Vehicle exhaust system, vehicle exhaust system control method, and vehicle

Abstract

This invention belongs to the field of engine technology and discloses a vehicle exhaust system, a vehicle exhaust system control method, and a vehicle. The vehicle exhaust system includes an engine, an LNT (Low Noise Reduction Turbine), and an ECU (Electronic Control Unit). The engine includes a cylinder and an injection mechanism for injecting fuel into the cylinder. The intake port of the LNT is connected to the exhaust port of the cylinder through a first exhaust pipe, and the exhaust port of the LNT is connected to a second exhaust pipe. A first NO (Noise Reduction Turbine) is provided on the first exhaust pipe. X A concentration sensor is installed on the second exhaust pipe, and a second NO concentration sensor is also installed. X Concentration sensor, first NO X Concentration sensor, second NO X Both the concentration sensor and the injection mechanism are connected to the ECU for communication. The ECU is used to determine the concentration of NO based on the first NO concentration. X The concentration sensor's detection value and the second NO X The concentration sensor detects the fuel concentration and controls the injection mechanism to inject fuel during the engine's exhaust stroke. This vehicle exhaust system not only improves fuel economy but also removes the limitations imposed on engine control strategies by repeated switching of operating conditions.

Description

Technical Field

[0001] This invention relates to the field of vehicle exhaust technology, and in particular to a vehicle exhaust system, a vehicle exhaust system control method, and a vehicle. Background Technology

[0002] To reduce NOx emissions from vehicles equipped with lean-burn engines X Emissions are typically addressed by installing exhaust aftertreatment devices on the vehicle's exhaust system. Currently, commonly used exhaust aftertreatment devices include selective catalytic reduction (SCR) and NOx. X Lean NO trap X (trap, LNT).

[0003] SCR includes a catalyst and a urea supply system, so the overall structure of SCR is more complex and requires more installation space, which increases the overall cost of the vehicle. LNT has a simpler structure than SCR, so it requires less installation space and is more suitable for installation in passenger cars.

[0004] LNT works by adsorbing NO in the exhaust pipe under lean-burn conditions. X Under rich combustion conditions, adsorbed NO is released. X In order to achieve LNT regeneration, the engine needs to repeatedly switch between lean-burn and rich-burn conditions, which not only reduces fuel economy but also limits the engine's control strategy.

[0005] Therefore, there is an urgent need to propose a vehicle exhaust system, a vehicle exhaust system control method, and a vehicle to solve the above-mentioned technical problems. Summary of the Invention

[0006] The first objective of this invention is to provide a vehicle exhaust system that can regenerate LNT without the engine repeatedly switching between lean-burn and rich-burn conditions.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The vehicle exhaust system includes:

[0009] An engine, which includes cylinders and an injection mechanism, is used to inject fuel into the cylinders;

[0010] LNT (Liquid Necklace) has an intake port and an exhaust port. The intake port is connected to the exhaust end of the cylinder through a first exhaust pipe. The first exhaust pipe is equipped with a first NO (Noise Leveling) valve. X The concentration sensor's outlet is connected to the second exhaust pipe, which is equipped with a second NO concentration sensor. X Concentration sensor;

[0011] ECU, the first NO X concentration sensor, the second NO X The concentration sensor and the injection mechanism are both in communication connection with the ECU, and the ECU is used for controlling the injection mechanism to inject fuel in the exhaust stroke of the engine according to the detection value of the concentration sensor and the first NO X concentration sensor and the second NO X The detection value of the concentration sensor controls the injection mechanism to inject fuel in the exhaust stroke of the engine.

[0012] The second object of the present application is to provide a vehicle exhaust system control method, which can realize the regeneration of the LNT without repeatedly switching the engine between the lean combustion condition and the rich combustion condition.

[0013] To achieve the object, the present application adopts the following technical solutions:

[0014] The vehicle exhaust system control method is applied to the above vehicle exhaust system, and the vehicle exhaust system control method comprises:

[0015] Obtaining the NO X concentration N1 in the first exhaust pipe and the NO X concentration N2 in the second exhaust pipe;

[0016] Judging whether to enter the LNT regeneration step;

[0017] If the LNT regeneration step is entered, the injection mechanism injects fuel in the exhaust stroke of the engine, so that the fuel and the NO X in the LNT perform catalytic reduction reaction.

