DE102016117949B4 - diagnostic device - Google Patents

Abstract

Diagnostic apparatus for a urea water supply system, the urea water supply system comprising a tank (6) configured to store urea water, a pump (8) configured to draw urea water stored in the tank (6), and the urea water and having a pipe (9) configured to lead the urea water discharged from the pump (8) to an injector (5), comprising:an engine control unit (S4, S6) configured is to perform motor control to change a rotation state of a motor (10) of the pump (8);a rotation behavior obtaining unit (S11, S31) configured to obtain a rotation behavior of the motor while the motor control is being performed;a Pressure behavior obtaining unit (S11, S31) configured to obtain a pressure behavior in the pipe (9) while the engine control is being performed; and a diagnostic unit (S12 to S20, S32 to S40, S8) configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior, wherein the engine control unit (S4, S6) is configured to perform the motor control more than once to change the motor to rotating states different from each other,the rotating behavior obtaining unit (S11, S31) is configured to obtain the rotating behavior each time the motor control is performed, the pressure behavior obtaining unit (S11, S31) is configured to obtain the pressure behavior each time the engine control is performed, and the diagnosing unit comprises: a preliminary diagnosis unit (S12 to S20, S32 to S40) configured to determine each times to perform a preliminary diagnosis when performing the engine control rt is used to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior obtained in the engine control performed at the same time; anda comprehensive diagnosis unit (S8) configured to calculate, by collating results of the preliminary diagnosis performed by the preliminary diagnosis unit (S12 to S20, S32 to S40), a concentration or a viscosity of the urea water and a diagnosing abnormality in the urea water supply system, and wherein the engine control unit (S4, S6) comprises: an increase control unit (S4) configured to perform an increase control to increase the rotational state of the engine in a direction to increase a rotational speed of the engine , to change; anda reduction control unit (S6) configured to perform reduction control to change the rotation state of the motor in a direction to reduce the rotation speed of the motor,the rotation behavior extraction unit (S11, S31) comprises:an extraction unit (S 11) a rotation-increasing behavior configured to obtain a rotation-increasing behavior, which is a rotation behavior of the motor when the boost control is performed; anda rotation-reducing behavior obtaining unit (S31) configured to obtain a rotation-reducing behavior, which is a rotation behavior of the motor when the reduction control is performed,the pressure behavior obtaining unit (S11, S31) comprises:an obtaining unit (S11 ) a pressure-increasing behavior configured to obtain a pressure-increasing behavior that is a pressure behavior in the tube (9) when the increase control is performed; and a pressure-decreasing behavior obtaining unit (S31) configured to obtain a pressure-decreasing behavior that is a pressure behavior in the tube (9) when the decrease control is performed, the preliminary Diagnosis comprises:a first diagnosis unit (S12 to S20) configured to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotation-increasing behavior and the pressure-increasing behavior; anda second diagnosis unit (S32 to S40) configured to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotation-decreasing behavior and the pressure-decreasing behavior, andconfigured the comprehensive diagnosis unit (S8). is to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on a result of the preliminary diagnosis performed by the first diagnostic unit and a result of the preliminary diagnosis performed by the second diagnostic unit .

Description

TECHNICAL AREA

The present disclosure relates to a diagnostic apparatus for a urea water supply system to supply urea water to an injector, for diagnosing a quality of urea water and an abnormality in the urea water supply system.

BACKGROUND

A urea selective catalytic reduction (SCR) system has been used as one of systems to purify an exhaust gas emitted from an internal combustion engine. In the urea SCR system, a NOx catalyst and an injector are provided on an exhaust pipe of the internal combustion engine. The NOx catalyst is for purifying NOx in an exhaust gas selectively by a reducing action with urea water. The injector is for mixing urea water to an upstream side of the NOx catalyst in an exhaust gas flow. A urea water supply system that supplies urea water to the injector is further provided to the urea SCR system. The urea water supply system includes a tank in which urea water is stored, a pump that discharges urea water in the tank by drawing in urea water, and a pipe that leads urea water discharged from the pump to the injector.

As for a concentration of urea water used in the urea SCR system, a desired value such as 32.5% is determined. It should be noted that urea water having a concentration outside a range expected by a reference concentration equivalent to the desired value may be used. Furthermore, a concentration of urea water that was originally at the reference concentration may vary with time. In a case where a vehicle is used in a cold region where a temperature falls below zero, the urea water in the tank may be cooled to freeze while the vehicle is parked. In freezing and thawing processes, urea may be inhomogeneously distributed in urea water. As a result, a concentration of urea water supplied to the injector may be outside of an expected range.

When a concentration of urea water supplied to the injector is higher than expected, the NOx catalyst is excessively supplied with urea. A phenomenon known as slippage, where ammonia is released from the NOx catalyst, may occur. Conversely, when a concentration of urea water is lower than expected, a NOx purification rate at the NOx catalyst may possibly be deteriorated.

Meanwhile, apart from a method related to a diagnosis of a concentration of urea water, a method to calculate a fuel viscosity based on an operating state of an electric pump that discharges fuel by drawing in the fuel has been proposed in the related art (see Patent Document 1) proposed. According to Patent Document 1, a fuel viscosity is calculated based on a time taken when an operational state of the electric pump changes from a first steady state to a second steady state.

(Patent Document 1)

Publication of the Japanese patent JP 4 840 531 B2

In order to diagnose a concentration or a viscosity of urea water, a sensor that detects a quality (a concentration or a viscosity) of urea water may be provided inside the tank. However, as described above, urea may be distributed inhomogeneously in urea water, in which case a concentration or viscosity of urea water detected by the sensor differs from concentration or viscosity of urea water with which the injector of actually supplied by the pump. That is to say, in a case where the quality sensor is provided in a region where a concentration of urea water is low while the pump is provided in a region where a concentration of urea water is high, the quality sensor is low Concentration detected when a concentration of urea water discharged from the pump is high. The provision of the quality sensor also increases the effort.

Also, an abnormality such as freezing of urea water, abnormality of a pump motor, and leakage of urea water from the pipe may possibly occur in the urea water supply system.

Further disclosed WO 2014/118 248 A1 a method for monitoring urea concentration and quality in a urea solution stored in a tank of an SCR system. The System includes a pump driven by a motor and the pressure of which is controlled by a regulator. The method comprises the steps of: - measuring a parameter value characteristic of the energy transmitted from the motor to the pump; - determining a urea concentration value based on the parameter value that is characteristic of the energy transferred from the engine to the pump.

Further prior art can be found in JP 2013-7 371 A and JP 2006- 86 117 A .

SHORT VERSION

An object of the present disclosure is to provide a diagnostic device configured to diagnose a concentration or a viscosity of urea water supplied to an injector and an abnormality in a urea water supply system without using a quality sensor that uses a Quality of urea water recorded.

This object is solved by the features of the independent claims. Further advantageous embodiments and further developments are the subject matter of the subsequent claims.

According to an aspect of the present disclosure, a diagnostic device for a urea water supply system is provided. The urea water supply system has a tank configured to store urea water, a pump configured to draw urea water stored in the tank and discharge the urea water, and a pipe configured to Leading urea water discharged from the pump to an injector. The diagnostic device includes a motor control unit configured to perform motor control to change a rotating state of a motor of the pump. The diagnostic device further includes a rotational behavior obtaining unit configured to obtain a rotational behavior of the engine while the engine control is being performed. The diagnostic device further includes a pressure behavior obtaining unit configured to obtain a pressure behavior in the pipe while the engine control is performed. The diagnostic device further includes a diagnostic unit configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior.

character list

• 1 eine Ansicht, die eine Gesamtkonfiguration eines Harnstoff-SCR-Systems zeigt;
• 2 eine Ansicht, die durch Entnehmen eines Teils, der sich auf eine Versorgung eines Injektors mit Harnstoffwasser bezieht, aus der Konfiguration des Harnstoff-SCR-Systems eine interne Konfiguration einer Pumpeneinheit zeigt
• 3 eine Ansicht, die Korrelationscharakteristiken zwischen einer Konzentration und einer Viskosität von Harnstoffwasser zeigt;
• 4 eine Ansicht, die Beispiele eines Verhaltens einer Motordrehgeschwindigkeit und eines Druckverhaltens in einem Rohr zeigt, wenn eine Motorerregung gestartet und gestoppt wird;
• 5 ein Flussdiagramm, das eine Verarbeitung darstellt, die durch eine ECU durchgeführt wird, um eine Konzentration von Harnstoffwasser und eine Systemabnormität zu diagnostizieren;
• 6 ein Flussdiagramm, das genauer eine Verarbeitung bei S5 von 5 darstellt, um vorläufig eine Konzentration von Harnstoffwasser und eine Systemabnormität zu diagnostizieren, wenn die Motorerregung gestartet wird;
• 7 ein Flussdiagramm, das genauer eine Verarbeitung bei S7 von 5 darstellt, um vorläufig eine Konzentration von Harnstoffwasser und eine Systemabnormität zu diagnostizieren, wenn die Motorerregung gestoppt wird; und
• 8 ein Flussdiagramm, das genauer eine Verarbeitung bei S8 von 5 darstellt, um auf der Basis eines vorläufigen Diagnoseresultats, wenn die Motorerregung gestartet wird, und eines vorläufigen Diagnoseresultats, wenn die Motorerregung gestoppt wird, eine umfassende Diagnose durchzuführen.

