Patent Description:
Conventional electric valves, in which a shaft fitted with a valve element and rotated by a motor is supported by a molded resin component integrated with a metal part by insertion molding, are known (see, for example, <CIT> (paragraph [<NUM>] to [<NUM>], <FIG>, <FIG>, etc.)).

<CIT>, <CIT>, <CIT>, and <CIT> disclose further motor-driven valves. <CIT> discloses a refrigerant flow control valve.

Development of a technique that can keep production cost down for the conventional electric valve described above is desired.

According to one aspect of the present disclosure made to solve the above problem, there is provided an electric valve according to claim <NUM> or <NUM> or <NUM> or <NUM>.

<FIG> shows an electric valve <NUM> according to the first embodiment. The electric valve <NUM> includes a stator <NUM>, a rotor <NUM> rotatably disposed inside the stator <NUM>, and a shaft <NUM> that moves linearly inside the stator <NUM> by rotation of the rotor <NUM>. The electric valve <NUM> includes a valve port <NUM> disposed midway in a flow passage of a fluid, and this valve port <NUM> is opened and closed by a valve element <NUM> at a tip of the shaft <NUM> (see <FIG> and <FIG>).

The stator <NUM> has a body <NUM>, with a stator field coil <NUM> fixed on the outside of the body <NUM>. The body <NUM> is a hollow structure made by a substantially cylindrical tubular main body <NUM> closed at one end by a lid member <NUM>, and accommodates the rotor <NUM> and the shaft <NUM> mentioned above. The stator field coil <NUM> is in an annular shape and has electromagnetic coils <NUM> aligned with each other. Hereinafter, where applicable, one side of the body <NUM> where the lid member <NUM> is positioned will be referred to as an upper side, and the other side as a lower side.

Inside the body <NUM> is provided a rotor compartment <NUM> that accommodates the rotor <NUM> on the upper side. A valve element compartment <NUM> that accommodates the valve element <NUM> is provided on the lower side inside the body <NUM>. The valve element compartment <NUM> communicates with the valve port <NUM> at the lower end. An inner part <NUM> that separates the body <NUM> from the rotor compartment <NUM> and the valve element compartment <NUM> is fixed to an inner surface of the body midway along the shaft.

The body <NUM> is made of metal. The tubular main body <NUM> of the body <NUM> is made up of a sleeve <NUM> disposed on the upper side and a tubular base portion <NUM> disposed on the lower side, which are fixed together by welding, for example. The sleeve <NUM> and the tubular base portion <NUM> are disposed coaxially.

The sleeve <NUM> accommodates the rotor <NUM> mentioned above inside. The stator field coil <NUM> mentioned above is fixed on an outer circumferential surface of the sleeve <NUM> near the lower end. A lower end portion of the sleeve <NUM> is bent perpendicularly and forms an annular extension 21E that extends radially inward. In this embodiment, the sleeve <NUM> corresponds to a "rotor accommodating portion" in the claims.

The tubular base portion <NUM> accommodates the valve element <NUM> at the lower end (distal end) of the shaft <NUM>. A through hole <NUM> that extends axially through the tubular base portion <NUM> is tapered downward in a middle part to form the valve port <NUM> mentioned above. The valve element compartment <NUM> inside the tubular base portion <NUM> (i.e., the portion above the valve port <NUM>) is formed with lateral holes <NUM> that extend through laterally. The opening at the lower end of the through hole <NUM> of the tubular base portion <NUM> is in communication with a flow passage <NUM> of an external body <NUM> in which the electric valve <NUM> is mounted, and lateral holes <NUM> are in communication with flow passages <NUM> of the external body <NUM>. The valve element <NUM> changes the degree of opening of the valve port <NUM> to change the flow amount of a fluid flowing through the valve port <NUM> between the flow passages <NUM> and <NUM> (see <FIG> and <FIG>).