[0018] Optionally, the method for judging whether to enter the LNT regeneration step comprises:

[0019] If N2>Ny and N≤Nq, the LNT regeneration step is entered;

[0020] Wherein,

[0021] Ny is a preset threshold value of the NO X concentration in the second exhaust pipe;

[0022] N is the real-time adsorption rate of the LNT calculated according to a preset calculation model;

[0023] Nq is the first preset threshold value of the adsorption rate of the LNT.

[0024] Optionally, after entering the LNT regeneration step, it is judged whether to end the LNT regeneration step, and if the LNT regeneration step is ended, the injection mechanism stops injecting fuel, and the method for judging whether to end the LNT regeneration step comprises:

[0025] If N>Nt, the LNT regeneration step is ended;

[0026] wherein,

[0027] Nt is a second preset threshold of the adsorption rate of the LNT, and Nt≥Nq.

[0028] Optionally, the method of determining whether to enter the LNT regeneration step further comprises: selecting N2, N and Nq in multiple sampling periods, and if N2 in each sampling period is greater than Ny, and N in each sampling period is less than or equal to Nq, then entering the LNT regeneration step.

[0029] The method of determining whether to end the LNT regeneration step further comprises: selecting N and Nt in multiple sampling periods, and if N in each sampling period is greater than Nt, then ending the LNT regeneration step.

[0030] Optionally, the pre-designed calculation model is N=(N1-N2) / N1×100%.

[0031] Optionally, the cylinder comprises a main combustion chamber and a pre-chamber in communication, the intake port is in communication with the exhaust end of the main combustion chamber, the injection mechanism comprises a main injector and a sub-injector, the main injector is used for injecting fuel into the main combustion chamber, and the sub-injector is used for injecting fuel into the pre-chamber, and the vehicle exhaust system control method further comprises:

[0032] If the LNT regeneration step is entered, the main injector is preferentially used to inject fuel.

[0033] Optionally, the minimum injection pulse width of the main injector is t1, the minimum injection pulse width of the sub-injector is t2, and t1>t2, and when the LNT regeneration step is entered, the injection pulse width preset threshold of the fuel is t.

[0034] When the LNT regeneration step is entered, if t≥t1, the main injector is used to inject fuel.

[0035] Optionally, when the LNT regeneration step is entered, if the sub-injector is used to inject the carbon-based liquid fuel, and the actual temperature T in the first exhaust pipe is less than the temperature preset threshold Td of the first exhaust pipe, the pre-chamber ignition mechanism of the pre-chamber ignites in the exhaust stroke of the engine and after the end of the injection of the sub-injector, so as to heat the carbon-based liquid fuel.

[0036] A third object of the present application is to provide a vehicle with higher fuel economy, and the engine control strategy of the vehicle is not limited to the regeneration of the LNT.

[0037] To achieve this object, the present application adopts the following technical solutions:

[0038] The vehicle adopts the above-mentioned vehicle exhaust system control method to control the regeneration of the LNT.

[0039] Beneficial effects:

[0040] The vehicle exhaust system provided by the present application sets a first exhaust pipe at the air inlet of the LNT, and sets a first NO X concentration sensor at the first exhaust pipe, sets a second exhaust pipe at the air outlet of the LNT, and sets a second NO X concentration sensor at the second exhaust pipe, the first NO X concentration sensor is used for detecting the NO X concentration of the exhaust gas of the engine before entering the LNT, the second NO X concentration sensor is used for detecting the NO X concentration of the exhaust gas of the engine after being treated by the LNT, the first NO X concentration sensor, the second NO X concentration sensor, and the injection mechanism are all in communication connection with the ECU, so that the ECU can judge whether the LNT needs to be regenerated according to the detection value of the first NO X concentration sensor and the detection value of the second NO X concentration sensor, when the ECU judges that the LNT needs to be regenerated, the ECU controls the injection mechanism to inject fuel in the exhaust stroke of the engine, so that the fuel enters the LNT through the first exhaust pipe, since the fuel is injected in the exhaust stroke of the engine, the fuel does not participate in combustion work, but is only used for catalyzing reaction with the NO X in the LNT to realize the regeneration of the LNT, it can be seen that the vehicle exhaust system does not need the engine to repeatedly switch between the lean combustion condition and the rich combustion condition, only needs the ECU to control the injection mechanism according to the detection value of the first NO X concentration sensor and the detection value of the second NO X concentration sensor, the ECU controls the injection mechanism to inject fuel in the exhaust stroke of the engine, so that the fuel enters the LNT through the first exhaust pipe, since the fuel is injected in the exhaust stroke of the engine, the fuel does not participate in combustion work, but is only used for catalyzing reaction with the NO

[0041] The vehicle exhaust system control method provided by the present application is applied to the above-mentioned vehicle exhaust system, judges whether to enter the LNT regeneration step according to the NO X concentration N1 in the first exhaust pipe and the NO X concentration N2 in the second exhaust pipe, when entering the LNT regeneration step, the injection mechanism injects fuel in the exhaust stroke of the engine, so that the fuel does not participate in combustion work, but is only used for catalyzing reaction with the NO X in the LNT to realize the regeneration of the LNT, thereby eliminating the repeatedly switching between the lean combustion condition and the rich combustion condition of the engine, improving the fuel economy, and eliminating the limitation of the repeatedly switching between the two conditions on the control strategy of the engine.

