JP2020097913A - Exhaust device of engine - Google Patents

Abstract

To provide an exhaust device of an engine which can effectively oxidize an unburnt component in an exhaust gas by using air introduced into an exhaust passage.SOLUTION: An engine having an engine main body 1 in which a cylinder 7 is formed, an exhaust passage 13 in which an exhaust gas discharged from the cylinder 7 circulates, and a catalyst device 34 arranged in the exhaust passage 13, and having a catalyst for purifying the exhaust gas comprises: an upstream-side air introduction part 81 for introducing air from the outside into the exhaust passage 13 at an upstream side rather than the catalyst device 34; and a downstream-side air introduction part 41 for introducing air from the outside into the exhaust passage 13 at a downstream side rather than a portion into which air is introduced by the upstream-side air introduction part 81.SELECTED DRAWING: Figure 1

Description

The present invention relates to an engine exhaust system including an engine body having a cylinder and an exhaust passage through which exhaust gas discharged from the cylinder flows.

As an exhaust system for an engine, one disclosed in Patent Document 1 below is known. In the exhaust device of Patent Document 1, a turbocharger turbine is provided in the middle of the exhaust passage, and a catalyst device including a three-way catalyst is provided in the exhaust passage further downstream than the turbine. A secondary air supply passage for introducing air (secondary air) from the outside into the exhaust passage is connected to the exhaust passage located between the turbine and the engine body.

JP, 2013-167188, A

If secondary air is introduced into the exhaust passage as in Patent Document 1, it is possible to cause an oxidation reaction between unburned components (HC and the like) in the exhaust gas and the secondary air. The reaction heat can raise the temperature of the exhaust gas on the downstream side of the introduction position of the secondary air to promote the activation of the catalyst.

Here, when the temperature of the exhaust gas is low, the above oxidation reaction cannot be sufficiently caused. Therefore, it is desirable that the secondary air is supplied to a portion on the upstream side of the exhaust passage where the temperature of the exhaust gas is maintained at a high temperature. However, immediately after the start of the exhaust stroke, high-pressure exhaust gas is discharged from the cylinder, and the pressure at the upstream side portion of the exhaust passage becomes extremely high. Therefore, in this case, it becomes difficult to introduce the secondary air from the outside to the upstream side portion of the exhaust passage, and the unburned component cannot be appropriately oxidized.

The present invention has been made in view of the above circumstances, and provides an exhaust system for an engine capable of effectively oxidizing unburned components in exhaust gas by air introduced into an exhaust passage. With the goal.

As a solution to the above problems, the present invention provides an engine body having a cylinder, an exhaust passage through which exhaust gas discharged from the cylinder flows, and an exhaust passage provided in the exhaust passage to purify the exhaust gas. A catalyst device including a catalyst for performing, an upstream air introduction part for introducing air from the outside into the exhaust passage on the upstream side of the catalyst device, and a part to which air is introduced by the upstream air introduction part And a downstream air introduction section for introducing air from the outside into the exhaust passage on the downstream side of the exhaust passage (claim 1).

In the present invention, air introduction portions for introducing air into the exhaust passage are provided at different positions in the upstream and downstream directions of the exhaust passage. Therefore, air can be introduced into the exhaust gas that is still maintained at a high temperature from the air introduction section on the upstream side, and the oxidation reaction between air and unburned components can be promoted. Then, for exhaust gas exhausted from the cylinder immediately after the start of the exhaust stroke and for which it is difficult to supply air from the upstream air introduction portion, a predetermined time has elapsed since the start of the exhaust stroke. When this exhaust gas moves to the downstream side after the passage of time and when the pressure in the exhaust passage decreases, air can be supplied from the air introduction section on the downstream side, and the unburned component of this exhaust gas Can also be appropriately oxidized. Therefore, the unburned components in the exhaust gas can be effectively oxidized. Here, the temperature of the exhaust gas discharged from the cylinder is very high immediately after the start of the exhaust stroke, and even if the exhaust gas moves to the downstream side, the temperature is maintained high. Therefore, even in the vicinity of the air introduction portion on the downstream side, it is possible to appropriately oxidize the unburned components in the exhaust gas discharged from the cylinder immediately after the start of the exhaust stroke.

In the above configuration, preferably, an upstream side switching device that allows or stops the introduction of air from the upstream side air introduction part to the inside of the exhaust passage, and from the downstream side air introduction part to the inside of the exhaust passage. A downstream side switching device that allows or stops the introduction of air is further provided, and the upstream side switching device and the downstream side switching device include the upstream side switching device when at least the temperature of the catalyst is lower than a predetermined value. Air is allowed to be introduced into the exhaust passage from the introduction portion and the downstream air introduction portion, respectively (claim 2).

According to this configuration, the catalyst in the catalyst device can be rapidly activated by utilizing the exhaust gas whose temperature is raised due to the oxidation of the unburned components as described above.

In the above configuration, preferably, further comprising an air-fuel ratio changing means capable of changing an air-fuel ratio in the cylinder, wherein the upstream side switching device and the downstream side switching device are the upstream side air introduction part and the downstream side air introduction part. To allow the introduction of air into the exhaust passage, the air-fuel ratio changing means sets the air-fuel ratio in the cylinder to less than the theoretical air-fuel ratio (claim 3).

According to this configuration, a larger amount of unburned components is introduced into the exhaust passage, and the air introduced from each air introduction section and the unburned components are oxidized in the exhaust passage to generate in the exhaust passage. The combustion energy can be increased. Then, this energy can be utilized for early activation of the catalyst as described above.

In the above configuration, preferably, the downstream air introduction section includes a first tube section through which exhaust gas passes inside, a second tube section arranged so as to surround an outer circumference of the first tube section, and the second tube section. A downstream side intake part for taking in air into a gap formed between the first pipe part and the second pipe part, and the downstream end part of the first pipe part is the second pipe part of the second pipe part. The flow passage area of the downstream end of the first pipe portion is set to a value smaller than the flow passage area of the exhaust gas passage that flows upstream from the downstream end portion. (Claim 4).

According to this structure, the downstream air introducing portion including the first pipe portion and the second pipe portion arranged so as to form the double pipe structure is provided in the exhaust passage, so that the air passes through the first pipe portion. The exhaust gas generated can be kept warm, and the oxidation reaction between the exhaust gas and unburned components can be promoted. In addition, the flow passage area of the downstream end portion of the first pipe portion is smaller than the flow passage area of the exhaust gas passage that flows upstream of the downstream end portion (the passage area of the passage through which the exhaust gas flows). Therefore, the flow velocity of the exhaust gas after passing through the first pipe portion is higher than the flow velocity before passing through the first pipe portion. Such an increase in the speed of the exhaust gas causes a so-called ejector effect, and makes the pressure in the gap between the first pipe portion and the second pipe portion negative. As a result, the inflow of air from the outside into the exhaust passage via the downstream intake portion can be promoted.

In the above configuration, preferably, the engine body is formed with an exhaust port that constitutes an upstream end of the exhaust passage, and the upstream air introducing portion is formed with a passage communicating with the exhaust port inside. The upstream side pipe part, an upstream side intake part for taking in air inside the upstream side pipe part, and an upstream side intake part extending from the upstream side intake part to the inside of the exhaust port. A guide portion for guiding the taken-in air into the exhaust port (claim 5).

With this configuration, air can be introduced to a position closer to the cylinder and the temperature of the exhaust gas is maintained higher, and the oxidation reaction of the unburned components in the exhaust gas can be further promoted.

Here, in the rotary piston engine, the pressure of the exhaust gas discharged from the cylinder is higher than in the reciprocating engine, and the pressure in the exhaust passage immediately after the start of the exhaust stroke tends to be high, that is, from the air introduction portion on the upstream side to the exhaust passage. It is easy to introduce air. Therefore, it is effective when the present invention is applied to a rotary piston engine (claim 6).

