JP5284228B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device. More specifically, the present invention relates to an exhaust emission control device including an exhaust emission purification filter that collects particulate matter (PM) contained in exhaust gas of an internal combustion engine.

  A technique of providing an exhaust gas purification filter for collecting PM in an exhaust system of an internal combustion engine to reduce the PM emission amount is widely used. Since there is a limit to the amount of PM that can be collected by the exhaust purification filter, a filter regeneration operation for burning the PM accumulated on the exhaust purification filter is appropriately executed. In this filter regeneration operation, for example, fuel injection in the exhaust process (hereinafter referred to as “post injection”) is performed. When such post injection is executed, the oxidation reaction in the oxidation catalyst provided on the upstream side of the exhaust purification filter is promoted, so the temperature of the exhaust gas flowing into the exhaust purification filter rises and the accumulated PM burns.

  However, the exhaust purification filter may be melted by heat generated by burning PM. Such a melting loss of the exhaust purification filter is considered to occur when the amount of heat taken away from the exhaust purification filter via the exhaust is smaller than the amount of heat generated by the accumulated PM burning. Therefore, conventionally, a technique has been proposed in which the exhaust gas flow rate is increased to promote heat dissipation from the exhaust gas purification filter and prevent the exhaust gas purification filter from being melted.

  For example, in Patent Document 1, when the temperature of the exhaust purification filter becomes equal to or higher than a predetermined value during the regeneration operation of the exhaust purification filter, the exhaust flow rate is prevented from excessively decreasing by increasing the idle speed. Technology is shown.

  Further, for example, in Patent Document 2, when it is determined that there is a possibility that PM accumulated on the exhaust purification filter may rapidly burn based on the operating state of the internal combustion engine, the intake throttle valve is set to the opening side more than normal. The technology to control is shown. As a result, the flow rate of the exhaust gas flowing through the exhaust purification filter can be increased, and the heat radiation from the exhaust purification filter can be promoted.

JP 60-206923 A JP 2007-2111788 A

  As described above, there are two known techniques for preventing the exhaust purification filter from being melted by increasing the exhaust flow rate: increasing the idle speed and controlling the throttle valve to the open side. These two techniques will be discussed in more detail assuming a situation where the internal combustion engine is in an idling operation state during the filter regeneration operation.

  When the technique of Patent Document 1 is applied, the combustion cycle is accelerated by increasing the idling speed, so that both the exhaust flow rate and the exhaust temperature during idling increase, so the PM combustion and the heat dissipation from the exhaust purification filter It is thought that both can be promoted. However, if the idling speed is increased too much, sudden start at the time of start-up and large noise may be caused. Therefore, increasing the idling speed as in the technique of Patent Document 1 may impair the merchantability. There is.

  On the other hand, when the technique of Patent Document 2 is applied, the exhaust flow rate is increased by controlling the throttle valve to the open side, but as compared with the case where the idling speed is increased as described above. The exhaust temperature is lowered. For this reason, when the throttle valve is controlled to open, in order to promote both PM combustion and heat release from the exhaust purification filter, for example, it is necessary to increase the temperature of the exhaust by increasing the post injection amount. . However, when the post-injection amount is increased, there is a risk that the oil performance may be reduced or the fuel efficiency may be deteriorated due to oil dilution.

  The present invention provides an exhaust that can prevent the exhaust purification filter from being melted while suppressing problems that occur with an increase in the exhaust flow rate, such as sudden start-up at startup, noise, a decrease in oil performance, or a deterioration in fuel consumption. An object is to provide a purification device.

  In order to achieve the above object, the present invention provides an exhaust purification filter that is provided in an exhaust system (for example, an exhaust pipe 4 described later) of an internal combustion engine (for example, an engine 2 described later) and collects particulate matter contained in the exhaust gas. (For example, DPF 45 described later), accumulation amount estimation means (for example, ECU 7 described later) for estimating the accumulation amount of particulate matter in the exhaust purification filter, and particulate matter deposited on the exhaust purification filter is burned and removed. Filter regeneration means for executing the filter regeneration operation (for example, an injector 22, a throttle valve 32, an ECU 7, and a means for executing step S2 in FIG. 2), and an idle that is the number of revolutions during idle operation of the internal combustion engine Idle rotation speed control means for controlling the rotation speed (for example, an injector 22, a throttle valve 32, an ECU 7, which will be described later, and FIG. (Means relating to execution of step S5) and the idling engine speed control means are different means, and an exhaust flow rate control means for controlling the flow rate of the exhaust gas flowing into the exhaust purification filter (for example, a throttle valve 32 described later, An exhaust purification device (for example, an exhaust purification device 1 to be described later) provided with an ECU 7 and means for executing step S7 in FIG. 2 is provided. In the exhaust purification apparatus, when the internal combustion engine is in an idling operation state and the filter regeneration operation is being performed, the accumulation amount is larger than a predetermined first determination amount (for example, a first determination amount M1 described later). The idle rotation speed control means makes the idle rotation speed higher than the rotation speed during normal idle operation, and the accumulation amount is a predetermined second determination amount (for example, a second determination amount described later) larger than the first determination amount. If it is larger than the judgment amount M2), the idle speed control means makes the idle speed higher than the speed during the normal idle operation, and the exhaust flow rate control means causes the exhaust purification filter to Control to increase the flow rate of inflowing exhaust gas.

According to the present invention, the amount of particulate matter deposited on the exhaust purification filter is estimated. Then, when the internal combustion engine is in the idling operation state and the filter regeneration operation is being performed and the accumulation amount is larger than the first determination amount, the idling engine speed control means sets the idling engine speed to the engine speed during normal idling operation. And increase the flow rate of the exhaust gas flowing into the exhaust purification filter. Further, when the accumulation amount is larger than the second determination amount that is larger than the first determination amount, in addition to increasing the idle rotation speed by the idle rotation speed control means, the exhaust flow rate control means causes the exhaust purification filter to Control is performed to increase the flow rate of the inflowing exhaust gas, and the flow rate of the exhaust gas flowing into the exhaust gas purification filter is further increased. As a result, the flow rate of the exhaust gas flowing into the exhaust gas purification filter can be made appropriate in accordance with the amount of particulate matter accumulated in the exhaust gas purification filter, and the exhaust gas purification filter can be prevented from being melted.
Thus, until the accumulation amount becomes larger than the second determination amount, the flow rate of the exhaust gas flowing into the exhaust gas purification filter is increased only by the increase of the idle rotation speed by the idle rotation speed control means. Since it is not necessary to increase the post-injection amount in order to keep the temperature at a high level, the occurrence of oil dilution and the deterioration of fuel consumption can be suppressed. Further, after the accumulation amount becomes larger than the second determination amount, in addition to the increase in the idle rotation speed by the idle rotation speed control means, the exhaust flow rate control means increases the exhaust flow rate so that the idle rotation speed becomes excessive. Since the exhaust purification filter can be protected without increasing the height, the merchantability is not impaired as described above.
As described above, priority is given to the control of the idle speed by the idle speed control means, and the exhaust flow rate control by the exhaust flow rate control means is used together as necessary, so that sudden start, noise, oil at the start It is possible to prevent the exhaust purification filter from being melted while suppressing problems that occur with an increase in the exhaust flow rate, such as a decrease in performance or a deterioration in fuel consumption.

  In this case, when the internal combustion engine is in the idling operation state and the accumulation amount is larger than the second determination amount during the execution of the filter regeneration operation, the idling engine speed control means sets the idling engine speed to a predetermined value. It is preferable to control to the upper limit value.

  As described above, when the exhaust gas flow rate is increased by means other than an increase in the idle speed during the filter regeneration operation, it may be necessary to increase the post injection amount in order to keep the exhaust gas temperature high. Therefore, there is a risk that oil dilution may occur or fuel consumption may deteriorate. According to the present invention, when the accumulation amount is larger than the second determination amount, the idle rotation speed control means controls the idle rotation speed to the upper limit value. That is, by increasing the idle speed as much as possible, the amount of increase in the exhaust gas flow rate by the exhaust gas flow rate control means can be reduced, so that the occurrence of oil dilution and the deterioration of fuel consumption can be suppressed.

  In order to achieve the above object, the present invention provides an exhaust purification filter that is provided in an exhaust system (for example, an exhaust pipe 4 described later) of an internal combustion engine (for example, an engine 2 described later) and collects particulate matter contained in the exhaust gas. (For example, DPF 45 described later), accumulation amount estimation means (for example, ECU 7 described later) for estimating the accumulation amount of particulate matter in the exhaust purification filter, and particulate matter deposited on the exhaust purification filter is burned and removed. Filter regeneration means for executing the filter regeneration operation (for example, an injector 22, a throttle valve 32, an ECU 7, and a means for executing step S12 in FIG. 7), and an idling speed that is the number of revolutions during idle operation of the internal combustion engine Idle rotation speed control means for controlling the rotation speed (for example, an injector 22, a throttle valve 32, an ECU 7 described later, and a diagram) (Means related to execution of step S16) and the idling engine speed control means are different means, and an exhaust flow rate control means (for example, a throttle valve 32 described later) for controlling the flow rate of the exhaust gas flowing into the exhaust purification filter. , ECU 7 and means relating to execution of step S19 in FIG. 7) and exhaust gas flow detection means (for example, ECU 7 described later) for detecting or estimating the flow rate of the exhaust gas flowing into the exhaust gas purification filter. (For example, an exhaust purification device 1 described later) is provided. The exhaust gas purification device obtains a flow rate lower limit value (for example, an inflow exhaust gas flow rate target lower limit value QEIN_TRGT, which will be described later) with respect to an exhaust flow rate at which the exhaust gas purification filter does not reach an excessive temperature while the filter regeneration operation is being performed. Flow rate lower limit value calculation means (for example, ECU 7 to be described later, and means related to execution of step S14 in FIG. 7) for calculating based on the accumulation amount is further provided. The exhaust emission control device is configured such that when the internal combustion engine is in an idle operation state and the detected value or estimated value of the exhaust gas flow rate is smaller than the lower flow rate lower limit value while the filter regeneration operation is being executed, Control is performed to increase the idle speed toward a predetermined upper limit value so that the detected value or the estimated value is equal to or higher than the lower limit value by the control means, and even if the idle speed reaches the upper limit value. When the detected value or the estimated value is smaller than the flow rate lower limit value, the exhaust gas flow control means controls the exhaust gas flowing into the exhaust purification filter so that the detected value or the estimated value is equal to or higher than the flow rate lower limit value. Control to increase the flow rate.