[0042] The vehicle provided by the present application adopts the vehicle exhaust system control method described above, so that the vehicle has higher fuel economy, and the engine control strategy of the vehicle is not limited to LNT regeneration. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a structural schematic diagram of a vehicle exhaust system provided by the present embodiment;

[0044] Figure 2 is a structural schematic diagram of a pre-chamber provided by the present embodiment;

[0045] Figure 3 is a flow chart of a vehicle exhaust system control method provided by the present embodiment.

[0046] IN THE DRAWINGS:

[0047] 100, engine; 200, intake manifold; 310, main injector; 320, main fuel supply mechanism; 410, pre-chamber; 420, auxiliary injector; 430, auxiliary fuel supply mechanism; 440, pre-chamber spark plug; 450, pre-chamber ignition mechanism; 460, injection hole; 500, LNT; 600, ECU; 710, first exhaust pipe; 720, second exhaust pipe; 810, first NO X concentration sensor; 820, second NO X concentration sensor; 830, temperature sensor. DETAILED DESCRIPTION

[0048] The present application will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, and not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings, and not all the structures.

[0049] In the description of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrated; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0051] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0052] This embodiment provides a vehicle exhaust system that can achieve LNT regeneration without the engine repeatedly switching between lean-burn and rich-burn conditions.

[0053] Specifically, such as Figure 1 As shown, the vehicle's exhaust system includes an engine 100, an LNT 500, and an engine 100 control unit (ECU) 600. The engine 100 includes cylinders and an injection mechanism for injecting fuel into the cylinders. The LNT 500 has an intake port and an exhaust port. The intake port is connected to the exhaust end of the cylinder via a first exhaust pipe 710. The first exhaust pipe 710 is equipped with a first NO... X Concentration sensor 810 and temperature sensor 830, first NO X Concentration sensor 810 is used to detect NO in the exhaust gas inside the first exhaust pipe 710. X Concentration (i.e., NO concentration before engine exhaust enters LNT500) X (Concentration), temperature sensor 830 is used to detect the temperature of the exhaust gas in the first exhaust pipe 710 (i.e., the exhaust temperature of the engine 100), the outlet of which is connected to the second exhaust pipe 720, and the second exhaust pipe 720 is equipped with a second NO concentration. X Concentration sensor 820, second NO X Concentration sensor 820 is used to detect NO in the exhaust gas inside the second exhaust pipe 720. X Concentration (i.e., NO concentration after engine exhaust gas is treated by LNT500) XConcentration), first NO X Concentration sensor 810, second NO X Both the concentration sensor 820 and the injection mechanism are connected to the ECU 600. The ECU 600 is used to determine the concentration of NO based on the first NO concentration. X The detection value of concentration sensor 810 and the second NO X The concentration sensor detects the fuel concentration and controls the injection mechanism to inject fuel during the exhaust stroke of the engine 100.

[0054] The vehicle exhaust system provided in this embodiment has a first exhaust pipe 710 installed at the air intake of the LNT500, and a first NO is installed on the first exhaust pipe 710. X Concentration sensor 810, first NO X Concentration sensor 810 detects NO in the exhaust gas inside the first exhaust pipe 710. X The concentration (hereinafter referred to as N1), that is, the NO concentration of engine exhaust before it enters the LNT500. X The concentration is N1. A second exhaust pipe 720 is installed at the outlet of the LNT500, and a second NO is installed on the second exhaust pipe 720. X Concentration sensor 820, second NO X Concentration sensor 820 detects NO in the exhaust gas inside the second exhaust pipe 720. X The concentration (hereinafter referred to as N2), that is, the NO concentration after the exhaust gas of engine 100 is treated by LNT500. X The concentration of N2 is the first NO X Concentration sensor 810, second NO X Both the concentration sensor 820 and the injection mechanism are connected to the ECU 600. The ECU 600 determines whether the LNT 500 needs regeneration based on the values ​​of N1 and N2. When the LNT 500 needs regeneration, the ECU 600 controls the injection mechanism to inject fuel during the exhaust stroke of the engine 100 (before the intake valve of the engine 100 opens). This fuel enters the LNT 500 sequentially through the exhaust end of the cylinder and the first exhaust pipe 710. Since this fuel is injected during the exhaust stroke of the engine 100, it does not participate in combustion and only serves to react with the NO in the LNT 500. X A catalytic reaction is carried out to regenerate LNT500. Therefore, the vehicle's exhaust system does not require the engine to repeatedly switch between lean and rich combustion conditions; the ECU only needs to react according to the first NO... X The detection value of concentration sensor 810 and the second NO XThe detection value of the concentration sensor 820 controls the injection mechanism to inject fuel in the exhaust stroke of the engine 100, i.e. to realize the regeneration of the LNT 500, which not only improves the fuel economy, but also eliminates the limitation of the control strategy of the engine 100 caused by the repeated switching of the working conditions.

