阅读说明：本技术 尿素箱温度传感器故障的诊断方法及系统 (Method and system for diagnosing faults of temperature sensor of urea box ) 是由 刘宏君 李�杰 张焕岩 张申祥 邝小明 张应兵 于 2021-08-11 设计创作，主要内容包括：本发明公开了一种尿素箱温度传感器故障的诊断方法及系统,所述方法包括：利用尿素箱温度传感器获取第一当前电压；利用尿素溶液温度传感器获取第二当前电压；温度传感器控制单元根据第一当前电压得到电路诊断结果,并以CAN报文的形式发送,根据第一当前电压得到温度超限诊断结果,并以CAN报文的形式发送；发动机控制单元接收并解析CAN报文形式的电路和温度超限诊断结果,并将解析结果报出,并根据第一当前电压和第二当前电压,得到温度合理性诊断结果。本发明的尿素箱温度传感器故障的诊断方法及系统,在尿素箱内增加一路尿素溶液传感器,通过尿素箱温度和尿素溶液温度对比,提升了尿素箱温度传感器信号合理性监测的准确性,减少故障误报警。(The invention discloses a method and a system for diagnosing faults of a temperature sensor of a urea box, wherein the method comprises the following steps: acquiring a first current voltage by using a urea box temperature sensor; acquiring a second current voltage by using a urea solution temperature sensor; the temperature sensor control unit obtains a circuit diagnosis result according to the first current voltage and sends the circuit diagnosis result in a CAN message form, and obtains a temperature overrun diagnosis result according to the first current voltage and sends the temperature overrun diagnosis result in a CAN message form; and the engine control unit receives and analyzes the circuit in the CAN message form and the temperature overrun diagnosis result, reports the analysis result and obtains a temperature rationality diagnosis result according to the first current voltage and the second current voltage. According to the method and the system for diagnosing the faults of the temperature sensor of the urea box, the urea solution sensor is additionally arranged in the urea box, and the accuracy of monitoring the reasonability of the signal of the temperature sensor of the urea box is improved and false fault alarms are reduced by comparing the temperature of the urea box with the temperature of the urea solution.)

1. A method for diagnosing faults of a temperature sensor of a urea box is characterized by comprising the following steps:

acquiring a first current voltage of a urea box temperature detection circuit by using a urea box temperature sensor;

acquiring a second current voltage of the urea solution temperature detection circuit by using the urea solution temperature sensor;

the temperature sensor control unit obtains a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, sends the circuit fault diagnosis result to the engine control unit in a CAN message mode, obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to the engine control unit in a CAN message mode;

and the engine control unit receives and analyzes the circuit fault diagnosis result and the temperature overrun fault diagnosis result in a CAN message form, reports the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

2. The method for diagnosing the fault of the urea box temperature sensor according to claim 1, wherein the temperature sensor control unit obtains a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sends the circuit fault diagnosis result to an engine control unit in a CAN message form, and specifically comprises:

obtaining a circuit fault diagnosis result of the urea box temperature sensor according to a comparison result between the first current voltage and a preset voltage fault threshold;

if the first current voltage is higher than the upper limit value of the fault voltage, determining that the urea box temperature detection circuit has an open-circuit fault, and sending a CAN message of the open-circuit fault or a power supply short-circuit fault to the engine control unit;

and if the first current voltage is lower than the lower limit value of the fault voltage, determining that the urea box temperature detection circuit has a short-circuit fault, and sending a CAN message of the short-circuit fault to the ground to the engine control unit.

3. The method for diagnosing the fault of the urea box temperature sensor according to claim 1, wherein the temperature sensor control unit obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to an engine control unit in a CAN message form, and specifically comprises:

when no circuit fault is detected, the temperature sensor control unit converts the first current voltage into a first current temperature physical value;

the temperature sensor control unit obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to a comparison result of the first current temperature physical value and a preset temperature fault threshold value;

and if the first current temperature physical value is larger than a preset temperature fault threshold value, determining that the temperature of the urea box temperature sensor exceeds the working temperature upper limit fault, and sending a CAN message of the zero drift of the sensor or the overtemperature of the urea solution temperature to the engine control unit.

