JP2005330836A - Supercharging type multi-cylinder internal combustion engine controlled by passage communication control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance supercharging efficiency during high-load operation to enable higher engine output also by a smaller supercharger, and to increase internal exhaust gas recirculation amount during low-load operation to suppress NOx emission, in a multi-cylinder internal combustion engine operated with a twin entry turbosupercharger into which exhaust gas from cylinders having different exhaust strokes mutually is introduced via parallel exhaust passages. <P>SOLUTION: The multi-cylinder internal combustion engine is provided with a passage communication control valve selectively communicating middles of the parallel exhaust passages for introducing exhaust gas to the twin entry turbosupercharger with each other, and the passage communication control valve is opened during low output torque operation of the engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a supercharged internal combustion engine, and more particularly to a supercharged multicylinder internal combustion engine that performs supercharging control in connection with the internal combustion engine being a multi-cylinder internal combustion engine.

Supercharging in an internal combustion engine is to rotate a turbine by exhaust and thereby rotate a compressor to pressurize intake air. When the internal combustion engine is a multi-cylinder internal combustion engine, the exhaust from each cylinder is manifolded. It is conventionally performed to collect them together and lead them to the exhaust turbine. In this case, in a multi-cylinder internal combustion engine, the operation phases of the cylinders are shifted from each other. For example, in a 4-cylinder internal combustion engine arranged in series, the operation phases are generally the first cylinder, the third cylinder, and the fourth cylinder. Since the cylinders are arranged in the order of the second cylinder, when the exhaust from each cylinder is collected together by the manifold and sent to the exhaust turbine, the first cylinder and the fourth cylinder are avoided in order to avoid interference of the exhaust from each cylinder. The exhaust from the engine is combined into one merged exhaust passage, the exhaust from the second and third cylinders are combined into one other combined exhaust passage, and both are combined into one. Furthermore, when the internal combustion engine is operated at a high load, the communication valve is used to select the middle of the two combined exhaust passages in order to reduce the temperature in response to the exhaust temperature becoming higher. Communicate with each other The following Patent Document 1 describes that the temperature of the exhaust gas flowing into the exhaust turbine is reduced by opening the communication valve during the high load operation of the engine and expanding the exhaust passage that effectively acts on each cylinder. Yes.
JP-A-3-172535

  A variable valve timing technique for adjusting the opening / closing timing (phase) of an intake valve in an internal combustion engine so as to be advanced or delayed in accordance with the rotational speed of the engine is known as VVT (Variable Valve Timing). However, in the above-mentioned Patent Document 1, when the engine speed is increased, the intake valve opening / closing timing is switched to the delay side before the engine speed reaches such a speed that opens the communication valve, and knocking is performed. It is described to suppress the occurrence of.

  The exhaust of the internal combustion engine is ejected vigorously from the exhaust port of the engine with the aftermath of fuel deflagration in the engine explosion stroke, so it has considerable kinetic energy, and the supercharged exhaust turbine In general, it is advantageous to configure it as a dynamic pressure turbine so that it can be used effectively. When the turbine is a dynamic pressure type, the turbine is a twin entry type for a multi-cylinder internal combustion engine, and the exhaust from the cylinders whose exhaust strokes are shifted from each other is supplied to the twin nozzles of the turbine via parallel exhaust passages. This is preferable in order to increase the operation efficiency of the turbine and increase the engine output by obtaining a high supercharging effect with a supercharger as small as possible.

  On the other hand, the internal combustion engine has a problem of air pollution due to NOx emission. However, NOx emission is suppressed by mixing the exhaust gas with fresh air and lowering the combustion temperature. During low-load operation, it is desirable to operate with a sufficient amount of exhaust gas mixed with fresh air. In order to mix exhaust gas with fresh air, in addition to external exhaust gas recirculation that introduces part of the exhaust gas from the exhaust system through the gas pipe and introduces it into the intake system, when moving from the exhaust stroke to the intake stroke, There is an internal exhaust gas recirculation that leaves the air in the cylinder and mixes it with fresh air. Internal exhaust gas recirculation increases as the back pressure of the exhaust system increases.

