JP4965870B2 - Multi-cylinder engine - Google Patents

Description

  In a multi-cylinder engine equipped with a turbocharger, the present invention aims at high supercharging / mass EGR while suppressing deterioration of pumping loss in a wide operating range in order to improve exhaust measures (reduction of NOx, etc.) and improve output and fuel consumption. It is related with the technology for realizing.

  As an engine EGR (Exhaust Gas Recirculation) system, a system that circulates part of the exhaust gas from the exhaust system to the intake system is often used. In such an EGR device, when exhaust gas is circulated from the turbine upstream of the turbocharger to the compressor downstream, an operation region in which the supercharging pressure becomes higher than the exhaust pressure is likely to occur, and EGR cannot be sufficiently obtained.

In order to increase the EGR rate, exhaust throttling by a butterfly valve or intake throttling by a throttle valve can be considered (Patent Document 4), but deterioration of pumping loss becomes a problem. The VNT (variable nozzle turbocharger) throttle increases not only the exhaust manifold pressure but also the intake manifold pressure. Therefore, to improve the EGR rate, the VNT throttle is increased until the exhaust manifold pressure is higher than the intake manifold pressure. It is necessary to make it effective, and the pumping loss is worsened. Therefore, a method of performing EGR by exhaust pulsation using a reed valve (check valve) (Patent Document 1) and a method of increasing exhaust pulsation (dynamic pressure of EGR gas) using a mixing section in the EGR passage (Patent Document 2) ), A system that performs internal EGR using a variable valve (Patent Document 3), and a system that prevents the exhaust pulse from flowing backward by providing a tapered nozzle section toward the exhaust gas merging section (Patent Document 5) ,It has been known.
JP 2000-249004 Special table 2003-534488 JP 2001-107810 A JP 2002-021625 A JP-A-2005-147011

  In Patent Document 1 and Patent Document 2, when the turbocharger connected to the split-type exhaust manifold is a single entry system (one turbine inlet), exhaust pulses having different phases cancel each other, so that a sufficient EGR rate Cannot be obtained. In the case of Patent Document 3, the exhaust (EGR gas) sucked into the cylinder cannot be cooled.

  In Patent Document 5, the tapered nozzle portion prevents the exhaust pulse from flowing back between the exhaust manifolds. Therefore, the exhaust pulse is transmitted to the check valve in the EGR passage without weakening, and the EGR rate is improved. However, since the opening area of the tapered nozzle portion is constant, setting is difficult, and depending on the operating state, the exhaust resistance (pumping loss) may be excessive, which may impair improvement in output and fuel consumption.

  In order to solve such problems, the present invention achieves both high supercharging and large volume while suppressing pumping loss in a wide operating range in order to achieve both exhaust measures (reduction of NOx, etc.) and improvement of output and fuel consumption. The purpose is to provide a means to realize EGR.

In a first aspect of the present invention, in a multi-cylinder engine equipped with a turbocharger, an exhaust manifold divided for each cylinder group in which exhaust strokes do not overlap, and a downstream portion of the exhaust manifold gathering portion is narrowed toward a converging portion. nozzle means for said variable to control simultaneously and equally substantial opening area facing the merging portion with the one property that is set in accordance with the operating state of each nozzle section, said turbine upstream of the turbocharger EGR passage which connects the same compressor downstream of the intake manifold and the exhaust manifold, a check valve interposed in said EGR passage, comprising a means for varying the opening area of each nozzle of each nozzle Based on the detection signal of the driving state at the same time with one characteristic that is set according to the driving state the substantial opening area facing the junction It means for controlling the like, characterized by comprising a.

According to a second aspect of the present invention, in a multi-cylinder engine equipped with a turbocharger, an exhaust manifold divided for each cylinder group where the exhaust strokes do not overlap, an intake manifold divided for each cylinder group where the intake strokes do not overlap, and these exhaust manifolds nozzle portion to narrow the set portion downstream of the shape tapered toward these merging section, the one property with it and evenly simultaneously set in accordance with the operating state a substantial opening area facing the confluent portion of the nozzle portion means for variable to control, EGR passage connecting between said exhaust manifold and also compressor downstream of the intake manifold of the turbine upstream of the turbocharger, comprising a check valve, interposed in said EGR passage, The means for making the opening area of each nozzle part variable means that the substantial opening area facing the merging part of each nozzle part is in an operating state. Depending characterized by comprising a means for controlling simultaneously and evenly on the basis of one of the detection signals of the characteristics with the operating state that is set.

