Engine

Abstract

The present invention provides an engine capable of suppressing fluctuations in the composition of EGR gas flowing into an EGR passage. The engine (1) is provided with: a plurality of cylinders (2a, 2b, 2c); exhaust passages (5, 5a) that communicate with the cylinders (2a, 2b, 2c) and through which exhaust gas from the cylinders flows; an engine (1) for recirculating exhaust gas from cylinders (2a, 2b, 2c) to an intake passage on the upstream side of the cylinders (2a, 2b, 2c) is provided with: a diffusion chamber (6) that is connected to exhaust gas passages (5, 5a) and has a diffusion wall (6f) that diffuses the exhaust gas by the exhaust gas injected from the exhaust gas passages (5, 5a) colliding with the diffusion wall (6f), and an EGR passage (9) that recirculates the exhaust gas from the cylinders (2a, 2b, 2c) to the intake passage on the upstream side of the cylinders (2a, 2b, 2c); and a connection passage (7) that connects the diffusion chamber (6) and an exhaust gas purification device (8) that purifies the exhaust gas, and one end of the EGR passage (9) is connected to the connection passage (7).

Description

Technical Field

[0001] The present invention relates to an engine having an EGR passage and an exhaust purification device, wherein the EGR passage recirculates exhaust gas generated by the combustion air-fuel mixture back to the cylinder for combustion of the mixture, and the exhaust purification device purifies the exhaust gas. Background Technology

[0002] Patent Document 1 describes an engine comprising an exhaust manifold that merges exhaust gases from multiple cylinders and an exhaust purification device (catalytic converter) connected to the downstream side of the exhaust manifold. This engine is configured such that, in order to reduce the heat resistance of the oxygen sensor used to detect the oxygen concentration in the exhaust gas within the exhaust manifold, a recessed space is formed on the outer wall of the merging section of the exhaust manifold, and an oxygen sensor is disposed from this recessed space towards the merging section in the exhaust manifold. Furthermore, the engine described in Patent Document 1 includes an EGR passage for recirculating exhaust gas from the exhaust manifold back into the intake passage, one end of which communicates with the recessed space.

[0003] [Existing Technical Documents]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-236053 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] The engine described in Patent Document 1 has an oxygen sensor installed in the recessed space, and the EGR passage is connected to this recessed space, thus enabling proper detection of the oxygen concentration of the EGR gas flowing in the EGR passage. On the other hand, in engines with multiple cylinders, the cylinders that discharge exhaust gas are switched sequentially during operation, so the composition of the exhaust gas may change during the cycle. When the composition of the exhaust gas changes in this way, the oxygen concentration of the EGR gas flowing first in the EGR passage differs from the oxygen concentration of the EGR gas flowing later, so the control of the EGR valve that changes the flow rate of the EGR gas flowing in the EGR passage may become complicated. Alternatively, if the flow rate of the EGR gas cannot be properly controlled, too much EGR gas may be supplied to the cylinder, resulting in misfire, or conversely, insufficient EGR gas may be supplied to the cylinder, failing to suppress the generation of nitrogen oxides (NOx).

[0008] The present invention was conceived in view of the above-mentioned technical problems, and its purpose is to provide an engine capable of suppressing changes in the composition of EGR gas flowing into the EGR passage.

[0009] [Methods used to solve problems]

[0010] To achieve the above objectives, the engine of the present invention comprises: a plurality of cylinders; an exhaust passage communicating with the cylinders for supplying exhaust flow to the cylinders; and an EGR passage for returning the exhaust from the cylinders to an intake passage upstream of the cylinders. The engine is characterized by comprising: a diffuser chamber connected to the exhaust passages and having a diffuser portion, the diffuser portion causing the exhaust to diffuse by colliding with exhaust gas ejected from the exhaust passages; and a connecting passage connecting the diffuser chamber to an exhaust gas purification device for purifying the exhaust gas, one end of the EGR passage being connected to the connecting passage.

[0011] Alternatively, in this invention, the engine may further include: an EGR valve for changing the opening degree of the EGR passage; a sensor for outputting a signal corresponding to the amount of oxygen contained in the exhaust; and a controller for controlling the EGR valve based on the detection value of the sensor, the sensor being disposed in the connection passage.

[0012] Alternatively, in this invention, the diffuser may be formed orthogonally to the streamline of the exhaust gas jetting from the exhaust passage.

[0013] Furthermore, in this invention, the end of the exhaust passage may protrude into the interior of the diffusion chamber.

[0014] [Invention Effects]

[0015] The engine of the present invention includes a diffuser chamber with a diffuser section. The diffuser section diffuses exhaust gas by colliding with exhaust gas ejected from the exhaust passage, thus enabling the exhaust gas discharged from multiple cylinders to diffuse within the diffuser chamber. Therefore, when exhaust gas with different compositions is discharged from each cylinder, or when exhaust gas with different compositions is discharged in each cycle, the composition of the exhaust gas can be averaged by diffusing these exhaust gases within the diffuser chamber. Furthermore, the exhaust gas discharged from the diffuser chamber is discharged to a connecting passage connected to an EGR passage, so the exhaust gas, after being averaged by the diffuser chamber, flows back to the cylinder via the EGR passage. Therefore, deviations in the oxygen concentration, carbon dioxide concentration, and other components of the air-fuel mixture within the cylinder can be suppressed. As a result, the composition of the air-fuel mixture within the cylinder can be appropriately controlled, suppressing misfires caused by low oxygen concentration (high carbon dioxide concentration) or NOx generation caused by high oxygen concentration (low carbon dioxide concentration). Attached Figure Description

[0016] Figure 1 This is a front view schematically illustrating an example of an engine in an embodiment of the present invention.

[0017] Figure 2 These are top views (a) and front views (b) used to illustrate an example of a diffusion chamber.

[0018] Figure 3 These are top views (a) and front views (b) showing an example of an exhaust passage protruding into a diffuser chamber.

[0019] Figure 4 This is a top view showing an example of multiple exhaust passages connected to the diffuser chamber.

[0020] [Explanation of reference numerals in the attached figures]

[0021] 1. Engine

[0022] Cylinders 2, 2a, 2b, and 2c

[0023] 5. Exhaust manifold

[0024] 5a Collection exhaust passage

[0025] 5b, 6c discharge outlets

[0026] 6. Diffusion Chamber

[0027] 6e, 14a, 14b, 14c (Entry point)

[0028] Diffusion sections 6f, 15a, 15b, and 15c

[0029] 7. Connecting Path

[0030] 8. Exhaust gas purification device

[0031] 9 EGR pathway

[0032] 10 EGR valve

[0033] 11 A / F sensor

[0034] 12 controllers

[0035] Exhaust passages 13a, 13b, and 13c Detailed Implementation

[0036] Embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments shown below are merely examples of how the present invention is embodied and do not limit the scope of the invention.

[0037] exist Figure 1 An example of an engine in an embodiment of the present invention is illustrated schematically. Figure 1 The engine 1 shown can be composed of a gasoline engine, a diesel engine, etc., and for example, includes a cylinder block 3 having multiple cylinders 2, a cylinder head 4 located at the upper end of the cylinder block 3, and a crankcase (not shown) connected to the lower end of the cylinder block 3. Figure 1The diagram shows a three-cylinder engine, therefore, three cylinders 2 are formed in the cylinder block 3: a first cylinder 2a, a second cylinder 2b, and a third cylinder 2c.

[0038] It should be noted that the following description will be based on a four-stroke gasoline engine driven by four processes: intake process of introducing fresh air into cylinder 2, compression process of compressing the mixture of fresh air and fuel, combustion process of burning the compressed mixture, and exhaust process of expelling the exhaust gas generated by burning the mixture.

[0039] Each of the aforementioned cylinders 2 is equipped with a piston (not shown) that reciprocates along the axial direction of the cylinder 2, and the piston is connected to a crankshaft (not shown) via a connecting rod (not shown).

[0040] The cylinder head 4 is configured to close the opening on the upper side of the cylinder 2. The cylinder head 4 is provided with an air intake port (not shown) for taking in fresh air into the cylinder 2, an exhaust port (not shown) for expelling exhaust generated in the cylinder 2, and a spark plug (not shown) for igniting the air-fuel mixture in the cylinder 2.

[0041] Additionally, on cylinder head 4, an intake manifold (not shown) is connected to the upstream side of cylinder 2, and an exhaust manifold 5 is connected to the downstream side of cylinder 2. This intake manifold consists of a main intake passage through which external gas flows via an air filter and throttle valve, and multiple intake passages branching off downstream of the main intake passage and connecting to each intake port. Furthermore, the exhaust manifold 5 consists of multiple exhaust passages (not shown) connected to each exhaust port, and a combined exhaust passage 5a connected to these exhaust passages. Figure 1 Only the combined exhaust passage 5a in the exhaust manifold 5 is shown.

[0042] As described above, in an engine 1 having multiple cylinders 2, the timing of exhaust discharge from the first cylinder 2a, the timing of exhaust discharge from the second cylinder 2b, and the timing of exhaust discharge from the third cylinder 2c are staggered.

[0043] Furthermore, the composition of the exhaust gas varies depending on factors such as the oxygen concentration of the air-fuel mixture and the timing of ignition. Therefore, the exhaust gas composition from each cylinder 2 may sometimes differ. In such cases, the composition of the exhaust gas discharged first from the exhaust manifold 5 may differ from the composition of the exhaust gas discharged subsequently.

[0044] Furthermore, because the oxygen concentration of the air-fuel mixture is controlled and the timing of ignition is determined in each cycle, there are cases where the exhaust composition differs in each cycle. In such cases, similarly to the above, the composition of the exhaust gas discharged first from exhaust manifold 5 may differ from the composition of the exhaust gas discharged subsequently.

[0045] As described above, the composition of the exhaust gas discharged from the exhaust manifold 5 changes. Therefore, when controlling the composition of the mixture, such as the oxygen concentration, by recirculating the exhaust gas into the intake passage to mix with the fresh air, there is a possibility that the composition of the mixture cannot be properly controlled due to the change in the composition of the recirculated exhaust gas, or that controlling the flow rate of the recirculated exhaust gas becomes complicated in order to properly control the composition of the mixture.

[0046] Therefore, in Figure 1 In the engine 1 shown, a diffuser chamber 6 is configured to diffuse exhaust gas discharged from the exhaust manifold 5 and connect to the output side of the exhaust manifold 5. Figure 2 The figure shows an example of the structure of the diffusion chamber 6.

[0047] Figure 2 The diffuser chamber 6 shown is configured such that the exhaust gas discharged from the exhaust manifold 5 collides with the inner wall surface of the diffuser chamber 6, thereby causing the exhaust gas to diffuse in three dimensions and temporarily store the exhaust gas, allowing the exhaust gas that first flows into the diffuser chamber 6 to mix with the exhaust gas that subsequently flows into the diffuser chamber 6. Specifically, Figure 2 The diffuser chamber 6 shown is composed of a cylindrical portion 6a, an upper wall surface 6b that hermetically seals the upper end of the cylindrical portion 6a, and a lower wall surface 6d on which an outlet 6c is formed. An exhaust manifold 5 is connected to the side of the cylindrical portion 6a. That is, an intake port 6e for taking in exhaust gas discharged from the exhaust manifold 5 is formed on the side of the cylindrical portion 6a.

[0048] Furthermore, the inner wall surface of the cylindrical portion 6a opposite to the aforementioned inlet 6e, or in other words, opposite to the end of the exhaust collection passage 5a, becomes a diffuser portion 6f, where the exhaust flowing into the diffuser chamber 6 collides with this surface, causing the exhaust to diffuse three-dimensionally. Specifically, the diffuser portion 6f is formed opposite to the end of the exhaust collection passage 5a and is approximately orthogonal to the streamline of the exhaust discharged from the exhaust collection passage 5a. In other words, the angle between the tangent of the diffuser portion 6f and the streamline of the exhaust discharged from the exhaust collection passage 5a is approximately 90 degrees.

[0049] Furthermore, when the exhaust passage 5a is formed as a straight line, the exhaust flow line from the exhaust passage 5a runs along the central axis of the end of the exhaust passage 5a, so the diffuser 6f can be formed orthogonally to the central axis of the exhaust passage 5a. Alternatively, when the exhaust passage 5a is formed as a curve, the exhaust flows along the inner wall surface of the outer periphery of the curve closest to the end of the exhaust passage 5a, so the diffuser 6f can also be formed orthogonally to the axis of the end of the exhaust passage 5a in that inner wall surface.

[0050] Furthermore, a connection passage 7 is connected to the exhaust port 6c in the aforementioned diffusion chamber 6, and the exhaust purification device 8 is connected to the diffusion chamber 6 via this connection passage 7. The exhaust purification device 8 purifies the exhaust by removing carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), or particulate matter (PM) contained in the exhaust. In addition, the exhaust purification device 8 can be configured in the same way as the exhaust purification device installed in conventional vehicles equipped with an engine 1 as the driving power source, and can be composed of a catalytic converter or the like.

[0051] Additionally, an EGR (Exhaust Gas Recirculation) passage 9 is connected downstream (to the exhaust purification device 8) of the connection passage 7 connected to the diffuser chamber 6, for recirculating exhaust gas back to the intake passage such as the intake manifold. Furthermore, an EGR valve 10 is provided in the EGR passage 9 to control the amount of exhaust gas flowing in the EGR passage 9.

[0052] Furthermore, an A / F sensor 11 is provided on the upstream side (diffusion chamber 6 side) of the connection passage 7, which outputs a signal corresponding to the amount of oxygen contained in the exhaust gas flowing in the connection passage 7. The output signal of the A / F sensor 11 is configured to be input to the EGR valve 10, the controller 12 for controlling the fuel injection device, etc.

[0053] Furthermore, like conventional controllers for controlling EGR valves installed in engines, the controller 12 can be configured as an electronic control device based on a microcomputer, and can control the intake air volume, fuel injection volume, or opening degree of EGR valve 10 based on the torque required by engine 1, the speed of engine 1, or signals input from A / F sensor 11.

[0054] In the engine 1 configured as described above, exhaust gas generated by the combustion of the air-fuel mixture in each cylinder 2 is sequentially discharged from each cylinder 2 to the exhaust manifold 5. That is, the composition of the exhaust gas in the exhaust manifold 5 varies according to the composition of the exhaust gas discharged from each cylinder 2. Thus, exhaust gas is sequentially supplied from each cylinder 2 to the exhaust manifold 5, and therefore the exhaust gas in the exhaust manifold 5 is compressed and flows toward the diffuser chamber 6.

[0055] This compressed exhaust gas, such as Figure 2 As indicated by the middle arrow, the jet of air towards the diffuser chamber 6 collides with the diffuser section 6f, which is positioned opposite the end of the exhaust passage 5a. Therefore, as... Figure 2 As shown in (a), the exhaust gas exiting from the combined exhaust passage 5a is dispersed and bounced back in a manner that forms a double vortex on both sides. Additionally, as... Figure 2As shown in (b), the exhaust gas flowing from the collection exhaust passage 5a is dispersed and bounced back in a double vortex formation. As a result, the exhaust gas flowing into the diffuser chamber 6 does not immediately exit from the outlet 6c, but diffuses within the diffuser chamber 6. Consequently, the exhaust gas that first flows into the diffuser chamber 6 and remains there mixes with the exhaust gas that subsequently flows into and diffuses within the diffuser chamber 6. Thus, the exhaust gas flowing sequentially into the diffuser chamber 6 is mixed within the diffuser chamber 6, and its composition is averaged. The averaged exhaust gas then exits from the diffuser chamber 6 into the connecting passage 7.

[0056] It should be noted that, as described above, the diffuser 6 averages the composition of the exhaust gas by temporarily retaining the incoming exhaust gas within the diffuser 6. Therefore, it is preferable to suppress the situation where the exhaust gas that bounces back after colliding with the diffuser 6f is immediately discharged from the outlet 6c. Therefore, the outlet 6c is preferably formed at a position separated from the diffuser 6f by a distance determined through experiments, simulations, etc.

[0057] A portion of the exhaust gas discharged into the connecting passage 7 flows back through the EGR passage 9 to the intake manifold or other intake passages used to supply fresh air to cylinder 2. The remaining exhaust gas flows in the exhaust purification device 8, whereby CO, HC, NOx, or PM contained in the exhaust gas are removed before being discharged to the outside. Furthermore, in the following description, for convenience, the exhaust gas flowing in the EGR passage 9 will be referred to as EGR gas.

[0058] As described above, the EGR passage 9 is connected to the connection passage 7 that connects the diffuser chamber 6 and the exhaust gas purification device 8. Therefore, the exhaust gas, whose composition has been averaged by the diffuser chamber 6, flows back to the cylinder 2 via the EGR passage 9, thus suppressing deviations in the oxygen concentration, carbon dioxide concentration, and other components of the air-fuel mixture in the cylinder 2. As a result, the composition of the air-fuel mixture in the cylinder 2 can be appropriately controlled, suppressing misfires caused by low oxygen concentration (high carbon dioxide concentration) or NOx production caused by high oxygen concentration (low carbon dioxide concentration).

[0059] Furthermore, by installing an A / F sensor 11 in the connection passage 7, the amount of variation in the detection value of the A / F sensor 11 can be reduced. Therefore, it is not necessary to frequently change the opening of the EGR valve 10 used to control the flow rate of EGR gas flowing in the EGR passage 9, or the amount of variation in the opening can be reduced, thus preventing the control of the EGR valve 10 from becoming complicated.

[0060] Furthermore, by connecting the EGR passage 9 upstream of the exhaust purification device 8, the pressure on the upstream side (connection passage 7 side) of the EGR passage 9 can be higher than the pressure on the downstream side (intake passage side) of the EGR passage 9. In other words, the pressure difference required for exhaust gas recirculation can be ensured, allowing the EGR gas to properly recirculate to the intake passage side.

[0061] Furthermore, by placing the A / F sensor 11 in the connection passage 7, the flow rate of exhaust gas flowing near the A / F sensor 11 can be increased, enabling stable sensing using the A / F sensor 11. Additionally, by placing the A / F sensor 11 upstream of the connection point of the EGR passage 9 in the connection passage 7, the A / F sensor 11 can sense the exhaust gas flow rate before it decreases, thus suppressing any decrease in the sensing accuracy of the A / F sensor 11.

[0062] The aforementioned diffuser chamber 6 is configured such that the exhaust gas from the jet collides with the diffuser portion 6f, causing the exhaust gas to diffuse and mix within the diffuser chamber 6. Therefore, it is preferable to suppress the situation where the exhaust gas flows along the inner wall surface of the diffuser chamber 6 due to wall adhesion effects or the like when it flows into the diffuser chamber 6. Therefore, as Figure 3 As shown, the exhaust outlet of the exhaust manifold 5 (combined exhaust passage 5a) can also be configured to protrude into the diffuser chamber 6.

[0063] In this way, by setting the outlet 5b of the exhaust manifold 5 (collecting exhaust passage 5a) to protrude inward into the diffuser chamber 6, exhaust gas can be discharged by jetting. As a result, the energy reduction at the moment of collision between the exhaust gas and the diffuser 6f can be suppressed, and the diffusion efficiency of the exhaust gas can be improved. In addition, by jetting the exhaust gas, the reduction in exhaust gas flow velocity can be suppressed, so that the exhaust gas accumulating near the outlet 5b of the exhaust manifold 5 (collecting exhaust passage 5a) can flow towards the diffuser 6f, thereby improving the diffusion efficiency of the exhaust gas.

[0064] In addition, the engine 1 described above is configured to supply the exhaust gas after it is combined with the exhaust passage 5a through the exhaust manifold 5 to the diffuser chamber 6, but it can also be configured to supply the exhaust gas discharged from each cylinder 2 directly to the diffuser chamber 6. Figure 4 The diagram shows an example of its structure, which includes a first exhaust passage 13a connected to the outlet of the first cylinder 2a, a second exhaust passage 13b connected to the outlet of the second cylinder 2b, and a third exhaust passage 13c connected to the outlet of the third cylinder 2c.

[0065] Furthermore, the diffusion chamber 6 is provided with a first intake 14a for gas to flow in from the first exhaust passage 13a, a second intake 14b for gas to flow in from the second exhaust passage 13b, and a third intake 14c for gas to flow in from the third exhaust passage 13c. Additionally, the inner wall of the diffusion chamber 6 is provided with a first diffusion section 15a that is opposite to the end of the first exhaust passage 13a and orthogonal to the flow line of the gas discharged from the first exhaust passage 13a, a second diffusion section 15b that is opposite to the second exhaust passage 13b and orthogonal to the flow line of the gas discharged from the second exhaust passage 13b, and a third diffusion section 15c that is opposite to the end of the third exhaust passage 13c and orthogonal to the flow line of the gas discharged from the third exhaust passage 13c.

[0066] Even with multiple exhaust passages connected to the diffuser chamber 6, the exhaust gas discharged from each exhaust passage 13a, 13b, and 13c into the diffuser chamber 6 collides with and diffuses into the diffuser sections 15a, 15b, and 15c, respectively. Figure 1 Similarly, the example shown allows for mixing and averaging of exhaust gas composition within the diffuser chamber 6. As a result, deviations in the composition of exhaust gas returning via the EGR passage 9 can be suppressed, thus enabling proper control of the air-fuel mixture composition within cylinder 2. This suppresses misfires caused by low oxygen concentrations (high carbon dioxide concentrations) or NOx generation caused by high oxygen concentrations (low carbon dioxide concentrations).

Claims

1. An engine comprising: a plurality of cylinders; an exhaust passage communicating with the cylinders for supplying exhaust gas flow to the cylinders; and an EGR passage for returning exhaust gas from the cylinders to an intake passage upstream of the cylinders, characterized in that, The engine has the following features: A diffusion chamber, connected to the exhaust passage and having a diffusion section, wherein the exhaust gas is diffused by the collision of the exhaust gas jetting from the exhaust passage with the diffusion section; as well as A connecting passage connects the diffusion chamber to an exhaust gas purification device for purifying exhaust gas. One end of the EGR path is connected to the connection path.

2. The engine according to claim 1, characterized in that, The engine also features: EGR valve, changing the opening degree of the EGR passage; The sensor outputs a signal corresponding to the amount of oxygen contained in the exhaust gas; and The controller controls the EGR valve based on the detection values ​​from the sensor. The sensor is located in the connection path.

3. The engine according to claim 1, characterized in that, The diffuser is formed orthogonally to the streamline of the exhaust gas jetting from the exhaust passage.

4. The engine according to claim 1, characterized in that, The end of the exhaust passage protrudes into the interior of the diffusion chamber.

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