JPS5932708B2 - Solenoid proportional valve drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving device for an electromagnetic proportional valve, and particularly to a driving device for stably controlling an excitation current.

The electromagnetic proportional valve is configured to adjust the flow rate of a fluid passage by electromagnetically sliding a spool that is slidably provided in an axial direction within a main body case. The end of the spool is biased in the axial direction by a spring, and the flow rate is adjusted by controlling the current in the excitation coil and sliding the spool to a position where the electromagnetic force and the biasing force of the spring are balanced. That's what I do. In this case, a frictional force acts between the circumferential surface of the spool and the inner wall surface of the hole in the case that this circumferential surface touches, and the magnitude of this frictional force varies depending on the position of the spool, temperature, etc. due to factors such as processing accuracy. There is some wobbling and flickering. Therefore, even if the electromagnetic force is slightly changed by slightly changing the excitation current, the spool cannot slide due to the friction and remains stuck to the inner wall of the hole, and the change in electromagnetic force becomes the frictional force. A phenomenon occurs in which the spool only moves when it is defeated. Moreover, since there are variations in the frictional force, the amount of change in the excitation current does not correspond to the displacement of the spool, which reduces the accuracy and resolution of position control with respect to the spool. As a countermeasure to this problem, conventionally, the spool is constantly vibrated by using a pulsating current or a DC superimposed with a pulsating current as the exciting current, thereby improving the linearity of the spool's displacement with respect to changes in the exciting current. It has been known. Providing pulsating current to the excitation current in this manner is called dithering. A conventional method for applying dither is to use a pulsating current obtained by rectifying a commercial AC power source with a full-wave rectifier circuit. However, in this method, the excitation current fluctuates due to power supply fluctuations, and the excitation current also fluctuates due to changes in coil resistance due to temperature. These current fluctuations are expressed as fluctuations in the output flow rate and pressure of the electromagnetic proportional valve. Therefore, a method is used in which the rectified output is made into a constant voltage using a constant voltage circuit, and then this constant voltage is converted into a pulse train of a predetermined frequency using a dither circuit, and this pulse train is applied to the excitation coil through a variable resistor. . Although this method eliminates current fluctuations due to power supply fluctuations, current fluctuations due to temperature cannot be avoided. In particular, as the above variable resistor for adjusting the excitation current, multiple variable resistors are connected in parallel,
In a system in which these are switched by a relay, the current is switched in steps, causing a shock when switching. In order to suppress the current fluctuations caused by the temperature mentioned above, a conventional method is to run a current through the coil for a certain period of time before using the electromagnetic proportional valve, saturate the coil temperature to the upper limit, and then start operation. It took a very long time to prepare for the start. In addition, in conventional electromagnetic proportional valves, when the fluid temperature changes during operation, the coil temperature is affected by the change, resulting in output fluctuations.Therefore, the object of the present invention is to avoid being affected by coil temperature changes. An object of the present invention is to provide an electromagnetic proportional valve drive device.

Another object of the present invention is to provide an electromagnetic proportional valve drive device in which the excitation current does not change suddenly when changing the current. Still another object of the present invention is to provide an electromagnetic proportional valve drive device that does not require preparation time before starting operation. Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a variable resistor for adjusting the supply voltage, including an upper limit setting variable resistor 8, a lower limit setting variable resistor 9, and voltage dividing resistors 10a, 10b, 10c connected in parallel.
, 10d1 relay contacts 11a, 11b, 11c, 11d
and relay coils 12a, 12b, 12c, 12d, etc. as shown in the figure.

Relay coils 12a to 12d are channel selection buttons CHa
, CHb, CHO, CHd are selectively energized and the corresponding contacts 11a to 11d are closed. Reference numeral 2 denotes an integrator whose time constant can be adjusted, and is constructed of variable resistors 13a, 13b, 13c, 13d and a capacitor 14 as shown in the figure.

3 is a voltage comparator that compares the integrated output of the integrator 2 with the amplified output of an amplifier 21, which will be described later, and outputs a signal of "1" (high level) when the integrated output exceeds the amplified output. Output.

5 is a rectangular wave oscillator, and 06 is an AND gate that outputs a rectangular wave signal with a predetermined frequency of, for example, 100 to 200 Bz.
The output of the comparator 3 and the square wave signal are added.

T is a switching transistor, which has a collector connected to an excitation coil 22 of an electromagnetic proportional valve, an emitter connected to an excitation current detection resistor 18, and is switched by a rectangular wave signal applied to its base through an AND gate 6. Reference numeral 4 denotes an integrating circuit, which is composed of a resistor 19, a capacitor 20, and a diode 23, and smoothes the voltage detected by the resistor 18 with a time constant of, for example, several Msec or less.

An amplifier 21 amplifies the output of the integrating circuit 4 and applies it to the comparator 3.

The integration circuit 4 charges the voltage through the diode 23→capacitor 20 when the detection voltage of the detection resistor 18 rises, and charges the capacitor 20 when the detection voltage falls.
->Resistor 19 -> Detector resistor 18 is discharged in the path, switching 0N and switching 0F of transistor 7.
This is provided in order to set the period of F to an appropriate size without depending only on the impedance of the excitation coil 22 of the electromagnetic proportional valve. Next, the operation of the circuit with the above configuration will be explained with reference to FIG.

In the following explanation, for the sake of simplicity, a case will be described in which three channels A, b, and c are adjusted. First, adjust the upper limit setting variable resistor 8 and set each voltage dividing resistor 10a, 10b, 10c.
Set the maximum output voltage of each voltage dividing resistor, and adjust the lower limit setting variable resistor 9 to set the minimum output voltage of each voltage dividing resistor. Next, adjust the voltage dividing resistors 10a, 10b, 10c, A, b, c Supply voltage A, Vb, c of each channel
Set.

Next, adjust the variable resistors 13a, 13b, and 13c to set the integration time constant of each channel to, for example, several 100 msec to several 1
Set to 0 sec In the above state, the channel selection button CH is pressed first, and at time t1 in Fig. 2, the relay contact 11a closes as shown in A in Fig. 2, and channel a is selected.
The output voltage of variable resistor 10a is applied to integrator 2.
As a result, the integrated output Vll rises at a slope determined by the resistance value of the resistor 13a and the capacitance of the capacitor 14 up to the voltage Va set by the resistor 10a, as shown in FIG. 2E. This integrated output Vil is applied to the comparator 3 and compared with the voltage obtained by amplifying the relative pressure generated in the detection resistor 18 with the amplifier 21. Since the output is zero, when the relay contact 11a closes, the output of the comparator 3 becomes "1" and the AND gate 6 is opened. As a result, the rectangular wave signal passes through the AND gate 6 and switches the transistor 7, and the exciting current t flows through the exciting coil 22 in a pulsed manner. While this switching is being performed, the integral output Vi increases. Now, assuming that the detection resistor 18 is RΩ, the gain of the amplifier 21 is K (times), and the voltage applied to the electromagnetic proportional valve is sufficiently high, when VIl>R-1t-K, the output of the comparator 3 is [1
'', the switching operation of the transistor 7 is 0N as shown in FIG.
The switching operation of the transistor 7 becomes 0FF.

As the transistor 7 becomes 0FF and the charge stored in the capacitor 20 is discharged through the resistors 19 and 18, the output of the amplifier 21 decreases. Then, since the integral output Vil becomes larger than the output of the amplifier 21, the comparator 3
The output becomes [1] again, causing transistor 7 to switch. Thereafter, by the same operation, the transistor 7 repeats the switching operation 0N and 0FF at a period determined by the time constant of the integrating circuit 4, the hysteresis of the comparator 3, the coil impedance, etc.

In this case, as shown in Fig. 2E, the peak value of R-1t-K is V
i, switching operation is 0N, 0FF along the curve
Therefore, the peak value of the excitation current 1t is VilOCR-1t
-K1: proportional to 5vi1. Therefore, excitation? If the current 11 is approximately a rectangular wave, its average current also increases in proportion to Vil until Vil is saturated and reaches the voltage Va. This causes the spool of the electromagnetic proportional valve to generate a square wave oscillator 5.
A dither is applied at a frequency of 1, and the flow rate is adjusted based on the average current.

