JP4248415B2 - Exhaust gas purification system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine.

  The exhaust gas from an internal combustion engine contains particulate matter mainly composed of carbon. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting particulate matter in an exhaust system of an internal combustion engine is known in order to prevent the emission of these particulate matter to the atmosphere.

  In such a filter, if the amount of collected particulate matter increases, the exhaust pressure increases due to clogging of the filter and the engine performance deteriorates. Therefore, the collected particles are collected by a method of increasing the exhaust temperature upstream of the filter. The exhaust gas purification performance of the filter is regenerated by oxidizing and removing the particulate matter (hereinafter referred to as “filter regeneration process”).

  However, if the operation state of the internal combustion engine becomes a decelerating operation state during the regeneration processing of the filter, the supply of fuel to the internal combustion engine may be stopped (hereinafter, this state is simply referred to as “deceleration operation state”). .) In this case, since the air flows into the exhaust passage without being burned in the cylinder of the internal combustion engine, the temperature of the exhaust gas flowing into the filter is lowered. As a result, the temperature of the filter may decrease, and the filter regeneration process may not be continued.

  On the other hand, as described above, when the operation state of the internal combustion engine becomes a deceleration operation state during the filter regeneration process, the intake throttle valve provided in the intake system of the internal combustion engine is throttled, and the internal combustion engine is operated by the EGR device. Has been proposed, the EGR valve is fully opened to reduce the amount of fresh air flowing into the internal combustion engine and increase the amount of exhaust gas recirculated by the EGR device (for example, , See Patent Document 1). With this conventional technique, the temperature drop of the exhaust gas flowing into the filter can be suppressed, and as a result, the filter temperature drop can be suppressed.

However, in the above prior art, depending on the state of the filter when the operating state of the internal combustion engine becomes the decelerating operation state, the amount of fresh air introduced into the internal combustion engine decreases abruptly. There was a risk that the temperature would rise and the filter could be damaged or melted.
Japanese Patent No. 2582972 JP 2002-188493 A

  The purpose of the present invention is to suppress the temperature decrease of the filter and the filter from being overheated when the operating state of the internal combustion engine is in a decelerating operation state during the regeneration process of the filter, It is to provide a technique capable of successfully continuing the filter regeneration process.

In order to achieve the above object, the present invention provides an intake control means for restricting the intake air amount by decreasing the opening of the intake throttle valve and increasing the amount of EGR gas by increasing the opening of the EGR valve. In the exhaust gas purification system for an internal combustion engine that operates the intake control means when the operation state of the internal combustion engine is in a decelerating operation state during the regeneration process of the filter,
During the regeneration process of the filter, it is determined that the operation state of the internal combustion engine is in a decelerating operation state in which the fuel supply is stopped, and that the filter does not overheat even if the intake control means is operated. It is the greatest feature that the intake control means is operated only in the case where it is detected.

More specifically, a filter that is provided in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust of the internal combustion engine;
A filter regeneration means for increasing the temperature of the exhaust gas of the internal combustion engine and oxidizing the particulate matter collected by the filter to regenerate the collection ability of the filter;
An intake throttle valve provided in an intake passage of the internal combustion engine for controlling the amount of air taken into the internal combustion engine;
An EGR device that recirculates part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine and increases or decreases the amount of exhaust gas to be recirculated by increasing or decreasing the opening of an EGR valve;
An intake control means for reducing the opening of the intake throttle valve to reduce the amount of intake air, and increasing the opening of the EGR valve to increase the amount of exhaust gas to be recirculated;
During the regeneration process of the filter by the filter regeneration means, the intake control means is operated when the operating state of the internal combustion engine is in a decelerating operation state where the fuel supply to the internal combustion engine is stopped and decelerated. Filter cooling prevention means,
An exhaust gas purification system for an internal combustion engine comprising:
OT determination means for determining whether or not the temperature of the filter overheats when the intake air amount is reduced and the amount of exhaust gas to be recirculated is increased by the operation of the intake control means;
The filter cooling prevention means, when the operation state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated during the regeneration process of the filter by the filter regeneration means, Even if the intake control means is operated, if the temperature of the filter does not overheat, the intake control means is not operated and the intake control means is operated before the determination by the OT determination means. If the filter does not overheat, the intake control means is actuated after being determined by the OT determination means.

Here, the intake control means throttles the intake air amount by decreasing the opening of the intake throttle valve, and increases the amount of exhaust gas to be recirculated by increasing the opening of the EGR valve. By the operation of this intake control means, a large amount of low temperature fresh air discharged into the exhaust passage without being combusted in the cylinder of the internal combustion engine is suppressed from flowing into the filter . This can suppress a decrease in the temperature of the filter. However, if this intake control means is operated when the temperature of the filter is high or the amount of particulate matter collected in the filter is large, the amount of fresh air flowing into the filter is drastically reduced. For this reason, there is a risk that the filter will overheat.

  However, if the present invention is applied, even if the operation state of the internal combustion engine becomes a decelerating operation state during the regeneration process of the filter, the filter can be operated even if the intake control unit is operated by the OT determination unit. The intake control means is not operated unless it is determined not to overheat. Therefore, it is possible to prevent the intake control means from being inadvertently operated when the temperature of the filter is high or the amount of accumulated particulate matter trapped in the filter is large, and the temperature of the filter increases excessively. Or causing the filter to break or melt.

  Here, the OT determination unit may determine that the temperature of the filter does not excessively increase even when the intake control unit is operated when the temperature of the filter is equal to or lower than a predetermined temperature.

That is, when the temperature of the filter before the intake control unit is activated is low, the temperature of the filter after the intake control unit is activated is lowered accordingly. Therefore, when the temperature of the filter before the intake control unit is activated is equal to or lower than the predetermined temperature, it can be determined that the temperature of the filter does not increase excessively. Here, if the temperature of the filter before the intake control unit is operated is lower than the predetermined temperature, the predetermined temperature is a temperature obtained as a limit temperature at which the filter does not overheat even after the intake control unit is operated. is there.