The foregoing and other objects, features and advantages of the present invention will be more apparent from the following detailed description made with reference to the accompanying drawings. Show it:

• 1 12 is a view showing an overall configuration of a urea SCR system;
• 2 12 is a view showing an internal configuration of a pump unit by extracting a part related to supply of urea water to an injector from the configuration of the urea SCR system
• 3 12 is a view showing correlation characteristics between a concentration and a viscosity of urea water;
• 4 12 is a view showing examples of a behavior of a motor rotation speed and a pressure behavior in a tube when motor energization is started and stopped;
• 5 14 is a flowchart showing processing performed by an ECU to diagnose a concentration of urea water and a system abnormality;
• 6 a flowchart detailing processing at S5 of 5 to preliminarily diagnose a concentration of urea water and a system abnormality when engine energization is started;
• 7 a flowchart detailing processing at S7 of 5 to preliminarily diagnose a concentration of urea water and a system abnormality when engine energization is stopped; and
• 8th a flowchart detailing processing at S8 of 5 to perform comprehensive diagnosis based on a preliminary diagnosis result when motor energization is started and a preliminary diagnosis result when motor energization is stopped.

DETAILED DESCRIPTION

(embodiment)

An embodiment of the present disclosure is described below with reference to the drawings. 1 12 shows an overall configuration of a urea SCR system to which the present disclosure is applied. The urea SCR system 1 is a system installed in a vehicle to remove NOx from a to purify exhaust gas emitted from an engine 2 as an internal combustion engine. The engine 2 is, for example, a diesel engine that has cylinders and injectors. Injectors inject fuel into the corresponding cylinders, respectively. Fuel injected by the injectors is spontaneously ignited in the cylinders.

In the urea SCR system 1 , an SCR (NOx) catalyst 4 and an injector 5 are provided on an exhaust pipe 3 of the engine 2 . The SCR catalyst 4 selectively purifies NOx in an exhaust gas by a reducing action. The injector 5 mixes urea water to an upstream side of the SCR catalyst 4 in an exhaust gas flow, or mixes urea water directly in the SCR catalyst 4 . The SCR catalyst 4 stores ammonia (NH3), which is a product of hydrolysis of urea water mixed from the injector 5, which is triggered by exhaust heat. The SCR catalyst 4 further carries a catalytic component that promotes a reduction reaction expressed by, for example, Chemical Equation 1, Chemical Equation 2, and Chemical Equation 3 below as a reducing action between ammonia (NH3) and NOx. An example of the catalyst component is a base metal oxide such as vanadium, molybdenum and tungsten. While an exhaust gas passes through the SCR catalyst 4, NOx is decomposed into water and nitrogen according to Chemical Equation 1, Chemical Equation 2, and that of Chemical Equation 3 as follows. 4NO + 4NH3 + O2 → 4N2 + 6H2O (chemical equation 1), 6NO2 + 8NH3 → 7N2 + 3H2O (chemical equation 2), NO + NO2 + 2NH3→2N2 + 3H2O (chemical equation 3).

Note that the SCR catalyst 4 is not capable of storing ammonia indefinitely, and a maximum storage amount of ammonia storable in the SCR catalyst 4 varies with a temperature of the SCR catalyst 4 (a catalyst temperature). A phenomenon called ammonia slip occurs when the catalyst temperature falls sharply, or the SCR catalyst 4 is supplied with too much ammonia (urea). When ammonia slip occurs, ammonia is released from the SCR catalyst 4 . In order to eliminate such a problem, an oxidation catalyst to purify ammonia released from the SCR catalyst 4 may be provided downstream of the SCR catalyst 4 .

The injector 5 has the same structure as a fuel injection valve from which fuel is injected into a cylinder or an intake port of a gasoline engine. That is to say, the injector 5 is formed as a solenoid on-off valve having a nozzle, a driving part, and a needle. The nozzle has an orifice. The driving part is made of an electromagnetic solenoid or the like. The needle serves to open and close a urea water passage in which urea water flows and the nozzle. When the electromagnetic solenoid is energized, the needle moves in a valve opening direction due to energization, and urea water is injected from the orifice provided at a tip end of the nozzle in association with movement of the needle.

The urea SCR system 1 further includes a urea water supply system that supplies the injector 5 with the urea water. The urea water supply system has a tank 6 , a pump unit 8 and a pipe 9 . The tank 6 stores urea water. The pump unit 8 draws and discharges urea water stored in the tank 6 . The pipe 9 leads urea water discharged from the pump unit 8 to the injector 5.

The tank 6 is fixed to, for example, a body frame of the vehicle and is exposed to the atmosphere. The tank 6 is formed of an airtight container having a supply port 7 . When urea water becomes scarce, urea water can be refilled from the supply port 7 into the tank 6 .

The pump unit 8 is an in-tank pump provided at a bottom of the tank 6 and immersed in urea water. Another type of pump having a pump main body installed outside of a tank can be used instead of the in-tank pump. The pump unit 8 is an electric pump driven to rotate by a drive signal from an ECU 19 . As in 2 1, the pump unit 8 includes a pump motor 10, a bladed impeller (impeller) 11, a urea water strainer 12, and a pump heater 13. The pump motor 10 is driven to rotate by a drive signal from the ECU 19. FIG. The bladed impeller (impeller) 11 is fixed to a rotating shaft of the pump motor 10 . The urea water filter 12 filters out foreign substances from the urea water. The pump heater 13 is provided to surround the pump motor 10 to heat an inside of the pump unit 8 including the pump motor 10 .

The pump motor 10 is, for example, a three-phase induction motor and capable of changing a rotation speed of a rotor by changing a frequency of a drive signal sent to a stator side (primary side). The pump motor 10 is further capable of switching a rotating direction of the rotor between a forward direction to discharge (pressure-feed) urea water toward the injector 5 and a reverse direction to draw urea water back into the tank 6 .

With the pump unit 8 configured as above, the bladed impeller 11 rotates in association with rotations of the pump motor 10, urea water in the tank 6 is drawn in and discharged, or urea water remaining in the pipe 9 becomes associated drawn back into the tank 6 with rotations of the bladed impeller 11 . In addition, the pump unit 8 is capable of variably adjusting a pressure feed amount (pump discharge amount) of urea water by changing a rotation speed of the pump motor 10 . A pressure-feed amount of urea water increases as a rotating speed of the pump motor 10 becomes higher, and an internal pressure of the pipe 9 increases as a pressure-feed amount increases.

A tank heater 14 is provided inside the tank 6 and immersed in urea water to heat urea water in the tank 6 . The tank heater 14 is connected to the pump heater 13 . Therefore, when the tank heater 14 is energized by the ECU 19, the pump heater 13 is also energized.

The pipe 9 is connected to a discharge port of the pump unit 8 at one end and connected to a urea water inlet of the injector 5 at the other end. Urea water discharged from the pump unit 8 flows into the pipe 9 to supply the injector 5 from the urea water inlet of the injector 5 .

The urea SCR system 1 is provided with various sensors to control the urea SCR system 1 . More specifically, the tank 6 is provided with a urea water temperature sensor 15 that detects a temperature of urea water in the tank 6 . The tube 9 is provided with a pressure sensor 16 that detects an internal pressure of the tube 9 . The pressure sensor 16 is provided closer to the injector 5 than to the pump unit 8 . An outside air temperature sensor 17 that detects an outside air temperature and an engine water temperature sensor 18 that detects a coolant temperature of the engine 2 are also provided. Detection values of the respective sensors are inputted into the ECU 19. Besides the sensors specified above, a rotational speed sensor that detects an engine rotational speed, an accelerator sensor that detects an amount of accelerator operation (accelerator position) by a driver, a NOx sensor that is provided downstream of the SCR catalyst 4 are also provided and a concentration of NOx in the exhaust gas is detected, and so on.

