JP7052422B2 - Anomaly detection device - Google Patents

Description

The present invention relates to an abnormality detection device applied to an exhaust purification system that adds a liquid reducing agent to an exhaust passage of an internal combustion engine.

In recent years, the urea SCR (Selective Catalytic Reduction) system has been developed as an exhaust purification system that purifies NOx (nitrogen oxides) in exhaust gas with a high purification rate in engines applied to vehicles (especially diesel engines). It is mass-produced.

The urea SCR system exhausts the engine from a pump that pumps urea water (urea aqueous solution) as a reducing agent stored in the tank to the reducing agent passage and urea water (urea aqueous solution) as a reducing agent stored in the tank. It is equipped with an addition valve that adds to the passage.

In the urea SCR system, the exhaust gas is purified by the reduction reaction of NOx on the NOx purification catalyst (hereinafter referred to as SCR catalyst) in the exhaust passage. In the reduction of NOx, first, the urea water injected from the injection valve into the exhaust passage is hydrolyzed by the exhaust heat to generate ammonia (NH3), which is adsorbed by the SCR catalyst. NOx is reduced and purified by performing a reduction reaction with ammonia on the SCR catalyst with respect to NOx in the exhaust gas.

In such a urea SCR system, when the operation of the injection valve is hindered by the crystallization of urea or foreign matter invades the injection valve from the exhaust passage side through the injection hole of the injection valve, urea water is used. An abnormality may occur in the injection amount. In order to deal with this, Patent Document 1 proposes a device for determining an abnormality of an injection valve by using a duty ratio for controlling a current supplied to a pump (hereinafter referred to as a pump duty ratio). There is. Specifically, a device for determining the presence or absence of an abnormality in the injection valve based on the pump duty ratio in the non-injection state of urea water during the injection control is disclosed.

Japanese Unexamined Patent Publication No. 2013-249801

However, in the urea SCR system described in Patent Document 1, the presence or absence of an abnormality in the injection valve is determined based on the pump duty ratio during injection control. Therefore, in a state where injection control is not performed, for example, when the SCR catalyst is inactive at a low temperature, it is difficult for a difference in the pump duty ratio for determining an abnormality to occur, so that the presence or absence of an abnormality in the injection valve can be accurately determined. Can't. There is a demand for a technique for suitably determining the presence or absence of an abnormality in an addition valve in a state where addition control such as injection control is not performed. It should be noted that such a problem is not limited to urea water, but is a common problem when another liquid is used as a reducing agent.

In view of the above circumstances, it is an object of the present invention to provide an abnormality detection device capable of suitably determining the presence or absence of an abnormality in an addition valve in a state where addition control is not performed.

The injection control device of the present invention is provided in the exhaust passage of an internal combustion engine, and has an addition valve that adds and supplies a liquid reducing agent to a NOx purification catalyst that purifies NOx in the exhaust, a tank that stores the reducing agent, and forward rotation. An abnormality detection device applied to an exhaust purification system including a pump that discharges the reducing agent in the tank and sucks the reducing agent back into the tank by reverse rotation, wherein the pump is rotated in the reverse direction. A switching unit that switches the addition valve between an open state and a closed state in the closed state, and an acquisition unit that acquires the amount of fluctuation in the rotation speed of the pump or its correlation value as a rotation fluctuation parameter due to the switching of the addition valve. A determination unit for determining the presence or absence of an abnormality in the addition valve based on the rotation fluctuation parameter.

In the present invention, the addition valve is switched between the open state and the closed state when the pump is rotated in the reverse direction in which the addition control is not performed. When the addition valve is normal, switching the open / closed state of the addition valve changes the pump load, so that, for example, the amount of fluctuation in the pump rotation speed becomes large. On the other hand, if the addition valve is abnormal, the amount of change in the pump load becomes small, so that the amount of change becomes small. That is, there is a correlation between the amount of fluctuation in the pump rotation speed and the presence or absence of an abnormality in the addition valve. Therefore, based on this fluctuation amount, it is possible to suitably determine the presence or absence of an abnormality in the addition valve in a state where the addition control is not performed.

The block diagram which shows the outline of the exhaust gas purification system of an engine. The flowchart which shows the abnormality determination processing which concerns on 1st Embodiment. A flowchart showing a fluctuation amount acquisition process. The figure which shows the transition of the rotation speed of a pump in the injection valve control. The figure which shows the transition of urea water in the abnormality determination processing. The transition of the pump duty ratio in the abnormality judgment processing is shown. The transition of the pump duty ratio in the abnormality judgment processing is shown. The transition of the pump duty ratio in the abnormality judgment processing is shown. The flowchart which shows the abnormality determination processing which concerns on 2nd Embodiment. The transition of the pump duty ratio in the abnormality judgment processing is shown.

(First Embodiment)
Hereinafter, the exhaust gas purification system 10 to which the pump control unit 70 according to the abnormality detection device of the first embodiment is applied will be described with reference to the drawings. The exhaust gas purification system 10 purifies NOx in the exhaust gas by using a selective reduction catalyst (hereinafter referred to as SCR catalyst), and is constructed as a urea SCR system. The exhaust purification system 10 can be applied to various vehicles equipped with a diesel engine (hereinafter referred to as an engine) 30 which is an internal combustion engine. The exhaust gas purification system 10 can also be applied to construction machinery such as mobile cranes, agricultural machinery such as tractors, and the like.

As shown in FIG. 1, in the exhaust purification system 10, in the engine exhaust system, an exhaust pipe 31 forming an exhaust passage 31a is connected to the engine 30, and the exhaust pipe 31 is connected to the exhaust pipe 31 in order from the exhaust upstream side. A Diesel Particulate Filter) 32 and an SCR catalyst 33 are arranged. Further, in the exhaust pipe 31, between the DPF 32 and the SCR catalyst 33, there is a urea water injection valve (hereinafter referred to as an injection valve) 50 that injects and supplies urea water (urea aqueous solution) as a liquid reducing agent to the exhaust passage 31a. It is provided. The injection valve 50 is attached so that only the tip side is located in the exhaust pipe 31 in order to avoid the influence of heat applied from the high temperature exhaust gas (for example, 600 ° C.) as much as possible. In the present embodiment, the SCR catalyst 33 corresponds to the "NOx purification catalyst" and the injection valve 50 corresponds to the "additional valve".