According to a third aspect of the present invention, in the multi-cylinder engine according to the first or second aspect of the invention, the means for changing the opening area of each nozzle portion is a protrusion or protrusion that extends the partition wall between the nozzle portions to the merging portion. And a means for supporting the valve plate so as to be capable of swinging in the expansion / contraction direction with the shortest distance between the protrusion and the valve body as a substantial opening area of the nozzle portion. .

According to a fourth aspect of the present invention, in the multi-cylinder engine according to the first or second aspect of the invention, the means for varying the opening area of each nozzle portion is a diffuser or nozzle that squeezes the merging portion facing each nozzle portion downstream And a means for supporting the valve plate so that the valve plate can be advanced and retracted in the expansion / contraction direction with the shortest distance between the valve body and the diffuser as a substantial opening area of the nozzle portion. .

  In the first aspect of the invention, the tapered nozzle portion accelerates the exhaust flow, increases the dynamic pressure, and lowers the static pressure (exhaust pressure). Therefore, the blowdown flow is generated from the exhaust manifold on the cylinder side during exhaust emission. Escape to the exhaust manifold on the cylinder side during the exhaust (push-out) stroke can be suppressed. For this reason, exhaust pulses with different phases are sent to the turbine of the turbocharger without being weakened, improving the turbine efficiency, and being transmitted to the check valve in the EGR passage without being weakened. The EGR rate can be increased in order to operate effectively. Further, when an ejector action is generated by the blow-down flow blown from the tapered nozzle portion, the exhaust is sucked downstream from the exhaust manifold on the cylinder side during the exhaust (pushing) stroke, and the pumping loss can be reduced.

The tapered nozzle portion provides exhaust resistance, but has means for controlling the substantial opening area facing each merge portion of each nozzle portion as variable , so that the substantial nozzle portion faces each merge portion based on the operating state. The optimal opening area can be optimally controlled . For example, based on the engine speed representing the operating state, the substantial opening area of the nozzle portion is set to be small in the low rotation range, and the substantial opening area of the nozzle portion is set to be large in the high rotation range. This makes it possible to carry out high supercharging and large-volume EGR while keeping the pumping loss small even in the high engine speed range, and achieves both exhaust measures (reduction of NOx, etc.) and improved output and fuel consumption in a wide operating range. Can be realized.

In the second invention, since the EGR passages 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 pumping loss is not deteriorated. The EGR rate can be improved efficiently. In addition, since it has means to control the substantial opening area facing each merge part of each nozzle as variable , it is possible to perform high supercharging and large volume EGR while keeping pumping loss small in a wide operation region, It is possible to achieve both exhaust measures (reducing NOx, etc.) and improving output and fuel consumption.

In the third aspect of the invention, when the valve body swings, the shortest distance between the valve body and the projection is expanded and reduced, and the substantial opening area of the nozzle portion can be made variable appropriately .

In the fourth invention, when the valve body advances and retreats, the shortest distance between the valve body and the diffuser (the inner surface of the passage narrowed downstream) is expanded and contracted, and the substantial opening area of the nozzle portion is appropriately variable. Can do. The joining portion is partitioned into a shape in which the tapered nozzle portion is extended by a valve body that can advance and retreat on an extension line between the nozzles. In other words, the valve body only needs to have one that can advance and retract between the openings of each nozzle portion along the center line of the diffuser, and the simple opening mechanism makes the substantial opening area of the nozzle portion accurate and easy. It can be variable. Moreover, it becomes advantageous in cost .

  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 formed at the junction 11 of these manifolds 9a and 9b. The exhaust pipe 8 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, a variable nozzle type having one turbine inlet (single entry type) is used. 12 is a muffler.