As described above, according to the exhaust system for an engine of the present invention, the unburned components in the exhaust gas can be effectively oxidized by the air introduced into the exhaust passage.

1 is a schematic system diagram showing a preferred embodiment of a turbocharged engine to which an exhaust system of the present invention is applied. It is a schematic sectional drawing which shows an engine main body. It is a partially enlarged view of FIG. 1 which shows the structure of a turbocharger and its peripheral components. It is sectional drawing for demonstrating the detailed structure of an air introduction part. 6 is a graph showing changes in each parameter with respect to eccentric angle. It is the block diagram which showed the control system of the engine. It is a figure for demonstrating other embodiment of this invention.

(1) Overall Configuration FIG. 1 is a schematic system diagram showing a preferred embodiment of an engine to which the exhaust system of the present invention is applied, and FIG. 2 is a schematic sectional view showing an engine body 1 of the engine. In addition, in FIG. 2, the illustration of the secondary air system 40 described later is omitted. The engine shown in this figure is a 4-cycle gasoline engine mounted on a vehicle as a power source for traveling, and includes an engine body 1 in which a rotor accommodating chamber 7 described later is formed, and an intake air introduced into the engine body 1. Includes an intake pipe 20 that circulates inside, an exhaust pipe 30 that exhaust gas discharged from the engine body 1 circulates inside, and a turbocharger 60 that is driven by the energy of the exhaust gas to supercharge intake air. ing. The engine also includes a secondary air system 40 that introduces air from the outside into the exhaust passage 13 through which the exhaust gas discharged from the rotor housing chamber 7 flows. The exhaust pipe 30 constitutes a part of the exhaust passage 13 through which exhaust gas flows. Further, the intake pipe 20 constitutes an intake passage 12 through which intake air introduced into the rotor accommodating chamber 7 flows.

The engine body 1 is a two-rotor type rotary piston engine (hereinafter referred to as a rotary engine) having two rotors 2 that rotate around a rotation axis X. Note that, hereinafter, the direction parallel to the rotation axis X is referred to as the front-back direction, of which one side (the left side in FIG. 1) of the rotation axis X is the front side and the other side of the rotation axis X (the right side in FIG. 1) is the rear side. And

The engine body 1 includes the two rotors 2 described above, two rotor housings 3 that house the rotors 2 therein, an intermediate housing 4 provided between the rotor housings 3, and the rotor housings 3 and the intermediate housings 4. It has two side housings 5 attached so as to sandwich the front housing 4 from the front and rear.

The front side housing 5, the front rotor housing 3, and the intermediate housing 4 form a rotor housing chamber 7 that houses the front rotor 2. Similarly, the side housing 5 on the rear side, the rotor housing 3 on the rear side, and the intermediate housing 4 form a rotor accommodating chamber 7 for accommodating the rotor 2 on the rear side. The rotor housing chamber 7 corresponds to the "cylinder" in the claims. In other words, the engine of this embodiment is a two-cylinder engine including two cylinders.

The inner peripheral surface of each rotor housing 3 (the peripheral surface of each rotor accommodating chamber 7) is formed so as to follow a peritrochoid curve of two nodes when viewed in the front-rear direction (FIG. 2 ). Hereinafter, the inner peripheral surface of the rotor housing 3 is referred to as a trochoid inner peripheral surface 3a. The rotor accommodating chamber 7 surrounded by the trochoid inner peripheral surface 3a is a substantially elliptical space that is similar to a cocoon in the front-rear direction.

The intermediate housing 4 functions as a partition wall that separates the two rotor housing chambers 7 in the front-rear direction. The front side housing 5 is attached to the front rotor housing 3 so as to close the front surface of the front rotor housing chamber 7, and the rear side housing 5 is arranged so as to close the rear surface of the rear rotor housing chamber 7. Mounted on the side rotor housing 3.

The rotor 2 is a block body having a substantially triangular shape when viewed in the front-rear direction, has substantially the same thickness as the rotor housing 3, and is formed so as to be inscribed in its inner peripheral surface (trochoid inner peripheral surface 3a). The rotor 2 has, as its outer peripheral surface, three flank surfaces 2a corresponding to the respective sides of the triangle, and each flank surface 2a is formed in a curved surface shape that bulges outwardly in the radial direction. There is.

The rotor 2 has an apex seal (not shown) at a position corresponding to each vertex of the triangle. The apex seal is attached so as to be in sliding contact with the trochoid inner peripheral surface 3 a of the rotor housing 3. Inside the rotor accommodating chamber 7, three working chambers 8 defined by the respective flank surfaces 2a of the rotor 2 and the trochoid inner peripheral surface 3a are formed.

An annular oil seal 18 is attached to the side surfaces (front surface and rear surface) of the rotor 2. The oil seal 18 prevents excess lubricating oil from flowing into the working chamber 8.

The engine body 1 has an eccentric shaft 6 provided along the rotation axis X of the rotor 2. The eccentric shaft 6 extends in the front-rear direction so as to pass through the intermediate housing 4 and the front and rear side housings 5, respectively, and has eccentric portions 6a that are eccentrically expanded in two front and rear positions corresponding to the position of the rotor 2. doing. A circular hole is formed in the center of the rotor 2, and the eccentric portion 6a is fitted into the hole through a rotor bearing (not shown).

The rotor 2 is supported so as to make a planetary rotational movement with respect to the eccentric shaft 6 and rotate along the inner peripheral surface of the rotor housing chamber 7. That is, the rotor 2 is supported so as to revolve around the eccentric portion 6a of the eccentric shaft 6 and revolve around the rotation axis X in the same direction as the rotation (in a broad sense, including this rotation and revolution). Simply called the rotation of the rotor). When the rotor 2 rotates, three working chambers 8 simultaneously move in the circumferential direction accordingly, and intake, compression, expansion (combustion), and exhaust strokes are sequentially performed in each working chamber 8. The rotational force generated by the combustion in each working chamber 8 is output from the eccentric shaft 6 via the rotor 2.

An internal gear (not shown) is formed on the inner peripheral surface of the rotor 2, and a stationary gear (fixed gear) that constitutes an external gear that meshes with the internal gear is attached to the side housing 5. The internal gear and the stationary gear are combined in a gear ratio such that the eccentric shaft 6 makes three revolutions while the rotor 2 makes one revolution.

In the case of this embodiment, the rotor 2 rotates in the clockwise direction (the direction of the arrow) in FIG. The right side of the rotor housing chamber 7, which is divided by the long axis Y of the rotor housing chamber 7 passing through the rotation axis X, is approximately the exhaust stroke and intake stroke areas, and the left side is the compression stroke and expansion stroke areas.

The intermediate housing 4 is formed with an intake port 10 communicating with the front rotor housing chamber 7, and the rear side housing 5 is formed with an intake port 10 communicating with the rear rotor housing chamber 7. ing. These intake ports 10 and 10 are formed at positions that open to the working chamber 8 in the intake stroke. That is, the intake port 10 is opened during the intake stroke, and the air (fresh air) supplied from the intake pipe 20 is introduced into the working chamber 8 through the opened intake port 10.

The engine body 1 is provided with one injector 15 for each rotor 2 for injecting fuel whose main component is gasoline into the intake port 10. The injector 15 for the front rotor 2 is attached to the intermediate housing 4 so as to face the corresponding intake port 10 (FIG. 2), and the injector 15 for the rear rotor 2 faces the corresponding intake port 10. Is attached to the rear side housing 5 (not shown).

