JP6620789B2 - Exhaust system for turbocharged engine - Google Patents

Description

  The present invention relates to an exhaust device for a turbocharged engine including a turbocharger that is driven by exhaust gas discharged from an engine body and supercharges intake air.

  As an exhaust device for a turbocharged engine, one disclosed in Patent Document 1 below is known. In the exhaust device disclosed in 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 an exhaust passage further downstream than the turbine. In addition, a secondary air supply passage for introducing air (secondary air) from the outside into the exhaust passage is connected to a portion of the exhaust passage located between the turbine and the engine body. An air pump is provided in the secondary air supply passage, and whether or not the secondary air is introduced is switched by driving / stopping the air pump.

  When the air pump is driven and secondary air is introduced into the exhaust passage, an oxidation reaction occurs between the unburned components (HC and the like) in the exhaust gas and the secondary air, and heat is generated. As a result, the temperature of the exhaust gas on the downstream side of the introduction position of the secondary air rises, so that the effect of increasing the driving force of the turbine and the activation of the catalyst located further downstream of the turbine are promoted. Such an effect can be expected.

JP-A-2015-214966

  Here, in the technique of the above-mentioned patent document 1, since the secondary air pumped by the air pump is introduced into the exhaust passage, for example, the pressure of the exhaust gas is reduced from the condition of the pressure of the exhaust passage being relatively low, that is, the pressure of the air pump. Under conditions where the subtracted pressure difference is large, a sufficient amount of secondary air can be introduced into the exhaust passage. However, when the pressure of the exhaust gas flowing through the exhaust passage is high, for example, immediately after the start of the exhaust stroke of a certain cylinder, the pressure difference is reduced or turned negative so that the secondary air enters the exhaust passage. Cannot be introduced or only a small amount can be introduced.

  As described above, in Patent Document 1, since the amount of secondary air that can be introduced into the exhaust passage varies greatly with time, the proportion of secondary air contained in the exhaust gas is large → small → along the flow direction. The pattern changes greatly from large to small. And in the area | region where the ratio of secondary air is small, the unburned component in exhaust gas cannot fully be oxidized, As a result, the temperature rising effect of exhaust gas falls on the average. For this reason, there has been a problem that the effect of increasing the turbine driving force described above cannot be sufficiently obtained.

  The present invention has been made in view of the above circumstances, and can stably oxidize unburned components in exhaust gas by air introduced into an exhaust passage upstream of the turbine, thereby driving the turbine. An object of the present invention is to provide an exhaust device for a turbocharged engine capable of sufficiently increasing the power.

In order to solve the above problems, the present invention relates to an engine main body including a plurality of cylinders, an intake passage through which intake air introduced into the engine main body flows, and an exhaust gas driven by exhaust gas discharged from the engine main body. An exhaust device applied to a turbocharged engine having a turbocharger that supercharges the exhaust gas, an exhaust passage through which the exhaust gas flows, and secondary air that introduces air into the exhaust passage from the outside The turbocharger includes a turbine that is rotationally driven by the exhaust gas, and a turbine housing that houses the turbine. wherein the turbine housing, around the turbine, a plurality of scroll portions partitioned by the partition walls, the exhaust passage, the plurality of cylinders and said plurality of scroll A plurality of single tubular independent exhaust pipe connecting the pole tip 1-one in relation, before Symbol the secondary air introducing portion respectively provided at a plurality of independent exhaust pipe, the secondary air introduction unit The first pipe part through which the exhaust gas passes, the second pipe part arranged so as to surround the outer periphery of the first pipe part, and the first pipe part and the second pipe part are formed. An intake portion for taking air into the annular gap, and the downstream end portion of the first pipe portion is separated from the inner peripheral surface of the second pipe portion by the annular gap. The flow passage area of the downstream end of the first pipe portion is smaller than the flow passage area of the exhaust gas passage flowing upstream from the downstream end portion. is set to the value, the turbine inside the turbine housing a predetermined distance away downstream from the downstream end of the first tubular portion The communication passage has a common communication pipe extending from the intake passage, and a plurality of independent communication pipes branched from a downstream end of the common communication pipe and connected to the secondary air introduction portions, Each independent communication pipe is provided with a check valve for preventing a backflow of air from each secondary air introduction portion to the intake passage (Claim 1).

  According to the present invention, the secondary air introduction part including the first pipe part and the second pipe part arranged so as to form a double pipe structure is provided in the exhaust passage, and the first pipe part and the second pipe part are provided. Since air is introduced into the annular gap formed between the pipe portions, the introduced air is distributed so as to surround the exhaust gas in the exhaust passage downstream of the secondary air introduction portion, that is, A radially stratified gas distribution is obtained. The air surrounding the exhaust gas functions as a heat insulating material that suppresses the heat of the hot exhaust gas from escaping to the wall of the exhaust passage, so the temperature of the exhaust gas remains until the exhaust gas reaches the turbine. Maintained at a sufficiently high temperature. For this reason, when the exhaust gas and the air around it are introduced into the turbine, the unburned components in the exhaust gas and oxygen in the air react reliably in a high-temperature environment as the turbine is stirred. The exhaust gas temperature rises sufficiently. As a result, energy input from the exhaust gas to the turbine increases, so that the driving force of the turbine can be sufficiently increased.