According to the present invention, the flow rate lower limit value for the exhaust gas flow rate at which the exhaust purification filter does not reach an excessive temperature rise during the filter regeneration operation is calculated based on the accumulation amount of the particulate matter. Then, when the internal combustion engine is in the idling operation state and the filter regeneration operation is being performed, it is determined that the detected value or the estimated value of the exhaust flow rate is smaller than the lower limit value of the flow rate, that is, the exhaust purification filter reaches an excessive temperature rise. In this case, the idle rotation speed control means performs control to increase the idle rotation speed toward a predetermined upper limit value so that the detected value or the estimated value is equal to or higher than the flow rate lower limit value. Thereby, the flow rate of the exhaust gas flowing into the exhaust purification filter can be made appropriate, and the exhaust purification filter can be prevented from being melted. Further, in this case, there is no need to perform control for increasing the exhaust flow rate by means of an exhaust flow rate control means different from the idle speed control means, so as described above, the post injection amount is increased in order to keep the exhaust temperature high. There is no need to do. For this reason, generation | occurrence | production of oil dilution and deterioration of a fuel consumption can be suppressed.
Further, if the detected value or estimated value is smaller than the lower limit of flow rate even when the idle speed reaches the upper limit value, the exhaust flow control means controls the detected value or estimated value to be equal to or higher than the lower limit of flow rate. Control is performed to increase the flow rate of the exhaust gas flowing into the exhaust gas purification filter. Thereby, the flow rate of the exhaust gas flowing into the exhaust purification filter can be made appropriate, and the exhaust purification filter can be prevented from being melted. Here, by controlling the exhaust flow rate by the exhaust flow rate control means in addition to the control of the idle rotational speed, the exhaust purification filter can be protected without excessively increasing the idle rotational speed. There is no loss.
As described above, priority is given to the control of the idling engine speed by the idling engine speed control means, and the exhaust gas flow rate control is performed only when it is determined that the exhaust purification filter reaches the excessive temperature even if the idling engine speed is increased to the upper limit value. By controlling the exhaust flow rate by means, it is possible to prevent the exhaust purification filter from being melted while suppressing problems that occur due to an increase in the exhaust flow rate, such as sudden start-up, noise, deterioration of oil performance, or deterioration of fuel consumption. Can be prevented.
Further, by controlling the flow rate of the exhaust gas by the idle speed control means and the exhaust flow rate control means so that the detected value or the estimated value is not less than the lower limit value of the flow rate, the exhaust purification filter can be more reliably prevented from being melted. Can do.

1 is a schematic diagram illustrating an exhaust emission control device according to a first embodiment of the present invention and a configuration of an engine to which the exhaust purification device is applied. FIG. It is a flowchart which shows the procedure of the DPF regeneration control process which concerns on the said embodiment. It is a figure which shows the relationship between PM accumulation amount in DPF during DPF regeneration operation execution, and the maximum temperature of DPF. It is a figure which shows the relationship between the idle rotation speed at the time of reproduction | regeneration, and PM deposition amount. It is a figure which shows the relationship between the throttle opening at the time of reproduction | regeneration, and PM accumulation amount. It is a flowchart which shows the procedure of the DPF regeneration control process which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the DPF regeneration control process which concerns on the said embodiment. It is a figure which shows the relationship between inflow exhaust gas flow target lower limit and PM deposition amount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description after the second embodiment, the description of the configuration common to the first embodiment is omitted.

[First Embodiment]
FIG. 1 is a schematic diagram showing a configuration of an exhaust purification device 1 according to a first embodiment and an internal combustion engine (hereinafter referred to as “engine”) 2 to which the exhaust purification device 1 is applied. The engine 2 is a diesel engine that directly injects fuel into the combustion chamber of each cylinder 21.

  A fuel supply system that supplies fuel to the engine 2 includes a fuel pump 24 that pressurizes the fuel stored in the fuel tank 23, and an injector that is provided for each cylinder 21 of the engine 2 with the fuel pressurized by the fuel pump 24. And a common rail 25 to be supplied to 22.

  The fuel injection amount QINJ from the injector 22 is set by an electronic control unit (hereinafter referred to as “ECU”) 7 described later. Further, the valve opening time of the injector 22 is controlled by a drive signal from the ECU 7 so as to obtain the set fuel injection amount QINJ.

  The engine 2 includes an intake pipe 3 through which intake air flows, an exhaust pipe 4 through which exhaust flows, an EGR passage 5 that recirculates part of the exhaust gas in the exhaust pipe 4 to the intake pipe 3, and intake air into the intake pipe 3. A supercharger 6 for pumping is provided.

  The intake pipe 3 is connected to the intake port of each cylinder 21 of the engine 2 through a plurality of branch portions of the intake manifold 31. The exhaust pipe 4 is connected to the exhaust port of each cylinder 21 of the engine 2 through a plurality of branch portions of the exhaust manifold 41. The EGR passage 5 branches from the exhaust manifold 41 and reaches the intake manifold 31.

  The supercharger 6 includes a turbine (not shown) provided in the exhaust pipe 4 and a compressor (not shown) provided in the intake pipe 3. The turbine is driven by the kinetic energy of the exhaust flowing through the exhaust pipe 4. The compressor is rotationally driven by the turbine, pressurizes the intake air, and pumps it into the intake pipe 3. The turbine includes a plurality of variable vanes (not shown), and is configured to change the turbine rotation speed (rotational speed) by changing the opening of the variable vanes. The vane opening of the turbine is electromagnetically controlled by the ECU 7.

  A throttle valve 32 for controlling the flow rate of fresh air sucked into the engine 2 (hereinafter referred to as “intake air amount”) is provided on the upstream side of the supercharger 6 in the intake pipe 3. The throttle valve 32 is connected to the ECU 7 via an actuator, and the opening degree thereof is electromagnetically controlled by the ECU 7. Further, an intercooler 33 for cooling the intake air pressurized by the supercharger 6 is provided on the downstream side of the supercharger 6 in the intake pipe 3.

  The EGR passage 5 connects the exhaust manifold 41 and the intake manifold 31, and returns a part of the exhaust discharged from the engine 2 to the intake air of the engine 2. Hereinafter, the gas recirculated to the intake air through the EGR passage 5 is referred to as EGR gas. The EGR passage 5 is provided with an EGR cooler 51 that cools the EGR gas and an EGR valve 52 that controls the flow rate of the EGR gas. The EGR valve 52 is connected to the ECU 7 via an actuator, and the valve opening degree is electromagnetically controlled by the ECU 7.

