JP5573701B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine including an exhaust gas recirculation system that guides a part of exhaust gas flowing through an exhaust passage to an intake passage.

  As an exhaust gas recirculation (EGR) system for an internal combustion engine, an exhaust gas recirculation (EGR) system that recirculates part of exhaust gas from an exhaust system to an intake system via an EGR passage is well known.

  For example, Patent Document 1 discloses a multi-cylinder engine devised to achieve high supercharging and large amount of EGR in a wide operating range. The engine includes a turbocharger, an exhaust manifold that is divided for each cylinder group in which the exhaust strokes do not overlap, an exhaust ejector that narrows the downstream portion of each exhaust manifold toward the turbine inlet of the turbocharger, and an intake stroke Intake manifolds divided for each cylinder group that do not overlap, intake resonance pipes set between the collection parts of the intake manifolds and branch parts of the intake pipes, downstream ends of the intake resonance pipes and collection parts of the exhaust manifolds And an EGR passage connecting the two and a check valve interposed in the EGR passage.

JP 2007-263017 A

  By the way, for example, when there is an acceleration request from the driver in a low / medium load driving state, it is desired to increase the torque response at the time of the acceleration request in order to improve drivability. On the other hand, in the technique described in Patent Document 1, since it is necessary to provide an intake resonance pipe between the manifold part of the intake manifold and the branch part of the intake pipe, the technique described in Patent Document 1 has an application range. It has the problem of being very narrow.

  Accordingly, the present invention has been made in view of such a point, and an object of the present invention is to provide a simple configuration when an acceleration is requested in an internal combustion engine including an EGR passage that guides a part of exhaust flowing through the exhaust passage to the intake passage. It is to increase the torque response.

  According to one aspect of the present invention, in an internal combustion engine having an EGR passage having one end communicating with an exhaust passage and the other end communicating with an intake passage, and an EGR valve disposed in the EGR passage, the EGR valve is closed When the first passage in the intake passage from the junction of the intake passage and the EGR passage to the intake valve and the second passage in the EGR passage from the junction to the EGR valve communicate with each other, the second passage There is provided an internal combustion engine characterized by having an air column natural frequency that synchronizes with an engine rotational speed within a predetermined engine rotational speed region.

  Preferably, the first passage has an air column natural frequency that synchronizes with an engine rotational speed within the predetermined engine rotational speed region.

  The intake passage and the EGR passage are configured such that a first distance from the joining portion to the intake valve in the first passage is equal to or less than a second distance from the joining portion to the EGR valve in the second passage. It is good to have. Alternatively, the intake passage and the EGR passage may be configured such that a first distance from the joining portion to the intake valve in the first passage is substantially equal to a second distance from the joining portion to the EGR valve in the second passage. Should be configured.

  It is preferable that an EGR cooler is further provided in a portion of the EGR passage other than the second passage.

  The internal combustion engine according to the present invention is an acceleration request determination unit that determines whether or not an acceleration request is present, and an EGR valve control unit that controls the EGR valve, and closes when the acceleration request determination unit determines that there is an acceleration request. And an EGR valve control means for controlling the EGR valve.

  It is preferable that a valve operating mechanism that makes variable the valve timing of at least one of the intake valve and the exhaust valve is further provided. When the acceleration request determining means determines that there is an acceleration request, the valve mechanism is configured such that the open period of the intake valve and the open period of the exhaust valve overlap and in the overlap period. The valve timing of at least one of the intake valve and the exhaust valve may be controlled so that the exhaust pressure is lower than the intake pressure. When the acceleration request determining means determines that there is an acceleration request, the valve operating mechanism is configured to switch between the intake valve and the exhaust valve according to the temperature of at least one of the first passage and the second passage. It is preferable to control at least one of the valve timings. Preferably, the valve mechanism is configured such that when the acceleration request determination means determines that there is an acceleration request, the valve opening mechanism opens the intake valve according to the temperature of at least one of the first passage and the second passage, and The valve timing of at least one of the intake valve and the exhaust valve may be controlled so as to adjust the overlap amount with the open period of the exhaust valve.

  The internal combustion engine according to the present invention may further include a second EGR valve provided in the second passage, and a second EGR valve control means for controlling the second EGR valve. In this case, the EGR valve control means is opened when the acceleration request determining means does not determine that there is an acceleration request, and is closed when the acceleration request determining means determines that there is an acceleration request. The EGR valve is controlled, and the second EGR valve control means adjusts the flow rate of the exhaust gas flowing through the EGR passage when the acceleration request determination means does not determine that there is an acceleration request, and the acceleration request determination The second EGR valve may be controlled to open when it is determined by the means that acceleration is requested.

