WO2016171029A1

WO2016171029A1 - Liquid level sensor abnormality detecting device and abnormality detecting method

Info

Publication number: WO2016171029A1
Application number: PCT/JP2016/061745
Authority: WO
Inventors: 英志中尾
Original assignee: ボッシュ株式会社
Priority date: 2015-04-22
Filing date: 2016-04-12
Publication date: 2016-10-27
Also published as: JPWO2016171029A1; JP6419315B2

Abstract

The objective of the present invention is to provide a liquid level sensor abnormality detecting device and abnormality detecting method with which it is possible to detect in a short time whether or not an abnormality has occurred in a liquid level sensor, which is provided in a storage tank storing a reducing agent to be injected into an exhaust gas passage of an internal-combustion engine, and which detects a residual quantity of an additive. Provided is a liquid level sensor abnormality detecting device which is provided in a storage tank storing a reducing agent to be injected into an exhaust gas passage of an internal-combustion engine, and which detects abnormalities occurring in the liquid level sensor, characterized in being provided with: a signal acquiring unit which acquires a signal output by the liquid level sensor; and an assessing unit which, if certain detection conditions are satisfied, uses the signal acquired by the signal acquiring unit to assess whether or not an abnormality has occurred in the liquid level sensor.

Description

Liquid level sensor abnormality detection device and abnormality detection method

The present invention relates to an abnormality detection device and an abnormality detection method for a liquid level sensor that detects an abnormality of a liquid level sensor provided in a tank in which a reducing agent injected into an exhaust passage of an internal combustion engine is stored.

NO _x (nitrogen oxide) is contained in the exhaust gas of an internal combustion engine such as a diesel engine mounted on a vehicle. As an apparatus for purifying exhaust by decomposing the reduced to nitrogen and water vapor, etc. Such NO _X, urea SCR (Selective Catalystic Reduction) system has been put into practical use. The urea SCR system is a system for decomposing NO _x by reacting NO _x in exhaust with ammonia using an aqueous urea solution as a reducing agent.

In addition to the urea SCR system using a selective reduction catalyst, the exhaust gas with the air-fuel ratio of the exhaust gas is occluded NO _X in the exhaust gas in a lean state, the air-fuel ratio to release replace the NO _X cut rich exhaust gas purification apparatus using the the NO _X storing catalyst to perform reduction purification of the NO _X with unburned fuel are known in the. As one aspect of this exhaust purification device, there is an exhaust purification device configured to add unburned fuel directly to the upstream side of the NO _X storage catalyst.

As a device for adding urea solution, unburned fuel, etc. in these exhaust purification devices, typically, the additive is pumped by a pump, and the additive is supplied into the exhaust passage through an injector connected to the exhaust pipe. There is an injection type additive supply device. In addition, the apparatus for spraying the urea solution is an air that atomizes the urea solution in advance in the mixing chamber using high-pressure air and then sprays the urea solution into the exhaust passage through the injection nozzle connected to the exhaust pipe. There is also an assist type reducing agent supply device.

Such an additive supply apparatus is provided with a tank for storing additives such as urea solution and unburned fuel. The tank is provided with a concentration sensor, a liquid level sensor, and a temperature sensor for detecting the state of the additive (see, for example, Patent Document 1).

JP 2010-7568 A

¡Sensors for detecting the state of additives must be kept rational. In Patent Document 1, a technique for diagnosing the rationality of a sensor for detecting the state of the additive is disclosed. However, in the rationality diagnosis of conventional sensors, particularly the rational diagnosis of liquid level sensors, a predetermined amount of additive was injected to determine that the value of the liquid level sensor was reasonable. It took time for a reason. Therefore, it is necessary to quickly determine whether or not a sensor for detecting the condition of the additive is properly provided, and in particular whether or not an abnormality has occurred in the liquid level sensor that detects the remaining amount of the additive in the tank. Is required to be detected in a short time.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to determine whether or not an abnormality has occurred in a liquid level sensor that detects the remaining amount of additive in a tank in a short time. It is an object of the present invention to provide a novel and improved liquid level sensor abnormality detection device and abnormality detection method that can be detected.

