JP3046684B2 - Drive circuit for electric expansion valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in starting torque of a stepping motor used for driving an electric expansion valve or the like.

[0002]

2. Description of the Related Art Conventionally, an electric expansion valve using a stepping motor is provided between a condenser and an evaporator in a refrigerant circuit of an air conditioner, and the capacity is controlled by controlling the electric expansion valve. . As a mechanism of this electric expansion valve, as shown in FIG.
A rotating torque is generated by a cylindrical permanent magnet 18 which is magnetized in a cylindrical direction with 4, 5, and 6, and the tip of the central axis of the rotor, which is the permanent magnet, is connected to the valve body 1.
9, the center axis is threaded, and the rotation of the rotor changes the distance between the valve body 19 and the valve seat 20 so that the flow rate of the refrigerant can be controlled.

In the case of the stepping motor type electric expansion valve, when the reference position of the valve opening is set, a pulse number corresponding to the entire opening and closing range from full opening to full closing is applied as an initializing operation, and the electric expansion is performed. After the valve is fully closed , the stepping motor rotates only the magnetic field, and the valve element 19 on the center axis of the rotor does not rotate, so that the fully closed state is set as an accurate reference position.

[0004]

However, at the time of the above initialization, even if the valve element 19 is fully closed with the valve body 19 seated on the valve seat 20, a further valve closing pulse is applied. Is rotated in the reverse direction, the valve is not reliably opened even if it is attempted to open the valve, and the normal operation cannot be performed thereafter.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and in a drive circuit of a stepping motor, a current is supplied to an excitation coil for generating a drive torque.
To generate a high voltage by charging the capacitor with the induced voltage generated in F, apply this high voltage to the exciting coil at a predetermined timing, and escape from the tightened state and open the valve with a high torque proportional to the voltage. It is intended for.

[0006]

A drive circuit for an electric expansion valve according to the present invention is an expansion valve for driving a valve element 19 to open and close by a pulse signal input to a stepping motor 17.
The induced electromotive voltage generated when the switching element 7 is turned off is supplied to the capacitor 1 by each excitation coil of the stepping motor 17 which is turned on / off by the switching element 7.
3, the switching circuit 14 is turned on by a predetermined timing signal applied to the timing signal input terminal 15, and the charging voltage of the capacitor 13 is applied to the exciting coils 3, 4, 5, and 6 of the stepping motor 17. It is characterized by being driven.

[0007]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a drive circuit of the electric expansion valve of the present invention, and FIG. 2 shows the structure of the electric expansion valve. The present invention
As shown in FIG. 1, in an electric expansion valve that drives a stepping motor 17 by an excitation pulse to an excitation pulse input terminal 1 to open and close a valve body 19, a driving power supply passes through a diode 2 and is turned on / off by a switching element 7.
The diodes 8, 9, 10, and 11 are connected to the switching element 7 side of the coils 3, 4, 5, and 6, which are the excitation coils of the stepping motor 17, respectively. the cathode side, both the Zener diode 12
The capacitor 13 is connected in parallel to both ends of the Zener diode 12, and the voltage stored in the capacitor 13 is applied by a switching circuit 14 to a predetermined timing signal applied to a timing signal input terminal 15. Thus, the excitation coil is applied to the coil 3, the coil 4, the coil 5, and the coil 6 through the diode 16.

Further, when the stepping motor is driven, as shown in FIG.
Since the switch is turned off, an excessive surge voltage such as an induced voltage V _S = L (di / dt) (L: coil inductance, t: time, i: current) is generated at the time of OFF depending on the nature of the coil. This surge voltage is passed through the Zener diode 12, it is bypassed to the drive power source to charge the capacitor 13 at the same time protecting the switching element 7 from being destroyed by the surge voltage to the zener voltage (drive power supply voltage +
Zener voltage) can be obtained. This high voltage by ON the switching circuit 14 by a predetermined timing signal applied to the timing signal input terminal 15
For example, torques applied to the respective excitation coils 3, 4, 5, 6 can be generated in proportion to the voltages.

[0009]

FIG. 4 is a diagram showing voltage waveforms at various points, where point A is the exciting coil n (n = 3, 4, 5, 6), point B is the voltage on the cathode side of the Zener diode 12, and point C is 4 shows a timing signal. At the time of initialization, if the timing signal is turned off, the switching circuit 14 is non-conductive, so that each time the exciting coil n repeats ON / OFF, the induced voltage of the coil gradually charges the capacitor 13, and the point B than the voltage V _C, the Zener diode 1
A voltage higher by the zener voltage V _{Z of} 2, that is, V _C + V _Z
High voltage can be obtained. Further, the surge voltage of V _C + V _Z or higher is bypassed to the drive power supply through the Zener diode 12, so that the switching element 7
_C + V _Z only voltage is not applied, it has also serves to protect the switching element 7 from the surge voltage.

At the time when the initialization is completed, it is highly probable that the tightening state is present. Therefore, just before the valve opening operation, the timing signal is turned on and the switching circuit 14 is turned on. _C +
A high voltage of V _Z is applied. At this time, the diode 12 does not flow back to the drive power supply . Since the switching element 7 is turned on by the pulse signal 1 for the valve operation ,
Exciting coil n at a voltage of V _C + V _Z is driven, the V _Z High
The torque corresponding to the high voltage increases, and it is possible to escape from the tightened state . At this time, the voltage V _Z charged by the capacitor 13 is discharged through the exciting coil n, so that the voltage at the point B gradually decreases.

[0011] 12V as the drive power supply voltage V _C, the Zener voltage 13V as a Zener diode 12, when using capacitance 2200μF is about twice the torque is generated immediately after ON of the timing signal 15. Assuming that the torque at the time of rotation of the stepping motor is 1, the normal tightening torque is 1.4, and the loosening torque is 0.9. From this, the torque required for loosening is 1 × 1.4.
X0.9 = 1.26, and 2.0 / 1.26 = 1.6 times more torque than 2.0 of the experimental example according to the embodiment. It is clear that a larger effect can be obtained by using a Zener diode 12 having a Zener voltage of 20 V or 30 V, and the practical effect is large.

[0012]

[Other Embodiments] In the above embodiment, the drive of the electric expansion valve has been described, but the present invention can also be used to drive a stepping motor. That is, in the conventional method, as shown in FIG. 5, the drive frequency and the torque have a pull-in characteristic at the time of startup and a pull-out characteristic at the time of synchronous rotation with the drive frequency. As shown in FIG. 6, complicated control was performed, such as gradually increasing the rotation speed from the start, or performing two-voltage driving using two power supplies.

However, according to this circuit, it is possible to generate a large torque by using the internally generated high voltage without using a special power supply, and thus to perform complicated control. A method is not necessary, and the pull-in characteristic and the pull-out characteristic can be reversed as shown in FIG. To obtain a high voltage, turn on / off the excitation coil.
It is sufficient to perform FF, and if the driving frequency is high so that the stepping motor does not rotate, or if the excitation pattern does not cause the rotation operation, preparation for high torque operation can be made without rotating the stepping motor. For the timing signal, if a signal by a timer that responds to the initial drive pulse signal after a certain period of stationary time is logically created, high torque operation can be performed automatically at startup, so the stepping motor is also small. It is possible to reduce power consumption and reduce costs at the same time.

[0013]

As described above, according to the present invention, in the drive circuit of the stepping motor 17 for driving the electric expansion valve, the coils 3, the coil 4, the coil 5, and the coil 6, which are the respective exciting coils of the stepping motor 17, are provided. , A diode 8, a diode 9,
The anode sides of the diodes 10 and 11 are connected, the respective cathode sides of the diodes are both connected to the cathode side of a Zener diode 12, a capacitor 13 is connected in parallel to both ends of the Zener diode 12, and a switching circuit 14 is connected. Thus, the voltage stored in the capacitor 13 is applied to the coils 3, 4, 5, and 6 as the exciting coils by a predetermined timing signal applied to the timing signal input terminal 15 through the diode 16. Therefore, each time the switching element 7 repeats ON / OFF by the pulse signal 1 which is a drive signal of the stepping motor , the induced electromotive voltage generated from the coil at the time of OFF is stored in the capacitor 13. that the driving power source, to obtain a higher voltage It can be. The switching circuit 14 is turned on by the timing signal 15 , and at this time, a high voltage is applied to the exciting coil. Therefore, a larger driving torque can be generated without fail until the capacitor 13 is completely discharged, and the electric expansion valve is initialized. In addition, when the stepping motor is viewed as a single unit, the pull-in characteristics at startup can be significantly improved, and the motor can be reduced in size and labor can be saved. is there.

[Brief description of the drawings]

FIG. 1 is a drive circuit of an expansion valve according to the present invention.

FIG. 2 is a longitudinal sectional view of an expansion valve.

FIG. 3 is an excitation sequence of a stepping motor.

FIG. 4 is a voltage waveform of a drive circuit of the present invention.

FIG. 5 shows characteristics of a stepping motor using a conventional circuit.

FIG. 6 shows a conventional stepping motor control method.

FIG. 7 shows characteristics of a stepping motor using the drive circuit of the present invention.

[Explanation of symbols]

1 Excitation pulse input terminal 2, 8, 9, 10, 1
1, 16 Diode 3, 4, 5, 6 Coil 7 Switching element 12 Zener diode 13 Capacitor 14 Switching circuit 15 Timing signal input terminal 17 Stepping motor 18 Permanent magnet 19 Valve body 20 Valve seat.

Claims (1)

(57) [Claims] In an expansion valve that opens and closes a valve element (19) by a pulse signal input to a stepping motor (17), each excitation coil of the stepping motor (17) turned on / off by the switching element (7) turns off the switching element (7). The induced voltage generated at the time is charged in the capacitor 13, and the switching circuit 1 is switched by a predetermined timing signal applied to the timing signal input terminal 15.
4 is turned on, and the charging voltage of the capacitor 13 is applied to the excitation coils 3, 4, 5, and 6 of the stepping motor 17 for driving.