[0055] It should be noted that the above-mentioned method for determining whether the LNT 500 needs to be regenerated according to the values of N1 and N2 can be determined according to the difference between N1 and N2, and when the difference between N1 and N2 is less than a preset value, it is considered that the LNT 500 needs to be regenerated; or it can also be determined according to the sum of N1 and N2, and when the value of the sum of N1 and N2 is greater than a preset value, it is considered that the LNT 500 needs to be regenerated; in addition, other calculation methods can also be used to determine whether the LNT 500 needs to be regenerated, which depends on the specific control method of the ECU 600, and will not be listed one by one here.

[0056] Optionally, as shown in Figure 1 and Figure 2 The cylinder includes a main combustion chamber and a pre-chamber 410, the pre-chamber 410 is installed in the cylinder head of the engine 100, and the pre-chamber 410 is provided with a plurality of injection holes 460. Exemplarily, the number of injection holes 460 in the present embodiment is two, and in other embodiments, one, three, four or more injection holes 460 can also be provided, preferably an even number of injection holes 460, and the even number of injection holes 460 are preferably uniformly distributed around the axis of the pre-chamber 410. The pre-chamber 410 communicates with the main combustion chamber through the injection hole 460, the gas inlet of the LNT 500 communicates with the exhaust end of the main combustion chamber, and the injection mechanism includes a main injector 310 and a sub-injector 420. The main injector 310 is installed on the intake manifold 200 in the form of port injection, so that the main injector 310 injects fuel into the intake manifold 200, and then the fuel enters the main combustion chamber through the intake manifold 200. The sub-injector 420 is installed on the pre-chamber 410, and the nozzle of the sub-injector 420 faces the pre-chamber 410, so that the sub-injector 420 can inject fuel into the pre-chamber 410, and then the fuel in the pre-chamber 410 can enter the main combustion chamber through the injection hole 460. It should be noted that in other embodiments, the main injector 310 can also be installed on the cylinder head of the engine 100 in the form of direct injection, so that the main injector 310 injects fuel into the main combustion chamber.

[0057] Further, as shown in Figure 1 and Figure 2As shown, the vehicle exhaust system further comprises a main fuel supply mechanism 320 for supplying fuel to the main injector 310, a sub-fuel supply mechanism 430 for supplying fuel to the sub-injector 420, a pre-chamber spark plug 440 installed on the pre-chamber 410, and a pre-chamber ignition mechanism 450 for controlling the pre-chamber spark plug 440 to ignite the fuel injected by the sub-injector 420 to heat and warm up the fuel, or to ignite the fuel injected by the sub-injector 420.

[0058] The embodiment further provides a vehicle exhaust system control method, which is applied to the vehicle exhaust system described above, and which can realize the regeneration of the LNT 500 without repeatedly switching the engine 100 between the lean combustion condition and the rich combustion condition.

[0059] Specifically, the vehicle exhaust system control method comprises: obtaining the NOx concentration N1 in the first exhaust pipe 710 and the NOx concentration N2 in the second exhaust pipe 720; determining whether to enter the LNT regeneration step; and if the LNT regeneration step is entered, injecting fuel by the injection mechanism in the exhaust stroke of the engine 100, so that the fuel and the NOx in the LNT 500 perform catalytic reduction reaction. X X X

[0060] The control method determines whether to enter the LNT regeneration step according to the NOx concentration N1 in the first exhaust pipe 710 and the NOx concentration N2 in the second exhaust pipe 720, and when the LNT regeneration step is entered, the injection mechanism injects fuel in the exhaust stroke of the engine 100 (before the intake valve of the engine 100 is opened), so that the fuel does not participate in combustion work and is only used for catalytic reaction with the NOx in the LNT 500 to realize the regeneration of the LNT 500. X X X