In order to solve the above problems, according to one aspect of the present invention, a liquid level for detecting occurrence of an abnormality in a liquid level sensor provided in a storage tank in which a reducing agent injected into an exhaust passage of an internal combustion engine is stored. A sensor abnormality detection device, wherein a signal acquisition unit for acquiring a signal output from the liquid level sensor and the liquid level using the signal acquired by the signal acquisition unit when a predetermined detection condition is satisfied An abnormality detection device for a liquid level sensor, comprising: a determination unit that determines whether or not an abnormality has occurred in the sensor.

The predetermined detection condition may be that the liquid level of the reducing agent stored in the storage tank is in a state of swinging.

The predetermined detection condition may be a case where a vehicle traveling by driving the internal combustion engine is accelerated or decelerated.

The predetermined detection condition may be a case where an inclination of a vehicle traveling by driving of the internal combustion engine varies.

The determination unit may determine that an abnormality has occurred in the liquid level sensor when the fluctuation of the signal in a predetermined period is within a predetermined range.

The determination unit may determine that an abnormality has occurred in the liquid level sensor when fluctuations in the signal in a predetermined period are continuously within a predetermined range a plurality of times.

In order to solve the above problems, according to another aspect of the present invention, the occurrence of an abnormality in a liquid level sensor provided in a storage tank in which a reducing agent injected into an exhaust passage of an internal combustion engine is stored is detected. An abnormality detection method for a liquid level sensor, the step of acquiring a signal output from the liquid level sensor, and an abnormality with respect to the liquid level sensor using the acquired signal when a predetermined detection condition is satisfied And a step of determining whether or not the occurrence of the liquid level sensor is provided.

As described above, according to the present invention, a new and improved liquid level sensor capable of detecting in a short time whether or not an abnormality has occurred in the liquid level sensor that detects the remaining amount of the additive in the tank. An abnormality detection device and an abnormality detection method can be provided.

It is the schematic which shows the urea SCR system provided with the reducing agent injection apparatus concerning embodiment of this invention. It is explanatory drawing which shows the example of the unauthorized modification | remodeling with respect to a liquid level sensor. It is explanatory drawing explaining the function structural example of a control apparatus. It is explanatory drawing which shows the example of the value which a liquid level sensor outputs. It is explanatory drawing which shows the example of the value output when abnormality generate | occur | produces in a liquid level sensor. It is a flowchart explaining the operation example of a control apparatus.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Example of overall configuration of SCR system>
First, with reference to FIG. 1, the example of whole structure of the urea SCR system 10 concerning one Embodiment of this invention is demonstrated. FIG. 1 is an explanatory diagram showing a schematic configuration of the urea SCR system 10. Hereinafter, the configuration of the urea SCR system 10 will be described with reference to FIG.

The urea SCR system 10 shown in FIG. 1 includes a reduction catalyst 13 and a reducing agent injection device 20 as main elements.

The urea SCR system 10 is a system that reduces and decomposes NO _X in exhaust gas using an aqueous urea solution as a reducing agent. The urea aqueous solution may be a 32.5% concentration urea aqueous solution having the lowest freezing temperature, for example. The freezing temperature in this case is about minus 11 ° C.

The reduction catalyst 13 is disposed in the middle of the exhaust pipe 11 connected to the engine 5, and has a function of selectively reducing NO _X contained in the exhaust of the engine 5. In the present embodiment, ammonia produced by decomposition of the urea aqueous solution injected by the reducing agent injection device 20 is adsorbed by the reduction catalyst 13, and NO _X in the exhaust gas flowing into the reduction catalyst 13 is selectively reduced by ammonia. Is done.

The reducing agent injection device 20 injects a urea aqueous solution as a reducing agent into the exhaust pipe 11 upstream of the reduction catalyst 13. The injection amount of the urea aqueous solution is controlled so that NO _X or ammonia does not flow to the downstream side of the reduction catalyst 13 based on the concentration of NO _X contained in the exhaust, the amount of ammonia that can be adsorbed by the reduction catalyst 13, and the like. The

A temperature sensor 15 for detecting the exhaust temperature Tgas is provided in the exhaust pipe 11 upstream of the reduction catalyst 13. The exhaust gas temperature Tgas detected by the temperature sensor 15 is also used for estimating the temperature of the reduction catalyst 13. However, the arrangement position of the temperature sensor 15 is not limited to such an example. In addition to the temperature sensor 15, the exhaust pipe 11, NO _X concentration sensor and the ammonia sensor or the like may be provided (not shown).