An exhaust port 11 communicating with the front rotor housing chamber 7 is formed in the front side housing 5, and an exhaust port 11 communicating with the rear rotor housing chamber 7 is formed in the intermediate housing 4. There is. These exhaust ports 11 and 11 are formed at positions that open to the working chamber 8 in the exhaust stroke. That is, the exhaust port 11 is opened during the exhaust stroke, and the exhaust gas in the working chamber 8 is discharged to the exhaust pipe 30 through the opened exhaust port 11. In this way, the exhaust gas discharged from the rotor housing chamber 7 flows inside the exhaust ports 11 and 11, and these exhaust ports 11 and 11 form a part of the exhaust passage 13. Further, the exhaust ports 11 and 11 are open to the rotor housing chamber 7 and constitute an upstream end portion of the exhaust passage 13 (an upstream end portion in the exhaust gas flow direction).

The engine body 1 is provided with two spark plugs 16 and 17 for each rotor 2 for igniting the air-fuel mixture. Each of the spark plugs 16 and 17 for the front rotor 2 and the rear rotor 2 is attached to the corresponding rotor housing 3 in a state of facing the working chamber 8 in a state where the compression stroke is completed (compression stroke is switched to expansion stroke). Each is installed. The spark plugs 16 and 17 are respectively arranged on the trailing side (lagging side) and the leading side (leading side) of the rotor accommodating chamber 7 with respect to the minor axis Z of the rotor accommodating chamber 7, and the mixing inside the working chamber 8 is performed. Ignition is performed to the air at the same time or with a predetermined phase difference.

The combustion cycle of the engine body 1 as described above proceeds as follows. First, the lower right working chamber 8 in FIG. 2 is in the intake stroke, and in this working chamber 8, the intake air introduced from the intake port 10 and the fuel injected from the injector 15 are mixed to form an air-fuel mixture. .. When the working chamber 8 moves to the lower left region as the rotor 2 rotates, the air-fuel mixture in the working chamber 8 is compressed, and the compression stroke is performed. When the rotor 2 rotates further, the compression stroke is almost completed, as in the working chamber 8 on the left side of FIG. 2, and ignition is performed by the spark plugs 16 and 17 in that state, and combustion of the air-fuel mixture is started. To be done. After that, the working chamber 8 moves to the upper left region, and the combustion gas in the working chamber 8 expands to perform the expansion stroke. When the rotor 2 further rotates and the working chamber 8 moves to the upper right region, the combustion gas in the working chamber 8 is discharged from the exhaust port 11, and the exhaust stroke is performed. After that, the procedure returns to the intake stroke again, and the same operation is repeated thereafter.

The intake pipe 20 has a single tubular common intake pipe 21, and a first independent intake pipe 22 and a second independent intake pipe 23 branched from the downstream end of the common intake pipe 21. The downstream end of the first independent intake pipe 22 is connected to the engine body 1 (intermediate housing 4) so as to communicate with the intake port 10 for the rotor 2 on the front side, and the downstream end of the second independent intake pipe 23 is , Is connected to the engine body 1 (rear side housing 5) so as to communicate with the intake port 10 for the rear rotor 2. In this specification, the downstream (or upstream) of the intake pipe 20 refers to the downstream (or upstream) in the flow direction of the intake air flowing through the intake pipe 20.

The common intake pipe 21 includes an air cleaner 24 that removes foreign matters contained in the intake air, a compressor 62 of the turbocharger 60, an intercooler 25 that cools the intake air supercharged by the turbocharger 60, and an intake air An openable/closable throttle valve 26 for adjusting the flow rate of intake air flowing through the pipe 20 is provided in this order from the upstream side.

The exhaust pipe 30 has a single tubular common exhaust pipe 33, and a first independent exhaust pipe 31 and a second independent exhaust pipe 32 that branch from the upstream end of the common exhaust pipe 33. The upstream end of the first independent exhaust pipe 31 is connected to the engine body 1 (front side housing 5) so as to communicate with the exhaust port 11 for the front rotor 2 and the upstream end of the second independent exhaust pipe 32. Is connected to the engine body 1 (intermediate housing 4) so as to communicate with the exhaust port 11 for the rear rotor 2. In this specification, the upstream (or downstream) of the exhaust pipe 30 and the exhaust passage 13 refers to the upstream (or downstream) of the exhaust gas flowing through the exhaust pipe 30 and the exhaust passage 13 in the flow direction.

The common exhaust pipe 33 is provided with a catalyst device 34. The catalyst device 34 contains a catalyst for purifying harmful components in the exhaust gas. In the present embodiment, the catalyst device 34 includes a three-way catalyst.

In the exhaust pipe 30, two downstream air introducing portions 41 for introducing air from the outside into the first and second independent exhaust pipes 31, 32, respectively, and outside each inside the exhaust ports 11, 11. Upstream air introduction portions 81, 81 for introducing air from the are provided. These air introduction parts 41, 41, 81, 81 are provided on the upstream side of exhaust gas from the catalyst device 34, and introduce air into the exhaust passage 13 on the upstream side of the catalyst device 34. The details of these air introduction parts 41, 41, 81, 81 will be described later.

FIG. 3 is an enlarged view of the turbocharger 60 and its peripheral components. As shown in FIG. 3 and FIG. 1 described above, the turbocharger 60 connects the turbine 61 provided in the exhaust pipe 30, the compressor 62 provided in the intake pipe 20, and the turbine 61 and the compressor 62 to each other. A connecting shaft 63, a turbine housing 64 that houses the turbine 61, and a compressor housing 65 that houses the compressor 62.

The turbine 61 rotates by receiving the energy of the exhaust gas flowing through the exhaust pipe 30, and rotates the compressor 62 via the connecting shaft 63. The compressor 62 rotates in conjunction with the turbine 61 to compress the intake air flowing through the intake pipe 20.

The compressor housing 65 is provided in the common intake pipe 21 in a portion located between the air cleaner 24 and the intercooler 25.

The turbine housing 64 is interposed between the downstream ends of the first independent exhaust pipe 31 and the second independent exhaust pipe 32 and the common exhaust pipe 33. The exhaust gas introduced into the turbine housing 64 from the first and second independent exhaust pipes 31, 32 is led out to the common exhaust pipe 33 after passing through the turbine 61.

The turbine housing 64 is a so-called twin scroll type, and has a first scroll portion 64a and a second scroll portion 64b therein. Both scroll parts 64a and 64b are partitioned by a partition wall S that divides the space around the turbine 61 into two in the axial direction of the turbine 61. The first scroll portion 64a communicates with the first independent exhaust pipe 31, and the second scroll portion 64b communicates with the second independent exhaust pipe 32. As a result, the exhaust gas from the first independent exhaust pipe 31 is introduced into the turbine 61 via the first scroll portion 64a, and the exhaust gas from the second independent exhaust pipe 32 is passed through the second scroll portion 64b to the turbine. It will be introduced in 61.

The turbine housing 64 is provided with a bypass passage 71 that connects the internal passage on the upstream side of the turbine 61 (first and second scroll portions 64 a and 64 b) and the internal passage on the downstream side of the turbine 61. The bypass passage 71 is provided with a wastegate valve 72 that is controlled to open and close so that the boost pressure does not exceed a predetermined upper limit value. Although the bypass passage 71 communicates only with the first scroll portion 64a in FIG. 1, the bypass passage 71 communicates not only with the first scroll portion 64a but also with the second scroll portion 64b. There is.

(2) Configuration of Secondary Air System As shown in FIG. 1, the secondary air system 40 includes the above-mentioned two downstream air introductions for introducing air into the first and second independent exhaust pipes 31, 32. Parts 41, 41, the above-mentioned two upstream side air introducing parts 81, 81 for introducing air into the exhaust ports 11, 11 from the outside, respectively, and the air introducing parts 41, 41, 81, 81 and intake air. It has a communication passage 42 that communicates with the pipe 20.

