JP2009162133A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to inhibit a fine particulate matter from being discharged to the outside without being trapped by a filter, in an exhaust emission control device for an internal combustion engine. <P>SOLUTION: This exhaust emission control device includes first and second exhaust passages 2a, 2b independently arranged at each cylinder group and first and second DPFs 3a, 3b provided in the exhaust passages 2a, 2b, respectively. When a rate of a change in a flow speed of exhaust gas flowing into the first and second DPFs 3a, 3b is higher than a predetermined speed (Yes in S103), it is determined that the PM is hardly trapped by the first and second DPFs 3a, 3b and easily discharged to the outside. Then, exhaust pulses passing through the first and second exhaust passages 2a, 2b are mutually offset when reaching the first and second DPFs 3a, 3b (S104). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

When a particulate filter (hereinafter simply referred to as a filter) that collects particulate matter (hereinafter simply referred to as PM) such as soot and SOF is disposed in the exhaust passage of the internal combustion engine, and the amount of PM collected reaches a specified amount There is a case where PM collection ability regeneration processing is performed in which PM collected by the filter is oxidized and removed to regenerate the PM collection ability of the filter. And immediately after PM collection ability regeneration processing, PM in exhaust gas is not collected by the filter and easily passes through the filter, so that it is difficult for the internal combustion engine to generate PM for a predetermined time after the PM collection ability regeneration processing. A technique for reducing the amount of EGR gas and the amount of intake air is disclosed (see, for example, Patent Document 1).
JP 2005-240587 A

  However, according to the knowledge of the present inventor, PM is not collected by the filter but discharged to the outside except when the PM in the exhaust gas immediately after the PM collection ability regeneration process is not collected by the filter and easily passes through the filter. There is an opportunity to end up.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technology for suppressing particulate matter from being discharged outside without being collected by a filter in an exhaust purification device of an internal combustion engine. It is to provide.

In the present invention, the following configuration is adopted. That is, the present invention
An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Determining means for determining that the particulate matter is not easily collected by the filter and is easily discharged to the outside when the flow rate change rate of the exhaust gas flowing into the filter is faster than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising:

  Here, the predetermined speed of the flow rate change speed of the exhaust gas flowing into the filter is a threshold speed at which the PM accumulated on the filter peels off and re-scatters when it is faster than that, or flows into the filter. This is the threshold speed at which PM in the exhaust gas passes through the filter, or at least one of the threshold speeds.

  When the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the PM accumulated on the filter peels off and re-scatters, or the PM in the exhaust gas flowing into the filter slips through the filter. . For this reason, PM is not easily collected by the filter and is easily discharged to the outside. If this is the case, PM may be discharged outside without being collected by the filter. Therefore, in the present invention, in this case, it is determined that the PM is not easily collected by the filter and is easily discharged to the outside. In this case, the PM is prevented from being discharged to the outside without being collected by the filter. Processing can be realized.

In the present invention, the following configuration is adopted. That is, the present invention
An independent exhaust passage for each cylinder group of the internal combustion engine;
A filter provided in each exhaust passage for collecting particulate matter in the exhaust;
A plurality of communication paths having different path lengths for communicating the exhaust passages upstream of the filter with each other;
An on-off valve that opens and closes each communication path;
When the flow rate change speed of the exhaust gas flowing into each filter is faster than a predetermined speed, the exhaust passage communicated with the engine speed among a plurality of on-off valves according to the engine speed of the internal combustion engine. By opening a desired on-off valve provided in a communication path having a path length that cancels passing exhaust pulsations when they reach the filter, the communication is established through the communication path provided with the desired on-off valve. First control means for canceling exhaust pulsations passing through the exhaust passage when reaching the filter;
An exhaust emission control device for an internal combustion engine, comprising:

  When the flow rate change speed of the exhaust gas flowing into each filter is faster than a predetermined speed, the PM accumulated in each filter peels off and re-scatters, or the PM in the exhaust gas flowing into each filter passes through each filter. I will. For this reason, in this case, PM is not easily collected by each filter and is easily discharged to the outside. According to the present invention, when the flow rate change speed of the exhaust gas flowing into each filter is higher than a predetermined speed, the exhaust gas is communicated by a communication path provided with a desired on-off valve that is opened according to the engine speed of the internal combustion engine. Exhaust pulsations passing through the exhaust passage can be canceled when reaching each filter. According to this, in this case, there is no portion where the exhaust speed is fast in the exhaust pulsation when reaching each filter, it is difficult for the PM accumulated on each filter to peel off and re-scatter and / or flow into each filter. It is possible to make it difficult for PM in the exhaust gas to pass through each filter. Therefore, it can suppress that PM is not collected by each filter but discharged | emitted outside.

In the present invention, the following configuration is adopted. That is, the present invention
An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
A plurality of sub-exhaust passages connected between a portion of the exhaust passage in the exhaust passage upstream of the filter with a path length different from the length of a portion of the exhaust passage;
An on-off valve for opening and closing each auxiliary exhaust passage;
When the flow rate change speed of the exhaust gas flowing into the filter is higher than a predetermined speed, a sub exhaust passage connected in conformity with the engine speed of the plurality of on-off valves according to the engine speed of the internal combustion engine The desired on-off valve is opened by opening a desired on-off valve provided in the sub-exhaust passage having a path length that cancels out the exhaust pulsation passing through the exhaust passage and the exhaust pulsation passing through the exhaust passage. A second control means for canceling out the exhaust pulsation passing through the provided sub exhaust passage and the exhaust pulsation passing through the exhaust passage when reaching the filter;
An exhaust emission control device for an internal combustion engine, comprising:

  When the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the PM accumulated on the filter peels off and re-scatters, or the PM in the exhaust gas flowing into the filter slips through the filter. . For this reason, in this case, PM is not easily collected by the filter and is easily discharged to the outside. According to the present invention, when the flow rate change speed of the exhaust gas flowing into the filter is higher than a predetermined speed, the exhaust gas passes through the auxiliary exhaust passage provided with a desired on-off valve that is opened according to the engine speed of the internal combustion engine. The exhaust pulsation and the exhaust pulsation passing through the exhaust passage can be canceled when the filter reaches the filter. According to this, in this case, there is no portion where the exhaust speed is fast in the exhaust pulsation when reaching the filter, it is difficult for the PM accumulated on the filter to peel off and re-scatter and / or in the exhaust gas flowing into the filter It is possible to make it difficult for the PM to slip through the filter. Therefore, it can suppress that PM is not collected by a filter but discharged | emitted outside.

In the present invention, the following configuration is adopted. That is, the present invention
An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Third control means for controlling the operating state of the internal combustion engine to an operating state in which the flow rate changing speed of the exhaust gas flowing into the filter is slow when the flow rate changing speed of the exhaust gas flowing into the filter is faster than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising:

  When the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the PM accumulated on the filter peels off and re-scatters, or the PM in the exhaust gas flowing into the filter slips through the filter. . For this reason, in this case, PM is not easily collected by the filter and is easily discharged to the outside. According to the present invention, when the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the operation state of the internal combustion engine can be controlled to an operation state in which the flow speed change speed of the exhaust gas flowing into the filter becomes slow. According to this, in this case, the flow rate change speed of the exhaust gas flowing into the filter becomes slow, it is difficult for the PM deposited on the filter to peel off and re-scatter and / or PM in the exhaust gas flowing into the filter Makes it difficult to slip through the filter. Therefore, it can suppress that PM is not collected by a filter but discharged | emitted outside.

