Method and device for controlling exhaust temperature of scr, and exhaust aftertreatment system

Abstract

The embodiment of the application discloses a kind of SCR exhaust temperature control method, device, exhaust gas aftertreatment system, engine and vehicle.The exhaust temperature control method includes: obtaining the DOC parameter, DPF parameter, SCR heating temperature threshold and SCR exhaust flow under current working condition;According to the DOC parameter and SCR heating temperature threshold, determine the DOC carrier temperature deviation, according to the DPF parameter and SCR heating temperature threshold, determine the DPF carrier temperature deviation;According to the DOC carrier temperature deviation, DPF carrier temperature deviation and SCR exhaust flow, determine the correction value of SCR heating temperature threshold;According to SCR heating temperature threshold and correction value, determine the SCR heating temperature correction threshold.The exhaust temperature control method provided in the embodiment of the application dynamically adjusts the temperature threshold whether SCR is heated according to the carrier (DOC, DPF) temperature upstream of SCR, to reduce the overshoot of SCR temperature control.

Description

Technical Field

[0001] This invention relates to the field of engine control technology, and in particular to an exhaust temperature control method, device, and exhaust aftertreatment system for an SCR. Background Technology

[0002] The technical challenge in developing China VI diesel engines lies in balancing fuel consumption and emissions. The nitrogen oxides (NOx) produced by this lean-burn method often require a reducing agent to convert them into nitrogen and water. Even with the aid of a catalytic converter, a temperature of 200℃~300℃ is still needed to facilitate the chemical reaction. From a fuel-saving perspective, the exhaust temperature of diesel engines under a wide range of low-load conditions is insufficient to support the operation of the catalytic converter. Therefore, it is necessary to increase the exhaust temperature at the expense of fuel consumption.

[0003] The common exhaust temperature management method is to sacrifice fuel consumption for heating when the SCR carrier temperature is insufficient, and not to heat when the temperature is sufficient. However, the problem is that the aftertreatment system has a large heat capacity. Using this method often causes a large temperature overshoot when switching between heating and non-heating, which affects the NOx conversion efficiency of the SCR and wastes fuel. Summary of the Invention

[0004] This invention provides an exhaust temperature control method, device, and exhaust gas aftertreatment system for an SCR. The exhaust temperature control method dynamically adjusts the temperature threshold for whether the SCR is heated based on the temperature of the carriers (DOC, DPF) upstream of the SCR, thereby reducing SCR temperature control overshoot.

[0005] According to one aspect of the present invention, an exhaust temperature control method for an SCR is provided, applicable to an exhaust aftertreatment system in which a DOC, DPF, and SCR are sequentially arranged in the exhaust pipe, the exhaust temperature control method comprising: Obtain the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions; The DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, and the DPF carrier temperature deviation is determined based on the DPF parameters and the SCR heating temperature threshold. The correction value for the SCR heating temperature threshold is determined based on the temperature deviation of the DOC carrier, the temperature deviation of the DPF carrier, and the SCR exhaust flow rate. The SCR heating temperature correction threshold is determined based on the SCR heating temperature threshold and the correction value.

[0006] Optionally, after determining the SCR heating temperature correction threshold, the following steps are also included: The operating mode of the SCR is controlled based on the SCR heating temperature correction threshold.

[0007] Optionally, controlling the SCR operating mode based on the SCR heating temperature correction threshold includes: When the current carrier temperature of the SCR is lower than the SCR heating temperature correction threshold, the SCR heating mode is entered. When the current carrier temperature of the SCR is greater than or equal to the SCR heating temperature correction threshold, the SCR heating mode is exited.

[0008] Optionally, the DOC parameters include DOC space velocity and DOC carrier temperature, and the DPF parameters include DPF space velocity and DPF carrier temperature. Determining the DOC carrier temperature deviation based on the DOC parameters and the SCR heating temperature threshold includes: The reference DOC carrier temperature is calculated by referring to the first lookup table corresponding to the DOC space velocity and the SCR heating temperature threshold. Calculate the DOC carrier temperature deviation based on the reference DOC carrier temperature and the DOC carrier temperature; Determining the DPF carrier temperature deviation based on the DPF parameters and the SCR heating temperature threshold includes: The reference DPF carrier temperature is calculated by referring to the second lookup table corresponding to the DPF space velocity and the SCR heating temperature threshold. Calculate the DPF carrier temperature deviation based on the reference DPF carrier temperature and the DPF carrier temperature; The first lookup table and the second lookup table are pre-calibrated.

