JP2007231906A - Multi-cylinder engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-cylinder engine provided with a turbocharger and capable of realizing high supercharging and large amount of EGR (Exhaust Gas Recirculation) while suppressing pumping loss in a wide operation range to carry out measures to control exhaust emission and improve output and fuel economy. <P>SOLUTION: This multi-cylinder engine is provided with exhaust ejectors 23a, 23b for dividing exhaust manifolds per group of cylinders for preventing an exhaust process from being overlapped and restricting the downstream side of a collection part of these exhaust manifolds 9a, 9b into a tapered shape becoming thinner and thinner toward an inlet 15 of a turbine of the turbocharger 6 and movable vanes 30a, 30b for changing effective nozzle area of the exhaust ejectors. The movable vanes 30a, 30b are arranged to serve also as movable vanes of a means for increasing or reducing effective area of the inlet 15 of the turbine and an angle for letting exhaust gas flow into a scroll part 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention is a technology for realizing high supercharging and large-volume EGR in a wide operating region while suppressing deterioration of pumping loss in a wide operating region in order to improve exhaust measures and improve output and fuel consumption in a multi-cylinder engine equipped with a turbocharger. About.

In order to promote improvement in engine output and fuel consumption, a turbocharger that supercharges intake air using exhaust energy is often mounted (Patent Documents 1 to 4). In a multi-cylinder engine equipped with a turbocharger, there is an operating region where the supercharging pressure is higher than the exhaust pressure, so that EGR (Exhaust Gas Recirculation) cannot be performed sufficiently. In a turbocharger, if the narrowest cross-sectional area of the scroll part or the opening of the variable nozzle vane is reduced, the supercharging pressure also increases at the same time as the exhaust pressure, so that the EGR rate cannot be sufficiently improved (Patent Documents 1 to 5) 3).
JP-A-10-008978 Japanese Utility Model Sho 63-009427 JP-A-11-31124 JP 2005-016313 A

  In Patent Document 2, the exhaust manifold upstream of the turbine is divided for each cylinder group in which the exhaust strokes do not overlap. However, when the turbocharger is of a single entry system (one turbine inlet), the exhaust side of the cylinder in which exhaust is being ejected is divided. The exhaust pulse easily escapes from the exhaust manifold to the exhaust manifold on the cylinder side of the exhaust (push-out) stroke, and improvement in turbine efficiency and EGR rate cannot be effectively promoted (Patent Document 2). In Patent Document 4, a pulse converter is set at the inlet of the turbine housing so that the backflow of the exhaust pulse can be suppressed. However, because the throttle of the pulse converter is constant, setting is difficult, and depending on the operating state, There is a possibility that the exhaust pressure downstream of the throttle will be excessive, and the output and fuel consumption will be greatly impaired.

  In order to solve such a problem, the present invention, in a multi-cylinder engine equipped with a turbocharger, in order to promote exhaust countermeasures and improved output and fuel consumption, suppresses pumping loss in a wide operating range, and achieves high supercharging / The purpose is to provide a means to achieve mass EGR.

  In a first aspect of the present invention, in a multi-cylinder engine equipped with a turbocharger, the exhaust manifold is divided into cylinder groups that do not overlap in the exhaust stroke, and a tapered shape is formed such that the downstream of the exhaust manifold is directed to the turbine inlet of the turbocharger. An exhaust ejector that is narrowed down to a movable vane that changes the effective nozzle area of the exhaust ejector is provided.

  According to a second aspect of the invention, in the multi-cylinder engine according to the first aspect of the invention, the movable vane is also used as a movable vane that increases or decreases the effective area of the turbine inlet of the turbocharger and the exhaust inflow angle to the scroll portion. To do.

  According to a third aspect of the invention, in the multi-cylinder engine according to the first aspect of the invention, the movable vane is assembled to a spacer that connects the exhaust ejector and the turbine inlet.

  According to a fourth aspect of the invention, in the multi-cylinder engine according to the third aspect of the invention, the spacer is partitioned through a partition wall into a plurality of connection paths corresponding to the nozzle openings of the exhaust ejector.