  In addition, the flow passage area at the downstream end of the first pipe portion is set to a value smaller than the flow passage area of the exhaust gas passage flowing upstream from the downstream end portion, so that it passes through the first pipe portion. After that, the flow rate of the exhaust gas becomes faster than the flow rate before passing through the first pipe portion. Such an increase in the exhaust gas speed causes a so-called ejector effect, and negative pressure is applied to the annular gap described above. As a result, for example, air supplied from the outside to the take-in portion can be naturally taken into the annular gap without pumping air using an air pump or the like.

Moreover, since the ejector effect is used, even if the flow rate (flow rate) of the exhaust gas passing through the first pipe portion changes from the start to the end of the exhaust stroke, the air follows the change. The amount of gas introduced is also adjusted naturally, and the ratio of exhaust gas and air is maintained substantially constant. For example, immediately after the start of the exhaust stroke, very high-speed exhaust gas passes through the first pipe portion, and as a result, the negative pressure generated by the ejector effect increases, resulting in a gap between the first pipe portion and the second pipe portion. The amount of air introduced into the annular gap also increases. On the other hand, when the exhaust stroke proceeds to some extent, the flow rate of the exhaust gas passing through the first pipe portion also decreases, so that the negative pressure generated by the ejector effect becomes weak, and as a result, the amount of air introduced into the annular gap also decreases. . Thus, in the present invention, the amount of air introduced is naturally adjusted according to the exhaust gas flow velocity (flow rate), so at any position in the exhaust gas flow direction from the secondary air introduction section to the turbine. However, the ratio of exhaust gas to air is maintained substantially constant. As a result, while the exhaust gas discharged during the exhaust stroke passes through the turbine, the action of oxidizing the unburned components in the exhaust gas is stably exhibited. And the driving force of the turbine can be effectively increased.
Further, the exhaust passage has a plurality of independent exhaust pipes communicating with a plurality of cylinders, and is formed so as not to cause so-called exhaust interference in any of the independent exhaust pipes. Gas circulates inside each independent exhaust pipe while maintaining a sufficient speed. For this reason, an ejector effect is efficiently exhibited in the secondary air introduction part provided in each independent exhaust pipe, and a sufficient amount of air is introduced into each independent exhaust pipe. As a result, when the exhaust gas passes through the turbine, the oxidation reaction of the unburned components in the exhaust gas proceeds sufficiently, so that the high temperature of the exhaust gas by the oxidation reaction can be efficiently achieved.

  Preferably, a catalyst device including a catalyst for purifying the exhaust gas is disposed in an exhaust passage further downstream than the turbine.

  According to this configuration, the catalyst in the catalyst device can be rapidly activated using the exhaust gas heated to a high temperature as the unburned components are oxidized as described above. For example, when the temperature of the catalyst in the catalyst device is lower than a predetermined value when the engine is cold, it is required to quickly raise the catalyst and activate it. The amount of fuel discharged into the exhaust passage increases without being burned. Thus, if the unburned components are oxidized using the air introduced from the secondary air introduction section when the unburned components in the exhaust gas increase as described above, the temperature of the exhaust gas can be increased. Can be sufficiently increased, and the activation of the catalyst can be effectively promoted.

More preferably, the switching valve that allows or stops supplying air to the intake portion of the front Symbol secondary air introducing portion is provided on the common communicating pipe, the switching valve, the temperature of the catalyst is less than a predetermined value At least when the engine is cold, the valve is opened.

  According to this configuration, air can be introduced into the exhaust passage only under conditions where the temperature of the catalyst is low and the exhaust gas is required to have a high temperature. In other words, the introduction of air into the exhaust passage can be stopped when it is unnecessary, so that the exhaust gas can be prevented from becoming unnecessarily high in temperature, and the reliability of the parts group provided in the exhaust passage downstream of the turbine is improved. Can be made.

When the switching valve is provided in the common communication pipe as described above, this switching valve may be opened at least under an operating condition in which the engine load is high and the rotation speed is low. ).

  According to this configuration, the output torque of the engine at the time of low speed / high load operation can be increased, and the acceleration performance of the vehicle can be improved.

  As described above, according to the exhaust system for a turbocharged engine of the present invention, unburned components in the exhaust gas can be stably oxidized by the air introduced into the exhaust passage upstream of the turbine. The driving force can be sufficiently increased.

