Rotary piston engine

Abstract

To provide a rotary piston engine that can stabilize a detection value detected by an O2 sensor.SOLUTION: A rotary piston engine includes: a first inner pipe defining a flow passage which is bent and continuous to a first exhaust port; a second inner pipe defining a flow passage which is bent and continuous to a second exhaust port; and a common outer pipe connected to a first side housing and a second side housing with the inner pipes accommodated in the outer pipe. A downstream end of the first inner pipe and a downstream end of the second inner part are opposite each other in an output shaft direction across an annular clearance which functions as an outlet of exhaust gas flowing out of the inner pipe into the outer pipe.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a rotary piston engine. [Background technology]

[0002] Exhaust manifolds (hereinafter, "exhaust manifolds") that introduce high-temperature exhaust gas discharged from an engine and discharge it outside a vehicle are well known. For example, there is an exhaust manifold (same meaning exhaust manifold) in Patent Document 1. Patent Document 1 discloses a technique for welding a reinforcing plate to the outer wall of the exhaust manifold to prevent membrane vibration caused by pulsation of exhaust gas flowing inside the exhaust manifold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-108751 A Summary of the Invention [Problem to be solved by the invention]

[0004] An O2 sensor is provided downstream of the exhaust manifold in the flow direction of the exhaust gas, and the fuel injection amount is adjusted as needed by exhaust gas feedback control using the oxygen concentration detected by the O2 sensor. Here, in a well-known rotary piston engine, it is known that the amount of unburned fuel contained in the exhaust gas discharged during the exhaust stroke changes greatly. In relation to this, the fluctuation range of the oxygen concentration of the exhaust gas detected by the O2 sensor also increases. As a result, there is a risk that the controllability of the feedback control will decrease. In addition, when the amount of unburned fuel contained in the exhaust gas temporarily increases, the amount of unburned fuel that reaches the catalyst provided downstream of the exhaust manifold increases, and the purification performance of the catalyst may decrease.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a rotary piston engine that can reduce the fluctuation range of the oxygen concentration detected by the O2 sensor and suppress a decrease in controllability and a decrease in the purification performance of the catalyst. [Means for solving the problem]

[0006] In order to solve the above problem, the present invention provides a compressor comprising: a rotor that rotates around an output shaft; a cylindrical rotor housing that defines a peripheral wall of a rotor accommodating chamber that accommodates the rotor; a first side housing that is attached to the rotor housing so as to cover the rotor accommodating chamber from one side in an output axial direction that is parallel to an axis of the output shaft, and has a first exhaust port that receives exhaust gas discharged from the rotor accommodating chamber; a second side housing that is attached to the rotor housing so as to cover the rotor accommodating chamber from the other side in the output axial direction, and has a second exhaust port that receives exhaust gas discharged from the rotor accommodating chamber; and an exhaust passage that receives exhaust gas discharged to the outside of each side housing through the first exhaust port and the second exhaust port, wherein the exhaust passage has a first inner pipe that is continuous with the first exhaust port and defines a flow path that bends toward the other side in the output shaft direction, a second inner pipe that is continuous with the second exhaust port and defines a flow path that bends toward one side in the output shaft direction, and a common outer pipe connected to the first side housing and the second side housing in a state in which the first inner pipe and the second inner pipe are accommodated, and the downstream end of the first inner pipe and the downstream end of the second inner pipe face each other in the output shaft direction across an annular gap that functions as an outlet for exhaust gas flowing out from both inner pipes to the outer pipe.

[0007] In this configuration, the exhaust gases discharged from the downstream end of the first inner pipe and the downstream end of the second inner pipe collide with each other and mix. At this time, the exhaust gas is homogenized, and the fluctuation of the oxygen concentration detected by the O2 sensor installed downstream of the exhaust passage can be reduced. In addition, when the exhaust gases collide, the unburned fuel reacts with the remaining air, promoting combustion in the exhaust passage, and reducing the amount of unburned fuel that reaches the catalyst installed downstream of the exhaust passage.

[0008] Preferably, the outer circumferential area of ​​the annular gap is 1.1 to 1.3 times the sum of the minimum cross-sectional area of ​​the first exhaust port and the minimum cross-sectional area of ​​the second exhaust port.

[0009] In this embodiment, the outer peripheral area of ​​the annular gap has an appropriate value, and the exhaust gas pressure can be prevented from becoming high while maintaining the effect of homogenizing the exhaust gas by mixing it.

[0010] Preferably, the outer pipe has a shape extending from the first side housing and the second side housing toward one side in the output shaft direction so that exhaust gas flowing out from the annular gap flows toward one side in the output shaft direction, and an intermediate position between the downstream end of the first inner pipe and the downstream end of the second inner pipe is located on the other side in the output shaft direction than an intermediate position between the downstream end of the first exhaust port and the downstream end of the second exhaust port.

[0011] In this embodiment, by colliding the exhaust gas upstream of the midpoint between the downstream end of the first exhaust port and the downstream end of the second exhaust port, the time it takes for the exhaust gas to reach the O2 sensor and catalyst is increased, making the exhaust gas detected by the O2 sensor more homogenous.

[0012] Preferably, a reinforcing member is joined to a peripheral surface of the outer pipe overlapping with the annular gap when viewed in a direction perpendicular to the output shaft direction.

[0013] In this aspect, the portion of the outer pipe that the exhaust gas impinges on is reinforced by the reinforcing member, so that vibration of the outer pipe caused by the collision of the exhaust gas and radiated sound caused by the vibration can be suppressed.