  According to a fifth aspect of the invention, in the multi-cylinder engine according to the first or second aspect of the invention, the multi-cylinder engine includes means for controlling the opening degree of the movable vane based on the operating state.

  According to a sixth aspect of the invention, in the multi-cylinder engine according to the first aspect of the invention, the multi-cylinder engine includes an EGR passage connecting the exhaust manifold and the intake manifold, and a check valve interposed in the EGR passage.

  In the first aspect of the invention, since the movable vane for changing the effective nozzle cross section of the exhaust ejector is provided, the optimum effective nozzle cross section of the exhaust ejector can be set in a wide operation region. For example, by adjusting the opening of the movable vane in the low speed range and increasing the opening of the movable vane in the high speed range, the optimal effective nozzle cross section of the exhaust ejector can be used in both the low speed range and the high speed range. It can be set to. The optimal effective nozzle cross-section of the exhaust ejector accelerates the exhaust flow and increases the dynamic pressure. As a result, the exhaust pulse escapes from the exhaust manifold on the cylinder side during exhaust emission to the exhaust manifold on the cylinder side in the exhaust (push-out) stroke. Can be suppressed. Therefore, even when the turbocharger is of a single entry system (one turbine inlet), the exhaust pulse for each cylinder group is sent to the turbine of the turbocharger without being weakened, and not only the turbine efficiency is improved. When an EGR device that circulates part of the exhaust gas from the turbine upstream to the compressor downstream is provided, the EGR gas exhaust pulse is also recirculated without being weakened, and the EGR rate can be increased. Further, since the static pressure is lowered by the blowdown flow blown out from the optimum effective nozzle section of the exhaust ejector, the exhaust is sucked from the exhaust manifold on the cylinder side during the exhaust (pushing) stroke, and the pumping loss can be reduced. The optimal effective nozzle cross section of the exhaust ejector varies depending on the operating conditions, but since it has variable vanes, it is possible to set the optimal effective nozzle cross section of the exhaust ejector and minimize pumping loss in a wide operating range. This makes it possible to perform high supercharging and large-volume EGR while limiting the amount to the limit, and to achieve both exhaust measures (reduction of NOx, etc.) and improvements in output and fuel consumption.

  In the second aspect of the invention, the movable vanes can set the optimum effective area of the turbine inlet and the optimum exhaust inflow angle to the scroll portion in a wide operation region. For example, by adjusting the opening of the movable vane in the low speed range and decreasing the opening of the movable vane in the high speed range, the optimal effective area of the turbine inlet and the optimal exhaust inflow angle to the scroll unit can be obtained. It can be set. When the opening of the movable vane decreases, the effective area of the turbine inlet decreases, the inflow angle into the scroll portion increases, and the flow velocity of the exhaust gas flowing outside (or inside) the scroll portion increases, while the movable vane increases. When the opening of the turbine is increased, the effective area of the turbine inlet is increased, the inflow angle to the scroll portion is reduced, the flow of exhaust gas is expanded to the inside (or the outside) of the scroll portion, and the flow velocity is reduced. . Since the movable vane is also used (shared) as the movable vane of the exhaust ejector, it is highly supercharged even during a large amount of EGR (especially at low speed and high load range), and the intake flow rate can be secured sufficiently, improving the combustion state In addition, NOx and PM (particulate) can be simultaneously reduced. By using the movable vane, the number of parts can be reduced and the cost can be reduced. Since the turbocharger is also of a variable displacement type due to the movable vanes, the configuration is simple and advantageous in terms of cost compared to a variable nozzle type turbocharger having a large number of movable nozzle vanes.

  In the third aspect of the invention, the movable vane can be easily and easily assembled together with the spacer, and can be easily replaced.

  In the fourth aspect of the invention, the nozzle opening of the exhaust ejector is extended by the partition wall, and the effective nozzle area of the exhaust ejector is easily changed accurately by the opening of the movable vane.

  In 5th invention, a movable vane can be controlled to the optimal opening according to a driving | running state. For example, by controlling based on the engine speed and engine load representing the operating state, it is possible to perform high supercharging and large-volume EGR while minimizing the pumping loss even in the low speed and high load range. .