<2. Configuration Example of Reducing Agent Injection Device>
Next, the configuration of the reducing agent injection device 20 will be described in detail with reference to FIG. As shown in FIG. 1, the reducing agent injection device 20 pumps the injection valve 31 fixed to the exhaust pipe 11 upstream of the reduction catalyst 13 and the urea aqueous solution in the storage tank 50 toward the injection valve 31. A pump module 40 having a pump 41.

The injection valve 31 and the pump module 40 are connected by a first supply passage 57. The first supply passage 57 is provided with a pressure sensor 43 for detecting the pressure of the urea aqueous solution supplied to the injection valve 31. Further, the pump module 40 and the storage tank 50 are connected by a second supply passage 58. Further, the pump module 40 and the storage tank 50 are also connected by a circulation passage 59. The circulation passage 59 branches from the first supply passage 57 and is connected to the storage tank 50. An orifice 45 is provided in the middle of the circulation passage 59. The orifice 45 has a function of passing the excess urea aqueous solution to the storage tank 50 side while maintaining the pressure in the first supply passage 57.

Further, the urea SCR system 10 includes a control device 100 that controls each control element of the reducing agent injection device 20. The control device 100 is configured to be able to acquire information of the engine control device 70 via communication means such as a CAN (Controller Area Network) (not shown). For example, the control device 100 can acquire information related to the operating state such as the fuel injection amount, injection timing, and engine speed of the engine 5. In the urea SCR system 10 according to the present embodiment, the control device 100 and the engine control device 70 are separate control devices, but the control device 100 and the engine control device 70 are configured as one control device. It may be.

The pump 41 provided in the pump module 40 includes, for example, an electric diaphragm pump or a motor pump. The output of the pump 41 is controlled based on a control signal from the control device 100. In the present embodiment, the control device 100 is configured to feedback control the output of the pump 41 so that the pressure of the urea aqueous solution detected by the pressure sensor 43 is maintained at a predetermined target value. Further, when the urea aqueous solution is frozen when the engine 5 is started, the pump 41 starts to be driven after waiting until the urea aqueous solution is thawed.

The injection valve 31 is an electromagnetic injection valve that can be switched between open and closed by energization control. The injection valve 31 includes a coil, and has a structure in which the valve body is moved and opened by a magnetic force generated by energizing the coil. As described above, the pressure of the urea aqueous solution supplied to the injection valve 31 is maintained at a constant pressure, and the control device 100 adjusts the valve opening time according to the target injection amount of the urea aqueous solution.

The pump module 40 is provided with a flow path switching valve 71. The flow path switching valve 71 switches the direction in which the urea aqueous solution pumped by the pump 41 flows. When injecting the urea aqueous solution into the exhaust passage, the flow path switching valve 71 causes the urea aqueous solution to go from the storage tank 50 side to the injection valve 31 side. In this case, the suction port of the pump 41 is connected to the second supply passage 58, and the discharge port of the pump 41 is connected to the first supply passage 57. When recovering the urea aqueous solution to the storage tank 50, the flow path switching valve 71 causes the urea aqueous solution to go from the injection valve 31 side to the storage tank 50 side. In this case, the suction port of the pump 41 is connected to the first supply passage 57, and the discharge port of the pump 41 is connected to the second supply passage 58.

Further, the reducing agent injection device 20 includes a first cooling water passage 85 and a second cooling water passage 87 that are configured so that the cooling water of the engine 5 can be circulated. The first cooling water passage 85 and the second cooling water passage 87 branch from the cooling passage 86 of the engine cooling device 60 provided in the engine 5 and merge with the cooling passage 86 again. The first cooling water passage 85 is disposed through the storage tank 50 and the pump module 40. In the present embodiment, the first cooling water passage 85 is also disposed along the first supply passage 57 and the second supply passage 58 of the urea aqueous solution. Further, the second cooling water passage 87 is disposed through the periphery of the injection valve 31. An opening / closing valve 81 is provided between the branch point of the second cooling water passage 87 and the storage tank 50 in the first cooling water passage 85. The opening / closing valve 81 is switched between opening and closing by the control device 100, and the opening / closing of the first cooling water passage 85 is controlled. For example, when the temperature of the reducing agent detected by the temperature sensor 51 provided in the storage tank 50 is low, the control device 100 opens the on-off valve 81 so that the reducing agent is heated by the cooling water.