  Here, the control for setting the operating state in which the flow rate change speed of the exhaust gas flowing into the filter becomes slow is, for example, in the case of acceleration operation of a vehicle in which the exhaust gas flow rate change speed becomes faster than a predetermined speed. Control that slows down the acceleration operation of some of the vehicles so that the flow rate change speed of the exhaust gas becomes a predetermined speed or less.

In the present invention, the following configuration is adopted. That is, the present invention
An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Fourth control means for controlling the operating state of the internal combustion engine to an operating state in which particulate matter is difficult to be generated in the internal combustion engine when the flow rate change speed of the exhaust gas flowing into the filter is higher than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising:

  When the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the PM accumulated on the filter peels off and re-scatters, or the PM in the exhaust gas flowing into the filter slips through the filter. . For this reason, in this case, PM is not easily collected by the filter and is easily discharged to the outside. According to the present invention, when the flow rate change speed of the exhaust gas flowing into the filter is faster than a predetermined speed, the operating state of the internal combustion engine can be controlled to an operating state in which PM is not easily generated by the internal combustion engine. According to this, in this case, the amount of PM generated by the internal combustion engine and exhausted from the internal combustion engine can be reduced, and it is difficult for the PM in the exhaust gas to be reduced and the PM in the exhaust gas flowing into the filter to pass through the filter. Can be. Therefore, it can suppress that PM is not collected by a filter but discharged | emitted outside.

  Here, for example, an EGR device that takes in part of the exhaust gas flowing through the exhaust passage as EGR gas and recirculates the EGR gas to the intake passage of the internal combustion engine is provided as control for setting the operation state in which PM is hardly generated in the internal combustion engine. In this case, the amount of EGR gas recirculated by the EGR device may be reduced, the in-cylinder fuel injection pressure of the internal combustion engine may be increased to make the spray atomized, and the in-cylinder fuel injection timing of the internal combustion engine may be set. To change.

  According to the present invention, in the exhaust gas purification apparatus for an internal combustion engine, it is possible to suppress the particulate matter from being discharged outside without being collected by the filter.

  Specific examples of the present invention will be described below.

<Example 1>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is applied and an exhaust system thereof. An internal combustion engine 1 shown in FIG. 1 has a V-type in which a first cylinder group (first bank) 1a having four cylinders and a second cylinder group (second bank) 1b having four cylinders are arranged in a V-type. This is an 8-cylinder compression ignition internal combustion engine (diesel engine).

  Connected to the first bank 1a is a first exhaust passage 2a through which exhaust gas after combustion in each cylinder flows. A second exhaust passage 2b is connected to the second bank 1b. A first DPF (diesel particulate filter) 3a that collects particulate matter (PM) in the exhaust is disposed in the first exhaust passage 2a. A second DPF 3b is disposed in the second exhaust passage 2b. The first and second DPFs 3a and 3b correspond to the filter of the present invention. The first and second DPFs 3a and 3b have a catalyst having oxidation ability such as an oxidation catalyst, an occlusion reduction type NOx catalyst, and a three-way catalyst in the previous stage. The catalyst having oxidation ability may be disposed in the exhaust passages 2a and 2b immediately upstream of the first and second DPFs 3a and 3b, or may be supported on the carriers of the first and second DPFs 3a and 3b.

  The first exhaust passage 2 a upstream from the first DPF 3 a and the second exhaust passage 2 b upstream from the second DPF 3 b are connected by a communication passage 4. A first on-off valve 5 a that switches between exhaust gas flowing through the communication path 4 or blocking the exhaust gas flow is provided in the middle of the communication path 4.

  In addition, the communication path 4 has a branch path 6 in which a part of the communication path 4 is connected with a path length different from that of a part of the communication path 4. In the middle of the branch path 6, there is provided a second on-off valve 5 b that switches between exhaust gas flowing through the branch path 6 and blocking the exhaust gas flow. The communication path 4 of the present embodiment and the communication path 4 including the branch path 6 in part correspond to the communication path of the present invention.

  The internal combustion engine 1 configured as described above is provided with an ECU 7. The ECU 7 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 7 includes an air flow meter 8 that detects the amount of intake air (fresh air amount) taken into the internal combustion engine, and first and second exhaust temperature sensors 9a that detect exhaust temperatures flowing into the first and second DPFs 3a and 3b. 9b etc. are connected via electrical wiring, and the output signals of these devices are input to the ECU 7. The ECU 7 is connected to the first and second on-off valves 5a and 5b via electric wiring, and these devices are controlled by the ECU 7.

  The ECU 7 receives an output signal from a crank position sensor, an accelerator position sensor, or the like (not shown) to determine the operating state of the internal combustion engine 1, and electrically controls the internal combustion engine 1 and the above devices based on the determined engine operating state. To do.

By the way, when the flow rate change speed of the exhaust gas flowing into the first and second DPFs 3a and 3b is higher than a predetermined speed, the PM accumulated on the first and second DPFs 3a and 3b may be peeled off and scattered again. The PM in the exhaust gas flowing into the second DPFs 3a and 3b may pass through the first and second DPFs 3a and 3b. For this reason, PM is not easily collected by the first and second DPFs 3a and 3b, and is easily discharged to the outside. In particular, exhaust pulsation corresponding to the explosion timing of each cylinder occurs in the exhaust gas flowing through the first and second exhaust passages 2a and 2b. Exhaust pulsation has a part where the exhaust speed is fast, and when the exhaust of the part where the exhaust speed is fast flows into the first and second DPFs 3a and 3b, PM is not easily collected by the first and second DPFs 3a and 3b and is discharged from the outside. It becomes easy to be done. If this is the case, PM may be discharged outside without being collected by the first and second DPFs 3a and 3b.

  Here, if the predetermined speed of the flow rate change speed of the exhaust gas flowing into the first and second DPFs 3a and 3b is higher than that, the PM accumulated in the first and second DPFs 3a and 3b is peeled off and re-scattered. Or a threshold speed at which PM in the exhaust gas flowing into the first and second DPFs 3a and 3b passes through the first and second DPFs 3a and 3b, and a speed that is at least one of the threshold values. It is.

  Therefore, in this embodiment, when the flow velocity change speed of the exhaust gas flowing into the first and second DPFs 3a and 3b is higher than a predetermined speed, the exhaust pulsations passing through the first and second exhaust passages 2a and 2b are related to each other. When the first or second DPF 3a, 3b is reached, it cancels out.

