Engine exhaust structure

Abstract

To provide an engine exhaust structure that can more homogenize exhaust gases. [Solution] A plurality of exhaust gas outlets 300A, 300B are provided, each communicating with the combustion chamber R and each leading out exhaust gas from the combustion chamber R, and a collection section 51 is provided where the exhaust gases led out from the exhaust gas outlets 300A, 300B are collected inside. The collection section 51 is cylindrical with a circular cross-section perpendicular to the front-rear direction, and the collection section and the exhaust gas outlets 300A, 300B are connected such that each outlet end 301A, 301B opens on one side of the collection section 51 in the left-right direction. The diameter d10 of the circular cross-section of the collection section 51 is made shorter than the front-rear dimension d3 of the collection section 51, and in the vertical direction, the center X50 of the collection section 51 is positioned offset from the centers X31, 32 of each outlet end 301A, 301B.

Description

Technical Field

[0004] ,

[0005] ,

[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 applied to a multi-cylinder engine. Specifically, in Patent Document 1, a plurality of exhaust gas lead-out portions (a portion constituted by an exhaust port and a branch pipe in Patent Document 1) for leading out exhaust gas from each cylinder are arranged side by side in the front-rear direction, and a collecting portion (an expansion chamber in Patent Document 1) is provided on the downstream side of these exhaust gas lead-out portions, and a structure in which each exhaust gas lead-out portion is connected to one side surface in the left-right direction of the collecting portion in a state inclined with respect to the front-rear direction is disclosed. In this structure, the exhaust gas led out from each exhaust gas lead-out portion can be swirled around an axis extending in the vertical direction while being collected in the collecting portion.

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 led out during the same exhaust stroke from the same combustion chamber, the properties such as its concentration change depending on the timing of leading out. When a catalytic device for purifying exhaust gas is provided, if the properties of the exhaust gas flowing into the catalytic device change greatly, 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 greatly, there is a risk that each part cannot be stably controlled.

[0005] In contrast, the structure of Patent Document 1 allows exhaust gases to swirl within the manifold, thus enabling mixing and homogenization of the exhaust gases. However, in the structure of Patent Document 1, the exhaust gases swirl around an axis extending vertically, and the maximum diameter of the exhaust gas vortex formed within the manifold is relatively long, exceeding the length of the manifold in the front-to-back direction, i.e., the length of the entire exhaust gas outlet in the front-to-back direction. Consequently, the number of times the exhaust gases swirl within the manifold is kept low, resulting in a reduced mixing effect. 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 comprises a plurality of exhaust gas outlets that each discharge exhaust gas from a combustion chamber formed in the engine body, and a collection section into which the exhaust gas discharged from each of the exhaust gas outlets is collected. The exhaust gas outlets, which are the downstream ends of each of the exhaust gas outlets in the direction of exhaust gas flow, are arranged along a predetermined direction. When the direction in which the exhaust gas outlets are arranged is the front-rear direction, and the two directions perpendicular to this are the left-right direction and the up-down direction, the collection section has a cylindrical shape with a circular cross-section perpendicular to the front-rear direction, and is connected to each of the exhaust gas outlets such that each of the exhaust gas outlets opens on one side in the left-right direction. The diameter of the circular cross-section of the collection section is shorter than the front-rear dimension of the collection section, and the center of the collection section is located offset from the center of each of the exhaust gas outlets in the up-down direction.

[0008] In this configuration, the exhaust gases discharged from each exhaust gas outlet are collected inside the manifold, allowing exhaust gases from different exhaust gas outlets to be mixed within the manifold.

[0009] Furthermore, in this configuration, the cross-section of the manifold is circular, with each exhaust gas outlet opening on one side of the manifold in the left-right direction, and the center of the manifold and the center of the exhaust gas outlet are offset in the vertical direction. As a result, the exhaust gas discharged from the exhaust gas outlet can be swirled around an axis extending in the front-rear direction within the manifold. Moreover, since the diameter of the circular cross-section of the manifold is set to be shorter than the front-rear dimension of the manifold, i.e., the dimension in the direction in which the exhaust gas outlets are aligned, the swirling diameter of the exhaust gas within the manifold can be reduced. Consequently, this configuration promotes mixing of exhaust gases discharged from the same exhaust gas outlet during the same exhaust stroke, and the exhaust gas can be made more homogenized within the manifold.

[0010] In the above configuration, preferably, the center of the manifold is located above the center of each exhaust gas outlet, each exhaust gas outlet is inclined to be lower on the downstream side with respect to the direction of exhaust gas flow, and when viewed along the front-rear direction, it has a shape that extends upstream from the exhaust gas outlet along the tangent to the lower end of the manifold (Claim 2).

[0011] With this configuration, the exhaust gas flowing from the exhaust gas outlet into the manifold can be smoothly swirled along the inner surface of the manifold, thereby further promoting exhaust gas mixing.

