JP2016079927A - Exhaust device of engine with turbosupercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress degradation of supercharging efficiency of a turbosupercharger, in an engine with the turbosupercharger.SOLUTION: An exhaust passage 13 has a collective passage 132 connected to at least one of a plurality of exhaust ports 10 in each cylinder 31 of an engine, collected among the different cylinders, and connected to a turbine 51 of the turbosupercharger 5, and an independent passage 131 connected to the other exhaust port in each cylinder and connected to the turbine without collected among the different cylinders. An EGR passage 91 is connected to the collective passage.SELECTED DRAWING: Figure 2

Description

  The technology disclosed herein relates to an exhaust device for an engine with a turbocharger.

  In Patent Document 1, as an exhaust device of a reciprocating engine with a turbocharger, a downstream end portion of an independent passage of an exhaust manifold connected to each of a plurality of cylinders is formed in a nozzle shape, and an independent passage is assembled on the downstream side thereof The structure which provides the assembly part which performs is described. In the exhaust system of this configuration, negative pressure is generated in the collecting part due to the ejector effect, and exhaust gas (blowdown gas) from each cylinder is prevented from flowing into the independent passages of other cylinders, thereby suppressing exhaust interference At the same time, the exhaust effect of the other cylinders can be sucked out by the ejector effect, and the scavenging performance is improved and the exhaust energy supplied to the turbine is increased.

  In Patent Document 2, as an exhaust device for a rotary piston engine with a turbocharger, an exhaust port is provided in a rotor housing having a trochoid inner peripheral surface, and the exhaust ports of two cylinders are assembled by an exhaust passage, and then the turbocharger is assembled. A communication passage which penetrates in the thickness direction so as to communicate with the intermediate chamber disposed between the two rotors in the exhaust stroke of the two rotor accommodating chambers while being connected to the turbine upstream of the feeder. And a configuration in which a bypass path for bypassing the turbine is connected to the communication path is described. An open / close valve is interposed in the bypass passage. In this exhaust system, the rotary piston engine is discharged from each cylinder through the exhaust port by closing the open / close valve except in the high-rotation high-load region. The exhaust gas is collected by the exhaust passage and then supplied to the turbine of the turbocharger.

JP 2009-114991 A Japanese Patent Publication No. 6-47942

  Incidentally, as described in Patent Document 1, an EGR passage that recirculates a part of the exhaust gas to the intake side of the engine is generally connected to the upstream side of the turbocharger in the exhaust passage. is there. For this reason, when the exhaust gas is recirculated, the exhaust energy supplied to the turbine is reduced correspondingly, and the turbocharging efficiency of the turbocharger is lowered.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to suppress a decrease in supercharging efficiency of a turbocharger in an engine with a turbocharger.

  The technology disclosed herein relates to an exhaust device for an engine with a turbocharger. The exhaust device is provided in an engine having a plurality of cylinders, and a plurality of exhaust devices are provided for each cylinder so as to discharge exhaust gas in each cylinder. An exhaust port provided, an exhaust passage configured to connect to each of the exhaust ports, and a turbocharger turbine disposed in the exhaust passage and configured to be driven by energy of the exhaust gas And an EGR passage configured to communicate with the exhaust passage and to recirculate a part of the exhaust gas to the intake side of the engine.

  The exhaust passage is connected to at least one of a plurality of exhaust ports in each cylinder, and is gathered between different cylinders and then connected to the turbine, and another exhaust in each cylinder. And an independent passage connected to the turbine without being collected between different cylinders, and the EGR passage is connected to the collecting passage.

  According to this configuration, the exhaust passage that connects the exhaust port of the engine and the turbine of the turbocharger has two types of passages, that is, a collecting passage and an independent passage. After gathering between different cylinders, it is connected to the turbine. Since the collecting passage can cause exhaust interference, the exhaust energy supplied to the turbine can be reduced.

  On the other hand, the independent passage is connected to the turbine without being assembled between different cylinders. Thereby, exhaust interference does not occur in the independent passage. Here, when each passage is connected to the scroll of the turbine, a configuration in which a plurality of independent passages substantially merge immediately upstream of the scroll is “connected to the turbine without being assembled between different cylinders”. Included. This is because there is substantially no exhaust interference with this configuration. In this way, the independent passages that are substantially free of exhaust interference can provide relatively high exhaust energy to the turbine.

  The EGR passage that recirculates a part of the exhaust gas to the intake side of the engine is connected to a collecting passage that may cause exhaust interference. Thereby, the independent passage in which high exhaust energy can be secured does not cause a decrease in exhaust energy due to the recirculation of EGR gas. Therefore, even when the operating state of the engine is in a state where the EGR gas is recirculated, the turbocharging efficiency of the turbocharger can be maintained high.

  Further, by connecting the EGR passage to the collecting passage, the exhaust gas can be evenly taken out from the plurality of cylinders. The collecting passage is also connected to the turbine, and exhaust gas sequentially discharged from each cylinder passes through the collecting passage and flows into the turbine. The EGR passage takes out the exhaust gas evenly from a plurality of cylinders, thereby Homogenization of exhaust pulsation sent to

  The collective passage includes a nozzle portion that is tapered so as to eject the exhaust gas while a passage connected to each of a plurality of cylinders remains in an independent state, and a plurality of downstream portions from the nozzle portion. It is good also as having the gathering part in which the area where the above-mentioned passage gathers and a negative pressure occurs by the ejector effect is formed.

  Here, the “ejector effect” is achieved by increasing the flow rate of the exhaust gas by the tapered nozzle portion, and exhausting the exhaust gas at the collecting portion where a plurality of passages are gathered downstream from the nozzle portion. It means that negative pressure is generated.

