JP2010174786A - Reducing agent injection control device, exhaust emission control device, and abnormality diagnosis device for reducing agent supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reducing agent injection control device accurately controlling injection of a reducing agent even in abnormality of a pressure sensor detecting pressure of the reducing agent, and an abnormality diagnosis device accurately diagnosing abnormality of an exhaust emission control device, a pressure sensor, and a reducing agent supply system. <P>SOLUTION: The reducing agent injection control device includes a first pressure operation part 53 calculating pressure in a reducing agent passage based on sensor value of the pressure sensor disposed in the reducing agent passage, a pressure change storage part 55 modeling pressure change in the reducing agent passage based on at least flow rate of the reducing agent, and quantity of reducing agent flowing from the reducing agent supply system to an outside, a second pressure operation part 57 calculating estimated pressure in the reducing agent passage based on pressure change in the reducing agent passage modeled by the pressure change storage part in abnormality of the pressure sensor, and a pressure feed means control part executing feedback control of a reducing agent pressure feed means to set pressure in the reducing agent passage to a prescribed value based on pressure calculated by the first pressure operation part and estimated pressure calculated by the second pressure operation part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reducing agent injection control device that injects a reducing agent into an exhaust passage of an internal combustion engine, an exhaust purification device, and an abnormality diagnosis device for a reducing agent supply device. Particularly, a reducing agent injection control device that includes a pressure sensor in a reducing agent supply path and performs reducing agent injection control using a sensor value of the pressure sensor, an exhaust purification device including such a reducing agent injection control device, and a reducing agent. The present invention relates to an abnormality diagnosis device for a supply device.

The exhaust gas discharged from an internal combustion engine such as a diesel engine contains nitrogen oxide (NO _x ) that may affect the environment. As an exhaust gas purification apparatus used to purify the NO _X, the reducing agent unburned fuel and urea water solution or the like on the upstream side of the disposed in an exhaust passage catalyst injection-supply, the exhaust gas and the reducing agent catalyst There is known an exhaust emission control device that reduces NO _x in exhaust gas by contacting with NOx.

In such an exhaust purification device, when the injection amount of the reducing agent becomes excessive, the reducing agent flows out to the downstream side of the catalyst, while when the injection amount of the reducing agent is insufficient, NO _x flows out to the downstream side of the catalyst. . Therefore, in the reducing agent supply apparatus for injecting and supplying the reducing agent to the exhaust passage so that the injection amount of the reducing agent does not become excessive or insufficient with respect to the NO _x amount, the operating state of the internal combustion engine, the reduction efficiency of the catalyst, etc. In consideration of the above, the target injection amount of the reducing agent is calculated, and control is performed so that the reducing agent corresponding to the target injection amount is injected.

  The reducing agent supply device provided in the exhaust emission control device includes a storage tank for storing the reducing agent, a reducing agent injection valve for injecting the reducing agent into the exhaust passage, and a reducing agent in the storage tank directed toward the reducing agent injection valve. And a reducing agent pump for pumping. In such a reducing agent supply device, the pressure of the reducing agent supplied to the reducing agent injection valve becomes a constant value in order to accurately control the injection amount of the reducing agent by the opening / closing control of the reducing agent injection valve. The output of the reducing agent pump is controlled.

  More specifically, a reducing agent pressure sensor is provided in a reducing agent passage connecting the reducing agent pressure feed pump and the reducing agent injection valve, and the pressure in the reducing agent passage detected by the reducing agent pressure sensor has a predetermined value. As shown, feedback control of the output of the reducing agent pump is performed (see Patent Document 1).

JP 2008-223770 A (paragraphs [0025] and [0027], FIG. 1)

However, in the reducing agent supply apparatus described in Patent Document 1, if the pressure sensor fails or the error between the detected value and the actual value increases, the feedback control of the pump cannot be performed accurately. As a result, the injection amount of the reducing agent becomes excessive and insufficient, and NO _x or the reducing agent may flow out downstream of the catalyst.
In particular, when the reducing agent is urea aqueous solution, ammonia generated by hydrolysis because of high toxicity in comparison with the NO _X, ammonia when the injection amount of the reducing agent may become excessive catalyst In order not to flow out to the downstream side, it is necessary to reduce the amount of reducing agent injected by the reducing agent supply device or to stop the reducing agent injection control. As a result, part of the NO _X in the exhaust gas will be directly flowing downstream of the catalyst, it is impossible to perform purification of the NO _X which is the original purpose successfully.

  Therefore, the inventor of the present invention diligently worked to model a pressure control system controlled by hardware that pressure-feeds the reducing agent in the storage tank to the reducing agent injection valve with a normal pressure sensor. In other words, if the pressure sensor fails, the present invention can be solved by driving the hardware using the pressure calculation value using the transfer function, and the present invention has been completed. That is, an object of the present invention is to provide a reducing agent injection control device capable of accurately performing the reducing agent injection control even when the pressure sensor that detects the pressure of the reducing agent supplied to the reducing agent injection valve is abnormal, and such reduction. An exhaust emission control device including an agent injection control device is provided. Another object of the present invention is to provide an abnormality diagnosing device for a reducing agent supply device capable of diagnosing an abnormality of a pressure sensor and a reducing agent supply system using the above-mentioned pressure control system model. .

  According to the present invention, the reducing agent is pumped to the reducing agent injection valve provided in the exhaust passage of the internal combustion engine by the reducing agent pumping means, and the reducing agent is injected into the exhaust passage by controlling the opening and closing of the reducing agent injection valve. In the reducing agent injection control device, the first pressure for calculating the pressure in the reducing agent passage based on the sensor value of the pressure sensor provided in the reducing agent passage connecting the reducing agent pumping means and the reducing agent injection valve. Pressure change in the reducing agent passage based on the calculation unit, at least the flow rate of the reducing agent by the reducing agent pumping means, and the amount of reducing agent flowing out from the reducing agent supply system including the reducing agent pumping means and the reducing agent passage. And a second pressure calculation unit for calculating an estimated pressure in the reducing agent passage based on a pressure change in the reducing agent passage modeled by the pressure change storage unit when the pressure sensor is abnormal. And the first Based on the pressure calculated by the force calculation unit or the estimated pressure calculated by the second pressure calculation unit, the pumping unit control for performing feedback control of the reducing agent pumping unit so that the pressure in the reducing agent passage becomes a predetermined value. And a reducing agent injection control device that calculates a target injection amount of the reducing agent and performs an opening / closing control of the reducing agent injection valve. be able to.

  Further, in configuring the reducing agent injection control device of the present invention, the pressure change storage unit is a waste of time until the pressure sensor starts to respond after the output of the reducing agent pumping means changes due to the characteristics of the reducing agent supply system. Based on the relationship between the time (L) and the secondary delay (D) from when the pressure sensor responds until the pressure in the reductant passage reaches the target value, the pressure change in the reductant passage is modeled. Is preferable.

  Further, in configuring the reducing agent injection control device of the present invention, the pressure change storage unit changes the target pressure in the reducing agent passage in steps when the reducing agent injection is not performed by the reducing agent injection valve. It is preferable to perform modeling based on a change in pressure in the reducing agent passage.