[0012] In the above configuration, preferably, a downstream passage connected to the front end of the manifold is provided through which exhaust gas is introduced from the manifold, and the manifold has a volume portion that extends in the front-rear direction from the connection portion with the downstream passage to a position behind the rearmost exhaust gas outlet (Claim 3).

[0013] In this configuration, the volume of the manifold can be increased without increasing the diameter of the circular cross-section of the manifold. Therefore, it is possible to secure a mixing space for the exhaust gas while keeping the diameter of the swirling flow of the exhaust gas small. Consequently, the mixing of exhaust gases within the manifold can be further promoted, and the exhaust gas can be made more homogenized.

[0014] In the above configuration, preferably, the volume portion has a shape that follows a spherical surface that is convex towards the rear (Claim 4).

[0015] With this configuration, the swirling flow that flows backward to the upstream end of the manifold, i.e., in the direction of exhaust gas flow, due to exhaust pulsation, etc., can be guided along a spherical surface, thereby suppressing the attenuation of the swirling flow. As a result, the exhaust gas mixing effect within the manifold can be more reliably enhanced.

[0016] In the above configuration, preferably, a downstream passage is provided which is connected to the front end of the manifold and into which exhaust gas is introduced from the manifold, and the downstream passage has a shape in which the flow area decreases towards the downstream side with respect to the direction of exhaust gas flow (Claim 5).

[0017] This configuration allows for a compact shape by reducing the flow area of ​​the downstream passage, while still allowing the exhaust gas to move downstream while maintaining its swirling motion. Therefore, exhaust gas mixing is possible even within the downstream passage.

[0018] In the above configuration, preferably, a catalytic converter is provided downstream of the manifold to purify the exhaust gas (Claim 6).

[0019] As described above, in the present invention, exhaust gas mixing is promoted in the manifold. Therefore, by installing a catalytic converter downstream of the manifold, 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.

[0020] In the above configuration, preferably, an eccentric shaft extending in the front-rear direction, a rotor that rotates around the eccentric shaft, a rotor housing that surrounds the outer periphery 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, and the engine body composed of a rotary engine having the above, and two exhaust gas lead-out portions, one of the exhaust gas lead-out portions includes an exhaust port formed in the first side housing, and the other exhaust gas lead-out portion includes an exhaust port formed in the second side housing (Claim 7).

[0021] Due to the fuel being likely to adhere near the apex of the rotor in the rotary engine, the concentration of the exhaust gas led out from the combustion chamber to the exhaust port is likely to change according to the positional relationship between the exhaust port and the rotor. In contrast, in the present invention, since the exhaust gas led out from the combustion chamber is more homogenized as described above, higher effects can be obtained by applying the present invention to an engine configured as described above.

Advantages of the Invention

[0022] As described above, according to the present invention, the exhaust gas can be made more homogeneous.

Brief Description of the Drawings

[0023] [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 a cross section taken along line V-V of FIG. 4. [Figure 6] It is a view showing a part of a cross section taken along line VI-VI of FIG. 4. [Figure 7] It is a view showing a part of a cross section taken along line VII-VII of FIG. 4. [Figure 8] This figure shows the time change in the air-fuel ratio of the exhaust gas. [Figure 9] Figure 6 shows a schematic representation of the exhaust gas flow. [Figure 10] This figure shows the simulation results of the exhaust gas flow within the exhaust manifold. [Modes for carrying out the invention]

[0024] (Overall engine configuration) Figure 1 is a system diagram showing the schematic configuration of an engine to which the exhaust structure according to an embodiment of the present invention is applied. Figure 1 shows the schematic configuration of engine 1. Figure 2 is a schematic plan view of the powertrain system 200, which includes engine 1 and is mounted on a vehicle, Figure 3 is a schematic front view of engine 1, and Figure 4 is a schematic side view of engine 1. Note that the intake passage 2 and EGR device 23, which will be described later, are not shown in Figures 2, 3, and 4.

[0025] 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.

[0026] (Intake passage) The intake passage 2 forms a passage through which intake air introduced into the engine body 10 passes. The intake passage 2 is equipped with an air cleaner 21 for removing 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 that order from the upstream side.

[0027] (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.

[0028] 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.

[0029] 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 direction along the axis of the shaft 12 and the rotational axis of the rotor 11, is referred to as the front-rear direction. 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 front-rear direction corresponds to the "front-rear direction" in the claim, and the vertical direction corresponds to the "up-down direction" in the claim.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (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.

[0035] 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.

[0036] The exhaust manifold 4A is fixed to the right side of the engine body 10, communicating with the respective exhaust ports 15A and 15B. The detailed structure of the exhaust manifold 4A and its surroundings will be described later.

[0037] 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. Although not shown in the diagram, 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] (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).