The urea SCR system 1 further includes the ECU 19 . The ECU 19 comprises a known microcomputer having CPU, ROM, RAM and so on. The ECU 19 controls an addition amount of urea water by the injector 5 based on, for example, a running state of the engine 2 and a detection value of the NOx sensor. is generated and therefore controls rotation of the pump motor 10. The ECU 19 further has a drive state detection circuit 21 that detects a signal (such as a drive current or a drive voltage) actually generated in the pump motor 10 in response to a drive signal (such as a drive voltage) output from the motor drive circuit 20. The ECU 19 additionally controls energization of the heaters 13 and 14.

The ECU 19 performs processing such as determination of a concentration of urea water stored in the tank 6 and determination of an abnormality in the urea water supply system such as freezing of urea water. Concentration and freezing of urea water are now described before the processing is described in detail. A desired value such as 32.5% is determined for a concentration of urea water (concentration of urea contained in the urea water) used in the urea SCR system 1 . The concentration of urea water is a concentration of urea contained in the urea water. Note that urea water having a concentration that is outside a range expected by a reference concentration equivalent to the predetermined value may be used in some cases. In addition, in a case where the vehicle is used in a cold region where a temperature falls below zero, urea water in the tank 6 may be cooled to freeze while the vehicle is parked. Urea water freezes at -11°C. However, urea water does not start to be frozen homogeneously in respective regions in the tank 6, and urea water starts to to freeze from a surface side near an outside air. In addition, moisture contained in the urea water freezes first in a process of freezing, and thus urea accumulates on a liquid side where freezing does not occur. Therefore, in a state where urea water is partially frozen, a concentration of urea in a non-frozen portion may become higher than the reference concentration. In the foregoing manner, urea may be distributed inhomogeneously in urea water in the process of freezing, and the same applies to urea distribution in a process of thawing.

When the injector 5 is supplied with a urea water having a concentration that is outside an expected range, ammonia slip may occur to release excess ammonia from the SCR catalyst 4, or a NOx purification rate at the SCR catalyst 4 may deteriorate be. In order to limit such troubles, it is useful to determine a concentration of urea water actually supplied to the injector 5 .

In a case where the urea water freezes completely, the injector 5 cannot be supplied with the urea water, and the driver has to wait for the frozen urea water to thaw. On the other hand, in a case where the urea water partially freezes and the remainder remains unfrozen, if the pump unit 8 is provided in the unfrozen region, the injector 5 can be supplied with urea water. In such a case, cleaning of NOx by the SCR catalyst 4 is delayed when the driver waits for the urea water that is partially frozen to completely thaw. It is therefore necessary to determine a freezing state of urea water in as short a time as possible.

In the present embodiment, a concentration determination is performed using a correlation between a concentration and a viscosity of urea water. Correlation characteristics between a concentration and a viscosity of urea water are now referred to in FIG 3 described. As in 3 1, correlation characteristics between a concentration and a viscosity of urea water at a specific concentration have an inflection point, and a tendency of a viscosity variation in response to a concentration variation changes before and after the inflection point. To be more specific, a viscosity variation in response to a concentration variation is small in a region where a concentration is lower than a normal concentration indicating the break point. In short, a viscosity takes a substantially constant value even when a concentration varies. In contrast, a viscosity variation in response to a concentration variation is large in a region where a concentration is higher than the normal concentration. To be more specific, a viscosity increases as a concentration becomes higher.

In 3 the normal concentration is set as the break point near the reference concentration (32.5%) of urea water. In 3 On a line (solid line) showing the correlation characteristics at a normal temperature, viscosities when concentrations are 34.2% and 40% are about 1.05 times and 1.3 times higher, respectively, than a viscosity when a concentration is 32.5%.

Also, a viscosity of urea water varies with a temperature. To be more specific, a viscosity increases as a temperature becomes lower. In 3 a viscosity (broken line) at a low temperature (0°C) is about 1.8 times higher than a viscosity (solid line) at a normal temperature (20°C). A rate of viscosity variation with respect to a concentration variation is the same in the correlation characteristics (solid line) between a concentration and a viscosity at a normal temperature and in the correlation characteristics (broken line) at a low temperature.

When control to change a rotating state of the pump motor 10 in response to a viscosity varying in response to a concentration or a temperature is performed, a rotating behavior of the pump motor 10 changes as described above. An internal pressure of the pipe 9 varies in association with rotations of the pump motor 10. Therefore, when control to change a rotating state of the pump motor 10 is performed, pressure behavior changes in response to viscosity. Such a change in behavior is now described in more detail with reference to FIG 4 described.

In 4 are a state of energization of a pump motor (further referred to as motor energization hereinafter), a variation in rotational speed of the pump motor, and a variation in pipe pressure are all with respect to time in lines (a), (b) and (c), respectively. shown from top to bottom. In the lines (b) and (c), a line (broken line) (1) represents a behavior when urea water is used at a normal temperature and the reference concentration. In addition, an alternate long and short dashed line (2) represents a behavior when urea water is used at a low temperature and the reference concentration. A solid line (3) represents behavior when urea water is used at a normal temperature and a concentration higher than the reference concentration. Like referring to it 3 as described above, viscosity increases as concentration becomes higher, and viscosity increases as temperature becomes lower. Therefore, a viscosity is higher in the order of lines (1), (2), and (3).

A turning behavior when motor excitation is started is described. A time from when the motor excitation is turned ON until the motor actually starts rotating (rotation start delay time) becomes longer as a viscosity, that is, a concentration, becomes higher. In other words, the rotation start delay time becomes longer in (2) than in (1), and becomes longer in (3) than in (2), this relationship being expressed by an inequality: (1)<(2)<(3). A rate of increase in rotational speed with respect to time in a process of changing a steady state since the engine started rotating (a rate of increase in a part 100 in the row (b) of 4 ) is lower when a concentration is high (3) than when a concentration is low ((1) and (2)). A reason of such a difference in the rate of increase in rotating speed is that viscosity increases as concentration becomes higher, and resistance increases as viscosity becomes higher, and higher resistance makes it difficult for the motor to rotate to turn.

A pressure behavior when motor excitation is started is described. A delay time since the motor excitation was turned ON until a pipe pressure actually starts rising becomes longer as a viscosity, that is, a concentration, becomes higher. To be more specific, like the rotation start delay time, a relationship is expressed by an inequality: (1)<(2)<(3).

A turning behavior when motor excitation is terminated will now be described. A time since the motor energization was turned OFF until a rotational speed of the motor actually starts decreasing (decrease start delay time) becomes longer as a viscosity, that is, a concentration, becomes higher. A rate of decrease in rotational speed with respect to time in a process of changing to a stationary state (the rotation stops) since the rotation started decreasing (a rate of decrease in a part 101 in the row (b) of 4 ) is lower when a concentration is high (3) than when a concentration is low ((1) and (2)). A reason for such a difference in the rate of reduction in rotational speed is that a viscosity increases as a concentration becomes higher, and urea water acting on a bladed impeller does not easily separate from the bladed impeller , and a flow of urea water acting on the bladed wheel allows the engine to keep rotating longer after the engine excitation is turned OFF by inertia (habit).

A pressure behavior when motor energization is terminated will now be described. A time since the motor excitation was turned OFF until a pipe pressure actually starts falling becomes longer as a viscosity, that is, a concentration, becomes higher. To be more specific, the time becomes longer in (2) than in (1) and becomes longer in (3) than in (2), this relationship being expressed by an inequality: (1) < (2) < (3 ). A rate of decrease in pressure with respect to time in a process of changing to a steady state (zero pressure) since the pressure started falling is lower when concentration is high (3) than when concentration is low is ((1) and (2)). A reason for such a difference in the rate of reduction of the pressure is, as described above, that the motor keeps rotating longer by inertia as concentration becomes higher.

Viscosity increases as concentration becomes higher, and therefore resistance to rotations of the engine also increases. Therefore, it can be considered that a rotation speed decreases rapidly when motor excitation is turned OFF. That is to say, it can be considered that the reduction start delay time at the time of turning OFF the motor excitation is shorter, and a rate of reduction in rotation and a rate of reduction in pressure are higher when concentration (viscosity) is high, than when a concentration (viscosity) is low. However, as described above, the present embodiment utilizes the knowledge that the decrease start delay time at the time of turning OFF the motor excitation becomes longer when a concentration is high than when a concentration is low, and hence the rates become one Reduction in rotation and the rate of reduction in pressure lower.

