Exhaust gas recirculation system, control method thereof and engine

Abstract

The invention relates to the technical field of engines, and discloses an exhaust gas recirculation system, a control method thereof and an engine which are used for improving the exhaust gas inlet capacity. The exhaust gas recirculation system comprises an exhaust gas inlet pipe and a plurality of exhaust gas inlet valves communicating with the exhaust gas inlet pipe. The multiple waste gas inlet valves correspond to the multiple air cylinders one to one, are arranged on cylinder covers of the air cylinders and communicate with the interiors of the air cylinders. The waste gas inlet valve has an open state and a closed state, and when the waste gas inlet valve is in the open state, waste gas in the waste gas inlet pipe and air in an inlet manifold arranged on the cylinder cover synchronously enter the air cylinder through the waste gas inlet valve.

Description

Technical Field

[0001] The present application relates to the field of engine technology, and in particular to an exhaust gas recirculation system and a control method thereof, and an engine. Background Art

[0002] Exhaust Gas Recirculation (EGR) is a technology that sends part of the exhaust gas generated by the engine back to the cylinder for re-combustion, so as to reduce the emission of nitrogen oxides (NOx) in the exhaust gas. Therefore, most engines currently use EGR technology.

[0003] The current EGR technology uses a supercharger to provide a pressure difference before and after EGR to drive the exhaust gas into the engine intake. However, since the supercharger needs to meet the excess air coefficient of each operating condition, it cannot take into account the driving capacity of EGR, and the EGR intake capacity cannot be effectively improved. Summary of the invention

[0004] The present application provides an exhaust gas recirculation system and a control method thereof, and an engine, which are used to improve the exhaust gas intake capacity.

[0005] In a first aspect, the present application provides an exhaust gas recirculation system, which is applied to an engine, wherein the engine comprises a plurality of cylinders; the exhaust gas recirculation system comprises an exhaust gas intake pipe and a plurality of exhaust gas intake valves respectively connected to the exhaust gas intake pipe;

[0006] The plurality of exhaust gas intake valves are arranged in one-to-one correspondence with the plurality of cylinders, the exhaust gas intake valves are arranged on cylinder heads of the cylinders, and the exhaust gas intake valves are communicated 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 arranged in the cylinder head through the exhaust gas intake valve.

[0008] The exhaust gas recirculation system provided by the present application is provided with an exhaust gas intake valve, which is provided on the cylinder head. The exhaust gas intake valve can be opened during the opening of the intake valve, so that the exhaust gas in the exhaust gas intake pipe is sent into the cylinder through the exhaust gas intake valve. When the piston in the cylinder moves downward to achieve the engine intake, the pressure value in the exhaust gas intake pipe is relatively fixed, while the pressure at the exhaust gas intake valve is reduced, so that the intake pressure difference of the exhaust gas intake valve can be increased, and the intake capacity of the exhaust gas can be improved without relying on the supercharging effect of the supercharger, so that the exhaust temperature and nitrogen oxide emissions of the engine can be better controlled.

[0009] In some possible implementation schemes, an exhaust gas flow detection module and a control module are also included, wherein the exhaust gas flow detection module is used to detect the exhaust gas flow in the exhaust gas intake pipe, and the control module is used to control the opening duration of the exhaust gas intake valve according to the information detected by the exhaust gas flow detection module.

[0010] In some possible implementation schemes, an exhaust gas cooler is also included, and the exhaust gas cooler is used to cool the exhaust gas entering the exhaust gas intake pipe.

[0011] In some possible implementation schemes, a pressure sensor and a temperature sensor are further included. 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 implementation schemes, the control module is further used to control the opening duration of the exhaust gas intake valve according to the information monitored by the pressure sensor and the information monitored by the temperature sensor.

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

[0014] In a second aspect, the present application provides a control method for an exhaust gas recirculation system according to any possible implementation scheme in the first aspect, the control method comprising:

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

[0016] Obtaining an actual exhaust gas flow rate in the exhaust gas intake pipe;

[0017] A control module is used to control the opening time of the exhaust gas intake valve according to the required exhaust gas flow rate and the actual exhaust gas flow rate.

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

[0019] Establish the exhaust gas intake valve flow model;

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

[0021] Acquiring the pressure of the exhaust gas after passing through the exhaust gas cooler, acquiring the temperature of the exhaust gas after passing through the exhaust gas cooler, and acquiring the pressure of the intake manifold;

[0022] Substituting the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time;

[0023] The control module is used to process the required exhaust gas flow rate, the actual exhaust gas flow rate and the model exhaust gas intake valve opening time to determine the exhaust gas intake valve opening time.

[0024] In some possible implementation schemes, the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 substituted into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time, including:

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

[0026] calculating the current density of the exhaust gas 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;

[0027] The model exhaust gas intake valve opening time length is determined by using the required exhaust gas flow rate, the pressure of the intake manifold and the ratio of the pressure of the exhaust gas after passing through the exhaust gas cooler, and the density of the current exhaust gas.