[0014] Preferably, the outer tube, the first inner tube, and the second inner tube are all sheet metal members formed by processing a plate material.

[0015] In this embodiment, the wall thicknesses of the outer pipe, the first inner pipe, and the second inner pipe are thinner than when they are manufactured by casting or the like, so that the weight of the exhaust manifold can be reduced. Effect of the Invention

[0016] As described above, according to the present invention, by homogenizing the exhaust gas, it is possible to reduce the fluctuation in the oxygen concentration detected by the O2 sensor, and suppress deterioration of controllability and deterioration of the purification performance of the catalyst. [Brief description of the drawings]

[0017] [Figure 1] 1 is a system diagram showing a schematic configuration of an engine according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic plan view of a powertrain system including an engine. [Diagram 3] FIG. 2 is a schematic front view of the powertrain system. [Figure 4] FIG. 2 is a schematic side view of the engine and its surroundings. [Diagram 5] 5 is a diagram showing a part of a cross section taken along line VV in FIG. 4. [Figure 6] 6 is a diagram showing a state in which a first member constituting an outer tube in FIG. 5 has been removed. [Figure 7] 7 is a view of FIG. 6 as seen in the direction of arrow X. [Figure 8] FIG. 1 is a diagram illustrating the operating state of a conventional rotary piston engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (Overall engine configuration) Fig. 1 is a system diagram showing a schematic configuration of a rotary piston engine 1 according to an embodiment of the present invention. Hereinafter, the rotary piston engine 1 will be simply referred to as the engine 1. Fig. 2 is a schematic plan view of a powertrain system 200 that includes the engine 1 and is mounted on a vehicle, Fig. 3 is a schematic front view of the powertrain system 200, and Fig. 4 is a schematic side view of the periphery of the engine 1 in the powertrain system 200. Note that an intake passage 3, which will be described later, is omitted from Fig. 2.

[0019] The engine 1 according to this embodiment is mounted on a vehicle. 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 in a powertrain system 200 including the motor and the like, which is mounted on the vehicle. Specifically, as shown in FIG. 2, the powertrain system 200 has the 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 by 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 for driving the generator 202 as described above.

[0020] The engine 1 includes an engine body 10, an intake passage 3 through which intake air introduced into the engine body 10 flows, an exhaust passage 5 through which exhaust gas discharged from the engine body 10 flows, and an EGR device 4 that recirculates a portion of the exhaust gas flowing through the exhaust passage 5 to the intake passage 3.

[0021] (Engine body) The engine body 10 is of a one-rotor type. The engine body 10 includes a rotor 11 that rotates around an eccentric shaft 12 (hereinafter, shaft 12) that extends in a predetermined direction, a cylindrical rotor housing 13 that defines a peripheral wall of a rotor accommodating chamber R that accommodates the rotor 11, a first side housing 14A that is attached to the rotor housing 13 so as to cover the rotor accommodating chamber R from one side in an output shaft direction (hereinafter, axial direction of shaft 12) that is parallel to the axis of the shaft 12, a second side housing 14B that is attached to the rotor housing 13 so as to cover the rotor accommodating chamber R from the other side in the axial direction, and an exhaust passage 5 that is connected to the first side housing 14A and the second side housing 14B. The rotor accommodating chamber R is surrounded and defined by the rotor housing 13, the first side housing 14A, and the second side housing 14B. The rotor housing 13 has a peripheral wall that follows a peritrochoid curve with two nodes. The rotor 11 rotates along the inner circumferential surface of a rotor housing 13 by planetary rotation relative to a shaft 12. The shaft 12 corresponds to the "output shaft" in the claims.

[0022] The engine body 10 has a rear cover 20 that is connected to the second side housing 14B on the opposite side to the rotor housing 13 and that houses a flywheel. The engine body 10 also has a front cover 22 that is connected to the first side housing 14A on the opposite side to the rotor housing 13.

[0023] The engine 1 is mounted on the vehicle with the axis of the shaft 12 extending horizontally or approximately horizontally. In the following description, the direction along the axial direction of the shaft 12 is referred to as the front-rear direction. In the following description, the side where the rear cover 20 is provided is referred to as the rear side, and the side where the front cover 22 is provided is referred to as the front side. In the following description, the up-down direction when the engine 1 is mounted on the vehicle is simply referred to as the up-down direction, and the left-right direction when the engine body 10 is viewed from behind is simply referred to as the left-right direction. In this embodiment, the "front side" in the front-rear direction corresponds to the "one side" in the claims, and the "rear side" in the front-rear direction corresponds to the "other side" in the claims.

[0024] The powertrain system 200 is configured such that the engine 1, the generator 202, the reduction gear 203, and the motor 201 are arranged in this order from the front. Specifically, the generator 202 is connected to the rear surface of the engine 1, i.e., the rear surface of the rear cover 20, 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.

[0025] In this embodiment, the engine 1 is mounted on the vehicle in a position in which the front-rear direction (axial direction of the shaft 12) of the engine 1 coincides with the vehicle width direction, and the left-right direction coincides with the vehicle front-rear direction. The view of the engine body 10 in Fig. 1 is a schematic cross-sectional view as seen from the front. Also, Fig. 2 is a view of the powertrain system 200 as seen from above, Fig. 3 is a view of the powertrain system 200 as seen from the front, and Fig. 4 is a view of the peripheral portion of the engine 1 in the powertrain system 200 as seen from the right.