[0042] (Detailed structure of the exhaust port) The detailed structure of each exhaust port 15A, 15B and exhaust manifold 4A will be described. Figure 5 shows a portion of the cross-section along line VV in Figure 4. Figure 6 shows a portion of the cross-section along line VI-VI in Figure 4. Figure 7 shows a portion of the cross-section along line VII-VII in Figure 7.

[0043] As shown in Figure 5, the first exhaust port 15A includes a first upstream port portion 111A extending forward from the rotor housing chamber R, and a first downstream port portion 112A extending left and right in front of the first upstream port portion 111A in communication with it. The rear end of the first upstream port portion 111A opens to the rear surface of the first side housing 14A, and this rear end constitutes the upstream opening end of the first exhaust port 15A. The front end of the first upstream port portion 111A opens to the rear side surface of the first downstream port portion 112A. Hereinafter, the front end of the first upstream port portion 111A that is formed in the first downstream port portion 112 will be referred to as the first intermediate opening end 114A. The right end of the first downstream port portion 112A opens to the right side surface of the first side housing 14A, and this right end constitutes the downstream opening end of the first exhaust port 15A. Hereafter, the downstream opening end of this first exhaust port 15A will be referred to as the first downstream opening end 115A.

[0044] As shown in Figure 6, the first downstream port portion 112A is inclined diagonally downward to the right in a front view (viewed along the front-to-back direction), so that it is located lower to the right, i.e., further downstream. Specifically, the central axis X1 of the first downstream port portion 112A is inclined diagonally downward to the right in a front view. The shape of the cross section perpendicular to the central axis X1 of the first downstream port portion 112A is substantially constant along the central axis X1, and the upper surface 117A and lower surface 116A of the first downstream port portion 112A are inclined diagonally downward to the right, substantially parallel to the central axis X1 in a front view. In this embodiment, as shown in Figure 4, the cross sections of the first downstream opening end 115A and the first downstream port portion 112A have a substantially rectangular shape that extends vertically with rounded corners.

[0045] The first intermediate opening end 114A is formed at the left end of the first downstream port portion 112A. Furthermore, the first intermediate opening end 114A is formed at the upper part of the left end of the first downstream port portion 112A. Specifically, the first intermediate opening end 114A is formed in a region extending from near the upper end of the first downstream port portion 112A to a position near the center of the central axis X1 and the lower end of the first downstream port portion 112A in the vertical direction.

[0046] The second exhaust port 15B has a shape that is almost symmetrical to the first exhaust port 15A in the front-to-back direction. Therefore, only a brief explanation will be given for the second exhaust port 15B.

[0047] Similar to the first exhaust port 15A, the second exhaust port 15B includes a second upstream port portion 111B that constitutes its upstream portion, and a second downstream port portion 112B that communicates with it and extends in the left-right direction. The upstream opening end of the second exhaust port 15B and the front end of the second upstream port portion 111B open to the front surface of the second side housing 14B. The second intermediate opening end 114B, which is the rear end of the second upstream port portion 111B, opens to the front side surface of the second downstream port portion 112B. The downstream opening end of the second exhaust port 15B and the second downstream opening end 115B, which is the right end of the second downstream port portion 112B, open to the right side surface of the second side housing 14B. The second intermediate opening end 114B is located above the left end of the second downstream port portion 112B. The second downstream port section 112B and its central axis X2 are inclined diagonally downward to the right when viewed from the front, such that they are located lower to the right, or further downstream.

[0048] (Detailed structure of the exhaust manifold) 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. The exhaust manifold 4A includes a first inlet section 40A, a second inlet section 40B, a first exhaust manifold section 50, a second exhaust manifold section 60, and a mounting flange 49. These inlet sections 40A, 40B, the first exhaust manifold section 50, the second exhaust manifold section 60, and the mounting flange 49 are all metal components and are integrally formed by welding or the like. Here, the first exhaust manifold section 50 corresponds to the "collector section" of the present invention, and the second exhaust manifold section 60 corresponds to the "downstream passage" of the present invention.

[0049] The mounting flange 49 is plate-shaped and extends in the front-rear and up-down directions along the right side of the engine body 10. The mounting flange 49 is a component for fixing the exhaust manifold 4A to the engine body 10. The exhaust manifold 4A is fixed to the engine body 10 by the mounting flange 49 being fixed to the right side of the engine body 10 with multiple bolts. Although not shown in the illustration, a thin plate-shaped sealing member is sandwiched between the right side of the engine body 10 and the mounting flange 49.

[0050] The first inlet section 40A has a cylindrical shape extending in the left-right direction. The first inlet end 41A, which is the left-side opening end of the first inlet section 40A, and the first downstream opening end 115A are opposite each other and are in communication.

