JPS607106A - Driving circuit for proportional solenoid - Google Patents

Abstract

PURPOSE:To pass a current exactly proportional to a control signal by detecting the current flowing through a solenoid, and then driving the element for current control, while the detected current is compared with the control signal. CONSTITUTION:The solenoid 5 is connected to the titled circuit 1 via ground line 4. When the control signal is impressed on an input terminal 2, an output signal having a pulse width according to the signal is outputted from an error amplifier 18 to a current controlling element 8. A current supplied to the solenoid 5 is detected by means of a resistor 9, and this detected signal is amplified in a feedback amplifier 15 and given to the amplifier 18.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for driving a solenoid in an electromagnetic valve, and more particularly to a proportional solenoid drive circuit for operating a solenoid by passing a current proportional to a control signal through the solenoid.

Conventional proportional solenoid drive circuits that control the current to the solenoid by controlling a current control element connected in series with the solenoid using the control signal described above are suitable for systems where the power supply voltage fluctuates. As a result, the electric current flowing through the solenoid fluctuates and is no longer proportional to the control signal. In order to solve this problem, it was considered to install a current detection resistor to detect the current flowing through the solenoid, and to control the current control element based on the detected value, but in that case, the solenoid and drive Not only did it require two wires to connect it to the circuit, but the solenoid also floated away from the ground, making it noncompliant with standards when used in vehicles.

Therefore, the present invention is designed to eliminate the above-mentioned problems.
In addition to being able to flow a current correctly proportional to the control signal to the solenoid, even with the above configuration, only seven wires are required to connect the drive circuit and the solenoid, making it possible to connect both economically. It is an object of the present invention to provide a proportional solenoid drive circuit which can be connected easily and with less effort, and which also allows one end of the solenoid to be grounded.

The drawings showing the embodiments of the present application will be described below.

In FIG. 1, l represents a proportional solenoid drive circuit, which is mounted on, for example, a construction vehicle. In this circuit 1, reference numeral 2 denotes an input terminal to which a manual controller (for example, a potentimeter) or various automatic controllers for emitting a control signal (analog signal) is connected. One end 5a of the solenoid 5 is connected to the 3Fi output terminal via a connection 1134. The solenoid 5 is used, for example, to operate various hydraulic solenoid valves in the vehicle, and the other end 5
b is connected (earthed) to the metal rib of the vehicle.

6 is the power supply terminal, which is a grounded power supply, that is, one end (negative side)
is the other end of the power supply (glass side) that is grounded to the metal part above.
is connected. The power source may be a battery (/2■ or 24ZV) mounted on the vehicle. 7 is a ground terminal, which is connected to the metal part 13. Next, 8 is a current control element, for example, an L transistor that performs a switching operation is used. 9 is a current detection resistor connected in series with element 8, with a small resistance value (
A voltage drop of a few ohms to several ohms is used so that the voltage drop during energization has almost no effect on the current supply to the solenoid 5. 10
is a surge absorption circuit, which consists of a unidirectional element (diode) 11 and a resistor ν for limiting the current flowing therein. Next, 14 shows a control circuit. In this, 15 is the return jψ
The amplifier uses a differential amplification circuit to amplify the potential difference generated across the current detection resistor 9 and output it. The error amplifier is used to accept the signal from input terminal 2 and the signal from the amplifier board, and output a signal corresponding to the difference between the two as a pulse-like repetitive signal as shown in Figure 8.3. It is configured with a well-known circuit so as to output. Note that the period of the above-mentioned pulse-like signal is constant (it may vary), and the width W increases as the value of the control signal input to the input terminal 2 increases, as shown in the figure. It looks like this.

In the above configuration, when a control signal is applied to the input terminal 2, an output signal having a pulse width corresponding to the control signal is outputted from the amplifier to the element 8. Then, the element 8 repeats the operation of being conductive during the pulse period and cut off during the Noculus period, and the power supply current from the power supply terminal 6 is repeatedly supplied to the output terminal 3. Therefore, the solenoid 5 is supplied with such a repeated (intermittent) current. The current flows from the positive side of the grounded power supply (the above battery),
power supply terminal 6, current control element 8, output terminal 3, connection line 4,
The flow passes through the solenoid 5, a metal part of the vehicle, and returns to the negative side of the power source.

As mentioned above, the current value supplied to the solenoid 5 is determined by the resistance 9
Detected in That is, it is detected as a potential difference in the electric potential (4) generated between the two ends. This detected potential difference is amplified by a feedback amplifier L5 and provided to an error amplifier. If the signal from the amplifier circuit (hereinafter referred to as a feedback signal) has a value corresponding to the control signal, the error amplifier continues to output the output signal at that time. - if the force feedback signal becomes larger than the value corresponding to the control signal (if the supply voltage increases or otherwise), the output signal for the amplifier is a signal that controls the element 8 such that the value of the current through said element 8 is lower; (The pulse width W decreases), and the current flowing through the solenoid 5 decreases. As a result of this continuous action,
The current flowing through the solenoid 5 has a value that is correctly proportional to the control signal. On the other hand, in the case opposite to the above, the opposite operation is performed without needing explanation, and the current flowing through the solenoid 5 becomes a value that is correctly proportional to the control signal.

When the operation is performed as described above, solenoid 5
Since the is intermittently energized, a reverse voltage (abnormally high voltage) is generated each time the energization is interrupted. The current due to the high voltage flows through the solenoid 5, the resistor 9, and the circuit 10, and the high voltage is absorbed.

Since the circuit 10 is placed between both ends of the connection circuit between the solenoid 5 and the resistor 9, the resistor 9 also detects the current caused by the abnormally high voltage. As a result, the element 9 can detect the value of the current flowing through the solenoid 5 including that current, and can operate the error amplifier accordingly. Therefore, the current flowing through the solenoid 5 is exactly proportional to the control signal.

Next, FIG. 2 shows a concrete circuit of an example of the feedback amplifier L5. In the figure, 21 is an operational amplifier, in which 21B and 21b are positive and negative power supply receiving terminals, respectively;
2IC indicates a non-inverting input terminal, and 21d indicates an inverting input terminal. 21e is an output terminal connected to an error amplifier. Also R1. R8 represents an input resistance, and R2 and R4 represent feedback resistances, respectively. The thorn is a protective one-way element and is connected in the direction shown in the figure using a diode between the non-inverting input terminal 21c and the positive power supply receiving terminal 21&. 23 is a power supply terminal for the operational amplifier 4, and although not shown, a power supply current is supplied from the positive side of the power supply through a constant voltage circuit (because of the presence of the constant voltage circuit, the voltage is equal to the voltage on the glass side, for example, 2.7 V) For example, it is now slightly lower than , for example, . Incidentally, this terminal filling may be directly connected to the glass side of the power source to receive current supply.

The amplifier 15 as described above acts as a differential amplifier and outputs a signal proportional to the potential difference generated across the current detection resistor 9 from the output terminal 21e.

Furthermore, in the amplifier L5, even if the abnormal high voltage occurs due to the intermittent energization of the solenoid 5, the non-inverting input terminal 2 of the operational amplifier 4
1C is the power supply receiving terminal 21a, and the voltage never becomes high (even if the voltage tries to become high, it will not become high because it will be discharged through the element η), so the operational amplifier 2
1 damage is prevented.

As described above, in this invention, (a) when operating the solenoid 5, the current control element 8 is controlled by the control signal input to the input terminal 2 (7), and the current control element 8 is controlled in proportion to the control signal. It has the feature that current can be passed from the output terminal 3 to the solenoid 5 to operate the solenoid.

(b) Furthermore, in the case of (a) above, the current flowing through the solenoid 5 is detected by the current detection resistor 9, and the detected value is compared with the above control signal to control the above element 8. Even if the current that would normally flow through the solenoid fluctuates without depending on the control signal due to fluctuations in the temperature of the solenoid, it is possible to keep the current flowing through the solenoid 5 in proportion to the control signal at all times. This has the effect of enabling highly accurate control.

(C) Furthermore, even if control is performed while detecting the current as described above, the detection resistor 9 is connected in series with the current control cable 8 between the output terminal 3 and the power supply terminal 6. Therefore, when a vehicle is equipped with the drive circuit 1 and the solenoid 5 driven by the drive circuit 1, the wiring between the drive circuit 1 and the solenoid 5 is for supplying current from the output terminal 3 to the solenoid 5. It has the advantage of being able to hold up with just 7 wires (8). This has the effect of reducing the amount of wire used, making it economical, and requiring less wiring work.In addition, the solenoid 5 has one end connected to the output terminal 3 and the other end grounded. It also has the effect of meeting standards that require one end to be grounded.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIG. 1 is a circuit diagram showing a drive circuit and a solenoid connected thereto, FIG. 2 is a circuit diagram showing a feedback amplifier and its related structure with a solenoid, and a current detection resistor. FIG. 3 is a waveform diagram showing an example of the output signal of the error amplifier, and FIG. 3 is a graph showing the relationship between the input signal (control signal) of the error amplifier and the pulse width. 2... Input terminal, 3... Output terminal, 5... Solenoid, 6... Power supply terminal, 8... Current control element, 9...
...Current detection resistor. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] It has an input terminal for inputting a control signal, an output terminal for connecting the solenoid, and a power terminal for connecting the glass side of the grounded power supply. A current control cable is connected between the solenoid and the solenoid to control the current flowing from the power supply terminal to the output terminal in accordance with the control signal input to the input terminal, while detecting the current flowing through the solenoid. The current control element compares the current value detected by the current detection resistor with the control signal, and determines that the current value is proportional to the control signal. In a proportional solenoid drive circuit connected to a control circuit configured to control the current control element, the current detection resistor is connected between the power supply terminal and the output terminal to A proportional solenoid drive circuit characterized by being connected in series with an element.