[0026] The engine body 10 is formed with a pair of intake ports 16 connected to the intake passage 3 to introduce the intake air in the intake passage 3 into the rotor housing chamber R, and a pair of exhaust ports 15 connected to the exhaust passage 5 to lead the exhaust air from the rotor housing chamber R to the exhaust passage 5. Each intake port 16 opens to the upper right side of the rotor housing chamber R, and each exhaust port 15 opens to the lower right side of the rotor housing chamber R. In other words, 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 areas in which the intake stroke, compression stroke, expansion stroke, and exhaust stroke are performed, respectively. In other words, the engine 1 is mounted on the vehicle so that the areas in which each stroke is performed are located at the above positions in the vertical direction.

[0027] The engine body 10 is a side port type rotary piston engine, and each intake port 16 and each exhaust port 15 are formed in the first side housing 14A and the second side housing 14B, one each. Specifically, a first intake port 16A is formed in the upper part of the first side housing 14A, and a second intake port 16B is formed in the upper part of the second side housing 14B. Each intake port 16A, 16B opens at the upper part of the right side surface (right wall surface) of each side housing 14A, 14B. In addition, a first exhaust port 15A is formed in the lower part of the first side housing 14A, and a second exhaust port 15B is formed in the lower part of the second side housing 14B. Each exhaust port 15A, 15B is a passage for receiving exhaust gas discharged from the rotor housing chamber R and guiding the exhaust gas to the exhaust passage 5. Each exhaust port 15A, 15B opens at the lower part of the right side surface of each side housing 14A, 14B. The first exhaust port 15A and the second exhaust port 15B are shaped substantially symmetrically in the front-rear direction and open at substantially the same height on the right side surface of each of the side housings 14A and 14B. Similarly, the intake ports 16A and 16B are shaped substantially symmetrically in the front-rear direction and open at substantially the same height on the right side surface of each of the side housings 14A and 14B.

[0028] A fuel injection device 17 that injects fuel into the rotor accommodating chamber R, and an ignition plug 18 that ignites a mixture of fuel and air formed in the rotor accommodating chamber R are attached to the engine body 10. The fuel injection device 17 is attached so as to face the upper end of the rotor accommodating chamber R (more specifically, at a position offset from the upper end toward the spark plug 18), and the ignition plug 18 is attached so as to face the lower left part of the rotor accommodating chamber R.

[0029] (intake passage) In the intake passage 3, an air cleaner 31 that removes foreign matter contained in the intake air and a throttle valve 32 that can adjust the amount of intake air introduced into the engine body 10 (rotor housing chamber R) by opening and closing the intake passage 3 are provided in this order from the upstream side. The throttle valve 32 is accommodated in a throttle valve case 33 and is driven by an actuator 34 fixed to the throttle valve case 33. The portion of the intake passage 3 downstream of the throttle valve case 33 constitutes an intake manifold 38 that communicates with each of the intake ports 16A, 16B and distributes the intake air to each of the intake ports 16A, 16B. The intake manifold 38 is fixed to the right side surface 10C of the engine body 10 in a position extending upward from the vicinity of the openings of each of the intake ports 16A, 16B in the right side surface 10C (see FIG. 5) of each of the side housings 14A, 14B.

[0030] An air flow meter sensor SN1 that detects the flow rate of the intake air passing through the intake passage 3 is provided downstream of the air cleaner 31. Also, an intake pressure sensor SN2 that detects the intake pressure of the intake air passing through the intake manifold 38 is provided.

[0031] (Exhaust passage) The exhaust passage 5 receives exhaust gas discharged to the outside of each side housing 14A, 14B through each exhaust port 15A, 15B, and forms a path for discharging the exhaust gas to the outside of the vehicle. A purification device 51 for purifying the exhaust gas is provided in the exhaust passage 5. The exhaust passage 5 includes an exhaust manifold 52 (also called an exhaust manifold) that communicates with each exhaust port 15A, 15B and where exhaust gases led out from each exhaust port 15A, 15B join together on the inside, and a downstream exhaust passage 53 that extends downstream (in the flow direction of exhaust gas) from the downstream end of the exhaust manifold 52. The purification device 51 is provided in the middle of the downstream exhaust passage 53.

[0032] A first O2 sensor 56 is provided upstream of the purification device 51 in the exhaust gas flow direction, and a second O2 sensor is provided downstream of the purification device 51 in the exhaust gas flow direction. The first O2 sensor 56 is a sensor that detects the oxygen concentration of the exhaust gas, and is used for exhaust gas feedback control that adjusts the fuel injection amount based on the air-fuel ratio calculated from the oxygen concentration. The second O2 sensor 58 is used to detect a failure of the first O2 sensor 56 or as a spare sensor when the first O2 sensor 56 fails.

[0033] The exhaust manifold 52 is fixed to the right side surface 10C of each of the side housings 14A, 14B in a state in which it communicates with each of the exhaust ports 15A, 15B below the intake manifold 38. The detailed structure of the exhaust manifold 52 will be described later.

[0034] (EGR device) The EGR device 4 includes an EGR passage 40 that communicates between the exhaust passage 5 and the intake passage 3. In the EGR passage 40, an EGR cooler 41 that cools the EGR gas, which is exhaust gas flowing through the EGR passage 40, and an EGR valve 42 that opens and closes the EGR passage 40 to adjust the amount of EGR gas introduced into the intake manifold 38 are provided in this order from the upstream side (in terms of the flow direction of the EGR gas). The EGR valve 42 is housed in an EGR valve case 43, and is driven by an EGR valve actuator 44 fixed to the EGR valve case 43.