  By performing such control, it is possible to easily determine whether or not the temperature of the filter excessively increases.

  In addition, the OT determination unit includes a deposition amount detection unit that detects a deposition amount of the particulate matter in the filter, and the deposition amount of the particulate matter in the filter detected by the deposition amount detection unit is equal to or less than a predetermined amount. In such a case, it may be determined that the filter does not overheat.

  That is, the smaller the amount of particulate matter deposited on the filter, the smaller the temperature rise of the filter due to the operation of the intake control means. This is because the amount of particulate matter deposited as a heat source that generates heat when oxidized in the filter is small. Therefore, if the amount of particulate matter deposited on the filter is equal to or less than a predetermined amount before the intake control unit is operated, it is determined that the filter does not overheat even if the intake control unit is operated. be able to. Here, the predetermined amount is a limit at which the filter does not overheat even after the intake control unit is operated if the amount of particulate matter deposited on the filter is less than that before the intake control unit is operated. This is the amount of particulate matter deposited as a quantity.

  Further, as described above, when the temperature of the filter is equal to or lower than a predetermined temperature, the OT determination unit determines that the filter does not overheat even when the intake control unit is operated. The OT determination unit further includes a deposition amount detection unit that detects a deposition amount of the particulate matter in the filter, and as the deposition amount of the particulate matter in the filter detected by the deposition amount detection unit increases, The predetermined temperature may be set low.

  That is, as described above, when the temperature of the filter before operating the intake control unit is higher than the predetermined temperature, the temperature of the filter after operating the intake control unit is increased accordingly. Further, before the intake control unit is activated, the greater the amount of particulate matter deposited on the filter, the greater the temperature rise of the filter after the intake control unit is activated.

  This means that even if the temperature of the filter before operating the intake control means is lower than a predetermined temperature, if the amount of particulate matter deposited on the filter increases, the filter temperature after operating the intake control means will increase. It shows that it becomes.

  Therefore, the more the amount of particulate matter deposited on the filter before the intake control means is activated, the more accurately the lower the predetermined temperature as a threshold for determining that the temperature of the filter does not overheat. It can be determined whether or not the filter is overheated.

The present invention further includes a fuel supply means for supplying fuel as a reducing agent to the filter,
During the regeneration process of the filter by the filter regeneration means, when the operating state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated, the OT determination means Even if the intake control unit is operated, the fuel supply unit may supply the fuel to the filter before it is determined that the temperature of the filter does not excessively increase.

Here, when the operation state of the internal combustion engine becomes a decelerating operation state during the filter regeneration process, the intake control means is operated until the OT determination means determines that the filter does not overheat. Absent. Therefore, during the filter regeneration process, even during a period from when the operating state of the internal combustion engine becomes a decelerating operation state until the OT determination means determines that the filter does not overheat, combustion is not performed in the cylinder of the internal combustion engine. In addition, low temperature exhaust gas discharged into the exhaust passage is introduced into the filter. As a result, the temperature of the filter suddenly decreases, the operation of the intake control means may not be in time, and the filter regeneration process may not be continued. Moreover, since the temperature of the filter changes abruptly, the detection accuracy of the temperature of the filter may be deteriorated.

  Accordingly, during the filter regeneration process, when the operating state of the internal combustion engine becomes a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated, the OT determination means determines that the filter does not overheat. In the period up to, it is necessary to suppress a decrease in the temperature of the filter as long as the filter does not overheat. Therefore, in the present invention, a fuel supply means for supplying fuel as a reducing agent to the filter is further provided, and fuel is supplied to the filter by the fuel supply means for the period described above.

  In this way, the fuel as the reducing agent supplied to the filter causes an oxidation reaction in the filter, and a decrease in the temperature of the filter is suppressed by the oxidation heat at that time. In this case, even if a reducing agent is supplied to the filter, the temperature of the filter may gradually decrease. When the temperature of the filter is lowered to some extent, there is a possibility that the oxidation reaction of the supplied fuel does not occur and the phenomenon that the fuel passes through the filter as it is. Therefore, in the present invention, the fuel supply from the fuel supply means to the filter may be stopped when the temperature of the filter decreases to some extent.

  When the fuel supply from the fuel supply means to the filter is stopped, it is desirable that the intake control means is operated after a predetermined time has elapsed. Here, since the fuel supplied to the filter undergoes an oxidation reaction after being adsorbed on the filter carrier, there is a time difference between the supply of the fuel to the filter and the occurrence of the oxidation reaction. When the intake control means operates in a state where the fuel is adsorbed on the filter, the fuel adsorbed on the filter may be oxidized in a short period of time, leading to an excessive temperature rise of the filter.

  Therefore, after the fuel supply from the fuel supply means to the filter is stopped, an interval of a predetermined period is set to wait for the completion of the oxidation reaction of the fuel adsorbed on the filter, and then the intake control means is operated. By doing so, it is possible to prevent overheating of the filter due to the fuel adsorbed on the filter being oxidized at once.

Further, in the present invention, a filter provided in an exhaust passage of the internal combustion engine and collecting particulate matter in the exhaust of the internal combustion engine,
A filter regeneration means for increasing the temperature of the exhaust gas of the internal combustion engine and oxidizing the particulate matter collected by the filter to regenerate the collection ability of the filter;
An intake throttle valve provided in an intake passage of the internal combustion engine for controlling the amount of air taken into the internal combustion engine;
An EGR device that recirculates a part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine and increases or decreases the amount of the exhaust gas to be recirculated by increasing or decreasing the opening of an EGR valve;
Filter state detection means for detecting the temperature of the filter and / or the amount of particulate matter deposited on the filter;
According to the temperature of the filter and / or the amount of particulate matter deposited on the filter detected by the filter state detecting means, a limit intake air amount that is a substantially minimum intake air amount at which the filter does not overheat is set. A limit intake air amount calculating means for calculating;
During the regeneration process of the filter by the filter regeneration means, when the operation state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated, the limit intake air is supplied to the internal combustion engine. The intake throttle valve and the intake throttle valve so that the intake corresponding to the amount is introduced; and
Filter heat retaining means for controlling the valve opening of the EGR valve;
You may make it provide.

