperature and the deterioration state of the fuel reforming catalyst 36 and the actual EGR gas flow rate. Correct the injection amount.

[Deterioration judgment routine]
The deterioration determination routine shown in FIG. 5 is repeatedly executed at a predetermined period during the execution of the reforming control, and serves as a reformed gas amount calculating means, a deterioration determining means, and a correcting means as defined in the claims.

  When this routine is started, first, in step 201, it is determined whether or not the catalyst deterioration determination mode switching condition is satisfied, for example, whether or not the reform control execution period has exceeded a predetermined value, and reforming fuel. It is determined by whether or not the total injection amount exceeds a predetermined value, whether or not the combustion fluctuation exceeds a predetermined value, and the like.

  If it is determined in step 201 that the catalyst deterioration determination mode switching condition is satisfied, the process proceeds to step 202, where the target EGR rate when the reforming control is stopped is determined from the map of the target EGR rate during the reforming control. The target EGR rate when the reforming control is stopped according to the current engine operating state is calculated using the map of the target EGR rate when the reforming control is stopped. As a result, the target EGR rate during the reforming control is switched to the target EGR rate during the reforming control stop, and the EGR gas flow rate is changed to the target EGR gas flow rate during the reforming control stop (the target EGR rate during the reforming control stop). To EGR gas flow rate). Further, the injection amount of the reforming fuel is changed based on the temperature of the fuel reforming catalyst 36 and the EGR gas flow rate (for example, the EGR gas flow rate estimated from the target EGR rate).

  Thereafter, the process proceeds to step 203, and the reforming control execution pressure is detected by the intake pressure sensor 19 while the reforming control is being executed in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate during which the reforming control is stopped. The reforming control execution pressure is learned.

  Thereafter, the process proceeds to step 204, and the reforming control is performed by stopping the reforming fuel injection by the reforming fuel injection valve 35 in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate during the reforming control stop. Stop.

  Thereafter, the process proceeds to step 205, and the reforming control stop pressure is detected by the intake pressure sensor 19 while the reforming control is stopped in a state where the EGR gas flow rate is controlled to the target EGR gas flow rate during the reforming control stop. When the learned value of the reforming control stop pressure is used in step 207 (processing for estimating the reforming control stop pressure during the reforming control) to be described later, the detected reforming control stop pressure is used. Learning is performed for each operation condition (for example, EGR gas flow rate).

  In this way, when the reforming control is shifted from the execution to the stop, the intake pressure sensor 19 detects the reforming control in-execution pressure and the reforming control in-stop pressure, and then proceeds to step 208 to execute the reforming control. Based on the pressure difference between the intermediate pressure and the reforming control stop pressure (= reforming control executing pressure-reforming control stop pressure), the reformed gas amount is calculated by a map or the like.

  On the other hand, if it is determined in step 201 that the catalyst deterioration determination mode switching condition is not satisfied, the process proceeds to step 206, and the reforming control execution pressure is detected by the intake pressure sensor 19 during the execution of the reforming control. The reforming control execution pressure is learned.

Thereafter, the process proceeds to step 207, and the reforming control stoppage pressure under the current operating conditions (for example, EGR gas flow rate) is estimated as follows.
By interpolating with the learning value (a plurality of learning values) of the reforming control stop pressure learned for each operating condition while the reforming control is stopped, the reforming control stopping pressure at the current operating condition is obtained. Estimate the reforming control stop pressure under operating conditions. At this time, the learned value of the reforming control stop pressure may be the value learned in step 102 of FIG. 4 or step 205 of FIG. Alternatively, the reforming control is stopped by the intake pressure sensor 19 while the reforming control is stopped before the reforming control execution condition is satisfied or when the reforming control is stopped after the reforming control execution condition is not satisfied. The pressure may be detected, the reforming control stop pressure may be learned for each operation condition, and the reforming control stop pressure learning value may be used.

  Alternatively, the reforming control stop pressure under the current operating conditions may be estimated (calculated) using a map that defines the relationship between the operating conditions and the reforming control stop pressure. In this case, a map for estimating (calculating) the reforming control stoppage pressure is created in advance based on design data, test data, and the like, and stored in the ROM of the ECU 37.