When the engine 5 is started, the on-off valve 81 is opened, and cooling water flows through the first cooling water passage 85. Therefore, the urea aqueous solution in the storage tank 50 is heated. That is, when the urea aqueous solution in the storage tank 50 is frozen, thawing of the frozen urea aqueous solution is promoted as the temperature of the cooling water rises. Thereafter, when the temperature of the urea aqueous solution in the storage tank 50 detected by the temperature sensor 51 provided in the storage tank 50 reaches a predetermined threshold value, the on-off valve 81 is closed. Thereby, the urea aqueous solution in the storage tank 50 is prevented from being heated more than necessary.

In addition, during operation of the engine 5, cooling water always flows through the second cooling water passage 87. Therefore, during the operation of the engine 5, the injection valve 31 is cooled by the cooling water in a state where the injection valve 31 is heated by high-temperature exhaust heat or the like.

In addition, heating devices such as an electric heater for thawing the frozen aqueous urea solution may be provided at appropriate positions such as the pump module 40, the first supply passage 57, and the second supply passage 58.

In addition to the temperature sensor 51, the storage tank 50 is provided with a liquid level sensor 52 for measuring the liquid level of the urea aqueous solution. Sensor values detected by the temperature sensor 51 and the liquid level sensor 52 are output as signals representing information related to the remaining amount and temperature of the urea aqueous solution in the storage tank 50. Although not shown, the storage tank 50 may be provided with a concentration sensor for measuring the concentration of the urea aqueous solution in addition to the temperature sensor 51 and the liquid level sensor 52.

These sensors are provided for monitoring whether the urea aqueous solution is stored in the storage tank 50 in a normal state.

For example, when determining the injection amount of the urea aqueous solution, it is assumed that the urea aqueous solution is maintained at a concentration within a predetermined range. If the concentration of the aqueous urea solution in the storage tank 50 exceeds or falls below a predetermined range, the amount of ammonia generated by hydrolysis may be excessive or insufficient. Therefore, a concentration sensor is provided for monitoring whether the concentration of the urea aqueous solution is maintained within a predetermined range.

Further, if the remaining amount of the urea aqueous solution is insufficient or the urea aqueous solution is frozen, there is a possibility that the amount of urea aqueous solution determined by the control device 100 cannot be accurately injected. Therefore, the storage tank 50 is provided with a temperature sensor 51 and a liquid level sensor 52 in order to monitor whether the remaining amount of the urea aqueous solution is more than a predetermined value and whether the urea aqueous solution is higher than the freezing temperature. ing.

Then, as a result of sensing the concentration, temperature, and remaining amount by each sensor provided in the storage tank 50, for example, when abnormality is found in the concentration or liquid level of the urea aqueous solution, the injection control of the urea aqueous solution is stopped, and Is configured to issue a warning signal to stop the internal combustion engine promptly, or to control the temperature of the urea aqueous solution by the engine cooling water described above when an abnormality is found in the temperature of the urea aqueous solution. .

The liquid level sensor 52 applies a predetermined AC voltage to a detection unit composed of a pair of electrodes arranged at a predetermined height, and urea is converted based on the voltage obtained by converting the current flowing through the detection unit at this time. It is configured to monitor the remaining amount of the aqueous solution.

That is, the relative permittivity of urea aqueous solution is significantly higher than the relative permittivity of air. Therefore, when the urea aqueous solution is interposed between the electrodes, current easily flows between the pair of electrodes, and is generated between the pair of electrodes. The capacitance to be increased. The liquid level sensor 52 outputs a voltage value corresponding to the liquid level of the urea aqueous solution.

The liquid level sensor 52 is of a type that detects the remaining amount of liquid finely based on the value of the capacitance that continuously changes in accordance with the remaining amount of liquid, and a plurality of liquid level sensors 52 while shifting the height. A type that detects whether or not the liquid is present up to the height position by a detection unit arranged at the height position, a type that detects the liquid level by ultrasonic waves, a float that floats on the liquid Various types can be used, such as a type in which the liquid level is detected by the vertical movement of.