The communication passage 42 includes a common communication pipe 55 that branches from the common intake pipe 21 of the intake pipe 20 and extends, and a first independent communication pipe 56 and a second independent communication pipe 57 that branch from the downstream end of the common communication pipe 55. doing.

The upstream end of the common communication pipe 55 is connected to the portion of the common intake pipe 21 located downstream of the compressor 62 (between the compressor 62 and the intercooler 25). The downstream end of the first independent communication pipe 56 is connected to the downstream air introduction portion 41 and the upstream air introduction portion 81 for the first independent exhaust pipe 31 (for the front rotor 2). The downstream end portion of the second independent communication pipe 57 is connected to the downstream air introduction portion 41 and the upstream air introduction portion 81 for the second independent exhaust pipe 32 (for the rear rotor 2).

Into the common communication pipe 55, air is introduced from the intake pipe 20 to the air introduction parts 41, 41, 81, 81, and by extension, from the air introduction parts 41, 41, 81, 81 of the exhaust passage 13. A switching valve 58 is provided to allow or stop the introduction of air inside. Further, in the first independent communication pipe 56 and the second independent communication pipe 57, it is possible to prevent air from flowing back from the air introduction portions 41, 41, 81, 81 to the intake pipe 20 when the switching valve 58 is opened. A check valve 59 is provided for each.

The switching valve 58 corresponds to the "upstream switching device" and the "downstream switching device" in the claims. In addition, here, the case where the introduction of the air from the upstream side air introduction sections 81, 81 and the downstream side air introduction sections 41, 41 to the inside of the exhaust passage 13 is permitted or stopped by one switching valve 58 has been described. A switching device that allows or stops the introduction of air from the upstream air introduction parts 81, 81 into the exhaust passage 13 and the introduction of air from the downstream air introduction parts 41, 41 into the exhaust passage 13 Alternatively, a switching device that stops may be provided separately.

When the switching valve 58 is opened, a part of the air flowing through the intake pipe 20 (common intake pipe 21) is diverted to the communication passage 42 and supplied to the air introduction parts 41, 41, 81, 81. ..

The downstream air introducing portion 41 for the first independent exhaust pipe 31 and the downstream air introducing portion 41 for the second independent exhaust pipe 32 have the same structure. The upstream air introducing portion 81 for the first independent exhaust pipe 31 and the upstream air introducing portion 81 for the second independent exhaust pipe 32 have the same structure. FIG. 4 is a schematic cross-sectional view showing the details of the air introducing portions 41 and 81.

The upstream air introduction portion 81 includes an upstream outer pipe portion 82 in which a passage that extends downstream from the downstream opening end of the exhaust port 11 and communicates with the internal passage of the exhaust port 11 is formed inside, and an upstream outer pipe portion 82. The upstream inner pipe portion 83 is provided inside the pipe portion 82, and a passage through which exhaust gas passes is formed inside. In addition, the upstream air introduction portion 81 has an upstream intake portion 84 that opens into the outer peripheral surface of the upstream outer pipe portion 82 and takes in air inside the upstream outer pipe portion 82.

The upstream outer pipe portion 82 is attached to the engine body 1 so that the inner peripheral surface thereof is continuous with the inner peripheral surface of the downstream end of the exhaust port 11 in the upstream and downstream directions. Specifically, the upstream outer pipe portion 82 communicating with the exhaust port 11 for the rotor 2 on the front side is coupled to the side housing 5 on the front side, and the upstream outer pipe portion 82 communicating with the exhaust port 11 for the rotor 2 on the rear side. The outer side tube portion 82 is coupled to the intermediate housing 4. In the present embodiment, the upstream outer pipe portion 82 has a flange portion 82a at its upstream end, and the flange portion 82a and the housings 4 and 5 are joined together.

The upstream inner pipe portion 83 has a shape extending in the upstream/downstream direction across the upstream outer pipe portion 82 and the exhaust port 11. That is, the downstream end portion of the upstream inner pipe portion 83 is arranged inside the upstream outer pipe portion 82, and the portion upstream of this is arranged inside the exhaust port 11. The upstream-side inner pipe portion 83 extends from a position facing the downstream end of the upstream-side outer pipe portion 82 to the upstream end of the exhaust port 11, that is, the vicinity of the open end that opens to the rotor accommodating chamber 7. The upstream end and the downstream end of the upstream inner pipe portion 83 are open, and as described above, the exhaust gas discharged from the exhaust port 11 passes inside the upstream inner pipe portion 83.

The outer diameter of the upstream inner pipe portion 83 has an annular gap D1 (hereinafter, appropriately, in a cross-sectional view) between the outer peripheral surface thereof and the inner peripheral surface of the upstream outer pipe portion 82 and the inner peripheral surface of the exhaust port 11. The upstream side gap D1) is set to be partitioned. The upstream gap D1 is formed over the entire outer peripheral surface of the upstream inner pipe portion 83 in the upstream and downstream directions. The upstream outer pipe portion 82 and the upstream inner pipe portion 83 are arranged such that their central axes are substantially the same so that the radial dimension of the upstream gap D1 is substantially the same over the entire circumference. It

The upstream air introducing portion 81 has an annular shape that connects the outer peripheral surface of the downstream end portion of the upstream inner pipe portion 83 and the inner peripheral surface of the downstream end portion of the upstream outer pipe portion 82 over their entire circumferences. It has a wall 85, and the downstream end of the upstream gap D1 is closed by this annular wall 85. On the other hand, the upstream end of the upstream gap D1 is open inside the exhaust port 11.

The upstream-side intake portion 84 communicates with the upstream-side clearance D1, and the air flowing into the upstream-side outer pipe portion 82 via the upstream-side intake portion 84 is introduced into the upstream-side clearance D1. This air moves upstream through the upstream gap D1 and is drawn into the exhaust port 11. Then, this air is mixed with the exhaust gas near the upstream end of the upstream gap D1, that is, near the upstream end of the upstream inner pipe portion 83. In the present embodiment, the upstream intake portion 84 is provided near each of the housings 4 and 5, that is, near the downstream opening end of the exhaust port 11. As described above, in the present embodiment, the upstream clearance D1 is defined by the outer peripheral surface of the upstream inner pipe portion 83, and the air is guided from the upstream intake portion 84 to the upstream side through the upstream clearance D1. The inner pipe portion 83 on the upstream side functions as the "guide portion" in the claims. The upstream outer pipe portion 82 corresponds to the "third pipe portion" in the claims.

The downstream air introducing portion 41 includes a downstream inner pipe portion 53 through which the exhaust gas passing through the upstream inner pipe portion 83 passes, and a downstream side arranged so as to surround the outer peripheral surface of the downstream inner pipe portion 53. And an outer tube portion 52. Further, the downstream air introduction portion 41 has a downstream intake portion 54 that is open to the outer peripheral surface of the downstream outer pipe portion 52 and takes in air inside the downstream outer pipe portion 52. The downstream inner pipe portion 53 corresponds to the "first pipe portion" in the claims, and the downstream outer pipe portion 52 corresponds to the "second pipe portion" in the claims.

The downstream outer pipe portion 52 extends from the downstream end of the upstream outer pipe portion 82 to the downstream side, and is connected to the engine body 1 (the front side housing 5 or the intermediate housing 4) via the upstream outer pipe portion 82. Are combined.

The downstream outer pipe portion 52 has a straight tubular shape having an inner diameter larger than the outer diameter of the downstream inner pipe portion 53. The downstream end of the downstream side outer pipe portion 52 is coaxially arranged on the upstream side of the first independent exhaust pipe 31 or the second independent exhaust pipe 32, and the first independent exhaust pipe 31 or the second independent exhaust pipe 32. Is connected to the upstream end of the via a flange.

