JP4133288B2 - Variable valve timing control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve timing control method for an internal combustion engine equipped with a variable valve timing mechanism capable of changing the opening / closing timing of at least one of an intake valve and an exhaust valve.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, some internal combustion engines (hereinafter referred to as engines) mounted on vehicles such as automobiles can change the opening and closing timings of intake valves and exhaust valves according to operating conditions. Usually, such a mechanism for changing the timing of the intake valve and the exhaust valve is called a variable valve timing mechanism, and for example, the opening timing of the intake valve with respect to the exhaust valve can be changed. The change of the opening / closing timing is executed so as to become a target opening / closing timing set according to the driving situation, and is intended to increase output, improve fuel consumption, and drivability.
[0003]
As a control of such a variable valve timing mechanism, for example, the advance angle of the intake valve is determined based on the throttle opening and the engine speed, for example, based on the opening / closing timing during idling operation, A device that sets a target opening / closing timing by advancing the opening / closing timing is known (for example, Patent Document 1). In this example, the load is determined based on the throttle opening, and it is determined whether the operating state is the partial load range or the full load range based on the throttle opening and the engine speed. In the full load range where the throttle valve is fully opened, the target valve overlap amount that defines the period during which the exhaust valve and the intake valve are simultaneously opened is made smaller than the partial load range where the throttle valve is not fully opened. Thus, torque and output are increased.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-93713
[Problems to be solved by the invention]
However, with such a configuration, if the load is estimated based on the throttle opening, the engine load, in other words, the intake air amount may not be detected accurately, so the target overlap amount setting accuracy decreases. There are things to do.
[0006]
On the other hand, the engine load is generally detected from the intake pipe pressure. In the case where the load is detected by the intake pipe pressure in this way, a map of the advance amount for the target opening / closing timing is created by the intake pipe pressure and the engine speed, and the map is used to Target opening and closing timings are determined in all operation ranges from the load range to the full load range.
[0007]
As shown in FIG. 8, the intake pipe pressure changes so as to be substantially proportional to the throttle opening when the throttle opening is small, but more than a certain opening, particularly from the opening before the throttle valve is fully opened. In the fully open state, there is almost no change, that is, almost the same value is exhibited. For this reason, the throttle valve is operated in a state where it is almost fully opened, and if output is required for acceleration or climbing thereafter, there is almost no change in the intake pipe pressure even if the operation is made to fully open. The amount does not change, and therefore the target opening / closing timing does not change, so the output requested by the driver may not be achieved.
[0008]
The object of the present invention is to eliminate such problems.
[0009]
[Means for Solving the Problems]
In other words, the variable valve timing control method for an internal combustion engine of the present invention has a throttle valve in the intake system, can adjust the intake air amount according to the throttle opening, and controls the opening / closing timing of the intake valve and the exhaust valve. In an internal combustion engine that can be operated, the internal combustion engine that controls the opening / closing timing of at least one of the intake valve and the exhaust valve by a target control amount that is set according to the operating state so that the opening / closing timing corresponds to the operating state in the valve timing control method, corresponding throttle opening is in the partial load range to full load range, if less than a predetermined opening degree that is set by a throttle opening degree to be partial load region and the boundary between the full load region determines a target control amount based on the intake pipe pressure and the engine rotational speed and, when the throttle opening is full-load range of not lower than the predetermined opening degree, the intake pipe pressure and the machine Based on the rotational speed and the throttle opening, and wherein the determining the target control amount so overlap as the exhaust valve and the intake valve throttle opening is large are open at the same time is increased.
[0010]
According to such a configuration, when the throttle opening is less than the predetermined opening, the opening / closing timing of at least one of the intake valve and the exhaust valve is determined based on the intake pipe pressure and the engine speed. The target control amount is controlled. Therefore, when the internal combustion engine is operated, for example, in a partial load range that is less than the full load range, the opening / closing timing of at least one of the intake valve and the exhaust valve with high accuracy corresponding to the actual intake air amount, It becomes possible to control the opening / closing timing according to the operating state.
[0011]
On the other hand, when the throttle opening is equal to or greater than the predetermined opening, the opening / closing timing of at least one of the intake valve and the exhaust valve is determined based on the intake pipe pressure, the engine speed, and the throttle opening. It is controlled by the target control amount. Therefore, when the internal combustion engine is operated in the full load range, the opening / closing timing of at least one of the intake valve and the exhaust valve is accurately determined according to the operation amount of the throttle valve that reflects the driver's request, It becomes possible to control the opening / closing timing according to the operating state.
