Engine exhaust structure

Abstract

To provide an engine exhaust structure that can more homogenize exhaust gases. [Solution] A storage chamber 90 is provided to accommodate the downstream end 72 of the first exhaust passage 70 and the upstream end 82 of the second exhaust passage 80. The storage chamber 90 is provided with a first wall portion 91 through which the first exhaust passage 70 is inserted, a second wall portion 92A provided to the left of the first wall portion 91 through which the second exhaust passage 80 is inserted, an extension portion 92B extending forward from the second wall portion 92A, and a front wall portion 93 extending from the front end of the first wall portion 91 to the front end of the extension portion 92B. The front wall portion 93 is provided with an inclined portion 93A that extends to the left from the first wall portion 91 and is inclined so that the left side is further forward. Within the storage chamber 90, the first exhaust passage 70 is configured to extend along the inclined portion 93A toward the extension portion 92B, and the second exhaust passage 80 is configured to extend to the right from the second wall portion 92 to a position to the right of the left end of the first exhaust passage 70.

Description

Technical Field

[0001] The present invention relates to an exhaust structure of an engine.

Background Art

[0002] As an exhaust structure of an engine, for example, Patent Document 1 discloses a structure in which an expansion chamber with an enlarged flow passage area is provided in the middle of an exhaust passage. Specifically, in the structure of Patent Document 1, a substantially rectangular expansion chamber is provided in the exhaust passage, and the upstream exhaust passage and the downstream exhaust passage open to two opposing side walls of the expansion chamber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even for exhaust gas discharged during the same exhaust stroke from the same combustion chamber, the properties such as its concentration change with time. When a catalytic device for purifying exhaust gas is provided, if the properties of the exhaust gas flowing into the catalytic device change significantly, there is a risk that the purification performance by the catalytic device cannot be sufficiently obtained. Also, when controlling each part of the engine based on the properties of the exhaust gas, if the properties of the exhaust gas change significantly, there is a risk that each part cannot be stably controlled.

[0005] In the structure of Patent Document 1, the presence of an expansion chamber prevents exhaust gas from moving directly from the upstream exhaust passage to the downstream exhaust passage, thus allowing the exhaust gas to be mixed within the expansion chamber. However, in the structure of Patent Document 1, the downstream end of the upstream exhaust passage and the upstream end of the downstream exhaust passage open into two opposing side walls. Therefore, the exhaust gas generally moves along the direction of these two side walls, and there is a risk that the exhaust gas that enters the expansion chamber first and the exhaust gas that enters later will not be sufficiently mixed. In other words, the structure of Patent Document 1 has room for improvement in terms of exhaust gas mixing and, consequently, exhaust gas homogenization.

[0006] This invention has been made in view of the above circumstances, and aims to provide an engine exhaust structure that can further homogenize exhaust gases. [Means for solving the problem]

[0007] To solve the above problems, the engine exhaust structure of the present invention is an engine exhaust structure having an engine body through which a combustion chamber is formed, comprising: a first exhaust passage through which exhaust gas discharged from the combustion chamber passes; a second exhaust passage into which exhaust gas led out from the first exhaust passage is introduced; and a housing chamber that houses the downstream end of the first exhaust passage and the upstream end of the second exhaust passage in the direction of exhaust gas flow, and when the direction along the axial direction of the upstream end of the second exhaust passage is defined as the left-right direction and the direction perpendicular thereto is defined as the front-rear direction, the housing chamber has a first wall portion through which the first exhaust passage is inserted. The present invention relates to a structure comprising: a second wall portion provided to the left of the first wall portion through which the second exhaust passage is inserted; an extension portion extending forward from the second wall portion; and a front wall portion extending in the left-right direction from the front end of the first wall portion to the front end of the extension portion, wherein the front wall portion extends to the left from the first wall portion and includes an inclined portion that is inclined so as to the left it is located further forward, and within the containment chamber, the first exhaust passage extends from the first wall portion toward the extension portion along the inclined portion, and the second exhaust passage extends to the right from the second wall portion to a position to the right of the downstream end of the first exhaust passage.

[0008] In this configuration, the exhaust gas led from the first exhaust passage into the containment chamber collides with the extension section and splits into gas that heads toward the second wall section and gas that heads toward the front wall section. Since the second exhaust passage is inserted through the second wall section, the gas that moves toward the second wall section flows into the second exhaust passage relatively quickly. On the other hand, the gas that heads toward the front wall section moves toward the first wall section through the gap between the first exhaust passage and the inclined section before flowing into the second exhaust passage. Therefore, with this configuration, the timing of the inflow of exhaust gases that entered the containment chamber at the same time into the second exhaust passage can be staggered. Consequently, it is possible to mix exhaust gases that entered the containment chamber at different times with each other as they flow into the second exhaust passage, that is, to promote mixing of exhaust gases that were led out during the same exhaust stroke, and thus make the exhaust gas more homogenized.

[0009] In the above configuration, preferably, the containment chamber includes a rear wall portion extending in the left-right direction from the rear end of the first wall portion to the rear end of the second wall portion, and within the containment chamber, the second exhaust passage extends along the rear wall portion (Claim 2).

[0010] This configuration allows exhaust gas to flow smoothly into the second exhaust passage along the rear wall, preventing it from accumulating in the containment chamber for an excessively long period of time.

