JPH0614596A - Method and device for driving expansion valve - Google Patents

Abstract

PURPOSE:To provide a method and a device for driving an expansion valve wherein an accurate position of rotation in accordance with a number of supply pulses can be attained regardless of increasing a driving speed. CONSTITUTION:In a driving gear for an expansion valve 3 driven by a stepping motor, there are provided DC power supplies 15, 16, 17 possible to selectively output small power Va and large power Vb and a control means 18 for performing control so as to supply the small power Va first and the large power Vb last from the DC power supplies, of driving pulses in one step, to driving coils W1 to W4 of the stepping motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for driving an expansion valve provided in a refrigeration cycle and driven by a stepping motor.

[0002]

2. Description of the Related Art As a motor for driving a direct-acting expansion valve used in a refrigeration cycle of an air conditioner or the like, the pressure condition of the refrigerant acting on the valve and the mechanical escape condition from the fully closed state are considered. Then, a relatively large stepping motor having a relatively large driving torque is used.

FIG. 4 shows a general expansion valve driven by a stepping motor. An expansion valve 3 is interposed between the pipes 1 and 2 of the refrigeration cycle. The expansion valve 3 moves the needle 4 up and down in the axial direction to change the clearance between the needle 5 and the orifice 5 provided between the pipes 1 and 2 to adjust the refrigerant flow rate. The needle 4 is connected to the rotor 7 via the feed screw 6. The rotor 7 is driven by the drive winding 9 from the outside of the can 8 that separates the refrigeration cycle side and the outside. The rotor 7 and the drive winding 9 constitute a stepping motor.

In the case of a two-phase motor, the drive winding 9 has, for example, four drive coils W1, W2, W as shown in FIG.
It consists of 3 and W4. These drive coils W1 to W
4, as shown in FIG. 6, the driving pulse voltages P1, P are arranged in a predetermined order according to the opening direction or the closing direction of the expansion valve.
By giving 2, P3 and P4, the rotor 7 rotates in the predetermined direction by the number of rotations (rotation angle) according to the number of supply pulses. The rotary motion of the rotor 7 is converted into a linear motion via the feed screw 6, and the linear motion is transmitted to the needle 1 as a vertical motion. The vertical movement of the needle 1 changes the gap between the needle 1 and the orifice 6.

When controlling the flow rate of the refrigerant by using the expansion valve 3 as described above, first, a pulse in the closing direction is applied to the drive winding 9 to once bring the needle 4 into a fully closed state, and an extra closing direction is added. A certain fully closed position is achieved by applying several pulses to idle the motor. By applying a predetermined number of pulses in the opening direction from the fully closed position, a predetermined accurate valve opening position is achieved.

[0006]

In such a conventional expansion valve, the rotor 7 becomes relatively large, and the rotor 7 and the drive winding 9 are shielded from the outside. Since the can 8 is interposed, the magnetic gap between the rotor 7 and the drive winding 9 also becomes large. Therefore, it is quite difficult to actually obtain the characteristics and behavior expected of the stepping motor, which causes the motor to be out of tune.

As illustrated in FIG. 6, conventionally, the applied voltage of the same value is supplied without distinguishing the time contributing to driving the rotor in one step of the motor and the time contributing to braking. Therefore, when the moment of inertia of the rotor 7 is large, or when the distance between the rotor 7 and the drive winding 9, that is, the magnetic gap is large, braking does not work well within one step as shown in FIG. This is also a cause of step out and disorder.

FIG. 7 shows the rotation angle θ of the rotor 7 when the drive pulse voltages P1 to P4 are applied to the drive coils W1 to W4.
It shows the transition of. This figure is an exaggerated illustration of overrunning due to the driving force and overbraking due to the braking force within one step because braking is not successful.

It is an object of the present invention to provide an expansion valve drive method and device capable of achieving an accurate rotational position according to the number of supply pulses, despite increasing the drive speed.

[0010]

In order to achieve the above object, the driving method of the present invention is such that the excitation power supplied to the stepping motor is set to a value that is more last than the first value within one step driving pulse. It is characterized by making it larger.

Further, the driving apparatus of the present invention supplies the DC power source capable of selectively outputting the small power and the large power and the driving coil of the stepping motor with the small power from the DC power source at the beginning of the driving pulse for one step. And a control means for controlling to supply a large amount of electric power at the end.

[0012]

According to the present invention, within one drive pulse for one step, a small electric power is supplied at the beginning to contribute to the rotor driving, and a large electric power is supplied at the end to contribute to the rotor braking. Therefore, the stepping motor can be operated while driving and braking are reliably performed.
It is possible to achieve reliable rotor drive for each pulse, increase the drive speed, and prevent overrun.

[0013]

1 shows a circuit diagram of an apparatus for carrying out the method of the invention.

The drive coils W1, W2, W3 and W4 have transistors 11 and 1 as switching elements, respectively.
2, 13, 14 are connected in series. The transistors 11 to 14 are driven by the control device 18 in the order and the number of drive pulse voltages V according to the rotation direction and the rotation angle of the rotor 7.
The conduction is controlled so that 1 to V4 are given to the drive coils W1 to W4. One ends of the drive coils W1 to W4 are commonly connected to each other and connected to the movable contact of the changeover switch 15. The first fixed contact of the changeover switch 15 has a voltage Va.
Connected to the DC power supply 16 of the
It is connected to a DC power supply 17 having a higher voltage Vb. An auxiliary relay can be used as the changeover switch 15. In that case, for example, the b contact (normally closed contact) may be used as the first fixed contact, and the a contact (normally open contact) may be used as the second fixed contact.

Using the circuit of FIG. 1, the driving pulse voltages V1 to V4 as shown in FIG. 2 are supplied to the drive winding 9 to drive the stepping motor. This pulse voltage V1 to V
Reference numeral 4 divides one pulse into a first half ta and a second half tb. In the first half ta, the driving coils W1 to W4 are switched via the changeover switch 15.
The lower voltage Va is applied from the DC power supply 16, the changeover switch 15 is switched in the latter half tb, and the higher voltage Vb is applied from the DC power supply 17.

By doing so, the exciting force (voltage, current or power) of the first half ta contributing to the driving force and the latter half tb contributing to the braking force is changed, and the exciting force of the latter half is increased. The rotor 7 can be reliably driven to a desired stop position for each pulse, and can be reliably stopped there.

In order to explain the behavior of the rotor 7 with respect to the drive pulse at this time, by increasing the voltage of the latter half tb contributing to the braking with respect to the voltage of the first half ta contributing to the driving,
As shown in FIG. 3, it is possible to surely stop at a desired stop position while suppressing the overrun of the stepping motor while more accurately driving and braking. Therefore, overrun or the like can be prevented even without holding the brake after continuous driving.

In the above embodiment, the example in which the time for one step of the motor is divided into two equal parts and the voltages of different voltage values are applied is shown. However, from the point of the present invention, the two parts are equally divided.
Without dividing the time, for example, the time for applying the low voltage is set to about 2/3 to 3/4 of the first step, and the time for applying the high voltage is set to about 1/3 to 1/4 of the end. Good.

Further, in the above embodiment, as the DC power supply capable of selectively outputting the small power and the large power, an example in which two DC power supplies having different voltages are switched by the changeover switch has been shown. However, it is also possible to replace them with one DC power source whose voltage is variable.

[0020]

As described above, according to the present invention, the rotor of the expansion valve can be reliably driven pulse by pulse.
Therefore, the drive speed of the expansion valve can be increased. In addition, overrun can be prevented without holding braking after continuous driving.

[Brief description of drawings]

FIG. 1 is a connection diagram of an expansion valve driving device showing an embodiment of the present invention.

FIG. 2 is a time chart showing the voltage supplied to each drive coil in the device of FIG.

FIG. 3 is a time chart showing the supply voltage of FIG. 2 together with the rotation angle of the rotor.

FIG. 4 is a vertical sectional view of a known expansion valve to which the present invention is applied.

5 is an explanatory view showing details of a drive winding in the expansion valve of FIG.

6 is a time chart showing the voltage supplied to each drive coil in the device of FIG.

7 is a time chart showing the supply voltage of FIG. 6 together with the rotation angle of the rotor.

[Explanation of symbols]

 1, 2 Piping 3 Expansion valve 4 Needle 5 Orifice 6 Feed screw 7 Rotor 8 Can 9 Drive winding W1, W2, W3, W4 Drive coil 11, 12, 13, 14 Transistor 15 Changeover switch 16, 17 DC power supply 18 Control device

Claims (2)

[Claims] 1. A method of driving an expansion valve, which is provided in a refrigeration cycle and driven by a stepping motor, wherein the exciting power supplied to the stepping motor ends within a driving pulse for one step rather than the initial value. A method for driving an expansion valve, characterized by increasing the value of. 2. A drive device for an expansion valve provided in a refrigeration cycle and driven by a stepping motor, wherein a direct current power source capable of selectively outputting a small amount of electric power and a large amount of electric power and a drive coil of the stepping motor are At the beginning of the driving pulse for the step, a small amount of electric power is supplied from the DC power source,
An expansion valve drive device comprising: a control means for controlling to supply a large amount of electric power at the end.