EGR system and vehicle

Abstract

To provide an EGR system capable of suppressing accumulation of PMs and an unburned HC constituent on an inner wall of an EGR cooler, and a vehicle.SOLUTION: An EGR system 12 includes: an EGR flow passage 21 connecting a secondary side and a primary side of an internal combustion engine 11; an EGR cooler 22 that is provided in the EGR flow passage 21 and in which part of exhaust gas of the internal combustion engine 11 flows; a tank 23 connected to the EGR flow passage 21 on the primary side of the EGR cooler 22 and storing compressed air; and a control section 18 that opens a valve 26 when an operating condition of the internal combustion engine 11 is a predetermined operating condition that is an operating condition where a concentration of PMs and / or unburned HC included in exhaust gas of the internal combustion engine 11 increases.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an EGR system and a vehicle that recirculates a portion of the exhaust gas. [Background technology]

[0002] A technology using an EGR (Exhaust Gas Recirculation) system in a vehicle that mixes a portion of exhaust gas emitted from an internal combustion engine with the intake air of the internal combustion engine has been known for some time (see, for example, Patent Document 1). Such an EGR system has an EGR flow path that connects the exhaust side and intake side of the internal combustion engine and an EGR cooler provided in the EGR flow path, and a portion of the burned gas emitted from the combustion chamber of the internal combustion engine flows directly into the EGR flow path and is cooled by the EGR cooler. The EGR system also has an EGR valve that adjusts the exhaust gas mixed with the intake air, and adjusts the mixture ratio of the intake air and the exhaust gas by the opening degree of the EGR valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-031258 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned EGR system, even when high concentrations of PM (Particle Matter) and unburned HC (Hydrocarbon) components are emitted from the combustion chamber, the exhaust gas passes through the EGR cooler as is, causing the PM and unburned HC components to accumulate on the inner walls of the EGR cooler in a short period of time, which causes a problem of accelerating the deterioration of the internal combustion engine and exhaust purification performance.

[0005] Therefore, an object of the present invention is to provide an EGR system and a vehicle that can suppress accumulation of PM and unburned HC components on the inner wall of an EGR cooler. [Means for solving the problem]

[0006] According to one aspect of the present invention, an EGR system includes an EGR flow path connecting the secondary side and primary side of an internal combustion engine, an EGR cooler provided in the EGR flow path and through which a portion of the exhaust gas from the internal combustion engine flows, a tank for storing compressed air connected to the EGR flow path on the primary side of the EGR cooler, a valve provided between the tank and the EGR flow path on the primary side of the EGR cooler, and a control unit that opens the valve when the operating conditions of the internal combustion engine are predetermined operating conditions that result in a high concentration of PM and / or unburned HC contained in the exhaust gas from the internal combustion engine. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an EGR system and a vehicle that can suppress accumulation of PM and unburned HC components on the inner wall of an EGR cooler. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram that schematically shows the configuration of a vehicle according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram that schematically shows the configuration of an internal combustion engine and an EGR system of a vehicle according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing an example of control of the EGR system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle 1 according to one embodiment of the present invention will be described below with reference to Figs. 1 to 3. Fig. 1 is an explanatory diagram that shows a schematic configuration of the vehicle 1. Fig. 2 is an explanatory diagram that shows a schematic configuration of an EGR system 12 used in the vehicle 1. Fig. 3 is a flowchart that shows an example of control of the EGR system 12 of the vehicle 1. Note that in each figure, the configuration is enlarged, reduced, or omitted as appropriate.

[0010] As shown in Figures 1 and 2, vehicle 1 has an internal combustion engine 11 as a power source and an EGR system 12 that recirculates exhaust gas from the internal combustion engine 11. Note that vehicle 1 may be a hybrid electric vehicle (HEV) that is equipped with one or more motors as a power source in addition to the internal combustion engine 11. Vehicle 1 is, for example, a truck. Vehicle 1 is, for example, a flatbed vehicle, a wing vehicle, a covered vehicle, a crane vehicle, an on-board vehicle, a tanker truck, etc. Note that vehicle 1 is not limited to a truck and may be a bus, a passenger car, a special-purpose vehicle, etc.

[0011] As a specific example, vehicle 1 includes an internal combustion engine 11, an EGR system 12, an exhaust gas temperature sensor 13, an exhaust gas pressure sensor 14, an accelerator opening sensor 15, an engine speed sensor 16, a memory unit 17, and a control unit 18. Vehicle 1 also includes a drive shaft, an automatic transmission, a power transmission device, a chassis 19 having four or more wheels, a cabin, a battery, a cooling fan including a heat exchanger, etc. The exhaust gas temperature sensor 13, the exhaust gas pressure sensor 14, the accelerator opening sensor 15, the engine speed sensor 16, and portions of the memory unit 17 and the control unit 18 are included in the configuration of EGR system 12.

[0012] The internal combustion engine 11 is, for example, a diesel engine. In the following description, the "internal combustion engine" may also be referred to as the "engine." The internal combustion engine 11 is, for example, a multi-cylinder engine having a plurality of combustion chambers 11a. The internal combustion engine 11 is connected to a fuel tank. The internal combustion engine 11 is supplied with fuel from the fuel tank and operates to generate power (torque) as a driving force. The internal combustion engine 11 is equipped with an intake manifold 11b that introduces air into each combustion chamber 11a, and an exhaust pipe 11c that joins and exhausts burned gases from each combustion chamber 11a. In addition, for example, the exhaust pipe 11c is provided with an aftertreatment device such as a supplementary catalyst or filter for reducing SOF (Soluble Organic Fraction), particulate matter, and NOx in the exhaust of the internal combustion engine 11, or a urea SCR (Exhaust Gas Recirculation) system.

[0013] The EGR system 12 is a system that recirculates EGR gas, which is part of the exhaust gas from the internal combustion engine 11, and mixes it with intake air to reduce the amount of oxygen in the intake air and lower the combustion temperature in the combustion chamber of the internal combustion engine 11, thereby reducing NOx in the exhaust gas. The EGR system 12 includes an EGR pipe 21, an EGR cooler 22, a compressed air tank 23, a compressor 24, a compressed air pressure sensor 25, and a compressed air valve 26. The EGR system 12 also includes an EGR valve that controls the flow rate of the exhaust gas to be recirculated, and a supply device that supplies a cooling medium such as cooling water or outside air to the EGR cooler 22.

[0014] The EGR pipe 21 is a pipe that constitutes an EGR flow path. The EGR pipe 21, which is an EGR flow path, connects an exhaust pipe 11c, which is an exhaust path on the secondary side of the internal combustion engine 11, to an intake manifold 11b, which is an intake path on the primary side of the internal combustion engine 11. The EGR pipe 21 is connected to the exhaust side of the internal combustion engine 11 on the secondary side of the junction of the exhaust pipes 11c and the internal combustion engine 11 on the primary side of the branching part of the intake manifold 11b.

[0015] The EGR cooler 22 is provided in the EGR pipe 21. The EGR cooler 22 is provided on the EGR flow path formed by the EGR pipe 21, and EGR gas passes through the inside of the EGR cooler 22.

[0016] The compressed air tank 23 stores compressed air. For example, if an air brake is used in the brake system of the vehicle 1, the compressed air tank 23 may also serve as a compressed air tank for driving the air brake, or may be provided separately from the compressed air tank for driving the air brake. The compressed air tank 23 is connected to the EGR pipe 21 on the primary side (upstream side) of the EGR cooler 22. Here, the "primary side" refers to the upstream side in the direction of fluid flow, and the "primary side of the EGR cooler 22" refers to the upstream side in the direction of flow of EGR gas flowing into the EGR cooler 22, in other words, the exhaust pipe 11c side of the EGR cooler 22.

[0017] The compressor 24 compresses the air and supplies it to the compressed air tank 23 .

[0018] The compressed air pressure sensor 25 detects the pressure in the compressed air tank 23 and outputs a signal corresponding to the detected pressure value to the control unit 18 .

[0019] The compressed air valve 26 is an automatic on-off valve whose opening and closing is controlled by the control unit 18. The compressed air valve 26 is, for example, normally closed and is opened under the control of the control unit 18. The compressed air valve 26 is provided between the compressed air tank 23 and the EGR pipe 21 on the primary side (upstream side) of the EGR cooler 22.

[0020] The exhaust temperature sensor 13 detects the temperature of the exhaust gas from the internal combustion engine 11 and outputs a signal corresponding to the detected temperature to the control unit 18. The exhaust temperature sensor 13 is provided, for example, on the secondary side of the junction of the exhaust pipe 11c.

[0021] The exhaust pressure sensor 14 detects the pressure of the exhaust from the internal combustion engine 11 and outputs a signal corresponding to the detected pressure value to the control unit 18. The exhaust pressure sensor 14 is provided, for example, on the secondary side of the junction of the exhaust pipe 11c.

[0022] The accelerator opening sensor 15 detects the opening of the accelerator and outputs a signal corresponding to the opening to the control unit 18. The accelerator opening sensor 15 is a position sensor that detects the position of the accelerator.

[0023] The rotation speed sensor 16 detects the rotation speed (engine rotation speed) of the internal combustion engine 11, and outputs a signal corresponding to the detected rotation speed to the control unit .

[0024] The memory unit 17 is a storage medium. The memory unit 17 is a memory device such as a read-only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a solid state drive (SSD), or an integrated circuit storage device that stores various data. The memory unit 17 may be physically implemented as a single memory device or as multiple physically separated memory devices. The memory unit 17 stores various control setting values ​​and various control programs for controlling the vehicle 1. The memory unit 17 also stores information detected by various sensors, including the exhaust temperature sensor 13, the exhaust pressure sensor 14, the accelerator position sensor 15, the rotation speed sensor 16, and the compressed air pressure sensor 25. The memory unit 17 includes a database 17a that stores an exhaust temperature score Se indicating the degree of influence of the exhaust temperature on PM emissions, an accelerator position score Sl indicating the degree of influence of the accelerator position on PM emissions, and an engine rotation speed score Sr indicating the degree of influence of the engine rotation speed on PM emissions.

[0025] The storage unit 17 stores a program for acquiring a total score Sc (first total score) based on the various scores stored in the database 17a and the driving conditions of the vehicle 1 detected by the exhaust temperature sensor 13, the accelerator opening sensor 15, and the rotation speed sensor 16, a program for acquiring a total score St from the sum of the differences between the first total score (total score Sc) and multiple total scores Sc (second total scores) for the past k steps acquired before the first total score using the k-nearest neighbor method, and a program for determining from the total score St whether the driving conditions are such that EGR gas, which is part of the exhaust gas flowing through the EGR cooler 22, may cause deterioration of the EGR cooler 22. For example, an example of a formula for calculating the total score Sc is

[0026]

number

[0027] An example of the formula for calculating the total score Sti at step i is:

[0028]

number

[0029] Here, the total score Sti is the total score for the past k steps.

[0030] Furthermore, the memory unit 17 stores a preset threshold value to be compared with the sum score St in order to determine whether or not the operating conditions are likely to cause deterioration of the EGR cooler 22. Here, the operating conditions that are likely to cause deterioration of the EGR cooler 22 refer to operating conditions (predetermined conditions) in which PM and / or unburned HC in the exhaust gas of the internal combustion engine 11 are at or above a predetermined concentration, i.e., are at a high concentration, and therefore there is a high risk that components such as PM will move toward and accumulate on the inner wall of the EGR cooler 22, which is at a relatively low temperature, due to reduced thermophoresis and diffusion of substances.

[0031] The control unit 18 is a computing device. The control unit 18 is, for example, an ECU (Electronic Control Unit). The control unit 18 controls at least one of various electrical components, such as chassis control, motor control, headlight control, air conditioning system control, fuel cell system control, brake system control, lane keeping system control, inter-vehicle distance control system control, and car navigation system control. Various sensors, including an exhaust temperature sensor 13, an exhaust pressure sensor 14, an accelerator opening sensor 15, an RPM sensor 16, and a compressed air pressure sensor 25, are connected to the control unit 18, and output signals from these various sensors are input to the control unit 18. The control unit 18 is connected to the internal combustion engine 11, the compressor 24, etc., and controls these components.

[0032] The control unit 18 includes, for example, a score calculation unit and a supply determination unit as software configurations. The score calculation unit calculates a comprehensive score Sc and a total score St based on the exhaust temperature, accelerator opening, and engine speed obtained from the exhaust temperature sensor 13, accelerator opening sensor 15, and engine speed sensor 16. Furthermore, the supply determination unit determines whether to supply compressed air to the EGR gas flowing into the EGR cooler 22 when the obtained total score St exceeds a threshold value.

[0033] For example, when the supply determination unit determines to supply compressed air to the EGR cooler 22, the control unit 18 opens the compressed air valve 26 to supply the compressed air to the EGR cooler 22. Also, for example, when the supply determination unit determines to supply compressed air to the EGR cooler 22, the control unit 18 compares the pressure value detected by the exhaust pressure sensor 14 (exhaust pressure P1) with the pressure value detected by the compressed air pressure sensor 25 (compressed air pressure P2), and does not open the compressed air valve 26 if the exhaust pressure P1 is higher than the compressed air pressure P2.

[0034] Next, an example of a method for controlling the EGR system 12 of the vehicle 1 configured as above will be described with reference to the flowchart of FIG.

[0035] First, while vehicle 1 is traveling, control unit 18 calculates a total score Sc from exhaust temperature score Se, accelerator opening score Sl, and engine rotation speed score Sr (step ST1). As a specific example, control unit 18 calculates exhaust temperature, accelerator opening, and engine rotation speed from signals acquired from exhaust temperature sensor 13, accelerator opening sensor 15, and rotation speed sensor 16 at regular intervals. Control unit 18 then uses the calculated values ​​of exhaust temperature, accelerator opening, and engine rotation speed as input information, and, based on this input information, refers to database 17a to acquire a total score Sc of the corresponding exhaust temperature score Se, accelerator opening score Sl, and engine rotation speed score Sr at regular intervals. Control unit 18 stores the total score Sc acquired at regular intervals in memory unit 17.

[0036] Next, the control unit 18 calculates a total score St from the overall scores Sc for the past k steps (step ST2). The control unit 18 compares the calculated total score St with a threshold value stored in the memory unit 17, and determines whether the total score St exceeds the threshold value (step ST3). If the total score St does not exceed the threshold value (NO in step ST3), the control unit 18 determines that the operating situation is not one in which deterioration of the EGR cooler 22 is likely to progress, and returns to step ST1, where the control unit 18 calculates the total score Sc and the total score St at regular time intervals.

[0037] If the sum score St exceeds the threshold value (YES in step ST3), the control unit 18 determines that the operating conditions are such that deterioration of the EGR cooler 22 may progress. Next, the control unit 18 detects the exhaust pressure P1 and the compressed air pressure P2 from the output signals of the exhaust pressure sensor 14 and the compressed air pressure sensor 25 (steps ST4 and ST5). The control unit 18 compares the detected exhaust pressure P1 and the compressed air pressure P2, and determines whether the exhaust pressure P1 is lower than the compressed air pressure P2 (step ST6).

[0038] If the exhaust pressure P1 is lower than the compressed air pressure P2 (YES in step ST6), the control unit 18 opens the closed compressed air valve 26 (step ST7). When the compressed air valve 26 opens, compressed air that joins the EGR gas from the internal combustion engine 11 is supplied to the EGR pipe 21 on the primary side (upstream side) of the EGR cooler 22, causing the EGR gas flowing into the EGR cooler 22 to mix with the compressed air. This reduces the temperature of the EGR gas flowing into the EGR cooler 22. Therefore, even in an operating condition that may cause deterioration of the EGR cooler 22, the difference between the temperature of the inner wall of the EGR cooler 22 and the temperature of the exhaust gas is reduced, and components such as PM are prevented from moving toward the inner wall of the EGR cooler 22 and accumulating therein. After opening the compressed air valve 26, for example, the control unit 18 returns to step ST1 and keeps the compressed air valve 26 open until the total score St becomes lower than the threshold value, and closes the compressed air valve 26 when the total score St becomes higher than the threshold value.

[0039] If the exhaust pressure P1 is equal to or higher than the compressed air pressure P2 (NO in step ST6), there is a risk that EGR gas will flow into the compressed air tank 23 if the compressed air valve 26 is opened, and the control unit 18 drives the compressor 24 while keeping the compressed air valve 26 closed to increase the pressure in the compressed air tank 23. Then, the control unit 18 returns to step ST4 and performs the following steps.

[0040] The EGR system 12 and vehicle 1 configured as described above use the memory unit 17 and the control unit 18 to construct a control algorithm using the k-nearest neighbor algorithm. The control algorithm determines whether the driving conditions are likely to cause deterioration of the EGR cooler 22 from the total score St based on the exhaust gas temperature, accelerator position, and engine speed. The EGR system 12 also opens the compressed air valve 26 to supply compressed air to the EGR gas when the driving conditions are likely to cause deterioration of the EGR cooler 22. This allows the EGR system 12 to reduce the concentration of PM and other contaminants in the EGR gas and lower the temperature of the EGR gas flowing into the EGR cooler 22. This allows the EGR system 12 to prevent PM and other contaminants from migrating toward the inner wall of the EGR cooler 22 and accumulating thereon. Therefore, the EGR system 12 slows down the deterioration of engine performance and exhaust purification performance, and makes it possible to achieve a longer life for the EGR flow path through which EGR gas passes, such as the EGR pipe 21 and the EGR cooler 22, and the intake parts provided on the secondary side of the EGR system 12, i.e., the intake side of the internal combustion engine 11.

[0041] Furthermore, mixing compressed air with EGR gas reduces the temperature of the EGR gas that passes through the EGR cooler 22 and is supplied to the intake air, thereby enabling the size of the EGR cooler 22 to be reduced. This contributes to weight reduction and cost reduction of the EGR system 12 and the vehicle 1. Furthermore, the EGR system 12 scores the driving conditions by correlating the driving conditions with the PM concentration, HC emissions, and other factors using a control algorithm using k-nearest neighbors, and can appropriately mix compressed air with the EGR gas when emissions of components such as PM and HC increase. Therefore, the EGR system 12 can reduce the amount of compressed air charged into the compressed air tank 23 and suppress energy loss due to driving the compressor 24. Furthermore, the EGR system 12 determines whether the driving conditions are likely to cause deterioration of the EGR cooler 22 based on the total score St calculated from the overall score Sc over the past k steps, thereby preventing excessive opening and closing of the compressed air valve 26.

[0042] Furthermore, the various sensors used in the EGR system 12, such as the exhaust temperature sensor 13, exhaust pressure sensor 14, accelerator position sensor 15, rotation speed sensor 16, and compressed air pressure sensor 25, are common sensors that have also been installed in conventional vehicles. Therefore, there is no need to introduce additional sensors to control the EGR system 12. Furthermore, among conventional vehicles, large commercial vehicles employ air brakes that use compressed air for braking, etc., and therefore are equipped with a compressed air tank 23. Therefore, the additional parts required to supply compressed air to the EGR gas are small parts such as piping and compressed air valve 26, and no additional large parts are installed. Therefore, the EGR system 12 can suppress increases in cost and does not involve a reduction in design freedom or an increase in weight.

[0043] As described above, with the EGR system 12 and vehicle 1 according to the embodiment, under operating conditions in which the internal combustion engine 11 emits PM and unburned HC at a predetermined concentration or higher, compressed air is supplied to the EGR gas, which is part of the exhaust gas flowing into the EGR cooler 22, thereby making it possible to suppress the accumulation of PM and unburned HC components on the inner walls of the EGR cooler.

[0044] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0045] 1...vehicle, 11...internal combustion engine, 11a...combustion chamber, 11b...intake manifold, 11c...exhaust pipe, 12...EGR system, 13...exhaust temperature sensor, 14...exhaust pressure sensor, 15...accelerator opening sensor, 16...rotation speed sensor, 17...memory unit, 17a...database, 18...control unit, 19...chassis, 21...EGR pipe (EGR flow path), 22...EGR cooler, 23...compressed air tank, 24...compressor, 25...compressed air pressure sensor, 26...compressed air valve.

Claims

1. an EGR flow path connecting a secondary side and a primary side of the internal combustion engine; an EGR cooler provided in the EGR flow path through which a portion of the exhaust gas from the internal combustion engine flows; a tank for storing compressed air, the tank being connected to the EGR flow path on the primary side of the EGR cooler; a valve provided between the tank and the EGR flow path on a primary side of the EGR cooler; a control unit that opens the valve when the operating condition of the internal combustion engine is a predetermined operating condition that increases the concentration of PM and / or unburned HC contained in the exhaust gas of the internal combustion engine; An EGR system comprising:

2. 2. The EGR system according to claim 1, wherein the control unit determines whether the operating conditions of the internal combustion engine satisfy the predetermined conditions based on input information such as an exhaust gas temperature, an accelerator opening, and an engine speed.

3. a memory unit that stores an exhaust temperature score indicating the degree of influence of the exhaust temperature on the amount of PM emissions, an accelerator opening score indicating the degree of influence of the accelerator opening on the amount of PM emissions, and an engine rotation speed score indicating the degree of influence of the engine rotation speed on the amount of PM emissions; The control unit At regular intervals, a total score of the corresponding exhaust temperature score, the accelerator opening score, and the engine rotation speed score is obtained based on the input information; opening the valve when a sum of differences between a first total score and each of a plurality of second total scores obtained before the first total score exceeds a threshold value; The EGR system of claim 2 .

4. an internal combustion engine; The EGR system according to any one of claims 1 to 3; A vehicle equipped with:

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