1 is a schematic system diagram showing a preferred embodiment of a turbocharged engine to which an exhaust device of the present invention is applied. It is a schematic sectional drawing which shows the engine main body of the said engine. FIG. 2 is a partially enlarged view of FIG. 1 showing a structure of a turbocharger and its peripheral parts. It is sectional drawing for demonstrating the detailed structure of a secondary air introduction part. It is a figure for demonstrating the effect | action by the said secondary air introduction part. It is a graph which shows the relationship between the flow volume of exhaust gas, and the introduction amount of the air from the said secondary air introduction part in time series. 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 a turbocharged engine to which an exhaust system of the present invention is applied, and FIG. 2 is a schematic sectional view showing an engine body 1 of the engine. is there. The engine shown in the figure is a four-cycle gasoline engine mounted on a vehicle as a driving power source. The engine body 1, an intake passage 20 through which intake air introduced into the engine body 1 flows, and the engine body 1, an exhaust passage 30 through which exhaust gas discharged from 1 circulates, a secondary air system 40 that introduces air from the outside into the exhaust passage 30, and a turbocharger that is driven by the energy of the exhaust gas to supercharge intake air 60.

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

  Specifically, the engine body 1 includes the two rotors 2 described above, two rotor housings 3 that house the rotors 2, an intermediate housing 4 provided between the rotor housings 3, and these rotors. It has two side housings 5 attached so as to sandwich the housing 3 and the intermediate 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 storage chamber 7 that stores the front rotor 2. Similarly, the rear side housing 5, the rear rotor housing 3, and the intermediate housing 4 form a rotor accommodating chamber 7 that accommodates the rear rotor 2. The rotor accommodating chamber 7 corresponds to a “cylinder” in the claims. In other words, the engine of this embodiment is a two-cylinder engine having 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 two-node peritrochoidal curve 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 approximates a ridge in the front-rear direction.

  The intermediate housing 4 functions as a partition 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 rear so as to close the rear surface of the rear rotor housing chamber 7. It is attached to the rotor housing 3 on the side.

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

  The rotor 2 has apex seals (not shown) at positions corresponding to the apexes 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. Three working chambers 8 defined by the respective flank surfaces 2 a of the rotor 2 and the trochoid inner peripheral surface 3 a are formed in the rotor accommodating chamber 7.

  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 penetrate the intermediate housing 4 and the front and rear side housings 5, and has eccentric portions 6 a that are eccentrically expanded at two front and rear positions corresponding to the position of the rotor 2. are doing. A circular hole is formed in the center of the rotor 2, and an eccentric part 6a is fitted into the hole via 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. That is, the rotor 2 is supported so as to revolve around the rotation axis X in the same direction as the rotation while rotating around the eccentric portion 6a of the eccentric shaft 6 (in a broad sense including this rotation and revolution). Simply called rotation of the rotor). When the rotor 2 rotates, the three working chambers 8 simultaneously move in the circumferential direction, and each stroke of intake, compression, expansion (combustion), and exhaust is 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) constituting an external gear meshing with the internal gear is attached to the side housing 5. The internal gear and the stationary gear are combined at a gear ratio such that the eccentric shaft 6 rotates three times while the rotor 2 rotates once.

  In the case of this embodiment, the rotor 2 rotates clockwise (in the direction of the arrow) in FIG. The right side of the rotor accommodating chamber 7 divided with the long axis Y of the rotor accommodating chamber 7 passing through the rotation axis X is generally an intake stroke and exhaust stroke region, and the left side is generally a compression stroke and expansion stroke region.

  The intermediate housing 4 is formed with an intake port 10 communicating with the front rotor accommodating chamber 7, and the rear side housing 5 is formed with an intake port 10 communicating with the rear rotor accommodating 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 air (fresh air) supplied from the intake passage 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 mainly composed of 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 And attached to the rear side housing 5 (not shown).

  The front side housing 5 is formed with an exhaust port 11 communicating with the front rotor housing chamber 7, and the intermediate housing 4 is formed with an exhaust port 11 communicating with the rear rotor housing chamber 7. Yes. 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 passage 30 through the opened exhaust port 11.

  The engine main body 1 is provided with two spark plugs 16 and 17 for each rotor 2 for igniting the air-fuel mixture. The spark plugs 16, 17 for the front rotor 2 and the rear rotor 2 face the working chamber 8 in a state where the compression stroke has been completed (switching from the compression stroke to the expansion stroke), and the corresponding rotor housing 3. Each is attached. The spark plugs 16, 17 are arranged on the trailing side (delay side) and the leading side (advance side) in the rotor rotation direction across the short axis Z of the rotor accommodating chamber 7, respectively. Ignition is performed 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. 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 a compression stroke is performed. When the rotor 2 further rotates, as shown in the working chamber 8 on the left side of FIG. 2, the compression stroke is almost completed, and ignition is performed by the spark plugs 16 and 17 in this state, and combustion of the air-fuel mixture starts. Is done. Thereafter, the working chamber 8 moves to the upper left region, the combustion gas in the working chamber 8 expands, and an expansion stroke is performed. 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 an exhaust stroke is performed. Thereafter, the process returns to the intake stroke again, and thereafter the same operation is repeated.

  The intake passage 20 includes 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 front rotor 2. The downstream end of the second independent intake pipe 23 is The engine body 1 (the rear side housing 5) is connected to the intake port 10 for the rear rotor 2. In this specification, the downstream (or upstream) in the intake passage 20 refers to the downstream (or upstream) in the flow direction of the intake air flowing through the intake passage 20.

