Exhaust gas recirculation system and method of controlling the same, engine

Abstract

The application relates to the engine technical field, discloses a kind of exhaust gas recirculation systems and its control method, engine, for improving exhaust gas intake capacity.Exhaust gas recirculation system includes exhaust gas intake pipe and multiple exhaust gas intake valves respectively communicated with exhaust gas intake pipe.Multiple exhaust gas intake valves are set one by one with multiple cylinders, and exhaust gas intake valve is set in the cylinder head of cylinder, and exhaust gas intake valve is communicated with the inside of cylinder.Exhaust gas intake valve has open state and closed state, when exhaust gas intake valve is in open state, exhaust gas in exhaust gas intake pipe enters cylinder synchronously with air in intake manifold set in cylinder head through exhaust gas intake valve.

Description

Technical Field

[0001] This application relates to the field of engine technology, and in particular to an exhaust gas recirculation system and its control method, and an engine. Background Technology

[0002] Exhaust Gas Recirculation (EGR) is a technology that returns a portion of the exhaust gases produced by the engine to the cylinders for re-combustion, thereby reducing nitrogen oxide (NOx) emissions. Therefore, most engines currently employ EGR technology.

[0003] Current EGR technology uses a turbocharger to provide a pressure difference across the EGR circuit, driving exhaust gases into the engine intake. However, because the turbocharger needs to meet the excess air coefficient for various operating conditions, it cannot simultaneously ensure the driving capability of EGR, thus failing to effectively improve EGR intake capacity. Summary of the Invention

[0004] This application provides an exhaust gas recirculation system and its control method, as well as an engine, for improving exhaust gas intake capacity.

[0005] In a first aspect, this application provides an exhaust gas recirculation system applied to an engine, the engine including multiple cylinders; the exhaust gas recirculation system includes an exhaust gas intake pipe and multiple exhaust gas intake valves respectively connected to the exhaust gas intake pipe;

[0006] The plurality of exhaust gas inlet valves are configured one-to-one with the plurality of cylinders. The exhaust gas inlet valves are located on the cylinder heads of the cylinders and are in communication with the interior of the cylinders.

[0007] The exhaust gas intake valve has an open state and a closed state. When the exhaust gas intake valve is in the open state, the exhaust gas in the exhaust gas intake pipe enters the cylinder synchronously with the air in the intake manifold provided in the cylinder head through the exhaust gas intake valve.

[0008] The exhaust gas recirculation system provided in this application, by setting an exhaust gas intake valve in the cylinder head, allows the exhaust gas in the exhaust intake manifold to be opened during the intake manifold opening process, thus allowing exhaust gas to be sent into the cylinder through the exhaust gas intake valve. When the piston in the cylinder moves downward to achieve engine intake, the pressure value in the exhaust gas intake manifold is relatively fixed, while the pressure at the exhaust gas intake valve decreases. This increases the intake pressure differential at the exhaust gas intake valve, improving the intake capacity of exhaust gas without relying on the boost effect of a turbocharger, thereby better controlling the engine's exhaust temperature and nitrogen oxide emissions.

[0009] In some possible implementations, an exhaust gas flow detection module and a control module are also included. The exhaust gas flow detection module is used to detect the exhaust gas flow rate in the exhaust gas inlet pipe, and the control module is used to control the opening duration of the exhaust gas inlet valve based on the information detected by the exhaust gas flow detection module.

[0010] In some possible implementations, an exhaust gas cooler is also included for cooling the exhaust gas entering the exhaust gas inlet pipe.

[0011] In some possible implementations, a pressure sensor and a temperature sensor are also included, wherein the pressure sensor is used to detect the pressure of the exhaust gas after passing through the exhaust gas cooler, and the temperature sensor is used to detect the temperature of the exhaust gas after passing through the exhaust gas cooler.

[0012] In some possible implementations, the control module is also configured to control the opening duration of the exhaust gas inlet valve based on information monitored by the pressure sensor and information monitored by the temperature sensor.

[0013] In some possible implementations, the control module includes a PID controller.

[0014] Secondly, this application provides a control method for an exhaust gas recirculation system based on any possible embodiment of the first aspect, the control method comprising:

[0015] Determine the required exhaust gas flow rate of the engine;

[0016] Obtain the actual exhaust gas flow rate in the exhaust gas inlet pipe;

[0017] The control module controls the opening duration of the exhaust gas inlet valve based on the required exhaust gas flow rate and the actual exhaust gas flow rate.

