JP2017025740A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable appropriate estimation of the amount of PMs accumulated on a DPF.SOLUTION: An exhaust emission control device includes: a PM sensor 60 capable of detecting the amount of PMs trapped; a differential pressure sensor 54 for detecting a differential pressure between the upstream side and the downstream side of a DPF 220; a pressure sensor 53 for detecting a pressure on the upstream side of the DPF 220; a temperature sensor 52 for detecting an exhaust gas temperature on the upstream side of the DPF 220; a path dependent exhaust gas amount estimating part 42 for estimating a first exhaust gas amount flowing into a bypass flow path 130 on the basis of the differential pressure, the pressure on the upstream side, and the exhaust gas temperature, detecting a total exhaust gas amount flowing from a DOC 210 to the downstream side, and calculating a second exhaust gas amount flowing into the DPF 220; and a DPF PM amount estimating part 44 for estimating the amount of PMs accumulated on the DPF 220 on the basis of the ratio between the first exhaust gas amount and the second exhaust gas amount, and the amount of PMs trapped by the PM sensor 60.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust emission control device capable of estimating the amount of PM deposited in a diesel particulate filter (Diesel Particulate Filter: DPF) that collects particulate matter (PM) provided in an exhaust system. About.

  As an exhaust purification catalyst provided in an exhaust system of a diesel engine or the like, an oxidation catalyst (Diesel Oxidation Catalyst: DOC) that oxidizes hydrocarbon (HC), carbon monoxide (CO), and nitrogen monoxide (NO) contained in exhaust gas. ), DPFs and the like that collect PM contained in exhaust gas are known.

  As a method of regenerating the function of the DPF by removing the PM collected and accumulated in the DPF, the gas temperature is forcibly increased by oxidizing hydrocarbons with an oxidation catalyst arranged upstream of the DPF. So-called forced regeneration, in which PM accumulated on the DPF is incinerated, is known.

  The standard for starting execution of forced regeneration is, for example, when the amount of PM accumulated in the DPF exceeds a predetermined threshold.

  As a method for estimating the amount of PM collected and accumulated in the DPF, for example, the capacitance is changed according to the amount of PM accumulated in the bypass flow path connecting the inlet side and the outlet side of the DPF. The sensor (PM sensor) to be disposed and the PM amount of the DPF is estimated based on the PM amount accumulated on the sensor, or the capacity of the sub exhaust line branched from the main exhaust line where the DPF is disposed A method of estimating the amount of PM deposited on the DPF based on the differential pressure between the inlet side and the outlet side of the sub DPF is known (see, for example, Patent Document 1). ).

JP 2012-184768 A

  For example, a sensor that changes the capacitance according to the amount of accumulated PM is disposed in a bypass flow path that connects the inlet side and the outlet side of the DPF, and the DPF is based on the amount of PM accumulated on the sensor. In the method for estimating the amount of PM, for example, the amount of PM deposited in the DPF was estimated on the assumption that the ratio of the amount of exhaust gas flowing to the sensor side and the amount of exhaust gas flowing to the DPF side is constant. .

  For example, when PM accumulates on the DPF or sensor, the ratio of the amount of exhaust gas flowing between the sensor side and the DPF side changes, so the ratio of the amount of exhaust gas flowing between the sensor side and the DPF side is assumed to be constant. The estimated PM amount deviates from the actual PM amount.

  For example, in the case where forced regeneration is executed based on the estimated PM amount, if the estimated PM amount has deviated from the actual PM amount, the forced regeneration is not yet required. There is a possibility that the forced regeneration is performed or the forced regeneration is not performed when the forced regeneration is necessary.

  An object of the present invention is to provide a technique capable of appropriately estimating the amount of PM accumulated in a DPF.

