engine

Abstract

To provide an engine suppressing variation of components of EGR gas flowing into an EGR passage.SOLUTION: An engine 1 includes: a plurality of cylinders 2a, 2b, 2c; exhaust air passages 5, 5a which are communicated with the cylinders 2a, 2b, 2c and through which exhaust gas in the cylinders flows; an EGR passage 9 reflowing the exhaust gas in the cylinders 2a, 2b, 2c to an intake passage on the upstream side of the cylinders 2a, 2b, 2c; a diffusion chamber 6 to which the exhaust gas passages 5, 5a are connected and which has a diffusion wall 6f diffusing the exhaust gas by crash of the exhaust gas jetted from the exhaust gas passages 5, 5a; and a connector passage 7 connecting the diffusion chamber 6 and an exhaust gas purifying device 8 purifying the exhaust gas. One edge part of the EGR passage 9 is connected to the connector passage 7.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an engine equipped with an EGR passage that returns exhaust gas generated by burning a mixture of air and fuel to a cylinder that burns the mixture, and an exhaust gas purification device that purifies the exhaust gas. [Background technology]

[0002] Patent Document 1 describes an engine equipped with an exhaust manifold that combines exhaust gases discharged from multiple cylinders and an exhaust purification device (catalytic converter) connected downstream of the exhaust manifold. This engine is configured such that a recessed, concave space is formed in the outer wall surface of the exhaust manifold at the junction to reduce the heat resistance of an oxygen sensor that detects the oxygen concentration of the exhaust gas in the exhaust manifold, and the oxygen sensor is provided facing the junction in the exhaust manifold from the recessed space. The engine described in Patent Document 1 is also provided with an EGR passage for returning exhaust gas in the exhaust manifold to the intake passage, and one end of the EGR passage is connected to the recessed space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-236053 Summary of the Invention [Problem to be solved by the invention]

[0004] The engine described in Patent Document 1 has an oxygen sensor installed in a recessed space, and the recessed space is connected to an EGR passage, allowing it to properly detect the oxygen concentration of the EGR gas flowing through the EGR passage. On the other hand, in an engine with multiple cylinders, the cylinders that emit exhaust gas are switched sequentially during operation, which can cause the exhaust gas components to fluctuate between cycles. When the exhaust gas components fluctuate in this way, the oxygen concentration of the EGR gas flowing first through the EGR passage differs from the oxygen concentration of the EGR gas flowing second through the EGR passage, which can complicate control of the EGR valve that controls the flow rate of EGR gas flowing through the EGR passage. Alternatively, if the EGR gas flow rate cannot be properly controlled, excessive EGR gas may be supplied to the cylinder, causing a misfire. Conversely, insufficient EGR gas may be supplied to the cylinder, making it impossible to suppress the generation of nitrogen oxides (NOx).

[0005] The present invention has been devised in view of the above technical problems, and has as its object to provide an engine that can suppress fluctuations in the components of EGR gas flowing into the EGR passage. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides an engine having a plurality of cylinders, an exhaust passage communicating with the cylinders and through which the exhaust gas from the cylinders flows, and an EGR passage for returning the exhaust gas from the cylinders to an intake passage upstream of the cylinders, the engine further comprising: a diffusion chamber to which the exhaust passages are connected and which has a diffusion section that diffuses the exhaust gas when exhaust gas jetted from the exhaust passage collides with the diffusion chamber; and a connector passage connecting the diffusion chamber to an exhaust purification device that purifies the exhaust gas, wherein one end of the EGR passage is connected to the connector passage.

[0007] In addition, the present invention may further include an EGR valve that changes the opening of the EGR passage, a sensor that outputs a signal corresponding to the amount of oxygen contained in the exhaust gas, and a controller that controls the EGR valve based on the detection value of the sensor, and the sensor may be provided in the connector passage.

[0008] In the present invention, the diffusion portion may be formed perpendicular to a streamline of the exhaust gas jetted out from the exhaust passage.

[0009] In the present invention, an end of the exhaust passage may protrude into the diffusion chamber. [Effects of the Invention]

[0010] The engine of this invention includes a diffusion chamber with a diffusion section that diffuses exhaust gases by collision with the exhaust gases jetted from the exhaust passage. This allows exhaust gases discharged from multiple cylinders to be diffused within the diffusion chamber. Therefore, even if different exhaust gases with different components are discharged from each cylinder or different exhaust gases are discharged from each cycle, the exhaust gases can be diffused within the diffusion chamber to average their components. The exhaust gases discharged from the diffusion chamber are then discharged into a connector passage connected to an EGR passage. The exhaust gases, the components of which have been averaged by the diffusion chamber, are then returned to the cylinders via the EGR passage. This reduces variations in the oxygen and carbon dioxide concentrations of the air-fuel mixture within the cylinders. As a result, the air-fuel mixture components within the cylinders can be appropriately controlled, preventing misfires due to low oxygen concentrations (high carbon dioxide concentrations) and NOx emissions due to high oxygen concentrations (low carbon dioxide concentrations). [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a front view schematically showing an example of an engine according to an embodiment of the present invention. [Figure 2] 1A is a plan view illustrating an example of a diffusion chamber, and FIG. 1B is a front view illustrating the diffusion chamber. [Figure 3] 10A and 10B are a plan view and a front view showing an example in which the end of a collective exhaust passage protrudes into a diffusion chamber. [Figure 4] FIG. 10 is a plan view showing an example in which a plurality of exhaust passages are connected to a diffusion chamber. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0013] An example of an engine according to an embodiment of the present invention is shown schematically in Figure 1. The engine 1 shown in Figure 1 can be a gasoline engine, a diesel engine, or the like, and includes, for example, a cylinder block 3 in which a plurality of cylinders 2 are formed, a cylinder head 4 provided 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 1 shows a three-cylinder engine, and therefore the cylinder block 3 has three cylinders 2: a first cylinder 2a, a second cylinder 2b, and a third cylinder 2c.

[0014] In the following explanation, we will use as an example a four-stroke gasoline engine that operates by performing four processes: an intake process in which fresh air is taken into cylinder 2; a compression process in which a mixture of fresh air and fuel is compressed; a combustion process in which the compressed mixture is burned; and an exhaust process in which exhaust gas generated by the combustion of the mixture is discharged.

[0015] Each of the cylinders 2 is provided with a piston (not shown) that reciprocates in the axial direction of the cylinder 2, and the piston is connected to a crankshaft (not shown) via a connecting rod (not shown).

[0016] The cylinder head 4 is configured to close the opening on the upper side of the cylinder 2, and is provided with an intake port (not shown) that takes in fresh air into the cylinder 2, an exhaust port (not shown) that discharges exhaust gas generated in the cylinder 2, and a spark plug (not shown) that ignites the mixture of air and fuel in the cylinder 2.

[0017] An intake manifold (not shown) is connected to the cylinder head 4 on the upstream side of the cylinder 2, and an exhaust manifold 5 is connected to the downstream side of the cylinder 2. This intake manifold is made up of a main intake passage through which outside air flows via an air cleaner and a throttle valve, and multiple intake passages that branch off from the downstream side of the main intake passage and are connected to each intake port. The exhaust manifold 5 is made up of multiple exhaust passages (not shown) connected to each exhaust port, and a collective exhaust passage 5a to which these exhaust passages are connected. Only the collective exhaust passage 5a of the exhaust manifold 5 is shown in Figure 1.

[0018] As described above, in an engine 1 equipped with multiple cylinders 2, the timing at which exhaust gas is discharged from the first cylinder 2a, the timing at which exhaust gas is discharged from the second cylinder 2b, and the timing at which exhaust gas is discharged from the third cylinder 2c are offset.

[0019] Furthermore, since the components of the exhaust gas generated vary depending on the oxygen concentration of the air-fuel mixture, the timing of ignition of the air-fuel mixture, and other factors, different exhaust gas components may be discharged from each cylinder 2. In such cases, the components of the exhaust gas discharged first from the exhaust manifold 5 may differ from the components of the exhaust gas discharged subsequently.

[0020] Furthermore, because the oxygen concentration of the air-fuel mixture and the timing of ignition of the air-fuel mixture are controlled for each cycle, the exhaust components discharged from each cycle may differ. In such a case, similar to the above, the components of the exhaust discharged first from the exhaust manifold 5 may differ from the components of the exhaust discharged subsequently.

[0021] As described above, the exhaust components discharged from the exhaust manifold 5 fluctuate. Therefore, when controlling components such as the oxygen concentration of the mixture by recirculating the exhaust gas into the intake passage and mixing it with fresh air, the fluctuations in the components of the recirculated exhaust gas may make it impossible to appropriately control the components of the mixture, or may make it difficult to control the flow rate of the recirculated exhaust gas in order to appropriately control the components of the mixture.

[0022] For this reason, in the engine 1 shown in Fig. 1, a diffusion chamber 6 configured to diffuse the exhaust gas discharged from the exhaust manifold 5 is connected to the output side of the exhaust manifold 5. Fig. 2 shows a diagram for explaining an example of the configuration of the diffusion chamber 6.

[0023] The diffusion chamber 6 shown in Fig. 2 is configured so that exhaust gas discharged from the exhaust manifold 5 collides with the inner wall surface of the diffusion chamber 6, thereby diffusing the exhaust gas three-dimensionally and temporarily storing the exhaust gas, thereby mixing the exhaust gas that previously flowed into the diffusion chamber 6 with the exhaust gas that subsequently flows into the diffusion chamber 6. Specifically, the diffusion chamber 6 shown in Fig. 2 is configured with a cylindrical portion 6a, an upper wall surface 6b that airtightly closes the upper end of the cylindrical portion 6a, and a lower wall surface 6d in which an exhaust port 6c is formed, and the exhaust manifold 5 is connected to the side surface of the cylindrical portion 6a. That is, an intake port 6e for taking in the exhaust gas discharged from the exhaust manifold 5 is formed in the side surface of the cylindrical portion 6a.

[0024] Furthermore, the surface of the inner wall of the cylindrical portion 6a facing the intake port 6e, in other words, the surface facing the end of the collective exhaust passage 5a, serves as a diffusion portion 6f where the exhaust gas flowing into the diffusion chamber 6 collides and diffuses it three-dimensionally. Specifically, the diffusion portion 6f faces the end of the collective exhaust passage 5a and is formed so as to be approximately perpendicular to the streamline of the exhaust gas discharged from the collective exhaust passage 5a. In other words, the angle between the tangent to the diffusion portion 6f and the streamline of the exhaust gas discharged from the collective exhaust passage 5a is approximately 90 degrees.

[0025] If the collecting exhaust passage 5a is formed in a straight line, the flow line of the exhaust gas discharged from the collecting exhaust passage 5a will follow the central axis of the end of the collecting exhaust passage 5a, so the diffusion section 6f may be formed perpendicular to the central axis of the collecting exhaust passage 5a. If the collecting exhaust passage 5a is formed in a curved shape, the exhaust gas will flow along the inner wall surface on the outer periphery of the bent section closest to the end of the collecting exhaust passage 5a, so the diffusion section 6f may be formed on that inner wall surface perpendicular to the axis at the position of the end of the collecting exhaust passage 5a.

[0026] A connector passage 7 is connected to the outlet 6c of the diffusion chamber 6, and an exhaust purification device 8 that purifies the exhaust by removing carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), or particulate matter (PM) contained in the exhaust is connected to the diffusion chamber 6 via the connector passage 7. The exhaust purification device 8 can be configured in the same way as an exhaust purification device provided in a conventional vehicle that has the engine 1 as a driving force source, and can be configured using a catalytic converter or the like.

[0027] An EGR (Exhaust Gas Recirculation) passage 9 for recirculating exhaust gas to an intake passage such as an intake manifold is connected to the downstream side (exhaust gas purification device 8 side) of the connector passage 7 connected to the diffusion chamber 6. An EGR valve 10 for controlling the amount of exhaust gas flowing through the EGR passage 9 is provided in the EGR passage 9.

[0028] Furthermore, an A / F sensor 11 is provided on the upstream side (diffusion chamber 6 side) of the connector passage 7, and outputs a signal corresponding to the amount of oxygen contained in the exhaust gas flowing through the connector passage 7. The output signal of the A / F sensor 11 is input to a controller 12 for controlling an EGR valve 10, a fuel injection device, etc.

[0029] The controller 12 can be configured as an electronic control device mainly including a microcomputer, similar to a controller for controlling an EGR valve provided in a conventional engine, and is configured to control the intake air amount, fuel injection amount, or opening degree of the EGR valve 10 based on the torque required for the engine 1, the engine speed of the engine 1, or a signal input from the A / F sensor 11.

[0030] In the engine 1 configured as described above, exhaust gas generated by burning the air-fuel mixture in each cylinder 2 is discharged sequentially from each cylinder 2 into the exhaust manifold 5. That is, the components of the exhaust gas in the exhaust manifold 5 vary depending on the components of the exhaust gas discharged from each cylinder 2. As exhaust gas is sequentially supplied to the exhaust manifold 5 from each cylinder 2 in this manner, the exhaust gas in the exhaust manifold 5 is pressure-fed and flows toward the diffusion chamber 6.

[0031] The exhaust gas thus pumped is jetted into the diffusion chamber 6 as shown by the arrows in FIG. 2 and collides with the diffusion section 6f, which is provided opposite the end of the collecting exhaust passage 5a. As a result, the exhaust gas bounces off, forming twin vortices on both sides of the exhaust gas flow path discharged from the collecting exhaust passage 5a, as shown in FIG. 2(a). Also, as shown in FIG. 2(b), the exhaust gas bounces off, forming twin vortices above and below the exhaust gas flow path discharged from the collecting exhaust passage 5a. As a result, the exhaust gas flowing into the diffusion chamber 6 is not immediately discharged from the exhaust port 6c but is diffused within the diffusion chamber 6. As a result, the exhaust gases flowing into the diffusion chamber 6 sequentially are mixed within the diffusion chamber 6, and the components of the exhaust gases are averaged. The averaged components of the exhaust gas are then discharged from the diffusion chamber 6 to the connector passage 7.

[0032] As described above, the diffusion chamber 6 temporarily retains the exhaust gas that flows in, thereby averaging the components of the exhaust gas within the diffusion chamber 6. Therefore, it is preferable to prevent the exhaust gas that collides with the diffusion section 6f and bounces back from being immediately discharged from the discharge port 6c. Therefore, it is preferable to form the discharge port 6c at a position separated from the diffusion section 6f by a distance determined by experiments, simulations, etc.

[0033] A portion of the exhaust gas discharged into the connector passage 7 is recirculated via an EGR passage 9 to an intake passage such as an intake manifold that supplies fresh air to the cylinder 2, and the remaining exhaust gas flows through an exhaust gas purification device 8, whereby CO, HC, NOx, and PM contained in the exhaust gas are removed and the exhaust gas is discharged to the outside. For convenience, the exhaust gas flowing through the EGR passage 9 will be referred to as EGR gas in the following description.

[0034] As described above, the EGR passage 9 is connected to the connector passage 7 that connects the diffusion chamber 6 and the exhaust purification device 8. Therefore, the exhaust gas whose components have been averaged by the diffusion chamber 6 is returned to the cylinder 2 via the EGR passage 9, thereby suppressing variations in the components, such as the oxygen concentration and carbon dioxide concentration, of the air-fuel mixture in the cylinder 2. As a result, the components of the air-fuel mixture in the cylinder 2 can be appropriately controlled, suppressing misfires caused by low oxygen concentrations (high carbon dioxide concentrations) or suppressing the generation of NOx caused by high oxygen concentrations (low carbon dioxide concentrations).

[0035] Furthermore, by providing the A / F sensor 11 in the connector passage 7, it is possible to reduce the amount of change in the value detected by the A / F sensor 11. As a result, there is no need to frequently change the opening of the EGR valve 10 for controlling the flow rate of EGR gas flowing through the EGR passage 9, or the amount of change in the opening can be reduced, which prevents the control of the EGR valve 10 from becoming complicated.

[0036] Furthermore, by connecting the EGR passage 9 upstream of the exhaust purification device 8, the pressure on the upstream side of the EGR passage 9 (the connector passage 7 side) can be made higher than the pressure on the downstream side of the EGR passage 9 (the intake passage side).In other words, the pressure difference required to recirculate the exhaust gas can be secured, and the EGR gas can be appropriately recirculated to the intake passage side.

[0037] Furthermore, by providing the A / F sensor 11 in the connector passage 7, the flow rate of exhaust gas flowing near the A / F sensor 11 can be increased, enabling stable sensing by the A / F sensor 11. Furthermore, by providing the A / F 11 upstream of the connection to the EGR passage 9 in the connector passage 7, the A / F sensor 11 can perform sensing before the exhaust gas flow rate decreases, preventing a decrease in the sensing accuracy of the A / F sensor 11.

[0038] The above-mentioned diffusion chamber 6 is configured to diffuse and mix the exhaust gas within the diffusion chamber 6 by causing the jetting exhaust gas to collide with the diffusion section 6f, so it is preferable to prevent the exhaust gas from flowing along the inner wall surface of the diffusion chamber 6 due to the Coanda effect or the like when it enters the diffusion chamber 6. For this reason, the outlet of the exhaust manifold 5 (collected exhaust passage 5a) may be disposed so as to protrude into the inside of the diffusion chamber 6, as shown in FIG.

[0039] By providing the exhaust port 5b of the exhaust manifold 5 (collecting exhaust passage 5a) so that it protrudes into the inside of the diffusion chamber 6 in this way, the exhaust gas can be discharged in a jet stream. As a result, it is possible to suppress a decrease in energy when the exhaust gas collides with the diffusion section 6f, and the diffusion efficiency of the exhaust gas can be improved. Furthermore, by jetting the exhaust gas, it is possible to suppress a decrease in the flow rate of the exhaust gas, so that the exhaust gas can flow toward the diffusion section 6f along with the exhaust gas that is accumulating near the exhaust port 5b of the exhaust manifold 5 (collecting exhaust passage 5a), and the diffusion efficiency of the exhaust gas can be improved.

[0040] Furthermore, although the engine 1 described above is configured to supply the exhaust gases joined by the collective exhaust passage 5a of the exhaust manifold 5 to the diffusion chamber 6, it may also be configured to supply the exhaust gases discharged from each cylinder 2 directly to the diffusion chamber 6. Figure 4 shows an example of such a configuration, with a first exhaust passage 13a connected to the exhaust port of the first cylinder 2a, a second exhaust passage 13b connected to the exhaust port of the second cylinder 2b, and a third exhaust passage 13c connected to the exhaust port of the third cylinder 2c.

[0041] The diffusion chamber 6 is also formed with a first inlet 14a through which exhaust gas flows in from the first exhaust passage 13a, a second inlet 14b through which exhaust gas flows in from the second exhaust passage 13b, and a third inlet 14c through which exhaust gas flows in from the third exhaust passage 13c. The inner wall surface of the diffusion chamber 6 is further formed with a first diffusion section 15a that faces the end of the first exhaust passage 13a and is perpendicular to the streamline of the exhaust gas discharged from the first exhaust passage 13a, a second diffusion section 15b that faces the second exhaust passage 13b and is perpendicular to the streamline of the exhaust gas discharged from the second exhaust passage 13b, and a third diffusion section 15c that faces the end of the third exhaust passage 13c and is perpendicular to the streamline of the exhaust gas discharged from the third exhaust passage 13c.

[0042] Even when multiple exhaust passages are connected to the diffusion chamber 6 in this way, the exhaust gases discharged from the exhaust passages 13a, 13b, and 13c into the diffusion chamber 6 collide with and are diffused by the diffusion sections 15a, 15b, and 15c, respectively, and thus the exhaust gases can be mixed in the diffusion chamber 6 to average their components, as in the example shown in Fig. 1. As a result, the variation in the components of the exhaust gas recirculated through the EGR passage 9 can be suppressed, making it possible to appropriately control the components of the mixture in the cylinder 2, suppressing misfires due to low oxygen concentration (high carbon dioxide concentration), or suppressing the generation of NOx due to high oxygen concentration (low carbon dioxide concentration). [Explanation of symbols]

[0043] 1 engine 2, 2a, 2b, 2c cylinder 5 exhaust manifold 5a Collecting exhaust passage 5b,6c outlet 6. Diffusion chamber 6e, 14a, 14b, 14c intake ports 6f, 15a, 15b, 15c Diffusion section 7 Connector passage 8 Exhaust purification device 9 EGR passage 10 EGR valve 11 A / F sensor 12 Controllers 13a, 13b, 13c Exhaust passage

Claims

1. An engine including a plurality of cylinders, an exhaust passage communicating with the cylinders and through which exhaust gas from the cylinders flows, and an EGR passage that recirculates the exhaust gas from the cylinders to an intake passage upstream of the cylinders, a diffusion chamber connected to the exhaust passage and having a diffusion section that diffuses the exhaust gas by collision with the exhaust gas jetted from the exhaust passage; a connector passage for connecting the diffusion chamber to an exhaust purification device that purifies exhaust gas, One end of the EGR passage is connected to the connector passage. An engine characterized by:

2. 2. The engine of claim 1, an EGR valve that changes the opening degree of the EGR passage; a sensor that outputs a signal corresponding to the amount of oxygen contained in the exhaust gas; a controller that controls the EGR valve based on a detection value of the sensor, The sensor is provided in the connector passage. An engine characterized by:

3. 2. The engine of claim 1, The diffusion portion is formed perpendicular to the flow line of the exhaust gas jetted from the exhaust passage. An engine characterized by:

4. 2. The engine of claim 1, The end of the exhaust passage projects into the diffusion chamber. An engine characterized by:

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