  The junction 11 is configured as shown in FIG. The exhaust manifolds 9 a and 9 b are formed in nozzle portions 23 a and 23 b that converge at one flange on the downstream side of the collecting portion and narrow the passage toward the joining portion 11. Reference numeral 25 denotes a turbine housing, and a spacer 27 is formed between the flange of the turbine inlet 26 and the flanges of the exhaust manifolds 9a and 9b. In order to make the substantial opening area of the nozzle portions 23a and 23b facing the merge portion 11 variable, inside the spacer 27, a projection 29 extending the partition wall 28 between the nozzle portions 23a and 23b to the merge portion 11 and the projection 29 Means for supporting the valve bodies 30a, 30b so as to be swingable in the expansion / contraction direction with the shortest distance x between the valve bodies 30a, 30b arranged on both sides of the nozzles 23 and the projection 29 as a substantial opening area of the nozzle portions 23a, 23b. Are provided.

  The rotary shafts 31a and 31b support the valve bodies 30a and 30b, and are coupled to one end of the links 32a and 32b outside the spacer 27 (see FIG. 3). Reference numeral 34 denotes an actuator that can expand and contract the rod 34a. The tip of the rod 34a is connected to the other ends of the links 32a and 32b via elongated holes 33a and 33b, and when the rod 34a expands and contracts, the valve bodies 30a and 30b rotate. It swings integrally with 31a and 31b. In FIG. 3, θ is the opening degree of the valve bodies 30a, 30b and corresponds to the shortest distance x.

  In FIG. 1, reference numeral 35 denotes an EGR device that circulates a 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. The exhaust manifolds 9a and 9b 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 (reed valve) 39 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.

  Regarding the valve bodies 30a and 30b (see FIGS. 2 and 3), when the rod 34a is in the initial (extension) position, the valve body 30a and 30b is held in a retracted state that does not affect the flow of the exhaust gas blown from the nozzle portions 23a and 23b. When 34a contracts, it swings in the direction of shortening the shortest distance x (substantial opening area of the nozzle portions 23a, 23b) with the protrusion 29, while the shortest distance x with the protrusion 29 when the rod 34a extends to the initial position. It swings in the direction of expanding the angle. In this case, since the substantial opening area of the nozzle portions 23a and 23b is maximized at the initial position of the valve body 30a30b, the nozzle portions 23a and 23b have an optimum opening area (EGR ratio sufficient for the high speed range). In the range to be increased, the opening area is set such that the pumping loss is minimized. On the low speed range side, the substantial opening area (shortest distance x) of the nozzle portions 23a and 23b is caused by the swinging of the valve bodies 30a and 30b. Is set to an optimum opening area on the low speed region side (an opening area that minimizes the pumping loss in a range where the EGR rate is sufficiently increased) (see FIGS. 8 and 9).

  When the substantial opening area of the nozzle portion is the optimum value, the flow of exhaust gas is accelerated by the tapered nozzle portions 23a and 23b, the dynamic pressure increases, and the static pressure (exhaust pressure) decreases. It is possible to prevent the blowdown flow from escaping from the cylinder side exhaust manifold 9a or 9b to the cylinder side exhaust manifold 9b or 9a in the exhaust (push-out) stroke. For this reason, the exhaust pulses having different phases are sent to the turbine 6b of the turbocharger 6 without being weakened to improve the turbine efficiency, and the exhaust pulses are weakened to the check valves 39 of the EGR passages 36a and 36b. 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). Moreover, since the ejector action is generated by the blow-down flow blown out from the tapered nozzle portions 23a and 23b, the peak P2 during the exhaust (push-out) stroke becomes lower and the pumping loss becomes smaller (see FIGS. 13 and 15). ).

  When the opening area of the nozzle portions 23a and 23b is larger than the optimum value, the dynamic pressure of the blowdown flow blown out from the nozzle portions 23a and 23b is small, and the blowdown flow is exhausted from the exhaust manifold 9a or 9b on the cylinder side during exhaust discharge. Escape to the exhaust manifold 9b or 9a on the cylinder side of the (push-out) stroke cannot be sufficiently suppressed, and the exhaust ejector action tends to be insufficient. 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). Further, the peak P2 during the exhaust (pushing) stroke becomes higher, and the pumping loss becomes larger (see FIGS. 10 and 12). When the opening areas of the nozzle portions 23a and 23b are smaller than the optimum value, the exhaust manifold pressure is generally higher at the peak P1 of the exhaust pulse during the exhaust ejection and the peak P2 during the exhaust (pushing) stroke. Although sufficient improvement can be obtained, the pumping loss becomes excessive (see FIGS. 16 to 18).