  Specifically, the ECU 7 calculates the flow rate change speed of the exhaust gas flowing into the first or second DPF 3a, 3b, and determines the case where the flow rate change speed becomes faster than a predetermined speed. In this case, the ECU 7 corresponds to the engine speed of the internal combustion engine 1 and the first and second of the first and second on-off valves 5a and 5b are adapted to communicate with the engine speed at that time. A communication path provided with a desired on-off valve by opening a desired on-off valve provided in the communication path 4 or the branch path 6 having a path length that cancels exhaust pulsations passing through the exhaust passages 2a, 2b. Exhaust pulsations passing through the first and second exhaust passages 2a and 2b communicated by the four or branch passages 6 are canceled when the first and second DPFs 3a and 3b arrive.

  Here, the configuration for canceling the exhaust pulsations passing through the first and second exhaust passages 2a and 2b when they reach the first and second DPFs 3a and 3b will be described in detail. FIG. 2 is a model of the path length in each passage for canceling the exhaust pulsations passing through the first and second exhaust passages 2a and 2b when they reach the first and second DPFs 3a and 3b.

  In FIG. 2, the path lengths of the first and second exhaust passages 2 a and 2 b on the upstream side of the connection portion with the communication passage 4 are L. The path length of the first and second exhaust passages 2a and 2b to the first and second DPFs 3a and 3b on the downstream side of the connection portion with the communication passage 4 is L2. The path length of the communication path 4 including the communication path 4 or a part of the branch path 6 is L1.

  In the relationship between the path lengths, the condition that the exhaust pulsations passing through the first and second exhaust passages 2a and 2b cancel each other (cancelled) when they reach the first DPF 3a passes through the communication passage 4 from the second exhaust passage 2b. The wavelength of the exhaust pulsation passing through the first exhaust passage 2a and reaching the first DPF 3a (L + L1 + L2) and the wavelength of the exhaust pulsation passing through the first exhaust passage 2a and the path reaching the first DPF 3a (L + L2) Is a half wavelength shift.

  That is, (L + L1 + L2) − (L + L2) = λ / 2 may be satisfied. Here, λ is the wavelength of exhaust pulsation. Therefore, L1 = λ / 2 is obtained from the above equation.

  Here, in the V-type 8-cylinder internal combustion engine 1 according to the present embodiment, the explosion timing is 90 ° out of phase between the first bank 1a and the second bank 1b. For this reason, L1 also needs to shift by λ / 4. Therefore, L1 = λ / 2−λ / 4 = λ / 4 is calculated.

  Therefore, if the path length of L1 is set to a multiple of λ / 4, the exhaust pulsations passing through the first and second exhaust passages 2a and 2b are canceled when they reach the first DPF 3a.

  Here, λ = Vs × 60 / N rpm. Vs is the speed of sound (≈340 m / s), and Nrpm is the engine speed of the internal combustion engine 1.

  Therefore, L1 = (60/4) × (Vs / N rpm) ≈5100 / N rpm (m). Therefore, for example, if the engine speed (N rpm) is 1000 rpm, L1 is 5.1 m, if 2000 rpm, L1 is 2.6 m, and if 4000 rpm, L1 is 1.3 m.

  Thus, according to the engine speed of the internal combustion engine 1, the path length of L1 in which the exhaust pulsations passing through the first and second exhaust passages 2a and 2b are canceled when they reach the first DPF 3a is different.

  In the above description, the path length of L1 is calculated so that the exhaust pulsations passing through the first and second exhaust passages 2a and 2b cancel each other when they reach the first DPF 3a. However, they pass through the first and second exhaust passages 2a and 2b. The path length of L1 that cancels out the exhaust pulsations when they reach the second DPF 3b is also obtained in the same way.

  Therefore, in this embodiment, the path length of only the communication passage 4 is set to 1.3 m that can cancel out the exhaust pulsations passing through the first and second exhaust passages 2a and 2b when the engine speed is 4000 rpm, and is partially branched. The path length of the communication path 4 including the path 6 is set to 5.1 m so that the exhaust pulsations passing through the first and second exhaust paths 2a and 2b can be offset when the engine speed is 1000 rpm.

  When the engine speed is 2000 rpm, the exhaust pulsations passing through the first and second exhaust passages 2a and 2b cancel each other out when the other passage is further provided and the path length of the communication passage 4 partially including the branch passage is 2000 rpm. It may be 2.6m. Further, a plurality of other branch paths may be provided with a path length that can cancel the exhaust pulsations passing through the first and second exhaust passages 2a and 2b in accordance with the engine speed.

  In this embodiment, the communication path having a path length that cancels out the exhaust pulsations passing through the first and second exhaust paths 2a and 2b, which are obtained as described above, and communicate with each other in conformity with the engine speed. 4 or a communication passage 4 partially including the branch path 6 is provided.

  Therefore, when the exhaust pulsations passing through the first and second exhaust passages 2a and 2b are canceled when the first and second DPFs 3a and 3b arrive, the first passage provided in the communication passage 4 when the engine speed is 4000 rpm. 1 Open the on-off valve 5a. When the engine speed is 1000 rpm, the second on-off valve 5b provided in the branch path 6 is opened. That is, in this embodiment, the desired on-off valve is the first on-off valve 5a when the engine speed is 4000 rpm, and the desired on-off valve is the second on-off valve 5b when the engine speed is 1000 rpm.

  According to this embodiment, when the flow rate change speed of the exhaust gas flowing into the first and second DPFs 3a and 3b is faster than a predetermined speed, the exhaust pulsations passing through the first and second exhaust passages 2a and 2b are first and second. It can be canceled when the second DPF 3a, 3b is reached. According to this, in this case, there is no fast exhaust speed portion in the exhaust pulsation when the first and second DPFs 3a and 3b reach, and it is difficult for the PM deposited on the first and second DPFs 3a and 3b to peel off and re-scatter. And / or PM in the exhaust gas flowing into the first and second DPFs 3a and 3b can be made difficult to pass through the first and second DPFs 3a and 3b. Therefore, it can suppress that PM is not collected by 1st, 2nd DPF3a, 3b, but is discharged | emitted outside.

  Next, an exhaust pulsation canceling control routine according to this embodiment will be described. FIG. 3 is a flowchart showing an exhaust pulsation canceling control routine according to this embodiment. This routine is repeatedly executed every predetermined time. Moreover, ECU7 which performs this routine is equivalent to the 1st control means of this invention.

  In step S101, the ECU 7 detects the operating state of the internal combustion engine 1 from the output values of various sensors. At this time, the air flow meter 8 detects the intake air amount Ga and also detects the fuel injection amount Q injected into the cylinder of the internal combustion engine 1. Further, the first and second exhaust temperature sensors 9a and 9b detect the temperature Tin of the exhaust flowing into the first and second DPFs 3a and 3b.

  In step S102, the ECU 7 calculates the flow velocity change speed ΔV of the exhaust gas flowing into the first and second DPFs 3a and 3b. Specifically, based on the intake air amount Ga detected by the air flow meter 8 and the fuel injection amount Q injected into the cylinder of the internal combustion engine 1, the change amount per unit time of the sum of Ga and Q is “Δ ( The value of “Ga + Q) / sec” is calculated. The value of “ΔTin / sec”, which is a change amount of Tin per unit time, based on the exhaust temperature Tin flowing into the first and second DPFs 3a and 3b detected by the first and second exhaust temperature sensors 9a and 9b. Is calculated. Then, based on “Δ (Ga + Q) / sec” and “ΔTin / sec”, the flow velocity change speed ΔV (m / sec) of the exhaust gas flowing into the first and second DPFs 3a and 3b is calculated.

