JP2500064B2 - Proportional valve drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proportional valve driving device for controlling a proportional valve with a pulse modulation signal sent from a microcomputer.

[0002]

2. Description of the Related Art As shown in FIG. 3, a power supply circuit 500 is conventionally provided with an electronic switch 511 (switching circuit),
And a proportional valve circuit 510 in which the coils 512 of the proportional valve are connected in series, a current detection circuit 513 for detecting a current flowing through the coil 512, a microcomputer 520 for sending a pulse width modulation signal 521, and pulse width modulation. A proportional valve drive device B having a constant current circuit 530 for monitoring proportional valve current, to which the signal 521 and the output of the current detection circuit 513 are input, is known.

[0003]

However, the conventional proportional valve drive device B has the drawback that the constant current circuit 530 occupies a large mounting space and requires many parts. As shown in 4, the electronic switch 6
11 and a proportional valve coil 612 connected in series, a current detection circuit 613 for detecting a current flowing through the coil 612, and a microcomputer 6
20 and a microcomputer 620
And a pulse width modulation signal 621 based on the target value signal 640.
To the control terminal 611a of the electronic switch 611 to drive the electronic switch 611, and a correction means 662 that corrects the target value signal 640 based on the output of the current detection circuit 613. C
Was prototyped. However, in the proportional valve drive device C, when the coil 612 of the proportional valve is short-circuited, the power supply voltage (2) is applied to the AD input port 663 of the microcomputer 620.
It was found that there is a possibility that the microcomputer 620 and the transistor 611b may be destroyed because an excessive current flows through the transistor 611b of the electronic switch 611, and the microcomputer 620 and the transistor 611b may be destroyed. An object of the present invention is to provide a proportional valve drive device that does not require a constant current circuit and that does not damage a microcomputer or an electronic switch even if the coil of the proportional valve is short-circuited.

[0004]

In order to solve the above-mentioned problems,
The present invention is a proportional valve circuit in which an electronic switch having a control terminal and a coil of a proportional valve are connected in series to a power supply circuit,
A current detection circuit for detecting a current flowing through the coil of the proportional valve and an overvoltage limiting circuit connected between the current detection circuit and a microcomputer are provided, and the microcomputer is modulated based on a target value signal. Drive means for sending the pulse-modulated signal to the control terminal to drive the electronic switch, and correction means for correcting the target value signal based on the output of the current detection circuit via the overvoltage limiting circuit. And a holding means for stopping and holding the transmission of the pulse modulated signal when the output of a predetermined value or more is detected.

[0005]

The driving means modulates the periodic pulse on the basis of the target value signal corresponding to the target valve opening degree, and sends this pulse modulation signal to the control terminal of the electronic switch. The electronic switch performs switching operation based on the pulse modulation signal,
The proportional valve has a target valve opening. Even if the electrical resistance of the coil of the proportional valve changes due to energization or heat reception, the correction means of the microcomputer uses the output of the current detection circuit via the overvoltage limiting circuit so that the proportional valve maintains the target valve opening. Correct the target value signal. When the coil of the proportional valve is short-circuited or is in a state close to a short-circuit, the current detection circuit detects approximately the power supply voltage. However, the overvoltage limiting circuit suppresses the value of the voltage applied to the correcting means of the microcomputer to the safety limit value, so that the microcomputer is not destroyed. Also,
When the output of the overvoltage limiting circuit exceeds a predetermined value, the holding means of the microcomputer operates so as to stop and hold the output of the pulse modulation signal, so that the electronic switch is not destroyed.

[0006]

EFFECTS OF THE INVENTION It is possible to prevent the destruction of the microcomputer and the electronic switch due to the short circuit of the coil of the proportional valve.
The constant current circuit, which has a large number of parts and occupies a large mounting space, is unnecessary.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. The proportional valve drive device A includes a switching circuit 1
And the proportional valve circuit 8 in which the coil 2 of the governor proportional valve is connected in series and is connected to the power supply circuit 4, the current detection circuit 3 for detecting the energizing current of the coil 2, the current detection circuit 3 and the AD input port 71. It has an integrating circuit 5 and an overvoltage limiting circuit 6 connected between the two, and a microcomputer 7.

The switching circuit 1 includes resistors 11-14,
It is composed of transistors 15 and 16 and a diode 17. In this switching circuit 1, the collector-emitter of the transistor 16 corresponds to the electronic switch body, and the one end 111 of the resistor 11 corresponds to the control terminal. Coil 2
When the temperature of the coil is 20 ° C, the electric resistance of the coil is 7
Although it is 8.5Ω ± 10%, it becomes about 100Ω when the coil temperature reaches 90 ° C. due to energization or the like. Further, the governor proportional valve determines the opening degree in proportion to the proportional valve current 20 flowing through the coil 2 and adjusts the flow rate of the fuel gas. The current detection circuit 3 detects the proportional valve current 20 and is 10Ω,
It consists of a cement resistance of 2W. The power supply circuit 4 is a commercial 10
An alternating current obtained by stepping down 0V by a transformer is rectified using a silicon bridge and an electrolytic capacitor (neither is shown) to obtain DC 40V containing a power supply ripple of 60Hz or 50Hz.