[0011] In the above configuration, preferably, the inclined portion constitutes the right portion of the front wall portion, and the front wall portion has a straight portion extending in the left-right direction from the left end of the inclined portion to the front end of the second wall portion (Claim 3).

[0012] This configuration allows exhaust gases to be guided into the gap between the inclined section and the front wall, while also shortening the front-to-back dimensions of the containment chamber compared to the case where the entire front wall is inclined so that the left side is positioned further forward.

[0013] Preferably, the above configuration further includes a catalytic converter provided downstream of the second exhaust passage in the direction of exhaust gas flow to purify the exhaust gas (Claim 4).

[0014] As described above, in this invention, homogenization of the exhaust gas is promoted in the containment chamber. Therefore, by installing a catalytic converter downstream of the containment chamber, the properties of the exhaust gas flowing into the catalytic converter can be stabilized, and the exhaust gas purification performance of the catalytic converter can be improved.

[0015] In the above configuration, preferably, a volumetric section is provided upstream of the first exhaust passage in the direction of exhaust gas flow and partitions a space that communicates with an exhaust port formed in the engine body, wherein the flow area of ​​the volumetric section is larger than the flow area of ​​the exhaust port (Claim 5).

[0016] This configuration allows for mixing of exhaust gases even within the volumetric section, resulting in a more homogeneous exhaust gas mixture.

[0017] In the above configuration, preferably, the engine body is a rotary engine having an eccentric shaft extending in the front-rear direction, a rotor rotating around the eccentric shaft, a rotor housing surrounding the outer circumference of the rotor, a first side housing provided on the front side of the rotor housing, and a second side housing provided on the rear side of the rotor housing (Claim 6).

[0018] In rotary engines, fuel tends to adhere near the top of the rotor, which causes the concentration of exhaust gas discharged from the combustion chamber to the exhaust port to vary depending on the relative position of the exhaust port and the rotor. In contrast, the present invention makes the exhaust gas discharged from the combustion chamber more homogenized, so applying the present invention to an engine configured as described above can yield even greater results. [Effects of the Invention]

[0019] As explained above, the present invention makes it possible to make exhaust gases more homogeneous. [Brief explanation of the drawing]

[0020] [Figure 1]It is a system diagram showing a schematic configuration of an engine according to an embodiment of the present invention. [Figure 2] It is a schematic plan view of a power train system including an engine. [Figure 3] It is a schematic front view of the engine. [Figure 4] It is a schematic side view of the engine. [Figure 5] It is a view showing a part of the cross section taken along the line V-V of FIG. 4. <000009--0>It is a view showing the internal structure of the housing chamber. [Figure 7] It is a view showing a part of the cross section taken along the line VII-VII of FIG. 3. [Figure 8] It is a view showing a part of the cross section taken along the line VIII-VIII of FIG. 2. [Figure 9] It is a view showing the time change of the air-fuel ratio of the exhaust gas. [Figure 10] It is a view schematically showing the flow of the exhaust gas in the housing chamber added. [[Embodiments for Carrying Out the Invention]]

[0021] (Overall Configuration of Engine) FIG. 1 is a system diagram showing a schematic configuration of an engine to which an exhaust structure according to an embodiment of the present invention is applied. FIG. 1 shows a schematic configuration of an engine 1. FIG. 2 is a schematic plan view of a power train system 200 including the engine 1 and mounted on a vehicle, FIG. 3 is a schematic front view of the engine 1, and FIG. 4 is a schematic side view of the engine 1. In FIGS. 2, 3 and 4, illustration of an intake passage 2 and an EGR device 23 described later is omitted.

[0022] The engine 1 according to this embodiment is mounted on a vehicle. The engine 1 comprises an engine body 10, an intake passage 2, an exhaust passage 4, and an EGR device 23. For example, the engine 1 is mounted on a hybrid vehicle equipped with a motor as a drive source for the wheels. In this embodiment, the engine 1 is incorporated into a powertrain system 200 that includes a motor and the like. Specifically, as shown in Figure 2, the powertrain system 200 includes an engine 1, a generator 202, a reduction gear 203, and a motor 201. The generator 202 is driven by the engine 1 to generate electricity and charge a battery (not shown). The motor 201 rotates using power supplied from the battery. The reduction gear 203 reduces the rotation of the motor 201 and transmits it to the wheels. In this embodiment, the engine 1 is used as a device to drive the generator 202 as described above.

[0023] (Intake passage) The intake passage 2 forms a passage through which intake air is introduced into the engine body 10. The intake passage 2 is equipped with an air cleaner 21 that removes foreign matter contained in the intake air, and a throttle valve 22 that can open and close the intake passage 2 to adjust the amount of intake air introduced into the engine body 10, in this order from the upstream side.

[0024] (EGR device) The EGR device 23 recirculates a portion of the exhaust gas flowing through the exhaust passage 4 as EGR gas to the intake passage 2. The EGR device 23 includes an EGR passage 24 that connects the exhaust passage 4 and the intake passage 2. The EGR passage 24 is equipped with an EGR cooler 25 for cooling the EGR gas, which is the exhaust gas flowing through the EGR passage 24, and an EGR valve 26 for opening and closing the EGR passage 24 to adjust the amount of EGR gas introduced into the intake passage 2, in this order from the upstream side (in the direction of EGR gas flow).

[0025] (Engine body) The engine body 10 is a single-rotor rotary piston engine. The engine body 10 has an eccentric shaft 12 (hereinafter referred to as shaft 12) extending in a predetermined direction and a rotor 11 that rotates around shaft 12. The engine body 10 has a rotor housing 13, a first side housing 14A, and a second side housing 14B. The rotor housing 13 surrounds the outer circumference of the rotor 11 and defines the peripheral wall of the rotor housing chamber R that houses the rotor 11. The first side housing 14A is attached to the rotor housing 13 so as to cover the rotor housing chamber R from one side in a direction parallel to the axis of shaft 12 (hereinafter referred to as the output axis direction as appropriate). The second side housing 14B is attached to the rotor housing 13 so as to cover the rotor housing chamber R from the other side in the output axis direction. The rotor housing chamber R is partitioned by the rotor housing 13, the first side housing 14A, and the second side housing 14B. The inner surface of the rotor housing 13 follows a 2-node peritrochoidal curve. The rotor 11 rotates along the inner surface of the rotor housing 13 in a planetary rotational motion relative to the shaft 12.

[0026] The engine body 10 has a rear cover 101 that houses the flywheel and is connected to the side of the second side housing 14B opposite to the rotor housing 13 in the output axial direction. The engine body 10 also has a front cover 102 that is connected to the side of the first side housing 14A opposite to the rotor housing 13 in the output axial direction.

[0027] Engine 1 is mounted on the vehicle in a position where the axis of the shaft 12 and the rotational axis of the rotor 11 extend horizontally or substantially horizontally. In the following description, the direction along the output axis, that is, the axis of the shaft 12 and the rotational axis of the rotor 11, is referred to as the longitudinal direction. Furthermore, the side of the rotor housing 13 with respect to the rear cover 101 is referred to as the rear, and the opposite side as the front. Of the pair of side housings, the side housing located on the front side is referred to as the first side housing 14A, and the side housing located on the rear side is referred to as the second side housing 14B. Furthermore, in the following description, the vertical direction when the engine 1 is mounted on the vehicle is simply referred to as the vertical direction, and the left-right direction when the engine body 10 is viewed from the rear is simply referred to as the left-right direction. Note that the above longitudinal direction corresponds to the "longitudinal direction" in the claim, and the left-right direction corresponds to the "left-right direction" in the claim.

[0028] In this embodiment, the engine 1 is mounted on the vehicle in a position where its output axial direction coincides with the vehicle width direction and its left-right direction coincides with the vehicle's front-rear direction. An oil pan 19 for storing lubricating oil to lubricate various parts of the engine body 10 is connected to the engine body 10. The oil pan 19 is connected to the lower surface of the engine body 10. In this embodiment, the generator 202 is connected to the rear surface of the engine 1. The reduction gear 203 is connected to the rear surface of the generator 202, and the motor 201 is connected to the rear surface of the reduction gear 203. Figure 1 shows the engine body 10 as viewed from the front. Figure 2 shows the powertrain system 200 as viewed from above. Figure 3 shows the engine 1 as viewed from the front. Figure 4 shows the engine 1 as viewed from the right.

[0029] The engine body 10 has a pair of intake ports connected to the intake passage 2, which introduce intake air from the intake passage 2 into the rotor housing chamber R. The engine body 10 also has a pair of exhaust ports connected to the exhaust passage 4, which discharge exhaust gas from the rotor housing chamber R into the exhaust passage 4. The engine body 10 is a side-port rotary piston engine, and one intake port and one exhaust port are formed in the first side housing 14A and the second side housing 14B, respectively. In this embodiment, the engine body 10 is configured such that the rotor 11 rotates clockwise when viewed from the front, and the upper right, upper left, lower left, and lower right regions of the rotor housing chamber R are roughly the regions where the intake stroke, compression stroke, expansion stroke, and exhaust stroke are performed, respectively. Correspondingly, a first intake port 16A is formed in the upper right portion of the first side housing 14A, and a second intake port 16B is formed in the upper right portion of the second side housing 14B. Furthermore, a first exhaust port 15A is formed in the lower right side of the first side housing 14A, and a second exhaust port 15B is formed in the lower right side of the second side housing 14B.

[0030] The engine body 10 is fitted with a fuel injector 17 that injects fuel into the rotor chamber R, and a spark plug 18 that ignites the fuel-air mixture formed in the rotor chamber R. The fuel injector 17 is fitted so as to face the upper end of the rotor chamber R (more specifically, a position offset from the upper end toward the spark plug 18), and the spark plug 18 is fitted so as to face the lower left part of the rotor chamber R. In this embodiment, the fuel injector 17 injects fuel mainly composed of gasoline.

[0031] The fuel injected into the rotor chamber R from the fuel injector 17 and the air introduced into the rotor chamber R from the intake port 16 are ignited by the spark plug 18 and burn in the rotor chamber R, causing the rotor 11 to rotate due to the expansion force from this combustion. The rotor chamber R described above corresponds to the "combustion chamber" of the present invention.

[0032] (Exhaust passage) The exhaust passage 4 forms a passage through which exhaust gas discharged from the engine body 10 passes. In the following description, the downstream direction in terms of exhaust gas flow is simply referred to as downstream, and the upstream direction in terms of exhaust gas flow is simply referred to as upstream.

[0033] The exhaust passage 4 comprises an exhaust manifold 4A, an intermediate exhaust passage 4B extending from the downstream end of the exhaust manifold 4A, and a downstream exhaust passage 4C extending from the downstream end of the intermediate exhaust passage 4B.