The DPF 32 is a PM removal filter that collects PM (particulate matter) in the exhaust gas. DPF32 carries a platinum-based oxidation catalyst and removes HC and CO together with a soluble organic component (SOF) which is one of the PM components. The PM collected in the DPF 32 can be burned and removed by post-injection or the like after the main fuel injection in the engine 30, whereby the DPF 32 can be continuously used.

The SCR catalyst 33 promotes a NOx reduction reaction (exhaust gas purification reaction), for example.
4NO + 4NH3 + O2 → 4N2 + 6H2O ... (Equation 1)
6NO2 + 8NH3 → 7N2 + 12H2O ... (Equation 2)
NO + NO2 + 2NH3 → 2N2 + 3H2O ... (Equation 3)
It promotes such a reaction and purifies NOx in the exhaust gas. In these reactions, the injection valve 50 provided on the upstream side of the SCR catalyst 33 jets and supplies urea water for producing ammonia (NH3) which is a reducing agent for NOx.

An oxidation catalyst as an ammonia removing device may be provided on the downstream side of the SCR catalyst 33 in the exhaust pipe 31. This oxidation catalyst removes ammonia (NH3) discharged from the SCR catalyst 33, that is, excess ammonia.

Next, each configuration of the urea water injection system 20 that injects urea water by the injection of the injection valve 50 in the exhaust purification system 10 will be described. In the following description, for convenience, the tank 40 side is on the upstream side and the injection valve 50 side is on the downstream side, based on the case where urea water is supplied to the injection valve 50 from the urea water tank (hereinafter referred to as tank) 40. Described as the side.

In FIG. 1, the tank 40 is composed of a closed container with a liquid supply cap, and urea water having a predetermined concentration is stored in the tank 40. In this embodiment, the urea concentration is 32.5%, which is the lowest freezing temperature (freezing point). When the urea concentration is 32.5%, it freezes at -11 ° C or lower.

The tank 40 and the injection valve 50 are connected by a supply pipe 42. The upstream end of the supply pipe 42 is connected to substantially the center of the bottom surface of the tank 40, and the urea water stored in the tank 40 flows into the supply pipe 42. In this embodiment, the supply pipe 42 corresponds to the “reducing agent passage”.

A urea water pump (hereinafter referred to as a pump) 44 is provided in the middle of the supply pipe 42. The pump 44 is an electric pump that is rotationally driven by a current supplied from the pump control unit 70, and pressurizes and supplies urea water from the tank 40 to the injection valve 50 via the supply pipe 42.

The pump 44 has a gear 45 and supplies urea water according to the rotation speed of the gear 45. Further, in the pump 44, the gear 45 can rotate in either the forward or reverse direction. The forward rotation of the pump 44 discharges the urea water in the tank 40, and the reverse rotation of the pump 44 sucks the urea water back into the tank 40.

The pump 44 is provided with a rotation detection unit 46. The rotation detection unit 46 detects the rotation speed N, which is the rotation speed of the pump 44 per unit time, and for example, detects the discharge (pumping) speed of urea water by the pump 44.

The supply pipe 42 is provided with a pressure detection unit 48 on the downstream side of the pump 44. The pressure detection unit 48 detects the pressure (hereinafter referred to as pipe pressure) P in the supply pipe 42, and detects, for example, the discharge pressure of urea water by the pump 44.

The injection valve 50 is connected to the downstream end of the supply pipe 42. The injection valve 50 has almost the same configuration as the existing fuel injection valve (injector), and a known configuration can be adopted. Therefore, the configuration will be briefly described here. The injection valve 50 is configured as an electromagnetic on-off valve including a drive unit including an electromagnetic solenoid or the like and a valve body portion having a needle 52 for opening and closing the tip injection port, and is driven from the pump control unit 70. Open or close based on the signal. That is, when the electromagnetic solenoid is energized based on the drive signal, the needle 52 moves in the opening direction along with the energization, and the tip injection port is opened by the movement of the needle 52 to inject urea water.

A branch pipe 54 is connected to the supply pipe 42. The branch pipe 54 connects the branch portion B on the downstream side of the pump 44 in the supply pipe 42 and the tank 40. The pressure detection unit 48 is provided in a portion of the supply pipe 42 between the pump 44 and the branch portion B.

One end of the branch pipe 54 is connected to the bottom surface of the tank 40, and a check valve 60 is provided at one end of the branch pipe 54. The check valve 60 closes when the pressure in the branch pipe 54 is lower than the predetermined pressure, and prevents the urea water stored in the tank 40 from flowing into the branch pipe 54. Further, the check valve 60 is opened when the pressure in the branch pipe 54 is higher than a predetermined pressure, and the urea water flowing from the supply pipe 42 into the branch pipe 54 is allowed to return to the tank 40.

A heating element 62 is provided in the tank 40. For example, the heating element 62 is an electric heater, and the urea water frozen in the tank 40 is thawed by energization based on a command signal from the pump control unit 70. The heating element 62 may be provided at a position where the frozen urea water can be thawed, and may be provided near the suction port of the supply pipe 42.

A heating element 64 is provided on the outer periphery of the supply pipe 42. For example, the heating element 64 is an electric heater, and the frozen urea water is thawed in the supply pipe 42 by energization from the pump control unit 70.

A temperature sensor 66 is provided in the tank 40. For example, the temperature sensor 66 is a temperature sensitive diode or a thermistor, and measures the temperature of urea water in the tank 40. Further, an outside air temperature sensor 68 is provided outside the tank 40. For example, the outside air temperature sensor 68 is a temperature-sensitive diode or a thermistor, which is arranged apart from the tank 40 and measures the temperature of the outside air around the vehicle on which the engine 30 is mounted.

The pump control unit 70 is an ECU (Electronic Control Unit) that controls exhaust purification, and is composed of a microcomputer including a CPU, a ROM, a RAM, an input / output interface, and the like. The pump control unit 70 acquires the rotation speed N from the rotation detection unit 46, acquires the pipe pressure P from the pressure detection unit 48, acquires the temperature of the urea water in the tank 40 from the temperature sensor 66, and acquires the temperature of the urea water in the tank 40 from the temperature sensor 66, and the outside air temperature sensor 68. Get the outside temperature from. The pump control unit 70 controls each unit of the urea water injection system 20 based on these acquired values. In the present embodiment, the pump control unit 70 corresponds to the "abnormality detection device".

Specifically, when urea water is pressure-fed to the injection valve 50 side, the pump 44 is rotationally driven in the forward rotation direction by energizing the pump 44. As a result, the urea water in the tank 40 is discharged and flows to the downstream side. Then, urea water is pumped from the pump 44, and the urea water is supplied to the injection valve 50. Further, the excess urea water is returned to the tank 40 through the check valve 60.