  In step S103, the ECU 7 determines whether or not the exhaust gas flow velocity change speed ΔV is faster than a predetermined speed α. In addition, ECU7 which performs this step is equivalent to the determination means of this invention. The flow rate change rate ΔV of the exhaust is the value calculated in step S102. Further, the predetermined speed α is a speed obtained in advance by experiments or the like, and if it is faster than that, it is a threshold speed at which PM deposited on the first and second DPFs 3a and 3b peels off and re-scatters. Or the threshold speed at which PM in the exhaust gas flowing into the first and second DPFs 3a and 3b passes through the first and second DPFs 3a and 3b, or at least one of the threshold values.

  If it is determined in step S103 that the exhaust gas flow rate change speed ΔV is not more than the predetermined speed α, this routine is temporarily ended. On the other hand, if it is affirmed that the exhaust gas flow rate change speed ΔV is faster than the predetermined speed α, the process proceeds to step S104.

  In step S104, the ECU 7 opens either the first or second on-off valve 5a, 5b according to the current engine speed of the internal combustion engine 1.

  That is, when the engine speed of the internal combustion engine 1 is 4000 rpm, the first on-off valve 5a is opened. On the other hand, when the engine speed of the internal combustion engine 1 is 1000 rpm, the second on-off valve 5b is opened. By the control in step S104, the exhaust pulsations passing through the first and second exhaust passages 2a and 2b can be canceled when they reach the first and second DPFs 3a and 3b.

  In step S105, the ECU 7 detects the operating state of the internal combustion engine 1 from the output values of the various sensors as in step S101.

  In step S106, the ECU 7 calculates the flow velocity change speed ΔV of the exhaust gas flowing into the first and second DPFs 3a and 3b, similarly to step S102.

  In step S107, the ECU 7 determines whether or not the exhaust gas flow velocity change speed ΔV is equal to or lower than a predetermined speed α. The flow rate change rate ΔV of the exhaust is the value calculated in step S106. The predetermined speed α is the same value as that used in step S103.

  If it is determined in step S107 that the exhaust gas flow rate change speed ΔV is faster than the predetermined speed α, the process returns to step S104. On the other hand, if an affirmative determination is made that the exhaust gas flow velocity change speed ΔV is equal to or lower than the predetermined speed α, the process proceeds to step S108.

In step S108, the ECU 7 closes the opened first or second on-off valve 5a, 5b. By the control in step S108, the exhaust discharged from the internal combustion engine 1 does not pass through the communication passage 4 or the branch passage 6, but flows through the first and second exhaust passages 2a and 2b, respectively, and the first and second DPF 3a, It passes through each of 3b and is discharged.

  When the flow rate change speed of the exhaust gas flowing into the first and second DPFs 3a and 3b is equal to or lower than a predetermined speed, the PM deposited on the first and second DPFs 3a and 3b will not be peeled off and scattered again, and / or Alternatively, PM in the exhaust gas flowing into the first and second DPFs 3a and 3b will not slip through the first and second DPFs 3a and 3b. Therefore, PM is easily collected by the first and second DPFs 3a and 3b, and is difficult to be discharged to the outside. Therefore, in this case, exhaust gas having an exhaust pulsation in which the first and second DPFs 3a and 3b have a portion where the exhaust speed is fast is caused to flow as usual.

  Then, after the control in step S108, this routine is temporarily terminated.

  By performing the above routine, when the flow rate change speed ΔV of the exhaust gas flowing into the first and second DPFs 3a and 3b is faster than the predetermined speed α, PM is not collected by the first and second DPFs 3a and 3b. It can suppress discharging to the outside.

  In the present embodiment, the configuration including the communication path 4 and the branch path 6 has been described. However, the present invention is not limited to this, and a plurality of communication passages 4a and 4b may be provided as communication paths by changing the connection positions of the first and second exhaust passages 2a and 2b as shown in FIG. As described above, the condition that the exhaust pulsations passing through the first and second exhaust passages 2a and 2b cancel each other when they reach the first and second DPFs 3a and 3b is the path length L1 = λ of the plurality of communication passages 4a and 4b. It may be a multiple of / 4. Therefore, even if the connection position of the communication passages 4a and 4b with the exhaust passages 2a and 2b changes, the path length L of the first and second exhaust passages 2a and 2b upstream of the connection position with the communication passages 4a and 4b. Or the length L2 of the first and second exhaust passages 2a and 2b to the first and second DPFs 3a and 3b on the downstream side of the connection position with the communication passages 4a and 4b is between the first and second exhaust passages 2a and 2b. This is because it is sufficient that the relative relationship is maintained.

<Example 2>
Next, Example 2 will be described. Here, a configuration different from the above-described embodiment will be described, and description of the same configuration will be omitted.

  FIG. 5 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is applied and its exhaust system. An internal combustion engine 1c shown in FIG. 5 is an inline 4-cylinder compression ignition internal combustion engine (diesel engine).

  An exhaust passage 2 is connected to the internal combustion engine 1c. A DPF 3 is disposed in the exhaust passage 2. The DPF 3 corresponds to the filter of the present invention.

  The first and second auxiliary exhaust passages 11a, 11a, 11b connected to the exhaust passage 2 upstream of the DPF 3 with a part of the exhaust passage 2 having a different path length from the length of the part of the exhaust passage 2. 11b is provided. A first on-off valve 12a is arranged in the middle of the first sub exhaust passage 11a. A second on-off valve 12b is arranged in the middle of the second sub exhaust passage 11b.

  The internal combustion engine 1c configured as described above is provided with an ECU 7. The ECU 7 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

The ECU 7 includes an air flow meter 8 that detects an intake air amount (fresh air amount) taken into the internal combustion engine.
In addition, an exhaust temperature sensor 9 for detecting an exhaust temperature flowing into the DPF 3 is connected via an electrical wiring, and output signals of these devices are input to the ECU 7. The ECU 7 is connected to the first and second on-off valves 12a and 12b through electric wiring, and these devices are controlled by the ECU 7.

  The ECU 9 receives an output signal from a crank position sensor or an accelerator position sensor (not shown), determines the operating state of the internal combustion engine 1c, and electrically controls the internal combustion engine 1c and the above devices based on the determined engine operating state. To do.

  By the way, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the PM accumulated in the DPF 3 peels off and re-scatters, or the PM in the exhaust gas flowing into the DPF 3 passes through the DPF 3. I'll be relaxed. For this reason, PM is not easily collected by the DPF 3 and is easily discharged to the outside. In particular, exhaust pulsation corresponding to the explosion timing of each cylinder occurs in the exhaust gas flowing through the exhaust passage 2. The exhaust pulsation has a portion with a high exhaust speed. When the exhaust with this high exhaust speed flows into the DPF 3, the PM is not easily collected by the DPF 3, and is easily discharged to the outside. If this is the case, PM may be discharged outside without being collected by the DPF 3.

