JPS6037603Y2 - Solenoid valve drive circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a solenoid valve drive circuit that feedback-controls the duty ratio of the current supplied to a solenoid valve (linear valve) that operates proportionally in accordance with a control input voltage. The present invention can be applied to a device that controls the correction air amount of an automobile carburetor or the secondary air amount to an exhaust system by linearly controlling the flow rate, opening degree, or position.

2. Description of the Related Art Conventionally, as a drive circuit for a so-called proportional control electromagnetic valve in which the stroke, that is, the degree of valve opening changes depending on the supplied current, a drive circuit as shown in FIG. 1 has been proposed.

In this circuit, the current flowing cross-sectionally from the power source 1B to the coil 3 and output circuit 4 of the solenoid valve is detected by the current detection circuit 5.
The voltage is detected in the form of voltage ■6 proportional to the current, and the voltage
, and the control input voltage ■3 are input to a deviation integrator 1 which performs integration according to the difference between these voltages, and the output of the deviation integrator 1 is a triangular wave oscillator 6 which outputs a triangular wave of a predetermined frequency.
The comparator 2 compares the output ■r with the on/off output ■ of the comparator 2.

The output circuit 4 is configured to turn on and off the current flowing through the coil 3.

Here, the oscillation frequency of the oscillator 6 has a limited setting range and must be set to a predetermined value that is suitable for the usage conditions in order to eliminate hysteresis caused by mechanical distortion and magnetic circuits inherent to the solenoid valve. It's decided.

Further, since the time constant of the deviation integrator 1 is for integrating the waveform of the frequency, it is selected to have a value larger than at least the time corresponding to one cycle of the frequency.

The operation of the conventional circuit configuration shown in FIG. 1 will be explained with reference to FIG.

Now, an example will be considered in which the above-mentioned time constant is set to a value corresponding to 2 to 3 periods of the oscillation output signal of the oscillator 6.

Control input voltage■. suddenly changed as shown in Figure 2 1,
Consider the case where the current in the coil 3 is increased from zero to a predetermined value.

The period of T1; Since ■Y is zero, ■ and ■ are below the lower limit voltage of ■, and the output of comparator 2 is ■.

Since is off, the output vd of the current detector 5 is also zero.

Period T2: Control input voltage (3) rises stepwise to a predetermined value, and since Va is zero, Vb rises at the highest possible slope, but since it is still lower than Vr, (2)o is off.

Period of T3; ■b≧■, and ■.

turns on and current begins to flow through coil 3.

This current increases as shown in FIG. 3Va with a time constant L/R formed by the coil inductance L1 and the resistance R.

At this time, the deviation between ■Y and ■6 becomes gradually smaller as ■6 rises, so the upward slope of ■ becomes gradually smaller.

The period of T, 9Vl)≦■, then V.

is turned off. At this time, a back electromotive force is generated in the coil 3,
The output circuit 4 is provided with a circuit for absorbing the back electromotive force, and the coil current decreases as shown in FIG. 2, 3Va.

In this case, since V(+ gradually decreases, the upward slope of Vb gradually increases.

Period T5: Vb≧Yr again and V.

is turned on, and the coil current increases as shown in (6).

(2) Since 6 gradually rises, the rising slope of (2) becomes gradually smaller, and the slope becomes zero when Vd=V-, and after that, Vb starts to fall.

In this way, the area integral value (i.e. effective value) of ■6 and V
When Y becomes equal, the current value of the coil 3 becomes constant, so the current flowing through the coil can be controlled by the control input voltage (1).

However, in the conventional type, the control input voltage ■8
When the current suddenly changes, the delay in the rise of the current due to the inductance of the coil 3 and the response delay depending on the time constant of the deviation integrator 1 and the frequency of the oscillator 6 are combined.
There was a problem that the rise of the current was very slow.

That is, as can be seen from Fig. 2, until the coil current reaches a predetermined value (V, = Vd), 1 of the period of vf
There was a delay of ~2 times.

The purpose of the present invention is to take into account the problems with the conventional type,
In a solenoid valve drive circuit that performs feedback control of the duty ratio of the current supplied to a solenoid valve, the oscillation frequency of the triangular wave oscillator is made higher than the set value for a predetermined period of time in response to a sudden change in the control input voltage. An object of the present invention is to provide a solenoid valve drive circuit that can speed up the rise of current in a solenoid valve coil because response delay depending on the oscillation frequency of an oscillator is reduced.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a solenoid valve drive circuit according to an embodiment of the present invention.

In the figure, 3 is a solenoid valve coil whose one end is connected to the power supply 1B, 4 is a solenoid valve drive output circuit, 41 is a transistor that supplies on/off current to the coil 3, 42 is a base resistor, 43, 44 are a resistor and a Zener diode connected between the collector and emitter of the transistor 41, respectively, for absorbing a reverse surge when the current of the coil 3 is turned off.

Further, 5 is a current detection circuit that detects the current flowing through the coil 3, 51 is a current detection resistor, and 52 is an operational amplifier (
(hereinafter referred to as an OP amplifier), which amplifies the voltage across the resistor 51 with an amplification factor determined by the resistors 53 and 54.

55 is an input resistance of the OP amplifier 52.

Reference numeral 1 denotes a deviation integration circuit, which performs integration according to the deviation between the control input voltage 8 and the output d of the detection circuit 5.

11 is an OP amplifier, 12 is a capacitor, and 14 is a resistor. The capacitor 12 and the resistor 14 determine the time constant of the integrating circuit.

13 is an input resistance of the OP amplifier 11. 6 is an oscillation circuit that generates a triangular wave signal of a predetermined frequency; 61 is a comparator; 62 is a capacitor; 63 and 64 are resistors; 65 is a well-known analog switch; The time constant determined by resistors 63, 64 and capacitor 62 is switched.

66 and 67 are resistors that together with the feedback resistor 68 determine the upper and lower limits of the triangular wave output, and 69 is the input resistor of the comparator 61.

2 is a comparison circuit that compares the deviation integrator output 5 with the triangular wave oscillation output Vr and outputs an on/off signal; 21 is a comparator; and 22.23 is an input resistor.

7 is a differentiating circuit, 71 is a comparator, 72 is a differentiating capacitor to which the control input voltage V is applied to one end, 73 is a charging resistor, 74 is a discharging diode, 75 is an input resistor, 7
6.77 is a comparison voltage setting resistor.

78 is a resistor that transmits the output signal 8 of the comparator 71 to the analog switch 65, and when the output signal 8 is at a high level, the analog switch 65 closes and the oscillation circuit 6
Resistors 63 and 64, which determine the time constant of , are connected in parallel.

Next, the operation of the above circuit configuration will be explained.

In FIG. 3, the operations of the parts other than the oscillation circuit 6 and the differentiation circuit 7 are the same as those of the conventional circuit shown in FIG.

The oscillation circuit 6 and the differentiating circuit 7 operate as follows.

When the control input voltage v4 suddenly changes from zero to a predetermined value as shown in FIG.
, draws a waveform as shown in FIG. The predetermined time T as shown in FIG.

will be at the same level. On the other hand, the analog switch 65 of the oscillation circuit 6 receives the output signal ■ of the differentiating circuit 7.

receive the corresponding output signal ■. When is at a low level, the analog switch 65 is open, and the oscillation frequency of the oscillation circuit 6 is controlled by the resistor 6.
3 and the value of the capacitor 62, the output signal ■
8 becomes high level, the analog switch 65 is closed and the oscillation frequency is determined by the parallel resistance value of the resistors 63 and 64 and the value of the capacitor 62.

Therefore, when the output signal 8 is at a high level, the oscillation circuit 6
Since the oscillation frequency of becomes higher, the output V of the deviation integrator 1,
increases faster, and ■5 reaches the predetermined value expected by ■Y more quickly.

Therefore, the response delay depending on the frequency of the oscillator 6 is reduced.

In addition, when the above-mentioned oscillation frequency is normally 100Hz, for example,
■The frequency is set to 200 to 300 Hz during fishing periods.

As described above, according to the present invention, in a solenoid valve drive circuit that is controlled by changing the on-off time ratio of the current supplied to the solenoid valve coil, the triangular wave oscillator is activated for a predetermined period of time in response to a sudden change in the control input voltage. By setting the frequency higher than the set value, it is possible to speed up the rise of the current in the solenoid valve coil when the control input voltage suddenly changes.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the configuration of a conventional solenoid valve drive circuit, FIG. 2 is a waveform diagram showing operating waveforms of each part of the circuit configuration in FIG. 1, and FIG. 3 is a solenoid valve according to the present invention. FIG. 4 is an electric circuit diagram showing one embodiment of the drive circuit, and FIG. 4 is a waveform diagram showing operating waveforms of various parts of the circuit of FIG. 1... Deviation integration circuit, 2... Comparison circuit, 3... Solenoid valve coil, 4... Output circuit, 5... Current detection circuit, 6... triangular wave oscillation circuit, 7... differential circuit.

Claims (1)

[Scope of utility model registration request] a current detection resistor that detects the current supplied to the solenoid valve;
an integrator that compares and integrates a voltage proportional to the current detected by the current detection resistor and a control input voltage that controls the opening degree of the solenoid valve; a triangular wave oscillator that outputs a triangular wave of a predetermined frequency; In a solenoid valve drive circuit that includes a comparator that compares an oscillation output and an output of the integrator, and controls on/off the current supplied to the solenoid valve based on the output signal of the comparator, the control input voltage may suddenly change. A solenoid valve drive circuit, characterized in that the frequency of the triangular wave oscillator is increased above a set value for a predetermined period of time.