  In the common intake pipe 21, an air cleaner 24 that removes foreign matters contained in the intake air, an intercooler 25 that cools the intake air supercharged by the turbocharger 60, and the flow rate of the intake air that flows through the intake passage 20 are adjusted. An openable / closable throttle valve 26 is provided in this order from the upstream side.

  The exhaust passage 30 includes 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 rotor 2 on the rear side. In the present specification, upstream (or downstream) in the exhaust passage 30 means upstream (or downstream) in the flow direction of the exhaust gas flowing through the exhaust passage 30.

  A catalyst device 34 is provided in the common exhaust pipe 33. The catalyst device 34 has a built-in catalyst (for example, a three-way catalyst) for purifying harmful components in the exhaust gas.

  The exhaust passage 30 is provided with two secondary air introduction portions 41 for introducing air from the outside into the first and second independent exhaust pipes 31 and 32, respectively. Each secondary air introduction part 41 is an element which constitutes a part of secondary air system 40, and the details are mentioned below.

  FIG. 3 is an enlarged view showing the turbocharger 60 and its peripheral components. As shown in FIG. 3 and FIG. 1 above, the turbocharger 60 connects the turbine 61 provided in the exhaust passage 30, the compressor 62 provided in the intake passage 20, and the turbine 61 and the compressor 62. 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 passage 30 and rotates the compressor 62 via the connecting shaft 63. The compressor 62 compresses the intake air flowing through the intake passage 20 by rotating in conjunction with the turbine 61.

  The compressor housing 65 is interposed in the middle portion of the common intake pipe 21, specifically, a portion of the common intake pipe 21 positioned 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 and 32 is led to the common exhaust pipe 33 after passing through the turbine 61.

  The turbine housing 64 is of a so-called twin scroll type, and has a first scroll part 64a and a second scroll part 64b therein. Both scroll portions 64 a and 64 b 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 part 64 a communicates with the first independent exhaust pipe 31, and the second scroll part 64 b communicates with the second independent exhaust pipe 32. Thereby, the exhaust gas from the first independent exhaust pipe 31 is introduced into the turbine 61 through the first scroll part 64a, and the exhaust gas from the second independent exhaust pipe 32 is introduced into the turbine through the second scroll part 64b. 61 is introduced.

  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 waste gate valve 72 that is controlled to be opened and closed so that the supercharging pressure does not exceed a predetermined upper limit value. In FIG. 1, the bypass passage 71 is shown as communicating only with the first scroll portion 64a, but the bypass passage 71 communicates not only with the first scroll portion 64a but also with the second scroll portion 64b. Yes.

(2) Configuration of Secondary Air System As shown in FIG. 1, the secondary air system 40 includes the above-described two secondary air introductions for introducing air into the first and second independent exhaust pipes 31 and 32. And a communication passage 42 that communicates each secondary air introduction portion 41 with the intake passage 20.

  The communication path 42 includes a common communication pipe 55 that branches off from the common intake pipe 21 of the intake passage 20, 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. are doing.

  The upstream end portion of the common communication pipe 55 is connected to a 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 secondary air introduction part 41 for the first independent exhaust pipe 31. The downstream end of the second independent communication pipe 57 is connected to the secondary air introduction part 41 for the second independent exhaust pipe 32.

  The common communication pipe 55 is provided with a switching valve 58 for allowing or stopping the flow of air flowing from the intake passage 20 to the secondary air introduction part 41. The first independent communication pipe 56 and the second independent communication pipe 57 include a check valve for preventing air from flowing backward from the secondary air introduction portion 41 to the intake passage 20 when the switching valve 58 is opened. 59 are provided.

  The switching valve 58 is opened when the engine is cold when the temperature of the catalyst in the catalyst device 34 is less than a predetermined value, and is closed under other conditions. When the switching valve 58 is opened when the engine is cold, a part of the air flowing through the intake passage 20 (common intake pipe 21) is diverted to the communication passage 42 and supplied to the secondary air introduction portion 41. It is introduced into the exhaust passage 30 (the first independent exhaust pipe 31 or the second independent exhaust pipe 32). The introduced air is used to oxidize unburned components (HC, etc.) in the exhaust gas.

  The secondary air introduction part 41 for the first independent exhaust pipe 31 and the secondary air introduction part 41 for the second independent exhaust pipe 32 both have the same structure, details of which are shown in FIG. It is shown. As shown in the figure, each secondary air introduction part 41 is disposed so as to surround the first pipe part 51 through which the exhaust gas discharged from the exhaust port 11 passes and the outer peripheral surface of the first pipe part 51. The second pipe portion 52 and the intake portion 53 for taking air into the annular gap P formed between the first tube portion 51 and the second tube portion 52 are provided.

