Patent Description:
<CIT> describes an example of an electric valve according to the related art. The electric valve <NUM> according to the related art illustrated in <FIG> includes a valve member <NUM>. A thrust transmitting member <NUM> is fixed to the valve member <NUM>. The valve member <NUM> opens and closes a valve port 913a that is open to a valve chamber <NUM>.

The electric valve <NUM> includes a stepping motor. The stepping motor includes a stator <NUM> and a rotor <NUM>. Rotational force of the stepping motor is transmitted to a rotary elevation shaft <NUM> via a planetary gear mechanism <NUM>. The rotary elevation shaft <NUM> is screwed into a bearing member <NUM>. A screw-feed action moves the rotary elevation shaft <NUM> in an up-and-down direction. When the rotary elevation shaft <NUM> moves downwards, the rotary elevation shaft <NUM> pushes the thrust transmitting member <NUM> downwards via a ball <NUM> and a ball receiving seat <NUM>. When the rotary elevation shaft <NUM> moves upwards, a spring receiving member <NUM>, which is pushed upwards by a valve opening spring <NUM>, pulls the thrust transmitting member <NUM> upwards. The valve member <NUM> moves in the up-and-down direction with the thrust transmitting member <NUM>.

In the electric valve <NUM>, the valve member <NUM> is disposed in a valve-member guide hole 921c of a supporting member <NUM>. A sealing member <NUM> is disposed between the valve member <NUM> and the supporting member <NUM>. The sealing member <NUM> separates the valve chamber <NUM> from a space next to the upper side of the valve member <NUM> (a back-pressure chamber <NUM>) in the valve-member guide hole 921c. When the lower end of the valve member <NUM> comes into contact with a valve seat 913b and closes the valve port 913a, the electric valve <NUM> is in a valve-closing state. In the valve-closing state, the valve port 913a is connected to the back-pressure chamber <NUM> via a pressure equalizing passage <NUM>, which is provided in the valve member <NUM> and the thrust transmitting member <NUM>. In this structure, an upward fluid pressure applied to the valve member <NUM> is counterbalanced by a downward fluid pressure applied to the valve member <NUM>.

<CIT> discloses a speed reduction mechanism, comprising: A speed reduction mechanism housing; a reduction gear train disposed in the reduction mechanism housing; an output shaft connected to the reduction gear train; and an axial limiting mechanism provided in the speed reduction mechanism, characterized in that the axial limiting mechanism includes a shaft-side limiting member integrally formed on or fixedly connected to the output shaft and a housing-side limiting member integrally formed on or fixedly connected to the reduction mechanism housing, and the shaft-side limiting member and the housing-side limiting member are suitable for cooperating with each other to limit the axial displacement of the output shaft.

<CIT> discloses a pressure balance type motor valve including a valve member mounted on a connection rod via a bearing as a rotary bearing, the connection rod being adapted to be moved up and down by the rotation of a rotor of a stepping motor and a screw feed mechanism, for maintaining the stable operating performance of the bearing. An outside space and an inside space of the valve member, the inside of the bearing, and a conduction path constitute a pressure equalization flow path to conduct a valve port and a back pressure chamber. In a valve element of the valve member, a coil spring and a strainer are arranged between the bearing and a snap ring. The strainer is held between the coil spring and the snap ring and thereby fixed to the inside of the valve element.

The electric valve <NUM> may be used in a system with a relatively large difference between inlet and outlet fluid pressure. In the electric valve <NUM>, the sealing member <NUM> is strongly pressed to the supporting member <NUM> and slides on the supporting member <NUM> to suppress fluid leakage between the valve chamber <NUM> and the back-pressure chamber <NUM>. This causes the frictional force of the sealing member <NUM> to be large, and the electric valve <NUM> should have a large rotational force of the stepping motor and a large spring force of the valve opening spring <NUM>.

In the electric valve <NUM>, the ball <NUM> slides with respect to the rotary elevation shaft <NUM> (or the ball receiving seat <NUM>). The ball <NUM> transmits only downward pushing force of the rotary elevation shaft <NUM> to the thrust transmitting member <NUM> and transmits no rotational force of the rotary elevation shaft <NUM>. Forces concentrate on the ball <NUM>, and the ball <NUM> wears out fast. Wearing of the ball <NUM> is one factor that reduces the life of the electric valve <NUM>. Additionally, when the rotary elevation shaft <NUM> moves downwards, the stepping motor outputs the rotational force including a force component to compress the valve opening spring <NUM>. Therefore, the electric valve <NUM> has a high power consumption.

In view of this, it is an object of the present invention to provide an electric valve with a long life and a low power consumption.

To achieve the object above, an electric valve according to one aspect of the present invention includes a valve body that includes a valve chamber and a valve port, a valve member that opens and closes the valve port, a supporting member that supports the valve member to be capable of advancing and retracting with respect to the valve port, a driving shaft that includes an external thread portion and is disposed in a direction of advancing and retracting the valve member, a rolling bearing that rotatably supports the driving shaft and is held by the supporting member, a planetary gear mechanism that is connected to the driving shaft, and an internal thread member with a cylindrical shape that is fixed to the valve member and into which the external thread portion is screwed. The supporting member supports the internal thread member in a manner that restricts rotation of the internal thread member about an axis and allows movement of the internal thread member in a direction of the axis.

In the electric valve according to the present invention, the rolling bearing rotatably supports the driving shaft. The external thread portion of the driving shaft is screwed into the internal thread member. The supporting member supports the internal thread member in the manner that restricts the rotation of the internal thread member about the axis and allows the movement of the internal thread member in the direction of the axis. As a result, when the driving shaft connected to the planetary gear mechanism rotates, a screw-feed action moves the internal thread member in the direction of the axis (the direction of advancing and retracting the valve member). The movement of the internal thread member applies force in the direction of the axis to the driving shaft, and the force is distributed to multiple rolling elements of the rolling bearing. Therefore, concentration of the force can be suppressed in the electric valve, and it is possible to enhance the life of the electric valve. Additionally, the screw-feed action advances and retracts the valve member with respect to the valve port. Therefore, the electric valve has a low power consumption compared to an electric valve with a structure including a valve opening spring.

In the present invention, the supporting member includes a valve-member guide hole in which the valve member is disposed. The internal thread member includes a lateral hole that extends from an outer surface to an inner surface of the internal thread member. An inner space of the internal thread member and the lateral hole of the internal thread member are a pressure equalizing passage that connects, in a valve-closing state where a first end of the valve member is in contact with a valve seat of the valve port, the valve port to a back-pressure chamber, which is a space next to a second end of the valve member in the valve-member guide hole. The external thread portion enters the internal thread member to a position where the external thread portion closes the lateral hole in a full-open state where the valve member is farthest from the valve seat. As a result, in the electric valve, the external thread portion of the driving shaft closes the pressure equalizing passage in the full-open state. Therefore, entry of foreign matter included in fluid into the back-pressure chamber can be suppressed.

In the present invention, preferably, the driving shaft includes a base portion that is integrally coupled to the external thread portion and is connected to an output part of the planetary gear mechanism. Preferably, the rolling bearing is a radial ball bearing. Preferably, the supporting member supports an outer ring of the rolling bearing. Preferably, the base portion and a nut screwed onto the external thread portion hold an inner ring of the rolling bearing therebetween. As a result, the rolling bearing can support the driving shaft with a simple structure combining the external thread portion and the nut. Additionally, the pressurization of the inner ring of the rolling bearing can be easily controlled by using the nut compared to a structure in which the driving shaft is press-fitted into the inner ring of the rolling bearing.

In the present invention, preferably, a transverse sectional contour of the internal thread member has a polygonal shape. Preferably, the supporting member includes a partition wall that divides an inner space of the supporting member in the direction of the axis. Preferably, the partition wall includes a supporting hole in which the internal thread member is disposed. Preferably, the supporting hole has a same shape as the transverse sectional contour of the internal thread member. As a result, the supporting member can support the internal thread member in the manner that restricts the rotation of the internal thread member about the axis and allows the movement of the internal thread member in the direction of the axis in a relatively simple structure.

According to the present invention, it is possible to enhance the life of the electric valve and reduce the power consumption of the electric valve.

Hereinafter, an electric valve according to an embodiment of the present invention is described with reference to <FIG>.

<FIG> and <FIG> are longitudinal sectional views (sectional views taken along an axis L) of an electric valve according to one embodiment of the present invention. <FIG> illustrates the electric valve in a valve-closing state. <FIG> illustrates the electric valve in a full-open state. <FIG> is a sectional view taken along line III-III of <FIG>. <FIG> is a sectional view taken along line IV-IV of <FIG>.

An electric valve <NUM> according to the present embodiment is used as an expansion valve in, for example, a heat pump heating and cooling system or the like. The electric valve <NUM> is capable of allowing fluid (refrigerant) to flow in both directions.

The electric valve <NUM> includes a valve body <NUM>, a can <NUM>, a supporting member <NUM>, a rolling bearing <NUM>, a driving shaft <NUM>, a valve member <NUM>, an internal thread member <NUM>, a sealing member <NUM>, and a valve-member driving section <NUM>.

The valve body <NUM> includes a tubular member <NUM>, a holder <NUM>, and a valve seat member <NUM>.

The tubular member <NUM> has a substantially circular cylindrical shape. The tubular member <NUM> has a valve chamber <NUM> inside.

The holder <NUM> has a stepped, substantially circular cylindrical shape. A lower portion of the holder <NUM> has an outer diameter larger than that of an upper portion of the holder <NUM>. The lower portion of the holder <NUM> is fitted into an upper end opening 11a of the tubular member <NUM>. The holder <NUM> is welded to the tubular member <NUM>. The holder <NUM> includes a portion which is disposed in the tubular member <NUM> and which has a length in a direction of the axis L enough to maintain a fitting relationship between the tubular member <NUM> and the holder <NUM> even after welding. The holder <NUM> includes a holding surface 12a. The holding surface 12a is a circular annular plane facing downwards and is disposed inside the holder <NUM>.

The valve seat member <NUM> has a substantially circular cylindrical shape. The valve seat member <NUM> is housed in the valve chamber <NUM>. A lower portion of the valve seat member <NUM> is fitted into a lower end opening 11b of the tubular member <NUM>. The valve seat member <NUM> is brazed to the tubular member <NUM>. The valve seat member <NUM> has a valve port 13a, which is a circular hole. The valve port 13a is open to the valve chamber <NUM>. A valve seat 13b is provided in the inner peripheral edge of the upper end of the valve seat member <NUM>. The valve seat 13b has a circular annular shape. The valve seat 13b encloses the valve port 13a.