4 12 shows a difference in turning behavior and pressure behavior due to a difference in concentration (viscosity) of urea water. In the event of an abnormality such as urea water freezing, the rotational behavior and the pressure behavior change by reflecting a type of the abnormality that has occurred, such as urea water freezing, an engine abnormality, and/or a pipe leak.

The ECU 19 makes a determination of a concentration of urea water and an abnormality such as freezing of urea water by using the knowledge referred to above 3 and 4 is described before. Processing performed by the ECU 19 is described in detail below. 5 FIG. 12 is a flowchart showing the processing performed by the ECU 19. FIG. The processing of 5 starts when a predetermined condition is met, for example, when the engine 2 is started.

If the processing of 5 is started, a determination of complete freezing of urea water in the tank 6 is first made (S1). Complete freezing herein represents a state where it is obvious that the injector 5 cannot be supplied with urea water. In other words, complete freezing represents a state in which urea water is frozen as a whole. More specifically, the determination of complete freezing is made as follows. That is, it is determined that the urea water is completely frozen when, for example, a urea water temperature detected by the urea water temperature sensor 15 is as high as or lower than a predetermined threshold A, an outside air temperature detected by the outside air temperature sensor 17 , is as high as or lower than a predetermined threshold B, and a coolant temperature detected by the engine water temperature sensor 18 is as high as or lower than a predetermined threshold C. When at least one of the urea water temperature, the outside air temperature, and the coolant temperature is higher than the corresponding threshold, it is determined that the urea water is not completely frozen. For example, the thresholds are set to temperatures (e.g. -20°C) lower than -11°C, which is a freezing temperature of urea water. The thresholds A, B and C can be set to an equal temperature or can be set to different temperatures from each other. By making a complete freezing determination based on the urea water temperature, the outside air temperature, and the coolant temperature as above, the complete freezing can be determined accurately compared to a case where a determination is made based on a temperature of the urea water alone .

When the complete freezing is determined (S2: YES), energization of the pump motor 10 (hereinafter also referred to as the motor energization) by the motor drive circuit 20 is stopped (S3) to protect the pump motor 10. Urea water in the pump unit 8 and urea water in the tank 6 are additionally heated by energizing the heaters 13 and 14 (S3) to thaw frozen urea water. The processing of 5 will then be terminated.

On the other hand, when complete freezing is not determined (S2: NO), energization of the pump motor 10 by the motor drive circuit 20 is started (S4). That is to say, by rotating the pump motor 10 in the forward direction, supply of the urea water to the injector 5 is started. A target value of the pipe pressure is set therein, and a frequency of a drive signal output from the motor drive circuit 20 to the pump motor 10 is set for the pump pressure to match the target value. The processing at S4 is an example of boost control to change a rotating state of the pump motor 10 in a direction to increase a rotating speed of the pump motor 10 .

A concentration of urea water, freezing of urea water, and so on are then determined based on the rotational behavior of the pump motor 10 and the pressure behavior in the pipe 9 when motor energization was started (S5). To be more specific, processing of 6 accomplished.

If an establishment for the processing of 6 is switched, a rotation behavior of the pump motor 10 and a pressure behavior in the pipe 9 when the motor energization was started are first obtained (S11). More specifically, a rotational performance is obtained by detecting a signal (e.g., a drive current) actually generated in the pump motor 10 after motor energization is started using the drive state detection circuit 21 . The generated signal varies in cycles corresponding to a rotational speed of the pump motor 10 (hereinafter also referred to as a motor rotational speed). A motor rotation speed is therefore based on the Found based on cycles of generated signal. The motor rotation speed found in the foregoing manner is successively obtained during a period since the pump motor has started rotating after motor energization has started until motor rotation reaches a steady state. Herein, a steady state of engine rotation represents a state where a rotation speed remains constant with time. In other words, the stationary state of engine rotation is a state in which a rate of variation in rotation speed with respect to time is substantially 0. Alternatively, a sensor that detects a rotation speed of the pump motor 10 may be provided inside the pump unit 8 to obtain a motor rotation speed by the sensor.

At S11, based on the obtained behavior of a motor rotation speed, a rotation start delay time (corresponding to an increase delay time of the present disclosure) since motor energization is started until the pump motor 10 actually starts rotating is calculated. In addition, a rate of increase in rotation speed with respect to time (rotation increase rate) in a process of changing the steady state since the pump motor 10 actually started rotating it is calculated based on the behavior of the motor rotation speed. More specifically, an instantaneous rotation increasing rate at each point during a period of rotation increasing since rotation started until rotation reaches the steady state is found point by point, for example. An average of the instantaneous rate of spin increase at each point thus found is adopted as a final rate of spin increase. Alternatively, the rotation increasing duration may be divided into plural sections by a predetermined length of time to calculate a rotation increasing rate section by section, and a maximum value among the rotation increasing rates in all sections may be adopted as a final rotation increasing rate.

A pressure behavior in the pipe 9 is obtained by successively obtaining a detection value of the pressure sensor 16 during a period since a pipe pressure has started increasing after motor energization has started until the pipe pressure reaches a steady state. A steady-state pipe pressure herein represents a condition where the pipe pressure remains constant at a target value over time. In other words, it is a state where a rate of variation of the pipe pressure with respect to time is substantially 0.

At S11, in a process of changing to the steady state since the pressure started rising, a rate of increase in the pipe pressure (pressure increase rate) with respect to time is calculated based on the obtained pressure behavior. The pressure increase rate is calculated in the same manner as the rotation increase rate. The turning behavior (the turning start delay time and the turning increasing rate) and the pressure behavior (the pressure increasing rate) obtained at S<b>11 are stored in an internal memory of the ECU 19 . The rotation start delay time and the rotation increase rate may be calculated at a determination timing at S12 or S14 described below, and the pressure increasing rate may be calculated at a determination timing at S15 or S18 described below.

Whether the rotation start delay time obtained at S11 is shorter or longer than a preset threshold T1 is then determined (S12). Referring to line (b) of 4 the threshold T1 is set to a value above the spin start delay times of lines (1) and (2) and below a spin start delay time of line (3). When the rotation start delay time is shorter than the threshold T1, it is tentatively diagnosed that the urea water has the reference concentration (for example, 32.5%) and the pump motor 10 is operating normally (S13). Preliminary diagnosis is performed in a manner as above because a viscosity of urea water at the reference concentration becomes lower than that at a high concentration (see 3 ), and the rotation start delay time becomes shorter as the viscosity becomes lower (see the line (b) of 4 ). Even when the urea water has the reference concentration, the rotation start delay time becomes longer unless the pump motor 10 is normally operated. In short, a short rotation start delay time represents that the pump motor 10 is normal.

On the other hand, when the spin start delay time is longer than the threshold T1, whether the spin increase rate obtained at S11 is higher or lower than a preset threshold R1 is determined (S14). Referring to line (b) of 4 the threshold R1 is set to a value below a rotation increasing rate of lines (1) and (2) and above a rotation increasing rate of line (3). When the rotation increase rate is higher than the threshold R1, the motor pump 10 is assumed to be normal, and then it becomes determines (S15) whether the pressure increase rate obtained at S11 is higher or lower than a predetermined threshold P1. When a determination that urea water has the reference concentration and the pump motor 10 is normal is made in step S13, it is then further determined (S15) whether the pressure increase rate is higher or lower than the threshold P1. A processing S15 is for discriminating whether urea water is at the reference concentration or a pipe leak occurs, not for discriminating whether the urea water is at the reference concentration or a high concentration. Referring to line (c) of 4 the threshold P1 is set to a value below the pressure increase rates of lines (1) and (2).

Finally, when the pressure increase rate is higher than the threshold P1, it is determined that urea water has the reference concentration and the pump motor 10 is normal as a determination when motor energization is started (S16). As described, when processing 6 a determination that urea water has the reference concentration and the pump motor 10 is normal is made when either the rotation start delay time is shorter than the threshold T1, or the rotation increase rate is higher than the threshold R1, and when the pressure increase rate is higher than the threshold P1. A determination is made in the same manner as the foregoing since, as in lines (b) and (c) of 4 is shown, the spin start delay time is shorter and the spin increasing rate is higher in the behaviors of lines (1) and (2) at the reference concentration than in the behavior of line (3) at a high concentration. A comparison of the behavior between lines (1) and (2) in line (b) of 4 reveals that the rotation start delay time varies with a difference in temperature even when urea water has the same reference concentration, more specifically, the rotation start delay time becomes longer as the temperature becomes lower. When processing 6 Therefore, even in a case where it is provisionally determined based on a temperature drop that the spin start delay time is longer than the threshold T1, whether the urea water is the reference concentration can be detected in a reliable manner by confirming the spin increasing rate and also the pressure increasing rate Has. In addition, the rotation increase rate and the pressure increase rate increase under the condition that the pump motor 10 is normally operated. Therefore, in addition to whether the urea water has the reference concentration, it is further determined at S16 whether the pump motor 10 is normal. The processing of 6 is terminated after S16, and the operation returns to the processing of 5 back.