  In the sixth aspect of the invention, the check valve prevents the backflow of EGR gas, and the action of the exhaust ejector increases the differential pressure before and after the check valve, so that the EGR rate can be effectively increased.

  In FIG. 1, reference numeral 2 denotes an intake passage of a multi-cylinder engine 1 (6-cylinder diesel engine), which includes intake manifolds 3 a and 3 b and an intake pipe 4. The intake manifolds 3a and 3b are divided into cylinder groups (# 1, 2, 3 and # 4, 5, 6) in which the intake strokes do not substantially overlap. The intake pipe 4 is branched on the downstream side of the intercooler 5 and connected to the collective part of the manifolds 3a and 3b. 6a is a compressor of the turbocharger 6, and 7 is an air cleaner.

  Reference numeral 8 denotes an exhaust passage of the engine 1 and includes exhaust manifolds 9 a and 9 b and an exhaust pipe 10. The exhaust manifolds 9a and 9b are divided into cylinder groups (# 1, 2, 3 and # 4, 5, 6) in which the exhaust strokes do not substantially overlap, and a turbocharger is disposed downstream of the manifold unit 9a, 9b. The exhaust pipe 10 is connected via a turbine 6b. The compressor 6a of the turbocharger 6 is driven by the rotation of the turbine 6b and supercharges intake air to each cylinder. As the turbocharger 6, one having one turbine inlet (single entry system) is used. 7 is a muffler.

  In FIGS. 2 to 3, the exhaust manifolds 9 a and 9 b are formed in nozzle portions 23 a and 23 b (exhaust ejectors) that converge at one flange on the downstream side of the collecting portion and narrow toward the turbine inlet 15. 18 is a turbine housing, and a spacer 25 is interposed between the flange of the turbine inlet 15 and the flanges of the exhaust manifolds 9a and 9b. In order to make the effective nozzle area of the exhaust ejectors 23 a and 23 b variable, the flow path 26 is partitioned by a partition wall 29 inside the spacer 25, and each nozzle opening of the exhaust ejectors 23 a and 23 b extends straight to the turbine inlet 15. The movable vanes 30a and 30b are formed to open and close the flow paths 26a and 26b (connection paths). The movable vanes 30a and 30b are disposed so as to be used as movable vanes for the means for increasing and decreasing the effective area of the turbine inlet 15 and the exhaust inflow angle to the scroll portion 16 surrounding the turbine wheel 17. Reference numeral 31 denotes a rotary shaft that supports the movable vanes 30a and 30b so as to be swingable. Outside the spacer 25, a lever 32 of the rotary shaft 31 is connected to a telescopic rod 34a of an actuator 34 (for example, an electromagnetic solenoid), When the rod 34 a expands and contracts, the movable vanes 30 a and 30 b swing (open and close) integrally with the rotary shaft 31.

  When the rod 34a is in the initial (contracted) position, the movable vanes 30a and 30b are held in a fully opened state. When the rod 34a is extended, the opening degree of the movable vanes 30a and 30b is reduced, and when the rod 34a is contracted, the opening degree of the movable vanes 30a and 30b is increased. Inside the turbine housing 18, when the opening degree of the movable vanes 30 a and 30 b is reduced, the effective area of the turbine inlet 15 is reduced, the inflow angle to the scroll part 16 is increased, and the exhaust gas is exhausted outside the turning part of the scroll part 16. While the flow rate and the flow velocity increase, when the opening degree of the movable vanes 30a and 30b increases, the effective area of the turbine inlet 15 increases, the inflow angle to the scroll unit 16 decreases, and the exhaust gas enters the inside of the scroll unit 16 orbits. The flow spreads and the flow velocity decreases (see FIGS. 4 and 3). In the upstream of the turbine housing 18, when the opening degree of the movable vanes 30a and 30b is reduced, the effective nozzle area of the exhaust ejectors 23a and 23b is reduced, and the flow of the exhaust gas to the turbine inlet 15 is accelerated, while the movable vanes 30a and 30b are accelerated. As the opening degree of 30b increases, the effective nozzle area of the exhaust ejectors 23a and 23b increases, and the flow rate of the exhaust gas to the turbine inlet 15 decreases.