[0034] Figure 5 shows a portion of the cross-section along line VV in Figure 4. Both the first exhaust port 15A and the second exhaust port 15B open to the right side of the engine body 10. The exhaust manifold 4A is connected to the right side of the engine body 10 in communication with the first exhaust port 15A and the second exhaust port 15B.

[0035] The exhaust manifold 4A is composed of a first exhaust manifold section 41 which constitutes its upstream portion and a second exhaust manifold section 42 which constitutes its downstream portion. Both the first exhaust manifold section 41 and the second exhaust manifold section 42 are made of metal and are integrally formed with each other. The first exhaust manifold section 41 corresponds to the "volume section" of the claim.

[0036] The first exhaust manifold section 41 has a cylindrical shape that extends in the front-rear direction along the right side of the engine body 10. A pair of inlet sections 41A and 41B protrude to the left from the left side of the first exhaust manifold section 41. These inlet sections 41A and 41B are arranged in the front-rear direction. The front inlet section 41A is connected to the first exhaust port 15A, and the rear inlet section 41B is connected to the second exhaust port 15B. Exhaust gas that has passed through the respective exhaust ports 15A and 15B is introduced into the first exhaust manifold section 41 and the exhaust manifold 4A through these inlet sections 41A and 41B.

[0037] The first exhaust manifold section 41 has a roughly cylindrical shape with a roughly circular cross-section perpendicular to the front-rear direction. The flow area of ​​the first exhaust manifold section 41, i.e., the cross-sectional area of ​​the circular cross-section, is set to be larger than the flow area of ​​each exhaust port 15A, 15B.

[0038] The second exhaust manifold section 42 curves diagonally to the left and forward from the front end of the first exhaust manifold section 41 to a position in front of the engine body 10. The downstream end of the second exhaust manifold section 42 is connected to the intermediate exhaust passage 4B. An EGR opening 43 is formed on the upper surface of the second exhaust manifold section 42, to which the EGR passage 24 is connected.

[0039] The intermediate exhaust passage 4B comprises a first passage 70 which constitutes its upstream portion, a second passage 80 which constitutes its downstream portion, and a diffusion chamber 90 which accommodates the downstream end of the first passage 70 and the upstream end of the second passage 80. As will be described in detail later, the downstream end of the first passage 70 and the upstream end of the second passage 80 are open to the inner space of the diffusion chamber 90. In other words, the downstream end of the first passage 70 and the upstream end of the second passage 80 are not connected. As a result, exhaust gas is released into the diffusion chamber 90 from the downstream end of the first passage 70, and then flows into the second passage 80 and passes through it towards the downstream exhaust passage 4C. The first passage 70 corresponds to the "first exhaust passage" of the present invention, and the second passage 80 corresponds to the "second exhaust passage" of the present invention. The diffusion chamber 90 corresponds to the "containment chamber" of the present invention.

[0040] A purification device 30 for purifying exhaust gas is provided in the middle of the downstream exhaust passage 4C. The purification device 30 includes a catalytic converter 31 that includes a catalyst for purifying exhaust gas, and a filter 32 provided downstream of the catalytic converter 31. The catalytic converter 31 includes a three-way catalytic converter and reduces NOx (nitrogen oxides) while oxidizing HC (hydrocarbons) and CO (carbon monoxide) when the air-fuel ratio of the exhaust gas passing through the catalytic converter 31 is at or near the stoichiometric air-fuel ratio. The filter 32 is a so-called GPF (Gasoline Particulate Filter) that collects PM (Particulate Matter) contained in the exhaust gas and removes it by burning it.

[0041] The downstream exhaust passage 4C is equipped with an upstream O2 sensor 35 and a downstream O2 sensor 36. Both the upstream O2 sensor 35 and the downstream O2 sensor 36 are sensors that detect the oxygen concentration of exhaust gas. The upstream O2 sensor 35 is located upstream of the catalytic converter 31 in the downstream exhaust passage 4C and detects the oxygen concentration of exhaust gas passing through this section. The downstream O2 sensor 36 is located between the catalytic converter 31 and the GPF 32 in the downstream exhaust passage 4C and detects the oxygen concentration of exhaust gas passing through this section.

[0042] The value detected by the upstream O2 sensor 35 is mainly used to control the fuel injector 17. Specifically, the engine 1 is equipped with a control device (not shown) for controlling various parts of the engine 1, such as the fuel injector 17 and spark plugs 18. This control device feedback-controls the injection amount of the fuel injector 17 based on the value detected by the upstream O2 sensor 35 so that the air-fuel ratio of the mixture (fuel and air mixture) in the rotor chamber R is at or near the stoichiometric air-fuel ratio, that is, so that the excess air ratio λ of the mixture is about 1. The output of the downstream O2 sensor 36 is used for correction of the output of the upstream O2 sensor 35, etc.

[0043] (Diffusion chamber) The arrangement of the diffusion chamber 90 and the first passage 70 and the second passage 80 within the diffusion chamber 90 will be described next. Figure 6 shows the internal structure of the diffusion chamber 90. Specifically, Figure 6 is a view of the inside of the diffusion chamber 90 from the direction indicated by arrow Y1 in Figure 3. Figure 7 shows a part of the cross section along line VII-VII in Figure 3. Figure 8 shows a part of the cross section along line VIII-VIII in Figure 2.

[0044] The intermediate exhaust passage 4B, when viewed from the front (along the front-to-back direction), includes a portion extending to the left from the downstream end of the exhaust manifold 4A and a portion curving diagonally upward and to the left from this portion. The diffusion chamber 90 is located in this curved portion, and when viewed from the front, the central axis of the diffusion chamber 90 extends diagonally upward and to the left along approximately the arc that is convex diagonally downward and to the left. Hereafter, the central axis R1 of the diffusion chamber 90 in this front view will be simply referred to as the central axis R1.

[0045] The diffusion chamber 90 is a box-shaped member that partitions a space on its interior. The diffusion chamber 90 has a first horizontal wall portion 91 which is plate-shaped and perpendicular to the left-right direction, and a second horizontal wall portion 92 which is plate-shaped and located to the left of the first horizontal wall portion 91. In a front view, the first horizontal wall portion 91 is approximately perpendicular to the central axis R1. In a front view, the second horizontal wall portion 92 is approximately perpendicular to the central axis R1 and is inclined so that the lower part is located further to the right in a front view. In other words, the central axis R1 is an arc centered at the intersection of a line along the first horizontal wall portion 91 and a line along the second horizontal wall portion 92 in a front view. The first horizontal wall portion 91 corresponds to the "first wall portion" of the present invention, and the second horizontal wall portion 92 corresponds to the "second wall portion" of the present invention.

[0046] The diffusion chamber 90 has a front wall portion 93 that extends in the left-right direction from the front end of the first side wall portion 91 to the front end of the second side wall portion 92. The diffusion chamber 90 has a rear wall portion 94 that extends in the left-right direction from the rear end of the first side wall portion 91 to the rear end of the second side wall portion 92. The diffusion chamber 90 has a plate-shaped bottom wall portion 95 that closes the portion enclosed by the lower ends of each wall portion 91 to 94 from below and forms the lower surface of the diffusion chamber 90. The diffusion chamber 90 has a plate-shaped top wall portion 96 that closes the portion enclosed by the upper ends of each wall portion 91 to 94 from above and forms the upper surface of the diffusion chamber 90.

[0047] The diffusion chamber 90 is configured to be divisible vertically near its center, and the other wall sections 91-94, excluding the bottom wall section 95 and the top wall section 96, are each divisible vertically.

[0048] The first lateral wall portion 91 has a substantially square shape, with the length of one side slightly larger than the outer diameter of the first passage 70. The first passage 70 is inserted through the first lateral wall portion 91. Specifically, an opening is formed in the first lateral wall portion 91 through which the first passage 70 is inserted. The first passage 70 is inserted through the opening formed in the first lateral wall portion 91 and penetrates the first lateral wall portion 91 in the left-right direction.

[0049] The second lateral wall portion 92 has a substantially rectangular shape extending in the front-rear direction. The second passage 80 is inserted through the rear portion of the second lateral wall portion 92. Specifically, an opening is formed in the rear portion of the second lateral wall portion 92 through which the second passage 80 is inserted, and the second passage 80 penetrates the opening-forming portion 92A and the second lateral wall portion 92 in the left-right direction through this opening. Hereinafter, the portion of the second lateral wall portion 92 through which the second passage 80 is inserted will be referred to as the opening-forming portion 92A, and the portion in front of it will be referred to as the extension portion 92B. In other words, the second lateral wall portion 92 consists of an opening-forming portion 92A which constitutes the rear portion and through which the second passage 80 is inserted, and an extension portion 92B which extends forward from the opening-forming portion 92A and constitutes the front portion of the second lateral wall portion 92.

[0050] As shown in Figure 6, in a top view (viewed along the vertical direction), the opening-forming portion 92A and the first lateral wall portion 91 face each other. That is, the opening-forming portion 92A of the first lateral wall portion 91 and the second lateral wall portion 92 are located in approximately the same range in the front-rear direction. The extension portion 92B extending forward from the opening-forming portion 92A is located in front of the front end of the first lateral wall portion 91 in the front-rear direction.

[0051] The first passage 70 and the second passage 80 are circular tubes, and their cross-sections are circular. The outer diameters of the first passage 70 and the second passage 80 are approximately the same. In this embodiment, the height dimension of the diffusion chamber 90 is generally constant and is set to a value slightly larger than the outer diameters of the first passage 70 and the second passage 80.

[0052] The front wall portion 93 consists of an inclined portion 93A that extends to the left from the front end of the first side wall portion 91 and constitutes the right side portion of the front wall portion 93, and a straight portion 93B that extends to the left from the inclined portion 93A and constitutes the left side portion of the front wall portion 93. In this embodiment, the inclined portion 93A occupies approximately half of the front wall portion 93.

[0053] The inclined section 93A is inclined such that the left side is positioned further forward. On the other hand, the straight section 93B extends along the left-right direction from the left end of the inclined section 93A to the front end of the extension section 92B, and extends almost straight to the left from the left end of the inclined section 93A.

[0054] The rear wall portion 94 is flat. The rear wall portion 94 is approximately perpendicular to the front-to-back direction and extends almost straight in the left-to-right direction.