  According to the above configuration, the collective passage has the nozzle part and the aggregate, and the negative pressure is generated in the collective part due to the ejector effect, so that the exhaust gas discharged from one cylinder rotates toward the other cylinder. It is suppressed that it flows. That is, exhaust interference in the collecting passage is suppressed. By suppressing the exhaust interference, the exhaust energy supplied from the collecting passage to the turbine is increased, and the supercharging efficiency of the turbocharger can be further improved.

  In addition, the ejector effect sucks residual exhaust gas from other cylinders with open exhaust ports, improving scavenging performance and increasing the exhaust energy supplied to the turbine by the amount of exhaust gas that has been sucked out. It becomes possible. This also increases the turbocharging efficiency of the turbocharger.

  The collecting passage is connected to each of the plurality of cylinders on the upstream side of the collecting portion, and the independent passages are arranged to extend in parallel while being partitioned from each other by a partition wall. It is good also as having.

  With this configuration, the angle when the passages connected to each of the plurality of cylinders gather is shallow, and the ejector effect is further enhanced. This enhances the effect of suppressing the exhaust interference and enhances the effect of sucking out the residual exhaust gas. As a result, the exhaust energy supplied from the collecting passage to the turbine is increased.

  The ratio a / D between the diameter a of the perfect circle corresponding to the minimum cross-sectional area of the nozzle portion and the diameter D of the perfect circle corresponding to the cross-sectional area at the downstream end of the collecting portion is set to 0.5 or more and less than 1. It is good as it is.

  From the knowledge of the inventors of the present application, when a / D is less than 0.5, it becomes impossible to form a negative pressure region in the gathering portion, and as a / D approaches 1 (in other words, minimum disconnection of the nozzle portion). The closer the area a and the cross-sectional area of the downstream end of the gathering portion), the more advantageous for the generation of negative pressure. However, when a / D is equal to or greater than 1, the cross-sectional area of one of the plurality of passages gathering at the gathering portion is the same as the cross-sectional area of the passage after gathering, which is larger than that. It is not possible to obtain the suction effect of sucking out the residual exhaust gas. Therefore, in order to suppress the exhaust interference in the collecting passage and to increase the turbocharging efficiency of the turbocharger, it is preferable to set a / D to 0.5 or more and less than 1.

  The EGR passage is provided with an EGR valve configured to adjust the recirculation amount of the exhaust gas to the intake side, and the EGR passage communicates with a region where negative pressure is generated in the collecting portion. The EGR valve opens when the engine operating state is in a predetermined region of low rotation and low load, and closes when the engine is in a low rotation and high load region where the load is higher than the predetermined region. It is good.

  By opening the EGR passage to the negative pressure generation region in the collecting passage, the exhaust gas is suppressed from flowing toward the EGR passage when the EGR passage is closed. This is equivalent to a reduction in the volume of the collecting passage connecting the exhaust port and the turbine. As a result, the exhaust energy supplied to the turbine through the collecting passage is increased. This is particularly effective in increasing the turbocharging efficiency of the turbocharger when the engine does not recirculate EGR gas.

  When the engine operating state is within a predetermined range of low rotation and low load, the amount of fuel is small and the amount of fresh air introduced into the cylinder is also small. Therefore, the pump loss is reduced by recirculating EGR gas to the intake side. . That is, when the operating state of the engine is in a predetermined range of low rotation and low load, the fuel efficiency is improved by opening the EGR valve.

  When the load is in the low rotation and high load region where the load is higher than the predetermined region, the amount of fuel increases, so that the EGR gas does not need to be recirculated and the EGR valve is closed. On the other hand, when the engine is in a low rotation and high load region, an improvement in supercharging efficiency is required. However, when the engine is operating in a low rotation region, the exhaust energy is relatively low. At this time, the configuration in which the EGR passage is opened to the negative pressure generation region in the collecting passage, as described above, suppresses the exhaust gas from flowing toward the EGR passage, and supplies the exhaust gas to the turbine through the collecting passage. Exhaust energy can be increased. As a result, it is advantageous for improving the engine torque in a low rotation and high load region where the EGR gas is not recirculated.

  An EGR valve configured to adjust the recirculation amount of the exhaust gas to the intake side and an EGR cooler configured to cool the exhaust gas recirculated to the intake side are arranged in the EGR passage. The EGR passage communicates with the downstream side of the region where the negative pressure is generated in the collecting portion, and the EGR valve is opened when the engine operating state is in a high rotation / high load region. You may do it.

  Unlike the above configuration, by opening the EGR passage downstream of the negative pressure generation region in the collecting passage, the negative pressure in the negative pressure generation region is reduced when the EGR passage is opened and a part of the exhaust gas is taken out. It becomes possible to strengthen. As a result, the effect of suppressing exhaust interference is enhanced, and the effect of sucking out residual exhaust gas from other cylinders is enhanced. This is particularly effective in increasing the supercharging efficiency of the turbocharger when the engine is recirculating EGR gas.

  When the operating state of the engine is in the region of high rotation and high load, the back pressure of the engine becomes high, so that it is difficult for negative pressure to be generated in the collecting portion. On the other hand, when the operating state of the engine is in the region of high rotation and high load, exhaust gas is cooled by the EGR cooler and then recirculated to the intake side, thereby reducing the exhaust gas temperature.

  Therefore, the configuration in which the EGR passage is opened to the downstream side of the negative pressure generation region in the collecting passage has the negative pressure generation region in the high rotation and high load region where the EGR gas is recirculated for the purpose of reducing the exhaust gas temperature. Since the pressure can be increased and the effect of suppressing exhaust interference and the effect of sucking out residual exhaust gas can be enhanced, the turbocharging efficiency of the turbocharger is increased in the high rotation and high load region where the back pressure of the engine is high. That is, it is advantageous for improving the torque in the region of high rotation and high load.