  In FIG. 1, reference numeral 35 denotes an EGR device that circulates part of the exhaust gas from the upstream side of the turbine 6b of the turbocharger 6 to the downstream side of the compressor 6a of the turbocharger 6, and includes exhaust manifolds 9a and 9b and intake manifolds 3a and 3b (intake pipes 4). EGR passages 36a and 36b are provided for connecting the branch passages 40a and 40b) to the relationship between the same cylinder groups. In the EGR passages 36a and 36b, an EGR cooler 37 for cooling the EGR gas, an EGR valve 38 for adjusting the EGR flow rate, and a check valve 39 (reed valve) for regulating the backflow of the EGR gas are interposed. The check valve 39 is disposed downstream of the EGR passages 36a and 36b. An EGR valve 38 is disposed upstream of the check valve 39 and an EGR cooler 37 is disposed upstream thereof. Since the EGR passages 36a and 36b are connected to each other in the same cylinder group, the exhaust stroke and the intake stroke overlap between the cylinders belonging to the same cylinder group, so that the improvement of the EGR rate can be promoted.

  FIG. 8 shows the relationship between the EGR rate and the nozzle opening area, and FIG. 9 shows the relationship between the pumping loss and the nozzle opening area. The optimum nozzle opening area (in the range where the EGR rate can be sufficiently increased). The nozzle opening area that can minimize the pumping loss differs depending on the operating state, and the low speed region side is small and the high speed region side is large. In this case, since the movable vanes 30a and 30b are provided, for example, the opening degree of the movable vanes 30a and 30b is small in the low speed range, and the opening degree of the movable vanes 30a and 30b is largely adjusted in the high speed range. The effective nozzle area of the exhaust ejectors 23a and 23b can be set optimally in both the low speed range and the high speed range.

  Due to the optimum effective nozzle area of the exhaust ejectors 23a and 23b, the flow of exhaust is accelerated and the dynamic pressure increases. Therefore, the exhaust pulse is exhausted from the exhaust manifold 9a or 9b on the cylinder side during exhaust emission, and the cylinder side in the exhaust (push-out) stroke Escape to the exhaust manifold 9b or 9a. Therefore, the exhaust pulse between the cylinder groups is sent to the turbine 6b of the turbocharger 6 without being weakened, and not only the turbine efficiency is improved, but also the exhaust pulse is weakened to the check valve 39 of the EGR passages 36a, 36b. Therefore, the EGR rate can be increased because the check valve 39 is effectively operated. As for the exhaust manifold pressure, the peak P1 of the exhaust pulse during exhaust ejection becomes high, and the EGR rate is sufficiently improved (see FIGS. 13 and 14). Further, since the ejector action of the blow-down flow is caused by the optimum effective nozzle area of the exhaust ejectors 23a and 23b, the peak P2 during the exhaust (push-out) stroke is lowered, and the pumping loss is reduced (FIGS. 13 and 15). ,reference).

  When the effective nozzle area of the exhaust ejectors 23a and 23b is larger than the optimum value, the dynamic pressure of the blow-down flow is small, and the exhaust pulse is exhausted from the exhaust manifold 9a or 9b on the cylinder side during exhaust discharge. The exhaust manifold 9b or 9a cannot be sufficiently prevented from escaping, and the ejector action of the blow-down flow cannot be sufficiently obtained. For this reason, the exhaust manifold pressure is such that the peak P1 of the exhaust pulse during exhaust ejection becomes lower, and the EGR rate cannot be sufficiently improved (see FIGS. 10 and 11). In addition, the peak P2 during the exhaust (pushing) stroke becomes higher, and the pumping loss increases (see FIGS. 10 and 12). When the effective nozzle area of the exhaust ejectors 23a and 23b is smaller than the optimum value, the exhaust manifold pressure increases as a whole including the peak P1 of the exhaust pulse during exhaust ejection and the peak P2 during the exhaust (extrusion) stroke. However, the pumping loss becomes excessive (see FIGS. 16 to 18).