The integrating circuit 5 comprises a resistor 51 of 47 kΩ and a capacitor 52 of 1 μF, and integrates the voltage waveform of the output of the current detecting circuit 3 to output an integrated signal 53. The overvoltage limiting circuit 6 includes a resistor 61 whose right end is connected to the integrator circuit 5, a resistor 62 whose left end is connected to the A-D input port 71, and a diode 63 whose cathode is connected to a DC power supply (+ about 5V). 2 and limits the value of the output 64 applied to the AD input port 71 to 5 volts, as shown in FIG.

The microcomputer 7 sends a square wave pulse of 1 kHz to a target value signal 70 corresponding to the target proportional valve opening.
Pulse width modulation is performed by using the pulse width modulation signal 72.
11 (control terminal) to drive the switching circuit 1 by driving means 73, correction means 74 for correcting the target value signal 70 based on the output 64 input to the AD input port 71, and 3 volts or more And a holding means 75 for forcibly stopping the operation of the driving means 73 and stopping and holding the output of the pulse width modulation signal 72.

Next, the operation of the proportional valve driving device A will be described. The driving unit 73 sends the pulse width modulation signal 72 to the one end 111 (control terminal) of the switching circuit 1. The transistor 16 of the switching circuit 1 causes a current based on the pulse-on time to flow through the coil 2 of the governor proportional valve, and the governor proportional valve reaches the target valve opening degree. By the way, when the temperature of the coil 2 of the governor proportional valve rises due to energization or heat reception,
The electric resistance value of the coil 2 increases, and the proportional valve current 20 decreases. However, the correction means 74 of the microcomputer 7 corrects the target value signal 70 based on the output 64 (the output of the current detection circuit 3 that has passed through the integrating circuit 5 and the overvoltage limiting circuit 6), and the pulse width modulation signal 72 is turned on. Since the time is changed so that the time becomes longer, the proportional valve is maintained at the target valve opening. Since the voltage waveform of the current detection circuit 3 is smoothed by the integration circuit 5, noise and power supply ripple are rarely input to the AD input port 71 of the microcomputer 7. Here, the coil 2 of the governor proportional valve
However, when a short circuit or a state close to a short circuit occurs, a high voltage (approximately 40 volts) is applied to the current detection circuit 3 and the integrated signal 53 also has a high voltage. However, since the diode 63 of the overvoltage limiting circuit 6 bypasses this overvoltage to the DC power supply, the voltage on the anode side does not exceed 5 volts, and the voltage applied to the AD input port 71 also falls within 5 volts or less. The microcomputer 7 is not destroyed. Also,
In this case, the holding means 75 detects the output 64 of 3 volts or more and forcibly stops the operation of the driving means 73, and stops and holds the pulse width modulation signal 72 until a reset button (not shown) is pressed. 16 becomes non-conductive and transistor 16 is not destroyed.

The present invention includes the following embodiments in addition to the above embodiments. a. In addition to pulse width modulation (PWM), pulse modulation signals include pulse amplitude modulation (PAM) and pulse number modulation (PN).
M) or the like. b. The electronic switch may use another semiconductor element such as a FET.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a proportional valve driving device according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between an integral signal and an output of an overvoltage limiting circuit in the proportional valve driving device.

FIG. 3 is an electric circuit diagram of a conventional proportional valve driving device.

FIG. 4 is an electric circuit diagram of a prototype proportional valve driving device.

[Explanation of symbols]

 A proportional valve drive device 1 switching circuit (electronic switch) 2 coil 3 current detection circuit 4 power supply circuit 6 overvoltage limiting circuit 7 microcomputer 8 proportional valve circuit 64 output 70 target value signal 72 pulse width modulation signal (pulse modulation signal) 73 drive Means 74 Correction means 75 Holding means 111 One end (control terminal)

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-229982 (JP, A) JP-A-5-18475 (JP, A) JP-A-63-43080 (JP, A) Actual development Sho-59- 6805 (JP, U)

Claims (1)

(57) [Claims] 1. A proportional valve circuit in which an electronic switch having a control terminal and a coil of a proportional valve are connected in series to a power supply circuit, a current detection circuit for detecting a current flowing through the coil of the proportional valve, and the current. An overvoltage limiting circuit connected between the detection circuit and the microcomputer, wherein the microcomputer sends a pulse modulation signal modulated based on a target value signal to the control terminal to drive the electronic switch. Driving means for correcting the target value signal based on the output of the current detection circuit via the overvoltage limiting circuit, and sending the pulse modulation signal when the output of a predetermined value or more is detected. A holding means for stopping and holding the proportional valve drive device.