4. The method for diagnosing the fault of the temperature sensor of the urea tank according to claim 3, wherein the engine control unit receives and analyzes the circuit fault diagnosis result and the temperature overrun fault diagnosis result in a CAN message form, reports the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage, and specifically comprises:

the engine control unit receives and analyzes the circuit fault diagnosis result in the CAN message form and reports the analyzed circuit fault diagnosis result;

the engine control unit receives and analyzes the temperature overrun fault diagnosis result in a CAN message form, and reports the analyzed temperature overrun fault diagnosis result;

and the engine control unit obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

5. The method for diagnosing the fault of the temperature sensor of the urea box according to claim 4, wherein the engine control unit obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage, and specifically comprises the following steps:

the temperature sensor control unit converts the second current voltage into a second current temperature physical value;

the temperature sensor control unit sends the first current temperature physical value and the second current temperature physical value to the engine control unit in a CAN message mode;

and the engine control unit obtains a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

6. The method for diagnosing the fault of the temperature sensor of the urea box according to the claim 5, wherein the engine control unit obtains a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value, and specifically comprises the following steps:

the engine control unit receives and analyzes the first current temperature physical value in the CAN message form to obtain the temperature of the urea box, and receives and analyzes the second current temperature physical value to obtain the temperature of the urea solution;

the engine control unit obtains a temperature signal rationality diagnosis result according to the difference value between the temperature of the urea box and the temperature of the urea solution;

and if the difference value between the temperature of the urea box and the temperature of the urea solution exceeds a set threshold range, the engine control unit determines that the temperature signal unreasonable fault exists in the temperature sensor of the urea box and reports the temperature signal incredible fault.

7. The method for diagnosing faults of the temperature sensor of the urea box according to claim 5, wherein before the engine control unit obtains the temperature signal rationality diagnosis result according to the first current voltage and the second current voltage before the engine control unit obtains the temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value, the obtaining of the temperature signal rationality diagnosis result by the engine control unit further comprises:

and judging whether the rationality fault diagnosis enabling condition of the temperature signal is met, and executing the step of determining the rationality diagnosis result of the temperature signal under the condition that the rationality fault diagnosis enabling condition is met.

8. The method for diagnosing the fault of the urea tank temperature sensor according to claim 7, wherein the judging whether the rationality fault diagnosis enabling condition is satisfied specifically includes:

determining that a temperature signal rationality fault diagnosis enabling condition is satisfied when the following conditions are simultaneously satisfied:

powering on the vehicle;

urea is not injected into the urea box in the fault diagnosis process;

the deviation of the maximum value from the minimum value among the ambient temperature, the engine cooling water temperature, and the upstream temperature of the selective reduction system is lower than the set threshold value.

9. A system for diagnosing a fault in a temperature sensor of a urea tank using the method of any one of claims 1 to 8, comprising:

the urea tank temperature sensor and the urea solution temperature sensor are arranged in the urea tank and connected with the temperature sensor control unit, the temperature sensor control unit is connected with the engine control unit through a CAN bus, wherein,

the urea box temperature sensor is used for acquiring a first current voltage of the urea box temperature detection circuit;

the urea box is used for storing urea solution;

the urea solution temperature sensor is used for acquiring a second current voltage of the urea solution temperature detection circuit;

the temperature sensor control unit is used for obtaining a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, sending the circuit fault diagnosis result to the engine control unit in a CAN message mode, obtaining a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sending the temperature overrun fault diagnosis result to the engine control unit in a CAN message mode;

the engine control unit is used for receiving and analyzing the circuit fault diagnosis result and the temperature overrun fault diagnosis result in the CAN message form, reporting the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtaining a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

10. The system for diagnosing faults of the urea box temperature sensor according to claim 9, wherein the temperature sensor control unit is further configured to obtain a circuit fault diagnosis result of the urea box temperature sensor according to a comparison result between the first current voltage and a preset voltage fault threshold; converting the first current voltage acquired by the urea box temperature sensor into a first temperature physical value; obtaining a temperature overrun fault diagnosis result of the urea box temperature sensor according to a comparison result of the first current temperature physical value and a preset temperature fault threshold value; converting the second current voltage acquired by the urea solution temperature sensor into a second temperature physical value; sending the first current temperature physical value and the second current temperature physical value to the engine control unit in a CAN message mode;

and the engine control unit is specifically used for obtaining and reporting a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

Technical Field

The invention relates to the technical field of temperature signal detection, in particular to a method and a system for diagnosing faults of a temperature sensor of a urea box.

Background

As automotive emissions regulations become more stringent, engine exhaust emission aftertreatment technology becomes more important, and Selective Catalytic Reduction (SCR) is an important technological route in engine aftertreatment control strategies. In SCR, urea aqueous solution is used as a reducing agent, ammonia gas is generated through hydrolysis at high temperature, and NOx is converted into nitrogen and oxygen under the action of a catalyst. Therefore, the temperature signal of the urea box is an extremely important index in the exhaust emission treatment process, especially in cold regions when the urea needs to be thawed in the cold start process of the vehicle. The faults of the urea box temperature sensor are mainly sensor open circuit, sensor short circuit, sensor working temperature overrun, unreasonable sensor signal and the like.

The traditional urea temperature sensor is directly connected with an Engine Control Unit (ECU) through a hard wire, then the electric signal of the temperature sensor is used for diagnosing the circuit fault of the sensor, and the reasonability of the temperature signal is diagnosed by comparing the measured temperature of the urea box temperature sensor with the ambient temperature. The fault diagnosis of the traditional urea temperature sensor has the following defects: on the one hand, the urea box temperature sensor is installed in the urea box, and in cold regions, the deviation ratio of the temperature in the urea box and the ambient temperature is large, the temperature comparability of the temperature in the urea box and the ambient temperature is not strong, the error reporting fault is easy to occur, and the control of tail gas emission is not facilitated. On the other hand, the traditional urea temperature sensor is connected with an Engine Control Unit (ECU) through a hard wire, along with the implementation of national emission, electronic control components are more and more, the ECU is not enough in pin joint, and one temperature sensor cannot be additionally installed in the urea box for transverse comparison, so that the diagnosis accuracy of the urea box temperature sensor is improved.

Therefore, a method and a system for diagnosing the fault of the temperature sensor of the urea box are needed.

Disclosure of Invention

The invention aims to provide a method and a system for diagnosing faults of a temperature sensor of a urea box, which are used for solving the problems in the prior art, realizing dynamic monitoring of urea temperature and ensuring the accuracy of temperature control of the urea box.

The invention provides a method for diagnosing faults of a temperature sensor of a urea box, which comprises the following steps:

acquiring a first current voltage of a urea box temperature detection circuit by using a urea box temperature sensor;

acquiring a second current voltage of the urea solution temperature detection circuit by using the urea solution temperature sensor;

the temperature sensor control unit obtains a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, sends the circuit fault diagnosis result to the engine control unit in a CAN message mode, obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to the engine control unit in a CAN message mode;

and the engine control unit receives and analyzes the circuit fault diagnosis result and the temperature overrun fault diagnosis result in a CAN message form, reports the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

The method for diagnosing a fault of a urea tank temperature sensor as described above, wherein preferably, the temperature sensor control unit obtains a circuit fault diagnosis result of the urea tank temperature sensor according to the first current voltage, and sends the circuit fault diagnosis result to the engine control unit in a CAN message, specifically including:

obtaining a circuit fault diagnosis result of the urea box temperature sensor according to a comparison result between the first current voltage and a preset voltage fault threshold;

if the first current voltage is higher than the upper limit value of the fault voltage, determining that the urea box temperature detection circuit has an open-circuit fault, and sending a CAN message of the open-circuit fault or a power supply short-circuit fault to the engine control unit;

and if the first current voltage is lower than the lower limit value of the fault voltage, determining that the urea box temperature detection circuit has a short-circuit fault, and sending a CAN message of the short-circuit fault to the ground to the engine control unit.

The method for diagnosing the fault of the urea tank temperature sensor, in which preferably, the temperature sensor control unit obtains a temperature overrun fault diagnosis result of the urea tank temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to the engine control unit in the form of a CAN message, specifically includes:

when no circuit fault is detected, the temperature sensor control unit converts the first current voltage into a first current temperature physical value;

the temperature sensor control unit obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to a comparison result of the first current temperature physical value and a preset temperature fault threshold value;

and if the first current temperature physical value is larger than a preset temperature fault threshold value, determining that the temperature of the urea box temperature sensor exceeds the working temperature upper limit fault, and sending a CAN message of the zero drift of the sensor or the overtemperature of the urea solution temperature to the engine control unit.

The method for diagnosing a fault of a temperature sensor of a urea tank as described above, wherein preferably, the engine control unit receives and analyzes the circuit fault diagnosis result and the temperature overrun fault diagnosis result in the form of a CAN message, reports the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage, and specifically includes:

the engine control unit receives and analyzes the circuit fault diagnosis result in the CAN message form and reports the analyzed circuit fault diagnosis result;

the engine control unit receives and analyzes the temperature overrun fault diagnosis result in a CAN message form, and reports the analyzed temperature overrun fault diagnosis result;

and the engine control unit obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

The method for diagnosing a fault of a temperature sensor of a urea tank as described above, wherein preferably, the engine control unit obtains a result of diagnosing rationality of the temperature signal according to the first current voltage and the second current voltage, and specifically includes:

the temperature sensor control unit converts the second current voltage into a second current temperature physical value;

the temperature sensor control unit sends the first current temperature physical value and the second current temperature physical value to the engine control unit in a CAN message mode;

and the engine control unit obtains a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

The method for diagnosing a fault of a temperature sensor of a urea tank as described above, wherein preferably, the engine control unit obtains a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value, and specifically includes:

the engine control unit receives and analyzes the first current temperature physical value in the CAN message form to obtain the temperature of the urea box, and receives and analyzes the second current temperature physical value to obtain the temperature of the urea solution;

the engine control unit obtains a temperature signal rationality diagnosis result according to the difference value between the temperature of the urea box and the temperature of the urea solution;

and if the difference value between the temperature of the urea box and the temperature of the urea solution exceeds a set threshold range, the engine control unit determines that the temperature signal unreasonable fault exists in the temperature sensor of the urea box and reports the temperature signal incredible fault.

In the method for diagnosing a fault of a temperature sensor of a urea tank as described above, it is preferable that before the engine control unit obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage before the engine control unit obtains the temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value, the engine control unit further includes:

and judging whether the rationality fault diagnosis enabling condition of the temperature signal is met, and executing the step of determining the rationality diagnosis result of the temperature signal under the condition that the rationality fault diagnosis enabling condition is met.

The method for diagnosing a fault of a temperature sensor of a urea tank as described above, wherein preferably, the determining whether the rationality fault diagnosis enabling condition is satisfied specifically includes:

determining that a temperature signal rationality fault diagnosis enabling condition is satisfied when the following conditions are simultaneously satisfied:

powering on the vehicle;

urea is not injected into the urea box in the fault diagnosis process;

the deviation of the maximum value from the minimum value among the ambient temperature, the engine cooling water temperature, and the upstream temperature of the selective reduction system is lower than the set threshold value.

The invention also provides a system for diagnosing the fault of the temperature sensor of the urea box by adopting the method, which comprises the following steps:

the urea tank temperature sensor and the urea solution temperature sensor are arranged in the urea tank and connected with the temperature sensor control unit, the temperature sensor control unit is connected with the engine control unit through a CAN bus, wherein,

the urea box temperature sensor is used for acquiring a first current voltage of the urea box temperature detection circuit;

the urea box is used for storing urea solution;

the urea solution temperature sensor is used for acquiring a second current voltage of the urea solution temperature detection circuit;

the temperature sensor control unit is used for obtaining a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, sending the circuit fault diagnosis result to the engine control unit in a CAN message mode, obtaining a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sending the temperature overrun fault diagnosis result to the engine control unit in a CAN message mode;

the engine control unit is used for receiving and analyzing the circuit fault diagnosis result and the temperature overrun fault diagnosis result in the CAN message form, reporting the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtaining a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

The system for diagnosing the fault of the urea box temperature sensor is characterized in that the temperature sensor control unit is further configured to obtain a circuit fault diagnosis result of the urea box temperature sensor according to a comparison result between the first current voltage and a preset voltage fault threshold; converting the first current voltage acquired by the urea box temperature sensor into a first temperature physical value; obtaining a temperature overrun fault diagnosis result of the urea box temperature sensor according to a comparison result of the first current temperature physical value and a preset temperature fault threshold value; converting the second current voltage acquired by the urea solution temperature sensor into a second temperature physical value; sending the first current temperature physical value and the second current temperature physical value to the engine control unit in a CAN message mode;

and the engine control unit is specifically used for obtaining and reporting a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

The invention provides a method and a system for diagnosing faults of a temperature sensor of a urea box.A urea solution sensor is additionally arranged in the urea box, and the accuracy of monitoring the rationality of signals of the temperature sensor of the urea box is improved and false fault alarms are reduced by comparing the temperature of the urea box with the temperature of the urea solution; the urea temperature sensor circuit fault and the working temperature overrun fault diagnosis are carried out in the temperature sensor control unit, and the temperature signal rationality diagnosis is only carried out in the engine control unit, so that the load of an engine control unit can be reduced; two paths of temperature sensors are integrated to a temperature sensor control unit, CAN network communication is adopted, feet of an engine control unit are not occupied, and more information CAN be transmitted to the engine control unit.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings, in which:

FIG. 1 is a flow chart of an embodiment of a method of diagnosing a fault in a urea tank temperature sensor provided by the present invention;

FIG. 2 is a flow diagram of an embodiment of circuit fault diagnosis and over temperature fault diagnosis provided by the present invention;

FIG. 3 is a flow chart of an embodiment of a temperature signal rationality diagnostic provided by the present invention;

FIG. 4 is a flowchart of an embodiment of a system for diagnosing a fault in a urea tank temperature sensor provided by the present invention.

Detailed Description

Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is in no way intended to limit the disclosure, its application, or uses. The present disclosure may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that: the relative arrangement of parts and steps, the composition of materials, numerical expressions and numerical values set forth in these embodiments are to be construed as merely illustrative, and not as limitative, unless specifically stated otherwise.

As used in this disclosure, "first", "second": and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element preceding the word covers the element listed after the word, and does not exclude the possibility that other elements are also covered. "upper", "lower", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

In the present disclosure, when a specific component is described as being located between a first component and a second component, there may or may not be intervening components between the specific component and the first component or the second component. When it is described that a specific component is connected to other components, the specific component may be directly connected to the other components without having an intervening component, or may be directly connected to the other components without having an intervening component.

All terms (including technical or scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs unless specifically defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate.

As shown in fig. 1, in an actual implementation process, the method for diagnosing a fault of a urea tank temperature sensor provided in this embodiment specifically includes the following steps:

and step S1, acquiring a first current voltage of the urea box temperature detection circuit by using the urea box temperature sensor.

After the vehicle is powered on, a first current voltage is obtained through a urea box temperature sensor.

And step S2, acquiring a second current voltage of the urea solution temperature detection circuit by using the urea solution temperature sensor.

And step S3, the temperature sensor control unit obtains a circuit fault diagnosis result of the urea box temperature sensor according to the first current voltage, sends the circuit fault diagnosis result to the engine control unit in a CAN message mode, obtains a temperature overrun fault diagnosis result of the urea box temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to the engine control unit in a CAN message mode.

The urea box temperature sensor and the urea solution temperature sensor are arranged in the urea box and connected with the temperature sensor control unit.

In an embodiment of the present invention, as shown in fig. 2, the obtaining, by the temperature sensor control unit, a circuit fault diagnosis result of the urea tank temperature sensor according to the first current voltage, and sending the circuit fault diagnosis result to the engine control unit in the form of a CAN message by the temperature sensor control unit may specifically include:

and A1, obtaining a circuit fault diagnosis result of the urea box temperature sensor according to the comparison result between the first current voltage and a preset voltage fault threshold value.

Step A2, if the first current voltage is higher than the upper limit value of the fault voltage, determining that the urea box temperature detection circuit has an open-circuit fault, and sending a CAN message of the open-circuit fault or the power supply short-circuit fault to the engine control unit.

Step A3, if the first current voltage is lower than the lower limit value of the fault voltage, determining that the urea box temperature detection circuit has a short-circuit fault, and sending a CAN message of the short-circuit fault to the ground to the engine control unit.

Further, in an embodiment of the present invention, as shown in fig. 2, the temperature sensor control unit obtains a temperature overrun fault diagnosis result of the urea tank temperature sensor according to the first current voltage, and sends the temperature overrun fault diagnosis result to the engine control unit in a form of a CAN message, which may specifically include:

step B1, when no circuit fault is detected, the temperature sensor control unit converts the first present voltage into a first present temperature physical value.

And step B2, the temperature sensor control unit obtains the temperature overrun fault diagnosis result of the urea box temperature sensor according to the comparison result of the first current temperature physical value and a preset temperature fault threshold value.

And step B3, if the first current temperature physical value is larger than a preset temperature fault threshold value, determining that the temperature of the urea box temperature sensor exceeds the upper limit of the working temperature, and sending a CAN message of zero drift of the sensor or overtemperature of the urea solution temperature to the engine control unit.

And step S4, the engine control unit receives and analyzes the circuit fault diagnosis result and the temperature overrun fault diagnosis result in the form of a CAN message, reports the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

The temperature sensor control unit and the engine control unit are connected through a CAN bus. In an embodiment of the method for diagnosing a fault of a temperature sensor of a urea tank according to the present invention, as shown in fig. 3, the step S4 may specifically include:

and step S41, the engine control unit receives and analyzes the circuit fault diagnosis result in the CAN message form, and reports the analyzed circuit fault diagnosis result.

And step S42, the engine control unit receives and analyzes the temperature overrun fault diagnosis result in the form of a CAN message, and reports the analyzed temperature overrun fault diagnosis result.

And step S43, the engine control unit obtains a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

In an embodiment of the method for diagnosing a fault of a temperature sensor of a urea tank according to the present invention, the step S43 may specifically include:

step S431, the temperature sensor control unit converts the second present voltage into a second present temperature physical value.

Step S432, the temperature sensor control unit sends the first current temperature physical value and the second current temperature physical value to the engine control unit in the form of a CAN message.

And S433, the engine control unit obtains a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

Specifically, in an embodiment of the method for diagnosing a fault of a temperature sensor of a urea tank according to the present invention, the step S433 may specifically include:

step S4331, the engine control unit receives and analyzes the first current temperature physical value in the form of the CAN message to obtain the temperature of the urea box, and receives and analyzes the second current temperature physical value to obtain the temperature of the urea solution.

And S4332, obtaining a temperature signal rationality diagnosis result by the engine control unit according to the difference value between the temperature of the urea box and the temperature of the urea solution.

And S4333, if the difference value between the temperature of the urea box and the temperature of the urea solution exceeds a set threshold range, determining that the temperature signal of the urea box temperature sensor has an unreasonable fault by the engine control unit, and reporting the temperature signal untrusty fault.

Further, as shown in fig. 3, before step S43, the obtaining, by the engine control unit, a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage further includes:

judging whether the rationality fault diagnosis enabling condition of the temperature signal is met, and executing the step S43 under the condition that the rationality fault diagnosis enabling condition is met; in the case where the rationality failure diagnosis enabling condition is not satisfied, the diagnosis process is ended. Specifically, it is determined that the temperature signal rationality failure diagnosis enabling condition is satisfied when the following conditions are simultaneously satisfied:

(a) powering on the vehicle;

(b) urea is not injected into the urea box in the fault diagnosis process;

(c) the deviation of the maximum value from the minimum value among the ambient temperature, the engine cooling water temperature, and the upstream temperature of the selective reduction system is lower than the set threshold value.

Therefore, when circuit fault diagnosis is carried out, the temperature sensor control unit firstly realizes circuit fault diagnosis (including circuit open-circuit fault diagnosis and circuit short-circuit fault diagnosis) of the urea box temperature sensor through comparison of the sensor circuit voltage and a calibration threshold value, then sends a diagnosis result to the CAN bus in the form of a CAN message, and the engine control unit analyzes and reports the fault diagnosis result after receiving related message information. When the temperature overrun fault diagnosis is carried out, the temperature sensor control unit obtains a corresponding temperature physical value through monitoring voltage conversion of a sensor circuit, then the temperature overrun fault diagnosis is carried out through comparison of the physical value and a calibration threshold value, finally a diagnosis result is sent to a CAN bus in a CAN message mode, and the engine control unit analyzes and reports the fault diagnosis result after receiving related message information. When the rationality of the temperature signal is diagnosed, the temperature sensor control unit sends the physical temperature values acquired by the urea box temperature sensor and the urea solution temperature sensor to the CAN bus in the form of CAN messages, the engine control unit receives the relevant message information and analyzes the message information to obtain the temperatures of the urea box and the urea solution, and then the temperatures of the urea box and the urea solution are compared to diagnose the rationality of the temperature signal.

According to the method for diagnosing the faults of the temperature sensor of the urea box, provided by the embodiment of the invention, the urea solution sensor is additionally arranged in the urea box, and the accuracy of monitoring the signal reasonability of the temperature sensor of the urea box is improved and false fault alarms are reduced by comparing the temperature of the urea box with the temperature of the urea solution; the urea temperature sensor circuit fault and the working temperature overrun fault diagnosis are carried out in the temperature sensor control unit, and the temperature signal rationality diagnosis is only carried out in the engine control unit, so that the load of an engine control unit can be reduced; two paths of temperature sensors are integrated to a temperature sensor control unit, CAN network communication is adopted, feet of an engine control unit are not occupied, and more information CAN be transmitted to the engine control unit.

Accordingly, as shown in fig. 4, the present invention also provides a diagnosis of a fault of a temperature sensor of a urea tank, comprising:

a urea box temperature sensor 1, a urea box 2, a urea solution temperature sensor 3, a temperature Sensor Control Unit (SCU)4, and an Engine Control Unit (ECU)5, wherein the urea box temperature sensor 1 and the urea solution temperature sensor 3 are arranged in the urea box 2 and connected with the temperature sensor control unit 4, the temperature sensor control unit 4 and the engine control unit 5 are connected through a CAN bus, wherein,

the urea box temperature sensor 1 is used for acquiring a first current voltage of the urea box temperature detection circuit;

the urea box 2 is used for storing urea solution;

the urea solution temperature sensor 3 is used for acquiring a second current voltage of the urea solution temperature detection circuit;

the temperature sensor control unit 4 is configured to obtain a circuit fault diagnosis result of the urea tank temperature sensor according to the first current voltage, send the circuit fault diagnosis result to the engine control unit in the form of a CAN message, obtain a temperature overrun fault diagnosis result of the urea tank temperature sensor according to the first current voltage, and send the temperature overrun fault diagnosis result to the engine control unit 5 in the form of a CAN message;

the engine control unit 5 is used for receiving and analyzing the circuit fault diagnosis result and the temperature overrun fault diagnosis result in the form of a CAN message, reporting the analyzed circuit fault diagnosis result and the temperature overrun fault diagnosis result, and obtaining a temperature signal rationality diagnosis result according to the first current voltage and the second current voltage.

Wherein the urea tank temperature sensor 1 and the urea solution temperature sensor 3 are integrated in the same temperature sensor control unit 4. The temperature sensor control unit 4 performs information interaction with the engine control unit 5 through CAN communication. CAN message information interaction is realized through a vehicle controller local area network.

According to the invention, a temperature sensor (urea solution temperature sensor 3) is additionally arranged in a CAN communication mode, so that the problem of inaccurate signal rationality comparison of the urea box temperature sensor caused by insufficient pin splicing of an engine control unit is solved.

Further, the temperature sensor control unit 4 is further configured to obtain a circuit fault diagnosis result of the urea tank temperature sensor according to a comparison result between the first current voltage and a preset voltage fault threshold; converting the first current voltage acquired by the urea box temperature sensor into a first temperature physical value; obtaining a temperature overrun fault diagnosis result of the urea box temperature sensor according to a comparison result of the first current temperature physical value and a preset temperature fault threshold value; converting the second current voltage acquired by the urea solution temperature sensor into a second temperature physical value; sending the first current temperature physical value and the second current temperature physical value to the engine control unit 5 in the form of a CAN message;

the engine control unit 5 is specifically configured to obtain and report a temperature signal rationality diagnosis result according to the first current temperature physical value and the second current temperature physical value.

According to the urea box temperature sensor fault diagnosis system provided by the embodiment of the invention, the urea solution sensor is additionally arranged in the urea box, and the urea box temperature is compared with the urea solution temperature, so that the signal rationality monitoring accuracy of the urea box temperature sensor is improved, and false fault alarm is reduced; the urea temperature sensor circuit fault and the working temperature overrun fault diagnosis are carried out in the temperature sensor control unit, and the temperature signal rationality diagnosis is only carried out in the engine control unit, so that the load of an engine control unit can be reduced; two paths of temperature sensors are integrated to a temperature sensor control unit, CAN network communication is adopted, feet of an engine control unit are not occupied, and more information CAN be transmitted to the engine control unit.

Thus, various embodiments of the present disclosure have been described in detail. Some details that are well known in the art have not been described in order to avoid obscuring the concepts of the present disclosure. It will be fully apparent to those skilled in the art from the foregoing description how to practice the presently disclosed embodiments.

Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the foregoing examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. It will be understood by those skilled in the art that various changes may be made in the above embodiments or equivalents may be substituted for elements thereof without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.