[0051] As shown in Figures 5 and 6, the first inlet end 41A has almost the same shape as the first downstream opening end 115A. The inner circumferential surfaces of the first inlet end 41A and the first downstream opening end 115A overlap almost completely around the entire circumference when viewed from the side (along the left-right direction), and the inner circumferential surface of the first inlet section 40A is almost continuous with the inner circumferential surface of the first downstream port section 112A. In this embodiment, the first inlet section 40A and the first downstream port section 112A are in communication with a small gap in the left-right direction. However, this gap is very small, and the inner circumferential surface of the first inlet section 40A and the inner circumferential surface of the first downstream port section 112A are substantially continuous.

[0052] As described above, the first downstream port section 112A and the first inlet section 40A are almost continuous, and they define a passage extending in the left-right direction. Hereinafter, the combined portion of the first downstream port section 112A and the first inlet section 40A, or more specifically, the portion from the first intermediate opening end 114A to the downstream end of the first inlet section 40A in the direction of exhaust gas flow, will be referred to as the first outlet section 300A.

[0053] The first inlet section 40A is inclined diagonally downward to the right when viewed from the front, such that it is located lower on the right side. Specifically, the upper surface 43A of the first inlet section 40A extends almost straight in the left-right direction. On the other hand, the lower surface 42A of the first inlet section 40A is inclined diagonally downward to the right when viewed from the front. Consequently, the central axis X3 of the first inlet section 40A is inclined diagonally downward to the right when viewed from the front. At the connection point between the first inlet end 41A and the first downstream opening end 115A, the central axis X31 of the first inlet section 40A and the central axis X1 of the first downstream port section intersect.

[0054] As described above, the first downstream port section 112A is also inclined diagonally downward to the right when viewed from the front. Therefore, the first outlet section 300A, which consists of the first downstream port section 112A and the first inlet section 40A, is inclined diagonally downward to the right as a whole.

[0055] The second inlet section 40B has a cylindrical shape that extends in the left-right direction. The second inlet section 40B is positioned behind the first inlet section 40A and parallel to it. The second inlet end 41B, which is the left opening end of the second inlet section 40B, and the second downstream opening end 115B are opposite each other and are in communication.

[0056] The second inlet section 40B has a structure that is substantially symmetrical to the first inlet section 40A in the front-to-back direction. Furthermore, the relationship between the second inlet section 40B and the second exhaust port 15B is substantially symmetrical to the relationship between the first inlet section 40A and the first exhaust port 15A in the front-to-back direction. The second inlet section 40B and the relationship between the second inlet section 40B and the second exhaust port 15B will now be briefly explained.

[0057] The inner surface of the second inlet section 40B is substantially continuous with the inner surface of the second downstream port section 112B, and the second downstream port section 112B and the second inlet section 40B define a passage extending in the left-right direction. Hereinafter, the combined portion of the second downstream port section 112B and the second inlet section 40B will be referred to as the second outlet section 300B. The second inlet section 40B, its central axis X4, and the second outlet section 300B are each inclined diagonally downward to the right when viewed from the front.

[0058] The first outlet section 300A and the second outlet section 300B described above correspond to the "exhaust gas outlet section" of the claim, respectively.

[0059] The first exhaust manifold section 50 has a cylindrical shape as a whole, extending in the front-rear direction. The front-rear dimension of the first exhaust manifold section 50 is longer than the distance between the two outlet sections 300A and 300B, and the first exhaust manifold section 50 is located in a region in the front-rear direction that extends from a position behind the second downstream opening end 115B to a position in front of the first downstream opening end 115A. The first exhaust manifold section 50 includes a cylindrical section 51 and a volume section 55.

[0060] The cylindrical portion 51 is the part of the first exhaust manifold portion 50 that is located in the front-rear direction from the second downstream opening end 115B. As shown in Figure 6, the cylindrical portion 51 has a cylindrical shape with a cross-section perpendicular to the front-rear direction. More specifically, the cylindrical portion 51 has circular cross-sections on both its inner and outer surfaces. The central axis X50 of the cylindrical portion 51 and the first exhaust manifold portion 50, which passes through the center of each circular cross-section of the cylindrical portion 51, extends substantially straight in the front-rear direction. Here, "circular" in this specification is not limited to a strictly circular shape, but also includes shapes that are slightly deviated from a circle but can be considered generally circular. Similarly, "cylindrical" is not limited to a strictly cylindrical shape, but also includes shapes that are slightly deviated from a cylinder but can be considered generally cylindrical.

[0061] The diameter d1 of the circular cross-section of the cylindrical portion 51 (more specifically, the diameter of the cross-section of the inner circumferential surface of the cylindrical portion 51) is substantially constant in the longitudinal direction. This diameter d1 is smaller than the longitudinal dimension d2 of the cylindrical portion 51 and the longitudinal dimension d3 of the first exhaust manifold portion 50, so the cylindrical portion 51 has a long cylindrical shape in the longitudinal direction.