[0035] The EGR device 4 is disposed to the right of the engine body 10. Specifically, as shown in Figures 3 and 4, an EGR valve case 43 incorporating an EGR valve 42 and an EGR valve actuator 44 are disposed to the right of the engine body 10 and behind the intake manifold 38. The EGR cooler 41 is disposed to the right of the engine body 10 at a position between the intake manifold 38 and the exhaust manifold 52 in the up-down direction, with an orientation extending in the front-rear direction.

[0036] (Detailed structure of the exhaust manifold) The detailed structure of the exhaust manifold 52 will be described. Fig. 5 is a diagram showing a part of the cross section taken along line VV in Fig. 4, and is a diagram showing the structure of the upstream portion of the exhaust manifold 52 (a first exhaust manifold portion 61 described later). Fig. 6 is a diagram showing a state in which a second member 70B constituting an outer pipe 70 described later in Fig. 5 has been removed. Fig. 7 is a diagram showing Fig. 6 as viewed from the direction of arrow X, and corresponds to Fig. 6 as viewed from the right side.

[0037] 5, the first exhaust port 15A extends from the opening on the rotor accommodating chamber R while bending toward the right, and opens at the right side surface 10C of the first side housing 14A. Similarly, the second exhaust port 15B extends from the opening on the rotor accommodating chamber R while bending toward the right, and opens at the right side surface 10C of the second side housing 14B. Although not shown, each intake port 16A, 16B also extends from the opening on the rotor accommodating chamber R toward the right while bending, and opens at the right side surface 10C of each side housing 14A, 14B.

[0038] In the following description of the exhaust manifold 52, the upstream and downstream in the exhaust gas flow direction are referred to as upstream and downstream, respectively. Also, the open ends formed on the right side surfaces 10C of the side housings 14A and 14B of the exhaust ports 15A and 15B are simply referred to as open ends. Also, the first side housing 14A is located on the front side in the front-rear direction, and is located on "one side" in the claims. The second side housing 14B is located on the rear side in the front-rear direction, and is located on "the other side" in the claims.

[0039] 5 and other figures, the exhaust manifold 52 has a first exhaust manifold portion 61 constituting the upstream portion of the exhaust manifold 52, a second exhaust manifold portion 62 constituting the downstream portion, and a mounting flange 63. The first exhaust manifold portion 61, the second exhaust manifold portion 62, and the mounting flange 63 are all made of metal and are integrally formed by welding or the like.

[0040] The first exhaust manifold portion 61 has a shape that extends in the front-rear direction, i.e., along the axial direction of the shaft 12, and is provided to the right of the engine body 10. The second exhaust manifold portion 62 has a shape that bulges diagonally forward and right, and curves diagonally forward and left from the front end of the first exhaust manifold portion 61 to a position in front of the engine body 10. A downstream end portion of the second exhaust manifold portion 62 is connected to the downstream exhaust passage 53.

[0041] The mounting flange 63 has a plate shape extending in the front-rear and up-down directions along the right side surface 10C of the engine body 10. The mounting flange 63 is a member for fixing the exhaust manifold 52 to the engine body 10, and the mounting flange 63 is fixed to the right side surface 10C of the engine body 10 with a plurality of bolts, thereby fixing the exhaust manifold 52 to the engine body 10. In this embodiment, the mounting flange 63 is composed of a first flange 63A connected to the first side housing 14A and a second flange 63B connected to the second side housing 14B. Although not shown in the figure, a thin plate-shaped seal member is sandwiched between the right side surface 10C of the engine body 10 and the mounting flange 63.

[0042] (First exhaust manifold section) The first exhaust manifold portion 61 extends from the opening end 115B of the second exhaust port 15B to a position forward of the opening end 115A of the first exhaust port 15A. The first exhaust manifold portion 61 communicates with the opening ends 115A, 115B of these exhaust ports 15A, 15B.

[0043] The first exhaust manifold 61 has a first inner pipe 72A that is continuous with the first exhaust port 15A and defines a flow path that bends toward the rear side in the front-rear direction (the axial direction of the shaft 12) (the other side in the output shaft direction in the claims), a second inner pipe 72B that is continuous with the second exhaust port 15B and defines a flow path that bends toward the front side in the front-rear direction (the axial direction of the shaft 12) (one side in the output shaft direction in the claims), and a common outer pipe 70 that is connected to the first side housing 14A and the second side housing 14B in a state in which the first inner pipe 72A and the second inner pipe 72B are housed. The outer pipe 70, the first inner pipe 72A, and the second inner pipe 72B are all made of sheet metal members processed from plate material.

[0044] The outer pipe 70 has a shape extending in the front-rear direction from the first side housing 14A and the second side housing 14B, and extends from the open end 115B of the second exhaust port 15B to a position forward of the open end 115 of the first exhaust port 15A. Since the exhaust gas flowing in the outer pipe 70 flows from the rear side to the front side in the front-rear direction, the front side in the front-rear direction corresponds to the downstream side in the flow direction of the exhaust gas in the outer pipe 70, and the rear side in the front-rear direction corresponds to the upstream side in the flow direction of the exhaust gas in the outer pipe 70.