  Here, when the operation state of the internal combustion engine becomes a deceleration operation state during the filter regeneration process, the filter state detection means detects the temperature of the filter at that time and the amount of particulate matter deposited on the filter. Based on the detected value, a limit intake air amount that is a substantially minimum intake air amount at which the filter temperature does not overheat is calculated. Then, the valve openings of the intake throttle valve and the EGR valve are controlled so that intake air corresponding to the limit intake air amount is introduced into the internal combustion engine.

  As a result, when the operation state of the internal combustion engine becomes a deceleration operation state during the filter regeneration process, a substantially minimum intake air amount at which the filter does not overheat is supplied to the internal combustion engine. As a result, by reducing the amount of intake air within a range where the temperature of the filter does not excessively increase, it is possible to suppress a decrease in the filter temperature and to suppress an excessive increase in the temperature of the filter.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, when the operating state of the internal combustion engine becomes a decelerating operation state during the regeneration process of the filter, the temperature of the filter is suppressed and the temperature of the filter is suppressed from being excessively increased. The reproduction process can be continued satisfactorily.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust purification system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a multi-cylinder diesel engine having four cylinders 2.

  The internal combustion engine 1 includes a fuel injection valve 3 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure. The common rail 4 communicates with the fuel pump 6 through the fuel supply pipe 5.

  An intake branch pipe 8 is connected to the internal combustion engine 1, and an upstream side of the intake branch pipe 8 is further connected to an intake passage 9. The intake passage 9 is provided with an intake throttle valve 10 that controls the amount of intake air that passes through the intake passage 9 and flows into the internal combustion engine 1. The intake throttle valve 10 is provided with an intake throttle actuator 14 that is configured by a stepper motor or the like and that drives the intake throttle valve 10 to open and close.

  Further, on the further upstream side of the intake passage 9, a compressor housing 15a of a centrifugal supercharger (turbocharger) 15 and an intercooler 16 for cooling the intake air that has been compressed in the compressor housing 15a and heated to a high temperature. Is attached. Further, an air flow meter 37 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake passage 9 is provided further upstream of the intake passage 9.

On the other hand, an exhaust branch pipe 18 is connected to the internal combustion engine 1, and the exhaust branch pipe 18 is connected to a turbine housing 15 b of the centrifugal supercharger 15. The turbine housing 15 b is connected to the exhaust passage 19. The exhaust passage 19 is connected to a muffler (not shown) downstream.

  A filter 20 that collects particulate matter (for example, soot) in the exhaust gas is disposed in the middle of the exhaust passage 19.

  Examples of the filter 20 include a wall flow type filter made of a porous base material that collects fine particles contained in exhaust gas, a filter carrying an oxidation catalyst typified by platinum (Pt), an oxidation catalyst and potassium. Examples thereof include a filter in which a NOx storage agent typified by (K) or cesium (Cs) is supported.

  An upstream exhaust pressure sensor 28 that outputs an electrical signal corresponding to the pressure of the exhaust gas flowing upstream with respect to the filter 20 is attached to the exhaust pipe 19 upstream of the filter 20. The exhaust pipe 19 downstream of the filter 20 corresponds to the exhaust temperature sensor 23 that outputs an electrical signal corresponding to the temperature of the exhaust gas flowing through the exhaust pipe 19 and the pressure of the exhaust gas flowing downstream from the filter 20. A downstream exhaust pressure sensor 29 that outputs an electrical signal is attached.

  Further, the internal combustion engine 1 is provided with an exhaust gas recirculation device 40 that recirculates a part of the exhaust gas flowing through the exhaust system of the internal combustion engine 1 to the intake system. The exhaust gas recirculation device 40 includes an EGR passage 25 formed from the exhaust branch pipe 18 to the gathering portion of the intake branch pipe 8, an electromagnetic valve, etc., and an EGR that flows in the EGR passage 25 according to the magnitude of the applied voltage. An EGR valve 26 that adjusts the gas flow rate and an EGR cooler 27 that is provided in the EGR passage 25 upstream of the EGR valve 26 and cools the EGR gas flowing through the EGR passage 25 are provided.

  In the exhaust gas recirculation device 40 configured as described above, when the EGR valve 26 is opened, a part of the exhaust gas flowing in the exhaust branch pipe 18 passes through the EGR passage 25 and is cooled by the EGR cooler 27. Then, it flows into the collecting portion of the intake branch pipe 8. The EGR gas flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 8.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operating state of the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the above-described upstream exhaust pressure sensor 28, downstream exhaust pressure sensor 29, exhaust temperature sensor 23, air flow meter 37, and the like, an accelerator position sensor 33 is connected to the ECU 35 via electric wiring, and an output signal is input to the ECU 35. It has come to be. The accelerator position sensor 33 outputs a signal corresponding to the accelerator opening that is linked to the movement of the accelerator pedal 32 operated by the driver. On the other hand, in addition to the fuel injection valve 3, the intake throttle valve 10, the EGR valve 26, and the like are connected to the ECU 35 via electric wiring and are controlled by the ECU 35.

  The ECU 35 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. A filter cooling prevention routine in the present invention, which will be described later, is also one of programs stored in the ROM of the ECU 35.