  In this way, while reforming control is being performed, the pressure during reforming control is detected by the intake pressure sensor 19, and the pressure during reforming control stop is estimated based on the learned value. Based on the pressure difference between the pressure during the quality control execution and the pressure during the reforming control stop (= the pressure during the reforming control execution-the pressure during the reforming control stop), the reformed gas amount is calculated by a map or the like.

  Thereafter, the process proceeds to step 209, where the reformed gas amount is calculated based on the operating conditions (for example, the temperature of the fuel reforming catalyst 36 and the reforming fuel injection amount). A reference reformed gas amount is calculated. Here, the reference reformed gas amount is a reformed gas amount (ideal reformed gas amount) when the fuel reforming catalyst 36 is in a state without deterioration (for example, a new state). A map for calculating the reference reformed gas amount is created in advance based on design data, test data, and the like, and is stored in the ROM of the ECU 37.

  Thereafter, the process proceeds to step 210, and the ratio (= reformed gas amount / reference reformed gas amount) between the reformed gas amount and the reference reformed gas amount in the operation condition for which the reformed gas amount is calculated is determined as the fuel reforming catalyst. 36 is calculated as a deterioration rate (deterioration state), and it is determined whether or not the deterioration rate of the fuel reforming catalyst 36 is larger than a deterioration determination value (for example, 0.3). The deterioration determination value may be set based on, for example, a reproduction control execution condition.

  If it is determined in step 210 that the deterioration rate of the fuel reforming catalyst 36 is larger than the deterioration determination value, it is not necessary to execute regeneration control for recovering the fuel reforming performance of the fuel reforming catalyst 36. to decide.

  In this case, the process proceeds to step 211, where the map of the target EGR rate during the reforming control stop is switched to the map of the target EGR rate during the reforming control, and the map of the target EGR rate during the reforming control is used. A target EGR rate during execution of reforming control according to the current engine operating state is calculated. Furthermore, the actual EGR gas flow rate is calculated by a map or the like based on the reformed gas amount, and the target EGR rate during the reforming control is corrected based on the actual EGR gas flow rate. As a result, the target EGR rate during the reforming control stop is switched to the target EGR rate during the reforming control, and the target EGR rate during the reforming control is corrected based on the reformed gas amount. Further, the reforming fuel is corrected based on the reformed gas amount by correcting the injection amount of the reforming fuel based on at least one of the temperature and the deterioration state of the fuel reforming catalyst 36 and the actual EGR gas flow rate. The reforming fuel is injected by the reforming fuel injection valve 35 and reforming control is executed.

  On the other hand, if it is determined in step 210 that the deterioration rate of the fuel reforming catalyst 36 is equal to or less than the deterioration determination value, it is necessary to execute regeneration control for recovering the fuel reforming performance of the fuel reforming catalyst 36. to decide.

  In this case, the process proceeds to step 212 and reproduction control is executed. In this regeneration control, for example, carbon is deposited on the fuel reforming catalyst 36 by performing dither control or the like that alternately changes the air-fuel ratio of the exhaust gas between rich and lean to supply oxygen to the fuel reforming catalyst 36. The fuel reforming performance of the fuel reforming catalyst 36 is recovered by burning the fuel.

  Thereafter, the process proceeds to step 213, and reforming fuel is started by the reforming fuel injection valve 35 to perform reforming control. At this time, the EGR gas flow rate and the reforming fuel injection amount are calculated based on at least one of the temperature and the deterioration state of the fuel reforming catalyst 36.

  The reforming control stop pressure is detected by the intake pressure sensor 19 before the reforming control is started (stopped), and the reforming control is executed by the intake pressure sensor 19 after the reforming control is started (running). The intermediate pressure may be detected, and the reformed gas amount may be calculated based on the pressure difference between the reforming control execution pressure and the reforming control stoppage pressure.

In the first embodiment described above, the pressure of the gas on the downstream side of the fuel reforming catalyst 36 increases according to the amount of reformed gas generated by the fuel reforming catalyst 36 during the execution of reforming control, Focusing on the characteristic that the pressure difference between the reforming control execution pressure and the reforming control stop pressure increases, the reforming control is performed based on the pressure difference between the reforming control execution pressure and the reforming control stop pressure. Since the amount of reformed gas generated during the execution of control is calculated, the amount of reformed gas can be obtained with high accuracy. In addition, it is not necessary to provide a special sensor (an expensive sensor that is rarely used in a general engine control system) such as an H ₂ sensor or a CO sensor in order to detect the amount of reformed gas. Further, it is not necessary to provide a pressure sensor or a temperature sensor on both the upstream side and the downstream side of the fuel reforming catalyst 36. For this reason, the request | requirement of the cost reduction which is an important technical subject in recent years can be satisfy | filled.

