JP2013130170A - Engine valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine valve gear which can satisfactorily adjust the amount of an internal EGR gas in a transition operation.SOLUTION: The engine valve gear 1A includes a variable valve gear mechanism 57A which can individually change an opening period and a closing period of an intake valve 54 provided in a combustion chamber E of an engine 50A at a constant lift amount. The engine valve gear individually changes the valve closing period of the intake valve 54 depending on an actual EGR ratio and a target EGR ratio so that separation between the actual EGR ratio, which is an actual value of the EGR ratio and the target EGR ratio, which is a target value in the transition operation of the engine 50A. More specifically, when the actual EGR ratio is larger than the target EGR ratio, the valve closing period is individually delayed, and when the actual EGR ratio is smaller than the target EGR ratio, the valve opening period is individually advanced.

Description

  The present invention relates to an engine valve operating device.

  In an engine, valve characteristics of an intake valve and an exhaust valve may be variable. Also, EGR (exhaust gas recirculation) may be performed. In this regard, as a technique considered to be related to the present invention, the exhaust side VVT delays the closing timing of the exhaust valve over the recirculation delay period in which the recirculation delay of the low pressure EGR gas occurs in the operation state transition period, For example, Patent Document 1 discloses an internal combustion engine with an EGR device that increases the amount of internal EGR gas.

  In addition, as a technique that is considered to be related to the present invention, for example, in Patent Document 2, it is possible to make the valve characteristics variable with a constant lift amount by making the drive shaft and the camshaft interlock at an unequal speed. A variable valve device and a valve lift characteristic detection device for a variable valve device of an internal combustion engine that detects a valve characteristic that the variable valve device makes variable are disclosed.

JP 2008-150957 A JP 2006-336659 A

  In the engine, specifically, EGR may be performed by external EGR that recirculates exhaust gas from the exhaust system to the intake system without passing through the combustion chamber, and internal EGR that recirculates exhaust gas from the exhaust system to the intake system via the combustion chamber. it can. And the quantity of EGR gas which is exhaust gas recirculated can be adjusted, for example according to an engine operating state. However, when adjusting the amount of EGR gas, when the amount of external EGR gas is adjusted, a reflux delay occurs due to the long reflux path during transient operation. For this reason, in this case, there is a possibility that an increase in unburned HC, misfire, or NOx spike may occur as a result of insufficient intake air amount or excessive supply of intake air amount.

  On the other hand, the amount of internal EGR gas can be adjusted to adjust the amount of EGR gas. In this case, since the reflux path is short, the response of reflux can be improved. In order to increase the amount of internal EGR gas when adjusting the amount of EGR gas, the valve closing timing of the exhaust valve is retarded by, for example, a variable valve mechanism to increase the valve overlap amount of the intake and exhaust valves. Can do. However, when the variable valve mechanism is configured so that, for example, the valve closing timing of the exhaust valve is retarded together with the valve opening timing, the valve opening timing is set to the optimum point between expansion work and extrusion loss. As a result, the fuel consumption may be deteriorated and the output may be reduced. For this reason, the technique which can adjust the quantity of internal EGR gas suitably at the time of transient operation is desired.

  In view of the above problems, an object of the present invention is to provide an engine valve operating apparatus that can suitably adjust the amount of internal EGR gas during transient operation.

  The present invention comprises a variable valve mechanism capable of individually changing the valve opening timing and the valve closing timing of at least one of an intake valve and an exhaust valve provided for a combustion chamber of an engine with a constant lift amount, The actual EGR rate, which is the actual value of the EGR rate, which is the ratio of the amount of exhaust gas recirculated by exhaust gas recirculation to the total amount of gas sucked into the cylinder during the transient operation, and the target EGR rate, which is the target value An engine that individually changes at least one of the valve opening timing of the intake valve and the valve closing timing of the exhaust valve in accordance with the actual EGR rate and the target EGR rate so that the difference between the actual EGR rate and the target EGR rate is reduced. This is a valve operating device.

  In the present invention, when the actual EGR rate is greater than the target EGR rate, at least one of the retarded timing of the intake valve and the advanced timing of the exhaust valve is individually performed. It can be configured.

  In the present invention, when the actual EGR rate is smaller than the target EGR rate, at least one of the advance angle of the intake valve opening timing and the delay angle of the exhaust valve closing timing is individually performed. It can be configured.

  According to the present invention, the amount of internal EGR gas can be suitably adjusted during transient operation.

1 is an overall configuration diagram of Example 1. FIG. 1 is a schematic configuration diagram of an engine according to Embodiment 1. FIG. It is explanatory drawing of the valve opening timing change control of an intake valve. It is a figure which shows the control of Example 1 with a flowchart. FIG. 6 is a diagram illustrating a first parameter change example according to the first embodiment. FIG. 6 is a first explanatory diagram of a change in valve characteristics in the first embodiment. FIG. 6 is a diagram illustrating a second parameter change example according to the first embodiment. FIG. 6 is a second explanatory diagram of valve characteristic change in the first embodiment. FIG. 3 is a schematic configuration diagram of an engine according to a second embodiment. It is explanatory drawing of the valve closing timing change control of an exhaust valve. It is a figure which shows the control of Example 2 with a flowchart. FIG. 6 is a diagram illustrating a first parameter change example of the second embodiment. FIG. 10 is a first explanatory diagram of a change in valve characteristics in the second embodiment. FIG. 10 is a diagram illustrating a second parameter change example according to the second embodiment. FIG. 10 is a second explanatory diagram of valve characteristic change in the second embodiment.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of the engine 50A and its surroundings. FIG. 2 is a schematic configuration diagram of the engine 50A. Each component shown in FIG. 1 is mounted on a vehicle. As shown in FIG. 1, the intake system 10 includes an air flow meter 11, an intercooler 12, and an intake manifold 13. The air flow meter 11 measures the amount of intake air. The intercooler 12 cools the intake air. Intake manifold 13 distributes intake air to each cylinder 51a of engine 50A. The exhaust system 20 includes an exhaust manifold 21 and a catalyst 22. The exhaust manifold 21 merges exhaust from each cylinder 51a into one exhaust passage on the downstream side. The catalyst 22 purifies the exhaust.

  The supercharger 30 supercharges intake air to the engine 50A. The supercharger 30 is an exhaust-driven supercharger and includes a compressor unit 31 and a turbine unit 32. The compressor unit 31 is provided in the intake system 10, and the turbine unit 32 is provided in the exhaust system 20. The exhaust gas recirculation system 40 includes an EGR pipe 41, an EGR cooler 42, and an EGR valve 43. The EGR pipe 41 communicates the intake system 10 and the exhaust system 20. Specifically, the EGR pipe 41 communicates the upstream collecting portion of the intake manifold 13 with the downstream collecting portion of the exhaust manifold 21. The EGR cooler 42 cools the recirculated exhaust gas. The EGR valve 43 adjusts the amount of exhaust gas recirculated.

  The engine 50A is a compression self-ignition engine. As shown in FIG. 2, the engine 50A includes a cylinder block 51, a cylinder head 52, a piston 53, an intake valve 54, an exhaust valve 55, a fuel injection valve 56, and a variable valve mechanism 57A. A cylinder 51 a is formed in the cylinder block 51. A piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber E is formed as a space surrounded by the cylinder block 51, the cylinder head 52 and the piston 53.

  The cylinder head 52 is formed with an intake port 52a and an exhaust port 52b. An intake valve 54 and an exhaust valve 55 are provided. The intake port 52 a guides intake air to the combustion chamber E, and the exhaust port 52 b exhausts gas from the combustion chamber E. The intake valve 54 opens and closes the intake port 52a, and the exhaust valve 55 opens and closes the exhaust port 52b. The intake port 52a is provided with a SCV (swirl control valve) (not shown) capable of generating a swirl flow in the cylinder. The cylinder head 52 is provided with a fuel injection valve 56 and a variable valve mechanism 57A. The fuel injection valve 56 injects fuel into the combustion chamber E. The variable valve mechanism 57A makes the valve characteristic of the intake valve 54 variable.

  In this regard, the variable valve mechanism 57A has a cam speed variable mechanism that makes the valve characteristic of the intake valve 54 variable with a constant lift by making the drive shaft and the camshaft interlock at an unequal speed. It is configured. In addition, it is configured to have a phase variable mechanism that varies the relative phase of the drive shaft with respect to the crankshaft. Further, the combination of the cam speed variable mechanism and the phase variable mechanism is a variable valve mechanism that can individually change the valve opening timing and the valve closing timing of the intake valve 54 with a constant lift amount. The fact that the valve opening timing and the valve closing timing can be individually changed includes that the valve opening timing and the valve closing timing can be individually changed as a result of a combination of changing operations.

  In this regard, the variable valve mechanism 57A specifically advances or retards one of the opening timing and closing timing of the intake valve 54 by the cam speed variable mechanism, and opens the intake valve 54 by the phase variable mechanism. By adjusting so that the other of the valve timing and the valve closing timing is not changed, the valve opening timing and the valve closing timing of the intake valve 54 can be individually changed with a constant lift amount. For example, the variable valve operating device disclosed in Patent Document 1 described above can be applied to the cam speed variable mechanism. The variable valve mechanism 57A can be realized, for example, by an electromagnetic drive device when the intake valve 54 is driven electromagnetically.

  An ECU 70A is provided for the engine 50A. The ECU 70A is an electronic control unit, and an EGR valve 43, a fuel injection valve 56, and a variable valve mechanism 57A are electrically connected as control objects to the ECU 70A as shown in FIGS. The air flow meter 11, the first phase sensor 81 that can detect the phase of the drive shaft relative to the phase of the crankshaft, the second phase sensor 82 that can detect the phase of the camshaft relative to the phase of the drive shaft, A sensor group 83 capable of detecting the state of 50A is electrically connected as sensors and switches.