  Further, in configuring the reducing agent injection control device of the present invention, the relationship between the dead time (L) and the secondary delay (D) is recalculated during or after the injection control of the reducing agent, and the modeled relationship It is preferable to provide an abnormality diagnosis unit that performs abnormality diagnosis of the pressure sensor by comparing with the above.

  In configuring the reducing agent injection control apparatus of the present invention, it is preferable that the abnormality diagnosis unit further performs abnormality diagnosis of the reducing agent supply system.

  Further, in configuring the reducing agent injection control device of the present invention, the difference between the pressure calculated by the first pressure calculation unit and the estimated pressure calculated by the second pressure calculation unit is shifted by a predetermined value or more. In this case, it is preferable to include a sensor value correction unit that corrects the sensor value used in the first pressure calculation unit by using a correction coefficient indicated by the ratio of the estimated pressure to the pressure.

  According to another aspect of the present invention, there are provided a reducing catalyst disposed in an exhaust passage of an internal combustion engine, a reducing agent supply device for injecting a reducing agent into the exhaust passage on the upstream side of the reducing catalyst, and a reducing agent supply device. In the exhaust gas purification apparatus for an internal combustion engine provided with a reducing agent injection control device for controlling the fuel and injecting the reducing agent into the exhaust passage, the reducing agent supply device is provided in a storage tank in which the reducing agent is stored and an exhaust passage. A reducing agent injection valve and a reducing agent pumping means for pumping the reducing agent to the reducing agent injection valve, and the reducing agent injection control device connects the reducing agent pumping means and the reducing agent injection valve. A first pressure calculation unit that calculates the pressure in the reducing agent passage based on the sensor value of the pressure sensor provided in the inside, the flow rate of the reducing agent by at least the reducing agent pumping means, the reducing agent pumping means, and the reducing agent passage. Out of the reducing agent supply system containing A pressure change storage unit that models the pressure change in the reducing agent passage based on the amount of the reducing agent, and a reduction based on the pressure change in the reducing agent passage modeled by the pressure change storage unit when the pressure sensor is abnormal Based on the second pressure calculation unit that calculates the estimated pressure in the agent passage and the pressure calculated by the first pressure calculation unit or the estimated pressure calculated by the second pressure calculation unit, A pressure-feeding means control unit that performs feedback control of the reducing agent pressure-feeding means so that the pressure becomes a predetermined value; and an injection valve control unit that calculates a target injection amount of the reducing agent and performs opening / closing control of the reducing agent injection valve. An exhaust emission control device for an internal combustion engine characterized by the above.

  According to another aspect of the present invention, the reducing agent is pumped to the reducing agent injection valve provided in the exhaust passage of the internal combustion engine by the reducing agent pumping means, and the reducing agent is discharged by controlling the opening and closing of the reducing agent injection valve. Sensor value of a pressure sensor provided in a reducing agent passage connecting a reducing agent pumping means and a reducing agent injection valve in an abnormality diagnosing device of a reducing agent supply device for diagnosing an abnormality of a reducing agent supply device injected into the passage And a reducing agent so that the pressure in the reducing agent passage becomes a predetermined value based on the pressure calculated by the first pressure calculating portion and the first pressure calculating portion. A pressure-feeding means control unit that performs feedback control of the pressure-feeding means, a flow rate of the reducing agent by at least the reducing agent pressure-feeding means, an amount of the reducing agent that flows out from the reducing agent supply system including the reducing agent pressure-feeding means and the reducing agent passage, Based reducing agent A pressure change storage unit that models the pressure change in the passage, and a pressure change by recalculating the model of the pressure change in the reducing agent passage during or after the injection control of the reducing agent and comparing it with the stored model. An abnormality diagnosing device for a reducing agent supply apparatus, comprising: an abnormality diagnosing unit that performs abnormality diagnosis of a sensor and a reducing agent pumping system.

  According to the reducing agent injection control device of the present invention, the reducing agent in the reducing agent passage before and after the injection of the reducing agent based on at least the flow rate of the reducing agent by the reducing agent pumping means and the amount of the reducing agent flowing out from the reducing agent supply system. Since the pressure change storage unit for modeling the pressure change is provided, the pressure in the reducing agent passage is accurately estimated by the second pressure calculation unit even when the pressure sensor is abnormal. And since the pressure feeding means control part of the reducing agent injection control device of the present invention can perform feedback control of the reducing agent pressure feeding means based on the estimated pressure in the reducing agent passage calculated by the second pressure calculation part. Furthermore, feedback control is performed so that the pressure in the reducing agent passage becomes a predetermined value even when the pressure sensor is abnormal. Therefore, even when the pressure sensor has an abnormality, the reducing agent injection control by the reducing agent supply device is performed with high accuracy, and the exhaust gas purification is normally performed.

  Further, in the reducing agent injection control device of the present invention, the pressure change storage unit is configured so that the pressure in the reducing agent passage is based on the relationship between the dead time (L) and the secondary delay (D) caused by the characteristics of the reducing agent supply system. By modeling the change, the pressure change in the reducing agent passage according to the characteristics of the reducing agent supply system can be accurately obtained.

  Further, in the reducing agent injection control device of the present invention, the pressure change storage unit models the relationship between the dead time (L) and the secondary delay (D) in advance when the reducing agent is not injected. The characteristics of the reducing agent supply system are modeled without affecting the injection amount of the reducing agent.

  Further, the reducing agent injection control device of the present invention compares the relationship between the dead time (L) and the second order delay (D) recalculated during or after the reducing agent injection control with the modeled relationship. By providing an abnormality diagnosis unit that diagnoses the abnormality of the pressure sensor, it is quickly grasped that the sensor value of the pressure sensor has started to deviate from the sensor value that has been shown under the same conditions so far, Existence is accurately diagnosed.

  Further, in the reducing agent injection control device of the present invention, the abnormality diagnosis unit diagnoses the abnormality of the reducing agent supply system as well as the pressure sensor, thereby grasping the failure of the reducing agent supply system and the like. Repair and replacement can be performed promptly.

  Further, when the reducing agent injection control device of the present invention has a difference between the pressure based on the sensor value of the pressure sensor and the estimated pressure based on the pressure change modeled by the pressure change storage unit, a predetermined value or more is deviated. By providing a sensor value correction unit that corrects the sensor value of the pressure sensor used in the first pressure calculation unit by the correction coefficient of the pressure, pressure based on the sensor value of the pressure sensor that occurs during the period until the pressure sensor is diagnosed as abnormal The deviation is corrected, and the reducing agent injection control is performed accurately.

  Further, according to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the reducing agent injection control device performs reduction based on at least the flow rate of the reducing agent by the reducing agent pumping means and the amount of reducing agent flowing out from the reducing agent supply system. Since the pressure change storage unit that models the pressure change in the reducing agent passage before and after the injection of the agent is provided, the pressure in the reducing agent passage can be accurately estimated by the second pressure calculation unit even when the pressure sensor is abnormal. Is done. The pressure feeding means control unit of the reducing agent injection control device can perform feedback control of the reducing agent pressure feeding means using the estimated pressure calculated by the second pressure calculation unit. Even if it exists, feedback control is performed so that the pressure in the reducing agent passage becomes a predetermined value. Therefore, even when the pressure sensor has an abnormality, the reducing agent injection control by the reducing agent supply device is performed with high accuracy, and the exhaust gas purification is normally performed.