Next, the filter cooling prevention routine in this embodiment will be described with reference to FIG. This routine is a routine that is repeatedly executed at predetermined intervals during the regeneration process of the filter 20 in the internal combustion engine 1. When the operation state of the internal combustion engine 1 is in a decelerating operation state in which no fuel is supplied to the internal combustion engine. In addition, the temperature of the filter 20 is lowered to prevent the regeneration process from being continued.

  When this routine is executed, first, in S101, it is determined whether or not the operation state of the internal combustion engine 1 is the above-described deceleration operation state. Specifically, the output signal of the accelerator position sensor 33 is read into the ECU 35, and it is determined whether or not the output value is smaller than a predetermined value. Further, for this determination, an engine speed obtained from a signal from a crank position sensor (not shown) may be supplementarily used. Here, when it is determined that the operation state of the internal combustion engine 1 is the deceleration operation state, it can be determined that the fuel is not supplied to the internal combustion engine 1. That is, it is determined that there is a possibility that the temperature of the filter 20 is lowered by introducing the low-temperature exhaust gas that has not been burned into the filter 20, and the process proceeds to S102.

  In S102, it is determined whether or not the intake throttle valve 10 in the internal combustion engine 1 is throttled and the filter cooling prevention control for fully opening the EGR valve 26 is being performed. Here, when it is determined that the filter cooling prevention control is being performed, the present routine is temporarily ended. On the other hand, if it is determined that the filter cooling prevention control is not being performed, a timer is started in S103. That is, the measurement of the elapsed time t after the operation state of the internal combustion engine 1 becomes the deceleration operation state in S101 is started. Here, in practice, there is a time lag between the time when the operation state of the internal combustion engine 1 is determined to be the deceleration operation state at S101 and the time when the timer is started at S103, but this is a minute time. No problem.

Then, the process proceeds to S104, the operating state of the internal combustion engine 1 the time t elapsed after a decelerating operation state, whether longer than the predetermined time t ₀ is determined. Here, t ₀ indicates that the temperature of the filter 20 is lowered to some extent when a longer time has elapsed after the operating state of the internal combustion engine 1 has become a decelerating operation state, and if the filter cooling prevention control is performed at this timing, This is the elapsed time when it is determined that the regeneration process of the filter 20 can be continued satisfactorily without the temperature of the filter 20 rising excessively.

Here, if it is determined that the elapsed time t from when the operating state of the internal combustion engine 1 is in the decelerating operation state is equal to or less than the predetermined time t ₀ , if the filter cooling prevention control is performed at this time, the filter 20 there it is determined that there is a possibility of excessive temperature rise, return to the previous S104, in S104 again, the elapsed time t is, whether longer than the predetermined time t ₀ is determined. Then, this process is repeated until the elapsed time t is determined to be longer than the predetermined time t _0.

On the other hand, in S104, the time t elapsed after the operating state of the internal combustion engine 1 becomes the decelerating operation state, if it is determined that longer than the predetermined time t _0, the timer proceeds to S105 are stopped, yet t The value is reset to 0. Then, the process proceeds to S106, and after the filter cooling prevention control is performed, this routine is once ended.

  If it is determined in S101 that the internal combustion engine 1 is not in the decelerating operation state, it is not necessary to perform the filter cooling prevention control. Therefore, the process proceeds to S107, and when the filter cooling prevention control is performed, After stopping this, this routine is once ended.

As described above, in this routine, when the operation state of the internal combustion engine 1 is in a decelerating operation state, the filter cooling prevention control is performed after a predetermined time t ₀ has elapsed. Yes. Therefore, the filter cooling prevention control can be performed after the temperature of the filter 20 is sufficiently lowered within the range in which the regeneration process can be continued, and the excessive temperature rise of the filter 20 can be prevented.

In the present routine, to start the timer in S103, in S104, by t to determine if longer than the predetermined time t _0, but the filter cooling prevention control is performed is judged whether or feasible, this , for example, to detect the temperature of the filter 20 in the exhaust gas temperature sensor 23 at S103, in S104, with the temperature of the filter 20 detected in step S103 is lower than the predetermined temperature _{T 0,} it can be implemented in the filter cooling prevention control The flow may be determined as follows.

In this case, T ₀ is determined that if the temperature of the filter 20 is lower than this, when the filter cooling prevention control is performed, the regeneration process of the filter 20 can be satisfactorily continued without excessive temperature rise of the filter 20. It is the limit temperature. Further, in S104, when the temperature of the filter 20 is determined to be the predetermined temperature _{T 0} or more, as well as to return to the previous S103, step S105 is not required.

  Similarly, for example, the amount of particulate matter accumulated in the filter 20 is detected in S103, and the amount of particulate matter accumulated in the filter 20 is smaller than a predetermined amount in S104, so that the filter cooling prevention control is performed. The flow may be determined to be possible.

  In this case, in S103, specifically, the output signal of the upstream exhaust pressure sensor 28 provided on the exhaust upstream side of the filter 20 and the output of the downstream exhaust pressure sensor 29 provided on the exhaust downstream side of the filter 20 are provided. From the signal, the differential pressure between the exhaust gas upstream side and the exhaust gas downstream side of the filter 20 may be obtained, and the accumulated amount of particulate matter collected by the filter 20 may be detected from the value of this differential pressure. Further, the predetermined amount in S104 is determined that the regeneration process of the filter 20 can be satisfactorily continued without overheating of the filter 20 if the accumulated amount of the particulate matter collected by the filter 20 is smaller than this. It is the limit amount of deposition.

  If it is determined in S104 that the amount of particulate matter deposited on the filter 20 is greater than or equal to a predetermined amount, the process returns to S103, and in S104, the amount of particulate matter deposited on the filter 20 is the prescribed amount. This process is repeated until it is determined that there are fewer. In this case, it waits for the amount of particulate matter deposited on the filter 20 to decrease due to the regeneration process of the filter 20 that is still ongoing at that time. Also in this case, the process of S105 is not necessary.

