JP2013029055A - Dpf regeneration control device for internal combustion engine - Google Patents

Abstract

When the engine temperature is raised due to a cold state or a heating request from a heating device, DPF regeneration is also performed to reduce the frequency of raising the engine temperature and improve fuel efficiency.
A filter DPF for collecting suspended particulate matter PM in exhaust gas is provided in an exhaust system of an internal combustion engine. When the suspended particulate matter accumulation amount rPM deposited on the filter is equal to or larger than the first determination value PMs1, filter regeneration accompanying increase in engine temperature is performed assuming that the filter regeneration condition is satisfied (step S12). Further, at the time of detecting a predetermined engine temperature increase request accompanied by an increase in engine temperature, filter regeneration is performed even if the suspended particulate matter deposition amount rPM is less than the first determination value PMs1 (steps S14, S17, S21). .
[Selection] Figure 2

Description

  The present invention relates to an internal combustion engine provided with a DPF for collecting PM in an exhaust system of the internal combustion engine, and more particularly to regeneration control of the DPF.

  In an internal combustion engine such as a diesel engine that performs lean burn operation or an in-cylinder direct injection gasoline engine, in order to prevent PM (particulate matter), which is a suspended particulate matter in exhaust gas, from being released to the atmosphere, A DPF (diesel particulate filter) that collects the PM is provided in the exhaust system. As described in Patent Document 1, in an internal combustion engine equipped with such a DPF, if the amount of PM deposited on the DPF exceeds a predetermined value, the DPF is increased to cause a deterioration in fuel consumption due to an increase in back pressure. So-called DPF regeneration is performed, in which DPF is regenerated by burning and removing PM deposited on the DPF by heating.

JP-A-8-165918

  As a technique for raising the temperature of the DPF during DPF regeneration, post injection that injects a small amount of fuel for raising the temperature of the exhaust after main injection, or after injection that injects fuel in the expansion stroke or the exhaust stroke so that combustion is performed in the exhaust system As described above, a method of increasing the temperature of the DPF with an increase in the exhaust gas temperature (engine temperature) by injecting and supplying additional fuel separately from the main injection is often used. Such a method is simpler, lower cost, and easier to apply than a method using a dedicated component such as a heater for raising the temperature of the DPF. However, during the regeneration of the DPF, fuel consumption is improved by additional fuel injection. It is preferable to reduce the frequency and time of DPF regeneration because it causes deterioration.

  Apart from such DPF regeneration, when there is a heating request by a heating device mounted on the vehicle, or when there is an engine temperature increase request for raising the engine temperature, such as when the engine temperature is low, As in the case of the DPF regeneration described above, a control process is generally performed in which the engine temperature is raised by additional fuel injection / fuel increase such as after injection.

  Here, if the engine temperature increase control process is performed separately at the time of DPF regeneration and when the engine temperature increase is requested, the frequency and time of engine temperature increase increase, resulting in a decrease in fuel consumption and an increase in exhaust emissions. There is a fear. In particular, in a diesel engine that performs lean burn operation, the engine temperature tends to be lower because of the higher thermal efficiency than a gasoline engine that burns near the stoichiometric air-fuel ratio, which causes an engine temperature increase request such as a heating request. Frequency / time is high.

  The present invention has been made in view of such circumstances. That is, the exhaust system of the internal combustion engine according to the present invention is provided with a DPF that collects PM in the exhaust gas, and a predetermined DPF including that the amount of PM deposited on the DPF is equal to or greater than the first determination value. When regeneration conditions are satisfied, DPF regeneration is performed by raising the temperature of the DPF (first DPF regeneration means). Then, at the time of detecting a predetermined engine temperature increase request accompanied by a rise in engine temperature, the DPF is reduced even if the PM accumulation amount is less than the first determination value and the DPF regeneration condition is not satisfied. DPF regeneration is performed by raising the temperature (second DPF regeneration means).

