Urea quality sensor false alarm prevention method based on SCR efficiency diagnosis

Abstract

The invention provides a urea quality sensor false alarm prevention method based on SCR efficiency diagnosis, and relates to the technical field of urea concentration false alarm prevention. S2, collecting SCR upstream and downstream nitrogen oxide concentrations through an ECU; s3, the SCR efficiency is calculated according to the following publication; sCR efficiency = 1-(downstream nitrogen oxide concentration / upstream nitrogen oxide concentration); after the SCR efficiency is obtained, the following two conditions are divided: a, when the SCR efficiency is also lower than the minimum limit value, the fault that the urea concentration is too low is reported; and b, when the SCR efficiency is not lower than the minimum limit value, the fault that the urea concentration is too low is not reported. The problem that the current urea concentration is easy to report mistakenly is solved, and the accuracy of reporting the urea quality fault is improved.

Description

Technical Field

[0001] This application relates to the field of urea concentration false alarm prevention, and more specifically, to a method for preventing false alarms of a urea quality sensor based on SCR efficiency diagnosis. Background Technology

[0002] SCR (Selective Catalytic Reduction) devices reduce nitrogen oxide (NOx) emissions from engine exhaust by injecting urea, which reacts with the exhaust gases.

[0003] For example, Chinese patent application CN201610769928.5 discloses a mechanical pump engine SCR device, control method, and control device. Urea is injected towards the direction of engine exhaust emissions to cause a reaction between the two, reducing nitrogen oxide (NOx) emissions in the exhaust.

[0004] Because purchasing urea incurs costs, regulations require urea quality diagnostics to prevent drivers from substituting urea with water to falsify the product.

[0005] Currently, urea quality diagnosis is achieved using ultrasonic sensors. Different concentrations of urea result in different frequencies of returned ultrasound waves, allowing the urea concentration to be calculated based on these frequencies. An alarm is triggered when the urea concentration received from the urea quality sensor by the engine control unit (ECU) is below a minimum limit.

[0006] However, in the process of implementing the technical solutions in the embodiments of this application, the inventors of this application discovered that the above-mentioned technology has at least the following technical problems:

[0007] Before leaving the factory, urea is added into the urea tank. During operation, the urea liquid in the tank is jolted, which can cause air bubbles to form near the urea quality sensor. This affects the ultrasonic return frequency, resulting in an incorrect calculation of the urea concentration. Consequently, even when the urea itself is of acceptable quality, a urea quality fault will still be reported. Summary of the Invention

[0008] To overcome the shortcomings of the existing methods, this application provides a method for preventing false alarms of urea quality sensors based on SCR efficiency diagnosis. This method can solve the problem of easy false alarms of urea concentration and improve the accuracy of urea quality fault reporting to a certain extent.

[0009] The technical solution adopted by the embodiments of this application to solve its technical problem is: a method for preventing false alarms of urea quality sensor based on SCR efficiency diagnosis.

[0010] Includes the following steps:

[0011] S1. When the urea concentration of the urea quality sensor is lower than the minimum limit;

[0012] S2. Collect nitrogen oxide concentrations upstream and downstream of the SCR via the ECU;

[0013] S3. Calculate the SCR efficiency using the following formula;

[0014] SCR efficiency = 1 - (downstream nitrogen oxide concentration / upstream nitrogen oxide concentration);

[0015] After obtaining the SCR efficiency, there are two cases:

[0016] a. When the SCR efficiency is also lower than the minimum limit mentioned above, a fault of low urea concentration will be reported;

[0017] b. When the SCR efficiency is not lower than the minimum limit mentioned above, a fault of low urea concentration will not be reported.

[0018] In one specific implementation, in step S1, if the urea concentration of the urea quality sensor is not lower than the minimum limit, then the urea concentration too low fault will not be reported directly.

[0019] In one specific implementation, the urea quality sensor is fixedly installed inside the urea tank of the SCR device to monitor the concentration of the urea solution inside the urea tank.

