JP2017031856A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable appropriate control of the temperature of gas to be supplied to the exhaust downstream via an oxidation catalyst.SOLUTION: An exhaust emission control device includes a basic injection amount determination part 44 for determining a basic injection amount to be supplied on the basis of an inlet temperature of a DOC 21, an exhaust gas flow amount, and a target temperature for an outlet temperature of the DOC 21, a first estimation part 46 for estimating a temperature change in the outlet temperature of the DOC 21 on the basis of a response model for the outlet temperature of the DOC 21 to a change in the supply amount of hydrocarbon, a second estimation part 47 for estimating the outlet temperature on the basis of a response model for the outlet temperature to a change in the inlet temperature of the DOC 21, a feedback operation part 49 for finding the corrected injection amount of the hydrocarbon to be corrected to eliminate a deviation between the estimated outlet temperature of the DOC 21 based on the temperature change in the estimated outlet temperature and the outlet temperature, and the detected outlet temperature, and a regeneration control part 41 for controlling a controlled injection amount obtained by adding the basic injection amount and the corrected injection amount to be output to an in-exhaust-pipe injection device 23.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust purification device that controls the gas temperature on the outlet side of a catalyst provided in an exhaust system.

  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. )It has been known. Further, a diesel particulate filter (DPF) that collects particulate matter (PM) contained in exhaust gas is also known.

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

  In forced regeneration, the higher the gas temperature, the higher the combustion efficiency of PM trapped in the DPF, so the processing time can be shortened and the deterioration of fuel consumption can be suppressed, but the DPF is damaged or carried by the DPF. There is a risk of causing deterioration of the catalyst.

  Therefore, temperature control for maintaining the gas temperature in forced regeneration at an appropriate temperature is required.

  For example, in forced regeneration, a technique for controlling the temperature of the DPF to be close to a predetermined target temperature is known (see, for example, Patent Document 1).

JP 2012-72666 A

  In the temperature control of the gas temperature in forced regeneration, it is very important to shorten the time until the temperature rises to the target temperature and to stabilize the gas temperature at the target temperature, and more appropriate temperature control is required. ing.

  An object of this invention is to provide the technique which can control appropriately the temperature of the gas supplied downstream of exhaust_gas | exhaustion via an oxidation catalyst.

  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 purification device comprising a filter capable of collection and a forced regeneration means capable of performing forced regeneration for supplying hydrocarbons to an oxidation catalyst and burning and removing particulate matter deposited on the filter, wherein the inlet of the oxidation catalyst Inlet temperature detecting means for detecting the inlet temperature which is the exhaust gas temperature of the exhaust gas, outlet temperature detecting means for detecting the outlet temperature which is the exhaust gas temperature of the outlet of the oxidation catalyst, and exhaust gas for detecting the flow rate of the exhaust gas passing through the oxidation catalyst Based on the gas flow rate detection means, the inlet temperature, the exhaust gas flow rate, and the target temperature of the oxidation catalyst outlet temperature, this is the amount of hydrocarbon injection that needs to be supplied to the oxidation catalyst to reach the target temperature. Basic jet Based on the basic injection amount determining means for determining the amount and the first response delay model showing the response of the outlet temperature of the oxidation catalyst to the change in the supply amount of hydrocarbon to the oxidation catalyst, the basic injection amount of hydrocarbon was supplied In the case where the inlet temperature is based on the first estimating means for estimating the temperature change of the oxidation catalyst outlet temperature and the second response delay model indicating the response of the oxidation catalyst outlet temperature to the change in the oxidation catalyst inlet temperature. The difference between the second estimation means for estimating the outlet temperature at the outlet, the estimated outlet temperature of the oxidation catalyst based on the estimated temperature change of the outlet temperature and the estimated outlet temperature, and the outlet temperature detected by the outlet temperature detecting means On the basis of the feedback calculation means for obtaining the corrected injection amount that is the hydrocarbon injection amount to be corrected to eliminate the deviation, and the control injection that adds the basic injection amount and the corrected injection amount. Having a reproduction control means for controlling so as to output the amount of forced regeneration means.