On the other hand, when the pressure increase rate is lower than the threshold P1, it is determined that urea water is leaking from the pipe 9 on the basis that a pipe pressure does not increase although the pump motor 10 is normal (S17). Pipe leakage is one of the abnormalities in the urea water supply system. In a case where advancement to S17 is made via S13, pipe leakage occurs when the urea water has the reference concentration and the pump motor 10 is normal. The processing of 6 is terminated after S17, and the operation returns to the processing of 5 back.

If the rotation increase rate is found to be lower than the threshold R1 at S14, it is determined (S18) whether the pressure increase rate obtained at S11 is higher or lower than a preset threshold P2. Processing at S18 is to discriminate whether the urea water has a high concentration or a system abnormality occurs, not to discriminate whether the urea water has the reference concentration or a high concentration. Referring to line (c) of 4 the threshold P2 is set to a value below a pressure increase rate of the line (3). The threshold P2 and the threshold P1 may be set to the same value at S15 or may be set to values different from each other.

When the pressure increase rate is higher than the threshold P2, it is determined that the urea water has a higher concentration than the reference concentration (S19). When processing 6 a determination that the urea water has a high concentration is made when the spin start delay time is longer than the threshold T1, the spin increase rate is lower than the threshold R1, and the pressure increase rate is higher than the threshold P2. A determination is made in a manner as before because, as in lines (b) and (c) of 4 is shown, the spin start delay time is longer and the spin increase rate is lower in the behavior of the line (3) at a high concentration than in the behaviors of the lines (1) and (2) at the reference concentration. The processing of 6 is terminated after S19, and the operation returns to the processing of 5 back.

If it is found at S18 that the pressure increase rate is lower than the threshold P2, on the basis that a motor rotation does not increase and a pipe pressure slowly increases (S20), an abnormality in the pump motor 10 or a circuit that controls the pump motor 10 drives (hereinafter referred to simply as an engine abnormality) or a freeze determined by urea water. Engine abnormality and urea water freezing are abnormalities in the urea water supply system. The processing of 6 is terminated after S20, and the operation returns to the processing of 5 back. A result of determination as to a concentration of urea water or the like by the processing of 6 , that is, a determination result at S16, S17, S19, or S20 is stored in the internal memory of the ECU 19. It should be noted that the processing of 6 is a processing to preliminarily diagnose a concentration of the urea water or the like, and a diagnosis result is given at S8 of 5 , which is described below, is given the final form.

If the operation to the processing of 5 returns, energization of the pump motor 10 is stopped after S5 (S6). The processing at S6 is an example of decrease control to change a rotating state of the pump motor 10 in a direction to decrease a rotating speed of the pump motor 10B.

A concentration of urea water, freezing of urea water, and so on are then determined based on a rotational behavior of the pump motor 10 and a pressure behavior in the pipe 9 when motor energization is stopped (S7). To be more specific, processing of 7 accomplished.

If the operation to the processing of 7 is switched, as in S11 of 6 , a behavior of a rotational speed of the pump motor 10 and a pressure behavior in the pipe 9 when the motor energization is stopped are obtained (S31). At S31, based on the obtained behavior of a rotational speed of the pump motor 10, a decrease start delay time since the motor energization stopped until the pump motor 10 actually starts to decelerate (a rotational speed decreases) is calculated. In addition, a rate of decrease in rotation speed (rotation reduction rate) with respect to time in a process of changing a steady state (rotation stops) since the pump motor 10 started to decelerate is calculated based on the obtained behavior of rotation speed of the pump motor 10 calculated. The rotation decrease rate is calculated in the same manner as the rotation increase rate set at S11 of 6 is calculated, calculated.

At S31, based on the obtained pressure behavior, a rate of decrease in pipe pressure (pressure decrease rate) with respect to time in a process of changing to a stopped rotation state since the pump motor 10 started to decelerate is calculated. The turning behavior (the turning start delay time and the turning decrease rate) and the pressure behavior (the pressure decrease rate) obtained at S<b>31 are stored in the internal memory of the ECU 19 . The decrease start delay time and the rotation decrease rate may be calculated at a determination timing at S32 or S34 described below, and the pressure decrease rate may be calculated at the determination timing at S35 or S38 described below.

Whether the decrease start delay time obtained at S31 is shorter or longer than a preset threshold T2 is then determined (S32). Referring to line (b) of 4 the threshold T2 is set to a value above the decrease start delay times of lines (1) and (2) and below a decrease start delay time of line (3). When the decrease start delay time is shorter than the threshold T2, it is preliminarily diagnosed that urea water has the reference concentration (S33). Preliminary diagnosis is performed in a manner as above since, as referred to in FIG 4 is described, a viscosity at the reference concentration becomes lower than that at a high concentration, and as a viscosity becomes lower, the pump motor 10 further rotates by inertia shorter after the motor energization is turned OFF.

On the other hand, when the reduction start delay time is longer than the threshold T2, whether the rotation reduction rate obtained at S31 is higher or lower than a preset threshold R2 is determined (S34). Referring to line (b) of 4 the threshold R2 is set to a value below the rotation reduction rates of lines (1) and (2) and above the rotation reduction rate of line (3). If the rotation reduction rate is higher than the threshold R2, the pump motor 10 is assumed to be normal, and whether the pressure reduction rate obtained at S31 is higher or lower than a preset threshold P3 is then determined (S35). When a determination that urea water has the reference concentration is made at S33, whether the pressure decrease rate is higher or lower than the threshold P3 is also subsequently determined (S35). Processing at S35 is to discriminate whether urea water is at the reference concentration or a pipe leak occurs, not to discriminate whether urea water is at the reference concentration or high concentration. relation taking on the line (c) of 4 the threshold P3 is set to a value above the pressure reduction rates of lines (2) and (2).

When the pressure decrease rate is lower than the threshold P3, it is determined that urea water has the reference concentration (S36). As described, when processing 7 a determination that urea water has the reference concentration is made when either the decrease start delay time is shorter than the threshold T2, or the rotation decrease rate is higher than the threshold R2, and when the pressure decrease rate is lower than the threshold P3. The processing of 7 is terminated after S36, and the operation returns to the processing of 5 back.

On the other hand, when the pressure decrease rate is higher than the threshold P3, it is determined that the urea water is leaking from the pipe 9 on the basis that the pressure falls abnormally rapidly (S37). In a case where advancement is made to S37 via S33, pipe leakage occurs when urea water has the reference concentration. The processing of 7 is terminated after S37, and the operation returns to the processing of 5 back.

If the rotation decrease rate is found to be lower than the threshold R2 at S34, it is then determined (S38) whether the pressure decrease rate obtained at S31 is higher or lower than a preset threshold P4. Processing at S38 is to discriminate whether urea water has a high concentration or whether a system abnormality occurs, not to discriminate whether urea water has the reference concentration or a high concentration. Referring to line (c) of 4 the threshold P4 is set to a value above a pressure decrease rate of the line (3). The threshold P4 and the threshold P3 at S35 may be set to the same value or may be set to different values from each other.

When the pressure decrease rate is lower than the threshold P4, it is determined that urea water has a higher concentration than the reference concentration (S39). A determination is made as above because, as in line (c) of 4 is shown, the pressure decrease rate of the line (3) at a high concentration is lower than the pressure decrease rates of the lines (1) and (2) at the reference concentration. As described, when processing 7 a determination that urea water has a high concentration is made when the reduction start delay time is longer than the threshold T2, the rotation reduction rate is lower than the threshold R2, and the pressure reduction rate is lower than the threshold P4. The processing of 7 is terminated after S39, and the operation returns to the processing of 5 back.

When it is found at S38 that the pressure decrease rate is higher than the threshold P4, it is determined (S40) that urea water is leaking from the pipe 9 on the basis that a pressure falls although the pump motor 10 rotates. The processing of 7 is terminated after S40, and the operation returns to the processing of 5 back. A result of determination as to a concentration of urea water or the like by the processing of 7 , that is, a determination result at S36, S37, S39, or S40 is stored in the internal memory of the ECU 19. It should be noted that the processing of 7 is processing to preliminarily diagnose a concentration of urea water or the like, and a diagnosis result is returned at S8 of 5 , which is described below, is given its final form.

