Exhaust gas purification system

Abstract

To suppress uneven accumulation of particulate matter in a filter.SOLUTION: An exhaust gas purification device comprises a filter provided in an exhaust flow path connected to an engine, and an injection unit that injects gas to a region of a downstream end part of the filter where uneven accumulation of particulate matter is expected.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device.

Background Art

[0002] Exhaust gas exhausted from an engine contains particulate matter (PM) such as soot. For this reason, in the exhaust gas flow path of a vehicle, a DPF (Diesel Particulate Filter) or a GPF (Gasoline Particulate Filter) is provided as a filter for removing particulate matter (for example, Patent Document 1). In such a filter, particulate matter is removed from the exhaust gas by capturing the particulate matter with holes formed in the filter. The filter becomes clogged with particulate matter as use continues.

[0003] Therefore, a differential pressure sensor for measuring the differential pressure before and after the filter is provided in the vehicle, and based on the differential pressure, the deposition amount of particulate matter in the filter is estimated. When the differential pressure becomes equal to or higher than a predetermined value, it is estimated that the deposition amount is equal to or more than a predetermined amount, and a regeneration process is executed on the filter. The regeneration process is a process of sending air to the filter and burning the particulate matter to remove it from the filter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, depending on the shape of the exhaust gas flow path or the like, particulate matter may accumulate unevenly in the filter. Then, in the regeneration process, the portion where relatively more particulate matter has accumulated becomes unexpectedly high in temperature, and a problem occurs in the filter.

[0006] In view of these problems, the present invention aims to provide an exhaust gas purification device that can suppress uneven deposition of particulate matter in a filter. [Means for solving the problem]

[0007] To solve the above problems, an exhaust gas purification device according to one embodiment of the present invention is provided. A filter installed in the exhaust passage connected to the engine, An injection unit that injects gas into the region of the downstream end of the filter where uneven deposition of particulate matter is expected, Equipped with 、 The aforementioned exhaust passage is The large-diameter channel in which the filter is provided, A downstream small-diameter channel is provided downstream of the large-diameter channel and has a smaller diameter than the large-diameter channel, It has, The central axis of the large-diameter channel is positioned closer to the vehicle body than the central axis of the downstream small-diameter channel. The aforementioned region is Of the downstream end of the filter, the portion facing the step between the large-diameter flow path and the downstream small-diameter flow path, Determined by simulation based on the shape of the exhaust flow path and the installation configuration of the filter. ru. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress uneven deposition of particulate matter in the filter. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a vehicle according to an embodiment of the present invention. [Figure 2] Figure 2 is a diagram illustrating a GPF according to an embodiment of the present invention. [Figure 3] Figure 3 is a diagram illustrating a region according to an embodiment of the present invention. [Figure 4] Figure 4 illustrates the gas injection process by the injection unit according to an embodiment of the present invention. [Figure 5]FIG. 5 is a block diagram showing an example of the functional configuration of the control device according to an embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing the processing flow of the filter management method according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to omit redundant explanations, and elements not directly related to the present invention are not shown.

[0011] FIG. 1 is a schematic diagram showing the configuration of a vehicle 100 according to an embodiment of the present invention. In FIG. 1, the dashed arrows indicate the signal flow.

[0012] As shown in FIG. 1, the vehicle 100 includes an engine 110, an intake passage 120, an exhaust passage 130, an exhaust gas purification device 150, and a muffler 160.

[0013] The vehicle 100 is provided with an engine 110 as a drive source. The engine 110 is a gasoline engine. However, the vehicle according to the present invention is not limited to this example, and for example, a hybrid vehicle provided with a motor as a drive source in addition to the engine 110 may be used.

[0014] An intake manifold is connected to the intake port of the engine 110. An intake passage (intake pipe) 120 is connected to the collecting portion of the intake manifold.