[0018] In some possible implementations, the control method further includes:

[0019] Establish an exhaust gas inlet valve flow model;

[0020] Determine the opening time of the intake valve in the current cylinder;

[0021] The pressure of the exhaust gas after passing through the exhaust gas cooler, the temperature of the exhaust gas after passing through the exhaust gas cooler, and the pressure of the intake manifold are obtained.

[0022] Substitute the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, the exhaust gas pressure after passing through the exhaust gas cooler, the exhaust gas temperature after passing through the exhaust gas cooler, and the pressure of the intake manifold into the exhaust gas intake valve flow rate model to obtain the model exhaust gas intake valve opening time.

[0023] The control module processes the required exhaust gas flow rate, the actual exhaust gas flow rate, and the opening duration of the model exhaust gas inlet valve to determine the opening duration of the exhaust gas inlet valve.

[0024] In some possible implementations, the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, the exhaust gas pressure after passing through the exhaust gas cooler, the exhaust gas temperature after passing through the exhaust gas cooler, and the intake manifold pressure are substituted into the exhaust gas intake valve flow rate model to obtain the model exhaust gas intake valve opening duration, including:

[0025] Calculate the ratio of the pressure in the intake manifold to the pressure of the exhaust gas after passing through the exhaust gas cooler;

[0026] The density of the current exhaust gas is calculated based on the gas pressure and temperature of the exhaust gas after passing through the exhaust gas cooler.

[0027] The model exhaust gas inlet valve opening duration is determined using the ratio of the required exhaust gas flow rate, the pressure in the intake manifold, and the pressure of the exhaust gas after passing through the exhaust gas cooler, along with the current exhaust gas density.

[0028] Thirdly, this application provides an engine including an exhaust gas recirculation system as described in any possible embodiment of the first aspect. Attached Figure Description

[0029] Figure 1 This is a partial structural diagram of the engine in an embodiment of this application;

[0030] Figure 2 This is a logical schematic diagram of the control method in an embodiment of this application;

[0031] Figure 3 This is another logical diagram of the control method in the embodiments of this application.

[0032] In the picture:

[0033] 1-Exhaust gas intake pipe; 2-Exhaust gas intake valve; 3-Intake manifold; 4-Intake main pipe. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0035] This application provides an exhaust gas recirculation system applied to an engine to re-introduce a portion of the exhaust gas generated during combustion into the cylinder, allowing the exhaust gas to participate in the next combustion cycle.

[0036] refer to Figure 1 , Figure 1 This is a partial structural diagram of the engine in an embodiment of this application. The exhaust gas recirculation system may include an exhaust gas intake pipe 1 and multiple exhaust gas intake valves 2, each of which is connected to the exhaust gas pipe. The engine may include multiple cylinders, and the multiple exhaust gas intake valves 2 are configured in a one-to-one correspondence with the multiple cylinders; that is, each exhaust gas intake valve 2 is connected to one cylinder.

[0037] The cylinder includes a cylinder block and a cylinder head. The interior of the cylinder block provides space for fuel and air combustion. The exhaust gas intake valve 2 is located on the cylinder head and communicates with the interior of the cylinder block. The exhaust gas intake pipe 1 is connected to the exhaust pipe of the cylinder, so that a portion of the exhaust gas discharged through the exhaust pipe can enter the exhaust gas intake pipe 1, and then be diverted by the exhaust gas intake pipe 1 to each exhaust gas intake valve 2, and enter the interior of the cylinder block through the exhaust gas intake valve 2.

[0038] like Figure 1 As shown, the engine may also include an intake manifold 4 and multiple sets of intake manifolds 3, each of which is connected to the intake manifold 4. Each set of intake manifolds 3 is configured to correspond one-to-one with a plurality of cylinders, and each set of intake manifolds 3 is located on the cylinder head and connected to an intake valve connected to the cylinder head, so that air in the intake manifold 4 enters the cylinder block after passing through the intake manifold 3 and the intake valve.