[0045] A first introduction section 74A into which exhaust gas discharged from the opening end 115A of the first exhaust port 15A is introduced is provided on the front side in the front-rear direction of the outer pipe 70. A second introduction section 74B into which exhaust gas discharged from the second exhaust port 15B is introduced is provided on the rear side of the first introduction section 74A in the front-rear direction of the outer pipe 70. The first introduction section 74A and the second introduction section 74B are formed integrally with the outer pipe 70.

[0046] The first introduction part 74A is a cylindrical member with a circular or elliptical cross section that extends in the left-right direction perpendicular to the front-rear direction. The open end of the first introduction part 74A that communicates with the first exhaust port 15A is inserted without any gap into the first through hole 76A that penetrates the first flange 63A. In this state, the first introduction part 74A and the through hole 76A of the first flange 63A are welded around the entire circumference, thereby preventing the exhaust gas introduced into the first introduction part 74A from leaking out to the outside.

[0047] The second introduction part 74B is a cylindrical member extending in the left-right direction and having a circular or elliptical cross section. The open end of the second introduction part 74B, which communicates with the second exhaust port 15B, is inserted without a gap into the second through hole 76B that penetrates the second flange 63B. In this state, the second introduction part 74B and the through hole 76B of the second flange 63B are welded to each other around the entire circumference, thereby preventing the exhaust gas introduced into the second introduction part 74B from leaking out to the outside.

[0048] The outer tube 70 is composed of two members, a first member 70A and a second member 70B, which are obtained by dividing the outer tube 70 into approximately two equal parts in the left-right direction. The first member 70A constitutes a portion on the side (left side) approaching the first side housing 14 and the second side housing 14B in the left-right direction. The second member 70B constitutes a portion on the side (right side) away from the first side housing 14A and the second side housing 14B in the left-right direction. The first member 70A and the second member 70B are integrally formed by welding the mutually contacting portions. The welded portions of the first member 70A and the second member 70B correspond to the cross-hatched portions in FIG. 5.

[0049] The first member 70A and the second member 70B each have a generally trough-shaped cross section formed by a semicircular arc. When the first member 70A and the second member 70B are joined by welding, the rear end of the outer pipe 70 in the front-rear direction is closed, so that exhaust gas discharged from each exhaust port 15A, 15B moves toward the front side (downstream side) in the front-rear direction. The first member 70A is integrally formed with the first introduction section 74A and the second introduction section 74B.

[0050] When assembling the exhaust manifold 52, the first inner pipe 72A and the second inner pipe 72B are attached to the first inlet portion 74A and the second inlet portion 74B, respectively, formed in the first member 70A, and then the first member 70A and the second member 70B are welded together, whereby the first inner pipe 72A and the second inner pipe 72B are housed within the outer pipe 70.

[0051] The first inner pipe 72A is composed of a curved pipe having a circular (or elliptical) cross section formed in an L-shape. The first inner pipe 72A includes a first upstream section 78 that is connected to the open end 115A of the first exhaust port 15A and constitutes the upstream side in the flow direction of the exhaust gas in the first inner pipe 72A, and a first downstream section 80 that is connected to the downstream end of the first upstream section 78 and constitutes the downstream side in the flow direction of the first inner pipe 72A. The connecting portion of the first upstream section 78 and the first downstream section 80 has a curved shape that allows the exhaust gas to flow smoothly.

[0052] The first upstream section 78 is provided along the left-right direction. The left end of the first upstream section 78 is connected to the open end 115A of the first exhaust port 15A. The right end of the first upstream section 78 is connected to the first downstream section 80. The first downstream section 80 is provided along the front-rear direction, i.e., the axial direction of the shaft 12. One end of the first downstream section 80 is connected to the first upstream section 78. The other end of the first downstream section 80 opens toward the second inner pipe 72B. In this embodiment, the first downstream section 80 is formed with a longer pipe path than the first upstream section 78.

[0053] The second inner pipe 72B is composed of a curved pipe having a circular (or elliptical) cross section formed into an L-shape. The second inner pipe 72B includes a second upstream section 82 that is connected to the open end 115B of the second exhaust port 15B and constitutes the upstream side in the flow direction of the exhaust gas in the second inner pipe 72B, and a second downstream section 84 that is connected to the downstream end of the second upstream section 82 and constitutes the downstream side in the flow direction of the second inner pipe 72B. The connecting portion of the second upstream section 82 and the second downstream section 84 has a curved shape that allows the exhaust gas to flow smoothly.

[0054] The second upstream section 82 is provided so as to extend along the left-right direction. A left end portion of the second upstream section 82 is connected to the open end 115B of the second exhaust port 15B. A right end portion of the second upstream section 82 is connected to the second downstream section 84. The second downstream section 84 is provided so as to extend along the front-rear direction, i.e., the axial direction of the shaft 12. One end portion of the second downstream section 84 is connected to the second upstream section 82. The other end portion of the second downstream section 84 opens toward the first inner pipe 72A.

[0055] A portion of the first upstream section 78 facing the first introduction section 74A is connected in a state where it is inserted into the opening of the first introduction section 74A. Specifically, the outer diameter of the end of the first upstream section 78 connected to the first introduction section 74 is set to a dimension that allows sliding contact with the inner circumferential surface of the first introduction section 74A, and the end of the first upstream section 78 is welded and connected in a state where it is inserted into the opening of the first introduction section 74A.