  As described above, according to the exhaust system for an engine with a turbocharger, the exhaust passage that connects the exhaust port of the engine and the turbine of the turbocharger to each other is a collection passage that collects between different cylinders. In addition to being divided into two types of passages, an independent passage that does not collect, and connecting the EGR passage to the collection passage, high exhaust energy is supplied to the turbine through an independent passage that does not cause exhaust interference. The supercharging efficiency can be kept high.

It is a section explanatory view showing the composition of a rotary piston engine. It is a conceptual diagram which shows the structure of the exhaust apparatus of the rotary piston engine with a turbocharger. (A) The characteristic of the turbocharger of a rotary piston engine, (b) The illustration of the characteristic of the turbocharger of a reciprocating engine. It is a figure which compares the change of the opening area of the exhaust port of a rotary piston engine, and the change of the lift amount of the exhaust port of a reciprocating engine. It is a conceptual diagram which expands and shows the structure of the nozzle part in a gathering path, and the gathering part vicinity. FIG. 6 is a conceptual diagram showing an enlarged configuration of a nozzle portion and a vicinity of a collecting portion in a collecting passage having a configuration different from that of FIG. It is explanatory drawing which illustrates the torque curve of an engine.

  Hereinafter, an exhaust system for an engine with a turbocharger will be described with reference to the drawings. The following description is an example. FIG. 1 shows the structure of a rotary piston engine 1 (hereinafter also simply referred to as a rotary engine 1). As shown in FIG. 2, the rotary engine 1 is a two-rotor type including two rotors 2, and includes a front side (for convenience, the left side in FIG. 2) and a rear side (for convenience, the right side in FIG. 2). The rotor housings 3 and 3 are integrated by being sandwiched by two side housings 41 and 41 from both sides of the intermediate housing (that is, the side housing) 4 sandwiched therebetween. ing. The number of rotors 2 (the number of cylinders) is not limited to this.

  A rotation axis X is defined by a trochoid inner peripheral surface 3 a drawn by a parallel trochoid curve of the rotor housing 3, an inner surface of a side housing 41 sandwiching the rotor housing 3 from both sides, and an inner surface 4 a on both sides of the intermediate housing 4. When the rotary piston engine 1 is viewed in a direction along the rotation axis X from one side of the rotor, the rotor housing chamber 31 having a substantially elliptical shape like a bag is divided into two sides, a front side and a rear side, One rotor 2 is housed in each of the rotor housing chambers 31. Since each rotor accommodating chamber 31 is arranged symmetrically with respect to the intermediate housing 4 and has the same configuration except that the position and phase of the rotor 2 are different, hereinafter, one rotor accommodating chamber 31 is provided. Will be described.

  The rotor 2 is composed of a substantially triangular block body in which the central portion of each side bulges when viewed from the direction of the rotation axis X, and has three substantially rectangular flank surfaces 2a, 2a on the outer periphery thereof. 2a.

  The rotor 2 has apex seals (not shown) at the respective tops, and these apex seals are in sliding contact with the trochoid inner peripheral surface 3 a of the rotor housing 3, and the trochoid inner peripheral surface 3 a of the rotor housing 3 and the intermediate housing 4. Three working chambers 8, 8, 8 are defined in the rotor accommodating chamber 31 by the inner surface 4 a, the inner surface of the side housing 41, and the flank surface 2 a of the rotor 2. Accordingly, the engine 1 has a total of six working chambers, that is, the first to third working chambers 8 on the front side in the vehicle front-rear direction and the fourth to sixth working chambers 8 on the rear side. ing.

  A phase gear is provided inside the rotor 2 (not shown). That is, the inner gear (rotor gear) on the inner side of the rotor 2 and the outer gear (fixed gear) on the side housing 41 mesh with each other, and the rotor 2 passes through the intermediate housing 4 and the side housing 41, and the output shaft X Is supported so as to make a planetary rotational movement. Reference numeral 21 denotes an oil seal provided on the side surface of the rotor 2 and prevents excess lubricating oil from flowing into the working chamber 8.

  The rotational motion of the rotor 2 is defined by the meshing of the internal gear and the external gear. The rotor 2 has an eccentric ring (eccentric ring) of the eccentric shaft 6 while the three seal portions are in sliding contact with the trochoid inner peripheral surface 3a of the rotor housing 3, respectively. While rotating around the axis 6a, it revolves around the rotation axis X in the same direction as the rotation (inclusive of this rotation and revolution, it simply refers to the rotation of the rotor). The three working chambers 8, 8, and 8 move in the circumferential direction while the rotor 2 makes one rotation, and intake, compression, expansion (combustion), and exhaust strokes are performed in each of them, and are generated thereby. A rotational force is output from the eccentric shaft 6 via the rotor 2.

  More specifically, the rotor 2 rotates clockwise as indicated by an arrow, and the right side of the rotor housing chamber 31 that is divided by the long axis Y of the rotor housing chamber 31 passing through the rotation axis X is generally the intake and exhaust strokes. The left side is generally the compression and expansion stroke area.

  On the other hand, in the rotary piston engine of the conventional configuration, the left side of the rotor housing chamber 31 that is divided by the long axis Y is a region for intake and exhaust strokes, and the right side is a region for compression and expansion strokes. That is, the rotary piston engine of this configuration is mounted on the vehicle in a state where the rotary piston engine of the conventional configuration is rotated 180 ° about the rotation axis X.

  Focusing on the lower right working chamber 8 in FIG. 1, this shows an intake stroke in which an air-fuel mixture is formed by intake air and injected fuel, and when this working chamber 8 shifts to a compression stroke as the rotor 2 rotates. The air-fuel mixture is compressed inside. Thereafter, as in the working chamber 8 shown on the left side of FIG. 1, the ignition plugs 82 and 83 are ignited at a predetermined timing from the final stage of the compression stroke to the expansion stroke, and the combustion / expansion stroke is performed. When the exhaust stroke such as the working chamber 8 in the upper right of FIG. 1 is finally reached, the combustion gas is exhausted from the exhaust port 10 and then returns to the intake stroke to repeat each stroke.

  An intake port 11 communicates with the working chamber 8 in the intake stroke state. More specifically, the intake port 11 is formed on the inner side surface 4a of the intermediate housing 4 facing the working chamber 8 in the intake stroke state, on the outer peripheral side of the rotor storage chamber 31, and on the rotor storage chamber 31 passing through the rotation axis X. Of the intermediate housing 4 extends in a substantially horizontal direction and opens in the side surface of the engine 1. Although not shown, another intake port is opened on the inner surface of the side housing 41 facing the working chamber 8 in the intake stroke state so as to face the intake port 11. The port also extends in the side housing 41 in a substantially horizontal direction and opens on the side surface of the engine 1. An intake manifold 12 communicating with the intake port 11 is attached to the side surface of the engine 1.

  An exhaust port 10 communicates with the working chamber 8 in the exhaust stroke state. In more detail, the exhaust port 10 opens to the inner side surface 4a of the intermediate housing 4 facing the working chamber 8 in the exhaust stroke state, near the short axis Z on the outer peripheral side of the rotor accommodating chamber 31, and It extends obliquely upward in the light housing 4 and opens near the corner between the upper surface and the side surface of the engine 1. As shown in FIG. 2, another exhaust port 10 is opened on the inner surface of the side housing 41 facing the working chamber 8 in the exhaust stroke state so as to face the exhaust port 10. The exhaust port formed in the side housing 41 also extends obliquely upward in the side housing 41 and opens near the corner between the upper surface and the side surface of the engine 1. This engine 1 employs a so-called side exhaust system, and the opening position and shape of the exhaust port 10 are set so that the intake open timing and the exhaust open timing do not overlap. As a result, residual exhaust gas brought into the next process is reduced. Further, the opening of the exhaust port 10 of the side housing 41 and the opening of the exhaust port 10 of the intermediate housing 4 have the same shape, so that the opening timing of both the exhaust ports 10 is the same. And the closing timing of both exhaust ports 10 is also the same. In the following, the exhaust port 10 formed in the side housing 41 will be referred to as a primary port 10a, and the exhaust port formed in the intermediate housing 4 will be referred to as a secondary port 10b. May be simply referred to as the exhaust port 10. An exhaust passage 13 that communicates with the exhaust port 10 is connected to the engine 1. Details of the configuration of the exhaust passage 13 will be described later.

  A reference numeral 103 in FIG. 1 is a secondary air passage for supplying secondary air into the exhaust passage 13.

  An injector 81 for supplying fuel into the working chamber 8 is attached to the intermediate housing 4 and injects fuel into an intake port 11 provided in the intermediate housing 4.

  A T-side spark plug 82 and an L-side spark plug are respectively provided at a trailing side (lag side) position and a leading side (lead side) position in the rotor rotation direction across the short axis Z at the side of the rotor housing 3. 83 is attached. These two spark plugs 82 and 83 face the working chamber 8 in a compressed / expanded state, and ignite the air-fuel mixture in the working chamber 8 simultaneously or sequentially with a phase difference.

  FIG. 2 conceptually shows the configuration of the exhaust device of the rotary engine 1 with a turbocharger. FIG. 2 is a diagram conceptually showing the connection relationship between elements included in the exhaust system, and the connection position, merging position, branching position, passage shape, etc. of each passage are not necessarily specific. It does not represent

  The exhaust device includes a turbine 51 of the turbocharger 5, a catalyst device 100 on the downstream side thereof, and an EGR system 9 that recirculates a part of the exhaust gas to the intake side. The catalyst device 100 includes a three-way catalyst, for example.

  As described above, in the rotary engine 1 of the two-rotor type, each cylinder (that is, the rotor accommodating chamber 31 that accommodates the rotor 2 is referred to as a front cylinder 31a. The right cylinder in FIG. 2 is referred to as a rear cylinder 31b), and a primary port 10a that opens to the side housing 41 and a secondary port 10b that opens to the intermediate housing are provided. In this exhaust system, the primary port 10 a and the secondary port 10 b of each cylinder 31 are connected to different exhaust passages 13. Specifically, the primary port 10 a is connected to the independent passage 131, and the secondary port 10 b is connected to the collective passage 132.

  The independent passage 131 is configured to connect the primary port 10a of the front cylinder 31a and the primary port 10a of the rear cylinder 31b to the turbine 51 without being assembled. Therefore, the independent passage 131 is composed of two passages: a passage connected to the primary port 10a of the front cylinder 31a and a passage connected to the primary port 10a of the rear cylinder 31b. Since the two passages do not gather, the exhaust gas discharged from each primary port 10a does not cause exhaust interference. In this way, each independent passage 131 can supply exhaust energy to the turbine 51 without loss. Specifically, the independent passage 131 connected to the primary port 10a of the front cylinder 31a and the independent passage 131 connected to the primary port 10a of the rear cylinder 31b are independent from each other until just upstream of the turbine 51. The two independent passages 131 and the collective passage 132 are merged and connected to the turbine 51 immediately upstream of the turbine 51. Note that the independent passage 131 connected to the primary port 10a of the front cylinder 31a and the independent passage 131 connected to the primary port 10a of the rear cylinder 31b can be joined at an appropriate location.

