JP2008267159A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the exhaust emission control device to prevent an EGR (Exhaust Gas Recirculation) from recirculating debris of a DPF (Diesel Particulate Filter) into an intake system of the engine when there is a possibility that the DPF might be damaged. <P>SOLUTION: An ECU 17 determines during regeneration of the DPF 12 if there is a possibility that the DPF 12 is damaged according to a value (exhaust gas temperature TDPF) detected by an exhaust gas temperature sensor 15 in view of a threshold value T1, and if affirmative, immediately outputs a control signal to the EGR valve 161 so as to completely close the valve 161. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purifying device for an internal combustion engine, and more specifically, a supercharger provided with an exhaust system including a particulate matter collection device (so-called DPF) and an exhaust gas recirculation device (so-called EGR). The present invention relates to an exhaust gas purification device for a diesel engine with a valve.

  Conventionally, in an exhaust gas purification device of this type of diesel engine, a DPF that collects particulate matter (so-called PM) in the exhaust gas is interposed in the exhaust passage downstream of the exhaust manifold, By providing an EGR between the exhaust passage downstream of the DPF and the intake passage of the engine, it has been proposed to recirculate part of the exhaust gas from which PM has been removed to the intake system of the engine (for example, , See Patent Document 1).

JP 2004-324630 A

By the way, the above-described conventional diesel engine exhaust gas purification device has the following problems. That is, PM collected by the DPF is heated by a heater or fuel injection control (post-injection) to raise the temperature of the DPF and burned by a catalytic reaction, but a large amount of PM burns rapidly. When this occurs, the temperature may increase excessively, and the DPF may be damaged (melting and cracking).
Then, if the fragments when the DPF is broken are recirculated to the intake system of the engine by EGR, engine parts may be damaged, or the intake and exhaust valves and the combustion chamber may be clogged and the engine may be locked.

  The present invention has been made in view of such circumstances, and in the case of an internal combustion engine that can prevent DPF fragments from being recirculated to the intake system of the engine by EGR when the DPF may be damaged. An object is to provide an exhaust gas purification device.

In order to achieve the above object, the invention according to claim 1 is a particulate matter trap for collecting particulate matter from exhaust gas of an internal combustion engine and burning the collected particulate matter to regenerate the filter. Collecting means, exhaust pressure detecting means for detecting exhaust gas pressure upstream and downstream of the particulate matter collecting means, and exhaust for detecting exhaust gas temperature downstream of the particulate matter collecting means A temperature detection unit, an on-off valve that enables recirculation of a part of the exhaust gas in which the particulate matter is collected by the particulate matter collection unit to the intake system of the internal combustion engine, and the on-off control of the on-off valve An exhaust gas recirculation device comprising a control means, and an exhaust gas purification device for an internal combustion engine comprising a control means,
The control means determines a combustion state of the particulate matter collected by the particulate matter collection means based on the detection value and threshold value of the exhaust pressure detection means and the exhaust temperature detection means, and the combustion When it is determined that there is a possibility that the particulate matter collecting means is damaged, a closing control signal for fully closing the on-off valve is output.

  According to the first aspect of the present invention, when the control means determines that the particulate matter collecting means may be damaged, it immediately outputs a close control signal to the open / close valve to fully close the open / close valve. . As a result, even if a large amount of particulate matter burns suddenly in the particulate matter collecting means and the temperature rises too much, and the particulate matter collecting means is damaged, the fragments at that time will be exhaust gas recirculated. Recirculation to the engine intake system by the device can be reliably prevented.

  In order to achieve the above object, according to a second aspect of the present invention, the control means is configured such that the differential pressure between the upstream exhaust gas pressure and the downstream exhaust gas pressure detected by the exhaust pressure temperature detecting means exceeds a predetermined pressure. And, if the exhaust gas temperature detected by the exhaust temperature detecting means exceeds a predetermined temperature, the regeneration of the particulate matter collecting means is detected.