  In the first embodiment, when a predetermined condition is satisfied during the execution of the reforming control, the reforming control is stopped by detecting the pressure during the reforming control by the intake pressure sensor 19, and the intake pressure sensor 19 is stopped. The pressure during stoppage of reforming control is detected. In this way, the reformed gas amount can be calculated every time a predetermined condition is satisfied during the execution of the reforming control.

  At this time, in the first embodiment, as indicated by a solid line in FIG. 3, before the reforming control execution pressure is detected, the target EGR rate during the reforming control is changed from the target EGR rate during the reforming control execution. In the state where the EGR gas flow rate is controlled to the target EGR gas flow rate when the reforming control is stopped (the EGR gas flow rate corresponding to the target EGR rate when the reforming control is stopped). The pressure is detected while quality control is stopped. In this way, the reforming control execution pressure and the reforming control stop pressure detected in the state of being controlled to the same EGR gas flow rate (EGR gas flow rate corresponding to the target EGR rate during the stoppage of reforming control). The reformed gas amount can be calculated using the pressure difference, and the calculation accuracy of the reformed gas amount can be improved.

  Further, as shown in the comparative example indicated by the broken line in FIG. 3, when the reforming control is shifted from the execution to the stop, the EGR gas flow rate is controlled to the EGR gas flow rate corresponding to the target EGR rate during the reforming control execution. When the reforming control execution pressure and the reforming control stop pressure are detected, it is necessary to stop the reforming control while maintaining the target EGR rate during the reforming control execution. Can get worse.

  In this regard, in the first embodiment, as indicated by a solid line in FIG. 3, the reforming control can be stopped after switching to the target EGR rate during which the reforming control is stopped, and the combustibility of the engine 11 is deteriorated. Can be prevented.

  If the deterioration of the combustibility of the engine 11 can be suppressed within an allowable range, the EGR gas flow rate is changed to the target EGR rate (or reforming control) during the reforming control when shifting from the reforming control to the stop. The pressure during reforming control and the pressure during stopping reforming control are detected in a state in which the EGR gas flow rate is controlled to correspond to the target EGR rate between the target EGR rate being executed and the target EGR rate being stopped during reforming control. You may make it do.

  In the first embodiment, the reforming control execution pressure is detected by the intake pressure sensor 19 while reforming control is being executed, and the reforming control stop pressure under the current operating conditions is estimated. In this way, the reformed gas amount can be calculated many times during execution of the reforming control, and the frequency of calculating the reformed gas amount can be increased.

  At this time, in the first embodiment, the reforming control stop pressure is detected by the intake pressure sensor 19 while the reforming control is stopped, the reforming control stopping pressure is learned for each operating condition, and the reforming control is performed. When the reforming control execution pressure is detected by the intake pressure sensor 19 during the execution of the above, the reforming control stop pressure under the current operating conditions is estimated based on the learned value of the reforming control stop pressure. In this way, the reforming control stop pressure can be accurately estimated during the reforming control.

  Alternatively, a map that prescribes the relationship between the operating conditions and the reforming control stop pressure is stored in advance, and when the reforming control executing pressure is detected by the intake pressure sensor 19 during the reforming control, The pressure during the reforming control stop under the current operating conditions is estimated using the map. Even in this way, the reforming control stop pressure can be accurately estimated during the reforming control.

  Further, in the first embodiment, when the reforming control execution condition is satisfied while the reforming control is stopped, the reforming control is executed after the reforming control stopping pressure is detected by the intake pressure sensor 19, and the intake air The pressure sensor 19 detects the pressure during reforming control execution. In this way, the reformed gas amount can be calculated when the reforming control execution condition is satisfied and the reforming control is executed while the reforming control is stopped.

  At this time, in the first embodiment, as shown by a solid line in FIG. 2, the EGR gas flow rate is changed to the target EGR gas flow rate while the reforming control is stopped (EGR gas flow rate corresponding to the target EGR rate when the reforming control is stopped). In a controlled state, the pressure during reforming control stop and the pressure during reforming control are detected, and after the pressure during reforming control is detected, the target during reforming control is determined from the target EGR rate when reforming control is stopped. Switching to the EGR rate is made. By doing this, the reforming control execution pressure and the reforming control stop pressure detected in the state of being controlled to the same EGR gas flow rate (EGR gas flow rate corresponding to the target EGR rate during the stop of reforming control) The amount of reformed gas can be calculated using the pressure difference, and the calculation accuracy of the reformed gas amount can be improved.