  In order to achieve the above object, an exhaust emission control device according to one aspect of the present invention includes an oxidation catalyst capable of oxidizing hydrocarbons in exhaust gas, and particulate matter in exhaust gas provided on the exhaust gas downstream side of the oxidation catalyst. An exhaust emission control device comprising: a filter capable of collecting; and a forced regeneration means capable of performing forced regeneration by supplying hydrocarbons to an oxidation catalyst and burning and removing particulate matter deposited on the filter. A bypass channel that connects the upstream side and the downstream side of the exhaust gas, and particles that are arranged in the bypass channel and that can collect particulate matter in the exhaust gas flowing through the bypass channel and detect the amount of collected particulate matter A particulate matter sensor, a differential pressure detecting means for detecting a differential pressure between the exhaust upstream side and the exhaust downstream side of the filter, a pressure detecting means for detecting a pressure on the exhaust upstream side of the filter, and an exhaust gas flowing through the exhaust upstream side of the filter Detecting the temperature of the exhaust Based on the degree of pressure detection means, the total exhaust gas amount detection means for detecting the total exhaust gas amount flowing from the oxidation catalyst to the exhaust downstream side, the differential pressure, the pressure on the upstream side of the exhaust gas, and the temperature of the exhaust gas. Sensor-side exhaust gas amount estimating means for estimating the first exhaust gas amount flowing in; filter-side exhaust gas estimating means for estimating the second exhaust gas amount flowing into the filter by subtracting the first exhaust gas amount from the total exhaust gas amount; The amount of particulate matter on the filter side for estimating the amount of particulate matter accumulated on the filter based on the ratio of the amount of exhaust gas 1 and the amount of second exhaust gas and the amount of particulate matter collected by the particulate matter sensor And estimating means.

  In the exhaust emission control device, the sensor side increase amount detection that detects the increase amount of the particulate matter deposited on the particulate matter sensor from a predetermined time point based on the particulate matter amount detected by the particulate matter sensor. The filter-side particulate matter amount estimation means is deposited on the filter based on the ratio between the first exhaust gas amount and the second exhaust gas amount and the increase amount of the particulate matter in the particulate matter sensor. The amount of particulate matter that has accumulated from a certain point in time is identified, and the amount of particulate matter that has accumulated on the filter at a certain point in time is increased from the certain point in time. You may make it estimate the amount of particulate matter currently accumulated in the said filter by adding quantity.

  In the exhaust purification apparatus, the sensor-side exhaust gas amount estimation means may estimate the first exhaust gas amount based on a relationship indicated by a Darcy-Weissbach pressure loss equation.

  Further, in the exhaust purification device, forced regeneration is executed by the forced regeneration means when the particulate matter amount deposited on the filter estimated by the filter side particulate matter amount estimation means exceeds a predetermined first threshold value. Further, a filter regeneration control unit may be provided.

  The exhaust emission control device further includes sensor regeneration control means for regenerating the filter member of the particulate matter sensor when the amount of particulate matter deposited on the particulate matter sensor exceeds a predetermined second threshold value. You may do it.

  According to the present invention, it is possible to appropriately estimate the amount of PM accumulated in the DPF.

1 is a schematic configuration diagram illustrating an exhaust system of a vehicle engine to which an exhaust emission control device according to an embodiment of the present invention is applied. (A) is a typical perspective view of PM sensor concerning one embodiment of the present invention, and (B) is a typical exploded perspective view of PM sensor concerning one embodiment of the present invention. 1 is a block diagram showing an electronic control unit and related components constituting an exhaust emission control device according to an embodiment of the present invention. It is a flowchart of the DPF side accumulation PM amount estimation processing in the exhaust gas purification apparatus according to one embodiment of the present invention. It is a timing chart explaining the timing of forced regeneration of DPF and forced regeneration of PM sensor in the exhaust emission control device concerning one embodiment of the present invention.

  Hereinafter, a vehicle according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram showing an exhaust system of an engine of a vehicle to which an exhaust emission control device according to an embodiment of the present invention is applied.

  In an exhaust pipe 110 of a diesel engine (hereinafter simply referred to as an engine) 100 in a vehicle, an oxidation catalyst 210 and a DPF 220 are provided in order from the exhaust upstream side.

  The oxidation catalyst 210 is formed, for example, by supporting a catalyst component on the surface of a ceramic carrier such as a cordierite honeycomb structure. When hydrocarbon (HC) is supplied to the oxidation catalyst 210 by an exhaust pipe injection device 120 described later or post-injection, the oxidation catalyst 210 oxidizes this to raise the exhaust gas temperature.