  As described above, when the engine is in an operating state in which a high supercharging effect is obtained and a high engine power is output, the twin entry turbocharger uses a parallel exhaust passage for each exhaust from the cylinders whose exhaust strokes are shifted from each other. Since it is supplied in an orderly manner, it operates at a high turbine operating efficiency, and even a smaller supercharger can produce a higher engine output, but at low load operation, the turbine operating efficiency is Now it doesn't matter. It is more effective to suppress NOx emission as much as possible during low load operation.

  The present invention pays attention to the above circumstances, and relates to a multi-cylinder internal combustion engine that operates with a twin entry turbocharger in which exhaust from cylinders whose exhaust strokes are shifted from each other is introduced through parallel exhaust passages. Increases supercharging efficiency during load operation and enables higher engine output even with a smaller supercharger, and increases internal exhaust gas recirculation during low load operation to reduce NOx emissions. It is a problem to suppress.

  In order to solve the above main problems, the present invention is a multi-cylinder internal combustion engine that operates with a twin entry turbocharger, and exhausts from cylinders whose exhaust strokes deviate from each other pass through parallel exhaust passages. A passage communication control valve that is introduced in parallel to the twin entry turbocharger and selectively communicates with each other in the middle of the parallel exhaust passages is provided, and the passage communication control valve is provided during low-output torque operation of the engine. The present invention proposes a multi-cylinder internal combustion engine characterized by being opened.

  The passage communication control valve may be opened even in a high rotational speed operation state in which overcharging occurs.

  The passage communication control valve may be temporarily closed during the transition from the low output torque and low rotational speed operating state to the high output torque and low rotational speed operating state to the high rotational speed operating state. .

  Further, the engine is provided with intake valve opening / closing phase changing means, and when the intake valve opening / closing phase is advanced by the intake valve opening / closing phase changing means as the passage communication control valve is closed, the intake valve opening / closing phase is changed. The advancement of the intake valve opening / closing phase by the phase changing means may be performed at the time when the passage communication control valve is closed.

  The parallel exhaust passages may have a portion separated by a common passage wall, and the passage communication control valve may be configured to open and close a hole opened in the common passage wall with a valve plate. .

  As described above, in a multi-cylinder internal combustion engine that operates with a twin entry turbocharger, exhaust from cylinders with different exhaust strokes is parallel to the twin entry turbocharger via parallel exhaust passages. And a passage communication control valve that selectively communicates the middle of the parallel exhaust passages with each other, and the passage communication control valve is opened during low output torque operation of the engine, During low-power torque operation of the engine, for any cylinder that sends exhaust gas in parallel to the dynamic pressure turbine via the parallel exhaust passage, the exhaust passage leading to the turbine has a ratio of the flow passage cross-sectional area to the exhaust gas flow rate from the middle. The exhaust gas stagnation occurs in the parallel exhaust passages downstream of the passage communication control valve, and the back pressure during the exhaust stroke rises for all cylinders. Exhaust gas recirculation amount increases.

  If the passage communication control valve is opened even in the high rotational speed operation state in which overcharging occurs, the exhaust passage leading to the turbine for any cylinder during the high rotational speed operation of the engine. Since the ratio of the cross-sectional area of the exhaust passage to the exhaust flow rate is doubled from the middle, the output of the dynamic pressure turbine decreases relative to the exhaust flow rate, and supercharging becomes excessive in the high engine speed operating region of the engine This can be avoided, and it is possible to omit the waste gate valve that bypasses the turbine to the exhaust gas flow when overcharging.

  The passage communication control valve is temporarily closed during the transition from the low output torque and low rotation speed operation state to the high output torque and low rotation speed operation state to the high rotation speed operation state. In the process of shifting the engine from the low output torque and low rotation speed operation state to the high output torque and high rotation speed operation state, the engine output torque increases by opening the throttle, but it is delayed from the increase in the engine rotation speed. When the high-output torque and low-speed operation is generated, the supercharging effect can be enhanced and the engine output can be raised as quickly as possible by closing the passage communication control valve.