The inner part <NUM> mentioned above is made of resin and substantially cylindrical. The inner part <NUM> has a through hole <NUM> that extends through axially (see <FIG>), for the shaft <NUM> mentioned above to pass through. Internal threads 60N are formed on the inner surface of the through hole <NUM> of the inner part <NUM>. Rotation of the rotor <NUM> is converted into linear motion of the valve element <NUM> of the shaft <NUM> by these internal threads 60N engaging with external threads 70N formed on the outer circumferential surface of the shaft <NUM>. To achieve smooth motion of the shaft <NUM> that is made of metal, the inner part <NUM> is composed of a resin having a high mechanical strength (e.g., polyphenylene sulfide or the like), with polytetrafluoroethylene, carbon fiber and the like added thereto, for example. The inner part <NUM> will be described in more detail later.

The mechanism that moves the shaft <NUM> is configured as follows, for example. As shown in <FIG>, the rotor <NUM> is made up of a cylindrical rotation tube <NUM> open at both ends, and a magnetic rotor field coil <NUM> fixed on the outer side of the rotation tube <NUM>. A motor <NUM> (e.g., stepping motor) is configured with these rotor field coil <NUM> and stator field coil <NUM> as main parts, and the rotor field coil <NUM> is positioned at predetermined rotation position by changing magnetization pattern of the electromagnetic coils <NUM> of the stator field coil <NUM>. The electric valve <NUM> is provided with a stopper (not shown) for restricting the rpm of the rotor <NUM> within a certain range.

Ball bearings <NUM> are set, each between the upper end of the rotor <NUM> and the lid member <NUM>, and between the lower end portion of the rotor <NUM> and the sleeve <NUM>. The outer race and inner race of the upper ball bearing <NUM> that sandwich balls are fixed to an upper end portion of the rotation tube <NUM> of the rotor <NUM> and the lid member <NUM>, respectively. The outer race and inner race of the lower ball bearing <NUM> that sandwich balls are fixed to a lower end portion of the sleeve <NUM> of the body <NUM> and a lower end portion of the rotation tube <NUM> of the rotor <NUM>, respectively.

The rotation tube <NUM> of the rotor <NUM>, at the lower end portion of its center hole, is formed with a fit hole 31A that is non-circular when viewed from the axial direction of the rotor <NUM>. The shaft <NUM> fits in this fit hole 31A. The shaft <NUM> has a non-circular fit portion <NUM> near the upper end for fitting into the fit hole 31A of the rotor <NUM>. This enables the shaft <NUM> to rotate with the rotor <NUM> as well as to move linearly relative to the rotor <NUM>. As mentioned above, when the rotor rotates <NUM>, the shaft <NUM> rotates, and moves along the direction of the rotating axis of the rotor <NUM>, by the external threads 70N of the shaft <NUM> engaging with the internal threads 60N of the inner part <NUM> that is fixed to the body <NUM>.

The inner part <NUM> is press-fitted into and fixed to the tubular base portion <NUM>. Specifically, as shown in <FIG>, the tubular base portion <NUM> is made up of a large diameter base portion <NUM> disposed on the upper side and a small diameter base portion <NUM> disposed on the lower side, these being connected together. The inner part <NUM> is press-fitted into the large diameter base portion <NUM> from below. The sleeve <NUM> is fixed to the large diameter base portion <NUM> from above. The small diameter base portion <NUM> has the valve port <NUM> and lateral holes <NUM> mentioned above. The small diameter base portion <NUM> is press-fitted into and fixed to the large diameter base portion <NUM>.

As shown in <FIG> and <FIG>, the large diameter base portion <NUM> has a press-fit reception portion inside where the inner part <NUM> is press-fitted. This press-fit reception portion is formed by a small diameter hole portion <NUM> where the inside diameter of the center hole of the large diameter base portion <NUM> is smallest along the axial direction.