[0009] Optionally, a correction value for the SCR heating temperature threshold is determined based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate, including: Based on the SCR exhaust flow rate, locate the exhaust volume flow rate chart and determine the DOC correction factor and DPF correction factor; Multiply the temperature deviation of the DOC carrier by the DOC correction factor to obtain the DOC correction value; Multiply the DPF carrier temperature deviation by the DPF correction factor to obtain the DPF correction value; The correction value of DOC is added to the correction value of DPF to obtain the correction value of SCR heating temperature threshold. The exhaust volume flow rate chart is pre-calibrated.

[0010] Optionally, determining the SCR heating temperature correction threshold based on the SCR heating temperature threshold and the correction value includes: The SCR heating temperature threshold and the correction value of the SCR heating temperature threshold are added together to obtain the SCR heating temperature correction threshold.

[0011] According to another aspect of the present invention, an exhaust temperature control device for an SCR is provided, suitable for an exhaust aftertreatment system in which a DOC, DPF, and SCR are sequentially arranged in the exhaust pipe, the exhaust temperature control device comprising: The acquisition module is used to acquire the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions. The temperature deviation determination module is used to determine the DOC carrier temperature deviation based on the DOC parameters and the SCR heating temperature threshold, and to determine the DPF carrier temperature deviation based on the DPF parameters and the SCR heating temperature threshold. The correction value determination module is used to determine the correction value of the SCR heating temperature threshold based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate. The SCR heating temperature correction threshold determination module is used to determine the SCR heating temperature correction threshold based on the SCR heating temperature threshold and the correction value.

[0012] According to another aspect of the present invention, an exhaust gas aftertreatment system is provided, comprising the exhaust temperature control device of the above-mentioned SCR and DOC, DPF and SCR arranged sequentially on the exhaust pipe, wherein the exhaust temperature control device is used for the exhaust temperature control method of the above-mentioned SCR.

[0013] According to another aspect of the present invention, an engine is provided, including the exhaust aftertreatment system described above.

[0014] According to another aspect of the present invention, a vehicle is provided, comprising the engine described above.

[0015] The SCR exhaust temperature control method provided in this embodiment of the invention first obtains the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions. The DOC parameters include DOC space velocity and DOC carrier temperature, and the DPF parameters include DPF space velocity and DPF carrier temperature. Then, the DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, and the DPF carrier temperature deviation is determined based on the DPF parameters and the SCR heating temperature threshold. The DOC carrier temperature deviation is the difference between the reference DOC carrier temperature determined based on the DOC parameters and the SCR heating temperature threshold, and the DPF carrier temperature deviation is the difference between the reference DPF carrier temperature determined based on the DPF parameters and the SCR heating temperature threshold. Next, a correction value for the SCR heating temperature threshold is determined based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate. Finally, the SCR heating temperature threshold is corrected based on the SCR heating temperature threshold and the correction value to obtain the SCR heating temperature correction threshold. The technical solution of this invention dynamically adjusts the temperature threshold for whether the SCR is heated based on the temperature of the carriers (DOC, DPF) upstream of the SCR, thereby reducing SCR temperature control overshoot and improving the fuel-saving performance of the engine.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart of an SCR exhaust temperature control method provided in an embodiment of the present invention; Figure 2 A schematic flowchart of another SCR exhaust temperature control method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the exhaust temperature control device for an SCR provided in an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Figure 1 This is a schematic flowchart of an SCR exhaust temperature control method provided by an embodiment of the present invention. This exhaust temperature control method is applicable to an exhaust aftertreatment system in which a DOC, DPF, and SCR are sequentially installed on the exhaust pipe. DOC is an abbreviation for "Diesel Oxidation Catalyst," and typically uses metal or ceramic as the catalyst carrier. The main active components in the coating are precious and rare metals such as platinum and palladium groups. When diesel engine exhaust passes through the catalyst, HC (hydrocarbons) and CO (carbon monoxide) can quickly react chemically with oxygen in the exhaust at relatively low temperatures to generate pollution-free H2O and CO2. The DOC achieves the purpose of purifying HC and CO in the exhaust. DPF is an abbreviation for "Diesel Particulate Filter," installed in the exhaust system. The DPF filters and captures PM (particulate matter) in the exhaust, reducing the amount of PM in the exhaust. SCR is an abbreviation for "Selective Catalytic Reduction," which primarily removes NOx from exhaust gases. It uses urea as a reducing agent, and under the reduction action of a selective catalyst, the NOx in the exhaust gas is reduced to nitrogen and water. (Reference) Figure 1 The exhaust temperature control method includes: S110: Obtain the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions.