  Therefore, in this embodiment, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the exhaust pulsation passing through one of the first and second auxiliary exhaust passages 11a and 11b and the exhaust passage 2 are set. The passing exhaust pulsation is canceled when the DPF 3 is reached.

  Specifically, the ECU 7 calculates the flow rate change speed of the exhaust gas flowing into the DPF 3, and determines a case where the flow rate change speed becomes faster than a predetermined speed. In this case, the ECU 7 uses the auxiliary exhaust passage connected to the engine speed of the first and second on-off valves 12a and 12b in accordance with the engine speed of the internal combustion engine 1 in accordance with the engine speed at that time. The auxiliary exhaust passage provided with the desired opening / closing valve is opened by opening the desired opening / closing valve provided in the auxiliary exhaust passage having a path length that cancels out the exhaust pulsation passing through and the exhaust pulsation passing through the exhaust passage 2. The exhaust pulsation passing through the exhaust passage 2 and the exhaust pulsation passing through the exhaust passage 2 are offset when the DPF 3 reaches a temperature higher than the exhaust temperature.

  Here, the configuration for canceling the exhaust pulsation passing through the first or second auxiliary exhaust passage 11a, 11b and the exhaust pulsation passing through the exhaust passage 2 when reaching the DPF 3 will be described in detail. FIG. 6 is a model of the path length in each passage for canceling the exhaust pulsation passing through the first or second sub exhaust passage 11a, 11b and the exhaust pulsation passing through the exhaust passage 2 when reaching the DPF 3.

  In FIG. 6, the length of a part of the exhaust passage 2 from the upstream connection portion to the downstream connection portion with the first or second sub exhaust passage 11a, 11b is L3. The path length of the first or second sub exhaust passage 11a, 11b is L4.

  In the relationship between the path lengths, the exhaust pulsation passing through the first or second sub-exhaust passages 11a and 11b and the exhaust pulsation passing through the exhaust passage 2 cancel each other (cancelled) when reaching the DPF 3. 2, the wavelength of exhaust pulsation passing through the path reaching the DPF 3 through the first or second auxiliary exhaust passages 11 a, 11 b and the wavelength of exhaust pulsation passing through the path reaching the DPF 3 through the exhaust path 2. Is a half wavelength shift. Therefore, the difference between these routes is L4−L3.

  That is, L4−L3 = λ / 2 may be satisfied. Here, λ is the wavelength of exhaust pulsation. From the above equation, L4 = L3 + λ / 2 is obtained.

Therefore, if the path length of L4 is set to a multiple of (L3 + λ / 2), the first time when reaching DPF3
Alternatively, the exhaust pulsation passing through the second sub exhaust passages 11a and 11b and the exhaust pulsation passing through the exhaust passage 2 are offset.

  Here, λ = Vs × 60 / N rpm. Vs is the speed of sound (≈340 m / s), and Nrpm is the engine speed of the internal combustion engine 1c.

  Therefore, L4 = L3 + (60/2) × (Vs / Nrpm) ≈L3 + 10200 / Nrpm (m). Therefore, for example, if the engine speed (Nrpm) is 1000 rpm, L4 is (L3 + 10.2) m, and if it is 2000 rpm, L4 is (L3 + 5.1) m, and if it is 4000 rpm, L4 is (L3 + 2.6). ) M.

  Thus, the L4 path in which the exhaust pulsation passing through the first or second auxiliary exhaust passages 11a and 11b and the exhaust pulsation passing through the exhaust passage 2 are canceled out by the DPF 3 in accordance with the engine speed of the internal combustion engine 1c. The length is different.

  Therefore, in the present embodiment, when the engine speed is 4000 rpm, the exhaust pulsation passing through the first auxiliary exhaust passage 11a and the exhaust pulsation passing through the exhaust passage 2 can be offset when the path length of the first auxiliary exhaust passage 11a is 4000 rpm (L3 + 2). .6) m, and when the engine speed is 1000 rpm, the exhaust pulsation passing through the second auxiliary exhaust passage 11b and the exhaust pulsation passing through the exhaust passage 2 can be offset (L3 + 10.m). 2) m.

  In addition, when the engine speed is 2000 rpm, the exhaust pulsation passing through the sub-exhaust passage and the exhaust pulsation passing through the exhaust passage 2 can be offset (L3 + 5). .1) m may be used. Further, a plurality of other sub exhaust passages may be provided with a path length that can cancel out the exhaust pulsation passing through the other sub exhaust passage and the exhaust pulsation passing through the exhaust passage 2 according to the engine speed.

  In the present embodiment, the exhaust pulsation passing through the first or second auxiliary exhaust passages 11a, 11b and the exhaust passage passing through the exhaust passage 2 obtained in the manner described above and connected in conformity with the engine speed. First or second auxiliary exhaust passages 11a and 11b having a path length that cancels out pulsation are provided.

  Therefore, when the exhaust pulsation passing through the first or second sub exhaust passage 11a, 11b and the exhaust pulsation passing through the exhaust passage 2 are canceled when the DPF 3 is reached, when the engine speed is 4000 rpm, the first sub exhaust The first on-off valve 12a provided in the passage 11a is opened. When the engine speed is 1000 rpm, the second on-off valve 12b provided in the second auxiliary exhaust passage 11b is opened. That is, in this embodiment, when the engine speed is 4000 rpm, the desired on-off valve is the first on-off valve 12a, and when the engine speed is 1000 rpm, the desired on-off valve is the second on-off valve 12b.

  According to the present embodiment, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the exhaust pulsation passing through the first or second auxiliary exhaust passage 11a, 11b and the exhaust pulsation passing through the exhaust passage 2 Can be offset when the DPF 3 reaches a temperature higher than the exhaust temperature. According to this, in this case, there is no portion where the exhaust speed is high in the exhaust pulsation when reaching the DPF 3, it is difficult for the PM deposited on the DPF 3 to peel off and re-scatter and / or in the exhaust flowing into the DPF 3. It is possible to make it difficult for the PMs to pass through the DPF 3. Therefore, it can suppress that PM is not collected by DPF3 but discharged | emitted outside.

Next, an exhaust pulsation canceling control routine according to this embodiment will be described. FIG. 7 is a flowchart showing an exhaust pulsation canceling control routine according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 7 that executes this routine corresponds to the second control means of the present invention.

  In step S201, the ECU 7 detects the operating state of the internal combustion engine 1c from the output values of various sensors. At this time, the intake air amount Ga is detected from the air flow meter, and the fuel injection amount Q injected into the cylinder of the internal combustion engine 1c is also detected. Further, the exhaust gas temperature sensor 9 detects the temperature Tin of the exhaust gas flowing into the DPF 3.

  In step S202, the ECU 7 calculates the flow velocity change speed ΔV of the exhaust gas flowing into the DPF 3. Specifically, the value of “Δ (Ga + Q) / sec” is calculated based on the intake air amount Ga detected by the air flow meter and the fuel injection amount Q injected into the cylinder of the internal combustion engine 1. Further, a value of “ΔTin / sec” is calculated based on the temperature Tin of the exhaust gas flowing into the DPF 3 detected by the exhaust gas temperature sensor 9. Then, based on “Δ (Ga + Q) / sec” and “ΔTin / sec”, the flow velocity change speed ΔV (m / sec) of the exhaust gas flowing into the DPF 3 is calculated.