A first conduit <NUM> is brazed to the tubular member <NUM>. The first conduit <NUM> extends through the tubular member <NUM> in a lateral direction (a direction perpendicular to the axis L) and is connected to the valve chamber <NUM>. A second conduit <NUM> is brazed to the valve seat member <NUM>. The second conduit <NUM> is connected to the valve port 13a. Preferably, the first conduit <NUM> includes a portion which is disposed in the tubular member <NUM> and which is long enough to suppress the entry of the molten solder (a fillet) into the first conduit <NUM> from the end of the first conduit <NUM> in the valve chamber <NUM>.

The can <NUM> has a circular cylindrical shape with its upper end closed. The lower end of the can <NUM> is welded to the upper portion of the holder <NUM>.

The supporting member <NUM> includes a valve-member supporting portion <NUM> and a driving-shaft supporting portion <NUM>.

The valve-member supporting portion <NUM> has a circular cylindrical shape. An upper portion of the valve-member supporting portion <NUM> is press-fitted into the holder <NUM>. A lower portion of the valve-member supporting portion <NUM> and the valve seat member <NUM> are arranged in an up-and-down direction (the direction of the axis L) with a space therebetween. The lower portion of the valve-member supporting portion <NUM> faces the valve seat member <NUM> in the up-and-down direction. The valve-member supporting portion <NUM> includes a partition wall 21a. The partition wall 21a divides an inner space of the valve-member supporting portion <NUM> into spaces in the up-and-down direction. The space next to the upper side of the partition wall 21a is a spring chamber 21b. The space next to the lower side of the partition wall 21a is a valve-member guide hole 21c. The partition wall 21a has a supporting hole 21d. The supporting hole 21d has a square shape.

An upper portion 22a of the driving-shaft supporting portion <NUM> has a circular columnar shape. A lower portion 22b of the driving-shaft supporting portion <NUM> has a circular cylindrical shape. The upper portion 22a of the driving-shaft supporting portion <NUM> has a stem hole 22c. The stem hole 22c extends through the upper portion 22a in the up-and-down direction. A projecting portion 22d, which has a circular annular shape, is disposed at the lower end of the lower portion 22b of the driving-shaft supporting portion <NUM> and projects radially outwards. The holding surface 12a of the holder <NUM> and the upper portion of the valve-member supporting portion <NUM>, which is press-fitted into the holder <NUM>, hold the projecting portion 22d therebetween. The lower portion 22b of the driving-shaft supporting portion <NUM> defines the spring chamber 21b together with the valve-member supporting portion <NUM>. The lower portion 22b of the driving-shaft supporting portion <NUM> includes a receiving surface 22e. The receiving surface 22e is a circular annular plane facing downwards and is disposed inside the lower portion 22b.

The rolling bearing <NUM> is a radial ball bearing. The rolling bearing <NUM> includes an outer ring 23a, an inner ring 23b, and balls 23c. The balls 23c are multiple rolling elements disposed between the outer ring 23a and the inner ring 23b. The rolling bearing <NUM> is disposed inside the lower portion 22b of the driving-shaft supporting portion <NUM>. The upper end of the outer ring 23a is in contact with the receiving surface 22e of the lower portion 22b of the driving-shaft supporting portion <NUM>. A holding spring <NUM>, which is in a compressed state, is disposed between the lower end of the outer ring 23a and the partition wall 21a. The holding spring <NUM> presses the outer ring 23a to the receiving surface 22e. The holding spring <NUM> pressurizes the outer ring 23a. A thrust bearing can be employed as the rolling bearing <NUM>.

The driving shaft <NUM> is disposed in the up-and-down direction. The driving shaft <NUM> integrally includes an external thread portion <NUM> and a base portion <NUM>. The driving shaft <NUM> is formed, for example, by cutting a metal workpiece made of stainless steel or the like. The external thread portion <NUM> has a circular columnar shape. The external thread portion <NUM> includes an external thread 26c. The external thread 26c is disposed on the outer circumferential surface of the external thread portion <NUM>. The base portion <NUM> includes a first stem portion 27a, a second stem portion 27b, and a connecting portion 27c.

The first stem portion 27a has a circular columnar shape. The first stem portion 27a is coupled to the upper end of the external thread portion <NUM>. The diameter of the first stem portion 27a is larger than the diameter of the external thread portion <NUM> and is equal to the inner diameter of the inner ring 23b of the rolling bearing <NUM>. The first stem portion 27a is inserted into the inner ring 23b. The first stem portion 27a is disposed in the inner ring 23b. The first stem portion 27a is supported rotatably about the axis L by the rolling bearing <NUM>.

The second stem portion 27b has a circular columnar shape. The second stem portion 27b is coupled to the upper end of the first stem portion 27a. The diameter of the second stem portion 27b is larger than the diameter of the first stem portion 27a and is equal to the diameter of the stem hole 22c of the driving-shaft supporting portion <NUM>. The second stem portion 27b is inserted into the stem hole 22c. The second stem portion 27b is disposed in the stem hole 22c. The second stem portion 27b is supported rotatably about the axis L by the driving-shaft supporting portion <NUM>. The second stem portion 27b and a nut <NUM>, which is screwed onto the external thread portion <NUM>, hold the inner ring 23b of the rolling bearing <NUM> therebetween. The degree of tightening of the nut <NUM> determines the pressure applied to the inner ring 23b.

The connecting portion 27c projects from the upper surface of the second stem portion 27b. The connecting portion 27c has a circular columnar shape or a prismatic columnar shape. The connecting portion 27c is connected to a planetary gear mechanism <NUM> of the valve-member driving section <NUM>.

