JPS6355358A - Drive circuit of fuel atomizer for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the efficiency, by feedback controlling an exciting frequency such that the current flowing through a high voltage generating coil for applying voltage across a supersonic vibration chip and atomizing fuel is maximized, thereby exciting a supersonic vibration chip near a resonant point. CONSTITUTION:An A.C. voltage is applied across a piezoelectric element in a supersonic vibration chip 1 so as to cause supersonic vibration thereof thus atomizing fuel. A high voltage generating coil 2 for applying a high A.C. voltage across said supersonic vibration chip 1 is fed with power from a power source 3 so as to produce a high voltage corresponding to a winding ratio of secondary winding through primary winding current being interrupted alternately by power transistors 4, 5. The oscillation frequency of an oscillation circuit 100 for interrupting the power transistors 4, 5 alternately is feedback controlled so that the driving current flowing through the emitters of the power transistors 4, 5 is maximized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a drive circuit for a fuel atomization device for an internal combustion engine that atomizes fuel using an ultrasonic vibrator provided in a fuel passage of the internal combustion engine, and particularly The present invention relates to a drive circuit for a fuel atomization device for an internal combustion engine that can stably obtain maximum output by automatically controlling the excitation frequency of an ultrasonic vibrator to near the resonance point of the vibrator.

[Conventional technology]

As a drive circuit for a fuel atomization device for an internal combustion engine using a conventional ultrasonic vibrator, for example, Japanese Patent Application Laid-Open No. 58-210354
As described in the above publication, a circuit is known that changes the excitation frequency of an ultrasonic transducer at a predetermined period near a resonance point.

[Problem that the invention seeks to solve]

The above conventional technology is a method of raising and lowering the excitation frequency at a predetermined period and width near the resonance point of the ultrasonic transducer, so the time that the excitation frequency is at the resonance point is a fraction of the total, resulting in efficiency. A problem arose in that the value decreased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a drive circuit for a fuel atomization device for an internal combustion engine that can automatically control the excitation frequency of an ultrasonic vibrator to near the resonance point to stably obtain maximum output.

[Means for solving the problem] - The above purpose is to detect the drive current of the ultrasonic transducer and adjust the drive current of the ultrasonic transducer so that the drive current becomes constant in the region where the drive current rapidly increases near the resonance point. This is achieved by a drive circuit for a fuel atomizer for an internal combustion engine that is equipped with means for feedback controlling the excitation frequency.

[Effect]

In the drive circuit of the fuel atomization device for an internal combustion engine according to the above means, the excitation frequency of the ultrasonic vibrator is controlled by detecting a sudden increase in the drive current from the drive circuit near the resonance point of the ultrasonic vibrator. Therefore, the excitation frequency can be stably tracked near the resonance point.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is an overall configuration diagram showing one embodiment of a drive circuit of a fuel atomization device for an internal combustion engine according to the present invention.

In FIG. 1, an ultrasonic vibrator 1 is installed in the middle of a fuel passage of an internal combustion engine, and is vibrated ultrasonically by an alternating current voltage applied to the piezoelectric element to atomize the fuel of the internal combustion engine.

2 is a high voltage generation coil that consists of a primary winding with a center tap, a secondary winding, and an iron core; 3 is a power supply; 4 and 5 are power transistors; high voltage generation coil 2 receives power from power supply 3; The supplied primary winding current, which is alternately turned on and off by the power transistor 4.5, generates a high-voltage AC voltage in the secondary winding according to the turns ratio and is applied at the ultrasonic frequency 1.

In addition, 100 is an oscillation circuit with an ultrasonic frequency of, for example, 28 k.
It oscillates at a frequency of about Hz to 40 kHz and supplies a base current that alternately blocks the reverse flow of the power transistors 4 and 5. 200 is a frequency control circuit and an oscillation circuit 100
The oscillation frequency is controlled and the oscillation frequency is changed by the output of the current detection circuit. Reference numeral 300 denotes a current detection circuit which detects the current of the high voltage generation coil 2 by the drive current flowing to the emitter of the power transistor 4.5, and controls the operation of the frequency control circuit 200 by its output.

FIG. 2 is an output characteristic diagram of the ultrasonic transducer 1 shown in FIG. 1.

In FIG. 2, the output of the ultrasonic transducer 1 reaches its maximum value when the excitation frequency rapidly increases near the resonance point of the transducer and coincides with the resonance point, and the output decreases as the distance from the resonance point increases. Furthermore, since the change in the output of the ultrasonic transducer 1 is relatively consistent with the change in the input to the high voltage generation coil 2, the current flowing through the power transistors 4 and 5, that is, the current in the high voltage generation coil 2, also changes to the transducer 1. It rises rapidly near the resonance point and reaches its maximum at the resonance point.

The operation of the drive circuit shown in FIG. 1 with the above configuration will be explained as follows.
First, the oscillation frequency of the oscillation circuit 100 is determined by the frequency control circuit 20.
With an output of 0, for example, the vibrating hand 1 oscillates at a certain predetermined frequency higher than its resonance point, and gradually decreases from that frequency. Then, as this oscillation frequency approaches the resonant frequency of the vibrator 1, the current in the high voltage generating coil 2 increases rapidly. The current of this high voltage generating coil 2 is detected by the current detection port 1300 as a driving IjJ current flowing to the emitter of the power transistor 5.6, and when this detected current value reaches a set value, an output signal is sent to the frequency control circuit 200. is sent to apply feedback to stop the drop in the oscillation frequency of the oscillation circuit 100. By appropriately selecting this amount of feedback, the oscillation frequency can be fixed at a certain set value near the resonance point of the vibrator 1.

In this way, it is possible to stably excite the transducer 1 at an oscillation frequency slightly higher than the resonance point of the ultrasonic transducer 1, and it can also automatically follow changes in the vibration frequency of the i-oscillator 1. It becomes stable near its resonance point. Note that when the oscillation frequency of the oscillation circuit 10''O is changed to gradually increase from a frequency lower than the resonance point of the vibrator 1, the oscillation frequency is stabilized at a slightly lower frequency than the resonance point by a similar control operation.

Next, FIG. 3 is a circuit diagram showing an embodiment of the oscillation circuit IC)O shown in FIG. In FIG. 3, for example, a voltage controlled oscillation circuit can be used as the oscillation circuit 100. 101,
102, 103. i04 is a resistor, 105 is a capacitor, 106 is an operational amplifier, ro7.16's,' 109
, 110. t 11 is a resistor, 112 is a comparator, 113
．． I14 and 115 are resistors, and 116 is a comparator, which constitute a voltage controlled oscillator. 117 is a transistor.

118 is a resistor, 119 is a transistor, 120°12
1 is a resistor, 122 is a transistor, 123 is a resistor,
124 is a transistor, and 125 is a resistor.

Since the voltage controlled oscillator of the oscillation circuit 100 having the above configuration is well known, a detailed explanation of its operation will be omitted.

A rectangular wave voltage whose oscillation frequency changes is generated at the output of the comparator 112 according to the input voltage v1 at the connection point of the resistors 101 and 102. The transistor 117 forms an emitter follower circuit, and the resistor 118 is connected to the emitter.
, 121 prevents the output voltage of the comparator 112 from changing and the oscillation frequency from changing. transistor 11
9 amplifies the oscillation output to drive the power transistor 4; transistors 122 and 124 drive the power transistor 4;
The power transistor 5 is driven by an oscillation output whose phase is inverted.

In this way, the oscillation circuit 100 is controlled by the frequency control circuit 200.
The power transistors 4 and 5 are driven by generating two rectangular wave voltages whose phases are inverted at an oscillation frequency determined by the input voltage Vl from the input voltage Vl.

FIG. 4 is a circuit diagram showing an embodiment of the frequency control circuit 200 of FIG. 1. In FIG. 4, resistors 201 and 202 divide the voltage Vcc to determine the maximum value of the voltage Vl that determines the oscillation frequency of the oscillation circuit 100. In FIG. 203,20
4 is a resistor, 205 is a transistor, 206 is a resistor,
207 constitutes a constant current circuit with a transistor;
A capacitor 08 is charged by the constant current circuit to lower the voltage at point A of the capacitor 208. Reference numeral 209 is an operational amplifier which feeds back the output to the negative input and converts the impedance so that there is no change in voltage increase of the capacitor 208 due to the value of the output voltage v1. A diode 210 supplies current only from the output voltage Vl side to the capacitor 208 side and prevents it from flowing in the opposite direction.

211 is a resistor f, +; 212 is a transistor that discharges the capacitor 208 by the output of the current detection circuit 300, lowers the charging 1ffi pressure, and increases the A point voltage of the capacitor 208;

In the frequency control circuit with the above configuration, capacitor 2
The sum of the A point voltage of 08 and the voltage drop of the diode 210 is higher than the divided voltage of the resistor 201 and the resistor 202. t pressure Vl that determines the air vibration frequency of the oscillation circuit 100
is determined by the value obtained by dividing the voltage Vcc by resistors 201 and 202. Then, when the capacitor 208 is charged with a constant current and the sum of the voltage at the point A and the voltage drop of the diode 210 becomes lower than the divided voltage, the voltage V is determined by the voltage at the point A of the capacitor 208.