If the operation to the processing of 5 returns, based on the determination result at S5 and the determination result at S7, comprehensive determination is made after S7 as to a concentration of urea water or the like (S8). To be more specific, processing of 8th accomplished.

If the operation to the processing of 8th is switched, the determination result at S5 and the determination result at S7 are first read from the memory (determination result gathering) (S51). A presence or absence of a problem for continuing operation of the urea SCR system 1 is then determined based on a compiled determination result (S52 to S55). More specifically, whether the compiled determination result includes a pipe leak determination is determined (S52). Since a pipe leak is a time-critical abnormality among the system abnormalities, a pipe leak is diagnosed first before an engine abnormality, freezing of urea water, and concentration of urea water. Finally, when the pipe leak determination is included (S52: YES), a pipe leak is diagnosed (S53). As described, in a case where at least one of the determination result at S5 and the determination result at S7 includes the pipe leak determination, the pipe leak is diagnosed regardless of whether the determination result at S5 and the determination result at S7 agree with each other. The processing of 8th will ended after S53, and the operation returns to the processing of 5 back.

When the pipe leak determination is not positive (S52: NO), whether a determination of engine abnormality or urea water freezing in the determination results collated at S51 is positive is determined (S54). Finally, when a determination of engine abnormality or urea water freezing is positive (S54: YES), engine abnormality or urea water freezing is diagnosed (S55). As described, in a case where at least one of the determination result at S5 and the determination result at S7 includes a determination of engine abnormality or urea water freezing, engine abnormality or urea water freezing is diagnosed regardless of whether the determination result at S5 and the determination result at S7 agree with each other. The processing of 8th is terminated after S55, and the operation returns to the processing of 5 back.

When neither determination of engine abnormality nor freezing of urea water is included in the composed determination result (S54: NO), concentration of urea water is diagnosed at S56 and subsequent steps on the basis that system operation can be continued. More specifically, whether determination of a high concentration is included in the compiled determination result is determined (S56). When the high concentration determination is included (S56: YES), a determination is made as to whether the two determination results collated into one result, that is, the determination result at S5 and the determination result at S7, agree with each other as to high concentration ( S57). Finally, when the two determination results compiled into one result agree with each other (S57: YES), it is diagnosed that the urea water has a higher concentration than the reference concentration (S58). The processing of 8th is terminated after S58, and the operation returns to the processing of 5 back.

When it is found at S57 that the two determination results compiled into one result do not agree with each other, that is, when one determination result indicates that the urea water has a high concentration and the other determination result indicates that the urea water has the reference concentration and the pump motor 10 is normal (S57: NO), diagnosis by determining that a concentration of urea water is unknown is prohibited (S61). Herein, it is provisionally determined that the urea water has the reference concentration and that the pump motor 10 is operating normally, and the processing of 5 until 8th is performed again to diagnose a concentration of urea water or the like again. The processing of 8th is terminated after diagnosis is performed again, and operation returns to the processing of 5 back.

On the other hand, when it is found at S56 that the determination of a high concentration is not included in the compiled determination result (S56: NO), a determination is made as to whether the two determination results (the determination result at S5 and the determination result at S7) contained in one result are collated agree with each other as to whether the urea water has the reference concentration and the pump motor 10 is normal (S59). Finally, when the two determination results agree with each other (S59: YES), it is diagnosed that the urea water has the reference concentration and the pump motor 10 is operating normally (S60). In contrast, when the two determination results do not agree with each other (S59: NO), advancement to S61 described above is made. The processing of 8th is terminated after S60 or S61, and the operation returns to the processing of 5 back.

If the operation to the processing of 5 returns, processing (system operation) corresponding to a diagnosis result at S8 is performed after S8 (S9). More specifically, if a pipe leak at S58 from 8th is diagnosed, by rotating the pump motor 10 in the reverse direction, for example, urea water in the pipe is drawn back into the tank 6 and then an operation of the pump motor 10 is stopped. Consequently, pipe leakage can be restricted since pressure-feeding of urea water by the pump unit 8 is stopped.

In the case where a pipe leak is diagnosed (pipe leak diagnosis), a warning is given using a display or the like provided on the vehicle to inform a possibility of a system abnormality (pipe leak), for example. By informing a driver of the presence of a system abnormality with the warning, the driver is enabled to send the vehicle for repair and solve the pipe leak abnormality.

In addition, in the case of pipe leak diagnosis, an output of the engine 2 is restricted to restrict emission of NOx (for example, the engine 2 is not subjected to a run at high load by limiting a fuel injection amount). Consequently, even if the urea SCR system 1 does not function normally due to a pipe leak, by running the engine 2 to limit emission of NOx, an amount of NOx passing through the SCR catalyst 4 can be reduced.

A system action when an engine abnormality at S55 of 8th is, for example, stopping pressure-feeding of urea water by the pump unit 8 by stopping an operation of the pump motor 10 . Consequently, the pump motor 10 can be protected from further damage. When an engine abnormality is diagnosed, such as the pipe leak, a warning may be given, or an output of the engine 2 may be limited.

A system action when freezing of the urea water at S55 from 8th is diagnosed is, for example, to perform control to thaw frozen urea water by energizing the heaters 13 and 14 (see 2 ). After the control (heater energization) is continued for a predetermined time, the processing of 5 until 8th carried out again in order to diagnose freezing of the urea water again. System operation while the urea water is frozen can therefore be restricted. When freezing of the urea water is diagnosed, such as the pipe leak, a warning may be issued or an output of the engine 2 may be limited.

A system action if at S58 from 8th when a high concentration is diagnosed is, for example, to decrease an addition amount of urea water by the injector 5 from an addition amount when urea water is the reference concentration. Accordingly, an excessive supply of urea (ammonia) to the SCR catalyst 4 can be restricted, and therefore ammonia slip and wastage of urea water can be restricted. In addition, when a high concentration is diagnosed, a warning may be issued to inform that urea water having a high concentration is used. In such a case, for example, by replenishing urea water with the reference concentration, continuous use of urea water with a high concentration can be restricted.

If at S60 from 8th it is diagnosed that the urea water has the reference concentration and the pump motor 10 is normal, normal system operation is continued. When a re-diagnosis completion is diagnosed at S61, a concentration of urea water or the like is re-diagnosed as described above. The processing of 5 is terminated after S9.

As described, according to the present embodiment, a concentration of urea water and a system abnormality such as freezing of urea water can be diagnosed without using a sensor that detects a quality of urea water. Accordingly, system abnormalities such as pipe leakage, engine abnormality, and urea water freezing can be diagnosed. By observing a rotational behavior of the pump motor 10 and a pressure behavior in the pipe 9, freezing of urea water actually drawn in and discharged by the pump unit 8 can be detected in a short time. For example, in a case where urea water in the tank 6 is only partially frozen, when the pump unit 8 draws in frozen urea water, it can be determined that the urea water is frozen, and when the pump unit 8 draws in non-frozen urea water, it can be determined that that the urea water is not frozen.

A concentration of urea water and a system abnormality are comprehensively diagnosed by collating a preliminary diagnosis result (result at S5) when engine energization is started and another preliminary diagnosis result (result at S7) when engine energization is stopped. Therefore, accuracy of diagnosis can be improved. In the comprehensive diagnosis, when at least one of the two preliminary diagnosis results indicates a system abnormality, the system abnormality is adopted as a final diagnosis result. Therefore, an oversight of a system abnormality can be restricted. In the comprehensive diagnosis, when the two preliminary diagnosis results agree with each other in a concentration of urea water, the agreed concentration is adopted as a final diagnosis result. On the other hand, when the two preliminary diagnosis results do not agree with each other on a concentration of urea water, a concentration is left as unknown in the current diagnosis. Therefore, an accuracy of a concentration diagnosis can be improved.

It is obvious that the present disclosure is not limited to the embodiment described above and can be modified in various ways can. For example, the foregoing embodiment describes a case where a concentration of urea water is diagnosed. However, a viscosity of urea water can be diagnosed instead of a concentration. That is to say, as in 3 it is shown that since a viscosity at a high concentration (e.g. 40%) is higher than that at the reference concentration (e.g. 32.5%), in processing of 5 until 8th the reference concentration can be replaced by a reference viscosity, and a high concentration can be replaced by a high viscosity.

In the foregoing embodiment, a concentration of urea water and a system abnormality are diagnosed based on a rotational behavior and a pressure behavior when engine energization is started. However, a concentration of urea water and a system abnormality can be diagnosed based on a rotating behavior and a pressure behavior under control to change a rotating state of the pump motor 10 rotating in the stationary state in a direction to further increase a rotating speed will.