  In step S203, the ECU 7 determines whether or not the exhaust gas flow velocity change speed ΔV is faster than a predetermined speed α. In addition, ECU7 which performs this step is equivalent to the determination means of this invention. The flow rate change rate ΔV of the exhaust is the value calculated in step S202. In addition, the predetermined speed α is a speed obtained in advance by experiments or the like, and if it is faster than that, the threshold speed at which the PM deposited on the DPF 3 peels off and re-scatters or flows into the DPF 3. It is a threshold speed at which PM in the exhaust gas passes through the DPF 3, or a speed that is at least one of the threshold values.

  If it is determined in step S203 that the exhaust gas flow velocity change speed ΔV is not more than the predetermined speed α, this routine is temporarily terminated. On the other hand, when it is affirmed that the exhaust gas flow rate change speed ΔV is faster than the predetermined speed α, the process proceeds to step S204.

  In step S204, the ECU 7 opens either the first or second on-off valve 12a, 12b according to the current engine speed of the internal combustion engine 1c.

  That is, when the engine speed of the internal combustion engine 1c is 4000 rpm, the first on-off valve 12a is opened. When the engine speed of the internal combustion engine 1c is 1000 rpm, the second on-off valve 12b is opened. By the control in step S204, the exhaust pulsation passing through the first or second auxiliary exhaust passage 11a, 11b and the exhaust pulsation passing through the exhaust passage 2 can be canceled when the DPF 3 is reached.

  In step S205, the ECU 7 detects the operating state of the internal combustion engine 1c from the output values of various sensors as in step S201.

  In step S206, the ECU 7 calculates the flow velocity change rate ΔV of the exhaust gas flowing into the DPF 3 as in step S202.

  In step S207, the ECU 7 determines whether or not the exhaust gas flow velocity change speed ΔV is equal to or lower than a predetermined speed α. The flow rate change rate ΔV of the exhaust is the value calculated in step S206. The predetermined speed α is the same value as that used in step S203.

  If it is determined in step S207 that the exhaust gas flow velocity change speed ΔV is faster than the predetermined speed α, the process returns to step S204. On the other hand, if an affirmative determination is made that the exhaust flow velocity change speed ΔV is equal to or lower than the predetermined speed α, the process proceeds to step S208.

  In step S208, the ECU 7 closes the opened first or second on-off valve 12a, 12b. By the control in step S208, the exhaust discharged from the internal combustion engine 1c does not pass through the first or second sub exhaust passages 11a and 11b, passes through the exhaust passage 2 and passes through the DPF 3, and is discharged.

  When the flow rate change speed of the exhaust gas flowing into the DPF 3 becomes a predetermined speed or less, the PM accumulated in the DPF 3 will not peel off and re-scatter and / or the PM in the exhaust gas flowing into the DPF 3 No more slipping through. Therefore, PM is easily collected by the DPF 3 and is not easily discharged to the outside. Therefore, in this case, exhaust gas having exhaust pulsation in which the DPF 3 has a portion with a high exhaust speed is allowed to flow as usual.

  Then, after the control in step S208, this routine is temporarily terminated.

  By carrying out the above routine, it is possible to prevent PM from being collected in the DPF 3 and discharged outside when the flow velocity change speed ΔV of the exhaust gas flowing into the DPF 3 is faster than the predetermined speed α.

<Example 3>
Next, Example 3 will be described. Here, a configuration different from the above-described embodiment will be described, and description of the same configuration will be omitted.

  FIG. 8 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is applied and its exhaust system. An internal combustion engine 1d shown in FIG. 8 has a configuration without the first and second sub exhaust passages 11a and 11b in the internal combustion engine 1c shown in FIG. The internal combustion engine 1c is mounted on a vehicle.

  When the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the PM accumulated in the DPF 3 peels off and re-scatters, or the PM in the exhaust gas flowing into the DPF 3 passes through the DPF 3. . For this reason, PM is not easily collected by the DPF 3 and is easily discharged to the outside. If this is the case, PM may be discharged outside without being collected by the DPF 3.

  Therefore, in this embodiment, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the operation state of the internal combustion engine is controlled to be an operation state where the flow speed change speed of the exhaust gas flowing into the DPF 3 becomes slow. did.

  Specifically, the ECU 7 calculates the flow velocity change speed of the exhaust gas flowing into the DPF 3 during the acceleration operation of the vehicle, and determines a case where the flow velocity change speed becomes faster than a predetermined speed. In this case, the ECU 7 slows the acceleration so that the flow velocity change speed of the exhaust gas flowing into the DPF 3 is not more than a predetermined speed for a predetermined time during the acceleration operation of the vehicle.

  According to this embodiment, when the flow velocity change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the flow velocity change speed of the exhaust gas flowing into the DPF 3 can be slowed. According to this, in this case, the flow rate change speed of the exhaust gas flowing into the DPF 3 becomes slow, it is difficult for the PM deposited on the DPF 3 to peel off and re-scatter, and / or PM in the exhaust gas flowing into the DPF 3 Makes it difficult to pass through the DPF 3. Therefore, it can suppress that PM is not collected by DPF3 but discharged | emitted outside.

Next, a vehicle acceleration / slowness control routine according to this embodiment will be described. FIG. 9 is a flowchart showing a vehicle acceleration / slowness control routine according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 7 that executes this routine corresponds to the third control means of the present invention. Steps S201 to S203 are the same as the control routine of FIG.

  If it is determined in step S203 that the exhaust gas flow velocity change speed ΔV is not more than the predetermined speed α, this routine is temporarily terminated. On the other hand, if it is determined affirmative that the flow rate change speed ΔV of the exhaust gas is faster than the predetermined speed α, the process proceeds to step S304.

  In step S304, the ECU 7 slows the vehicle acceleration operation so that the flow velocity change speed of the exhaust gas flowing into the DPF 3 during the acceleration operation of the vehicle is equal to or less than the predetermined speed α.

  In other words, the vehicle is accelerated by limiting the intake air amount with a throttle valve or limiting the fuel injection amount injected into the cylinder of the internal combustion engine 1d so that the flow rate change speed of the exhaust gas becomes a predetermined speed α or less. Slow down. By the control in step S304, the flow rate change speed of the exhaust gas becomes a predetermined speed α or less.

  In step S305, the ECU 7 waits for the elapse of a predetermined time in a state where the control in step S304 is executed. The predetermined time may be a minute time such that a slow feeling of vehicle acceleration caused by the vehicle operator slowing down the acceleration is not felt. As a result, in the case of an acceleration operation of a vehicle in which the exhaust gas flow rate change speed becomes faster than the predetermined speed α within a predetermined time period, the acceleration operation of some of the vehicles is made slow to change the exhaust gas flow rate. The speed is set to be equal to or lower than a predetermined speed α.