The downstream outer pipe portion 52 is arranged so that a part of the upstream side thereof surrounds the outer peripheral surface of the downstream inner pipe portion 53. As a result, an annular gap D2 (hereinafter referred to as the downstream gap D2) in cross section is formed between the outer peripheral surface of the downstream inner pipe portion 53 and the inner peripheral surface of the downstream outer pipe portion 52. It is like this. The upstream end of the downstream gap D2 is closed by an annular wall 85 over the entire circumference. On the other hand, the downstream end of the downstream gap D2 is open to the inside of the downstream outer pipe portion 52. It should be noted that the downstream inner pipe portion 53 and the downstream outer pipe portion 52 are arranged so that their central axes are substantially the same so that the radial dimension of the downstream gap D2 is substantially the same over the entire circumference. ing.

The downstream side inner pipe portion 53 extends from the downstream end of the upstream side inner pipe portion 83 to the downstream side, and through the upstream side inner pipe portion 83, the annular wall 85 and the upstream side outer pipe portion 82, the engine main body 1 (front side It is connected to the side housing 5 or the intermediate housing 4).

The downstream side inner pipe portion 53 has a part of the upstream side in a throttle shape such that the flow passage area becomes smaller toward the downstream side. Therefore, the flow passage area of the downstream end portion of the downstream inner pipe portion 53, that is, the outlet area A2 of the downstream inner pipe portion 53 is smaller than the flow passage area of the upstream portion of the downstream inner pipe portion 53. Further, the flow passage area of the downstream end portion of the upstream side inner pipe portion 83, that is, the outlet area A1 of the upstream side inner pipe portion 83 is set to be substantially the same as the flow passage area of the upstream end portion of the downstream side inner pipe portion 53, It is larger than the outlet area A2 of the downstream inner pipe portion 53. In other words, the outlet area A2 of the downstream inner pipe portion 53 is set to a value smaller than both the flow passage area of the upstream portion of the downstream inner pipe portion 53 and the outlet area A1 of the upstream inner pipe portion 83. There is. When the exhaust gas introduced from the upstream inner pipe portion 83 to the downstream inner pipe portion 53 passes through the downstream inner pipe portion 53 having such a shape and thus passes through the upstream inner pipe portion 83. It is discharged from the downstream side inner pipe portion 53 in a state where the flow velocity is higher than that.

The downstream-side intake portion 54 is formed near the upstream end of the downstream-side outer pipe portion 52, and communicates with the downstream-side gap D2. As a result, the air that has flowed into the downstream outer pipe portion 52 via the downstream intake portion 54 is introduced into the downstream gap D2. This air moves downstream through the downstream gap D2. Then, this air is mixed with the exhaust gas that has passed through the downstream inner pipe portion 53 near the downstream end of the downstream gap D2, that is, near the downstream end of the downstream inner pipe portion 53.

Immediately after the start of the exhaust stroke (exhaust port), the position of the downstream end of the downstream-side inner pipe portion 53 in the upstream/downstream direction is at the time when the pressure in the exhaust port 11 drops to a reference pressure lower than the pressure at the upstream end of the communication passage 42. Immediately after the opening of 11), it is set at a position where the exhaust gas discharged from the rotor housing chamber 7 to the exhaust port 11 exists. As described above, the upstream end of the communication passage 42 is connected to the common intake pipe 21 on the downstream side of the compressor 62, and the pressure at the upstream end of the communication passage 42 substantially matches the boost pressure. Therefore, the reference pressure is set to a pressure higher than the atmospheric pressure. Further, in the present embodiment, as will be described later, air is introduced into the exhaust passage 13 from each of the air introduction parts 41 and 81 when performing catalyst warm-up control for promoting activation of the catalyst device 34. Along with this, the downstream side inner pipe portion 53 is located at a position where the pressure of the exhaust port 11 drops to less than the reference pressure in a state where the engine is driven at a predetermined rotation speed at which the catalyst warm-up control is often performed. The downstream end of is disposed. The predetermined engine speed is, for example, 1500 rpm.

Details will be described with reference to FIG. In FIG. 5, eccentric angles (rotation of the eccentric shaft) of the pressure in the exhaust port 11, the moving distance of the exhaust gas discharged to the exhaust port 11 immediately after the start of the exhaust stroke, and the opening area of the exhaust port 11 are shown in this order from the top. Angle) is shown. FIG. 5 shows each change when the engine speed is the predetermined engine speed.

When the eccentric angle is t1, the exhaust port 11 starts opening the valve. Along with this, high-pressure exhaust gas is discharged to the exhaust port 11, and the pressure in the exhaust port 11 rapidly increases. After that, the pressure in the exhaust port 11 decreases as the exhaust stroke proceeds. When a predetermined time has elapsed (from t1) after the exhaust port 11 starts opening (when the eccentric angle is t2), the pressure in the exhaust port 11 decreases to the reference pressure. In the present embodiment, the engine body 1 is a rotary engine, and the exhaust port 11 opens and closes when the rotor 2 passes through a region facing the exhaust port 11. Therefore, as shown in FIG. Immediately after the opening, the opening area of the exhaust port 11 increases. As a result, a large amount of high-pressure exhaust gas is discharged to the exhaust port 11 immediately after the opening of the exhaust port 11 (immediately after the start of the exhaust stroke), and the pressure inside the exhaust port 11 becomes highest immediately after the opening of the exhaust port 11.

As shown in the second graph from the top of FIG. 5, the exhaust gas discharged from the rotor housing chamber 7 to the exhaust port 11 immediately after the opening of the exhaust port 11 moves to the downstream side with the passage of time. At the eccentric angle t2 where the pressure in the exhaust port 11 has dropped to the reference pressure, this exhaust gas (exhaust gas discharged from the rotor housing chamber 7 to the exhaust port 11 immediately after the opening of the exhaust port 11) is upstream of the exhaust port 11. It moves to the position on the downstream side by the distance L shown in FIG. 5 from the end.

As a result, the position of the downstream end of the downstream inner pipe portion 53 in the upstream/downstream direction is set to the position downstream of the upstream end of the exhaust port 11 by the distance L. The distance L is a distance along the flow path of the exhaust gas. This distance L is set to about 100 mm, for example.

(3) Control System FIG. 6 is a block diagram showing a control system of the engine. A PCM 90 for integrally controlling an engine and the like is mounted on the vehicle. The PCM 90 is a microprocessor and includes a well-known CPU, ROM, RAM and the like.

Detection signals from various sensors are input to the PCM 90. For example, the PCM 90 includes a rotation speed sensor SN1 that detects an engine speed, an air flow sensor SN2 that detects a flow rate of intake air flowing through the common intake pipe 21, and an intake pressure that detects a pressure of intake air flowing through the common intake pipe 21. The sensor SN3 and the catalyst temperature sensor SN4 for detecting the catalyst temperature which is the temperature of the catalyst device 34 are electrically connected. The air flow sensor SN2 is attached to a portion of the common intake pipe 21 between the air cleaner 24 and the compressor 62, and detects the intake flow rate of this portion. The intake pressure sensor SN3 is attached to a part of the common intake pipe 21 between the compressor 62 and the intercooler 25, and detects the intake pressure of this part, that is, the supercharging pressure. The PCM 90 performs various calculations based on information detected by these sensors (that is, engine speed, intake air flow rate, intake pressure, in-cylinder pressure, catalyst temperature), and the injector 15, throttle valve 26, spark plugs 16, 17 , The switching valve 58, the waste gate valve 72, etc. are controlled.

In this embodiment, when the temperature of the catalyst device 34 is lower than a predetermined reference temperature and the catalyst device 34 is not sufficiently activated, the catalyst device 34 is heated to accelerate the activation of the catalyst device 34. Machine control is implemented. The reference temperature is set to 350° C., for example.

The PCM 90 determines whether the catalyst temperature detected by the catalyst temperature sensor SN4 is lower than the reference temperature. The PCM 90 executes the catalyst warm-up control when it is determined that the catalyst temperature is lower than the reference temperature, and executes the normal control when it is determined that the catalyst temperature is equal to or higher than the reference temperature.