[0061] Further, the method for determining whether to enter the LNT regeneration step comprises: if N2>Ny and N≤Nq, entering the LNT regeneration step; wherein,

[0062] Ny is a preset threshold value of the NOx concentration in the second exhaust pipe 720, and in actual application, the NOx concentration allowed by the exhaust emission of the automobile is used as the threshold value. X X ​​​​​​​The concentration is a range (Nymin-Nymax). Here, Ny can be set to the minimum value Nymin of the range or the maximum value Nymax of the range.

[0063] N represents the real-time adsorption rate of LNT500 calculated according to a preset calculation model. The preset calculation model is N = (N1 - N2) / N1 × 100%. If N > 0, it indicates that LNT500 effectively adsorbs NO. X If N≤0, it means that LNT500 has not effectively adsorbed NO. X Its function;

[0064] Nq is the first preset threshold for the adsorption rate of LNT500. Here, Nq can be regarded as the theoretical minimum adsorption rate of LNT500. Comparing N with Nq means comparing the actual adsorption rate of LNT500 with the theoretical minimum adsorption rate. When the actual adsorption rate N of LNT500 is less than or equal to the first preset threshold Nq of LNT500, it indicates that the adsorption capacity of LNT500 has decreased significantly. It should be noted that the adsorption rate of LNT500 varies with the engine speed, load, and exhaust temperature of engine 100. Therefore, the aforementioned Nq value also varies with the engine speed, load, and exhaust temperature of engine 100. In practical applications, multiple Nq values ​​can be obtained experimentally first, and then these multiple Nq values ​​can be pre-input into ECU600. When determining whether to enter the LNT regeneration step, ECU600 selects the corresponding Nq value based on the real-time operating conditions of engine 100 and compares the Nq value with the N value. The above-mentioned experimental method for obtaining multiple Nq values ​​and the method for ECU600 to obtain the actual operating conditions of engine 100 are both mature existing technologies in this field and will not be elaborated here.

[0065] As can be seen, in this embodiment, when NO in the second exhaust pipe 720 X The N2 concentration exceeded the permissible NO emission level in vehicle exhaust. X When the concentration of N2 > Ny is high and the adsorption capacity of LNT500 decreases significantly (N ≤ Nq), it is considered that the adsorption capacity of LNT500 is insufficient to meet the NO emission standards for automobile exhaust. X The concentration requirement triggers the LNT regeneration step. This control method not only determines whether the LNT500 needs regeneration but also reduces fuel consumption.

[0066] Specifically, when N2≤Ny and N≤Nq, although the actual adsorption rate of LNT500 is lower than the theoretical adsorption rate, since N2≤Ny, it indicates that the NO in the second exhaust pipe 720 is lower than the theoretical adsorption rate. X The concentration of N2 is lower than the allowable NO emission level in vehicle exhaust. XThe concentration is low, therefore, no regeneration of LNT500 is required at this time. In other words, no additional fuel injection is needed to neutralize the NO in LNT500. X Catalytic reactions are carried out, thereby reducing fuel consumption;

[0067] When N2 > Ny and N > Nq, although NO in the second exhaust pipe 720 at this time X The N2 concentration exceeded the permissible NO emission level in vehicle exhaust. X The concentration is [not specified], but since N > Nq, this indicates that LNT500 is in a state of efficient NO capture. X During this stage, the LNT500 has a strong adsorption capacity. If additional fuel is injected at this time for LNT regeneration, the regeneration efficiency will be low. The fuel that does not participate in LNT regeneration will be discharged into the external environment through the second exhaust pipe 720, which will waste this part of the fuel and increase fuel consumption.

[0068] Preferably, since LNT regeneration is not performed when N2 > Ny and N > Nq, in order to ensure the NO in the second exhaust pipe 720 X If the concentration is within the range of Nymin-Nymax, where Ny is Nymin in this embodiment, and if N2 > Ny and N > Nq, and the value of N2 continues to rise, then within a certain period of time, N2 can still meet the allowable NO emission standards for automobile exhaust. X For concentration requirements, and within this time period, LNT500, with its strong adsorption capacity, efficiently adsorbs NO. X This causes N2 to decrease rapidly.

[0069] It should be noted that the comparison between N2 and Ny and the comparison between N and Nq can be performed simultaneously or sequentially. In this embodiment, the comparison between N2 and Ny is performed first, and when N2 > Ny, the comparison between N and Nq is performed to simplify the control logic.

[0070] Optionally, after entering the LNT regeneration step, it is determined whether the LNT regeneration step should be ended. If the LNT regeneration step is ended, the injection mechanism stops injecting fuel to avoid fuel waste. The method for determining whether to end the LNT regeneration step includes: if N > Nt, then the LNT regeneration step is ended, where Nt is the second preset threshold of the adsorption rate of LNT500, and Nt ≥ Nq. That is, when the actual adsorption rate N of LNT500 is greater than the second preset threshold Nt of the adsorption rate of LNT500, it indicates that the adsorption capacity of LNT500 has been improved, and at this time the injection mechanism stops injecting fuel.

[0071] Preferably, in the embodiment, Nt>Nq, to ensure that LNT 500 has sufficient adsorption capacity before stopping the regeneration step. As described above, the adsorption rate of LNT 500 varies with the engine speed, load and exhaust temperature of engine 100, and therefore, the value of Nt also varies with the engine speed, load and exhaust temperature of engine 100. In practical applications, a plurality of Nt values can be obtained through experiments, and the plurality of Nt values can be pre-input into ECU 600. When determining whether to end the LNT regeneration step, ECU 600 selects a corresponding Nt value according to the real-time operating conditions of engine 100, and compares the Nt value with N. The method of obtaining a plurality of Nt values and the method of obtaining the operating conditions of engine 100 by ECU 600 are both mature prior art in the field, and therefore, will not be described here.

[0072] Alternatively, the method of determining whether to enter the LNT regeneration step further comprises: selecting N2, N and Nq in a plurality of sampling periods, and if N2 in each sampling period is greater than Ny, and N in each sampling period is less than or equal to Nq, then entering the LNT regeneration step, to improve the accuracy of determining whether to enter the LNT regeneration step, and to avoid frequent switching between the regeneration operating condition and the non-regeneration operating condition of engine 100. Preferably, the plurality of sampling periods comprises more than ten continuous sampling periods, to improve the accuracy of determination while simplifying the control logic of ECU 600.

[0073] The method of determining whether to end the LNT regeneration step further comprises: selecting N and the second adsorption rate threshold Nt in a plurality of sampling periods, and if N in each sampling period is greater than the second adsorption rate threshold Nt, then ending the LNT regeneration step, to improve the accuracy of determining whether to end the regeneration step, and to avoid frequent switching between the regeneration operating condition and the non-regeneration operating condition of engine 100. Preferably, the plurality of sampling periods comprises more than ten continuous sampling periods, to improve the accuracy of determination while simplifying the control logic of ECU 600.

[0074] Alternatively, in the embodiment, the injection mechanism comprises a main injector 310 and a sub-injector 420. The fuel injected by main injector 310 enters LNT 500 through the main combustion chamber and the first exhaust pipe 710 in sequence. The fuel injected by sub-injector 420 enters LNT 500 through the pre-chamber 410, the injection hole 460, the main combustion chamber and the first exhaust pipe 710 in sequence. It can be seen that the fuel injected by sub-injector 420 may be left in pre-chamber 410, and the fuel left in pre-chamber 410 will not enter LNT 500 to participate in the regeneration of LNT 500, thereby causing the problem of waste of the part of fuel. Therefore, the control method provided by the embodiment further comprises: if entering the LNT regeneration step, then preferentially using main injector 310 to inject fuel, to reduce the probability of fuel being left in pre-chamber 410, and to improve the fuel utilization rate.

[0075] Specifically, the minimum injection pulse width of the main injector 310 is regarded as t1, the minimum injection pulse width of the auxiliary injector 420 is regarded as t2, and the theoretical value of the fuel injection pulse width during the LNT regeneration (i.e., the injection pulse width preset threshold) is regarded as t. When the main injector 310 and the auxiliary injector 420 are selected, t1 > t2 is satisfied. When the LNT regeneration step is entered, fuel is injected using the main injector 310 when t ≥ t1 and fuel is injected using the auxiliary injector 420 when t < t1, so that the use of the main injector 310 for fuel injection is given priority. It should be noted that the theoretical value t of the fuel injection pulse width during the LNT regeneration varies with the engine speed, the load, the intake pressure, or the intake mass flow rate of the engine 100, so in actual applications, a plurality of t values can be obtained through experiments first, and then the plurality of t values are input into the ECU 600 in advance. When the LNT regeneration step is entered, the ECU 600 selects a corresponding t value according to the real-time operating condition of the engine 100, and compares the t value with t1. The experimental method for obtaining the plurality of t values and the method for obtaining the operating condition of the engine 100 by the ECU 600 are both mature prior art in the field, and thus will not be described here.

[0076] It can be understood that in other embodiments, if the engine 100 does not have the pre-chamber 410 and the auxiliary injector 420, the auxiliary fuel supply mechanism 430, the pre-chamber spark plug 440, and the pre-chamber ignition mechanism 450, when the LNT regeneration step is entered, fuel is directly injected using the main injector 310 to achieve the regeneration of the LNT 500 in the exhaust stroke of the engine 100.

[0077] Optionally, during the LNT regeneration, if the carbon-based liquid fuel is injected by the sub-injector 420, the temperature of the fuel injected into the pre-chamber 410 can be low, and the fuel with low temperature cannot achieve good atomization and mixing effect in the pre-chamber 410, and then the regeneration efficiency of the LNT 500 after entering the first exhaust pipe 710 is low. To solve the technical problem, the control method provided in the embodiment further includes: during the LNT regeneration step, if the carbon-based liquid fuel (such as gasoline or kerosene, etc.) is injected by the sub-injector 420, and the actual temperature T in the first exhaust pipe 710 is less than the temperature preset threshold value Td of the first exhaust pipe 710, the pre-chamber ignition mechanism 450 of the pre-chamber 410 is ignited during the exhaust stroke of the engine 100 (before the intake valve of the engine 100 is opened) and after the sub-injector 420 is injected to heat the carbon-based liquid fuel, increase the temperature of the carbon-based liquid fuel, and then improve the atomization and mixing effect, and finally improve the regeneration efficiency of the LNT 500. It should be pointed out that if the sub-injector 420 injects hydrogen or natural gas or other gas fuel, it is not necessary to heat by ignition. It should be pointed out that the above-mentioned temperature preset threshold value Td of the first exhaust pipe 710 is the best temperature value for atomization and mixing of the carbon-based liquid fuel. In actual operation, the Td value corresponding to different carbon-based liquid fuels can be input into the ECU 600 in advance. The Td value of different carbon-based liquid fuels is a relatively well-known parameter in the art, which can be obtained by checking the technical manual, and will not be listed one by one here.

[0078] It should be pointed out that the engine 100 provided in the embodiment can work with single fuel or dual fuel, that is, the fuel injected by the main injector 310 and the fuel injected by the sub-injector 420 can be the same or different, which can be determined according to the actual use.

[0079] The main control method of the vehicle exhaust system provided in the embodiment will be briefly described as follows:

[0080] As shown in Figure 3 After the engine 100 is started, the ECU 600 detects the first NO X concentration sensor 810 and the second NO X concentration sensor 820, and calculates the real-time adsorption rate N of the LNT 500 in real time.

[0081] When N2>Nymin, N and Nq are compared;

[0082] When N2>Nymin and N≤Nq, the LNT regeneration step is entered, and the main injector 310 or the auxiliary injector 420 injects fuel in the exhaust stroke of the engine 100 (before the intake valve of the engine 100 opens) so that the fuel enters the LNT 500 through the first exhaust pipe 710 and reacts with the NOx in the LNT 500 X carries out a catalytic reaction;

[0083] After the LNT regeneration step is entered, it is determined whether to end the LNT regeneration;

[0084] If the LNT regeneration is ended, the fuel injection is stopped;

[0085] The ECU 600 detects whether the engine 100 is shut down, and if the engine 100 is not shut down, the above control steps are repeated, and if the engine 100 is shut down, the control steps are terminated.

[0086] The embodiment also provides a vehicle, which uses the above vehicle exhaust system control method to control the regeneration of the LNT 500. When the LNT 500 needs to be regenerated, the ECU 600 controls the main injector 310 or the auxiliary injector 420 to inject fuel in the exhaust stroke of the engine 100 so that the fuel enters the LNT 500 through the exhaust end of the cylinder and the first exhaust pipe 710 in turn. Since the fuel is injected in the exhaust stroke of the engine 100, the fuel does not participate in combustion work, but is only used to react with the NOx in the LNT 500 X carries out a catalytic reaction to achieve the regeneration of the LNT 500, thereby eliminating the need for the engine 100 of the vehicle to repeatedly switch between the lean combustion mode and the rich combustion mode, effectively improving the fuel economy of the vehicle, and also eliminating the limitation of the control strategy of the engine 100 due to the repeated switching between the lean combustion mode and the rich combustion mode.