[0015] An exhaust manifold is connected to the exhaust port of engine 110. An exhaust passage (exhaust pipe) 130 is connected to the collector section of the exhaust manifold. The exhaust gas emitted from engine 110 flows through the exhaust passage 130. Hereafter, the upstream direction in the direction of exhaust gas flow may simply be referred to as "upstream." Similarly, the downstream direction in the direction of exhaust gas flow may simply be referred to as "downstream."

[0016] The exhaust passage 130 is equipped with the catalytic converter 210, GPF 220, and pressure sensors 240 and 242 of the exhaust gas purification device 150 (described later), as well as the muffler 160.

[0017] The catalytic converter 210 is installed between the engine 110 and the muffler 160 in the exhaust passage 130. The GPF 220 is installed between the catalytic converter 210 and the muffler 160 in the exhaust passage 130. The pressure sensor 240 is installed between the catalytic converter 210 and the GPF 220 in the exhaust passage 130. The pressure sensor 242 is installed between the GPF 220 and the muffler 160 in the exhaust passage 130. The exhaust gas purification device 150 will be described in detail later.

[0018] [Exhaust gas purification device 150] Next, the exhaust gas purification device 150 according to this embodiment will be described. The exhaust gas purification device 150 purifies the exhaust gas discharged from the engine 110. In this embodiment, the exhaust gas purification device 150 includes a catalytic converter 210, a GPF 220, pressure sensors 240 and 242, an injection unit 250, and a control device 260.

[0019] The catalytic converter 210 includes, for example, a three-way catalyst. The three-way catalyst is composed of catalytic components such as platinum (Pt), palladium (Pd), and rhodium (Rh). The catalytic converter 210 removes hydrocarbons, carbon monoxide, and nitrogen oxides from the exhaust gas emitted from the engine 110.

[0020] The GPF220 (filter) captures particulate matter (soot) in the exhaust gas emitted from the engine 110.

[0021] Figure 2 is a diagram illustrating a GPF220 according to an embodiment of the present invention. In Figures 2 to 4 of this embodiment, the perpendicularly intersecting X, Y, and Z axes are defined as shown in the figures. Also, in Figures 2 and 3, the arrows indicate the flow of exhaust gas.

[0022] As shown in Figure 2, the exhaust passage 130 has an upstream small-diameter passage 132, an enlarged-diameter passage 134, a large-diameter passage 136, a narrowed-diameter passage 138, and a downstream small-diameter passage 140.

[0023] The upstream small-diameter channel 132 is a channel connected to the downstream side of the catalyst device 210. The widening channel 134 is a channel connected to the downstream side of the upstream small-diameter channel 132. The diameter of the widening channel 134 gradually increases as it moves from the upstream side to the downstream side.

[0024] The large-diameter channel 136 is a channel connected to the downstream side of the enlarged-diameter channel 134. The large-diameter channel 136 has a larger diameter than the upstream small-diameter channel 132. The large-diameter channel 136 is, for example, cylindrical in shape. In this embodiment, the GPF 220 is provided in the large-diameter channel 136.

[0025] The reduced-diameter channel 138 (stepped section) is a channel connected to the downstream side of the large-diameter channel 136. The diameter of the reduced-diameter channel 138 gradually decreases as it moves from the upstream side to the downstream side. The downstream small-diameter channel 140 (small-diameter channel) is a channel connected to the downstream side of the reduced-diameter channel 138. The downstream small-diameter channel 140 has a smaller diameter than the large-diameter channel 136. In this embodiment, the diameter of the downstream small-diameter channel 140 is substantially equal to the diameter of the upstream small-diameter channel 132.

[0026] Furthermore, in this embodiment, the upstream small-diameter channel 132 and the downstream small-diameter channel 140 are coaxial. On the other hand, the central axis of the large-diameter channel 136 is different from the central axis of the downstream small-diameter channel 140. For example, the central axis of the large-diameter channel 136 is positioned closer to the vehicle body than the central axis of the downstream small-diameter channel 140. This ensures that a gap is maintained between the large-diameter channel 136 and the road (ground) when the vehicle 100 is traveling. Therefore, it is possible to avoid the large-diameter channel 136 coming into contact with the road. In this embodiment, the central axis of the large-diameter channel 136 is parallel to the central axis of the downstream small-diameter channel 140.