In the catalyst warm-up control, the air-fuel ratio in the rotor accommodating chamber 7 is less than the stoichiometric air-fuel ratio, and the ignition timing at which the spark plugs 16 and 17 ignite the air-fuel mixture is retarded. .. Further, in the catalyst warm-up control, the switching valve 58 is opened so that the air is introduced into the exhaust passage 13 from each of the air introduction parts 41, 41, 81, 81. In this embodiment, at this time, the switching valve 58 is fully opened. Further, in the present embodiment, the switching valve 58 is closed while the catalyst warm-up control is not performed, that is, when the catalyst temperature is equal to or higher than the reference temperature.

Specifically, when the PCM 90 determines that the catalyst temperature is lower than the reference temperature, the PCM 90 makes the opening of the throttle valve 26 closer to the closing side than the opening during normal control. That is, even if the engine speed and engine load are the same, the opening degree of the throttle valve 26 is lower during the catalyst warm-up control than during normal operation (when normal control is performed). Further, when the PCM 90 determines that the catalyst temperature is lower than the reference temperature, the PCM 90 causes the injector 15 to inject an amount of fuel such that the air-fuel ratio in the rotor housing chamber 7 becomes less than the stoichiometric air-fuel ratio. Specifically, the PCM 90 estimates the amount of air introduced into the rotor housing chamber 7 based on the detection value of the air flow sensor SN2 and the like, and the fuel whose air-fuel ratio becomes less than the theoretical air-fuel ratio with respect to the estimated air amount. Is calculated, and the injector 15 is driven so that the calculated amount of fuel is injected into the rotor housing chamber 7. As described above, in the present embodiment, the air-fuel ratio in the rotor housing chamber 7 is changed by the amount of fuel injected from the injector 15, and the injector 15 is the “air-fuel ratio changing means” in the claims. Equivalent to.

When the PCM 90 determines that the catalyst temperature is lower than the reference temperature, the PCM 90 sets the ignition timing to a timing that is on the retard side with respect to the timing during normal operation. That is, even if the engine speed and the engine load are the same, the ignition timing is set to be retarded when the catalyst warm-up control is performed as compared to during the normal operation. Then, the PCM 90 causes the spark plugs 16 and 17 to ignite at the set ignition timing.

Further, the PCM 90 uses the target value of the amount of air introduced into the rotor housing chamber 7 and the air introduced into the exhaust passage 13 by the air introduction parts 41, 41, 81, 81 according to the engine speed, the engine load, and the like. The target value of the amount is calculated, and the opening degree of the throttle valve 26 is controlled so that these target values are realized.

As described above, in the catalyst warm-up control, the combustion energy generated in the rotor housing chamber 7 is increased by setting the air-fuel ratio in the rotor housing chamber 7 to be less than the theoretical air-fuel ratio. Further, since the ignition timing is retarded, the timing at which the combustion energy is generated becomes closer to the opening start timing of the exhaust port 11, and the combustion energy generated in the rotor accommodating chamber 7 is exhausted. Efficiently discharged inside. Further, since the air-fuel ratio in the rotor accommodating chamber 7 is set to be less than the stoichiometric air-fuel ratio, unburned components (unburned fuel such as HC) are discharged to the exhaust passage 130. By introducing air from the introduction portions 41, 41, 81, 81, it is possible to cause an unburned component and air to undergo an oxidation reaction in the exhaust passage 13, and to suppress the discharge of the unburned component to the outside of the engine. At the same time, the heat of reaction raises the temperature of the exhaust gas. As described above, the air is introduced from each of the air introduction parts 41, 41, 81, 81 into the exhaust passage 13 on the upstream side of the catalyst device 34. Therefore, the exhaust gas heated by the reaction heat of the oxidation reaction is introduced into the catalyst device 34. In this way, by performing the catalyst warm-up control, the heat energy of the exhaust gas introduced into the catalyst device 34 is increased, and the catalyst device 34 is heated by receiving this heat energy.

(4) Functions and Effects, etc. As described above, in the present embodiment, when the temperature of the catalyst device 34 is lower than the reference temperature, the switching valve 58 is opened and the air introduction portions 41, 41, 81, 81. The air is introduced into the exhaust passage 13. Therefore, the unburned component (unburned fuel) in the exhaust gas and the air are oxidized in the exhaust passage 13 to increase the thermal energy of the exhaust gas, and the catalyst device 34 can be heated. Therefore, the catalyst device 34 can be activated early. Particularly, in the present embodiment, when the temperature of the catalyst device 34 is lower than the reference temperature, the catalyst warm-up control is performed so that the air-fuel ratio in the rotor housing chamber 7 becomes less than the theoretical air-fuel ratio. Therefore, by increasing the unburned component discharged into the exhaust passage 13 and reacting this with the air, the thermal energy of the exhaust gas can be reliably increased.

Further, in the present embodiment, as an air introduction portion for introducing air into the exhaust passage 13, an upstream air introduction portion 81 for introducing air into a portion on the upstream side of the exhaust passage 13 and a downstream side thereof. There are two air introducing parts, a downstream air introducing part 41 for introducing air into the part. Therefore, most of the unburned components contained in the exhaust gas discharged into the exhaust passage 13 can be reliably oxidized, and the thermal energy of the exhaust gas can be effectively increased. As a result, the catalyst device 34 can be activated early.

Specifically, the exhaust gas discharged from the rotor housing chamber 7 becomes lower in temperature as it moves to the downstream side, and the oxidation reaction is less likely to occur. On the other hand, in the present embodiment, the air can be introduced from the upstream air introducing portion 81 to the portion on the upstream side in the exhaust passage 13. Therefore, the exhaust gas can be mixed with air while being kept at a high temperature, and these reactions can be promoted. Particularly, in the present embodiment, the air is introduced into the exhaust ports 11, 11 by the upstream air introducing portions 81, 81. Therefore, more reliably, the air can be introduced into the exhaust gas in a state where the temperature of the exhaust gas is high, and the unburned component in the exhaust gas and the air can be oxidized.

However, as shown in FIG. 5, the pressure in the exhaust passage 13 immediately after the start of the exhaust stroke is very high. Therefore, if the air is simply introduced into the upstream portion of the exhaust passage 13, it must be provided after a predetermined time has elapsed from the start of the exhaust stroke and the pressure inside the exhaust passage 13 has dropped. In this case, it becomes difficult to introduce air into the exhaust passage 13. That is, air cannot be mixed into the exhaust gas discharged from the rotor housing chamber 7 immediately after the start of the exhaust stroke. On the other hand, in the present embodiment, since the downstream air introduction portion 41 capable of introducing air is provided in the portion on the more downstream side in the exhaust passage 13, the rotor accommodating chamber 7 immediately after the start of the exhaust stroke. Air can be mixed with the exhaust gas that has been discharged from the exhaust gas and then moved to the downstream side at the timing when the pressure in the exhaust passage 13 has decreased. Therefore, it is possible to introduce air into the exhaust gas discharged from the rotor accommodating chamber 7 immediately after the start of the exhaust stroke to cause an oxidation reaction of these. Here, as described above, the temperature of the exhaust gas decreases as the exhaust gas moves to the downstream side. However, the temperature of the exhaust gas discharged from the rotor housing chamber 7 immediately after the start of the exhaust stroke is very high. Therefore, the temperature of the exhaust gas is maintained relatively high even on the relatively downstream side. Therefore, even in the relatively downstream portion of the exhaust passage 13, the unburned components in the exhaust gas can be oxidized by the introduction of air.