Similarly, in the foregoing embodiment, a concentration of urea water and a system abnormality are diagnosed based on a rotational behavior and a pressure behavior when engine energization is stopped. However, a concentration of urea water and a system abnormality can be diagnosed based on a rotation behavior and a pressure behavior under control to change a rotation state of the pump motor 10 in a direction to decrease a rotation speed while motor energization is continued.

In the foregoing embodiment, two controls, namely, the increase control to change a rotating state of the pump motor 10 in a direction to increase a motor rotating speed, and the decrease control to change a rotating state of the pump motor 10 in a direction to decrease a motor rotating speed , to change, performed. However, both controls may be the increase control, or both controls may be the decrease control. When the increase control is performed as both controls, a content of one increase control and a content of the other increase control are made different. Specifically, one boost control may be control to start motor energization, and the other boost control may be control to further increase a motor rotation speed during motor energization. Even when configured as before, comprehensive diagnosis can be performed by collating a preliminary diagnosis result during one boost control and a preliminary diagnosis result during the other boost control. Therefore, an accuracy of a diagnosis can also be improved.

In the foregoing embodiment, preliminary diagnosis is performed twice when motor energization is started and stopped. It should be noted that by performing preliminary diagnosis three or more times and collating the respective preliminary diagnosis results, comprehensive diagnosis can be performed. Which diagnostic result is finally adopted is determined here by a majority rule from a plurality of preliminary diagnostic results. When configured as before, accuracy of diagnosis can be further improved.

In the foregoing embodiment, when a concentration of urea water is diagnosed, two levels of concentration, that is, the reference concentration and a high concentration, are diagnosed. However, three or more levels of concentration can be diagnosed. As an example, when diagnosing three levels of concentration, whether urea water has a concentration lower than the reference concentration, whether urea water has the reference concentration, and whether urea water has a concentration higher than the reference concentration can be diagnosed. As in 3 1, herein, at a concentration lower than the reference concentration (32.5%), a viscosity slightly decreases, and as a viscosity becomes lower, a rotation behavior of the pump motor 10 and a pressure behavior in the pipe 9 change from one Behavior at reference concentration. The rotation start delay time becomes even shorter than that in the reference concentration, for example. By finding such a difference in the rotating behavior and the pushing behavior, a concentration lower than the reference concentration can be determined.

Diagnosis when motor excitation is started alone can be performed by omitting diagnosis when motor excitation is stopped to adopt the determination result when motor excitation is started as a final determination result. That means in 5 can by omitting S6 to S8, a diagnosis result can be directly adopted at S5 as a final diagnosis result. If configured as before, diagnosis may be easier.

Conversely, diagnosis when motor energization is stopped alone can be performed by omitting diagnosis when motor energization is started to adopt the determination result when motor energization is stopped as a final determination result. That means in 5 For example, by omitting S5 and S8, a diagnosis result at S7 can be adopted directly as a final diagnosis result.

As described, a diagnostic device of the present disclosure is applied to a urea water supply system. The urea water supply system comprises the tank 6 in which urea water is stored, the pump 8 that discharges urea water stored in the tank by drawing urea water, and the pipe 9 that discharges the urea water discharged from the pump leads to the injector. The diagnostic device includes an engine control unit that may be equivalent to S4, S6, a rotational behavior obtaining unit that may be equivalent to S11, S31, a pressure behavior obtaining unit that may be equivalent to S11, S31, and a diagnostic unit that may be equivalent to S12 to S20 , S32 to S40, S8. The motor control unit performs control to change the rotating state of the motor 10 of the pump. The turning behavior obtaining unit obtains the turning behavior of the engine while the control is being performed. The pressure behavior obtaining unit obtains the pressure behavior in the pipe while the control is being performed. The diagnosis unit diagnoses a concentration or a viscosity of urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior.

The inventor has the finding that a viscosity of urea water varies with a concentration of the urea water. The present disclosure has been accomplished from this knowledge, that is, when the control is performed to change the rotating state of the motor of the pump in response to a viscosity of urea water varying with a concentration of the urea water, the rotating behavior of the motor changes . Further, by observing the pressure behavior in the pipe in addition to the rotation behavior, not only a concentration or a viscosity of urea water but also an abnormality in the urea water supply system can be diagnosed. That is to say, the spin behavior and pressure behavior change to behavior reflecting concentration or viscosity of urea water, while spin behavior and pressure behavior change to behavior different from behavior reflecting concentration or viscosity of urea water at the occurrence of a system abnormality. In the present disclosure, the diagnosis unit diagnoses a concentration or a viscosity of urea water and a system abnormality based on the rotational behavior and the pressure behavior. A diagnosis can therefore be carried out without having to use a quality sensor.

It will be appreciated that although the acts of the embodiments of the present disclosure are described herein as comprising a specific sequence of steps, further alternative embodiments comprising various other sequences of these steps and/or additional steps not disclosed herein are within of the steps of the present disclosure are intended to be.

Although the present disclosure has been described with reference to preferred embodiments thereof, it should be understood that the disclosure is not limited to the preferred embodiments and construction. The present disclosure is intended to cover various modifications and equivalent arrangements. In addition, while the various combinations and configurations are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.

Claims (14)

Diagnostic apparatus for a urea water supply system, the urea water supply system comprising a tank (6) configured to store urea water, a pump (8) configured to draw urea water stored in the tank (6), and the urea water to discharge, and having a pipe (9) configured to lead the urea water discharged from the pump (8) to an injector (5), comprising: an engine control unit (S4, S6) configured is to perform motor control to change a rotation state of a motor (10) of the pump (8); a turning behavior obtaining unit (S11, S31) configured to obtain a turning behavior of the engine while the engine control is being performed; a printing behavior acquisition unit (S11, S31) configured to extract a printing behavior in to win the tube (9) while the engine control is performed; and a diagnosis unit (S12 to S20, S32 to S40, S8) configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior, wherein the engine control unit (S4, S6) is configured to perform the motor control more than once to change the motor to turning states different from each other, the turning behavior obtaining unit (S11, S31) is configured to obtain the turning behavior each time the motor control is performed the pressure behavior obtaining unit (S11, S31) is configured to obtain the pressure behavior each time the engine control is performed, and the diagnosis unit comprises: a preliminary diagnosis unit (S12 to S20, S32 to S40) configured , to perform a preliminary diagnosis each time the engine control is perc is conducted to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior obtained in the engine control performed at the same time; and a comprehensive diagnosis unit (S8) configured to calculate, by collating results of the preliminary diagnosis performed by the preliminary diagnosis unit (S12 to S20, S32 to S40), a concentration or a viscosity of the urea water and diagnosing an abnormality in the urea water supply system, and wherein the engine control unit (S4, S6) comprises: an increase control unit (S4) configured to perform an increase control to change the rotational state of the engine in one direction by a rotational speed of the engine to increase, to change; and a reduction control unit (S6) configured to perform reduction control to change the rotation state of the motor in a direction to reduce the rotation speed of the motor, the rotation behavior obtaining unit (S11, S31) comprising: an obtaining unit ( S11) a rotation-increasing behavior configured to obtain a rotation-increasing behavior that is a rotation behavior of the motor when the boost control is performed; and a rotation-reducing behavior obtaining unit (S31) configured to obtain a rotation-reducing behavior, which is a rotation behavior of the motor when the reduction control is performed, the pressure behavior obtaining unit (S11, S31) comprises: an obtaining unit (S 11) a pressure-increasing behavior configured to obtain a pressure-increasing behavior that is a pressure behavior in the tube (9) when the increase control is performed; and a pressure-decreasing behavior obtaining unit (S31) configured to obtain a pressure-decreasing behavior that is a pressure behavior in the tube (9) when the decreasing control is performed, the unit (S12 to S20, S32 to S40) a The preliminary diagnosis comprises: a first diagnosis unit (S12 to S20) configured to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotation-increasing behavior and the pressure-increasing behavior; and a second diagnosis unit (S32 to S40) configured to preliminarily diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotation-decreasing behavior and the pressure-decreasing behavior, and the unit (S8) comprises a diagnosis is configured to determine, based on a result of the preliminary diagnosis performed by the first diagnostic unit and a result of the preliminary diagnosis performed by the second diagnostic unit, a concentration or a viscosity of the urea water and an abnormality in the urea water supply system to diagnose. diagnostic device claim 1 , wherein the comprehensive diagnosis unit (S8) comprises an abnormality diagnosis unit (S52 to S55) configured to adopt an abnormality in the urea water supply system as a final diagnosis result when at least one of a plurality of results of the preliminary diagnosis made by the preliminary diagnosis unit (S12 to S20, S32 to S40) is performed is a diagnosis result indicating the abnormality in the urea water supply system. diagnostic device claim 1 or 2 , wherein the comprehensive diagnosis unit (S8) comprises a concentration diagnosis unit (S56 to S61) configured to determine a concentration or a viscosity of the urea water as to adopt a final diagnosis result only when all of a plurality of preliminary diagnosis results performed by the preliminary diagnosis unit (S12 to S20, S32 to S40) are diagnosis results indicating an equal concentration or an equal viscosity of the urea water specify. Diagnostic device according to one of Claims 1 until 3 , in which when the diagnosis unit (S17, S20, S37, S40, S52 to S55) diagnoses an abnormality in the urea water supply system, the diagnosis unit (S17, S20, S37, S40, S52 to S55) diagnoses whether the abnormality is a leak of the urea water from the pipe (9), freezing of the urea water, or an abnormality in the engine. Diagnostic device according to one of Claims 1 until 4 , in which when the diagnostic unit (S16, S19, S36, S39, S58, S60) diagnoses a concentration or a viscosity of the urea water, the diagnostic unit (S17, S20, S37, S40, S52 to S55) diagnoses whether the concentration or the viscosity is a reference concentration or a reference viscosity expected at the urea water supply system or higher than the reference concentration or the reference viscosity. Diagnostic apparatus for a urea water supply system, the urea water supply system comprising a tank (6) configured to store urea water, a pump (8) configured to draw urea water stored in the tank (6), and the urea water to discharge, and having a pipe (9) configured to lead the urea water discharged from the pump (8) to an injector (5), with: a motor control unit (S4, S6) configured to perform motor control to change a rotating state of a motor (10) of the pump (8); a turning behavior obtaining unit (S11, S31) configured to obtain a turning behavior of the engine while the engine control is being performed; a pressure behavior obtaining unit (S11, S31) configured to obtain a pressure behavior in the pipe (9) while the engine control is being performed; and a diagnosis unit (S12 to S20, S32 to S40, S8) configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotation behavior and the pressure behavior, wherein the rotation behavior obtaining unit (S11, S31 ) is configured to vary, as the rotation behavior, a delay time since motor control was started until a rotation speed of the motor starts to vary, and a rate of variation in rotation speed with respect to time in an operation while the rotation speed of the motor varies to win. Diagnostic device according to one of Claims 1 until 6 wherein the pressure behavior obtaining unit (S11, S31) is configured to obtain as the pressure behavior a rate of variation of a pressure in the pipe (9) with respect to time since engine control was started. Diagnostic apparatus for a urea water supply system, the urea water supply system comprising a tank (6) configured to store urea water, a pump (8) configured to draw urea water stored in the tank (6), and the urea water to discharge, and having a pipe (9) configured to lead the urea water discharged from the pump (8) to an injector (5), comprising: an engine control unit (S4, S6) configured is to perform motor control to change a rotation state of a motor (10) of the pump (8); a turning behavior obtaining unit (S11, S31) configured to obtain a turning behavior of the engine while the engine control is being performed; a pressure behavior obtaining unit (S11, S31) configured to obtain a pressure behavior in the pipe (9) while the engine control is being performed; and a diagnosis unit (S12 to S20, S32 to S40, S8) configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior, wherein the engine controller (S4, S6) comprises an increase control unit (S4) configured to perform an increase control to change the rotation state of the motor in a direction to increase a rotation speed of the motor, the rotation behavior obtaining unit (S11, S31) an obtaining unit (S11) a rotation-increasing behavior configured to include, as the rotation behavior, an increase start delay time since the increase control was started until the rotation speed of the motor starts increasing, and a rate of increase in rotation speed with respect to time in a rotation speed increasing operation of the engine e.g u obtain, the pressure behavior obtaining unit comprises a pressure-increasing behavior obtaining unit (S11) configured to operate as the pressure behavior to obtain a rate of increase of the pressure in the pipe (9) with respect to the time since the increase control was started, and the diagnosis unit (S17, S20, S37, S40, S52 to S55) an engine abnormality and freezing diagnosis unit (S20) configured to diagnose an abnormality in the engine or freezing of the urea water as an abnormality in the urea water supply system when the increase start delay time is longer than a threshold, when the rate of increase in rotational speed is lower than a threshold, and when the rate of increase in pressure is lower than a threshold. diagnostic device claim 8 , wherein the diagnosis unit (S17, S20, S37, S40, S52 to S55) further comprises a high concentration diagnosis unit (S19) configured to diagnose that a concentration or a viscosity of the urea water is higher than a reference concentration or a reference viscosity expected at the urea water supply system is when the increase start delay time is longer than the threshold, when the rate of increase in rotational speed is lower than the threshold, and when the rate of increase in pressure is higher than the threshold. diagnostic device claim 8 or 9 , wherein the diagnosis unit (S17, S20, S37, S40, S52 to S55) further comprises a pipe leak diagnosis unit (S17) configured to diagnose, as an abnormality in the urea water supply system, that the urea water leaks from the pipe (9th ) leaks when at least either the increase start delay time is shorter than the threshold, or the rate of increase in rotational speed is higher than the threshold, or when the rate of increase in pressure is lower than the threshold. Diagnostic device according to one of Claims 8 until 10 , wherein the diagnosis unit (S17, S20, S37, S40, S52 to S55) further comprises a reference concentration diagnosis unit (S16) configured to diagnose that a concentration or a viscosity of the urea water is a reference concentration or a reference viscosity that is at the urea water supply system is when at least either the increase start delay time is shorter than the threshold, or the rate of increase in rotational speed is higher than the threshold, or when the rate of increase in pressure is higher than the threshold. Diagnostic apparatus for a urea water supply system, the urea water supply system comprising a tank (6) configured to store urea water, a pump (8) configured to draw urea water stored in the tank (6), and the urea water to discharge, and having a pipe (9) configured to lead the urea water discharged from the pump (8) to an injector (5), comprising: an engine control unit (S4, S6) configured is to perform motor control to change a rotation state of a motor (10) of the pump (8); a turning behavior obtaining unit (S11, S31) configured to obtain a turning behavior of the engine while the engine control is being performed; a pressure behavior obtaining unit (S11, S31) configured to obtain a pressure behavior in the pipe (9) while the engine control is being performed; and a diagnosis unit (S12 to S20, S32 to S40, S8) configured to diagnose a concentration or a viscosity of the urea water and an abnormality in the urea water supply system based on the rotational behavior and the pressure behavior, wherein the engine control unit (S4, S6) includes a reduction control unit (S6) configured to perform reduction control to change the rotation state of the motor in a direction to reduce a rotation speed of the motor, the rotation behavior obtaining unit (S11, S31) an obtaining unit (S31) a rotation-reducing behavior configured to include, as the rotation behavior, a reduction start delay time since the reduction control was started until the rotation speed of the motor starts increasing, and a rate of reduction in rotation speed with respect to time in a decreasing operation of the D rotational speed of the motor, the pressure behavior obtaining unit comprises a pressure decreasing behavior obtaining unit (S31) configured to obtain as the pressure behavior a rate of decrease in the pressure in the pipe (9) with respect to the time since the decrease control was started , and the diagnosis unit (S17, S20, S37, S40, S52 to S55) comprises a pipe leak diagnosis unit (37, 40) configured to diagnose, as an abnormality in the urea water supply system, that the urea water leaks from the pipe (9th ) leaks, in a case where the decrease delay time longer than one is threshold, the rate of decrease in rotational speed is lower than a threshold and the rate of decrease in pressure is higher than a threshold, or in a case where at least one of the decrease start delay time is shorter than the threshold and the rate of decrease of the rotational speed is higher than the threshold, or the rate of decrease in pressure is higher than the threshold. diagnostic device claim 12 , wherein the diagnosis unit (S17, S20, S37, S40, S52 to S55) further comprises a high concentration diagnosis unit (S39) configured to diagnose that a concentration or a viscosity of the urea water is higher than a reference concentration or a reference viscosity expected at the urea water supply system is when the decrease start delay time is longer than the threshold, when the rate of decrease in rotational speed is lower than the threshold, and when the rate of decrease in pressure is lower than the threshold. diagnostic device claim 12 or 13 , wherein the diagnosis unit (S17, S20, S37, S40, S52 to 55) further comprises a reference concentration diagnosis unit (S36) configured to diagnose that a concentration or a viscosity of the urea water is a reference concentration or a reference viscosity that is at the urea water supply system is when at least either the decrease start delay time is shorter than the threshold, or the rate of decrease in rotational speed is higher than the threshold, or when the rate of decrease in pressure is lower than the threshold.

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