  The engine is provided with intake valve opening / closing phase changing means, and when the intake valve opening / closing phase is advanced by the intake valve opening / closing phase changing means as the passage communication control valve is closed, the intake valve opening / closing phase change is performed. The advancement of the intake valve opening / closing phase by the means is performed in accordance with the time when the passage communication control valve is closed. By being considerably slower than the valve opening / closing phase changing operation speed, it is possible to avoid the occurrence of knocking or smoking by advancing the intake valve opening / closing phase when the passage communication control valve has not yet been closed.

  If the parallel exhaust passages have portions separated by a passage wall common to both, and the passage communication control valve opens and closes a hole opened in the common passage wall with a valve plate The function of selectively communicating between the parallel exhaust passages can be achieved with a very simple structure.

  FIG. 1 is a schematic view schematically showing the structure of a multi-cylinder internal combustion engine according to the present invention. In the figure, reference numeral 10 denotes a cylinder block of a multi-cylinder internal combustion engine. The multi-cylinder internal combustion engine is a four-cylinder internal combustion engine in the illustrated example, and four cylinders 12 a, 12 b, 12 c, and 12 d are provided in the cylinder block 10. The order of operation of these cylinders is 12a-12c-12d-12b. Accordingly, exhaust from the cylinders 12a and 12d whose operating phases are farthest from each other is collected by the exhaust sub-manifold 14, and exhaust from the cylinders 12b and 12c whose operating phases are also most distant from each other is collected by the exhaust sub-manifold 16. Exhaust gas from these two sub-manifolds is introduced into a twin-entry turbine 22 via two exhaust passages 18 and 20 arranged in parallel.

  Incidentally, the parallel introduction of the exhaust through the exhaust passages 18 and 20 to the twin entry turbine 22 is made along the axial direction of the turbine in the schematic representation of FIG. Two nozzle groups juxtaposed along the axial direction may be used. Alternatively, the two types of nozzles belonging to each of the exhaust passages 18 and 20 may be located at the same position in the axial direction of the turbine and The nozzles may be provided by being divided into half circumferences in the direction, or by various possible configurations such as dividing two types of nozzles into several nozzle groups and arranging them alternately along the circumferential direction.

  Exhaust gas from the turbine 22 is guided to the catalytic converter 26 via the exhaust pipe 24, and then released to the atmosphere via a silencer or the like not shown in the drawing.

  The intake air is guided to an inlet of a compressor 32 driven by a turbine 22 through an air cleaner 28 and an intake conduit 30. The intake air pressurized by the compressor 32 is supplied to the cylinders 12a to 12d via an intake conduit 34, an intercooler 36, an intake conduit 38, a throttle valve 40, and an intake manifold 42. Reference numeral 44 denotes an intake valve opening / closing phase changing device for changing the opening / closing phase of the intake valve, which is not shown in the drawings for the cylinders 12a to 12d, and a portion indicated by reference numeral 44 is a portion of the actuator.

  The operation of the throttle valve 40 and the intake valve opening / closing phase change device 44 is controlled by an electronic vehicle operation control device (ECU) 46 having a microcomputer. The electronic vehicle operation control device 46 is supplied with a signal indicating the opening / closing phase of the intake valve from the intake valve opening / closing phase sensor 48, and a signal indicating the temperature of the intake air supplied to the intake manifold from the intake air temperature sensor 50, as well as an internal combustion engine. In addition, various signals I relating to the driving state of a vehicle equipped with the same are supplied.

  As shown in more detail in FIG. 2, the exhaust passages 18 and 20 are provided with a passage communication control valve 52 that selectively communicates the exhaust passages 18 and 20 in the middle. In the illustrated example, the parallel exhaust passages have portions separated by a common passage wall 54, and the passage communication control valve 52 opens and closes a hole 56 opened in the common passage wall 54 with a valve plate 58. It is supposed to be. The valve plate 58 is carried by a valve shaft 60, and the valve shaft is rotated around its central axis by an actuator 62, thereby closing the hole 56 as shown by a two-dot chain line in the figure. As indicated by the solid line in the figure, the hole 56 is rotated between positions. The operation of the actuator 62 is controlled by the electronic vehicle operation control device 46.

  If the operating range of the internal combustion engine is represented by its rotational speed and output torque, it becomes as shown in FIG. 3, and in a region where the output torque is relatively low, exhaust gas recirculation (EGR) is performed over a considerably wide rotational speed region in order to suppress NOx emission. It is desirable to implement. This is the region indicated as the EGR region in the figure. On the other hand, when the intake air is supercharged by exhaust, the region where the conventional wastegate device needs to bypass the exhaust turbine to a part of the exhaust is shown as a WG region in the figure. It is an area. As shown in FIGS. 1 and 2, a structure in which exhaust from cylinders whose exhaust strokes are shifted from each other is introduced in parallel to the dynamic pressure turbine through a parallel exhaust passage, and the parallel exhaust passage is selectively communicated by a passage communication control valve. , Both adaptive control of engine operation for the EGR region and adaptive control of engine operation for the WG region are enabled.

  That is, in the EGR region as described above, since the flow rate of exhaust discharged from each cylinder is small, the flow rate of exhaust flowing through each of the parallel exhaust passages 18 and 20 is small. The flow is stagnant. When the passage communication control valve 52 is opened in such a state and the exhaust passages 18 and 20 are in communication with each other, the back pressure is increased for any cylinder, and the exhaust stroke is changed to the intake stroke. When moving, the amount of exhaust gas remaining in the cylinder increases, and the exhaust gas recirculation rate increases due to the increase in the internal exhaust gas recirculation amount. Therefore, the passage communication control valve 52 is opened in the EGR region as shown in FIG. 3 to increase the exhaust gas recirculation rate without impairing the engine output in the low torque operation region, and to release NOx. The function which suppresses as much as possible can be exhibited.

  Also, in a dynamic pressure turbine, if the cross-sectional ratio, which is the ratio of the cross-sectional area of the working fluid passage to the flow rate of the working fluid supplied to the nozzle of the turbine, increases from a value that maximizes the turbine output, the turbine output will increase accordingly. As shown in the figure, when the exhaust passages 18 and 20 that lead the exhaust from the two cylinders whose phases are shifted from each other in parallel to the dynamic pressure turbine 22 are communicated by the passage communication control valve 52 on the way, For the exhaust flow from one cylinder, the cross-sectional ratio is doubled from the middle, and the turbine output obtained by the exhaust flow from each one cylinder is correspondingly reduced. In the illustrated four-cylinder example, this occurs for any of the cylinders 12a-12d, so that the output of the turbine 22 as a whole decreases correspondingly. Therefore, by opening the passage communication control valve 52 in the WG region, an effect similar to that of a part of the turbine bypass of the exhaust gas by the conventional wastegate device can be obtained.

  Lines A and B showing changes in the two engine operating states indicated by arrows in FIG. 3 indicate the output of the internal combustion engine based on the control of the passage communication control valve 52 for the EGR region and the WG region as described above. When the starting torque is increased from the low torque operation state, the control of the passage communication control valve 52 is different depending on whether the initial engine speed is relatively low or relatively high. For this purpose, the intake valve opening / closing phase changing device 44 is also controlled in association with the control of the passage communication control valve 52. FIG. 4 is a table showing changes in the operation mode.

  When the engine output is increased from a low torque and relatively low engine speed, as shown by the path A, the passage communication control valve 52 is temporarily closed halfway from the initial opened state. Thus, the intake valve opening / closing phase is advanced from the initially advanced state to the maximum advanced position. This is because once the passage communication control valve 52 is opened in the low torque operation state, the stagnation of the exhaust gas that has occurred in each exhaust passage is once resolved, and at the same time, the intake valve opening / closing phase is advanced to the maximum. This is to increase the charging efficiency of the intake air. Thereafter, when the operation enters the WG region, the passage communication control valve 52 is opened again, and it is avoided that the supercharging becomes excessive. When the acceleration is finished, the intake valve opening / closing phase may be delayed.

  When the engine output is increased from a state where the engine speed is relatively low and the engine speed is relatively high, as indicated by the path B, the operation immediately enters the WG region when the torque increases, so that the passage communication control valve 52 is initially opened. What is necessary is just to hold | maintain a state as it is. In this case, the intake valve opening / closing phase may be retarded as it is from the initial slightly advanced state.