  In step S306, the ECU 7 returns the acceleration operation of the vehicle to normal. As a result, in the case of a vehicle acceleration operation in which the exhaust flow velocity change speed suddenly becomes higher than the predetermined speed α within a predetermined time period, the exhaust flow velocity change speed becomes higher than the predetermined speed α. Can be eliminated.

  Then, after the control in step S306, this routine is temporarily terminated.

  By carrying out the above routine, it is possible to prevent PM from being collected in the DPF 3 and discharged outside when the flow velocity change speed ΔV of the exhaust gas flowing into the DPF 3 is faster than the predetermined speed α.

<Example 4>
Next, Example 4 will be described. Here, a configuration different from the above-described embodiment will be described, and description of the same configuration will be omitted.

  FIG. 10 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is applied, and its intake system and exhaust system. An internal combustion engine 1e shown in FIG. 10 is a water-cooled four-stroke cycle diesel engine having four cylinders that form a combustion chamber together with a piston. The internal combustion engine 1 is mounted on a vehicle. Fuel, such as light oil, is supplied from the fuel tank 21 through the fuel supply passage 22 to each cylinder, and fuel with a fuel injection pressure determined by the common rail 23 is injected into the cylinder at an appropriate amount and at an appropriate timing. An injection valve 24 is provided. An intake passage 25 and an exhaust passage 2 are connected to the internal combustion engine 1.

In the middle of the intake passage 25 connected to the internal combustion engine 1, a compressor 26a of a turbocharger 26 that operates using exhaust energy as a drive source is disposed. A throttle valve 27 for adjusting the flow rate of intake air flowing through the intake passage 25 is disposed in the intake passage 25 upstream of the compressor 26a. The throttle valve 27 is opened and closed by an electric actuator. An intercooler 28 that performs heat exchange between the intake air and the outside air is disposed in the intake passage 25 downstream of the compressor 26a. The intake passage 25 and the devices arranged in the intake passage 25 constitute an intake system of the internal combustion engine 1e.

  On the other hand, a turbine 26b of the turbocharger 26 is disposed in the middle of the exhaust passage 2 connected to the internal combustion engine 1e. A DPF 3 is disposed in the exhaust passage 2 downstream of the turbine 26b. The exhaust passage 2 and the devices arranged in the exhaust passage 2 constitute an exhaust system of the internal combustion engine 1e.

  The internal combustion engine 1e is provided with a high pressure EGR device 30 that recirculates (recirculates) a part of the exhaust gas flowing through the exhaust passage 2 to the intake passage 25 at a high pressure. In this embodiment, the exhaust gas recirculated by the high pressure EGR device 30 is referred to as high pressure EGR gas. The high pressure EGR device 30 in this embodiment corresponds to the EGR device of the present invention.

  The high pressure EGR device 30 includes a high pressure EGR passage 31 through which the high pressure EGR gas flows, and a high pressure EGR valve 32 that adjusts the flow rate of the high pressure EGR gas through the high pressure EGR passage 31.

  The high pressure EGR passage 31 connects the exhaust passage 2 upstream of the turbine 26 b and the intake passage 25 downstream of the intercooler 28. Through this high pressure EGR passage 31, the exhaust gas is sent as high pressure EGR gas to the internal combustion engine 1e at a high pressure.

  The high pressure EGR valve 32 is disposed in the high pressure EGR passage 31 and adjusts the flow rate of the high pressure EGR gas flowing through the high pressure EGR passage 31 by adjusting the passage sectional area of the high pressure EGR passage 31. The high pressure EGR valve 32 is opened and closed by an electric actuator.

  The internal combustion engine 1e may be provided with a low pressure EGR device that recirculates (recirculates) a part of the exhaust gas flowing through the exhaust passage 2 to the intake passage 25 at a low pressure. The low-pressure EGR device has a low-pressure EGR passage that connects the exhaust passage 2 downstream of the turbine 26b and the intake passage 25 upstream of the compressor 26a, through which the exhaust gas is low-pressure EGR gas. Is sent to the internal combustion engine 1e at a low pressure. This low pressure EGR device also corresponds to the EGR device of the present invention.

  The internal combustion engine 1e configured as described above is provided with an ECU 7. The ECU 7 is a unit that controls the operation state of the internal combustion engine 1e in accordance with the operation conditions of the internal combustion engine 1e and the request of the driver.

  The ECU 7 is connected to an air flow meter 8 for detecting an intake air amount (fresh air amount) sucked into the internal combustion engine 1e, an exhaust gas temperature sensor 9 for detecting an exhaust gas temperature flowing into the DPF 3, and the like via electric wiring. The output signals of these devices are input to the ECU 7. Each actuator of the fuel injection valve 24, the throttle valve 27, and the high pressure EGR valve 32 is connected to the ECU 7 through electric wiring, and these devices are controlled by the ECU 7.

  The ECU 7 receives an output signal from a crank position sensor or an accelerator position sensor (not shown), determines the operating state of the internal combustion engine 1e, and electrically controls the internal combustion engine 1e and the above devices based on the determined engine operating state. To do.

By the way, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is faster than a predetermined speed, the PM accumulated in the DPF 3 peels off and re-scatters, or the PM in the exhaust gas flowing into the DPF 3 passes through the DPF 3. I'll be relaxed. For this reason, PM is not easily collected by the DPF 3 and is easily discharged to the outside. If this is the case, PM may be discharged outside without being collected by the DPF 3.

  Therefore, in this embodiment, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is higher than a predetermined speed, the operation state of the internal combustion engine 1e is controlled to an operation state in which PM is not easily generated by the internal combustion engine 1e.

  Specifically, the ECU 7 calculates the flow rate change speed of the exhaust gas flowing into the DPF 3, and determines a case where the flow rate change speed becomes faster than a predetermined speed. In this case, the ECU 7 controls the operation state of the internal combustion engine 1e to an operation state in which PM is not easily generated by the internal combustion engine 1e. Here, in an operation state where PM is hardly generated in the internal combustion engine 1e, the high-pressure EGR device 30 is injected from the fuel injection valve 24 by reducing the amount of high-pressure EGR gas to be recirculated and increasing the fuel injection pressure of the common rail 23. Implement in combination with or in combination with increasing the in-cylinder fuel injection pressure to atomize the injected fuel, changing the in-cylinder fuel injection timing from the fuel injection valve 24, etc. It is realized with.

  According to the present embodiment, when the flow rate change speed of the exhaust gas flowing into the DPF 3 is higher than a predetermined speed, the operation state of the internal combustion engine 1e is controlled to an operation state in which PM is not easily generated by the internal combustion engine 1e. Can reduce the amount of PM produced. For this reason, the PM discharged to the exhaust passage 2 is reduced, and it is difficult for the PM to pass through the DPF 3 and be discharged outside without being collected by the DPF 3. Therefore, it can suppress that PM is not collected by DPF3 but discharged | emitted outside.

  Next, the PM generation amount reduction control routine according to this embodiment will be described. FIG. 11 is a flowchart showing a PM generation amount reduction control routine according to this embodiment. This routine is repeatedly executed every predetermined time. The ECU 7 that executes this routine corresponds to the fourth control means of the present invention. Steps S201 to S203 and steps S205 to S207 are the same as the control routine of FIG.

