JPH0133674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive control device for an electromagnetic pump used in a heater or the like.

[Prior Art] The pumping action of an electromagnetic pump involves passing a current intermittently through a solenoid coil in the pump, and when the current flows, an electromagnetic force is generated in the solenoid coil, which causes the piston in the pump to move. It is driven to perform the discharge stroke due to its pump action, and while the current flow is extinguished, the suction stroke is performed by the biasing force of the internal spring, and the electromagnetic force is applied to the solenoid coil. It is proportional to the value of the current flowing.

Further, the power source for the current flowing to these solenoid coils is generally a DC power source obtained by full-wave rectification of normal commercial AC power.

In addition, when using such a DC power supply and applying current to the solenoid coil, turn on a switch circuit in the circuit from the DC power supply to the solenoid coil.
If you want to stop the current flowing through the solenoid coil, turn off the switch circuit.
I try to do this.

[Problems to be Solved by the Invention] The conventional configuration described above has the following problems.

As mentioned above, when the switch circuit is turned on and current starts flowing from the DC power supply to the solenoid coil, the current flowing to the solenoid coil is proportional to the voltage value at the DC power supply from the moment it is turned on. Rather than being a constant value, the current flowing through the solenoid coil due to the inductance in the solenoid coil gradually increases with respect to the elapsed time t, as shown in the current characteristic A1 in Fig. It becomes a constant value proportional to the voltage.

In other words, in Fig. 1, when the switch circuit is turned on, the solenoid current flows along the current characteristic A1.
Current I flows through the coil, and the switch circuit turns TO
When it is turned off after a certain period of time, the current I disappears from the position of the current characteristic A1 at that TO time.

In this case, if the voltage in the DC power supply fluctuates and the power supply voltage becomes lower than in the case of current characteristic A1 in FIG. decreases like the current characteristic A2. On the other hand, when the power supply voltage increases, the characteristic becomes higher than the current characteristic A1 in FIG. 1.

In addition, as mentioned above, the driving force of the piston in an electromagnetic pump, that is, the electromagnetic force, is generated by the solenoid.
It is proportional to the current value flowing through the coil, and the stronger the electromagnetic force, the greater the degree to which the piston is accelerated.

This means that in the discharge stroke of the electromagnetic pump,
When the power supply voltage changes, the electromagnetic force generated in the solenoid coil changes, and this change changes the speed at which the fluid is pushed out by the piston. As a result, the fluid discharge rate per unit time Q [ cc/min] will change.

For example, when these electromagnetic pumps are used as fuel pumps for heaters, it becomes impossible to set the fuel supply at a constant level, and the room temperature is set at a constant level by the heater. You end up not being able to keep it that way.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic pump driving device that is capable of setting a constant discharge flow rate of fluid per unit time even when the power supply voltage fluctuates as described above.

[Means for solving problems] The present invention consists of the following configuration.

In a configuration in which a current having a pulse width is periodically applied to a solenoid coil of an electromagnetic pump, a pulse generation circuit outputs a voltage signal in the form of a rectangular wave signal, and the output from the pulse generation circuit is used as a command signal, and the above-mentioned A current detection resistor is provided in series with the collector or emitter of a transistor that controls the current flowing through the solenoid coil, and the voltage detected by the current detection resistor is used as a feedback signal to perform current tracking control to control the current flowing through the solenoid coil. The constant current drive circuit controls the upper limit of the current to a value proportional to the voltage on the high level side of the rectangular wave signal from the pulse generating circuit.

[Function] The relationship between the electromagnetic force generated in the solenoid coil and the piston in the electromagnetic pump that performs the pumping action is the same as in the past: the electromagnetic force is proportional to the value of the current flowing to the solenoid coil, and the electromagnetic force is It is the driving force that causes the piston to compress the fluid during the discharge stroke, and when the electromagnetic force disappears, the piston is pushed back by the force of the spring installed in the pump, and the suction of the electromagnetic pump is It is supposed to be a process.

With the same configuration as the conventional pump part of such an electromagnetic pump, the present invention is such that the electromagnetic force that drives the pump becomes the action of generating electromagnetic force having the following characteristics by the above-mentioned means of the invention. , which provides reproducible electromagnetic force to the electromagnetic pump without being affected by fluctuations in the DC power supply voltage.

The pulse generating circuit alternately outputs a high constant value voltage and a low constant value voltage close to zero.
That is, the output voltage V outputs a command signal as shown in FIG. 3 to the constant current circuit for the elapsed time t.

Further, the constant current drive circuit compares the command signal from the pulse generation circuit with the feedback signal value of the detected current flowing through the solenoid coil, and adjusts the current flowing through the solenoid coil in proportion to the value of the command signal. The power is turned on.

That is, when the pulse generation circuit outputs a low voltage with a constant value close to zero, the constant current drive circuit makes the current flowing to the solenoid coil almost zero in proportion to the output. Therefore, in this state, almost no electromagnetic force is generated in the solenoid coil, the piston in the electromagnetic pump is not driven, and the piston is returned to the top dead center of the piston stroke.

On the other hand, the pulse generation circuit is VO (Fig. 3)
When the constant current drive circuit starts outputting a high constant value voltage, the constant current drive circuit
A current is passed through the solenoid coil in proportion to VO during the operating time TO, and the current value is constant I=IO.

However, the command voltage V from this pulse generation circuit
momentarily from the state where is almost zero, TO = 0 in Figure 3.
When V = VO in , current I momentarily tries to flow to the solenoid coil, but as mentioned above, the inductance in the solenoid coil influences it at the beginning of the flow, and it starts flowing to the solenoid coil. The current I has a current characteristic A1 of 0 to a in FIG. Note that in this case, it is assumed that the voltage at the DC power source is a voltage corresponding to the current characteristic A1.

In this way, the current I begins to flow through the solenoid coil, and when the current I eventually tries to exceed the value of the current I = IO, which is proportional to the command voltage V = VO from the pulse generation circuit, the constant current The drive circuit makes the current flowing through the solenoid coil constant I = IO in proportion to the output voltage V = VO, its characteristics are the characteristics a to b in Figure 1, and the command signal is as shown in Figure 3. Working time as TO
When the current I reaches zero again after , the current I decreases as shown by the characteristic B due to the characteristics of the solenoid coil.

In the above case, when the voltage of the DC power supply is a voltage corresponding to the current characteristic A2, the characteristics of the current flowing through the solenoid coil are as shown in 0 to a' to b.

In this way, even if the voltage of the DC power source fluctuates, the current I flowing through the solenoid coil only begins to flow during the operating time TO, and only during the initial period when the current I is I<IO. The difference is only affected by voltage fluctuations in the DC power supply, and the difference is as small as c in FIG.

Therefore, even if the power supply voltage in the DC power supply changes, the current I flowing to the solenoid coil will always be equal to the output voltage, except for a small initial change.
It becomes a constant value proportional to VO, which means that the electromagnetic force applied to the piston is almost unaffected by fluctuations in the power supply voltage, and is set almost constant by the command signal from the pulse generation circuit. .

Also, the electrical resistance of a solenoid coil changes when its temperature changes, but the above action always detects the value of the current flowing through the solenoid coil,
Since the value of the detected current is controlled in proportion to the value of the command signal from the pulse generation circuit,
Even when the temperature of the solenoid coil changes in this way, the value of the current flowing through the solenoid coil is set to be constant regardless of such changes in electrical resistance.

Furthermore, if the operating time TO is changed while the operating voltage VO is kept constant, the time during which the piston is driven will change, and the fluid discharge amount Q from the electromagnetic pump during that one operating time TO will also change. Characteristics B1, B2, or B3 in the figure can be changed. Note that the characteristics B1 and B2 are the first
Corresponding to current characteristics A1 and A2 in the figure, characteristic B3 corresponds to the case where the voltage of the DC power supply is further reduced than the current characteristic A2 in FIG.
Points d, h, e, i, f and j are experimental values,
The interval between t1 and t2 in Fig. 2 is experimentally determined as follows:
It is proportional to the voltage change of the DC power supply, and the fact that there is a small difference in the discharge flow rate Q due to the change in the power supply voltage of characteristics B1, B2, and B3 is due to the difference in the difference c in Fig. 1. It is equivalent.

Therefore, when correcting a small change in the discharge flow rate due to the difference in the part c in FIG. 1, the following procedure may be used.

That is, the voltage at the DC power supply has the characteristic B2
When the voltage becomes higher and the power supply voltage corresponds to characteristic B1, the operating time at characteristic B2
In contrast to TO=TO1, if the operating time TO in characteristic B1 is set to TO=TO1−t1, it becomes possible to obtain the same discharge flow rate Q=Q1 as in characteristic B2, and conversely, the power supply voltage decreases. The voltage is characteristic B
If it corresponds to 3, set the new operating time TO.
=TO1+t2, it is possible to obtain the same discharge flow rate Q=Q1 as in the case of characteristic B2.

For this reason, in the above invention, the time interval TO for outputting the voltage VO of the high constant value is
If the relationship is set to be longer in proportion to the decrease in the DC power supply voltage, when the voltage of the DC power supply changes, the relationship shown in Figure 2 will allow the first By correcting the change in portion c in the figure, the flow rate of fluid discharged from the electromagnetic pump can be made constant.

[Examples] The present invention will be described below based on Examples. The configuration of the pump part in an electromagnetic pump is omitted from illustration because it is the same as the conventional configuration, but as in the conventional pump, electromagnetic force is generated in proportion to the current flowing through the solenoid coil. The electromagnetic force is generated when the piston performs the discharge stroke.
This is the driving force that causes the piston to compress the fluid, and when the electromagnetic force disappears, the piston is pushed back by the force of the spring installed in the pump, and the electromagnetic pump performs the suction stroke. ing.

FIG. 4 shows an electric circuit diagram of the electromagnetic pump drive control device according to the present invention.
The pulse generation circuit 1 is an electric circuit that generates a rectangular wave voltage as shown in FIG. This is an electric circuit that controls energization, and solenoid coil 3
When a current flows through, the electromagnetic force proportional to the current is generated.

The input wire 3a of the solenoid coil 3 is connected to a DC power source that is the result of full-wave rectification of normal commercial AC electricity, and 4 is ground, R1, R2, R
3, R4 and R5 are resistors, VR1, VR2 and VR3 are variable resistors, C1 is a capacitor, D
1, D2, D3 and D4 are diodes, ZD1
is a Zener diode, IC1 and IC2 are operational amplifiers, and TR is a transistor, and solid thin lines indicate wiring.

The operation of the configuration of the above embodiment will be explained below.

At the start of operation, the transistor TR
Since no voltage has yet been generated at the base of the transistor TR, the connection between the collector and emitter of the transistor TR is off (off), and therefore the solenoid coil 3 is not energized by the power applied to the input wire 3a. It has become a state where there is no
Further, the capacitor C1 is still in a discharged state.

In this initial state, the operational amplifier IC
1, a constant voltage set by the Zener diode ZD1 is applied to the input wire 1b through the resistor R1.
In contrast, the input wire 1a of operational amplifier IC1 has a voltage value of zero, so the output of operational amplifier IC1 is not positive due to its nature. It is in a constant voltage state.

On the other hand, in this state the Zener diode
The constant voltage potential at node P1, set by ZD1, causes a current to flow through diode D2 and variable resistor VR2 to capacitor C1, charging it.

As a result, the voltage on the input wire 1a also increases over time, and when the voltage value eventually exceeds the constant voltage value on the input wire 1b, the output value of the operational amplifier IC1 becomes approximately negative due to its nature. Convert to a constant voltage value,
This voltage is a low value (about -0.6 volts) determined by the forward voltage of the Zener diode ZD1, and thereby the input electric wire 1b is also set to a constant low negative voltage value.

When the above state is reached, the positive voltage potential charged in the capacitor C1 is discharged through the variable resistor VR1 and the diode D1 with respect to the negative potential at the node P1.

Due to this discharge, the voltage at the input wire 1a also decreases over time, and when the voltage value eventually reaches the negative voltage value at the input wire 1b, the operational amplifier IC1, due to its nature, again reduces its output voltage. The same positive voltage as before is set and the cycle continues again.

As a result of the above, a cycle of rectangular wave voltage occurs at the connection point P1, and this rectangular wave voltage becomes a rectangular wave voltage divided by the resistor R4 and the variable resistor VR3 at the input wire 2a. This output rectangular wave voltage corresponds to the rectangular wave voltage V in FIG.

In this way, when the rectangular wave voltage shown in FIG. 3 is applied to the input wire 2a of the operational amplifier IC2, at the moment when the operating voltage VO occurs at the operating time TO (FIG. 3), the input wire of the operational amplifier IC2 Since no voltage is generated on 2b, the operational amplifier
A voltage proportional to the operating voltage VO is applied to the output of IC2, and as a result, a voltage is generated at the base of the transistor TR, causing conduction between the collector and emitter of the transistor TR, and the current I from the input wire 3a. is solenoid coil 3, electric wire 3
b, flows to ground 4 via transistor TR and resistor R5.

At this time, the rise of the current I flowing through the solenoid coil 3 depends on the resistance due to its inductance, and the current characteristic A1 or A shown in FIG.
It has a gradual rising characteristic like 0 to a or 0 to a' in 2.

In this way, when a current I flows through the solenoid coil 3, a voltage proportional to the current I is generated in the input power supply 2b due to the presence of the resistor R5, and the operational amplifier IC2 generates a feedback signal of the current I. The voltage value of the input electric wire 2b as a command signal is compared with the voltage value of the input electric wire 2a as a command signal, and a voltage corresponding to the difference is applied to the base of the transistor TR.

As a result, the current I flowing from the collector to the emitter of the transistor TR always acts to flow a current proportional to the value of the command signal applied to the input wire 2a, and the current I is as shown in FIG. A constant current IO occurs between a and b or between a' and b. However, 0 to a or 0 in Figure 1
In the period between ~ a', even if the transistor TR tries to cause the current I = IO to flow through the solenoid coil 3, the current I = IO due to the electrical resistance due to the inductance in the solenoid coil 3, as described above. The current is regulated until the current I reaches 0 to a or 0 to a' at the initial stage.

Also, as mentioned above, in FIG. 1, when the current I reaches point b while maintaining the state of I=IO,
Since the command voltage at the input wire 2a has a negative value close to zero, the transistor TR is turned off and the flow of current to the ground 4 is stopped.

However, in the solenoid coil 3, even after the elapsed time from point b, the current I exhibits a characteristic in which the current I decreases smoothly as shown in characteristic B due to the back electromotive force.

The above-mentioned action of the current I is performed repeatedly following the period of the rectangular wave voltage in FIG. 3 due to the periodic repetition of the rectangular wave voltage.

In the above action, variable resistors VR1, VR
2 and VR3 are the time setting and operating time in the range where the voltage V in Fig. 3 is almost zero.
The settings of TO and the operating voltage VO can be set arbitrarily, and the diode D3 is provided to protect the transistor TR.

In this way, the current I shown in FIG.
The fact that the current flows repeatedly like b or 0~a'~b means that even if the power supply voltage fluctuates like A1 or A2, the current flowing through the solenoid coil 3, except for the slight difference at point c in Figure 1. I is always a flow with the same reproducible current characteristics, and the solenoid coil 3 has the same current characteristics regardless of fluctuations in the DC power supply voltage.
Electromagnetic force will be generated.

As mentioned above, since the electromagnetic force directly becomes the discharge action force of the piston in the pump, the fluid discharge flow rate per unit time of the pump resulting from the discharge action is not affected by fluctuations in the DC power supply voltage. It will become constant.

FIG. 5 is a system diagram showing another embodiment of the electromagnetic pump drive control device according to the present invention, in which the pulse generating circuit 10 is connected to the trigger pulse generating circuit 10A and a monostable multi-channel system. It consists of a vibrator 10B, and this pulse generation circuit 10 replaces the pulse generation circuit 1 in FIG.
Reference numeral denotes a power supply voltage feedback wire, and other parts having the same reference numerals as in FIG. 4 indicate the same materials as in FIG. 4.

The operation of the configuration shown in FIG. 5 will be explained below.

In the trigger pulse generation circuit 10A, the monostable multivibrator 1 is activated by a trigger pulse p having a voltage V as shown in FIG.
0B generates a rectangular wave voltage of voltage V as shown in FIG. 7, and this rectangular wave voltage controls the constant current drive circuit 2 by the same effect as that explained in FIG. , feedback wire 1
Since 0a detects the voltage value at the input electric wire 3a, when the voltage value increases, the operation time TO in FIG. 7 is reduced, and in the opposite case, it is increased.

As explained in Figure 2, this means that
When the power supply voltage of the input wire 3a applied to the solenoid coil 3 changes, for example, when the flow rate characteristic at a certain voltage is B2, the command voltage applied to the constant current drive circuit 2 changes. If time TO is set to a constant state of TO1 (Figure 2), its operating point is point e, and from this state the voltage changes to another constant voltage. If the flow rate characteristic becomes B3, the operating point will newly move from point e to point g, resulting in a flow rate deviation q1 with respect to the target discharge flow rate Q1.

Therefore, in this case, the operating point is from point g to f
By moving the discharge flow rate to
Q1 can be maintained at a constant value, and in order to move this operating point from point g to point f, the feedback signal of the electric wire 10a where the voltage fluctuation was detected is transmitted to the monostable multi In vibrator 10B, operating time TO
The new operating time TO = corresponding to point f in Fig. 2
It is set to TO1 + t2.

As explained in Fig. 1, if the difference c can be set sufficiently small with respect to the operating time TO, the flow rate characteristics B1 etc. will hardly change, so the electric wire 10a in Fig. 5 is not necessary. In such a case, the setting of the operating time TO of the rectangular wave voltage in the monostable multivibrator 10B can be set manually without automatically adjusting the value using the feedback signal. By changing the setting from TO1 to TO2 (FIG. 2) or vice versa, the discharge flow rate Q can be adjusted as desired.

[Effects of the Invention] The fluid discharge flow rate per unit time in an electromagnetic pump is determined by the discharge stroke speed of the piston in the pump and the duration of the discharge stroke, that is, the driving force that causes the piston to perform the discharge stroke and the duration of the driving force. Determined by the time you are there.

In the present invention, the driving force applied to the piston, that is, the electromagnetic force generated in the solenoid,
Utilizing the fact that the current flowing through the coil is proportional to the rectangular wave voltage from the pulse generation circuit 1, the constant current circuit 2 generates the current I=0 to 0 as shown in FIG.
Since a to b or 0 to a' to b are passed through the solenoid coil, the discharge flow rate of fluid per unit time from the electromagnetic pump will have an error of the order of c in Figure 1, regardless of fluctuations in the DC power supply voltage. It is possible to set it to a constant value except for .

Furthermore, the device of the present invention does not require an expensive constant voltage device as the power source connected to the electromagnetic pump, and simply requires a pulse signal generation circuit and an operational amplifier.
The constant current drive circuit 2 consisting of the IC2, the transistor TR, and the resistor R5 makes it possible to construct an inexpensive drive control device for an electromagnetic pump.

Furthermore, since the present invention sets the current flowing through the solenoid coil in proportion to the command voltage,
Even if the temperature of the solenoid coil 3 changes and its electrical resistance changes, it is possible to maintain a constant value of the current flowing through the solenoid coil.

Furthermore, even if the electrical resistance in the solenoid coil 3 varies due to mass production of the electromagnetic pump, the discharge flow rate will not change due to the variation.

In particular, when the electromagnetic pump control device of the present invention is used as a fuel pump device for heating, the fuel discharge is always maintained at a predetermined setting even when the commonly used commercial power supply voltage fluctuates. It becomes possible to set and control the heating temperature to a certain value, which makes it possible to maintain the heating temperature constant and to make the heater inexpensive.

In addition, in the present invention, when a variation in the power supply voltage is detected and the operating time TO is adjusted according to the power supply voltage, the difference due to the voltage variation in part c in FIG. 1 is also corrected, Furthermore, regardless of changes in the power supply voltage, the fluid discharge flow rate can always be maintained in accordance with the command value.

[Brief explanation of drawings]

Figure 1 shows the current characteristics of the current flowing through the solenoid coil of an electromagnetic pump.
1 and A2 show the characteristics when the power supply voltage applied to the coil is constant, respectively, and the characteristic B in FIG. 1 shows the current characteristic when the electromagnetic pump drive control device of the present invention is used. FIG. 2 shows the discharge flow rate characteristics of the electromagnetic pump according to the electromagnetic pump drive control device according to the present invention,
FIG. 3 shows the command voltage (square wave voltage) for controlling the current flowing through the coil in order to realize the current characteristic B in FIG. 1, and FIG. 4 shows the driving of the electromagnetic pump in the present invention. One embodiment of the control device is shown by an electric circuit diagram, FIG. 5 shows another embodiment of the electromagnetic pump drive control device according to the present invention by a system diagram, and FIG. FIG. 7 shows the characteristics of the trigger pulse output by the trigger pulse generation circuit 10A in FIG.
This shows the characteristics of the rectangular wave voltage output by 0B. The main symbols used in the examples are as follows. 1 and 10: pulse generation circuit, 2: constant current drive circuit, 2a: input wire (wire for command signal input from pulse generation circuit 1 to constant current drive circuit 2),
2b: Input wire (wire for feedback signal that detects the current flowing through the solenoid coil 3),
3: Coil, 3a: Input wire (wire connected to DC power supply), IC2: Operational amplifier, TR: Transistor.

Claims (1)

[Scope of Claims] 1. A drive control device that periodically supplies a current with a pulse width to a solenoid coil of an electromagnetic pump, comprising: a pulse generation circuit that outputs a voltage signal in the form of a rectangular wave signal; and this pulse generation circuit. The output from the solenoid coil is used as a command signal, a current detection resistor is provided in series with the collector or emitter of the transistor that controls the current flowing through the solenoid coil, and the voltage detected by the current detection resistor is used as a feedback signal to perform current tracking control. and a constant current drive circuit that controls the upper limit of the current flowing through the solenoid coil to a value proportional to the voltage on the high level side of the rectangular wave signal from the pulse generation circuit. Control device.