[0027] As described above, the GPF220 is installed in the large-diameter flow path 136. The GPF220 is a wall-flow type filter. The GPF220 includes a filter wall 222, a first sealing portion 224, and a second sealing portion 226.

[0028] The filter wall 222 is a wall having multiple holes. In this embodiment, the filter wall 222 is composed of a first wall 222a and a second wall 222b. The first wall 222a is located on the XY plane in Figure 2 and extends in the Y-axis direction. The second wall 222b is located on the YZ plane in Figure 2 and extends in the Y-axis direction. The space surrounded by the two first walls 222a and the two second walls 222b is formed as a cell C.

[0029] Therefore, multiple cells C extend in the direction of the central axis (Y-axis direction in Figure 2) within the large-diameter channel 136, and are formed in parallel in directions perpendicular to the central axis (X-axis direction and Z-axis direction in Figure 2). There is no limit to the number of cells C.

[0030] The first sealing section 224 seals the downstream opening of cell CA, which is classified as belonging to the first cell group among the multiple cells C. The second sealing section 226 seals the upstream opening of cell CB, which is classified as belonging to the second cell group and is adjacent to cell CA of the first cell group. Cells CA and CB are arranged alternately. Therefore, the exhaust gas that reaches the GPF 220 is introduced into cell CA, passes through the filter wall 222 that partitions cell CA, and is introduced into cell CB. In other words, the exhaust gas that has passed through cell CA is introduced into cell CB. The exhaust gas introduced into cell CB is then guided to the muffler 160 (see Figure 1) through the downstream opening of cell CB.

[0031] Pressure sensor 240 detects the pressure between the catalytic converter 210 and the GPF 220. Pressure sensor 242 detects the pressure between the GPF 220 and the muffler 160.

[0032] The injection unit 250 injects gas into region R, part of the downstream end of the GPF 220, where uneven deposition of particulate matter is expected. The gas is, for example, air. The injection unit 250 injects gas, for example, while the engine 110 is stopped. In this embodiment, the injection unit 250 includes a nozzle 252 and a blower 254. The opening of the nozzle 252 faces region R. The blower 254 supplies gas to the nozzle 252.

[0033] Region R is a region within the GPF220 where particulate matter is more likely to accumulate compared to other regions. In other words, the amount of particulate matter accumulated in region R is greater than in other regions. Region R is determined by experiments or simulations based on the shape of the exhaust flow path 130 and the installation configuration of the GPF220.

[0034] Figure 3 is a diagram illustrating region R according to an embodiment of the present invention. In Figures 3 and 4, black circles indicate particulate matter. As described above, the central axis of the large-diameter channel 136 according to this embodiment is positioned closer to the vehicle body than the central axes of the upstream small-diameter channel 132 and the downstream small-diameter channel 140. For this reason, the central axis of the GPF220 is also positioned closer to the vehicle body than the central axes of the upstream small-diameter channel 132 and the downstream small-diameter channel 140.

[0035] Consequently, particulate matter contained in the exhaust gas accumulates (unevenly) in the region of the GPF220 that faces the narrowed diameter passage 138 and is on the vehicle body side. Therefore, in this embodiment, the injection unit 250 injects gas into the region R on the vehicle body side of the downstream end of the GPF220 that faces the narrowed diameter passage 138.

[0036] Figure 4 illustrates the gas injection process by the injection unit 250 according to an embodiment of the present invention. In Figure 4, the arrows indicate the flow of gas injected by the injection unit 250.

[0037] As shown in Figure 4, when the engine 110 is stopped, if gas is injected towards region R by the injection unit 250, the particulate matter deposited on the GPF 220 moves to the upstream side of the GPF 220. In other words, the injection unit 250 causes the particulate matter deposited on the GPF 220 to flow backward.

[0038] When the engine 110 is restarted, the particulate matter that has moved to the upstream side of the GPF 220 is captured again by the exhaust gas emitted from the engine 110. This allows the exhaust gas purification device 150 to average out the deposition distribution of particulate matter in the GPF 220. Therefore, the exhaust gas purification device 150 can suppress uneven deposition of particulate matter in the GPF 220.

[0039] Returning to Figure 1, the control device 260 includes one or more processors 262 and one or more memories 264 connected to the processors 262. The processors 262 include, for example, a CPU (Central Processing Unit). The memories 264 include, for example, ROM (Read Only Memory) and RAM (Random Access Memory). ROM is a memory element that stores programs and arithmetic parameters used by the CPU. RAM is a memory element that temporarily stores data such as variables and parameters used in processing performed by the CPU.

[0040] The control device 260 communicates with various devices installed in the vehicle 100 (for example, the engine 110, pressure sensors 240, 242, etc.). Communication between the control device 260 and each device is achieved, for example, using CAN (Controller Area Network) communication.

[0041] Figure 5 is a block diagram showing an example of the functional configuration of a control device 260 according to an embodiment of the present invention. For example, as shown in Figure 6, the control device 260 includes a signal acquisition unit 270, a deposit amount estimation unit 272, an injection control unit 274, an engine control unit 276, and a storage unit 280. Various processes, including those described below, performed by the signal acquisition unit 270, the deposit amount estimation unit 272, the injection control unit 274, and the engine control unit 276, can be executed by the processor 262. In detail, various processes are executed by the processor 262 executing a program stored in the memory 264.

[0042] The signal acquisition unit 270 acquires the detection values ​​from the pressure sensors 240 and 242. The signal acquisition unit 270 also acquires information on whether or not the engine 110 is stopped.

[0043] The sediment amount estimation unit 272 estimates the amount of particulate matter deposited in the GPF220 based on the detected values ​​of the pressure sensors 240 and 242. Specifically, the sediment amount estimation unit 272 calculates the difference between the detected value of the pressure sensor 240 and the detected value of the pressure sensor 242. This difference is the differential pressure between the upstream and downstream sides of the GPF220 (hereinafter simply referred to as "differential pressure"). Based on this difference (differential pressure), the sediment amount estimation unit 272 then estimates the amount of particulate matter deposited in the GPF220.

[0044] The deposition amount estimation unit 272 estimates that the amount of particulate matter deposited on the GPF 220 has reached a threshold amount when the differential pressure is equal to or greater than the threshold pressure. The threshold pressure is predetermined based on the differential pressure and the amount of particulate matter deposited. For example, the differential pressure is determined as the threshold pressure when the amount of deposit is the maximum amount of particulate matter that can be burned without abnormal combustion during the regeneration process. Information indicating the threshold pressure is stored in the storage unit 280.

[0045] The injection control unit 274 controls the injection unit 250 to inject gas. The injection control unit 274 injects gas, for example, when the engine 110 is stopped and a predetermined time has elapsed since the last injection process.

[0046] The engine control unit 276 controls the engine 110. In this embodiment, when the amount of particulate matter deposited on the GPF 220 exceeds a threshold amount, the engine control unit 276 cuts off fuel to the engine 110 and performs a regeneration process.

[0047] [Filter management method] Figure 6 is a flowchart showing the processing flow of a filter management method according to an embodiment of the present invention. In this embodiment, the filter management method is repeatedly performed by interrupts that occur at predetermined time intervals.

[0048] As shown in Figure 6, the filter management method includes a deposit amount determination process S110, an elapsed time determination process S120, a stopped state determination process S130, an injection process S140, and a regeneration process S150. Each process will be described in detail below.