[0022] The DOC parameters include DOC space velocity and DOC carrier temperature. Space velocity refers to the amount of gas processed per unit volume and time by the catalyst under specified conditions. The DOC carrier temperature can be calculated from the temperature signal obtained by the temperature sensor set within the DOC. The DPF parameters include DPF space velocity and DPF carrier temperature. The DPF carrier temperature can be calculated from the temperature signal obtained by the temperature sensor set within the DPF. The SCR heating temperature threshold is a preset temperature threshold based on different engines; heating is initiated when the temperature is below the threshold. The SCR exhaust flow rate can be obtained through a gas flow sensor.

[0023] S120. Determine the DOC carrier temperature deviation based on the DOC parameters and SCR heating temperature threshold, and determine the DPF carrier temperature deviation based on the DPF parameters and SCR heating temperature threshold.

[0024] Specifically, a corresponding chart of DOC space velocity and SCR heating temperature threshold can be pre-calibrated, and then the reference DOC carrier temperature can be calculated by looking up the table. The difference between the reference DOC carrier temperature and the DOC carrier temperature can be calculated to obtain the DOC carrier temperature deviation. Similarly, a corresponding chart of DPF space velocity and SCR heating temperature threshold can be pre-calibrated, and then the reference DPF carrier temperature can be calculated by looking up the table. The difference between the reference DPF carrier temperature and the DPF carrier temperature can be calculated to obtain the DPF carrier temperature deviation.

[0025] S130. Determine the correction value for the SCR heating temperature threshold based on the DOC carrier temperature deviation, DPF carrier temperature deviation, and SCR exhaust flow rate.

[0026] Specifically, the correspondence between SCR exhaust flow rate and the weights of DOC carrier temperature deviation and DPF carrier temperature deviation can be pre-defined. The weight ratios of DOC and DPF are obtained from a chart based on the SCR exhaust flow rate. These ratios are then multiplied by the corresponding deviations to obtain the DOC correction value and the DPF correction value. The two are then added together to obtain the correction value for the SCR heating temperature threshold. The weight ratios of DOC and DPF are both between 0 and 1. In one embodiment, the sum of their ratios can be set to 1.

[0027] S140. Determine the SCR heating temperature correction threshold based on the SCR heating temperature threshold and correction value.

[0028] For example, if the SCR heating temperature threshold is 200℃ and the correction value of the SCR heating threshold is 10℃, then the SCR heating temperature correction threshold is 210℃. If the SCR heating temperature threshold is 200℃ and the correction value of the SCR heating threshold is -10℃, then the SCR heating temperature correction threshold is 190℃.

[0029] The technical solution of this invention dynamically adjusts the temperature threshold for whether the SCR is heated based on the temperature of the carriers (DOC, DPF) upstream of the SCR, thereby reducing SCR temperature control overshoot and improving the fuel-saving performance of the engine.

[0030] Figure 2 A schematic flowchart of another SCR exhaust temperature control method provided in an embodiment of the present invention is shown below. Figure 2 The exhaust temperature control method includes: S210: Obtain the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions.

[0031] S220. Determine the DOC carrier temperature deviation based on the DOC parameters and SCR heating temperature threshold, and determine the DPF carrier temperature deviation based on the DPF parameters and SCR heating temperature threshold.

[0032] S230. Based on the DOC carrier temperature deviation, DPF carrier temperature deviation, and SCR exhaust flow rate, determine the correction value for the SCR heating temperature threshold.

[0033] S240. Determine the SCR heating temperature correction threshold based on the SCR heating temperature threshold and correction value.

[0034] S250: Control the operating mode of SCR based on the SCR heating temperature correction threshold.