Further, when the urea water is sucked back into the tank 40, the pump 44 is rotationally driven in the reverse rotation direction. As a result, the urea water in the supply pipe 42 is sucked into the tank 40. This prevents the urea water from remaining in the supply pipe 42 while the vehicle is left unattended after the engine 30 is stopped, and suppresses damage to the supply pipe 42 due to freezing and expansion of the urea water.

When urea water is pressure-fed to the injection valve 50 side, urea water is injected and supplied into the exhaust pipe 31 by the injection valve 50. Then, urea water is supplied to the SCR catalyst 33 together with the exhaust gas in the exhaust pipe 31, and the exhaust gas is purified by the reduction reaction of NOx in the SCR catalyst 33. When reducing NOx, for example,
(NH2) 2CO + H2O → 2NH3 + CO2 ... (Equation 4)
Urea water is hydrolyzed under high temperature due to exhaust heat. As a result, ammonia (NH3) is generated, and the ammonia is adsorbed on the SCR catalyst 33, and NOx in the exhaust gas is selectively reduced and removed by the ammonia in the SCR catalyst 33. That is, NOx is reduced and purified by performing a reduction reaction based on ammonia (the above reaction formulas (formula 1) to (formula 3)) on the SCR catalyst 33.

By the way, the pump control unit 70 controls the duty ratio (pump duty ratio) DU of the current supplied to the pump 44 when the urea water is pumped to the injection valve 50 side, so that the urea supplied to the injection valve 50 is supplied. The amount of water, that is, the injection amount Q is controlled. Therefore, when urea crystallizes or foreign matter invades the injection valve 50 from the exhaust pipe 31 side through the injection hole of the injection valve 50 and an abnormality occurs in the injection amount Q, the pump duty ratio The abnormality of the injection valve 50 can be determined from the DU.

However, in a state where urea water pressure feeding to the injection valve 50 side is not performed, for example, when the SCR catalyst 33 is inactive at a low temperature, the pump duty ratio DU for determining an abnormality is unlikely to differ. The abnormality of 50 cannot be accurately determined.

The pump control unit 70 of the present embodiment carries out an abnormality determination process in order to solve the above problem. The abnormality determination process switches the injection valve 50 between an open state (hereinafter referred to as an open state) and a closed state (hereinafter referred to as a closed state) in a situation where the pump 44 is rotating in the reverse direction, and the injection valve 50 is used. The fluctuation amount ΔDU of the pump duty ratio DU due to the switching of the pump duty ratio DU is acquired, and the presence or absence of an abnormality in the injection valve 50 is determined based on the acquired fluctuation amount ΔDU. Thereby, the abnormality of the injection valve 50 can be accurately determined in the state where the urea water pressure feeding to the injection valve 50 side is not performed.

FIG. 2 shows a flowchart of the abnormality determination process of the present embodiment. The abnormality determination process is repeatedly performed at predetermined time intervals while the engine 30 is being driven.

When the abnormality determination process is started, first, in step S10, it is determined whether the engine 30 is in operation. Specifically, it is determined whether the ignition switch of the vehicle on which the engine 30 is mounted is on.

If a negative determination is made in step S10, the abnormality determination process ends. On the other hand, if an affirmative determination is made in step S10, it is determined in step S12 whether the abnormality determination process can be performed. Specifically, the temperature sensor 66 and the outside air temperature sensor 68 are used to determine whether the urea water in the tank 40 is in a frozen state. Further, the rotation detection unit 46 is used to determine whether or not urea water pressure feeding to the injection valve 50 side has been started.

When the temperature measured by at least one of the temperature sensor 66 and the outside air temperature sensor 68 is -11 ° C or lower and the urea water is in a frozen state, or the pump 44 is rotating in the forward direction, urea to the injection valve 50 side. When the hydraulic feeding is started, a negative determination is made in step S12, and the abnormality determination process is terminated. In this case, necessary treatment such as thawing treatment of urea water may be carried out. On the other hand, when the urea water is not in a frozen state and the urea water pressure feeding to the injection valve 50 side has not been started, an affirmative determination is made in step S12, and the process proceeds to step S14.

In step S14, the injection valve 50 is closed. In the following step S16, when the injection valve 50 is closed, the pump 44 and the supply pipe 42 are filled with urea water by forward / reverse rotation of the pump 44. Specifically, the forward rotation and the reverse rotation of the pump 44 are alternately repeated a predetermined number of times. The specified number of times is, for example, 50 times. As a result, the air remaining in the pump 44 and the supply pipe 42 is discharged to the tank 40 via the check valve 60, and the supply pipe 42 is filled with urea water.

In the present embodiment, as a result of filling the pump 44 and the supply pipe 42 with urea water, the supply pipe 42 is filled with urea water in the range including the pump 44, and the supply pipe 42 is filled with urea. It is said to be filled with water.

In step S17, it is determined whether the filling of urea water is completed. For example, it is determined whether the forward rotation and the reverse rotation of the pump 44 are repeatedly performed a predetermined number of times. If a negative determination is made in step S17, the process returns to step S16. On the other hand, if an affirmative determination is made in step S17, the pump 44 is rotated in the reverse direction in step S18. Hereinafter, the pump 44 continues to rotate in the reverse direction until the abnormality determination process is completed.

In the following steps S20 and S22, the fluctuation amount ΔDU of the pump duty ratio DU is acquired, respectively. Hereinafter, the fluctuation amount ΔDU acquired in step S20 is referred to as a first fluctuation amount ΔDU1, and the fluctuation amount ΔDU acquired in step S22 is referred to as a second fluctuation amount ΔDU2.

The first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 are acquired by the fluctuation amount acquisition process shown in FIG. FIG. 3 shows a flowchart of the fluctuation amount acquisition process. In the fluctuation amount acquisition process, first, in step S70, the closed duty ratio DUc when the injection valve 50 is in the closed state is acquired. Next, in step S72, the injection valve 50 is switched from the closed state to the open state.

Next, in step S74, after a predetermined time after switching the injection valve 50 to the closed state, the open duty ratio DUo when the injection valve 50 is in the open state is acquired. Next, in step S76, the injection valve 50 is switched from the open state to the closed state. Finally, in step S78, the fluctuation amount ΔDU, which is the absolute value of the difference between the closed duty ratio DUc acquired in step S70 and the open duty ratio DUo acquired in step S70, is acquired, and the fluctuation amount acquisition process is terminated.

