JP2018162712A - Filter device - Google Patents

Abstract

An object of the present invention is to improve the collection rate in the initial state. A filter device (220) includes a filter wall (324) formed with a plurality of holes (360) for capturing particulate matter contained in the exhaust gas and allowing the exhaust gas to pass therethrough; a collection layer 350 comprising particles. By providing the trapping layer 350, it is possible to improve the particulate matter trapping rate in the initial state. [Selection drawing] Fig. 6

Description

  The present invention relates to a filter device that captures particulate matter contained in exhaust gas.

  2. Description of the Related Art DPF (Diesel Particulate Filter) and GPF (Gasoline Particulate Filter) are known as filter devices for vehicles that remove particulate matter such as soot and oil-derived ash contained in exhaust gas exhausted from an engine.

  In such a filter device, the particulate matter is removed from the exhaust gas by capturing the particulate matter through the holes formed in the filter (for example, Patent Document 1).

JP 2011-147931 A

  By the way, the particulate matter accumulated in the filter adsorbs the particulate matter contained in the exhaust gas. For this reason, the conventional filter device has a low collection rate of particulate matter in the initial state where almost no particulate matter is accumulated in the filter, and the collection rate increases as the use time (exhaust gas passage time) increases. Will improve. Therefore, there is a demand for development of a technique for improving the collection rate of particulate matter in the initial state.

  An object of this invention is to provide the filter apparatus which can improve the collection rate of an initial state.

  In order to solve the above problems, a filter device according to the present invention is provided on a filter wall having a plurality of holes through which the exhaust gas passes while capturing particulate matter contained in the exhaust gas. And a collection layer configured to include a plurality of carbon particles.

  The collection layer may be disposed on a surface of the filter wall that is located upstream of the exhaust gas flow direction.

  The collection layer may include carbon particles having the same structure as the carbon particles contained in the soot in the exhaust gas.

  According to the present invention, it is possible to improve the collection rate in the initial state.

It is the schematic which shows the structure of an engine system. It is the schematic which shows the structure of an exhaust-gas purification | cleaning unit. It is the schematic which shows the structure of a filter apparatus. It is a figure explaining the collection layer in a filter apparatus. It is a conceptual diagram explaining capture | acquisition of the particulate matter by the conventional filter apparatus. It is a conceptual diagram explaining capture | acquisition of the particulate matter by the filter apparatus of embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating 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 function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a schematic diagram showing the configuration of the engine system 100. In FIG. 1, the signal flow is indicated by broken arrows. As shown in FIG. 1, the engine system 100 is provided with an ECU (Engine Control Unit) 110 formed of a microcomputer including a central processing unit (CPU), a ROM storing programs and the like, a RAM as a work area, and the like. The ECU 110 performs overall control of the engine 120. However, the configuration and processing related to the present embodiment will be described in detail below, and the description of the configuration and processing unrelated to the present embodiment will be omitted.

  The engine 120 is a multi-cylinder engine having a plurality of cylinders 122a, and an intake manifold 126 is communicated with an intake port 124 of each cylinder 122a formed in the cylinder block 122. An intake passage 130 is communicated with a collection portion of the intake manifold 126 via an air chamber 128, an air cleaner 132 is provided on the upstream side of the intake passage 130, and a throttle valve 134 is provided on the downstream side of the air cleaner 132.

  An exhaust manifold 138 communicates with the exhaust port 136 of each cylinder 122 a formed in the cylinder block 122 of the engine 120. A muffler 142 is communicated with the collective portion of the exhaust manifold 138 via an exhaust path 140, and an exhaust gas purification unit 200 described later is provided in the exhaust path 140.

  The engine 120 is provided with a spark plug 148 for each of the cylinders 122a so that the tip thereof is located in the combustion chamber 146. An injector 150 is provided in the combustion chamber 146 of each cylinder 122a.

  In the engine system 100, an intake air amount sensor 160 that detects the amount of intake air flowing into the engine 120 between the air cleaner 132 and the throttle valve 134 in the intake passage 130, and the temperature of the air flowing into the engine 120 are detected. An intake air temperature sensor 162 is provided. The engine system 100 is also provided with a throttle opening sensor 164 that detects the opening of the throttle valve 134. The engine system 100 is also provided with a crank angle sensor 166 that detects the crank angle of the crankshaft and an accelerator opening sensor 168 that detects the opening of an accelerator (not shown).

  Each of these sensors 160 to 168 is connected to ECU 110, and outputs a signal indicating the detected value to ECU 110.

  ECU 110 acquires signals output from sensors 160 to 168 and controls engine 120. When the ECU 110 controls the engine 120, the signal acquisition unit 180, the target value derivation unit 182, the air amount determination unit 184, the injection amount determination unit 186, the throttle opening determination unit 188, the ignition timing determination unit 190, and the drive control unit 192. Function as.

  The signal acquisition unit 180 acquires signals indicating values detected by the sensors 160 to 168. The target value deriving unit 182 derives the current engine speed based on the signal indicating the crank angle acquired from the crank angle sensor 166. Further, the target value deriving unit 182 refers to the pre-stored map based on the derived engine speed and a signal indicating the accelerator opening acquired from the accelerator opening sensor 168, and the target torque and the target engine speed. Is derived.

  The air amount determination unit 184 determines a target air amount to be supplied to each cylinder 122a based on the target engine speed and the target torque derived by the target value deriving unit 182. The throttle opening determination unit 188 derives the total target air amount of each cylinder 122a determined by the air amount determination unit 184, and determines the target throttle opening for intake of the total amount of air from the outside.

  The injection amount determination unit 186 determines a target injection amount of fuel to be supplied to each cylinder 122a based on the target air amount of each cylinder 122a determined by the air amount determination unit 184. Further, the injection amount determination unit 186 is based on a signal indicating the crank angle detected by the crank angle sensor 166 in order to inject the fuel of the determined target injection amount from the injector 150 in the intake stroke or compression stroke of the engine 120. The target injection timing and target injection period of each injector 150 are determined.

  Based on the target engine speed derived by the target value deriving unit 182 and a signal indicating the crank angle detected by the crank angle sensor 166, the ignition timing determining unit 190 is a target of the spark plug 148 in each cylinder 122a. Determine the ignition timing.

  The drive control unit 192 drives a throttle valve actuator (not shown) so that the throttle valve 134 opens at the target throttle opening determined by the throttle opening determination unit 188. Further, the drive control unit 192 drives the injector 150 at the target injection timing and the target injection period determined by the injection amount determination unit 186, thereby causing the injector 150 to inject fuel of the target injection amount. Further, the drive control unit 192 ignites the spark plug 148 at the target ignition timing determined by the ignition timing determination unit 190.

  In this way, the exhaust gas generated by burning the fuel in the combustion chamber 146 is discharged to the outside through the exhaust path 140. The exhaust gas contains hydrocarbons (HC: Hydro Carbon), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM), and these must be removed. Therefore, the exhaust gas purification unit 200 is provided in the exhaust path 140, and the exhaust gas purification unit 200 removes hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter.

(Exhaust gas purification unit 200)
FIG. 2 is a schematic diagram showing the configuration of the exhaust gas purification unit 200. In FIG. 2, the signal flow is indicated by broken arrows. As shown in FIG. 2, the exhaust gas purification unit 200 includes a three-way catalyst 210, a filter device 220, and a differential pressure sensor 230.

  The three-way catalyst 210 is provided in the exhaust path 140. The three-way catalyst 210 is composed of, for example, a carrier supporting platinum (Pt), palladium (Pd), and rhodium (Rh), and hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas discharged from the exhaust port 136. Remove objects.

  The filter device 220 is provided on the downstream side of the three-way catalyst 210 in the exhaust passage 140 and captures particulate matter in the exhaust gas exhausted from the exhaust port 136. The filter device 220 of this embodiment is a wall flow type. The filter device 220 will be described in detail later.

  The differential pressure sensor 230 detects the differential pressure between the upstream side and the downstream side in the filter device 220. When the differential pressure detected by differential pressure sensor 230 exceeds a predetermined upper limit value, ECU 110 performs a regeneration process that burns and removes particulate matter (soot). In the regeneration process, pressure loss is reduced by burning other particulate matter while leaving a predetermined amount of particulate matter necessary for adsorbing new particulate matter.

  FIG. 3 is a schematic view showing the configuration of the filter device 220, FIG. 3 (a) shows a perspective view of the filter device 220, FIG. 3 (b) shows a front view of the filter device 220, and FIG. c) shows a YZ cross-sectional view of FIG. In FIG. 3A, the flow of exhaust gas is indicated by white arrows, and in FIG. 3C, the flow of exhaust gas is indicated by arrows. In addition, in order to facilitate understanding, the collection layer 350 is omitted in FIGS. 3B and 3C. Further, in FIG. 3 according to the present embodiment, the X axis, the Y axis (exhaust gas flow direction, the extending direction of the exhaust passage 140), and the Z axis that intersect perpendicularly are defined as illustrated.

  As shown in FIG. 3A, the filter device 220 is a wall flow type device and includes a filter structure 310 and a collection layer 350. As illustrated in FIGS. 3B and 3C, the filter structure 310 includes a filter unit 320, an upstream plug portion 330, and a downstream plug portion 340.

  The filter unit 320 includes a cylindrical outer cylinder 322 and a filter wall 324 that allows exhaust gas to pass therethrough. Further, as will be described in detail later, a collection layer 350 is laminated on the filter wall 324.

  In FIG. 3, the filter wall 324 is provided on a plane parallel to the XY plane, the first wall 324 a extending in the Y axis direction, and a plane parallel to the YZ plane, and in the Y axis direction. The second wall 324b extends. Then, as shown in FIG. 3B, the space surrounded by the two first walls 324a and the two second walls 324b, or the first wall 324a, the second wall 324b, and the outer cylinder 322 are surrounded. A space is formed as the cell 326.

  Accordingly, the plurality of cells 326 extend in the axial direction (Y-axis direction in FIG. 3) in the outer cylinder 322 (filter unit 320) and are orthogonal to the axial direction (X-axis direction in FIG. 3). And in the Z-axis direction). Note that the number of cells 326 is not limited.

  As shown in FIG. 3C, among the cells 326, the cell 326A classified into the first cell group has the upstream upstream opening 328a sealed with the upstream plug portion 330, and the other In the cell 326 (the cell 326B classified into the second cell group), the downstream opening 328b on the downstream side is sealed with the downstream plug 340.

  In the filter structure 310, since the cells 326A and the cells 326B are alternately arranged, the exhaust gas that has reached the filter structure 310 (filter device 220) is introduced into the cell 326B and the filter wall that partitions the cell 326B. It passes through 324 and is introduced into cell 326A. At this time, in the process of passing through the filter wall 324, particulate matter contained in the exhaust gas is captured by the filter wall 324 (a hole 360 described later). Then, the exhaust gas introduced into the cell 326A is guided to the muffler 142 (see FIG. 1) through the opening on the downstream side of the cell 326A.

  Hereinafter, the collection layer 350 disposed on the filter wall 324 will be specifically described. FIG. 4 is a diagram illustrating the collection layer 350 in the filter device 220.

  As shown in FIG. 4, the collection layer 350 is stacked on a surface (upstream surface) 324 c located on the upstream side in the exhaust gas flow direction (Z-axis direction in FIG. 4) in the filter wall 324. The collection layer 350 includes a plurality of carbon particles having the same structure as the carbon particles (for example, amorphous carbon) contained in the soot in the exhaust gas. The collection layer 350 is formed by being applied (sprayed) from the upstream side of the filter wall 324. The thickness of the collection layer 350 (the length in the Z-axis direction in FIG. 4) is thinner than the thickness of the filter wall 324. The collection layer 350 is applied to the filter wall 324 to such an extent that the holes formed in the filter wall 324 are not blocked.

  By providing the collection layer 350, the filter device 220 can improve the collection rate of the particulate matter in the initial state. Hereinafter, first, problems of the conventional filter device will be described, and then the filter device 220 of the present embodiment will be described.

  FIG. 5 is a conceptual diagram illustrating the trapping of particulate matter by the conventional filter device 10. As shown in FIG. 5A, the conventional filter device 10 includes only the filter wall 324 and does not include the collection layer 350. The hole 360 formed in the filter wall 324 has a channel cross-sectional area that is not constant and is curved.

  The conventional filter device 10 differs in the collection rate of particulate matter according to the accumulation state of particulate matter (indicated by black circles in FIG. 5). More specifically, the probability that the particulate matter can pass through the hole 360 varies depending on the amount of the particulate matter deposited in the hole 360. As shown in FIG. 5B, in the initial state in which the particulate matter is not trapped in the hole 360 (the state in which the amount of particulate matter deposited in the hole 360 is zero or small), Has no particulate matter attached. Therefore, the particulate matter that has reached the conventional filter device 10 is likely to slip through (highly likely to pass through), and the particulate matter is likely to pass through without being captured by the holes 360. That is, the particulate matter passes through the hole 360 of the filter wall 324 and flows out downstream of the filter wall 324. Therefore, in the initial state, the collection rate of the filter wall 324 is low.

