JPS6181542A - Control device for air-fuel ratio of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent step-out and abnormal motion of an actuator, by providing a voltage discriminating means, which discriminates whether a source voltage exceeds a specified value and a means which stops energization of the actuator during a specified time. CONSTITUTION:When a source voltage VB becomes below a specified value E1, a signal from an output terminal T1 of a source voltage discriminating circuit 50 produces a low level. As a result, an inverter 60 outputs a stop signal of a high level to a driving direction switching circuit 59, and control of the position of an actuator 61 is stopped. When a source voltage is recovered to higher than the specified value E1, a stop signal fed to the driving direction switching circuit 59 is rendered ineffective. A signal from a one shot multi 53 is fed to an initial processing circuit 55. This enables prevention of step-out and abnormal motion of the actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular to an electronic control unit or an applied voltage to an actuator that controls the air-fuel ratio of an air-fuel mixture. The present invention relates to an air-fuel ratio control device for an internal combustion engine that can appropriately drive the actuator according to the degree of decrease in the power supply voltage.

(Prior Art) A device for detecting the concentration of exhaust gas components of an internal combustion engine;
a fuel metering device that generates an air-fuel mixture to be supplied to the engine; and a concentration sensing device configured to feed back and control the air-fuel ratio of the air-fuel mixture to a set value in accordance with an output signal of the concentration sensing device. Said fuel VI4r? A device for controlling the air-fuel ratio of the air-fuel mixture supplied to the engine 2a, comprising an electric circuit coupled to the C device, is well known to those skilled in the art (for example, Japanese Patent Laid-Open No. 357-62955).

FIG. 2 is an overall configuration diagram of the air-fuel ratio control device as described above.

Reference numeral 1 designates an internal combustion engine, and an intake manifold (intake pipe) 2 connected to the engine 1 is provided with a carburetor generally designated by 3.

The carburetor 3 is formed with a fuel passage 5.6 that communicates the flows 1 to 4 with the primary intake passage, and these passages are connected to an air-fuel ratio control valve 9 via air passages 8a and 8b, respectively. ing.

Furthermore, fuel passages 7a and 7b are formed in the carburetor 3 to communicate the float chamber 4 and the secondary intake passage. The passage 7a is connected to the air-fuel ratio control valve 9 via an air passage 8C, and opens slightly downstream of the throttle valve 30b of the secondary intake passage.

Further, the passage 7b has an air passage 8d having a fixed throttle.
It communicates with the inside of the air cleaner through.

In the illustrated example, the control valve 9 consists of three flow control valves,
Each flow control valve includes a cylinder 10, a valve body 11 displaceably inserted into the cylinder 10, and a coil spring 12 mounted between the cylinder and the valve body to press each valve body in one direction. From (14).

The anti-coil spring side end 11a of each valve body 11 is formed into a tapered shape, and depending on the displacement of the valve body 11, the opposite end opening 10 of the cylinder 10 through which the valve body taper portion 11a is inserted
The opening area of a is changed.

One end (end opposite to the coil spring side) of each valve body 11 is in contact with a connecting plate 15 connected to a worm member 14 which is prevented from rotating so as to be able to reciprocate.

The worm member 14 is threadedly engaged with a rotor 17 of a stepper motor 13 rotatably disposed around the worm member 14 via a radial bearing 16 . Furthermore, on the outer periphery of the rotor 17,
A solenoid 18 as a stator is arranged.

The solenoid 18 is electrically connected to an electronic control unit (rEcUJ) 20.

When the solenoid 18 is energized by a drive pulse from the ECU 20, the rotor 17 rotates;
The worm member 14 that is threadedly engaged with the worm member 14 is displaced in the left-right direction in the figure. Therefore, the plate 15 connected to the arm member 14 is displaced in the left-right direction.

A permanent magnet 22 and a reed switch 23 are provided in a fixed housing 21 of the stepper motor 13 to face each other. On the other hand, a shielding plate 24 made of a magnetic material is attached to the peripheral edge of the plate 15 so as to be able to go in and out between the permanent magnet 22 and the reed switch 23.

As is clear from the above configuration, the shielding plate 24 is displaced from side to side as the plate 15 is displaced from side to side.

Further, according to this displacement, the reed switch 23
is performed on/off basis 121I.

That is, when the air-fuel ratio i, II fil valve 9 passes through the reference position determined by the mounting position of the permanent magnet 22, reed switch 23, and shielding plate 24, the reed switch 23 moves depending on the direction of movement. Can be turned on or off.

The reed switch 23 supplies a binary value (No. 15) to the ECU 20 according to this on/off switching.

An air intake port 25 communicating with the atmosphere is formed in the housing 21, and the air is introduced to each flow rate control valve through a filter 26 inserted into the intake port 25.

On the other hand, an Oz sensor 28 made of zirconium oxide or the like is provided on the inner wall of the exhaust manifold 27 of the engine so as to protrude into the manifold 27, and its output is supplied to the ECU 20.

Further, an atmospheric pressure sensor 29 is arranged to be able to detect the atmospheric pressure around the vehicle on which the engine is mounted. The atmospheric pressure sensor 2
The detection value signal No. 9 is also supplied to the ECU 20.

Further, a thermistor 33 is installed in the circumferential wall of the engine cylinder filled with engine cooling water, and detects the cooling water temperature representative of the engine temperature. The detection value signal of the thermistor 33 is also supplied to the ECU 20.

In addition, in FIG. 2, the reference numeral 39 indicates Co in the exhaust gas,
A three-way catalyst 31 for purifying HC and NOX is connected to the throttle valve 30a via a pipe 32.

