Control device for internal combustion engine

Abstract

To promote introduction of fresh air even when back pressure is high.SOLUTION: The control device 100 executes an obtaining process of obtaining a parameter correlated with a back pressure that is a pressure in the exhaust manifold 90 upstream of a turbine wheel 24T of the turbocharger 24, a determination process of determining whether the back pressure is equal to or higher than a predetermined pressure based on the obtained parameter, and an overlap limiting process of limiting a valve overlap amount between the intake valve 81 and the exhaust valve 82 of the internal-combustion engine 10 when it is determined that the back pressure is equal to or higher than the predetermined pressure. The overlap limiting process is a process of changing the closing timing of the exhaust valve 82 such that the valve overlap amount becomes smaller than that before the execution of the overlap limiting process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] For example, Patent Document 1 describes an internal combustion engine equipped with a supercharger. The supercharger of this internal combustion engine has a nozzle vane that is an adjustment mechanism for adjusting the amount of exhaust gas supplied to the turbine wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-169641 Summary of the Invention [Problem to be solved by the invention]

[0004] When the nozzle vanes are closed, back pressure, which is the pressure in the exhaust passage upstream of the turbine wheel, increases, which can make it difficult for fresh air to enter the cylinders of the internal combustion engine. [Means for solving the problem]

[0005] A control device for an internal combustion engine that solves the above-mentioned problems is applied to an internal combustion engine that uses hydrogen as fuel and includes a variable valve mechanism that changes the valve timing of an exhaust valve and a turbocharger provided in an exhaust passage and having an adjustment mechanism that adjusts the amount of exhaust gas supplied to a turbine wheel. The control device includes a processing circuit. The processing circuit executes an acquisition process to acquire a parameter correlated with a back pressure, which is the pressure in the exhaust passage upstream of the turbine wheel; a determination process to determine whether the back pressure is equal to or greater than a predetermined pressure based on the parameter; and an overlap limiting process to limit a valve overlap amount between an intake valve and an exhaust valve of the internal combustion engine if it is determined that the back pressure is equal to or greater than the predetermined pressure. The overlap limiting process is a process that changes the closing timing of the exhaust valve so that the valve overlap amount is smaller than before the overlap limiting process was executed. [Effects of the Invention]

[0006] This internal combustion engine control system can encourage the introduction of fresh air even when back pressure is high. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 3] FIG. 3 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 4] FIG. 4 is a timing chart showing the operation of this embodiment, where (a) shows the state of the execution flag, and (b) shows the transition of the valve overlap amount. [Figure 5] FIG. 5 is a graph showing the correspondence relationship between the opening degree difference and the upper limit value in a modification of the embodiment. [Figure 6] FIG. 6 is a flowchart showing the procedure of a process executed by the control device in the modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a description will be given of one embodiment of a control device for an internal combustion engine mounted on a vehicle. <Configuration of an internal combustion engine> As shown in FIG. 1, an internal combustion engine 10 includes a cylinder block 11, a cylinder head 12, a head cover 13, and the like.

[0009] A cylinder 16 is provided in the cylinder block 11. A piston 15 is disposed in the cylinder 16. The cylinder head 12 is provided with an intake port 30 that introduces intake air into a combustion chamber 17 of the internal combustion engine 10, and an exhaust port 70 that discharges exhaust gas from the combustion chamber 17. An intake valve 81 is provided in the intake port 30. A drive system for this intake valve 81 is provided with an intake-side variable valve mechanism 85, which is a variable valve mechanism that changes the valve timing, i.e., the opening and closing timing, of the intake valve 81.

[0010] An exhaust valve 82 is provided in the exhaust port 70. The drive system of this exhaust valve 82 is provided with an exhaust-side variable valve mechanism 86, which is a variable valve mechanism that changes the valve timing, i.e., the opening and closing timing, of the exhaust valve 82.

[0011] The cylinder head 12 is provided with a direct-injection type fuel injection valve 84 that directly injects hydrogen, which is the fuel for the internal combustion engine 10, into the combustion chamber 17, and an ignition plug 23. A crankcase 19 is provided below the cylinder block 11 and houses a crankshaft 18 which is the output shaft of the internal combustion engine 10 .

[0012] An intake manifold 29 equipped with a surge tank 60 is connected upstream of the intake port 30, and the intake pipe 20 is connected upstream of the surge tank 60. The intake pipe 20, the surge tank 60, the intake manifold 29, and the intake port 30 form an intake passage of the internal combustion engine 10.

[0013] In the intake pipe 20, there are installed, in order from upstream, an air cleaner 21, an air flow meter 51, a compressor wheel 24C of a supercharger 24 driven by exhaust gas discharged from the combustion chamber 17, an intercooler 27, a supercharging pressure sensor 54, and a throttle valve 28. In addition, an intake pressure sensor 55 is installed in the surge tank 60. The opening of the throttle valve 28 is changed by an electric motor.

[0014] The air cleaner 21 filters the intake air taken into the intake pipe 20. The supercharger 24 supercharges the air in the intake pipe 20. The intercooler 27 cools the air after it has passed through the compressor wheel 24C. The throttle valve 28 adjusts the amount of intake air by adjusting the valve opening.

[0015] An air flow meter 51 detects the intake air amount GA. A boost pressure sensor 54 detects a boost pressure PTC, which is the pressure in the intake pipe 20 downstream of the compressor wheel 24C. An intake pressure sensor 55 detects an intake pressure PIM, which is the pressure in a surge tank 60.

[0016] An exhaust pipe 90 that constitutes an exhaust passage is connected downstream of the exhaust port 70. A housing that accommodates a turbine wheel 24T of the turbocharger 24 is connected midway through the exhaust pipe 90. The turbocharger 24 is a variable displacement turbocharger, and is provided with nozzle vanes 24N that are driven by an actuator. The nozzle vanes 24N are an adjustment mechanism that adjusts the amount of exhaust gas supplied to the turbine wheel 24T. By changing the opening degree of the nozzle vanes 24N, the supercharging pressure of the intake air increased by the turbocharger 24 changes.

[0017] The control device 100 controls the internal combustion engine 10. The control device 100 operates various control target devices such as the throttle valve 28, the fuel injection valve 84, the spark plug 23, the intake side variable valve mechanism 85, and the exhaust side variable valve mechanism 86. The control device 100 also operates various control target devices such as the WGV 93 and the actuator of the nozzle vane 24N.

[0018] The control device 100 includes a CPU 110 that performs arithmetic processing, a memory 120 that stores control programs and data, etc. The control device 100 executes various control-related processes by having the CPU 110 execute the programs stored in the memory 120.

[0019] The control device 100 receives detection signals from the air flow meter 51, the boost pressure sensor 54, and the intake pressure sensor 55 described above. Furthermore, detection signals from various other sensors are also input to the control device 100. For example, the control device 100 receives a detection signal from an accelerator operation amount sensor 52 that detects an accelerator operation amount ACCP, which is the amount of operation of an accelerator pedal that adjusts the output of the internal combustion engine 10. Furthermore, the control device 100 receives a detection signal from a throttle sensor 53 that detects a throttle opening TA, which is the opening of the throttle valve 28. Furthermore, the control device 100 receives a detection signal from a crank angle sensor 50 that detects the rotation angle (crank angle) of the crankshaft 18 to calculate the engine rotation speed NE, and a detection signal from a vehicle speed sensor 56 that detects the vehicle speed SP.

[0020] The control device 100 calculates the engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL is a parameter that determines the amount of air filled into the combustion chamber 17, and is the ratio of the amount of inflow air per combustion cycle of one cylinder to a reference inflow air amount. The reference inflow air amount is variably set according to the engine speed NE.

[0021] The control device 100 calculates an intake-side target value VTint, which is a target valve timing for the intake valve 81, based on the engine speed NE, the engine load factor KL, and the like. After calculating this intake-side target value VTint, the control device 100 controls the drive of the intake-side variable valve mechanism 85 so that the actual valve timing of the intake valve 81 coincides with the intake-side target value VTint. In this embodiment, the state in which the valve timing of the intake valve 81 is at the most retarded timing is set to an initial value of "0," and the valve timing of the intake valve 81 is controlled using the amount of advance of the valve timing from this initial value.

[0022] The control device 100 calculates a target overlap value OLt, which is a target value for the valve overlap when the opening period of the intake valve 81 and the opening period of the exhaust valve 82 overlap. Then, based on this target overlap value OLt and the intake-side target value VTint, the control device 100 calculates an exhaust-side target value VText, which is a target valve timing for the exhaust valve 82. After calculating this exhaust-side target value VText, the control device 100 controls the drive of the exhaust-side variable valve mechanism 86 so that the actual valve timing of the exhaust valve 82 matches the exhaust-side target value VText. Note that in this embodiment, the state in which the valve timing of the exhaust valve 82 is at the most advanced timing is set to an initial value of "0," and the valve timing of the exhaust valve 82 is controlled using the amount of retardation of the valve timing from this initial value.

[0023] The control device 100 calculates the required torque based on the accelerator operation amount ACCP, the vehicle speed SP, and the like. Then, the control device 100 controls the required output Pe of the internal combustion engine 10 so as to satisfy the required torque. Here, hydrogen gas, which is the fuel for the internal combustion engine 10, has a wider range of combustible mixtures than gasoline, and can be combusted even in lean mixtures. Therefore, the control device 100 performs lean combustion, which burns a lean mixture, which is a mixture with an air-fuel ratio higher than the stoichiometric air-fuel ratio, and adjusts the output of the internal combustion engine 10 through the following combustion control.

[0024] That is, the control device 100 sets a required injection amount Qd based on the required output Pe. The required injection amount Qd is a target value of fuel injected from the fuel injection valve 84. The control device 100 calculates a required air amount GAd, which is a target value of the intake air amount required to obtain the target air-fuel ratio AFt, based on the target air-fuel ratio AFt and the required injection amount Qd. The target air-fuel ratio AFt in this embodiment is a lean air-fuel ratio, for example, an excess air ratio λ=2.5 to 3.0. Then, the control device 100 controls the fuel injection valve 84 so as to obtain the required injection amount Qd. Furthermore, the control device 100 controls the opening of the throttle valve 28 and the boost pressure of the turbocharger 24 so as to obtain the required air amount GAd.

[0025] When controlling the boost pressure of the turbocharger 24, the control device 100 calculates a target boost pressure PTCt. The control device 100 calculates a basic opening VNb of the nozzle vanes 24N based on the target boost pressure PTCt. The control device 100 calculates a feedback value FBV according to the deviation between the target boost pressure PTCt and the actual boost pressure PTC. The feedback value FBV is set to a larger value as the value obtained by subtracting the boost pressure PTC from the target boost pressure PTCt increases. The larger the feedback value FBV, the smaller the opening of the nozzle vanes 24N in the closing direction. The control device 100 calculates a command opening VN of the nozzle vanes 24N based on the basic opening VNb and the feedback value FBV. The control device 100 then controls the actuator of the nozzle vanes 24N so that the actual opening of the nozzle vanes 24N matches the command opening VN.

[0026] <About overlap limit processing> For example, when the actual boost pressure PTC is lower than the target boost pressure PTCt during a transient period in which the vehicle accelerates from a steady state, it is preferable to reach the target boost pressure PTCt more quickly. In this regard, in this embodiment, as described above, the feedback value FBV is calculated according to the deviation between the target boost pressure PTCt and the actual boost pressure PTC. Then, when calculating the command opening VN of the nozzle vanes 24N, this feedback value FBV is taken into consideration, so the opening of the nozzle vanes 24N is closed more than the basic opening VNb. When the opening of the nozzle vanes 24N becomes smaller, the energy imparted from the exhaust gas to the turbine wheel 24T increases, and the rotational speed of the turbine wheel 24T increases. When the rotational speed of the turbine wheel 24T increases, the rotational speed of the compressor wheel 24C also increases, so the actual boost pressure PTC increases earlier.

[0027] If the opening of the nozzle vane 24N decreases in the closing direction, the back pressure, which is the pressure in the exhaust pipe 90 upstream of the turbine wheel 24T, increases, which may make it difficult for fresh air to enter the cylinders of the internal combustion engine 10. This condition can be improved by reducing the valve overlap, which is the overlap between the opening periods of the intake valve 81 and the exhaust valve 82. Therefore, the control device 100 executes the overlap limiting process described below.

[0028] Fig. 2 shows the procedure of the process executed by the control device 100. The process shown in Fig. 2 is realized by the CPU 110 executing a program stored in the memory 120 of the control device 100 at predetermined intervals. Note that, below, the step number of each process is represented by a number preceded by "S."

[0029] 2, the control device 100 executes an acquisition process to acquire the basic opening VNb and the command opening VN of the nozzle vane 24N (S100). The command opening VN of the nozzle vane 24N is a parameter correlated with the back pressure described above. Note that, instead of the command opening VN, the actual opening of the nozzle vane 24N may be acquired.

[0030] Next, the control device 100 executes a determination process to determine whether the back pressure is equal to or greater than a predetermined pressure and therefore excessive (S110). The predetermined pressure is a back pressure at which the amount of fresh air introduced into the cylinder is reduced to such an extent that it is necessary to execute the overlap limiting process described below. In the process of S110, the control device 100 calculates an opening difference ΔVN, which is the difference between the acquired basic opening VNb and the command opening VN. The value of the opening difference ΔVN increases as the command opening VN is closer to the closing side than the basic opening VNb. Then, if the opening difference ΔVN is equal to or greater than a predetermined determination value α, it is determined that the back pressure is equal to or greater than the predetermined pressure and therefore excessive. The determination value α is a value corresponding to the above-mentioned predetermined pressure.

[0031] In the process of S110, if it is determined that the back pressure is equal to or greater than the predetermined pressure and is excessive (S110: YES), the control device 100 sets the execution flag F to "ON" (S120). The execution flag F is a flag that indicates whether or not the overlap limiting process can be executed. When the execution flag F is "ON", the overlap limiting process is executed. On the other hand, when the execution flag F is set to "OFF", the overlap limiting process that is currently being executed is stopped.

[0032] On the other hand, if it is determined in the processing of S110 that the back pressure is not equal to or greater than the predetermined pressure and is not excessive (S110: NO), the control device 100 determines whether the duration Td is equal to or greater than the clear time Tc (S130). The duration Td is the time during which the opening difference ΔVN has continued to be less than the determination value α. The clear time Tc is a value that is preset to set the execution flag F to "OFF" and is set to suppress hunting of the execution flag F.

[0033] In the process of S130, if it is determined that the duration Td is equal to or greater than the clear time Tc (S130: YES), the control device 100 sets the execution flag F to "OFF" (S140).

[0034] Then, when the process of S120 or the process of S140 is executed, or when a negative determination is made in the process of S130, the control device 100 ends this process in the current execution cycle.

[0035] Fig. 3 shows the procedure of the process executed by the control device 100. The process shown in Fig. 3 is realized by the CPU 110 executing a program stored in the memory 120 of the control device 100 at predetermined intervals.

[0036] In the series of processes shown in FIG. 3, the control device 100 acquires the execution flag F and determines whether the value is "ON" (S200). If it is determined that the execution flag F is "ON" (S200: YES), the control device 100 executes the overlap restriction process (S210).

[0037] The overlap limiting process is a process for changing the closing timing of the exhaust valve 82 so that the valve overlap amount is smaller than before the overlap limiting process was executed. In this overlap limiting process, in order to reduce the valve overlap amount, a value obtained by applying upper limit guard processing to overlap base value OLb is substituted for target overlap value OLt. The overlap base value OLb is a basic value of the valve overlap amount set by the control device 100 based on engine operating conditions such as the engine speed NE and the engine load factor KL. An upper limit value OLupp for applying the upper limit guard processing is set to a value smaller than overlap base value OLb. A minimum value A and a maximum value B are preset for this upper limit value OLupp. The minimum value A is set to the upper limit value OLupp while the overlap limiting process is being executed. This minimum value A is set to a value smaller than at least the minimum value of overlap base value OLb, such as "0°." Meanwhile, the maximum value B is set to the upper limit value OLupp while the overlap limiting process is not being executed. This maximum value B is set to a value larger than at least the maximum value of overlap base value OLb, such as "100°."

[0038] Furthermore, when executing the overlap restriction process, the control device 100 executes the following process. (a): At the start of overlap limiting processing, in order to suppress a sudden change in intake air volume that occurs when the upper limit value OLupp switches from maximum value B to minimum value A, a gradual change value OLc is calculated by gradually changing the upper limit value OLupp. Then, the upper limit guard of the overlap base value OLb is executed using this gradual change value OLc.

[0039] (b) In the gradual change process of the upper limit value OLupp, which is executed at the start of the overlap limit process, the value of the overlap base value OLb at the start of the overlap limit process is substituted for the initial value of the gradual change value OLc. This allows the upper limit of the overlap base value OLb to be promptly protected.

[0040] (c) At the end of the overlap limiting process, the upper limit value OLupp is gradually changed to calculate a gradually changed value OLc in order to suppress a sudden change in the intake air amount that occurs when the upper limit value OLupp switches from minimum value A to maximum value B. Then, the upper limit of the overlap base value OLb is guarded using this gradually changed value OLc.

[0041] The control device 100 then calculates the exhaust-side target value VText based on the upper limit-guarded target overlap value OLt. Because the target overlap value OLt has been subjected to upper limit guard processing, its value is smaller than when the upper limit guard processing is not performed. Therefore, the amount of retardation of the valve timing of the exhaust valve 82 calculated based on the upper limit-guarded target overlap value OLt is smaller than when the upper limit guard processing is not performed, and this retardation amount is limited.

[0042] Then, when the process of S210 above has been executed, or when a negative determination is made in the process of S200 above, the control device 100 ends this process in the current execution cycle. <Operation of this embodiment> 4(a) shows the state of the execution flag F, and FIG. 4(b) shows the change in the valve overlap amount over time. In FIG. 4(b), the solid line L1 shows the change in the target overlap value OLt, the dashed line L2 shows the change in the overlap base value OLb, the one-dot chain line L3 shows the change in the upper limit value OLupp, and the two-dot chain line L4 shows the change in the gradual-change value OLc.

[0043] At time t1, when it is determined that the back pressure is high and the execution flag F is switched from OFF to ON, the overlap limiting process is started and the upper limit value OLupp is switched from maximum value B to minimum value A. Also, the overlap base value OLb at time t1 is set to the initial value of the gradual change value OLc.

[0044] The gradual-change value OLc gradually decreases toward the upper limit value OLupp, which is set to the minimum value A, and finally coincides with the upper limit value OLupp (at time t2). During the period in which the gradual-change value OLc is calculated (from time t1 to time t2), the overlap base value OLb is greater than the gradual-change value OLc, so the overlap base value OLb is limited by the gradual-change value OLc. Therefore, during the period from time t1 to time t2, the gradual-change value OLc is substituted for the target overlap value OLt.

[0045] After time t2, the overlap base value OLb is greater than the upper limit value OLupp set to the minimum value A, so the overlap base value OLb is limited by the upper limit value OLupp. Therefore, after time t2, the upper limit value OLupp set to the minimum value A is substituted for the target overlap value OLt.

[0046] At time t3, when the execution flag F switches from ON to OFF, the overlap limiting process is stopped, and the upper limit value OLupp switches from the minimum value A to the maximum value B. Then, the minimum value A of the upper limit value OLupp is set as the initial value of the gradual change value OLc.

[0047] The gradual change value OLc gradually increases toward the upper limit value OLupp set to the maximum value B, and finally coincides with the upper limit value OLupp set to the maximum value B. As the gradual-change value OLc increases, the overlap base value OLb is greater than the gradual-change value OLc during the period from time t3 to time t4, during which the gradual-change value OLc serves as an upper limit guard for the overlap base value OLb. Therefore, the gradual-change value OLc is substituted for the target overlap value OLt during the period from time t3 to time t4.

[0048] On the other hand, as the gradual-change value OLc increases, after time t4 when the gradual-change value OLc becomes greater than the overlap base value OLb, the overlap base value OLb is no longer limited by the gradual-change value OLc, and therefore, after time t4, the overlap base value OLb is substituted for the target overlap value OLt.

[0049] <Effects of this embodiment> (1) The control device 100 executes an acquisition process to acquire parameters correlated with the back pressure, which is the pressure in the exhaust pipe 90 upstream of the turbine wheel 24T. The control device 100 executes a determination process to determine whether the back pressure is equal to or greater than a predetermined pressure based on the parameters. If the control device 100 determines that the back pressure is equal to or greater than the predetermined pressure, it executes an overlap limiting process to limit the amount of valve overlap between the intake valve 81 and the exhaust valve 82 of the internal combustion engine 10. This overlap limiting process is a process to change the closing timing of the exhaust valve 82 so that the amount of valve overlap is smaller than before the overlap limiting process was executed.

[0050] In the internal combustion engine 10 that uses hydrogen as fuel, if fuel is injected before the intake valve 81 closes, pre-ignition or the like may occur. For this reason, it is preferable to inject fuel after the intake valve 81 closes. On the other hand, if the opening timing of the intake valve 81 is retarded, the amount of valve overlap decreases, but if the opening timing of the intake valve 81 is retarded, the closing timing of the intake valve 81 is also retarded.

[0051] When the closing timing of the intake valve 81 is retarded, the period from when the intake valve 81 closes to when the air-fuel mixture is ignited becomes shorter, thereby shortening the period during which fuel injection can be performed. In this way, when the valve timing of the intake valve 81 is changed to reduce the valve overlap, the period during which fuel injection is possible becomes shorter. For this reason, restrictions are likely to be imposed on changing the valve timing of the intake valve 81.

[0052] In this regard, in this embodiment, when the back pressure is high, the closing timing of the exhaust valve 82 is changed so that the valve overlap amount is reduced. This reduction in the valve overlap amount reduces the amount of internal EGR, which can promote the introduction of fresh air into the cylinder.

[0053] Furthermore, when reducing the valve overlap amount in the hydrogen-fueled internal combustion engine 10, the valve timing of the exhaust valve 82 is changed, rather than the valve timing of the intake valve 81, which is more likely to be restricted as described above. Therefore, it is possible to reduce restrictions on the valve timing when reducing the valve overlap amount.

[0054] (2) When the opening of the nozzle vanes 24N is controlled to be closer than the basic opening VNb, the back pressure becomes high. Therefore, in this embodiment, when the command opening VN of the nozzle vanes 24N is controlled to be closer than the basic opening VNb set based on the target boost pressure PTCt of the turbocharger 24 by the determination value α or more, it is determined that the back pressure is equal to or higher than a predetermined pressure. Therefore, it is possible to determine that the back pressure is high based on the opening of the nozzle vanes.

[0055] (3) The overlap limiting process includes setting an upper limit value OLupp, which is used to provide an upper limit guard for the overlap base value OLb, which is the basic value of the valve overlap amount, to a value smaller than the overlap base value OLb.

[0056] Therefore, during the overlap limiting process, the upper limit value OLupp for applying upper limit guard processing to the overlap base value OLb is set to a value smaller than the overlap base value OLb, thereby making it possible to reduce the valve overlap amount compared to before the overlap limiting process was executed.

[0057] <Example of change> The above-described embodiments can be modified as follows: The embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0058] When the opening of the nozzle vanes 24N is controlled to be closer to the base opening VNb set based on the engine operating state, the back pressure increases as the difference between the command opening VN of the nozzle vanes 24N and the base opening VNb increases. Therefore, when this difference is large, it is preferable to reduce the valve overlap amount.

[0059] Therefore, when the opening of the nozzle vanes 24N is controlled to be closer to the basic opening VNb that is set based on the engine operating state, the upper limit value OLupp that is set during the overlap limiting process may be set as follows: That is, when the difference between the opening of the nozzle vanes 24N and the basic opening VNb is large, the upper limit value OLupp may be set to a smaller value than when the difference is small.

[0060] As shown in FIG. 5, the upper limit value OLupp may be set so that the value of the upper limit value OLupp decreases as the opening difference ΔVN increases. According to this modification, the upper limit value OLupp can be appropriately set in accordance with the magnitude of the estimated back pressure.

[0061] As shown by the two-dot chain line in FIG. 1 , an exhaust pipe 90 of the internal combustion engine 10 is connected between a portion upstream of the turbine wheel 24T and a portion downstream of the turbine wheel 24T via a bypass passage 92. A wastegate valve (hereinafter referred to as WGV) 93, the opening of which is adjusted by an actuator, is provided in the bypass passage 92. The WGV 93 is a valve that adjusts the amount of exhaust gas flowing through the bypass passage 92. In other words, the WGV 93 is a valve that adjusts the amount of exhaust gas that bypasses the turbine wheel 24T. The opening of the WGV 93 is feedback-controlled based on the target boost pressure PTCt, similar to the control of the opening of the nozzle vanes 24N, for example. As the opening of the WGV 93 increases, the amount of exhaust gas that bypasses the turbine wheel 24T and passes through the bypass passage 92 increases, and therefore the boost pressure of the intake air increased by the turbocharger 24 decreases.

[0062] If the internal combustion engine 10 is equipped with such a WGV 93, as in the case of the nozzle vane 24N, when the WGV 93 is closed to promote an increase in the boost pressure during acceleration of the vehicle, the back pressure may increase, hindering the introduction of a new boost. Therefore, in the process of S110 shown in Fig. 2, whether the back pressure is excessive or not is determined based on the opening degree of the nozzle vane 24N, but instead, whether the back pressure is excessive or not may be determined based on the opening degree of the WGV 93.

[0063] As shown in FIG. 6, for example, the control device 100 executes processing of S300 instead of the processing of S100 shown in FIG. 2. In the processing of S300, the control device 100 executes an acquisition process to acquire a basic opening WGb and a command opening WG of the WGV 93. The basic opening WGb of the WGV 93 is set based on the target boost pressure PTCt. The command opening WG of the WGV 93 is an output value of feedback control related to the opening of the WGV 93, and the control device 100 controls the actuator of the WGV 93 so that the actual opening of the WGV 93 matches the command opening WG. The command opening VN of the WGV 93 is a parameter correlated with the back pressure described above. Note that the actual opening of the WGV 93 may be acquired instead of the command opening VN.

[0064] Next, the control device 100 executes the process of S310 instead of the process of S110 shown in FIG. 2. In the process of S310, the control device 100 executes a determination process to determine whether the back pressure is equal to or greater than a predetermined pressure and therefore excessive. The predetermined pressure is the same as the specified pressure in the process of S110. In the process of S310, the control device 100 calculates an opening difference ΔWG, which is the difference between the acquired basic opening WGb and the command opening WG. The value of the opening difference ΔWG increases as the command opening WG is closer to the closing side than the basic opening WGb. Then, if the opening difference ΔWG is equal to or greater than a predetermined determination value β, the control device 100 determines that the back pressure is equal to or greater than the predetermined pressure and therefore excessive. The determination value β is a value corresponding to the above-mentioned predetermined pressure.

[0065] In the process of S310, if it is determined that the back pressure is equal to or greater than the predetermined pressure and is excessive (S310: YES), the control device 100 sets the execution flag F to "ON" (S120) and ends this process.

[0066] On the other hand, if it is determined in the processing of S310 that the back pressure is not above the predetermined pressure and is not excessive (S310: NO), the control device 100 executes the processing of S130 and S140 described above and terminates this processing.

[0067] In this way, when the command opening WG of the WGV 93 is controlled to be closed by a predetermined value or more relative to the basic opening WGb set based on the target boost pressure PTCt, it is determined that the back pressure is excessive. If it is determined that the back pressure is excessive, the execution flag F may be set to ON and the overlap limiting process may be executed, as in the above embodiment. In this case, the same effects as in the above embodiment can be obtained.

[0068] 2, it is determined that the back pressure is excessive when the opening difference ΔVN is equal to or greater than the determination value α. In addition, other conditions for determining that the back pressure is excessive may be added, such as a condition that the feedback value FBV related to the opening of the nozzle vanes 24N is equal to or greater than a predetermined value, or a condition that the amount of change in the accelerator operation amount ACCP is equal to or greater than a predetermined value.

[0069] In the process of S110 shown in Fig. 2, whether the back pressure is excessive or not is determined based on the opening degree of the nozzle vane 24N, but instead, a sensor for detecting the back pressure may be provided, and whether the back pressure is excessive or not may be determined based on the pressure detected by the sensor.

[0070] The gradual change process of the upper limit value OLupp, which is executed at the start and end of the overlap limit process, may be omitted. The internal combustion engine 10 may be provided with a port injection type fuel injection valve that injects fuel into the intake port 30.

[0071] The internal combustion engine 10 does not have to be equipped with the intake-side variable valve mechanism 85. The control device 100 is not limited to a device equipped with a CPU and memory and executing software processing. For example, the control device 100 may be equipped with a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of the software processing performed in the above embodiments. That is, the control device 100 may include a processing circuit having any of the following configurations (a) to (c): (a) a processing circuit equipped with one or more processing devices that execute all of the above processing according to a program and one or more program storage devices, such as ROM, that store the program; (b) a processing circuit equipped with one or more processing devices and one or more program storage devices that execute part of the above processing according to a program, and one or more dedicated hardware circuits that execute the remaining processing; (c) a processing circuit equipped with one or more dedicated hardware circuits that execute all of the above processing. Program storage devices, i.e., computer-readable media, include any available media that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0072] 10...Internal combustion engine 24...Turbocharger 24C...Compressor wheel 24N...Nozzle vane 24T...Turbine wheel 28...Throttle valve 29...Intake manifold 30...Intake port 60...Surge tank 81...Intake valve 82...Exhaust valve 84...Fuel injection valve 85...Intake side variable valve mechanism 86...Exhaust side variable valve mechanism 90...Exhaust pipe 92...Bypass passage 93...Wastegate valve 100...Control device

Claims

1. A control device applicable to an internal combustion engine that uses hydrogen as fuel, the control device comprising: a variable valve mechanism that changes the valve timing of an exhaust valve; and a turbocharger that is provided in an exhaust passage and has an adjustment mechanism that adjusts the amount of exhaust gas supplied to a turbine wheel, It has a processing circuit, The processing circuitry an acquisition process for acquiring a parameter correlated with a back pressure, which is a pressure in an exhaust passage upstream of the turbine wheel; a determination process for determining whether the back pressure is equal to or greater than a predetermined pressure based on the parameter; When it is determined that the back pressure is equal to or greater than the predetermined pressure, an overlap limiting process is executed to limit a valve overlap amount between an intake valve and an exhaust valve of the internal combustion engine; The overlap limiting process is a process of changing the closing timing of the exhaust valve so that the valve overlap amount is smaller than before the overlap limiting process was executed. Control device for internal combustion engines.

2. the turbocharger is a variable displacement turbocharger and has a nozzle vane as the adjustment mechanism, the acquisition process is a process of acquiring an opening degree of the nozzle vane as the parameter, The determination process is a process of determining that the back pressure is equal to or greater than the predetermined pressure when the nozzle vane opening is controlled to be closer than the opening set based on the target supercharging pressure of the supercharger by a predetermined value or more. The control device for an internal combustion engine according to claim 1.

3. The overlap limiting process includes a process of setting an upper limit value for performing upper limit guard process on a basic value of the valve overlap amount, which is set based on an engine operating state, to a value smaller than the basic value. The control device for an internal combustion engine according to claim 1.

4. the turbocharger is a variable displacement turbocharger and has a nozzle vane as the adjustment mechanism, When the opening of the nozzle vanes is controlled to be closer than a basic opening set based on an engine operating state, the upper limit value is set to a smaller value when the difference between the opening of the nozzle vanes and the basic opening is large compared to when the difference is small. The control device for an internal combustion engine according to claim 3.

5. the adjusting mechanism is a wastegate valve that adjusts the amount of exhaust gas that bypasses the turbine wheel, the acquisition process is a process of acquiring an opening degree of the wastegate valve as the parameter, The determination process is a process for determining that the back pressure is equal to or greater than the predetermined pressure when the wastegate valve is controlled in a state where the opening degree is closed by a predetermined value or more compared to the opening degree set based on the target supercharging pressure of the supercharger. The control device for an internal combustion engine according to claim 1.

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