[0056] Here, it is preferable that the first upstream portion 78 and the first introduction portion 74A are partially welded. Specifically, in a state where the end of the first upstream portion 78 is inserted into the opening of the first introduction portion 74A, the outer peripheral surface of the first upstream portion 78 and the inner peripheral surface of the first introduction portion 74A are welded along the circumferential direction. At this time, it is preferable to partially weld at a plurality of points in the circumferential direction rather than welding continuously over the entire circumferential direction. By partially welding these, relative deformation between the members is permitted, so that cracks in the welded portion are suppressed. Note that, although there is a risk of exhaust gas leaking if these are partially welded, since the outer pipe 70 and the first flange 63A are welded over the entire circumference, exhaust gas does not leak to the outside.

[0057] The portion of the second upstream section 82 facing the second introduction section 74B is connected in a state where it is inserted into the opening of the second introduction section 74B. Specifically, the outer diameter of the end of the second upstream section 82 connected to the second introduction section 74B is set to a dimension that allows sliding contact with the inner peripheral surface of the second introduction section 74B, and the end of the second upstream section 82 is welded and connected in a state where it is inserted into the opening of the second introduction section 74B. At this time, similar to the welding of the first upstream section 78 and the first introduction section 74A, it is preferable that the second upstream section 82 and the second introduction section 74B are partially welded together.

[0058] The downstream end of the first inner pipe 72A in the exhaust gas flow direction and the downstream end of the second inner pipe 72B in the exhaust gas flow direction are arranged to face each other in the axial direction of the shaft 12, separated by an annular gap L that functions as an outlet for exhaust gas flowing out from both inner pipes 72A, 72B to the outer pipe 70. In other words, the downstream end of the first inner pipe 72A (first downstream section 80) and the downstream end of the second inner pipe 72B (second downstream section 84) face each other across a gap in the front-to-rear direction (the flow direction of the outer pipe 70 or the axial direction of the shaft 12).

[0059] When the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B are disposed with the annular gap L between them, the exhaust gases discharged from the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B collide with each other. At this time, the exhaust gases are mixed together in the outer pipe 70, thereby homogenizing the exhaust gases. The colliding exhaust gas flows out from the annular gap L and moves toward the downstream side (one side in the output shaft direction in the claims) within the outer pipe 70.

[0060] Incidentally, when the area through which the exhaust gas flows out from the annular gap L formed between the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B is defined as the outer peripheral area S, the larger the outer peripheral area S, the weaker the degree of collision of the exhaust gas discharged from the downstream ends of the first inner pipe 72A and the second inner pipe 72B, making it difficult to homogenize the exhaust gas. On the other hand, the smaller the outer peripheral area S of the annular gap L, the easier it is to homogenize the exhaust gas, but the exhaust efficiency in the rotor accommodating chamber R may deteriorate or the outer pipe 70 may vibrate due to the exhaust gas exhaust pressure in the outer pipe 70 becoming high. In response to this, the outer peripheral area S of the annular gap L is appropriately adjusted so that the exhaust gas exhaust pressure is suppressed from becoming high while maintaining the effect of homogenizing the exhaust gas. Here, the outer peripheral area S of the annular gap L corresponds to the area of ​​a virtual cylinder formed by connecting the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B facing each other.

[0061] Preferably, the outer peripheral area S of the annular gap L is set to be 1.1 times or more and 1.3 times or less of the sum St (=SAm+SBm) of the cross-sectional area SAm, which is the minimum value of the cross-sectional area SA of the first exhaust port 15A, and the cross-sectional area SBm, which is the minimum value of the cross-sectional area SB of the second exhaust port 15B. The cross-sectional area SA of the first exhaust port 15A corresponds to the cross-sectional area obtained by cutting the first exhaust port 15A perpendicularly to the flow direction of the exhaust gas. In this embodiment, the cross-sectional area SA of the most upstream portion of the first exhaust port 15A, that is, the connection portion of the first exhaust port 15A with the rotor housing chamber R, corresponds to the minimum cross-sectional area SAm. The cross-sectional area SB of the second exhaust port 15B corresponds to the cross-sectional area obtained by cutting the second exhaust port 15B perpendicularly to the flow direction of the exhaust gas. In this embodiment, the cross-sectional area SB of the most upstream portion of the second exhaust port 15B, that is, the connection portion of the second exhaust port 15B with the rotor housing chamber R, corresponds to the minimum cross-sectional area SBm.

[0062] 7, an intermediate position M1 in the front-rear direction (axial direction of shaft 12) between the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B is located rearward (the other side in the claims) of an intermediate position M2 in the front-rear direction between the opening end 115A (downstream end) of the first exhaust port 15A and the opening end 115B (downstream end) of the second exhaust port 15B. In other words, the intermediate position M1 is located upstream of the intermediate position M2 in the flow direction of exhaust gas in the outer pipe 70.

[0063] Here, when exhaust gas collides in the outer pipe 70, the change in exhaust pressure of the exhaust gas in the outer pipe 70 becomes large, causing the outer pipe 70 to vibrate, and there is a risk of radiating sound due to the vibration of the outer pipe 70. In response to this, a first reinforcing member 90 and a second reinforcing member 92 are joined to the outer peripheral surface of the outer pipe 70 corresponding to the position where the exhaust gas collides in the outer pipe 70. Specifically, the first reinforcing member 90 and the second reinforcing member 92 are joined to the outer peripheral surface of the outer pipe 70 overlapping with the annular gap L when viewed in a direction perpendicular to the axial direction of the shaft 12. The first reinforcing member 90 and the second reinforcing member 92 reinforce the outer pipe 70 corresponding to the position where the exhaust gas collides in the outer pipe 70. The first reinforcing member 90 and the second reinforcing member 92 correspond to the "reinforcing member" in the claims.