[0062] The right end of the first inlet 40A, that is, the downstream end of the first outlet 300A, is the first outlet end 301A, which opens onto the left side surface 51A of the cylindrical portion 51. Similarly, the right end of the second inlet 40B, that is, the downstream end of the second outlet 300B, is the second outlet end 301B, which opens onto the left side surface 51A of the cylindrical portion 51. The first outlet end 301A and the second outlet end 301B are aligned in the front-to-back direction. In other words, two outlet ends 301A and 301B, aligned in the front-to-back direction, open onto the left side surface 51A of the cylindrical portion 51, and the first inlet 40A (first outlet 300A) and the second inlet 40B (second outlet 300B) extend to the left from these outlet ends 301A and 301B, respectively. The first outlet end 301A and the second outlet end 302A described above correspond to the "exhaust gas outlet end" of the present invention, respectively. Furthermore, the left side surface 51A of the cylindrical portion 51 corresponds to "one side surface in the left-right direction of the manifold portion" of the present invention.

[0063] As shown in Figure 6, the center X31 of the first lead end 301A and the center X50 of the cylindrical portion 51 are offset in the vertical direction. In this embodiment, the center X31 of the first lead end 301A is located below the center X50 of the cylindrical portion 51. The first lead end 301A and the second lead end 301B have symmetrical shapes in the front-rear direction, and their positions are the same in the vertical direction. Therefore, although detailed illustration is omitted, similar to the first lead end 301A, the center of the second lead end 301B is located offset in the vertical direction from the center X50 of the cylindrical portion 51. Also, in this embodiment, the center of the second lead end 301B is located below the center X50 of the cylindrical portion 51.

[0064] In this embodiment, the first lead end 301A and the second lead end 301B are formed on the left side surface 51A of the cylindrical portion 51, in a region from a position slightly above the lower end of the cylindrical portion 51 to a position above the center X50 of the cylindrical portion 51 and below the upper end of the cylindrical portion 51. Furthermore, the amount of offset d10 downward from the center X31 of the first lead end 301A relative to the center X50 of the cylindrical portion 51 is set to approximately 1 / 8 of the diameter d1 of the cylindrical portion 51.

[0065] The lower surface of the first outlet portion 300A extends to the left along the tangent L10 (the tangent L10 to the inner surface of the cylindrical portion 51) passing through the lower end P1 of the first outlet end 301A. More specifically, the lower surface 42A (the lower surface on the inner side of the first outlet portion 40A) extends along the tangent L10 (the tangent L10 to the inner surface of the cylindrical portion 51). Although detailed illustrations are omitted, similarly, the lower surface 42B (the lower surface of the inner surface of the second outlet portion 40B) and thus the lower surface of the first outlet portion 300A extend to the left along the tangent L10 (the tangent L10 to the inner surface of the cylindrical portion 51) passing through the lower end of the second outlet end 301B.

[0066] The volumetric section 55 is the portion of the first exhaust manifold section 50 rearward from the cylindrical section 51, and defines a space that communicates with the inner space of the cylindrical section 51. Specifically, the volumetric section 55 constitutes the portion of the first exhaust manifold section 50 rearward from the second downstream opening end 115B and the second outlet end 301B.

[0067] The volume section 55 has a hemispherical shape that bulges towards the rear, and the inner circumferential surface of the volume section 55 follows a spherical surface that is convex towards the rear. In this embodiment, the diameter of the volume section 55 (diameter of the inner circumferential surface) is approximately the same as the diameter d1 (diameter of the inner circumferential surface) of the cylindrical section 51, and the volume section 55 (its inner circumferential surface) and the cylindrical section 51 (its inner circumferential surface) are continuous without any steps.

[0068] The second exhaust manifold section 60 curves diagonally to the left and forward from the front end of the cylindrical section 51 to a position in front of the engine body 10. The downstream end, formed by the left end of the second exhaust manifold section 60, is connected to the intermediate exhaust passage 4B.

[0069] As shown in Figure 5, the width dimension of the second exhaust manifold section 60 in a top view (viewed along the vertical direction) decreases towards the downstream side, and the flow area of ​​the second exhaust manifold section 60 decreases towards the downstream side. Specifically, the flow area of ​​the second exhaust manifold section 60 gradually decreases towards the downstream side, except near its downstream end. The flow area near the downstream end is generally constant. An EGR opening 61 is formed on the upper surface of the second exhaust manifold section 60, to which the EGR passage 24 is connected.

[0070] (effect, etc.) In the engine 1 configured as described above, exhaust gas (combusted gas) in the rotor chamber R is discharged to the first upstream port section 111A and the second upstream port section 111B. The exhaust gas that has passed through the first upstream port section 111A flows into the first outlet section 300A (first downstream port section 112A and first inlet section 40A) from the first intermediate opening end 114A, moves to the right within the first outlet section 300A, and is then discharged to the first exhaust manifold section 50 from the first outlet end 301A. The exhaust gas that has passed through the second upstream port section 111B flows into the second outlet section 300B (second downstream port section 112B and second inlet section 40B) from the second intermediate opening end 114B, moves to the right within the second outlet section 300B, and is then discharged to the first exhaust manifold section 50 from the second outlet end 301B. The exhaust gas directed to the first exhaust manifold section 50 is then introduced into the downstream exhaust passage 4C through the second exhaust manifold section 60 and the intermediate exhaust passage 4B, and after passing through the catalytic converter 31 and GPF 32, it is released into the atmosphere.