  In the present embodiment, the intake control means includes the intake throttle valve 10, the EGR valve 26, and the ECU 35 that controls them. The filter cooling prevention means includes an ECU 35 that performs the process of S106 when the filter cooling prevention routine is executed. The OT determination means includes an ECU 35 that performs the process of S104 when the filter cooling prevention routine is executed. Further, as described above, the accumulation amount detecting means captures the filter 20 when the filter cooling prevention control routine is performed when the accumulation amount of the particulate matter collected by the filter 20 is smaller than a predetermined amount. An upstream exhaust pressure sensor 28, a downstream exhaust pressure sensor 29, and an ECU 35 are configured to detect the amount of collected particulate matter.

  In addition, the regeneration process of the filter 20 in the present embodiment is such that the exhaust temperature of the internal combustion engine 1 becomes high when the internal combustion engine 1 is in an operating state with a high load and a high rotational speed, and the particles automatically collected by the filter 20 It does not mean that the particulate matter is oxidized and removed. In other words, this means processing in a case where the particulate matter collected by the filter 20 is positively oxidized and removed by a method such as raising the exhaust gas temperature upstream of the filter 20 according to a command from the ECU 35. Therefore, the filter regeneration means in the present embodiment is configured including the ECU 35.

  Next, Example 2 will be described. Since the hardware configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment, the description thereof is omitted.

  In this embodiment, when the operation state of the internal combustion engine 1 is in a decelerating operation state in which no fuel is supplied to the internal combustion engine, it is determined whether or not the filter cooling prevention control can be performed based on the temperature of the filter 20. . Furthermore, in the present embodiment, the amount of particulate matter accumulated in the filter 20 is detected, and the temperature serving as a criterion for determining whether or not the filter cooling prevention control can be performed is changed according to the amount of accumulation. .

  FIG. 3 is a flowchart showing a filter cooling prevention routine in the present embodiment. Similar to the first embodiment, this routine is a routine that is repeatedly executed at predetermined intervals during the regeneration process of the filter 20 in the internal combustion engine 1.

  When this routine is executed, first, similarly to the first embodiment, in S101, it is determined whether or not the operating state of the internal combustion engine 1 is a decelerating operation state, and it is determined that the operating state of the internal combustion engine 1 is a decelerating operation state. In this case, in S102, it is determined whether the filter cooling prevention control is being performed. Here, when it is determined that the filter cooling prevention control is being performed, the present routine is temporarily ended. On the other hand, if it is determined in S102 that the filter cooling prevention control is not being performed, the amount of particulate matter collected by the filter 20 in S201 is detected. Specifically, from the output signal of the upstream exhaust pressure sensor 28 provided on the exhaust upstream side of the filter 20 and the output signal of the downstream exhaust pressure sensor 29 provided on the exhaust downstream side of the filter 20, the filter 20 The differential pressure between the exhaust gas upstream side and the exhaust gas downstream side is obtained, and the amount of particulate matter accumulated in the filter 20 is detected from the differential pressure value.

Then, the process proceeds to S202, the amount of the particulate matter deposited in the filter 20 obtained in S201, OT avoidance limit floor temperature T ₁ in which the filter cooling prevention control becomes criteria whether feasible is derived . Here, the greater the amount of particulate matter collected by the filter 20, the greater the temperature rise of the filter 20 when the filter cooling prevention control is performed. Accordingly, in S202, to derive an optimum OT avoidable limit floor temperature T ₁ with respect to the detected value of the particulate matter accumulation amount in S201, it is judged whether or not the accuracy if the filter cooling prevention control can be carried out Improve.

Specifically, the deposition amount of trapped in the filter 20 particulate matter, it is previously obtained experimentally the relationship between the optimum OT avoidable limit floor temperature T ₁ and mapped, it is detected in S201 from the map It was derived by reading the OT avoidance limit floor temperature T ₁ corresponding to the accumulated amount of particulates trapped in the filter 20.

  Next, it progresses to S203 and the temperature of the filter 20 is detected. Specifically, the temperature of the exhaust gas after passing through the filter 20 is detected by the exhaust gas temperature sensor 23, and the temperature of the filter 20 is estimated from the temperature.

Then, the process proceeds to S204, the temperature T of the filter 20 detected in S203 whether higher than OT avoidable limit floor temperature _{T 1} is determined. Here, if T is determined to be higher than T ₁ is, by performing the filter cooling prevention control at that time, since the filter 20 is judged to be excessive temperature rise, it returns to the previous processing of S203, in S203 The temperature of the filter is detected again. Then, in S204 again, whether T is greater than _{T 1} is determined. Then, in S204, T These steps are repeated until it is determined to be T ₁ or less. On the other hand, if T is determined to be T ₁ or less in S204, even if subjected to filter cooling prevention control, since the filter 20 is determined not to excessive temperature rise, the process proceeds to S106, the filter cooling prevention control After executing, this routine is temporarily terminated.

If it is determined in S101 that the internal combustion engine 1 is not in the deceleration operation state,
When the process proceeds to S107 and the filter cooling prevention control is being performed, the routine is terminated once after stopping this, as in the control in the first embodiment.

As described above, in this routine, when the operating state of the internal combustion engine 1 is in a decelerating operation state, first, the accumulation amount of the particulate matter collected by the filter 20 is detected, and the accumulation is detected. deriving the OT avoidance limit floor temperature T ₁ corresponding to the amount. Then, after confirming that the temperature T of the filter 20 becomes T ₁ below, have implemented filter cooling prevention control.