[0064] The first reinforcing member 90 is joined to the first member 70A side of the outer pipe 70. The first reinforcing member 90 is made of a sheet metal member processed from a plate material, and is formed into a curved shape that conforms to the outer peripheral surface of the first member 70A. The outer peripheral surface of the first member 70A and the first reinforcing member 90 are partially welded along the outer edge of the first reinforcing member 90.

[0065] The second reinforcing member 92 is joined to the second member 70B side of the outer pipe 70. The second reinforcing member 92 is made of a sheet metal member processed from a plate material, and is formed into a curved shape that conforms to the outer peripheral surface of the second member 70B. The outer peripheral surface of the second member 70B and the second reinforcing member 92 are partially welded along the outer edge of the second reinforcing member 92.

[0066] (action, etc.) FIG. 8 is a diagram for explaining the operating state of a conventional rotary piston engine. The triangle in the upper part of FIG. 8 indicates the rotor, and the circle circumscribing the rotor indicates the rotor housing chamber. The rotor housing chamber is divided into three chambers (chamber 1, chamber 2, and chamber 3) by the rotor, and the position of each chamber moves in the circumferential direction as the rotor rotates clockwise. The state of the rotor at the left end of FIG. 8 is set as the reference position, and the rotation angle θ (rotation position) is defined as zero degrees. In addition, the state when the rotor rotates clockwise is shown every 90 degrees.

[0067] The middle part of Figure 8 shows the strokes for each room. Specifically, intake shows the intake stroke in which the intake port opens and air is drawn into the room. Compression shows the compression stroke in which the intake port is closed and the air in the room is compressed as the rotor rotates. Expansion shows the combustion and expansion stroke in which combustion takes place in the room and the air in the room expands. Exhaust shows the exhaust stroke in which the exhaust port opens and the exhaust gas after combustion in the rotor housing chamber is discharged to the outside. The arrowed section in the middle part of Figure 8 shows the period in which the exhaust port is open. As shown in the middle part of Figure 8, in a rotary piston engine, the period from when the exhaust port is closed to when it is opened again is short.

[0068] The lower part of FIG. 8 shows the change in the unburned fuel concentration λ (≒ exhaust air-fuel ratio) contained in the exhaust gas. The unburned fuel concentration shown by the dashed line in FIG. 8 shows the conventional structure in which the above-mentioned inner pipes 72A and 72B are not provided. As shown in the lower part of FIG. 8, when the exhaust port starts to open (rotation angle θ is zero degrees), the unburned fuel concentration λ is in a lean state where it is low, but as the rotor 11 rotates, the unburned fuel concentration λ increases, and the unburned fuel concentration λ becomes the highest rich state just before the exhaust port closes (rotation angle θ is 360 degrees). As described above, in a rotary piston engine, the time change in the unburned fuel concentration λ is large, so the fluctuation of the detection value of the oxygen concentration detected by the O2 sensor becomes large, and there is a problem that the controllability (robustness) of the feedback control of the exhaust gas based on the air-fuel ratio calculated from the oxygen concentration is reduced.

[0069] In contrast, in this embodiment, the first inner pipe 72A and the second inner pipe 72B are housed in the outer pipe 70 so that their downstream ends face each other, and the exhaust gases discharged from the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B collide and mix with each other. At this time, the exhaust gas is homogenized and moves downstream, so that the change in the unburned fuel concentration λ is smaller than that in the conventional structure, as shown by the solid line in Figure 8. As a result, the fluctuation of the oxygen concentration detected by the first O2 sensor 56 is reduced, improving the controllability (robustness) of the feedback control.

[0070] Furthermore, the collision of the exhaust gases promotes the combustion of unburned fuel contained in the exhaust gases, thereby reducing the amount of unburned fuel that reaches the purification device 51. As a result, the exhaust gases are effectively purified by the purification device 51, and the amount of harmful components discharged from the purification device 51 is further reduced.

[0071] Furthermore, by setting the outer peripheral area S of the annular gap L in the range of 1.1 to 1.3 times the sum of the minimum cross-sectional area SAm of the first exhaust port 15A and the minimum cross-sectional area SBm of the second exhaust port 15B, it is possible to suppress the exhaust pressure of the exhaust gas from becoming high while maintaining the effect of homogenizing the exhaust gas. As a result, it is possible to suppress a deterioration in exhaust efficiency caused by the exhaust pressure of the exhaust gas in the outer pipe 70 becoming high, and vibration of the outer pipe 70 caused by changes in exhaust pressure.

[0072] In addition, since the intermediate position M1 between the downstream end of the first inner pipe 72A and the downstream end of the second inner pipe 72B is located upstream of the intermediate position M2 between the downstream end of the first exhaust port 15A and the downstream end of the second exhaust port 15B in the axial direction of the shaft 12, the exhaust gas collides upstream of the intermediate position M2 between the downstream end of the first exhaust port 15A and the downstream end of the second exhaust port 15B. As a result, the time required for the exhaust gas to reach the first O2 sensor 56 becomes longer, so that the exhaust gas becomes more homogenous, and the fluctuation of the oxygen concentration detected by the first O2 sensor 56 can be further reduced. In addition, the amount of unburned fuel that is burned before reaching the purification device 51 can be increased.