However, regardless of which type is used, it is not known whether the value detected by the liquid level sensor 52 indicates the true liquid level of the aqueous urea solution in the storage tank 50. If an unauthorized modification or the like is performed on the liquid level sensor 52 by the user and an abnormality of the liquid level sensor occurs, the value detected by the liquid level sensor 52 does not indicate the true liquid level of the urea aqueous solution in the storage tank 50.

For example, as shown in FIG. 2, the liquid level sensor 52 is illegally modified so that the liquid level sensor 52 is accommodated in the container 53 and a liquid (not limited to an aqueous urea solution) is injected into the container 53. Think about the case. When such an unauthorized modification is made, as shown in FIG. 2, even if the liquid level of the actual urea aqueous solution is lowered, the liquid level sensor 52 detects the liquid level of the actual urea aqueous solution. Therefore, it becomes impossible to issue a warning signal to stop the internal combustion engine as described above quickly. Further, for example, in the case of a liquid level sensor that detects the level of the liquid level by moving the float up and down, if the float is fixed, the float does not move up and down according to the liquid level. Therefore, a liquid level sensor that detects the liquid level by the vertical movement of the float will detect the actual liquid level of the aqueous urea solution if an unauthorized modification is made that would fix the float. Therefore, it becomes impossible to issue a warning signal to stop the internal combustion engine as described above quickly.

In order to determine whether or not an abnormality of the liquid level sensor has occurred due to such unauthorized modification, there has been a technology for performing a rational diagnosis of the storage sensor. For example, after the level of the urea aqueous solution in the storage tank 50 is detected by the

liquid level sensor

52, 1 liter of the urea aqueous solution is injected, and the level of the urea aqueous solution remaining in the storage tank 50 after the injection is detected by the liquid level sensor. By detecting again at 52, it is possible to determine whether or not an abnormality of the liquid level sensor has occurred due to unauthorized modification or the like. However, since this method cannot be determined unless 1 liter of urea aqueous solution is injected, it takes time from the start of determination to the end of determination.

Furthermore, in order for the liquid level sensor 52 to detect the liquid level of the urea aqueous solution in the storage tank 50, it is necessary to detect the urea aqueous solution in the storage tank 50 in a stable state. It takes more time from the start of the determination to the end of the determination by waiting for the stability of.

Therefore, for example, a technique capable of detecting in a short time whether or not an abnormality has occurred in the liquid level sensor 52 due to unauthorized modification to the liquid level sensor 52 as shown in FIG. 2 is required. The inventors have made extensive studies on a technique that can detect in a short time whether or not an abnormality has occurred in the liquid level sensor 52. As a result, as will be described below, the present inventor has developed a technology that can detect in a short time whether or not an abnormality has occurred in the liquid level sensor 52 using a raw signal output from the liquid level sensor 52. It came to devise.

<3. Configuration example of control device>
Next, the structural example of the control apparatus 100 used for control of the reducing agent injection apparatus 20 concerning this embodiment is demonstrated. FIG. 3 is an explanatory diagram illustrating a part related to determination of whether or not an abnormality has occurred in the liquid level sensor 52 in the configuration of the control device 100. Hereinafter, a configuration example of the control device 100 will be described with reference to FIG.

As shown in FIG. 3, the control device 100 includes a signal acquisition unit 102, a determination unit 104, and a processing unit 106.

The signal acquisition unit 102 acquires a signal output from the liquid level sensor 52 or the like. The signal acquired by the signal acquisition unit 102 is used for determining whether or not an abnormality has occurred in the liquid level sensor 52 in the determination unit 104. In the present embodiment, in particular, the signal output from the liquid level sensor 52 and acquired by the signal acquisition unit 102 is used to determine whether or not an abnormality has occurred in the liquid level sensor 52 in the determination unit 104.