Furthermore, when feedback is generated from the output side by the currents of the power transistors 4 and 5 driven by the oscillation circuit 100 and the transistor 212 is turned on by the output signal from the current detection circuit 300, the width of the output signal and the resistor 211 and capacitor are The voltage of the capacitor 208 decreases by a voltage determined by the time constant due to the capacitance of the capacitor 208, and the voltage at the point A increases by 1.

In this way, the output voltage Vi of the frequency control circuit 300 that determines the oscillation frequency of the oscillation circuit 100 is
The capacitor 208 is charged, and when the sum of the A-point voltage of the capacitor 208 and the voltage drop of the diode 210 becomes less than the above-mentioned divided voltage, the A-point voltage increases. Gradually descend. Furthermore, when feedback is applied from the output side and the output signal from the current detection circuit 300 is input, the voltage V
, is controlled to rise temporarily and fall again when the output of the current detection circuit 300 disappears, and the oscillation circuit 100
automatically controls the oscillation frequency to a predetermined value.

FIG. 5 is a circuit diagram showing an embodiment of the current detection circuit 300 of FIG. 1. In FIG. 5, 301 is a resistor that detects the current from the power transistors 4 and 5. A capacitor 302 smoothes the voltage drop of the resistor 301.

303 is a comparator, and 304 and 305 are resistors that determine the pressure of the comparator 303 and 1. A resistor 306 transmits the output of the comparator 303 to the frequency control circuit 200.

In the current detection circuit 300 with the above configuration, the current flowing through the emitters of the power transistors 4 and 5 is connected to the resistor 30.
1, and when the voltage drop value due to this current value exceeds the reference voltage value set by the dividing resistors 304 and 305, an output signal is sent from the comparator 303 to the frequency control circuit 200.

According to the above embodiment, in the drive circuit of a fuel atomization device for an internal combustion engine using an ultrasonic vibrator, if the excitation frequency of the vibrator is not near the resonance point, the required vibration amplitude cannot be changed; It does not work effectively at a fixed frequency because the point changes depending on the adhesion of fuel to the vibrator and temperature characteristics, but the high voltage generation coil current is cut off to prevent the drive current from increasing rapidly near the vibrator's resonance point. By detecting the current of the power transistor and applying feedback for automatic control, it is possible to always stably excite the resonator near the resonance point, and it is also possible to compensate for fluctuations in the oscillation frequency of the oscillation circuit due to temperature. be done.

〔Effect of the invention〕

According to the present invention, by automatically controlling the oscillation frequency of the drive circuit so that the current flowing through the high voltage generating coil of a fuel atomization device for an internal combustion engine using an ultrasonic vibrator is maximized, fuel adhesion to the vibrator can be prevented. The device efficiency can be improved because the excitation frequency of the vibrator can always be stably controlled near the resonance point and the maximum output can be changed, regardless of load fluctuations, temperature characteristics, temperature characteristics of the oscillation circuit, etc.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram showing an embodiment of a drive circuit of a fuel atomization device for an internal combustion engine according to the present invention, FIG. 2 is an output characteristic diagram of the ultrasonic vibrator shown in FIG. 1, and FIG. 1, FIG. 4 is a circuit diagram of the frequency control circuit of FIG. 1, and FIG. 5 is a circuit diagram of the current detection circuit of FIG. 1. DESCRIPTION OF SYMBOLS 1... Ultrasonic transducer, 2'... Coil for high voltage generation, 4° 5... Power transistor, 100... Oscillation circuit, 200... Frequency control circuit, 300... Current detection circuit.

Claims (1)

[Claims] 1. An ultrasonic vibrator provided in the middle of a fuel passage of an internal combustion engine, an oscillation circuit that excites the ultrasonic vibrator, and boosting the output of the oscillation circuit to apply voltage to the ultrasonic vibrator. A high voltage generation coil, a current detection circuit that detects the current of the high voltage generation coil, and a current detection circuit that changes the oscillation frequency of the oscillation circuit from a predetermined frequency that is different from the resonance frequency of the ultrasonic transducer toward the resonance frequency. and a frequency control circuit that stops changing the oscillation frequency by the output of the current detection circuit when the current of the high voltage generating coil reaches a set value.