  The fuel injection control means for controlling the fuel injection from the fuel injection valve may control the fuel injection timing according to the amount of exhaust gas in the second passage when the EGR valve is closed by the EGR valve control means.

  The internal combustion engine according to the present invention includes a plurality of merging portions in which the EGR passage and the intake passage can communicate with each other, the EGR passage provided in at least one merging portion of the merging portions, and the And an adjustment valve for adjusting a communication state with the intake passage.

1 is a schematic diagram of an internal combustion engine system to which a first embodiment according to the present invention is applied. 2 is a flowchart showing an example of control of the internal combustion engine of FIG. 2 is a graph showing experimental results for explaining a pressure change of an intake port in the internal combustion engine of FIG. 1. It is a figure for demonstrating the fuel-injection control in the internal combustion engine of FIG. FIG. 2 is a diagram for explaining valve timings of an intake valve and an exhaust valve in the internal combustion engine of FIG. 1. FIG. 2 is a diagram for explaining valve timings of an intake valve and an exhaust valve in the internal combustion engine of FIG. 1. It is a schematic diagram for demonstrating the structure of the internal combustion engine to which 2nd Embodiment which concerns on this invention was applied. It is the schematic of the internal combustion engine system to which 3rd Embodiment which concerns on this invention was applied. It is the schematic of the internal combustion engine system to which 4th Embodiment which concerns on this invention was applied. It is the schematic of the internal combustion engine system to which 5th Embodiment concerning this invention was applied. It is a figure for demonstrating each control of the EGR valve and 2nd EGR valve in the internal combustion engine of FIG.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the following, the same or corresponding parts are denoted by the same reference numerals throughout the plurality of embodiments.

  First, a first embodiment according to the present invention will be described. FIG. 1 shows the concept of an internal combustion engine system for a vehicle to which the first embodiment of the present invention is applied. The internal combustion engine 10 in the first embodiment is a type of internal combustion engine, that is, a diesel engine, that spontaneously ignites by directly injecting light oil as fuel into the combustion chamber from the fuel injection valve 12.

  An intake port that faces the combustion chamber of the cylinder 14 and defines a part of the intake passage 16 is formed in the cylinder head and is opened and closed by an intake valve (not shown). An intake manifold 18 that defines a portion of the intake passage 16 is connected to the cylinder head, and an intake pipe 20 that also defines a portion of the intake passage 16 is connected to the upstream side thereof. An air cleaner 22 is provided on the upstream end side of the intake pipe 20 in order to remove dust and the like in the air guided to the intake passage 16. A throttle valve 26 whose opening is adjusted by the throttle actuator 24 is provided in the intake passage 16.

  On the other hand, an exhaust port that faces the combustion chamber of the cylinder 14 and defines a part of the exhaust passage 28 is formed in the cylinder head and is opened and closed by an exhaust valve (not shown). An exhaust manifold 30 that defines a part of the exhaust passage 28 is connected to the cylinder head, and an exhaust pipe 32 that also defines a part of the exhaust passage 28 is connected to the downstream side thereof. An exhaust purification device 34 is provided in the middle of the exhaust passage 28. Here, in the exhaust purification device 34, an oxidation catalyst and a DPF are installed in this order from the upstream side, but other catalysts and filters can be provided.

  The operations of the intake valve and the exhaust valve are controlled by a valve mechanism. The valve operating mechanism is a mechanism capable of individually controlling an intake valve and an exhaust valve at an arbitrary opening degree and timing in synchronization with rotation of a crankshaft to which a piston is connected via a connecting rod. Specifically, the valve operating mechanism includes solenoids individually provided for the intake valve and the exhaust valve. The valve operating mechanism can realize valve overlap in which the intake valve and the exhaust valve open simultaneously, and the amount of overlap can be changed. The valve operating mechanism that makes the valve timing variable may be provided only for at least one of the intake valve and the exhaust valve. Moreover, it can replace with such a structure and can employ | adopt other various mechanisms as a valve operating mechanism.

  Further, a turbine 36 including a turbine wheel that is rotationally driven by exhaust gas is provided in the middle of the exhaust passage 28. However, the turbine 36 is disposed upstream of the exhaust purification device 34. Correspondingly, a compressor 38 including a compressor wheel that is coaxially connected to the turbine wheel and rotated by the rotational force of the turbine wheel is provided in the intake passage 16. That is, the internal combustion engine 10 is provided with a turbocharger 40 that includes a turbine 36 that extracts exhaust energy, and a compressor 38 that supercharges the internal combustion engine 10 with the exhaust energy extracted by the turbine 36. An intercooler 42 is provided on the downstream side of the compressor 38 in order to cool the air compressed by the compressor 38.

  The internal combustion engine 10 is provided with an exhaust gas recirculation (EGR) system 44 that guides part of the exhaust gas flowing through the exhaust passage 28 to the intake passage 16. The EGR system 44 has an EGR passage 46 defined by an EGR pipe 48 that connects the exhaust passage 28 and the intake passage 16, and an EGR valve 50 for adjusting the communication state of the EGR passage 46. Here, one end on the upstream side of the EGR passage 46 communicates with the exhaust manifold 30, and the other end on the downstream side thereof is a portion of the intake passage 16 upstream of the collection portion of the intake branch passages communicating with each cylinder 14. Communicating with It should be noted that the downstream end of the EGR passage 46 may communicate with a collection portion of a plurality of intake branch passages, and the collection portion may be configured as a surge tank. The EGR valve 50 is disposed relatively near the exhaust passage 28, and its opening degree is adjusted by the actuator 52. However, here, the EGR valve 50 is a poppet valve. The EGR system 44 does not have an EGR cooler, but can have an EGR cooler. When the EGR cooler is provided, the EGR cooler may be provided in a portion of the EGR passage 46 on the upstream side of the EGR valve 50.

  The above-described EGR passage 46 and intake passage 16 are configured to have a specific relationship. The relationship will be specifically described below.

  The first passage A in the intake passage 16 from the junction C between the intake passage 16 and the EGR passage 46 to the intake valve and the second passage B in the EGR passage 46 from the junction C to the EGR valve 50 are the EGR valve 50. Is configured to communicate when the is closed. Here, in particular, the first passage A and the second passage B are configured to communicate with each other at the junction C when the EGR valve 50 is closed. The intake passage 16 and the EGR passage 46 are configured such that the first distance La from the joining portion C to the intake valve in the first passage A is shorter than the second distance Lb from the joining portion C to the EGR valve 50 in the second passage B. Is structured. However, the junction C is defined at the boundary between the intake passage 16 and the EGR passage 46 as a single passage. In FIG. 1, the boundary between the first passage A and the second passage B, that is, The joining portion is shown to have a certain width. However, the junction C can be defined as a narrower, for example, only one part that is uniquely defined or a virtual plane. In the internal combustion engine 10, there are four cylinders 14, and the first passage A and the first distance La can be determined for each of the cylinders 14. Furthermore, the first distance La and the second distance Lb can each be the length between two points on the virtual axis that can be defined in the approximate center of the passage.

  The second passage B is configured to have an air column natural frequency that synchronizes with the engine rotation speed within a predetermined engine rotation speed region. The predetermined engine rotation speed region is a low / medium speed region, for example, a rotation speed region of 1200 rpm to 3000 rpm, particularly a rotation speed region of 1500 to 2500 rpm, but is not limited to these rotation speed regions. Further, the engine rotation speed in the predetermined engine rotation speed region may be 1600 rpm, 2000 rpm, or 2400 rpm, for example, but is not limited to these rotation speeds and may vary. Further, the first passage A is configured to have an air column natural frequency that is also synchronized with the engine rotational speed within the predetermined engine rotational speed region. However, the air column natural frequency of the first passage A may be different from the air column natural frequency of the second passage, but may be substantially equal.

  The internal combustion engine 10 includes various sensors that electrically output signals for detecting (including estimation) various values to an electronic control unit (ECU) 60. Here, some of them will be specifically described. An air flow meter 62 for detecting the amount of intake air is provided in the intake passage 16. An intake air temperature sensor 64 for detecting the temperature of the intake air is provided near the air flow meter 62, and an intake air temperature sensor 66 for detecting the temperature is also provided downstream of the intercooler 42. Here, the intake air temperature sensor 66 is provided so as to detect the temperature of the first passage A. A pressure sensor 68 for detecting the supercharging pressure is provided in the intake passage 16. Further, an accelerator opening sensor 70 for detecting a position corresponding to the depression amount of the accelerator pedal operated by the driver, that is, an accelerator opening is provided. A throttle position sensor 72 for detecting the opening of the throttle valve 26 is also provided. A crank position sensor 74 for detecting a crank rotation signal of the crankshaft is attached to a cylinder block in which the piston reciprocates. Here, the crank position sensor 74 is also used as an engine speed sensor for detecting the engine speed (engine speed).

  The ECU 60 includes a CPU, a ROM, a RAM, an A / D converter, an input interface, an output interface, and the like, and is configured as a so-called computer. The various sensors are electrically connected to the input interface. Based on the output signals (detection signals) from these various sensors, the ECU 60 electrically sends an operation signal (drive signal) from the output interface so that the internal combustion engine 10 can be smoothly operated according to a preset program. Output. Thus, the operation of the fuel injection valve 12, the opening degrees of the throttle valve 26 and the EGR valve 50, the operation of the valve operating mechanism, and the like are controlled. However, the ECU 60 outputs operation signals to the actuators 24 and 52 in order to control the opening degrees of the throttle valve 26 and the EGR valve 50.