[0035] Optionally, the operating mode of the SCR can be controlled based on a threshold correction for the SCR heating temperature, including: When the current SCR carrier temperature is lower than the SCR heating temperature correction threshold, the SCR heating mode is entered, and SCR heating can be achieved by increasing the exhaust temperature; when the current SCR carrier temperature is greater than or equal to the SCR heating temperature correction threshold, the SCR heating mode is exited, and this can be achieved by decreasing the exhaust temperature.

[0036] In this embodiment, after determining the SCR heating temperature correction threshold, i.e., determining a new SCR heating temperature threshold, the SCR is controlled to operate according to the new SCR heating temperature threshold to avoid SCR temperature control overshoot.

[0037] Optionally, the DOC parameters include DOC space velocity and DOC carrier temperature, and the DPF parameters include DPF space velocity and DPF carrier temperature. The DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, including: Based on the first lookup table corresponding to DOC space velocity and SCR heating temperature threshold, the reference DOC carrier temperature is calculated; based on the reference DOC carrier temperature and the DOC carrier temperature, the DOC carrier temperature deviation is calculated.

[0038] The DPF carrier temperature deviation is determined based on DPF parameters and SCR heating temperature threshold, including: Based on the second lookup table corresponding to the DPF space velocity and SCR heating temperature threshold, the reference DPF carrier temperature is calculated; based on the reference DPF carrier temperature and the DPF carrier temperature, the DPF carrier temperature deviation is calculated.

[0039] The first and second reference tables are pre-calibrated.

[0040] For example, the calibration process includes: uniformly finding 16 operating points (according to the combination of speed and torque) in the engine's universal characteristics, stabilizing each point for 20 minutes, and recording the SCR carrier temperature, DOC carrier temperature, DPF carrier temperature, and exhaust flow rate after stabilization; converting the exhaust mass flow rate into volumetric flow rate (mass flow rate divided by density, which can be calculated based on exhaust temperature and pressure); fitting a two-dimensional graph of the DOC reference carrier temperature with the SCR carrier temperature and volumetric flow rate as X and Y, and the DOC carrier temperature as Z; similarly fitting a two-dimensional graph of the DPF reference carrier temperature with the SCR carrier temperature and volumetric flow rate as X and Y, and the DPF carrier temperature as Z.

[0041] Given a standard mode switching temperature threshold, such as 200℃ or 210℃ (with hysteresis to prevent jump), when the temperature rises above 210℃, it switches to non-heating mode, and when the temperature is below 200℃, it switches to heating mode.

[0042] Optionally, a correction value for the SCR heating temperature threshold is determined based on the DOC carrier temperature deviation, DPF carrier temperature deviation, and SCR exhaust flow rate, including: Based on the SCR exhaust flow rate, locate the exhaust volume flow rate chart and determine the DOC correction factor and DPF correction factor.

[0043] The DOC correction value is obtained by multiplying the temperature deviation of the DOC carrier by the DOC correction factor.

[0044] The DPF correction value is obtained by multiplying the DPF carrier temperature deviation by the DPF correction factor.

[0045] Add the DOC correction value to the DPF correction value to obtain the correction value for the SCR heating temperature threshold.

[0046] The exhaust volume flow rate icon is pre-calibrated.

[0047] For example, observe the data to determine how much the SCR carrier temperature increases by 1°C for each increase in DOC and DPF carrier temperatures under different exhaust volume flow rates. For instance, assuming an exhaust volume flow rate of 100 and an SCR carrier temperature increase of 0.5°C, the correction scale chart uses space velocity as input and outputs a ratio between 0 and 1, as shown in the chart below: Multiply the output weight of the table by the result of subtracting the reference carrier temperature from the current actual DOC and DPF carrier temperatures, and then add the two correction values ​​of DOC and DPF to obtain the final correction value. This correction value (e.g., 10℃) is added to the basic threshold of the switching temperature to obtain the corrected switching temperature threshold (200+10℃, 210+10℃).

[0048] In the transient step test, the SCR temperature is stepped from low temperature and low load to medium load. The temperature is compared with the temperature after stabilization. The overshoot of temperature or the speed at which it approaches the stabilization value is observed. If the temperature overshoot is large, the proportion in the weight chart is increased. Conversely, if the speed at which it approaches the stabilization value is relatively slow, the proportion is decreased.