In the fluctuation amount acquisition process, in steps S72 and S76, the injection valve 50 is switched between the open state and the closed state while the pump 44 is rotated in the reverse direction. Then, in step S78, the fluctuation amount ΔDU of the pump duty ratio DU accompanying the switching of the injection valve 50 is acquired. In the present embodiment, the processing of steps S72 and S76 corresponds to the "switching unit", the processing of step S78 corresponds to the "acquisition unit", and the fluctuation amount ΔDU corresponds to the "correlation value" and the "rotation fluctuation parameter". ..

Specifically, in the process of step S20, in the situation where the supply pipe 42 is filled with urea water, the injection valve 50 is switched from the closed state to the open state while the pump 44 is rotated in the reverse direction, and the injection valve 50 is used. Acquires the first fluctuation amount ΔDU1 when switching from the closed state to the open state. By continuously executing the process of step S20 and the process of step S22, the injection valve 50 is switched from the closed state to the open state a plurality of times while the pump 44 is rotated in the reverse direction. The fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 are acquired.

When the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 are acquired, in steps S24 to S54, it is determined whether or not there is an abnormality in the injection valve 50 based on the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2. .. In the present embodiment, the processes of steps S24 to S54 correspond to the "determination unit".

Specifically, first, in step S24, it is determined whether the first fluctuation amount ΔDU1 is larger than the predetermined first threshold value K1. The predetermined first threshold value K1 is a threshold value for determining an abnormality of the injection valve 50 based on the fluctuation amount ΔDU in a situation where the supply pipe 42 is filled with urea water.

If an affirmative determination is made in step S24, it is determined in step S26 whether the second fluctuation amount ΔDU2 is larger than the predetermined second threshold value K2. The predetermined second threshold value K2 is a threshold value for determining an abnormality of the injection valve 50 based on the fluctuation amount ΔDU in a situation where urea water is not contained in the supply pipe 42.

When the injection valve 50 is normal, the injection valve 50 is switched from the closed state to the open state in the process of step S20 (S72), so that the urea water in the pump 44 and the supply pipe 42 is discharged to the tank 40 by the reverse rotation of the pump 44. Is sucked back to. Therefore, the amount of urea water filled in the supply pipe 42 (in other words, injection) between the first switching of the injection valve 50 (S20) and the second switching of the injection valve 50 (S22). There is a difference in the amount of air flowing in from the valve 50). In the present embodiment, the second threshold value K2 is made different from the first threshold value K1 in consideration of this difference. Specifically, the second threshold value K2 is set to a value smaller than the first threshold value K1.

If an affirmative determination is made in step S26, it is determined in step S28 that the injection valve 50 is normal, and the abnormality determination process is terminated. On the other hand, if a negative determination is made in step S26, the fluctuation amount ΔDU of the pump duty ratio DU is acquired again in step S30. Hereinafter, the fluctuation amount ΔDU acquired in step S26 is referred to as a third fluctuation amount ΔDU3. The third fluctuation amount ΔDU3 is acquired by the fluctuation amount acquisition process shown in FIG.

In step S32, it is determined whether the third fluctuation amount ΔDU3 is larger than the second threshold value K2. If an affirmative determination is made in step S32, the process proceeds to step S28 and the abnormality determination process is terminated.

If a negative determination is made in step S32, the difference ΔGA of the fluctuation amount ΔDU is acquired in step S34. Here, the difference ΔGA is the absolute value of the difference between the first fluctuation amount ΔDU1 acquired in step S20 and the second fluctuation amount ΔDU2 acquired in step S22, and the first fluctuation amount ΔDU1 and step S30 acquired in step S20. It is the smaller of the absolute values of the difference from the acquired third fluctuation amount ΔDU3.

In step S36, it is determined whether the difference ΔGA is larger than the predetermined third threshold value K3. The predetermined third threshold value K3 is injected based on the difference ΔGA between the fluctuation amount ΔDU in the situation where the supply pipe 42 is filled with urea water and the fluctuation amount ΔDU in the situation where the supply pipe 42 does not contain urea water. It is a threshold value for determining the presence or absence of an abnormality in the valve 50, which is smaller than the first threshold value K1 and larger than the second threshold value K2. In this embodiment, the state in which urea water does not exist in the supply pipe 42 in the range including the pump 44 is referred to as the state in which urea water is not contained in the supply pipe 42.

If an affirmative determination is made in step S36, the process proceeds to step S28 to end the abnormality determination process. On the other hand, if a negative determination is made in step S36, it is determined in step S38 that the injection valve 50 is abnormal, and the abnormality determination process is terminated.

On the other hand, if a negative determination is made in step S24, it is determined in step S40 whether the second fluctuation amount ΔDU2 is larger than the second threshold value K2. If affirmative determination is made in step S40, the difference ΔGA of the fluctuation amount ΔDU is acquired in step S42. The difference ΔGA in step S42 is an absolute value of the difference between the first fluctuation amount ΔDU1 acquired in step S20 and the second fluctuation amount ΔDU2 acquired in step S22.

In the following step S44, it is determined whether the difference ΔGA is larger than the third threshold value K3. If an affirmative determination is made in step S44, the process proceeds to step S28 and the abnormality determination process is terminated. On the other hand, if a negative determination is made in step S44, it is determined in step S46 that the injection valve 50 is abnormal, and the abnormality determination process is terminated.

On the other hand, if a negative determination is made in step S40, the third fluctuation amount ΔDU3 is acquired in step S48. In the following step S50, it is determined whether the third fluctuation amount ΔDU3 is larger than the second threshold value K2. If a negative determination is made in step S50, the process proceeds to step S46 and the abnormality determination process is terminated.

If affirmative determination is made in step S50, the difference ΔGA of the fluctuation amount ΔDU is acquired in step S52. The difference ΔGA in step S52 is an absolute value of the difference between the first fluctuation amount ΔDU1 acquired in step S20 and the third fluctuation amount ΔDU3 acquired in step S48.

In the following step S54, it is determined whether the difference ΔGA is larger than the third threshold value K3. If an affirmative determination is made in step S54, the process proceeds to step S28 and the abnormality determination process is terminated. On the other hand, if a negative determination is made in step S54, the process proceeds to step S46 and the abnormality determination process is terminated.

Subsequently, FIG. 4 shows an example of control of the injection valve 50 including the abnormality determination process. Here, FIG. 4 shows the transition of the rotation speed N in the control of the injection valve 50. Here, FIG. 4A shows the transition of the piping pressure P, FIG. 4B shows the transition of the rotation speed N, and FIG. 4C shows the transition of the open / closed state of the injection valve 50. .. In FIG. 4, the pulsation due to the disturbance other than the injection of the injection valve 50 is removed from the piping pressure P and the rotation speed N. The same applies to FIGS. 6 and 7.

