JPH0443653Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a control current detection circuit for a solenoid valve that controls the flow rate of oil pressure, air pressure, etc. The present invention relates to detection of a control current of a control mechanism that performs control. This idea is suitable for clutch control in automobiles.

〔overview〕

This invention is a control current detection circuit for a solenoid valve that detects the control current value by detecting the voltage generated in a resistor inserted in series with the drive coil of the solenoid valve. By providing a second resistor, detecting the voltage generated in the second resistor, and adding the detected output to the detected output of the voltage generated in the resistor inserted in series with the drive coil, This compensates for the control current detection error caused by the inductance of the drive coil and reduces the control error.

[Conventional technology]

In a control mechanism using a fluid such as hydraulic pressure, a solenoid valve controls the opening and closing of hydraulic oil from a hydraulic pump, and the opening/closing control controls the flow rate of the hydraulic oil to control a hydraulic cylinder.

The same applies to control using pneumatic pressure, so hydraulic control will be described below as an example.

When this fluid control is applied to the control of an automobile's clutch by a microprocessor, it is necessary to gradually engage the clutch by taking in information about the engine speed and vehicle speed for clutch control at the time of starting. In this case, to gradually engage the clutch, a solenoid valve is opened and closed intermittently to control the required flow rate of hydraulic fluid. The flow rate at this time is determined by the duty ratio of the control pulses that open and close the solenoid valve.

By the way, since the control amount of the hydraulic oil due to the opening and closing of this solenoid valve is determined by the control current value of the solenoid valve, this control current value is input to the microprocessor and processed as a controlled value.

A control current detection circuit for a solenoid valve is used to measure this controlled value. The configuration of the control current detection circuit is shown in FIG.

One side of the electromagnetic valve drive coil L is connected to the drive power source, and the other side is connected to the transistor T _r ,
A resistor _R1 is connected in series to the emitter of the transistor _Tr , and one end of the resistor _R1 is grounded. Resistance R ₁
The connection point between and the transistor T _r is connected to the non-inverting input of the operational amplifier OP via the resistor R ₂ .
The output of the operational amplifier OP is led to an analog-to-digital converter (not shown) via a smoothing circuit composed of a resistor _R5 and a capacitor C.

In the operation of this conventional circuit, the transistor T _r is turned on and off by a control input pulse from a control input terminal, and as a result, the current of the drive coil L is controlled. By on/off control of transistor T _r ,
Current flows intermittently through the resistor _R1 , and a voltage is generated across the resistor _R1 . This voltage value is amplified by an operational amplifier OP, converted to a digital value by an analog-to-digital converter, and taken into the microprocessor as a control current input.

[Problem that the invention attempts to solve]

By the way, since electromagnetic energy is accumulated in the current flowing through the drive coil due to the inductance of the drive coil, the response current waveform to the control pulse voltage waveform shown in Fig. 3a is the waveform diagram shown in Fig. 3b. becomes.

However, in this conventional circuit example, as a result of the transistor T _r turning on and off, the control current flows through the resistor R ₁ only when the transistor T _r is on.
The current shown in the shaded area shown in FIG. 3b does not appear at both ends of the resistor _R1 , and the control current when it is off cannot be measured.

That is, since the opening and closing of the solenoid valve is performed at the current value indicated by the dashed-dotted line in FIG. 3b, the actual solenoid valve is open for the time _t1 . However, in the conventional circuit, once the control pulse is turned off, the subsequent control current is not taken in, so the control current is only measured for the time t ₂ , which is different from the actual operation of the solenoid valve.
This means that an error for the time t ₁ − _{t 2} has occurred.

For this reason, in the conventional control current detection circuit, it was not possible to obtain a more accurate control current, that is, a controlled value, and this resulted in a drawback that a control error occurred.

An object of the present invention is to provide a control current detection circuit for a solenoid valve that can detect a control current more accurately than conventional detection circuits.

[Means for solving problems]

The control current detection circuit of the present invention consists of a first resistor inserted in series with the drive coil of a solenoid valve that repeats opening and closing at a constant cycle and controls the amount of fluid passing through depending on the opening duty ratio for the cycle; A control current detection device for a solenoid valve, which includes a first detection circuit that detects a voltage generated in a device, and a series circuit of a backflow prevention diode and a second resistor, and a series circuit of a backflow prevention diode and a second resistor in parallel with the drive coil. The present invention is characterized by comprising a second detection circuit that detects the voltage generated in the resistor, and a circuit that adds the detection output of the second detection circuit to the detection output of the first detection circuit.

[Effect]

Based on the control input, the solenoid valve control transistor is turned on and off to control the current to the solenoid valve drive coil.

When the transistor is on, that is, when the control pulse is high, the voltage generated across the first resistor is measured via the first operational amplifier to determine the control current value.

When the transistor is off, that is, when the control pulse is low, the voltage generated across the second resistor, which is connected in parallel to the drive coil through a backflow prevention diode, is amplified by the second operational amplifier, and the voltage generated at the second operational amplifier is amplified by the first operational amplifier. Find the control current value by adding it to

Thereby, it is possible to measure both current values when the control pulse is on and off, and a more accurate control current value can be detected.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

One end of the drive coil L is connected to a drive power source, and the other end is connected in series with the collector of a transistor T _r that is turned on and off by a control input. A resistor _R1 is connected in series to the emitter side of the transistor _Tr , and the other end of the resistor _R1 is grounded.

The connection point between this resistor R ₁ and the transistor T _r is a resistor
Connected via R ₂ to the non-inverting input of operational amplifier OP ₁ .

Now, a backflow prevention diode D is connected in parallel to the drive coil, a resistor _R6 is connected in series to this diode D, and the other end of the resistor _R6 is connected to the drive power supply side.

Both ends of the resistor R ₆ connected in parallel to the drive coil L are connected to a resistor voltage divider circuit including a resistor R ₇ , a resistor R ₉ , a resistor R ₈ , and a resistor R ₁₀ . The voltage dividing terminal of this resistive voltage dividing circuit is connected to the input of the operational amplifier OP ₂ via a resistor R ₁₁ , a resistor R ₁₂ , and a resistor R ₁₃ .

The output of this operational amplifier OP ₂ is connected via a resistor R ₁₅ to the non-inverting input of the above-mentioned operational amplifier OP ₁ .

The output of operational amplifier OP ₁ is connected to resistor R ₅ and capacitor C
The signal is led to an analog-to-digital converter (not shown) through a smoothing circuit configured by the following.

Next, the operation of this control current detection circuit will be explained.

When a high-level control pulse that opens the solenoid valve is input to the control input terminal, the transistor T _r
is turned on, and current flows from the drive power supply to the drive coil L. This current flows through resistor _R1 and creates a voltage there. This voltage is input to the non-inverting input of the operational amplifier OP ₁ via the resistor R ₂ and is amplified, and its waveform is smoothed by the resistor R ₅ and the capacitor C. is converted into a digital signal by At this time, no current flows through the resistor _R6 due to the backflow prevention diode D.

When a low-level control pulse that closes the solenoid valve is input to the control input terminal, the transistor T _r
is turned off, and the current flowing from the drive power source through the drive coil L is cut off. At this time, an induced current generated by electromagnetic induction flows from the drive coil L to the resistor _R6 through the diode D, and a voltage difference is generated between both ends thereof. In the example this resistance R ₆
The resistance value is 7.5Ω. The voltage difference generated at this resistor R ₆ is detected as the voltage difference between the connection points of the voltage divider circuit consisting of resistor R ₈ and resistor R ₁₀ and the voltage divider circuit consisting of resistor R ₇ and resistor R ₉ . Ru.

In this example, resistors R ₇ and R ₈ are 4.7KΩ, resistors
R ₉ and ₁₀ are 330Ω, and the voltage division ratio is 1/15. The voltage difference created between this connection point is the resistance
Operational amplifier via R ₁₁ , resistor R ₁₂ , resistor R ₁₃
Entered into OP ₂ .

The output of operational amplifier _OP2 is input to operational amplifier _OP1 via resistor _R15 , amplified by operational amplifier _OP1 , and guided to an analog-to-digital converter through a smoothing circuit.

In this way, the voltage due to the control current both on and off the control input is amplified by the operational amplifier,
The control current can be measured by leading to an analog-to-digital converter.

As a result, in the present invention, the current in the shaded area in FIG. 3b is measured for time _t3 . The error between the actual operating times t ₁ and t ₃ of the solenoid valve can be reduced by adjusting the partial pressure ratio or amplification setting of the bridge circuit, addition ratio, etc.

Note that, as described above, in the embodiment, the voltage division ratio of the bridge circuit is set to 1/15, but the ratio can be set freely. Further, although the amplification degree and addition ratio of the operational amplifier are set to 1, the amplification degree and addition ratio can be set freely.

[Effect of idea]

As described above, the present invention can detect the control current even when the control input is off, so the control current can be detected with a small error.

Therefore, errors in control of the solenoid valve can be reduced, making it possible to more accurately control the clutch of an automobile.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. Second
The figure is a conventional circuit diagram. FIG. 3 is a waveform diagram showing control pulse response. L...Drive coil, T _r ...Transistor, D
...Diode, OP...Operation amplifier, R...Resistor, C...Capacitor. D...S5277, OP...
TA75358, _R1 ...0.5Ω (2W), _R2 ...100kΩ, _R3
...8.2kΩ, R ₄ ...100kΩ, R ₅ ...220kΩ, R ₆ ...
…7.5Ω (1W), R ₇ …4.7kΩ, R ₈ …4.7kΩ, R ₉
...330Ω, R ₁₀ ...330Ω, R ₁₁ ...33kΩ, R ₁₂ ...
...33kΩ, R ₁₃ ...33kΩ, R ₁₄ ...33kΩ, R ₁₅ ...
100kΩ, C...473pF.

Claims (1)

[Claims for Utility Model Registration] A first resistor R ₁ inserted in series with the drive coil of a solenoid valve that repeats opening and closing at a constant cycle and controls the amount of fluid passing through depending on the opening duty ratio for the cycle; A control current detection device for a solenoid valve comprising a first detection circuit that detects a voltage generated in a resistor, and a series circuit of a backflow prevention diode D and a second resistor _R6 in parallel with the drive coil. , a second detection circuit that detects the voltage generated in the second resistor, and a circuit that adds the detection output of the second detection circuit to the detection output of the first detection circuit. A control current detection device for a solenoid valve, characterized by: