JP2001152929A - Air-fuel ratio control device for variable valve system engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve control precision of air-fuel ratio control of variable valve system engine. SOLUTION: An opening closing timing is controlled (S1-S3) so that target torque of a suction and exhaust valve is generated based on accelerator opening and an engine rotation speed. A volumetric intake air amount is calculated based on an engine rotation speed and the opening and closing timing of the intake and exhaust valve (S4 and S5). The volumetric intake air amount is corrected by an intake air temperature T and an intake air pressure P (S6 and S7). Based on a mass intake air amount, a fuel injection amount Tpi is calculated (S8), various correction factors COEF and a battery voltage correction value Ts are read (S9), an air-fuel ratio feedback correction factor α, and an air-fuel ratio learning value αL are read (S10), and based on the various correction amounts, a final fuel injection amount TIi is calculated (S11).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the air-fuel ratio of a variable valve engine having an intake valve capable of arbitrarily variably controlling an opening / closing timing such as an electromagnetic drive type.

[0002]

2. Description of the Related Art In a conventional general engine, the intake air amount is controlled by the opening degree of a throttle valve. In recent years, an intake / exhaust valve of an electromagnetic drive type is provided, and the intake air amount is mainly controlled by controlling the opening / closing timing of the intake valve. Is proposed (see Japanese Patent Application Laid-Open No. 8-2000025).

[0003]

In this type of controlling the intake air amount by the opening / closing timing of an intake valve, when the intake air amount is detected by a normal air flow meter, the influence of intake pulsation or the influence of intake pulsation at least under a predetermined operating condition is obtained. In some cases, a good detection of the intake air amount cannot be performed due to a response delay at the time of transition, and thus a good control of the fuel injection amount and the air-fuel ratio cannot be performed.

The present invention has been made in view of such a conventional problem, and enables the air-fuel ratio to be controlled with high accuracy while setting the fuel injection amount with a high response to a change in the intake air amount. It is an object of the present invention to provide an air-fuel ratio control device for a variable valve engine.

[0005]

Therefore, according to the present invention, as shown in FIG. 1, the opening and closing of an intake valve in a variable valve engine having an intake valve which can be variably controlled at an arbitrary opening / closing timing. Intake valve opening / closing timing detecting means for detecting timing;
An engine rotational speed detecting means for detecting an engine rotational speed, an intake air amount calculating means for calculating an intake air amount based on an opening / closing timing of an intake valve and the engine rotational speed, and supplied to the engine based on the intake air amount. A fuel injection amount calculating means for calculating a fuel injection amount to be detected, an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine, and an air-fuel ratio approaching a target air-fuel ratio based on the detected air-fuel ratio. Air-fuel ratio feedback correction means for feedback-correcting the fuel injection amount, and fuel injection means for supplying the feedback-corrected fuel injection amount to the engine. Fuel ratio control device.

According to the first aspect of the invention, in a variable valve engine in which the intake air amount is controlled mainly by the opening / closing timing of the intake valve, the intake air amount sucked into the cylinder based on the opening / closing timing of the intake valve and the engine speed. Is determined.

Therefore, based on the opening / closing timing of the intake valve detected by the intake valve opening / closing timing detecting means and the engine rotational speed detected by the engine rotational speed detecting means, the intake air amount calculating means calculates the intake air amount.

[0008] Thus, it is possible to detect a good intake air amount without the influence of the intake air pulsation and the influence of the response delay at the time of transition, and the fuel injection amount setting means sets the fuel injection amount corresponding to the intake air amount. You.

Further, by correcting the set fuel injection amount based on the air-fuel ratio detected by the air-fuel ratio detecting means, the variation of the air-fuel ratio is adjusted and the target air-fuel ratio is feedback-controlled. Here, the air-fuel ratio feedback correction is performed on the fuel injection amount set in accordance with the influence of intake air pulsation of the intake air amount and a change due to a response delay at the time of transition, so that high accuracy while ensuring responsiveness is achieved. Air-fuel ratio control can be performed.

The invention according to a second aspect of the present invention is a learning method in which the deviation of the feedback correction amount from the reference value by the air-fuel ratio feedback correction means is reduced for each of a plurality of divided engine operating regions. It is characterized by including an air-fuel ratio learning means for correcting the fuel injection amount using a value.

According to the second aspect of the present invention, the variation in the air-fuel ratio in each engine operating region can be quickly absorbed by correcting the fuel injection amount using the learning value, and the transient response is improved.

According to a third aspect of the present invention, there is provided an intake air temperature detecting means for detecting an intake air temperature, an intake pressure detecting means for detecting an intake pressure, and an intake air amount calculated by the intake air amount calculating means. The air-fuel ratio control device for a variable valve engine according to claim 1 or 2, further comprising an intake air amount correcting means for correcting the temperature with the intake pressure.

According to the third aspect of the present invention, the intake air amount detected by the intake air amount detecting means is a volume intake air amount. However, in order to control the air-fuel ratio to the target air-fuel ratio, the fuel injection amount is determined. Must be set in proportion to the mass intake air amount. Therefore, the mass intake air amount is calculated by correcting the volume intake air amount detected by the intake air amount detection unit based on the intake air temperature detected by the intake air temperature detection unit and the intake pressure detected by the intake pressure detection unit. I do. The fuel injection amount is also corrected by the air-fuel ratio feedback correction means to a value corresponding to the mass intake air amount, but the mass intake air amount is corrected and set in advance based on the intake air temperature and the intake pressure. By performing the air-fuel ratio feedback correction on the fuel injection amount corresponding to the mass intake air amount, air-fuel ratio control with good responsiveness without delay due to feedback control can be performed.

The invention according to claim 4 is characterized in that a plurality of the air-fuel ratio detecting means are provided for each of a plurality of cylinder groups.

According to the fourth aspect of the invention, in the intake air amount control based on the opening / closing timing of the intake valve, variation in the air-fuel ratio between cylinders tends to occur. Therefore, by providing a plurality of air-fuel ratio detecting means for each of the plurality of cylinder groups (including one for each cylinder), it is possible to perform highly accurate air-fuel ratio control in which variations in air-fuel ratio between cylinders are suppressed.

[0016]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of a variable valve engine showing one embodiment of the present invention.

The combustion chamber 3 defined by the piston 2 of each cylinder of the engine 1 is provided with an electromagnetically driven intake valve 5 and an exhaust valve 6 so as to surround the ignition plug 4. 7 is an intake passage, and 8 is an exhaust passage.

FIG. 3 shows the basic structure of the electromagnetic drive device for the intake valve 5 and the exhaust valve 6. A plate-like mover 22 is attached to a valve shaft 21 of the valve body 20, and the mover 22 is biased to a neutral position by springs 23 and 24.
The valve opening electromagnetic coil 25 is provided below the mover 22.
Is disposed, and the valve closing electromagnetic coil 26 is disposed on the upper side.

Therefore, when the valve is opened, after the power supply to the upper valve closing electromagnetic coil 26 is stopped, the current is supplied to the lower valve opening electromagnetic coil 25 to attract the movable element 22 to the lower side. As a result, the valve body 20 is lifted to open the valve. vice versa,
When the valve is closed, the energization of the lower valve opening electromagnetic coil 25 is stopped, and then the upper valve closing electromagnetic coil 26 is energized to attract the movable element 22 to the upper side.
Is seated on the seat and the valve is closed.

A lift sensor 32 is arranged at the upper end of the housing with a detection rod 31 engaged with the upper end of the valve shaft 21 of the intake valve 5. The lift sensor 32 detects the amount of movement of the detection rod 31 as the amount of lift of the valve body 20.
In addition, a contactless distance measuring sensor using infrared rays, ultrasonic waves, or the like can be used as the lift sensor. Further, the present invention requires that the lift amount of the intake / exhaust valve itself is not required to be detected, and the opening / closing timing need only be detected. What is detected can also be used.

Returning to FIG. 2, the intake passage 7 is provided with an electromagnetic fuel injection valve 9 at an intake port for each cylinder. As shown in FIG. 4, a plurality of air-fuel ratio sensors (for example, one for every two cylinders in a four-cylinder engine, two in total) are provided in the exhaust passage 8 as shown in FIG. 15A, 15B) A wide range sensor for detecting, an O ₂ sensor that outputs on / off for the stoichiometric air-fuel ratio
Is arranged.

Here, the operations of the intake valve 5, the exhaust valve 6, the fuel injection valve (fuel injection means) 9 and the spark plug 4 are controlled by a control unit 10, which synchronizes with the engine rotation. A crank angle sensor (engine rotation speed detecting means) capable of detecting the engine rotation speed by outputting a crank angle signal,
Accelerator pedal sensor 12 for detecting the accelerator opening (accelerator pedal depression amount), intake air temperature sensor for detecting the intake air temperature (intake air temperature detecting means) 13, intake pressure sensor for detecting the intake pressure (intake air pressure detecting means) 14, Signals are input from the air-fuel ratio sensors (air-fuel ratio detecting means) 15A and 15B, as well as lift sensors (intake valve opening / closing timing detecting means) 32 for detecting the opening / closing timing of the intake valves 5 and the exhaust valves 6. .

The target opening / closing timing of the intake valve 5 and the exhaust valve 6 is set so as to generate the target torque based on the engine operating conditions such as the accelerator opening and the engine rotation speed, and the target opening / closing timing is obtained. The opening / closing timing of the intake valve 5 and the exhaust valve 6 is controlled as described above.

On the other hand, the intake air amount is detected based on the values detected by the various sensors, and the air-fuel ratio sensor is set while setting the fuel injection amount from the fuel injection valve 9 based on the intake air amount. The fuel injection amount is feedback-corrected based on the air-fuel ratio detected by 15A and 15B, and is controlled so as to reach the target air-fuel ratio. Further, while performing the air-fuel ratio feedback control, learning is performed so as to reduce the deviation of the feedback correction amount from the reference value (for example, 1) for each operation region divided by the engine speed, the load (basic fuel injection amount Tp), and the like. The value is updated and the fuel injection amount is corrected with the learning value.

The air-fuel ratio control routine will now be described with reference to FIG.
This will be described in detail according to the flowchart of FIG. Step 1
Then, an accelerator opening detected by the accelerator pedal sensor 12 and an engine speed detected by the crank angle sensor 11 are read.

In step 2, a target opening / closing timing of the intake valve 5 and the exhaust valve 5 for generating a target torque for each operating state according to the accelerator opening and the engine speed is mapped (FIG. 6).
Search).

In step 3, the opening and closing of the intake valve 5 and the exhaust valve 5 are controlled according to the target opening / closing timing. In step 4, the intake valve 5 detected by the lift sensor 32
Read the actual opening / closing time of.

In step 5, a volume intake air amount Qv to be taken into the cylinder is calculated based on the opening / closing timing of the intake valve 5 and the engine speed. Specifically, as shown in FIG. 7, when the engine rotation speed is constant, the intake air amount becomes maximum when the intake valve closes at a predetermined timing, and when the close timing is earlier or later, The intake air volume decreases below the maximum value. On the other hand, as the engine speed increases, the delay of intake from the intake valve increases,
The closing timing of the intake valve at which the intake air amount becomes maximum shifts to the delay side. That is, in the case of the early closing control in which the intake valve 5 is closed before the bottom dead center, as shown in FIG. 8, as the closing timing of the intake valve is delayed, the target torque and therefore the intake air amount increases, but the engine rotation speed increases. As the speed increases, it is necessary to delay the intake valve closing timing to obtain the same intake air amount.

Then, the volume intake air amount Qv is calculated by the following equation. The function of step 5 constitutes the intake air amount calculating means. Qiv = QiMAX × IVCt Here, Qiv is the volume intake air amount of cylinder #i, QiMAX
Is the maximum volume intake air amount of the #i cylinder, and IVCt is the volume intake air amount Qiv with high precision by multiplying by a coefficient set based on the intake valve closing timing and the engine speed (for example, at every 400 rpm). Can be calculated.

In step 6, the intake air temperature T detected by the intake air temperature sensor 13 and the intake air pressure P detected by the intake air pressure sensor 14 are read. In step 7, the mass intake air amount Qiv is corrected by the intake air temperature T and the intake pressure P to calculate the mass intake air amount Qim.
The function of step 7 constitutes the intake air amount correcting means.

Qim = RT · P / Qiv (where R is a gas constant) In step 8, the basic fuel injection amount TPi = k · Qim is calculated in proportion to the mass intake air amount Qim of the cylinder i. . The function of step 8 constitutes a fuel injection amount calculating means.

In step 9, various correction coefficients COEF set based on the engine coolant temperature and the like and a correction value Ts set based on the voltage of the battery for driving the fuel injection valve 9 are read. In step 10, the air-fuel ratio feedback correction coefficient α and the air-fuel ratio learning value αL obtained by another routine are read.

The air-fuel ratio feedback correction coefficient α is, for example, I (integral) control, PI (proportional integration) control while comparing the detected value of the air-fuel ratio sensor 15A or 15B of the corresponding cylinder group with the target air-fuel ratio equivalent value. , PID (proportional-integral-derivative) control or the like. This function constitutes air-fuel ratio feedback correction means.

Further, the air-fuel ratio learning value αL is updated and set as follows so as to reduce the deviation between the air-fuel ratio feedback correction coefficient α and a reference value αo (for example, 1). αL = αL (old) + k · (αo−α) where αL (old) is the air-fuel ratio learning value αL for each operating region divided by the engine speed Ne and the load (basic fuel injection amount Tp). From the stored map, the air-fuel ratio learning value corresponding to the current operating region searched, k is a coefficient (0 <k <
1). The air-fuel ratio learning value αL (old) stored in the corresponding operation area of the map is rewritten by the air-fuel ratio learning value αL updated and set in this manner. This function constitutes the air-fuel ratio learning means.

Next, in step 11, the final fuel injection amount TIi is calculated based on the various correction amounts as in the following equation. In this way, the volume intake air amount calculated based on the opening / closing timing of the intake valve and the engine rotation speed is corrected by the intake air temperature and the intake pressure to obtain a mass TI i = TP i · COEF · α · αL + Ts By calculating the intake air amount, it is possible to detect a favorable intake air amount without the influence of intake air pulsation and the effect of a response delay during a transition, and to reduce the fuel injection amount set based on the intake air amount. Since the feedback correction is performed based on the detected fuel ratio, it is possible to control the target air-fuel ratio by adjusting the variation in the air-fuel ratio.

Further, by correcting the fuel injection amount using a learning value set based on the air-fuel ratio feedback correction amount, high-precision air-fuel ratio control in which variations in the air-fuel ratio in each operation region are suppressed is performed. Can be.

In the above-described embodiment, since the intake air amount is detected for each cylinder and the fuel injection amount is set for each cylinder, the fuel injection amount control can be performed with high accuracy for each cylinder. Average value QmAV of each intake air amount Qim [for example, in the case of a four-cylinder engine, QmAV = 1/4 (Q1m + Q2
m + Q3m + Q4m)] or the intake air amount Qi for each cylinder group
average value of m QmAV1 [= 1/2 (Q1m + Q2m)],
QmAV2 [= 1/2 (Q3m + Q4m)] may be calculated, and a common fuel injection amount TI for each cylinder or each cylinder group may be set corresponding to the average value QmAV, QmAV1, QmAV2. Torque fluctuations due to variations in the amount of intake air of the engine can be suppressed.

A three-dimensional map of the volume intake air amount may be created by using the closing timing of the intake valve and the engine speed as parameters, and the volume intake air amount may be calculated by searching the map.

Further, in order to finely adjust the target torque, the opening / closing timing of the intake valve may be adjusted, or the throttle valve opening may be adjusted if the throttle valve is provided.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of a variable valve engine showing one embodiment of the present invention.

FIG. 3 is a basic structural diagram of an electromagnetic drive device of the intake and exhaust valves.

FIG. 4 is a diagram showing an arrangement of an air-fuel ratio sensor.

FIG. 5 is a flowchart of an air-fuel ratio control routine.

FIG. 6 is a diagram showing target opening / closing timings of intake and exhaust valves.

FIG. 7 is a diagram showing a relationship between a closing timing of an intake valve and an intake air amount.

FIG. 8 is a diagram showing target torque characteristics using the closing timing of the intake valve and the engine speed as parameters.

[Explanation of symbols]

 Reference Signs List 1 engine 2 piston 3 combustion chamber 4 spark plug 5 electromagnetically driven intake valve 7 intake passage 8 exhaust passage 9 fuel injection valve 10 control unit 11 crank angle sensor 12 accelerator pedal sensor 13 intake temperature sensor 14 intake pressure sensors 15A, 15B empty Fuel ratio sensor 31 Detection rod 32 Lift sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 13/02 F02D 13/02 J 41/04 320 41/04 320 41/18 41/18 F 43/00 301 43/00 301E 301Z 45/00 312 45/00 312P F-term (Reference) 3G084 BA09 BA13 BA16 DA04 EB14 EB15 EB18 FA02 FA03 FA07 FA10 FA11 FA20 FA30 FA33 FA38 3G092 AA01 AA05 AA11 BA05 BA08 BB02 DA01 DA02 DA07 DC01 DE01 EB03 EC01 EC05 EC09 FA06 HA01Z HA04Z HA05Z HA13Z HD06X HD06Z HE01Z HE03Z HE08Z HF02Z HF08Z 3G301 HA01 HA19 JA11 LA01 LB02 LC01 MA01 MA11 NA03 NA04 NA05 NA06 NC02 ND01 ND33 NE14 PA01Z PA07Z PA10Z PE08Z PD08Z08 PD08Z08

Claims (4)

[Claims] 1. A variable valve engine having an intake valve which can be variably controlled at an arbitrary opening / closing timing. An intake valve opening / closing timing detecting means for detecting an opening / closing timing of the intake valve, and an engine rotational speed detecting for detecting an engine rotational speed. Means, an intake air amount calculating means for calculating an intake air amount based on an opening / closing timing of an intake valve and an engine rotation speed, and a fuel injection amount for calculating a fuel injection amount supplied to an engine based on the intake air amount. Calculation means; air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; and air for feedback-correcting the fuel injection amount based on the detected air-fuel ratio so that the air-fuel ratio approaches the target air-fuel ratio. And a fuel injection means for supplying the feedback-corrected fuel injection amount to the engine. Air-fuel ratio control system for variable valve engine. 2. For each of a plurality of divided engine operating regions,
An air-fuel ratio learning unit configured to correct the fuel injection amount using a learning value updated and corrected so as to reduce a deviation of a feedback correction amount from a reference value by the air-fuel ratio feedback correction unit. Claim 1
3. The air-fuel ratio control device for a variable valve engine according to claim 1. 3. An intake air temperature detecting means for detecting an intake air temperature, an intake pressure detecting means for detecting an intake pressure, and an intake air amount calculated by the intake air amount calculating means is corrected by the intake air temperature and the intake pressure. The air-fuel ratio control device for a variable valve engine according to claim 1, wherein the air-fuel ratio control device includes an intake air amount correction unit. 4. A plurality of said air-fuel ratio detecting means are provided for each of a plurality of cylinder groups.
An air-fuel ratio control device for a variable valve engine according to any one of the above.