  Further, according to the abnormality diagnosis device for the reducing agent supply apparatus of the present invention, the pressure change model in the reducing agent passage recalculated during or after the injection control of the reducing agent is compared with the already stored model. By doing so, the abnormality of the pressure sensor and the reducing agent supply system provided in the reducing agent supply device can be diagnosed, and the abnormal part can be accurately identified.

  In the present specification, the “reducing agent supply system” means hardware for supplying the reducing agent to the reducing agent injection valve, represented by a reducing agent pressure feed pump, a reducing agent passage, and the like.

It is a figure which shows the structural example of the exhaust gas purification apparatus of the internal combustion engine concerning embodiment of this invention. It is a figure for demonstrating the structural example of the reducing agent injection control apparatus with which the exhaust gas purification apparatus of embodiment of this invention was equipped. It is a figure for demonstrating the operation | movement flow of the feedback control of a reducing agent pressure feed pump. It is a figure for demonstrating the operation | movement flow of the feedback control of the reducing agent pumping pump using the learned approximate expression. It is a figure for demonstrating learning control. It is a figure for demonstrating the identification method of the abnormal part in abnormality diagnosis. It is a flow from the start of the internal combustion engine to the completion of learning control. It is a flow of learning control. It is a flow of feedback control of a reducing agent pressure feed pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to a reducing agent injection control device, an internal combustion engine exhaust gas purification device, and a reducing agent supply device abnormality diagnosis device according to the present invention will be specifically described below with reference to the drawings. However, this embodiment shows one aspect of the present invention and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention.
In addition, in each figure, what has attached | subjected the same code | symbol has shown the same member, and description is abbreviate | omitted suitably.

1. Basic Configuration of Exhaust Gas Purification Device for Internal Combustion Engine First, a basic configuration of an exhaust gas purification device for an internal combustion engine (hereinafter simply referred to as “exhaust gas purification device”) according to an embodiment of the present invention will be described.
FIG. 1 is a diagram in which a urea aqueous solution as a reducing agent is injected and supplied upstream of a reduction catalyst 13 disposed in an exhaust passage, and NO _x contained in exhaust gas is selectively reduced and purified by the reduction catalyst 13. 1 shows an exhaust purification device 10 of an embodiment. This exhaust purification device 10 is provided in the middle of an exhaust passage connected to the internal combustion engine 5, and includes a reduction catalyst 13 for selectively reducing NO _x contained in the exhaust gas, and a reduction catalyst 13. The main components are a reducing agent supply device 40 for injecting and supplying the reducing agent into the exhaust passage on the upstream side, and a reducing agent injection control device 30 for controlling the operation of the reducing agent supply device 40.

The exhaust purification device 10 of this embodiment is an exhaust purification device in which a urea aqueous solution is used as a liquid reducing agent. Aqueous urea solution, ammonia is generated by hydrolysis with mixed into the exhaust gas upstream from the reduction catalyst 13, used for the reduction of the NO _X ammonia is adsorbed by the reduction catalyst 13. However, the reducing agent used in the exhaust purification apparatus 10 of the present embodiment is not limited to the urea aqueous solution, and unburned fuel or the like can also be used.

2. Reduction catalyst The reduction catalyst 13 used in the exhaust purification device 10 of the present embodiment adsorbs ammonia produced by hydrolysis of an aqueous urea solution injected into exhaust gas by the reducing agent supply device 40, and flows into the exhaust gas. A catalyst that reduces NO _x in the gas is used. As the reduction catalyst 13, for example, a zeolite-based reduction catalyst having an ammonia adsorption function and capable of selectively reducing NO _x is used.
However, the type of the catalyst can be appropriately selected depending on the type of the reducing agent, and is particularly a catalyst that can reduce NO _x in the exhaust gas using the reducing agent supplied into the exhaust passage upstream of the catalyst. It can be used without limitation.

3. The reducing agent supply device 40 includes a reducing agent injection valve 43 fixed to the exhaust pipe 11 on the upstream side of the reduction catalyst 13, a storage tank 41 in which a liquid reducing agent is stored, and a storage tank 41. It is constituted by a reducing agent pumping pump 42 as a reducing agent pumping means for pumping the reducing agent toward the reducing agent injection valve 43. A first reducing agent passage 44 is connected between the reducing agent pumping pump 42 and the storage tank 41, and a second reducing agent passage 45 is connected between the reducing agent pumping pump 42 and the reducing agent injection valve 43. Has been. The second reducing agent passage 45 is provided with a reducing agent pressure sensor 47 used for driving control of the reducing agent pressure feed pump 42.
In the following embodiment, the reducing agent pressure pump 42, the first reducing agent passage 44, and the second reducing agent passage 45 are collectively referred to as a “reducing agent supply system”.

  The reducing agent supply pump 40 of the reducing agent supply device 40 is typically an electric pump, and pumps the reducing agent in the storage tank 41 and pumps it to the reducing agent injection valve 43. As this pump, for example, an electric diaphragm pump or a gear pump is used, and drive control is performed by the reducing agent injection control device 30. In the reducing agent supply device 40 provided in the exhaust purification device 10 of the present embodiment, the pressure of the second reducing agent passage 45 detected by the reducing agent pressure sensor 47 is maintained at a constant value, for example, 0.5 MPa. Thus, feedback control of the reducing agent pressure feed pump 42 is performed.

  Further, a reflux passage 46 branched from the second reducing agent passage 45 and connected to the storage tank 41 is provided. An orifice 48 is provided in the middle of the reflux passage 46. When the pressure in the second reducing agent passage 45 becomes excessively high, the reducing agent in the second reducing agent passage 45 opens the orifice 48. And the upper limit of the pressure in the second reducing agent passage 45 is defined.

  The reducing agent injection valve 43 is, for example, a reducing agent injection valve that is controlled to open and close by energization control. As described above, the reducing agent pumped from the reducing agent pumping pump 42 to the reducing agent injection valve 43 is maintained at a predetermined pressure, and the reducing agent injection control device 30 opens and opens the reducing agent injection valve 43. Time is controlled and the reducing agent is injected into the exhaust passage.

4). Reducing agent injection control device (abnormality diagnosis device)
FIG. 2 shows a configuration example in which the configuration of the reducing agent injection control device 30 provided in the exhaust purification device 10 of the present embodiment is represented by functional blocks.
This reducing agent injection control device 30 is broadly divided into a part for controlling the driving of the reducing agent pumping pump 42, a part for controlling the driving of the reducing agent injection valve 43, a reducing agent pressure sensor 47 and a reducing agent supply system. A portion for performing abnormality diagnosis and a portion for correcting the sensor value of the reducing agent pressure sensor 47 are provided. Each part which comprises the reducing agent injection control apparatus 30 is specifically implement | achieved by execution of the program by a microcomputer (not shown).