  In order to achieve the above object, according to a third aspect of the present invention, when the exhaust gas temperature detected by the exhaust temperature detecting means exceeds a predetermined temperature during regeneration of the particulate matter collecting means, the control means The particulate matter collecting means determines that there is a risk of melting.

  According to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, when the control unit determines that there is a possibility that the DPF is damaged, the EGR valve is immediately closed, so that fragments when the DPF is damaged are caused by EGR. Recirculation to the engine intake system can be prevented.

  An exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine to which the present invention is applied.

  As shown in FIG. 1, an exhaust gas purifying device 10 for an internal combustion engine includes a supercharged diesel engine 11 as an internal combustion engine, a particulate matter collecting device 12, first and second exhaust pressure sensors 13, 14. The exhaust gas temperature sensor 15, the exhaust gas recirculation device 16, and the ECU 17 as a control device are provided.

  More specifically, the supercharger-equipped diesel engine (hereinafter referred to as the engine) 11 controls the output and the rotational speed by injecting fuel into the compressed air in the combustion chamber of the engine 11 under the control of the ECU 17. Is done. The fuel injection amount is appropriately calculated by the microprocessor (MPU) in the ECU 17 by comparing the accelerator pedal opening, the engine speed, and many additional correction coefficients with the map data stored in the memory. When the combustion gas in the combustion chamber is exhausted from the engine 11 as exhaust gas, the compressor 112 coaxial with the turbine 111 of the supercharger 110 is driven to increase the intake air amount. An air cleaner 19 is interposed in the intake passage 18 upstream of the compressor 112 so as to filter the intake air.

  The particulate matter collection device (hereinafter referred to as DPF) 12 is provided in the exhaust passage 20 on the downstream side of the compressor 112, and removes particulate matter (hereinafter referred to as PM) contained in the exhaust gas of the engine 11. For example, it is collected by a filter made of ceramic fiber (silicon carbide monolith). When the ECU 17 determines that the PM collected by the DPF 12 has reached a predetermined amount, post-injection is performed in addition to normal fuel injection, and unburned fuel is supplied to the DPF 12 together with the exhaust gas so that the DPF 12 carries the fuel. It reacts on the catalyst and burns by the reaction heat.

The first and second exhaust pressure sensors 13, 14 are provided in the exhaust passage 20 so as to detect before and after passing through the DPF 12, that is, the upstream exhaust gas pressure PF and the downstream exhaust gas pressure PA of the DPF 12, respectively. Yes. The detection values detected by the first and second discharge pressure sensors 13 and 14 are input to the ECU 17 and are used when estimating the PM accumulation amount or performing EGR valve control.
Instead of the first and second discharge pressure sensors 13 and 14, a discharge differential pressure sensor that detects a discharge pressure difference before and after passing through the DPF 12 may be used.

  The exhaust temperature sensor 15 is a temperature sensor using a thermocouple, and is attached to the exhaust passage 20 downstream of the DPF 12 to detect the exhaust temperature TDPF of the exhaust gas that has passed through the DPF 12. The detected value detected by the exhaust temperature sensor 15 is input to the ECU 17 to estimate the PM accumulation amount and to control the temperature for regenerating the DPF 12 (because the catalyst deteriorates when the temperature of the DPF 12 rises more than necessary), Furthermore, it is used for EGR valve opening / closing control and the like.

  The EGR 16 as an exhaust gas recirculation device includes an EGR gas passage 160, an EGR valve 161, an EGR cooler 162, and an ECU 17.

The EGR gas passage 160 is disposed so as to communicate the exhaust passage 20 downstream of the DPF 12 and the intake passage 18 upstream of the compressor 112, and is an exhaust gas from which PM has been removed by the DPF 12. The part is again mixed with the intake air as EGR gas. EGR gas mixed with intake air lowers the oxygen concentration in the combustion chamber, moderates combustion, and reduces NOx.
The EGR 16 is provided with a check valve, a pressurizing device, etc. (not shown) for preventing the intake air of the intake passage 18 from flowing into the EGR gas passage 160.