  The collective passage 132 is a passage connected to the turbine 51 after collecting the secondary port 10b of the front cylinder 31a and the secondary port 10b of the rear cylinder 31b. Unlike the independent passage 131, the collecting passage 132 can cause exhaust interference. The secondary port 10b of the front cylinder 31a and the secondary port 10b of the rear cylinder 31b are opened adjacent to each other on the outer surface of the intermediate housing 4. The collecting passage 132 is configured to be connected to both of the openings of the two secondary ports 10b arranged side by side. The collective passage 132 has a partition wall 1321 disposed so as to extend from the outer surface of the intermediate housing 4 to the middle of the collective passage. The partition wall 1321 is configured such that a passage connected to the secondary port 10b of the front cylinder 31a and a passage connected to the secondary port 10b of the rear cylinder 31b extend in parallel while being independent of each other. . On the downstream side of the partition wall 1321, the two passages gather. As shown in FIG. 2, the downstream side of the collecting passage 132 gathers with two independent passages 131 and is connected to the turbine 51. Details of the configuration of the collecting passage 132 will be described later.

  The turbocharger 5 has a turbine 51 disposed on the exhaust passage 13 and a compressor 52 disposed on an intake passage (not shown). The turbine 51 is rotated by the exhaust gas flow, and the compressor 52 connected to the turbine 51 is operated by the rotation of the turbine 51, thereby obtaining a desired supercharging pressure. The downstream side of the turbine 51 is connected to the catalyst device 100 via the first passage 133. The turbocharger 5 also has a second passage 134 that bypasses the turbine 51 and is connected to the catalyst device 100, and a wastegate valve 1341 is interposed on the second passage 134. . When the wastegate valve 1341 is opened, the exhaust gas bypasses the turbine 51 and flows. Thereby, the supercharging of the turbocharger 5 is prevented.

  Here, the characteristics of the turbocharger attached to the rotary engine will be described. FIG. 3A shows the characteristics of the turbocharger attached to the rotary engine, and FIG. 3B shows the characteristics when the same turbocharger is attached to the reciprocating engine. First, the alternate long and short dash line in FIG. 3 (b) indicates the intercept point at which the waste gate valve is opened. In the reciprocating engine, the waste gate valve is closed in the low rotation range below the intercept point. Is higher than the turbine front back pressure indicated by a broken line in FIG. On the other hand, in the middle rotation range to the high rotation range exceeding the intercept point, the turbine front back pressure becomes higher than the boost pressure as the wastegate valve opens to limit the boost pressure. By opening the wastegate valve, the turbine front back pressure decreases, but the supercharging pressure decreases more than that.

  In the turbocharger attached to the rotary engine, as shown in FIG. 3 (a), the supercharging pressure indicated by the solid line in the figure is lower in the low rotation range below the intercept point at which the wastegate valve is closed. It becomes higher than the turbine front back pressure indicated by the broken line in the figure. This is the same as a reciprocating engine. On the other hand, in the middle to high rotation range exceeding the intercept point, although the wastegate valve is opened to limit the supercharging pressure, the supercharging pressure is maintained higher than the turbine front back pressure. This is considered to be because the valve opening characteristics of the exhaust port are different as described below.

  FIG. 4 compares the angle change of the opening area of the exhaust port in the rotary engine (change in the eccentric angle of the eccentric shaft 6) and the angle change of the lift amount of the poppet valve that opens and closes the exhaust port in the reciprocating engine (change in the crank angle). doing. FIG. 4 is a diagram for comparing the change characteristics of the opening state of the exhaust port with respect to the progress of the angle. The scale of the vertical axis is not the same between the rotary engine and the reciprocating engine, and the scale of the horizontal axis is also different from that of the rotary engine. It is not necessarily the same as the reciprocating engine. First, in a reciprocating engine that opens and closes an exhaust port by a vertical movement of a poppet valve, the lift amount gradually increases when the exhaust port is opened. On the other hand, in the rotary engine, as is apparent from FIG. 1, the exhaust port 10 that opens on the side surfaces of the side housing 41 and the intermediate housing 4 opens and closes as the rotor 2 rotates. When the valve 10 is opened, the opening area suddenly increases. As described above, the change characteristics of the opening state when the exhaust port is opened are greatly different between the rotary engine 1 and the reciprocating engine. When the exhaust port is opened, the exhaust gas is jetted into the exhaust passage at a high pressure by blowdown. However, the rotary engine 1 is more than the reciprocating engine due to the characteristic that the opening area is rapidly expanded when the exhaust port is opened. High blowdown energy can be supplied to the turbine. This is considered to cause a difference in characteristics of the turbocharger as shown in FIG. In FIG. 3 (a), the turbine front back pressure becomes higher than the supercharging pressure in a high rotation range where the flow rate increases, and this is due to a decrease in compressor efficiency.

  Returning to the exhaust system of FIG. 2, the EGR system 9 is disposed on the downstream side of the EGR cooler 92, the EGR passage 91 communicating with the collecting passage 132, the EGR cooler 92 interposed in the middle of the EGR passage 91. EGR valve 93 is provided. The EGR passage 91 is connected to a collecting passage 132 communicating with each of the front cylinder 31a and the rear cylinder 31b, so that exhaust gas from the front cylinder 31a and exhaust gas from the rear cylinder 31b are evenly extracted. It is possible. The EGR cooler 92 is configured to cool the exhaust gas with engine coolant. Cooled low temperature exhaust gas recirculates on the intake side. The EGR valve 93 is a flow rate adjustment valve that adjusts the amount of exhaust gas recirculated to the intake side.