(1) Drive Control of Reducing Agent Pressure Pump The reducing agent injection control device 30 includes a sensor value detection unit 51 that detects the sensor value Vp of the reducing agent pressure sensor 47 as a part that performs drive control of the reducing agent pressure feed pump 42, A first pressure calculation unit 53 that calculates a pressure Pact in the second reducing agent passage 45 based on the detected sensor value Vp, and a pressure change memory that models a pressure change in the second reducing agent passage 45. Unit 55, a second pressure calculation unit 57 that calculates an estimated pressure Pest in the second reducing agent passage 45 based on the modeled pressure change, and a pressure Pact calculated by the first pressure calculation unit 53 Alternatively, it is calculated by a pump control unit 59 as a pumping means control unit that performs feedback control of the reducing agent pumping pump 42 based on the estimated pressure Pest calculated by the second pressure calculation unit 57 and the first pressure calculation unit 53. Pressure Pact and second pressure A pressure comparison unit 65 that compares the estimated pressure Pest calculated by the calculation unit 57 and a learning control unit that outputs a control signal to the pump control unit 59 when the pressure change storage unit 55 performs modeling of the pressure change. 56.

(1) -1 Feedback Control by Sensor Value First, when the reducing agent pressure sensor 47 is normal, the reducing agent pressure feed pump 42 is driven by the sensor detection unit 51, the first pressure calculation unit 53, and the pump control unit 59. Control is performed.

  Among these, the sensor value detection unit 51 continuously reads the voltage Vp that is the sensor value of the reducing agent pressure sensor 47 at a predetermined interval and outputs it to the first pressure calculation unit 53. The first pressure calculation unit 53 calculates the pressure Pact in the second reducing agent passage 45 based on the voltage Vp output from the sensor value detection unit 51. That is, the pressure Pact calculated by the first pressure calculation unit 53 is a pressure value obtained based on the reducing agent pressure sensor 47.

  Further, the pump control unit 59 performs feedback control of the reducing agent pumping pump 42 based on the pressure Pact calculated by the first pressure calculation unit 53 in a state where the reducing agent pressure sensor 47 is not abnormal. FIG. 3 shows feedback control of the reducing agent pumping pump 42 using the pressure Pact calculated by the first pressure calculation unit 53, which is performed by the pump control unit 59 constituting the reducing agent injection control device 30 of the present embodiment. The operation flow is shown.

  In this operation flow, when a predetermined target pressure Ptgt is set, first, PID control (proportional, proportional to the difference ΔPact between the target pressure Ptgt and the current pressure Pact calculated by the first pressure calculation unit 53 is performed. The drive duty Duty of the reducing agent pumping pump 42 necessary to achieve the target pressure Ptgt is set by integration and differentiation control (part A in FIG. 3). Next, the rotational speed R of the reducing agent pumping pump 42 is obtained from the set drive duty Duty (part B in FIG. 3), and further, the reducing agent discharge amount Qpump corresponding to the rotational speed R is obtained (FIG. 3). 3 part C). Then, from the reducing agent discharge amount Qpump, the reducing agent injection amount Qact by the reducing agent injection valve 43 and the reducing agent recirculation amount Qof to the storage tank 41 are subtracted according to the remaining reducing agent discharge amount Qdmd. As a result of the fluctuation of the pressure Pact in the second reducing agent passage 45 (part D in FIG. 3), the reducing agent pressure sensor 47 detects the voltage Vp corresponding to the pressure Pact (part E in FIG. 3). .

  In order to perform the feedback control of the reducing agent pressure feed pump 42, the detected voltage Vp, which is the sensor value of the reducing agent pressure sensor 47, is converted back to the pressure Pact, and the difference between the target pressure Ptgt and the current pressure Pact is determined. Feedback is applied to the part for obtaining ΔPact (part F in FIG. 3). As a result, the drive duty Duty of the reducing agent pumping pump 42 is newly set, and the above-described flow is repeated, whereby feedback control of the reducing agent pumping pump 42 is performed.

(1) -2 Feedback Control Based on Estimated Pressure On the other hand, when the reducing agent pressure sensor 47 is abnormal, reducing agent pumping by the pressure change storage unit 55, the second pressure calculation unit 57, and the pump control unit 59. Drive control of the pump 42 is performed.

  Of these, the pressure change storage unit 55 responds to the dead time (L), which is the time from when the output of the reducing agent pressure pump 42 changes until the reducing agent pressure sensor 47 starts to respond, and when the reducing agent pressure sensor 47 responds. Based on the relationship with the second-order lag (D) until the pressure Pact in the second reducing agent passage 45 reaches the target pressure Ptgt from the start of the transfer, the pressure function in the second reducing agent passage 45 is transferred as a transfer function. As a model. Since the dead time (L) and the second-order lag (D) vary depending on the characteristics of the reducing agent supply system, the pressure change storage unit 55 stores the dead time (L) and the dead time (L) when the reducing agent pressure sensor 47 is in a normal state. A second-order lag (D) system is learned so that the pressure in the second reducing agent passage 45 can be accurately estimated even when the reducing agent pressure sensor 47 is abnormal.

Specifically, in the reducing agent injection control device 30 of the present embodiment, the reducing agent is determined from the output of the drive duty Duty by the pump control unit 59 indicated by B, C, D, E in the operation flow of FIG. 3 described above. Up to the output of the sensor value Vp of the pressure sensor 47 is collected as one system, and this system is approximated as a transfer function as a system of “dead time (L) + second-order lag (D)” by a Laplace transform equation. In this embodiment, parameters that characterize the system of “dead time (L) + second-order lag (D)” are dead time (L), damping coefficient (ξ), natural frequency (ω), and proportional gain ( The approximate expression of the transfer function represented by the following formula (1) using the coefficient of K) is used, and the pressure change storage unit 55 does not perform injection from the reducing agent injection valve 43 using these coefficients. Learn in state.

S in the above formula (1) is a variable when the sensor value Vp of the reducing agent pressure sensor 47 is expressed by the following formula (2) as a time function.
Vp (S) = ∫ ₀ ^∞ e ^-st Vp (t) δt (2)

  Further, the second pressure calculation unit 57 estimates the pressure Pest in the second reducing agent passage 45 based on the pressure change modeled as a transfer function in the pressure change storage unit 55. The second pressure calculator 57 of the reducing agent injection control device 30 of the present embodiment is based on the above equation (1) using the coefficients learned in the pressure change storage unit 55, and the second reducing agent passage 45. The estimated pressure Pest is calculated.

  When the abnormality diagnosis unit 67 described later determines that an abnormality has occurred in the reducing agent pressure sensor 47, the pump control unit 59 performs reduction based on the estimated pressure Pest calculated by the second pressure calculation unit 57. Feedback control of the agent pressure feed pump 42 is performed, and the pressure in the second supply path 45 is maintained at the target pressure Ptgt. FIG. 4 shows feedback control of the reducing agent pumping pump 42 using the estimated pressure Pest calculated by the second pressure calculation unit 53, which is performed by the pump control unit 59 constituting the reducing agent injection control device 30 of the present embodiment. The operation flow is shown.