  In the present invention, when detecting the heating request of the heating device by the driver, or at the time of detecting a predetermined engine temperature increase request accompanied by an increase in the engine temperature, such as at the time of engine cooling where warm-up operation is performed, PM Even when the accumulation amount is less than the first determination value and the predetermined DPF regeneration condition is not satisfied, DPF regeneration is actively performed. In this way, by performing DPF regeneration together with an engine temperature increase request in which engine temperature increase control processing is performed in the same manner as DPF regeneration, engine temperature increase control is individually performed at the time of DPF regeneration and at the time of engine temperature increase request. As compared with the case where the engine is implemented, the frequency and time for performing the engine temperature increase control can be saved, and the fuel consumption and the increase in exhaust emission can be suppressed accordingly. Further, by performing DPF regeneration together with the engine temperature increase request, the engine temperature increase is promoted, and the heating performance can be improved and the warm-up time can be shortened.

1 is a system configuration diagram showing a DPF regeneration control device for an internal combustion engine according to an embodiment of the present invention. The flowchart which shows the flow of DPF regeneration control of a present Example. Explanatory drawing which shows the DPF regeneration conditions of a present Example. Explanatory drawing which shows the relationship between the engine temperature at the time of the 2nd DPF regeneration of a present Example, and a temperature increase.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing a DPF regeneration control apparatus for an internal combustion engine according to an embodiment of the present invention. An intake passage 2 of a diesel engine 1 as an internal combustion engine is provided with an intake compressor of a variable nozzle type turbocharger 3. The intake air is supercharged by the intake compressor, cooled by an intercooler 4, and passed through an intake throttle valve 5. After that, it flows into the combustion chamber of each cylinder through the collector 6. The fuel is increased in pressure by the high-pressure fuel pump 7 of the common rail type fuel injection device, sent to the common rail 8, and directly injected from the fuel injection valve 9 of each cylinder into the combustion chamber. The air that has flowed into the combustion chamber and the injected fuel are combusted by compression ignition, and the exhaust gas after combustion flows out into the exhaust passage 10.

  Part of the exhaust gas flowing into the exhaust passage 10 is recirculated to the intake side via the EGR valve 12 through the EGR passage 11 as EGR gas. The remainder of the exhaust passes through the exhaust turbine of the variable nozzle type turbocharger 3 and drives it.

  A DPF (diesel particulate filter) 14 that collects PM (particulate matter), which is a suspended particulate matter in the exhaust gas, is disposed downstream of the exhaust turbine in the exhaust passage 10, and As an auxiliary catalyst, in this embodiment, a NOx trap catalyst 13 is disposed upstream of the DPF 14. The NOx trap catalyst 13 traps NOx in the exhaust flowing in when the exhaust air-fuel ratio is lean, and desorbs and purifies the trapped NOx when the exhaust air-fuel ratio is rich. The NOx trap catalyst 13 carries an oxidation catalyst (noble metal) and has a function of oxidizing the exhaust components (HC, CO) flowing in. The DPF 14 also has a function of carrying an oxidation catalyst (noble metal) and oxidizing the exhaust components (HC, CO) flowing in.

  The auxiliary catalyst is not limited to the NOx trap catalyst 13 described above, but a selective reduction catalyst (SCR) using ammonia as a reducing agent may be used, and the arrangement of the auxiliary catalyst is as in the above embodiment. Not only the upstream side of the DPF 14 but also the downstream side of the DPF 14 may be arranged as required. Further, the DPF 14 may be configured integrally with a NOx trap catalyst supported thereon.

  A heating device 27 is also provided for heating the passenger compartment of the vehicle. As is well known, the heating device 27 is provided with a heater core that exchanges heat with cooling water or exhaust gas of the internal combustion engine.

  Signals are input to the control unit 20 from the rotational speed sensor 21 for detecting the engine rotational speed Ne and the accelerator opening sensor 22 for detecting the accelerator opening APO for controlling the engine 1. Further, an LNT temperature sensor 23 for detecting the temperature of the NOx trap catalyst 13, that is, the LNT floor temperature, an exhaust pressure sensor 24 for detecting the exhaust pressure on the DPF 14 inlet side of the exhaust passage 10, and a DPF for detecting the temperature of the DPF 14, that is, the DPF floor temperature. A temperature sensor 25 and an air / fuel ratio sensor 26 for detecting an exhaust air / fuel ratio (hereinafter referred to as exhaust λ, which is expressed as an excess air ratio) are provided on the outlet side of the DPF 14 in the exhaust passage 10, and these signals are also controlled. Input to the unit 20. However, the temperature of the NOx trap catalyst 13 and the temperature of the DPF 14 may be indirectly detected from the exhaust temperature detected by the exhaust temperature sensor provided on the downstream side. Based on these input signals, the control unit 20 outputs control signals to the intake throttle valve 5, the fuel injection valve 9, the EGR valve 12, and the heating device 27 to control the operation thereof.