Next, at time point u, the relay contact 11a is opened, and when the relay contact 11b is closed and channel b is selected as shown in FIG.

As a result, the output of the integrator 2 falls with a slope determined by the resistance value of the resistor 13b and the capacitance of the capacitor 14 to the voltage Vb set by the resistor 10b. As a result, the same operation as described above is performed, and as the switching operation of 0N and 0FF is repeated at a predetermined period, the average current is proportional to the output Vi2 of the integrator 2, and Vi2 is saturated and the voltage V
decreases until reaching b. Next, at T3, relay contact 1
1b is opened and the relay contact 11c is closed as shown in FIG. 2D to select channel c, the output voltage of the resistor 10c becomes the voltage V set by the variable resistor 10c.

Until then, the voltage falls at a slope determined by the resistance value of the resistor 13c and the capacitance of the capacitor 14. Then, by the same operation as above, the average current of the excitation current 1t becomes proportional to the integral output 13, and Vi3 is saturated to the voltage V. decreases until it reaches . Next, when the relay contact 11c is opened at time T4, the charge stored in the capacitor 14 is discharged through the resistors 13c, 10c, and 9, the integral output becomes zero, and the exciting current returns to its initial state.

By integrating the above operations, the current t of the electromagnetic proportional valve is controlled based on a preset sequence.

v As described above, the configuration of the present invention selects the magnitude of the integrated voltage of this integrator and the speed of its rise and fall by selecting the input voltage and time constant of the integrator using the channel selector. It also includes a switching element (e.g., transistor 7) that causes an excitation current to flow through the excitation coil, and a detection circuit (e.g., resistor 1) that integrates a part of the excitation current and detects the magnitude of this excitation current as a voltage value.
8, a circuit consisting of an integrating circuit 4, an amplifier 21, etc.), a comparator for comparing the integrated voltage with the detected voltage of the detecting circuit, and a rectangular wave signal generator with a predetermined number of frequency plates, The switching device is characterized in that the switching element is driven by the rectangular wave signal based on the output signal of the comparator when the voltage exceeds the detection voltage (for example, by opening the AND gate 6). .

Therefore, according to the above configuration of the present invention, the following effects can be obtained.

(1) Since the excitation current 1t changes in proportion to the integral output Vin, it is not affected by fluctuations in coil resistance.

Therefore, constant output flow rate and pressure can be obtained according to the set voltage without being affected by coil temperature and fluid temperature. (2
) Since the excitation current is converted into an excitation current whose peak value changes along with the integrated output, there are few sudden changes in the excitation current.

Therefore, the shock during current switching is reduced, and the output flow rate and
Pressure can be controlled smoothly. (3) Unlike the conventional method, there is no need for preparation time until the coil temperature reaches saturation before starting operation.

In the embodiment shown in FIG. 1, an amplifier 21 is connected to the output of the integrator 4.
However, if the value of t-R is properly adjusted, this amplifier 21 is unnecessary.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the apparatus of the present invention, and FIG. 2 is a waveform diagram showing the output waveforms of the main parts of FIG.

Claims (1)

[Claims] 1. An excitation coil, an integrator whose time constant can be changed, and a channel that selects the input voltage of this integrator and the above-mentioned time constant to select the magnitude of the integrated output voltage and the speed of its rise and fall. a selector, a switching element that causes an excitation current to flow through the excitation coil, a detection circuit that integrates a portion of the excitation current and detects the magnitude of the excitation current as a voltage value, and an integrated output voltage of the integrator. a comparator for comparing the detection voltage of the detection circuit; a rectangular wave signal generator with a predetermined frequency; and when the output signal of the comparator is applied when the integrated output voltage exceeds the detection voltage, 1. An electromagnetic proportional valve drive device, comprising: a gate circuit for passing a wave signal and applying the rectangular wave signal to a control terminal of the switching element.