The valve member <NUM> opens and closes the valve port 13a. The valve member <NUM> has a substantially circular cylindrical shape. The outer diameter of the valve member <NUM> is equal to the diameter of the valve-member guide hole 21c of the supporting member <NUM>. The valve member <NUM> is inserted into the valve-member guide hole 21c. The valve member <NUM> is disposed in the valve-member guide hole 21c. A space next to the upper side of the valve member <NUM> in the valve-member guide hole 21c is a back-pressure chamber <NUM>. The valve member <NUM> can slide and move in the up-and-down direction in the valve-member guide hole 21c. The valve member <NUM> faces the valve seat member <NUM> in the up-and-down direction. The supporting member <NUM> guides an up-and-down movement of the valve member <NUM>. The supporting member <NUM> supports the valve member <NUM> so that the valve member <NUM> is allowed to advance and retract with respect to the valve port 13a.

The internal thread member <NUM> has a substantially quadrilateral cylindrical shape. The internal thread member <NUM> includes a main body portion <NUM> made of synthetic resin and a press-fitting frame portion <NUM> made of metal. The main body portion <NUM> and press-fitting frame portion <NUM> are integrated by insert molding.

The main body portion <NUM> has a substantially quadrilateral cylindrical shape. In the present embodiment, the transverse sectional contour of the main body portion <NUM> has a square shape. The supporting hole 21d of the supporting member <NUM> has a square shape that is the same shape as the transverse sectional contour of the main body portion <NUM>. The main body portion <NUM> is inserted into the supporting hole 21d. The main body portion <NUM> is disposed in the supporting hole 21d. In this specification, elements in an insertion relationship, such as "the valve member <NUM> and the valve-member guide hole 21c", "the main body portion <NUM> and the supporting hole 21d", or "the second stem portion 27b of the driving shaft <NUM> and the stem hole 22c of the driving-shaft supporting portion <NUM>", have the same shapes (diameters, contours), where the meaning of "the same shapes" includes a shape of a first element being slightly smaller than a shape of a second element and the first element being movable with respect to the second element in an insertion direction. The transverse sectional contour of the main body portion <NUM> and the shape of the supporting hole 21d may be a polygonal shape other than the square shape, for example, a regular hexagonal shape or the like. In the supporting hole 21d, rotation about the axis L of the main body portion <NUM> is restricted, and movement in the direction of the axis L of the main body portion <NUM> is allowed. That is, the supporting member <NUM> supports the main body portion <NUM> in a manner that restricts the rotation about the axis L of the main body portion <NUM> and allows the movement in the direction of axis L of the main body portion <NUM>.

An upper portion of the main body portion <NUM> is an internal thread portion 33a. The internal thread portion 33a includes an internal thread 33c. The internal thread 33c is disposed on the inner circumferential surface of the internal thread portion 33a. The external thread 26c of the driving shaft <NUM> is screwed into the internal thread 33c. Lubricant in a screwing section between the internal thread 33c of the main body portion <NUM> made of synthetic resin and the external thread 26c of the driving shaft <NUM> made of metal can be omitted. The main body portion <NUM> includes a lateral hole 33b. The lateral hole 33b is disposed below the internal thread portion 33a. The lateral hole 33b extends from the outer peripheral surface to the inner circumferential surface of the main body portion <NUM>. The lateral hole 33b is connected to an inner space 33d of the main body portion <NUM>. An inner space 30d of the valve member <NUM>, the inner space 33d of the main body portion <NUM>, and the lateral hole 33b of the main body portion <NUM> form a pressure equalizing passage <NUM>. The pressure equalizing passage <NUM> connects the valve port 13a to the back-pressure chamber <NUM> in the valve-closing state.

The press-fitting frame portion <NUM> includes a cylindrical portion 34a and a flange portion 34b. The transverse sectional contour of the cylindrical portion 34a has a square shape. The cylindrical portion 34a is embedded in a lower portion of the main body portion <NUM>. The cylindrical portion 34a is press-fitted into a hole 30c, which has a square shape and is provided in an upper surface 30a of the valve member <NUM>. The internal thread member <NUM> is fixed to the valve member <NUM>. The flange portion 34b has a circular annular plate-like shape. The flange portion 34b projects radially outwards at the upper end of the cylindrical portion 34a. The flange portion 34b is disposed on the upper surface 30a of the valve member <NUM>. The flange portion 34b forms an annular groove <NUM> together with a stepped cut-out portion disposed in the periphery of the upper surface 30a of the valve member <NUM>. The annular groove <NUM> holds the sealing member <NUM>, which has a circular annular shape.

The sealing member <NUM> is disposed between the valve member <NUM> and the supporting member <NUM> in a radially compressed state. The sealing member <NUM> seals a gap between the valve member <NUM> and the supporting member <NUM>. The sealing member <NUM> separates the back-pressure chamber <NUM> from the valve chamber <NUM>.

The sealing member <NUM> includes a sealing portion and an outer cap portion. The sealing portion is a component that has a circular annular shape and is made of a rubber-like elastic material (rubber material or synthetic resin with rubber-like elasticity). The sealing portion is, for example, an O-ring. The outer cap portion is a component that has a circular annular band shape and is made of synthetic resin with less elastic deformation than the sealing portion, such as polytetrafluoroethylene (PTFE) or the like. The outer cap portion covers the outer peripheral part of the sealing portion. The outer circumferential surface of the outer cap portion is in contact with the inner circumferential surface of the valve-member guide hole 21c. When the valve member <NUM> moves in the up-and-down direction, the outer circumferential surface of the outer cap portion slides on the inner circumferential surface of the valve-member guide hole 21c. Material of the outer cap portion is selected on the basis of a sliding property, a foreign matter resistance property, and a wear resistance property. The sealing member <NUM> does not have to include the outer cap portion as long as the sealing member <NUM> includes the sealing portion.