  In FIG. 1, reference numeral 50 denotes a control unit that controls a variable nozzle mechanism (not shown) of the turbine 6b, an EGR valve 38 of the EGR passages 36a and 36b, and an actuator 34 of the valve bodies 30a and 30b. As the detection means, an engine rotation sensor 51 that detects the engine speed from the flywheel rotation and an engine load sensor 52 that detects the engine load from the accelerator opening (the pedal operation amount) are provided.

FIG. 4 is a flowchart for explaining the control contents of the control unit. In S1 and S2, a detected value of the engine speed N and a detected value of the engine load L (accelerator opening) are read. In S3 to S5, the variable nozzle mechanism, the EGR valve 38, and the actuators 34 of the valve bodies 30a and 30b are sequentially controlled based on these detected values.

  5 to 7 exemplify the control characteristics of the control unit. In S3, the valve bodies 30a and 30b are detected from the detected value of the engine speed N and the detected value of the engine load L based on FIG. The shortest distance x with respect to the protrusion 29 (opening degree θ of the valve body, protrusion amount m in FIG. 20) is controlled. In S4, the turbine nozzle opening 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 S5, the opening degree EGR valve opening degree is controlled based on the detected value of the engine speed N and the engine load based on FIG. In FIG. 5, m is a protrusion amount of a valve body 45 (see FIG. 20) described later, and corresponds to the shortest distance x.

  With such a configuration, even in the single entry type turbocharger 6, the backflow of the exhaust pulse is suppressed by the tapered nozzles 23 a and 23 b, and the exhaust pulse to the turbine 6 b is strengthened by the ejector action of the merging portion 11. Therefore, the turbine efficiency can be improved. 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, since the exhaust manifold pressure on the cylinder side during the exhaust (pushing) stroke is reduced by the ejector action of the merging portion 11, an improvement in pumping loss can be obtained (see FIGS. 13 to 15).

  The tapered nozzle portions 23a and 23b are set to have an optimum opening area in the high speed range, but a substantial opening area (the shortest distance x between the valve element and the projection) facing the joining portion 11 of the nozzle portions 23a and 23b. Since it is equipped with a means for making the variable variable, the optimum shortest distance x is controlled even in the low rotation range, so that it is possible to perform high supercharging and large amount of EGR while keeping the pumping loss small, and in a wide operating range. , Both exhaust measures (reduction of NOx, etc.) and improvement of output and fuel consumption can be realized. In addition, the control characteristics (see FIG. 7) of the EGR valve 38 work together with the control characteristics (see FIG. 6) of the variable nozzle type turbocharger 6, so that high supercharging and large amount of EGR are possible even in the low speed and high load range. Therefore, it is possible to highly promote the coexistence of exhaust measures (NOx and PM reduction) and improved output and fuel consumption.

  The valve bodies 30a and 30b and the protrusion 29 may be arranged inside the turbine housing 25 (turbine inlet 26) as shown in FIG. In the EGR passages 36a and 36b, since the EGR valve 38 and the check valve 39 (reed valve) are arranged on the downstream side of the EGR cooler 37, the durability of these valves is also ensured.

  FIG. 20 shows another embodiment instead of the valve bodies 30a and 30b and the protrusion 29, and the merging portion 11 is integrally formed with the tapered nozzle portions 23a and 23b on the exhaust manifolds 9a and 9b side. The junction portion 11 is formed as a diffuser that narrows the passage downstream, and a valve plate 45 that can advance and retreat toward the minimum passage cross-section of the diffuser 11 is provided in the partition wall 28 between the nozzles 23a and 23b. 46 is a guide which supports the valve body 45 so that sliding is possible, and it is arrange | positioned so that a part of partition 28 between nozzles 23a and 23b may be comprised. Outside the exhaust manifolds 9a and 9b, an actuator 47 that can extend and contract the rod 47a is provided, and the valve plate 45 is connected to the tip of the rod 42a. When the rod 47a expands and contracts, the valve plate 45 is aligned with the center line of the junction portion 11. By advancing and retreating along, the shortest distance x (protrusion amount m of the valve body 45) between the tip of the valve body 45 and the passage surface of the diffuser 11 is expanded or reduced.