In particular, in the present embodiment, the downstream air introduction portion 41 is provided with the downstream inner pipe portion 53 and the downstream outer pipe portion 52, and the downstream outer pipe portion 52 is provided with the downstream intake portion 54. In addition, the outlet area A2 of the downstream inner pipe portion 53 is set to a value smaller than the upstream area thereof. Therefore, the flow velocity of the exhaust gas after passing through the downstream inner pipe portion 53 can be made higher than the flow velocity before passing through the downstream inner pipe portion 53. Such an increase in the speed of the exhaust gas causes a so-called ejector effect, so that the pressure in the downstream side gap D2 described above is made negative. As a result, the introduction of air from the downstream intake portion 54 into the downstream gap D2 can be promoted, and immediately after the start of the exhaust stroke described above, immediately after the start of the above-described exhaust stroke, from the rotor accommodating chamber 7 on the downstream side of the downstream inner pipe portion 53. Air can be more reliably introduced into the exhaust gas discharged.

In addition, the downstream side outer pipe portion 52 is provided so as to surround the outer periphery of the downstream side inner pipe portion 53 through which the exhaust gas passes inside, so that a so-called double pipe structure is realized. Therefore, the temperature of the exhaust gas passing through the inner pipe portion 53 on the downstream side can be kept warm, and the oxidation reaction between the unburned components in the exhaust gas and the air can be further promoted.

Similarly, in the present embodiment, in the upstream air introduction portion 81 as well, the upstream outer pipe portion 52 is provided so as to surround the outer circumference of the upstream inner pipe portion 83 through which exhaust gas passes, so that the upstream side The exhaust gas passing through the inner pipe portion 83 can be kept warm, and the oxidation reaction between the unburned component in the exhaust gas and the air can be further promoted.

In addition, in the present embodiment, the upstream outer pipe portion 82 in which the upstream intake portion 84 is formed is connected to the engine body 1 (the intermediate housing 4, the side housing 5) and is provided inside the upstream outer pipe portion 82. The upstream side inner pipe portion 83 is arranged, and the upstream side portion of the upstream side inner pipe portion 83 is inserted into the exhaust port 11. Then, as described above, the upstream gap D1 is defined by the outer peripheral surface of the upstream inner pipe portion 83, and the air introduced from the upstream intake portion 84 into the upstream outer pipe portion 82 is upstream of the upstream gap D1. It is adapted to be guided to the upstream side through the side gap D1. Therefore, air can be introduced to a position on the upstream side in the exhaust port 11 without significantly changing the structure of the engine body 1.

Further, in the present embodiment, since the switching valve 58 is opened only when the temperature of the catalyst device 34 is lower than the reference temperature, the catalyst is activated early as described above, and unnecessary air is used as exhaust gas. It is possible to avoid that the temperature rises due to the introduction of. As a result, the reliability of the component group provided in the exhaust pipe 30 on the downstream side of the turbine 61 can be improved.

In the above embodiment, the switching valve 58 is opened only when the temperature of the catalyst in the catalyst device 34 is lower than the reference temperature to introduce air from the air introducing portions 41, 41, 81, 81 into the exhaust pipe 30. However, it is possible that the temperature of the exhaust gas is raised or the driving force of the turbine 61 is increased due to the high temperature of the exhaust gas, for example, even at other times. For example, under operating conditions where the engine load is high and the rotation speed is low (during low speed/high load operation), sufficient driving force for the turbine 61 may not be obtained even if the wastegate valve 72 is fully closed. is there. Therefore, it is possible to open the switching valve 58 under such a condition. In this way, the unburned components in the exhaust gas can be oxidized by using the air introduced into the exhaust pipe 30 from the air introduction parts 41, 81, and the turbine 61 can be sufficiently heated by the exhaust gas having a high temperature. Different driving force can be applied. As a result, the output torque of the engine during low-speed/high-load operation can be increased, and the acceleration performance of the vehicle can be improved. The air-fuel ratio at high engine load is generally a power air-fuel ratio richer than the stoichiometric air-fuel ratio (for example, A/F=about 12 to 13), so the unburned components in the exhaust gas increase. There is a tendency. Therefore, when the switching valve 58 is opened as described above during the low speed/high load operation, a relatively large amount of unburned components is oxidized by using the air introduced from the air introducing portions 41 and 81. Therefore, the energy of the exhaust gas and thus the driving force of the turbine 61 can be sufficiently increased.

Moreover, although the said embodiment demonstrated the case where the downstream air introduction part 41 was made into a double pipe structure as mentioned above, a single pipe structure may be employ|adopted. That is, the downstream inner pipe portion 53 may be omitted. However, even in this case, in order to efficiently introduce the air into the exhaust passage 13 by utilizing the ejector effect, the downstream side outer pipe portion 52 is configured such that the downstream side has a smaller flow passage area. Is preferred.

Further, the upstream air introducing portion 81 may also have a single tube structure. Further, in the upstream air introduction portion 81, instead of the structure in which the air is guided from the outside of the engine body 1 into the exhaust port 11 by the upstream inner pipe portion 83 (upstream gap D1), the inside of the exhaust port 11 is replaced. Alternatively, a passage may be formed in the engine body 1 to directly connect the independent communication pipes 56 and 57 with each other, and air may be introduced into the exhaust port 11 via this passage. Further, the position where the air is introduced by the upstream air introduction portion 81 is not limited to the inside of the exhaust port 11.

(5) Other Embodiments In the above embodiment, an example in which the exhaust system of the present invention is applied to a rotary engine has been described, but the present invention can be applied to not only a rotary engine but also a reciprocating engine. An example thereof will be described in detail with reference to FIG.

FIG. 7 shows a modified embodiment in which the present invention is applied to an in-line four-cylinder type reciprocating engine. The engine shown in the drawing has an engine body 101 having four cylinders 102A to 102D arranged in a row, an intake passage 120 through which intake air supplied to each cylinder 102A to 102D flows, and exhaust from each cylinder 102A to 102D. The exhaust passage 130 through which the exhaust gas flows, a secondary air system 140 that introduces air into the exhaust passage 130 from the outside, and a turbocharger 160 that is driven by the energy of the exhaust gas to supercharge intake air. I have it.

Each of the cylinders 102A to 102D is provided with an injector and a spark plug (both not shown). In the cylinders 102A to 102D, the air-fuel mixture of the fuel injected from the injector and the air introduced from the intake passage 120 burns with ignition by the spark plug. A piston (not shown) is slidably housed in each of the cylinders 102A to 102D. Each piston receives the expansion force due to the combustion and reciprocates in the cylinders 102A to 102D, and the reciprocating motion is converted into rotational motion and is taken out from the output shaft (crank shaft).

If the cylinders 102A, 102B, 102C, and 102D arranged in order from the left side to the right side of FIG. 7 are the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder, respectively, in the engine of FIG. 7, the first cylinder 102A→the third cylinder Ignition (combustion) is performed in the order of the cylinder 102C→the fourth cylinder 102D→the second cylinder 102B.

The intake passage 120 includes a single tubular common intake pipe 121, a surge tank 122 to which the downstream end of the common intake pipe 121 is connected, and four independent intakes that branch from the surge tank 122 and communicate with the cylinders 102A to 102D. And a tube 123.

The common intake pipe 121 is provided with an air cleaner 124, an intercooler 125, and a throttle valve 126 in this order from the upstream side.

The exhaust passage 130 has a single tubular common exhaust pipe 133, and a first independent exhaust pipe 131 and a second independent exhaust pipe 132 branched from the upstream end of the common exhaust pipe 133.

The common exhaust pipe 133 is provided with a catalyst device 134.

The first and second independent exhaust pipes 131 and 132 are branched pipes whose upstream ends are bifurcated. That is, the first independent exhaust pipe 131 has a collecting pipe portion 131c communicating with the common exhaust pipe 133 and two branch pipe portions 131a and 131b branching from the upstream end of the collecting pipe portion 131c. Similarly, the second independent exhaust pipe 132 has a collecting pipe portion 132c communicating with the common exhaust pipe 133 and two branch pipe portions 132a and 132b branched from the upstream end of the collecting pipe portion 132c.