  Therefore, the filter 20 is excessively raised by performing the filter cooling prevention control from the two conditions of the temperature of the filter 20 at the time of starting the filter cooling prevention control and the accumulation amount of the particulate matter collected by the filter 20. It is possible to make a judgment as to whether or not the temperature is high, and it is possible to make a judgment with higher accuracy.

  Next, Example 3 will be described. With respect to the hardware configuration of the internal combustion engine 1 in the present embodiment, a fuel supply valve (not shown) that supplies fuel as a reducing agent to the filter 20 into the exhaust passage 19 of the filter 20 with respect to that described in the first embodiment. ) Is different. This fuel supply valve functions as a fuel supply means in this embodiment.

  In this embodiment, when the operation state of the internal combustion engine 1 is in a decelerating operation state, whether or not the filter cooling prevention control can be performed is determined based on the temperature of the filter 20. By supplying fuel as a reducing agent to the filter 20 from when the engine 1 enters the deceleration operation state to when the filter cooling prevention control is performed, the temperature of the filter 20 does not drop rapidly. The control to perform will be described.

  In other words, the present embodiment uses the principle that the HC component supplied from the fuel supply valve causes an oxidation reaction in the filter 20 so that the temperature decrease of the filter 20 is mitigated by the oxidation heat. . In this embodiment, during the regeneration process of the filter 20, the fuel as a reducing agent is supplied from the fuel injection valve to the exhaust gas upstream of the filter 20, thereby increasing the temperature of the filter 20 and capturing it in the filter 20. The collected particulate matter is removed by oxidation.

  FIG. 4 is a flowchart showing a filter cooling prevention routine in the present embodiment. Similar to the first embodiment, this routine is a routine that is repeatedly executed at predetermined intervals during the regeneration process of the filter 20 in the internal combustion engine 1.

  When this routine is executed, it is determined in S101 whether or not the operation state of the internal combustion engine 1 is a deceleration operation state. If it is determined that the operation state of the internal combustion engine 1 is a deceleration operation state, in S102, It is determined whether the filter cooling prevention control is being performed. Here, when it is determined that the filter cooling prevention control is being performed, the present routine is temporarily ended. On the other hand, if it is determined that the filter cooling prevention control is not being performed, the process proceeds to S301.

  In S301, for the regeneration process of the filter 20, it is determined whether fuel as a reducing agent is supplied to the filter 20 from the fuel supply valve at that time. In S301, when it is determined that the fuel as the reducing agent is not supplied to the filter 20 from the fuel supply valve for the regeneration process of the filter 20, the low-temperature exhaust discharged without being burned in the cylinder 2 is generated. Since it is introduced into the filter 20 and the temperature of the filter 20 may drop rapidly, it is determined that fuel as a reducing agent needs to be supplied from the fuel supply valve to the filter 20 at that time. Therefore, in this case, the process proceeds to S302.

  In S <b> 302, fuel as a reducing agent is injected into the exhaust gas from the fuel supply valve and supplied to the filter 20. On the other hand, if it is determined in S301 that fuel as a reducing agent is being supplied from the fuel supply valve to the filter 20 for the regeneration process of the filter 20, fuel is separately supplied from the fuel supply valve to the filter 20. Since it is determined that there is no need to do this, the process of S302 is skipped and the process proceeds to S203. In this embodiment, this process is based on the premise that the fuel supply by the fuel supply valve is not stopped even when the internal combustion engine 1 is in a decelerating operation state during the regeneration process of the filter 20. . Therefore, when the regeneration process of the filter 20 in this embodiment is a control that stops the fuel supply by the filter 20 when the internal combustion engine 1 is in a decelerating operation state during the process, the process of S301 is performed. Processing may be omitted.

  As a result of the above processing, the HC component supplied from the fuel supply valve causes an oxidation reaction in the filter 20, and the temperature decrease of the filter 20 is mitigated by the oxidation heat. Therefore, when the operation state of the internal combustion engine 1 is in a decelerating operation state, the regeneration process of the filter 20 cannot be continued until the temperature of the filter 20 rapidly decreases and the effect of the filter cooling prevention control appears. Since the temperature change of the filter 20 is abrupt, it is possible to suppress a problem that the accuracy of temperature detection in S203 deteriorates.

Then, the process proceeds to S203, the temperature of the filter 20 is detected, the process proceeds to S204, whether the temperature T of the filter 20 is higher than the predetermined temperature _{T 0} is determined. This T ₀ is the same as that described in the first embodiment. Then, in S204, if T is determined to be higher than T ₀ is, by performing the filter cooling prevention control at that time, since the filter 20 is judged to be excessive temperature rise, it returns to the previous processing of S203, processing of S203 and S204 is repeated until T is determined to be _{T 0} or less in S204. On the other hand, in S204, when T is judged to be T ₀ or less, it is subjected to filter cooling prevention control, since the filter 20 is determined not to excessive temperature rise, the process proceeds to S303.

  In S303, it is determined at that time whether it is necessary to supply fuel from the fuel supply valve to the filter 20 for the regeneration process of the filter 20. That is, it is determined whether or not it is time to inject fuel into the exhaust gas from the fuel supply valve in the regeneration process of the filter 20. If it is determined that it is not necessary to supply fuel from the fuel supply valve to the filter 20, the process proceeds to S304, and the fuel supply from the fuel supply valve is stopped. On the other hand, if it is determined in S303 that it is necessary to supply fuel from the fuel supply valve to the filter 20 for the regeneration process of the filter 20, the process of S304 is skipped. Then, the process proceeds to S106, and after executing the filter cooling prevention control, this routine is temporarily ended.

  If the regeneration process of the filter 20 in this embodiment is a control that stops the fuel supply by the filter 20 when the internal combustion engine 1 is in a decelerating operation state during the process, the process of S303 is performed. Processing may be omitted. If it is determined in S101 that the internal combustion engine 1 is not in the decelerating operation state, the process proceeds to S107. If the filter cooling prevention control is being performed, this routine is stopped and this routine is temporarily terminated. This is the same as the control in the first embodiment.