  Thus, by connecting the EGR passage 91 to the collecting passage 132 and not taking out the EGR gas from the independent passage 131, the exhaust energy supplied to the turbine 51 of the turbocharger 5 through the independent passage 131 is In the independent passage 131, it becomes high in relation to the fact that no exhaust interference occurs. In particular, since the rotary engine 1 can obtain high blowdown energy as described above, even if the EGR gas is taken out from the collecting passage 132, the high blowdown energy is supplied to the turbine 51 through the independent passage 131. The turbocharging efficiency of the turbocharger 5 can be increased.

  On the other hand, the collecting passage 132 communicates with each of the front cylinder 31a and the rear cylinder 31b, and as described above, the exhaust gas discharged from each cylinder 31 can be taken out evenly. The collecting passage 132 is also connected to the turbine 51, and the remaining exhaust gas is supplied to the turbine 51. The exhaust gas discharged from each cylinder 31 is evenly taken out and is sent to the turbine 51. It becomes possible to homogenize the pulsation of the exhaust gas. This is also advantageous in improving the supercharging efficiency of the turbocharger 5. Further, exhaust gas interference can be suppressed by taking out the EGR gas in the collecting passage 132 communicating with both the front and rear cylinders 31a and 31b.

  The exhaust device further includes a third passage 135 branched from the EGR passage 91 on the downstream side of the EGR cooler 92 and connected to the second passage 134 on the upstream side of the catalyst device 100. A flow rate adjustment valve 136 that adjusts the flow rate of exhaust gas flowing through the third passage 135 is interposed in the third passage 135.

  The ECU 20 controls the operation of the rotary engine 1. 2, the opening degree of the wastegate valve 1341, the opening degree of the EGR valve 93, and the opening degree of the flow rate adjustment valve 136 in the third passage 135 are respectively adjusted and controlled.

  Specifically, the ECU 20 adjusts the opening degree of the waste gate valve 1341 so that the supercharging pressure becomes a predetermined supercharging pressure according to the operating state of the rotary engine 1.

  Further, the ECU 20 adjusts the opening degree of the EGR valve 93 according to the operating state of the rotary engine 1. As a result, a desired amount of exhaust gas is taken out from the collecting passage 132, and after passing through the EGR cooler 92, is cooled and then returned to the intake side.

  A relatively low temperature exhaust gas that has passed through the turbine 51 and a relatively high temperature exhaust gas that bypasses the turbine 51 by the second passage 134 flow into the catalyst device 100 when the waste gate valve 1341 is open. To do. The temperature of the exhaust gas flowing through the catalyst device 100 is an appropriate temperature.

  When the operating state of the rotary engine 1 is in a high rotation and / or high load region, the temperature of the catalyst device 100 tends to increase. When the temperature of the ECU 20 increases according to the temperature of the catalyst device 100, the ECU 20 opens the flow rate adjustment valve 136 of the third passage 135, removes the exhaust gas cooled from the collecting passage 132 and cooled by the EGR cooler 92, It is introduced into the second passage 134 upstream of the device 100. Thereby, since the temperature of the exhaust gas flowing into the catalyst device 100 is lowered, it is avoided that the temperature of the catalyst device 100 becomes too high. This improves the durability of the catalyst device 100 as well as the reliability of the catalyst device 100.

  In the operation state where the temperature of the catalyst device 100 becomes high, the amount of recirculation of the EGR gas is small. Therefore, even if the exhaust gas that has passed through the EGR cooler 92 flows to the catalyst device 100 without flowing to the intake side, the EGR gas There is no shortage.

  Next, the configuration of the collecting passage 132 will be described in more detail with reference to FIG. FIG. 5 conceptually shows an enlarged view of the vicinity of the collection point of the two passages in the collection passage 132.

  As described above, the collecting passage 132 has the partition wall 1321, and on the upstream side of the collecting passage 132 (that is, the left side in FIG. 5), the partition wall 1321 causes the secondary port 10 b of the front cylinder 31 a to be connected. The two passages of the connected passage and the passage connected to the secondary port 10b of the rear cylinder 31b constitute a parallel portion 1322 that extends in parallel while remaining independent from each other. Although not shown in FIG. 5, the parallel portion 1322 is connected to the outer surface of the intermediate housing 4 of the rotary engine 1.

On the downstream side of the parallel portion 1322, the two passages remain independent by the partition wall 1321, while the nozzle portion 1323 having a tapered passage is formed so that the cross-sectional area of each passage gradually decreases. Configure. It can also be said that the nozzle portion 1323 constitutes a part of the parallel portion 1322. When passing through the nozzle portion 1323, the flow rate of the exhaust gas increases. (This corresponds to the cross-sectional area of the downstream end of the nozzle portion 1323) minimum cross-sectional area of the nozzle portion 1323, as described later, is set to a predetermined cross-sectional area S _1.

On the downstream side of the nozzle portion 1323, the partition wall 1321 is eliminated and a collecting portion 1324 where two passages gather is configured. The downstream end of the collecting portion 1324, as described later, configured to have a predetermined cross-sectional area S _2. As a result of the exhaust gas being ejected to the collecting portion 1324 with the exhaust gas flow rate being increased in the nozzle portion 1323 described above, negative pressure is generated in the collecting portion 1324 (that is, ejector effect). Due to this ejector effect, the exhaust gas (particularly blowdown gas) discharged from either the front cylinder 31a or the rear cylinder 31b is prevented from flowing into the other cylinders, and the front cylinder When blowdown gas is discharged from either one of 31a and the rear cylinder 31b, the remaining exhaust gas of the other cylinder in the exhaust stroke can be sucked out. In the two-rotor type rotary engine 1 shown in FIGS. 1 and 2, the phase difference between the front cylinder 31a and the rear cylinder 31b is set to 180 ° as an eccentric angle, and in each cylinder 31a, the intake stroke, Since each step of the compression stroke, the expansion stroke, and the exhaust stroke is set to 270 ° in terms of exhaust angle, the exhaust stroke of the front cylinder 31a and the exhaust stroke of the rear cylinder 31a partially overlap each other.

  The downstream side of the collecting portion 1324 is connected to the turbine 51 after gathering with the two independent passages 131 as described above.

Here, the minimum cross-sectional area S ₁ of the nozzle portion 1323 is expressed by S ₁ = π (a / 2) ² where a diameter of a perfect circle corresponding to the cross-sectional area is a, and is downstream of the collecting portion 1324. The cross-sectional area S ₂ at the end is represented by S ₂ = π (D / 2) ² where D is the diameter of a perfect circle corresponding to the cross-sectional area. The collecting passage 132 is configured such that the relationship between the diameter a and the diameter D satisfies 0.5 ≦ a / D <1. This is because as the value of a / D becomes smaller, negative pressure is less likely to be generated in the collective portion 1324, and when the value of a / D is less than 0.5, it is impossible to generate negative pressure in the collective portion 1324. Because. On the other hand, the closer a / D is to 1, the more advantageous is the generation of negative pressure in the collecting portion 1324. However, when a / D is 1 or more, the cross-sectional area of the nozzle portion 1323 of each passage gathering in the collecting portion 1324 However, since the same as the cross-sectional area of the passage after the assembly becomes larger than that, it becomes impossible to obtain the suction effect of sucking the residual exhaust gas from the other cylinder. Therefore, in order to suppress the exhaust interference in the collecting passage 132 and increase the supercharging efficiency of the turbocharger 5, it is preferable to set a / D to 0.5 or more and less than 1.

  In the collecting passage 132 communicating with each of the front cylinder 31a and the rear cylinder 31b, the exhaust gas interference is suppressed by the ejector effect and the suction effect is obtained, so that the turbine 51 of the turbocharger 5 is supplied from the collecting passage 132. The exhaust energy to be increased can be increased as much as possible.

  The collecting passage 132 is also configured such that the two passages on the upstream side with respect to the collecting portion 1324 are arranged in parallel to each other by the partition wall 1321, and therefore the angle when the two passages gather is shallow. This enhances the ejector effect, enhances the exhaust interference suppression effect described above, and improves the suction effect.

  Thus, the independent passage 131 that does not collect between the plurality of cylinders is provided to supply high exhaust energy to the turbine of the turbocharger 5, and the exhaust interference in the collecting passage 132 is prevented by the configuration of the collecting passage 132 described above. In combination with the suppression, the supercharging efficiency of the turbocharger 5 is improved.

  In the configuration example shown in FIG. 5, the EGR passage 91 connected to the collecting passage 132 is connected to a negative pressure generation region in the collecting portion 1324. This configuration is advantageous in increasing the exhaust energy supplied to the turbine 51 when the EGR valve 93 is closed and the exhaust gas is not recirculated through the EGR passage 91. That is, in the configuration in which the EGR passage 91 is connected to the negative pressure generation region, in the state where the EGR valve 93 is closed and the flow in the EGR passage 91 is eliminated, in the vicinity of the connection portion with the collecting passage 132 in the EGR passage 91 Can be in a negative pressure state. For this reason, when exhaust gas (especially blowdown gas) is discharged from the front cylinder 31a or the rear cylinder 31b, the blowdown gas is prevented from flowing to the EGR passage 91 side. It becomes possible. That is, the EGR passage 91 is similar to the configuration in which the valve opening and closing valve is attached in the vicinity of the connection portion with the collecting passage 132, and the dead volume due to the EGR passage 91 is eliminated and the volume of the collecting passage 132 is reduced. Is equivalent to that. Thus, the exhaust energy supplied to the turbine 51 is increased.

  FIG. 7 shows the torque curve of the engine. “EGR region 1” surrounded by a broken line in FIG. 7 has a low engine load (for example, a region approximately corresponding to a low load region when the load region is equally divided into a low load region and a high load region), and The EGR region 1 corresponds to a region where the rotational speed is low (for example, a region approximately corresponding to a low rotational region when the rotational region is divided into a low rotational region and a high rotational region). Therefore, from the viewpoint of reducing pump loss, the EGR valve 93 is opened to introduce EGR gas into the intake air. In a region where the load is higher than the EGR region 1, the amount of fuel, and hence the amount of fresh air introduced into the cylinder, increases, so that EGR gas is not introduced. That is, the EGR valve 93 is closed.

  Thus, when the operating state of the engine is in the low rotation and high load region where EGR gas is not recirculated, the EGR passage 91 is connected to the negative pressure generation region in the collecting portion 1324 as shown in FIG. As described above, the exhaust energy supplied to the turbine 51 of the turbocharger 5 can be increased. This is advantageous in a low-rotation and high-load region where high turbocharging efficiency of the turbocharger 5 is required. As a result, as shown by a one-dot chain line in FIG.

  FIG. 6 shows a configuration example different from FIG. Specifically, the connection position of the EGR passage 91 is different between the configuration example of FIG. 5 and the configuration example of FIG. 6. The other configuration of the collecting passage 132 is the same in the configuration example of FIG. 5 and the configuration example of FIG. As shown in FIG. 6, the EGR passage 91 is connected to the downstream side of the region where the negative pressure is generated in the collecting portion 1324. This configuration makes it possible to promote the generation of negative pressure in the collecting portion 1324 when part of the exhaust gas flowing through the collecting passage 132 is taken out and the EGR gas is recirculated through the EGR passage 91.