[0049] [Accumulation amount determination process S110] The deposition amount estimation unit 272 determines whether the amount of particulate matter deposited on the GPF220 has exceeded a threshold amount. If it determines that the amount of deposition has exceeded the threshold amount (YES in S110), the deposition amount estimation unit 272 moves the process to the regeneration process S150. On the other hand, if it determines that the amount of deposition has not exceeded the threshold amount, that is, that it is below the threshold amount (NO in S110), the deposition amount estimation unit 272 moves the process to the elapsed time determination process S120.

[0050] [Elapsed time determination process S120] The injection control unit 274 determines whether a predetermined time has elapsed since the last injection process S140. If it determines that the predetermined time has elapsed, the injection control unit 274 proceeds to the stop determination process S130. On the other hand, if it determines that the predetermined time has not elapsed, the injection control unit 274 terminates the filter management method. If no injection process has been performed, the injection control unit 274 proceeds to the stop determination process S130.

[0051] [Stopped state determination process S130] The injection control unit 274 determines whether the engine 110 is stopped or not. If it determines that the engine 110 is stopped (YES in S130), the injection control unit 274 proceeds to injection process S140. On the other hand, if it determines that the engine 110 is not stopped (NO in S130), the injection control unit 274 terminates the filter management method.

[0052] [Injection process S140] The injection control unit 274 controls the injection unit 250 to inject gas into region R.

[0053] [Playback process S150] The engine control unit 276 initiates a fuel cut-off for the engine 110 and performs a regeneration process.

[0054] As described above, the exhaust gas purification device 150 according to this embodiment includes an injection unit 250. By injecting gas from the injection unit 250, particulate matter accumulated in region R can be moved to the upstream side of the GPF 220. Then, the exhaust gas flow disperses the particulate matter that has moved to the upstream side of the GPF 220, allowing it to be captured again by the GPF 220. As a result, the exhaust gas purification device 150 can suppress uneven accumulation of particulate matter in the GPF 220.

[0055] Furthermore, the GPF220 recaptures particulate matter that has moved to the upstream side of the GPF220 by the injection of gas by the injection unit 250. Therefore, the exhaust gas purification device 150 can remove particulate matter from the exhaust gas without the need for a separate device to collect particulate matter.

[0056] Furthermore, as described above, the injection unit 250 injects gas while the engine 110 is stopped. This prevents the injection unit 250 from injecting gas against the flow of exhaust gas. Consequently, it becomes possible to reduce the power of the blower 254 that constitutes the injection unit 250.

[0057] Furthermore, as described above, the injection unit 250 injects gas multiple times until the amount of particulate matter accumulation reaches a threshold amount. This makes it possible for the exhaust gas purification device 150 to further suppress uneven accumulation of particulate matter in the GPF220.

[0058] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these embodiments. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention.

[0059] For example, in the above embodiment, the central axes of the upstream small-diameter passage 132, the widening passage 134, the large-diameter passage 136, the narrowing passage 138, and the downstream small-diameter passage 140 of the exhaust passage 130 are given as an example where they are parallel. However, one or more of the central axes of the upstream small-diameter passage 132, the widening passage 134, the large-diameter passage 136, the narrowing passage 138, and the downstream small-diameter passage 140 do not have to be parallel to the other central axes.

[0060] Furthermore, in the above embodiment, the case in which the upstream small-diameter channel 132 and the downstream small-diameter channel 140 are coaxial was given as an example. However, the central axis of the upstream small-diameter channel 132 and the central axis of the downstream small-diameter channel 140 may be different.

[0061] Furthermore, in the above embodiment, an example was given in which the central axis of the large-diameter flow path 136 of the exhaust flow path 130 is different from the central axis of the downstream small-diameter flow path 140. However, the large-diameter flow path 136 and the downstream small-diameter flow path 140 may be coaxial. Also, one or more of the upstream small-diameter flow path 132, the widening flow path 134, the large-diameter flow path 136, the narrowing flow path 138, and the downstream small-diameter flow path 140 may be coaxial.