  The EGR valve 161 is an electronically controlled on-off valve that is controlled to open and close based on the exhaust temperature TDPF, timing, flow rate, and the like under the control of the ECU 17. When the EGR valve 161 is controlled to open, EGR gas is supplied to the intake system. When the EGR valve 161 is closed (fully closed), the supply of EGR gas to the intake system is immediately stopped.

  The EGR cooler 162 is cooled by engine cooling water when high-temperature EGR gas passes through the inside. The EGR gas cooled by the EGR cooler 162 is mixed with the intake air to lower the combustion temperature further than the normal EGR gas, so that NOx is further reduced and the intake air density is increased. By increasing the amount of air and approaching complete combustion, PM and black smoke are further reduced.

  The ECU 17 is formed of a circuit including a microprocessor (MPU) that operates according to a computer program for performing fuel injection control, PM accumulation amount estimation processing, PM combustion processing, and EGR valve control. That is, the ECU 17 compares the accelerator pedal opening, the engine speed, and many additional correction coefficients with map data stored in a memory (not shown) so as to calculate and execute an appropriate fuel injection amount. Is set.

  The ECU 17 also includes a plurality of map data (numerical table) stored in the memory and detected values of the first and second exhaust pressure sensors 13 and 14 (DPF upstream exhaust gas pressure PF, DPF downstream exhaust gas). Pressure PM) and the detected value (exhaust temperature TDPF) of the exhaust temperature sensor 15 are set so as to estimate the PM accumulation amount. When it is determined that the estimated PM accumulation amount has reached a predetermined value, the ECU 17 performs post injection in addition to normal fuel injection in order to remove PM by combustion, and sets the temperature of the exhaust gas flowing into the DPF 12. Increase to the combustion temperature of PM.

  Further, the ECU 17 controls the EGR valve 161 to be closed so that the exhaust gas is not recirculated during cold, idle, and high load. Further, when the post-injection for regeneration of the DPF 12 is being performed, the ECU 17 determines the EGR valve 161 based on the detected value (exhaust temperature TDPF) of the exhaust temperature sensor 15 and the threshold value T1. It is determined whether to perform opening / closing control. When the exhaust gas temperature TDPF is higher than the threshold value T1, the EGR valve 161 is closed (fully closed control). When the exhaust gas temperature TDPF is lower than the threshold value T1, the EGR valve is controlled. 161 is set to open-control.

Here, the opening / closing control of the EGR valve 161 performed by the ECU 17 will be described with reference to the flowchart of FIG.
First, in step 10, the ECU 17 detects the information signal in the ECU or the detection values (exhaust gas pressure PF, PA) of the first and second exhaust pressure sensors 13 and 14 and the detection value (exhaust gas) of the exhaust temperature sensor 15. Based on the temperature TDPF), it is determined whether or not post injection is being performed, that is, whether or not regeneration of the DPF 12, that is, PM incineration is being performed.

  If it is determined that the DPF 12 is being regenerated, it is determined in step 11 whether or not the detected value detected by the exhaust temperature sensor 15 is greater than a predetermined threshold T1. This threshold value T1 is set as a risk that the DPF 12 may be damaged (melting and cracking) when the temperature of the DPF 12 is higher than that. If the exhaust gas temperature TDPF is smaller than the threshold value T1, the routine is exited. Further, if the exhaust gas temperature TDPF is larger than the threshold value T1, it is determined that the DPF 12 may be damaged, and the process proceeds to the next step 12 and immediately outputs a close control signal to the EGR valve 161 and the EGR valve 161. Is fully closed.

  In the present embodiment, the fuel injection control and the EGR valve 161 open / close control are configured to be performed by the ECU 17. However, the present invention is not limited to this, and the fuel injection control and the EGR valve 161 open / close control are performed. May be performed by independent control units. FIG. 2B shows a control flow performed in the control unit that performs opening / closing control of the EGR valve 161.