  In addition, as in the comparative example indicated by the broken line in FIG. 2, the state in which the EGR gas flow rate is controlled to the EGR gas flow rate corresponding to the target EGR rate during execution of the reforming control when the reforming control is stopped and executed. Thus, when the pressure during reforming control stop and the pressure during reforming control are detected, it is necessary to switch to the target EGR rate during reforming control while the reforming control is stopped, and the combustibility of the engine 11 is reduced. It can get worse.

  In this regard, in the present embodiment, as indicated by a solid line in FIG. 2, it is possible to switch to the target EGR rate during execution of the reforming control after executing the reforming control, and the combustibility of the engine 11 deteriorates. Can be prevented.

  If the deterioration of the combustibility of the engine 11 can be suppressed within an allowable range, the EGR gas flow rate is changed to the target EGR rate (or the reforming control) during the reforming control when the reforming control is stopped and executed. The pressure during reforming control stoppage and the pressure during reforming control execution are detected while controlling the EGR gas flow rate corresponding to the target EGR rate between the target EGR rate being executed and the target EGR rate during the stoppage of reforming control. You may make it do.

  Further, in the first embodiment, the deterioration state (deterioration rate) of the fuel reforming catalyst 36 is determined by comparing the calculated reformed gas amount with the reference reformed gas amount under the operation condition for which the reformed gas amount is calculated. Like to do. In this way, it is possible to accurately determine the deterioration state of the fuel reforming catalyst 36 using the actually calculated reformed gas amount.

  Further, in the first embodiment, the target EGR rate during the reforming control and the injection amount of the reforming fuel are corrected based on the calculated reformed gas amount. In this way, it is possible to accurately correct the target EGR rate during the reforming control and the injection amount of the reforming fuel using the actually calculated reformed gas amount.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. However, parts that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified, and parts different from those in the first embodiment are mainly described.

  In the second embodiment, as shown in FIG. 6, an EGR gas pressure sensor 38 (pressure information acquisition means) is provided downstream of the EGR cooler 33 and the EGR valve 34 in the EGR pipe 32, and this EGR gas pressure The sensor 38 detects the pressure of the gas (EGR gas including the reformed gas) on the downstream side of the fuel reforming catalyst 36.

  4 and 5 are executed by the ECU 37, the gas pressure detected by the EGR gas pressure sensor 38 during the reforming control (the reforming control execution pressure) and the stop of the reforming control are performed. The amount of reformed gas generated during the execution of reforming control is calculated based on the pressure difference from the gas pressure (pressure during stopping reforming control) detected by the EGR gas pressure sensor 38.

  In the second embodiment described above, substantially the same effects as those of the first embodiment can be obtained. Moreover, in the second embodiment, the pressure of the gas on the downstream side of the fuel reforming catalyst 36 can be directly detected by the EGR gas pressure sensor 38 provided in the EGR pipe 32. Therefore, the reformed gas amount based on the pressure difference The calculation accuracy can be further improved.

  Note that the gas pressure on the downstream side of the fuel reforming catalyst 36 is estimated (calculated) based on the output of the intake pressure sensor 19 or the like by using a map or a mathematical formula, and the gas pressure (reformation) estimated during the reforming control is executed. The amount of reformed gas generated during execution of reforming control is calculated based on the pressure difference between the pressure during control execution and the gas pressure estimated during reforming control stop (pressure during reforming control stop). Anyway. In this case, the EGR gas pressure sensor 38 may be omitted, and the ECU 37 serves as pressure information acquisition means in the claims.

  In each of the first and second embodiments, the reforming gas amount is detected by detecting (or estimating) the reforming control stoppage pressure and the reforming control execution pressure by the three methods (1) to (3) described above. However, the present invention is not limited to this. For example, the reforming control stop pressure and the reforming control execution pressure are detected by one or two methods (1) to (3) ( Alternatively, the reformed gas amount may be calculated by estimating.