  The first pipe portion 51 communicates directly with the exhaust port 11 for each rotor 2 between the first independent exhaust pipe 31 and the engine body 1 or between the second independent exhaust pipe 32 and the engine body 1. Is provided. Specifically, the first pipe portion 51 located between the first independent exhaust pipe 31 and the engine body 1 is coupled to the front side housing 5 so as to communicate with the exhaust port 11 for the front rotor 2. The first pipe 51 located between the second independent exhaust pipe 32 and the engine main body 1 is coupled to the intermediate housing 4 so as to communicate with the exhaust port 11 for the rear rotor 2.

  The first pipe portion 51 includes an annular flange portion 51b fixed to the engine body 1 (side housing 5 or intermediate housing 4), and a body portion 51a extending from the inner peripheral end of the flange portion 51b toward the downstream side. Have. The downstream end of the main body 51 a is an open end that is open to the inside of the second pipe 52 at a position separated from the inner peripheral surface of the second pipe 52 by the annular gap P.

  The main body 51a has a throttle shape in which a part of the upstream side has a channel area that decreases toward the downstream side. For this reason, the flow area of the downstream end of the main body 51a, that is, the outlet area A2 of the first pipe 51 is smaller than the flow area of the upstream portion of the main body 51a. Further, the flow area at the downstream end of the exhaust port 11, that is, the outlet area A1 of the exhaust port 11, is substantially the same as the flow area at the upstream end of the main body 51a, and the outlet area A2 of the first pipe portion 51. Bigger than. In other words, the outlet area A <b> 2 of the first pipe portion 51 is set to a value smaller than both the flow area of the upstream portion of the first pipe portion 51 and the outlet area A <b> 1 of the exhaust port 11. The exhaust gas introduced into the first pipe portion 51 from the exhaust port 11 passes through the first pipe portion 51 having such a shape, so that the flow velocity is higher than when the exhaust gas has passed through the exhaust port 11. Thus, the first pipe portion 51 is discharged.

  The second pipe part 52 includes a straight tubular main body part 52a having an inner diameter larger than the outer diameter of the main body part 51a of the first pipe part 51, and an annular flange part 52b formed at the downstream end of the main body part 52a. have. The second pipe portion 52 is disposed upstream of the first independent exhaust pipe 31 or the second independent exhaust pipe 32 in a coaxial manner, and the upstream end portion of the first independent exhaust pipe 31 or the second independent exhaust pipe 32. Are coupled to each other via a flange portion 52b. Further, in this state, the second pipe portion 52 is disposed so that a part of the upstream side of the main body portion 52 a surrounds the outer peripheral surface of the main body portion 51 a of the first pipe portion 51. As a result, an annular gap P is formed between the outer peripheral surface of the first tube portion 51 (main body portion 51a) and the inner peripheral surface of the second tube portion 52 in a sectional view. In addition, the 2nd pipe part 52 and the 1st pipe part 51 are arrange | positioned in the state in which both central axes correspond substantially so that the radial direction dimension of the annular clearance P may become substantially the same over the perimeter.

  The intake portion 53 is a cylindrical protrusion that protrudes from the outer peripheral wall of the second pipe portion 52 as an inlet portion for air introduced into the annular gap P. The intake 53 is connected to the downstream end of the first independent communication pipe 56 or the second independent communication pipe 57. Air supplied from the first independent communication pipe 56 or the second independent communication pipe 57 is introduced into the annular gap P through a through hole that penetrates the intake portion 53.

(3) Operational effects and the like As described above, in the present embodiment, the secondary air is supplied to the first independent exhaust pipe 31 and the second independent exhaust pipe 32 that are located upstream of the turbine 61 of the turbocharger 60, respectively. An introduction part 41 is provided, and each secondary air introduction part 41 includes a first pipe part 51 through which exhaust gas passes, and a second pipe part 52 arranged so as to surround the outer periphery of the first pipe part 51. And an intake portion 53 for taking air into an annular gap P formed between the first tube portion 51 and the second tube portion 52. The downstream end portion of the first pipe portion 51 is an open end opened to the inside of the second pipe portion 52 at a position separated from the inner peripheral surface of the second pipe portion 52 by the annular gap P, and the first pipe portion The outlet area A2 of the part 51 is defined by the flow area of the upstream part of the first pipe part 51 and the outlet area A1 of the exhaust port 11 (in other words, the exhaust gas passage flowing upstream from the downstream end part of the first pipe part 51). The flow area is set to a small value. According to such a configuration, there is an advantage that the unburned components in the exhaust gas flowing through the turbine 61 can be stably oxidized, and thereby the driving force of the turbine 61 can be sufficiently increased.