  According to this, only one valve plate 45 is required, and the projecting amount m of the valve body 45 has a 1: 1 relationship with the stroke amount of the actuator 43. Therefore, the control unit (see FIG. 1) It can be controlled accurately. 20, parts that are the same as those in FIGS. 1 and 2 are denoted by the same reference numerals, and a duplicate description thereof is omitted.

1 is an overall schematic configuration diagram according to an embodiment of the present invention. It is a block diagram which concerns on the confluence | merging part of an exhaust manifold. It is explanatory drawing which concerns on the opening / closing mechanism of a valve body. 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 explaining the control content of a control unit. It is a characteristic view which illustrates the relationship between an operation area, an EGR rate, and the shortest distance x. It is a characteristic view which illustrates the relationship between an operation area, pump loss, and the shortest distance x. 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 a block diagram which concerns on the confluence | merging part of an exhaust manifold. It is a block diagram which concerns on the confluence | merging part of an exhaust manifold.

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 23a, 23b Tapered nozzle part 25 Turbine housing 27 Spacer 28 Partition between nozzles 29 Projection 30a, 30b Valve body 31a, 31b Rotating shaft 32a, 32b of valve body Link 34 Valve body actuator 35 EGR device 37 EGR cooler 38 EGR valve 39 Check valve (reed valve)
45 Valve body 46 Guide 47 Valve body actuator 50 Control unit 51 Engine rotation sensor 52 Engine load sensor

Claims (4)

In a multi-cylinder engine equipped with a turbocharger,
Exhaust manifold exhaust stroke is divided for each cylinder group do not overlap, the nozzle portion to narrow the set portion downstream of the exhaust manifold in the shape tapered toward these merging portion, the substantially facing the confluent portion of the nozzle portion the opening area with one characteristic that is set according to operating conditions to control simultaneously and equivalent means for varying, also connects the compressor downstream of the intake manifold and the exhaust manifold of the turbine upstream of the turbocharger EGR passage, provided with a check valve, interposed in said EGR passage,
The means for making the opening area of each nozzle variable is the same and equal based on the detection signal of the operation state with one characteristic that sets the substantial opening area facing the merging portion of each nozzle portion according to the operation state. multi-cylinder engine, characterized in that it comprises means, for controlling the. In a multi-cylinder engine equipped with a turbocharger,
An exhaust manifold that is divided for each cylinder group that does not overlap the exhaust stroke, an intake manifold that is divided for each cylinder group that does not overlap the intake stroke, and a shape that tapers the downstream of the exhaust manifold's collecting part toward these merge parts nozzle throttling, means for said variable in order to simultaneously and uniformly controlled with one characteristic that is set according substantial opening area to the operating state facing the confluent portion of the nozzle portion, of the turbine upstream of the turbocharger EGR passage connecting between said intake manifold of the same compressor downstream to the exhaust manifold, comprising a check valve, interposed in said EGR passage,
The means for varying the opening area of each nozzle section is configured to simultaneously set a substantial opening area facing the merging section of each nozzle section based on an operation state detection signal with one characteristic set according to the operation state. A multi-cylinder engine characterized by comprising means for uniformly controlling . The means for making the opening area of each nozzle part variable includes a protrusion extending the partition wall between the nozzle parts to the joining part, a valve element disposed on both sides of the protrusion, and a minimum distance between the protrusion and the valve element. The multi-cylinder engine according to claim 1 or 2, further comprising means for supporting the valve plate so as to be swingable in an expansion / contraction direction as a general opening area. The means for making the opening area of each nozzle part variable includes a diffuser that squeezes downstream a joining part that each nozzle part faces, a valve body that forms a partition wall between the nozzles, and a minimum distance between the valve body and the diffuser. The multi-cylinder engine according to claim 1 or 2, further comprising means for supporting the valve plate so as to be able to advance and retreat in a direction of expansion and contraction as a general opening area.

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