  On the other hand, when the particulate matter adheres (deposits) to the wall surface of the hole 360 of the filter wall 324 as the usage time (exhaust gas passage time) of the conventional filter device 10 increases, FIG. As shown, the flow path (hole 360) is narrowed by the attached particulate matter, and the particulate matter contained in the exhaust gas is easily captured (depth filtration). For this reason, when the accumulation amount of the particulate matter in the hole 360 increases, the probability that the particulate matter can pass through the hole 360 is lowered, and the collection rate is improved.

  Thus, in the conventional filter device 10, when the usage time exceeds a predetermined time, the collection rate is improved to a predetermined value, but in the initial state, the collection rate is low.

  FIG. 6 is a conceptual diagram illustrating the trapping of the particulate matter by the filter device 220 of the present embodiment. As shown in FIG. 6A, the collection layer 350 of the filter device 220 is stacked on the upstream surface 324 c of the filter wall 324. As shown in FIG. 6A, in the initial state, on the wall surface of the hole 360 constituting the filter wall 324 of the filter device 220, the particulate matter (black circles in FIG. Is not attached. However, in the filter device 220, the collection layer 350 is stacked on the upstream surface 324 c of the filter wall 324. Therefore, in the initial state, the particulate matter contained in the exhaust gas is captured by the collection layer 350 (surface filtration). For this reason, the collection rate can be improved in the initial state. Note that exhaust gas other than the particulate matter passes through the collection layer 350 and flows into the holes 360.

  Then, when the usage time of the filter device 220 elapses and the differential pressure detected by the differential pressure sensor 230 exceeds a predetermined upper limit value, a regeneration process is performed. Then, as shown in FIG. 6 (b), the carbon particles and part of the particulate matter constituting the trapping layer 350 are burned, and become small particles that adhere to the wall surface of the hole 360. Thereby, in addition to the collection layer 350, the particulate matter contained in the exhaust gas is captured by the small particles (particulate matter) attached to the holes 360. That is, in the filter device 220, surface layer filtration and depth layer filtration are performed, and the collection rate of the particulate matter is improved.

  Thereafter, by repeating the regeneration process, the collection layer 350 can be burned out, and the pressure loss due to the collection layer 350 can be reduced. Even if the trapping layer 350 is burned out, the amount of particulate matter deposited in the holes 360 is maintained at a predetermined amount, so that the trapping rate is maintained at a predetermined value or more.

  As described above, the filter device 220 of the present embodiment can improve the collection rate of the particulate matter in the initial state by including the collection layer 350. In addition, since the collection layer 350 includes carbon particles, the collection layer 350 can be gradually reduced by the regeneration process. Therefore, as the usage time elapses, it is possible to ensure the same collection rate as that of the conventional filter device 10 and to avoid an increase in pressure loss.

  Moreover, as described above, the collection layer 350 includes a plurality of carbon particles contained in the soot. Thereby, the affinity (adsorption rate) with the particulate matter can be improved, and the collection rate can be improved. Moreover, since the carbon particles contained in the soot have static electricity, the adsorption rate of the particulate matter is high. Therefore, the collection layer 350 can further improve the collection rate.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  In the above embodiment, the filter device 220 has been described by taking a wall flow type filter device as an example. However, the configuration of the filter device 220 is not limited as long as it has a filter wall in which a plurality of holes through which the particulate matter contained in the exhaust gas is captured and the exhaust gas passes are formed.

  Moreover, in the said embodiment, the case where the collection layer 350 was comprised including multiple carbon particles contained in the soot was mentioned as an example, and was demonstrated. However, there is no limitation on the carbon particles constituting the collection layer 350. For example, graphite or other amorphous carbon (for example, activated carbon) may be adopted as the carbon particles constituting the collection layer 350.

  Further, in the above-described embodiment, the configuration in which the collection layer 350 is disposed on the upstream surface 324c of the filter wall 324 has been described as an example. However, as long as the collection layer 350 is provided on the filter wall 324, the installation position is not limited.

  The present invention can be used in a filter device that captures particulate matter contained in exhaust gas.

220 Filter Device 320 Filter Unit 324 Filter Wall 326A, 326B Cell 330 Upstream Plug Portion 340 Downstream Plug Portion 350 Collection Layer

Claims (3)

A filter wall having a plurality of holes through which the exhaust gas passes while capturing particulate matter contained in the exhaust gas;
A collection layer provided on the filter wall and comprising a plurality of carbon particles;
A filter device comprising:   2. The filter device according to claim 1, wherein the collection layer is disposed on a surface of the filter wall that is located on an upstream side in a flow direction of the exhaust gas.   The filter device according to claim 1 or 2, wherein the collection layer includes carbon particles having the same structure as the carbon particles contained in the soot in the exhaust gas.

Images