  In the exhaust purification apparatus, the first response delay model may be a model represented by a third-order damped vibration transfer function.

  In the above exhaust purification apparatus, the second response delay model may be a model represented by a third-order absolute convergence transfer function.

  The exhaust purification apparatus further includes a lead / lag adjusting means for adjusting a lead / lag of the phase with respect to the deviation, and the feedback calculation means has a correction injection amount for eliminating the deviation after the lead / lag adjustment. You may ask for it.

  In the exhaust gas purification apparatus, the advance / delay adjustment means may be a filter represented by a secondary advance / delay transfer function.

  According to the present invention, the temperature of the gas supplied to the exhaust downstream via the oxidation catalyst can be appropriately controlled.

1 is a schematic overall configuration diagram showing an intake / exhaust system of an engine to which an exhaust emission control device according to an embodiment of the present invention is applied. It is a block diagram which shows the electronic control unit and related component which concern on one Embodiment of this invention. It is a figure explaining the effect | action of the inlet temperature process part which concerns on one Embodiment of this invention. Feedback gain and noise when the advance / delay adjustment unit according to an embodiment of the present invention is configured with a secondary advance / delay filter and when the advance / delay adjustment unit according to the modification is configured with a primary advance / delay filter It is a figure explaining the influence of.

  Hereinafter, an exhaust emission control device 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 overall configuration diagram showing an intake / exhaust system of an engine to which an exhaust emission control device according to an embodiment of the present invention is applied.

  A diesel engine (hereinafter simply referred to as an engine) 10 is provided with an intake manifold 10a and an exhaust manifold 10b. An intake passage 11 for introducing fresh air is connected to the intake manifold 10a, and an exhaust passage 12 for releasing exhaust gas to the atmosphere is connected to the exhaust manifold 10b.

  In the intake passage 11, an air cleaner 30, a MAF sensor 31, a turbocharger compressor 32 a, an intercooler 33, and the like are provided in order from the intake upstream side. In the exhaust passage 12, a turbocharger turbine 32b, an exhaust aftertreatment device 20 and the like are provided in order from the exhaust upstream side. Also. The vehicle is provided with an outside temperature sensor 36. The outside air temperature sensor 36 detects the temperature of outside air. The detected value (outside temperature) of the outside temperature sensor 36 is output to an electrically connected ECU (electronic control unit) 40.

  The exhaust aftertreatment device 20 is configured by arranging a DOC 21 and a DPF 22 in order from the exhaust upstream side in a cylindrical catalyst case 20a. Also, the exhaust pipe injection device 23 is upstream of the DOC 21, the DOC inlet temperature sensor 25 is upstream of the DOC 21, the DOC outlet temperature sensor 26 is between the DOC 21 and the DPF 22, and the DPF outlet temperature sensor is downstream of the DPF 22. 27 are provided. Further, a differential pressure sensor 29 that detects a differential pressure between the upstream side and the downstream side of the DPF 22 is provided before and after the DPF 22.

  The exhaust pipe injection device 23 is an example of forced regeneration means, and in accordance with an instruction signal including a control injection amount output from the ECU 40, unburned fuel (mainly HC (hydrocarbon)) is supplied into the exhaust passage 12. Spray. In addition, when using post injection by the multistage injection of the engine 10, this in-pipe injection device 23 may be omitted. In the following description, the injection by the exhaust pipe injection device 23 will be mainly described as an example. However, when post injection is used, the operation with respect to the exhaust pipe injection device 23 and the operation by the exhaust pipe injection device 23 are the same as the engine 10. And the operation by the post injection of the engine 10 may be read.

  The DOC 21 is formed, for example, by supporting a catalyst component on the surface of a ceramic carrier such as a cordierite honeycomb structure. When HC is supplied by the in-pipe injection device 23 or post-injection, the DOC 21 oxidizes this and raises the exhaust temperature.