As shown in FIG. 4, at time t1, the ignition switch of the vehicle is turned on and the engine 30 is started. In the present embodiment, the urea water in the tank 40 is in a frozen state when the engine 30 is started. Therefore, a thawing process for thawing the urea water in the tank 40 is performed using the heating element 62.

When the urea water in the tank 40 is thawed at time t2 and the thawing process is completed, the abnormality determination process is performed during the period from time t2 to t3. The abnormality determination process will be described later. When the abnormality determination process is completed, the filling process is started at time t3. In the filling process, urea water is filled in the supply pipe 42 by rotating the pump 44 in the forward direction.

Specifically, at time t3, urea water is filled by rotation speed feedback control with the injection valve 50 open. After that, when the pipe pressure P reaches the reference pressure Po at time t4, urea water is filled by pressure feedback control with the injection valve 50 closed.

After that, when the pipe pressure P reaches the target pressure Ptg at time t5, the filling process is completed, and the injection process is performed in the period from time t5 to time t6. In the injection process, the pipe pressure P is maintained at the target pressure Ptg, the injection valve 50 is opened and closed based on the engine operating condition, and urea water is injected from the injection valve 50.

At time t6, when the ignition switch of the vehicle is turned off and the engine 30 is stopped, the injection process is terminated and the suction back process is started. In the suction back treatment, the urea water in the pump 44 and the supply pipe 42 is sucked back to the tank 40 by rotating the pump 44 in the reverse direction. After that, at time t7, when the suction back processing is completed, the control of the injection valve 50 is terminated.

Next, the abnormality determination process will be described. As shown in FIG. 4, when the abnormality determination process is started at time t3, urea water is filled in the supply pipe 42 by rotating the pump 44 forward and reverse at time t11. After that, when the filling of urea water is completed at time t12, the pump 44 is rotated in the reverse direction in the situation where the supply pipe 42 is filled with urea water at time t13.

FIGS. 5 to 8 show an example of the abnormality determination process after filling with urea water. More specifically, FIG. 5 shows a change in the urea water filling state in the supply pipe 42 when the injection valve 50 is switched between the closed state and the open state while the pump 44 is rotated in the reverse direction. Here, FIG. 5A shows a urea water filling state when the injection valve 50 is in the closed state, and FIG. 5B shows a urea water filling state when the injection valve 50 is switched to the open state. FIG. 5C shows a urea water filling state when the injection valve 50 is in the closed state, and when the urea water filled in the supply pipe 42 is less than a predetermined target amount, the urea water filling state is shown. It shows the state. In FIG. 5, the urea water injection system 20 is shown in a simplified manner, and the description of the pump control unit 70 and the like is omitted.

Further, FIGS. 6 to 8 show changes in the pump duty ratio DU in the abnormality determination process. In FIGS. 6 to 8, (a) shows the transition of the pump duty ratio DU, (b) shows the transition of the fluctuation amount ΔDU, and (c) shows the transition of the open / closed state of the injection valve 50.

In FIG. 6, the pump 44 is rotated in the reverse direction after the time t13, and under that state, the injection valve 50 is switched between the closed state and the open state. In FIG. 6, during the period from time t13 to t14, the pump 44 is rotated in the reverse direction with the injection valve 50 closed, and in such a state, the pump 44 is included in the supply pipe 42 as shown in FIG. 5A. The area is filled with urea water. At this time, the pump duty ratio DU becomes the first closed duty ratio DUc1.

Further, during the period from time t14 to t15, as the injection valve 50 is opened, air flows in from the injection hole of the injection valve 50, and as shown in FIG. 5B, the pump 44 is installed in the supply pipe 42. The included area is filled with air. As a result, the load on the pump 44 is reduced, so that the pump duty ratio DU is reduced to the open duty ratio DUo, and the first fluctuation amount ΔDU1 (ΔDU1 = DUc1-DUo) is acquired.

On the other hand, during the period from time t15 to t16, the injection valve 50 is closed, but the state in which urea water is not contained in the supply pipe 42 is maintained due to the reverse rotation of the pump 44. As a result, the pump duty ratio DU rises to the second closed duty ratio DUc2, but the second closed duty ratio DUc2 is smaller than the first closed duty ratio DUc1.

After that, in the period from time t16 to t17, the pump duty ratio DU is reduced to the open duty ratio DUo again as the injection valve 50 is opened again. As a result, the second fluctuation amount ΔDU2 (ΔDU2 = DUc2-DUo) is acquired.

When the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 are acquired, the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 are compared and determined using the threshold values K1 and K2. In this case, the first fluctuation amount ΔDU1 acquired at the time of the previous switching and the second fluctuation amount ΔDU2 acquired at the time of the later switching are compared and determined using different threshold values K1 and K2. Specifically, since the first fluctuation amount ΔDU1 acquired at the time of the previous switching has a large amount of urea water filled in the supply pipe 42 before the switching, a comparative determination is made using a relatively large first threshold value K1. Will be done. Further, the second fluctuation amount ΔDU2 acquired at the time of the subsequent switching is the first because the amount of urea water filled in the supply pipe 42 before the switching is small (the urea water is not contained in the supply pipe 42). The comparison is made using the second threshold value K2, which is smaller than the threshold value K1.

As shown in FIG. 6B, when the first fluctuation amount ΔDU1 is larger than the first threshold value K1 and the second fluctuation amount ΔDU2 is larger than the second threshold value K2, it is determined that the injection valve 50 is normal. Will be done. After that, the injection valve 50 is switched from the open state to the closed state in the state where the pump 44 is rotated in the reverse direction at the time t17, and then the reverse rotation of the pump 44 is stopped at the time t20, and the abnormality determination process is completed.

On the other hand, when a closing abnormality occurs in the injection valve 50 and the injection valve 50 is maintained in the closed state, the pump duty ratio DU is maintained at the closed duty ratio DUc regardless of the switching of the injection valve 50. Therefore, both the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2 become zero and become smaller than the first threshold value K1 and the second threshold value K2, so that it is determined that the injection valve 50 is abnormal.