[0020] In one specific implementation, the upstream nitrogen oxide concentration of the SCR is measured by an upstream nitrogen oxide sensor of the SCR device, which is electrically connected to the ECU.

[0021] In one specific implementation, the downstream nitrogen oxide concentration of the SCR is measured by a downstream nitrogen oxide sensor of the SCR device, which is also electrically connected to the ECU.

[0022] The advantages of the embodiments of this application are:

[0023] When the urea quality sensor detects that the urea concentration is below the minimum limit, the ECU collects the nitrogen oxide concentrations upstream and downstream of the SCR and calculates the SCR efficiency using the formula: SCR efficiency = 1 - (downstream nitrogen oxide concentration / upstream nitrogen oxide concentration). When the SCR efficiency is also below the aforementioned minimum limit, a urea concentration too low fault is reported. This solves the problem of easy false alarms in urea concentration and improves the accuracy of urea quality fault reporting. Attached Figure Description

[0024] Figure 1 The flowchart illustrates the structure of the urea quality sensor false alarm prevention method based on SCR efficiency diagnosis provided in this application. Detailed Implementation

[0025] The technical solution in this application embodiment aims to address the problem of frequent false alarms regarding urea concentration. The overall approach is as follows:

[0026] Example:

[0027] Please see Figure 1 A method for preventing false alarms in a urea quality sensor based on SCR efficiency diagnosis includes the following steps:

[0028] S1. When the urea concentration of the urea quality sensor is below the minimum limit.

[0029] Among them, the urea sensor is a tissue sensor that can detect urea. It consists of plant tissue (such as soybean flour) solidified into a film, which is then coated onto an ammonia or carbon dioxide gas-sensitive electrode. The detection mechanism is that soybean flour contains urease, which can quickly catalyze the decomposition of urea. Its working principle is that the gas-sensitive electrode can measure the amount of ammonia and carbon dioxide released, thereby calculating the urea content.

[0030] In step S1, if the urea concentration of the urea quality sensor is not lower than the minimum limit, the urea concentration too low fault will not be reported directly.

[0031] The urea quality sensor is fixedly installed inside the urea tank of the SCR device to monitor the concentration of the urea solution in the tank.

[0032] To further illustrate this point, it should be noted that SCR devices typically consist mainly of a urea injection system and a urea injection control unit, as disclosed in application number CN201610769928.5.

[0033] Specifically, the urea injection system mainly includes a urea tank, a urea pump, and a urea nozzle. The urea nozzle is connected to the bottom of the urea tank through a pipe, and the urea pump is installed on the pipe to guide the urea liquid in the urea tank to the urea nozzle for spraying out to react with the engine exhaust gas.

[0034] Specifically, the urea injection control unit can control the injection quantity of the urea injection system based on exhaust temperature signal, speed signal, intake pressure signal, and intake temperature signal.

[0035] An exhaust pipe is provided between the external engine and the SCR device. The specific connection relationship is existing technology and will not be described in detail here.

[0036] S2. Collect the nitrogen oxide concentrations upstream and downstream of the SCR via the ECU.

[0037] Specifically, the upstream nitrogen oxide concentration of the SCR is measured by the upstream nitrogen oxide sensor of the SCR device, which is electrically connected to the ECU. Referring to Chinese Patent Publication No. CN112696251A, which discloses an SCR conversion efficiency recovery method, device, and vehicle, it mentions that the upstream nitrogen oxide concentration of the SCR is measured by the upstream nitrogen oxide sensor of the SCR device, and will not be repeated here. After the upstream nitrogen oxide sensor measures the upstream nitrogen oxide concentration information, it transmits this information to the A / D converter, which then transmits it to the ECU.

[0038] Specifically, the upstream nitrogen oxide sensor is installed on the exhaust pipe. The upstream nitrogen oxide sensor is used to detect the emission value of the exhaust gas that has not passed through the SCR device, so as to control the amount of urea injection through the ECU.