The determination unit 104 determines whether or not an abnormality has occurred in the liquid level sensor 52 using the signal acquired by the signal acquisition unit 102. In the present embodiment, as will be described later, the determination unit 104 determines whether or not the signal output from the liquid level sensor 52 varies more than a predetermined amount when a predetermined detection condition is satisfied. Whether or not the liquid level sensor 52 is abnormal due to unauthorized modification of the liquid level sensor 52 or the like is determined. Specifically, the determination unit 104 acquires a value output from the liquid level sensor 52 for a predetermined time when a predetermined detection condition is satisfied, and uses the acquired value output from the liquid level sensor 52 to determine the liquid level. It is determined whether or not an abnormality has occurred in the sensor 52. The surface of the aqueous urea solution stored in the storage tank 50 is swung when the vehicle body is tilted or the engine 5 or the vehicle body vibrates. Accordingly, the determination unit 104 uses the value output from the liquid level sensor 52 acquired in a state where the liquid level of the urea aqueous solution stored in the storage tank 50 is swung, and the value exceeds a predetermined range. By determining whether or not it is fluctuating, it is possible to determine whether or not abnormality has occurred in the liquid level sensor 52 due to unauthorized modification or the like. The processing executed by the determination unit 104 will be described in detail later.

When the determination unit 104 determines that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52, the processing unit 106 operates, for example, the engine control device 70 illustrated in FIG. A predetermined post-process is executed for a control device (not shown) that controls the control. The predetermined post-processing includes control such as lighting a predetermined lamp in the driver's seat, limiting the vehicle speed and torque, sounding a predetermined buzzer, and making driving impossible. May be included.

The urea aqueous solution stored in the storage tank 50 tilts as the vehicle body travels on a slope during traveling, or the liquid level fluctuates when the engine 5 or the vehicle body vibrates. Therefore, while the engine 5 is driven and the vehicle is traveling, the value sent from the liquid level sensor 52 is inclined as the vehicle body travels on a slope during traveling, or the engine 5 or the vehicle body vibrates. It should be possible to change greatly in a short time by, for example.

FIG. 4 is an explanatory diagram showing an example of values output by the liquid level sensor 52. If there is no abnormality such as an unauthorized modification to the liquid level sensor 52, the liquid level fluctuates as the vehicle body tilts or the engine 5 or the vehicle body vibrates as described above. For this reason, the value output from the liquid level sensor 52 varies greatly as shown in FIG.

However, for example, when an abnormality such as unauthorized modification to the liquid level sensor 52 as shown in FIG. 2 occurs, the vehicle body tilts during traveling, or the engine 5 or the vehicle body vibrates. Also, the liquid level in the container 53 does not swing greatly, and the value sent from the liquid level sensor 52 does not fluctuate greatly in a short time.

FIG. 5 is an explanatory diagram showing an example of values output from the liquid level sensor 52 when the liquid level sensor 52 is illegally modified as shown in FIG. As shown in FIG. 2, if the liquid level sensor 52 is illegally modified so as to be surrounded by the vehicle, the vehicle body tilts, the engine 5 or the vehicle body vibrates, and the storage tank Even if the liquid level of the urea aqueous solution stored in 50 fluctuates greatly, the value output from the liquid level sensor 52 also fluctuates only within a predetermined extremely small range as shown in FIG.

Therefore, the determination unit 104 determines whether or not an abnormality has occurred in the liquid level sensor 52 by determining whether or not the value sent from the liquid level sensor 52 has fluctuated greatly when a predetermined detection condition is satisfied. To do. The predetermined detection condition is, for example, a urea aqueous solution stored in the storage tank 50 when the engine 5 is started or when a predetermined inclination or speed change is detected during traveling, as described below. This is a case where the liquid level of the liquid can be greatly swung.

The configuration example of the control device 100 has been described above with reference to FIG. Next, an operation example of the control device 100 will be described.

<4. Example of operation of control device>
FIG. 6 is a flowchart illustrating an operation example of the control device 100. FIG. 6 shows an example of the operation of the control device 100 when determining whether or not an abnormality has occurred in the liquid level sensor 52. Hereinafter, an operation example of the control device 100 will be described with reference to FIG. Note that the series of operations shown in FIG. 6 is performed in the ignition-on state.

The control device 100 first determines whether or not a predetermined detection condition is satisfied (step S101). For example, the determination unit 104 executes the determination process in step S101. The predetermined detection condition means that the liquid level of the urea aqueous solution stored in the storage tank 50 is in a state of swinging. The predetermined detection conditions include, for example, when the engine 5 is started, when the vehicle is accelerated or decelerated, and when the vehicle body is tilted more than a predetermined amount.