  The DPF 22 is formed, for example, by arranging a large number of cells partitioned by porous partition walls along the flow direction of the exhaust gas and alternately plugging the upstream side and the downstream side of these cells. The DPF 22 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 for performing combustion removal is executed. The forced regeneration is performed by supplying unburned fuel (HC) to the DOC 21 by the in-pipe injection device 23 or post injection, and raising the exhaust temperature flowing into the DPF 22 to the PM combustion temperature (for example, about 600 ° C.). . Further, the DPF 22 has an ability to oxidize unburned HC slipped without being oxidized by the upstream DOC 21.

  The DOC inlet temperature sensor 25 is an example of inlet temperature detection means, and detects the upstream exhaust gas temperature (hereinafter referred to as inlet temperature) flowing into the DOC 21. The DOC outlet temperature sensor 26 is an example of outlet temperature detection means, and detects the downstream exhaust gas temperature (hereinafter referred to as outlet temperature) flowing out from the DOC 21. This outlet temperature corresponds to the exhaust gas temperature upstream of the DPF 22. The DPF outlet temperature sensor 27 detects the exhaust gas temperature on the downstream side that flows out of the DPF 22 (hereinafter referred to as the DPF outlet temperature). The detection values of these temperature sensors 25 to 27 are output to the electrically connected ECU 40.

  The ECU 40 performs various controls of the engine 10, the exhaust pipe injection device 23, and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like.

  FIG. 2 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 regeneration control unit 41, an inlet temperature processing unit 42, an adjustment unit 43, a basic injection amount determination unit 44, an outlet temperature estimation unit 45, a feedback calculation unit 49, and an addition unit 55. As 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 regeneration control unit 41 is an example of a regeneration control unit, and starts the forced regeneration process when the detected value of the differential pressure sensor 29 becomes equal to or greater than a predetermined value. In the forced regeneration process, the regeneration control unit 41 outputs an outlet temperature (target temperature: 600 ° C., for example) targeted for the DOC 21 in the forced regeneration process to the adjusting unit 43. Further, the regeneration control unit 41 controls the exhaust pipe injection device 23 so as to inject the controlled injection amount of hydrocarbons input from the addition unit 55. This forced regeneration process is continuously executed, for example, for a predetermined time.

  The adjusting unit 43 subtracts the inlet temperature after processing in the inlet temperature processing unit 42 from the target temperature input from the regeneration control unit 41 to obtain a temperature difference from the target temperature, and determines the temperature difference as a basic injection amount. Input to the unit 44.

  The basic injection amount determination unit 44 is an example of a part of the exhaust gas flow rate detection unit and the basic injection amount determination unit, and the temperature difference input from the adjustment unit 43 and a common rail fuel injection device (not shown) within the engine 10. The injection amount (injection amount in the engine) to be injected, the air flow rate from the MAF sensor 31 (an example of a part of the exhaust gas flow rate detection means), and the outside air temperature from the outside air temperature sensor 36 are received. The basic injection amount determination unit 44 calculates the exhaust gas flow rate by adding the in-engine injection amount and the air flow rate. Next, the basic injection amount determination unit 44, based on the calculated exhaust gas flow rate, the temperature difference, and the outside air temperature, an injection amount (basic injection amount) corresponding to the amount of heat necessary for setting the outlet temperature of the DOC 21 to the target temperature. : Feed-forward value). The basic injection amount determined by the basic injection amount determination unit 44 is output to the outlet temperature estimation unit 45 and the addition unit 55.

  The basic injection amount determination unit 44 determines coefficients of transfer functions and gain values of each unit (inlet temperature processing unit 42, outlet temperature estimation unit 45, feedback calculation unit 49, etc.), and sets each unit. . For example, the coefficient of the transfer function of each part is optimal for a plurality of operating conditions (for example, conditions for at least one of exhaust gas flow rate, inlet temperature, outlet temperature, outside air temperature, or vehicle speed) in those operating conditions. A map in which values are associated with each other may be prepared in advance and determined from the map based on operating conditions detected by a sensor or the like. As for the gain of each part, a map in which correction values for the operating conditions are associated with a plurality of operating conditions is prepared in advance, and a predetermined calculation is performed based on the operating conditions detected by a sensor or the like. You may make it determine by correcting with respect to the value obtained by correcting by the correction value corresponding to the driving | running condition obtained from a map.

