JP2000274544A - Electric expansion valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the electric and mechanical resolutions by forming an output shaft by a male screw having a large lead and a screw efficiency of a specified ratio or more such as double-start thread. SOLUTION: The output shaft of a stepping motor with reduction gear 3 is formed of a male screw 2 having a large lead and a screw efficiency of 50% or more such as double-start thread or square screw. When the change gear ratio of the reduction gear is set to, for example, 1/10, the necessary output torque in the stepping motor 3 is about 1/10 output of a direct acting type motor, and the torque of the gear output shaft necessary for the propulsive load of an orifice to be controlled is provided. On the other hand, since the rotation of the gear output shaft is decelerated to 1/10, the pulse number necessary for one rotation of the output shaft is 48 pulse/rotation * 10=480 in case of '12-pole rotor, 1-2 phase exciting motor', and the electric resolution is sufficient. By use of the screw having a high lead and a screw efficiency of 50% or more, the necessary valve stroke can be taken by one rotation. This valve is conformable with a small motor by regulating the change gear ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric expansion valve used as an electronically controlled expansion valve used in a refrigerating cycle of a room air conditioner or a car air conditioner, or a proportional control valve used in combination with a microcomputer in general industrial fields. Regarding the valve, the electric resolution is improved by using a stepping motor as a motor with a speed reduction mechanism, and the mechanical resolution is improved by combining a screw with a large lead with the valve body driven by the output shaft of this speed reducer. And the screw efficiency of the screw is increased to 50% or more, and further, the frictional resistance at the seating surface is reduced by only moving straight without rotating the valve body. This is an electric expansion valve in which the reverse operation of (valve closing), that is, opening of the valve is easily possible without using a rotation stopper.

Conventionally, various types of electric expansion valves which are controlled by a microcomputer by combining a stepping motor and a valve have been devised. FIG. 6 shows the structure of a conventional electric expansion valve disclosed in Japanese Utility Model Publication No. 3-36770 (hereinafter referred to as a direct-acting stepping motor system for convenience), and the structure thereof will be described below. A conventional direct expansion stepping motor type electric expansion valve is a motor rotor integrally formed with a valve shaft 3 by energizing a stator coil 2 fixed to an outer peripheral portion of a cylindrical case 21 made of a non-magnetic material. 24, and the rotation is formed on the valve shaft 23 by a screw efficiency of 50%.
The linear movement of the valve shaft 23 is converted by the external thread 25 and the female screw 27 of the propulsion bearing 26 screwed thereto, and the opening degree of the valve is controlled by the needle valve 28 formed at the tip of the valve shaft 23. It is made to let.

A valve body 29 is provided at the lower end of the case 21. The valve body 29 has a first passage 30 and a second passage 31, and is provided between the two passages. An orifice 32 and a valve seat 33 are provided, and a chamber 34 is provided at the center of the valve body 29. The propulsion bearing 26 is provided in the chamber 34.
Is press-fitted and fixed.

A rotor sleeve 35 formed integrally with the rotor 24 has a convex portion 36 (a plate-like stopper piece) protruding radially at one location on the inner peripheral surface thereof.
Is provided.

A lid 37 is provided at the upper end of the case 21. The inner surface of the lid 37 is spaced apart from the center to a position where the stop pin 38 reaches the middle of the projection 36. Hanged and fixed.

The stop pin 38 and the side surface of the projection 36 are brought into contact with each other in a range of less than one rotation of the rotor 24 of the motor.
8 is regulated.

[0007]

The above-described conventional electric expansion valve controls the needle valve 28 with less than one rotation of the valve shaft 23.
Even when the valve 8 is closed, there is an advantage that the male screw 25 does not bite and the valve opening operation can be easily performed. However, with the conventional linear motion stepping motor, an electrical resolution of at most several tens of pulses was obtained. For example, when the rotor is a permanent magnet magnetized to 12 poles, even if the resolution is increased by controlling the energization of the coil to 1-2 phase excitation, one rotation / rotation is performed.
Since the number of pulses is 48, a resolution of only about 40 pulses can be obtained at most in consideration of the width of the stopper and the like.

On the other hand, in the case of a room air conditioner or the like, the use of an inverter for a compressor has been advanced, and the direction of cooling and heating with a lower input has been pursued in detail in accordance with the rotation of the compressor and fluctuations of the cooling and heating load. It is necessary to finely control the opening degree, that is, to increase the resolution. The resolution is set to several hundred pulses, for example, about 500 pulses.

As a specific means, a method of obtaining an electrical resolution of about 500 pulses by rotating the rotor 10 times when using the rotor is used. As another means to enhance the electrolysis, there is a method of increasing the resolution by duty controlling the coil energization while the rotor moves between the poles, such as "micro step drive", and increasing the focal length of the camera. Although it is practically used for adjustment and the like, it is always energized, so it is not suitable for control like a room air conditioner, contrary to energy saving.

Further, in the conventional structure, the valve body is directly driven to rotate by the rotation shaft of the stepping motor. However, since the propulsion screw has a large lead and the screw efficiency is 50%, for example, a JIS thin screw having the same diameter is used. As described above, when the screw having a small lead is used, the linear force of the valve body is much lower than that of the valve body.

[0011]

SUMMARY OF THE INVENTION The present invention uses a stepping motor with a speed reducer as a drive unit of an electric expansion valve to improve the electrical resolution and reduce the size of the motor unit. As a valve element driven by
By combining a valve element having a screw with a large lead, the required valve stroke can be obtained with less than one rotation to improve the geometrical resolution, the screw efficiency of the screw is set to 50% or more, and the valve element does not rotate. By reducing the frictional resistance on the seating surface by only moving straight, the reverse operation after the needle abuts the valve seat (closed valve), that is, the valve can be easily opened without using the rotation stopper It was done. In addition, the use of a gear motor eliminates the need for constant energization as in "micro-step control".
The effect is to provide a compact and inexpensive control valve by realizing the downsizing of the motor while keeping the electrical and geometrical resolution high, and simplifying the stopper mechanism. .

That is, the electric expansion valve according to claim 1 is
An output shaft having a stator coil disposed on the outer peripheral portion of the motor case or disposed on the inner peripheral portion of the motor case is provided in a cylindrical closed case 1 having an upper opening and a lower opening. Large lead and screw efficiency 50%
A stepping motor 3 with a speed reduction mechanism formed on the external thread 2 is provided, and a rotation restraining pin 4 is provided at the bottom of the motor case of the stepping motor 3 so as to be separated from the axis of the output shaft and to hang down. A lid 5 is provided at an upper end of the closed case 1, and a first passage 6 and a second passage 7 are provided at a lower end of the closed case 1, and an orifice 8 and a valve provided between both passages are provided. A valve body 11 having a seat 9 and a chamber 10 is provided.
The valve body 12 which comes in contact with and separates from the needle valve has a needle valve 13
And a rotation restricting piece 15 is provided on the upper outer peripheral surface of the valve body 12 in the lateral direction, so that the rotation restricting pin 4 and the valve
The rotation of the valve body 12 is restrained by a rotation restraining piece 15 provided above the valve body 2, and the needle valve 13 of the valve body is moved straight by moving the motor so as to be brought into and out of contact with the valve seat 9. It is assumed that.

The specific configuration will be further described. If the reduction ratio of the reduction gear is set to, for example, 1/10, the propulsion load is the same when the orifice diameter to be controlled is the same as that of the conventional structure. The output torque required by the motor of the present invention is approximately the same as that of the conventional motor when the output torque of the direct drive type motor is about 1/10. On the other hand, since the rotation of the gear output shaft is reduced to 1/10, the number of pulses required for one rotation of the output shaft is 48 pulses / rotation in the case of the “12-pole rotor, motor with 1-2 phase excitation”. * 10 = 480 pulses, and sufficient electrical resolution can be obtained.

It is obvious that the required valve stroke can be obtained in one rotation by using a valve element having a screw with a high lead and a screw efficiency of 50% or more. However, in the conventional direct acting type, the propulsive force is obtained. However, since it did not have a reduction gear, the motor was directly enlarged. In general, this type of motor-operated valve uses a screw with a diameter as small as possible and a fine lead to convert the rotational torque of the motor into a large linear force. Table 1 shows an example of the case of “screw”. In order to obtain the same thrust F, "a screw having a high lead and a screw efficiency of 50% or more" requires an output torque that is approximately 71.3 / 41.4 = 1.7 times that of a JIS screw. In other words, in the example given as the conventional embodiment, the motor is inevitably increased in size, but it is possible to cope with a small motor by using a speed reducer and adjusting the speed reduction ratio.

[0015]

[Table 1]

According to the first aspect of the present invention, since the stepping motor 3 with the speed reducer is housed in the closed case 1, the air gap between the rotor and the coil is small and the magnetic loss is reduced. Few. Further, a commercially available inexpensive stepping motor with a speed reducer can be used, and the resolution as an expansion valve can be increased by the stepping motor with a speed reducer. further,
Since the valve body 12 moves straight without rotating, the needle abuts on the valve seat surface, or even if the valve body rises upward and abuts on the motor bearing portion 16, no rotational torque is generated on the abutment seat surface. May not be required. Therefore, the structure can be simplified.

According to a second aspect of the present invention, the shaft of the valve body 12 having an inner surface provided with a female screw screwed into the external thread 2 of the output shaft and having an outer peripheral portion formed as a non-circular shaft is provided by the valve body. 2. The valve according to claim 1, wherein the valve is inserted straight into the upper portion of the chamber 10 having a non-circular hole as in the case of the shaft portion. According to this invention, the same operation and effect as those of the first aspect can be obtained.

According to a third aspect of the present invention, there is provided the electric expansion valve, wherein a lead wire of the motor is taken out from the hermetic terminal provided on the lid.
2. The method according to claim 1 or claim 2, wherein the processing is started from a. According to the present invention, the hermetic terminals 5a are provided on the lid 5, so that the motor leads can be easily airtight.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional side view of the electric expansion valve of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. The electric expansion valve of the present invention includes a stepping motor 3 having a speed reduction mechanism, a valve body 11 and a valve body 12.

The output shaft at the lower end of the stepping motor 3 with a speed reduction mechanism is formed of a screw 2 having a large lead such as a double thread screw or a square screw and having a screw efficiency of 50% or more. Reference numeral 16 denotes a motor bearing. Also, since the stepping motor has a speed reduction mechanism, the output shaft (male screw 2)
Is provided with a resolution of 500 pulse class in one rotation.
In the drawings, the stator coil is built in the motor case. However, the maintainability may be improved by disposing the stator coil outside the motor case so that the electric parts are separated and independent.

The closed case 1 is a cylindrical body having an opening at the top and bottom, and the stepping motor 3 with the speed reduction mechanism is provided inside the closed case 1 as a ring-shaped fixed spring having protruding teeth on its outer periphery. The cover 17 is pressed and fixed by a body 17 (trade name: SE ring or the like), and then the opening above the closed case 1 is closed by the lid 5. Reference numeral 6 denotes a hermetic terminal from which a lead wire of the motor is taken out and hermetic sealing is performed on the lead wire.

The valve body 11 is fixed to the lower end portion of the closed case 1 by brazing or the like. The valve body 11 has a first passage 6 similar to the conventional product shown in FIG.
And a second passage 7 between which an orifice 8 is provided.
And a valve seat 9, and a chamber 10 is provided above the valve seat 9.

The valve body 13 is provided with an internal thread having a large lead such as a double-start thread or a square thread on its inner surface and a screw efficiency of 50% or more, and is screwed to the external thread 2 of the motor output shaft. A needle valve 13 is provided at the tip of the valve body 13, and a rotation restricting piece 1 having a pin insertion hole 14 on the upper outer peripheral surface of the valve body 12 as shown in FIG.
5 is provided integrally with the valve body in the lateral direction.

The rotation restraining pin 4 is fitted in the pin insertion hole 14 of the rotation restraining piece 15 to stop the rotation of the valve body 12. The rotation restraining pin 4 is used for the motor case of the stepping motor 3. It is fixed to the bottom in a hanging manner away from the axis of the output shaft. Therefore, the valve element 12 engages with the external thread 2 of the motor output shaft and comes into contact with and separates from the valve seat 9 without rotating.

FIG. 3 is a partial cross-sectional view showing another embodiment of the valve element in the electric expansion valve of the embodiment shown in FIG.
FIG. 4 is a sectional view taken along the line BB of FIG. 3. The valve body 12 has a female screw which is screwed into the male screw 2 of the output shaft on the inner surface, and the outer peripheral portion is formed as a non-circular shaft portion. Needless to say, the chamber 10 corresponding to the valve body 12 has a non-circular hole shape like the shaft portion of the valve body 12.

FIG. 5 is a sectional view showing another embodiment of the present invention. In this embodiment, a stator coil of a stepping motor 3 having a speed reduction mechanism is arranged outside a closed case. In the present embodiment, the other components except for the hermetic terminal 5 shown in FIG.

[0027]

As described above, the motor used in the electric expansion valve of the present invention has a high electric resolution with a gear motor and a valve stroke secured with a high reed screw (geometric resolution).
The torque shortage caused by this is covered by the reduction gear, and the screw efficiency is 5
Because the valve body does not rotate and moves only straight due to 0% or more (self-releasing screw), even if the needle abuts on the valve seat surface or the valve body rises upward and abuts on the motor bearing, the abutment seat Since no rotational torque is generated on the surface, the overall characteristics as an electric expansion valve can be established without a stopper mechanism. In addition, since the stepping motor 3 is equipped with a speed reducer and is commercially available at a low cost, the resolution as an expansion valve can be improved.

The hermetic terminal 5 provided on the lid 5
Accordingly, the airtightness of the lead wire of the motor can be easily performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric expansion valve of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIGS. 1 and 5;

FIG. 3 is a partial sectional view showing another embodiment of the valve body.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a perspective view of a valve body showing another embodiment according to the electric expansion valve of the present invention.

FIG. 6 is a longitudinal sectional view of a conventional electric expansion valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Closed case 2 Male screw of output shaft 3 Stepping motor with reduction mechanism 4 Rotation restraining pin 5 Lid 5a Hermetic terminal 6 First passage 7 Second passage 8 Orifice 9 Valve seat 10 Chamber 11 Valve body 12 Valve body 13 Needle valve 14 Pin insertion hole 15 Rotation restricting piece 16 Motor bearing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 37/24 H02K 37/24 RF term (Reference) 3H062 AA02 AA15 BB10 BB30 CC02 DD01 DD11 EE06 HH04 HH08 HH09 5H607 AA00 BB01 BB10 BB25 CC03 CC09 DD03 DD19 EE31 EE53 FF01 HH01 HH07

Claims (3)

[Claims] 1. A cylindrical closed case having upper and lower openings.
(1) A stator coil is disposed on the outer peripheral portion of the motor case or disposed on the inner peripheral portion of the motor case. The output shaft has a large lead such as a double-start thread or a square thread and a screw efficiency of 50%. A stepping motor (3) with a speed reduction mechanism formed on the external thread (2) is provided. The motor case of the stepping motor (3) is rotatable in a drooping manner away from the axis of the output shaft. Restraint pin (4)
A lid (5) is provided at the upper end of the closed case (1), and a first passage (6) and a second passage (7) are provided at the lower end of the closed case (1). A valve body (11) having an orifice (8), a valve seat (9), and a chamber (10) provided between the two passages; A needle valve (13) is provided at the distal end of the valve body (12) which comes in contact with and separates from (9), and a rotation restricting piece (15) is provided on the outer peripheral surface above the valve body (12) in the lateral direction. The rotation of the valve body (12) is restrained by the rotation restraining pin (4) and the rotation restraining piece (15) provided above the valve body (12), and the needle valve of the valve body is rotated by rotating the motor. An electric expansion valve characterized in that (13) is made to move straight to be brought into and out of contact with a valve seat (9). 2. A valve body (12) having an internal thread on an inner surface thereof for screwing to an external thread (2) of an output shaft and having a non-circular outer peripheral portion.
The electric expansion according to claim 1, characterized in that the shaft is fitted into the upper part of the chamber (10) whose hole shape is non-circular like the shaft of the valve body, so that the valve body moves straight. valve. 3. The electric expansion valve according to claim 1, wherein the lead wire of the motor is taken out from a hermetic terminal (5a) provided on the lid (5).