Further, if an opening abnormality occurs in the injection valve 50 and the injection valve 50 cannot be closed, the pump duty ratio DU does not decrease to the closing duty ratio DUc regardless of the switching of the injection valve 50. Therefore, since the first fluctuation amount ΔDU1 is smaller than the first threshold value K1 and the second fluctuation amount ΔDU2 is smaller than the second threshold value K2, it is determined that the injection valve 50 is abnormal.

Even if no abnormality has occurred in the injection valve 50, for example, if air bubbles are mixed in the urea water filled in the supply pipe 42, the supply pipe 42 is filled as shown in FIG. 5 (c). The amount of urea water produced is less than the target amount. In this case, the pump duty ratio DU during the period from time t14 to t15 is the third closed duty ratio DUc3, which is smaller than the first closed duty ratio DUc1, and the first fluctuation amount ΔDU1 (ΔDU1 = DUc3-DUo) is the first threshold value K1. Is smaller than. On the other hand, since the injection valve 50 is normal, the second fluctuation amount ΔDU2 (ΔDU2 = DUc2-DUo) becomes larger than the second threshold value K2.

In the present embodiment, when the first fluctuation amount ΔDU1 is smaller than the first threshold value K1 and the second fluctuation amount ΔDU2 is larger than the second threshold value K2, the difference between the first fluctuation amount ΔDU1 and the second fluctuation amount ΔDU2. Obtain ΔGA. The amount of urea water filled in the supply pipe 42 before the switching is different between the first fluctuation amount ΔDU1 acquired at the time of the previous switching and the second fluctuation amount ΔDU2 acquired at the time of the subsequent switching. Therefore, a difference ΔGA is generated based on the difference in the amount of urea water filled in the supply pipe 42 before switching, and the presence or absence of an abnormality in the injection valve 50 can be determined based on this difference ΔGA. Specifically, the difference ΔGA is compared and determined using the third threshold value K3, and when the difference ΔGA is larger than the third threshold value K3, it is determined that the injection valve 50 is normal. On the other hand, when the difference ΔGA is smaller than the third threshold value K3, it is determined that the injection valve 50 is abnormal.

Further, even when an abnormality has not occurred in the injection valve 50, for example, in a situation where urea water is not contained in the supply pipe 42, the fluctuation amount ΔDU of the pump duty ratio DU due to switching is small. Therefore, as shown in FIG. 8A, when the disturbance other than the injection of the injection valve 50 is large such as noise, the second fluctuation amount ΔDU2 cannot be accurately acquired. In this case, as shown in FIG. 8B, the second fluctuation amount ΔDU2 acquired during the period from time t16 to t17 may be smaller than the second threshold value K2.

In the present embodiment, when the second fluctuation amount ΔDU2 is smaller than the second threshold value K2, the third fluctuation amount ΔDU3, which is the fluctuation amount ΔDU in the situation where the supply pipe 42 does not contain urea water, is acquired again. Specifically, when the injection valve 50 is closed during the period from time t17 to t18, the pump duty ratio DU rises to the second closing duty ratio DUc2, and the injection valve 50 is increased during the period from time t18 to t19. By opening, the pump duty ratio DU is reduced to the open duty ratio DUo. As a result, the third variable amount ΔDU3 (ΔDU3 = DUc2-DUo) is acquired.

When the third fluctuation amount ΔDU3 is acquired, the first fluctuation amount ΔDU1 and the third fluctuation amount ΔDU3 are compared and determined using the threshold values K1 and K2. Specifically, as shown in FIG. 8B, the acquired first fluctuation amount ΔDU1 is larger than the first threshold value K1, and the acquired third fluctuation amount ΔDU3 is larger than the second threshold value K2. If so, it is determined that the injection valve 50 is normal. After that, the injection valve 50 is switched from the open state to the closed state while the pump 44 is rotated in the reverse direction at time t19, and then the reverse rotation of the pump 44 is stopped at time t20, and the abnormality determination process is completed.

According to the present embodiment described above, the following effects are obtained.

In the present embodiment, the abnormality determination process is performed before the injection process. Therefore, the abnormality of the injection valve 50 can be detected earlier than the conventional technique of performing the abnormality determination processing in the middle of the injection processing.

In the present embodiment, in the abnormality determination process, the injection valve 50 is switched between the open state and the closed state (S72, S76) when the pump 44 rotates in the reverse direction (S18). When the injection valve 50 is normal, when the open / closed state of the injection valve 50 is switched, the load of the pump 44 changes, so that the fluctuation amount ΔDU of the pump duty ratio DU becomes large. On the other hand, if the injection valve 50 is abnormal, the fluctuation amount ΔDU of the pump duty ratio DU becomes small, so that the fluctuation amount ΔDU becomes small. That is, there is a correlation between the fluctuation amount ΔDU of the pump duty ratio DU and the presence or absence of an abnormality in the injection valve 50. Therefore, based on this fluctuation amount ΔDU, it is possible to suitably determine the presence or absence of an abnormality in the injection valve 50 in a state where the injection control is not performed.

In the present embodiment, the injection valve 50 is switched from the closed state to the open state in the state where the supply pipe 42 is filled with urea water (S16). When the injection valve 50 is normal, the fluctuation amount ΔDU of the pump duty ratio DU when the supply pipe 42 is filled with urea water, and the pump duty ratio DU when the supply pipe 42 does not contain urea water. It becomes larger than the fluctuation amount ΔDU. Therefore, it is possible to accurately determine the presence or absence of an abnormality in the injection valve 50 based on the fluctuation amount ΔDU of the pump duty ratio DU in the situation where the supply pipe 42 is filled with urea water.

In the present embodiment, the injection valve 50 is switched from the closed state to the open state a plurality of times in a state where the supply pipe 42 is filled with urea water (S20, S22). As a result, the amount of urea water filled in the supply pipe 42 changes before each switching, and the first fluctuation amount ΔDU1 acquired at the time of the previous switching and the second fluctuation amount ΔDU2 acquired at the time of the subsequent switching are changed. Can make a difference with.

In the present embodiment, the first fluctuation amount ΔDU1 acquired at the time of the previous switching and the second fluctuation amount ΔDU2 acquired at the time of the subsequent switching are compared and determined using different threshold values K1 and K2 (S24, S26). Therefore, the presence or absence of an abnormality in the injection valve 50 can be appropriately determined in consideration of the difference in the amount of urea water filled in the supply pipe 42.

Further, in the present embodiment, it is determined whether or not there is an abnormality in the injection valve 50 based on the difference ΔGA between the first fluctuation amount ΔDU1 acquired at the time of the previous switching and the second fluctuation amount ΔDU2 acquired at the time of the subsequent switching. (S36, S44, S54). Therefore, the presence or absence of an abnormality in the injection valve 50 can be appropriately determined based on the difference in the amount of urea water filled in the supply pipe 42.