  The DPF 220 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of exhaust gas and alternately plugging the upstream side and the downstream side of these cells. The DPF 220 collects PM in the exhaust gas in the pores and surfaces of the partition walls, and when the amount of accumulated PM reaches a predetermined amount, so-called forced regeneration is performed to remove the PM. In forced regeneration, unburned fuel (HC) is supplied to the oxidation catalyst 210 by the exhaust pipe injection device 120 or post injection, and the exhaust temperature flowing into the DPF 220 is raised to the PM combustion temperature (for example, about 600 ° C.). Done. Further, the DPF 220 has an ability to oxidize unburned HC slipped without being oxidized by the upstream side oxidation catalyst 210.

  Further, a bypass passage 130 is formed between the oxidation catalyst 210 and the DPF 220 in the exhaust pipe 110 and between the exhaust downstream of the DPF 220. The bypass flow path 130 is provided with a PM sensor 60 that collects PM in the exhaust gas flowing through the bypass flow path 130 and outputs a sensor value (capacitance) corresponding to the amount of PM collected and accumulated. Yes. Details of the PM sensor 60 will be described later.

  An exhaust pipe injection device 120 is provided upstream of the oxidation catalyst 210 in the exhaust pipe 110. The exhaust pipe injection device 120 is an example of forced regeneration means, and injects unburned fuel (mainly HC) into the exhaust pipe 110 in response to an instruction signal output from an electronic control unit (hereinafter, ECU) 40. By doing so, the forced regeneration of the DPF 220 is performed. When post injection by multistage injection of engine 100 is used for forced regeneration, this exhaust pipe injection device 120 may be omitted.

  An oxidation catalyst inlet temperature sensor 51 is provided upstream of the oxidation catalyst 210 in the exhaust pipe 110, and a DPF inlet temperature sensor 52 and a pressure sensor 53 are provided between the oxidation catalyst 210 and the DPF 220. It has been. Further, a differential pressure sensor 54 is provided before and after the DPF 220.

  The oxidation catalyst inlet temperature sensor 51 detects the exhaust gas temperature upstream of the exhaust gas flowing into the oxidation catalyst 210. The DPF inlet temperature sensor 52 is an example of an exhaust gas temperature detection unit, and detects the temperature (exhaust gas temperature) of the exhaust gas (exhaust gas upstream of the DPF 220) flowing out from the oxidation catalyst 210. The pressure sensor 53 is an example of a pressure detection unit, and detects the pressure of exhaust gas flowing out from the oxidation catalyst 210 (exhaust gas upstream of the DPF 220). The differential pressure sensor 54 detects a differential pressure (ΔP) between the exhaust gas pressure on the exhaust upstream side of the DPF 220 and the exhaust gas pressure on the exhaust downstream side.

  Further, the vehicle is provided with a MAF sensor 55 and an accelerator opening sensor 56. MAF sensor 55 detects the amount of air (MAF) taken into engine 100. The accelerator opening sensor 56 detects the accelerator opening by the driver of the vehicle. The accelerator opening corresponds to the fuel injection amount Q in the engine 100.

  The detection values of the various sensors 51 to 56 are output to the electrically connected ECU 40.

  The ECU 40 controls the engine 100, the exhaust pipe injection device 120, and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like.

  FIG. 2A is a schematic perspective view of a PM sensor according to an embodiment of the present invention, and FIG. 2B is a schematic exploded perspective view of the PM sensor according to an embodiment of the present invention. It is.

  The PM sensor 60 includes a plurality of filter layers (filter members) 61, a plurality of first and second electrode plates 62 and 63, and conductive wires 64 and 65.

  The filter layer 61 is, for example, plugged alternately upstream and downstream of a plurality of cells that are partitioned by partition walls such as porous ceramics to form an exhaust passage, and these cells are arranged in parallel in one direction. It is formed in a rectangular parallelepiped shape. The PM contained in the exhaust gas flows into the cell C12 whose upstream side is plugged from the cell C11 whose downstream side is plugged, as indicated by a broken line arrow in FIG. It is collected and deposited on the partition wall surface and pores of the cell C11. In the following description, the cell flow path direction is the length direction of the PM sensor 60 (arrow L in FIG. 2A), and the direction orthogonal to the cell flow path direction is the width direction of each PM sensor 60 (FIG. 2 (A) arrow W).

  The first and second electrode plates 62 and 63 are, for example, plate-like conductive members, and are formed so that the outer dimensions in the length direction L and the width direction W are substantially the same as those of the filter layer 61. The first and second electrode plates 62 and 63 are alternately stacked with the filter layer 61 interposed therebetween, and are connected to a capacitance detection circuit (not shown) built in the ECU 40 via the conductive lines 64 and 65, respectively. ing.