A pressure sensor, 35, that detects the intake pressure in the intake manifold 2 downstream from 30b and supplies its output to the ECLJ20.
37 is an ignition switch, and 38 is a voltage VB power source (battery).

Next, the conventional air-fuel ratio system mentioned above! The control details of the 2II device will be explained with reference to FIG.

First, when the ignition switch 37 is turned on when starting the engine, the E'CU 20 is initialized. Thereafter, the ECU 20 detects the reference position of the stepper motor 13, which is an actuator, via the reed switch 23.

Note that the reference position is detected based on the position when the reed switch 23 of the stepper motor 13 is turned on or off.

Next, the ECU 20 drives the stepper motor 13 from the reference position to a predetermined position (preset position) optimal for starting the engine (hereinafter referred to as rPscrJ), and adjusts the initial air-fuel ratio to a predetermined corresponding one shift. set.

Next, the ECU 20 selects 02t? activation state of sensor 28;
Then, the engine cooling water temperature Tw detected by the thermistor 33 is monitored, and it is determined whether the start condition for air-fuel conversion control is satisfied.

To accurately perform air-fuel ratio feedback control, (1)
It is necessary that two conditions are satisfied: the 02 sensor 28 is in an activated state due to a sufficiently high temperature, and (a) the engine is in a warm-oxidation completed state.

Further, the 02 sensor made of zirconium oxide or the like has a characteristic that its internal resistance decreases as the temperature increases.

If a current is supplied to the 02 sensor with such characteristics from a constant voltage source built into the ECU 20 through a resistor with an appropriate resistance value, the output voltage V will be the voltage of the constant voltage source when it is inactive. (e.g., 5 volts) and the output voltage decreases as its temperature increases.

So, 02t? (When the output voltage of
It generates an activation signal when the air-fuel ratio has dropped to a certain level, and when a predetermined period of time (for example, 1 minute) has elapsed since the generation of the signal, and the air-fuel ratio feedback system tit + me is activated until the opening is possible. After confirming that the cooling water ATV has reached a predetermined value, air-fuel ratio feedback control is started.

It should be noted that the stepper motor 13 is operated at the predetermined position HP mentioned above during the 02 sensor activation and cooling water temperature TW detection stage.
It is held at 3 cr.

When the above-mentioned control at the time of starting is completed, the process shifts to basic air-fuel ratio control.

In other words, the ECU 20 outputs 1 from the 02 sensor 28.
The stepper motor 13 is driven to a predetermined position according to the absolute pressure Pa in the intake manifold from the No. 8 V1 pressure sensor 31, the engine speed Ne from the rotation speed sensor 35, and the atmospheric pressure PΔ from the atmospheric pressure sensor 29, Set the air-fuel ratio to a predetermined value.

More specifically, this basic air-fuel ratio control consists of (1) open-loop control when the throttle valve is fully open, (2) idling, and (a-deceleration), and (4) closed-loop control during partial load. Note that all of these controls are performed after the engine has reached a warm-up state.

First, the open loop control condition when the throttle valve is fully open is the gauge pressure difference (PA-PB) between the absolute pressure PB detected by the pressure sensor 31 and the atmospheric pressure (absolute pressure) PA detected by the atmospheric pressure sensor 29. or is lower than a predetermined difference ΔP.

The ECU 20 compares the difference between the output signals of the sensors 29 and 31 with a predetermined ax ΔP stored therein.

Then, when the above conditions are satisfied, the stepper motor 13 is operated so that the optimal air-fuel ratio for engine emissions is lr? Predetermined position; 19 (pre-pit position) PSwo
It is driven until it reaches t and is stopped at the predetermined position.

Note that when the throttle valve is opened, a known economizer (not shown) or the like operates, and a rich air-fuel mixture (low air-fuel ratio) is supplied to the engine.

The oven loop 1III control condition at idle is satisfied when the engine rotation @Ne is lower than a predetermined idle rotation speed N1dl (for example, 101000 rpm).

The ECU 20 compares the output signal Ne of the rotation speed sensor 35 with a predetermined rotation speed Nidl stored therein, and when the above conditions are met, the ECU 20 controls the stepper motor 13 to the optimum speed for engine emissions. It is driven until it reaches a predetermined idle position (preset position) PSidl, and then stopped at the predetermined position.

Next, the A-Bunlube control condition during deceleration is established when the absolute pressure PB in the intake manifold is lower than the predetermined absolute pressure p 3 dec.

The ECU 20 compares the output signal PB of the pressure sensor 31 with a predetermined absolute pressure p 3 dec stored therein, and when the above-mentioned conditions are met, moves the stepper motor 13 to a predetermined deceleration position (preset position). ) It is driven until it reaches p3dec and is stopped at the predetermined position.

The basis for the above oven loop control conditions during deceleration is that when the absolute pressure PB in the intake manifold drops below a predetermined value due to deceleration, unburned HC (hydrocarbons) in the exhaust gas increases, and as a result, the 0□ sensor The air-fuel ratio feedback control based on the detected value signal cannot be performed accurately, and the stoichiometric mixture ratio or air-fuel ratio of the air-fuel mixture cannot be determined.

Therefore, as described above, the absolute pressure 1) B in the intake manifold detected by the pressure sensor 31 is equal to its predetermined value P.
When smaller than B dec, the actuator (stepper motor) is moved to a predetermined position (preset position) F'5 dec that provides the optimum air-fuel ratio for engine emissions when the oven loop control conditions during deceleration disappear. Control is performed using a loop.

In addition, in each open-loop control when the throttle valve is fully opened, when idling, and when decelerating, the predetermined position ffi of each stepper motor 13 is adjusted according to the atmospheric pressure PA.
It is desirable that Pswot, PSidl, and PSdec are each appropriately corrected.

On the other hand, the closed-loop control condition at partial load is satisfied when the engine is in an operating state other than when each of the oven loop control regulations described above is satisfied.

In this closed loop control, ECtJ20
Engine rotation speed N detected by rotation speed sensor 35
According to the output signal V of the 02 sensor 28, proportional control (hereinafter referred to as "two-term control") or integral control (hereinafter referred to as "[term control]") by feedback is performed.

More specifically, the output voltage of the 02 sensor 28 is a predetermined voltage V.
If the value changes only at a higher level or lower level than rer (a value corresponding to the stoichiometric mixture ratio or air-fuel ratio), one-term control is executed.

In other words, the output voltage of the 02 sensor is equal to the predetermined voltage Vref
On the other hand, the position of the stepper motor 13 is corrected according to the value obtained by integrating the binary signal corresponding to being on the high level side or the low level side, thereby performing stable and accurate position control.

On the other hand, when the output signal of the o2 sensor 28 changes from a high level side to a low level side, or conversely from a low level side to a high level side, one term υ control is executed. That is, 0
The position of the stepper motor 13 is corrected in accordance with a value directly proportional to a change in the output voltage of the two sensors, and control is performed more quickly and efficiently than one-term control.

In the control described above, the position of the stepper motor is changed according to the value obtained by integrating the binary signal based on the change in the output voltage of the 02 sensor, but the number of steps increased or decreased per second depends on the engine rotation speed. We are changing accordingly.

That is, the number of steps increased or decreased per second by one-term control in a low rotational speed range is small, but increases as the rotational speed increases, and the number of steps increased or decreased per second at high rotational speeds is controlled.

In addition, in the binary control that is performed when there is a change in the 02 sensor output from a high level side to a low level side or a change in the opposite direction with respect to the predetermined voltage V rer, the stepper motor which increases and decreases every second. The number of steps is
Regardless of the engine speed, it is set to the same predetermined value (for example, 6 steps).

Furthermore, the air-fuel ratio at engine zero start-acceleration is 1i11
R is the engine rotation speed Ne after the engine has been warmed up.
At the stage when the engine moves from a low speed rotation range to a high speed rotation range, the predetermined idle rotation speed N1dl (for example, 101000
This is done on the condition that it exceeds pp.

When this condition is met, the ECU 20 moves the stepper motor 13 to a predetermined acceleration position (preset position).
p3acc rapidly. Immediately after this, ECt
J20 starts the air-fuel ratio feedback control described above.

As described above, when the engine is zero-started and accelerated, the seventh engine position is moved to a preset position P S ace where the amount of harmful gas emissions is low.

Therefore, in so-called zero start, where an engine equipped with an engine is accelerated from a stopped position, it is advantageous in terms of exhaust gas countermeasures, and it is possible to perform good air-fuel ratio feedback.

The control motor is switched in the following manner when transitioning from the various oven loop controls described above to closed loop control at partial load, or vice versa.

First, when switching from a closed loop to a Δ-bun loop, the ECU 20 selects the various preset positions p3cr, p3cr,
p3wot, PSidl.

Stepper Tanabata 13 is rapidly moved to p 3 dcc or PSacc (corrected for atmospheric pressure as necessary). This allows oven loop control to be performed according to each engine operating state.
It can be started at l1ffi.

On the other hand, when switching from the oven loop to the closed loop, the stepper motor 13 starts air-fuel ratio feedback control in the 1-term mode in response to a command from the ECU 20.

The reason for this is that the timing at which the output signal level of the 02 sensor switches from the high level side to the low level side, or vice versa, is not necessarily constant with respect to the timing at which the oven loop changes to the closed loop. Sometimes, the position axis of the stepper motor 13 immediately after switching to the closed loop is made smaller when the feedback control is started using one-term control than when the air-fuel ratio feedback control is started using P rn tilI 1211. This is because accurate air-fuel ratio control can be performed quickly and high emission stability can be obtained.

Note that the IQ position of the stepper motor 13, which is used as an actuator for the air-fuel ratio control valve 9, is monitored by a position counter (up-down counter) in the E CtJ20, but due to step-out or disturbance of the stepper motor, , a discrepancy may also occur between the contents of the counter and the actual position of the stepper motor.

In such a case, the ECtJ20 will operate by regarding the count 1 of the counter as the actual position of the stepper motor 13, but in oven loop control where it is necessary to accurately grasp the actual position of the stepper motor 13, may interfere with control operations.

Therefore, in the air-fuel ratio control system shown in Figure 2,
At the same time, the stepper morph position at which the reed switch 23 opens and closes is grasped as the reference position (for example, 50 steps), and the number of reference position steps (for example, 50 steps) stored in the ECLJ 20 is determined.
For example, by presetting 50 steps in the position counter, subsequent control accuracy is ensured.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

As mentioned above, conventionally, the position of the stepper motor at which the reed switch opens is grasped as the reference position, and at the same time, the number of reference position steps stored in the ECU is preset in the position counter. This prevents a deviation between the count value and the actual position of the stepper motor.

However, if the voltage applied to the stepper motor decreases, the stepper motor may step out or out of step, and even if the count values are matched as described above, the count value of the position counter and the actual stepper motor may differ. There will be a discrepancy between the positions.

As a result, oven loop control has the disadvantage that the position of the stepper motor cannot be accurately controlled.

Also, in the feedback control 11v#, the stepper motor does not operate normally in response to pulse application, so there is a drawback that proper air-fuel ratio position control cannot be performed.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problem) In order to solve the above problem, the present invention provides a method for changing the level of the power supply voltage.
The specified value E1 or higher allows the actuator to operate accurately,
Even if a voltage is applied, the actuator is irregularly moved by an external force, so accurate position control is not possible. When the level of the power supply voltage becomes lower than the specified value E1, the operation of the actuator is stopped, and when the level of the power supply voltage once drops to a voltage lower than the lower limit filIE2 and then returns to E1 or higher, the operation of the actuator is stopped. A feature of the present invention is that an initial process is performed to match the actual position with the device counter that displays the position.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

45 in the figure, the same reference numerals as in FIG. 2 represent the same or equivalent parts.

The ECU 20i is composed of a computer section 200, an input interface 202 for connecting the computer section 200 to an external circuit, an output interface 204, and a driver 206 connected between the output interface 204 and the stepper motor 13.

The computer section 200 may be of a well-known type, and may include a CPU 20.
1, RAM 205, ROM 203J5, and a common bus 207 for exchanging data and instructions between them.

Each detection output of the 02 sensor 28, TW sensor 33, Ne sensor 35, TH sensor 208 that detects the angle of the throttle valve, etc., and the voltage VB from the power source (battery) 38
is supplied to the computer section 200 via the input interface 202.

Further, FIG. 3 is a functional block diagram for explaining the present invention in detail.

In FIG. 3, the ignition switch 37 is turned on, and the initial process 1! l! When the scheduled pulse signal is supplied to the circuit 55, the stepper motor 13 shown in FIG.
The actuator 61 consisting of the connecting plate 15 and the connecting plate 15 is set at the reference position.

That is, the initial processing of the actuator 61 is performed as described below.

In this case, the reference position is preferably a position in which the stepper motor 13 is driven to its full right or left end in FIG. 2.

Specifically, the reference position register 56 is set to "O11" by the output of the initial processing circuit 55 which receives the pulse signal from the one-shot multi 65.

At the same time, position counter (up/down counter)
57 is the opposite side of the pancreas (lii'i- corresponding to this)
For example, it is set to 100''.

When the power supply voltage is equal to or higher than the specified value E1, a high level signal is output from the output terminal T1 of the power supply voltage discrimination circuit 50, and a low level signal is output from the output terminal T2. Therefore, the output of inverter 60 is at a low level, and drive direction switching circuit 59 and driver 206 function normally.

On the other hand, the pulse signal from the one-shot/multiple 65 is also supplied to the reset terminal of the flip 70 knob 51 via the OR gate 63. For this purpose, the flip 70
The Q output of the knob 51 becomes low level.

Therefore, despite the high level signal from the output terminal T1 of the weight voltage discrimination circuit 50, the output of the AND gate 52 is low level, and therefore the one shot multi 53 does not produce any output.

The comparator 58 detects the difference between the preset value of the reference position register 56 and the count value of the up/down counter 57, and outputs a pulse signal corresponding to the difference.

That is, if the count value of the up/down counter 57 is larger than the reset value of the reference position register 56, for example, ! A pulse signal with a higher level than the level IIF is output, and if it is smaller, a pulse signal with a lower level than the reference level is output.

Note that this pulse signal is output until the count value of the up/down counter 57 becomes equal to the preset value of the reference position register 56, as will be described later.

The drive direction switching circuit 59 selects a (+) direction drive signal or a (+) direction drive signal depending on the high level or low level pulse signal.
) direction drive signal to the driver 206. As a result, the driver 206 transmits a drive pulse signal corresponding to the (+) direction or (-) direction drive signal to the seven output units 61.
supply to

Therefore, during the initial processing, the actuator 61, that is, the stepper motor 13 and the connecting plate 15 are driven to the full right or left end, as described above.

Furthermore, the (+) direction or (-) direction drive signals, which are the outputs of the five drive direction switching circuits, are also supplied to an up/down counter 57. For this reason, the count value of the up/down counter 57 is added or subtracted by 1' degrees in the direction toward the preset value of the reference position register 56.

Under the above assumption, the count value of the up/down counter 57 will be decremented by 1''.

Then, when the count value of the up/down counter 57 becomes equal to the preset value "0" of the reference position register 56, the output of the comparator 58 disappears.

Therefore, the drive pulse signal for driving the actuator 61 also disappears.

By the way, in the above-mentioned initial processing, irrespective of the actual position of the stepper motor 13 when the process is started, it is assumed that the stepper motor 13 is at one end of the movable range in FIG. The number of pulses necessary to drive the stepper motor 13 to the reference position is supplied to the solenoid 18.

Therefore, in general, according to this initial processing method, an extra drive pulse will be supplied to the solenoid 18 even when the stepper motor 13 reaches the 15 ill; position.

However, in this state, since the movement of the stepper motor 13 is mechanically blocked, it is not driven beyond the reference position, and the stepper motor 13 is completely set at the reference position.

Next, when the IIJ O1l mode becomes the open loop control mode, the reference position register 56 is set to a preset value that has been determined experimentally or empirically in advance, corresponding to the engine operating state at that time. A signal for making this setting is supplied from line A.

Note that a specific method for determining the engine operating state and setting the preset value will be described later with reference to FIG.

When the reference position register 56 is set to the expected preset value, the comparator 58 outputs the reference level according to the difference in the count value of the up/down counter 57 indicating the current 1q position of the actuator 61. A pulse signal of 5 levels or lower level is output.

Then, as described above, the actuator 61 is driven to a position corresponding to the preset value of the reference position register 56, and is fixed at that position until the control mode changes.

Also, control! When the 11-7 mode is feedback-controlled and becomes the 1-mode mode, the motor drive signal (pulse signal) is switched to the drive direction switching circuit 59 at each frequency division rate timing obtained in step S53 in FIG. 5, which will be described later. supplied to

Further, at this time, the output signal of the O2 sensor 28 is also supplied to the five drive direction switching circuits. However, the signal supply from comparator 58 is cut off in a known manner.

The drive direction switching circuit 59 determines whether the output of the 02 sensor 28 is a high level side or a low level side with respect to a predetermined voltage V ref, that is, whether it is a rich side or a lean side. A (-) direction drive signal is supplied to the driver 206, and a (+) direction drive signal is supplied to the driver 206 if it is on the lean side, and if it is on the rich side, a (+) direction drive signal is supplied.

As a result, the actuator 61, that is, the stepper motor 13 and the connecting plate 15 are moved to the lean side or the rich side by the drive pulse signal from the driver 206 output in response to the (-) direction drive signal and the (+) direction drive signal. It is driven one step at a time.

As described above, feedback control of the air-fuel ratio is performed based on the output signal of the 02 sensor 28, and the air-fuel ratio of the internal combustion engine is maintained at approximately the theoretical value.

By the way, the above description of each control mode of initial processing, open loop control, and feedback control is based on the case where the power supply voltage V B lfi is equal to or higher than the specified value E1, and the stepper motor 13 constituting the actuator 61 goes out of step.
In this case, there was no abnormal movement due to external force, and accurate position control was possible.

However, when the power supply voltage VB falls below the lower limit [2], the stepper motor 13 begins to be moved irregularly by external force, regardless of the application of the drive pulse signal to the solenoid 18, and then the specified value 51 Even if the system is restored beyond this point, accurate position control will not be possible.

In addition, the power supply voltage VB/fi specified value E1 and lower limit value E2
When the stepper motor 13 is between There is a possibility that the iIJ will not correspond accurately.

Therefore, when the power supply voltage is lower than the specified value E1,
If accurate position control (feedback control and oven loop control) of the stepper motor 13 is not maintained and the power supply voltage drops below the lower limit value E2, the actual position of the stepper motor 13 and the position that should represent said position are Accurate correspondence with the count 1 of the up/down counter 57 is no longer guaranteed.

Therefore, in FIG. 3, a power supply voltage discrimination circuit 50 is provided,
The level of the power supply voltage is determined, and the position control method of the actuator J-61 is changed depending on the result.

That is, when the power supply voltage V B /fi becomes lower than the specified field E1, the signal at the output terminal T1 that is supplied from the power supply voltage discrimination circuit 50 to the inverter 60 becomes low level.

As a result, inverter 60 outputs a high-level stop signal to drive direction switching circuit 59.

Therefore, the (+) direction or -) direction drive signal which is the output of the drive direction switching circuit 59 is no longer generated. Therefore, when the power supply voltage VB becomes lower than the specified value E1, the subsequent position control of the actuator 61 is stopped, regardless of the control mode.

Then, when the power supply voltage is restored to the specified value 51 or higher again, the stop signal that is the output of the inverter 60 disappears, so that a drive pulse signal corresponding to each Luli control mode is output. Therefore, the actuator 61 will continue to be moved in the predetermined direction according to the drive pulse signal.

Next, when the power supply voltage becomes lower than the lower limit value E2, the output of the output terminal T2 of the weight voltage discrimination circuit 50 becomes high level. As a result, the flip-flop 51 is set,
From the Q terminal of flip 70 knob 51, AND gate 5
A high level signal is output to the other terminal of 2.

Note that at this time, the same low level signal as that supplied to the inverter 60 is applied to one terminal of the AND gate 52. Therefore, at this time, the one-shot multi 53 is not triggered and no pulse signal is output.

From this state, when the power supply voltage subsequently recovers to the specified value 51 or higher, the stop signals supplied to the five drive direction switching circuits disappear. And at the same time, and gate 5
A high level signal will also be applied to one terminal of 2.

As a result, the output of the AND gate 52 becomes high level,
The one-shot multi 53 is triggered and a scheduled pulse signal is output.

The pulse signal is supplied to an initial processing circuit 55 via an OR gate 54. Therefore, in the same way as in the case described above when the ignition switch 37 was turned on,
Initial processing will be performed.

Note that the pulse signal that is the output of the one-shot multi 53 is sent to the flip 70 knob 51 via the OR gate 63.
Since it is also supplied to the R terminal of the flip-flop 51
will be reset.

After the initial processing is completed, open loop control or feedback control is of course performed depending on the engine operating state at that time.

Next, with reference to flowchart 1- in FIG. 4, determination of the power supply voltage level according to the embodiment of the present invention shown in FIG.
and the processing based on it.

Note that this FIG. 4 corresponds to step 316 in FIG. 5 which will be described later.
We will provide detailed information on the processing procedures to be carried out.

Step 51601: Execute reading of power supply voltage.

Step 51602...The value E of the power supply voltage is the specified value 5
Determine whether it is 1 or more. If it is equal to or greater than the specified value 51, the process proceeds to step 31606, and if it is lower than the specified value 1iiIE1, the process proceeds to step 51603.

Step 31603...The value E of the power supply voltage is set to the specified value E
Set a flag indicating that the voltage is lower than 1 (power supply voltage drop flag).

Step 51604: Determine whether the value E of the power supply voltage is lower than the lower limit 1-direction E2. If the lower limit value is 12 or more, the program returns to the main program. When it is lower than the lower limit E2, the process advances to step 51605.

Step 51605: The actuator initialized flag set in step S24 in FIG. 5, which is a later step in the main program, is reset, and the process returns to the main program.

Step 31606...J to previous step 81602
5, when it is determined that the 1st line E of the power supply voltage is equal to or higher than the specified 1st line E1, the power supply voltage drop flag set in step 51603 is reset. Then, return to the main program.

FIG. 5 is a flowchart illustrating the overall control operation of the air-fuel ratio control device for an internal combustion engine to which the present invention is applied. Note that this i, II fl[l ff
'The tour de force can be performed by an ECU having the configuration of FIG.

Step 311: When the ignition switch 37 is turned on, the ECU 2o is first initialized using a known method.

Step 812: Read the current interthrottle property and determine its open/closed state and opening range.

At the same time, it is determined whether the engine is in an accelerating state. When in an acceleration state, an acceleration flag is set, and an acceleration holding flag is set for a scheduled time after the end of acceleration.

Step S13: Read the output of the T W sensor 33, determine whether the engine temperature has risen above the scheduled value, and if it is above the scheduled value, it is assumed that 1rjifil has been completed, and the warm-up completion flag is set. Set the.

Step S14...021? It is determined whether or not the length 28 is activated. As described above regarding the conventional example, in order to accurately perform feedback control of the air-fuel ratio, it is necessary that the 02 sensor 28 be sufficiently activated.

In addition, its activation is based on the output voltage of the 02 sensor 28 (
This can be determined by comparing it with the target. 02
If it is confirmed that the sensor 28 is sufficiently activated, the activation flag of the 02 sensor 28 is set.

As is well known, the output of step 315...02 is lower on the lean side and higher on the rich side of the stoichiometric air-fuel ratio. In this step, it is determined whether the air-fuel mixture is on the lean side or the rich side based on the output characteristics of the 02 sensor 28, and the output changes from the lean side to the rich side or vice versa. Determine whether it has been reversed and set the respective flags.

Step S16...The determination and processing of the decrease in the power supply voltage VB is performed as described above (edited with reference to FIG. 4).

Step S17... Based on the states of various flags based on the processing in each step described so far and the results (flags) of engine rotation speed range determination described later with reference to FIG. 6, the operating state of the engine, It is determined whether the operating state is in the feedback control region or the oven loop control region, and the respective flags are set.

Engine operating status (stop, fetal movement, warm engine, hot restart, idling, zero start acceleration, deceleration, acceleration,
There are high speeds (all questions about throttle valves), etc.

In this step S17, it is advantageous to memorize both the currently detected operating state and the previous operating state detected immediately before that, as well as their respective control modes (feedback control, Δ-bun loop control, Σ). .

Step S1'8...actuator (i.e. stepper motor 13 and connection plate 1 shown in FIG. 2)
Determine whether the initialization in step 5) has been completed. This setting is performed by referring to an actuator initialized flag provided in the ECU 20.

-Step 31 if initialization is not completed
Proceed to 9. Note that this determination does not hold in the cycle immediately after the ignition switch 37 is turned on and immediately after the power supply voltage drops below the lower limit value E2.

Step S19: Determine whether the initial processing flag is hit. Since it is not set at first, the process advances to step S20. 111 is established, skip step 320 and proceed to step 32.
You will be able to proceed to 1.

Step S20...actuator 6] (Fig. 3),
That is, the reference positions of the stepper motor 13 and the connecting plate 15 shown in FIG. 2 are set.

As described above, the reference position is preferably the position in FIG. 2 where the stepper motor 13 is driven to its full right or left pant position.

As mentioned above, in the example of FIG. 3, this corresponds to setting the reference (target) position register 56 to, for example, O°'.

At the same time, the up/down counter 57 is set to f+rI-, for example, 100'', which corresponds to the opposite end from the above.After that, a flag indicating that initial processing is in progress is set.

Step S21...The count value (for example, '100') of the up/down counter 57 representing the current position of the stepper motor 13 corresponds to the base ill, ; whine (memory field of the reference position register 56) It is determined whether it is equal to I ('O'' in the present example).

At first, this determination does not hold, so the process goes to step S2.
Proceed to step 2. If the determination becomes true, the process proceeds to step 824.

Step S22: In step S16, it is determined whether a flag indicating that the power supply voltage is lower than the specified value E1 is set.

If the flag is set, there is a risk that accurate position control (initial processing) of actuators such as the stepper motor 13 may not be possible, so nothing is done and the process returns to step S12. If the flag is not set, the process advances to step 323.

Step S23...Moves the actuator such as the stepper motor 13 in the direction of JJtlt+ position set in step 320, and increments the up/down counter (direction) by +1 or -1. The stepper 13 is driven in a direction to decrease the count value of the counter 57, and at the same time, the up/down counter 57 is decremented by 1.

After that, the process returns to step 312, and thereafter steps 812 to 23 are repeated until the determination in step 321 is satisfied. However, in this case, since the determination in step S19 is established, the process in step S20 is omitted.

As described above, each time the loop of steps 312 to 23 is cycled, the stepper motor 13 is driven one step at a time toward the reference position, so that the determination at step 321 is finally established.

In this case, as described above, regardless of the actual position of the stepper motor 13 when the initial processing is started, the stepper motor 13 is assumed to be at one end of its movable range in FIG. The number of pulses necessary to drive the stepper motor 13 to the opposite end reference position will be supplied to the solenoid 18 during the cycle of steps 812-23.

Therefore, in general, according to this initial processing method, after the stepper motor 13 reaches the reference position,
Extra drive pulses are supplied to the solenoid 18, but in this state the movement of the stepper motor 13 is inhibited so that it is not driven beyond the normal level. The stepper motor 13 is completely set to the reference position and the initialization of the actuator is completed.

Step S24: The actuator initialization processing flag is reset, and at the same time, the actuator initialization 1 full flag is set.

Step S30: In the previous step 817, it is determined whether the current control mode is feedback control, that is, whether the feedback control flag is set. If the flag is set, the process proceeds to step S51 to perform feedback control, and if it is not set, the process proceeds to step 341 to perform oven loop control.

Step 341...Current carrot l/l set in the previous step 317: Standard corresponding to the preset position of the stepper motor 13 determined in advance (item t7> Select preset 1 of the position register 56 (for example, read from a table) and set it in the reference (target) position register 56.

Note that this preset shift 1 can also be set to one fixed position that is common to all engine operating states in which open loop control is performed.

Step S42: Determine whether the count value of the up/down counter 57 (i.e., the current position of the stepper motor 13) is directly equal to the preset set in the previous step. If they are equal, return to step S12. ,
If they are not equal, the process advances to step S43.

Step S43...Is the power supply voltage level 1'11 constant as in step S22 described above? Te now.

Step 344...The actuator such as the stepper motor 13 is driven one step in the direction approaching the prehit value set in the previous step 841, and the up/down counter is incremented by +1 or -1.

By repeating the processes of steps 841 to 44 described above, the actuator is driven to a position corresponding to the Bricht value set in step S41 and fixed there.

Step S51...In the previous step 317, it is determined whether the feedback flag was set to 1 as the previous control IIT need. If the determination is not established, the process proceeds to step 852, and if the determination is established, the process proceeds to step S53.

Step 352...According to which region (see Fig. 7) the engine operating state belongs to immediately before shifting to feedback control, the stop valve is moved to a predetermined transient position. drive the motor 13.

The processing content in this step is virtually the same as that in steps S/11 to S/44 described previously, except for the preset position of the stepper motor 13 and the difference between the preset position of the stepper motor 13 and the target K1 neck. A detailed explanation will be omitted.

When the count value of the up/down counter 57, which represents the position of the stepper motor 13, becomes equal to the stored content of the reference (target) position register 56, which represents the transient position, it is assumed that the transient position setting has been completed, and step S12
Return to

Note that this step 352 includes feedback 1. from open loop control. This was added to the nuC in order to make the transition to II fil quick and as smooth as possible, and it is not necessarily necessary and can be omitted. When this step is omitted, the previous step S51 is also unnecessary.

Step S53...Reference time/frequency division table (an example is shown in FIG. 8 and will be explained later)
From this, the basic frequency division ratio Do, which is determined in advance as a function of the elapsed time from the time when the output of the 02 sensor is reversed, is read out.

Next, the engine temperature T obtained in the previous step
The frequency division ratio is corrected by correcting the +) rf base frequency division 4t'DO according to W, the throttle opening 1 rotation, and the engine rotational speed range obtained by the process shown in FIG.

Alternatively, using the engine temperature - [W, throttle pressure value, and engine speed range as parameters, a number of time/frequency divisions corresponding to each combination of (・E) of these parameters can be used. It is also possible to prepare a ratio table t(mo), select a specific time/frequency division ratio table according to the combination of the engine parameters, and obtain the frequency division ratio based on this.

It should be noted that at the stage where the process first moves to step 353, it is impossible to know the elapsed time since the output of the 02 sensor was reversed unless a means such as a counter is specially prepared to measure this time. Since this is not possible, a preset value predetermined as the elapsed time is used, the basic frequency division ratio Do described above is calculated based on this, and fee 1 to hack system dll are started.

On the other hand, it is determined whether the status flag of the 02 center 28 obtained in step S15 is on the lean side or the ridge side of the air-fuel mixture, and the direction in which the snopper seventer 13 should be driven (the direction in which the air-fuel mixture should be driven) is determined. 2 fuel ratio).

Step S54: The power supply voltage range is determined in the same manner as in step S22 described above.

Step 355...According to the frequency division FD, the ECU2
It is determined whether or not the processing of step 0 has passed through the blocks of steps 353 to 55 D times, and at the D time, the stepper motor 13 is driven by one step in the direction specified in the previous step $53. As a result, the air-fuel ratio of the a gas is brought closer to the stoichiometric air-fuel ratio.

In addition, if you are in J5 at Noguchi-Chirate in Figure 5, step 31
The actuator initialization processes 9 to 24 are not necessarily necessary when performing feedback control.

Therefore, the processing steps of steps 318-24 may be performed between steps 330 and 41.

FIG. 6 is a flowchart showing the procedure for determining the engine speed range.

Step S71: When an engine pulse is generated by the Ne sensor 35, this interrupts the computer unit 200, reads the count value of the υ1-included Shumei counter, and resets the counter.

Alternatively, the engine rotation period can also be determined by reading the clock timer and calculating the difference between the clock timer reading and the reading value.

Step 872: Determine the engine rotational speed range based on the rotational period obtained in a multiplexed manner. The engine rotational speed range is determined, for example, as shown in FIG. 7.

In Fig. 7, the ll1lI axis is the engine speed Ne(
(in other words, the reciprocal of the rotation period), and the vertical axis is the inter-throttle stratification TH.

In this figure, the engine rotation speed range is divided into five regions using the rotation speeds N1 to N4 as boundary values, and further divided into two regions based on the interthrottle layer property TH. As a result, the engine operating range is divided into 10 ranges (1).
~ (10).

As can be easily understood from the figure, the regions [(1) and (2)
) is the start/idle region, (3) is the deceleration region, and (4) is the high speed region. When the engine operating condition falls into these regions, the open loop a111 is activated.

Further, the remaining regions (5) to (10) are normal cruise regions, and when the engine operating state belongs to these regions, feedback control is performed unless it is determined that the engine is in an acceleration state or an acceleration holding state.

J3, the apex of each arrow in Figure 7 indicates the feedback from the oven system i2'Il area relative of the source if, II
The transitional (15 constant) position when transitioning to the i2'll region (
The engine operating point corresponding to step S52 in FIG. 5 is shown.

FIG. 8(a) shows a time delay showing the inverted state of the output of the 02 sensor 28, and FIG. 8(b) shows a time delay showing a change in the position of the stepper motor 13 for controlling the empty store ratio.

When the output of the O2 sensor 28 is reversed, for example from the rich side to the lean side, the stepper motor 13 is driven to the side that makes the air-fuel mixture rich.

In this case, one step drive of the stepper motor 13 is performed at each relatively small frequency division ratio (small clock count) C1 immediately after the reversal, but as time elapses, a relatively long time One step drive of the stepper motor 13 is performed every C2.

Therefore, the moving speed of the stepper motor 13 is sharp immediately after the output of the 02 sensor 28 is reversed, but gradually decreases as time passes. The relationship between the elapsed time and the corresponding frequency division ratio or clock count number is stored in the time/frequency division/t table described above regarding step S53.

In addition, if a voltage state display means is provided for the signals of the output terminals T1 and T2 of the power supply voltage discriminating circuit 5o as shown in FIG. It can be visually confirmed that the value has decreased below the lower limit value E2. As a result, it becomes possible to quickly take the necessary steps due to a drop in the power supply voltage.

It is also clear that providing such a voltage display means is necessary in steps 51603 and 160 in FIG.
5 corresponds to the addition of voltage status display processing.

Furthermore, when the power supply voltage drops below the lower limit value E2,
It is clear that if a means for completely clamping at least one of the stepper motor 13 or the connecting plate 15 is provided, the initial processing when the power supply voltage is restored to the specified value (ltlE1 or higher) becomes unnecessary.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) When the level of the power supply voltage drops below a specified value E1 that allows accurate drive control of the actuator, the position control of the actuator is stopped. Therefore, it is possible to prevent the occurrence of a deviation between the contents of the position counter and the actual position of the actuator due to step-out or disorder of the actuator.

(If the level of the 2 power supply voltage falls below the lower limit value E2 at which the 17 Kubuyuator may be moved irregularly by external force, and then returns to the specified value E1 or higher, the Initial processing is performed. As a result, the position control of the actuator in d3 in each subsequent control mode can be performed accurately immediately after the initial processing.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of a conventional air-fuel pressure control system for an internal combustion engine, and Fig. 3 is a functional block diagram for explaining the present invention in detail. 4 is a flowchart for explaining the main operations of the present invention, FIG. 5 is a flowchart for explaining the overall control operation of the air-electric ratio control device for an internal combustion engine to which the present invention is applied, and FIG. The diagrams are flowcharts 1 to 1 showing the determination procedure for the engine rotation speed region, and FIG. 7 is the engine rotation speed vjNa
Fig. 8 (a) shows a time rate showing the output reversal state of the 02 sensor, and Fig. 8 (b) shows an example of the division of the engine operating range according to the throttle opening value TH.
+ There is no change in the position of the stepper motor for control! - It is. 13...Stepper motor, 20...-ECU, 28...
...02 sensor, 33...TW sensor, 35...engine speed sensor, 37...ignition switch, 38...voltage VB power source (battery), 50...
・Power supply voltage discrimination circuit, 51...Flip-flop, 5
2...and gate, 53...one shot multi,
54... OR gate, 55... Initial processing circuit, 56... Reference position register, 57... Up/down counter, 58... Comparator, 5... Drive direction switching circuit, 60... - Inverter, 61... Actuator, 62... Fuel metering device, 63... Off gate, - 200... Computer section, 202... Input interface, 204... Output interface,
206... Driver, 208... T H sensor representative patent attorney Michito Hiraki and 1 other person Figure 26 Figure 7 H

Claims (1)

[Claims] (1) A device for detecting the concentration of exhaust gas components of an internal combustion engine, a fuel metering device for generating an air-fuel mixture to be supplied to the engine, an actuator for controlling the air-fuel ratio of the air-fuel mixture, and the concentration detection device. In an air-fuel ratio control device for an internal combustion engine, the device includes a feedback control device that drives and controls the actuator so that the air-fuel ratio of the air-fuel mixture approaches a set value in accordance with an output signal of the device, wherein the power supply voltage is equal to or higher than a specified value. a first voltage determining means for determining whether the power supply voltage is lower than a lower limit; a second voltage determining means for determining whether the power supply voltage is lower than a specified value; means for stopping the energization of the actuator in response to the output of the first voltage determining means; and a means for stopping the energization of the actuator in response to the output of the first and second voltage determining means; , means for detecting that the value has since been restored to a specified value or higher, and means for performing initial processing to match the actual position of the actuator with a position counter that displays the position in response to the output of the detection means. The specified value of the power supply voltage is set to the lowest voltage that ensures accurate position control without causing the actuator to step out or move abnormally due to external force,
An air-fuel ratio control device for an internal combustion engine, characterized in that the lower limit value is set to a maximum voltage value that causes the actuator to be moved irregularly by an external force, regardless of the energizing current applied to the actuator.