  Further, the control unit 20 sequentially calculates and updates the PM accumulation amount rPM accumulated in the DPF 14 based on the engine operating state. As will be described later, this PM accumulation amount rPM is a first determination preset. When a predetermined DPF regeneration condition including the value PMs1 or more is satisfied, so-called DPF regeneration is performed in which PM accumulated on the DPF 14 is combusted and removed by raising the temperature of the DPF 14. In this DPF regeneration, by performing post injection that injects a small amount of fuel after main injection by the fuel injection valve 9 or after injection that injects fuel in the expansion stroke or exhaust stroke so that combustion is performed in the exhaust system, The DPF 14 is heated with an increase in engine temperature and exhaust gas temperature.

  Further, when a heating request is made by the heating device 27 by a driver's operation of an air conditioning switch or the like, the control unit 20 supplies cooling water or exhaust gas that exchanges heat with the heater core in order to increase the temperature in the passenger compartment. Perform engine temperature rise control. Specifically, similarly to the above DPF regeneration, engine temperature increase control by after injection or the like is performed.

  Next, with reference to FIG. 2 and FIG. 3, a description will be given of conditions for performing DPF regeneration control, particularly DPF regeneration, which is a main part of the present embodiment. FIG. 2 is a flowchart showing the flow of DPF regeneration control. In step S11, as one of the DPF regeneration conditions, it is determined whether the PM accumulation amount rPM accumulated in the DPF 14 is equal to or larger than a preset first determination value PMs1. If the PM deposition amount rPM is equal to or greater than the first determination value PMs1, the process proceeds to step S12, and the above-described DPF regeneration (hereinafter, this DPF regeneration is also referred to as “first DPF regeneration”) in order to reduce the PM deposition amount. . To implement. Here, only the PM accumulation amount determination condition is shown here. However, in actual control, DPF regeneration is performed in consideration of DPF regeneration conditions based on, for example, engine rotation speed and required load other than the PM accumulation amount. Is implemented.

  On the other hand, if the PM deposition amount rPM is less than the first determination value PMs1, in the past, DPF regeneration is not performed because the DPF regeneration condition is not satisfied, but in the present embodiment, steps S11 to S13 are performed. The process proceeds to DPF regeneration when the predetermined condition is satisfied even though the PM accumulation amount rPM is less than the first determination value PMs1 (hereinafter, this DPF regeneration is also referred to as “second DPF regeneration”). I am trying to do it positively. That is, based on the coolant temperature rTMP, which is the engine temperature, the heating request, and the PM accumulation amount rPM, a predetermined engine temperature increase request accompanied by an increase in engine temperature, in other words, an engine temperature increase control is performed. It is determined whether a temperature increase request has been detected, and the second DPF regeneration is performed when the engine temperature increase request is detected and a predetermined condition is satisfied.

  Specifically, in step S13, it is determined whether the coolant temperature rTMP is lower than the first determination temperature TMPs1. When the cooling water temperature rTMP is lower than the first determination temperature TMPs1, since the engine is in a cold state where the warm-up operation of the internal combustion engine is performed and the engine temperature is required to be raised quickly, the process proceeds to step S14. The DPF regeneration is forcibly performed except when the PM deposition amount rPM is 0 or extremely small. As described above, when the DPF regeneration is performed in the cold state, the frequency / time of the engine temperature increase control is reduced as compared with the case where the DPF regeneration is performed separately, and the fuel consumption is saved correspondingly. As well as improving the exhaust performance, it is possible to promote engine warming / warming and complete warm-up at an early stage by performing DPF regeneration together with warming-up.

  When the cooling water temperature rTMP is equal to or higher than the first determination temperature TMPs1, the process proceeds from step S13 to step S15, where the cooling water temperature rTMP is a preset second determination temperature that is higher than the first determination temperature TMPs1. It is determined whether it is less than TMPs2 (for example, around 60 ° C.). If the cooling water temperature rTMP is lower than the second determination temperature TMPs2, the process proceeds to step S16, and the PM accumulation amount rPM is equal to or higher than the preset second determination value PMs2 that is smaller than the first determination value PMs1. Determine if there is. If the PM deposition amount rPM is greater than or equal to the second determination value PMs2, the process proceeds to step S17, and the second DPF regeneration is performed. On the other hand, if the PM accumulation amount rPM is less than the second determination value PMs2, the routine is terminated without performing DPF regeneration.

  Thus, when the cooling water temperature rTMP is equal to or higher than the first determination temperature TMPs1 and lower than the second determination temperature TMPs2, the warm-up operation is performed as compared with the case where the cooling water temperature rTMP is lower than the first determination temperature TMPs1. Although it is in a cold state, the amount of increase in engine temperature required to complete the warm-up operation is small, so if DPF regeneration is performed together with a small amount of PM accumulation, exhaust temperature and DPF temperature will rise excessively In addition, the catalyst purification rate may be reduced and the catalyst may be thermally deteriorated. In this embodiment, therefore, DPF regeneration is prohibited when the PM deposition amount rPM is less than the second determination value PMs2, and DPF regeneration is performed only when the PM deposition amount rPM is equal to or greater than the second determination value PMs2. ing. As a result, the frequency / time for performing total engine temperature increase control is reduced by performing DPF regeneration in the engine cold state without causing excessive temperature increase of the catalyst, thereby reducing fuel consumption performance and exhaust performance. Improvements can be made.

  When the cooling water temperature rTMP is equal to or higher than the second determination temperature TMPs2, the process proceeds from step S15 to step S18, where the cooling water temperature rTMP is a preset third determination temperature that is higher than the second determination temperature TMPs2. It is determined whether it is less than TMPs3. If the cooling water temperature rTMP is lower than the third determination temperature TMPs3, the process proceeds to step S19, and it is determined whether the PM accumulation amount rPM is equal to or higher than the second determination value PMs2 as in step S16. If the PM accumulation amount rPM is greater than or equal to the second determination value PMs2, the process proceeds to step S20, and it is determined whether a heating request by the heating device 27 has been detected.

  When the cooling water temperature rTMP is equal to or higher than the second determination temperature TMPs2 and lower than the third determination temperature TMPs3, the PM accumulation amount rPM is equal to or higher than the second determination value PMs2, and the heating request by the heating device 27 is detected When all the determinations in steps S18 to S20 are affirmed and the process proceeds to step S21, DPF regeneration is performed. In other cases, for example, when the cooling water temperature rTMP is equal to or higher than the third determination temperature TMPs3, DPF regeneration is performed. This routine is finished without executing.

  As described above, even in the operation state after the warming-up in which the cooling water temperature rTMP is equal to or higher than the second determination temperature TMPs2, if there is an engine temperature increase request due to the heating request, the PM accumulation amount rPM is the second determination value. The DPF regeneration process is performed on condition that it is equal to or higher than PMs2. As a result, the engine temperature rise due to the heating request and the engine temperature rise due to the DPF regeneration can be performed together, and the consumption of excess heat energy is suppressed and the fuel consumption is reduced as compared with the case where the engine temperature rise control is performed individually. Improvements and reductions in exhaust emissions can be achieved. Further, even when there is a heating request, if the PM accumulation amount rPM is less than the second determination value PMs2, excessive temperature rise of the catalyst including the DPF 14 can be prevented by not performing DPF regeneration. .

  Further, as in the above-described steps S14, S17, and S21, the engine temperature increase request is performed at the time of the second DPF regeneration performed in response to the coolant temperature (engine temperature) or the engine temperature increase request from the heating device 27. When the is released, that is, when the warm-up operation ends or when the heating request is lost, the DPF regeneration is also forcibly terminated regardless of the PM accumulation amount rPM at that time. As a result, it is possible to reliably prevent the overheating and heating performance of the cooling system accompanying the continuation of the DPF regeneration from becoming excessively more than required.