  Further, in each of the first and second embodiments, as the pressure information (pressure or information correlated with the pressure) of the gas on the downstream side of the fuel reforming catalyst 36, the pressure of the gas on the downstream side of the fuel reforming catalyst 36 or The amount of reformed gas is calculated using the pressure of the gas in the intake pipe 12 (intake pressure). However, the present invention is not limited to this, and the gas flow rate downstream of the fuel reforming catalyst 36 or the gas flow rate (intake flow rate) of the intake pipe 12 is used as the pressure information of the gas downstream of the fuel reforming catalyst 36. The amount of reformed gas may be calculated.

  In this case, for example, the gas flow rate on the downstream side of the fuel reforming catalyst 36 is estimated (calculated) based on the output of the EGR gas pressure sensor 38 or the like by a map or a mathematical formula, and the gas estimated during the reforming control execution. The amount of reformed gas generated during reforming control based on the flow rate difference between the flow rate (flow rate during reforming control execution) and the gas flow rate estimated during reforming control stopping (flow rate during reforming control stoppage) May be calculated.

  Alternatively, the flow rate of the gas downstream of the fuel reforming catalyst 36 is estimated (calculated) based on the output of the intake pressure sensor 19 or the like by using a map or a mathematical formula, and the gas flow rate (improved during execution of reforming control) is corrected. The amount of reformed gas generated during the execution of reforming control is calculated based on the flow rate difference between the flow rate during quality control and the gas flow rate estimated during stopping of reforming control (the flow rate during reforming control stop). You may do it.

  Alternatively, a flow rate sensor for detecting the flow rate of the gas downstream of the fuel reforming catalyst 36 is provided, and the gas flow rate (reforming control execution flow rate) detected by the flow rate sensor during reforming control and reforming control. The amount of reformed gas generated during the execution of reforming control may be calculated based on the flow rate difference from the gas flow rate detected by the flow rate sensor during stoppage (flow rate during reforming control stoppage). .

  Alternatively, a flow rate sensor that detects the flow rate of the gas in the intake pipe 12 (for example, downstream of the throttle valve 16) is provided, and the gas flow rate (flow rate during execution of reforming control) detected by the flow rate sensor during reforming control. And the amount of reformed gas generated during execution of reforming control is calculated based on the flow rate difference between the gas flow rate detected by the flow sensor during reforming control stoppage (flow rate during reforming control stoppage) Anyway.

  In the first and second embodiments, the ratio between the reformed gas amount and the reference reformed gas amount (= reformed gas amount / reference reformed gas amount) is calculated as the deterioration state of the fuel reforming catalyst 36. However, the present invention is not limited to this. For example, the difference between the reference reformed gas amount and the reformed gas amount (= reference reformed gas amount−reformed gas amount) is calculated as the deterioration state of the fuel reforming catalyst 36. You may do it.

  In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1 and FIG. 6, but includes an in-cylinder injection type engine, a fuel injection valve for intake port injection, and a fuel injection valve for in-cylinder injection. The present invention can also be applied to a dual injection engine equipped with both.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 19 ... Intake pressure sensor (pressure information acquisition means), 21 ... Main fuel injection valve (main fuel injection means), 23 ... Exhaust pipe (exhaust passage) , 24 ... Catalyst, 32 ... EGR piping (EGR passage), 35 ... Reforming fuel injection valve (reforming fuel injection means), 36 ... Fuel reforming catalyst, 37 ... ECU (reforming control means, reformed gas) Quantity calculation means, deterioration determination means, correction means, pressure information acquisition means), 38... EGR gas pressure sensor (pressure information acquisition means)

Claims (11)

