JP2630648B2 - Air-fuel ratio control device for internal combustion engine for automobile - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an internal combustion engine for an automobile,
In particular, it relates to control of an air-fuel ratio accompanying a rise in water temperature during deceleration.

[Prior Art] The air-fuel ratio control device of an internal combustion engine measures the oxygen concentration in the exhaust gas using an oxygen concentration sensor provided in the exhaust system. When the oxygen concentration is low, the air-fuel ratio is low, and when the oxygen concentration is high, The position of an actuator that drives an open / close valve that opens and closes an air passage was controlled so as to increase the density.

In fuel cut control during deceleration,
While the temperature of the engine cooling water (hereinafter referred to as the water temperature) is low, the actuator is held with the air passage fully closed so that the rich air-fuel ratio is achieved regardless of fuel cut control.
However, when the water temperature rises to a high temperature, the actuator is held at a position that can quickly respond to the position of the actuator of the feedback control so that the fuel cut is released and the operation is shifted to the feedback control. Was.

[Problems to be Solved by the Invention] However, if the fuel cut control is released immediately after the temperature has been raised to a preset high temperature determined by the control device, the actuator may be activated even though the water temperature has not risen so much. Is held at the position when the water temperature becomes high, the actuator position at the start of the control in the feedback control after the fuel cut is released is the control position when the water temperature becomes further high. For this reason, when the fuel cut control is released while the water temperature is not rising so much, and the feed back control is performed, the drivability is affected.

Accordingly, an object of the present invention is to improve drivability when fuel cut control is canceled in a medium temperature range where the water temperature changes from a low temperature to a high temperature.

Means for Solving the Problems In order to solve the above problems, an air-fuel ratio control device for an internal combustion engine according to the present invention includes a fuel supply device that supplies a mixture of fuel and intake air to an internal combustion engine for an automobile, An air bleed control device having a needle valve for additionally supplying air to the supply device and an actuator for operating the needle valve, a valve body for opening and closing the fuel passage for slowing, and a fuel cut for slow fuel depending on the engine speed. A fuel cut control device for canceling the fuel cut, a circuit for determining whether fuel cut control is being performed, a circuit for determining whether the water temperature of the engine has reached a preset water temperature, and a determination whether the fuel cut has been released. If the water temperature of the engine reaches the preset water temperature during fuel cut control, the fuel A control signal is output to the actuator of the air bleed control device for holding the actuator holding position during the cut control at an intermediate position between the actuator holding position during the fuel cut control during warm-up and the step 0 for completely closing the control passage. An arithmetic and control unit.

[Operation] In the air-fuel ratio control device of the internal combustion engine, during fuel cut control, the position of the actuator of the air bleed control device is held (held) at a preset position, and when the fuel cut control is released, the actuator is shifted from the hold position. Start feedback control.

However, while the engine water temperature is low, the actuator is held at its fully closed position where air is not supplied to the air passage regardless of whether fuel cut control is being performed. When the water temperature rises and the engine reaches the water temperature set in advance as the temperature at which the warm-up operation is performed, if the operation state is under fuel cut control, this corresponds to the start of the feedback control when the actuator is warmed up. The position and the control passage are held at an intermediate position between Step 0 and the fully closed position, and the feedback control corresponding to the intermediate temperature at which the water temperature of the engine changes from a low temperature to a high temperature (around the high temperature judgment temperature) is smoothly performed.

Embodiment An embodiment of an air-fuel ratio control device for an internal combustion engine for a vehicle according to the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view of the overall configuration of an internal combustion engine for a vehicle. An arithmetic and control unit 8 for controlling the air-fuel ratio of the internal combustion engine (engine) 1 is provided with an air-fuel ratio signal from an oxygen concentration sensor 5 attached to the exhaust pipe 2. 9, an engine speed signal 7 detected from the ignition device 6, a water temperature sensor for detecting the temperature of the engine cooling water
Based on input signals such as water temperature signal 13 from 12
The output signal 10 is sent to the air bleed control device 4 attached to the fuel supply device 3 to control the air-fuel ratio of the engine 1. The exhaust pipe 2 is provided with a catalyst device 11 for purifying exhaust gas.

FIG. 2 is a sectional view showing details of the fuel supply device 3 and the air bleed control device 4.

The fuel supply device 3 includes an intake passage 31 communicating with an air cleaner.
And a throttle valve provided in a shaft 33 that rotates in accordance with the amount of depression of an accelerator petal in an intake passage 31.
Arrange 35 and.