  The sensor group 83 includes, for example, a water temperature sensor that detects the cooling water temperature THW of the engine 50A, an oil temperature sensor that detects the oil temperature of the engine 50A, a crank angle sensor that can detect the rotational speed NE of the engine 50A, and an intake of the engine 50A. It includes an intake air temperature sensor that detects air temperature and an atmospheric pressure sensor that detects atmospheric pressure. The ECU 70 </ b> A can detect the opening timing and closing timing of the intake valve 54 based on the outputs of the crank angle sensor and the phase sensors 81 and 82. Further, the fuel injection amount can be detected by the opening period of the fuel injection valve 56.

  In the ECU 70A, various functional units are realized by executing processing while the CPU uses a temporary storage area of the RAM as required based on a program stored in the ROM. In this regard, in the ECU 70A, for example, the following control unit is functionally realized.

  The control unit is an actual value of the EGR rate, which is the ratio of the amount of exhaust (EGR gas) recirculated by EGR (exhaust gas recirculation) during transient operation of the engine 50A to the total amount of gas sucked into the cylinder. The valve opening timing (hereinafter referred to as IVO) of the intake valve 54 is individually changed according to the actual EGR rate and the target EGR rate so that the difference between the actual EGR rate and the target EGR rate that is the target value becomes small. To do. Here, when the object of change is, for example, IVO, it means that IVO is changed in the closing timing of the IVO and the intake valve 54 (hereinafter referred to as IVC). The control unit individually changes the IVO by controlling the variable valve mechanism 57A.

In individually changing the IVO so that the difference between the actual EGR rate and the target EGR rate is small, the control unit determines the target EGR rate according to the engine operating state (here, the rotational speed NE and the fuel injection amount). . In addition, the actual EGR rate is estimated. In determining the target EGR rate, the ECU 70A stores in the ROM map data of the target EGR rate set in advance according to the engine operating state. And a control part determines a target EGR rate by reading the corresponding target EGR rate from the map data of a target EGR rate based on the detected engine operating state. The actual EGR rate can be estimated by, for example, the following expressions (1) and (2).
EGR _ratio = (G _all -G _new ) / G _all (1)
G _all = (P _in × V _ratio + A) × T _s / T _in (2)

_{Here, EGR ratio} is the actual EGR _rate, the amount of total gas _{G all} sucked into the _{cylinder, G new new} is the fresh air _{amount, P in} the intake pipe _{pressure, V ratio} is volumetric efficiency, A is the learning correction value, T _s is the standard temperature, and T _in is the intake air temperature. Among these, the amount of fresh air can be detected based on the output of the air flow meter 11, for example. The volumetric efficiency can be estimated by a model formula created according to, for example, the opening degree of the SCV, the coolant temperature THW, the rotational speed NE, and the atmospheric temperature. The intake air temperature can be estimated by a model formula created according to, for example, the exhaust gas temperature, the exhaust gas pressure, the cooling efficiency of the EGR cooler 42, or the outlet temperature of the EGR valve 43. In this regard, the sensor group 83 further includes various sensors and switches necessary for estimating the actual EGR rate.

  In individually changing the IVO so that the difference between the actual EGR rate and the target EGR rate is small, the control unit individually performs the retard or advance of the IVO as described below.

  FIG. 3 is an explanatory diagram of IVO change control. FIG. 3A shows a change in the amount of internal EGR gas according to the amount of deviation calculated by subtracting the actual EGR rate from the target EGR rate. FIG. 3B shows the change in the amount of internal EGR gas in response to IVO. As shown in FIG. 3A, the amount of internal EGR gas is set to zero when the amount of deviation is zero. And when the deviation | shift amount is negative (namely, when an actual EGR rate is larger than a target EGR rate), it sets so that it may reduce. Further, it is set to be increased when the deviation amount is positive (that is, when the actual EGR rate is smaller than the target EGR rate).

  The amount of the internal EGR gas is further reduced as the deviation amount is smaller in the negative region (that is, when the actual EGR rate is larger than the target EGR rate, the larger the actual EGR rate). Is set. Further, the amount of increase is set to be larger as the deviation amount is larger in the plus region (that is, when the actual EGR rate is smaller than the target EGR rate, the smaller the actual EGR rate is).

  In contrast, as shown in FIG. 3B, the amount of internal EGR gas is increased when the IVO is advanced, and is decreased when the IVO is retarded. For this reason, when the actual EGR rate is larger than the target EGR rate, the control unit individually retards the IVO. In this case, the IVO is changed so that the retardation amount increases as the actual EGR rate increases. Further, the control unit individually advances the IVO when the actual EGR rate is smaller than the target EGR rate. In this case, the IVO is changed so that the amount of advance is larger as the actual EGR rate is smaller.

  The control unit further controls IVO and IVC according to the engine operating state (here, the rotational speed NE and the fuel injection amount). In this regard, the ECU 70A stores IVO and IVC map data set in advance according to the engine operating state in the ROM. In controlling IVO and IVC according to the engine operating state, the control unit can individually change IVO and IVC. In this regard, when the change targets are IVO and IVC, individually means that IVO and IVC can be changed with different changes. In this embodiment, an engine valve gear (hereinafter referred to as a valve gear) 1A including an ECU 70A and a variable valve mechanism 57A is realized.

  Next, the control operation of the valve gear 1A performed by the ECU 70A will be described using the flowchart shown in FIG. In executing this flowchart, IVO and IVC are separately controlled in accordance with the engine operating state, and the detection necessary in this flowchart such as the engine operating state can be detected at this time. The ECU 70A determines whether or not the change amount ΔNE of the rotational speed NE is larger than the reference value α (step S1). Thus, it is determined whether or not it is a transient operation. The change amount ΔNE can be calculated separately based on the rotational speed NE. If a negative determination is made in step S1, this flowchart is temporarily terminated.

  If the determination in step S1 is affirmative, the ECU 70A determines the target EGR rate (step S2) and estimates the actual EGR rate (step S3). Subsequently, the ECU 70A determines whether or not the actual EGR rate is lower than the target EGR rate (step S4). Further, if a negative determination is made in step S4, it is determined whether or not the actual EGR rate is higher than the target EGR rate (step S5). If an affirmative determination is made in step S4, IVO is advanced (step S6A), and if an affirmative determination is made in step S5, IVO is retarded (step S7A). After step S6A or S7A, the process returns to step S3. On the other hand, if the determination in step S5 is negative, this flowchart is terminated.

  Next, the function and effect of the valve gear 1A will be described. FIG. 5 is a diagram showing a first parameter change example when the valve gear 1A individually changes the IVO during transient operation. FIG. 5 shows a change example of various parameters when the valve operating apparatus 1A individually performs IVO retardation when there is a supercharging delay during transient operation as a first parameter change example. Further, the accelerator opening, the intake air amount, A / F, IVO, and the amount of internal EGR gas are shown as various parameters. The intake air amount and A / F are indicated by broken lines even when the IVO is not particularly changed.

  When the accelerator opening is changed from a constant state to a larger state, the operating state of engine 50A shifts from a steady operating state to a transient operating state. If the IVO is not particularly changed, the intake air amount deviates downward from the target air amount due to a delay in supercharging during transient operation as indicated by a broken line. For this reason, as indicated by the broken line, A / F shifts to the rich side due to insufficient intake air amount. When there is a supercharging delay during the transient operation as described above, a shortage of intake air occurs, so that the actual EGR rate becomes larger than the target EGR rate.

  In contrast, the valve gear 1A individually performs the IVO retardation when the actual EGR rate is larger than the target EGR rate during transient operation, and the retardation amount increases as the actual EGR rate increases. Change the IVO. Then, the internal EGR gas is reduced in accordance with this, so that the intake air amount follows the target air amount. As a result, A / F is maintained at an appropriate value, and the increase in unburned HC and smoke and the occurrence of misfire are prevented or suppressed. Thus, the valve gear 1A for adjusting the amount of the internal EGR gas can suitably adjust the amount of the internal EGR gas at the time of transient operation in the following points.

  FIG. 6 is a first explanatory diagram of valve characteristics that the valve gear 1A makes variable. FIG. 6A shows changes in the lift amounts of the intake and exhaust valves 54 and 55 when the IVO is retarded by the valve gear 1A. FIG. 6B shows changes in the lift amounts of the intake and exhaust valves 54 and 55 when the IVO is retarded by a phase variable mechanism that makes the phase of the camshaft variable with respect to the crankshaft. FIG. 6C shows an intake / exhaust valve when the IVO is retarded by a combination of a phase variable mechanism that varies the phase of the drive shaft with respect to the crankshaft and a variable valve mechanism that varies the operating angle together with the lift amount. The change of the lift amount of 54 and 55 is shown. Regarding the lift amount of the intake valve 54, the solid line indicates the lift amount during steady operation, and the broken line indicates the lift amount during transient operation.

  In the case shown in FIG. 6A, the valve overlap amount of the intake / exhaust valves 54 and 55 can be reduced by individually performing the retard of the IVO with a constant lift amount. Thus, the amount of internal EGR gas can be adjusted by reducing the amount of internal EGR gas. Further, in the case shown in FIG. 6A, the IVC is controlled according to the engine operating state. In this regard, in the IVC map data, IVC is determined so as to be in an optimum phase for preventing or suppressing the occurrence of unburned HC, smoke, and misfire from the viewpoint of the actual compression ratio and the operating angle. For this reason, in the case shown in FIG. 6 (a), it is possible to maintain the state where the IVC is controlled to the optimum phase from the viewpoint of the actual compression ratio and the working angle by individually performing the retarding of the IVO. it can.

  On the other hand, in the case shown in FIG. 6B, the IVO can be retarded with a constant lift amount, while the IVC is similarly retarded. For this reason, in this case, the actual compression ratio decreases and deviates from the optimum point, and in the case of a light load, a situation in which unburned HC increases or misfires may occur. Further, in the case of a high load, a situation in which the combustion pressure is constrained by the maximum combustion pressure can occur.

  In the case shown in FIG. 6C, the IVO retardation can be performed individually, while the lift amount decreases as the operating angle decreases. For this reason, in this case, the pumping loss increases when the lift amount is reduced, which causes a situation in which fuel consumption is deteriorated. In addition, there is a concern that exhaust emission may deteriorate due to a decrease in the amount of intake gas.

  Accordingly, the valve operating apparatus 1A performs the IVO retardation individually when the actual EGR rate is larger than the target EGR rate during the transient operation, so that the above-described situation occurs in accordance with the change in the IVC and the change in the lift amount. The amount of internal EGR gas can be suitably adjusted during transient operation in that the amount of internal EGR gas can be reduced while preventing this. Thus, specifically, for example, an increase in unburned HC and smoke and the occurrence of misfire can be prevented or suppressed.

  FIG. 7 is a diagram showing a second parameter change example when the valve gear 1A individually changes the IVO during transient operation. In FIG. 7, as a second parameter change example, specifically, various cases in which the valve gear 1A individually advances the IVO advance angle when the amount of EGR gas is insufficient due to the recirculation delay of the external EGR gas during transient operation. An example of parameter change is shown. Further, the accelerator opening, the intake air amount, NOx, IVO, and the amount of internal EGR gas are shown as various parameters. As for the intake air amount and NOx, the case where the IVO is not particularly changed is indicated by a broken line.

  When the accelerator opening is changed from a constant state to a larger state, the operating state of engine 50A shifts from the steady operating state to the transient operating state. If the IVO is not particularly changed, the recirculation delay of the external EGR gas occurs during the transient operation. As a result, the intake air amount deviates upward from the target air amount as indicated by a broken line. For this reason, NOx increases due to excessive supply of the intake air amount as indicated by a broken line. When the amount of EGR gas becomes insufficient due to the recirculation delay of the external EGR gas during the transient operation as described above, the intake air amount is excessively supplied, so that the actual EGR rate becomes smaller than the target EGR rate.

  In contrast, the valve gear 1A individually performs the IVO advancement when the actual EGR rate is smaller than the target EGR rate during transient operation, and the advancement amount increases as the actual EGR rate decreases. Change the IVO. And according to this, internal EGR gas increases, and intake air amount follows target air amount. As a result, the occurrence of NOx spikes is prevented or suppressed. Thus, the valve gear 1A for adjusting the amount of the internal EGR gas can suitably adjust the amount of the internal EGR gas at the time of transient operation in the following points.

  FIG. 8 is a second explanatory diagram of the valve characteristics that the valve gear 1A makes variable. FIG. 8A shows changes in lift amounts of the intake and exhaust valves 54 and 55 when the IVO advance angle is individually performed by the valve gear 1A. FIG. 8 (b) has the same configuration as in FIG. 6 (b), and FIG. 8 (c) has the same configuration as in FIG. 6 (c), and intake / exhaust valves 54, 55 when the IVO is advanced. The change of the lift amount of each is shown. Regarding the lift amount of the intake valve 54, the solid line indicates the lift amount during steady operation, and the broken line indicates the lift amount during transient operation.

  In the case shown in FIG. 8A, the valve overlap amount of the intake / exhaust valves 54 and 55 can be increased by individually performing the IVO advance with a constant lift amount. Thereby, the amount of the internal EGR gas can be adjusted by increasing the amount of the internal EGR gas. In addition, in the case shown in FIG. 8A, the state where the IVC is controlled to the optimum phase from the viewpoint of the actual compression ratio and the working angle can be maintained by individually performing the IVO advance angle. .

  On the other hand, in the case shown in FIG. 8B, the IVO can be advanced with a constant lift amount, while the IVC is similarly advanced. Therefore, in this case, the actual compression ratio is improved and the deviation from the optimum point may occur, and the same situation as described above with reference to FIG. Further, in the case shown in FIG. 8C, the advance angle of the IVO can be performed individually, while the lift amount increases as the operating angle increases. For this reason, in this case, the same situation as described above with reference to FIG.

  Therefore, the valve operating apparatus 1A performs the IVO advance angle individually when the actual EGR rate is smaller than the target EGR rate during the transient operation, and the above-described situation occurs due to the change in the IVC and the change in the lift amount. The amount of internal EGR gas can be suitably adjusted during transient operation in that the amount of internal EGR gas can be increased while preventing this. Thus, specifically, for example, generation of NOx spikes can be prevented or suppressed.

  In this way, the valve gear 1A individually performs the retard and advance of the IVO during the transient operation, so that the difference between the actual EGR rate and the target EGR rate becomes small so that the actual EGR rate and the target EGR rate are reduced. The IVO is individually changed accordingly. As a result, the amount of internal EGR gas can be suitably adjusted for each of cases where the amount of internal EGR gas needs to be reduced and when it needs to be increased.

  When the actual EGR rate is larger than the target EGR rate, the valve gear 1A changes the IVO so that the retard amount becomes larger as the actual EGR rate is larger, thereby reducing the amount of internal EGR gas. It is also preferable in that the internal EGR gas can be reduced depending on the degree of necessity. Further, when the actual EGR rate is smaller than the target EGR rate, the IVO is changed so that the advance amount becomes larger as the actual EGR rate is further smaller, so that it is necessary when the internal EGR gas needs to be increased. It is also preferable in that the amount of internal EGR gas can be increased according to the degree.

  FIG. 9 is a schematic configuration diagram of the engine 50B. The engine 50B is substantially the same as the engine 50A except that the variable valve mechanism 57B is provided instead of the variable valve mechanism 57A. The variable valve mechanism 57B is substantially the same as the variable valve mechanism 57A except that the valve characteristic of the exhaust valve 55 is made variable instead of the intake valve 54.

  An ECU 70B is provided for the engine 50B. The ECU 70B is configured such that the variable valve mechanism 57B is electrically connected as a control target instead of the variable valve mechanism 57A, the control unit is realized as described below, and the map data of IVO and IVC The ECU 70A is substantially the same as the ECU 70A except that it includes map data of the opening timing of the exhaust valve 55 (hereinafter referred to as EVO) and the closing timing of the exhaust valve 55 (hereinafter referred to as EVC). The overall configuration of engine 50B and its surroundings is the same as the overall configuration shown in FIG. 1 except that engine 50B is applied instead of engine 50A and ECU 70B is applied instead of ECU 70A. For this reason, the entire configuration is not shown.

  In the ECU 70B, the control unit individually changes the EVC according to the actual EGR rate and the target EGR rate instead of the IVO so that the difference between the actual EGR rate and the target EGR rate becomes small during the transient operation. The actual EGR rate and the target EGR rate are determined and estimated as in the case of the ECU 70A. When individually changing the EVC so that the difference between the actual EGR rate and the target EGR rate is small, the control unit specifically performs the retard or advance of the EVC as follows.

  FIG. 10 is an explanatory diagram of EVC change control. FIG. 10A shows a change in the amount of internal EGR gas according to the amount of deviation. FIG. 10B shows a change in the amount of internal EGR gas according to EVC. As shown in FIG. 10A, the amount of internal EGR gas is set in the same manner as described above with reference to FIG. On the other hand, as shown in FIG. 10B, the amount of internal EGR gas is decreased when EVC is advanced, and is increased when EVC is retarded.

  Therefore, the control unit individually advances the EVC when the actual EGR rate is larger than the target EGR rate. In this case, the EVC is changed so that the advance amount becomes larger as the actual EGR rate is larger. Further, the control unit individually retards the EVC when the actual EGR rate is smaller than the target EGR rate. In this case, the EVC is changed so that the retardation amount increases as the actual EGR rate is further reduced.

  The control unit further controls EVO and EVC according to the engine operating state (here, the rotational speed NE and the fuel injection amount). In this regard, the ECU 70B stores EVO and EVC map data set in advance in accordance with the engine operating state in the ROM. In controlling EVO and EVC according to the engine operating state, the control unit can individually change EVO and EVC. In this embodiment, a valve gear 1B including an ECU 70B and a variable valve mechanism 57B is realized.

  Next, the control operation of the valve gear 1B performed by the ECU 70B will be described using the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 4 except that steps S6B and S7B are provided instead of steps S6A and S7A. For this reason, these steps are specifically described here. In executing this flowchart, EVO and EVC are separately controlled in accordance with the engine operating state, and the detection necessary in this flowchart such as the engine operating state can be detected at this time.

  The ECU 70B determines whether or not the actual EGR rate is lower than the target EGR rate in Step S4, and determines whether or not the actual EGR rate is higher than the target EGR rate in Step S5. If an affirmative determination is made in step S4, EVC is retarded (step S6B), and if an affirmative determination is made in step S5, EVC is advanced (step S7B). After step S6B or S7B, the process returns to step S3.

  Next, the function and effect of the valve gear 1B will be described. FIG. 12 is a diagram illustrating a first parameter change example in the case where the valve gear 1B individually changes EVC during transient operation. FIG. 12 shows a change example of various parameters when the valve gear 1B individually advances the advance angle of EVC when there is a supercharging delay during transient operation as a first parameter change example. Further, the accelerator opening, the intake air amount, A / F, EVC, and the amount of internal EGR gas are shown as various parameters. The intake air amount and A / F are indicated by broken lines even when the EVC is not particularly changed.

  When the EVC is not particularly changed, the intake air amount and the A / F change in the same manner as described above with reference to FIG. 5 after the accelerator opening is changed. Then, when the intake air amount is insufficient, the actual EGR rate becomes larger than the target EGR rate. On the other hand, the valve gear 1B individually performs the advance angle of the EVC when the actual EGR rate is larger than the target EGR rate during the transient operation, and the advance angle amount increases as the actual EGR rate increases. Change EVC. Then, the internal EGR gas is reduced in accordance with this, so that the intake air amount follows the target air amount. As a result, A / F is maintained at an appropriate value, and the increase in unburned HC and smoke and the occurrence of misfire are prevented or suppressed. Thus, the valve gear 1B that adjusts the amount of the internal EGR gas can suitably adjust the amount of the internal EGR gas during the transient operation in the following points.

  FIG. 13 is a first explanatory diagram of valve characteristics that the valve gear 1B makes variable. FIG. 13A shows changes in lift amounts of the intake and exhaust valves 54 and 55 when the EVC is advanced by the valve gear 1B. FIG. 13 (b) has the same configuration as in FIG. 6 (b), and FIG. 13 (c) has the same configuration as in FIG. 6 (c), and intake / exhaust valves 54, 55 when the EVC is advanced. The change of the lift amount of each is shown. Regarding the lift amount of the exhaust valve 55, the solid line indicates the lift amount during steady operation, and the broken line indicates the lift amount during transient operation.

  In the case shown in FIG. 13A, the valve overlap amounts of the intake and exhaust valves 54 and 55 can be reduced by individually performing the advance angle of the EVC with a constant lift amount. Thereby, the amount of the internal EGR gas can be adjusted by reducing the amount of the internal EGR gas. Further, in the case shown in FIG. 13A, the EVO is controlled according to the engine operating state. In this regard, in the EVO map data, the EVO is determined so as to have an optimum phase for fuel consumption and output from the viewpoint of the balance between expansion work and extrusion loss. For this reason, in the case shown in FIG. 13 (a), the advance of EVC is individually performed to maintain the state where EVO is controlled to the optimum phase from the viewpoint of the balance between expansion work and extrusion loss. Can do.

  On the other hand, in the case shown in FIG. 13B, the EVC can be advanced with a constant lift amount, while the EVO is also advanced similarly. For this reason, in this case, the EVO may deviate from the optimal point between the expansion work and the extrusion loss, thereby causing a situation where the fuel consumption is deteriorated and the output is reduced. Further, in the case shown in FIG. 13C, the advance angle of the EVC can be individually performed, while the lift amount decreases as the operating angle is reduced. For this reason, in this case, the pumping loss increases when the lift amount is reduced, which causes a situation in which fuel consumption is deteriorated. In addition, there is a concern that exhaust emission may deteriorate due to a decrease in the amount of intake gas.

  Therefore, the valve operating apparatus 1B performs the advance angle of the EVC individually when the actual EGR rate is larger than the target EGR rate during the transient operation, so that the above-described situation occurs due to the change in the EVO and the change in the lift amount. The amount of internal EGR gas can be suitably adjusted during transient operation in that the amount of internal EGR gas can be reduced while preventing this. Thus, specifically, for example, an increase in unburned HC and smoke and the occurrence of misfire can be prevented or suppressed.

  FIG. 14 is a diagram showing a second parameter change example in the case where the valve gear 1B individually changes EVC during transient operation. In FIG. 14, as a second parameter change example, specifically, various cases in which the valve operating apparatus 1B individually performs the retarding of the EVC when the amount of EGR gas is insufficient due to the recirculation delay of the external EGR gas during the transient operation. An example of parameter change is shown. Further, the accelerator opening, the intake air amount, NOx, EVC, and the amount of internal EGR gas are shown as various parameters. The intake air amount and NOx are indicated by broken lines even when the EVC is not particularly changed.

  When the EVC is not particularly changed, the intake air amount and NOx change in the same manner as described above with reference to FIG. 7 after the accelerator opening is changed. Then, when the excessive supply of the intake air amount occurs, the actual EGR rate becomes smaller than the target EGR rate. On the other hand, the valve gear 1B individually performs EVC retardation when the actual EGR rate is smaller than the target EGR rate during transient operation, and increases the retardation amount as the actual EGR rate is smaller. Change EVC. And according to this, internal EGR gas increases, and intake air amount follows target air amount. As a result, the occurrence of NOx spikes is prevented or suppressed. Thus, the valve gear 1B that adjusts the amount of the internal EGR gas can suitably adjust the amount of the internal EGR gas during the transient operation in the following points.

  FIG. 15 is a second explanatory diagram of the valve characteristics that are made variable by the valve gear 1B. FIG. 15A shows changes in the lift amounts of the intake and exhaust valves 54 and 55 when the retarding of the EVC is individually performed by the valve gear 1B. FIG. 15 (b) has the same configuration as in FIG. 6 (b), and FIG. 15 (c) has the same configuration as in FIG. 6 (c), and intake / exhaust valves 54, 55 when retarding the EVC. The change of the lift amount of each is shown. Regarding the lift amount of the exhaust valve 55, the solid line indicates the lift amount during steady operation, and the broken line indicates the lift amount during transient operation.

  In the case shown in FIG. 15A, the valve overlap amount of the intake / exhaust valves 54 and 55 can be increased by individually performing the retard of the EVC with a constant lift amount. Thereby, the amount of the internal EGR gas can be adjusted by increasing the amount of the internal EGR gas. In the case shown in FIG. 15 (a), the EVO is retarded individually to maintain the state where the EVO is controlled to the optimum phase from the viewpoint of the balance between expansion work and extrusion loss. it can.

  On the other hand, in the case shown in FIG. 15B, while EVC can be retarded with a constant lift amount, EVO is similarly retarded. Therefore, in this case, the same situation as described above with reference to FIG. 13B may occur. In addition, in the case shown in FIG. 15C, the retard angle of EVC can be individually performed, while the lift amount increases as the operating angle increases. For this reason, in this case, the same situation as described above with reference to FIG.

  Therefore, the valve operating apparatus 1B performs the retardation of the EVC individually when the actual EGR rate is smaller than the target EGR rate during the transient operation, so that the above-described situation occurs in accordance with the change in the EVO and the change in the lift amount. The amount of the internal EGR gas can be suitably adjusted during the transient operation in that the amount of the internal EGR gas can be increased while preventing this. Thus, specifically, for example, generation of NOx spikes can be prevented or suppressed.

  In this way, the valve gear 1B individually performs the advance and retard of the EVC during the transient operation, so that the difference between the actual EGR rate and the target EGR rate becomes small so that the actual EGR rate and the target EGR rate are reduced. Accordingly, the EVC is individually changed. As a result, the amount of internal EGR gas can be suitably adjusted for each of cases where the amount of internal EGR gas needs to be reduced and when it needs to be increased.

  When the actual EGR rate is larger than the target EGR rate, the valve gear 1B changes the EVC so that the advance amount becomes larger as the actual EGR rate is larger, thereby reducing the amount of internal EGR gas. It is also preferable in that the internal EGR gas can be reduced depending on the degree of necessity. Further, when the actual EGR rate is smaller than the target EGR rate, it is necessary when the internal EGR gas needs to be increased by changing the EVC so that the retardation amount increases as the actual EGR rate becomes smaller. It is also preferable in that the amount of internal EGR gas can be increased according to the degree.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  For example, the valve gear individually changes the IVO according to the actual EGR rate and the target EGR rate so that the difference between the actual EGR rate and the target EGR rate becomes small during the transient operation of the internal combustion engine, and individually sets the EVC. You may change to In this case, the variable valve mechanism can be realized by a combination of the variable valve mechanism 57A and the variable valve mechanism 57B, for example.

  For example, when the actual EGR rate is larger than the target EGR rate, it is not necessarily limited to the case where there is a supercharging delay during transient operation. Further, when the actual EGR rate is smaller than the target EGR rate, the amount of EGR gas is not necessarily insufficient due to the recirculation delay of the external EGR gas during transient operation.

  For example, the engine is not necessarily limited to a compression self-ignition engine. In this regard, the engine may be a spark ignition engine such as a gasoline engine. Even in this case, deterioration in fuel consumption and exhaust emission can be suppressed by realizing good combustion.

Valve train 1A, 1B
Engine 50A, 50B
Intake valve 54
Exhaust valve 55
Variable valve mechanism 57A, 57B
ECU 70A, 70B

Claims (3)

A variable valve mechanism that can individually change the opening timing and closing timing of at least one of the intake valve and the exhaust valve provided for the combustion chamber of the engine with a constant lift amount,
During transient operation of the engine, the actual EGR rate that is the actual value of the EGR rate that is the ratio of the amount of exhaust gas recirculated by exhaust gas recirculation to the total amount of gas sucked into the cylinder and the target that is the target value At least one of the opening timing of the intake valve and the closing timing of the exhaust valve is individually changed according to the actual EGR rate and the target EGR rate so that the deviation from the EGR rate becomes small The valve operating device of the engine. A valve operating apparatus for an engine according to claim 1,
When the actual EGR rate is larger than the target EGR rate, the engine operation for individually performing at least one of the retarded timing of the intake valve opening timing and the advanced timing of the exhaust valve closing timing. Valve device. A valve operating apparatus for an engine according to claim 1,
When the actual EGR rate is smaller than the target EGR rate, the engine operation that individually performs at least one of the advance angle of the intake valve opening timing and the retard angle of the exhaust valve closing timing is individually performed. Valve device.

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