JP3617610B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine (hereinafter referred to as an engine) provided with a continuously variable transmission (hereinafter referred to as CVT).
[0002]
[Related background]
As is well known, the fuel injection control of the internal combustion engine is executed by switching the operation mode in accordance with a preset region. For example, in the cylinder injection type engine shown in FIG. 2, the target average effective pressure Pe (engine load) ) And the engine speed Ne are low, the lean mode is selected, and the stoichiometric mode (S-F / B mode) and the rich mode (O / L) are increased as the target average effective pressure Pe and the engine speed Ne are both higher. The operation mode is switched in the order of (mode).
[0003]
When CVT is combined with this type of engine, when the accelerator operation is performed for acceleration in the lean region, first, the target average effective pressure Pe instantaneously reaches near the full opening torque while maintaining a substantially constant rotation, and thereafter Then, the CVT is controlled to the downshift (gear ratio increase) side with a response delay, and as a result, the engine rotational speed Ne is led to the high speed side and accelerated.
[0004]
[Problems to be solved by the invention]
Since the rich region is set in the vicinity of the fully open torque for securing the torque and preventing knocking, the rich region is temporarily passed during the acceleration described above. In the case of an automatic transmission that uses a planetary gear mechanism, the transition time changes linearly as indicated by the one-dot chain line arrow as the shift speed changes, so the residence time in the rich region is negligible, In CVT, due to the characteristic of continuously changing the gear position, the curve shifts as indicated by the solid line arrow and stays in the rich operation region for a considerably long time. Therefore, wasteful fuel consumption is performed during that period, which causes a deterioration in fuel consumption.
[0005]
An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can reduce fuel consumption by suppressing wasteful fuel consumption when passing through a rich region in the shifting process of a continuously variable transmission. is there.
[0006]
[Means for Solving the Problems]
To achieve the above object, in the invention of claim 1, stoichiometric mode for controlling the internal combustion engine to the stoichiometric air-fuel ratio, and is constituted the operation mode between the rich mode to be switched to control the rich air-fuel ratio, the operation mode Fuel injection control means for switching from the stoichiometric mode to the rich mode as the engine load increases, a continuously variable transmission for continuously changing the output of the internal combustion engine, and at the time of downshift of the continuously variable transmission according to the accelerator operation , when the operating mode with an increase in engine load based on the accelerator operation prior to downshift passes through the area of the rich mode from the region of the stoichiometric mode, the mode switching prohibiting means for prohibiting the switching of the Li Tchimodo I have. Therefore, when the continuously variable transmission is downshifted according to the accelerator operation, the operation mode passes from the stoichiometric mode region to the rich mode region as the engine load increases based on the accelerator operation prior to the downshift. However, at this time, switching to the rich mode is prohibited, and fuel efficiency is improved by continuing the stoichiometric mode.
[0007]
In the invention of claim 2, the spark ignition internal combustion engine that directly injects fuel into the combustion chamber is controlled to the stoichiometric air-fuel ratio, the rich mode that is controlled to the rich air-fuel ratio, and the lean mode that is controlled to the lean air-fuel ratio. The operation mode can be switched with the fuel injection control means for switching the operation mode from the lean mode to the rich mode through the stoichiometric mode as the engine load increases, and the continuously variable transmission for continuously changing the output of the internal combustion engine. When the engine and the continuously variable transmission according to the accelerator operation are downshifted, the operation mode is rich from the lean mode region to the stoichiometric mode region as the engine load increases based on the accelerator operation prior to the downshift. Mode switching prohibiting means for prohibiting switching to the rich mode when passing through the mode area.
Therefore, when the continuously variable transmission is downshifted in response to the accelerator operation, the operation mode is rich from the lean mode region to the stoichiometric mode region as the engine load increases based on the accelerator operation prior to the downshift. Although it passes through the mode region, at this time, switching to the rich mode is prohibited and fuel efficiency is improved. In addition, since the heat generation amount of the internal combustion engine is low during operation based on the lean air-fuel ratio, this configuration increases the chance that the operation state where the heat generation amount is sufficient continues and the stoichiometric mode can be continued, Since the fuel injection timing can be set freely, the so-called two-stage mixing in which the fuel injection is divided into the intake stroke and the compression stroke can be executed to further improve the knock resistance.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a fuel injection control device for a direct injection gasoline engine will be described.
In the overall configuration diagram of FIG. 1, reference numeral 1 denotes an engine, and a combustion chamber 2 and an intake system are designed exclusively for in-cylinder injection. The cylinder head 3 of the engine 1 is provided with an electromagnetic fuel injection valve 5 together with a spark plug 4 for each cylinder, and high-pressure fuel supplied from a fuel pump (not shown) is supplied from the fuel injection valve 5 to the combustion chamber 2. It is designed to be injected directly into the inside.
[0009]
An intake port 6 is formed in the cylinder head 3 in a substantially upright direction, and an intake passage 7 is connected to the intake port 6. The intake passage 7 is provided with a throttle valve 8 for adjusting the amount of intake air, and the throttle valve 8 is driven to open and close by a stepper motor 9. The intake air taken in from the intake passage 7 is introduced into the combustion chamber 2 from the intake port 6 through the throttle valve 8 as the intake valve 10 is opened, and fuel is injected from the fuel injection valve 5 into the intake air. Then, it burns by ignition of the spark plug 4.
[0010]
An exhaust port 15 is formed in the cylinder head 3 in a substantially horizontal direction, and an exhaust passage 16 is connected to the exhaust port 15. The exhaust gas after combustion is discharged into the atmosphere from the combustion chamber 2 through the exhaust port 15, the exhaust passage 16, a catalyst and a silencer (not shown) when the exhaust valve 17 is opened.
A belt-type CVT 21 is combined with the engine 1, and a crankshaft 1 a of the engine 1 is connected to a primary pulley 24 via a torque converter 22 and a clutch 23 of the CVT 21. The primary pulley 24 is connected to a secondary pulley 26 by an endless belt 25, and the secondary pulley 26 is connected to driving wheels 29 through a secondary reduction mechanism 27 and a differential gear 28. The oil pump 30 of the CVT 21 is rotationally driven by the crankshaft 1 a of the engine 1 via the transmission mechanism 31, and the hydraulic oil is supplied to the primary pulley 24 and the secondary pulley 26 according to switching of the solenoid 32. The transmission ratio of the pulleys 24 and 26 is changed according to the supply state of the hydraulic oil, and as a result, the engine torque transmitted to the drive wheels 29 is adjusted.
[0011]
In the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) used for storing control programs and control maps, an ECU (electronic device) equipped with a central processing unit (CPU), a timer counter, etc. Control unit) 41 is installed and performs overall control of the engine 1 and the CVT 21. On the input side of the ECU 41, an accelerator sensor 42 that detects an accelerator pedal operation amount APS by a driver, an engine rotation speed sensor 43 that detects a rotation speed Ne of the engine 1, and a water temperature sensor 44 that detects a cooling water temperature Tw of the engine 1. Various sensors such as a primary rotational speed sensor 45 for detecting the rotational speed Np of the primary pulley 24 and a secondary rotational speed sensor 46 for detecting the rotational speed Ns of the secondary pulley 26 are connected, and their detection information is input. It is like that.
[0012]
The ignition plug 4 is connected to the output side of the ECU 41 via an igniter 51 and an ignition coil 52, and a fuel injection valve 5 is connected. Further, an ETV-CU (electronic throttle valve control unit) 53 is connected to the output side of the ECU 41, and a throttle position sensor 54 for detecting the opening θth of the throttle valve 8 is connected to the input side of the ETV-CU 53. The stepper motor 9 is connected to the output side. Further, the solenoid 32 of the CVT 21 is connected to the output side of the ECU 41.
[0013]
The ECU 41 executes various controls described below based on detection information from each sensor. Regarding the fuel injection control of the engine 1, the fuel injection mode (representing a stroke for performing fuel injection as described later) and the fuel injection time are determined and the fuel injection valve 5 is driven and controlled. For ignition timing control, the igniter 51 controls the energization state of the ignition coil. Regarding the throttle control, the target throttle opening Tθth is determined and output to the ETV-CU 53 side, and the stepper motor 9 is driven and controlled by the ETV-CU 53 based on the target throttle opening Tθth and the actual throttle opening θth. On the other hand, regarding the gear ratio control of the CVT 21, the gear ratio of the pulleys 24 and 26 is changed by controlling the duty ratio of the drive signal to the solenoid 32.
[0014]
Next, the execution state of the fuel injection control by the ECU 41 configured as described above will be described. Prior to that, setting of the fuel injection mode will be described.
The fuel injection mode described above is determined according to the map shown in FIG. 2 from the target average effective pressure Pe representing the engine load and the engine speed Ne. As shown in the figure, in the region where the target average effective pressure Pe and the engine rotational speed Ne are low, the compression stroke injection lean mode is set, and as the target average effective pressure Pe and the engine rotational speed Ne are both higher, SF / B The mode and the O / L mode are switched in this order. The compression stroke injection lean mode is an operation mode in which fuel is injected in the compression stroke and the air-fuel ratio is controlled in the lean region (in the embodiment, about A / F 25 to 40), and fuel injection is performed in the intake stroke except for this compression stroke injection lean mode. In the SF / B mode, the operation mode is the stoichiometric air-fuel ratio, and the O / L mode is an operation mode in which the air-fuel ratio is controlled in the rich region.
[0015]
For example, when the engine 1 is in a low load range, such as during idling or low speed running, the fuel injection mode is set to the compression stroke injection lean mode, and fuel injection is performed in the compression stroke. On the other hand, when the engine 1 is in the middle / high load range, such as during medium / high speed running, the fuel injection mode is set to the SF / B mode or the O / L mode, and fuel injection is performed in the intake stroke.
[0016]
In addition, since the fuel injection timing can be set freely as described above, so-called two-stage mixing in which fuel injection is divided into an intake stroke and a compression stroke is executed as necessary as described later. This two-stage mixing is aimed at suppressing smoke and knocking, and preliminary fuel injection is performed in the intake stroke, and the remaining fuel is injected in the subsequent compression stroke. Since most of the fuel is injected in the compression stroke just before ignition, combustion is started without self-ignition, knocking is suppressed, and a lean flame generated in advance in the intake stroke by the bright flame of the combustion Since the air-fuel mixture starts to burn, the generation of smoke when the luminous flame is cooled is prevented.
[0017]
On the other hand, the ECU 41 executes the main routine shown in FIGS. 3 and 4 at a predetermined control interval. First, in step S2, the ECU 41 generates the driving wheel 29 in accordance with the map shown in FIG. 5 based on the output shaft rotational speed Nout (that is, the vehicle speed obtained from the secondary rotational speed Ns in consideration of the reduction ratio) and the accelerator operation amount APS. The power output shaft torque Tout is determined. As apparent from the figure, the larger the accelerator operation amount APS is and the higher the driver's acceleration request is, the larger the output shaft torque Tout is set. Further, in step S4, the output shaft torque Tout is multiplied by the output shaft rotation speed Nout to be converted into the output shaft horsepower Pout. The actual output shaft horsepower Pout needs to consider the transmission loss of the drive system, but for the sake of convenience, the following description assumes that the transmission loss is zero.
[0018]
Next, in step S6, it is determined whether the lean permission flag F1 is set. The lean permission flag F1 is set in a lean permission determination routine which will be described later as an index indicating whether or not the lean operation can be performed. When the determination is NO (negative), it is determined that the lean operation is disabled, and in step S8, the target primary rotational speed TNp is determined from the output shaft horsepower Pout according to the stoichiometric map shown by the solid line in FIG. In step S10, the target primary rotational speed TNp is determined according to the lean map indicated by the broken line in FIG. Thereafter, in step S12, the duty ratio of the drive signal is determined based on the target primary rotational speed TNp and the actual primary rotational speed Np, and is output to the solenoid 32 of the CVT 21.
[0019]
As is clear from FIG. 6, in the region where the output shaft horsepower Pout is not more than a predetermined value, a higher target primary rotational speed TNp (= engine rotational speed Ne) is determined on the lean map side than the stoichiometric map. This map setting considers the fuel consumption characteristics of the engine 1, and since the minimum fuel consumption can be obtained in a slightly higher rotation range during lean operation than during stoichiometric operation, the engine speed Ne is increased accordingly. .
[0020]
Thereafter, in step S14, the ECU 41 multiplies the duty ratio of the solenoid 32 determined in step S12 by a predetermined constant to calculate the inertia torque Ti required for the operation of the gear ratio of the CVT 21. Although details will not be described, the inertia torque Ti is a correction value for canceling the acceleration / deceleration G of the vehicle that occurs during the shifting operation of the CVT 21. Next, in step S16, the target shaft output P on the engine 1 side for achieving the output shaft horsepower Pout (a value obtained by considering the reduction ratio from the output shaft horsepower Pout) is divided by the current engine speed Ne. Then, the necessary basic engine torque Tbase is calculated. Further, at step S18, the inertia torque Ti described above is added to the basic engine torque Tbase to calculate the target engine torque Te.
[0021]
Further, in step S20, the maximum torque STmax that can be achieved during the stoichiometric operation is determined based on the current engine speed Ne according to the stoichiometric map shown by the solid line in FIG. The maximum torque RTmax that can be realized during rich operation in the O / L mode is determined according to the map. Next, in step S22, it is determined whether or not the target engine torque Te obtained in step S18 exceeds the maximum torque STmax during stoichiometric operation (Te> STmax). If NO, the process proceeds to step S24. In step S24, the target engine torque Te is converted into the target average effective pressure Pe, and based on the target average effective pressure Pe, the air-fuel ratio of the engine 1, the throttle opening θth, the fuel injection timing, the ignition timing, and the EGR valve opening (not shown) are opened. After controlling the degree, etc., this routine is finished.
[0022]
If the determination in step S22 is YES, it is determined in step S26 whether the target engine torque Te exceeds a value obtained by adding a predetermined value α to the maximum torque RTmax during rich operation (Te> RTmax + α). If the determination is YES, it means that the target engine torque Te cannot be achieved even if the rich operation is performed, but in this case, there is no other way than performing the rich operation to obtain the maximum engine torque. The maximum torque RTmax during operation is set as the target engine torque Te, the target air-fuel ratio is set to the rich side, and the process proceeds to step S24.
[0023]
Further, when the determination in step S26 is NO, it means that the target engine torque Te is in the range from the maximum torque STmax during stoichiometric operation to the maximum torque RTmax + α during enrichment operation. At this time, the process proceeds to step S30 to determine whether or not the delay flag F2 is set. The delay flag F2 is set by a delay determination routine described later as an index indicating the current knock resistance of the engine 1. When the determination in step S30 is NO, it is considered that the driving condition cannot be expected to prevent knocking, and the process proceeds to step S24 via step S28.
[0024]
Further, when the determination in step S30 is YES, it is assumed that there is an operating condition in which knock resistance can be expected, and the process proceeds to step S32. Then, the maximum torque STmax during stoichiometric operation is set as the target engine torque Te, the target air-fuel ratio is set to the stoichiometric air-fuel ratio, two-stage mixing is set as the fuel injection mode, and the process proceeds to step S24.
[0025]
On the other hand, the ECU 41 executes a lean permission determination routine shown in FIG. 8 at a predetermined control interval. First, the ECU 41 determines in step S42 whether or not the coolant temperature Tw is equal to or lower than a predetermined value Tw0, and in step S44 determines whether or not the above-mentioned various types of sensors have failed. The routine is terminated after clearing the lean permission flag F1. Further, when it is determined NO in both step S42 and step S44, after setting the lean permission flag F1 in step S48, this routine is ended.
[0026]
Further, the ECU 41 executes a delay determination routine shown in FIG. 9 at a predetermined control interval. First, the ECU 41 determines in step S52 whether or not the delay counter C is 0. If YES, the ECU 41 increments the delay counter C in step S54 and then proceeds to step S56. If NO, the process proceeds directly to step S56. This process is for guarding the lower limit of the delay counter C to zero.
[0027]
Next, in step S56, it is determined whether or not the current target effective effective pressure Pe of the engine 1 exceeds a preset maximum value Pe0 during stoichiometric operation. If YES, the delay counter C is decremented in step S58, the delay flag F2 is cleared in step S60, and then this routine ends.
On the other hand, when the determination in step S56 is NO, after the delay counter C is incremented in step S62, it is determined in step S64 whether or not the delay counter C has reached the predetermined value C0. Transition. If the determination in step S64 is yes, the delay flag F2 is set in step S66 and the delay counter C is decremented.
[0028]
That is, when the target average effective pressure Pe is less than or equal to the maximum stoichiometric value Pe0, stoichiometric operation or lean operation is estimated, and when this operating state continues for a predetermined value C0, the engine 1 is kept at a relatively low temperature and It can be estimated that there is a surplus in the amount of heat generation. The delay flag F2 is set when the engine 1 is in such an operating state.
[0029]
In this embodiment, the ECU 41 when executing the processes of the above steps S28 and S32 functions as a fuel injection control means, and the ECU 41 when executing the processes of steps S52 to S66, step S26 and step S30. It functions as a mode switching prohibiting means.
When accelerating from the lean region by the processing described above, the fuel injection mode is set as follows.
[0030]
When the accelerator operation is performed, the output shaft torque Tout is set to increase in step S2 and the output shaft horsepower Pout is increased in step S4 as the accelerator operation amount APS increases, and in step S18 based on the output shaft horsepower Pout. The target engine torque Te is set to increase. When the target engine torque Te is slightly higher than the maximum torque RTmax during rich operation (determination in step S26 is YES), it is considered that the stoichiometric operation can be continued in step S32 on condition that the delay flag F2 is set.
[0031]
That is, at this time, since the heat generation amount of the engine 1 has a margin, it is in an operation state that is basically difficult to knock, and can also be expected to suppress the knocking by the two-stage mixing. Therefore, it is possible to compensate for the torque shortage caused by, and to achieve acceleration close to the driver's request. Since the stoichiometric operation is continued in the region where the rich operation is originally performed in this way, wasteful fuel consumption can be suppressed and fuel consumption can be reduced. Therefore, the substantial stoichiometric region at this time is expanded to the high load side as shown by a broken line in FIG.
[0032]
In particular, in the cylinder injection type gasoline engine 1 as in the present embodiment, since the ultra-lean operation with a very low calorific value is performed, the frequency with which the delay flag F2 is set is significantly increased, and the stoichiometric mode is continued during acceleration. Possible opportunities increase. In addition, in a normal intake manifold injection engine, a phenomenon in which highly volatile components in the fuel are first evaporated and transferred into the combustion chamber is a cause of knocking. Since such a malfunction does not occur, the knock resistance is fundamentally high, and a larger ignition advance is possible. Therefore, the stoichiometric region can be further expanded to the high load side, and further fuel consumption reduction can be achieved.
[0033]
The determination value (RTmax + α) to be compared with the target engine torque Te in step S26 is determined in consideration of the specifications of the engine 1 and the like from the viewpoint of the range in which the originally rich operation region can be replaced by the stoichiometric operation. Should. In the above description, RTmax + α is set, but if a value larger than at least STmax is set as the determination value, the rich operation region is replaced by the stoichiometric operation, so this can be arbitrarily set as the lower limit. is there.
[0034]
By the way, in the said Example, although it actualized to the control apparatus of the cylinder injection type gasoline engine 1 combined with the belt type CVT21, the engine type, the operating principle of CVT, etc. are not limited to this, For example, It may be embodied in an engine control device that injects fuel into a normal intake manifold.
In the above embodiment, it is assumed that the vehicle passes through the rich region due to acceleration caused by the accelerator operation. In short, if the vehicle passes through the rich region during the shifting process of the CVT 21, the cause is It is not limited. Therefore, the control of this embodiment may be applied when passing through the rich region in the shifting process of the CVT 21 by operating auxiliary equipment such as an air conditioner.
[0035]
【The invention's effect】
As described above in detail, according to the fuel injection control device for an internal combustion engine of the present invention, fuel consumption can be reduced by suppressing wasteful fuel consumption when passing through the rich region during the shifting process of the continuously variable transmission. Can do.
[Brief description of the drawings]
1 is an overall configuration diagram showing a fuel injection control device for an internal combustion engine according to an embodiment;
FIG. 2 is an explanatory diagram showing a map for determining a fuel injection mode.
FIG. 3 is a flowchart showing a main routine executed by the ECU.
FIG. 4 is a flowchart showing a main routine executed by the ECU.
FIG. 5 is an explanatory diagram showing a map for determining an output shaft torque Tout.
FIG. 6 is an explanatory diagram showing a map for determining a target primary rotation speed TNp.
FIG. 7 is an explanatory diagram showing a map for determining maximum torques STmax and RTmax.
FIG. 8 is a flowchart showing a lean permission determination routine executed by the ECU.
FIG. 9 is a flowchart showing a delay determination routine executed by the ECU.
[Explanation of symbols]
1 engine (internal combustion engine)
21 CVT (continuously variable transmission)
41 ECU (fuel injection control means, mode switching prohibition means)

Claims (2)

Stoichiometric mode for controlling the internal combustion engine to the stoichiometric air-fuel ratio, and is constituted the operation mode between the rich mode to be switched to control the rich air-fuel ratio of the rich side than the stoichiometric air-fuel ratio, an increase in engine load the operating mode With this, fuel injection control means for switching from the stoichiometric mode to the rich mode ,
A continuously variable transmission that continuously changes the output of the internal combustion engine;
When the continuously variable transmission is downshifted according to the accelerator operation, the operation mode is changed from the stoichiometric mode region to the rich mode as the engine load increases based on the accelerator operation prior to the downshift . as it passes through the region, the fuel injection control apparatus for an internal combustion engine characterized by comprising a mode switching prohibiting means for prohibiting the switching to the rich mode. A stoichiometric mode that controls a spark ignition internal combustion engine that directly injects fuel into the combustion chamber to a stoichiometric air-fuel ratio, a rich mode that controls a rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio, and a leaner side than the stoichiometric air-fuel ratio A fuel injection control means configured to be able to switch the operation mode between lean modes for controlling to a lean air-fuel ratio, and for switching the operation mode from the lean mode to the rich mode through the stoichiometric mode as the engine load increases; ,
A continuously variable transmission that continuously changes the output of the internal combustion engine;
When the continuously variable transmission is downshifted according to the accelerator operation, the operation mode is changed from the lean mode region to the stoichiometric mode as the engine load increases based on the accelerator operation prior to the downshift. Mode switching prohibiting means for prohibiting switching to the rich mode when passing through the region of the rich mode through the region;
A fuel injection control device for an internal combustion engine, comprising:

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