  In this operation flow, when an abnormality occurs in the reducing agent pressure sensor 47 in a state where the predetermined target pressure Ptgt is set, the difference between the target pressure Ptgt and the current estimated pressure Pest calculated by the second pressure calculation unit 57. The driving duty Duty of the reducing agent pressure feed pump 42 necessary to achieve the target pressure Ptgt by PID control is set according to ΔPest. Then, the pressure change in the second reducing agent passage 45 is calculated based on the above equation (1) using the drive duty Duty, and the estimated pressure Pest is obtained (part G in FIG. 4). As a result, the drive duty Duty of the reducing agent pumping pump 42 is newly set, and feedback control of the reducing agent pumping pump 42 is performed.

(1) -3 Learning Control Each coefficient of the above equation (1) is learned at the start of operation of the internal combustion engine 5, for example, and thereafter, the pressure Pact calculated by the first pressure calculation unit 53 and the second When the estimated pressure Pest calculated by the pressure calculation unit 57 does not match, or when the difference between these two values exceeds a predetermined value, the learning is set to be learned again. Specifically, when the pressure Pact calculated by the first pressure calculation unit 53 compared by the pressure comparison unit 65 and the estimated pressure Pest calculated by the second pressure calculation unit 57 do not match, etc. The learning control unit 56 receives the learning execution signal, and outputs an instruction signal to the pump control unit 59 so that the value of the target pressure Ptgt in FIG.

  When the output of the reducing agent pressure pump 42 is changed by the instruction signal from the learning control unit 56, the pressure change storage unit 55 is a first pressure calculation unit 53 based on the sensor value Vp of the reducing agent pressure sensor 47. From the transition of the calculated pressure Pact, each coefficient of dead time (L), damping coefficient (ξ), natural frequency (ω) and proportional gain (K) is obtained.

  FIG. 5 shows the transition of the pressure Pact in the second reducing agent passage 45 when the learning control unit 56 changes the value of the target pressure Ptgt in steps. In FIG. 5, the solid line indicates the target pressure Ptgt, and the broken line indicates the pressure Pact calculated based on the sensor value of the reducing agent pressure sensor 47. In this embodiment, the learning control unit 56 instantaneously changes the target pressure Ptgt in steps, but each coefficient in the pressure change storage unit 55 can also be changed by changing the target pressure Ptgt in a short time. Can be calculated.

  From the transition of the pressure Pact based on the sensor value of the reducing agent pressure sensor 47, the period from the time t1 when the target pressure Ptgt is changed to the time t2 when the pressure Pact starts to respond is obtained as a dead time (L). It is done. Further, from the transition of the pressure Pact based on the sensor value of the reducing agent pressure sensor 47, the pressure value Pactmax when the calculated pressure Pact reaches the maximum value after the calculated pressure Pact reaches the target pressure Ptgt and the target The difference from the pressure Ptgt is obtained as a proportional gain (K). Further, the damping coefficient (ξ) and the natural frequency (ω) are obtained from the waveform of the pressure Pact based on the sensor value of the reducing agent pressure sensor 47.

  The pressure change storage unit 55 learns these coefficients when the pressure Pact calculated by the first pressure calculation unit 53 and the estimated pressure Pest calculated by the second pressure calculation unit 57 do not match. These coefficients are stored. Then, the learning control is repeated until the pressure Pact calculated by the first pressure calculation unit 53 matches the estimated pressure Pest calculated by the second pressure calculation unit 57 or falls within an error within a predetermined range. .

(2) Drive Control of Reducing Agent Injection Valve Further, the reducing agent injection control device 30 controls the operating state of the internal combustion engine 5, the exhaust temperature, the temperature of the reduction catalyst 13, etc. as a part that performs drive control of the reducing agent injection valve 43. A target injection amount calculation unit 61 that calculates a target injection amount Qtgt of the reducing agent based on the injection valve control that performs energization control of the reducing agent injection valve 43 so that the reducing agent for the calculated target injection amount Qtgt is injected. Part 63.

The target injection amount calculation unit 61 is estimated from, for example, the exhaust gas flow rate Fgas and NO _x mass flow rate Fnox exhausted from the internal combustion engine 5, the exhaust gas temperatures TUgas and TLgas upstream and downstream of the reduction catalyst 13. The target injection amount Qtgt of the urea aqueous solution is calculated by adding the actual adsorption amount Vact of ammonia in the reduction catalyst 13 to the temperature of the reduction catalyst 13 and the NO _x reduction efficiency η (%) in the reduction catalyst 13. Further, the target injection amount Qtgt may be corrected based on the sensor value Snox of the NO _X sensor 15 provided on the downstream side of the reduction catalyst 13.

(3) Abnormality diagnosis Further, the reducing agent injection control device 30 performs reduction based on each coefficient obtained by the pressure change storage unit 55 described above as a part for performing abnormality diagnosis of the reducing agent pressure sensor 47 and the reducing agent supply system. An abnormality diagnosis unit 67 for diagnosing the presence or absence of abnormality in the reducing agent pressure sensor 47 or the reducing agent pumping pump 42 constituting the reducing agent supply system and the first and second reducing agent passages 44 and 45 is provided. In order to perform feedback control based on the estimated pressure when the reducing agent pressure sensor 47 is abnormal, it is only necessary to determine whether or not the reducing agent pressure sensor 47 is abnormal. However, the abnormality diagnosis unit 67 of the reducing agent injection control device 30 of the present embodiment In addition to the reducing agent pressure sensor 47, the abnormality diagnosis of the reducing agent supply system can be executed together.

  In the abnormality diagnosis unit 67 of the present embodiment, the difference ΔP between the pressure Pact calculated using the sensor value Vp of the reducing agent pressure sensor 47 and the estimated pressure Pest calculated using the learned pressure change model is not zero. Timer count starts when in state. Then, when a predetermined time or more has elapsed with the difference ΔP being equal to or greater than the threshold ΔP0, the abnormality diagnosis unit 67 determines that some abnormality has occurred in the reducing agent supply device 40.

  When it is determined that some abnormality has occurred in the reducing agent supply device 40, the abnormality diagnosis unit 67 outputs a learning execution signal to the learning control unit 56. As a result, the learning control unit 56, as described above, The target pressure Ptgt in the second reducing agent passage 45 is changed in steps. Further, when the output of the reducing agent pressure pump 42 is changed by an instruction from the learning control unit 56, the pressure change storage unit 55 is a first pressure calculation unit 53 based on the sensor value Vp of the reducing agent pressure sensor 47. From the transition of the calculated pressure Pact, each coefficient of dead time (L), damping coefficient (ξ), natural frequency (ω) and proportional gain (K) is obtained. Then, the abnormality diagnosis unit 67 receives each coefficient obtained by the pressure change storage unit 55, and compares each coefficient with a preset threshold value, so that either the reducing agent pressure sensor 47 or the reducing agent supply system is selected. Identify whether there is an abnormality in the element.

FIG. 6 shows an example of a method for identifying an event that causes an abnormality based on the value of each coefficient.
In the example of FIG. 6, the dead time (L) exceeds the first L threshold (L1), which is the upper limit of the allowable range, and is set to a value that is larger than the first L threshold (L1). 2 or less than the L threshold (L2) of 2, it is considered that the time from when the drive duty is set to when the reducing agent is actually pumped by the reducing agent pumping pump 42 is excessively long. Therefore, the abnormality diagnosis unit 67 determines that the mechanical deterioration of the reducing agent pumping pump 42 is progressing. In addition, if the dead time (L) exceeds the second L threshold (L2), the pressure does not change regardless of the setting of the drive duty, and the validity of the measured pressure value Therefore, the abnormality diagnosis unit 67 determines that the reducing agent pressure sensor 47 is electrically frozen.