[0062] In any case, the injection unit 250 should inject gas into the region R at the downstream end of the GPF 220 where uneven deposition of particulate matter is expected. For example, the injection unit 250 may inject gas into the region R at the downstream end of the GPF 220 that faces the step between the large-diameter flow path 136 and the downstream small-diameter flow path 140, that is, the region R radially outward from the downstream small-diameter flow path 140.

[0063] Furthermore, in the above embodiment, air was given as an example of the gas injected by the injection unit 250. However, the gas injected by the injection unit 250 can be any gas that does not worsen the properties of the exhaust gas.

[0064] Furthermore, in the above embodiment, the example given was that the injection unit 250 injects gas while the engine 110 is stopped. However, the injection unit 250 may also inject gas while the engine 110 is running.

[0065] Furthermore, in the above embodiment, the exhaust gas purification device 150 was given as an example in which it includes pressure sensors 240, 242 and an accumulation amount estimation unit 272. However, the pressure sensors 240, 242 and the accumulation amount estimation unit 272 are not essential components. The control device 260 may estimate a threshold amount based on the cumulative operating time of the engine 110 since the last regeneration process was performed.

[0066] Furthermore, in the above embodiment, an example was given in which the injection unit 250 is equipped with one nozzle 252. However, the injection unit 250 may be equipped with multiple nozzles 252. For example, multiple nozzles 252 may be provided at equal intervals in the circumferential direction of the GPF 220. Also, if there are multiple regions R, a nozzle 252 may be provided for each region R.

[0067] Furthermore, in the above embodiment, the case where engine 110 is a gasoline engine was given as an example. However, engine 110 may also be a diesel engine. When engine 110 is a diesel engine, a DPF is provided in the exhaust passage 130 instead of the GPF 220. In this case, the DPF functions as the filter of the present invention. [Explanation of Symbols]

[0068] 110 engine 130 Exhaust passage 136 Large-diameter channel 138 Reduced diameter channel (stepped section) 140 Downstream small-diameter channel (small-diameter channel) 150 Exhaust gas purification device 220 GPF (filter) 250 Injection part

Claims

1. A filter installed in the exhaust passage connected to the engine, An injection unit that injects gas into the region of the downstream end of the filter where uneven deposition of particulate matter is expected, Equipped with, The aforementioned exhaust passage is The large-diameter channel in which the filter is provided, A downstream small-diameter channel is provided downstream of the large-diameter channel and has a smaller diameter than the large-diameter channel, It has, The central axis of the large-diameter channel is positioned closer to the vehicle body than the central axis of the downstream small-diameter channel. The aforementioned region is Of the downstream end of the filter, the portion facing the step between the large-diameter flow path and the downstream small-diameter flow path, An exhaust gas purification device determined by simulation based on the shape of the exhaust flow path and the installation configuration of the filter.

2. As the gas is injected by the injection unit, the particulate matter deposited on the filter moves to the upstream side of the filter. The exhaust gas purification device according to claim 1, wherein particulate matter that has moved to the upstream side of the filter is captured again by the filter by the exhaust gas discharged from the engine.

3. The control unit further comprises, which, when the amount of particulate matter deposited in the filter is greater than or equal to a threshold, performs a regeneration process on the filter, and when the amount of deposit is less than the threshold, controls the injection unit to inject the gas while the engine is stopped, The exhaust gas purification device according to claim 1 or 2, wherein the control unit controls the injection unit to inject the gas multiple times until the amount of deposit reaches the threshold.

4. The exhaust passage is An enlarged diameter channel is provided on the upstream side of the aforementioned large diameter channel, An upstream small-diameter channel is provided on the upstream side of the aforementioned widened channel, A reduced-diameter channel is provided between the large-diameter channel and the downstream small-diameter channel, It has, The exhaust gas purification device according to claim 1 or 2, wherein one or more of the central axes of the upstream small-diameter channel, the widening channel, the large-diameter channel, the narrowing channel, and the downstream small-diameter channel are not parallel to the other central axes.

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