JPH0779212B2 - Power amplifier for solenoid proportional control valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power amplifier for an electromagnetic proportional control valve, and more particularly, to a power amplifier that is used to drive a solenoid that constitutes an electromagnetic valve and that provides a stable output with little temperature drift. Regarding the amplifier.

2. Description of the Related Art Conventionally, a large number of electromagnetic proportional control valves have been adopted for continuously controlling the flow rate and pressure of air according to the magnitude of current. The solenoid proportional control valve incorporates a proportional solenoid therein. This proportional solenoid has a characteristic that the attractive force with respect to the exciting current is constant within the range of the effective stroke. Therefore, the electromagnetic proportional control valve controls the air flow rate and pressure by utilizing the relationship that the attraction force of the proportional solenoid is proportional to the magnitude of the electromagnetic current.

Generally, in an electromagnetic proportional control valve, an exciting coil is frequently energized in order to drive a solenoid to control a stroke of a cylinder or the like. As a result, the exciting coil itself generates heat, or the temperature around the electromagnetic proportional control valve changes, and the impedance of the exciting coil changes greatly due to the change in the temperature of the fluid flowing in the valve. . As a result, the exciting current changes greatly, which appears as a change in the output of the proportional solenoid.
That is, the desired control of the air flow rate or the pressure cannot be achieved only by applying the constant voltage to the exciting coil, and the disadvantage that stability and reproducibility are lacking is exposed.

Therefore, in order to eliminate such a drawback, a solution using a feedback circuit in a power amplifier for driving a solenoid is considered. However, in this case, if a differential amplifier is incorporated as a feedback circuit, another inconvenience is revealed in that the feedback accuracy is reduced due to temperature drift due to variations in resistance values of resistors constituting the amplifier itself or due to a difference in temperature coefficient. come. That is, these means that the exciting current forming the solenoid changes, and eventually the position control of the set valve itself becomes unstable and lacks reproducibility.

As a means for solving this inconvenience, in particular, a configuration in which the signal for driving the solenoid is directly fed back to the operational amplifier on the input side without passing through the differential amplifier for feedback can be considered. However, according to this method, since the feedback resistor is connected to the inverting input terminal of the operational amplifier, the potential generated after the feedback resistor is a negative potential with respect to the potential supplied from the operational amplifier driving power source. There is a need.
Therefore, in practice, a power supply system different from the power supply for driving the operational amplifier is connected so that the potential related to the feedback resistor becomes negative.

That is, in the above configuration, it is necessary to prepare two DC power supply systems, that is, a power supply for driving the operational amplifier and a power output power supply for holding the potential generated after the feedback resistor at a negative potential. This causes the inconvenience that the circuit configuration itself becomes complicated and that the demand for downsizing the control system of the electromagnetic proportional control valve using a substrate or the like cannot be met.

The present invention has been made to overcome the above-mentioned inconvenience, and drives an operational amplifier by a single DC power source and holds the potential of a feedback signal from a feedback system at a negative potential, and has little temperature drift. Therefore, it is an object of the present invention to provide a power amplifier suitable for use in an electromagnetic proportional control valve with stable operation.

To achieve the above object, the present invention provides a DC power supply, a first linear arithmetic unit, a comparator connected to the output side of the first linear arithmetic unit, and an output signal to the comparator. A function generator, an output section connected to the output side of the comparator for driving the solenoid of the electromagnetic proportional control valve, and receiving an output signal from the output section and sending a feedback signal to the first linear computing unit. And a linear adjuster connected to the first linear calculator, a period adjuster connected to the function generator, and a second linear calculator from the DC power supply. The electromagnetic proportional control valve is controlled by applying a common voltage supplied.

Next, a power amplifier for an electromagnetic proportional control valve according to the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a control circuit for driving a solenoid which constitutes an electromagnetic proportional control valve according to the present invention. The control circuit 10 basically includes a power supply circuit 12 and a function generator 1.
4, first linear calculator 16, second linear calculator 18, comparator 2
0 and an output unit 22. In the power circuit 12,
In this case, for example, the voltage of + 24V is introduced and G
An ND terminal 12a, a terminal 12b for supplying an output of -18V, a terminal 12c for supplying an output of -8V, and a terminal 12d for supplying an output voltage of -24V are provided. These terminals 12a, 12b, 12c and 12d are the function generator 14 surrounded by the broken line, the linear calculator 1
The 6, 18 and the comparator 20 are connected to terminals provided in a circuit that is integrally modularized.

Next, the first linear calculator 16 includes an operational amplifier 16a,
A gain adjuster 24 is provided at one input terminal of the operational amplifier 16a.
, The gain adjuster 24 serves as an input terminal for the control signal on the one hand. The output side of the zero adjuster 26 including a variable resistor is connected to the inverting input terminal of the operational amplifier 16a, and the output side of the period adjuster 28 is connected to the inverting input terminal of the operational amplifier 14a constituting the function generator 14. .

By the way, the operational amplifier that constitutes the first linear calculator 16
The output side of 16a is connected to one input terminal of the amplifier 20a that constitutes the comparator 20, and the function generator is connected to this input terminal.
The 14 outputs are also connected. On the other hand, the resistors R ₁ and R ₂ are connected to the non-inverting input terminal of the amplifier 20a, and the output side of the comparator 20 is connected to the switching transistor Tr ₁ which is cut off by its output signal. The output side of the transistor Tr ₁ is externally attached to the outside of the module.

As easily understood from the figure, the output unit 22 is substantially composed of a switching transistor Tr ₂ and a power transistor Tr ₃ , the output side of which is a current detection resistor R ₃ and electromagnetic proportional control. Connected to valve solenoid 30. In this case, the current detection resistor R ₃ is connected to the inverting input terminal and the non-inverting input terminal of the operational amplifier 18a that constitutes the second linear calculator 18 in the module,
As described above, the output side of the second linear calculator 18 is the first
It is connected to the non-inverting input terminal of the operational amplifier 16a that constitutes the linear calculator 16.

The power amplifier of the electromagnetic proportional control valve according to the present invention is basically constructed as described above. Next, its operation and effect will be described.

As described above, the power supply circuit 12 is supplied with a DC voltage of + 24V to obtain outputs of -24V, -18V and -8V. -24
The output voltage of V is applied to the emitter side of the transistor Tr ₃ forming the output section 22. On the other hand, the output voltage of −18V is applied to the zero point adjuster 26, the period adjuster 28, and the second linear calculator 18. That is, the -18V applied to the zero adjuster 26
Voltage plays a role of adjusting the offset voltage of the operational amplifier 14a constituting the function generator 14. On the other hand, the second linear calculator 18 is configured to be driven by the power supply voltage of -18V applied to the second linear calculator 18. That is, as apparent from the above description, in the present invention, in particular, the zero adjuster 26,
Power is supplied to the period adjuster 28 and the operational amplifier 18 in common so that −18 V is applied to them. By doing so, the power supply system can be further simplified.

Therefore, in the above setting state, the gain adjuster 24
Can be adjusted to select the target value, while the zero adjuster 26 can be adjusted to determine the offset voltage of the operational amplifier 16a, and a bias current can be passed through the solenoid proportional control valve. Therefore, a signal corresponding to the sum of the output signal of the gain adjuster 24, the output signal of the zero adjuster 26 and the output signal of the operational amplifier 18a of the second linear calculator 18 is output from the operational amplifier 16a to the comparator 2
Output to 0.

On the other hand, the output signal of the period adjuster 28 to which a voltage of −18V is applied is introduced to one input terminal of the operational amplifier 14a that constitutes the function generator 14, and the power supply circuit is provided to the other input terminal of the operational amplifier 14a. A reference voltage of −8V from 12 is applied. Thereby, in the function generator 14, for example,
A sawtooth wave is generated within an amplitude range of −8V to −3V, and this sawtooth wave is introduced into the operational amplifier 20a forming the comparator 20. As described above, the output signal of the first linear calculator 16 is introduced to the inverting input terminal of the comparator 20, and eventually, the output signal of the function generator 14 is supplied to the inverting input terminal. The signal of the sum with the output signal of the first linear calculator 16 is introduced. This signal is compared with the reference voltages V _H and V _L (V _H > V _L ) determined by the resistors R ₁ and R ₂ connected to the non-inverting input terminal side of the comparator 20 and the output level of the comparator. When it is higher than the reference voltage V _H , the low level signal L is output, while when it is lower than the reference voltage V _L , the high level signal H is output.

The switching transistor Tr ₁ receives the output signal from the comparator 20, and when the signal is high, the transistor Tr ₁ is conductive, while when the output signal is low, it is cut off. Therefore, the output signal Tsudan of the transistor Tr _1, the second switching transistor Tr
₂ and the power transistor Tr ₃ are cut off.
Of course, when the power transistor Tr ₃ is turned on, a predetermined current flows in the solenoid 30, and the exciting coil is excited to drive the solenoid (not shown).

In this case, as the amplitude of the sawtooth wave from the function generator 14 changes, the output signals H and L from the comparator 20 are inverted at a high speed corresponding to the cycle of the sawtooth wave. As a result, the power transistor Tr ₃ is turned off at high speed.
Therefore, the current flowing through the solenoid 30 is smoothed by the inductance component of the solenoid and has a waveform with ripples in the DC component. After all, the total sum of the pulse currents corresponds to the target value. Then, in the above configuration, the output side of the second linear calculator 18 that constitutes the negative feedback circuit is introduced to the first linear calculator 16. Therefore, the amount of electricity supplied to the solenoid 30 corresponds to the value set in the gain adjuster 24.

According to the present invention, as described above, the control system of the electromagnetic proportional control valve is driven by the single DC power source. In addition, the first and second linear arithmetic units, the function generators, and the comparators are integrally incorporated so as to be in contact with each other as much as possible to form a module. Therefore, miniaturization is further promoted and incorporated into it. The temperature drift of various resistors can be small. Therefore, there is an advantage that a stable operation can be obtained and an operation with further improved reliability can be obtained.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments,
It goes without saying that various improvements and design changes can be made without departing from the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram for driving and controlling a solenoid of an electromagnetic proportional control valve according to the present invention, and FIG. 2 is a circuit diagram for explaining in detail the contents of the block diagram of FIG. 10 …… control circuit, 12 …… power supply circuit 14 …… function generator, 16, 18 …… linear calculator 20 …… comparator, 22 …… output part 24 …… gain adjuster, 26 …… zero-point adjuster 28 …… Cycle adjuster, 30 …… Solenoid

Claims (2)

[Claims] 1. A DC power supply, a first linear arithmetic unit, a comparator connected to the output side of the first linear arithmetic unit, a function generator for sending an output signal to the comparator, and An output unit connected to the output side of the comparator to drive the solenoid of the electromagnetic proportional control valve, and the first signal receiving the output signal from this output unit
A second linear arithmetic unit for sending a feedback signal to the linear arithmetic unit, at least a zero-point adjuster connected to the first linear arithmetic unit, a period adjuster connected to the function generator, and a second linear arithmetic unit
A power amplifier for an electromagnetic proportional control valve, characterized in that a common voltage sent from the DC power supply is applied to a linear arithmetic unit to control the electromagnetic proportional control valve. 2. A power amplifier according to claim 1, for an electromagnetic proportional control valve in which a first linear operator, a second linear operator, a comparator and a function generator are incorporated in a single module. Power Amplifier.