[0055] Within the diffusion chamber 90, the first passage 70 extends from the first lateral wall 91 toward the extension 92B of the second lateral wall 92. As shown in Figure 6, within the diffusion chamber 90, the first passage 70 extends along the inclined section 93A and is inclined so that the left side is located further forward. In this embodiment, the first passage 70 curves gently in an S-shape when viewed from above, following the inclined section 93A and the straight section 93B. The left end, or downstream end 72, of the first passage 70 opens toward the extension 92B. The downstream end 72 of the first passage 70 and the extension 92B are close together, and the distance between them in the direction along the centerline of the first passage 70 and its extension is set to be smaller than the distance between the first lateral wall 91 and the second lateral wall 92. Specifically, the length of the first passage 70 within the diffusion chamber 90 (the portion of the first passage 70 housed within the diffusion chamber 90) is greater than half the distance between the first lateral wall 91 and the second lateral wall 92, and the distance between the downstream end 72 of the first passage 70 and the extension 92B is set to be less than half the distance between the first lateral wall 91 and the second lateral wall 92. For example, the length of the first passage 70 within the diffusion chamber 90 is set to about 7 / 8 of the distance between the first lateral wall 91 and the second lateral wall 92, and the distance between the downstream end 72 of the first passage 70 and the extension 92B is set to about 1 / 8 of the distance between the first lateral wall 91 and the second lateral wall 92.

[0056] As shown in Figure 8, in a front view, the first passage 70 within the diffusion chamber 90 extends along the central axis R1 and curves diagonally upward and to the left from the first side wall 91.

[0057] The first passage 70 outside the diffusion chamber 90, that is, the portion of the first passage 70 upstream of the diffusion chamber 90, extends almost straight to the left from the exhaust manifold 4A, and the first passage 70 penetrates the first side wall 91 at approximately a right angle to it.

[0058] As shown in Figure 8, in a front view, the second passage 80 within the diffusion chamber 90 (the portion of the second passage 80 housed in the diffusion chamber 90) extends along the central axis R1 and extends diagonally downward to the right from the second side wall 92.

[0059] As shown in Figure 6, etc., within the diffusion chamber 90, the second passage 80 extends almost straight to the right from the opening forming portion 92A of the second side wall portion 92. In other words, the axial direction of the upstream end of the second passage 80 housed within the diffusion chamber 90 extends along the left-right direction. As described above, the rear wall portion 94 has a flat plate shape that extends almost straight in the left-right direction, and within the diffusion chamber 90, the second passage 80 extends along the rear wall portion 94. The second passage 80 extends to the right from the opening forming portion 92A to a position to the right of the left end, i.e., the downstream end 72, of the first passage 70. That is, the right end, i.e., the upstream end 82, of the second passage 80 is located to the right of the left end, i.e., the downstream end 72, of the first passage 70, and the first passage 70 and the second passage 80 overlap in the left-right direction. In this embodiment, as shown in Figure 8, in a front view, the downstream end of the first passage 70 and the downstream end of the second passage 80 overlap.

[0060] The length of the second passage 80 within the diffusion chamber 90 is shorter than the length of the first passage 70 within the diffusion chamber 90. Specifically, the length of the second passage 80 within the diffusion chamber 90 is shorter than half the distance between the first lateral wall 91 and the second lateral wall 92 in the direction along the centerline and extension of the first passage 70, and the distance between the downstream end 72 of the first passage 70 and the first lateral wall 91 is set to be greater than half the distance between the first lateral wall 91 and the second lateral wall 92. For example, the length of the second passage 80 within the diffusion chamber 90 is set to about 1 / 4 of the distance between the first lateral wall 91 and the second lateral wall 92, and the distance between the downstream end 72 of the first passage 70 and the first lateral wall 91 is set to about 3 / 4 of the distance between the first lateral wall 91 and the second lateral wall 92. Furthermore, if the length of the second passage 80 within the diffusion chamber 90 and the length of the first passage 70 within the diffusion chamber 90 are set to approximately 1 / 4 and 7 / 8 of the distance between the first and second side walls 91 and 92, respectively, the overlap dimension of the first passage 70 and the second passage 80 in the left-right direction will be approximately 1 / 8 of the distance between the first and second side walls 91 and 92.

[0061] The second passage 80 outside the diffusion chamber 90, that is, the portion of the second passage 80 downstream of the diffusion chamber 90, extends upward from the diffusion chamber 90 and then curves backward.

[0062] As shown in Figure 6, in a top view, the central axis of the first passage 70 upstream of the diffusion chamber 90 and the central axis of the upstream portion of the second passage 80, which includes the part inside the diffusion chamber 90, extend almost straight in the left-right direction along the same straight line.

[0063] (effect, etc.) Figure 9 is a graph showing the change in the exhaust gas air-fuel ratio (hereinafter referred to as the exhaust air-fuel ratio as appropriate) in the engine 1 according to the above embodiment with respect to the eccentric angle (rotation angle of the eccentric shaft 12). Below this, Figure 9 also shows the strokes of the three working chambers (first chamber, second chamber, and third chamber) partitioned within the rotor housing chamber R by the rotor 11. The graph in Figure 9 shows the exhaust air-fuel ratio from slightly before the start of the exhaust stroke of the second chamber to slightly after the end of the exhaust stroke of the second chamber. The dashed line in the graph in Figure 9 represents the exhaust air-fuel ratio in the first exhaust port 15A. Note that the exhaust air-fuel ratio in the first exhaust port 15A and the exhaust air-fuel ratio in the second exhaust port 15B change in approximately the same way. The solid line in the graph in Figure 9 represents the exhaust air-fuel ratio of the portion of the intermediate exhaust passage 4B downstream of the diffusion chamber 90.