[0012]
Therefore, in the entire operation state of the partial load region and the full load region of the internal combustion engine, the opening / closing timing of at least one of the intake valve and the exhaust valve is set to the opening / closing timing corresponding to the operation state at that time by the target control amount. Thus, fuel efficiency and drivability can be improved in the partial load region, and an output reflecting the driver's request can be secured in the entire load region.
[0013]
In order to simplify the control when the throttle opening is greater than or equal to the predetermined opening, when the throttle opening is greater than or equal to the predetermined opening, the target control amount set based on the intake pipe pressure and the engine speed It is preferable to determine the target control amount by correcting the basic amount with a correction amount set according to the throttle opening.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0015]
An engine 100 schematically showing the configuration of one cylinder in FIG. 1 is an automotive three-cylinder engine, and an intake system 1 of the engine 100 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown). A surge tank 3 is provided on the downstream side, and intake air from the surge tank 3 is sucked into the cylinder 38 via the intake valve 37. A fuel injection valve 5 is further provided near the end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3 on the cylinder head 39 side, and this fuel injection valve 5 is controlled by the electronic control unit 6. ing. In the exhaust system 20, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas discharged from the combustion chamber 38 a through the exhaust valve 36 is disposed in a pipe line leading to a muffler (not shown). The three-way catalyst 22 is attached at a position upstream.
[0016]
The engine 100 includes a continuously variable valve timing mechanism (hereinafter referred to as VVT) 30. The VVT 30 uses a so-called oscillating cylinder mechanism, and a rotor (not shown) fixed to the exhaust camshaft 31, a housing (not shown) fitted on the rotor, and the housing rotated with respect to the rotor. An oil control valve 32 serving as an electromagnetic four-direction switching control valve for this purpose, and a pair of gears 34 and 35 having one fixed to the housing and the other fixed to the intake camshaft 33 so as to mesh with each other.
[0017]
Then, the direction and amount of hydraulic oil flowing into and out of the housing is controlled by the oil control valve 32 to change the relative angle of the housing with respect to the rotor, so that any rotational position between the exhaust camshaft 31 and the intake camshaft 33 The valve timing is variably controlled by generating a phase difference. That is, the opening / closing timing of the exhaust valve 36 and the opening / closing of the intake valve 37 are changed by changing the opening / closing timing of the intake valve 37 while always opening / closing the exhaust valve 36 at a constant opening / closing timing with respect to the rotation of the crankshaft (not shown). The relative phase difference from the timing can be freely changed within a predetermined angle range. Specifically, the opening / closing timing of the intake valve 37 is moved to the retard side during idling, for example, to minimize overlap, which is a period in which both the exhaust valve 36 and the intake valve 37 are open, and high At the time of load, the opening / closing timing at idling is moved to the advance side by a target advance amount VTTB, which will be described later, to increase the overlap, thereby contributing to improvement in engine fuel consumption, output, or drivability. A crank sensor 41 that outputs a crank angle signal m and an N signal for cylinder discrimination is attached to one end portion of the exhaust camshaft 31, and 240 ° is provided to one end portion of the intake camshaft 33. A timing sensor 42 that outputs an intake cam signal n every rotation of the CA (crank angle) is attached.
[0018]
The electronic control device 6 is mainly configured by a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, and an output interface 11. The central processing unit 7 controls the operation of the engine 100 by executing a program described later stored in the storage device 8. Information necessary for controlling the operation of the engine 100 is input to the central processing unit 7 via the input interface 9, and the central processing unit 7 receives the control signal via the output interface 11 as fuel. Output to the injection valve 5 and the oil control valve 33. Specifically, the input interface 9 has an intake pressure signal a output from the intake pressure sensor 13 for detecting the pressure in the surge tank 3 (intake pipe pressure PM), and a rotation for detecting the engine speed NE. The engine speed signal b output from the number sensor 14, the crank angle signal m output from the crank sensor 41, the intake cam signal n output from the timing sensor 42, and the idle switch 16 for detecting the open / closed state of the throttle valve 2 Is output from the IDL signal d, the opening signal e output from the throttle opening sensor 17 for detecting the opening of the throttle valve 2, that is, the throttle opening, and the output from the water temperature sensor 18 for detecting the cooling water temperature of the engine. The water temperature signal f and the voltage signal h output from the O ₂ sensor 21 are input. On the other hand, from the output interface 11, a drive pulse INJ as a fuel injection signal f for the fuel injection valve 5, an ignition signal g for the spark plug 19, and a target control amount VTTB for the oil control valve 32. Corresponding control signals are output respectively.
[0019]
The electronic control unit 6 uses the intake pressure signal a output from the intake pressure sensor 13 and the rotation speed signal b output from the rotation speed sensor 14 as main information, and various corrections determined according to the operating state of the engine 100. The basic fuel injection time, that is, the basic injection amount is corrected by the coefficient to determine the final injection time, that is, the fuel injection amount, which is the fuel injection valve opening time, and the fuel injection valve 5 is controlled based on the determined time to A program for injecting a fuel injection amount corresponding to the operating state from the fuel injection valve 5 into the intake system 1 is incorporated.
[0020]
In addition, the electronic control unit 6 sets the opening / closing timing of at least one of the intake valve 37 and the exhaust valve 36 according to the target control amount VTTB set according to the operating state so that the opening / closing timing according to the operating state is reached. and controls, in response throttle opening TA to a partial load range to full load range, if less than a predetermined opening degree KVTFTAH to be set, based on the intake pipe pressure PM and the engine speed NE target When the control amount VTTB is determined and the throttle opening degree TA is in the full load range above the predetermined opening degree KVTTAH, the throttle opening degree TA is determined based on the intake pipe pressure PM, the engine speed NE , and the throttle opening degree TA. programming for determining a target control amount KVTFTAH so large that the exhaust valve 36 and intake valve 37 is increased overlap is open at the same time Beam is are built.
[0021]
The general procedure of this variable valve timing control program will be described with reference to FIGS. In this embodiment, in order to execute the program, the basic amount VTTBF of the target control amount VTTB is set by the basic amount map based on the intake pipe pressure PA and the engine speed NE. In this embodiment, as described above, since the opening / closing timing of the intake valve 37 during idling operation is set to the most retarded angle side, the target control amount VTTB is an advance amount for advancing the opening / closing timing. The basic amount VTTBF is set based on the intake pipe pressure PM and the engine speed NE over the entire partial load range and full load range, and as shown in FIG. 5, the throttle valve 2 is closed. In the idling operation state, neither advance nor retard is set, and at the same engine speed NE, it is set to advance as the load increases.
[0022]
In addition, a correction amount VTTBFTA for correcting the target control amount VTTB when the throttle opening degree TA is equal to or larger than the predetermined opening degree KVTTAH is set by a correction amount map based on the engine speed NE and the throttle opening degree TA. is there. As shown in FIG. 6, the correction amount VTTBFTA is not advanced or retarded in the idling operation state where the throttle valve 2 is closed, and is advanced as the throttle opening TA increases at the same engine speed NE. It is set to do. Specifically, the predetermined opening degree KVTTAH is set to the throttle opening degree TA that is the boundary between the partial load range and the full load range, in other words, the throttle opening degree TA immediately before reaching the full load range, for example, about 70 °. This is because the intake pipe pressure PA increases as the throttle valve 2 is opened, but the intake pipe pressure PM does not substantially change when the throttle opening degree TA exceeds, for example, 10 °. This is based on the fact that the tube pressure PM does not increase. In the basic amount map and the correction amount map, a basic amount VTTBF and a correction amount VTTBFTA are set for a typical engine speed NE. For other cases, the basic amount VTTBF and the correction amount are calculated by interpolation. VTTBFTA is calculated. The basic amount VTTBF and the correction amount VTTBFTA are set in terms of the crank angle.
[0023]
In FIG. 2, in step S1, in order to detect the current operating state of the engine 100, the intake pipe pressure PM detected from the intake pressure signal a output from the intake pressure sensor 13 is taken into the program being executed, The engine rotational speed NE detected from the rotational speed signal b output from the rotational speed sensor 14 is captured. In step S2, the basic quantity VTTBF is calculated from the intake pipe pressure PM and the engine speed NE, which are taken in, using a basic quantity map. In step S3, the basic amount VTTBF obtained by the calculation is temporarily stored in the storage device 8.
[0024]
As described above, the basic amount VTTBF is set and the correction amount VTTBFTA is set according to the following procedure. In FIG. 3, first, in step S <b> 11, the engine rotational speed NE detected from the rotational speed signal b output from the rotational speed sensor 14 is captured and detected from the opening signal e output from the throttle opening sensor 17. The throttle opening TA is taken into the running program. In step S12, a correction amount VTTBFTA is calculated from the acquired engine speed NE and the throttle opening TA using a correction amount map. In step S13, the correction amount VTTBFTA obtained by calculation is temporarily stored in the storage device 8.
[0025]
Next, the target control amount VTTB is set according to the following procedure. In FIG. 4, first, in step S21, in order to determine whether or not the throttle valve 2 has been opened until it reaches the full load range in the operation state at this time, the throttle opening degree TA is taken in. In step S22, it is determined whether or not the captured throttle opening TA is equal to or greater than a predetermined opening KVTTAH. If the captured throttle opening TA is less than the predetermined opening KVTTAH, the process proceeds to step S23, and if it is greater than the predetermined opening KVTTAH, the process proceeds to step S24. By this determination, it is determined whether or not the throttle valve 2 has been opened until it reaches the full load range. In step S23, the target control amount VTTB at this time is set to the basic amount VTTBF. In step S24, the target control amount VTTB is set to the basic amount VTTBF plus the correction amount VTTBFTA. In step S25, the set target control amount VTTB is stored in the storage device 8. As shown in FIG. 7, the target control amount VTTB calculated as described above continuously changes with respect to the throttle opening TA because the basic amount VTTBF and the correction amount VTTBFTA are interpolated. Further, the target control amount VTTB in the region where the throttle opening TA is equal to or greater than the predetermined opening KVTTAH changes linearly in proportion to the increase in the throttle opening TA by adding the correction amount VTTBFTA to the basic amount VTTBF. It is.
[0026]
In the above configuration, during the idling operation in which the engine 100 is started and the throttle valve 2 is closed, the intake valve 37 is opened / closed at the most retarded opening / closing timing. In this case, since there is almost no overlap, there is little exhaust gas flowing into the intake system 1 during intake, and combustion with good fuel consumption can be achieved.
[0027]
After such idling, when the accelerator pedal is depressed by starting the vehicle or the like, the throttle valve 2 is opened at an opening less than the predetermined opening KVTTAH. Such an operation state is an operation state in a partial load region. Then, by executing Steps S1 to S3 and Steps S11 to S13, the basic amount VTTBF and the correction amount VTTBFTA in the operation state at this time are calculated from the respective maps. Thereafter, Steps S21 and S22 are executed, and if it is determined in Step S22 that the throttle opening degree TA at this time is less than the predetermined opening degree KVTTAH, Steps S23 and S25 are executed to set the target control amount VTTB to the basic amount. Set to VTTBF. A control signal h corresponding to the set target control amount VTTB is output from the output interface 11 to the oil control valve 33, and the oil control valve 33 is controlled to advance the intake valve 37. Therefore, the overlap amount is increased as compared with the idling operation, and the output can be ensured in a state where the fuel consumption is favorably maintained.
[0028]
If the accelerator pedal is further depressed from the operation state in the partial load range described above and the full load range, that is, the throttle opening degree TA becomes equal to or greater than the predetermined opening degree KVTTAH, the intake pipe pressure PM increases and the engine speed NE increases. , The basic amount VTTBF is increased, that is, an amount on the more advanced side. That is, the control executes steps S1 to S3, and the basic amount VTTBF corresponding to the increased intake pipe pressure PM and the engine speed NE is set. At the same time, since the throttle opening degree TA is equal to or greater than the predetermined opening degree KVTTAH, steps S11 to S13 are executed to set a correction amount VTTBFTA according to the throttle opening degree TA and the engine speed NE.
[0029]
When it is determined that the throttle opening TA of the throttle valve 2 opened by executing Step S21 and Step S22 is equal to or greater than the predetermined opening KVTTAH, the correction amount VTTBFTA is added to the basic amount VTTBF stored in Step S24. Then, the target control amount VTTB is calculated and stored (step S25). This target control amount VTTB is an amount that is advanced by the correction amount VTTBFTA, unlike the case of the operation state where the throttle opening degree TA is less than the predetermined opening degree KVTTAH. Therefore, the control signal h corresponding to the target control amount VTTB controls the oil control valve 33 from the output interface, whereby the intake valve 37 is advanced from the opening / closing timing in the operation state in the partial load region. Thus, a large amount of outside air flows into the cylinder 38 through the intake system 1.
[0030]
As described above, the intake air amount increases by advancing the intake valve 37 based on the degree of opening of the throttle valve 2, that is, the throttle opening TA, and the fuel injection amount corresponds to the increase in the intake air amount. Therefore, the output and torque of the engine 100 in the full load range can be increased according to the throttle opening degree TA.
[0031]
According to this embodiment, the target control amount VTTB required for controlling the opening / closing timing of the intake valve 37, that is, to advance to the target opening / closing timing, is set by the intake pipe pressure PA and the engine speed NE. Whether the basic amount VTTBF is determined by adding a correction amount VTTBFTA that is set based on the throttle opening TA to the basic amount VTTBF. Therefore, in the partial load region where the throttle opening TA is less than the predetermined opening KVTTAH, the opening / closing timing of the intake valve 37 matched to the actual intake air amount can be set, and the intake pipe pressure PA is set to the throttle Even when the vehicle is saturated without increasing the opening TA, that is, in the full load range, it can be opened according to the driver's request. It can be in the timing. Therefore, fuel consumption can be ensured in the partial load region, and required output and torque can be ensured in the full load region.
[0032]
In addition, when the operating state shifts from the partial load range to the full load range, the target control amount VTTB is determined by adding the correction amount VTTBFTA set based on the throttle opening degree TA to the basic amount VTTBF. The control amount VTTB does not change stepwise, and therefore drivability at the boundary of the load region can be improved. In addition, in the partial load range, the basic amount VTTBF set by the intake pipe pressure PM and the engine speed NE is set to be optimum independently of the control of the switching timing in the full load range. The target control amount VTTB can be determined, and fuel efficiency and combustion stability can be improved.
[0033]
In the embodiment described above, the intake valve 37 opening / closing timing is variable. However, the exhaust valve 36 opening / closing timing may be variable. In this case, the opening / closing timing at idling is set to the most advanced angle side, and the target control amount is set as the retard amount.
[0034]
In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
[0035]
【The invention's effect】
Since the present invention is configured as described above, when the throttle opening is less than the predetermined opening, at least one of the intake valve and the exhaust valve is accurately matched to the actual intake air amount. The opening / closing timing of the vehicle can be controlled so as to become the opening / closing timing according to the driving state, and fuel efficiency and drivability can be improved.
[0036]
Further, when the throttle opening is equal to or larger than the predetermined opening, when the internal combustion engine is operated in the full load range, for example, the intake air is accurately drawn according to the operation amount of the throttle valve that reflects the driver's request. The opening / closing timing of at least one of the valve and the exhaust valve can be controlled to be the opening / closing timing according to the driving state, and an output reflecting the driver's request can be ensured.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory diagram of an embodiment of the present invention.
FIG. 2 is a flowchart showing a control procedure of the embodiment.
FIG. 3 is a flowchart showing a control procedure of the embodiment.
FIG. 4 is a flowchart showing a control procedure of the embodiment.
FIG. 5 is a graph showing a basic quantity of the embodiment.
FIG. 6 is a table showing the contents of a correction amount map according to the embodiment;
FIG. 7 is a graph showing a change in a target control amount according to the embodiment.
FIG. 8 is a graph showing the change of the intake pressure with respect to the throttle opening in the conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Intake system 2 ... Throttle valve 36 ... Exhaust valve 37 ... Intake valve 6 ... Electronic control unit 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface

Claims (2)

In an internal combustion engine that has a throttle valve in the intake system and can adjust the intake air amount according to the throttle opening, and that can control the opening and closing timing of the intake valve and the exhaust valve, the opening and closing timing according to the operating state is reached In the variable valve timing control method for an internal combustion engine that controls the opening / closing timing of at least one of the intake valve and the exhaust valve by a target control amount set according to the operating state,
Throttle opening corresponding to the partial load range to full load range, part load region and when less than the predetermined opening degree set by the throttle opening degree at the boundary between the full load region, the intake pipe pressure and the engine The target control amount is determined based on the rotational speed,
When the throttle opening is in the full load range above the predetermined opening, the exhaust valve and the intake valve are opened simultaneously based on the intake pipe pressure, engine speed , and throttle opening, and the larger the throttle opening. A variable valve timing control method for an internal combustion engine , wherein a target control amount is determined so that an overlap is increased . If the throttle opening is equal to or greater than the predetermined opening, the target control amount set based on the intake pipe pressure and engine speed is taken as the basic amount, and the basic amount is adjusted by the correction amount set according to the throttle opening. The variable valve timing control method for an internal combustion engine according to claim 1, wherein the target control amount is determined by correction.

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