The valve-member driving section <NUM> moves the valve member <NUM> in the up-and-down direction to bring the valve member <NUM> into contact with the valve seat 13b of the valve seat member <NUM> and separate the valve member <NUM> from the valve seat 13b of the valve seat member <NUM>.

The valve-member driving section <NUM> includes a stator <NUM>, a rotor <NUM>, a rotor shaft <NUM>, a connecting member <NUM>, and the planetary gear mechanism <NUM>. The stator <NUM> is disposed outside the can <NUM>. The rotor <NUM> is rotatably disposed inside the can <NUM>. The rotor <NUM> is connected to the rotor shaft <NUM> via the connecting member <NUM>, which has a circular plate-like shape. The stator <NUM> and the rotor <NUM> are members of an electric motor. The planetary gear mechanism <NUM> reduces the rotational speed of the rotor <NUM>.

The planetary gear mechanism <NUM> is disposed in the rotor <NUM>. The planetary gear mechanism <NUM> includes a gear case <NUM>, a sun gear <NUM>, a fixed ring gear <NUM>, multiple planet gears <NUM>, a carrier <NUM>, and an output gear <NUM> as an output part. The gear case <NUM> has a circular cylindrical shape. The gear case <NUM> is fixed to an upper portion of the supporting member <NUM>. The sun gear <NUM> is integrated with the connecting member <NUM>. The rotor shaft <NUM> extends through the inside of the sun gear <NUM>. The fixed ring gear <NUM> is an annulus gear fixed to the upper end of the gear case <NUM>. The planet gears <NUM> surround the sun gear <NUM>. The planet gears <NUM> mate with the sun gear <NUM> and the fixed ring gear <NUM>. The carrier <NUM> rotatably supports the planet gears <NUM>. The output gear <NUM> is an internal gear that has a bottomed cylindrical shape. The output gear <NUM> mates with the planet gears <NUM>. The connecting portion 27c of the driving shaft <NUM> is press-fitted into a through hole in the bottom of the output gear <NUM>. The driving shaft <NUM> rotates with the output gear <NUM>.

The electric valve <NUM> includes the planetary gear mechanism <NUM>, whose mechanism type is <NUM>, as a reduction mechanism. The electric valve <NUM> may include a reduction mechanism whose mechanism type is other than <NUM>. The electric valve <NUM> may include, for example, a planetary gear mechanism combined with two or more <NUM>-H-type planetary gear mechanisms, or a reduction mechanism including a worm drive (a worm and a worm wheel).

In the present embodiment, each axis of the tubular member <NUM>, the holder <NUM>, the valve seat member <NUM> (the valve port 13a, the valve seat 13b), the supporting member <NUM> (the valve-member guide hole 21c, the supporting hole 21d, the stem hole 22c), the rolling bearing <NUM>, the driving shaft <NUM>, the valve member <NUM>, the rotor shaft <NUM>, and the output gear <NUM> coincide with the axis L. The direction of the axis L is also a direction of advancing and retracting the valve member <NUM>.

Next, an example of the operation of the electric valve <NUM> according to the present embodiment is described.

In the electric valve <NUM>, the rotational force of the rotor <NUM> is generated by applying current to the stator <NUM>. The planetary gear mechanism <NUM> reduces the speed of the rotational force of the rotor <NUM> and transmits the rotational force from the output gear <NUM> to the driving shaft <NUM>. When the driving shaft <NUM> rotates, a screw-feed action moves the internal thread member <NUM> in the up-and-down direction according to the rotational direction of the driving shaft <NUM>. The valve member <NUM> moves in the up-and-down direction with the internal thread member <NUM>.

When the internal thread member <NUM> moves downwards, the valve member <NUM> moves downwards. A lower end 30b of the valve member <NUM> comes into contact with the valve seat 13b, and the valve port 13a closes (the valve-closing state). In the valve-closing state, the valve port 13a is connected to the back-pressure chamber <NUM> via the pressure equalizing passage <NUM>. Therefore, an upward fluid pressure applied to the valve member <NUM> is counterbalanced by a downward fluid pressure applied to the valve member <NUM>.

In the valve-closing state, when the internal thread member <NUM> moves upwards, the valve member <NUM> moves upwards. The lower end 30b of the valve member <NUM> separates from the valve seat 13b, and the valve port 13a opens (a valve-opening state). Then, as illustrated in <FIG>, when the valve member <NUM> moves to an upper-limit position where the valve member <NUM> is farthest from the valve seat 13b, the electric valve <NUM> is in the full-open state. In the full-open state, the external thread portion <NUM> of the driving shaft <NUM> enters the inner space 33d of the internal thread member <NUM> to a position where the external thread portion <NUM> closes the lateral hole 33b of the internal thread member <NUM>. Therefore, the pressure equalizing passage <NUM> is closed by the external thread portion <NUM>.