That is, as shown in FIG. 2B, according to this control flow, first, the detected values (exhaust gas pressures PF, PA) detected by the first and second exhaust pressure sensors 13, 14 and the exhaust temperature sensor. The detected values (exhaust temperature TDPF) detected by 15 are read (step 101).
Then, it is determined whether or not the difference between the detection values detected by the first and second discharge pressure sensors 13 and 14 is larger than a predetermined threshold value P1 (step 102). This is because when the amount of PM collected by the DPF 12 increases, the pressure difference of the exhaust gas increases before and after passing through the DPF 12.

  Here, if the pressure difference of the exhaust gas is larger than the threshold value P1, it is determined whether or not the detected value of the exhaust temperature sensor 15 is larger than a predetermined threshold value T2 (step 103), and the exhaust gas temperature TDPF is the threshold value T2. If it is higher, it is determined that the DPF 12 is being regenerated (step 104), and the process proceeds to step 11. Step 11 and subsequent steps are the same as the control float of FIG. Note that the threshold value T2 is set so as to reach a temperature at which PM burns.

  As described above, according to the present invention, when the ECU 17 determines that the DPF 12 may be damaged, it immediately outputs a close control signal to the EGR valve 161 to fully close the EGR valve 161. As a result, even if a large amount of PM burns rapidly and the temperature rises too much and the DPF is damaged, it is possible to prevent the fragments at that time from being recirculated to the intake system of the engine 11 by the EGR 16. it can. Therefore, the engine parts are not damaged by the fragments when the DPF 12 is damaged, and the intake / exhaust valve and the combustion chamber are not clogged and the engine is locked.

It is a block diagram of the exhaust-gas purification apparatus of the internal combustion engine to which this invention was applied. (A) is a flowchart showing EGR valve opening / closing control performed by the ECU, and (b) is a flowchart showing EGR valve opening / closing control different from (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Exhaust gas purification apparatus 11 of internal combustion engine ... Diesel engine with a supercharger (internal combustion engine)
12 ... DPF (particulate matter collector)
13: First exhaust pressure sensor (exhaust pressure detection means)
14 ... Second exhaust pressure sensor (exhaust pressure detecting means)
15 ... Exhaust temperature sensor (exhaust temperature detection means)
16 ... EGR (exhaust gas recirculation system)
161 ... EGR valve 17 ... ECU (control device)
18 ... Intake passage 20 ... Exhaust passage PM ... Particulate matter

Claims (3)

Particulate matter collecting means for collecting particulate matter from exhaust gas of an internal combustion engine and burning the collected particulate matter to regenerate the filter;
Exhaust pressure detection means for detecting exhaust gas pressure upstream and downstream of the particulate matter collection means;
An exhaust gas temperature detecting means for detecting an exhaust gas temperature downstream from the particulate matter collecting means;
An opening / closing valve for recirculating a part of the exhaust gas in which the particulate matter is collected by the particulate matter collecting means to the intake system of the internal combustion engine, and a control means for controlling the opening / closing of the opening / closing valve. An exhaust gas recirculation device;
In an exhaust gas purification apparatus for an internal combustion engine equipped with
The control means determines a combustion state of the particulate matter collected by the particulate matter collection means based on the detection value and threshold value of the exhaust pressure detection means and the exhaust temperature detection means, and the combustion An exhaust gas purifying apparatus for an internal combustion engine that outputs a close control signal for fully closing the on-off valve when it is determined that there is a possibility that the particulate matter collecting means is damaged.   The control means is configured such that a differential pressure between the upstream exhaust gas pressure and the downstream exhaust gas pressure detected by the exhaust pressure temperature detection means exceeds a predetermined pressure, and the exhaust gas temperature detected by the exhaust temperature detection means 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein regeneration of the particulate matter collecting means is detected when the temperature exceeds a predetermined temperature.   If the exhaust gas temperature detected by the exhaust gas temperature detection unit exceeds a predetermined temperature during regeneration of the particulate matter collection unit, the control unit may cause the particulate matter collection unit to melt. The exhaust gas purifying device for an internal combustion engine according to claim 1 or 2, wherein the determination is made.

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