[0039] In this embodiment, the exhaust gas intake valve 2 has an open state and a closed state. When the exhaust gas intake valve 2 is in the open state, the exhaust gas in the exhaust gas intake pipe 1 can enter the cylinder body through the exhaust gas intake valve 2, and at the same time, the air in the intake manifold 3 also enters the cylinder body synchronously through the intake valve. That is to say, when the exhaust gas intake valve 2 is open, the intake valve is also in the open state, so that the exhaust gas and air can enter the cylinder body synchronously. When the exhaust gas intake valve 2 is in the closed state, the exhaust gas in the exhaust gas intake pipe 1 cannot enter the cylinder body through the exhaust gas intake valve 2.

[0040] Understandably, in this embodiment, by setting the exhaust gas intake valve 2 and placing it in the cylinder head, the exhaust gas intake valve 2 is opened during the opening of the intake valve. When the piston in the cylinder moves downward to draw in air, the intake pressure difference of the exhaust gas intake valve 2 can be increased. Without relying on the supercharging effect of the turbocharger, the intake capacity of the exhaust gas can be improved, thereby enabling better control of the engine's exhaust temperature and nitrogen oxide emissions.

[0041] Furthermore, the exhaust gas recirculation system in this embodiment may also include an exhaust gas cooler, which may be installed, for example, at the inlet of the exhaust gas inlet pipe 1, or, for example, outside the exhaust gas inlet pipe 1. Before the exhaust gas in the exhaust pipe flows into the exhaust gas inlet pipe 1, the exhaust gas cooler can also cool the exhaust gas, thereby reducing the temperature of the exhaust gas and thus improving the combustion efficiency.

[0042] In some embodiments, the exhaust gas recirculation system may further include an exhaust gas flow detection module and a control module. The exhaust gas flow detection module can be used to detect the exhaust gas flow rate in the exhaust gas intake pipe 1. Since the engine requires a certain exhaust gas flow rate under different operating conditions, the control module can compare the detected actual exhaust gas flow rate with the preset required flow rate to control the opening duration of the exhaust gas intake valve 2, thereby controlling the exhaust gas flow rate entering the cylinder. It should be understood that the longer the exhaust gas intake valve 2 is open, the greater the exhaust gas flow rate that the engine can draw in during the intake process.

[0043] The exhaust gas flow detection module can be, for example, a venturi tube, which can accurately detect exhaust gas flow while also simplifying the structure.

[0044] To further improve the precise control of the exhaust gas flow rate entering the cylinder, the exhaust gas recirculation system in this embodiment may also include a pressure sensor and a temperature sensor. The pressure sensor can be used to detect the gas pressure of the exhaust gas after passing through the exhaust gas cooler, and the temperature sensor can be used to detect the temperature of the exhaust gas after passing through the exhaust gas cooler. The pressure sensor and temperature sensor can be disposed between the exhaust gas cooler and the exhaust gas inlet pipe 1. For example, the exhaust gas cooler can be located outside the exhaust gas inlet pipe 1, and the pressure sensor and temperature sensor can be disposed near the inlet end of the exhaust gas inlet pipe 1 to facilitate accurate detection of the pressure and temperature of the exhaust gas entering the exhaust gas inlet pipe 1.

[0045] By detecting the pressure and temperature of the exhaust gas in the current exhaust gas intake pipe 1, the parameters of the current exhaust gas can be calculated more accurately. When the exhaust gas flow is controlled by the control module, the opening duration of the exhaust gas intake valve 2 can be controlled more accurately, thereby achieving fast and accurate control and ensuring the combustion effect of the engine.

[0046] In this embodiment, the control module can also be used to receive the pressure value of the intake manifold 4, and combine it with the above-mentioned parameters such as the temperature and pressure of the exhaust gas to further accurately calculate the opening time of the exhaust gas intake valve 2.

[0047] As an optional implementation, the control module may include a PID (proportion integration differentiation) controller. In this case, when only the actual current exhaust gas flow rate is detected, the PID controller can also control the opening duration of the exhaust gas inlet valve 2 based on two parameters: the required exhaust gas flow rate and the actual non-exhaust gas flow rate. Of course, the more parameters provided, the more accurately the PID controller can control the opening duration of the exhaust gas inlet valve 2, so that the actual exhaust gas flow rate equals the required exhaust gas flow rate.

