JP2020037908A - Control device of internal combustion engine - Google Patents

Abstract

To utilize delay closing of an intake valve to an intake bottom dead center while suppressing rise of oil, in a control device of an internal combustion engine including a variable valve device including a function for making an opening/closing period of the intake valve variable while fixing a working angle of the intake valve.SOLUTION: A control device controls an internal combustion engine including a variable valve device having a function for making an opening/closing period of an intake valve variable while fixing a working angle of the intake valve, and a function for making a negative valve overlap (O/L) period when both of the intake valve and an exhaust valve are closed, variable. A driving mode by the variable valve device includes a delay closing mode for delaying a closing period IVC of the intake valve with respect to the intake bottom dead center, and forming the negative O/L period in an intake stroke. The control device controls the variable valve device S106, S108 so that the negative O/L period positioned in the intake stroke becomes short in a case where a cylinder internal pressure of the intake stroke during the execution of the delay closing mode is less than a negative threshold value S102 (Yes).SELECTED DRAWING: Figure 6

Description

  The present invention relates to a control device for an internal combustion engine.

  For example, Patent Literature 1 discloses a hybrid vehicle including an internal combustion engine. This internal combustion engine includes an electric VVT (Variable Valve Timing) device for changing the operation characteristics of the intake valve. In this hybrid vehicle, in order to reduce the compression pressure in the cylinder when the internal combustion engine is started, decompression control is performed using an electric VVT device to delay the closing timing of the intake valve from the intake bottom dead center. More specifically, according to the decompression control, the amount of retard of the closing timing of the intake valve with respect to the intake bottom dead center is increased.

JP-A-2006-205195

  The electric VVT device described in Patent Literature 1 is a “fixed operating angle” mechanism in which the opening and closing timing of the intake valve is variable while the operating angle of the intake valve is fixed. Therefore, when the closing timing of the intake valve is retarded using the electric VVT device in the decompression control, the opening timing of the intake valve is also retarded. As a result, when a negative valve overlap period in which both the intake valve and the exhaust valve are closed is formed during the intake stroke, the in-cylinder pressure becomes negative. As a result, there is a possibility that a phenomenon (so-called “oil rising”) in which oil existing between the piston and the cylinder bore wall is sucked into the combustion chamber side.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a variable valve operating device including a function of changing the opening / closing timing of an intake valve while fixing the operating angle of the intake valve. An object of the present invention is to make it possible to use the late closing of an intake valve with respect to the intake bottom dead center while suppressing oil rise in a control device for an internal combustion engine.

The control device for an internal combustion engine according to the present invention has a function of changing the opening / closing timing of the intake valve while fixing the operating angle of the intake valve, and a negative valve overlap period in which the intake valve and the exhaust valve are both closed. And an internal combustion engine provided with a variable valve device having a function of making the variable.
The driving mode by the variable valve operating device includes a late closing mode in which the closing timing of the intake valve is retarded from the intake bottom dead center, and the negative valve overlap period is formed during the intake stroke.
When the cylinder pressure in the intake stroke is less than a negative threshold during the execution of the late closing mode, the control device may control the negative valve overlap period located in the intake stroke to be shorter. Control the variable valve device.

  According to the present invention, when the in-cylinder pressure in the intake stroke is less than the negative threshold value during the execution of the late closing mode, the variable valve operating device is configured to shorten the negative valve overlap period located in the intake stroke. Controlled. Thus, a decrease in the in-cylinder pressure (combustion chamber pressure) during execution of the slow closing mode can be suppressed. Therefore, it is possible to use the late closing of the intake valve with respect to the intake bottom dead center while suppressing oil rise.

FIG. 1 is a diagram for describing a system configuration according to a first embodiment of the present invention. FIG. 8 is a diagram illustrating an operation example of a valve timing selected when a decompression mode is selected. It is the figure which represented the rise of oil typically. FIG. 4 is a diagram illustrating a relationship between an in-cylinder pressure and an engine rotation speed NE in a state where a throttle valve is closed. It is a figure for explaining in-cylinder negative pressure control. 6 is a flowchart illustrating a routine of a process related to in-cylinder negative pressure suppression control during execution of a decompression mode according to Embodiment 1 of the present invention. It is a figure for explaining an effect of in-cylinder negative pressure control.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the embodiments described below, when referring to the number of each element, such as the number, quantity, amount, range, etc., unless otherwise specified or in principle clearly specified by the number, the reference The present invention is not limited to the numbers set forth above. In addition, structures, steps, and the like described in the embodiments described below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

1. Example of System Configuration FIG. 1 is a diagram for explaining a system configuration according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine (for example, a spark ignition engine) 10. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. The internal combustion engine 10 is, for example, a hybrid vehicle including an electric motor (not shown) as a power source together with the internal combustion engine 10. The internal combustion engine 10 is a naturally aspirated engine, but may be a supercharged engine.

  A piston 14 is arranged in each cylinder 12 of the internal combustion engine 10. The piston 14 reciprocates inside the cylinder 12. Each cylinder 12 includes a combustion chamber 16 formed on the top side of a piston 14. An intake passage 18 and an exhaust passage 20 communicate with the combustion chamber 16. An airflow sensor 22 that outputs a signal corresponding to the intake air flow rate is provided near the inlet of the intake passage 18. An electronically controlled throttle valve 24 is disposed in the intake passage 18 downstream of the air flow sensor 22.

  The internal combustion engine 10 includes a fuel injection valve 26 for each cylinder 12. The fuel injection valve 26 injects fuel to the intake port 18a as an example. However, a fuel injection valve that injects fuel directly into the cylinder 12 may be provided instead of, or in addition to, the fuel injection valve 26. In each cylinder 12, an ignition plug 28 of an ignition device and an in-cylinder pressure sensor 30 for detecting an in-cylinder pressure are arranged. Further, the internal combustion engine 10 includes an intake valve 32 that opens and closes the intake port 18a, and an exhaust valve 34 that opens and closes the exhaust port 20a.

  The “variable valve operating device” included in the internal combustion engine 10 for driving the intake valve 32 and the exhaust valve 34 has a function of changing the opening / closing timing of the intake valve 32 while fixing the operating angle of the intake valve 32, A function of making the “negative valve overlap period” in which both the valve 32 and the exhaust valve 34 are closed variable. In order to realize these functions, the variable valve train includes an intake variable valve train 36 and an exhaust variable valve train 38.

  The former function (the variable phase function of the intake valve 32) is realized by the variable intake valve operating device 36 continuously varying the phase of the intake valve 32 during the valve opening period within a predetermined crank angle range. More specifically, the intake variable valve operating device 36 has, as an example, an electric variable valve timing mechanism that can change the rotation phase of the camshaft with respect to the rotation phase of the crankshaft using an electric motor (not shown). The exhaust variable valve train 38 has, as an example, a hydraulic variable valve timing mechanism that can change the rotational phase of the camshaft relative to the rotational phase of the crankshaft using hydraulic pressure. The latter function (change of the negative valve overlap period) can be realized by retarding the closing timing EVC of the exhaust valve 34 using the exhaust variable valve operating device 38. Further, the latter function can be realized by advancing the opening timing IVO of the intake valve 32 by using the intake variable valve operating device 36 instead of or together with the retarding of the closing timing EVC. In addition, according to the electric type, the variable width of the valve timing can be set wider than that of the hydraulic type.

  The system according to the present embodiment includes a control device 40 for controlling the internal combustion engine 10. The control device 40 is an electronic control unit (ECU) having a processor 40a and a memory 40b. The memory 40b stores a program for controlling the internal combustion engine 10. The processor 40a reads a program from the memory 40b and executes the program. The control device 40 may be composed of a plurality of ECUs.

  The control device 40 captures sensor signals from various sensors. The various sensors include, for example, a crank angle sensor 42 in addition to the airflow sensor 22 described above. The crank angle sensor 42 outputs a signal corresponding to the crank angle. The control device 40 can calculate the engine speed NE using the signal from the crank angle sensor 42. The processor 40a executes various programs using the received sensor signals, and executes the above-described actuators (the throttle valve 24, the fuel injection valve 26, the ignition device, the intake variable valve device 36, and the exhaust variable valve device 38). ) Is output.