[0071] As described above, the exhaust gas led from the rotor housing chamber R to the first upstream port section 111A and subsequently to the first exhaust port 15A, and the exhaust gas led from the rotor housing chamber R to the second upstream port section 111B and subsequently to the second exhaust port 15B, are both led to the first exhaust manifold section 50. In other words, within the first exhaust manifold section 50, the exhaust gases led from the different outlet sections 300A, 300A are collected. Therefore, according to the above embodiment, these exhaust gases can be mixed within the first exhaust manifold section 50, and the exhaust gas can be homogenized.

[0072] Furthermore, in the above embodiment, having the structure described above, mixing of exhaust gases discharged from the same outlet sections 300A and 300B during the same exhaust stroke is promoted within the cylindrical section 51 of the first exhaust manifold section 50, thereby further homogenizing the exhaust gas. In addition, as the exhaust gas is homogenized, according to the above embodiment, the controllability of the engine 1 can be improved, and the exhaust gas purification performance can be improved.

[0073] This will be explained in detail using Figures 8 and 9. Figure 8 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 Figure 8, the strokes of the three working chambers (first chamber, second chamber, and third chamber) partitioned within the rotor housing chamber R are also shown. The dashed line in the graph of Figure 8 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 of Figure 8 represents the exhaust air-fuel ratio near the downstream end of the exhaust manifold 4A. Figure 9 is a diagram with the exhaust gas flow schematically added to Figure 6.

[0074] In the example shown in Figure 8, at a predetermined first eccentric angle Ec1, the second chamber and the upstream opening end 113A of the first exhaust port 15A begin to communicate, and at a predetermined second eccentric angle Ec2, this communication ends. In other words, between the first eccentric angle Ec1 and the second eccentric angle Ec2, the first exhaust port 15A is open in the second chamber. As shown by the dashed line in Figure 8, even though the exhaust gas is led from a common working chamber to a common first exhaust port 15, the exhaust air-fuel ratio in the first exhaust port 15 changes over time. Specifically, the exhaust air-fuel ratio in the first exhaust port 15 is lean (high air-fuel ratio) immediately after the opening of the first exhaust port 15, then becomes rich (low air-fuel ratio) before becoming lean again. Furthermore, the exhaust air-fuel ratio in the first exhaust port 15 becomes significantly richer near the point where the first exhaust port 15 closes. In engine 1, the exhaust air-fuel ratio changes as shown by the dashed line in Figure 8 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 led to the exhaust port tends to change depending on the positional relationship between the upstream opening end 113A and the rotor 11.

[0075] 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.

[0076] In contrast, in the above embodiment, the first exhaust manifold section 50 is provided with a cylindrical section 51 having a circular cross-section perpendicular to the front-rear direction. Furthermore, the outlet sections 300A and 300B are connected to the left side surface 51A of this cylindrical section 51, such that the centers X31 and X32 of the downstream outlet ends 301A and 301B and the center X50 of the cylindrical section 51 are offset in the vertical direction. As a result, as shown by arrow Y1 in Figure 9, the exhaust gas discharged from the outlet ends 301A and 301B can be swirled around an axis extending in the front-rear direction within the cylindrical section 51. Moreover, the diameter d1 of the circular cross-section of the cylindrical section 51 is shorter than the front-rear dimension d2 of the cylindrical section 51. Therefore, the swirling diameter of the swirling flow formed in the cylindrical section 51 can be reduced. Thus, according to the above embodiment, the exhaust gas that has been discharged from each outlet end 301A, 301B into the cylindrical section 51 can be returned to the vicinity of each outlet end 301A, 301B in a short time and mixed with the exhaust gas newly discharged from the outlet ends 301A, 301B. Therefore, within the cylindrical section 51, exhaust gases discharged from the same outlet ends 301A, 301B during the same exhaust stroke can be mixed and homogenized, and as shown by the solid line in Figure 8, the time change of the exhaust air-fuel ratio near the downstream end of the exhaust manifold 4A can be reduced. In this way, the exhaust gas is homogenized within the cylindrical section 51 and, consequently, within the first exhaust manifold section 50 and the exhaust manifold 4A. According to the above embodiment, exhaust gas with an averaged exhaust air-fuel ratio can be introduced to the upstream O2 sensor 35 and the catalytic converter 31, improving the controllability of the feedback control of the exhaust gas injection amount and improving the exhaust gas purification performance of the catalytic converter 31.