Above the small diameter hole portion <NUM> of the center hole of the large diameter base portion <NUM> is provided an upper large diameter hole portion <NUM> having a larger diameter than the small diameter hole portion <NUM>. The lower end portion of the sleeve <NUM> fits in this upper large diameter hole portion <NUM>, with the annular extension 21E abutted on the large diameter base portion <NUM> from above. Below the small diameter hole portion <NUM> of the center hole of the large diameter base portion <NUM> is provided an intermediate diameter hole portion <NUM> having a larger diameter than the small diameter hole portion <NUM>. Below the intermediate diameter hole portion <NUM> is provided a lower large diameter hole portion <NUM> having a larger diameter than the intermediate diameter hole portion <NUM>. The intermediate diameter hole portion <NUM> receives a flange 60F to be described later of the inner part <NUM>. Inside the lower large diameter hole portion <NUM> is press-fitted the small diameter base portion <NUM> from below. Engaging recesses <NUM> extend along the axial direction of the large diameter base portion <NUM> from the lower end of the intermediate diameter hole portion <NUM> to a midway point of the small diameter hole portion <NUM>. The engaging recess <NUM> is located at two points circumferentially spaced apart by <NUM> degrees of the large diameter base portion <NUM> (see <FIG>).

Next, the inner part <NUM> will be described in more detail. As shown in <FIG> and <FIG>, the inner part <NUM> increases in diameter in two steps at midway points along the axial direction to form an intermediate diameter portion <NUM> and the flange 60F. The intermediate diameter portion <NUM> has an outer circumferential shape smaller than and similar to the inner circumferential shape of the small diameter hole portion <NUM> of the large diameter base portion <NUM>. At the outer edge on the upper end face of the flange 60F is formed an annular protrusion 60T. As shown in <FIG>, with the flange 60F sandwiched between the large diameter base portion <NUM> and the small diameter base portion <NUM> of the body <NUM>, the inner part <NUM> is set in position in the direction of the rotating axis of the rotor <NUM>. Specifically, the flange 60F of the inner part <NUM> is sandwiched between a step surface 40D between the small diameter hole portion <NUM> and the intermediate diameter hole portion <NUM> of the large diameter base portion <NUM>, and an upper end face 50D of the small diameter base portion <NUM> that forms a step surface inside the body <NUM>. More particularly, the annular protrusion 60T of the flange 60F abuts on the step surface 40D of the large diameter base portion <NUM>. <FIG> illustrates a cross section of D-D shown in <FIG>. In this embodiment, the step surface 40D and upper end face 50D correspond to a "positioning step surface" in the claims. The intermediate diameter portion <NUM> corresponds to a "tubular portion" in the claims.

In the lower surface of the flange 60F, as shown in <FIG> and <FIG>, there are formed diameterly extending linear grooves 60U at two points circumferentially spaced apart by <NUM> degrees, as well as circular recesses <NUM> at a plurality of positions along the circumferential direction. After the inner part <NUM> has been molded, when a thread portion of the mold is rotated to be removed from the internal threads 60N, these linear grooves 60U and circular recesses <NUM> can prevent the inner part <NUM> from rotating with the thread part.

In the configuration in which the interior of the body <NUM> is divided by the inner part <NUM> with the shaft <NUM> passing therethrough into the rotor compartment <NUM> and the valve element compartment <NUM>, an issue of pressure instability around the valve port <NUM> can arise because any pressure difference between the rotor compartment <NUM> and the valve element compartment <NUM> can lead to a gradual release of pressure from between the inner surface of the internal threads 60N of the inner part <NUM> and the outer surface of the external threads 70N of the shaft <NUM>. To address this issue, for a conventional electric valve that uses an inner part integrated with the body <NUM> by insertion molding, a communication hole may be drilled through axially in the inner part separately from the hole in which the shaft <NUM> passes through, for example, so that the rotor compartment <NUM> and the valve element compartment <NUM> communicate with each other. However, this configuration would require the mold for forming the inner part to have a thin pin or the like to form such a communication hole in the inner part, which makes the mold complex and causes the problem of higher production cost. Another problem is poor productivity because the inner part would be more prone to defects due to burrs or the like, for example, around the communication hole in the inner part. In such cases, the entire body <NUM> has to be replaced if the inner part is insertion-molded therein as is conventional.

In this embodiment, the inner part <NUM> has an uneven portion 60A on its outer circumferential surface that creates gaps S between the inner part <NUM> and the inner surface of the large diameter base portion <NUM> (i.e., body <NUM>). These gaps S allow communication between the rotor compartment <NUM> and the valve element compartment <NUM> (see <FIG>).

Specifically, as shown in <FIG> and <FIG>, the uneven portion 60A of the inner part <NUM> has a plurality of (e.g., eight) bosses <NUM> protruding from the outer circumferential surface of the intermediate diameter portion <NUM> of the inner part <NUM>. In this embodiment, the plurality of bosses <NUM> is in the form of ridges extending along the axial direction of the inner part <NUM>, equally spaced in the circumferential direction of the inner part <NUM>, and configured the same (i.e., same shape with the same amount of protrusion). The plurality of bosses <NUM> bulges out when viewed from the axial direction of the inner part <NUM> and has a bulging surface in a circular arc shape. When the inner part <NUM> is press-fitted into the large diameter base portion <NUM>, the plurality of bosses <NUM> is pressed by the inner surface of the small diameter hole portion <NUM> of the large diameter base portion <NUM>, and the tips of the plurality of bosses <NUM> are flattened (see <FIG>). At this time, axially extending gaps S are formed around the inner part <NUM> between adjacent ones of the plurality of bosses <NUM>. Since the plurality of bosses <NUM> is flattened by press-fitting, the distance between the center axis of the inner part <NUM> and the tip of the boss <NUM> before the press-fitting of the inner part <NUM> (radius of a circle circumscribing the tips of the plurality of bosses <NUM>) is larger than the radius of the small diameter hole portion <NUM> of the large diameter base portion <NUM>.

Further, engaging protrusions <NUM> protrude from two points of the intermediate diameter portion <NUM> of the inner part <NUM> circumferentially spaced apart by <NUM> degrees, and are connected with the flange 60F. As shown in <FIG>, the engaging protrusions <NUM> engage with the engaging recesses <NUM> mentioned above of the large diameter base portion <NUM> of the body <NUM> (see <FIG>). Thus, the inner part <NUM> is prevented from rotating relative to the large diameter base portion <NUM> (i.e., body <NUM>). The engaging protrusions <NUM> are circumferentially located at different positions from the plurality of bosses <NUM>. Namely, each engaging protrusion <NUM> is positioned between a pair of adjacent bosses <NUM>. In this embodiment, the engaging protrusion <NUM> and engaging recess <NUM> correspond to a "concavo-convex engagement portion" in the claims.

As shown in <FIG>, when viewed from the axial direction of the inner part <NUM>, the semicircular outwardly bulging tip of the engaging protrusion <NUM> is cut off and made substantially flat. Accordingly, when the inner part <NUM> is fixed, gaps S are formed between the inner surface of the engaging recesses <NUM> of the large diameter base portion <NUM> formed in a round groove shape as viewed from the axial direction and the tips of the engaging protrusions <NUM>. These gaps S extend between pairs of adjacent bosses <NUM> as described above, and the rotor compartment <NUM> and the valve element compartment <NUM> communicate with each other via the linear grooves 60U, as shown in <FIG> illustrates a cross section of C-C shown in <FIG>.

The electric valve <NUM> of this embodiment is produced as described below, for example. First, as shown in <FIG>, the sleeve <NUM> is welded to the upper end of the large diameter base portion <NUM>. In particular, a lower end portion of the sleeve <NUM> fits into the upper large diameter hole portion <NUM> of the large diameter base portion <NUM>.

Next, as shown in <FIG> and <FIG>, the inner part <NUM> is press-fitted from below into the large diameter base portion <NUM> (i.e., opposite side to the sleeve <NUM>). At this time, the plurality of bosses <NUM> on the inner part <NUM> is pressed by the inner surface of the small diameter hole portion <NUM> of the large diameter base portion <NUM>, and the engaging protrusions <NUM> of the inner part <NUM> engage with the engaging recesses <NUM> of the large diameter base portion <NUM>. As described above, gaps S are formed between the outer surface of the inner part <NUM> and the inner surface of the large diameter base portion <NUM>. The upper end of the inner part <NUM> passes through the lower end opening of the sleeve <NUM> and enters into the sleeve <NUM>. The lower end portion of the inner part <NUM> protrudes out of the large diameter base portion <NUM> downward.

Next, as shown in <FIG>, the small diameter base portion <NUM> is press-fitted into the large diameter base portion <NUM> with the inner part <NUM> having been press-fitted therein. Specifically, the small diameter base portion <NUM> is press-fitted into the lower large diameter hole portion <NUM> at the lower end of the large diameter base portion <NUM>. The lower end of the inner part <NUM> is positioned inside the small diameter base portion <NUM>. The inner part <NUM> is set in position in the axial direction by being sandwiched between the step surface 40D of the large diameter base portion <NUM> and the upper end face 50D of the small diameter base portion <NUM>.

Once the small diameter base portion <NUM> has been press-fitted into the large diameter base portion <NUM> and fixed, these together form the tubular base portion <NUM> as shown in <FIG>. The valve element compartment <NUM> is formed by a region inside the tubular base portion <NUM> between the inner part <NUM> and the valve port <NUM>.

Next, the shaft <NUM>, rotor <NUM>, and others are set inside the sleeve <NUM> from above, and the upper end opening of the sleeve <NUM> is closed by the lid member <NUM> (see <FIG>). The body <NUM> is thus formed, and the region above the inner part <NUM> inside the body <NUM> forms the rotor compartment <NUM>. The stator field coil <NUM> (see <FIG>) is fixed to the outer circumferential surface of the sleeve <NUM>, and abutted on the upper end face of the tubular base portion <NUM> (large diameter base portion <NUM>). O-rings are placed into annular grooves in the outer circumferential surface of the large diameter base portion <NUM> and small diameter base portion <NUM> to provide a seal between the inner surfaces of an electric valve mounting hole <NUM> in the external body <NUM> and the outer surface of the body <NUM>. The electric valve <NUM> of this embodiment is thus completed.

Next, the effects of the electric valve <NUM> of this embodiment will be described. The inner part <NUM> of the electric valve <NUM> of this embodiment is fixed to the body <NUM> by a press fit, so that, as compared to the case where the inner part <NUM> is integrally formed with the body <NUM> by insertion molding, there is no need to replace the entire body <NUM> in the event of a defect occurring in the inner part <NUM>, and thus the production cost can be kept down. Moreover, a pressure difference is hardly generated between the rotor compartment <NUM> and the valve element compartment <NUM> in the electric valve <NUM> because of the gaps S between the inner surface of the body <NUM> and the inner part <NUM>, which are formed by the uneven portion 60A on the outer surface of the inner part <NUM>, so that the rotor compartment <NUM> and the valve element compartment <NUM> communicate with each other. With an inner part integrally formed with the body <NUM> by insertion molding, forming such gaps would require a complex mold structure, which will raise the production cost of the electric valve. With the electric valve <NUM>, however, gaps S can be formed by the uneven portion 60A on the outer surface of the inner part <NUM>, and by press-fitting the inner part <NUM> into the body <NUM>. This way, the production cost of the electric valve with gaps S inside can be kept down. To form the inner part by insertion molding as is conventional, it is necessary to use a resin material for the inner part suitable for insertion molding such as a resin readily bondable to the body <NUM>. The inner part <NUM> of this embodiment in this respect allows for a wider selection of resin materials.

The inner part <NUM> of the electric valve <NUM> has the uneven portion 60A that includes a plurality of bosses <NUM> formed at several circumferential locations on the outer surface of the inner part <NUM> and pressed by the inner surface of the body <NUM>. This configuration, in which the inner part <NUM> is press-fitted into the body <NUM> such as to flatten the tips of the plurality of bosses <NUM>, allows for easy formation of gaps between the plurality of bosses <NUM>. This configuration, in which the gaps S are formed on the outer surface of the inner part <NUM>, can also prevent a loss in rigidity of the inner part <NUM> to withstand the press-fitting, as compared to a case where a through hole that connects the rotor compartment <NUM> and the valve element compartment <NUM> is formed in the inner part <NUM>.

Since the plurality of bosses <NUM> is circumferentially equally spaced on the inner part <NUM>, gaps between the outer surface of the inner part <NUM> and the inner surface of the body <NUM> can be formed at equal distance in the circumferential direction of the inner part <NUM>. The intermediate diameter portion <NUM> of the inner part <NUM> has an outer circumferential shape similar to the inner circumferential shape of the small diameter hole portion <NUM> of the body <NUM>, so that the inner part <NUM> can readily be set coaxial with the rotating axis of the rotor by making the protruding height of the plurality of bosses <NUM> equal.

The plurality of bosses <NUM> of the electric valve <NUM> is a ridge extending along the axial direction of the through hole <NUM> of the inner part <NUM>, which helps secure the inner part <NUM> in a stable manner along the axial direction. Moreover, the gaps S between the outer surface of the inner part <NUM> and the inner surface of the body <NUM>, which are formed between the plurality of bosses <NUM>, extend in the axial direction, and allow for easier fluid communication between the rotor compartment <NUM> and the valve element compartment <NUM>. This can better prevent a pressure difference between the rotor compartment <NUM> and the valve element compartment <NUM>.

The engaging protrusions <NUM> and engaging recesses <NUM> prevent rotation of the inner part <NUM> relative to the body <NUM> of the electric valve <NUM>. This way, the inner part <NUM> can be fixed stably, which helps stabilize the linear motion of the shaft <NUM>.

Moreover, gaps S through which the rotor compartment <NUM> and the valve element compartment <NUM> communicate with each other are formed between the tips of the engaging protrusions <NUM> and the inner surface of the engaging recesses <NUM> in the electric valve <NUM>, and thus a pressure difference between the rotor compartment <NUM> and the valve element compartment <NUM> can be made even less likely to occur.

The body <NUM> of the electric valve <NUM> has step surfaces 40D and 50D inside, which set the inner part <NUM> in position in the direction along the rotating axis of the rotor <NUM>. Therefore, the inner part <NUM> can be fixed more stably.

Claim 1:
An electric valve (<NUM>) comprising:
a body (<NUM>, <NUM>, <NUM>, <NUM>) made of metal including a rotor compartment (<NUM>) accommodating a rotor (<NUM>) of a motor (<NUM>) that is a drive source of a valve element (<NUM>), and a valve element compartment (<NUM>) accommodating the valve element (<NUM>) and communicating with a valve port (<NUM>);
an inner part (<NUM>) made of resin disposed inside the body (<NUM>, <NUM>, <NUM>, <NUM>) and separating the rotor compartment (<NUM>) from the valve element compartment (<NUM>); and
a shaft (<NUM>) passing through a through hole (<NUM>) extending through the inner part (<NUM>), rotating with the rotor (<NUM>), and including the valve element (<NUM>) disposed in a tip of the shaft (<NUM>), rotation of the rotor (<NUM>) being converted to linear motion of the valve element (<NUM>) by engagement between respective threads (60N, 70N) formed in the through hole (<NUM>) and the shaft (<NUM>), wherein
the inner part (<NUM>) is press-fitted and fixed in a press-fit reception portion (<NUM>) between the rotor compartment (<NUM>) and the valve element compartment (<NUM>) inside the body (<NUM>, <NUM>, <NUM>, <NUM>),
the inner part (<NUM>) is formed with an uneven portion (60A) on an outer surface of the inner part (<NUM>), which forms a gap (S) between the inner part (<NUM>) and an inner surface of the body (<NUM>, <NUM>, <NUM>, <NUM>) so that the rotor compartment (<NUM>) and the valve element compartment (<NUM>) communicate with each other, and
the body (<NUM>, <NUM>, <NUM>, <NUM>) is formed with a positioning step surface (40D, 50D) inside that sets the inner part (<NUM>) in position in a direction of a rotating axis of the rotor (<NUM>).