[0064] In the graph of Figure 9, communication between the second chamber and the first exhaust port 15A begins at a predetermined first eccentric angle Ec1, and this communication ends at a predetermined second eccentric angle Ec2. In other words, the first exhaust port 15A is open in the second chamber between the first eccentric angle Ec1 and the second eccentric angle Ec2. As shown by the dashed line in Figure 9, despite the exhaust gas being led from a common working chamber to a common first exhaust port 15A, the exhaust air-fuel ratio in the first exhaust port 15A changes over time. Specifically, the exhaust air-fuel ratio in the first exhaust port 15A is lean (high air-fuel ratio) immediately after the opening of the first exhaust port 15A, then becomes rich (low air-fuel ratio) before becoming lean again. Furthermore, the exhaust air-fuel ratio in the first exhaust port 15A becomes significantly richer near the point where the first exhaust port 15A closes. In engine 1, the exhaust air-fuel ratio changes as shown by the dashed line in Figure 9 because fuel tends to adhere to the area near the top of the rotor 11 in a rotary engine. In other words, the concentration of exhaust gas discharged to the exhaust port changes easily depending on the positional relationship between the exhaust port 15 and the rotor 11.

[0065] Here, if the exhaust gas reaches the upstream O2 sensor 35 while the above-mentioned time-dependent change in exhaust air-fuel ratio is maintained, the fluctuation in the oxygen concentration detected by the upstream O2 sensor 35 will increase, and the controllability of the injection amount feedback control performed based on this detected value will decrease. Also, if the exhaust gas reaches the catalytic converter 31 while the above-mentioned time-dependent change in exhaust air-fuel ratio is maintained, even if the average air-fuel ratio of the exhaust gas is near the stoichiometric air-fuel ratio, the exhaust gas that deviates from the stoichiometric air-fuel ratio at each time point will flow into the catalytic converter 31, preventing the catalytic converter 31 from adequately purifying HC, CO, or NOx.

[0066] In contrast, according to the above embodiment, exhaust gas mixing can be promoted in the diffusion chamber 90, and the exhaust gas can be homogenized. In other words, as shown by the solid line in Figure 9, the time change in the exhaust air-fuel ratio downstream of the diffusion chamber 90 in the intermediate exhaust passage 4B, and consequently the time change in the air-fuel ratio of the exhaust gas supplied to the upstream O2 sensor 35 and catalytic converter 31 located downstream of the diffusion chamber 90, can be reduced. Therefore, the controllability of the injection amount feedback control can be improved, and the exhaust gas purification performance of the catalytic converter 31 can be enhanced.

[0067] This will be explained in detail using Figure 10. Figure 10 is a schematic diagram showing the flow of exhaust gas in the diffusion chamber 90 according to the above embodiment. As shown by arrow Y10 in Figure 10, the exhaust gas that has passed through the first passage 70 is led into the diffusion chamber 90 from its downstream end 72. As described above, the first passage 70 extends from the first side wall 91 toward the extension 92B of the second side wall 92, and the downstream end 72 of the first passage 70 opens toward the extension 92B. Also, the upstream end 82 of the second passage 80 is located to the right of the downstream end 72 of the first passage 70, that is, toward the first side wall 91. Therefore, the exhaust gas led out from the first passage 70 does not flow directly into the second passage 80 but collides with the extension 92B. Upon collision with the extension portion 92B, some of the exhaust gas is directed toward the opening-forming portion 92A of the second side wall portion 92, as indicated by arrow Y11, and some of the exhaust gas is directed toward the front wall portion 93, as indicated by arrow Y21.

[0068] As indicated by arrow Y12, the exhaust gas directed toward the opening forming section 92A moves to the right by at least the amount of the overlap between the first passage 70 and the second passage 80 in the left-right direction, before flowing into the second passage 80.

[0069] Meanwhile, the exhaust gas directed toward the front wall 93 moves to the right through the gap between the straight section 93B and the inclined section 93A of the front wall 93 and the first passage 70, as shown by arrow Y22. Then, near the first side wall 91, it changes direction and moves to the left toward the second passage 80, as shown by arrow Y23.

[0070] As the exhaust gas moves within the diffusion chamber 90 as described above, the time it takes for the exhaust gas directed toward the front wall portion 93 to flow into the second passage 80 after being led into the diffusion chamber 90 is longer than the time it takes for the exhaust gas directed toward the opening forming portion 92A.

[0071] Thus, according to the above embodiment, the timing of the inflow of exhaust gases into the second passage 80 from the first passage 70 into the diffusion chamber 90 can be dispersed. Therefore, exhaust gases introduced into the exhaust passage 4 at an earlier timing in a predetermined exhaust stroke and exhaust gases introduced into the exhaust passage 4 at a later timing in the same exhaust stroke can be mixed in the diffusion chamber 90. In other words, mixing of exhaust gases in the same exhaust stroke can be promoted. Accordingly, according to the above embodiment, exhaust gases can be introduced downstream from the diffusion chamber 90 in a more homogenized state.

[0072] Furthermore, in the above embodiment, the flow area of ​​the first exhaust manifold section 41 of the exhaust manifold 4A, which communicates with the exhaust ports 15A and 15B, is larger than the flow area of ​​the exhaust ports 15A and 15B. Therefore, the exhaust gas can be diffused within the first exhaust manifold section 41, promoting the mixing of the exhaust gases. Consequently, the exhaust gas can be made even more homogenized.

[0073] Furthermore, in the above embodiment, the second passage 80 within the diffusion chamber 90 extends along the rear wall 94. Therefore, as shown by arrow Y23, the exhaust gas that has reversed direction near the first side wall 91 can be smoothly directed to the right along the rear wall 94 and ultimately to the second passage 80. Consequently, it is possible to prevent the exhaust gas from remaining in the diffusion chamber 90 for an excessively long period of time.

[0074] Furthermore, in the above embodiment, the inclined portion 93A constitutes the right-side portion of the front wall portion 93, and the portion spanning from the inclined portion 93A to the front end of the extension portion 92B of the second side wall portion 92 is a straight portion 93B that extends along the left-right direction. Therefore, as shown by the dashed line in Figure 10, compared to the case where the entire front wall portion 93 is inclined as an inclined portion, the dimensions of the diffusion chamber 90 in the front-rear direction can be reduced, making the diffusion chamber 90 more compact.

[0075] (modified version) In the above embodiment, the case where engine 1 is a single-rotor rotary piston engine was described, but engine 1 may be a rotary piston engine having two or more rotors. Also, engine 1 may be a reciprocating engine having one or more cylinders.

[0076] In the above embodiment, the case described is that the direction along the output axis, that is, the axis of the shaft 12 and the rotational axis of the rotor 11, corresponds to the "front-rear direction" of the claim. However, the "front-rear direction" of the claim is not limited to the above direction. Similarly, in the above embodiment, the case described is that the vertical direction when the engine 1 is mounted on a vehicle corresponds to the "vertical direction" of the claim, and the direction perpendicular to this vertical direction and the output axis corresponds to the "left-right direction" of the claim. However, the "vertical direction" and "left-right direction" of the claim are not limited to the directions according to the above embodiment. [Explanation of symbols]

[0077] 1 Rotary Piston Engine 4A Exhaust Manifold 5. Exhaust passage 11 rotors 12 Eccentric Shaft 13 Rotor Housing 14A First side housing 14B Second side housing 15A First exhaust port (exhaust port) 15B Second exhaust port (exhaust port) 31 Catalyst device 41. First exhaust manifold section (volumetric section) 70. First Passage (First Exhaust Passage) 80 Second Passage (Second Exhaust Passage) 90 Diffusion Chamber (Containment Chamber) 91. First horizontal wall section (first wall section) 92 Second side wall section (second wall section) 93 Front wall 93A Slope 93B Straight section 92A Opening forming part (second wall part) 92B Extension part 94 Rear wall R Rotor housing chamber (combustion chamber)

Claims

1. In an exhaust structure for an engine having an engine body in which a combustion chamber is formed, A first exhaust passage through which exhaust gas discharged from the combustion chamber passes, A second exhaust passage into which the exhaust gas led out from the first exhaust passage is introduced, The system includes a containment chamber that houses the downstream end of the first exhaust passage and the upstream end of the second exhaust passage in the direction of exhaust gas flow, When the direction along the axial direction of the upstream end of the second exhaust passage is defined as the left-right direction, and the direction perpendicular to it is defined as the front-back direction, The containment chamber comprises a first wall through which the first exhaust passage is inserted, a second wall provided to the left of the first wall through which the second exhaust passage is inserted, an extension extending forward from the second wall, and a front wall extending in the left-right direction from the front end of the first wall to the front end of the extension. The front wall portion includes an inclined portion that extends to the left from the first wall portion and is positioned further forward on the left side. An engine exhaust structure characterized in that, within the containment chamber, the first exhaust passage extends from the first wall portion toward the extension portion along the inclined portion, and the second exhaust passage extends to the right from the second wall portion to a position to the right of the downstream end of the first exhaust passage.

2. In the exhaust structure of the engine according to claim 1, The aforementioned accommodation chamber includes a rear wall portion that extends in the left-right direction across the rear end of the first wall portion and the rear end of the second wall portion, An engine exhaust structure characterized in that, within the containment chamber, the second exhaust passage extends along the rear wall.

3. In the exhaust structure of the engine according to claim 1, The inclined portion constitutes the right-side portion of the front wall, The engine exhaust structure is characterized in that the front wall portion has a straight portion extending in the left-right direction from the left end of the inclined portion to the front end of the extended portion.

4. In the exhaust structure of the engine according to claim 1, An engine exhaust structure characterized by further comprising a catalytic converter provided downstream of the second exhaust passage in the direction of exhaust gas flow, for purifying exhaust gas.

5. In the exhaust structure of the engine according to claim 1, The engine further comprises a volumetric section provided upstream of the first exhaust passage in the direction of exhaust gas flow, which partitions a space that communicates with an exhaust port formed in the engine body, An engine exhaust structure characterized in that the flow area of ​​the volumetric section is larger than the flow area of ​​the exhaust port.

6. In the exhaust structure of an engine according to any one of claims 1 to 5, The exhaust structure for an engine is characterized in that the engine body is a rotary engine having an eccentric shaft extending in the front-rear direction, a rotor rotating around the eccentric shaft, a rotor housing surrounding the outer circumference of the rotor, a first side housing provided on the front side of the rotor housing, and a second side housing provided on the rear side of the rotor housing.

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