  That is, the first electrode plate 62 and the second electrode plate 63 are arranged to face each other, and the filter layer 61 is sandwiched between the electrode plates 62 and 63, whereby the entire cell C11 forms a capacitor. . Thus, in the PM sensor 60, the entire cell C11 is made a capacitor by the flat electrode plates 62 and 63, so that the electrode surface area can be effectively secured, and the detectable capacitance absolute value can be obtained. It becomes possible to increase. In addition, since the interelectrode distance becomes the cell pitch and is made uniform, variations in the initial capacitance can be effectively suppressed.

  When PM accumulated in the cell C11 of the PM sensor 60 is removed by combustion, that is, when the PM sensor 60 is forcibly regenerated, a voltage is directly applied to the electrode plates 62 and 63, or the filter layer 61 and A heater substrate (not shown) is interposed between the electrode plates 62 and 63, and electric power is applied to the heater substrate and the like.

  FIG. 3 is a block diagram showing an electronic control unit and related components constituting the exhaust gas purification apparatus according to one embodiment of the present invention.

  The ECU 40 includes a flow resistance coefficient map 41, a total exhaust gas amount detection unit, a sensor side exhaust gas amount estimation unit, a path-specific exhaust gas amount estimation unit 42 as an example of a filter side exhaust gas amount estimation unit, and a sensor side increase amount detection unit. Sensor PM amount estimation unit 43 as an example, DPFPM amount estimation unit 44 as an example of filter-side particulate matter amount estimation means, filter regeneration control unit 45 as an example of filter regeneration control means and sensor regeneration control means, As a part of functional elements. Each of these functional elements will be described as being included in the ECU 40 which is an integral hardware, but any one of them can be provided in separate hardware.

The path-specific exhaust gas amount estimation unit 42 uses the equation (2) derived from the Darcy-Weissbach pressure loss equation shown in equation (1) to determine the amount of exhaust gas m ₁ [g / s] is estimated. Here, the exhaust gas amount m ₁ flowing into the bypass passage 130 corresponds to the first exhaust gas amount.

^{ΔP = α · ρ · v 2} /2 ··· (1)
m ₁ = S {2P · ΔP / (R ′ · T · α)} ^1/2 (2)
Note that ΔP [kPa] is a differential pressure detected by the differential pressure sensor 54. α is a flow resistance coefficient, which is obtained by referring to the flow resistance coefficient map 41. ρ [kg / m ³ ] is the exhaust gas density. v [m / s] is the flow rate of the exhaust gas. S [m ² ] is a cross-sectional area of the portion where the exhaust gas of the PM sensor 60 flows, and the value is stored in advance in the path-specific exhaust gas amount estimation unit 42. P [kPa] is the pressure of the exhaust gas upstream of the DPF 220 and is the pressure detected by the pressure sensor 53. R ′ is a gas constant of exhaust gas (for example, a value per kg of gas), and the value is stored in advance in the path-specific exhaust gas amount estimation unit 42. T is the temperature of the exhaust gas upstream of the DPF 220 and is the temperature detected by the DPF inlet temperature sensor 52.

  Here, the process of deriving equation (2) from the Darcy wise buffer pressure loss equation shown in equation (1) will be described.

The exhaust gas density ρ is expressed as shown in the following formula (3) using the exhaust gas volume flow rate V [m ³ / s] passing through the PM sensor 60.

ρ = m ₁ / V (3)
Further, the flow velocity v of the exhaust gas is expressed by the following equation (4) using the cross-sectional area S of the PM sensor 60.

v = V / S (4)
When Expressions (3) and (4) are substituted for ρ and v in Expression (1), the following Expression (5) is obtained.

ΔP = 1/2 · α · m ₁ · V / S ² (5)
The exhaust gas volume flow rate V is expressed as shown in the following formula (6) by using the exhaust gas pressure P and the exhaust gas temperature T upstream of the DPF 220 by the gas state equation.

V = m ₁ · R ′ · T / P (6)
By substituting this equation (6) into equation (5) and solving for m ₁ , the above equation (2) can be derived.