  A catalytic converter 43 for purifying exhaust gas and a diesel particulate filter (hereinafter referred to as “DPF (Diesel Particulate Filter)”) 45 as an exhaust purification filter are disposed on the downstream side of the supercharger 6 in the exhaust pipe 4. It is provided in this order.

The catalytic converter 43 includes, for example, an oxidation catalyst, purifies the exhaust gas by a reaction between the catalyst and the exhaust gas, and raises the temperature of the exhaust gas with heat generated by the reaction between the exhaust gas and the catalyst. More specifically, in the catalytic converter 43, for example, platinum (Pt) acting as a catalyst is supported on an alumina (Al ₂ O ₃ ) carrier, zeolite having excellent HC adsorption action, HC What added rhodium (Rh) excellent in the steam reforming action is used.

  When the exhaust gas passes through fine holes in the filter wall, the DPF 45 collects PM mainly composed of carbon in the exhaust gas by depositing it on the surface of the filter wall and the holes in the filter wall. As a constituent material of the filter wall, for example, a porous body made of aluminum titanate or cordierite is used.

  When PM is collected to the limit of the collection capability of the DPF 45, that is, the accumulation limit, the pressure loss increases. Therefore, it is necessary to appropriately execute the DPF regeneration operation for burning the PM accumulated on the DPF 45 and regenerating the DPF 45. This DPF regeneration process is performed, for example, by performing post injection, increasing the temperature of the exhaust gas flowing into the DPF 45 by promoting the oxidation reaction in the catalytic converter 43, and burning PM. The procedure for executing this DPF regeneration operation will be described in detail later with reference to FIG.

  An exhaust temperature sensor 82 and an air flow sensor 83 are connected to the ECU 7. The exhaust temperature sensor 82 detects the temperature TE of the exhaust gas downstream of the DPF 45 in the exhaust pipe 4 and transmits a signal substantially proportional to the detected value to the ECU 7. The air flow sensor 83 detects the intake air amount QAIR of the engine 2 and transmits a signal substantially proportional to the detected value to the ECU 7.

  In addition, a crank angle sensor 84, an accelerator opening sensor 85, and an ignition switch 86 are connected to the ECU 7. The crank angle sensor 84 transmits a CRK signal, which is a pulse signal, to the ECU 7 as the crankshaft of the engine 2 rotates. The CRK signal is transmitted every predetermined crank angle (for example, 30 °). The accelerator opening sensor 85 detects a depression amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown), and transmits a signal substantially proportional to the detected value to the ECU 7. The ignition switch 86 is provided in a driver's seat of a vehicle (not shown), and transmits a signal for instructing start or stop of the vehicle to the ECU 7.

  Here, the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 2 is calculated by the ECU 7 based on the CRK signal transmitted from the crank angle sensor 84. The fuel injection amount QINJ from the injector 22 described above is calculated by the ECU 7 by searching a predetermined map (not shown) according to the engine speed NE and the accelerator pedal opening AP. Further, the estimated value (hereinafter simply referred to as “inflow exhaust flow rate”) QEIN of the exhaust gas discharged from the engine 2 and flowing into the DPF 45 is based on the intake air amount QAIR, the fuel injection amount QINJ, and the engine speed NE. , Calculated by the ECU 7.

  The ECU 7 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter referred to as “a processing unit”). CPU ”). In addition, the ECU 7 includes a storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, and an output circuit that outputs control signals to the injector 22, the throttle valve 32, and the like. With the hardware configuration as described above, the ECU 7 includes a module that executes the following DPF regeneration control process (see FIG. 2).

The DPF regeneration control process according to this embodiment will be described with reference to FIGS.
FIG. 2 is a flowchart showing a procedure of a DPF regeneration control process in which PM deposited on the DPF is burned and removed to regenerate the DPF.
FIG. 3 is a diagram illustrating a relationship between the PM accumulation amount in the DPF during execution of the DPF regeneration operation and the maximum temperature of the DPF. FIG. 3 shows the relationship between the PM accumulation amount and the maximum DPF temperature for different inflow exhaust flow rates Q1, Q2, and Q3. Here, the maximum temperature of the DPF refers to the temperature of the highest temperature portion of the DPF.

In FIG. 3, Q1 indicates the inflow exhaust flow rate during normal idling operation, that is, the inflow exhaust flow rate when the engine is idling at a predetermined normal idling speed.
Q2 indicates the inflow exhaust gas flow rate when the idling operation is performed with the idling speed higher than the normal idling speed, and is larger than Q1.
Q3 indicates the inflow exhaust flow rate when the idling speed is set higher than the normal idling speed and the throttle valve is fully opened, and is larger than Q2.

  As shown in FIG. 3, when the PM accumulation amount is increased under a constant inflow exhaust flow rate, the DPF maximum temperature increases. This is because the amount of heat generated when PM burns increases as the amount of accumulated PM increases. Further, when the inflow exhaust gas flow rate is increased under a certain amount of accumulated PM, the DPF maximum temperature is lowered. This is because increasing the inflow exhaust flow rate promotes heat dissipation from the DPF.

  On the other hand, as shown by a broken line in FIG. 3, the DPF has a limit temperature depending on the material used. For this reason, while the DPF regeneration operation is being executed, it is necessary to prevent the DPF from exceeding the limit temperature due to excessive temperature rise. Therefore, in the DPF regeneration control process of the present embodiment, the DPF regeneration operation is appropriately controlled in accordance with the state of the DPF together with the execution of the DPF regeneration operation so that the DPF does not exceed the limit temperature. Hereinafter, a specific procedure of the DPF regeneration control process of the present embodiment based on such a concept will be described with reference to FIG.

  As shown in FIG. 2, in this DPF regeneration control process, idle up control (step S5) and exhaust flow rate increase control (step S7) are performed as necessary in conjunction with the execution of DPF temperature increase control (step S2). By executing this, the inflow exhaust flow rate of the DPF is increased to prevent overheating. This DPF regeneration control process is repeatedly executed every predetermined control period after the engine is started.

  In step S1, it is determined whether or not a DPF regeneration operation flag FDPFREG is “1”. The DPF regeneration operation flag FDPFREG is a flag indicating that the DPF regeneration operation is being performed, that is, a period in which execution of DPF temperature increase control (see step S2 described later) is instructed. Updated sequentially. If the determination in step S1 is YES and the DPF regeneration operation is being executed, the process proceeds to step S2. If the determination in step S1 is NO, this process is immediately terminated.

  In the process of updating the DPF regeneration operation flag FDPFREG, an estimated value (hereinafter simply referred to as “PM accumulation amount”) QPM of the DPF in the DPF is appropriately calculated, and this PM accumulation amount QPM is a predetermined start determination amount REGSTART. Is exceeded, the DPF regeneration operation flag FDPFREG is set to “1” to start the DPF regeneration operation. When the PM accumulation amount QPM falls below the predetermined end determination amount REGEND, the DPF regeneration operation flag FDPFREG is reset to “0” to end the DPF regeneration operation.

The PM accumulation amount QPM while the DPF regeneration operation is not performed is calculated by adding the PM amount ΔPM newly collected in the DPF during the current control cycle to the value of the PM accumulation amount during the previous control cycle. Is done. The PM amount ΔPM discharged from the engine and collected in the DPF at the time of the control at this time is, for example, a basic value calculated based on the fuel injection amount QINJ and the engine speed NE, and the engine coolant temperature and the intake air amount QAIR. It is calculated by adding a correction term calculated based on the above.
On the other hand, the PM accumulation amount QPM during the DPF regeneration operation is calculated by subtracting the PM amount ΔPM burned and removed by the DPF during the current control cycle from the value of the PM accumulation amount during the previous control cycle. Is done. The PM amount ΔPM burned and removed during the control this time is calculated based on, for example, the inflow exhaust gas flow rate QEIN and the exhaust gas temperature TE.

  In step S2, DPF temperature increase control is executed, and the process proceeds to step S3. More specifically, in this DPF temperature increase control, for example, the throttle valve opening is set to a predetermined opening, the intake air amount is reduced, and post-injection is executed to promote the oxidation reaction in the catalytic converter. As a result, the temperature of the exhaust gas flowing into the DPF is raised. Thereby, PM deposited on the DPF is removed by combustion.

  In step S3, it is determined whether or not the engine is in an idle operation state. Specifically, for example, when the three conditions of the accelerator opening is “0”, the engine speed NE is smaller than a predetermined value, and the vehicle speed is “0”, the engine is satisfied. It is determined that the operation state is an idle operation state. If this determination is YES, the process proceeds to step S4, and if this determination is NO, this process is immediately terminated.

  In step S4, it is determined whether or not the PM accumulation amount QPM is equal to or less than a predetermined first determination amount M1. If this determination is YES, it is determined that no PM has accumulated to the extent that the DPF reaches an excessive temperature rise, and this processing is immediately terminated. If this determination is NO, the process proceeds to step S5 in order to prevent overheating of the DPF.

  In step S5, the inflow exhaust gas flow rate of the DPF is increased by executing idle-up control for increasing the engine idle speed to the regeneration idle speed NE_IDLUP that is set higher than the engine speed during normal idle operation. The process proceeds to step S6. More specifically, the regeneration idle speed NE_IDLUP suitable for the PM accumulation amount QPM of the DPF is calculated, and the intake air amount and the fuel injection amount are calculated according to the regeneration idle speed NE_IDLUP from the normal idle operation. Is also increased to increase the idle speed to the idle speed NE_IDLUP during reproduction.

  The idling engine speed NE_IDLUP during regeneration is an idling engine speed suitable for the DPF during the DPF regeneration operation, that is, the exhaust gas at a flow rate at which the DPF does not reach an excessive temperature during the DPF regeneration operation. This is the minimum value of the idle speed that can be supplied, and is set to a value that is equal to or higher than the speed during normal idle operation.

FIG. 4 is a diagram showing a relationship between the regeneration idle speed NE_IDLUP and the PM accumulation amount QPM, and shows an example of a control map referred to when calculating the regeneration idle speed NE_IDLUP.
When the PM accumulation amount QPM is larger than the first determination amount M1, the regeneration idle rotation speed NE_IDLUP is set to be higher than the rotation speed during normal idle operation in proportion to the PM accumulation amount QPM. Further, a predetermined upper limit value is set for the idle rotation speed, and the idle rotation speed NE_IDLUP at the time of reproduction is limited to a value equal to or less than this upper limit value. That is, the regeneration idle speed NE_IDLUP is substantially proportional to the PM accumulation amount QPM when the PM accumulation amount QPM is between the first determination amount M1 and the second determination amount M2 larger than the first determination amount M1. When the PM accumulation amount QPM is larger than the second determination amount M2, the upper limit value is set.
The upper limit value of the idling engine speed indicates the maximum value of the engine speed that can be accepted as the idling engine speed. If the idling speed is set too high, there is a risk of sudden start at the start or noise in the engine. Therefore, by setting such an upper limit value to an appropriate value, it is possible to prevent a decrease in merchantability due to an excessive increase in the idle speed.

  Returning to FIG. 2, in step S6, it is determined whether or not the PM accumulation amount QPM is equal to or less than the second determination amount M2. If this determination is YES, it is determined that the DPF can be prevented from being overheated only by executing the idle-up control, and this process is immediately terminated. When this determination is NO, it is determined that the DPF may reach an excessive temperature rise only by performing the idle up control, and the process proceeds to step S7 to execute the exhaust flow rate increasing control in addition to the above-described idle up control. .

  In step S7, the exhaust gas flow rate increase control is performed to open the throttle valve until the throttle valve opening reaches a regeneration throttle opening TO_REG that is set larger than the opening during normal DPF regeneration operation. The inflow exhaust gas flow rate is further increased, and this process is terminated.

  The throttle opening during regeneration TO_REG is the throttle opening suitable for the DPF during the DPF regeneration operation, that is, the exhaust at a flow rate at which the DPF does not reach an excessive temperature during the DPF regeneration operation is stably converted to the DPF. This is the opening of the throttle valve that can be supplied, and is set to an opening that is greater than that during normal DPF regeneration operation.

FIG. 5 is a diagram showing the relationship between the throttle opening TO_REG during regeneration and the PM accumulation amount QPM, and shows an example of a control map that is referred to when calculating the throttle opening TO_REG during regeneration.
When the PM accumulation amount QPM is larger than the second determination amount M2, the regeneration throttle opening TO_REG is set to be larger than the opening during normal DPF regeneration operation in proportion to the PM accumulation amount QPM. . That is, when the PM accumulation amount QPM is between the second determination amount M2 and the third determination amount M3 larger than the second determination amount M2, the regeneration throttle opening TO_REG is larger than that during the normal DPF regeneration operation. Each time, it is set to become substantially proportional to the PM accumulation amount QPM. When the PM accumulation amount QPM is larger than the third determination amount M3, the regeneration throttle opening TO_REG is set to a fully open opening.

According to this embodiment, the following effects can be obtained.
(1) According to the present embodiment, when the engine is in the idle operation state and the DPF regeneration operation is being executed and the PM accumulation amount QPM is larger than the first determination amount M1, the idle up control is executed. As a result, the idling engine speed is increased to the regeneration idle engine speed NE_IDLUP which is set to be higher than the engine engine speed during normal idling operation, and the inflow exhaust gas flow rate of the DPF is increased. Further, when the PM accumulation amount QPM is larger than the second determination amount M2, which is larger than the first determination amount M1, in addition to increasing the idle speed by the idle up control, the exhaust flow rate increase control is executed. As a result, the inflow exhaust flow rate of the DPF is further increased. Thereby, the inflow exhaust flow rate of DPF can be made appropriate according to the PM accumulation amount QPM of DPF, and this DPF can be prevented from being melted.
As described above, until the PM accumulation amount QPM becomes larger than the second determination amount M2, the DPF inflow flow rate is increased only by the increase in the idling speed by the idle-up control, so that the exhaust temperature is kept high. Since there is no need to increase the post injection amount, the occurrence of oil dilution and the deterioration of fuel consumption can be suppressed. Further, after the PM accumulation amount QPM becomes larger than the second determination amount M2, in addition to the increase in the idle speed by the idle up control, the exhaust flow rate increase control for opening the throttle valve is executed to reduce the inflow exhaust flow rate. By increasing the DPF, the DPF can be protected without excessively increasing the idling speed, so that merchantability is not impaired.
As described above, priority is given to the control of the idling speed by the idle-up control, and if necessary, the control of the inflowing exhaust gas flow rate by the execution of the exhaust gas flow rate increasing control is used together, so that sudden start-up, noise, oil It is possible to prevent the DPF from being melted while suppressing problems that occur with an increase in the exhaust flow rate such as a decrease in performance or a deterioration in fuel consumption.

  (2) According to the present embodiment, when the PM accumulation amount QPM is larger than the second determination amount M2, the idle speed is controlled to the upper limit value by executing the idle up control. That is, by increasing the idle speed as much as possible, the exhaust flow rate increase control is executed, and the amount of increase of the inflow exhaust flow rate can be reduced by opening the throttle valve, so that oil dilution occurs and fuel consumption deteriorates. Can be suppressed.

  In the exhaust flow rate increase control in step S7, the throttle valve is opened toward the throttle opening TO_REG during regeneration, and the intake air flow rate is increased to increase the DPF inflow exhaust flow rate. The means for controlling the exhaust flow rate is not limited to this. In this exhaust flow rate increase control, in addition to the throttle valve, for example, the EGR valve is closed toward the predetermined EGR opening degree EO_REG, and the DGR inflow exhaust flow rate is controlled to increase by decreasing the EGR gas flow rate. You can also In addition, in the exhaust gas flow rate increase control, the inflow exhaust gas flow rate of the DPF may be controlled to the increase side by using both the throttle valve and the EGR valve.

FIG. 6 is a diagram showing a relationship between the regeneration EGR opening EO_REG and the PM accumulation amount QPM, and an example of a control map referred to when calculating the regeneration EGR opening EO_REG based on the PM accumulation amount QPM. Show.
As shown in FIG. 6, basically, the regeneration EGR opening EO_REG is set to a smaller value as the PM accumulation amount QPM increases. More specifically, when the PM accumulation amount QPM is between the second determination amount M2 and the third determination amount M3, the regeneration EGR opening EO_REG is smaller than that during normal DPF regeneration operation. It is set so as to decrease substantially in proportion to the quantity QPM. When the PM accumulation amount QPM is larger than the third determination amount M3, the regeneration EGR opening EO_REG is set to a fully closed opening.

  In addition, for example, by supplying a gas different from the engine exhaust to the upstream side of the DPF in the exhaust pipe, the inflow exhaust gas flow rate of the DPF may be controlled to the increase side.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 7 is a flowchart showing a procedure of DPF regeneration control processing according to the present embodiment.
In FIG. 7, steps S11 to S13 correspond to steps S1 to S3 of FIG. 2, respectively, and thus detailed description thereof is omitted.

  In step S14, an inflow exhaust flow rate target lower limit value QEIN_TRGT is calculated based on the PM accumulation amount QPM, and the process proceeds to step S15. This inflow exhaust gas flow target lower limit value QEIN_TRGT is a target value for the inflow exhaust gas flow rate of the DPF. More specifically, the lower limit for the inflow exhaust gas flow rate at which the DPF does not reach an excessive temperature rise during the DPF regeneration operation. Value.

FIG. 8 is a diagram showing the relationship between the inflow exhaust flow rate target lower limit value QEIN_TRGT and the PM accumulation amount QPM, and shows an example of a control map referred to when calculating the inflow exhaust flow rate target lower limit value QEIN_TRGT.
As shown in FIG. 8, the inflow exhaust flow rate target lower limit value QEIN_TRGT is set to increase substantially in proportion to the PM accumulation amount QPM.

  Returning to FIG. 7, in step S15, it is determined whether or not the DPF inflow exhaust gas flow rate QEIN is smaller than the inflow exhaust gas flow rate target lower limit value QEIN_TRGT calculated in step S14. If this determination is YES, it is determined that it is necessary to execute control for increasing the inflow exhaust flow rate, and the process proceeds to step S16. If this determination is NO, this process is immediately terminated.

  In step S16, idle-up control is executed, and the process proceeds to step S17. More specifically, in this idle-up control, the idling engine speed is set to the upper limit value of the idling engine speed so that the idling engine speed feedback control, that is, the inflowing exhaust gas flow rate QEIN is equal to or larger than the inflowing exhaust gas flow target lower limit value QEIN_TRGT. Control that increases. The upper limit value of the idle rotation speed indicates the maximum value of the rotation speed allowable as the idle rotation speed, as in the first embodiment.

  In step S17, it is determined whether or not the inflow exhaust gas flow rate QEIN of the DPF has become equal to or greater than the inflow exhaust gas flow rate target lower limit value QEIN_TRGT by executing the idle up control. If this determination is YES, it is determined that control for increasing the inflow exhaust flow rate is unnecessary, and this process is immediately terminated. On the other hand, if this determination is NO, the process proceeds to step S18.

  In step S18, it is determined whether or not the idle speed is smaller than the upper limit value. If this determination is YES, this processing is immediately terminated. That is, the idle up control is continued without executing the next step S19 until the idle speed reaches the upper limit value. On the other hand, if this determination is NO, it is determined that the inflow exhaust gas flow rate QEIN cannot be made equal to or greater than the inflow exhaust gas flow rate target lower limit value QEIN_TRGT even if the idle speed is increased until the upper limit value is reached, and the process proceeds to step S19.

  In step S19, exhaust gas flow rate increase control is executed, and this process ends. More specifically, in this exhaust flow rate increase control, the throttle valve opening is set to the open side so that the inflow exhaust flow rate QEIN is equal to or greater than the inflow exhaust flow rate target lower limit value QEIN_TRGT. Control to increase the inflow exhaust flow rate is executed.

Here, referring to FIG. 8, the DPF regeneration control process of the first embodiment and the second embodiment will be compared.
In the first embodiment, the idle up control is executed when the PM accumulation amount QPM is larger than the first determination amount M1. When the PM accumulation amount QPM is larger than the second determination amount M2, the exhaust flow rate increase control is executed in addition to the idle up control to control the throttle valve to the open side. On the other hand, in the present embodiment, when the inflow exhaust flow rate target lower limit value QEIN_TRGT is larger than QE1 corresponding to the first determination amount M1, the idle up control is executed. Further, when the inflow exhaust flow target lower limit QEIN_TRGT is larger than QE2 corresponding to the second determination amount M2, it is determined that there is a possibility that the excessive temperature rise of the DPF cannot be prevented only by the idle up control, and the exhaust flow amount increase is increased. Control is executed.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(3) According to the present embodiment, the lower limit value for the inflow exhaust gas flow rate at which the DPF does not reach an excessive temperature rise during the DPF regeneration operation is calculated based on the PM accumulation amount QPM, and this is calculated as the inflow exhaust gas flow rate. The target lower limit value is QEIN_TRGT. Then, when the engine is in an idle operation state and the DPF regeneration operation is being performed, it is determined that the estimated value QEIN of the inflow exhaust flow rate is smaller than the inflow exhaust flow rate target lower limit value QEIN_TRGT, that is, the DPF reaches an excessive temperature rise. In this case, the idle up control is executed so that the inflow exhaust flow rate QEIN is equal to or higher than the inflow exhaust flow rate target lower limit value QEIN_TRGT, and the idle speed is increased toward a predetermined upper limit value. Thereby, the inflow exhaust flow rate of the DPF can be made appropriate, and the DPF can be prevented from being melted. In this case, since it is not necessary to increase the inflow exhaust flow rate by the exhaust flow rate increase control different from the idle up control, it is not necessary to increase the post injection amount in order to keep the exhaust temperature high. For this reason, generation | occurrence | production of oil dilution and deterioration of a fuel consumption can be suppressed.
Further, if the inflow exhaust flow rate QEIN is smaller than the inflow exhaust flow rate target lower limit value QEIN_TRGT even when the idle speed reaches the upper limit value by performing idle up control, the inflow exhaust flow rate QEIN is equal to or greater than the inflow exhaust flow rate target lower limit value QEIN_TRGT. Thus, the exhaust gas flow rate increase control is executed to increase the inflow exhaust gas flow rate of the DPF. Thereby, the inflow exhaust flow rate of the DPF can be made appropriate, and the DPF can be prevented from being melted. Here, by executing the exhaust gas flow rate increase control in addition to the idling engine speed control, the DPF can be protected without excessively increasing the idling engine speed, so that the merchantability is not impaired as described above.
As described above, priority is given to the control of the idling speed by the idling up control, and the exhaust gas flow rate increasing control is executed only when it is determined that the DPF reaches an excessive temperature rise even if the idling speed is increased to the upper limit value. By controlling the inflow exhaust gas flow rate, it prevents the DPF from damaging while suppressing problems that occur due to an increase in the exhaust flow rate, such as sudden start-up, noise, reduced oil performance, or worsened fuel consumption at the start. Can do.
Further, by controlling the inflow exhaust flow rate by the idle-up control and the exhaust flow rate increase control so that the inflow exhaust flow rate QEIN is equal to or greater than the inflow exhaust flow rate target lower limit value QEIN_TRGT, it is possible to more reliably prevent the DPF from being damaged. it can.