  Further, in the second DPF regeneration (steps S14, S17, and S21) performed at the time of the engine temperature increase request, the first DPF regeneration (step S14) performed in accordance with normal DPF regeneration conditions (PM deposition amount) (step S14). Compared to S12), the lower limit value of the PM accumulation amount at which DPF regeneration is terminated is set lower. That is, at the time of the second DPF regeneration performed together with the engine temperature increase request, by sufficiently performing the DPF regeneration until the PM accumulation amount becomes smaller than at the time of the first DPF regeneration performed alone, The frequency and time of the first DPF regeneration performed independently can be shortened, and the fuel efficiency and exhaust performance can be improved as much as possible.

  Further, when the DPF regeneration is forcibly terminated in this way, the engine temperature decrease rate is limited to a predetermined value or less so that the engine temperature decrease becomes smooth. That is, engine temperature decrease control is performed so that the engine temperature decrease is within a predetermined gradient. As a result, it is possible to suppress / avoid the engine temperature, and hence the heater blowout temperature, from drastically decreasing and giving the driver an uncomfortable feeling.

  Further, as shown in FIG. 4, in the second DPF regeneration due to the engine temperature increase request such as the heating request or the engine cooling state, the temperature increase of the engine temperature (exhaust temperature) decreases as the engine temperature increases. In order to achieve this, engine temperature increase control is performed. As a result, it is possible to suppress and avoid an excessive increase in engine temperature associated with the combined use of DPF regeneration.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, the engine temperature increase request accompanied by the second DPF regeneration is not limited to the heating request or the cold state described above. For example, even in the state after the warm-up, the engine temperature rises such as the engine oil temperature increase. Other engine temperature increase requests may be used.

1 ... Diesel engine (internal combustion engine)
14 ... DPF (diesel particulate filter)
20 ... Control unit 27 ... Heating device

Claims (9)

A DPF that is provided in an exhaust system of an internal combustion engine and collects PM in exhaust gas;
First DPF regeneration means for performing DPF regeneration by raising the temperature of the DPF when a predetermined DPF regeneration condition including that the amount of PM deposited on the DPF is equal to or greater than a first determination value is satisfied; ,
Second DPF regeneration means for performing DPF regeneration by increasing the temperature of the DPF even when the PM accumulation amount is less than the first determination value when detecting a predetermined engine temperature increase request accompanied by an increase in the engine temperature. When,
A DPF regeneration control device for an internal combustion engine, comprising:   2. The DPF regeneration unit according to claim 1, wherein the second DPF regeneration unit performs the DPF regeneration based on a PM accumulation amount, an engine temperature, and a heating request of a heating device mounted on a vehicle. A DPF regeneration control device for an internal combustion engine.   3. The DPF regeneration control apparatus for an internal combustion engine according to claim 2, wherein the second DPF regeneration means performs the DPF regeneration when the engine temperature is equal to or lower than a predetermined first determination temperature.   The second DPF regeneration means has an engine temperature that is lower than a second determination temperature that is higher than the first determination temperature, and a PM accumulation amount that is smaller than the first determination value. 4. The DPF regeneration control apparatus for an internal combustion engine according to claim 3, wherein the DPF regeneration is performed when the value is equal to or greater than a second determination value.   In the second DPF regeneration means, the engine temperature is lower than a third determination temperature that is higher than the second determination temperature, the PM accumulation amount is equal to or higher than the second determination value, and the above 5. The DPF regeneration control apparatus for an internal combustion engine according to claim 4, wherein the DPF regeneration is performed when there is a heating request.   6. The DPF regeneration of an internal combustion engine according to claim 1, wherein when the DPF regeneration by the second DPF regeneration means is performed, the DPF regeneration is forcibly terminated with the cancellation of the engine temperature increase request. Control device.   2. The lower limit value of the PM accumulation amount at which DPF regeneration is completed is set lower during DPF regeneration by the second DPF regeneration means than when DPF regeneration by the first DPF regeneration means is performed. The DPF regeneration control device for an internal combustion engine according to any one of -6.   The DPF regeneration control apparatus for an internal combustion engine according to any one of claims 1 to 7, wherein when the DPF regeneration by the second DPF regeneration means is completed, the rate of decrease in engine temperature is limited.   9. The DPF regeneration by the second DPF regeneration means, wherein control is performed to raise the engine temperature so that the increase in temperature becomes smaller as the engine temperature becomes higher. A DPF regeneration control device for an internal combustion engine as described.

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