(Second Embodiment)
Next, the pump control unit 70 according to the second embodiment will be described with reference to FIGS. 9 and 10. The pump control unit 70 according to the second embodiment has a different abnormality determination process than the pump control unit 70 according to the first embodiment. Hereinafter, the abnormality determination process according to the second embodiment will be described.

The difference between the abnormality determination process of the second embodiment and the abnormality determination process of the first embodiment is that the supply pipe 42 is not filled with urea water. In FIG. 9, the same contents as those described in FIG. 2 above will be omitted.

As shown in FIG. 9, in the abnormality determination process, when the injection valve 50 is closed in step S14, the acquisition number M (M: natural number) is set to "1" in step S80. Here, the acquisition frequency M is the number of acquisitions of the fluctuation amount ΔDU. In the following step S82, the fluctuation amount ΔDU is acquired. The fluctuation amount ΔDU is acquired by the fluctuation amount acquisition process shown in FIG. That is, in the process of step S82, in the situation where the supply pipe 42 does not contain urea water, the injection valve 50 is switched from the closed state to the open state while the pump 44 is rotated in the reverse direction, and the injection valve 50 is closed. The amount of fluctuation ΔDU when switching from to the open state is acquired.

In step S84, it is determined whether the acquisition number M has reached the target number Mtg (Mtg: a natural number of 2 or more). If a negative determination is made in step S84, the number of acquisitions M is increased by "1" in step S86, and the process returns to step S82. As a result, the process of step S82 is executed a plurality of times, and the fluctuation amount ΔDU at each switching is acquired.

On the other hand, if an affirmative determination is made in step S84, in step S88, the total fluctuation amount ΔDUM, which is the sum of the fluctuation amounts ΔDU of the Mtg pieces acquired in step S82, is acquired. In the following step S90, it is determined whether or not there is an abnormality in the injection valve 50 based on the total fluctuation amount ΔDUM. That is, in the process of step S90, it is determined whether or not there is an abnormality in the injection valve 50 based on the plurality of fluctuation amounts ΔDU acquired at each switching.

Specifically, it is determined whether the total fluctuation amount ΔDUM is larger than the predetermined threshold value KM. The predetermined threshold value KM is a threshold value for determining an abnormality of the injection valve 50 based on the fluctuation amount ΔDU in a situation where urea water is not contained in the supply pipe 42, and is larger than the second threshold value K2. If an affirmative determination is made in step S90, it is determined in step S92 that the injection valve 50 is normal, and the abnormality determination process is terminated. On the other hand, if a negative determination is made in step S90, it is determined in step S94 that the injection valve 50 is abnormal, and the abnormality determination process is terminated.

Subsequently, FIG. 10 shows an example of the abnormality determination process. FIG. 10 shows an example in which the target number of times Mtg is “4”. That is, an example is shown in which the injection valve 50 is continuously switched from the closed state to the open state four times in a state where the pump 44 is rotated in the reverse direction in a situation where the supply pipe 42 does not contain urea water. ..

Here, FIG. 10 (a) shows the transition of the pump duty ratio DU, FIG. 10 (b) shows the transition of the total fluctuation amount ΔDUM, and FIG. 10 (c) shows the transition of the state of the injection valve 50. show. Note that the fluctuation amount ΔDU is normal means that the fluctuation amount ΔDU is larger than the second threshold value K2, and the fluctuation amount ΔDU is abnormal means that the fluctuation amount ΔDU is smaller than the second threshold value K2.

In FIG. 10, the pump 44 is rotated in the reverse direction after the time t21, and under that state, the injection valve 50 is switched between the closed state and the open state. In FIG. 10, in each period of time t21 to t22, t23 to t24, t25 to t26, and t27 to t28, the pump 44 is in a state where the injection valve 50 is closed in a situation where the supply pipe 42 does not contain urea water. Is rotated in the reverse direction. At this time, the pump duty ratio DU becomes the closed duty ratio DUc.

Further, in each period of time t22 to t23, t24 to t25, t26 to t27, and t28 to t29, the load of the pump 44 decreases as the injection valve 50 is opened, and the pump duty ratio DU is the open duty ratio. It decreases to DUo. As a result, the fluctuation amount ΔDU (ΔDU = DUc-DUo) is acquired, and the total fluctuation amount ΔDUM obtained by summing the fluctuation amount ΔDU is acquired.

When the fluctuation amount ΔDU is acquired four times and the total fluctuation amount ΔDUM which is the sum of the four fluctuation amounts ΔDU is acquired, the total fluctuation amount ΔDUM is compared and determined using the threshold value KM. As shown in FIG. 10B, when the total fluctuation amount ΔDUM is larger than the threshold value KM, it is determined that the injection valve 50 is normal. After that, the injection valve 50 is switched from the open state to the closed state while the pump 44 is rotated in the reverse direction at time t19, and then the reverse rotation of the pump 44 is stopped at time t30, and the abnormality determination process is completed.

As described above, in the present embodiment, the injection valve 50 is switched between the open state and the closed state a plurality of times in a situation where the supply pipe 42 does not contain urea water (S82). When urea water is not contained in the supply pipe 42, the fluctuation amount ΔDU of the pump duty ratio DU due to switching is small, so the presence or absence of an abnormality in the injection valve 50 is accurately determined using only one fluctuation amount ΔDU. It's difficult.

In the present embodiment, the presence or absence of an abnormality in the injection valve 50 is determined based on a plurality of fluctuation amounts ΔDU. Specifically, the presence or absence of an abnormality in the injection valve 50 is determined based on the total fluctuation amount ΔDUM which is the sum of the plurality of fluctuation amounts ΔDU. Therefore, the presence or absence of an abnormality in the injection valve 50 can be accurately determined.

In particular, in the present embodiment, since the supply pipe 42 is not filled with urea water, the process of filling the urea water is unnecessary in the abnormality determination process, and the time required for the abnormality determination process can be shortened. In addition, disturbances caused by filling urea water, for example, disturbances in which the filling amount of urea water is less than the target amount, or disturbances in which air is mixed into urea water when filling urea water due to shaking or tilting of the vehicle, etc. It is possible to accurately determine the presence or absence of an abnormality in the injection valve 50 by suppressing the influence of.

The present invention is not limited to the description of the above embodiment, and may be implemented as follows.

The liquid reducing agent is not limited to urea water, and may be, for example, one that injects an ammonia-derived compound other than urea water.