A large bench lily 34a and a small bench lily 34b are provided inside the intake passage 31, and a main nozzle 36 is provided inside the small bench lily 34b.
Open the tip of. The other end of the main nozzle 36 communicates with the fuel float chamber 37, and the fuel is sucked out of the main jet 36 by the negative pressure of the air passing through the small bench lily 34b, which changes according to the opening of the throttle valve 35, and a known mode. Is supplied to the engine 1 as a mixture.

An upper slow port 38b and a lower slow port 38a are opened in the vicinity of the throttle valve 35 in the intake passage 31, so that fuel from the slow fuel passage 39 is additionally supplied to the engine for an air-fuel mixture such as when the engine 1 is idling. . The lower slow port 38a has a needle 38d at the tip for adjusting the throw.
38c, and move the needle back and forth to lower slow port 38a.
Adjust the degree of opening.

A fuel cut device 391 is provided on the base of the fuel supply device 3 upstream of the upper slow port 38b. The fuel cut device 391 has a fuel passage 39 at the tip thereof.
An opening / closing valve for closing / opening the slow fuel passage 39 is formed by entering / leaving the valve body 392. When the engine speed decreases without a load (in this state, the vehicle is operating and the engine brake is operating), the fuel cut device 391 moves the valve body 392 forward to close the slow fuel passage 39. Then, the fuel supply of the slow fuel to the engine 1 is stopped, and when the engine is loaded or the idling state in which the engine speed is reduced to a predetermined speed or less, the valve body 392 moves backward to open the slow fuel passage 39. Then, the slow fuel is supplied to the engine 1.

The air bleed control device 4 is covered with an airtight case 48. The case 48 has air passages 41a, 41b communicating with the air cleaner, and has air passages 41a, 41b open at one end. And in the case 48 respectively.

Inside the case 48, two needles 42, 43 are provided with a holder 46.
A shaft 47, which is a rotating shaft of an actuator for moving the needles 42 and 43 in the axial direction, is rotatably inserted into the center of the holder 46. In this embodiment, a stepping motor 49 is used as an actuator.

The stepping motor 49 is a known motor whose rotation direction and rotation angle are controlled in accordance with an input signal 10 from the arithmetic and control unit 8. Driving of the stepping motor 49 moves in units of one step based on a pulse signal. The speed (stepping motor movement speed) depends on the pulse frequency. Axis 47 of motor 49
The holder 46 moves in the axial direction by the rotation of. The two needles 42 and 43 supported by the holder 46 move in the axial direction in accordance with the step position by this movement, and the air passages 41a and 44 and the air passage 41 in accordance with the movement position of the needles 42 and 43.
The opening areas of the control passages 42a and 43a for making the b and 45 communicate with each other are adjusted to form two needle open / close valves.

The outlet side of the control passage 42a into which the needle 42 is inserted communicates with the air passage 44, and the other end of the air passage 44 is connected to the main nozzle.
Connect to 36. Therefore, an air amount corresponding to the position of the needle 42 is additionally sent to the main nozzle 36. That is, the mixture formed by the intake air passing through the bench lily 34b and the fuel from the main nozzle is set to be a rich mixture, and additional air (bleed) supplied from the air bleed control device 4 to the main nozzle 36 is set. By controlling the amount of (air), an optimal air-fuel ratio for the operating state of the engine 1 can be secured.

Similarly, the outlet of the control passage 43a controlled by the needle 43 communicates with the upper slow port 38b and the lower slow port 38a through the air passage 45, and the upper and lower slow ports 38a, 38b
The optimum air-fuel ratio is secured by controlling the amount of additional air sent to

In the air-fuel ratio control device configured as described above, in a normal operating state of the engine 1, the arithmetic and control unit 8 controls the air-fuel ratio signal 9 sent from the oxygen concentration sensor 5, depressing an accelerator pedal, When the load of the engine 1 changes, the rotation speed of the engine 1 is detected by the signal 7 from the ignition device 6 and the water temperature 13 from the cooling water temperature sensor 12 is used to determine the air-fuel ratio most suitable for the operating state of the engine 1 at that time. The feedback control (closed loop) of the air bleed control device 4 is performed so as to be as follows.

Further, when the engine speed decreases without depressing the accelerator pedal, control is performed so that the valve element 392 of the fuel cut device 391 advances to close the fuel passage 39 for throwing (fuel cut). When it is detected that the deceleration has been released due to a change in the engine speed caused by depressing the accelerator pedal to accelerate the engine 1, or that the engine speed has decreased to a predetermined value or less. When the engine is idle (during idle operation), feedback control is performed so that the valve body 392 of the fuel cut device 391 is retracted to open the fuel passage 39 for slowing, and fuel supply to the engine 1 is restarted (release of fuel cut control). I do.

Further, while the water temperature is low, regardless of the fuel cut control, the position of the stepping motor 49 of the air bleed control device 4 is set on the side (rich side) where the mixture becomes a rich mixture, and the control passages 42a, 43a is held at the fully closed position (step 0), and open loop control is performed. And
When the water temperature rises, the stepping motor 49 moves to a position (STH2) that can quickly respond to feedback control after warm-up.
Hold the step position of.

However, the stepping motor hold position step 0 when the water temperature is low and the stepping motor hold position STH2 when the water temperature is high have a large temperature width and a large step difference, so that when the feedback control is performed, the driveability is reduced. A worsening problem has arisen. Therefore, according to the present invention, when the water temperature rises while the fuel cut control is being executed, and a transition period occurs in which the temperature shifts from the low temperature range to the high temperature range, the stepping motor 49 is stepped while the fuel cut control is being executed. It is configured so as to be held at a substantially intermediate position STH1 between 0 and the hold position STH2, so as to make a transition to smooth feedback control after releasing the fuel cut in a transition period when the water temperature shifts from a low temperature range to a high temperature range.

Incidentally, the high temperature zone of the water temperature of the engine, the low temperature region determination is previously determined determination temperature C _1, a low temperature range the temperature C ₁ or less, the water temperature
C ₁ or higher is defined as a high temperature range. Further, a water temperature switch or the like may be used instead of the detection by the water temperature sensor.

 Next, the arithmetic and control unit 8 of the present invention will be described.

The signals input to the ECU (Electronic Control Unit) of the arithmetic and control unit 8 are an engine speed, an air-fuel ratio signal from an oxygen concentration sensor, a vehicle speed, a water temperature, and the like. Determine the step position of the ping motor.

Here, the relationship between the water temperature, the fuel cut control mode, and the step position of the stepping motor will be described with reference to a timing chart shown in FIG.

Water temperature so on are gradually increased from a low temperature, a coolant temperature C ₁ or more high temperature zone from the water temperature C ₁ following a low temperature range. Step position of the scan Tetsu ping motors, the water temperature is the position of the scan Tetsu ping motor regardless of the Fuyuerukatsuto control mode F ₁ during the low temperature zone is held in step 0. When the water temperature rises to the temperature C ₁ between Fuyuerukatsuto controller is summer control mode F _2, scan Tetsu ping motor in transition of the hold position STH1 is fed back control position of the water temperature input switch being set in advance of moving the step position, Fuyuerukatsuto control mode F ₂ is held in step STH1 until the end. Fuel cut control mode
At the same time the scan Tetsu ping the F ₂ releases the motor starts moving step positions by fed back control from the hold position STH1.

Then, after the water temperature is summer and completely high temperature range when the Fuyuerukatsuto control mode F ₃ simultaneously scan Tetsu ping motor Fuyuerukatsuto control mode F ₃ starting with the at warm-up that is preset the step position Hold at step position STH2. When Fuyuerukatsuto F ₃ releases, scan Tetsu ping motor starts moving step positions of the fed back control from step position STH2.

Here, the step position STH2 is a step position that is set in advance so that the feedback control after warm-up can be quickly performed, and the step position STH1 is a substantially intermediate position between the step 0 and the step position STH2, and is predetermined. Have been.

Thus, if the water temperature is at a temperature C ₁ and summer were time t ₁ is determined to a high temperature range of Fuyuerukatsuto control mode F _2, when the fed back control is started by releasing the Fuyuerukatsuto control mode F _2, fed back control start since holding the step position of the water temperature C ₂ optimum temperature input changeover scan Tetsu ping motors fed back control position (STH1) to the time point t _2, step position of the scan Tetsu ping motor during fed back control start from Fuyuerukatsuto control released The control is started from the step position STH1, so that the air-fuel ratio can be quickly and appropriately controlled, and the drivability is improved.

This control mode will be described with reference to the control flowchart of FIG.

Starting from step 100, if the water temperature of the engine is in a low temperature range in step 101, a command is output in step 102 to hold the step position of the stepping motor at step position 0 (fully closed state). At step 103, it is determined whether or not the fuel cut control mode is set. If it is not in the fuel cut control mode, the operation proceeds through the NO circuit to output a command to keep the stepping motor at the step position 0. When the fuel cut control mode is set, the YES circuit is advanced, and in step 104, a command to set the stepping motor hold position SFH during fuel cut control to the step position 0 is output. Determines Taka not decreased to the judgment temperature C ₁ to a high temperature range from low temperature range the water temperature of the engine is set at step 105. If the water temperature of the engine is not decreased to the determination temperature C ₁ advances the NO circuit, it outputs a command to hold the Fuyuerukatsuto control during scan Tetsu ping motor hold position of the scan Tetsu ping motor at step 106 to step position 0. At step 107, it is determined whether or not the fuel cut control has been canceled. If the release of Fuyuerukatsuto control has not been advances the NO circuit and determines whether the temperature was elevated to determine the temperature C ₁ engine water temperature is set.
When the fuel cut control is released, the control proceeds to the YES circuit,
At step 108, the control is started in the low temperature region from the step position 0 of the stepping motor, and the operation is ended at step 113.

When the water temperature of the engine is determined temperature C ₁ at step 105 Y
Proceed through the ES circuit, and in step 109, output a command to set the stepping motor hold position SFH at the time of fuel cut control to the feedback control position STH1 at the time of water temperature input switching,
At step 110, a command to hold the step position of the stepping motor at the feedback control position at the time of water temperature input switching is output. At step 111, it is determined whether or not the fuel cut is released. NO during fuel cut control
The circuit proceeds to output a command to keep the step position of the stepping motor at the feedback control position STH1 at the time of water temperature input switching. If the fuel cut control is cancelled, the operation proceeds to the YES circuit. In step 112, control is started from the feedback control position at the time of water temperature input switching, and step 113 is executed.
Ends with

The arithmetic and control unit 8 incorporating the control circuit as described above converts a command from the control circuit into a signal and sends it to the stepping motor 49 of the air bleed control unit 4, and the stepping motor 49 moves to the instructed step position. Control passage 42a,
The main nozzle 36 and the slow port 3 are opened and closed via the air passages 44 and 45 to open and close the 43a and achieve the desired air-fuel ratio.
Send to 8a, 38b.

[Effects of the Invention] In the control of the actuator in the air-fuel ratio control device for an internal combustion engine of the present invention, since the temperature of the cooling water of the engine is set to a low temperature range, a medium temperature range, and a high temperature range, optimal control for the water temperature is performed. Drivability is improved. That is, if the water temperature of the engine is an intermediate temperature that is not as high as the water temperature at which the engine temperature changes from a low temperature to a high temperature and the engine is in a warm-up operation state, and if the fuel cut control is being performed at the time of a predetermined determination temperature rise that is determined to be a high temperature, the intermediate temperature Since the actuator is held at the intermediate step, which is the feedback control center position, which can quickly respond to the feedback control start position of
The engine water temperature is higher than the judgment temperature,
The feedback control in the intermediate temperature range, which is lower than the water temperature after the warm-up, is started smoothly. In addition, the drivability is improved as compared with the conventional air-fuel ratio control, in which the feedback control is started from the control position of the actuator after warm-up in the middle temperature range.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the overall configuration of an internal combustion engine for a vehicle, FIG. 2 is a sectional view of a fuel supply device and an air bleed control device, and FIG. 3 is a diagram showing a relationship between a water temperature, a fuel cut control mode, and a step position of a stepping motor. FIG. 4 is a timing chart, and FIG. 4 is a control chart. 1 ... internal combustion engine, 3 ... fuel supply device, 4 ... air bleed control device, 5 ... oxygen concentration sensor, 6 ... ignition device, 7 ... engine rotation signal, 8 ... arithmetic control device, 12 ... … Cooling water temperature sensor, 39… throw fuel passage, 391… fuel cut device, 392… valve body, 42, 43… needle, 49… stepping motor.

Claims (1)

(57) [Claims] A fuel supply device for supplying a mixture of fuel and intake air to an internal combustion engine for a vehicle, a needle valve for additionally supplying air to the fuel supply device, and an air having an actuator for operating the needle valve. A bleed control device, a fuel valve for opening and closing the fuel passage for the throw, a fuel cut control device for releasing the fuel cut and the fuel cut of the fuel for the throw depending on the engine speed, and a rotation speed provided to the ignition device of the internal combustion engine are detected. An engine rotation sensor, an oxygen concentration sensor provided in an exhaust pipe, a water temperature sensor for detecting the temperature of engine cooling water, and air bleed control based on a signal from the engine rotation sensor and input signals from the oxygen concentration sensor and the water temperature sensor. Air-fuel ratio of an internal combustion engine for a vehicle, comprising an arithmetic and control unit for outputting an actuator control signal to the device In the control device, the arithmetic and control unit includes a circuit for determining whether fuel cut control is being performed, a circuit for determining whether the temperature of engine coolant has reached a preset temperature, and a circuit for determining whether fuel cut control has been released. A circuit for determining whether or not the temperature of the engine coolant reaches a preset temperature during the fuel cut control. An air-fuel ratio control device for an internal combustion engine for a vehicle, which outputs a command to the actuator to maintain the actuator at an intermediate position between the position and the position at which the actuator completely closes the air passage.