JPH07189770A - Control device for lean combustion engine - Google Patents

Abstract

PURPOSE:To suppress torque fluctuation at the time of changeover between stoichio operation/rich operation and lean operation of a lean combustion engine. CONSTITUTION:An electronic control unit obtains a reference opening D0 and a target intake pressure P0 of an idling engine speed control valve as an air bypass valve from a map, at the starting time 6f shifting stoichio operation to lean operation, based on an engine speed Ne and a throttle opening TP at the start of the shifting. The electronic control unit then feds driving pulses N by a number corresponding to the reference opening D0 to a stepper motor 32 of the idling engine speed control valve. Next, the driving pulses are fed to the stepper motor by a number corresponding to an opening correction rate D1 according to deviation between the target intake pressure P0 and an actual intake pressure PB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lean burn engine control device, and more particularly to a lean burn engine control device capable of suppressing engine output torque fluctuation during switching between rich operation and lean operation of the engine. .

[0002]

2. Description of the Related Art In order to improve the exhaust gas characteristics or fuel consumption of an internal combustion engine, the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to an air-fuel ratio leaner than the stoichiometric air-fuel ratio,
It is known to run the engine lean (lean combustion operation). In this type of air-fuel ratio control, the air-fuel ratio is controlled near the stoichiometric air-fuel ratio in the acceleration operating region to prevent the engine output from becoming insufficient in the acceleration operating region, etc. ). Therefore, for example, when the accelerator pedal is released and the accelerator operation area is disengaged, only the fuel amount is reduced and the rich operation is switched to the lean operation. In this case, the engine output suddenly decreases and a shock occurs, which hinders drivability.

Therefore, in order to keep the engine output constant during the transition from the rich operation to the lean operation, an air-fuel ratio control device that changes only the intake air amount without changing the fuel supply amount to the engine is provided. Japanese Patent Laid-Open No. 5-187295
Has been proposed in the issue. This proposed device performs a rich operation when the engine is in a specific operation state and performs a lean operation at other times, and has two bypass passages that bypass the throttle valve, and one of the bypass passages has an idle rotation speed. A numerical control (ISC) valve is provided, and a negative pressure responsive valve is provided in the other bypass passage. During lean operation, the bypass valve provided in the control pressure passage that connects the throttle valve installation portion of the intake passage and the control chamber of the negative pressure responsive valve is opened, which allows the negative pressure in the intake passage, and thus the engine operating state. The amount of bypass air that conforms to the above is supplied to the engine through the bypass passage on the negative pressure responsive valve side. Further, the target intake air amount for achieving the air-fuel ratio on the lean fuel side is calculated according to the throttle valve opening, and the ISC valve opening is calculated according to the deviation between the target intake air amount and the actual intake air amount. Is duty-controlled so that the target intake air amount is supplied to the engine.

[0004]

According to the above proposed device, the fluctuation of the engine output torque at the time of switching between the rich operation and the lean operation can be suppressed to a considerable extent. However, the intake air amount control of the proposed device basically controls the opening degree of the negative pressure responsive valve in accordance with the intake negative pressure in the throttle valve installation portion of the intake pipe, and thus during operation switching. There is a certain limit to the optimization of the intake air amount control and the suppression of torque fluctuation.

That is, when the lean operation is performed in the air-fuel ratio region where the fuel consumption is good and the amount of nitrogen oxides generated is small, the amount of bypass air becomes insufficient, resulting in insufficient torque, or the amount of bypass air becomes excessive. The engine may be accelerated. Then, when the air-fuel ratio is brought close to the stoichiometric air-fuel ratio in order to eliminate the torque shortage, the amount of nitrogen oxides generated increases and the fuel efficiency decreases.

According to the knowledge of the inventor of the present invention, as shown in FIG. 1, the required bypass air flow rate is obtained from, for example, the volume efficiency and the engine speed, but in the actual bypass air control, the low rotation speed and high volume efficiency side is achieved. Insufficient bypass air will occur in the operating range, and excessive bypass air will occur in the operating range on the high rotation speed and low volumetric efficiency side. The present invention was devised in consideration of the above circumstances, and suppresses engine output torque fluctuations at the time of switching between stoichio operation or rich operation of the engine and lean operation to reduce shock and improve drivability. An object of the present invention is to provide a control device for a lean burn engine that can be achieved.

[0007]

A lean burn engine control apparatus according to the present invention detects a value of a first predetermined parameter indicating an engine load state and a value of a second predetermined parameter indicating an engine rotation speed. A detection unit, an air amount adjusting unit for adjusting the amount of intake air supplied to the engine through a bypass passage that bypasses the throttle valve, and an engine before and after the transition from stoichio operation or rich operation to lean operation A control unit for driving and controlling the air amount adjusting unit according to a control amount set based on the detected values of the first and second predetermined parameters so that the output torque difference is reduced or canceled. Characterize.

[0008]

When the stoichio operation or the rich operation is changed to the lean operation, the control means sets the first load indicating the engine load state.
Second, which represents the detected value of the predetermined parameter and the engine speed
The control amount of the air amount adjusting means during the transition is determined on the basis of the detected value of the predetermined parameter. Then, during the operation transition, the air amount adjusting means is controlled by the control means by the control amount determined as described above, whereby the intake air amount to the engine through the bypass passage is appropriately controlled and transitions. The difference between the front and rear engine output torque is reduced or canceled.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2, an intake manifold 2a connected to each cylinder of a lean burn engine 1 is provided with an electromagnetic fuel injection valve 3 for each cylinder, and fuel pressure is supplied from a fuel pump (not shown). Fuel having a constant pressure is supplied to each fuel injection valve 3 via a regulator (not shown).
Further, the intake manifold 2a is connected to an intake pipe 2b which forms an intake passage 2 in cooperation with the intake manifold 2a through a surge tank 2c, and an air cleaner 4 is arranged at an outer end of the intake pipe 2b. A throttle valve 5 is provided in the middle of the intake pipe 2b. An ignition plug (not shown) attached to each cylinder of the engine 1 is connected to an igniter (not shown) via a distributor (not shown), and the secondary coil is cut off when the supply current to the primary coil of the igniter is cut off. The high voltage generated in the engine causes a spark to fly to the spark plug to ignite the air-fuel mixture in the engine cylinder.

The control device according to the first embodiment of the present invention is provided with an electronic control unit (ECU) 10 which functions as a control means or the like in bypass air control which will be described later. The control unit 10 has a central processing unit and a nonvolatile memory. It has a storage device including a battery backup ram for storing various control programs and the like, an input / output device and the like (all not shown).

The present control device further includes an ISC valve 30 which is provided as a bypass air valve in the bypass passage 20 provided in the intake pipe 2b, bypassing the throttle valve 5. The ISC valve 30 is a control unit 10
In cooperation with the air amount adjusting means and also functioning as an idle speed control valve for opening and closing the bypass passage 20 to allow or block air supply to the engine 1 via the passage 20. A valve body 31 and a stepper motor (pulse motor) 32 for driving the valve body 31 to open and close.
Including and The pulse motor 32 is connected to the output side of the control unit 10 together with the fuel injection valve 3 and the igniter.

Further, the present control device is provided with various sensors as engine operating parameter detecting means. These sensors are, for example, an air flow sensor 41 provided on the intake passage 2 side for detecting the intake air amount from the Karman vortex information, and a potentiometer type throttle sensor attached to the throttle valve 5 for detecting the throttle opening. 42, an O 2 sensor 43 provided on the exhaust passage 6 side of the engine 1 for detecting the oxygen concentration in the exhaust gas, a water temperature sensor 44 for detecting the engine cooling water temperature, and a predetermined crank angle position provided at the distributor 7. For example, a crank angle sensor 45 that outputs a pulse signal (TDC signal) each time the top dead center is detected, and a cylinder discrimination sensor 46 that detects that a specific cylinder, for example, the first cylinder is at a predetermined crank angle position, Pressure attached to the surge tank 2c for detecting negative pressure in the intake pipe downstream of the throttle valve 5. And a sensor 47. The various sensors described above are connected to the input side of the electronic control unit 10.

The electronic control unit 10 is a TDC which is sent from the crank angle sensor 45 every 180 degrees in crank angle.
The engine speed is calculated from the stroke cycle of the engine detected based on the signal generation interval, and the ignition / fuel supply is performed based on the output from the cylinder discrimination sensor 46 and the preset ignition / fuel supply sequence in the engine cylinder. It is designed to determine which cylinder should be used.

Further, the electronic control unit 10 discriminates the engine operating range based on the outputs of various sensors, and determines the fuel injection amount according to the engine operating range, that is, the opening time of the fuel injection valve 3 and the optimum ignition timing. A drive signal corresponding to the calculated valve opening time is supplied to each fuel injection valve 3 to supply a required fuel amount to each cylinder, and a drive signal corresponding to the calculated ignition timing is supplied from the drive circuit to the igniter. It is designed to supply and ignite the air-fuel mixture. The entire engine operating range is shown in Fig. 4.
As illustrated in FIG. 2, the engine is divided into a rich operating range, a lean feedback operating range III and a fuel cut operating range IV according to the engine load such as the throttle opening and the engine speed, and the rich operating range is the rich feedback operating range I.
And the stoichio feedback operation area II. In the figure, the symbol WOT indicates that the throttle valve is fully opened.

In the above configuration, the electronic control unit 1
0 determines the present engine operating range based on the engine load parameter, for example, the output of the throttle sensor 42 and the engine speed Ne calculated from the generation cycle of the output of the crank angle sensor 45. In addition, the electronic control unit 1
0 calculates the valve opening time Tinj of the fuel injection valve 3 according to the following equation.

Tinj = A / N ÷ λ × K1 × K2 + T0 where A / N is the intake air amount per intake stroke obtained from the Karman vortex frequency detected by the air flow sensor 41 and the engine speed Ne. is there. λ is a target air-fuel ratio, which is a stoichiometric air-fuel ratio or a value close thereto (for example, air-fuel ratio 14.7) in the stoichiometric feedback operation range.
Further, in the rich feedback operation region, the value is set to the fuel rich side from the stoichiometric air-fuel ratio, and in the lean feedback operation region, the value is set to the fuel lean side from the stoichiometric air-fuel ratio. K1
Represents a coefficient for converting the fuel flow rate into the valve opening time. K
Reference numeral 2 is a correction coefficient value set by various parameters indicating the engine operating state, for example, the engine water temperature sensor 4
4 is set in accordance with the engine water temperature TW detected by No. 4 and the oxygen concentration in exhaust gas detected by the O2 sensor 43. T0 is a correction value set according to the battery voltage or the like detected by a battery sensor (not shown).

Then, the electronic control unit 10 supplies a drive signal corresponding to the valve opening time Tinj to the fuel injection valve 3 corresponding to the cylinder which is the target of fuel supply at this time, thereby corresponding to the valve opening time Tinj. Fuel quantity is supplied to the cylinder.
In connection with bypass air control, electronic control unit 10
Is functionally equipped with various functional units shown in FIG.

That is, the control unit 10 uses the engine speed calculator 11 for calculating the engine speed Ne based on the output of the crank angle sensor 45, the output Ne of the engine speed Ne and the output TPS of the throttle sensor 42, and the ISC.
A target opening pressure setting unit 12 for finding the basic opening D0 of the valve 30, and a target intake pressure setting for finding the target intake manifold pressure P0 during lean operation from the engine speed calculation unit output Ne and the throttle sensor output TPS. And a section 13. The subtraction unit 14 outputs the target intake pressure setting unit output P0.
From this, the output PB of the pressure sensor 47 is subtracted, and the opening correction unit 15 obtains the opening correction amount D1 corresponding to the output of the subtraction unit 14. The target intake pressure setting unit output D0 and the opening correction unit output D1 are added by the addition unit 16, and the addition unit output indicating the target ISC valve opening is sent to the valve drive unit 17.

The valve drive unit 17 determines the drive pulse number N and ISC based on the target ISC valve opening D0 + D1 and the current ISC valve opening stored in, for example, a register (not shown) built in the control unit 10. The valve operation direction is determined, and the output pulses of the number equal to the driving step number N are sent to each phase magnetic pole (not shown) of the stepper motor 32 of the ISC valve 30 in the phase order corresponding to the valve operation direction. As a result, the opening of the ISC valve 30 becomes the target opening D.
Controlled to 0 + D1.

The bypass air control operation of the control device shown in FIGS. 2 and 3 will be described below. While the engine 1 is running
The electronic control unit 10 executes the bypass air control routine shown in FIG. 5 at a predetermined cycle. In this control routine, the control unit 10 reads the output from the water temperature sensor 44, and first determines whether or not the engine cooling water temperature represented by this sensor output exceeds a preset feedback start water temperature (step S1). If the determination result is affirmative, the control unit 10 determines that the throttle sensor 4
2 and the output from the crank angle sensor 45,
Based on the throttle sensor output TPS and the engine speed Ne calculated from the generation cycle of the crank angle sensor output, it is determined whether the engine 1 is operating in the lean feedback operation range, that is, whether the lean condition is satisfied. It is determined whether or not (step S2).

If the determination result in step S2 is affirmative, the control unit 10 determines whether or not a system failure relating to the present control device has been detected in a failure determination routine (not shown) (step S3). If negative, the bypass air control during lean operation, which will be described later, is started. On the other hand, when it is determined in step S1 that the engine cooling water temperature has not reached the feedback start water temperature, or in step S2 that the lean condition is not satisfied, or when the system failure is determined in step S3, the control unit 10 determines that the current Output pulses of the driving step number N corresponding to the ISC valve opening are sent to the stepper motor 32 in the phase sequence corresponding to the valve closing direction (thus, I
If the SC valve 30 is already closed, the drive pulse is not sent out), so that the ISC valve 30 is closed (step S4), and the execution of the bypass air control routine in this cycle ends.

If the determination results in steps S1 and S2 described above are positive and the determination result in step S3 is negative, for example, the feedback start water temperature is reached and the rich operating range (rich or strike If lean conditions are satisfied after engine operation in the (Ikio feedback operation range), bypass in lean operation in this control routine to shift from rich operation (rich operation in a narrow sense or stoichio operation) to lean operation. Air control is started. In parallel with this, in the control routine relating to the above-described fuel supply control, the target air-fuel ratio during rich operation is switched to the target air-fuel ratio during lean operation. The air-fuel ratio may be switched in multiple stages.

More specifically, at the start of the bypass air control during lean operation, the throttle sensor output TPS and the engine speed at the start of the transition from rich operation to lean operation, which were used to determine whether the lean condition is satisfied in step S2. Based on Ne, the control unit 10 has a block 1 of FIG.
Referring to the TPS Ne-D0 map shown in 2 above, I
The basic opening D0 of the SC valve 30 is determined (step S
5). ISC valve 30 at the beginning of the transition to lean operation
Is in the valve closed state, the control unit 10 sends the drive pulse of the drive step number N corresponding to the basic opening D0 to the magnetic poles of each phase of the stepper motor 32 in the phase order corresponding to the ISC valve opening direction. Then, the ISC valve 30 is opened by the basic opening D0 and the basic opening D0 is stored as the current set valve opening (step S6).

Next, based on the throttle sensor output TPS and the engine speed Ne at the start of the shift to the lean operation, the control unit 10 refers to the TPS.Ne-P0 map shown in the block 13 of FIG. To determine the target intake manifold pressure P0 during lean operation (step S
7). This TPS / Ne-P0 map is set to give a target intake manifold pressure P0 that produces the same torque as the engine output torque in the rich operation at the same throttle opening TPS during the lean operation.

Next, the control unit 10 reads the output of the pressure sensor 47 indicating the actual intake manifold pressure PB (step S8) and compares the pressure sensor output PB with the target intake manifold pressure P0 (step S9). Then, when the actual intake pressure PB is lower than the target intake pressure P0, the control unit 10 applies the drive pulse of the drive step number N corresponding to the opening correction amount D1 corresponding to the pressure deviation P0-PB to the stepper motor 32. It is sent to each phase magnetic pole in the phase order corresponding to the ISC valve opening direction, the ISC valve opening is increased by the opening correction amount D1 (step S10), and the process returns to step S8. Further, when the actual intake pressure PB exceeds the target intake pressure P0, drive pulses of the drive step number ΔN are sent to the magnetic poles of each phase of the stepper motor 32 in the phase sequence corresponding to the ISC valve closing direction. The opening is reduced by the opening correction amount D1 (step S1
1) The control program returns to step S8.

Thereafter, steps S8 to S11 are executed, and when it is determined in step S9 that the actual intake pressure PB becomes equal to the target intake pressure P0, this control routine ends. As described above, during the switching from the rich operation to the lean operation, the ISC valve opening degree and thus the intake air amount are feedback-controlled so that the intake manifold pressure that produces the same torque as that in the rich operation is obtained. As a result, engine output torque fluctuation due to operation switching is suppressed, and shock is reduced and drivability is improved.

The control device of the second embodiment of the present invention will be described below. In the control device of the first embodiment, the stepper is used to feedback control the intake manifold pressure during the transition to the lean operation to the target pressure obtained from the throttle opening TPS and the engine speed Ne at the start of the transition to the lean operation. Although the motor-driven air bypass valve 30 is used, the apparatus according to the present embodiment controls the time-average opening degree of the negative pressure-responsive air bypass valve by controlling the duty of the control negative pressure supply. The intake manifold pressure is feedback-controlled.

That is, as shown in FIG.
A negative pressure responsive valve 130 provided as an air bypass valve in a bypass passage 120 provided in parallel with the intake passage 2 bypassing the throttle valve 5, and a negative pressure chamber of the negative pressure responsive valve 130 and the surge tank 2c are communicated with each other. A solenoid valve 15 provided in the negative pressure passage 140 for opening and closing the passage 140.
It has 0 and.

The negative pressure responsive valve 130 includes a bypass passage 120.
A valve body 131 for opening and closing the valve body, a spring 132 for urging the valve body 131 in the valve closing direction, and a diaphragm 133 formed integrally with the valve body 131 to define a negative pressure chamber. The valve body 131 is adapted to open by a corresponding lift amount. In FIG. 6, reference numeral 30 'denotes an ISC valve dedicated to air supply control during idle operation.

In connection with the air bypass control, an electronic control unit (ECU) 110, as shown in FIG. 7, receives an output Ne of an engine speed calculating section (not shown) and a throttle sensor output TPS to a solenoid. A basic duty ratio setting unit 112 for obtaining a basic duty ratio D10 of the valve 150, a target intake pressure setting unit 113, a subtracting unit 114, an adding unit 116, and a subtracting unit corresponding to the elements 13, 14 and 16 of FIG. 3, respectively. The duty ratio correction unit 115 for obtaining the duty ratio correction amount D11 from the output P0-PB and the target duty ratio D10 + D11 sent from the addition unit 116.
And a solenoid valve drive unit 117 for on / off controlling the exciting coil 151 of the solenoid valve 150.

The bypass air control operation of the control device shown in FIGS. 6 and 7 will be described below with reference to FIG. Figure 8
In the bypass air control routine shown in FIG. 5, the control unit 110 determines whether the result of the determination in either one of steps S101 and S102 corresponding to steps S1 and S2 in FIG. 5 is negative, or in step S3 corresponding to step S3.
If the determination result in 103 is affirmative, the solenoid valve 15
The exciting coil 151 of 0 is deenergized, and 0% is stored as the current set duty ratio of the solenoid valve 150 (step S104).

As a result, the negative pressure supply from the intake passage 2 through the negative pressure passage 140 to the negative pressure chamber of the negative pressure responsive valve 130 is cut off by the valve body 152 of the solenoid valve 150.
The atmosphere introducing passage of the solenoid valve 150 is opened, and the atmosphere is introduced into the negative pressure chamber of the negative pressure responsive valve 130 through the same passage, and the valve body 131 of the negative pressure responsive valve 130 is closed by the spring force of the spring 132. Be energized. Therefore, the air bypass valve (AB
The negative pressure responsive valve 130 as V) is closed, and the bypass air supply to the engine 1 via the bypass passage 120 is cut off.

On the other hand, if the determination results in both steps S101 and S102 are affirmative and the determination result in step S103 is negative, the control unit 110 causes the Ne.TPS-D10 map shown in block 112 of FIG. Engine speed N at the start of shifting to lean operation
Solenoid valve 1 based on e and throttle opening TPS
The basic duty ratio D10 of 50 is calculated and stored as the current set duty ratio (step S105), and the exciting coil 151 of the solenoid valve 150 is turned on / off at this set duty ratio D10 (step S106).

As a result, when the exciting coil 151 is excited, the solenoid valve 150 is opened and the negative pressure from the surge tank 2c is introduced into the negative pressure chamber of the negative pressure responsive valve 130 via the negative pressure passage 140. Further, when the exciting coil 151 is deenergized,
The solenoid valve 150 is closed to block the introduction of the negative pressure through the negative pressure passage 140, and the solenoid valve 1 is placed in the negative pressure chamber.
Atmosphere is introduced via 50. Therefore, the negative pressure responsive valve 1
The negative pressure chamber pressure of 30, and thus the valve body position, that is, the opening degree, corresponds to the set duty ratio, whereby the intake air of an amount corresponding to the set duty ratio is supplied to the engine 1 via the bypass passage 120. .

Next, the TP shown in block 113 of FIG.
Referring to the S.Ne-P0 map, the control unit 110
Determines the target intake manifold pressure P0 at the time of transition to the lean operation based on the throttle sensor output TPS at the start of the transition to the lean operation and the engine speed Ne (step S107). This TPS / Ne-P0 map is set to give a target intake manifold pressure P0 that produces the same torque as the engine output torque in the rich operation at the same throttle opening TPS during the lean operation.

Next, the control unit 110 reads the output of the pressure sensor 47 indicating the actual intake manifold pressure PB (step S108), and compares the pressure sensor output PB with the target intake manifold pressure P0 (step S1).
09). When the actual intake pressure PB is lower than the target intake pressure P0, the control unit 110 stores the sum of the corrected duty ratio D11 corresponding to the pressure deviation P0-PB and the current set duty ratio as a new set duty ratio. The solenoid valve 150 is driven on / off at this duty ratio (step S110). This increases the bypass air supply amount. Then, the process returns to step S108. When the actual intake pressure PB exceeds the target intake pressure P0, a new set duty ratio obtained by subtracting the correction duty ratio D11 from the current set duty ratio is stored, and the solenoid valve 150 is driven at this duty ratio. As a result, the bypass air supply amount is reduced (step S111). Then, the control program returns to step S108.

Thereafter, steps S108 to S111 are executed, and when it is determined in step S108 that the actual intake pressure PB becomes equal to the target intake pressure P0, this control routine ends. The controller of the third embodiment of the present invention will be described below. In the control device of the second embodiment, the intake manifold pressure is feedback-controlled to the target pressure by controlling the opening of the negative pressure responsive air bypass valve, but the control device of the present embodiment is similar to the air bypass valve. Is similarly duty controlled to feedback control the lift amount of the valve to a target value.

As shown in FIG. 9, the present control device is basically constructed similarly to the control device of FIG. Therefore, the same elements as those of the control device shown in FIG. 6 are designated by the same reference numerals and the description of the configuration is omitted. However, unlike the one shown in FIG. 6, the negative pressure responsive valve 130 of the present control device is provided with a position sensor 160 for detecting its opening. The position sensor 160 has a movable portion via the diaphragm 133 of the negative pressure responsive valve 130 and the valve body 1
It is connected to 31 and sends a detection output indicating the lift amount of the valve body 131 and thus the opening degree of the negative pressure responsive valve 130 to the electronic control unit (ECU) 210.

In connection with air bypass control, the electronic control unit 210, as shown in FIG.
2, 116 and 117 are provided with a basic duty ratio setting unit 212, an addition unit 216 and a solenoid valve drive unit 217, respectively, and a negative pressure is output from an output Ne of an engine speed calculation unit (not shown) and a throttle sensor output TPS. A target opening setting unit 213 for obtaining a target opening (target lift amount) L0 of the response valve 130, and an output L0 of the setting unit
The subtraction unit 214 for subtracting the output of the position sensor 160 representing the actual opening (lift amount) LA from the above, and the duty ratio correction unit 215 for obtaining the duty ratio correction amount D21 from the subtraction unit output L0-LA. ing. The exciting coil 151 of the solenoid valve 150 is turned on / off by the solenoid valve driving unit 217 at the target duty ratio D20 + D21 sent from the adding unit 216.

9 and 1 with reference to FIG.
The bypass air control operation of the control device shown in 0 will be described.
In the bypass air control routine shown in FIG. 11, the control unit 210 has steps S101 and S102 of FIG.
If the determination result in either one of steps S201 and S202 corresponding to the above is negative or the determination result in step S203 corresponding to step S103 is affirmative, the exciting coil 151 of the solenoid valve 150 is deenergized. At the same time, 0% is stored as the current set duty ratio of the solenoid valve 150 (step S204). As a result, the negative pressure responsive valve 130 is closed, and the bypass air supply to the engine 1 via the bypass passage 120 is cut off.

On the other hand, if the determination results in both steps S201 and S202 are affirmative and the determination result in step S203 is negative, the control unit 210 determines that
Referring to the Ne.TPS-D20 map shown in block 212, the basic duty ratio D20 of the solenoid valve 150 is calculated based on the engine speed Ne and the throttle opening TPS at the start of the shift to lean operation, and this is calculated. The current set duty ratio is stored (step S205), and the exciting coil 151 of the solenoid valve 150 is driven on / off at the set duty ratio D20 (step S206).
As a result, the engine 1 is supplied with intake air in an amount corresponding to the set duty ratio.

Next, T shown in block 213 of FIG.
Referring to the PS / Ne-L0 map, the control unit 21
0 is the target opening degree L0 of the negative pressure responsive valve 130 during the shift to the lean operation, based on the throttle sensor output TPS and the engine speed Ne at the start of the shift to the lean operation.
Is determined (step S207). This TPS / Ne-
The L0 map is set to give a target opening L0 that produces the same torque as the engine output torque in the rich operation at the same throttle opening TPS during the lean operation.

Next, the control unit 10 controls the position sensor 160 which indicates the actual opening LA of the negative pressure responsive valve 130.
Is read (step S208), and the position sensor output LA is compared with the target opening L0 (step S2).
09). When the actual opening LA is less than the target opening L0, the control unit 10 stores the sum of the corrected duty ratio D21 corresponding to the opening deviation P0-PA and the current set duty ratio as a new set duty ratio. Then, the solenoid valve 150 is turned on / off at this duty ratio (step S210). This increases the bypass air supply amount. Then, the process returns to step S208. If the actual opening LA exceeds the target opening L0, a new set duty ratio obtained by subtracting the correction duty ratio D21 from the current set duty ratio is stored, and the solenoid valve 150 is driven at this duty ratio. The bypass air supply amount is reduced (step S211). Then, the control program returns to step S208.

After that, steps S208 to S211 are executed, and when it is determined in step S208 that the actual opening LA has become equal to the target opening L0, this control routine ends. The present invention is not limited to the above first to third embodiments,
It can be variously modified. For example, in the first to third embodiments, the basic amounts D0, D10 of the opening (duty ratio, lift amount) of the ISC valve during the transition to the lean operation based on the throttle sensor output indicating the throttle opening TPS, D2
Although 0 and the target intake pressure P0 are set, the volume efficiency ηv may be used instead of the throttle opening TPS in setting the basic amount and the target intake pressure. In this case, for example, the intake air amount A / N per intake stroke is calculated based on the output of the air flow sensor and the output of the engine speed sensor.
The volume efficiency equivalent value is obtained by dividing / N by the fully open A / N in the same engine rotation state.

In the first to third embodiments, the opening amounts of the air bypass valve are set to the basic amounts D0, D10, D20, and the target intake pressure P0 and the actual intake pressure PB on the downstream side of the throttle valve are set. The valve opening is feedback-controlled so that the deviation or the deviation between the target valve opening L0 and the actual valve opening LA becomes "0". The intake pressure is used as a control parameter in the feedback control of the first and second embodiments. Instead of the first intake stroke, the intake air quantity per intake stroke may be used.
The feedback control in the third embodiment may be omitted. That is, the valve opening or the like may be simply open-loop controlled to the values D0, D10, D20.

In the first and second embodiments, the correction amount D corresponding to the pressure deviation P0-PB or the opening deviation L0-LA.
Although the air bypass valve opening etc. are corrected to be increased or decreased by 1, D11 and D21, in this correction, the correction amount D
The procedure of increasing or decreasing the valve opening degree or the like by the correction amount set in advance to a value smaller than 1, D11 and D21 may be repeated until the pressure deviation or the opening degree deviation disappears. Further, the correction control procedure can be modified in various ways, and for example, the air bypass valve opening degree and the like can be controlled by PI control (proportional / integral control).

In the second and third embodiments, as shown in FIGS. 6 and 9, the air bypass valve is replaced by the negative pressure responsive valve 130.
However, the air bypass valve applicable to the present invention is not limited to this. 12
Shows a modified example of the air bypass valve. The air bypass valve is composed of a negative pressure responsive valve 130 and first and second solenoid valves 150 ′ and 150 ″.
The solenoid valve 150 ′ is different from the solenoid valve 150 in that the solenoid valve 150 ′ of FIG. The second solenoid valve 150 ″ is arranged in the middle of an air passage 141 having one end communicating with the negative pressure passage 140 and the other end communicating with the intake pipe 2 b upstream of the throttle valve 5. That is, FIG.
The air bypass valve is installed so that the negative pressure of the negative pressure responsive valve 130 can be introduced into the negative pressure chamber through the negative pressure passage 140 and the air can be introduced into the negative pressure chamber through the air passage 141. The negative pressure chamber pressure is controlled by controlling the on / off duty of the solenoid valves 150 ′ and 150 ″.

[0048]

As described above, the control device for a lean burn engine according to the present invention detects the value of the first predetermined parameter indicating the engine load state and the value of the second predetermined parameter indicating the engine rotation speed. Detecting means, an air amount adjusting means for adjusting the intake air amount supplied to the engine through a bypass passage that bypasses the throttle valve, and during the transition from stoichio operation or rich operation to lean operation, before and after the transition. And a control unit for driving and controlling the air amount adjusting unit according to a control amount set based on the detection values of the first and second predetermined parameters so as to reduce or cancel the engine output torque difference. Therefore, engine output torque fluctuation during engine stoichio operation or switching between rich operation and lean operation is suppressed to reduce shock and dry. It attained the capability improvement.

[Brief description of drawings]

FIG. 1 is a graph showing a required bypass air flow rate and a bypass air shortage region and an excess region by volume efficiency and engine speed.

FIG. 2 is a schematic view showing a control device according to a first embodiment of the present invention together with peripheral elements.

3 is a block diagram of the electronic control unit (ECU) shown in FIG.
It is a block diagram showing various functional parts related to bypass air control.

FIG. 4 is a graph showing an engine rich feedback operating range, a stoichio feedback operating range, a lean feedback operating range, and a fuel cut operating range by engine load and engine speed.

FIG. 5 is a flowchart of a bypass air control routine executed by the electronic control unit shown in FIGS. 2 and 3.

FIG. 6 is a partial schematic view showing a main part of a control device according to a second embodiment of the present invention together with peripheral elements.

7 is a block diagram showing various functional units related to bypass air control of the electronic control unit shown in FIG.

8 is a flowchart of a bypass air control routine executed by the electronic control unit shown in FIGS. 6 and 7.

FIG. 9 is a partial schematic view showing a main part of a control device according to a third embodiment of the present invention together with peripheral elements.

10 is a block diagram showing various functional units related to bypass air control of the electronic control unit shown in FIG.

11 is a flowchart of a bypass air control routine executed by the electronic control unit shown in FIGS. 8 and 9.

12 is a partial schematic view showing a modified example of the air bypass valve shown in FIGS. 6 and 9. FIG.

[Explanation of symbols]

 1 engine 2 intake passage 3 fuel injection valve 5 throttle valve 10, 110, 210 electronic control unit 12 basic opening setting unit 13, 113 target intake pressure setting unit 14, 114, 214 subtraction unit 15 opening correction unit 16, 116, 216 Adder 17 Valve drive 20, 120 Bypass passage 30 ISC valve 32 Stepper motor 41 Air flow sensor 42 Throttle sensor 45 Crank angle sensor 47 Boost sensor 112, 212 Basic duty ratio setting unit 115, 215 Duty ratio correction unit 117, 217 Solenoid Valve drive unit 130 Negative pressure responsive valve 140 Negative pressure passage 141 Air passage 150, 150 ', 150 "Solenoid valve 160 Position sensor 213 Target opening degree setting unit

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02D 45/00 301 G

Claims (1)

[Claims] 1. A detection means for detecting a value of a first predetermined parameter indicating an engine load state and a value of a second predetermined parameter indicating an engine rotation speed, and an engine via a bypass passage bypassing a throttle valve. And an air amount adjusting means for adjusting the amount of intake air supplied to the first and second so as to reduce or offset the engine output torque difference before and after the transition during the transition from stoichio operation or rich operation to lean operation. 2. A control device for a lean burn engine, comprising: a control unit for driving and controlling the air amount adjusting unit according to a control amount set based on a detected value of the second predetermined parameter.