Motor operated valve with reduction gear

A small-sized motor operated valve is disclosed that has high output and high resolution by housing a reduction gear together with a rotor in a single can. A valve shaft 32 having a valve member 30 is inserted to a motor operated valve body 10. A rotor 170 is disposed inside a can 100 attached to the body 10, and inside the rotor 170 is housed a reduction gear 200. The output of the rotor is input to a sun gear 220 and transmitted to planetary gears 230. The planetary gears 230 are engaged both with the fixed gear 250 and the output gear 260, and the output gear 260 is driven at reduced speed by a large reduction ratio. The output of the output gear 260 is transmitted via a driver 300 to a screw shaft 320, where it is converted into a linear movement and transmitted to the valve shaft 32.

The present application is based on and claims priority of Japanese patent application No. 2005-39446 filed on Feb. 16, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor operated valve with a reduction gear.

2. Description of the Related Art

Heretofore, there are known two main types of motor operated valves for opening and closing a valve via an electric motor. The first type opens and closes the valve by transmitting the rotation of a rotor directly to a screw mechanism, the example of which is disclosed for example in Japanese Patent Application Laid-Open Publication No. 2000-356278 (patent document 1). The second type is equipped with a reduction gear that reduces the rotation of the rotor via a reduction gear before transmitting the same to the screw mechanism, the examples of which are disclosed in Japanese Patent Application Laid-Open Publication No. 2002-84732 (patent document 2) and Japanese Patent Application Laid-Open Publication No. 2003-232465 (patent document 3).

The first type of motor operated valves is relatively compact, but the valve can be only used when the load is small, and it is difficult to enhance the resolution of the valve opening per single drive pulse.

The second type of motor operated valves can be applied to the case where the load is high, and the resolution of the valve opening per single drive pulse can be enhanced, but the overall size of the motor valve is large since the gear box for the reduction gear is disposed separately from the motor.

SUMMARY OF THE INVENTION

Therefore, the present invention aims at providing a motor operated valve with a reduction gear that is compact in size and capable of exerting enhanced valve operation ability and high-resolution valve opening performance, by having a reduction gear together with a rotor housed inside a single can.

In order to achieve the above-mentioned object, the present invention provides a motor operated valve with a reduction gear comprising a valve body having a valve chamber and a valve seat, a valve member disposed movably in the valve chamber to open and close an opening of the valve seat, a valve shaft for operating the valve member, a cylindrical can fixed to the valve body, a motor exciter mounted on an outer circumference portion of the can, a permanent magnet-type rotor rotatably supported at an inner circumference portion of the can and driven to rotate by the exciter, a reduction gear for reducing the rotation of the rotor, and a screw mechanism for moving the valve member toward and away from the valve seat via the reduction gear by the rotary movement of the rotor, wherein the reduction gear is disposed together with the rotor in a space defined by the valve body and the can.

The reduction gear is preferably disposed inside the rotor.

However, the reduction gear can be disposed under the rotor.

More preferably, the reduction gear includes a planetary gear mechanism.

However, the reduction gear can be composed of a multistage train of gears.

Even more preferably, the valve chamber includes a bellows for sealing the gap between the inner side of the can.

As described, the motor operated valve according to the present invention houses a reduction gear together with a rotor in a single can, so the present invention enables to provide a compact-sized, high-output motor operated valve with high resolution at a low cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated inFIG. 1, the motor operated valve according to the present invention comprises a valve body10having a valve seat12and a valve chamber14. A valve member30is disposed inside the valve chamber14. The valve member30is moved along a longitudinal central axis31toward and away from the valve seat12. Two pipes20and22communicated with the valve chamber14are attached to the valve body10.

A valve shaft32is connected to the valve main body30. A ring member38is mounted on an opening portion formed to the upper portion of the valve body10, and in the present embodiment, for example, it is fixed to the body via a crimping portion K1. The fixing of the ring member38can be performed by soldering, by which the member is sealed to the body. A bellows40is disposed between the ring member38and the valve shaft32, which provides a seal to prevent refrigerant from entering the valve. A receive member34of a ball36is inserted and fixed to the upper end portion of the valve shaft32.

A screw shaft320is in contact with the upper portion of the ball36, which conducts a thrust generated via a screw mechanism in the axial direction to the valve shaft32centered on the longitudinal axis31with other moving portions of the valve.

A flange member70constituting a part of the valve body is fixed via welding or the like to the outer circumference on the upper end of the valve body10, which keeps out the outer air and prevents gas and moisture from entering the valve. On the upper portion of the flange member70is fixed a receive member80. A cylindrical member82is attached to the outer circumference of the receive member80, and a female screw member90is mounted to the inner circumference of the receive member80.

On the other hand, a cylindrical can100formed of a nonmagnetic metal called a can is fixed via welding or the like to the upper portion of the flange member70. On the outer side of the can100is mounted an exciter M for a stepping motor, which is one example of a driving motor.

The exciter M comprises a resin mold120, a coil140wound around a bobbin130disposed therein, and a stator S being excited when power is fed to the coil, wherein power is fed to the coil140via a lead142.

The exciter M has a mounting clasp180disposed on the lower portion thereof, and by engaging a hole182of the mounting clasp180to a projection102formed to the can100, the exciter M can be removably attached to the can100.

A cylindrical projection104is formed to the uppermost area of the can100, and a support member150is press fit to the inner side of the projection104. The support member150supports a fixing shaft152.

A permanent magnet-type motor170for the stepping motor is disposed in a rotatable manner inside the can100. The rotor170is a cylindrically shaped member formed by permanent magnet material, and is integrally formed with a rotary member160made of resin or the like. The turning force of the rotary member160is transmitted to a reduction gear denoted as a whole by reference numeral200. The reduction gear200and the rotor170are disposed together in the can and are centered on and rotatable about the longitudinal axis31to form a compact coaxial motor operated valve.