  FIG. 5 is a graph showing that when the engine output is increased by the path A described above, the passage communication control valve 52 is temporarily closed in the middle and further improvement of the control is performed when the intake valve opening / closing phase is advanced to the maximum advance position. It is. In this case, the passage communication control valve 52 is temporarily closed by temporarily eliminating the stagnation of exhaust gas that has occurred in each exhaust passage due to the passage communication control valve 50 being opened in the low torque operation state as described above. The intake valve opening / closing phase is advanced by the intake valve opening / closing phase changing device 44 to increase the intake charging efficiency by increasing the intake valve opening / closing phase to the maximum. Since it is slower than the speed, if the valve closing control of the passage communication control valve 52 and the advance angle control of the intake valve opening / closing phase changing device 44 are started at the same time, the stagnation of exhaust due to interference between the parallel exhaust passages is not solved. The opening / closing phase of the intake valve is advanced, and the ratio of residual exhaust in the cylinder increases, which may cause smoking, knocking, abnormal combustion, and the like. Therefore, the advance of the intake valve opening / closing phase by the intake valve opening / closing phase changing device 44 is changed from the broken line to the solid line so that the operation of the intake valve opening / closing phase changing device 44 is performed when the passage communication control valve 50 is actually closed. If the correction is made as shown in the figure, it can be reduced as shown by the solid line without increasing the residual exhaust in the cylinder as shown by the broken line in the figure.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

1 is a schematic view schematically showing the structure of a multi-cylinder internal combustion engine according to the present invention. Schematic shown in detail about an example of a passage communication control valve for selectively communicating in the middle of parallel exhaust passages. The graph which shows the driving | operation area | region of an internal combustion engine with the rotation speed and output torque. The table | surface which shows the change of the operation | movement aspect by the change paths A and B of two engine operation states shown by the arrow in FIG. FIG. 4 is a graph showing a further improvement in control when the passage communication control valve is temporarily closed on the way and the intake valve opening / closing phase is advanced to the maximum advance position when the engine output is increased by the path A in FIG. 3.

Explanation of symbols

  10 ... Cylinder block, 12a, 12b, 12c. 12d ... Cylinder, 14, 16 ... Sub-manifold, 18, 20 ... Exhaust passage, 22 ... Turbine, 24 ... Exhaust conduit, 26 ... Catalytic converter, 28 ... Air cleaner, 30 ... Intake conduit, 32 ... Compressor, 34 ... Intake conduit 36 ... Intercooler, 38 ... Intake conduit, 40 ... Throttle valve, 42 ... Intake manifold, 44 ... Intake valve opening / closing phase change device, 46 ... Electronic vehicle operation control device, 48 ... Intake valve opening / closing phase sensor, 50 ... Intake valve Air temperature sensor, 52 ... passage communication control valve, 54 ... common passage wall, 56 ... hole, 58 ... valve plate, 60 ... valve shaft, 62 ... actuator

Claims (5)

  In a multi-cylinder internal combustion engine that operates with a twin entry turbocharger, exhaust from cylinders with different exhaust strokes is introduced into the twin entry turbocharger in parallel through parallel exhaust passages. A multi-cylinder characterized in that a passage communication control valve for selectively communicating the middle of the parallel exhaust passages with each other is provided, and the passage communication control valve is opened during low output torque operation of the engine. Internal combustion engine.   2. The multi-cylinder internal combustion engine according to claim 1, wherein the passage communication control valve is opened even at a high rotational speed operation in which overcharging occurs. 3.   The passage communication control valve is configured to be temporarily closed during the transition from the low output torque and low rotation speed operation state to the high output torque and low rotation speed operation state to the high rotation speed operation state. The multi-cylinder internal combustion engine according to claim 2,   The engine is provided with intake valve opening / closing phase changing means, and when the intake valve opening / closing phase is advanced by the intake valve opening / closing phase changing means as the passage communication control valve is closed, the intake valve opening / closing phase change is performed. 4. The multi-cylinder internal combustion engine according to claim 3, wherein the advancement of the intake valve opening / closing phase by the means is performed in accordance with a point in time when the passage communication control valve finishes closing. The parallel exhaust passages have portions separated by a passage wall common to both, and the passage communication control valve is configured to open and close a hole opened in the common passage wall with a valve plate. The multi-cylinder internal combustion engine according to any one of claims 1 to 4.

Images