As described above, in this routine, when the operation state of the internal combustion engine 1 is in the deceleration operation state, first, fuel as a reducing agent is supplied from the fuel supply valve to the filter 20. It suppresses that the temperature of the filter 20 falls rapidly. After that, when the temperature of the filter 20 is detected and the temperature becomes equal to or lower than T ₀ , the filter cooling prevention control is performed. Therefore, the effect of the filter cooling prevention control appears due to the rapid temperature drop of the filter 20. By this, it is possible to prevent the regeneration process of the filter 20 from being continued or the accuracy of temperature detection of the filter 20 from being deteriorated.

In this embodiment, the same T ₀ as in the first embodiment is used as a reference temperature for determining whether or not the filter cooling prevention control can be performed, but another temperature may be used as the reference temperature. Good. Here, when the temperature of the filter 20 is lowered to some extent, the fuel supplied from the fuel supply valve does not cause an oxidation reaction in the filter 20, and there is a possibility that the fuel may pass through the filter 20 as it is. Therefore, in this embodiment, it is desirable to adopt a temperature higher than the temperature T _{2 at which the} phenomenon that the fuel passes through the filter 20 as it is is determined as the reference temperature for determining whether or not the filter cooling prevention control can be performed. By doing so, the fuel supplied to the filter 20 from the fuel supply valve can be prevented from passing through the filter 20 as it is, and the deterioration of the emission can be suppressed.

Further, in S304 in the present embodiment, after the fuel supply from the fuel supply valve to the filter 20 is stopped, since the predetermined time t ₁ has elapsed, the process proceeds to S106, and the flow so as to implement the filter cooling prevention control Also good. Here, the fuel supplied to the filter 20 causes an oxidation reaction after being adsorbed on the carrier of the filter 20, so there is a time difference between the time when the fuel is supplied to the filter 20 and the time when the oxidation reaction occurs. When the filter cooling prevention control is performed in a state where the fuel is adsorbed on the filter 20, the fuel adsorbed on the filter 20 is oxidized in a short period of time, which may cause the filter 20 to overheat.

Therefore, in S304, after the fuel supply from the fuel supply valve to the filter 20 is stopped, since the predetermined time t ₁ has elapsed, the process proceeds to S106, by the flow of implementing the filter cooling prevention control, the filter 20 It is possible to wait for the oxidation reaction of the adsorbed fuel to finish, and then to perform filter cooling prevention control. As a result, it is possible to prevent excessive temperature rise of the filter 20 due to the fuel adsorbed on the filter 20 being oxidized at once.

  Next, Example 4 will be described. The hardware configuration of the internal combustion engine 1 in the present embodiment is the same as that described in the first embodiment.

  In the present embodiment, when the operation state of the internal combustion engine 1 is in a decelerating operation state, the filter cooling prevention control is performed in which the intake throttle valve 10 in the internal combustion engine 1 is throttled and the EGR valve 26 is fully opened. In addition, after deriving the OT avoidance limit intake air amount that is the minimum intake air amount in a range where the filter 20 does not overheat from the accumulated amount of the particulate matter collected by the filter 20 and the temperature of the filter 20, The intake throttle valve 10 and the EGR valve 26 are controlled so that the OT avoidance limit intake air amount is introduced into the filter 20. This control for controlling the intake throttle valve 10 and the EGR valve 26 so that the OT avoidance limit intake air amount is introduced into the filter 20 is hereinafter referred to as “OT avoidance limit intake control”.

  FIG. 5 is a flowchart showing a filter cooling prevention routine in the present embodiment. Similar to the first embodiment, this routine is a routine that is repeatedly executed at predetermined intervals during the regeneration process of the filter 20 in the internal combustion engine 1.

  When this routine is executed, first, similarly to the first embodiment, in S101, it is determined whether or not the operating state of the internal combustion engine 1 is a decelerating operation state, and it is determined that the operating state of the internal combustion engine 1 is a decelerating operation state. In this case, the accumulation amount of the particulate matter collected by the filter 20 in S201 is detected. Details of this processing are the same as those described in the second embodiment. Next, it progresses to S203 and the temperature of the filter 20 is detected. The specific contents of this processing are also the same as those described in the second embodiment.

  Next, the process proceeds to S401, and the OT avoidance limit intake air amount is derived based on the accumulated amount of the particulate matter collected in the filter 20 detected in S201 and the temperature of the filter 20 detected in S203. . This OT avoidance limit intake air amount is a value experimentally obtained in advance in relation to the amount of particulate matter accumulated in the filter 20 and the temperature of the filter 20, and the filter 20 does not overheat. The minimum intake air amount in the range.

  In S401, specifically, the value of the OT avoidance limit intake air amount corresponding to the combination of the accumulation amount of the particulate matter collected in the filter 20 detected in S201 and the temperature of the filter 20 detected in S203. Is read from the map, the value of the OT avoidance limit intake air amount is derived.

  In S402, the opening degree of the intake throttle valve 10 and the EGR valve 26 is controlled so that the intake air corresponding to the OT avoidance limit intake air amount derived in S401 is introduced into the internal combustion engine 1, and the OT avoidance limit is controlled. Intake control is performed. After this control is performed, this routine is temporarily terminated.

  If it is determined in S101 that the internal combustion engine 1 is not in the decelerating operation state, it can be determined that it is not necessary to perform the OT avoidance limit intake control, so the process proceeds to S403 and the OT avoidance limit intake control is performed. If this is the case, this routine is terminated after stopping this.

  As described above, in this routine, when the operation state of the internal combustion engine 1 is in a decelerating operation state, the accumulation amount of the particulate matter collected by the filter 20 and the temperature of the filter 20 are detected. Based on these values, the OT avoidance limit intake air amount, which is the minimum intake air amount within a range in which the filter 20 does not overheat, is obtained, and the intake throttle valve 10 is introduced so that the OT avoidance limit intake air amount is introduced. And the EGR valve 26 is controlled.