  Here, the fuel injection control means includes a part of the ECU 60. Further, the EGR valve control means includes a part of the ECU 60. The throttle valve control means includes a part of the ECU 60. The acceleration request determination means includes an accelerator opening sensor 70 and a part of the ECU 60. Further, the valve mechanism is configured to include a part of the ECU 60. In addition, a temperature detection device that detects the temperature of the first passage A includes the intake air temperature sensor 66 as a temperature detection means and a part of the ECU 60.

  Specifically, in the internal combustion engine 10, the intake air amount obtained based on the output signal from the air flow meter 62, the engine rotation speed obtained based on the output signal from the crank position sensor 74, that is, the engine load and the engine rotation A fuel injection amount (fuel amount) and fuel injection timing are set based on the operating state represented by the speed. Based on the fuel injection amount and the fuel injection timing, fuel is injected from the fuel injection valve 12. In general, the combustion in the combustion chamber is less likely to occur as the flow rate of the exhaust gas (EGR gas) flowing through the EGR passage 46 increases. Therefore, in the internal combustion engine 10, as the amount of exhaust gas flowing through the EGR passage 46 increases, the fuel injection Fuel injection control is executed so that the timing is advanced (advanced).

  Further, the opening degree of the EGR valve 50 is controlled based on the operation state of the internal combustion engine 10 determined based on output signals from the various sensors. The high load region (including the full load) is defined as a region where the EGR valve 50 is closed to the fully closed state (outside EGR region), and most of the low and medium load regions are regions where the EGR valve 50 is opened ( EGR area). However, as will be described later, when the accelerator pedal is depressed by the driver and the ECU 60 determines that there is an acceleration request in the driving state in the low / medium load region, the fully closed opening set here as the predetermined opening degree is set. Each time the EGR valve 50 is controlled. The other opening degree of the EGR valve 50 may be hereinafter referred to as a normal opening degree with respect to the opening degree of the EGR valve 50 when the acceleration request is made.

  The throttle valve 26 is opened and closed in conjunction with the accelerator pedal operation by the driver. However, as will be described later, when the accelerator pedal is depressed by the driver in the driving state in the low / medium load region and the ECU 60 determines that the acceleration is requested, the predetermined opening is set as the predetermined opening. At the same time, the throttle valve 26 is controlled. The other opening degree of the throttle valve 26 may be hereinafter referred to as a normal opening degree with respect to the opening degree of the throttle valve 26 when the acceleration request is made.

  Here, an example of the control of the internal combustion engine 10 will be described based on the flowchart of FIG. The flowchart of FIG. 2 shows the control of the EGR valve 50 and the throttle valve 26 when the internal combustion engine 10 is requested to accelerate.

  First, the ECU 60 determines whether or not there is an acceleration request, that is, whether or not there is an acceleration request (step S201). This determination is generally equivalent to detecting the acceleration start time, and is made based on the accelerator opening. Here, this determination is performed based on both the magnitude of the accelerator opening and the changing speed. When the accelerator opening is greater than or equal to a predetermined value and the accelerator opening is increased, the amount of change in the unit predetermined time, that is, the opening speed (accelerator opening opening speed) exceeds the predetermined speed. Sometimes, the ECU 60 determines that acceleration, that is, there is an acceleration request. More specifically, the ECU 60 determines the accelerator opening based on the output signal from the accelerator opening sensor 70, the accelerator opening is equal to or greater than a predetermined opening, and the accelerator opening opening speed is When a predetermined speed, which is a reference speed set in advance and stored in the ROM, is exceeded, it is determined that the vehicle is accelerating. The determination as to whether or not there is an acceleration request is not limited to such determination logic, and may be performed based on only one of the magnitude of the accelerator opening and the change speed, and further, the engine speed, It is also possible to make a judgment based on the overall speed of the vehicle. For example, when it is detected that the accelerator pedal is depressed and shifts to the non-EGR region when the driving state is in the EGR region, it can be determined that there is an acceleration request (positive determination in step S201). .

  When it is not determined that there is an acceleration request, that is, when there is no acceleration request (No in step S201), the EGR valve 50 and the throttle valve 26 are each controlled to the normal opening as described above (step S203). ). On the other hand, if there is an acceleration request (Yes determination in step S201), the EGR valve 50 is controlled to be fully closed, and the throttle valve 26 is controlled to be fully open (step S205).

  Hereinafter, the operational effects of the internal combustion engine 10 will be described based on the graph of FIG. 3 showing the experimental results.

  In the graph of FIG. 3, a change in the pressure of the intake port in one cylinder in the state where the EGR valve 50 is closed in the internal combustion engine such as the internal combustion engine 10 shown in FIG. 1 is represented by a solid line. In addition, FIG. 3 shows the intake port of one corresponding cylinder in an internal combustion engine that does not have an EGR system (an internal combustion engine in which the EGR system 44 is removed from the internal combustion engine 10 in FIG. 1). The change in pressure is represented by a dotted line. As is apparent from FIG. 3, the intake port pressure in the latter half of the intake stroke in the internal combustion engine provided with the EGR system, that is, the second passage B is the second passage when the engine rotation speed is 1600 rpm, 2000 rpm, 2400 rpm. Compared to the intake port pressure in the latter half of the intake stroke in the internal combustion engine without B. This is configured so that the second passage B in the internal combustion engine provided with the EGR system has an air column natural frequency that synchronizes with the engine rotational speed within the predetermined engine rotational speed region, and the predetermined engine rotational speed region is This is because the region includes 1600 rpm to 2400 rpm. This is also due to the fact that the first passage A in the internal combustion engine provided with the EGR system is configured to have an air column natural frequency that synchronizes with the engine rotational speed within the predetermined engine rotational speed region. .

  Thus, in the internal combustion engine 10 having the above-described configuration, when there is a request for acceleration in the operation state in the low / medium speed range, the EGR valve 50 is closed to effectively cause the air column vibration through the intake passage and the EGR passage. As a result, the intake charge efficiency can be increased quickly. That is, the above configuration can provide a supercharging effect due to the resonance effect in the air column vibration in the first passage A and the second passage B, and can increase the torque response with a simple configuration when acceleration is requested. To do. This helps to effectively improve the rise delay of the supercharging pressure by the turbocharger 40.

  When the acceleration request is made, the EGR valve 50 is closed as described above. Exhaust gas, that is, EGR gas exists in the EGR passage 46, particularly the second passage B, immediately after the EGR valve 50 is closed. Since such exhaust gradually flows out from the EGR passage 46 to the intake passage 16 and flows into the combustion chamber, it is desired to more appropriately control the combustion in the combustion chamber in consideration of the presence of the exhaust.

  Therefore, in the internal combustion engine 10, when the EGR valve 50 is closed at the time of acceleration request, the fuel injection timing is controlled according to the amount of exhaust in the second passage B, that is, the EGR gas amount. An example of this fuel injection control will be described with reference to FIG. In FIG. 4, changes in the accelerator opening, the EGR valve opening, and the fuel injection timing are shown on the same time axis. When the accelerator pedal is depressed at time t and it is determined that there is an acceleration request (positive determination in step S201), the EGR valve 50 is closed (step S203), and the fuel injection timing is advanced according to the EGR gas amount so far. It is controlled from the injection timing on the corner side to gradually return (return) to the retard side.

  The ECU 60 has a function of an exhaust amount detection means that detects (estimates) the amount of exhaust in the second passage B when the EGR valve 50 is closed based on the opening degree of the EGR valve 50 at the time of acceleration request. Have. However, the amount of exhaust in the second passage B when the EGR valve 50 is closed may be detected by other methods or means.

  In addition, in the internal combustion engine 10, when the EGR valve 50 is closed at the time of acceleration request (step S205), the valve operating mechanism functions to further enhance the supercharging effect as described above. In the internal combustion engine 10, the valve mechanism is configured such that when there is an acceleration request, the open period of the intake valve and the open period of the exhaust valve overlap, and the exhaust pressure is higher than the intake pressure during the overlap period. The valve timing of each of the intake valve and the exhaust valve is controlled so that the pressure becomes low. This valve timing control will be described based on the experimental result example of FIG.

  FIG. 5A shows an example of the exhaust valve open period and the intake valve open period near the exhaust top dead center in the low and medium load operation state. Examples of changes in the exhaust pressure) and the intake port pressure (intake pressure) are shown. As shown in FIG. 5 (a), in the internal combustion engine 10, the intake valve and the exhaust valve are driven based on predetermined data in the operation state at low and medium loads, so that the vicinity of the exhaust top dead center is obtained. The exhaust pressure tends to be higher than the intake pressure. However, by changing at least one of the valve timing of the exhaust valve, particularly the closing timing, and the valve timing of the intake valve, particularly the opening timing, the exhaust pressure can be made lower than the intake pressure near the exhaust top dead center. An example of this is shown in FIG.

  FIG. 5B shows an example in which the valve timings of the intake valve and the exhaust valve are changed so that the open periods of the intake valve and the exhaust valve overlap each other by a predetermined amount. These valve timings are determined so that the exhaust pressure is lower than the intake pressure in a predetermined time region including the exhaust top dead center, in other words, in the valve overlap period (see FIG. 5B). As a result, the exhaust pressure can be made lower than the intake pressure in the cylinder 14 in which the piston is near the exhaust top dead center, so that the intake charge efficiency can be increased more effectively. Note that such valve overlap is desirably stopped or released when the exhaust pressure becomes higher than the intake pressure.

  However, such valve timing is made variable in accordance with the temperature of the first passage A obtained based on the output signal from the intake air temperature sensor 66 here. This is because the sound velocity in the first passage A changes according to the temperature of the first passage A (the temperature of the member that forms the first passage A), so that the resonance effect as described above is obtained in the first passage A. This is because the engine speed to be changed can vary.

  FIG. 6 shows an example of the relationship between the engine speed at each temperature of the first passage A and the overlap amount (overlap angle). In FIG. 6, the temperature T1 is lower than the temperature T2, and the temperature T2 is lower than the temperature T3. Based on the relationship shown in FIG. 6, here, the valve timings of the intake valve and the exhaust valve are controlled (variably controlled) so as to adjust the valve overlap amount according to the temperature of the first passage A. ). It should be noted that the valve timings of the intake valve and the exhaust valve can be further made variable in accordance with the engine rotation speed, particularly the engine rotation speed when acceleration is requested.

  More preferably, the valve timing described above may be further variably controlled according to the temperature of the second passage B in addition to or instead of the temperature of the first passage A. This is because the speed of sound in the second passage B changes according to the temperature of the second passage B (the temperature of the member that forms the second passage B), and the resonance effect as described above is obtained in the second passage B. This is because the engine speed to be changed can vary. In this case, the temperature detection means such as a temperature sensor for detecting the temperature of the second passage B is provided, and the ECU 60 has a temperature detection function for detecting the temperature of the second passage based on the output of the temperature detection means. It is good to have.

  In the internal combustion engine 10, as described above, when there is an acceleration request, the valve mechanism is configured so that the opening period of the intake valve and the opening period of the exhaust valve overlap and The valve timing of each of the intake valve and the exhaust valve is controlled so that the exhaust pressure becomes lower than the intake pressure during the period. However, in such a case, only the valve timing of either the intake valve or the exhaust valve may be variably controlled.

  Next, a second embodiment according to the present invention will be described. Here, differences from the first embodiment will be described. In the internal combustion engine 10A according to the second embodiment, the intake passage 16 and the EGR passage 46 are configured such that the first distance La of the first passage A is substantially equal to the second distance Lb of the second passage B. This relationship will be described based on FIG.

  In FIG. 7, the internal combustion engine 10 </ b> A is schematically shown with respect to the first passage A and the second passage B. However, in FIG. 7, the first distance La is expressed with respect to the cylinder 14a located at one end. Although not shown in FIG. 7, the intake manifold 18 is shaped so that the first distance La of the first passage A for each cylinder 14 is approximately equal to the second distance Lb of the second passage B, respectively. Yes.

  Since the first distance La of the first passage A is substantially equal to the second distance Lb of the second passage B, the EGR valve 50 is closed at the time of acceleration request (step S205), so that the junction C in the passages A and B is used. Thus, the wave W where the node Wc is substantially located can be generated more actively (see FIG. 7). Accordingly, the resonance effect can be maximized in the passages A and B, and the intake charge efficiency at the time of the acceleration request can be increased more effectively. In the wave W in FIG. 7, there is one node, but there may be a plurality of nodes.

  In the internal combustion engine 10A, the intake passage 16 and the EGR passage 46 are configured such that the first distance La of the first passage A is substantially equal to the second distance Lb of the second passage B. However, the intake passage 16 and the EGR passage 46 may be configured such that the first distance La of the first passage A is completely equal to the second distance Lb of the second passage B.

  Next, a third embodiment according to the present invention will be described. Here, differences from the first embodiment will be described. An internal combustion engine system for a vehicle to which the third embodiment is applied is shown in FIG. However, in FIG. 8, the various sensors 62 to 74 and the ECU 60 as shown in FIG. 1 are omitted.

  The internal combustion engine 10B according to the third embodiment is provided in a plurality of junctions C1 and C2 in which the EGR passage 50 and the intake passage 26 can communicate with each other, and one junction C2 among the plurality of junctions C1 and C2. And an adjustment valve 80 for adjusting the communication state between the EGR passage 50 and the intake passage 26. The control valve 80 is opened and closed when the actuator 82 is operated by an operation signal from the ECU 60. The control valve control means includes a part of the ECU 60.

  The control valve 80 is opened and closed according to the engine speed at the time of acceleration request. Normally, the adjustment valve 80 is closed so that the EGR passage 50 and the intake passage 26 do not communicate with each other. However, the control valve 80 is opened when the engine speed at the time of the acceleration request is a specific speed. Thereby, the confluence | merging location of the intake passage 16 and the EGR channel | path 46 will switch substantially, and the substantial effective length of the 1st channel | path A and the 2nd channel | path B can each be changed. As a result, air column vibrations can be generated more effectively in the passages A and B, and a resonance effect corresponding to the engine rotation speed can be more appropriately brought about. As described above, the configuration of the internal combustion engine 10 </ b> B substantially contributes to expanding the engine rotation speed region in which the resonance effect occurs in the EGR passage 46 and the intake passage 16.

  In the internal combustion engine 10B, two merging portions C1 and C2 are provided, but three or more merging portions may be provided.

  Next, a fourth embodiment according to the present invention will be described. Here, differences from the first embodiment will be described. An internal combustion engine system for a vehicle to which the fourth embodiment is applied is shown in FIG. In FIG. 9, various sensors 62 to 74 and the ECU 60 as shown in FIG. 1 are omitted.

  In the internal combustion engine 10C according to the fourth embodiment, the EGR system 44 includes an EGR cooler 86, a bypass passage 90 defined by a bypass pipe 88 that bypasses the EGR cooler 86, and an EGR passage 46 in addition to the above-described configuration. A switching valve 92 for switching the flow of exhaust is provided. The switching valve 92 is opened and closed when the actuator 94 is operated by an operation signal from the ECU 60. The switching valve control means includes a part of the ECU 60.

  Normally, the switching valve 92 is fully opened, and the flow rate of the exhaust gas flowing through the EGR passage 46 is controlled by the EGR valve 50. On the other hand, when there is an acceleration request (Yes in step S201), the EGR valve 50 is closed (step S205) and the switching valve 92 is closed. Thereby, when there is an acceleration request, the passage not including the EGR cooler 86 substantially functions as the second passage B. Therefore, the attenuation of the air column vibration in the EGR cooler 86 can be substantially avoided, and the air column vibration can be generated more appropriately in the second passage B. This substantially corresponds to the EGR cooler 86 being provided in the portion of the EGR passage 46 other than the second passage.

  The switching valve 92 may be a three-way valve provided at a branching part or a joining part of the bypass passage 90.

  Next, a fifth embodiment according to the present invention will be described. Here, differences from the first embodiment will be described. An internal combustion engine system for a vehicle to which the fifth embodiment is applied is shown in FIG. In FIG. 10, various sensors 62 to 74 and the ECU 60 as shown in FIG. 1 are omitted.

  In the internal combustion engine 10D according to the fifth embodiment, the EGR system 44 includes a second EGR valve 96 in addition to the above configuration. The second EGR valve 96 is disposed near the junction C with respect to the EGR valve 50. The second EGR valve 96 is opened and closed when the actuator 98 is actuated by an actuation signal from the ECU 60. The second EGR valve control means includes a part of the ECU 60.

  FIG. 11 shows the operations of the EGR valve 50 (EGR valve-1) and the second EGR valve 96 (EGR valve-2) when there is an acceleration request. FIG. 11 shows the case where it is determined that the acceleration pedal is depressed and the acceleration request is made at time t (Yes determination in step S201).

  Here, the EGR valve 50 is normally maintained open when there is no acceleration request (negative determination in step S201) (step S203), and closed when there is an acceleration request (positive determination in step S201). (Step S205). On the other hand, the second EGR valve 96 is normally controlled to adjust the flow rate of the exhaust gas flowing through the EGR passage 46 when it is not determined that there is an acceleration request (negative determination in step S201). When it is determined that there is an acceleration request (Yes determination in step S201), the second EGR valve 96 is controlled to open to the fully open state.

  As described above, since the EGR gas amount is controlled by controlling the second EGR valve 96 that is normally located near the intake passage 16, it becomes possible to improve the responsiveness of the EGR gas and enable precise EGR control. Become. On the other hand, when the acceleration is requested, the second EGR valve 96 is opened and the EGR valve 50 is closed, so that the second passage B as described above can be sufficiently secured to enhance the intake air charging effect.

  As mentioned above, although this invention was demonstrated based on several above-described embodiment, this invention is not limited to these. The present invention also allows embodiments in which various combinations of the above-described embodiments are combined or any combination thereof.

  Each of the turbochargers 40 of the internal combustion engines 10 to 10D described above includes a plurality of variable nozzle vanes disposed at an exhaust inlet of the turbine, and an angle control mechanism that controls the angles of the plurality of variable nozzle vanes. it can. In this case, the angle control mechanism may control the angles of the plurality of variable nozzle vanes to the closed side in step S205, that is, when the acceleration request determination unit determines that there is an acceleration request.

  In the above embodiment, the present invention is applied to a diesel engine. However, the present invention is not limited to this, and the present invention can be applied to various internal combustion engines such as a port injection type gasoline engine and a cylinder injection type gasoline engine. It is applicable to. The fuel used is not limited to light oil or gasoline, but may be alcohol fuel, LPG (liquefied natural gas), or the like. Further, the number of cylinders of the internal combustion engine to which the present invention is applied may be any number.

  Although the present invention has been described with a certain degree of specificity in the above-described embodiments and modifications thereof, various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that changes are possible. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

10, 10A, 10B, 10C, 10D Internal combustion engine 16 Intake passage 28 Exhaust passage 46 EGR passage 50 EGR valve A First passage B Second passage

Claims (10)

In an internal combustion engine having an EGR passage having one end communicating with an exhaust passage and the other end communicating with an intake passage, and an EGR valve disposed in the EGR passage,
When the EGR valve is closed, the first passage in the intake passage from the junction between the intake passage and the EGR passage to the intake valve and the second passage in the EGR passage from the junction to the EGR valve are: Communication,
The second passage have a predetermined engine rotational speed tuned air column natural frequency in the engine rotational speed in the region,
The internal combustion engine
An acceleration request determination means for determining whether or not there is an acceleration request;
EGR valve control means for controlling the EGR valve, the EGR valve control means for controlling the EGR valve so as to be closed when the acceleration request determination means determines that there is an acceleration request;
A second EGR valve provided in the second passage;
Second EGR valve control means for controlling the second EGR valve;
With
The EGR valve control means opens the EGR valve so as to open when the acceleration request determination means determines that there is an acceleration request, and closes when the acceleration request determination means determines that there is an acceleration request. Control
The second EGR valve control means adjusts the flow rate of the exhaust gas flowing through the EGR passage when the acceleration request determining means does not determine that the acceleration request is present, and the acceleration request determining means determines that the acceleration request is present. The internal combustion engine , wherein the second EGR valve is controlled to open when judged .   2. The internal combustion engine according to claim 1, wherein the first passage has an air column natural frequency that synchronizes with an engine rotation speed within the predetermined engine rotation speed region.   The intake passage and the EGR passage are configured such that a first distance from the joining portion to the intake valve in the first passage is equal to or less than a second distance from the joining portion to the EGR valve in the second passage. The internal combustion engine according to claim 1, wherein the internal combustion engine is provided.   The intake passage and the EGR passage are configured such that a first distance from the joining portion to the intake valve in the first passage is substantially equal to a second distance from the joining portion to the EGR valve in the second passage. The internal combustion engine according to claim 1, wherein the internal combustion engine is provided.   5. The internal combustion engine according to claim 1, wherein an EGR cooler is further provided in a portion of the EGR passage other than the second passage. A valve mechanism that makes variable the valve timing of at least one of the intake valve and the exhaust valve;
When the acceleration request determining means determines that there is an acceleration request, the valve mechanism is configured such that the open period of the intake valve and the open period of the exhaust valve overlap and in the overlap period. The internal combustion engine according to any one of claims 1 to 5, wherein the valve timing of at least one of the intake valve and the exhaust valve is controlled so that an exhaust pressure becomes lower than an intake pressure. The valve mechanism is configured to control at least one of the intake valve and the exhaust valve according to a temperature of at least one of the first passage and the second passage when the acceleration request determination unit determines that there is an acceleration request. The internal combustion engine according to claim 6 , wherein one of the valve timings is controlled. When the acceleration request determining means determines that there is an acceleration request, the valve mechanism is configured to open the intake valve and the exhaust valve according to the temperature of at least one of the first passage and the second passage. 8. The internal combustion engine according to claim 6 , wherein the valve timing of at least one of the intake valve and the exhaust valve is controlled so as to adjust an overlap amount with an open period. Fuel injection control means for controlling fuel injection from the fuel injection valve controls fuel injection timing in accordance with the amount of exhaust gas in the second passage when the EGR valve is closed by the EGR valve control means. An internal combustion engine according to any one of claims 1 to 8 . A plurality of merging portions that allow the EGR passage and the intake passage to communicate with each other;
From claim 1, characterized in that it comprises a regulating valve for adjusting the state of communication between the EGR passage and the intake passage provided in at least one of the merging portion of the merging portion of the plurality of 9 An internal combustion engine according to any one of the above.

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