  If it is determined in step S203 that the exhaust gas flow velocity change speed ΔV is not more than the predetermined speed α, this routine is temporarily terminated. On the other hand, if it is affirmed that the exhaust gas flow rate change speed ΔV is faster than the predetermined speed α, the process proceeds to step S404.

  In step S404, the ECU 7 controls the operation state of the internal combustion engine 1e to an operation state in which the PM generation amount is reduced in which the internal combustion engine 1e hardly generates PM.

  That is, the amount of high-pressure EGR gas recirculated by the high-pressure EGR device 30 is reduced, the fuel injection pressure of the common rail 23 is increased, the in-cylinder fuel injection pressure from the fuel injection valve 24 is increased, and the injected fuel is atomized. Any one of spraying, changing the in-cylinder fuel injection timing from the fuel injection valve 24, or the like is implemented or used together to make it difficult for the internal combustion engine 1e to generate PM. In addition, since the method for making it into the driving | running state which makes it difficult to generate | occur | produce PM in the internal combustion engine 1e changes with the types and structures of an engine, it is not restricted only to the said method, You may employ | adopt another method. . For example, if the internal combustion engine includes a low pressure EGR device, the amount of low pressure EGR gas recirculated by the low pressure EGR device may be reduced. The change in the in-cylinder fuel injection timing from the fuel injection valve 24 may be not only advanced but also delayed. In addition, during this control, if PM becomes difficult to be generated, a method of increasing the amount of NOx generated may be used.

  After the control in step S404, the process proceeds to step S205. And control of step S205-S207 is performed.

If it is determined in step S207 that the exhaust gas flow rate change speed ΔV is faster than the predetermined speed α, the process returns to step S404. On the other hand, if an affirmative determination is made that the flow rate change speed ΔV of the exhaust gas is equal to or less than the predetermined speed α, the process proceeds to step S408.

  In step S408, the ECU 7 returns the operating state of the internal combustion engine 1e to normal operation. By the control in step S408, the internal combustion engine 1e is in a normal operation state, the amount of PM generated in the internal combustion engine 1e is also normal, and PM is discharged to the exhaust passage 2 as usual.

  When the flow rate change speed of the exhaust gas flowing into the DPF 3 becomes a predetermined speed or less, the PM accumulated in the DPF 3 is not peeled off and re-scattered, and the PM in the exhaust gas flowing into the DPF 3 passes through the DPF 3. Nothing will happen. For this reason, PM is easily collected by the DPF 3 and is not easily discharged to the outside. Therefore, in this case, PM is allowed to flow into the DPF 3 as usual, and PM in the exhaust gas is collected by the DPF 3.

  Then, after the control in step S408, this routine is temporarily terminated.

  By carrying out the above routine, it is possible to prevent PM from being collected in the DPF 3 and discharged outside when the flow velocity change speed ΔV of the exhaust gas flowing into the DPF 3 is faster than the predetermined speed α.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention. The above-described embodiments may be combined as much as possible.

1 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to a first embodiment. 3 is a model of a path length in each passage according to the first embodiment. 3 is a flowchart illustrating an exhaust pulsation canceling control routine according to the first embodiment. 2 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to another example of Embodiment 1. FIG. It is a figure which shows schematic structure of the internal combustion engine which concerns on Example 2, and its exhaust system. 10 is a model of a path length in each passage according to the second embodiment. 7 is a flowchart illustrating an exhaust pulsation canceling control routine according to a second embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to a third embodiment. 7 is a flowchart illustrating a vehicle acceleration / slowness control routine according to a third embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an internal combustion engine and an intake system / exhaust system thereof according to a fourth embodiment. 10 is a flowchart illustrating a PM generation amount reduction control routine according to a fourth embodiment.

Explanation of symbols

1, 1c, 1d, 1e Internal combustion engine 1a First bank 1b Second bank 2 Exhaust passage 2a First exhaust passage 2b Second exhaust passage 3 DPF
3a 1st DPF
3b Second DPF
4, 4a, 4b Communication path 5a First on-off valve 5b Second on-off valve 6 Branch path 7 ECU
8 Air Flow Meter 9 Exhaust Temperature Sensor 9a First Exhaust Temperature Sensor 9b Second Exhaust Temperature Sensor 11a First Sub Exhaust Passage 11b Second Sub Exhaust Passage 12a First Open / Close Valve 12b Second Open / Close Valve 23 Common Rail 24 Fuel Injection Valve 26 Turbocharger 26a Compressor 26b Turbine 30 High pressure EGR device 31 High pressure EGR passage 32 High pressure EGR valve

Claims (5)

An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Determining means for determining that the particulate matter is not easily collected by the filter and is easily discharged to the outside when the flow rate change rate of the exhaust gas flowing into the filter is faster than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising: An independent exhaust passage for each cylinder group of the internal combustion engine;
A filter provided in each exhaust passage for collecting particulate matter in the exhaust;
A plurality of communication paths having different path lengths for communicating the exhaust passages upstream of the filter with each other;
An on-off valve that opens and closes each communication path;
When the flow rate change speed of the exhaust gas flowing into each filter is faster than a predetermined speed, the exhaust passage communicated with the engine speed among a plurality of on-off valves according to the engine speed of the internal combustion engine. By opening a desired on-off valve provided in a communication path having a path length that cancels passing exhaust pulsations when they reach the filter, the communication is established through the communication path provided with the desired on-off valve. First control means for canceling exhaust pulsations passing through the exhaust passage when reaching the filter;
An exhaust emission control device for an internal combustion engine, comprising: An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
A plurality of sub-exhaust passages connected between a portion of the exhaust passage in the exhaust passage upstream of the filter with a path length different from the length of a portion of the exhaust passage;
An on-off valve for opening and closing each auxiliary exhaust passage;
When the flow rate change speed of the exhaust gas flowing into the filter is higher than a predetermined speed, a sub exhaust passage connected in conformity with the engine speed of the plurality of on-off valves according to the engine speed of the internal combustion engine The desired on-off valve is opened by opening a desired on-off valve provided in the sub-exhaust passage having a path length that cancels out the exhaust pulsation passing through the exhaust passage and the exhaust pulsation passing through the exhaust passage. A second control means for canceling out the exhaust pulsation passing through the provided sub exhaust passage and the exhaust pulsation passing through the exhaust passage when reaching the filter;
An exhaust emission control device for an internal combustion engine, comprising: An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Third control means for controlling the operating state of the internal combustion engine to an operating state in which the flow rate changing speed of the exhaust gas flowing into the filter is slow when the flow rate changing speed of the exhaust gas flowing into the filter is faster than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising: An exhaust passage connected to the internal combustion engine;
A filter provided in the exhaust passage for collecting particulate matter in the exhaust;
Fourth control means for controlling the operating state of the internal combustion engine to an operating state in which particulate matter is difficult to be generated in the internal combustion engine when the flow rate change speed of the exhaust gas flowing into the filter is higher than a predetermined speed;
An exhaust emission control device for an internal combustion engine, comprising:

Images