  Therefore, during the regeneration process of the filter 20, when the operation state of the internal combustion engine 1 becomes a deceleration operation state, it is possible to prevent the regeneration process from continuing due to the temperature of the filter 20 being lowered, and at the same time the filter 20 Temperature rise can also be suppressed.

  In this embodiment, the filter state detecting means includes an exhaust temperature sensor 23, an upstream exhaust pressure sensor 28, a downstream exhaust pressure sensor 29, and an ECU 35. The limit intake air amount calculation means includes an ECU 35 that performs the process of S401 of the filter cooling prevention routine. The filter heat retaining means includes an ECU 35 that performs the process of S402 of the filter cooling prevention routine.

  In addition, the OT avoidance limit intake air amount in the present embodiment is the minimum inhalation within a range in which the filter 20 does not overheat in relation to the accumulation amount of the particulate matter collected by the filter 20 and the temperature of the filter 20. Although the amount of air is used, this value does not necessarily need to be the minimum amount of intake air within the above range. Even if the intake air amount is large enough to suppress the excessive temperature rise of the filter 20 and low-temperature air that is not burned in the internal combustion engine 1 is introduced into the filter 20, the regeneration process of the filter 20 is not continued. The intake air amount is not limited to the above as long as it is not possible.

  In addition, in the above-described embodiment, an example in which the present invention is applied to a multi-cylinder diesel engine has been described, but it is needless to say that the present invention may be applied to a gasoline engine.

1 is a diagram showing a schematic configuration of an internal combustion engine and an exhaust purification system thereof according to the present invention. It is a flowchart which shows the filter cooling prevention routine in Example 1 of this invention. It is a flowchart which shows the filter cooling prevention routine in Example 2 of this invention. It is a flowchart which shows the filter cooling prevention routine in Example 3 of this invention. It is a flowchart which shows the filter cooling prevention routine in Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Fuel supply pipe 6 ... Fuel pump 8 ... Intake branch pipe 9 ... Intake passage 10 ... Intake throttle valve 14 ... Intake throttle actuator 15 ... Centrifuge supercharger 15a ... Compressor housing 15b ... Turbine housing 16 ... Intercooler 18 ... Exhaust branch pipe 19 .... -Exhaust passage 20 ... Filter 23 ... Exhaust temperature sensor 25 ... EGR passage 26 ... EGR valve 27 ... EGR cooler 28 ... Upstream exhaust pressure sensor 29 ... Downstream exhaust pressure Sensor 32 ... Accelerator pedal 33 ... Accelerator position sensor 35 ... ECU
37 ... Air flow meter 40 ... Exhaust gas recirculation device

Claims (5)

A filter provided in the exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust of the internal combustion engine;
A filter regeneration means for increasing the temperature of the exhaust gas of the internal combustion engine and oxidizing the particulate matter collected by the filter to regenerate the collection ability of the filter;
An intake throttle valve provided in an intake passage of the internal combustion engine for controlling the amount of air taken into the internal combustion engine;
An EGR device that recirculates part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine and increases or decreases the amount of exhaust gas to be recirculated by increasing or decreasing the opening of an EGR valve;
An intake control means for reducing the opening of the intake throttle valve to reduce the amount of intake air, and increasing the opening of the EGR valve to increase the amount of exhaust gas to be recirculated;
During the regeneration process of the filter by the filter regeneration means, the intake control means is operated when the operating state of the internal combustion engine is in a decelerating operation state where the fuel supply to the internal combustion engine is stopped and decelerated. Filter cooling prevention means,
An exhaust gas purification system for an internal combustion engine comprising:
OT determination means for determining whether or not the temperature of the filter overheats when the intake air amount is reduced and the amount of exhaust gas to be recirculated is increased by the operation of the intake control means;
The filter cooling prevention means, when the operation state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated during the regeneration process of the filter by the filter regeneration means,
Even if the intake control means is operated, if the temperature of the filter does not overheat, the intake control means is not operated and the intake control means is operated before the determination by the OT determination means. An exhaust gas purification system for an internal combustion engine, wherein the intake control means is operated after it is determined by the OT determination means that the filter does not overheat. When the temperature of the filter is equal to or lower than a predetermined temperature, the OT determination unit is configured to reduce the intake air amount and increase the amount of exhaust gas to be recirculated by the operation of the intake control unit. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein it is determined that the filter does not overheat. The OT determination unit includes a deposition amount detection unit that detects a deposition amount of the particulate matter in the filter, and the deposition amount of the particulate matter in the filter detected by the deposition amount detection unit is equal to or less than a predetermined amount. In some cases, it is determined that the temperature of the filter does not excessively increase even when the amount of intake air is reduced and the amount of exhaust gas to be recirculated is increased by the operation of the intake control unit. Item 6. An exhaust purification system for an internal combustion engine according to Item 1. The OT determination means has a deposition amount detection means for detecting a deposition amount of particulate matter in the filter,
3. The exhaust gas purification system for an internal combustion engine according to claim 2, wherein the predetermined temperature is set to be lower as the accumulation amount of particulate matter in the filter detected by the accumulation amount detection means is larger. A fuel supply means for supplying fuel as a reducing agent to the filter;
During the regeneration process of the filter by the filter regeneration means, when the operating state of the internal combustion engine is in a decelerating operation state in which the fuel supply to the internal combustion engine is stopped and decelerated, the OT determination means 2. The internal combustion engine according to claim 1, wherein the fuel is supplied to the filter by the fuel supply means before it is determined that the temperature of the filter does not excessively increase even when the intake control means is operated. Engine exhaust purification system.

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