  That is, in the above-described embodiment, air is introduced through the intake portion 53 between the first tube portion 51 and the second tube portion 52 (annular gap P) arranged so as to form a double tube structure. Therefore, for example, as shown in FIG. 5, in the exhaust passage 30 (the first independent exhaust pipe 31 or the second independent exhaust pipe 32) on the downstream side of the secondary air introduction portion 41, the introduced air is around the exhaust gas. Is distributed so as to surround the gas, that is, a gas distribution layered in the radial direction is obtained. The air surrounding the exhaust gas functions as a heat insulating material that suppresses the heat of the high-temperature exhaust gas from escaping to the wall surface of the exhaust passage 30, and therefore, until the exhaust gas reaches the turbine 61, The temperature is maintained at a sufficiently high temperature. For this reason, when the exhaust gas and the air on the outer periphery thereof are introduced into the turbine 61, the unburned components in the exhaust gas and oxygen in the air react with each other as the turbine 61 rotates, and the exhaust gas is exhausted. The temperature of the gas rises sufficiently. As a result, the energy input from the exhaust gas to the turbine 61 increases, so that the driving force of the turbine 61 can be sufficiently increased.

  Further, since the outlet area A2 of the first pipe portion 51 is set to a smaller value than the outlet area A1 of the exhaust port 11, the flow rate of the exhaust gas after passing through the first pipe portion 51 is the first pipe portion 51. It will be faster than the flow velocity before passing through. Such an increase in the exhaust gas speed causes a so-called ejector effect, and negative pressure is applied to the annular gap P described above. Thereby, for example, even if air is not pumped using an air pump or the like, it is possible to naturally take in the annular gap P via the take-in portion 53 through the air diverted from the intake passage 20 (air in the communication passage 42). .

  Moreover, since the ejector effect is used, even if the flow rate (flow rate) of the exhaust gas passing through the first pipe portion 51 changes between the start and end of the exhaust stroke, the change is followed. The amount of air introduced is also adjusted naturally, and the ratio of exhaust gas to air is maintained substantially constant.

  This will be described with reference to FIG. FIG. 6 is a graph showing the flow rate of the exhaust gas passing through the secondary air introduction part 41 and the amount of air introduced from the secondary air introduction part 41 in time series. The eccentric angle (EA) described on the horizontal axis of the graph is the rotational angle of the eccentric shaft 6. In the rotary engine, the exhaust port 11 opens in each rotor accommodating chamber 7 every 270 ° EA, so that the flow rate of exhaust gas and the introduction of air are introduced in the secondary air introduction portions 41 provided in the independent exhaust passages 31 and 32. The amount varies with 270 ° EA as one cycle.

  As shown in FIG. 6, immediately after the exhaust port 11 is opened (immediately after the start of the exhaust stroke), exhaust gas is exhausted vigorously from the exhaust port 11 to the secondary air introduction portion 41, so the first pipe portion As the flow velocity (flow rate) of the exhaust gas passing through 51 rises rapidly, the negative pressure generated in the annular gap P by the ejector effect increases. As a result, the amount of air introduced into the annular gap P increases so as to follow the flow rate of the exhaust gas. On the other hand, when the exhaust stroke proceeds to some extent, the flow rate of the exhaust gas passing through the first pipe portion 51 also decreases, so that the negative pressure generated by the ejector effect becomes weak, and as a result, the amount of air introduced into the annular gap P also increases. Decrease. As described above, in the above embodiment, the amount of air introduced is naturally adjusted according to the flow rate (flow rate) of the exhaust gas. Therefore, any of the flow directions of the exhaust gas from the secondary air introduction unit 41 to the turbine 61 is selected. Even in this position, the ratio of exhaust gas to air is maintained substantially constant. Thereby, while the exhaust gas discharged during the exhaust stroke passes through the turbine 61, the action of oxidizing the unburned components in the exhaust gas is stably exhibited. Therefore, the driving force of the turbine 61 can be effectively increased.

  Further, in the above embodiment, the catalyst device 34 is disposed on the downstream side of the turbine 61, so that the catalyst in the catalyst device 34 is used by utilizing the exhaust gas that has been heated as the unburned components are oxidized as described above. It can be activated quickly. For example, when the temperature of the catalyst in the catalyst device 34 is cold when the temperature of the engine is lower than a predetermined value, it is required that the catalyst be quickly heated and activated, but on the other hand, the catalyst is injected into the rotor accommodating chamber 7. As the fuel vaporization rate decreases, the amount of fuel discharged to the exhaust passage 30 while remaining unburned increases. Therefore, when the unburned components are oxidized using the air introduced from the secondary air introducing portion 41 when the unburned components in the exhaust gas increase as described above, The temperature can be sufficiently increased, and the activation of the catalyst can be effectively promoted.

  In particular, in the above embodiment, the switching valve 58 is provided in the communication passage 42 through which the air supplied to the secondary air introduction unit 41 flows, and the switching valve 58 has a temperature of the catalyst in the catalyst device 34 that is less than a predetermined value. Since the valve is opened only when the engine becomes cold, air can be introduced into the exhaust passage 30 only under a condition that requires a high temperature of the exhaust gas. In other words, since introduction of air into the exhaust passage 30 can be stopped when unnecessary, it is possible to prevent the exhaust gas from being heated to an unnecessarily high temperature, and the reliability of the parts group provided in the exhaust passage 30 on the downstream side of the turbine 61. Can be improved. Further, since the diversion of air from the intake passage 20 is stopped except when the engine is cold, for example, it is possible to prevent the amount of air supplied to the engine body 1 from being insufficient when the engine is operated at a high load. .