[0077] In particular, in the above embodiment, each outlet section 300A and 300B is inclined diagonally downward to the right, and extends to the left from the lower end of each outlet end 301A and 301B along the tangent to the cylindrical section 51 passing through this lower end. Therefore, as shown by arrow Y1 in Figure 9, exhaust gas can be introduced into the cylindrical section 51 from each outlet section 300A and 300B along the inner circumferential surface of the cylindrical section 51. As a result, the exhaust gas can be guided along the inner circumferential surface of the cylindrical section 51 while maintaining its velocity, and a strong swirling flow can be formed inside the cylindrical section 51. Consequently, exhaust gas mixing can be further promoted, and the exhaust gas can be homogenized more reliably.

[0078] Furthermore, in the above embodiment, the volume section 55 is provided behind the cylindrical section 51 of the first exhaust manifold section 50. Therefore, the volume of the first exhaust manifold section 50 can be increased without increasing the diameter d1 of the cylindrical section 51. As a result, the diameter of the swirling flow of the exhaust gas can be kept small while securing a mixing space for the exhaust gas and promoting exhaust gas mixing. Consequently, the exhaust gas can be made even more homogenized.

[0079] Furthermore, in the above embodiment, the volumetric section 55, specifically the portion of the first exhaust manifold section 50 rearward of the second exhaust gas outlet end 00B, is hemispherical in shape, and the inner circumferential surface of the volumetric section 55 follows a spherical surface that is convex to the rear. Therefore, by directing the swirling flow that has flowed back to the rear end of the first exhaust manifold section 50, i.e., the upstream end of the first exhaust manifold section 50, due to exhaust pulsation or the like, along the spherical surface, the swirling motion of the swirling flow can be maintained. Consequently, the exhaust gas mixing effect within the first exhaust manifold section 50 can be more reliably enhanced. This will be explained in detail using Figure 10.

[0080] Figure 10 shows the results of a simulation of the exhaust gas flow in the exhaust manifold 4A. The four figures (a) to (d) in Figure 10 show the exhaust gas distribution at different times. In the four figures (a) to (d) in Figure 10, time progresses in the order from (a) to (d).

[0081] As described above, and as indicated by the arrow Y10 in Figures 10(a) and 10(b), within the first exhaust manifold section 50, the exhaust gas swirls around an axis that extends in the front-rear direction along the inner circumferential surface of the cylindrical section 51.

[0082] Here, pressure pulsations occur within the exhaust passage 4, and as shown by arrows Y2 in Figure 10(b) and Y3 in Figure 10(c), pressure waves are generated in the first exhaust manifold section 50 that are directed downstream, i.e., towards the rear. This pushes the exhaust gas towards the rear of the first exhaust manifold section 50, and some of the exhaust gas is reflected at the rear end of the first exhaust manifold section 50. Therefore, near the rear end of the first exhaust manifold section 50, the exhaust gas moving backward and the exhaust gas that has been reflected and is moving forward collide, which may cause the swirling flow of the exhaust gas to be attenuated.

[0083] In contrast, in the above embodiment, as shown by arrow Y30 in Figures 10(c) and 10(d), the exhaust gas swirls along the inner circumferential surface of the hemispherical volume section 55. Therefore, the diameter of the swirling flow of exhaust gas reflected at the rear end of the volume section 55 and the first exhaust manifold section 50 can be reduced. When the diameter of the swirling flow is reduced, the reflected exhaust gas, when it moves downstream on the pressure pulsation directed downstream as shown by the dashed arrow Y5 in Figure 10(d), moves so as to pass inside the rearward swirling flow (Y40), as shown by the dashed arrow Y6. Therefore, according to the above embodiment, collisions between exhaust gases can be suppressed and attenuation of the exhaust gas swirling flow can be prevented. In other words, the swirling of the swirling flow can be maintained, and exhaust gas mixing can be promoted more reliably.

[0084] In addition to pressure pulsations, exhaust gas may also backflow if a force is generated that draws the gas in the exhaust ports 15A and 15B into the rotor housing chamber R due to the opening of the intake ports 16A and 16B. Even in this case, in the above embodiment, the damping of the swirling flow is suppressed by the action described above, and exhaust gas mixing is reliably promoted.

[0085] Furthermore, in the above embodiment, the second exhaust manifold section 60 has a shape in which the flow path area decreases towards the downstream side in the direction of exhaust gas flow.

[0086] Therefore, by reducing the flow area of ​​the second exhaust manifold section 60 to give it a compact shape, the exhaust gas can be moved downstream within the second exhaust manifold section 60 while maintaining its swirling motion, as shown by arrow Y20 in Figure 10(a). Consequently, the exhaust gas can be mixed within the second exhaust manifold section 60, further homogenizing the exhaust gas.

[0087] (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.

[0088] However, as mentioned above, in a rotary engine, fuel tends to adhere near the top of the rotor 11, which causes the concentration of exhaust gas discharged from the rotor housing chamber R to the exhaust ports 15A and 15B to change depending on the positional relationship between the exhaust ports 15A and 15B and the rotor 11. Therefore, applying the exhaust structure according to the above embodiment to a rotary engine can yield even greater results.