  In FIG. 1, reference numeral 50 denotes a control unit for controlling the EGR valve 38 of the EGR passages 36a, 36b and the movable vanes 30a, 30b of the exhaust ejectors 23a, 23b. An engine rotation sensor 51 that detects flywheel rotation and an engine load sensor 52 that detects an engine load from an accelerator opening (a pedal operation amount) are provided. FIG. 5 is a flowchart for explaining the control contents of the control unit 50. In S1 and S2, the detected value of the engine speed N and the detected value of the engine load L (accelerator opening) are read. In S3, the opening degree of the EGR valve is controlled based on the detected value of the engine speed N and the detected value of the engine load L based on FIG. In S4, the opening degree of the movable vane is controlled based on the detected value of the engine speed N and the detected value of the engine load L based on FIG. 6 and 7 show control characteristics of the movable vane and the EGR valve, and are stored in the memory of the control unit 50 as map data.

  With such a configuration, even in the single entry type turbocharger 6, the backflow of the exhaust pulse is suppressed by the optimum effective nozzle area of the exhaust ejectors 23a and 23b, and the exhaust pulse is transmitted to the turbine 6b without being weakened. Improved turbine efficiency is obtained. In addition, since the back flow of the exhaust pulse is suppressed, the exhaust pulse is transmitted to the check valve 39 in the EGR passages 36a and 36b without being weakened, and the check valve 39 is effectively operated, so that a high EGR rate is obtained. is there. Further, the exhaust manifold pressure 9b or 9a on the cylinder side during the exhaust (push-out) stroke is reduced by the ejector action of the blowdown flow, so that the pumping loss can be improved (see FIGS. 13 to 15).

  In this embodiment, the movable vanes 30a and 30b can optimally set the effective nozzle area of the exhaust ejectors 23a and 23b even in a low rotation range, so that high supercharging and a large amount of EGR can be achieved while keeping the pumping loss small. This makes it possible to achieve both exhaust measures (reducing NOx, etc.) and improving output and fuel consumption in a wide operating range. Further, the effective area of the turbine inlet 15 and the exhaust inflow angle to the scroll portion 16 are also controlled to the optimum state according to the operating state by the movable vanes 30a and 30b, and during a large amount of EGR (especially at a low speed and high load region). However, since the intake flow rate can be sufficiently secured, the combustion state is improved and NOx and PM (particulate) can be simultaneously reduced.

  By combining the movable vanes 30a and 30b, the number of parts can be reduced and the cost can be reduced. Since the turbocharger 6 is also of a variable displacement type by the movable vanes 30a and 30b, the configuration is simple and advantageous in terms of cost compared to a variable nozzle type turbocharger having a large number of movable nozzle vanes. In the EGR passages 36a and 36b, since the EGR valve 38 and the check valve 39 (reed valve) are disposed on the downstream side of the EGR cooler 37, the durability of these valves is also ensured.

  FIGS. 19 and 20 show another embodiment, and the spacer 25A is formed in the engaging portion 24 whose downstream end face of the partition wall 29A regulates the minimum vane opening, and the passages on both sides sandwiching the partition wall 29A. A movable vane 30 that opens and closes is disposed. The movable vane 30 is not a separate one for each of the flow paths 26a and 26b, but is configured as a single piece that is applied to the flow paths 26a and 36 on both sides. Thereby, in the spacer 25A, the movable vane 30 can be assembled easily and easily, and the cost can be reduced. Reference numeral 31 denotes a rotating shaft of the movable vane 30, which is connected to a rotating shaft 44 a of an actuator 44 (for example, a stepping motor) outside the spacer 25 A. When the actuator 44 is driven, the movable vane 30 swings integrally with the rotating shaft 31. It moves (opens and closes). 20 and 21, the same parts as those in FIGS. 2 to 4 are denoted by the same reference numerals, and redundant description is omitted.

  The movable vanes 30a and 30b (see FIGS. 2 to 4) and the rotary shaft 31 of the movable vane 30 (FIGS. 19 and 20) are not limited to the arrangement shown in the figure, and are opposed to sandwich the center of the turbine inlet. Setting to the side (symmetrical position) is also conceivable. In that case, in the turbine housing, when the opening degree of the movable vanes 30, 30a, 30b is reduced, the effective area of the turbine inlet 15 is reduced, the inflow angle to the scroll part 16 is increased, and the inside of the scroll part is turned. As the flow velocity of the exhaust gas flowing through increases, the opening of the movable vane increases, the effective area of the turbine inlet increases, the inflow angle to the scroll portion decreases, and the flow of exhaust gas spreads outside the scroll portion, The flow rate decreases.

1 is an overall schematic configuration diagram according to an embodiment of the present invention. It is sectional drawing explaining the structure of an exhaust ejector. FIG. 3 is a sectional view taken along the line XX in FIG. 2. It is sectional drawing explaining the structure of an exhaust ejector. It is a flowchart explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is a characteristic view explaining the control content of a control unit. It is a characteristic view which illustrates the relationship between an operation area, a nozzle opening area, and an EGR rate. It is a characteristic view which illustrates the relationship between an operation area, a nozzle opening area, and pump loss. It is a characteristic view which illustrates the simulation result of intake / exhaust pulsation. It is a characteristic view which illustrates the simulation result of an EGR flow rate. It is a characteristic view which illustrates the simulation result of in-cylinder pressure. It is a characteristic view which illustrates the simulation result of intake / exhaust pulsation. It is a characteristic view which illustrates the simulation result of an EGR flow rate. It is a characteristic view which illustrates the simulation result of in-cylinder pressure. It is a characteristic view which illustrates the simulation result of intake / exhaust pulsation. It is a characteristic view which illustrates the simulation result of an EGR flow rate. It is a characteristic view which illustrates the simulation result of in-cylinder pressure. It is sectional drawing explaining the structure of an exhaust ejector. It is a YY arrow line view of FIG. 19 similarly.

Explanation of symbols

1 Multi-cylinder engine (6-cylinder diesel engine)
2 Intake passage 3a, 3b Intake manifold 5 Intercooler 6 Turbocharger (variable nozzle type turbocharger)
6a Compressor 6b Turbine 8 Exhaust passage 9a, 9b Exhaust manifold 15 Turbo inlet 16 Scroll part 17 Turbine wheel 18 Turbine housing 23a, 23b Exhaust ejector 25, 25A Spacer 26a, 26b Connection path (flow path)
29, 29A Partition 30, 30a. 30b Movable vane 34, 44 Movable vane actuator 35 EGR device 36a, 36b EGR passage 37 EGR cooler 38 EGR valve 39 Check valve (reed valve)
50 Control unit 51 Engine rotation sensor 52 Engine load sensor

Claims (6)

  In a multi-cylinder engine equipped with a turbocharger, an exhaust manifold is divided into groups of cylinders that do not overlap in the exhaust stroke, and an exhaust ejector and exhaust that narrows the downstream side of the exhaust manifold toward the turbine inlet of the turbocharger. A multi-cylinder engine comprising a movable vane that changes an effective nozzle area of an ejector.   The multi-cylinder engine according to claim 1, wherein the movable vane is also used as a movable vane that increases or decreases an effective area of a turbine inlet of the turbocharger and an exhaust inflow angle to the scroll portion.   The multi-cylinder engine according to claim 1, wherein the movable vane is assembled to a spacer that connects between the exhaust ejector and the turbine inlet.   The multi-cylinder engine according to claim 3, wherein the spacer is partitioned by a plurality of connection paths corresponding to the nozzle openings of the exhaust ejector via partition walls.   The multi-cylinder engine according to claim 1 or 2, further comprising means for controlling the opening degree of the movable vane based on an operating state.   The multi-cylinder engine according to claim 1, further comprising: an EGR passage connecting between the exhaust manifold and the intake manifold, and a check valve interposed in the EGR passage.

Images