[0048] Based on the exhaust gas recirculation system in the foregoing embodiments, and also referring to... Figure 1 and Figure 2 This application may also provide a control method based on the above-mentioned waste gas recirculation system, which may include the following steps:

[0049] Step S11: Determine the required exhaust gas flow rate of the engine;

[0050] Step S12: Obtain the actual exhaust gas flow rate in exhaust gas inlet pipe 1;

[0051] Step S13: Control the opening duration of the exhaust gas inlet valve 2 according to the required exhaust gas flow rate and the actual exhaust gas flow rate.

[0052] In the above control method, a PID controller can be used to process the required exhaust gas flow rate and the actual exhaust gas flow rate to output the opening duration of the exhaust gas inlet valve 2. The opening time of the exhaust gas inlet valve 2 is controlled according to the opening duration output by the PID controller, ensuring that the actual exhaust gas flow rate equals the required exhaust gas flow rate, thereby meeting the actual exhaust gas flow rate requirement and improving the exhaust gas intake capacity.

[0053] Since the control process only requires detecting the actual exhaust gas flow rate in the exhaust gas inlet pipe 1, the control process is simple and easy to implement.

[0054] Furthermore, to more precisely control the opening duration of the exhaust gas intake valve 2, and to achieve precise control within a short period of time, the following also refers to... Figure 1 and Figure 3 Based on the above control method, the control method in this embodiment may further include the following steps:

[0055] Step S21: Establish the exhaust gas intake valve flow model;

[0056] Step S22: Determine the opening time of the intake valve of the current cylinder;

[0057] Step S23: Obtain the pressure of the exhaust gas after passing through the exhaust gas cooler, obtain the temperature of the exhaust gas after passing through the exhaust gas cooler, and obtain the pressure of the intake manifold 3.

[0058] Step S2:4: Substitute the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, the exhaust gas pressure after passing through the exhaust gas cooler, the exhaust gas temperature after passing through the exhaust gas cooler, and the pressure of the intake manifold 3 into the exhaust gas intake valve flow rate model to obtain the model exhaust gas intake valve opening time.

[0059] Step S25: Use the control module to monitor the required exhaust gas flow rate, the actual exhaust gas flow rate, and the opening duration of the model exhaust gas inlet valve to determine the opening duration of exhaust gas inlet valve 2.

[0060] In the above control method, an exhaust gas intake valve flow model can be pre-established. By detecting parameters such as exhaust gas pressure, temperature, and air pressure, and then substituting these parameters into the exhaust gas intake valve flow model, the opening duration of exhaust gas intake valve 2 can be obtained. Because the parameters of the current exhaust gas and intake pipe are taken into account, the opening duration of exhaust gas intake valve 2 can be controlled more precisely.

[0061] Specifically, in step S24 above, the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, the exhaust gas pressure after passing through the exhaust gas cooler, the exhaust gas temperature after passing through the exhaust gas cooler, and the pressure of the intake manifold 3 are substituted into the exhaust gas intake valve flow rate model to obtain the model exhaust gas intake valve opening time. The specific steps are as follows:

[0062] Step S31: Calculate the ratio of the pressure in the intake manifold 3 to the pressure of the exhaust gas after passing through the exhaust gas cooler;

[0063] Step S32: Calculate the density of the current exhaust gas based on the gas pressure and temperature of the exhaust gas after passing through the exhaust gas cooler.

[0064] Step S33: Determine the model exhaust gas inlet valve opening time using the ratio of the required exhaust gas flow rate, the pressure of intake manifold 3, and the exhaust gas pressure after passing through the exhaust gas cooler, as well as the current exhaust gas density.

[0065] In step S31 above, when calculating the pressure ratio, the smaller the pressure ratio, the greater the pressure difference before and after, and the shorter the time required for the exhaust gas inlet valve 2 to open under the same flow rate.

[0066] In step S33, when the pressure ratio and the current exhaust gas density are obtained, the pressure ratio, the current exhaust gas density and the required exhaust gas flow rate can be substituted into the formula to determine the model exhaust gas inlet valve opening time under the current pressure ratio.

[0067] Alternatively, in step S33, a table can be pre-established, which records different exhaust gas inlet valve opening durations corresponding to different pressure ratios and required volumetric flow rates. Therefore, when the current exhaust gas density is obtained, the required exhaust gas flow rate can be divided by the current exhaust gas density to obtain the required volumetric flow rate. Then, the table can be consulted based on the pressure ratio and required volumetric flow rate to obtain the corresponding exhaust gas inlet valve 2 opening duration. It is worth noting that the exhaust gas inlet valve opening duration obtained here is the model exhaust gas inlet valve opening duration obtained using the model.

[0068] Finally, by utilizing the opening duration of the model exhaust gas inlet valve, along with adjustments to the PID controller, the opening duration of exhaust gas inlet valve 2 can be quickly and accurately controlled, thereby ensuring that the actual exhaust gas flow rate is equal to the required exhaust gas flow rate.

[0069] Based on the same inventive concept, this application may also provide an engine that may include the exhaust gas recirculation system described in the foregoing embodiments. Because the exhaust gas recirculation system can improve exhaust gas intake capacity, it can better control engine exhaust temperature and nitrogen oxide emissions.

[0070] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. An exhaust gas recirculation system applied to an engine, the engine including a plurality of cylinders; characterized by, The exhaust gas recirculation system comprises an exhaust gas intake pipe and a plurality of exhaust gas intake valves respectively communicating with the exhaust gas intake pipe; The plurality of exhaust gas intake valves are arranged one-to-one with the plurality of cylinders, and the exhaust gas intake valve is arranged on the cylinder head of the cylinder, and the exhaust gas intake valve communicates with the inside of the cylinder; The exhaust gas intake valve has an open state and a closed state, when the exhaust gas intake valve is in the open state, the exhaust gas in the exhaust gas intake pipe enters the cylinder synchronously with the air in the intake manifold arranged in the cylinder head through the exhaust gas intake valve; Further comprising an exhaust gas flow detection module, a pressure sensor, a temperature sensor and a control module, the exhaust gas flow detection module is used for detecting the exhaust gas flow in the exhaust gas intake pipe, the pressure sensor is used for detecting the gas pressure of the exhaust gas after passing through the exhaust gas cooler, the temperature sensor is used for detecting the temperature of the exhaust gas after passing through the exhaust gas cooler, and the control module is used for controlling the opening time of the exhaust gas intake valve according to the information detected by the exhaust gas flow detection module, the information monitored by the pressure sensor and the information monitored by the temperature sensor.

2. The exhaust gas recirculation system of claim 1, wherein, Further comprising an exhaust gas cooler, which is used for cooling and cooling the exhaust gas entering the exhaust gas intake pipe.

3. The exhaust gas recirculation system of claim 1, wherein, The control module comprises a PID controller.

4. A control method for an exhaust gas recirculation system according to any one of claims 1 to 3, characterized by The control method comprises: determining the required exhaust gas flow of the engine; obtaining the actual exhaust gas flow in the exhaust gas intake pipe; controlling the opening time of the exhaust gas intake valve by the control module according to the required exhaust gas flow and the actual exhaust gas flow; The control method further comprises: establishing an exhaust gas intake valve flow model; determining the opening time of the intake valve of the current cylinder; obtaining the gas pressure of the exhaust gas after passing through the exhaust gas cooler, obtaining the temperature of the exhaust gas after passing through the exhaust gas cooler, and obtaining the pressure of the intake manifold; Substitute the required exhaust gas flow, the opening time of the intake valve of the current cylinder, the gas pressure of the exhaust gas after passing through the exhaust gas cooler, the temperature of the exhaust gas after passing through the exhaust gas cooler and the pressure of the intake manifold into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time; Using the control module to process the required exhaust gas flow, the actual exhaust gas flow and the model exhaust gas intake valve opening time to determine the opening time of the exhaust gas intake valve.

5. The control method according to claim 4, characterized by Substitute the required exhaust gas flow, the opening time of the intake valve of the current cylinder, the gas pressure of the exhaust gas after passing through the exhaust gas cooler, the temperature of the exhaust gas after passing through the exhaust gas cooler and the pressure of the intake manifold into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time, comprising: Calculate the ratio of the pressure of the intake manifold and the gas pressure of the exhaust gas after passing through the exhaust gas cooler; According to the gas pressure of the exhaust gas after passing through the exhaust gas cooler and the temperature of the exhaust gas after passing through the exhaust gas cooler, the density of the current exhaust gas is calculated; Using the required exhaust gas flow, the ratio of the pressure of the intake manifold and the gas pressure of the exhaust gas after passing through the exhaust gas cooler and the density of the current exhaust gas to determine the model exhaust gas intake valve opening time.

6. An engine characterized by, An exhaust gas recirculation system comprising the device according to any one of claims 1 to 3.

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