A main fuel injection means (21) for injecting main fuel supplied to the internal combustion engine (11), and an intake passage (12) using EGR gas as a part of exhaust gas from the exhaust passage (23) of the internal combustion engine (11). An EGR passage (32) for recirculation, reforming fuel injection means (35) for injecting reforming fuel into the EGR passage (32), and the reforming fuel disposed in the EGR passage (32). A fuel reformer for an internal combustion engine, comprising a fuel reforming catalyst (36) for reforming the reforming fuel injected by the fuel injection means (35).
When a predetermined reforming control execution condition is satisfied, the reforming fuel is injected by the reforming fuel injection means (35), and the reforming fuel is reformed by the fuel reforming catalyst (36). Reforming control means (37) for executing reforming control to generate reformed gas
Pressure information acquisition means (19, 37, 38) for detecting or estimating the pressure of the gas downstream of the fuel reforming catalyst (36) or information correlated therewith (hereinafter collectively referred to as “pressure information”). )When,
Pressure information detected or estimated by the pressure information acquisition means (19, 37, 38) during execution of the reforming control (hereinafter referred to as “pressure information during reforming control execution”) and while the reforming control is stopped Based on the difference from the pressure information detected or estimated by the pressure information acquisition means (19, 37, 38) (hereinafter referred to as “reforming control stop pressure information”), it is generated during the execution of the reforming control. And a reformed gas amount calculating means (37) for calculating a reformed gas amount.   The pressure information acquisition means (19, 37, 38) uses, as the pressure information, the pressure or flow rate of the gas downstream of the fuel reforming catalyst (36) and the pressure or flow rate of the gas in the intake passage (12). 2. The fuel reformer for an internal combustion engine according to claim 1, wherein any one of them is detected or estimated.   The reformed gas amount calculating means (37) uses the pressure information acquisition means (19, 37, 38) to obtain the pressure information during execution of the reforming control when a predetermined condition is satisfied during the execution of the reforming control. 3. After the detection or estimation, the reforming control is stopped, and the pressure information acquisition means (19, 37, 38) detects or estimates the pressure information during the reforming control stop. A fuel reformer for an internal combustion engine according to claim 1.   The reformed gas amount calculating means (37) determines the target EGR during the stop of the reforming control from the target EGR rate during the reforming control before detecting or estimating the pressure information during the reforming control. The reforming control execution pressure information and the reforming control stop pressure information in a state where the EGR gas flow rate is controlled to the EGR gas flow rate corresponding to the target EGR rate during the stop of the reforming control. 4. The fuel reformer for an internal combustion engine according to claim 3, wherein the fuel is detected or estimated.   The reformed gas amount calculating means (37) detects or estimates the pressure information during execution of reforming control by the pressure information acquisition means (19, 37, 38) during execution of the reforming control, and also performs the current operation. 5. The fuel reformer for an internal combustion engine according to claim 1, wherein pressure information during stoppage of reforming control under conditions is estimated.   The reformed gas amount calculating means (37) detects or estimates the pressure information during stoppage of the reforming control by the pressure information acquisition means (19, 37, 38) while the reforming control is stopped. The control stop pressure information is learned for each operation condition, and the reforming control stop pressure information in the current operation condition is estimated based on the learned value of the reforming control stop pressure information during execution of the reforming control. The fuel reformer for an internal combustion engine according to claim 5, wherein   The reformed gas amount calculating means (37) stores in advance a map that prescribes the relationship between operating conditions and pressure information during the reforming control stop, and uses the map during the reforming control. 6. The fuel reformer for an internal combustion engine according to claim 5, wherein pressure information during stoppage of reforming control under current operating conditions is estimated.   The reformed gas amount calculating means (37) stops the reforming control by the pressure information acquiring means (19, 37, 38) when the reforming control execution condition is satisfied while the reforming control is stopped. After the medium pressure information is detected or estimated, the reforming control is executed, and the pressure information acquisition means (19, 37, 38) detects or estimates the pressure information during the reforming control execution. Item 8. A fuel reformer for an internal combustion engine according to any one of Items 1 to 7.   The reformed gas amount calculating means (37) controls the reforming control stop pressure information and the EGR gas flow rate in a state in which the flow rate of the EGR gas is controlled to an EGR gas flow rate corresponding to the target EGR rate when the reforming control is stopped. After reforming control execution pressure information is detected or estimated, and after the reforming control execution pressure information is detected or estimated, the target EGR during execution of the reforming control is determined from the target EGR rate when the reforming control is stopped. 9. The fuel reformer for an internal combustion engine according to claim 8, wherein the rate is switched to a rate.   The deterioration state of the fuel reforming catalyst (36) is determined by comparing the reformed gas amount calculated by the reformed gas amount calculating means (37) with the reference reformed gas amount under the operating conditions for which the reformed gas amount is calculated. 10. The fuel reformer for an internal combustion engine according to claim 1, further comprising a deterioration determination means (37) for determining   Correction means (37) for correcting the target EGR rate during execution of the reforming control and the injection amount of the reforming fuel based on the reformed gas amount calculated by the reformed gas amount calculating means (37). The fuel reformer for an internal combustion engine according to any one of claims 1 to 10, wherein the fuel reformer is provided.

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