JP2013217233A - Method of diagnosing urea water heating valve and device for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of diagnosing an urea water heating valve and a device for the same, capable of accurately determining failure of the urea water heating valve.SOLUTION: In a method of diagnosing an urea water heating valve 30, which is for supplying engine cooling water to unfreeze urea water 14 frozen in an urea water tank 16 by the engine cooling water, existence or nonexistence of failure of the urea water heating valve 30 is diagnosed from changes with time of water temperature of the engine cooling water after opening operation of the urea water heating valve 30.

Description

  The present invention relates to a urea SCR system that injects urea water into an SCR that removes NOx in exhaust gas, and in particular, when engine urea water in a urea tank mounted on a vehicle is frozen, engine cooling water is introduced and defrosted. The present invention relates to a diagnostic method and apparatus for a urea water heating valve.

  An SCR (Selective Catalytic Reduction) system has been developed as an exhaust gas purification system for removing NOx in exhaust gas of a diesel engine.

  The urea SCR system connects the SCR to the exhaust pipe, injects urea water into the exhaust pipe upstream of the SCR, hydrolyzes the urea water with the heat of the exhaust gas, generates ammonia, and this ammonia is stored in the SCR. And NOx to react with NOx (Patent Document 1).

  The urea water having a concentration of 32.5% is usually stored in the urea tank and injected according to the NOx concentration in the exhaust gas. However, when the outside air temperature becomes -11 ° C. or less in the severe cold season, the urea water is It will freeze.

  In this urea SCR system, a thawing pipe is provided in the urea tank in order to thaw the urea water frozen in the severe cold season with the engine cooling water, and the thawing pipe is connected to the engine cooling water supply pipe. The urea water heating valve for flowing engine cooling water into the thawing pipe is connected to the cooling water supply pipe (Patent Documents 2 and 3). Since this heating valve causes malfunctions such as deterioration of urea water and deterioration of the heater performance in the passenger compartment at the time of failure, it is desired to detect this and alert the driver when the failure occurs. Moreover, since it is an exhaust gas-related part, the failure diagnosis of a heating valve is also required by law.

  As a failure diagnosis of the heating valve, it is judged whether or not the heating valve is operating based on a detection value of a temperature sensor provided in the urea tank, or a urea water supply module as proposed in Patent Document 2 Or the temperature rise of the coil that opens and closes the heating valve, as proposed in Japanese Patent Application Laid-Open No. H10-228707.

JP 2000-303826 A JP 2012-002062 A JP 2012-013060 A

  However, if the temperature sensor in the urea tank is used to diagnose the temperature rise in the urea water tank after the heating valve is opened, the urea water around the temperature sensor is frozen and the temperature of the urea water Since the rise of the valve is extremely gradual, it is difficult to determine whether the valve is opened as instructed or in a fixed state, and it takes a long time to complete the diagnosis.

  Further, if the determination is made based on the pressure of the supply module as in Patent Document 2, there is a problem that although the injection timing of the urea water can be determined, the failure of the heating valve cannot be diagnosed.

  Furthermore, in detecting the temperature rise of the coil of the heating valve of Patent Document 3, it is possible to detect the closed fixing state of the heating valve (a failure state in which cooling water does not flow even though the coil is energized). However, there is a problem that it is not possible to detect an open fixing state (a failure state in which cooling water always flows).

  Accordingly, an object of the present invention is to solve the above-described problems and provide a diagnostic method and apparatus for a urea water heating valve that can accurately determine the failure of the urea water heating valve.

  In order to achieve the above object, the invention according to claim 1 is a method for diagnosing a urea water heating valve for supplying engine cooling water in order to thaw the urea water frozen in the urea tank with the engine cooling water. A method for diagnosing a urea water heating valve, characterized by diagnosing the presence or absence of a failure of the urea water heating valve from a temporal change in the water temperature of engine cooling water after the opening operation of the water heating valve.

  According to the second aspect of the present invention, when the engine speed is within the specified range and the fuel injection amount is within the specified range, and the temperature of the engine cooling water rises while this state continues, the urea water heat 2. The diagnosis of the urea water heating valve according to claim 1, wherein when the engine cooling water after the opening operation is defrosted, the engine cooling water is defrosted by opening the cooling valve from the closed position to the open position, and diagnosing the temperature as normal. Is the method.

  According to a third aspect of the present invention, when the engine speed is within a specified range and the fuel injection amount is within a specified range, and the engine water temperature rises while this state continues, the urea water heating valve is The urea water heating valve diagnosis method according to claim 1, wherein the urea water is defrosted from the closed state to the open state, and the urea water is thawed by the engine cooling water, and the engine cooling water after the opening operation is judged to be abnormal when there is no temperature drop.

  The invention of claim 4 is the method for diagnosing the urea water heating valve according to any one of claims 1 to 3, wherein the detection of the water temperature of the engine cooling water is performed using a water temperature sensor provided in advance in the engine.

  The invention according to claim 5 detects the temperature of the engine cooling water in the diagnostic device for the urea water heating valve for supplying the engine cooling water in order to thaw the urea water frozen in the urea tank with the engine cooling water. A water temperature sensor, a heating valve control unit that opens and closes a urea water heating valve, and an engine operating region information and an engine cooling water temperature from the water temperature sensor are input, based on the operating region information and the water temperature A heating valve diagnostic control unit that outputs an instruction to open the urea water heating valve to the heating valve control unit and then diagnoses the presence or absence of failure of the urea water heating valve from a change in water temperature. It is a diagnostic device for a urea water heating valve.

  According to the present invention, when diagnosing the presence or absence of a failure of the urea water heating valve, it is possible to accurately diagnose the failure by determining whether or not the urea water heating valve is in an operating state from the change in the engine coolant water temperature over time. Exhibits an excellent effect.

It is a system figure showing one embodiment for diagnosing the urea water heating valve of the present invention. It is a figure which shows the flowchart of the failure diagnosis of the urea water heating valve of this invention. It is a figure which shows the time-dependent change of the water temperature of engine cooling water in this invention. It is the schematic of the urea SCR system in this invention.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  First, the outline of the urea SCR system in the present invention will be described with reference to FIG.

  In FIG. 4, an SCR device 12 is connected to an exhaust pipe 11 that exhausts exhaust gas from an engine 10 such as a diesel engine, and an injection nozzle 13 that injects urea water is provided upstream of the SCR device 12. An SCR system is configured. Although not shown in the figure, a turbocharger and a DPF (diesel particulate filter) are connected to the exhaust pipe 11 between the engine 10 and the SCR device 12.

  The SCR device 12 is filled with an SCR catalyst and an ammonia slip catalyst, and reacts ammonia generated by thermal decomposition of urea water with NOx in the exhaust gas to denitrate and adsorb excess ammonia.

  The urea water 14 is stored in the urea tank 16, and the urea water in the urea tank 16 is sucked up through the liquid supply line 18 in the supply module 17 composed of a pump, supplied to the injection nozzle 13, and injected. The urea water is returned from the supply module 17 to the urea tank 16 through the recovery line 19.

  The amount of urea water injected from the injection nozzle 13 is controlled by a DCU (Dosing Control Unit) 20. The DCU 20 is connected to an ECU (engine control unit) 21 and injects the engine based on the engine speed-load from the ECU 21 and the detected values of the exhaust temperature sensor 21 and the NOx sensor 22 provided on the upstream side of the exhaust pipe 11. The amount of urea water is determined, and based on this, the supply module 17 and the injection nozzle 13 are controlled.

  The urea tank 16 is provided with a urea sensor 23 for detecting the concentration, water level, and temperature of the urea water 14, and the detected values (concentration, water level, temperature) of the urea sensor 23 are input to the DCU 20 and based on the detected values. Then, the ECU 21 performs lighting of warning lights in the alarm device 24 provided in the passenger compartment, an alarm buzzer alarm, and a display of the urea water remaining amount meter.

  Next, the cooling water system of the engine 10 will be described.

  First, engine cooling water circulates through a cooling circulation path 26 in which a radiator (not shown), a pump 25, and a jacket formed in a cylinder block and a cylinder head in the engine 10 are sequentially connected, and is cooled by the radiator. The engine 10 is cooled through the jacket in the engine 10, cooled again with a radiator, sucked into the pump 25, and circulated.

  Although not shown in the drawing, a bypass line that bypasses the radiator and returns to the suction side of the pump 25 is connected to the cooling circuit 26, and a thermostat valve is provided in the bypass line, depending on the temperature of the engine cooling water The thermostat valve is opened to control the bypass amount. Further, the engine cooling water can be supplied and circulated also to the EGR cooler (not shown).

  A cooling water supply pipe 27 for supplying engine cooling water to the injection nozzle 13, the urea tank 16, and the supply module 17 is connected to the cooling circulation path 26. The cooling water supply pipe 27 is branched into two, and one cooling water supply pipe 27a is connected with a urea water heating valve 30 and a cooling water supply pipe 27a downstream of the urea water heating valve 30. The U-shaped thawing pipe 31 is inserted into the urea tank 16, the cooling water supply pipe 27 a on the downstream side of the thawing pipe 31 is connected to the supply module 17, and the engine from the supply module 17 is connected. The cooling water is returned to the suction side of the pump 25 through the cooling water return pipe 28a.

  The other branched cooling water supply pipe 27b is supplied to the injection nozzle 13 to cool the injection nozzle 13 with the engine cooling water, and the cooled engine cooling water is cooled by the cooling water return pipe 28b. It merges with the engine cooling water in the water return pipe 28 a and returns to the suction side of the pump 25 through the cooling water return pipe 28.

  The cooling of the injection nozzle 13 with the engine cooling water is to prevent the urea water in the injection nozzle 13 from being heated to high temperature by the exhaust gas because the injection nozzle 13 faces the exhaust pipe 11 and is exposed to a high temperature. It is intended to cool down.

  On the other hand, the supply of engine cooling water to the thawing pipe 31 of the urea tank 16 is detected by the DCU 20 when the urea water 14 in the urea tank 16 freezes in the severe cold season, and the urea water heating valve 30 is turned on. The engine cooling water is supplied to the thawing pipe 31 through the cooling water supply pipe 27a, and the frozen urea water is heated with the engine cooling water to be thawed.

  At this time, according to the present invention, the diagnosis of whether the urea water heating valve 30 is properly opened or closed is performed based on the temperature of the engine cooling water (hereinafter referred to as water temperature).

  A diagnostic control system for the urea water heating valve 30 will be described with reference to FIG.

  In FIG. 1, the control unit 40 collectively shows the functions of the DCU 20 and the ECU 21 described in FIG. 3, and the cooling water system for supplying the engine cooling water of the engine 10 to the thawing pipe 31 of the urea tank 16 is as follows. The supply system path to the injection nozzle 13 and the supply module 17 is omitted.

  The control unit 40 includes an information unit 41 such as an accelerator pedal position, a fuel injection amount calculation unit 42, a heating valve diagnosis permission condition determination unit 43, a heating valve failure diagnosis control unit 44, and a heating valve control unit 45.

  The engine 10 is provided with an engine rotation sensor 33 that detects the number of revolutions of the engine 10 and a water temperature sensor 34 that detects the temperature of engine cooling water. The engine speed of the engine rotation sensor 33 is input to the heating valve diagnosis permission condition determination unit 43, and the water temperature of the water temperature sensor 34 is input to the heating valve failure diagnosis control unit 44, and is detected by the urea sensor 23 of the urea tank 16. The detected urea water temperature and water level are input to the heating valve controller 45.

  Next, control of the heating valve 30 of the control unit 40 and failure diagnosis thereof will be described.

  First, information such as the accelerator pedal position from the information unit 41 is input to the fuel injection amount calculation unit 42. Based on this information, the fuel injection amount calculation unit 42 determines the fuel injection amount, and the engine 10 is determined based on the determined value. To drive. This fuel injection amount is input to the heating valve diagnosis permission condition determination unit 43. The heating valve diagnosis permission condition determination unit 43 grasps the operation region information from the fuel injection amount and the engine speed, and outputs this to the heating valve failure diagnosis control unit 44.

  The heating valve failure diagnosis control unit 44 freezes the urea water 14 in the urea tank 16 based on the heating valve control information (ON / OFF information) input from the heating valve control unit 45 and the urea water temperature. If the engine is not frozen, the heating valve 30 is kept closed. If it is determined that the engine is frozen, the engine coolant temperature from the water temperature sensor 34 and the heating valve diagnosis permission condition determination unit 43. When the heating valve 30 is opened based on the operation area information from 43, and when it is determined that the temperature of the engine cooling water has risen to a temperature sufficient to thaw the frozen urea water, The heating valve 30 is opened from the closed state via the control unit 45.

  As a result, the engine cooling water is supplied from the cooling water supply pipe 27a through the heating valve 30 to the thawing pipe 31 in the urea tank 16, and is returned from the thawing pipe 31 to the pump 25 through the cooling water return pipe 28a. Circulate.

  When the engine cooling water is supplied to the thawing pipe 31 in this way, the water temperature of the cooling water after the circulation is lower than the water temperature before the circulation. The heating valve failure diagnosis control unit 44 monitors the presence or absence of the lowering (lowering). If there is no lowering, the heating valve 30 is faulty. If there is a lowering, the heating valve 30 is normal. Judge.

  Thereafter, when the urea water 14 in the urea tank 16 is thawed and the temperature of the urea water 14 rises, the heating valve failure diagnosis control unit 44 performs the heating valve 30 based on the temperature detection value of the urea sensor 23. To close the fault diagnosis.

  By determining the failure of the heating valve 30 using the engine coolant temperature, the failure diagnosis of the heating valve 30 can be performed accurately. At this time, the temperature of the engine cooling water changes over time through the cooling circulation path 26 of the engine 10, but the temperature of the engine cooling water when thawing is sufficiently low, and the operation of the engine 10 Initially, since the water temperature rises at a constant rate of rise, opening the heating valve 30 will surely cause a change in the water temperature, so the accuracy of the detection value of the water temperature sensor 34 provided in advance in the engine 10 is high. Can judge well.

  Although the cooling water circulation amount of the pump 25 varies depending on the vehicle and the engine speed, it is normally 100 to 400 L / min, and the capacity of the urea tank 16 is 5 to 15% of the volume (100 to 500 L) of the fuel tank. The amount of engine cooling water that is set and flows to the thawing pipe 31 is made to flow at a constant distribution ratio according to the capacity of the urea tank 16 with respect to the total circulation amount of the engine cooling water, and the urea remaining in the urea tank 16 Since the amount of water can also be grasped by the urea sensor 23, the amount of heat for thawing the urea water can be calculated. Therefore, when the engine coolant having a predetermined water temperature is flowed at a predetermined flow rate, the temperature decrease required for thawing can be easily obtained.

  Next, a flowchart of failure diagnosis of the heating valve 30 by the control unit 40 will be described with reference to FIG.

  When diagnosis is started in step S1, it is determined in step S2 whether the engine speed is within the specified range. If the engine speed is in the specified range in step S2 (Yes), then In step S3, it is determined whether or not the fuel injection amount is within the specified value. If it is within the specified value (Yes), whether or not the state within the specified value in steps S3 and S4 is continued in step S4. If it is determined that the heating valve is in the closed state in step S5, the closed valve is opened. Next, in step S6, it is determined whether or not there is a decrease in the engine coolant temperature. If there is a decrease in the water temperature (Yes), it is determined in step S7 that the heating valve is normal, and the decrease in the water temperature does not occur. If not (No), it is determined in step S8 that the heating valve is abnormal. If the determination in each of steps S2 to S5 is No, the diagnosis is performed again after returning to the start of step S1.

  As described above, if the engine speed is within the specified range in the determination in step S2, then it is determined in step S3 whether the fuel injection amount is within the specified value. The engine cooling water temperature has been found to have reached a temperature within the set range, and it is confirmed in step S4 that the water temperature is stable by determining whether or not this state continues. After that, the normality and the abnormality can be accurately determined by opening the heating valve from the closed state and determining the subsequent water temperature change.

  FIG. 3 shows the change over time in the engine coolant temperature at the time of failure diagnosis of the heating valve.

  In FIG. 3, when the engine is started, the temperature of the engine cooling water rises as shown by a solid line. For example, when the heating valve is opened when it rises to about 74 ° C., the frozen urea water is thawed. Since the water temperature decreases to nearly 70 ° C., it can be seen that the heating valve is normally opened as the water temperature decreases, and that the urea water is thawed by the engine cooling water. As indicated by the dotted line, when the engine cooling water temperature continues to rise, it can be determined that the heating valve is abnormal because the urea water has not been thawed. When the heating valve is abnormal, the amount of heat required for thawing the frozen urea water is higher than the rising gradient of the temperature rise of the solid engine cooling water temperature after opening the heating valve. Even if the amount of remaining urea water is small and the temperature drop is slight, the difference between the solid line and the dotted line can be easily determined.

  In FIG. 3, the example in which the heating valve is opened when the temperature of the engine cooling water rises to about 74 ° C. has been described. However, the timing of opening the heating valve depends on the outside air temperature. Since the frozen state is different, the water temperature is appropriately set in the range of 50 ° C to 80 ° C.

  As described above, according to the present invention, since the failure diagnosis of the urea water heating valve can be performed based on the change in the coolant temperature of the engine cooling water, it is determined whether the heating valve has been opened from the closed state. It is possible to accurately judge that it is maintained.

DESCRIPTION OF SYMBOLS 10 Engine 14 Urea water 16 Urea tank 26 Cooling circulation path 27a Engine cooling water supply piping 30 Urea water heating valve 31 Thawing pipe 40 Control unit

Claims (5)

  In the diagnosis method of the urea water heating valve for supplying the engine cooling water to thaw the urea water frozen in the urea tank with the engine cooling water, the temperature of the engine cooling water after the opening operation of the urea water heating valve A method for diagnosing a urea water heating valve, characterized by diagnosing the presence or absence of a failure of the urea water heating valve from a change with time.   When the engine speed is within the specified range and the fuel injection amount is within the specified range, and the temperature of the engine cooling water rises while this state continues, the urea water heating valve is opened from the closed state. The method for diagnosing urea water heating valve according to claim 1, wherein the urea water is thawed by the engine cooling water, and the engine cooling water after the opening operation is diagnosed as normal when the temperature falls.   When the engine speed is within the specified range and the fuel injection amount is within the specified range, and the engine water temperature rises while this state continues, the urea water heating valve is opened from closed to cool the engine. The method for diagnosing a urea water heating valve according to claim 1, wherein the urea water heating valve is defrosted with water and is judged abnormal when there is no temperature drop in the engine coolant after the opening operation.   The urea water heating valve diagnosis method according to any one of claims 1 to 3, wherein the detection of the engine coolant temperature is performed using a water temperature sensor provided in advance in the engine. In the urea water heating valve diagnostic device for supplying engine cooling water to thaw the urea water frozen in the urea tank with the engine cooling water,
A water temperature sensor for detecting the temperature of the engine cooling water;
A heating valve controller for opening and closing the urea water heating valve;
The engine operating area information is input and the engine coolant temperature from the water temperature sensor is input. Based on the operating area information and the water temperature, an instruction to open the urea water heating valve is output to the heating valve controller. And a heating valve diagnosis control unit for diagnosing the presence or absence of failure of the urea water heating valve based on a change in the water temperature.