The path-specific exhaust gas amount estimation unit 42 uses the flow resistance based on the accumulated PM amount notified from the sensor PM amount estimation unit 43 for the flow resistance coefficient α shown in Equation (2) for estimating the exhaust gas amount m _1. This is obtained by referring to the coefficient map 41.

Further, the path-specific exhaust gas amount estimating section 42, a DPF220, total exhaust gas flowing out of the PM sensor 60., i.e., estimates the total amount of exhaust gas _{m 3.} Here, the total exhaust gas amount m ₃ is the same as the exhaust gas amount m ₀ flowing out of the oxidation catalyst 210. The exhaust gas amount m ₃ is calculated by the equation (7).

m ₃ = MAF + Q (7)
Here, MAF is a detection value detected by the MAF sensor 55, and Q is a fuel injection amount detected by the accelerator opening sensor 56.

Further, the path-specific exhaust gas amount estimation unit 42 calculates the exhaust gas amount m ₂ (second exhaust gas amount) flowing into the DPF 220 by the equation (8).

m ₂ = m ₃ −m ₁ (8)
The path-specific exhaust gas amount estimation unit 42 notifies the DPFPM amount estimation unit 44 of the calculated exhaust gas amount m ₁ flowing into the PM sensor 60 and the exhaust gas amount m ₂ flowing into the DPF 220.

  The flow resistance coefficient map 41 is a map showing a correspondence relationship between the flow resistance coefficient α in the PM sensor 60 and the amount of PM accumulated on the PM sensor 60 (sensor-side accumulated PM amount). According to this map, the flow resistance coefficient α in the PM sensor 60 at that time can be specified from the sensor side accumulated PM amount of the PM sensor 60. The flow resistance coefficient α tends to increase as the sensor-side accumulated PM amount increases.

  The correspondence relationship between the flow resistance coefficient α and the sensor-side accumulated PM amount can be grasped by conducting an experiment using the PM sensor 60, for example. More specifically, for example, in the case where a plurality of sensor-side accumulated PM amounts of the PM sensor 60 are changed, various data are measured by flowing gas, and the following formula (9) modified from formula (1): ) Can be used to calculate the corresponding flow resistance coefficient α.

α = 2 · ΔP / ρ · v2 (9)
Here, ΔP [N / m ² ] is the differential pressure between the upstream and downstream of the PM sensor 60, ρ [kg / m ³ ] is the gas density, and v [m / s] is the gas flow velocity. It is. Note that ρ can be grasped from the characteristics of the gas used by measuring the gas temperature in the experiment, and the flow velocity v is obtained by measuring the gas flow rate in the experiment, and the sectional area of the gas flow path of the PM sensor 60. This can be determined by dividing by S.

  The sensor PM amount estimation unit 43 estimates the amount of PM accumulated on the PM sensor 60 (sensor-side accumulated PM amount) based on the capacitance of the PM sensor 60 detected by a capacitance detection circuit (not shown). The sensor-side accumulated PM amount is notified to the path-specific exhaust gas amount estimation unit 42 and the filter regeneration control unit 45. Here, the sensor-side accumulated PM amount has a predetermined relationship (for example, a proportional relationship) with respect to the difference in capacitance from the capacitance in the initial state (or the state immediately after the forced regeneration). Alternatively, it can be estimated by specifying the difference in capacitance from the capacitance in the state immediately after forced regeneration).

  Further, the sensor PM amount estimating unit 43 calculates the difference between the sensor-side accumulated PM amount at the previous estimation (processing timing) and the sensor-side accumulated PM amount at the current estimation, that is, the current estimation from the previous estimation. The PM amount increased by the time (sensor-side increased PM amount) is specified sequentially (for example, every predetermined time), and the sensor-side increased PM amount is notified to the DPFPM amount estimating unit 44. When the notification that the PM sensor 60 has been forcibly regenerated is received from the filter regeneration control unit 45, the sensor PM amount estimation unit 43 sets the sensor-side accumulated PM amount at the time of the previous estimation to 0, At the next processing timing, the difference from 0 is specified as the sensor-side increased PM amount.

The DPFPM amount estimation unit 44 estimates immediately before based on the sensor-side increased PM amount notified from the sensor PM amount estimation unit 43 and the exhaust gas amounts m ₁ and m ₂ notified from the path-specific exhaust gas amount estimation unit 42. The amount of PM increase in the DPF 220 from the time (DPF side increase PM amount) is estimated. In the present embodiment, the estimated DPFPM amount 44 is obtained by multiplying the sensor-side increased PM amount by the ratio (m ₂ / m ₁ ) of the amount of exhaust gas flowing between the DPF 220 and the PM sensor 60, thereby increasing the DPF-side increased PM. Calculate the amount.