  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 a predetermined value and the air is introduced into the exhaust passage 30 from the secondary air introduction portion 41. However, for example, even when the engine is not cold, it may be required to raise the exhaust gas temperature or to increase the driving force of the turbine 61. For example, when the engine load is high and the rotation speed is low (low speed / high load operation), even if the wastegate valve 72 is fully closed, sufficient driving force of the turbine 61 may not be obtained. is there. Therefore, it is conceivable to open the switching valve 58 under such conditions. In this way, it is possible to oxidize unburned components in the exhaust gas using the air introduced into the exhaust passage 30 from the secondary air introduction part 41, and the exhaust gas having a high temperature is sufficient for the turbine 61. A sufficient driving force can be applied. Thereby, the output torque of the engine at the time of low speed and high load operation can be increased, and the acceleration performance of the vehicle can be improved. Note that the air-fuel ratio at the time of high engine load is generally a power air-fuel ratio that is richer than the stoichiometric air-fuel ratio (for example, about A / F = 12 to 13), so that the unburned components in the exhaust gas increase. There is a tendency. For this reason, when the switching valve 58 is opened as described above during low-speed / high-load operation, a relatively large amount of unburned components are oxidized using the air introduced from the secondary air introduction unit 41. Thus, the energy of the exhaust gas and thus the driving force of the turbine 61 can be sufficiently increased.

  In the above embodiment, the secondary air introduction portion 41 is provided at the upstream end of each of the first and second independent exhaust pipes 31 and 32. However, the secondary air introduction is provided in the middle of each independent exhaust pipe 31 and 32. The part 41 may be provided.

(4) Other Embodiments In the above embodiment, an example in which the exhaust device of the present invention is applied to a rotary engine has been described. However, the present invention is applicable not only to a rotary engine but also to a reciprocating engine. One example 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 reciprocating engine. The engine shown in this figure includes 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. An exhaust passage 130 through which exhaust gas to be circulated, a secondary air system 140 for introducing 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.

  The cylinders 102A to 102D are each provided with an injector and a spark plug (both not shown). In the cylinders 102A to 102D, an air-fuel mixture of the fuel injected from the injector and the air introduced from the intake passage 120 is combusted with ignition by the spark plug. Pistons (not shown) are slidably accommodated in the cylinders 102A to 102D, respectively. Each piston receives the expansion force due to the combustion and reciprocates in the cylinders 102A to 102D. The reciprocating motion is converted into rotational motion and 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 in FIG. 7 are respectively the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder, the first cylinder 102A → the third cylinder in the engine of FIG. 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 intake air that branches from the surge tank 122 and communicates with the cylinders 102A to 102D. Tube 123.

  In the common intake pipe 121, an air cleaner 124, an intercooler 125, and a throttle valve 126 are provided 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 that branch from the upstream end of the common exhaust pipe 133.

  A catalyst device 134 is provided in the common exhaust pipe 133.

  Each of the first and second independent exhaust pipes 131 and 132 is a branch pipe whose upstream side is bifurcated. That is, the first independent exhaust pipe 131 has a collecting pipe part 131c communicating with the common exhaust pipe 133 and two branch pipe parts 131a and 131b branched from the upstream end of the collecting pipe part 131c. Similarly, the second independent exhaust pipe 132 has a collecting pipe part 132c communicating with the common exhaust pipe 133 and two branch pipe parts 132a and 132b branched from the upstream end of the collecting pipe part 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. Yes. The second independent exhaust pipe 132 is connected to the engine main 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 exhaust ports not shown. Has been. The set of the first cylinder 102A and the fourth cylinder 102D communicating with the first independent exhaust pipe 131 and the set of the second cylinder 102B and the third cylinder 102C communicating with the second independent exhaust pipe 132 are respectively in the ignition order. The exhaust stroke order (exhaust order) is a combination of cylinders that do not continue.

  The turbocharger 160 includes 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 includes two secondary air introduction portions 141 provided in the first independent exhaust pipe 131 and the second independent exhaust pipe 132, respectively, and air that has been diverted from the intake passage 120. 141, and a communication passage 142 for supplying to 141.

  The secondary air introduction part 141 is provided in each of the collecting pipe part 131 c of the first independent exhaust pipe 131 and the collecting pipe part 132 c of the second independent exhaust pipe 132. The structure of each secondary air introduction part 141 is the same as that shown in the above-described embodiment (FIGS. 1 to 5), and the first pipe part 51, the second pipe part 52, and the intake shown in FIG. It has the same elements as the part 53. 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 when the switching valve 158 is opened passes through the secondary air introduction portions 141. Two independent exhaust pipes 131 and 132 are introduced.