  The outlet temperature estimation unit 45 estimates the outlet temperature of the DOC 21 according to a DOC response delay model that approximates the response of the outlet temperature of the DOC 21. The outlet temperature estimation unit 45 includes a first estimation unit 46 as an example of first estimation means, a second estimation unit 47 as an example of second estimation means, and an addition unit 48.

  The first estimation unit 46 is based on a DOC response delay model that approximates a response of the outlet temperature of the DOC 21 to a change in the injection amount of forced regeneration hydrocarbons (a DOC response delay model for a change in injection amount: a first response delay model). Then, the rising temperature of the outlet temperature of the DOC 21 when the basic injection amount of hydrocarbons input from the basic injection amount determining unit 44 is supplied by the in-pipe injection device 23 is estimated, and the estimated rising temperature is output to the adding unit 48 To do.

Here, the transfer function G _r (s) in the complex number s region indicating the DOC response delay model with respect to the injection amount change with respect to the DOC 21 can be expressed by, for example, a third-order damped vibration transfer function shown in Expression (1).

G _r (s) = k _r / ((c * s ² + d * s + 1) (e * s + 1)) (1)
Here, _kr is a gain, and c, d, and e are coefficients. Further, since the response delay model with respect to the change in the injection amount is damped vibration, the coefficients c and d satisfy the discriminant, that is, satisfy d ² −4 * c * 1 <0. Hereinafter, the transfer function means a transfer function in a complex number s region.

  According to the DOC response delay model represented by the third-order damped vibration transfer function, the response of the outlet temperature of the DOC 21 to the change in the injection amount of the forced regeneration hydrocarbon can be approximated with high accuracy.

  The 1st estimation part 46 is comprised with the filter represented by the tertiary attenuation | damping vibration transfer function shown by Formula (2).

K _r / ((C * s ² + D * s + 1) (E * s + 1)) (2)
Here, _Kr is a gain, and C, D, and E are coefficients.

In the present embodiment, in Equation (2), K _r = k _r , C = c, D = d, and E = e are set. Therefore, the transfer function shown in the equation (2) of the first estimating unit 46 is the same as the transfer function of the DOC response delay model with respect to the injection amount change shown in the equation (1).

  Here, since the CPU in the ECU 40 can only perform operations that are discrete in time, strictly speaking, regarding the calculation of the transfer function in the complex S region by each functional unit in the ECU 40, strictly speaking, an appropriate function corresponding to the calculation of the transfer function is required. It is converted into a discrete function and executed. In this specification, for the sake of convenience, each functional unit will be described using a transfer function that is the basis of a discrete function calculation to be executed.

  The second estimation unit 47 calculates the DOC inlet temperature based on a DOC response delay model that approximates the response of the outlet temperature of the DOC 21 to a change in the inlet temperature of the DOC 21 (DOC response delay model for the inlet temperature change: second response delay model). The outlet temperature in the case of the inlet temperature detected by the sensor 25 is estimated, and the estimated outlet temperature is output to the adding unit 48.

Here, the transfer function G _t (s) indicating the DOC response delay model with respect to the inlet temperature change with respect to the DOC 21 can be expressed by, for example, a third-order absolute convergence transfer function represented by Expression (3).

G _t (s) = k _t / (f * s + 1) ³ (3)
Here, _{k t} is the gain, f is a coefficient.

  According to the DOC response delay model for the inlet temperature change represented by the third-order absolute convergence transfer function, the response of the outlet temperature of the DOC 21 to the change of the inlet temperature of the DOC 21 can be approximated with high accuracy.

  The 2nd estimation part 47 is comprised with the filter represented by the 3rd-order absolute convergence transfer function shown by Formula (4), for example.

K _t / (F * s + 1) ³ (4)
Here, K _t is a gain, and F is a coefficient.

In the present embodiment, in Equation (4), K _t = k _t and F = f are set. Therefore, the transfer function shown in the equation (4) of the second estimation unit 47 is the same transfer function as the DOC response delay model for the inlet temperature change shown in the equation (3).

  The adding unit 48 adds the temperature change of the outlet temperature estimated by the first estimating unit 46 and the outlet temperature estimated by the second estimating unit 47 to obtain the estimated outlet temperature, and feeds the estimated outlet temperature. Output to the back calculation unit 49. The estimated outlet temperature is an outlet temperature (control target temperature) that is a control target of feedback by the feedback calculation unit 49.

  The inlet temperature processing unit 42 performs advance compensation processing for advancing the response delay until the outlet temperature changes from the change in the injection amount in the first response delay model, with respect to the inlet temperature from the DOC inlet temperature sensor 25. The inlet temperature after the advance compensation processing is output to the adjusting unit 43. For example, the inlet temperature processing unit 42 includes a filter having a third-order advance / delay transfer function expressed by the following equation (5).

K _t * (C * s ² + D * s + 1) (E * s + 1) / (F * s + 1) ³ (5)
Here, K _t is a gain, and C, D, E, and F are coefficients.

In the present embodiment, in Expression (5), K _t = k _t , C = c, D = d, E = e, and F = f are set.

  The transfer function shown in Expression (5) of the inlet temperature processing unit 42 includes a denominator component of the transfer function shown in Expression (2) (Expression (1)) as a numerator component, and Expression (4) (Expression (3)) ) Including all components of the transfer function shown in FIG.

  According to the inlet temperature processing unit 42, the delay in the response of the outlet temperature to the change in the injection amount can be reflected in advance with respect to the change in the inlet temperature. For this reason, even if the inlet temperature of the DOC 21 fluctuates, the influence does not appear on the outlet temperature, so that the outlet temperature can be appropriately controlled to the target temperature. The details of the operation and effect of the inlet temperature processing unit 42 will be described later.

  The feedback calculation unit 49 is an example of a feedback calculation unit, and outputs a correction injection amount (feedback value) for correcting the basic injection amount based on the deviation between the control target temperature and the outlet temperature. Perform feedback control. The feedback calculation unit 49 includes an adjustment unit 50, an advance / delay adjustment unit 51, and a PID calculation unit 52.

  The adjusting unit 50 calculates a deviation between the control target temperature and the actual outlet temperature by subtracting the outlet temperature from the DOC outlet temperature sensor 26 from the control target temperature input from the outlet temperature estimating unit 45. Is output to the advance / delay adjustment unit 51.

  The advance / delay adjustment unit 51 is an example of an advance / delay adjustment unit. In order to improve the gain (feedback gain) in the feedback process with respect to the deviation input from the addition / subtraction unit 50, the advance / delay of the phase is delayed. And output to the PID calculation unit 52. The advance / delay adjustment unit 51 includes, for example, a filter (secondary advance / delay filter) represented by a second-order advance / delay transfer function shown in Expression (6).

(E * s + 1) / (G * s + 1) ² (6)
Here, E and G are coefficients.

  In the present embodiment, E = e is set in Equation (6).

  The PID calculation unit 52 includes a gain 53 and a PID control unit 54. The gain 53 gives a gain H to the deviation input from the advance / delay adjustment unit 51 and outputs the gain H to the PID control unit 54. The PID control unit 54 performs a calculation on the value input from the gain 53 based on the transfer function represented by Expression (7), and outputs the calculation result to the adding unit 55. Here, the calculation result by the PID control unit 54 corresponds to the corrected injection amount (feedback value).

(A * s ² + B * s + 1) / s (7)
Here, A and B are coefficients.

  In the present embodiment, in equation (7), A = c and B = d are set.

  The adder 55 adds the basic injection amount input from the basic injection amount determination unit 44 and the corrected injection amount input from the feedback calculation unit 49 to obtain the control injection amount, and regenerates the control injection amount. Output to the unit 41.

  Next, the operation and effect of the outlet temperature estimation unit 45 will be described.

As the gain and coefficient of the transfer function of the outlet temperature estimation unit 45, the gain and coefficient of the transfer function of the first response delay model and the second response delay model that match the operating conditions at that time are set. That is, the transfer functions k _r , k _t , c, d, e, and f of the first response delay model and the second response delay model that match the operating conditions are K _r , K _t , C, D, and E, respectively. , F.

  The outlet temperature estimation unit 45 uses the basic injection amount and the inlet temperature as inputs and estimates the control target temperature using the first and second response delay models corresponding to the actual DOC 21. The outlet temperature of the DOC 21 coincides with the possibility that these deviations become zero. That is, there is a high possibility that the deviation output from the adjusting unit 50 of the feedback calculation unit 49 becomes zero. For this reason, there is a high possibility that the corrected injection amount output by the feedback calculation unit 49 becomes zero. For this reason, it is possible to appropriately suppress the occurrence of overshooting and undershooting due to unnecessary insertion of the I term (integral term) of the PID control unit 54.

  Next, the operation and effect of the inlet temperature processing unit 42 will be described.

Here, the gains and coefficients of the transfer functions of the inlet temperature processing unit 42 and the outlet temperature estimation unit 45 include the gains and coefficients of the transfer functions of the first response delay model and the second response delay model that match the operating conditions at that time. Is set. That is, the transfer functions k _r , k _t , c, d, e, and f of the first response delay model and the second response delay model that match the operating conditions are K _r , K _t , C, D, and E, respectively. , F.

The adjusting unit 43 outputs the target temperature −K _t * (inlet temperature after passing through the filter 42) to the basic injection amount determining unit 44. The basic injection amount determination unit 44 calculates the basic injection amount by calculating (target temperature−K _t * (inlet temperature after passing through the filter 42)) / K _r and sends the basic injection amount to the outlet temperature estimation unit 45. Output.

When the basic injection amount indicated by (target temperature−K _t * (inlet temperature after passing through the filter 42)) / K _r is input to the first estimating unit 46 of the outlet temperature estimating unit 45, the first estimating unit 46 Is equivalent to the output shown in the range 63 of FIG. That is, the output of the first estimation unit 46 is equivalent to the target temperature (60) subtracted from the output obtained by inputting the inlet temperature to the filter 61 having the same transfer function as that of the second estimation unit 47. .

  Further, since the filter 61 and the second estimation unit 47 have the same input and the same transfer function, the two output values shown in the range 64 in FIG. 3 are the same. Since the outputs of the filter 61 and the second estimation unit 47 are in opposite phases, they are canceled out by the addition / subtraction unit 62.

  As a result, the target temperature is output from the adjusting unit 62 as the control target temperature. Therefore, even if the inlet temperature fluctuates, the influence does not reach the control target temperature.

  Further, since the outlet temperature estimation unit 45 is a model that approximates the actual DOC 21, a situation similar to the state illustrated in FIG. 3 occurs in the actual DOC 21. Therefore, when the basic injection amount is supplied, in the DOC 21, even if the inlet temperature fluctuates, the outlet temperature matches the target temperature with high accuracy.

  Next, the operation and effect of the advance / delay adjustment unit 51 will be described.

  Here, the gain and coefficient of the transfer function of the first response delay model that matches the operating conditions at that time are set in the gain and coefficient of the transfer function of the advance / delay adjustment unit 51 and the PID control unit 54. That is, the transfer functions c, d, and e of the first response delay model that matches the operating conditions are set to A (differential gain), B (proportional gain), and E, respectively.

  An example in which the basic injection amount and the inlet temperature are assumed to be constant will be described below.

  The response (transfer function) of the corrected injection amount (feedback value) output from the feedback calculation unit 49 to the control target temperature output from the outlet temperature estimation unit 45 is expressed as shown in Expression (8). The

H * k _r / (G ² * s ³ + 2 * G * s ² + s + H * k _r ) (8)
Further, the response of the outlet temperature to the control target temperature is expressed as shown in Equation (9). Here, the transfer function of the response delay of the DOC 21 is expressed using the transfer functions of the first response delay model and the second response delay model of the DOC 21 (Equation (1) and Equation (3)). .