The present invention is not limited to the embodiment described above, and various modifications can be made.
In the embodiment described above, the inflow exhaust flow rate QEIN of the DPF is estimated based on the intake air amount QAIR, the fuel injection amount QINJ, and the engine speed NE, but is not limited thereto. The inflow exhaust flow rate of the DPF may be directly detected by a flow rate sensor.

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification device 2 ... Engine (internal combustion engine)
22 ... Injector (filter regeneration means)
32. Throttle valve (filter regeneration means)
4 ... Exhaust pipe (exhaust system)
45 ... DPF (exhaust gas purification filter)
7. ECU (filter regeneration means, idle speed control means, exhaust flow rate control means, accumulation amount estimation means)

Claims (2)

An exhaust purification filter provided in an exhaust system of an internal combustion engine for collecting particulate matter contained in the exhaust;
A throttle valve provided in an intake system of the internal combustion engine for controlling a flow rate of fresh air sucked into the internal combustion engine;
An EGR valve that is provided in an EGR passage that connects the exhaust system and the intake system, and that controls a flow rate of exhaust gas recirculated to the intake air through the EGR passage;
A deposition amount estimating means for estimating a deposition amount of particulate matter in the exhaust purification filter;
Filter regeneration means for performing filter regeneration operation for burning and removing particulate matter deposited on the exhaust purification filter;
Idle up control means for increasing the idle rotational speed that is the rotational speed during idle operation of the internal combustion engine from the rotational speed during normal idle operation ;
It is a means different from the idle- up control means, and operates at least one of the throttle valve and the EGR valve to increase the exhaust flow rate from the opening at the time of a predetermined idle operation. An exhaust gas flow rate increase control means for increasing the flow rate of the exhaust gas flowing into the filter,
When the internal combustion engine is in an idle operation state and the filter regeneration operation is being executed,
When the amount of the deposit is less than the second determination amount of multi KuKatsu given than a predetermined first threshold quantity, without increasing the exhaust flow rate by the exhaust gas flow amount increase control means, idle by the idle-up control means the rotational speed was the higher the speed during normal idle operation until a predetermined reproduction idle speed set between the predetermined upper limit value,
When the accumulation amount is larger than a predetermined second determination amount larger than the first determination amount, the exhaust flow rate increase control is performed in addition to increasing the idle speed to the upper limit value by the idle up control means. An exhaust gas purification apparatus characterized by performing control to increase the flow rate of exhaust gas flowing into the exhaust gas purification filter by means. An exhaust purification filter provided in an exhaust system of an internal combustion engine for collecting particulate matter contained in the exhaust;
A throttle valve provided in an intake system of the internal combustion engine for controlling a flow rate of fresh air sucked into the internal combustion engine;
An EGR valve that is provided in an EGR passage that connects the exhaust system and the intake system, and that controls a flow rate of exhaust gas recirculated to the intake air through the EGR passage;
A deposition amount estimating means for estimating a deposition amount of particulate matter in the exhaust purification filter;
Filter regeneration means for performing filter regeneration operation for burning and removing particulate matter deposited on the exhaust purification filter;
Idle up control means for increasing the idle rotational speed that is the rotational speed during idle operation of the internal combustion engine from the rotational speed during normal idle operation ;
It is a means different from the idle- up control means, and operates at least one of the throttle valve and the EGR valve to increase the exhaust flow rate from the opening at the time of a predetermined idle operation. Exhaust flow rate increase control means for increasing the flow rate of the exhaust gas flowing into the filter;
An exhaust gas flow rate detecting means for detecting or estimating the flow rate of the exhaust gas flowing into the exhaust gas purification filter,
A flow rate lower limit value calculating means for calculating a flow rate lower limit value for the flow rate of the exhaust gas that does not reach an excessive temperature rise during the filter regeneration operation based on the accumulation amount;
When the internal combustion engine is in an idle operation state and the filter regeneration operation is being executed,
If the detected value or estimated value of the flow rate of the exhaust gas is smaller than the lower limit value of the flow rate, the detected value or estimated value is not increased by the exhaust flow rate increasing control unit and the detected value or estimated value is increased by the idle up control unit. Control is performed to increase the idle rotation speed toward a predetermined upper limit value so that the flow rate is lower than the lower limit value,
If the detected value or estimated value is smaller than the flow rate lower limit value even when the idle speed reaches the upper limit value, the exhaust flow rate increase control means maintains the idle speed at the upper limit value by the exhaust flow rate increase control means. An exhaust gas purification apparatus that performs control to increase the flow rate of exhaust gas flowing into the exhaust gas purification filter so that a detected value or an estimated value is equal to or higher than the lower limit value of the flow rate.

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