  Next, the DPFPM amount estimating unit 44 adds the estimated DPF-side increased PM amount to the DPF-side accumulated PM amount at the time of the previous estimation stored by itself, thereby calculating the DPF estimated PM amount at that time (current time). And the filter regeneration control unit 45 is notified of the updated DPF estimated PM amount. The DPFPM amount estimating unit 44 sets the DPF-side accumulated PM amount to 0 when receiving a notification from the filter regeneration control unit 45 that the DPF 220 has been forcibly regenerated.

  The filter regeneration control unit 45 controls execution of forced regeneration on the DPF 220 when the DPF-side accumulated PM amount notified from the DPFPM amount estimating unit 44 exceeds a predetermined threshold (first threshold). In the forced regeneration, the filter regeneration control unit 45 causes the exhaust pipe injecting device 120 to inject hydrocarbons so that the inlet temperature of the DPF 220 becomes a predetermined target temperature. In the forced regeneration process of the DPF 220, part of the exhaust gas also flows into the bypass flow path 130, so that the PM accumulated in the PM sensor 60 is combusted, that is, the PM sensor 60 is forced as well. Will be played.

  Further, the filter regeneration control unit 45 controls execution of forced regeneration on the PM filter 60 when the filter-side accumulated PM amount exceeds a predetermined threshold (second threshold). In forced regeneration with respect to the PM filter 60, the filter regeneration control unit 45 applies a voltage directly to the electrode plates 62 and 63, or powers the heater substrate established between the filter layer 61 and the electrode plates 62 and 63. Is added, the inside of the PM filter 60 is heated, and the PM in the PM sensor 60 is incinerated.

  When the forced regeneration for the PM filter 60 is performed, the filter regeneration control unit 45 notifies the sensor PM amount estimating unit 43 to that effect. When the forced regeneration is performed for the DPF 220, the filter regeneration control unit 45 informs the sensor PM amount. The estimation unit 43 and the DPFPM amount estimation unit 44 are notified.

  Next, the DPF-side accumulated PM amount estimation processing for estimating the DPF-side accumulated PM amount executed by the exhaust purification device will be described.

  FIG. 4 is a flowchart of DPF-side accumulated PM amount estimation processing in the exhaust gas purification apparatus according to one embodiment of the present invention.

  The DPF-side accumulated PM amount estimation process is started simultaneously with, for example, turning on the power of the vehicle (key switch of the ignition switch is turned on).

  The path-specific exhaust gas amount estimation unit 42 refers to the flow resistance coefficient map 41 based on the sensor-side accumulated PM amount notified from the sensor PM amount estimation unit 43 to obtain the flow resistance coefficient α used for the calculation. (S11).

  Next, the path-specific exhaust gas amount estimation unit 42 acquires the differential pressure ΔP from the differential pressure sensor 54 (S12), acquires the temperature T from the DPF inlet temperature sensor 52, and acquires the pressure P of the exhaust gas from the pressure sensor 53 ( S13).

Next, the path-specific exhaust gas amount estimation unit 42 uses the MAF by the MAF sensor 55 and the fuel injection amount Q corresponding to the accelerator opening by the accelerator opening sensor 56 to cause the total exhaust gas to flow out from the DPF 220 and the PM sensor 60. m ₃ is estimated (S14).

Next, the path-specific exhaust gas amount estimation unit 42 estimates the exhaust gas amount m ₁ [g / s] flowing into the bypass passage 130 using the equation (2) derived from the relationship of the pressure loss equation of Darcy Weisbach. (S15).

Next, the path-specific exhaust gas amount estimation unit 42 calculates the exhaust gas amount m ₂ flowing into the DPF 220 according to the equation (8), and calculates the exhaust gas amount m ₂ flowing into the DPF 220 and the exhaust gas amount flowing into the bypass passage 130. and m _1, and notifies the DPFPM amount estimating unit 44 (S16).

  Next, the sensor PM amount estimation unit 43 estimates the amount of PM accumulated on the PM sensor 60 (sensor-side accumulated PM amount) based on the capacitance detected from the PM sensor 60, and at the time of the previous estimation. The difference between the sensor-side accumulated PM amount and the sensor-side accumulated PM amount at the time of the current estimation, that is, the PM amount (sensor-side increased PM amount) increased from the immediately preceding estimated value to the current estimation time is specified, and the sensor The side increase PM amount is notified to the DPFPM amount estimation unit 44 (S17).

Next, the DPFPM amount estimation unit 44 immediately before the sensor-side increased PM amount notified from the sensor PM amount estimation unit 43 and the exhaust gas amounts m ₁ and m ₂ notified from the path-specific exhaust gas amount estimation unit 42. The PM increase amount (DPF side increase PM amount) in the DPF 220 from the time of the estimation is estimated (S18).

  Next, the DPFPM amount estimation unit 44 adds the DPF-side increased PM amount estimated in step S18 to the DPF-side accumulated PM amount stored at the time of the previous estimation, which is stored by itself, at that time (current time). The DPF estimated PM amount is updated, the updated DPF estimated PM amount is notified to the filter regeneration control unit 45 (S19), and the process proceeds to step S11.

According to this DPF-side accumulated PM amount estimation process, the ratio between the exhaust gas amount m ₂ flowing into the DPF 220 and the exhaust gas amount m ₁ flowing into the bypass passage 130 is estimated, and captured by the PM sensor 60 based on the ratio. Since the amount of PM accumulated in the DPF 220 is estimated from the amount of PM that has been produced, the ratio between the amount of exhaust gas m ₂ flowing into the DPF 220 and the amount of exhaust gas m ₁ flowing into the bypass passage 130 changes. Even in this case, the amount of PM accumulated in the DPF 220 can be estimated appropriately.

  FIG. 5 is a timing chart for explaining the timing of the forced regeneration of the DPF and the forced regeneration of the PM sensor in the exhaust gas purification apparatus according to one embodiment of the present invention. Note that the scale of the vertical axis of the DPF-side accumulated PM amount and the vertical axis indicating the PM sensor-side accumulated PM amount are different.

  Here, it is assumed that the accumulated PM amounts of the DPF 220 and the PM sensor 60 are zero at time T0.

  When the operation of the engine 100 of the vehicle on which the exhaust purification device is mounted is started, the amount of accumulated PM in the DPF 220 and the PM sensor 60 sequentially increases. The sensor-side accumulated PM amount is estimated by the sensor PM amount estimating unit 43, and the DPF-side accumulated PM amount is estimated by the DPFPM amount estimating unit 44.

  Thereafter, at time T1, the sensor-side accumulated PM amount reaches the second threshold value, and as a result, the filter regeneration control unit 45 performs forced regeneration on the PM sensor 60. As a result, the PM sensor 60 is regenerated and the sensor-side accumulated PM amount becomes zero.

  Further, when the operation of the engine 100 is continued, at time T2, the sensor-side accumulated PM amount reaches the second threshold again, and as a result, the filter regeneration control unit 45 executes forced regeneration on the PM sensor 60. As a result, the PM sensor 60 is regenerated and the sensor-side accumulated PM amount becomes zero.

  Furthermore, when the operation of the engine 100 is continued, at time T3, the DPF-side accumulated PM amount reaches the first threshold value, and as a result, the filter regeneration control unit 45 executes forced regeneration on the DPF 220. Here, in the forced regeneration with respect to the DPF 220, a part of the exhaust gas also flows into the bypass flow path 130, so that the forced regeneration with respect to the PM sensor 60 is performed. As a result, the sensor-side accumulated PM amount and the DPF-side accumulated PM amount become zero.

  Further, when the operation of the engine 100 is continued, at time T4, the sensor-side accumulated PM amount reaches the second threshold again, and as a result, the filter regeneration control unit 45 executes forced regeneration on the PM sensor 60. As a result, the PM sensor 60 is regenerated and the sensor-side accumulated PM amount becomes zero.

  As described above, in the exhaust gas purification apparatus according to this embodiment, the forced regeneration for the DPF 220 can be executed at an appropriate timing.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

For example, in the above-described embodiment, in the DPF deposition PM amount estimation process, the processes of steps S11 to S16 are always performed before the processes of steps S17 to S19 are performed to obtain the latest m ₁ and m ₂ . However, if there is not much change in the ratio of m ₁ and m ₂ , the processing in steps S11 to S16 may be temporarily omitted and the processing in steps S16 to S19 may be repeatedly executed. Good.

  In the above embodiment, the DPF inlet temperature sensor 52 is provided between the oxidation catalyst 210 and the DPF 220 to detect the exhaust temperature of the inlet of the DPF 220. However, the present invention is not limited to this, for example, The exhaust gas temperature at the inlet of the DPF 220 is estimated (detected) by adding the amount of heat generated at the oxidation catalyst 210 to the value detected by the oxidation catalyst inlet temperature sensor 51 disposed at the inlet of the oxidation catalyst 210. Also good.

40 ECU
41 Flow resistance coefficient map 42 Path-specific exhaust gas amount estimation unit 43 Sensor PM amount estimation unit 44 DPFPM amount estimation unit 45 Filter regeneration control unit 52 DPF inlet temperature sensor 53 Pressure sensor 54 Differential pressure sensor 55 MAF sensor 56 Accelerator opening sensor 60 PM Sensor 100 Engine 110 Exhaust pipe 120 Exhaust pipe injection device 130 Bypass passage 210 Oxidation catalyst 220 DPF

Claims (5)

An oxidation catalyst capable of oxidizing hydrocarbons in the exhaust, a filter provided on the exhaust downstream side of the oxidation catalyst and capable of collecting particulate matter in the exhaust, and supplying the hydrocarbons to the oxidation catalyst and supplying the filter An exhaust purification device comprising forced regeneration means capable of performing forced regeneration to burn and remove particulate matter deposited on
A bypass flow path connecting the exhaust upstream side of the filter and the exhaust downstream side;
A particulate matter sensor that is disposed in the bypass passage, collects particulate matter in the exhaust gas flowing through the bypass passage, and can detect the amount of the collected particulate matter;
Differential pressure detecting means for detecting a differential pressure between the exhaust upstream side and the exhaust downstream side of the filter;
Pressure detecting means for detecting the pressure on the exhaust upstream side of the filter;
Exhaust temperature detecting means for detecting the temperature of the exhaust flowing on the exhaust upstream side of the filter;
A total exhaust gas amount detecting means for detecting the total exhaust gas amount flowing from the oxidation catalyst to the exhaust downstream side;
Sensor-side exhaust gas amount estimation means for estimating a first exhaust gas amount flowing into the bypass flow path based on the differential pressure, the exhaust upstream pressure, and the exhaust temperature;
Filter-side exhaust gas amount estimating means for calculating a second exhaust gas amount flowing into the filter by subtracting the first exhaust gas amount from the total exhaust gas amount;
A filter that estimates the amount of particulate matter accumulated in the filter based on the ratio between the first amount of exhaust gas and the amount of second exhaust gas and the amount of particulate matter collected by the particulate matter sensor Side particulate matter amount estimation means;
Exhaust gas purification apparatus. Sensor-side increase amount detection means for detecting an increase amount of the particulate matter deposited on the particulate matter sensor from a predetermined time point based on the particulate matter amount detected by the particulate matter sensor Prepared,
The filter-side particulate matter amount estimation means is deposited on the filter based on a ratio between the first exhaust gas amount and the second exhaust gas amount and the increase amount of the particulate matter in the particulate matter sensor. The amount of increase in the particulate matter from the predetermined time point is specified, and the amount of the particulate matter deposited on the filter at the predetermined time point is added to the particulate matter deposited on the specified filter. The exhaust emission control device according to claim 1, wherein the amount of particulate matter accumulated in the filter at the present time is estimated by adding the amount of increase from the predetermined time. The exhaust gas purification apparatus according to claim 1 or 2, wherein the sensor side exhaust gas amount estimation means estimates the first exhaust gas amount based on a relationship indicated by a pressure loss equation of Darcy-Weissbach. Filter regeneration control for performing forced regeneration by the forced regeneration means when the particulate matter amount accumulated in the filter estimated by the filter side particulate matter amount estimation means exceeds a predetermined first threshold value The exhaust emission control device according to any one of claims 1 to 3, further comprising means. The sensor regeneration control means for regenerating the filter member of the particulate matter sensor when the amount of particulate matter deposited on the particulate matter sensor exceeds a predetermined second threshold value. The exhaust emission control device according to any one of 4.

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