The embodiment in which urea water is supplied to the exhaust passage 31a by injection has been exemplified, but the present invention is not limited to this, and for example, water droplet-shaped urea water may be added and supplied to the exhaust passage 31a.

As the rotation fluctuation parameter, the fluctuation amount ΔDU of the pump duty ratio DU has been exemplified, but the present invention is not limited to this. The rotation fluctuation parameter may be the fluctuation amount of the current supplied to the pump 44 or the fluctuation amount of the rotation speed N of the pump 44. Further, the fluctuation amount of the piping pressure P may be used.

In the first embodiment, the example in which the filling of the supply pipe 42 with urea water is performed only once in the abnormality determination process is shown, but the present invention is not limited to this, and for example, the urea in the supply pipe 42 is filled with urea. Water filling may be performed multiple times. By making the amount of urea water filled in the supply pipe 42 different in each filling, it is possible to determine the presence or absence of an abnormality in the injection valve 50 based on the difference ΔGA of the pump duty ratio DU acquired after each filling. can.

In the second embodiment, the variation amount ΔDU is acquired by switching the injection valve 50 from the closed state to the open state, but the present invention is not limited to this, and for example, the injection valve 50 is closed from the open state. The fluctuation amount ΔDU may be acquired by switching to the state. Further, the fluctuation amount ΔDU may be acquired in both the switching from the closed state to the open state of the injection valve 50 and the switching from the open state to the closed state of the injection valve 50.

In the second embodiment, as a method of determining the presence or absence of an abnormality in the injection valve 50 based on a plurality of fluctuation amounts ΔDU, an example of determining the presence or absence of an abnormality in the injection valve 50 based on the total fluctuation amount ΔDUM is shown. , Not limited to this. For example, the presence or absence of an abnormality in the injection valve 50 may be determined based on the maximum value of the plurality of fluctuation amounts ΔDU, or the presence or absence of an abnormality in the injection valve 50 may be determined based on the median value of the maximum values of the plurality of fluctuation amounts ΔDU. You may judge.

ΔDU ... Fluctuation amount, 30 ... Engine, 31a ... Exhaust passage, 40 ... Tank, 44 ... Pump, 50 ... Injection valve.

Claims (4)

An addition valve (50) provided in the exhaust passage (31a) of the internal combustion engine (30) to add and supply a liquid reducing agent to a NOx purifying catalyst for purifying NOx in the exhaust, and a tank (40) for storing the reducing agent. It is applied to an exhaust purification system including a pump (44) that discharges the reducing agent in the tank by forward rotation and sucks the reducing agent back into the tank by reverse rotation.
With the pump rotated in the reverse direction (S18), the switching unit (S72, S76) for switching the addition valve between the open state and the closed state,
An acquisition unit (S78) that acquires the amount of fluctuation in the rotation speed of the pump or its correlation value as a rotation fluctuation parameter (ΔDU) due to the switching of the addition valve.
A determination unit (S24 to S56) for determining the presence or absence of an abnormality in the addition valve based on the rotation fluctuation parameter,
Equipped with
The switching unit performs switching from the closed state to the open state of the addition valve a plurality of times with the pump rotated in the reverse direction (S20, S22).
The determination unit differs between the rotation fluctuation parameter acquired at the time of the previous switching and the rotation fluctuation parameter acquired at the later switching with respect to the rotation fluctuation parameter acquired by the acquisition unit at the time of each switching. (S24, S26) Anomaly detection device for comparison and determination using threshold values (K1, K2). An addition valve (50) provided in the exhaust passage (31a) of the internal combustion engine (30) to add and supply a liquid reducing agent to a NOx purifying catalyst for purifying NOx in the exhaust, and a tank (40) for storing the reducing agent. It is applied to an exhaust purification system including a pump (44) that discharges the reducing agent in the tank by forward rotation and sucks the reducing agent back into the tank by reverse rotation.
With the pump rotated in the reverse direction (S18), the switching unit (S72, S76) for switching the addition valve between the open state and the closed state,
An acquisition unit (S78) that acquires the amount of fluctuation in the rotation speed of the pump or its correlation value as a rotation fluctuation parameter (ΔDU) due to the switching of the addition valve.
A determination unit (S24 to S56) for determining the presence or absence of an abnormality in the addition valve based on the rotation fluctuation parameter,
Equipped with
The switching unit performs switching from the closed state to the open state of the addition valve a plurality of times with the pump rotated in the reverse direction (S20, S22).
The determination unit determines the difference between the rotation fluctuation parameter acquired at the time of the previous switching and the rotation fluctuation parameter acquired at the later switching with respect to the rotation fluctuation parameter acquired by the acquisition unit at each switching. ΔGA), an abnormality detection device for determining the presence or absence of an abnormality in the addition valve (S36, S44, S54) . In the switching unit, in a situation where the reducing agent passage connecting the pump and the addition valve is filled with the reducing agent (S16), the addition valve is opened from the closed state while the pump is rotated in the reverse direction. Switch to,
A claim that the determination unit determines whether or not there is an abnormality in the addition valve based on the rotation fluctuation parameter acquired by the acquisition unit when the switching unit switches the addition valve from the closed state to the open state. 1 or the abnormality detection device according to claim 2 . An addition valve (50) provided in the exhaust passage (31a) of the internal combustion engine (30) to add and supply a liquid reducing agent to a NOx purifying catalyst for purifying NOx in the exhaust, and a tank (40) for storing the reducing agent. It is applied to an exhaust purification system including a pump (44) that discharges the reducing agent in the tank by forward rotation and sucks the reducing agent back into the tank by reverse rotation.
With the pump rotated in the reverse direction (S18), the switching unit (S72, S76) for switching the addition valve between the open state and the closed state,
An acquisition unit (S78) that acquires the amount of fluctuation in the rotation speed of the pump or its correlation value as a rotation fluctuation parameter (ΔDU) due to the switching of the addition valve.
A determination unit (S24 to S56) for determining the presence or absence of an abnormality in the addition valve based on the rotation fluctuation parameter,
Equipped with
The switching unit switches between the open state and the closed state of the addition valve in a state where the pump is rotated in the reverse direction in a situation where the reducing agent passage connecting the pump and the addition valve does not contain the reducing agent. Was carried out multiple times (S82),
The determination unit is an abnormality detection device that determines the presence or absence of an abnormality in the addition valve based on a plurality of rotation fluctuation parameters (ΔDUM) acquired at each switching by the acquisition unit.

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