[0089] In the above embodiment, the case in which each outlet portion 300A and 300B is inclined diagonally downward to the right was described, but the specific shape of each outlet portion 300A and 300B is not limited to this. For example, each outlet portion 300A and 300B may extend straight in the left-right direction. Also, the centers X31 and X32 of each outlet end 301A and 301B may be shifted upward with respect to the center X50 of the cylindrical portion 51.

[0090] In the above embodiment, the case in which the volume section 55 is convex to the rear and has a hemispherical shape was described, but the specific shape of the volume section 55 is not limited to this. For example, the volume section 55 may have a shape that follows a surface that is less than or more than half of the sphere. Also, the volume section 55 may be omitted. Furthermore, the flow area of ​​the second exhaust manifold section 60 may be constant with respect to the direction of exhaust gas flow.

[0091] In the above embodiment, the case was described in which each outlet section 300A, 300B that introduces exhaust gas into the cylindrical section 51 includes each inlet section 40A, 40B that constitute a part of the exhaust manifold 4A. However, these inlet sections 40A, 40B may be omitted, and each downstream port section 112A, 112B may be directly connected to the cylindrical section 51. In this configuration, each downstream port section 112A, 112B functions as an introduction section.

[0092] In the above embodiment, the case was described in which the output axis direction, that is, the direction along the axis of the shaft 12, corresponds to the "front-rear direction" of the claim, that is, the direction in which the first lead end 301A and the second lead end 302B are aligned. However, the direction in which the first lead end 301A and the second lead end 302B are aligned is not limited to the output axis direction. Similarly, the "up-down direction" and "left-right direction" of the claim are not limited to the up-down direction and left-right direction when the engine 1 is mounted on a vehicle. [Explanation of symbols]

[0093] 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 15B Second Exhaust Port 31 Catalyst device 50. First exhaust manifold section (collector section) 55 Volume section 300A First outlet (exhaust gas outlet) 300B Second outlet section (exhaust gas outlet section) 301A First outlet end (exhaust gas outlet end) 301B Second outlet end (exhaust gas outlet end) R Rotor housing chamber (combustion chamber)

Claims

1. Multiple exhaust gas outlets that each discharge exhaust gas from the combustion chamber formed in the engine body, Each of the exhaust gas outlets comprises a collection section in which the exhaust gases discharged from each outlet are collected. The exhaust gas outlet ends, which are the downstream ends of each exhaust gas outlet in the direction of exhaust gas flow, are arranged along a predetermined direction. When the direction in which the exhaust gas outlet ends are aligned is the front-to-back direction, and the two directions perpendicular to this are the left-to-right direction and the up-and-down direction, The manifold has a cylindrical shape with a circular cross-section perpendicular to the front-rear direction, and is connected to each of the exhaust gas outlets such that each of the exhaust gas outlet ends opens on one side in the left-right direction. The diameter of the circular cross-section of the aforementioned manifold is shorter than the dimension of the manifold in the front-to-back direction. The exhaust structure of an engine is characterized in that the center of the manifold is located at a position offset in the vertical direction from the center of each of the exhaust gas outlets.

2. In the exhaust structure of the engine according to claim 1, The center of the manifold is located above the center of each of the exhaust gas outlet ends. The exhaust structure for an engine is characterized in that each of the exhaust gas outlets is inclined to be located lower on the downstream side with respect to the direction of exhaust gas flow, and when viewed along the front-to-back direction, it has a shape that extends upstream from the exhaust gas outlet end along the tangent to the lower end of the manifold.

3. In the exhaust structure of the engine according to claim 1, It is provided with a downstream passage connected to the front end of the aforementioned manifold, through which exhaust gas is introduced from the manifold, The exhaust structure for an engine is characterized in that the manifold has a volumetric portion that extends in the front-rear direction from the connection portion with the downstream passage to a position behind the rearmost exhaust gas outlet end.

4. In the exhaust structure of the engine according to claim 3, The exhaust structure for an engine is characterized in that the volume portion has a shape that follows a spherical surface that is convex towards the rear.

5. In the exhaust structure of the engine according to claim 1, It is provided with a downstream passage connected to the front end of the aforementioned manifold, through which exhaust gas is introduced from the manifold, The exhaust structure for an engine is characterized in that the downstream passage has a shape in which the flow area decreases as it moves downstream in the direction of exhaust gas flow.

6. 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 aforementioned manifold for purifying exhaust gases.

7. In the exhaust structure of an engine according to any one of claims 1 to 6, The engine body comprises 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. It comprises two of the aforementioned exhaust gas outlets, An engine exhaust structure characterized in that one of the exhaust gas outlets includes an exhaust port formed in the first side housing, and the other exhaust gas outlet includes an exhaust port formed in the second side housing.

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