[0073] In addition, since the first reinforcing member 90 and the second reinforcing member 92 are joined to the circumferential surface of the outer pipe 70 overlapping with the annular gap L when viewed in a direction perpendicular to the axial direction of the shaft 12, the portion of the outer pipe 70 where the exhaust gas collides is reinforced, and vibration of the outer pipe 70 caused by the collision of the exhaust gas is suppressed. As a result, vibration of the outer pipe 70 and the radiated sound caused by the vibration can be suppressed.

[0074] In addition, since the outer pipe 70, the first inner pipe 72A, and the second inner pipe 72B are all sheet metal components processed from plate material, their wall thicknesses are thinner than if they were manufactured by casting, etc., and the exhaust manifold 52 can be made lighter.

[0075] (Modification) In the above embodiment, the dimension of the annular gap L in the front-rear direction is the same at any position in the circumferential direction of the first inner pipe 72A and the second inner pipe 72B, but this is not necessarily limited to this. For example, the dimension of the annular gap L in the front-rear direction may vary in the circumferential direction. In addition, the downstream end of each of the inner pipes 72A, 72B may be formed in a sawtooth or wavy shape along the circumferential direction of the pipe. In addition, a hole penetrating the pipe may be formed near the downstream end of each of the inner pipes 72A, 72B.

[0076] In the above embodiment, the intermediate position M1 in the front-rear direction of the annular gap L is located upstream of the intermediate position M2 between the downstream end of the first exhaust port 15A and the downstream end of the second exhaust port 15B in the exhaust gas flow direction, but this is not necessarily limited to this. For example, the intermediate position M1 and the intermediate position M2 may be located at the same position in the axial direction of the shaft 12.

[0077] In the above embodiment, the reinforcing member for reinforcing the outer pipe 70 is composed of the first reinforcing member 90 and the second reinforcing member 92, but this is not necessarily limited to this. For example, the reinforcing member may be composed of one member, which is joined so as to cover the entire outer peripheral surface of the outer pipe 70. Furthermore, if vibrations generated in the outer pipe 70 are not a problem, the reinforcing member may be omitted.

[0078] In the above embodiment, the rotary piston engine 1 is a one-rotor type having only one rotor 11, but the above configuration may be applied to a rotary piston engine having a plurality of rotors 11. [Explanation of symbols]

[0079] 1: Rotary piston engine 5: Exhaust passage 11: Rotor 12: Eccentric shaft (output shaft) 13: Rotor housing 14A: First side housing 14B: Second side housing 15A: First exhaust port 15B: Second exhaust port 70:Outer tube 72A: 1st inner pipe 72B:Second inner pipe 90: First reinforcing member (reinforcing member) 92: Second reinforcing member (reinforcing member) L: Annular gap M1: Midpoint between the downstream end of the first inner pipe and the downstream end of the second inner pipe M2: Midpoint between the downstream end of the first exhaust port and the downstream end of the second exhaust port R: Rotor Containment Room S: Peripheral area SAm: Minimum cross-sectional area of ​​the first exhaust port SBm: Minimum cross-sectional area of ​​the second exhaust port

Claims

1. A rotor that rotates around an output shaft; a cylindrical rotor housing that defines a peripheral wall of a rotor accommodating chamber that accommodates the rotor; a first side housing attached to the rotor housing so as to cover the rotor accommodating chamber from one side in an output axial direction parallel to an axis of the output shaft, the first side housing having a first exhaust port for receiving exhaust gas discharged from the rotor accommodating chamber; a second side housing attached to the rotor housing so as to cover the rotor accommodating chamber from the other side in the output shaft direction, the second side housing having a second exhaust port that receives exhaust gas discharged from the rotor accommodating chamber; an exhaust passage connected to the first side housing and the second side housing, for receiving exhaust gas discharged to the outside of each side housing through the first exhaust port and the second exhaust port, the exhaust passage includes a first inner pipe that is continuous with the first exhaust port and defines a flow path that bends toward the other side in the output axial direction, a second inner pipe that is continuous with the second exhaust port and defines a flow path that bends toward one side in the output axial direction, and a common outer pipe that is connected to the first side housing and the second side housing in a state in which the first inner pipe and the second inner pipe are accommodated therein, The downstream end of the first inner pipe and the downstream end of the second inner pipe face each other in the output shaft direction across an annular gap that functions as an outlet for exhaust gas flowing from both the inner pipes to the outer pipe. A rotary piston engine characterized by:

2. 2. The rotary piston engine according to claim 1, The outer circumferential area of ​​the annular gap is 1.1 to 1.3 times the sum of the minimum cross-sectional area of ​​the first exhaust port and the minimum cross-sectional area of ​​the second exhaust port. A rotary piston engine characterized by:

3. The rotary piston engine according to claim 1 or 2, the outer pipe has a shape extending from the first side housing and the second side housing toward one side in the output shaft direction such that exhaust gas flowing out from the annular gap flows toward one side in the output shaft direction, An intermediate position between the downstream end of the first inner pipe and the downstream end of the second inner pipe is located on the other side in the output shaft direction with respect to an intermediate position between the downstream end of the first exhaust port and the downstream end of the second exhaust port. A rotary piston engine characterized by:

4. The rotary piston engine according to claim 1 or 2, A reinforcing member is joined to a peripheral surface of the outer pipe that overlaps with the annular gap when viewed in a direction perpendicular to the output shaft direction. A rotary piston engine characterized by:

5. The rotary piston engine according to claim 1 or 2, The outer tube, the first inner tube, and the second inner tube are all sheet metal members formed by processing a plate material. A rotary piston engine characterized by:

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