With this configuration, in the electric valve <NUM> according to the present embodiment, the rolling bearing <NUM> rotatably supports the driving shaft <NUM>. The external thread portion <NUM> of the driving shaft <NUM> is screwed into the internal thread member <NUM> fixed to the valve member <NUM>. The supporting member <NUM> supports the internal thread member <NUM> in the manner that restricts the rotation of the internal thread member <NUM> about the axis L and allows the movement of the internal thread member <NUM> in the direction of the axis L. As a result, when the driving shaft <NUM> connected to the planetary gear mechanism <NUM> rotates, the screw-feed action moves the internal thread member <NUM> in the direction of the axis L. The movement of the internal thread member <NUM> applies force in the direction of the axis L to the driving shaft <NUM>, and the force is distributed to the balls 23c of the rolling bearing <NUM>. Therefore, concentration of the force can be suppressed in the electric valve <NUM>, and it is possible to enhance the life of the electric valve <NUM>. Additionally, the screw-feed action advances and retracts the valve member <NUM> with respect to the valve port 13a. Therefore, the electric valve <NUM> has a low power consumption compared to an electric valve with a structure including a valve opening spring.

In the electric valve <NUM>, the supporting member <NUM> includes the valve-member guide hole 21c in which the valve member <NUM> is disposed. The internal thread member <NUM> includes the lateral hole 33b that extends from the outer circumferential surface to the inner circumferential surface of the internal thread member <NUM>. The inner space 30d of the valve member <NUM>, the inner space 33d of the internal thread member <NUM>, and the lateral hole 33b of the internal thread member <NUM> form the pressure equalizing passage <NUM> that connects the valve port 13a to the back-pressure chamber <NUM> in the valve-closing state. In the full-open state where the valve member <NUM> is farthest from the valve seat 13b, the external thread portion <NUM> of the driving shaft <NUM> enters the internal thread member <NUM> to the position where the external thread portion <NUM> closes the lateral hole 33b. As a result, the external thread portion <NUM> of the driving shaft <NUM> closes the pressure equalizing passage <NUM> in the full-open state. Therefore, entry of foreign matter included in fluid into the back-pressure chamber <NUM> can be suppressed.

In the electric valve <NUM>, the driving shaft <NUM> includes the base portion <NUM> that is integrally coupled to the external thread portion <NUM> and is connected to the output gear <NUM> of the planetary gear mechanism <NUM>. The rolling bearing <NUM> is the radial ball bearing. The supporting member <NUM> supports the outer ring 23a of the rolling bearing <NUM>. The second stem portion 27b of the base portion <NUM> and the nut <NUM>, which is screwed onto the external thread portion <NUM>, hold the inner ring 23b of the rolling bearing <NUM> therebetween. As a result, the rolling bearing <NUM> can support the driving shaft <NUM> with a simple structure combining the external thread portion <NUM> and the nut <NUM>. Additionally, the pressurization of the inner ring 23b of the rolling bearing <NUM> can be easily controlled by using the nut <NUM> compared to a structure in which the driving shaft <NUM> is press-fitted into the inner ring 23b of the rolling bearing <NUM>.

In the electric valve <NUM>, the transverse sectional contour of the internal thread member <NUM> has the square shape. The valve-member supporting portion <NUM> of the supporting member <NUM> includes the partition wall 21a that divides the inner space of the supporting member <NUM> in the direction of the axis L. The partition wall 21a includes the supporting hole 21d in which the internal thread member <NUM> is disposed. The supporting hole 21d has the square shape that is the same shape as the transverse sectional contour of the internal thread member <NUM>. As a result, the supporting member <NUM> can support the internal thread member <NUM> in the manner that restricts the rotation of the internal thread member <NUM> about the axis L and allows the movement of the internal thread member <NUM> in the direction of the axis L in a relatively simple structure.

The electric valve <NUM> according to the present embodiment, as illustrated in <FIG>, has a distance D1 between the nut <NUM> and the internal thread member <NUM>, and a distance D2 between the partition wall 21a of the supporting member <NUM> and the internal thread member <NUM>. The maximum movement distance of the valve member <NUM> is limited to the minimum one of the distances D1 or D2 in the valve-closing state.

On the other hand, the electric valve <NUM> according to the related art, as illustrated in <FIG>, has a distance E1 in a slit 957a of an output stem <NUM> of the planetary gear mechanism <NUM>, a distance E2 between the output stem <NUM> and the rotary elevation shaft <NUM>, a distance E3 between the bearing member <NUM> and the spring receiving member <NUM>, a distance E4 between the bearing member <NUM> and the thrust transmitting member <NUM>, and a distance E5 between the valve member <NUM> and a partition wall 921a. The maximum movement distance of the valve member <NUM> is limited to the minimum one of the distances E1 to E5 in the valve-closing state.

Where the maximum movement distance of the valve member is α, two distances (the distances D1, D2) should be set to α or more in the electric valve <NUM> according to the present embodiment, while all five distances (the distances E1 to E5) should be set to α or more in the electric valve <NUM> according to the related art. Therefore, when the electric valve <NUM> according to the present embodiment has the same size as the electric valve <NUM> according to the related art, the electric valve <NUM> has the maximum movement distance of the valve member <NUM> greater than that of the electric valve <NUM>.

Electric valves 1A and 1B, according to other embodiments of the present invention, are described below with reference to <FIG> and <FIG>. In the description below, elements that differ from those of the electric valve <NUM> are mainly described. Elements that are the same (including elements with substantially the same functions) as those of the electric valve <NUM> are denoted by the same reference signs as those of the electric valve <NUM>, and detailed descriptions of these elements are omitted.

The electric valve 1A, illustrated in <FIG>, includes a supporting member 20A, a valve member 30A, and an internal thread member 32A.

The supporting member 20A includes a valve-member supporting portion 21A and a driving-shaft supporting portion <NUM>.

The valve-member supporting portion 21A includes a first member <NUM> and a second member <NUM>.

The first member <NUM> has a substantially circular cylindrical shape. An upper portion of the first member <NUM> is press-fitted into a holder <NUM>. A lower portion of the first member <NUM> and a valve seat member <NUM> are arranged in an up-and-down direction with a space therebetween. The lower portion of the first member <NUM> faces the valve seat member <NUM> in the up-and-down direction. An inner space of the first member <NUM> is a valve-member guide hole 21c in which the valve member 30A is disposed. The first member <NUM> includes a spring receiving surface 211a. The spring receiving surface 211a is a circular annular plane facing upwards and is disposed in the inner circumferential surface of the first member <NUM>.

The second member <NUM> includes a cylindrical portion 212a and a flange portion 212b. The cylindrical portion 212a is disposed inside the first member <NUM>. The transverse sectional outer contour of the cylindrical portion 212a has a circular shape, and the transverse sectional inner contour of the cylindrical portion 212a has a square shape. An inner space of the cylindrical portion 212a is a supporting hole 21d in which the internal thread member 32A is disposed. The flange portion 212b has a circular annular shape. The flange portion 212b projects radially outwards at the upper end of the cylindrical portion 212a. The outer peripheral edge of the flange portion 212b is bonded to the upper end of the first member <NUM>. The second member <NUM> restricts the rotation about an axis L of the internal thread member 32A.

A second stem portion 27b of a driving shaft <NUM> and a retaining ring 28A fitted into a groove of a first stem portion 27a hold an inner ring 23b of a rolling bearing <NUM> therebetween.

The valve member 30A opens and closes a valve port 13a. The valve member 30A has a substantially circular cylindrical shape. The outer diameter of the valve member 30A is equal to the diameter of the valve-member guide hole 21c of the supporting member 20A. The valve member 30A is inserted into the valve-member guide hole 21c. The valve member 30A is disposed in the valve-member guide hole 21c. The valve member 30A can slide and move in the up-and-down direction in the valve-member guide hole 21c. The valve member 30A faces the valve seat member <NUM> in the up-and-down direction. The supporting member 20A guides an up-and-down movement of the valve member 30A. The supporting member 20A supports the valve member 30A so that the valve member 30A is allowed to advance and retract with respect to the valve port 13a.

The internal thread member 32A includes a main body portion 33A and a press-fitting frame portion 34A.

The main body portion 33A has a substantially quadrilateral cylindrical shape. In the present embodiment, the transverse sectional contour of the main body portion 33A has a square shape. The supporting hole 21d of the supporting member 20A has a square shape that is the same shape as the transverse sectional contour of the main body portion 33A. The main body portion 33A is inserted into the supporting hole 21d. The main body portion 33A is disposed in the supporting hole 21d. The supporting member 20A (the second member <NUM>) supports the main body portion 33A in a manner that restricts the rotation about the axis L of the main body portion 33A and allows the movement in the direction of the axis L of the main body portion 33A.

An upper portion of the main body portion 33A is an internal thread portion 33a. The internal thread portion 33a includes an internal thread 33c. The internal thread 33c is disposed on the inner circumferential surface of the internal thread portion 33a. An external thread 26c of the driving shaft <NUM> is screwed into the internal thread 33c. The main body portion 33A includes a lateral hole 33b. The lateral hole 33b is disposed below the internal thread portion 33a. The lateral hole 33b extends from the outer circumferential surface to the inner circumferential surface of the main body portion 33A. The lateral hole 33b is connected to an inner space 33d of the main body portion 33A. An inner space 30d of the valve member 30A, the inner space 33d of the main body portion 33A, and the lateral hole 33b of the main body portion 33A form a pressure equalizing passage <NUM>. The pressure equalizing passage <NUM> connects the valve port 13a to a back-pressure chamber <NUM> in the valve-closing state.

The press-fitting frame portion 34A includes a cylindrical portion 34c and a flange portion 34d. A lower portion of the main body portion 33A is disposed in a lower portion of the cylindrical portion 34c. The lower portion of the cylindrical portion 34c is press-fitted into a hole 30c disposed in an upper surface 30a of the valve member 30A. As a result, the internal thread member 32A (the main body portion 33A and the press-fitting frame portion 34A) is fixed to the valve member 30A. In the hole 30c of the valve member 30A, a filter 37A is disposed between the valve member 30A and the main body portion 33A. The filter 37A catches foreign matter included in fluid flowing through the pressure equalizing passage <NUM>. The flange portion 34d has a circular annular plate-like shape. The flange portion 34d projects radially outwards at the upper end of the cylindrical portion 34c. The flange portion 34d and the spring receiving surface 211a of the first member <NUM> are arranged in the up-and-down direction with a space therebetween. A valve opening spring 38A, which is in a compressed state, is disposed between the flange portion 34d and the spring receiving surface 211a. The valve opening spring 38A pushes the flange portion 34d (i.e., the valve member 30A) upwards.

A space in which the press-fitting frame portion 34A in the valve-member guide hole 21c is disposed is the back-pressure chamber <NUM>. A sealing member <NUM> is held by an annular groove 35A formed by the valve member 30A and the internal thread member 32A. The sealing member <NUM> is disposed between the internal thread member 32A (the press-fitting frame portion 34A) and the supporting member 20A (the first member <NUM>) in a radially compressed state. The sealing member <NUM> seals a gap between the valve member 30A and the supporting member 20A. The sealing member <NUM> separates the back-pressure chamber <NUM> from a valve chamber <NUM>.

The electric valve 1B, illustrated in <FIG>, includes a supporting member 20B, the valve member 30A, an internal thread member 32A, two rolling bearings 23B, and a driving shaft 25B.

The supporting member 20B includes a valve-member supporting portion 21A and a driving-shaft supporting portion 22B.

The driving-shaft supporting portion 22B has a substantially circular cylindrical shape as a whole. A projecting portion 22f, which has a circular annular shape, is provided at the upper end of the driving-shaft supporting portion 22B and projects radially inwards. The projecting portion 22f includes a receiving surface <NUM>. The receiving surface <NUM> is a circular annular plane facing downwards.

The driving shaft 25B integrally includes an external thread portion <NUM> and a base portion 27B. The base portion 27B includes a first stem portion 27a, a second stem portion 27b, a connecting portion 27c, and a flange portion 27d. The flange portion 27d has a circular annular plate-like shape. The inner peripheral edge of the flange portion 27d is connected to the outer circumferential surface of the second stem portion 27b.

The two rolling bearings 23B are thrust ball bearings. The rolling bearing 23B includes an upper bearing washer 23d, a lower bearing washer 23e, and balls 23f. The balls 23f are multiple rolling elements disposed between the upper bearing washer 23d and the lower bearing washer 23e. The two rolling bearings 23B are arranged in the driving-shaft supporting portion 22B in an up-and-down direction (a direction of an axis L). The flange portion 27d of the driving shaft 25B is disposed between the two rolling bearings 23B. The upper bearing washer 23d of the upper one of the two rolling bearings 23B is in contact with the receiving surface <NUM> disposed at the upper end of the driving-shaft supporting portion 22B. A holding spring <NUM>, which is in a compressed state, is disposed between the lower bearing washer 23e of the lower one of the two rolling bearings 23B and a second member <NUM> of the supporting member 20B. The lower one of the two rolling bearings 23B is pressed upwards by the holding spring <NUM>. The upper bearing washer 23d of the upper one of the two rolling bearings 23B is pressed to the receiving surface <NUM>. The second stem portion 27b of the driving shaft 25B is disposed in the two rolling bearings 23B. The two rolling bearings 23B rotatably support the driving shaft 25B. The upper one of the two rolling bearings 23B mainly receives an upward force applied to the valve member 30A. The lower one of the two rolling bearings 23B mainly receives a downward force applied to the valve member 30A.

The electric valves 1A and 1B also have the functions and effects similar to or the same as those of the electric valve <NUM> described above.

Especially, in the electric valve 1A, because the valve member 30A is pushed by the valve opening spring 38A, it is possible to reduce hysteresis characteristics in the electric valve 1A when the valve member 30A moves in the up-and-down direction. Additionally, in the electric valve 1B, because the two rolling bearings 23B receive the pressure applied to the valve member 30A and the driving shaft 25B, it is possible to effectively enhance the life of the electric valve 1B used in a system with a relatively large difference between inlet and outlet fluid pressure.

The embodiments of the present invention are described above. The present invention, however, is not limited to the configurations of these embodiments. Embodiments obtained by appropriately adding, removing, or modifying components according to the embodiment described above by a person skilled in the art, and an embodiment obtained by appropriately combining features of the embodiment are included in the scope of the present invention without departing from the spirit of the present invention.

Claim 1:
An electric valve (<NUM>) comprising:
a valve body (<NUM>) that includes a valve chamber (<NUM>) and a valve port (13a);
a valve member (<NUM>) that opens and closes the valve port (13a);
a supporting member (<NUM>) that supports the valve member (<NUM>) to be capable of advancing and retracting with respect to the valve port (13a);
a driving shaft (<NUM>) that includes an external thread portion (<NUM>) and is disposed in a direction of advancing and retracting the valve member (<NUM>);
a rolling bearing (<NUM>) that rotatably supports the driving shaft (<NUM>) and is held by the supporting member (<NUM>);
a planetary gear mechanism (<NUM>) that is connected to the driving shaft (<NUM>); and
an internal thread member (<NUM>) with a cylindrical shape that is fixed to the valve member (<NUM>) and into which the external thread portion (<NUM>) is screwed,
wherein the supporting member (<NUM>) supports the internal thread member (<NUM>) in a manner that restricts rotation of the internal thread member (<NUM>) about an axis (L) and allows movement of the internal thread member (<NUM>) in a direction of the axis (L),
wherein
the supporting member (<NUM>) includes a valve-member guide hole (21c) in which the valve member (<NUM>) is disposed,
characterized in that,
the internal thread member (<NUM>) includes a lateral hole (33b) that extends from an outer surface to an inner surface of the internal thread member (<NUM>),
wherein an inner space (33d) of the internal thread member (<NUM>) and the lateral hole (33b) of the internal thread member (<NUM>) form a pressure equalizing passage (<NUM>) that connects, in a valve-closing state where a first end of the valve member (<NUM>) is in contact with a valve seat (13b) of the valve port (13a), the valve port (13a) to a back-pressure chamber (<NUM>), which is a space next to a second end of the valve member (<NUM>) in the valve-member guide hole (21c), and
wherein the external thread portion (<NUM>) enters the internal thread member (<NUM>) to a position where the external thread portion (<NUM>) closes the lateral hole (33b) in a full-open state where the valve member (<NUM>) is farthest from the valve seat (13b).