  In the modified embodiment of FIG. 7 described above, two cylinders communicating with a set of cylinders whose exhaust strokes do not overlap (a set of the first and fourth cylinders 102A and 102D and a set of the second and third cylinders 102B and 102C) are communicated. Since each of the independent exhaust pipes 131 and 132 is provided with the secondary air introduction part 141, a sufficient amount of air can be introduced into the exhaust gas via each secondary air introduction part 141. That is, a period during which exhaust gas from the first cylinder 102A flows through the first independent exhaust pipe 131 (that is, an exhaust stroke of the first cylinder 102A) and a period during which exhaust gas from the fourth cylinder 102D flows through the first independent exhaust pipe 131. (That is, the exhaust stroke of the fourth cylinder 102D) does not overlap with each other, and the exhaust gas discharged from the first cylinder 102A and the fourth cylinder 102D is sufficient in the first independent exhaust pipe 131 without causing interference with each other. Circulate while maintaining speed. Similarly, the exhaust gas from the second cylinder 102B flows through the second independent exhaust pipe 132 (that is, the exhaust stroke of the second cylinder 102B), and the exhaust gas from the third cylinder 102C flows through the second independent exhaust pipe 132. Since the period (that is, the exhaust stroke of the third cylinder 102C) does not overlap, the exhaust gases exhausted from the second cylinder 102B and the third cylinder 102C are sufficient in the second independent exhaust pipe 132 without causing interference with each other. Circulate while maintaining a high speed. For this reason, the ejector effect is efficiently exhibited in the secondary air introduction portions 141 provided in the independent exhaust pipes 131 and 132, and a sufficient amount of air is introduced into the independent exhaust pipes 131 and 132. As a result, when the exhaust gas passes through the turbine 161, the oxidation reaction of the unburned components in the exhaust gas proceeds sufficiently, so that it is possible to efficiently achieve a high temperature of the exhaust gas by the oxidation reaction.

1 Engine body 7 Rotor storage chamber (cylinder)
DESCRIPTION OF SYMBOLS 8 Working chamber 30 Exhaust passage 31 Independent exhaust pipe 32 Independent exhaust pipe 34 Catalytic device 41 Secondary air introduction part 42 Communication path 51 1st pipe part 52 2nd pipe part 53 Intake part 58 Switching valve 60 Turbocharger 61 Turbine DESCRIPTION OF SYMBOLS 101 Engine main body 102A-102D Cylinder 130 Exhaust passage 131 Independent exhaust pipe 132 Independent exhaust pipe 141 Secondary air introduction part 158 Switching valve 160 Turbocharger 161 Turbine

Claims (4)

A turbocharger comprising an engine body including a plurality of cylinders, an intake passage through which intake air introduced into the engine body flows, and a turbocharger that is driven by exhaust gas discharged from the engine body to supercharge intake air An exhaust system applied to a feed engine,
An exhaust passage through which the exhaust gas flows;
A secondary air introduction section for introducing air from the outside into the exhaust passage;
A communication passage communicating the secondary air introduction part and the intake passage;
The turbocharger includes a turbine that is rotationally driven by the exhaust gas, and a turbine housing that houses the turbine.
The turbine housing has a plurality of scroll portions partitioned by a partition wall around the turbine,
The exhaust passage has a plurality of single tubular independent exhaust pipes that connect the plurality of cylinders and the plurality of scroll portions in a one-to-one relationship ,
Said secondary air introducing portion respectively provided in front Symbol plurality of independent exhaust pipes,
The secondary air introduction part includes a first pipe part through which exhaust gas passes, a second pipe part disposed so as to surround an outer periphery of the first pipe part, the first pipe part, and the second pipe. An intake part for taking air into the annular gap formed between the part and
The downstream end portion of the first pipe portion is an open end opened to the inside of the second pipe portion at a position separated from the inner peripheral surface of the second pipe portion by the amount of the annular gap,
The flow area of the downstream end portion of the first pipe portion is set to a value smaller than the flow area of the exhaust gas passage flowing upstream from the downstream end portion,
The turbine is disposed inside the turbine housing at a predetermined distance from the downstream end of the first pipe portion to the downstream side;
The communication passage has a common communication pipe extending from the intake passage, and a plurality of independent communication pipes branched from the downstream end of the common communication pipe and connected to the secondary air introduction portions,
The turbocharged engine exhaust system according to claim 1, wherein each of the independent communication pipes is provided with a check valve for preventing a backflow of air from each of the secondary air introduction portions to the intake passage. The exhaust system of the turbocharged engine according to claim 1,
An exhaust device for a turbocharged engine, wherein a catalyst device including a catalyst for purifying the exhaust gas is disposed in an exhaust passage further downstream than the turbine. The exhaust system of the turbocharged engine according to claim 2,
A switching valve that allows or stops supplying air to the intake portion of the secondary air introduction portion is provided in the common communication pipe,
The exhaust system for a turbocharged engine, wherein the switching valve is opened at least when the temperature of the catalyst is lower than a predetermined value when the engine is cold. The exhaust system of the turbocharged engine according to any one of claims 1 to 3,
A switching valve that allows or stops supplying air to the intake portion of the secondary air introduction portion is provided in the common communication pipe,
The exhaust device for a turbocharged engine, wherein the switching valve is opened at least under an operating condition in which the engine load is high and the rotational speed is low.

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