[0087] Obviously, the above embodiment of the present application is merely an example for clarity, and is not a limitation on the embodiments of the present application. Those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the scope of the present application. It is not necessary or possible to exhaust all embodiments here. Any modification, equivalent substitution and improvement within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A vehicle exhaust system control method, applied to a vehicle exhaust system, the vehicle exhaust system comprising: An engine (100) includes a cylinder and an injection mechanism for injecting fuel into the cylinder; LNT(500), the LNT(500) has an air inlet and an air outlet, the air inlet is connected to the exhaust end of the cylinder through a first exhaust pipe (710), the first exhaust pipe (710) is provided with a first NO X A concentration sensor (810) is provided, the outlet of which is connected to a second exhaust pipe (720), and the second exhaust pipe (720) is equipped with a second NO concentration sensor. X Concentration sensor (820); ECU (600), the first NO X Concentration sensor (810), second NO X The concentration sensor (820) and the injection mechanism are both communicatively connected to the ECU (600), which is used to determine the concentration of NO based on the first NO concentration. X The detection value of the concentration sensor (810) and the second NO X The detection value of the concentration sensor (820) controls the injection mechanism to inject the fuel during the exhaust stroke of the engine (100); The vehicle exhaust system control method is characterized by comprising: Obtain NO from the first exhaust pipe (710) X Concentration N1 and NO in the second exhaust pipe (720) X Concentration of N2; Determine whether to proceed with the LNT regeneration step; If the LNT regeneration step is initiated, the injection mechanism injects the fuel during the exhaust stroke of the engine (100), causing the fuel to react with the NO in the LNT (500). X To carry out a catalytic reduction reaction; The method for determining whether to proceed to the LNT regeneration step includes: If N2 > Ny and N ≤ Nq, then proceed to the LNT regeneration step; in, Ny is the NO in the second exhaust pipe (720) X Preset concentration threshold; N is the real-time adsorption rate of the LNT(500) calculated according to the preset calculation model; Nq is the first preset threshold for the adsorption rate of the LNT(500); The preset calculation model is N = (N1 - N2) / N1 × 100%; The cylinder includes a main combustion chamber and a pre-combustion chamber (410) connected to each other. The air intake is connected to the exhaust end of the main combustion chamber. The injection mechanism includes a main injector (310) and a secondary injector (420). The main injector (310) is used to inject fuel into the main combustion chamber, and the secondary injector (420) is used to inject fuel into the pre-combustion chamber (410). The vehicle exhaust system control method further includes: If the LNT regeneration step is entered, the main injector (310) is used preferentially to inject fuel; The minimum injection pulse width of the main injector (310) is t1, the minimum injection pulse width of the auxiliary injector (420) is t2, and t1 > t2. When entering the LNT regeneration step, the preset threshold value of the fuel injection pulse width is t. When entering the LNT regeneration step, if t≥t1, then the main injector (310) is used to inject fuel.

2. The vehicle exhaust system control method according to claim 1, characterized in that, After entering the LNT regeneration step, it is determined whether the LNT regeneration step should be ended. If the LNT regeneration step is ended, the injection mechanism stops injecting the fuel. The method for determining whether the LNT regeneration step should be ended includes: If N > Nt, then the LNT regeneration step ends; in, Nt is the second preset threshold for the adsorption rate of the LNT(500), and Nt≥Nq.

3. The vehicle exhaust system control method according to claim 2, characterized in that, The method for determining whether to enter the LNT regeneration step further includes: selecting N2, N and Nq of multiple sampling periods; if N2 in each sampling period is greater than Ny and N in each sampling period is less than or equal to Nq, then the LNT regeneration step is entered. The method for determining whether to end the LNT regeneration step further includes: selecting N and Nt for multiple sampling periods; if N is greater than Nt in each sampling period, then the LNT regeneration step is ended.

4. The vehicle exhaust system control method according to claim 1, characterized in that, When entering the LNT regeneration step, if the auxiliary injector (420) is used to inject carbon-based liquid fuel, and the actual temperature T in the first exhaust pipe (710) is less than the preset temperature threshold Td of the first exhaust pipe (710), then the pre-combustion chamber ignition mechanism (450) of the pre-combustion chamber (410) ignites during the exhaust stroke of the engine (100) and after the auxiliary injector (420) finishes injecting, in order to heat the carbon-based liquid fuel.

5. A vehicle, characterized in that, The vehicle uses the vehicle exhaust system control method as described in any one of claims 1-4 to control the regeneration of LNT (500).

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