The first independent exhaust pipe 131 is connected to the engine body 101 so that the upstream ends of the branch pipe portions 131a and 131b communicate with the first cylinder 102A and the fourth cylinder 102D via exhaust ports (not shown). There is. The second independent exhaust pipe 132 is connected to the engine body 101 so that the upstream ends of the branch pipe portions 132a and 132b communicate with the second cylinder 102B and the third cylinder 102C via an exhaust port (not shown). Has been done. The set of the first cylinder 102A and the fourth cylinder 102D, which communicates with the first independent exhaust pipe 131, and the set of the second cylinder 102B and the third cylinder 102C, which communicate with the second independent exhaust pipe 132, respectively, and thus the ignition order. The combination of cylinders whose exhaust stroke order (exhaust order) is not continuous.

The turbocharger 160 has a turbine 161, a compressor 162, and a connecting shaft 163. The turbine 161 is provided between the downstream ends of the first independent exhaust pipe 131 and the second independent exhaust pipe 132 and the common exhaust pipe 133, and the compressor 162 is provided in the middle of the common intake pipe 121.

The secondary air system 140 is divided from the two downstream side air introduction sections 141 and the four upstream side air introduction sections 181 respectively provided in the first independent exhaust pipe 131 and the second independent exhaust pipe 132, and the intake passage 120. And a communication passage 142 for supplying the air to each of the air introduction portions 141 and 181.

The downstream air introducing section 141 is provided in each of the collecting pipe portion 131c of the first independent exhaust pipe 131 and the collecting pipe portion 132c of the second independent exhaust pipe 132. The structure of each downstream side air introduction part 141 is almost the same as that of the above-mentioned embodiment, and the downstream side inner pipe part through which exhaust gas flows, the downstream outer pipe part surrounding this, and the downstream outer pipe part are provided. And a formed downstream intake portion. A switching valve 158 is provided in the communication passage 142, and when the switching valve 158 is opened, the air supplied from the intake passage 120 through the communication passage 142 passes through the respective downstream side air introducing portions 141 to the first and the first. The two independent exhaust pipes 131 and 132 are introduced into the inside.

The upstream air introducing portion 181 is provided in each of the branch pipe portions 131 a and 131 b of the first independent exhaust pipe 131 and each of the branch pipe portions 132 a and 132 b of the second independent exhaust pipe 132. The structure of each upstream air introduction portion 181 is almost the same as that of the above-described embodiment, and the upstream inner pipe portion, which is inserted inside the exhaust port and through which the exhaust gas flows, and the downstream end of the upstream inner pipe portion. It has an upstream side outer pipe part connected to the engine body and an upstream side intake part formed in the upstream side outer pipe part. The respective branch pipe portions 131a and 131b of the first independent exhaust pipe 131 are connected to the communication passage 142 via the same route as the downstream side air introduction portion 141 provided in the collecting pipe portion 131c of the first independent exhaust pipe 131. ing. Each branch pipe part 132a, 132b of the second independent exhaust pipe 132 is connected to the communication passage 142 via the same path as the downstream air introduction part 141 provided in the collecting pipe part 132c of the second independent exhaust pipe 132. ing. Then, like the downstream air introducing portions 141 and 142, when the switching valve 158 is opened, the air supplied from the intake passage 120 through the communication passage 142 passes through the upstream air introducing portions 181 to the first and second air passages 181. It is adapted to be introduced into the independent exhaust pipes 131 and 132.

Also in the modified embodiment of FIG. 7 described above, the air introduction portions 141 are provided at different positions in the upstream and downstream directions of the exhaust passages (first and second independent exhaust pipes 131 and 132) through which the exhaust gas discharged from each cylinder flows. , 181 are respectively provided, the unburned fuel contained in the exhaust gas can be effectively reacted with the air.

Moreover, in the said embodiment, each air introduction part 41, 81 (141, 181) and the part of the common intake pipe 21 (121) downstream of the compressor 62 are connected by the communicating path 42 (142), The case where air is supplied to the exhaust passage 13 (130) via the air introduction portions 41, 81 (141, 181) by the pressure difference between the supercharging pressure and the exhaust passage 13 (130) has been described. You may comprise so that air may be supplied to the air introduction parts 41 and 81 (141, 181) using a pressure feeding device. For example, a pump may be provided in the middle of the communication passage 42 (142).

1 engine body 13 exhaust passage 15 injector (air-fuel ratio changing means)
34 Catalyst device 41 Downstream air introduction part 52 Downstream outer pipe part (2nd pipe part)
53 Downstream side inner pipe part (first pipe part)
54 Downstream side intake part 58 Switching valve (upstream side switching device, downstream side switching device)
81 upstream air introducing portion 82 upstream outer pipe portion (third pipe portion)
83 Upstream side inner pipe (guide)
84 Upstream side intake part

Claims (6)

An engine body with a cylinder formed,
An exhaust passage through which exhaust gas discharged from the cylinder flows,
A catalyst device that is provided in the exhaust passage and includes a catalyst for purifying the exhaust gas;
An upstream air introducing portion for introducing air from the outside into the exhaust passage on the upstream side of the catalyst device,
An exhaust device for an engine, comprising: a downstream air introduction unit that introduces air from the outside into the exhaust passage on the downstream side of a portion where the air is introduced by the upstream air introduction unit. The exhaust system for an engine according to claim 1,
An upstream switching device that allows or stops the introduction of air from the upstream air introduction portion to the inside of the exhaust passage,
Further comprising a downstream switching device that allows or stops the introduction of air from the downstream air introduction part to the inside of the exhaust passage,
The upstream side switching device and the downstream side switching device respectively introduce air from the upstream side air introduction part and the downstream side air introduction part into the exhaust passage at least when the temperature of the catalyst is lower than a predetermined value. An engine exhaust system, characterized in that it is allowed to be operated. The exhaust system for an engine according to claim 2,
Further comprising air-fuel ratio changing means capable of changing the air-fuel ratio in the cylinder,
When the upstream switching device and the downstream switching device allow air to be introduced into the exhaust passage from the upstream air introducing portion and the downstream air introducing portion, respectively, the air-fuel ratio change An exhaust system for an engine, characterized in that the means makes the air-fuel ratio in the cylinder less than the stoichiometric air-fuel ratio. The exhaust system for an engine according to any one of claims 1 to 3,
The downstream side air introducing section has a first pipe section through which exhaust gas passes inside, a second pipe section arranged so as to surround the outer periphery of the first pipe section, the first pipe section, and the second pipe section. It has a downstream side intake part for taking in air in a gap formed between the pipe part,
The downstream end of the first pipe portion is an open end opened inside the second pipe portion,
The flow passage area of the downstream end portion of the first pipe portion is set to a value smaller than the flow passage area of the exhaust gas passage that flows upstream from the downstream end portion of the engine. Exhaust system. The exhaust system for an engine according to any one of claims 1 to 4,
An exhaust port that forms an upstream end of the exhaust passage is formed in the engine body,
The upstream air introducing portion is formed on a third pipe portion in which a passage communicating with the exhaust port is formed inside, and is formed on an outer peripheral surface of the third pipe portion to take in air inside the third pipe portion. An upstream-side intake portion and a guide portion that extends from the upstream-side intake portion to the inside of the exhaust port and guides the air taken in from the upstream-side intake portion into the exhaust port. Exhaust system for engines. The exhaust system for an engine according to any one of claims 1 to 5,
The exhaust system for an engine, wherein the engine body is a rotary piston engine having a rotor that rotates along an inner peripheral surface of the cylinder.