FIGS. 2 through 5are explanatory views of a reduction gear200assembled in the rotor.

According to the present embodiment, the reduction gear200exerts a large reduction ratio by utilizing a planetary gear mechanism.

The reduction gear200has a sun gear220formed integrally with a rotary member160disposed integrally with the rotor170shown inFIG. 1. The sun gear220is engaged with planetary gears230, and the planetary gears230are supported by a carrier.

According to the present gear, the carrier is composed of a pair of disks240and242and a shaft232connecting the two disks240and242, and the three planetary gears230are attached in rotatable manner to the carrier.

As illustrated inFIG. 4, the carrier240has three support pillars244, wherein the plate242supports the shafts232of three planetary gears230, and the plate242is fixed to support pillars244via screws and the like.

The whole body of the carrier is supported so as to rotate freely on an output gear260described later. The planetary gears230are simultaneously engaged with a ring-shaped fixed gear250and an output gear260. The fixed gear250is fixed to the inner side of a cylindrical member82fixed to the valve body10. The output gear260has a number of internal tooth that differs from the number of tooth on the fixed gear250, and is supported rotatably above the receive member80, with a driver300protruding downward from the bottom surface thereof.

The driver300has a drive unit310shaped like a flat-blade screwdriver, which is inserted to a screw shaft320. The rotation of the screw shaft320is converted into a movement in the axial direction, which is transmitted via the ball36to the valve shaft32.

A disc spring190is disposed between the rotary member160on the rotor and the fixed gear250on the reduction gear, by which the rotary member160(sun gear220) is biased toward the support member150.

According to this reduction gear200, if the number of tooth on the output gear260is greater than the number of tooth on the fixed gear250, the rotation of the sun gear220that rotates integrally with the rotor170in the clockwise direction (CW) causes the planetary gears230to rotate in the counterclockwise direction (CCW). The carrier240is rotated in reduced speed in the clockwise direction (CW). The output gear260is rotated in the clockwise direction (CW).

In contrast, if the number of tooth on the output gear260is smaller than the number of tooth on the fixed gear250, the rotation of the sun gear220in the clockwise direction (CW) causes the output gear260to rotate in the counterclockwise direction (CCW).

According to the present reduction gear with a planetary gear mechanism, when the number of tooth on the sun gear220, the planetary gear230, the fixed gear250and the output gear260are respectively represented by Za, Zb, Zc and Zf, the output gear ratio of the output gear260is represented by the following formula.
(Za·Zf−Za·Zc)/[Zf·(Za+Zc)]

provided that Zf≠Zc

Incidentally, when Za=12, Zb=18, Zc=48 and Zf=54, the output gear ratio of the output gear260has a reduction ratio as large as 1/45.

Since the rotation of the rotor is transmitted by a large reduction ratio to the screw shaft320, the opening of the valve can be controlled in minute scales, in other words, by high resolution.

Since the rotor170and the reduction gear200for reducing the rotation of the rotor170are both sealed in a single can100, the intrusion of outer air, moisture and the like can be prevented completely. Therefore, no condensation occurs inside the valve, and the valve can exert an accurate flow control even under severe environments.

FIG. 6is an explanatory view showing the structure of a motor operated valve according to another embodiment of the present invention.

In the present motor operated valve, the structure of the valve body, the arrangement for removably attaching the exciter M of the stepping motor as one example of a drive motor to the outer side of the can100and the arrangement for assembling a reduction gear in the rotor of the stepping motor are similar to those of the motor operated valve according to the previous embodiment, so the components are denoted by the same reference numbers and detailed descriptions thereof are omitted.

According to the present motor operated valve, a flange member70A is fixed to the upper outer side of the valve body10, and the flange member70A supports a can100.

A female screw member420is fixed to the inner side of the upper portion of the valve body10, and the female screw member420supports a cylindrical member82via a receive member80.

A male screw member410engaged via a screw portion S1to the female screw member420has a valve shaft400slidably inserted to the inner side thereof. A valve portion402is formed to the leading end of the valve shaft400, which comes into contact with a valve seat12.

The valve shaft400is inserted to the male screw member410via a coil spring430and a plate432. On the outer side of the male screw member410is integrally formed a drive transmission member440made of resin. The drive transmission member440has a groove442formed in parallel with the axis line of the male screw member.

On the other hand, an output gear260which is the output member of a reduction gear200disposed on the inner side of the rotor170has an arm-like drive unit262that extends toward the drive transmission member440.

According to this arrangement, the turning force of the output gear260is transmitted to the drive transmission member440, and thus the male screw member410is driven to rotate. The rotation of the male screw member410is converted into a movement in the axial direction by the screw portion S1, by which the valve shaft400is moved up and down.

The rotation of the rotor170driven by the stepping motor is reduced by a large reduction ratio, and drives the valve shaft400. Thus, it becomes possible to provide a motor operated valve having a large capacity and a high resolution performance at low cost by using a small stepping motor with small torque.

The embodiments described above utilizes a reduction gear having a planetary gear mechanism, but it can be replaced with a mechanical reduction gear using multistage train of gears having multiple spur gear groups.

Moreover, the embodiments described above have a reduction gear that is housed inside a rotor170, but the reduction gear can also be disposed below the rotor.

Furthermore, the flow control performance of the valve with respect to the rotor rotation can be determined arbitrarily by selecting a preferable screw pitch of the screw mechanism or by changing the shape of the leading end of the valve member opposing the valve seat.

Therefore, the present invention can provide a motor operated valve having valve performances that satisfies the demands of the users.