  On the other hand, when the dead time (L) is less than the third L threshold (L3), which is the lower limit of the allowable range, the motor driving force is caused by dropping of the rotating member inside the driving motor of the reducing agent pumping pump 42. Therefore, the abnormality diagnosis unit 67 determines that the mechanical deterioration of the reducing agent pumping pump 42 is progressing.

  In addition, when the damping coefficient (ξ) exceeds the first ξ threshold value (ξ1) that is the upper limit of the allowable range, the pressure increase is small with respect to the pumping amount of the same reducing agent, or the same Since it is considered that the pumping amount at the drive duty setting is small, the abnormality diagnosis unit 67 has a low elastic modulus of the second reducing agent passage 45 or mechanical deterioration of the reducing agent pumping pump 42 proceeds. It is determined that

  On the other hand, when the damping coefficient (ξ) is below the second ξ threshold value (ξ2), which is the lower limit of the allowable range, the pressure increase is large relative to the pumping amount of the same reducing agent, or the same Since it is considered that the pumping amount at the drive duty setting is increased, the abnormality diagnosis unit 67 determines that the elastic coefficient of the second reducing agent passage 45 is high or the reducing agent pumping pump 42 is mechanically deteriorated. Is determined to be in progress.

  Also, the second ω threshold value in which the natural frequency (ω) exceeds the first ω threshold value (ω1), which is the upper limit of the allowable range, and is set to a value larger than the first ω threshold value (ω1). If (ω 2) or less, the portion most likely to affect the elasticity in the reducing agent supply system is considered to be piping, so the abnormality diagnosis unit 67 determines the elastic coefficient of the second reducing agent passage 45. Is determined to be high. Further, when the natural frequency (ω) exceeds the second ω threshold value (ω2), not only physical vibration but also electrical signal noise, for example, signal line interruption or electromagnetic noise The abnormality diagnosis unit 67 determines that a high-frequency abnormality has occurred in the reducing agent pressure sensor 47 because it is considered that it has occurred.

  On the other hand, when the natural frequency (ω) is lower than the third ω threshold value (ω3), which is the lower limit of the allowable range, the portion most likely to affect the elasticity in the reducing agent supply system is considered to be piping. Therefore, the abnormality diagnosis unit 67 determines that the elastic coefficient of the second reducing agent passage 45 is low.

  Further, a second K threshold (K) in which the proportional gain (K) exceeds the first K threshold (K1) that is the upper limit of the allowable range and is set to a value larger than the first K threshold (K1). K2), the pressure increase is considered to be large (the pressure gain is high) with respect to the same reducing agent pumping amount. Therefore, the abnormality diagnosis unit 67 is connected to the second reducing agent passage 45. It is determined that the volume is small, that is, clogging has occurred in the second reducing agent passage 45. Also, if the proportional gain (K) exceeds the second K threshold (K2), it is considered that the pressure gain has increased to a level that cannot be caused by physical factors. The unit 67 determines that an abnormality has occurred in the A / D converter provided in the reducing agent pressure sensor 47.

  On the other hand, a fourth K threshold value (K) in which the proportional gain (K) is lower than the third K threshold value (K3), which is the lower limit of the allowable range, and set to a value smaller than the third K threshold value (K3). K4) or more, it is considered that the pressure increase is small with respect to the same reducing agent pumping amount, or the pumping amount is small with the same driving duty setting. It is determined that the reducing agent passage 45 is broken and the reducing agent is leaking, or that the reducing agent pressure feed pump 47 is fixed. Further, when the proportional gain (K) is also lower than the fourth K threshold (K4), it is considered that the sensor signal is not a physical factor but an electrical abnormality of the sensor signal. Then, it is determined that the reducing agent pressure sensor 47 is electrically frozen.

  Among the specified reducing agent supply system abnormalities, when the second reducing agent passage 45 specified based on the value of the proportional gain K is clogged or damaged, the reducing agent injection control cannot be continued. Since it is possible, the reducing agent injection control is stopped.

  Some of these factors can be affected by multiple events. For this reason, it becomes possible to specify a failure site more accurately by comprehensively determining an event that causes an abnormality by a combination of coefficients in which the abnormality appears.

  When the abnormality diagnosis unit 67 detects an abnormality of the reducing agent pressure sensor 47 based on such a determination method, the abnormality diagnosis unit 67 gives an instruction to a warning unit that notifies the driver or the like of the abnormality of the reducing agent pressure sensor 47. In addition to outputting, the pump control unit 59 is instructed to perform feedback control of the reducing agent pumping pump 42 based on the estimated pressure Pest calculated by the second pressure calculation unit 57. On the other hand, when the abnormality diagnosing unit 67 detects an abnormality in the reducing agent supply system, the abnormality diagnosing unit 67 outputs an instruction to a warning means that informs the driver of the abnormality in the reducing agent supply system and repairs the reducing agent supply system. , Encourage exchange.

  In addition, the abnormality diagnosis unit 67 of the present embodiment may reduce the reducing agent pressure sensor 47 or the reducing agent supply system when the difference ΔP is not zero or more and a predetermined time has passed without the difference ΔP being zero. It is determined that there is an error in the characteristics, and a correction execution signal is output to the sensor value correction unit 69 described later. On the other hand, the abnormality diagnosis unit 67 determines that the reducing agent pressure sensor 47 and the reducing agent supply system are in a normal state in a state other than the above. The value of the threshold value ΔP0 can be appropriately set in consideration of the allowable error of the reducing agent injection amount, and the allowable error of the reducing agent injection amount increases as ΔP0 increases.

(4) Sensor Value Correction of Reducing Agent Pressure Sensor Further, the reducing agent injection control device 30 has a difference ΔP between the pressure Pact and the estimated pressure Pest in the abnormality diagnosis unit 67 described above that is less than a predetermined threshold value ΔP0. In addition, a sensor value correction unit 69 is provided as a part for performing offset correction of the value of the pressure Pact calculated by the first pressure calculation unit 53 when a non-zero state continues for a predetermined time or more.

  That is, the pressure Pact calculated using the sensor value and the estimated pressure Pest calculated using the learned pressure change model are one, even though it cannot be said that an abnormality has occurred in the reducing agent pressure sensor 47. If not, the sensor value correction unit 69 determines that an error has occurred in the characteristics of the reducing agent pressure sensor 47 or the reducing agent supply system. Then, the sensor value correction unit 69 performs offset correction on the value of the pressure Pact calculated by the first pressure calculation unit 53 so that feedback control of the reducing agent pressure pump 42 is performed based on the correction value.

  In the sensor value correction unit 69 of the reducing agent injection control apparatus 30 of the present embodiment, the difference ΔP between the pressure Pact and the estimated pressure Pest is less than the predetermined threshold ΔP0 in the abnormality diagnosis unit 67 described above, and zero. When the non-continuous state continues for a predetermined number of times or more, the value of the estimated pressure Pest / pressure Pact is used as the correction coefficient α, and the correction pressure Pact ′ obtained by multiplying the pressure Pact calculated by the first pressure calculation unit 53 by the correction coefficient α is used. Is output to the pump control unit 59. By executing this offset correction, errors caused by the characteristics of the reducing agent pressure sensor 47 or the reducing agent supply system are reduced, and feedback control of the reducing agent pressure feed pump 42 is performed more accurately.

5). Next, regarding the feedback control of the reducing agent pressure feed pump in the control method of the exhaust purification device 10 by the reducing agent injection control device 30 of the present embodiment shown in FIG. 2, the flow of FIG. 7 to FIG. Based on
First, as shown in FIG. 7, after the internal combustion engine 5 is started, the sensor value detection unit 51 detects the sensor value Vp of the reducing agent pressure sensor 47 in step S <b> 1. Next, in step S2, the first pressure calculator 53 calculates the pressure Pact in the second reducing agent passage 45 based on the sensor value Vp. Next, in step S3, the pump control unit 59 performs feedback control of the reducing agent pressure feed pump 42 using the calculated pressure Pact.

In a state where the feedback control of the reducing agent pressure feed pump 42 is being performed, learning control is performed in step S4. FIG. 8 shows a specific flow of learning control.
First, in step S <b> 11, the learning control unit 56 changes the target pressure Ptgt in the second reducing agent passage 45 for performing drive control of the reducing agent pumping pump 42 in steps. Next, in step S12, the pressure change storage unit 55 returns the response of the pressure Pact calculated by the first pressure calculation unit 53 based on the sensor value Vp of the reducing agent pressure sensor 47 according to the step change of the target pressure Ptgt. Remember. Next, in step S13, the dead time (L), the damping coefficient (ξ), the natural frequency (ω), and the proportional gain (K) are obtained based on the stored response log of the pressure Pact. Adjust the coefficient.

  Next, after the learning control unit 56 changes the target pressure Ptgt again in step S14, the sensor value detection unit 51 detects the sensor value Vp of the reducing agent pressure sensor 47 in step S15, and in step S16, The first pressure calculator 53 calculates the pressure Pact based on the sensor value Vp. Furthermore, in step S17, the second pressure calculator 57 calculates the estimated pressure Pest based on the above equation (1) using each coefficient adjusted in step S13.

  In step S18, the pressure comparison unit 65 compares the pressure Pact calculated based on the sensor value Vp with the estimated pressure Pest calculated based on the approximate expression (1) into which each learned coefficient is substituted. If these two values match or fall within an error within a predetermined range, the pressure change storage unit 55 updates each learned coefficient as the latest value, and ends the learning control. On the other hand, if the two values do not match or there is a difference greater than the error within the predetermined range, the process returns to step S11 again, and the two values match or the error within the predetermined range. The following steps S11 to S18 are repeated until it stops. In this way, when the learning control in step S4 in FIG. 7 is performed and the approximate expression (1) is updated, the process proceeds to step S21 in FIG.

  In step S21, the sensor value detector 51 detects the sensor value Vp of the reducing agent pressure sensor 47, and then in step S22, the first pressure calculator 53 determines the second reducing agent passage based on the sensor value Vp. The pressure Pact within 45 is calculated. Further, in step S23, the second pressure calculator 57 calculates the estimated pressure Pest in the second reducing agent passage 45 using the updated approximate expression (1).

  Next, in step S24, the pressure comparison unit 65 compares the pressure Pact obtained based on the sensor value Vp with the estimated pressure Pest, and if these two values match or an error within a predetermined range is detected. Determine if it is trapped. If these two values match, there is no abnormality in the reducing agent pressure sensor 47, so the process proceeds to step S25, where the pump control unit 59 sets the pressure Pact obtained based on the sensor value Vp. The feedback control of the reducing agent pumping pump 42 is continued by using it.

  On the other hand, if the values of the two pressures do not match or if an error exceeding the predetermined range has occurred, there is a possibility that some abnormality has occurred in the reducing agent supply device 40, so the process proceeds to step S26, The calculation of the pressure Pact based on the sensor value Vp and the estimated pressure Pest using the approximate expression (1) is continued, and the pressure comparison unit 65 keeps the difference ΔP between the two pressures exceeding the preset threshold value ΔP0 for a predetermined time. It is determined whether or not T1 has elapsed. When the predetermined time T1 has passed with the difference ΔP between the two pressures exceeding the threshold value ΔP0, the learning control shown in FIG. 8 is performed again in step S27, and each coefficient is obtained.

  Next, in step S28, as already described with reference to FIG. 6, the abnormality diagnosis unit 67 compares the obtained coefficients with preset threshold values, thereby reducing the reducing agent pressure sensor 47 or the reducing agent supply system. In Step S29, the abnormality diagnosis unit 67 determines whether or not an abnormality has occurred in the reducing agent pressure sensor 47. If an abnormality has occurred in the reducing agent pressure sensor 47, in step S30, a warning instruction for informing the sensor abnormality is output, and then the process proceeds to step S31. The pump control unit 59 does not use the reducing agent pressure sensor 47. The feedback control of the reducing agent pressure feed pump 42 is performed using the estimated pressure Pest obtained based on the approximate expression (1).

  On the other hand, if it is determined in step S29 that no abnormality has occurred in the reducing agent pressure sensor 47, there is a high possibility that an abnormality has occurred in the reducing agent supply system, so the process proceeds to step S32 to supply the reducing agent. After outputting the warning display notifying the abnormality of the system, the abnormality diagnosis unit 67 determines whether or not the second reducing agent passage 45 is clogged or broken in step S33.

  Unless the clogging or breakage of the second reducing agent passage 45 has occurred, the reducing agent injection control can be continued. Therefore, the process proceeds to step S25 until the reducing agent supply system is repaired or replaced. The feedback control of the reducing agent pressure feed pump 42 using the sensor value Vp is continued. On the other hand, if the second reducing agent passage 45 is clogged or damaged, the reducing agent injection control cannot be continued, so the process proceeds to step S34, and the reducing agent injection control is stopped and terminated.

  If it is determined in step S26 that the difference ΔP between the pressure Pact based on the sensor value Vp and the estimated pressure Pest based on the approximate expression (1) does not exceed the threshold ΔP0 for a predetermined time T1, the process proceeds to step S35. Then, the abnormality diagnosis unit 67 determines whether or not the difference ΔP is not zero continuously for a predetermined time T1 or exceeds a predetermined range error. When the difference ΔP between the two pressures becomes zero within the predetermined time T1 or falls within a predetermined range of error, the risk of abnormality of the reducing agent supply device 40 is low, and the process proceeds to step S25. The pump control unit 59 continues the feedback control of the reducing agent pumping pump 42 using the pressure Pact based on the sensor value Vp.

  On the other hand, if the difference ΔP between the two pressures is not zero continuously for a predetermined time T1 or exceeds a predetermined range error, an error occurs in the characteristics of the reducing agent pressure sensor 47 or the reducing agent supply system itself. Since the sensor value correction unit 69 calculates the correction coefficient α (= Pest / Pact) in step S36, the process proceeds to step S37, where the pump control unit 59 sets the pressure Pact based on the sensor value Vp. Feedback control of the reducing agent pumping pump 42 is performed using the correction pressure Pact ′ corrected for offset.

  As described above, after determining in step S25, step S31, or step S37 which value is used for feedback control of the reducing agent pressure feed pump 42, the process returns to step S21 again. The subsequent steps are repeated.

  As described above, according to the reducing agent injection control device 30 of the present embodiment, the pressure change in the second reducing agent passage is modeled while the reducing agent pressure sensor 47 is normal, and the reducing agent pressure sensor 47 is modeled. When abnormality occurs, feedback control of the reducing agent pump is performed by the estimated pressure based on the modeled pressure change. Therefore, even when the reducing agent pressure sensor 47 is abnormal, the reducing agent injection amount control is appropriately performed, and the excess or deficiency of the reducing agent to be injected is reduced.

5: engine, 10: exhaust gas purification device, 11: exhaust pipe, 13: reduction catalyst, 15: NO _X sensor 30: reducing agent injection controller, 40: reducing agent supply device, 41: storage tank, 42: Reduction Agent pressure feed pump, 43: reducing agent injection valve, 47: reducing agent pressure sensor, 51: sensor value detection unit, 53: first pressure calculation unit, 55: pressure change storage unit, 56: learning control unit, 57: first 2 pressure calculation unit, 59: pump control unit, 61: target injection amount calculation unit, 63: injection valve control unit, 65: pressure comparison unit, 67: abnormality diagnosis unit, 69: sensor value correction unit

Claims (8)

A reducing agent that pumps the reducing agent to the reducing agent injection valve provided in the exhaust passage of the internal combustion engine by the reducing agent pumping means and controls the opening and closing of the reducing agent injection valve to inject the reducing agent into the exhaust passage. In the injection control device,
A first pressure calculation unit that calculates a pressure in the reducing agent passage based on a sensor value of a pressure sensor provided in a reducing agent passage connecting the reducing agent pumping means and the reducing agent injection valve;
In the reducing agent passage based on at least the flow rate of the reducing agent by the reducing agent pumping means and the amount of the reducing agent flowing out from the reducing agent supply system including the reducing agent pumping means and the reducing agent passage. A pressure change memory for modeling pressure changes;
A second pressure calculation unit that calculates an estimated pressure in the reducing agent passage based on a pressure change in the reducing agent passage modeled by the pressure change storage unit when the pressure sensor is abnormal;
Based on the pressure calculated by the first pressure calculation unit or the estimated pressure calculated by the second pressure calculation unit, the reducing agent pumping is performed so that the pressure in the reducing agent passage becomes a predetermined value. A pressure feeding means control unit for performing feedback control of the means;
An injection valve control unit that calculates a target injection amount of the reducing agent and performs opening / closing control of the reducing agent injection valve;
A reducing agent injection control device comprising:   The pressure change storage unit generates a dead time (L) from when the output of the reducing agent pumping means changes due to the characteristics of the reducing agent supply system until the pressure sensor starts to respond, and the pressure sensor responds. The pressure change in the reducing agent passage is modeled on the basis of the relationship between the second order delay (D) until the pressure in the reducing agent passage reaches a target value. Item 2. The reducing agent injection control device according to Item 1.   The pressure change storage unit changes the target pressure in the reducing agent passage in steps when the reducing agent is not injected by the reducing agent injection valve, and changes the pressure in the reducing agent passage at that time. 3. The reducing agent injection control apparatus according to claim 2, wherein the modeling is performed based on the model.   Abnormal diagnosis of the pressure sensor by recalculating the relationship between the dead time (L) and the second-order lag (D) during or after the injection control of the reducing agent and comparing it with the modeled relationship The reducing agent injection control device according to claim 2, further comprising an abnormality diagnosis unit that performs the operation.   The reducing agent injection control device according to claim 4, wherein the abnormality diagnosis unit further performs abnormality diagnosis of the reducing agent supply system.   When the difference between the pressure calculated by the first pressure calculation unit and the estimated pressure calculated by the second pressure calculation unit is more than a predetermined value, the ratio of the estimated pressure to the pressure 6. A reducing agent injection control according to claim 1, further comprising a sensor value correction unit configured to correct the sensor value used in the first pressure calculation unit according to a correction coefficient indicated. apparatus. A reduction catalyst disposed in an exhaust passage of the internal combustion engine; a reducing agent supply device for injecting a reducing agent into the exhaust passage upstream of the reduction catalyst; and controlling the reducing agent supply device to control the reducing agent In an exhaust gas purification apparatus for an internal combustion engine, comprising a reducing agent injection control device for injecting gas into the exhaust passage,
The reducing agent supply device includes: a storage tank in which the reducing agent is stored; a reducing agent injection valve provided in the exhaust passage; and a reducing agent pumping unit that pumps the reducing agent to the reducing agent injection valve. Prepared,
The reducing agent injection control device calculates a pressure in the reducing agent passage based on a sensor value of a pressure sensor provided in a reducing agent passage connecting the reducing agent pumping means and the reducing agent injection valve. 1 pressure calculation unit, at least the flow rate of the reducing agent by the reducing agent pumping unit, and the amount of the reducing agent flowing out from the reducing agent supply system including the reducing agent pumping unit and the reducing agent passage. A pressure change storage unit that models a pressure change in the reducing agent passage based on the pressure change storage unit that is modeled by the pressure change storage unit when the pressure sensor is abnormal. Based on the second pressure calculation unit for calculating the estimated pressure in the first pressure calculation unit and the pressure calculated by the first pressure calculation unit or the estimated pressure calculated by the second pressure calculation unit. The pressure in the passage is A pressure-feeding means control unit that performs feedback control of the reducing agent pressure-feeding means so as to be a value, and an injection valve control unit that calculates a target injection amount of the reducing agent and performs opening / closing control of the reducing agent injection valve. An exhaust emission control device for an internal combustion engine. A reducing agent that pumps the reducing agent to the reducing agent injection valve provided in the exhaust passage of the internal combustion engine by the reducing agent pumping means, and injects the reducing agent into the exhaust passage by controlling the opening and closing of the reducing agent injection valve. In the abnormality diagnosis device of the reducing agent injection device for diagnosing abnormality of the injection device,
A first pressure calculation unit that calculates a pressure in the reducing agent passage based on a sensor value of a pressure sensor provided in a reducing agent passage connecting the reducing agent pumping means and the reducing agent injection valve;
Based on the pressure calculated by the first pressure calculation unit, a pressure feeding means control unit that performs feedback control of the reducing agent pressure feeding means so that the pressure in the reducing agent passage becomes a predetermined value;
In the reducing agent passage based on at least the flow rate of the reducing agent by the reducing agent pumping means and the amount of the reducing agent flowing out from the reducing agent supply system including the reducing agent pumping means and the reducing agent passage. A pressure change memory for modeling pressure changes;
An abnormality that diagnoses an abnormality in the pressure sensor and the reducing agent pumping system by recalculating a model of pressure change in the reducing agent passage during or after the injection control of the reducing agent and comparing it with a stored model. A diagnostic department;
An abnormality diagnosis device for a reducing agent injection device, comprising: