JPH0118832Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an air-fuel ratio control device that uses a stepper motor as an actuator for adjusting the amount of air, and is particularly intended to improve engine startability.

This is a device that controls the air-fuel ratio by supplying adjustable secondary air in addition to primary air that is fixedly supplied to the carburetor, and uses a stepper motor as the actuator for adjusting the secondary air. When a microcomputer that receives signals from various sensors is used to control the motor, when the ignition switch is turned off, the stepper motor maintains its final rotational position and stops. Since the air-fuel ratio at this time is based on the immediately preceding running conditions, it usually does not satisfy the excess fuel condition required at startup. Therefore, if you try to restart the engine in this state, there will be too much air and the starting performance will be poor.

Figure 1 is a schematic diagram of this type of air-fuel ratio control device.
1 is a carburetor, 2 is an engine, 3 is a stepper motor, 4 is a control computer, 5 is a catalyst, 6
7 is an exhaust sensor that detects the concentration of exhaust gas components of the engine, and 7 is various sensors such as an engine rotation speed sensor, a radiator water temperature switch, a throttle switch, and a negative pressure sensor. The computer 4 receives the outputs from these sensors 6 and 7 and rotates the stepper motor 3 forward or reverse by an appropriate amount to adjust the amount of secondary air.

In this type of control device, in order to improve engine starting performance, the computer 4 controls the full-close control function to rotate the stepper motor 3 to the full-close position (the position that cuts off secondary air) immediately after the ignition switch is turned on. It is common to have the
However, if it takes 100 steps as shown in Figure 2 to rotate the motor 3 from the fully open position (the position where the maximum amount of secondary air can be supplied) to the fully closed position, then 1
Assuming that the step is 5ms, 100 steps requires 500ms of control time. Normally, the starter is turned together with the ignition switch to ignite the engine, but if the stepper motor is not in the fully closed position, the mixture will not be rich and starting performance will be poor. Of course, not all cases are stopped at the fully open position. However, since the previous stop position is unknown, it is clear that control must be performed assuming that the engine is fully open.

The present invention attempts to execute the above-mentioned fully closed control of the stepper motor when the ignition switch is turned off. Therefore, the present invention provides an air-fuel ratio control device that uses a stepper motor to adjust the amount of air supplied to the engine and controls the rotational position of the motor using a computer that receives signals from various sensors. A detection device supplies battery voltage directly to the motor and via an ignition switch to the computer, and outputs a detection output to the computer when the voltage supplied to the computer decreases. a fully closed control circuit that generates a sufficient number of pulses to rotate the stepper motor from fully open to fully closed when the detection output is detected; and a fully closed control circuit that supplies the battery voltage to a constant internal circuit of the computer. A constant voltage power supply that supplies voltage and the battery voltage are supplied, and even after the supply of the battery voltage is cut off, the fully closed control circuit generates a sufficient number of pulses to rotate the stepper motor from fully open to fully closed. The computer is characterized in that it is equipped with a backup power supply capable of supplying a constant voltage to the internal circuits of the computer, which will be described in detail below with reference to the illustrated embodiment.

FIG. 3 is a diagram showing an embodiment of the present invention, showing the stepper motor 3 and computer 4 portions of FIG. 1. The computer 4 has a constant voltage power supply 41 used for normal operation and an ignition switch IS.
The backup power supply 42 uses a capacitor that produces output for about one second even after the ignition switch IS is turned off, and the power supply line after passing through the ignition switch IS due to power cutoff due to the ignition switch IS turning off. A fully closed control circuit 43 that detects a voltage drop and rotates the motor 3 to a fully closed position, and a stepper drive circuit 44 that rotates the motor 3 forward or reverse by a predetermined amount depending on the clock input and polarity input.
Equipped with etc. This drive circuit 44 has four open collector type transistors (TR in FIG. 4) in its output stage that sequentially supply current to the four-phase coils of the stepper motor 3. In this example, the clock input and polarity input generation circuits that control these transistors during normal operation are omitted from the drawing.

Normal operating power is supplied from the constant voltage power supply 41 to the circuits 43 and 44 through the diode _D1 .
When the output of this power supply 41 is turned off, the diode
From the backup power supply 42 via D ₂ to both circuits 4
3 and 44 are temporarily supplied with backup power. Main power supply +B to these power supplies 41 and 42
is due to battery 8, which is supplied through the ignition switch IS. Motor 3 also operates with this +B power supply, but in this invention the switch IS
Since it is necessary to operate the motor 3 even after it is turned off, +B is supplied to the motor 3 without passing it through the switch IS.

The fully closed control circuit 43 detects that the +B power supply is cut off and supplies the stepper drive circuit 44 with a polarity signal in the closing direction and a clock for 120 steps.
The details are shown in FIG. 431 is a comparator that detects the cutoff of the +B power supply, and the cutoff detection signal turns on the transistor 432 to forcibly change the polarity signal to the closed direction, and also starts the one-shot timer 433. This timer 433 generates a pulse that opens gate 434 for 0.6 seconds from the time of activation.
435 is a 200 Hz clock oscillator, and its output is applied to the stepper driving circuit 44 for 0.6 seconds through gates 434 and 436. 0.6s of 200Hz clock
Since the number of pulses existing in between is 120, the stepper motor 3 is driven 120 steps in the closing direction. Note that 437 is a gate that opens during normal operation, which allows other clock signals to be routed to the drive circuit 44.
supplied to

As described above, according to the present invention, the stepper motor is already fully closed when the engine is started, so the air-fuel ratio of the air-fuel mixture is low. Therefore, startability is good (starting time is shortened).
If the battery voltage at startup is low and the stepper motor does not rotate, the problem will not occur unless it is fully closed. It also avoids the uncertain operation of computers. In the event of a computer failure other than the fully closed control circuit and stepper drive circuit, it is possible to run the vehicle by turning off the ignition switch, fully closing the stepper motor, and then removing the computer. Since the stepper motor is initialized by supplying a pulse for a certain period of time when the power supply voltage drops, there is no need for a detector or the like to detect the rotational position of the stepper motor, which simplifies the configuration. The motor is directly connected to the battery, and the control circuit is supplied with power from a constant voltage power supply and a backup power supply via the ignition key. Therefore, the constant voltage power supply and the backup power supply can be of simple construction because they supply power only to the control circuit that consumes less power. High reliability as it does not use mechanical parts such as relays. Ignition switch OFF
After a certain period of time has elapsed, all power supplies are cut off, so there is no wasted power consumption. Since it monitors fluctuations in the power supply voltage, it is also effective when restarting the engine. In other words, since it operates even with the power supply voltage from the starter motor when the engine stalls,
The stepper motor is also in the fully closed position when the engine is restarted.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an air-fuel ratio control device that uses a stepper motor to control the amount of air, Fig. 2 is a characteristic diagram of the stepper motor, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is an essential diagram. FIG. In the figure, 1 is a carburetor, 3 is a stepper motor, 4 is a computer, 42 is a backup power supply, 43 is a fully closed control circuit, 431 is a comparator for detecting power cutoff, 6 and 7 are sensors, 8 is a battery, and IS is an ignition switch. It's a switch.

Claims (1)

[Claims for Utility Model Registration] An air-fuel ratio control device that uses a stepper motor to adjust the amount of air supplied to the engine and controls the rotational position of the motor using a computer that receives signals from various sensors. supplying battery voltage directly to the computer and via an ignition switch, and the computer having a detection means for outputting a detection output when the voltage supplied to the computer decreases; a fully closed control circuit that generates a sufficient number of pulses to rotate the stepper motor from fully open to fully closed when a detection output is detected; and a regulator that is supplied with the battery voltage and supplies a constant voltage to the internal circuits of the computer. A voltage power supply and the battery voltage are supplied, and the time period for the fully closed control circuit to generate a sufficient number of pulses to rotate the stepper motor from fully open to fully closed even after the supply of the battery voltage is cut off is within the above-mentioned period. An air-fuel ratio control device characterized by being equipped with a backup power source capable of supplying a constant voltage to an internal circuit of a computer.