2. Valve timing control 2-1. FIG. 2 is a diagram illustrating an operation example of the valve timing selected when the decompression mode is selected. When starting the engine (more specifically, during cranking), the torque required to start the engine is reduced by performing decompression (hereinafter abbreviated as "decompression") to release the compression pressure in the cylinder. can do. The drive modes of the intake and exhaust valves 32 and 34 by the intake variable valve operating device 36 and the exhaust variable valve operating device 38 include a “decompression mode”. In the decompression mode, decompression is performed when the engine is started by using the late closing of the intake valve 32.

  More specifically, in the decompression mode, as shown in FIG. 2, the intake variable valve operating device 36 is controlled so as to close the intake valve 32 later than the intake bottom dead center (hereinafter abbreviated as “BDC”). . The valve opening period (operating angle) of the intake valve 32 is, for example, 190 ° CA, which is a small operating angle. In the example shown in FIG. 2, the intake valve 32 is opened by the intake variable valve device 36 at the opening timing IVO (60 ° CA before the intake bottom dead center) during the intake stroke, and the closing timing IVC (at the intake downward stroke) during the compression stroke. It is controlled to close at 130 ° CA after the dead center. Note that the decompression mode corresponds to an example of the “slow closing mode” according to the present invention.

  In addition, in the internal combustion engine 10 of the present embodiment, after the end of the decompression mode, the early closing Miller cycle operation mode is basically executed by advancing the closing timing IVC beyond BDC. Decompression in a conventional internal combustion engine that performs the early closing Miller cycle operation mode has been realized by increasing the amount of early closing (= IVC-BDC) using a mechanism of "variable working angle type". Here, when the early closing Miller cycle operation mode is performed using the “fixed working angle type” mechanism, there are the following problems. That is, when the early closing amount is increased, the advance amount of the opening timing IVO increases in conjunction therewith, and the lift amount of the intake valve near the exhaust top dead center increases. As a result, it is necessary to deepen the valve recess provided in the piston. This may cause a reduction in gas turbulence in the cylinder. In view of this point, in the present embodiment using the “fixed working angle type” intake variable valve operating device 36, the decompression mode at the time of starting the engine is performed using “slow closing”, and then the early closing mirror cycle operation is performed. Switch to "early close" to execute the mode. As a result, the decompression and the early closing combustion can be performed while reducing the cost by adopting the “fixed working angle type” and without increasing the valve recess (in a state where the gas turbulence in the cylinder 12 is appropriately secured). Can be compatible.

2-2. Problems Associated with Use of the Late-Close Decompression Mode When the closing timing IVC is retarded in the decompression mode using the “fixed working angle” intake variable valve device 36, the opening timing IVO is also retarded. As a result, as illustrated in FIG. 2, a negative valve overlap (O / L) period during which both the intake valve 32 and the exhaust valve 34 are closed is formed during the intake stroke. When a negative O / L period is formed in the intake stroke in which the piston 14 descends, the in-cylinder pressure becomes a negative pressure and a vacuum state is established (vacuum period).

  More specifically, in the example shown in FIG. 2, the closing timing EVC of the exhaust valve 34 is the exhaust top dead center (TDC). For this reason, in this example, a vacuum is drawn during the crank angle period from TDC to the opening timing IVO. Further, in an example in which the closing timing EVC is retarded from TDC, a vacuum is drawn during the crank angle period from the closing timing EVC to the opening timing IVC.

  FIG. 3 is a diagram schematically showing the rise of oil. When the in-cylinder pressure (the pressure in the combustion chamber 16) decreases as described above, the phenomenon that lubricating oil (oil) existing between the piston 14 and the cylinder bore wall 44 is sucked into the combustion chamber 16 as shown in FIG. So-called “oil rise”) may occur. The oil sucked into the combustion chamber 16 is consumed after being mixed with air and discharged or subjected to combustion. Thus, when the oil rises, the oil consumption increases. More specifically, in a hybrid vehicle in which the internal combustion engine 10 is intermittently stopped during traveling, there is a concern that the oil may increase each time the engine start accompanied by the decompression mode is repeatedly executed, thereby increasing the oil consumption. You. In addition, there is a concern that the combustion of the oil may increase the particulate matter PM and the PN (the number of PM particles).

  FIG. 4 is a diagram illustrating a relationship between the in-cylinder pressure and the engine rotation speed NE when the throttle valve 24 is closed. As shown in FIG. 4, as the engine speed NE increases, the in-cylinder pressure decreases. For this reason, if the decompression mode is used in the process of starting the internal combustion engine 10 and increasing the engine rotational speed NE, the oil tends to rise as the engine rotational speed NE increases. Therefore, valve timing control for maintaining the in-cylinder pressure during execution of the decompression mode at a certain value or more is required.

2-3. Outline of valve timing control (in-cylinder negative pressure suppression control) during decompression mode In view of the above-described problem, in the present embodiment, during execution of the decompression mode (late closing mode), the in-cylinder pressure during the intake stroke is less than a negative threshold. If so, the intake variable valve operating device 36 is controlled so that the negative O / L period located in the intake stroke is shortened (in-cylinder negative pressure suppression control). The in-cylinder pressure during one cycle takes a minimum value during the intake stroke as shown in FIG. 7 described later. Therefore, the in-cylinder negative pressure suppression control can be rephrased as control executed when the minimum value of the in-cylinder pressure is less than the threshold value during execution of the decompression mode. According to the in-cylinder negative pressure suppression control, the minimum value of the in-cylinder pressure is controlled to be equal to or more than the threshold, and the threshold is hereinafter referred to as “(control) target value”. Also called.

  FIG. 5 is a diagram for explaining the in-cylinder negative pressure suppression control. In the in-cylinder negative pressure suppression control according to the present embodiment, when the minimum value of the in-cylinder pressure is less than the target value (negative threshold), first, as shown in FIG. (VVT phase) is executed. Thereby, the closing timing EVC of the exhaust valve 34 is retarded, so that the evacuation period (negative O / L period) is shortened as compared with the valve timing shown in FIG. For this reason, the reduction range of the in-cylinder pressure can be reduced. As a result, oil consumption can be suppressed.

  In the in-cylinder negative pressure suppression control of the present embodiment, the closing timing EVC is at the most retarded position in a situation where the minimum value of the in-cylinder pressure is less than the target value. If it cannot be performed, the advance of the closing timing IVC of the intake valve 32 is executed. Although not shown, the evacuation period (negative O / L period) can also be shortened by such advance of the closing timing IVC.

2-4. FIG. 6 is a flowchart showing a routine of a process related to in-cylinder negative pressure suppression control during execution of the decompression mode according to Embodiment 1 of the present invention. Note that the processing of this routine is repeatedly executed for each cylinder and for each cycle during the execution of the decompression mode when the engine is started.

  In the routine shown in FIG. 6, the control device 40 first obtains the minimum value of the in-cylinder pressure during one cycle (the minimum value during the intake stroke) based on the in-cylinder pressure history of the most recent cycle (step S100). In the present step S100, as an example, the in-cylinder pressure history is acquired using the sensor value of the in-cylinder pressure sensor 30. In an internal combustion engine in which the in-cylinder pressure sensor is not installed in some or all cylinders, the minimum value of the in-cylinder pressure of a cylinder having no in-cylinder pressure sensor may be estimated by, for example, the following method. . That is, the value of the in-cylinder pressure for each predetermined crank angle is determined by the engine rotation speed, the intake pressure (intake pipe pressure), the intake temperature, the number of cycles during motoring (assuming that the engine is stopped is 0), the crank angle, and the VVT phase ( It may be estimated based on various information such as the rotation phase of the camshaft relative to the rotation phase of the crankshaft.

  Next, the control device 40 determines whether or not the minimum value of the in-cylinder pressure acquired by the process of step S100 is less than the target value (negative threshold) (step S102). As a result, if the result of this determination is negative (minimum value of in-cylinder pressure ≧ target value), the current processing cycle is ended.

  On the other hand, when the determination result of step S102 is affirmative (minimum value of in-cylinder pressure <target value), the process proceeds to step S104. In step S104, the controller 40 determines whether or not the VVT phase (EX-VVT phase) of the exhaust valve 34 is at the retard limit value (in other words, whether or not the closing timing IVC is at the most retarded position). judge.

  If the result of the determination in step S104 is negative (EX-VVT phase ≠ retardation limit value), the process proceeds to step S106. In step S106, the control device 40 controls the exhaust variable valve operating device 38 so that the EX-VVT phase is retarded by a predetermined amount (in other words, the closing timing EVC is retarded by a predetermined amount). This shortens the negative O / L period located in the intake stroke. The adjustment of the EX-VVT phase is performed using a cam angle sensor (not shown) provided for a camshaft that drives the exhaust valve 34 together with the crank angle sensor 42.

  On the other hand, if the result of the determination in step S104 is affirmative (EX-VVT phase = retardation limit value), the process proceeds to step S108. In step S108, the control device 40 controls the intake variable valve operating device 36 so that the IN-VVT phase is advanced by a predetermined amount (in other words, the opening timing IVO is advanced by a predetermined amount). This shortens the negative O / L period located in the intake stroke. Note that, similarly to the adjustment of the EX-VVT phase, the adjustment of the IN-VVT phase uses a cam angle sensor (not shown) provided for a camshaft that drives the intake valve 32 together with the crank angle sensor 42. Done.

3. Effect FIG. 7 is a diagram for explaining the effect of the in-cylinder negative pressure suppression control. More specifically, the broken line in FIG. 7 indicates the in-cylinder pressure waveform and the intake / exhaust valve timing in one cycle without performing the in-cylinder negative pressure suppression control. The solid line in the figure shows the in-cylinder pressure waveform during one cycle accompanied by the execution of the in-cylinder negative pressure suppression control (exemplifying the retardation of the EX-VVT phase (EVC)).

  FIG. 7 shows an example in which the minimum value of the in-cylinder pressure falls below the target value unless the in-cylinder negative pressure suppression control is performed, as indicated by the broken line. On the other hand, according to the in-cylinder negative pressure suppression control of the present embodiment, when the minimum value of the in-cylinder pressure is less than the target value (in other words, when the in-cylinder pressure during the intake stroke is less than the negative threshold value) , The negative O / L period located in the intake stroke is shortened.

  More specifically, when the negative O / L period is shortened due to the delay of the closing timing EVC, as shown in FIG. Begins to drop. By reducing the evacuation period (negative O / L period), the width of decrease in the in-cylinder pressure is reduced as compared with the example without the in-cylinder negative pressure suppression control (the excessive negative pressure of the in-cylinder pressure is suppressed). Is done). As a result, the in-cylinder pressure does not fall below the target value (negative threshold value) during the intake stroke. For this reason, oil rise can be suppressed, and oil consumption can be suppressed. Further, an increase in PM and PN due to oil combustion is also suppressed.

  In addition, according to the in-cylinder negative pressure suppression control of the present embodiment, if the EX-VVT phase can be retarded, the EX-VVT phase is retarded. According to such a method, since the closing timing IVC does not change, the decrease in the in-cylinder pressure can be reduced without reducing the effect of reducing the compression pressure by the decompression.

4. Another Example of Variable Valve Train In Embodiment 1 described above, the combination of the intake variable valve train 36 and the exhaust variable valve train 38 corresponds to an example of the “variable valve train” according to the present invention. I have. However, the "variable valve operating device" according to the present invention has a function of changing the opening / closing timing of the intake valve while fixing the operating angle of the intake valve, and a negative valve over in which both the intake valve and the exhaust valve are closed. The configuration is not necessarily limited to the above configuration as long as it has a function of changing the lap period. That is, another example of the “variable valve operating device” may be only the intake variable valve operating device 36. In this example, in-cylinder negative pressure suppression control is executed using only the advance angle of the IN-VVT phase (opening timing IVO).

Reference Signs List 10 internal combustion engine 12 cylinder 14 piston 16 combustion chamber 18 intake passage 20 exhaust passage 30 in-cylinder pressure sensor 32 intake valve 34 exhaust valve 36 intake variable valve operating device 38 exhaust variable valve operating device 40 control device

Claims (1)

A variable valve having a function of varying the opening / closing timing of the intake valve while fixing a working angle of the intake valve, and a function of varying a negative valve overlap period in which the intake valve and the exhaust valve are both closed. A control device for an internal combustion engine including the device,
The drive mode by the variable valve operating device includes a late closing mode in which the closing timing of the intake valve is retarded from the intake bottom dead center, and the negative valve overlap period is formed during an intake stroke.
When the cylinder pressure in the intake stroke is less than a negative threshold during the execution of the late closing mode, the control device may control the negative valve overlap period located in the intake stroke to be shorter. A control device for an internal combustion engine, which controls a variable valve device.

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