  This configuration is particularly effective in increasing the exhaust energy supplied to the turbine 51 of the turbocharger 5 when the engine operating state is in the “EGR region 2” surrounded by a broken line in FIG. In other words, the “EGR region 2” has a high engine load (for example, a region approximately corresponding to a high load region when the load region is equally divided into a low load region and a high load region) and a high rotational speed (for example, The EGR region 2 is an EGR cooler 92 from the viewpoint of reducing the exhaust gas temperature. The EGR region 2 corresponds to a region corresponding to a high rotation region when the rotation region is equally divided into a low rotation region and a high rotation region. The EGR gas cooled by the above is introduced into the intake air.

  On the other hand, when the operating state of the engine is in a region of high rotation and high load, the back pressure of the engine is increased and it is difficult for negative pressure to be generated at the collecting portion 1324 in the collecting passage 132. At this time, as shown in FIG. 6, by connecting the EGR passage 91 to the downstream side of the negative pressure generation region in the collecting portion 1324, as described above, as the EGR gas is taken out, the negative pressure in the collecting portion 1324 is obtained. It becomes possible to promote the generation of pressure. In this way, the ejector effect can be reliably ensured when in the region of high rotation and high load, and exhaust interference can be suppressed and residual exhaust gas can be sucked out. As a result, the exhaust energy supplied to the turbine 51 of the turbocharger 5 can be increased, and as shown by the one-dot chain line in FIG.

  As virtually shown in FIG. 6, an opening / closing valve 94, which is different from the EGR valve 93, may be provided in the vicinity of the connection portion of the EGR passage 91 with the collecting passage 132. When the on-off valve 94 is opened, the exhaust gas can be recirculated through the EGR passage 91, and as described above, it is advantageous in improving torque in the region of high rotation and high load. When one on-off valve 94 is closed, the recirculation of exhaust gas through the EGR passage 91 is prohibited. In this state, dead volume due to the EGR passage 91 is eliminated, and exhaust gas is not taken out. Therefore, as in the configuration example shown in FIG. 5, the effect of improving the supercharging efficiency in the low rotation range can be obtained. That is, the configuration in which the on-off valve 94 virtually shown in FIG. 6 is provided is similar to the configuration example shown in FIG. It is possible to improve the torque in the region.

  The technology disclosed herein is not limited to being applied to the rotary engine 1 but can also be applied to an exhaust device of a multi-cylinder reciprocating engine. The configuration of the reciprocating engine is not particularly limited, and may be any of an inline engine, a V-type engine, and a horizontally opposed engine. The reciprocating engine may be either a gasoline engine (that is, a spark ignition engine) or a diesel engine.

1 Rotary piston engine (engine)
10 Exhaust port 10a Primary port (exhaust port)
10b Secondary port (exhaust port)
13 Exhaust passage 131 Independent passage 132 Collecting passage 1321 Partition wall 1322 Parallel portion 1323 Nozzle portion 1324 Collecting portion 31 Rotor housing chamber (cylinder)
31a Front cylinder 31b Rear cylinder 5 Turbocharger 51 Turbine 91 EGR passage 92 EGR cooler 93 EGR valve

Claims (6)

An exhaust port that is provided in an engine having a plurality of cylinders and is provided for each cylinder so as to discharge exhaust gas in each cylinder;
An exhaust passage configured to connect to each of the exhaust ports;
A turbocharger turbine disposed in the exhaust passage and configured to be driven by energy of the exhaust gas;
An EGR passage configured to communicate with the exhaust passage and to recirculate a part of the exhaust gas to the intake side of the engine,
The exhaust passage is
In each cylinder, it is connected to at least one of a plurality of exhaust ports, and is assembled between different cylinders and is then connected to the turbine,
An independent passage that is connected to the other exhaust port in each cylinder and connected to the turbine without being assembled between different cylinders,
The EGR passage is an exhaust system for an engine with a turbocharger connected to the collecting passage. The exhaust system for an engine with a turbocharger according to claim 1,
The collective passage includes a nozzle portion that is tapered so as to eject the exhaust gas while a passage connected to each of a plurality of cylinders remains in an independent state, and a plurality of downstream portions from the nozzle portion. An exhaust system for an engine with a turbocharger, wherein the exhaust passage has a collecting portion in which a region where the passage is gathered and a negative pressure is generated by an ejector effect is formed. The exhaust system for an engine with a turbocharger according to claim 2,
The collecting passage is connected to each of the plurality of cylinders on the upstream side of the collecting portion, and the independent passages are arranged to extend in parallel while being partitioned from each other by a partition wall. An exhaust system for an engine with a turbocharger further comprising: The exhaust system for an engine with a turbocharger according to claim 2 or 3,
The ratio a / D between the diameter a of the perfect circle corresponding to the minimum cross-sectional area of the nozzle portion and the diameter D of the perfect circle corresponding to the cross-sectional area at the downstream end of the collecting portion is set to 0.5 or more and less than 1. Exhaust system for turbocharged engines. The exhaust system for an engine with a turbocharger according to any one of claims 2 to 4,
The EGR passage is provided with an EGR valve configured to adjust a recirculation amount of the exhaust gas to the intake side,
The EGR passage communicates with a region where negative pressure is generated in the collecting portion,
The EGR valve opens when the engine operating state is in a predetermined region of low rotation and low load, and is turbocharged that closes when the engine is in a low rotation and high load region where the load is higher than the predetermined region. Exhaust system for aircraft engine. The exhaust system for an engine with a turbocharger according to any one of claims 2 to 4,
An EGR valve configured to adjust the recirculation amount of the exhaust gas to the intake side and an EGR cooler configured to cool the exhaust gas recirculated to the intake side are arranged in the EGR passage. Has been established,
The EGR passage communicates with the downstream side of the region where the negative pressure is generated in the collecting portion,
The EGR valve is an exhaust system for an engine with a turbocharger that opens when the operating state of the engine is in a region of high rotation and high load.

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