[0028] In a third aspect, the present application provides an engine comprising an exhaust gas recirculation system as described in any possible implementation scheme of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a partial structural schematic diagram of an engine in an embodiment of the present application;

[0030] Figure 2 A logic diagram of the control method in the embodiment of the present application;

[0031] Figure 3 This is another logic schematic diagram of the control method in the embodiment of the present application.

[0032] In the figure:

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

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The embodiment of the present application can provide an exhaust gas recirculation system, which is applied to an engine to send part of the exhaust gas generated by combustion back into the cylinder so that the exhaust gas participates in the next combustion.

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

[0037] The cylinder includes a cylinder body and a cylinder head. The interior of the cylinder body is used to provide a space for fuel and air combustion. The exhaust gas intake valve 2 is arranged on the cylinder head, and the exhaust gas intake valve 2 is connected to the interior of the cylinder body. The exhaust gas intake pipe 1 is connected to the exhaust pipe connected to the cylinder, so that a part of the exhaust gas discharged through the exhaust pipe can enter the exhaust gas intake pipe 1, and then the exhaust gas intake pipe 1 is divided to each exhaust gas intake valve 2, and enters the interior of the cylinder body through the exhaust gas intake valve 2.

[0038] like Figure 1 As shown, the engine may further include an intake manifold 4 and multiple intake manifolds 3, and the multiple intake manifolds 3 are respectively connected to the intake manifold 4. The multiple intake manifolds 3 are arranged in a one-to-one correspondence with the multiple cylinders, and each intake manifold 3 is arranged on the cylinder head and is connected to the intake valve connected to the cylinder head, so that the air in the intake manifold 4 passes through the intake manifold 3 and the intake valve and then enters the cylinder body.

[0039] The exhaust gas intake valve 2 in this embodiment 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. In other words, when the exhaust gas intake valve 2 is opened, the intake valve is also in the open state, so that the exhaust gas and the 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] It can be understood that in this embodiment, by providing the exhaust gas intake valve 2, the exhaust gas intake valve 2 is provided on the cylinder head, and the exhaust gas intake valve 2 is opened during the opening of the intake valve. When the piston in the cylinder moves downward to inhale, the intake pressure difference of the exhaust gas intake valve 2 can be increased, and the intake capacity of the exhaust gas can be improved without relying on the supercharging effect of the supercharger, so that the exhaust temperature and the emission of nitrogen oxides of the engine can be better controlled.

[0041] Furthermore, the exhaust gas recirculation system in this embodiment may also include an exhaust gas cooler, which may be disposed, for example, at the inlet of the exhaust gas intake pipe 1, or, for example, the exhaust gas cooler may also be disposed outside the exhaust gas intake pipe 1. Before the exhaust gas in the exhaust pipe flows into the exhaust gas intake pipe 1, the exhaust gas cooler may also cool the exhaust gas, so that the temperature of the exhaust gas is reduced, thereby facilitating the improvement of the combustion effect.

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

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

[0044] In order 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 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 the temperature sensor can be arranged between the exhaust gas cooler and the exhaust gas intake pipe 1. For example, the exhaust gas cooler can be located outside the exhaust gas intake pipe 1, and the pressure sensor and the temperature sensor can be arranged near the intake end of the exhaust gas intake pipe 1, so as to accurately detect the pressure and temperature of the exhaust gas entering the exhaust gas intake pipe 1.

[0045] Since the air pressure and temperature of the exhaust gas in the current exhaust gas intake pipe 1 are detected, 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 time 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 further accurately calculate the opening time of the exhaust gas intake valve 2 in combination with the above-mentioned exhaust gas temperature, exhaust gas pressure and other parameters.

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

[0048] Based on the exhaust gas recirculation system in the above embodiment, reference is also made to Figure 1 and Figure 2 The present application may also provide a control method based on the above exhaust gas recirculation system, and the control method may include the following steps:

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

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

[0051] Step S13: Controlling the opening time of the exhaust gas intake valve 2 according to the required exhaust gas flow rate and the actual exhaust gas flow rate.

[0052] In the above control method, the PID controller can be used to process the required exhaust gas flow rate and the actual exhaust gas flow rate to output an opening duration of the exhaust gas intake valve 2. The opening time of the exhaust gas intake valve 2 is controlled according to the opening duration output by the PID controller, so that the actual exhaust gas flow rate and the required exhaust gas flow rate are equal, thereby meeting the actual exhaust gas flow rate demand and achieving the purpose of improving the exhaust gas intake capacity.

[0053] Since during the control process, only the actual exhaust gas flow rate in the exhaust gas intake pipe 1 needs to be detected, the control process is simple and easy to implement.

[0054] Furthermore, in order to more accurately control the opening time of the exhaust gas intake valve 2, so as to achieve a precise control effect in a short time, 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: establishing an exhaust gas intake valve flow model;

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

[0057] Step S23: obtaining the 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 3;

[0058] Step S2:4: Substitute the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 3 into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time;

[0059] Step S25: using the control module to perform processing on the required exhaust gas flow rate, the actual exhaust gas flow rate and the model exhaust gas intake valve opening time, and determine the opening time of the exhaust gas intake valve 2.

[0060] In the above control method, a waste gas intake valve flow model can be established in advance, and by detecting the pressure, temperature, and air pressure of the waste gas, and then substituting the parameters into the above waste gas intake valve flow model, an opening duration of the waste gas intake valve 2 can be obtained. Since the parameters of the current waste gas and the intake pipe are referenced, when actually controlling the opening duration of the waste gas intake valve 2, more precise control can be performed.

[0061] Specifically, in the above step S24, the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 3 are substituted into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time. For details, refer to the following steps:

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

[0063] Step S32: Calculating the current density of the exhaust gas 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;

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

[0065] In the above step S31, when calculating the pressure ratio, the smaller the pressure ratio is, the greater the pressure difference between the front and the back is, and the shorter the time the exhaust gas intake valve 2 needs to be opened at 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 obtain the model exhaust gas intake valve opening time at the current pressure ratio.

[0067] Alternatively, in step S33, a table may be pre-established, in which different exhaust gas intake valve opening durations may be recorded corresponding to different pressure ratios and required volume flows. Therefore, when obtaining the current exhaust gas density, the required exhaust gas flow rate may be divided by the current exhaust gas density to obtain the required volume flow rate, and then the table may be queried according to the pressure ratio and the required volume flow rate to obtain the corresponding exhaust gas intake valve 2 opening duration. It is worth noting that the exhaust gas intake valve opening duration obtained here is the model exhaust gas intake valve opening duration obtained using the model.

[0068] Finally, by using the model exhaust gas intake valve opening time and adjusting the PID controller, the exhaust gas intake valve 2 opening time can be quickly and accurately controlled to ensure that the actual exhaust gas flow rate is equal to the required exhaust gas flow rate.

[0069] Based on the same inventive concept, the present application may also provide an engine, which may include an exhaust gas recirculation system as described in the above embodiments. Since the exhaust gas recirculation system can improve the exhaust gas intake capacity, it can better control the exhaust temperature and nitrogen oxide emissions of the engine.

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

Claims

1. An exhaust gas recirculation system, applied to an engine, wherein the engine comprises a plurality of cylinders; characterized in that: The exhaust gas recirculation system includes an exhaust gas intake pipe and a plurality of exhaust gas intake valves respectively connected to the exhaust gas intake pipe; The plurality of exhaust gas intake valves are arranged in one-to-one correspondence with the plurality of cylinders, the exhaust gas intake valves are arranged on cylinder heads of the cylinders, and the exhaust gas intake valves are communicated with the interior of the cylinders; 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.

2. The exhaust gas recirculation system according to claim 1, characterized in that: It also includes an exhaust gas flow detection module and a control module, wherein the exhaust gas flow detection module is used to detect the exhaust gas flow in the exhaust gas intake pipe, and the control module is used to control the opening time of the exhaust gas intake valve according to the information detected by the exhaust gas flow detection module.

3. The exhaust gas recirculation system according to claim 2, characterized in that: It also includes an exhaust gas cooler, which is used to cool the exhaust gas entering the exhaust gas intake pipe.

4. The exhaust gas recirculation system according to claim 3, characterized in that: It also includes a pressure sensor and a temperature sensor. 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.

5. The exhaust gas recirculation system according to claim 4, characterized in that: The control module is further used to control the opening duration of the exhaust gas intake valve according to the information monitored by the pressure sensor and the information monitored by the temperature sensor.

6. The exhaust gas recirculation system according to claim 2, characterized in that: The control module includes a PID controller.

7. A control method for an exhaust gas recirculation system according to any one of claims 1 to 6, characterized in that: The control method comprises: determining a required exhaust gas flow rate of the engine; Obtaining an actual exhaust gas flow rate in the exhaust gas intake pipe; A control module is used to control the opening time of the exhaust gas intake valve according to the required exhaust gas flow rate and the actual exhaust gas flow rate.

8. The control method according to claim 7, characterized in that: The control method further comprises: Establish the exhaust gas intake valve flow model; Determine the opening time of the intake valve of the current cylinder; Acquiring the pressure of the exhaust gas after passing through the exhaust gas cooler, acquiring the temperature of the exhaust gas after passing through the exhaust gas cooler, and acquiring the pressure of the intake manifold; Substituting the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time; The control module is used to process the required exhaust gas flow rate, the actual exhaust gas flow rate and the model exhaust gas intake valve opening time to determine the exhaust gas intake valve opening time.

9. The control method according to claim 8, characterized in that: Substituting the required exhaust gas flow rate, the opening time of the intake valve of the current cylinder, 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 into the exhaust gas intake valve flow model to obtain the model exhaust gas intake valve opening time, including: Calculating a ratio of the pressure of the intake manifold to the pressure of the exhaust gas after passing through the exhaust gas cooler; calculating the current density of the exhaust gas 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 model exhaust gas intake valve opening time length is determined by using the required exhaust gas flow rate, the pressure of the intake manifold and the ratio of the pressure of the exhaust gas after passing through the exhaust gas cooler, and the density of the current exhaust gas.

10. An engine, characterized in that: It comprises the exhaust gas recirculation system as claimed in any one of claims 1 to 6.

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