Note that the control device 100 may determine whether the vehicle has been accelerated or decelerated based on whether the driver's accelerator operation or braking operation has been performed. If the acceleration sensor is provided on the vehicle body, the control device 100 may determine the acceleration or deceleration. Also good. The control device 100 may determine the tilt of the vehicle body based on a value of a tilt sensor or the like.

Further, the predetermined detection condition may include a case where excess urea aqueous solution is returned to the storage tank 50 from the circulation passage 59 through the orifice 45. When the excess urea aqueous solution is returned from the circulation passage 59 to the storage tank 50 through the orifice 45, the urea aqueous solution is dripped from the circulation passage 59. Therefore, the urea aqueous solution stored in the storage tank 50 is dropped along with the dripping. This is because the liquid level fluctuates.

The controller 100 waits until the predetermined detection condition is satisfied in Step S101 (Step S101, No), and determines that the predetermined detection condition is satisfied (Step S101, Yes). Subsequently, the control device 100 outputs the liquid level sensor 52. A value is acquired for a predetermined time (step S102). The signal acquisition unit 102 performs the acquisition process in step S102. In addition, the signal acquisition time in step S102 may be a short time, for example, a time of about 30 seconds or 1 minute.

When the value output from the liquid level sensor 52 is acquired for a predetermined time in step S102, the control device 100 subsequently uses the acquired value output from the liquid level sensor 52 to determine whether or not an abnormality has occurred in the liquid level sensor 52. Make a decision. Specifically, the control device 100 determines whether or not an abnormality has occurred in the liquid level sensor 52 by determining whether or not the value output from the liquid level sensor 52 fluctuates beyond a predetermined range. .

As described above, the urea aqueous solution stored in the storage tank 50 has its liquid surface oscillated by tilting the vehicle body or vibrating the engine 5 or the vehicle body. Therefore, the control device 100 uses the value output from the liquid level sensor 52 acquired in a state where the liquid level of the urea aqueous solution stored in the storage tank 50 is swung, and the value fluctuates beyond a predetermined range. By determining whether or not the liquid level sensor 52 is abnormal, it can be determined whether or not an abnormality due to unauthorized modification or the like has occurred. The determination process may be performed based on the value output from the liquid level sensor 52, or may be performed on the value output from the liquid level sensor 52 digitized at a predetermined sampling frequency.

The value output by the liquid level sensor 52 acquired in the above step S102 does not always change greatly in all the acquired times, and may change greatly only in a part of the period. Accordingly, the determination unit 104 determines that an abnormality due to unauthorized modification or the like has not occurred in the liquid level sensor 52 if there is a large variation in the value output from the liquid level sensor 52 during a certain period. Also good. In addition, the determination unit 104 causes an abnormality due to unauthorized modification or the like to the liquid level sensor 52 if a large fluctuation is observed in a predetermined period of time during which the value output by the liquid level sensor 52 is acquired. It may be determined that it is not.

The control device 100 determines whether or not abnormality has occurred in the liquid level sensor 52 due to unauthorized modification using the value output from the liquid level sensor 52. Specifically, the control device 100 determines whether or not the value output from the liquid level sensor 52 fluctuates beyond a predetermined range (step S103). The process of step S103 is executed by the determination unit 104, for example. When it is determined that the fluctuation of the value output from the liquid level sensor 52 is within a predetermined range (No in step S103), the control device 100 has an abnormality due to unauthorized modification or the like with respect to the liquid level sensor 52. For example, the engine control device 70 shown in FIG. 1 and other control devices (not shown) that control the operation of the vehicle are caused to perform predetermined post-processing (step S104). The process of step S104 is executed by the processing unit 106, for example. The predetermined post-processing includes control such as lighting a predetermined lamp in the driver's seat, limiting the vehicle speed and torque, sounding a predetermined buzzer, and making driving impossible. May be included. In addition, when it is determined that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52, the control device 100 may hold data indicating that the abnormality has occurred. On the other hand, when it determines with the fluctuation | variation of the value which the liquid level sensor 52 outputs exceeds the predetermined range (step S103, Yes), the control apparatus 100 complete | finishes a series of processes.

Note that even if the determination unit 104 determines that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52, there is a possibility that it may be erroneously determined only once. Therefore, the control device 100 may execute the above-described control process when the determination unit 104 determines that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52 a plurality of times. .