[0039] Specifically, the downstream nitrogen oxide concentration of the SCR is measured by the downstream nitrogen oxide sensor of the SCR device, which is also electrically connected to the ECU. Referring to the SCR conversion efficiency recovery method, device, and vehicle proposed in Chinese Patent Publication No. CN112696251A, it is mentioned that the downstream nitrogen oxide concentration of the SCR is measured by the downstream nitrogen oxide sensor of the SCR device, which will not be repeated here. After the downstream nitrogen oxide sensor measures the downstream nitrogen oxide concentration information, it transmits this information to the A / D converter, which then transmits it to the ECU.

[0040] Specifically, the upstream nitrogen oxide sensor is located on the exhaust pipe, while the downstream nitrogen oxide sensor is used to detect the emission values ​​of the exhaust gas passing through the SCR device.

[0041] S3. Calculate the SCR efficiency using the following formula.

[0042] SCR efficiency = 1 - (downstream nitrogen oxide concentration / upstream nitrogen oxide concentration).

[0043] After obtaining the SCR efficiency, there are two cases:

[0044] a. When the SCR efficiency is also lower than the minimum limit mentioned above, a fault of low urea concentration will be reported.

[0045] Specifically, when the SCR efficiency is also lower than the minimum limit mentioned above, the ECU controls the external alarm connected to it to report a urea concentration too low fault. This can avoid false alarms of urea quality faults caused by bubbles.

[0046] b. When the SCR efficiency is not lower than the minimum limit mentioned above, a fault of low urea concentration will not be reported.

[0047] When using:

[0048] First, the urea concentration is detected using a urea quality sensor. When the concentration is below the minimum limit, the concentration of nitrogen oxides upstream and downstream of the SCR is collected by the ECU, and the SCR efficiency is calculated using the formula: SCR efficiency = 1 - (downstream nitrogen oxide concentration / upstream nitrogen oxide concentration). When the SCR efficiency is also below the aforementioned minimum limit, a fault of low urea concentration is reported, thus solving the current problem of easy false alarms of urea concentration.

[0049] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preventing false alarms in a urea quality sensor based on SCR efficiency diagnosis, characterized in that, Includes the following steps: S1. When the urea concentration of the urea quality sensor is lower than the minimum limit; S2. Collect nitrogen oxide concentrations upstream and downstream of the SCR via the ECU; S3. Calculate the SCR efficiency using the following formula; SCR efficiency = 1 - (downstream nitrogen oxide concentration / upstream nitrogen oxide concentration); After obtaining the SCR efficiency, there are two cases: a. When the SCR efficiency is also lower than the minimum limit mentioned above, a fault of low urea concentration will be reported; b. When the SCR efficiency is not lower than the minimum limit mentioned above, a fault of low urea concentration will not be reported.

2. The method for preventing false alarms in a urea quality sensor based on SCR efficiency diagnosis as described in claim 1, characterized in that, In step S1, if the urea concentration of the urea quality sensor is not lower than the minimum limit, the urea concentration too low fault will not be reported directly.

3. The method for preventing false alarms in a urea quality sensor based on SCR efficiency diagnosis as described in claim 1, characterized in that, The urea quality sensor is fixedly installed inside the urea tank of the SCR device to monitor the concentration of urea solution in the urea tank.

4. The method for preventing false alarms of urea quality sensors based on SCR efficiency diagnosis as described in claim 1, characterized in that, The upstream nitrogen oxide concentration of the SCR is measured by an upstream nitrogen oxide sensor of the SCR device, which is electrically connected to the ECU.

5. The method for preventing false alarms of urea quality sensors based on SCR efficiency diagnosis as described in claim 1, characterized in that, The downstream nitrogen oxide concentration of the SCR is measured by a downstream nitrogen oxide sensor of the SCR device, which is also electrically connected to the ECU.

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