H * k _r * (G * s + 1) ² / ((e * s + 1) (G ² * s ³ + 2 * G * s ² + s + H * k _r )) (9)
In order to absolutely converge the transfer functions of Equation (8) and Equation (9), that is, not to generate overshoot and undershoot, the denominator (G ² * s ³ + 2 * G * s ² All of the roots of + s + H * k _r ) are real roots, that is, the discriminant of this formula needs to be 0 or more. Therefore, it is necessary that 4-27 * G * H * k _r ≧ 0, that is, H ≦ 4 / (27 * G * k _r ) (10).

  On the other hand, when there is no advance / delay adjustment unit 51, the response of the injection correction amount with respect to the control target temperature and the response of the outlet temperature with respect to the control target temperature are equal and expressed as shown in Expression (11).

H * k _r / (e * s ² + s + H * k _r ) (11)
In order to achieve absolute convergence of the transfer function of Expression (11), the discriminant of the denominator (e * s ² + s + H * k _r ) needs to be 0 or more.

Therefore, it is necessary that 1 ² −4 * e * H * k _r ≧ 0, that is, H ≦ 1 / (4 * e * k _r ) (12).

  Here, when Expression (10) and Expression (12) are compared, if G is set so that G <16 * e / 27, the advance / delay adjustment unit 51 is provided, and thus the advance / delay adjustment unit 51 is provided. It can be seen that a larger feedback gain H can be obtained than in the case of no. In the present embodiment, G of the advance / delay adjustment unit 51 is set to satisfy G <16 * e / 27. Therefore, the advance / delay adjustment unit 51 can increase the feedback gain, and the feedback performance of the feedback calculation unit 49 can be improved.

  Next, an exhaust emission control device according to a modification of the present invention will be described.

  In the exhaust emission control device according to the modification, the advance / delay adjustment unit 51 in the above embodiment is configured by a filter (first-order advance / delay filter) represented by a first-order advance / delay transfer function represented by Expression (13).

(E * s + 1) / (G * s + 1) (13)
Here, E and G are coefficients.

  In the exhaust emission control device according to the modified example, the response (transfer function) of the corrected injection amount output from the feedback calculation unit 49 to the control target temperature output from the outlet temperature estimation unit 45 is expressed by Expression (14). It is expressed as follows.

H ′ * k _r / (G * s ² + s + H ′ * k _r ) (14)
Here, H ′ represents the feedback gain in the modified example.

  On the other hand, the response of the outlet temperature to the control target temperature is expressed as shown in Equation (15). Note that the transfer function of the response delay of the DOC 21 is expressed by using the transfer functions of the first response delay model and the second response delay model of the DOC 21 (Equation (1) and Equation (3)).

_{H '* k r * (G} * s + 1) / (E * G * s 3 + (E + G) * s 2 + (E * H' * kr + 1) * s + H '* k r)) ··· (15)
In order to absolutely converge the transfer functions of the equations (14) and (15), that is, not to generate overshoot and undershoot, the denominator (G * s ² + s + H ′ * k _r ) has a real root, that is, the discriminant of this equation needs to be 0 or more. Therefore, it is necessary that 1 ² −4 * G * H ′ * k _r ≧ 0, that is, H ′ ≦ 1 / (4 * G * k _r ) (16).

Expression (16) and Expression (10) representing the feedback gain H when the filter represented by the second-order advance / delay transfer function is used in the advance / delay adjustment unit 51, that is, H ≦ 4 / (27 * G Comparing * k _r ), it can be seen that when the value of G is the same, the feedback gain H ′ is 27/16 = 1.6875 times the feedback gain H.

  Next, the performance comparison between the case where the advance / delay adjustment unit 51 is configured with a secondary advance / delay filter (embodiment) and the case where the advance / delay adjustment unit 51 is configured with a primary advance / delay filter (modified example) will be described. To do.

  FIG. 4 is a diagram illustrating a feed-through in the case where the advance / delay adjustment unit according to the embodiment of the present invention is configured with a secondary advance / delay filter, and the case where the advance / delay adjustment unit according to the modification is configured with a primary advance / delay filter. It is a figure explaining the influence of a back gain and noise. FIG. 4 shows the maximum feedback gain that can be obtained when the filter is used on the vertical axis and the output sensitivity to the noise of the outlet temperature signal when the filter is used, and G / E is taken on the horizontal axis. Yes.

  When the value of the coefficient G is the same, in the modified example, the feedback gain H ′ can be made larger than the feedback gain H in the embodiment. On the other hand, in the case of the same feedback gain, as shown by the arrows in the figure, the embodiment, that is, the advance / delay adjustment unit is a secondary advance / delay filter as compared to the modified example. The influence of noise can be reduced.

  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, the outside air temperature sensor 36 is provided and the outside air temperature is directly detected. However, the present invention is not limited to this. For example, a sensor that detects the intake air temperature is provided in the vicinity of the MAF sensor 31. An intake air temperature detected by this sensor may be used as the outside air temperature.

  Further, in the above embodiment, the temperature value is used as it is as the temperature related to the exhaust gas such as the inlet temperature, the outlet temperature, the target temperature, and the control target temperature. However, the present invention is not limited to this. A value obtained by performing predetermined conversion on the gas temperature value (for example, specific enthalpy of exhaust gas) may be used. Here, the concept of temperature referred to in the claims includes not only the case where the temperature value is used as it is, but also a value obtained by performing a predetermined conversion on the temperature.

10 engine 20 exhaust aftertreatment device 21 DOC
22 DPF
23 Injector in exhaust pipe 25 DOC inlet temperature sensor 26 DOC outlet temperature sensor 27 DPF outlet temperature sensor 36 Outside air temperature sensor 40 ECU
41 regeneration control unit 42 inlet temperature processing unit 43 adjustment unit 44 basic injection amount determination unit 45 outlet temperature estimation unit 46 first estimation unit 47 second estimation unit 48 addition unit 49 feedback calculation unit 50 adjustment unit 51 advance / delay adjustment unit 52 PID Calculation Unit 53 PID Gain 54 PID Control Unit 55 Addition Unit

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
An inlet temperature detecting means for detecting an inlet temperature which is an exhaust gas temperature at the inlet of the oxidation catalyst;
Outlet temperature detection means for detecting an outlet temperature which is an exhaust gas temperature at the outlet of the oxidation catalyst;
An exhaust gas flow rate detecting means for detecting an exhaust gas flow rate passing through the oxidation catalyst;
Based on the inlet temperature, the exhaust gas flow rate, and the target temperature of the outlet temperature of the oxidation catalyst, the basic injection amount of the hydrocarbon that needs to be supplied to the oxidation catalyst in order to reach the target temperature Basic injection amount determining means for determining the injection amount;
The oxidation catalyst when the basic injection amount of the hydrocarbon is supplied based on a first response delay model indicating a response of the outlet temperature of the oxidation catalyst to a change in the supply amount of the hydrocarbon to the oxidation catalyst First estimating means for estimating a temperature change of the outlet temperature of
Second estimation means for estimating the outlet temperature in the case of the inlet temperature based on a second response delay model indicating a response of the outlet temperature of the oxidation catalyst to a change in the inlet temperature of the oxidation catalyst;
The deviation is eliminated based on a deviation between the estimated outlet temperature of the oxidation catalyst based on the temperature change of the estimated outlet temperature and the estimated outlet temperature and the outlet temperature detected by the outlet temperature detecting means. A feedback calculation means for obtaining a corrected injection amount, which is a hydrocarbon injection amount to be corrected,
Regeneration control means for controlling the forced regeneration means to output a control injection amount obtained by adding the basic injection amount and the correction injection amount;
Exhaust gas purification apparatus. The exhaust emission control device according to claim 1, wherein the first response delay model is a model represented by a third-order damped vibration transfer function. The exhaust emission control device according to any one of claims 1 and 2, wherein the second response delay model is a model represented by a third-order absolute convergence transfer function. Further comprising a lead / lag adjusting means for adjusting a lead / lag of the phase with respect to the deviation,
The exhaust emission control device according to any one of claims 1 to 3, wherein the feedback calculation means obtains the corrected injection amount for eliminating the deviation after the advance / lag adjustment. The exhaust purification device according to claim 4, wherein the advance / delay adjustment means is a filter represented by a secondary advance / delay transfer function.

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