[0049] Optionally, based on the SCR heating temperature threshold and the correction value, the SCR heating temperature correction threshold is determined, including: The SCR heating temperature threshold and its correction value are added together to obtain the SCR heating temperature correction threshold.

[0050] For example, the standard mode switching temperature base threshold is 200℃ and 210℃ (with hysteresis to prevent jump). During the process of stepping from low temperature and low load to medium load, the final switching temperature dynamically changes between 190~200℃ and 200~210℃. When stepping from medium load to low load, the final switching temperature dynamically changes between 200~210℃ and 210~220℃, and the temperature overshoot decreases from 20℃ to 5℃.

[0051] Figure 3 This is a schematic diagram of the exhaust temperature control device for an SCR provided in an embodiment of the present invention. It is applicable to exhaust aftertreatment systems in which DOC, DPF and SCR are sequentially arranged on the exhaust pipe. (Refer to...) Figure 3 The exhaust temperature control device includes: The acquisition module 10 is used to acquire the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions; the temperature deviation determination module 20 is used to determine the DOC carrier temperature deviation based on the DOC parameters and SCR heating temperature threshold, and to determine the DPF carrier temperature deviation based on the DPF parameters and SCR heating temperature threshold; the correction value determination module 30 is used to determine the correction value of the SCR heating temperature threshold based on the DOC carrier temperature deviation, DPF carrier temperature deviation, and SCR exhaust flow rate; and the SCR heating temperature correction threshold determination module 40 is used to determine the SCR heating temperature correction threshold based on the SCR heating temperature threshold and the correction value.

[0052] The exhaust temperature control device for SCR provided in this embodiment of the invention can be used to execute any of the exhaust temperature control methods for SCR provided in the above embodiments, has corresponding functional modules, and has the same technical effect.

[0053] This invention also provides an exhaust gas aftertreatment system, including the exhaust temperature control device of the SCR described above, and DOC, DPF and SCR arranged sequentially on the exhaust pipe. The exhaust temperature control device is used for the exhaust temperature control method of the SCR provided in the above embodiments.

[0054] Since the exhaust gas aftertreatment system provided in this embodiment includes the exhaust temperature control device of the SCR provided in the above embodiment, it has the same or corresponding technical effects as the exhaust temperature control device, and will not be described in detail here.

[0055] This invention also provides an engine that includes the exhaust aftertreatment system described above.

[0056] Since the engine provided in this embodiment includes the exhaust gas aftertreatment system provided in the above embodiment and has the same or corresponding technical effects as the exhaust gas aftertreatment system, it will not be described in detail here.

[0057] This invention also provides a vehicle including the engine provided in the above embodiments.

[0058] Since the vehicle provided in this embodiment of the invention includes the engine provided in the above embodiment and has the same or corresponding technical effects as the engine, it will not be described in detail here.

[0059] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for controlling the exhaust temperature of an SCR, characterized in that, Applicable to exhaust aftertreatment systems in which DOC, DPF, and SCR are sequentially installed on the exhaust pipe, the exhaust temperature control method includes: Obtain the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions; The DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, and the DPF carrier temperature deviation is determined based on the DPF parameters and the SCR heating temperature threshold. The correction value for the SCR heating temperature threshold is determined based on the temperature deviation of the DOC carrier, the temperature deviation of the DPF carrier, and the SCR exhaust flow rate. Based on the SCR heating temperature threshold and the correction value, determine the SCR heating temperature correction threshold; The operating mode of the SCR is controlled according to the SCR heating temperature correction threshold. The DOC parameters include DOC space velocity and DOC carrier temperature, and the DPF parameters include DPF space velocity and DPF carrier temperature. The DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, including: The reference DOC carrier temperature is calculated by referring to the first lookup table corresponding to the DOC space velocity and the SCR heating temperature threshold. Calculate the DOC carrier temperature deviation based on the reference DOC carrier temperature and the DOC carrier temperature; Determining the DPF carrier temperature deviation based on the DPF parameters and the SCR heating temperature threshold includes: The reference DPF carrier temperature is calculated by referring to the second lookup table corresponding to the DPF space velocity and the SCR heating temperature threshold. Calculate the DPF carrier temperature deviation based on the reference DPF carrier temperature and the DPF carrier temperature; The first lookup table and the second lookup table are pre-calibrated; Based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate, a correction value for the SCR heating temperature threshold is determined, including: Based on the SCR exhaust flow rate, locate the exhaust volume flow rate chart and determine the DOC correction factor and DPF correction factor; Multiply the temperature deviation of the DOC carrier by the DOC correction factor to obtain the DOC correction value; Multiply the DPF carrier temperature deviation by the DPF correction factor to obtain the DPF correction value; The DOC correction value is added to the DPF correction value to obtain the correction value for the SCR heating temperature threshold. The exhaust volume flow rate chart is pre-calibrated.

2. The SCR exhaust temperature control method according to claim 1, characterized in that, Controlling the SCR operating mode based on the SCR heating temperature correction threshold includes: When the current carrier temperature of the SCR is lower than the SCR heating temperature correction threshold, the SCR heating mode is entered. When the current carrier temperature of the SCR is greater than or equal to the SCR heating temperature correction threshold, the SCR heating mode is exited.

3. The SCR exhaust temperature control method according to claim 1, characterized in that, Determining the SCR heating temperature correction threshold based on the SCR heating temperature threshold and the correction value includes: The SCR heating temperature threshold and the correction value of the SCR heating temperature threshold are added together to obtain the SCR heating temperature correction threshold.

4. A temperature control device for SCR exhaust, characterized in that, Applicable to exhaust aftertreatment systems in which DOC, DPF, and SCR are sequentially installed on the exhaust pipe, the exhaust temperature control device includes: The acquisition module is used to acquire the DOC parameters, DPF parameters, SCR heating temperature threshold, and SCR exhaust flow rate under the current operating conditions. The temperature deviation determination module is used to determine the DOC carrier temperature deviation based on the DOC parameters and the SCR heating temperature threshold, and to determine the DPF carrier temperature deviation based on the DPF parameters and the SCR heating temperature threshold. The correction value determination module is used to determine the correction value of the SCR heating temperature threshold based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate. The SCR heating temperature correction threshold determination module is used to determine the SCR heating temperature correction threshold based on the SCR heating temperature threshold and the correction value, and to control the SCR operating mode based on the SCR heating temperature correction threshold. The DOC parameters include DOC space velocity and DOC carrier temperature, and the DPF parameters include DPF space velocity and DPF carrier temperature. The DOC carrier temperature deviation is determined based on the DOC parameters and the SCR heating temperature threshold, including: The reference DOC carrier temperature is calculated by referring to the first lookup table corresponding to the DOC space velocity and the SCR heating temperature threshold. Calculate the DOC carrier temperature deviation based on the reference DOC carrier temperature and the DOC carrier temperature; Determining the DPF carrier temperature deviation based on the DPF parameters and the SCR heating temperature threshold includes: The reference DPF carrier temperature is calculated by referring to the second lookup table corresponding to the DPF space velocity and the SCR heating temperature threshold. Calculate the DPF carrier temperature deviation based on the reference DPF carrier temperature and the DPF carrier temperature; The first lookup table and the second lookup table are pre-calibrated; Based on the DOC carrier temperature deviation, the DPF carrier temperature deviation, and the SCR exhaust flow rate, a correction value for the SCR heating temperature threshold is determined, including: Based on the SCR exhaust flow rate, locate the exhaust volume flow rate chart and determine the DOC correction factor and DPF correction factor; Multiply the temperature deviation of the DOC carrier by the DOC correction factor to obtain the DOC correction value; Multiply the DPF carrier temperature deviation by the DPF correction factor to obtain the DPF correction value; The DOC correction value is added to the DPF correction value to obtain the correction value for the SCR heating temperature threshold. The exhaust volume flow rate chart is pre-calibrated.

5. A tail gas aftertreatment system, characterized in that, The device includes the exhaust temperature control device of the SCR as described in claim 4, and DOC, DPF and SCR arranged sequentially on the exhaust pipe, wherein the exhaust temperature control device is used to execute the exhaust temperature control method of the SCR as described in any one of claims 1 to 3.

6. An engine, characterized in that, Includes the exhaust gas aftertreatment system as described in claim 5.

7. A vehicle, characterized in that, Includes the engine as described in claim 6.

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