Further, the control device 100 may execute the above-described control process when it is determined at a predetermined ratio or more that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52. For example, when abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52, when it is determined at a rate of 80% or more of the latest 10 processes, that is, the control device 100 performs the above-described process. When the determination process has been performed 10 times most recently, the control process described above may be executed when it is determined that an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52 eight or more times.

The control device 100 determines whether or not an abnormality due to unauthorized modification or the like has occurred in the liquid level sensor 52 based on the value output from the liquid level sensor 52. Or when the fluctuation in the value output from the liquid level sensor 52 falls within a predetermined range at a predetermined ratio or more, for example, as shown in FIG. When no change is observed, it may be determined that an abnormality has occurred in the liquid level sensor 52 due to unauthorized modification or the like.

<5. Summary>
As described above, according to the embodiment of the present invention, the reducing agent injection device capable of determining in a short time whether or not an abnormality has occurred in the liquid level sensor 52 based on the signal output from the liquid level sensor 52. 20 is provided.

The control device 100 determines whether or not the signal obtained from the liquid level sensor 52 and obtained by the control device 100 fluctuates in a predetermined time in a state where the liquid level of the urea aqueous solution stored in the storage tank 50 can be swung. Then, it is determined whether or not an abnormality has occurred in the liquid level sensor 52.

In this way, the control device 100 determines whether the level of the urea aqueous solution stored in the storage tank 50 can be fluctuated and the state of the signal output from the liquid level sensor 52. For example, it is possible to determine in a short time whether or not an abnormality has occurred due to unauthorized modification or the like that does not output the remaining amount of the true urea aqueous solution as shown in FIG.

The control device 100 according to the present embodiment acquires a value from the liquid level sensor 52 in a state where the liquid level of the urea aqueous solution stored in the storage tank 50 can oscillate, and the occurrence of abnormality in the liquid level sensor 52 is detected. Since the presence or absence is determined, it can be determined in a short time whether or not an abnormality has occurred in the liquid level sensor 52 regardless of the form of the liquid level sensor 52.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

For example, in the above-described embodiment, a case where an unauthorized modification to the liquid level sensor 52 is given as an example of the occurrence of an abnormality, but the present invention is not limited to such an example. Even if the liquid level sensor 52 has not been illegally modified, the control device 100 determines whether or not an abnormality has occurred for a short time even when the liquid level sensor 52 fails and always outputs a constant value. Can be determined.

Claims

An abnormality detection device for a liquid level sensor for detecting occurrence of an abnormality of a liquid level sensor provided in a storage tank in which a reducing agent injected into an exhaust passage of an internal combustion engine is stored,
A signal acquisition unit for acquiring a signal output from the liquid level sensor;
A determination unit that determines whether or not an abnormality has occurred in the liquid level sensor using the signal acquired by the signal acquisition unit when a predetermined detection condition is satisfied;
An abnormality detection device for a liquid level sensor, comprising:
The liquid level sensor abnormality detection device according to claim 1, wherein the predetermined detection condition is that the liquid level of the reducing agent stored in the storage tank is in a state of swinging. .
3. The liquid level sensor abnormality detection device according to claim 2, wherein the predetermined detection condition is when a vehicle traveling by driving the internal combustion engine is accelerated or decelerated.
3. The liquid level sensor abnormality detection device according to claim 2, wherein the predetermined detection condition is a case where an inclination of a vehicle traveling by driving of the internal combustion engine varies.
2. The liquid level according to claim 1, wherein the determination unit determines that an abnormality has occurred in the liquid level sensor when fluctuations in the signal in a predetermined period are within a predetermined range. Sensor abnormality detection device.
The determination unit determines that an abnormality has occurred in the liquid level sensor when fluctuations in the signal within a predetermined period are continuously within a predetermined range a plurality of times. 5. An abnormality detection device for a liquid level sensor according to 5.
An abnormality detection method for a liquid level sensor for detecting occurrence of an abnormality in a liquid level sensor provided in a storage tank in which a reducing agent injected into an exhaust passage of an internal combustion engine is stored,
Obtaining a signal output by the liquid level sensor;
Determining whether or not an abnormality has occurred with respect to the liquid level sensor using the acquired signal when a predetermined detection condition is satisfied;
An abnormality detection method for a liquid level sensor, comprising: