Patent Description:
An example of a conventional flow channel switching valve is disclosed in Patent Literature <NUM>. This flow channel switching valve is used as a rotary three-way switching valve. The flow channel switching valve includes a valve body having a valve chamber, a circular tubular valve member rotatably disposed in the valve chamber, a rotation drive unit that rotates the valve member around a rotation axis, and a valve stem that transmits a rotational force of the rotation drive unit to the valve member. A protrusion having a D-cut shape for attachment of a rotation angle sensor that detects the rotation angle of the valve member is integrally provided on the upper end surface of the valve stem.

<CIT> discloses a known valve comprising a rotation angle detection unit.

<CIT> discloses a flow passage switching valve comprising a rotational position detection section for detecting rotational position of a ball valve body, having a potentiometer for detecting the rotational angle of a valve shaft, and also having a potentiometer base for supporting the potentiometer. The potentiometer base has a base body section mounted to a case, and a sensor support section to which the potentiometer is mounted and which is disposed facing a circular column section of the valve shaft. The sensor support section is provided with a circular arc-shaped positioning through hole extending along the outer peripheral surface of the circular column section of the valve shaft.

However, with such a flow channel switching valve, there has been a possibility that the output of the rotation angle sensor with respect to the rotational position of the valve member includes an error due to accumulation of the tolerances of the valve member, the valve stem, the rotation angle sensor, and so forth. Thus, there has been room for improvement in the precision of the rotational position of the valve member in a flow channel switching operation.

Therefore, an object of the present invention is to provide a flow channel switching valve capable of effectively improving precision of a rotational position of a valve member, and a method for assembling the flow channel switching valve.

To attain the above-described object, a flow channel switching valve according to an aspect of the present invention is a flow channel switching valve including a valve body provided with a valve chamber and a plurality of flow channels that communicate with the valve chamber, a valve member that is rotatably housed in the valve chamber and that switches connection of the flow channels in accordance with a rotational position, a valve stem that is attached to the valve member along a rotation axis of the valve member, and a drive unit that rotates the valve member via the valve stem. The flow channel switching valve includes a rotation angle output shaft that is press-fitted into an attachment hole provided in an end surface of the valve stem; and a rotation angle detection unit that detects a rotation angle of the rotation angle output shaft around the rotation axis. The rotation angle output shaft is supported rotatably around the rotation axis in the attachment hole in an inserted state before being press-fitted into the attachment hole.

In the present invention, the attachment hole includes a press-fit portion into which a portion of the rotation angle output shaft is press-fitted, and a guide portion with which another portion of the rotation angle output shaft comes into contact slidably in an insertion direction and a circumferential direction.

In the present invention, it is preferable that the rotation angle detection unit include a rotor and a signal output unit that outputs a signal corresponding to a rotation angle of the rotor, the rotor be provided with a fitting hole through which a fitting shaft portion provided at one end portion of the rotation angle output shaft passes, and the fitting shaft portion be fitted to the fitting hole such that the rotor rotates together with the fitting shaft portion.

In the present invention, it is preferable that the flow channel switching valve further include a base body to which the rotation angle detection unit is attached; and the base body be fixed to the valve body, and a through hole through which the rotation angle output shaft passes be provided at a position at which the rotation angle detection unit is attached.

To attain the above-described object, a method for assembling a flow channel switching valve according to another aspect of the present invention is a method for assembling a flow channel switching valve including a valve body provided with a valve chamber and a plurality of flow channels that communicate with the valve chamber, a valve member that is rotatably housed in the valve chamber and that switches connection of the flow channels in accordance with a rotational position, a valve stem that is attached to the valve member along a rotation axis of the valve member, a drive unit that rotates the valve member via the valve stem, a rotation angle output shaft that is press-fitted into an attachment hole provided in an end surface of the valve stem, and a rotation angle detection unit that detects a rotation angle of the rotation angle output shaft around the rotation axis. The method includes rotating the rotation angle output shaft inserted into the attachment hole of the valve stem around the rotation axis to perform positioning, then further inserting the rotation angle output shaft, and press-fitting the rotation angle output shaft into the attachment hole.

According to the present invention, the rotation angle output shaft that is press-fitted into the attachment hole provided in the end surface of the valve stem is supported rotatably around the rotation axis in the attachment hole in the inserted state before being press-fitted into the attachment hole. With this configuration, in the state in which the rotation angle output shaft has been inserted into the attachment hole, the rotation angle output shaft can be rotated around the rotation axis to perform positioning. Accordingly, it is possible to further reduce an error of the output of the rotation angle detection unit due to the tolerances of the valve member, the valve stem, and the rotation angle detection unit. Thus, it is possible to effectively improve the precision of the rotational position of the valve member.

A configuration of a flow channel switching valve according to an embodiment of the present invention will be described below with reference to <FIG>.

<FIG> is a perspective view including a partial section of the flow channel switching valve according to the embodiment of the present invention. <FIG> is a sectional view taken along line A-A of <FIG>. <FIG> is a six sided view of a ball valve member included in the flow channel switching valve of <FIG>. In the following description, " upper, lower, left, and right" are used to indicate the relative positional relationship between respective components in each of the drawings, but do not indicate the absolute positional relationship. In each of the drawings, a left-right direction is defined as an X-axis direction, a front-back direction is defined as a Y-axis direction, and an up-down direction is defined as a Z-axis direction. The X axis, the Y axis, and the Z axis are orthogonal to one another.

As illustrated in <FIG> and <FIG>, a flow channel switching valve <NUM> of the present embodiment includes a valve body <NUM>, a ball valve member <NUM>, seat members <NUM>, <NUM>, sealing members <NUM>, <NUM>, a drive unit <NUM>, and a valve stem <NUM>. The flow channel switching valve <NUM> also includes a potentiometer shaft <NUM> that is a rotation angle output shaft, a potentiometer base <NUM> that is a base body, and a potentiometer <NUM> that is a rotation angle detection unit.

The valve body <NUM> is made of synthetic resin and formed in a substantially cubic box shape. A substantially L-shaped first flow channel <NUM> is provided in a left wall portion 10a of the valve body <NUM>. A straight second flow channel <NUM> is provided in a front wall portion 10b of the valve body <NUM>. A substantially L-shaped third flow channel <NUM> is provided in a right wall portion 10c of the valve body <NUM>. The third flow channel is plane-symmetrical to the first flow channel <NUM>. An opening 11a of the first flow channel <NUM>, an opening 12a of the second flow channel <NUM>, and an opening 13a of the third flow channel <NUM> face the front direction (the forward direction from the paper in <FIG>, downward in <FIG>). The first flow channel <NUM>, the second flow channel <NUM>, and the third flow channel <NUM> communicate with a valve chamber <NUM> provided in the valve body <NUM>. As the flow channels that communicate with the valve chamber <NUM>, two or four or more flow channels may be provided.

The ball valve member <NUM> is formed in a hollow ball-like shape (spherical shape). The ball valve member <NUM> is made of, for example, metal or synthetic resin. The ball valve member <NUM> is rotatably supported by the seat members <NUM>, <NUM> (described later) and housed in the valve chamber <NUM>. At the rotational position illustrated in <FIG>, the ball valve member <NUM> has a first opening <NUM> open toward the left side, a second opening <NUM> open toward the front side, and a third opening <NUM> open toward the right side. A switching flow path <NUM> that connects the first opening <NUM>, the second opening <NUM>, and the third opening <NUM> to one another is provided inside the ball valve member <NUM>. The switching flow path <NUM> is formed in a substantially T-like shape in plan view. Alternatively, the ball valve member <NUM> may have, for example, only the first opening <NUM> and the second opening <NUM>, and may be provided with a switching flow path <NUM> that is substantially L-shaped in plan view and connects the first opening <NUM> and the second opening <NUM> to each other at the rotational position illustrated in <FIG>. Although the ball valve member <NUM> is used as a valve member in the present embodiment, a columnar valve member may be used.

The switching flow path <NUM> is configured to switch the connection of the first flow channel <NUM>, the second flow channel <NUM>, and the third flow channel <NUM> in accordance with the rotational position. Specifically, the switching flow path <NUM> connects the first flow channel <NUM>, the second flow channel <NUM>, and the third flow channel <NUM> to one another when the ball valve member <NUM> is at the rotational position illustrated in <FIG>. The switching flow path <NUM> connects the first flow channel <NUM> and the second flow channel <NUM> to each other when the ball valve member <NUM> is at a rotational position rotated <NUM> degrees clockwise in plan view from the rotational position illustrated in <FIG>. The switching flow path <NUM> connects the second flow channel <NUM> and the third flow channel <NUM> to each other when the ball valve member <NUM> is at a rotational position rotated <NUM> degrees counterclockwise in plan view from the rotational position illustrated in <FIG>.

A valve stem insertion hole <NUM> into which the valve stem <NUM> (described later) is inserted is provided in an upper portion of the ball valve member <NUM>. The valve stem insertion hole <NUM> is formed such that the ball valve member <NUM> rotates around an axis L that is a rotation axis of the ball valve member <NUM> as the valve stem <NUM> rotates. Specifically, the valve stem insertion hole <NUM> is formed in the same shape as the sectional shape (cross-sectional shape) in the direction orthogonal to the axial direction of an angular columnar portion <NUM> of the valve stem <NUM>. In the present embodiment, the valve stem insertion hole <NUM> is formed in a regular hexagonal shape (<FIG>).

The seat members <NUM>, <NUM> are made of, for example, synthetic resin such as polytetrafluoroethylene (PTFE) and are formed in an annular shape. The seat members <NUM>, <NUM> form a pair. The seat members <NUM>, <NUM> are housed in the valve chamber <NUM>. The seat members <NUM>, <NUM> are disposed to face each other with a gap in the X-axis direction. The seat members <NUM>, <NUM> rotatably support the ball valve member <NUM> in the valve chamber <NUM> with the ball valve member <NUM> interposed therebetween.

The sealing members <NUM>, <NUM> each are, for example, an O-ring made of an elastic material such as a rubber material. The sealing member <NUM> is disposed to be sandwiched in a compressed state between one of the seat members <NUM> and the left wall portion 10a of the valve body <NUM>. The sealing member <NUM> is disposed to be sandwiched in a compressed state between the other of the seat members <NUM> and the right wall portion 10c of the valve body <NUM>. In the present embodiment, the sealing member <NUM> is mounted in an annular groove 30a provided in the seat member <NUM>. Part of the sealing member <NUM> protrudes from the annular groove 30a. The sealing members <NUM>, <NUM> seal gaps between the valve body <NUM> and the ball valve member <NUM> together with the seat members <NUM>, <NUM>. Alternatively, the sealing members <NUM>, <NUM> may be omitted, and seat members <NUM>, <NUM> made of an elastic material such as a rubber material and also having a function of a sealing member may be employed.

The drive unit <NUM> includes a drive mechanism, a lower case <NUM>, and an upper case (not illustrated). The drive mechanism includes a combination of a motor (not illustrated) and a speed reducer that includes a gear <NUM>. The lower case <NUM> and the upper case are made of resin and in which the drive mechanism is housed. The upper case is attached to the lower case <NUM> by an attachment structure such as a screwing structure or a snap-fit structure. The drive unit <NUM> rotates the ball valve member <NUM> around the axis L via the valve stem (described later).

The lower case <NUM> integrally has a circular tubular bearing portion <NUM> at the center of a bottom wall 43a. The valve stem <NUM> is inserted into the bearing portion <NUM>. The bearing portion <NUM> rotatably supports the valve stem <NUM>. An inner peripheral wall portion 43b having a quadrangular tubular shape is provided on the bottom wall 43a of the lower case <NUM>. The inner peripheral wall portion 43b is disposed inside the valve body <NUM> and combined with an upper end portion of the valve body <NUM>. The inner peripheral wall portion 43b and the valve body <NUM> are joined (in the present embodiment, ultrasonically welded). Alternatively, the lower case <NUM> and the valve body <NUM> may be assembled with each other by a screwing structure or the like.

The valve stem <NUM> is made of synthetic resin and is formed in a columnar shape extending straight as a whole. The valve stem <NUM> includes a circular columnar portion <NUM> and the angular columnar portion <NUM> coaxially connected to a lower end of the circular columnar portion <NUM>. The valve stem <NUM> is disposed along the axis L.

The circular columnar portion <NUM> has an annular stopper portion <NUM> provided at a lower end portion of the circular columnar portion <NUM> and protruding radially outward. The stopper portion <NUM> is formed to have an outer diameter larger than the inner diameter of the bearing portion <NUM>.

Moreover, the circular columnar portion <NUM> has a groove provided in the lower end portion over the entire circumference at a position above the stopper portion <NUM>. An annular O-ring <NUM> made of a rubber material or the like is fitted to the groove. The circular columnar portion <NUM> is inserted into the bearing portion <NUM> and rotatably supported by the bearing portion <NUM>. The outer diameter of the circular columnar portion <NUM> is slightly smaller than the inner diameter of the bearing portion <NUM>. When the circular columnar portion <NUM> is inserted into the bearing portion <NUM>, the O-ring <NUM> seals a gap between the valve stem <NUM> and the bearing portion <NUM>. The sealing with the O-ring <NUM> prevents the fluid in the valve chamber <NUM> from leaking to the outside.

The gear <NUM> of the drive mechanism of the drive unit <NUM> is press-fitted onto an upper end portion of the circular columnar portion <NUM>. Moreover, the upper end portion of the circular columnar portion <NUM> is provided with a planar portion 51a for preventing the press-fitted gear <NUM> from slipping. The gear <NUM> may be attached to the valve stem <NUM> by a method other than press-fitting.

The angular columnar portion <NUM> is formed in a columnar shape having a regular hexagonal cross-sectional shape. The angular columnar portion <NUM> is inserted into the valve stem insertion hole <NUM> of the ball valve member <NUM>, and is attached to the ball valve member <NUM> along the axis L. The axis L of the ball valve member <NUM> serves as a rotation axis of the valve stem <NUM>. The valve stem <NUM> is rotated around the axis L as the gear <NUM> rotates. The valve stem insertion hole <NUM> is formed in the same regular hexagonal shape as the cross-sectional shape of the angular columnar portion <NUM>. Thus, the valve stem insertion hole <NUM> and the angular columnar portion <NUM> are fitted to each other. The ball valve member <NUM> is rotated around the axis L as the valve stem <NUM> rotates. The angular columnar portion <NUM> is formed to have an outer diameter smaller than that of the stopper portion <NUM>.

The angular columnar portion <NUM> may have a polygonal columnar shape such as a triangular columnar shape or a quadrangular columnar shape, or a columnar shape having a D-shaped section in which part of the side surface of a circular column is formed as a plane, other than the regular hexagonal shape. In this case, the valve stem insertion hole <NUM> is also formed in the same shape as the cross-sectional shape of the angular columnar portion <NUM>.

Moreover, an attachment hole <NUM> is provided at the center of an upward facing end surface 51b of the circular columnar portion <NUM>. The attachment hole <NUM> has a substantially circular columnar inner space along the axis L. The attachment hole <NUM> has a guide portion <NUM> and a press-fit portion <NUM> coaxially connected to the lower side of the guide portion <NUM> (<FIG>). The guide portion <NUM> and the press-fit portion <NUM> have circular cross-sectional shapes. The attachment hole <NUM> is formed such that the diameter of the guide portion <NUM> is larger than the diameter of the press-fit portion <NUM>. A step portion <NUM> is provided between the guide portion <NUM> and the press-fit portion <NUM>.

A small-diameter portion <NUM> that is a portion of the potentiometer shaft <NUM> (described later) is press-fitted into the press-fit portion <NUM>. A large-diameter portion <NUM> that is another portion of the potentiometer shaft <NUM> is in contact with the guide portion <NUM> slidably in the direction of the axis L (insertion direction) and the circumferential direction.

The potentiometer shaft <NUM> is made of metal such as stainless steel or brass, or synthetic resin such as polyphenylene sulfide (PPS). The potentiometer shaft <NUM> is a separate component from the valve stem <NUM>. The potentiometer shaft <NUM> is press-fitted into the attachment hole <NUM> of the valve stem <NUM>. The potentiometer shaft <NUM> is fixedly attached coaxially to the valve stem <NUM> by press-fitting. The potentiometer shaft <NUM> includes a fitting shaft portion <NUM>, an intermediate portion <NUM>, the large-diameter portion <NUM>, and the small-diameter portion <NUM> sequentially from the upper side to the lower side in the axial direction of the potentiometer shaft <NUM>.

The fitting shaft portion <NUM> is formed in a columnar shape (so-called D-cut shape) having a D-shaped section in which part of the side surface of a circular column is formed as a plane. The fitting shaft portion <NUM> is provided at one end portion of the potentiometer shaft <NUM>, and is fitted to a rotor <NUM> of the potentiometer <NUM> (described later). At least the distal end of the fitting shaft portion <NUM> protrudes from the attachment hole <NUM>. The intermediate portion <NUM> is formed in a circular columnar shape. The intermediate portion <NUM> connects the fitting shaft portion <NUM> and the large-diameter portion <NUM>. The large-diameter portion <NUM> is formed in a circular columnar shape having the same diameter (including substantially the same diameter) as the diameter of the guide portion <NUM> of the attachment hole <NUM>. The small-diameter portion <NUM> is formed in a circular columnar shape having a diameter smaller than the diameter of the large-diameter portion <NUM> and larger than the diameter of the press-fit portion <NUM> of the attachment hole <NUM>.

The potentiometer base <NUM> is made of synthetic resin. The potentiometer base <NUM> integrally has a base body portion <NUM> and a meter attachment portion <NUM>. The base body portion <NUM> is formed in a substantially flat plate shape. The base body portion <NUM> is fixed to bosses 43c, 43c protruding upward from the bottom wall 43a of the lower case <NUM> by screws <NUM>, <NUM>. The meter attachment portion <NUM> has a disk-shaped bottom wall portion 72a and a peripheral wall portion 72b standing upward from the peripheral edge of the bottom wall portion 72a. A recess 72c is provided at the center of the bottom wall portion 72a. The recess 72c is a portion to which the potentiometer <NUM> (described later) is attached. Moreover, a through hole 72d is provided in the recess 72c. The fitting shaft portion <NUM> of the potentiometer shaft <NUM> is passed through the through hole 72d. The diameter of the through hole 72d is larger than the diameter of the fitting shaft portion <NUM>.

The potentiometer <NUM> is a rotation angle sensor for detecting a rotation angle. The potentiometer <NUM> has the disk-shaped rotor <NUM> and a meter body portion <NUM>. The meter body portion <NUM> rotatably supports the rotor <NUM>. The meter body portion <NUM> is a signal output unit that outputs a signal (voltage) corresponding to the rotation angle of the rotor <NUM>. A fitting hole 81a having a D-like shape in plan view is provided at the center of the rotor <NUM>. The fitting shaft portion <NUM> of the potentiometer shaft <NUM> passes through the fitting hole 81a. The fitting shaft portion <NUM> is fitted to the fitting hole 81a so that the rotor <NUM> rotates together with the fitting shaft portion <NUM>. Rotation of the fitting shaft portion <NUM> makes the rotor <NUM> rotating. Thus, the potentiometer <NUM> detects the rotation angle of the potentiometer shaft <NUM> around the axis L.

In the flow channel switching valve <NUM>, the rotation of the motor of the drive unit <NUM> is output to the valve stem <NUM> through the gear <NUM>. The valve stem <NUM> is rotated around the axis L. The ball valve member <NUM> is rotated around the axis L as the valve stem <NUM> rotates, and is positioned at each rotational position. Thus, the connection of the flow channels corresponding to the rotational position is provided. Moreover, the potentiometer shaft <NUM> is rotated around the axis L together with the valve stem <NUM>. A signal corresponding to the rotation angle of the potentiometer shaft <NUM> is output from the potentiometer <NUM>. The rotational position of the ball valve member <NUM> can be monitored based on the signal output from the potentiometer <NUM>.

Next, an example of a method for assembling the flow channel switching valve <NUM> of the present embodiment will be described with reference to <FIG>.

<FIG> are views for explaining a method for assembling the flow channel switching valve of <FIG>, and are, sequentially, (<NUM>) a perspective view illustrating a state in which a gear is about to be attached after a valve stem is attached to a valve member, (<NUM>) a perspective view illustrating a state in which a potentiometer shaft is about to be inserted into an attachment hole of the valve stem, (<NUM>) a perspective view illustrating a state in which a potentiometer base is about to be fixed to a valve body, (<NUM>) a perspective view illustrating a state in which a potentiometer is about to be attached to the potentiometer base, (<NUM>) a perspective view illustrating a state in which the position of the potentiometer shaft is adjusted after the potentiometer is attached to the potentiometer base, and (<NUM>) a sectional view illustrating a state in which the potentiometer shaft is press-fitted into the attachment hole of the valve stem. <FIG> illustrates a state in which the potentiometer shaft has been inserted into the attachment hole of the valve stem (inserted state before being press-fitted), and <FIG> illustrates a state in which the potentiometer shaft has been press-fitted into and fixed to the attachment hole of the valve stem.

First, the ball valve member <NUM>, the seat members <NUM>, <NUM>, and the sealing members <NUM>, <NUM> are housed in the valve chamber <NUM> of the valve body <NUM>. Then, a jig (not illustrated) is inserted from the second flow channel <NUM> to position the ball valve member <NUM>. The angular columnar portion <NUM> of the valve stem <NUM> is inserted into the valve stem insertion hole <NUM> to attach the valve stem <NUM> to the ball valve member <NUM>. In this state, the valve stem <NUM> is disposed along the axis L (Z-axis direction). Then, the valve body <NUM> and the lower case <NUM> are assembled with each other while the circular columnar portion <NUM> of the valve stem <NUM> is inserted into the bearing portion <NUM>. Ultrasonic waves are applied to the lower case <NUM> to ultrasonically weld the lower case <NUM> to the valve body <NUM>.

Next, as illustrated in <FIG>, the circular columnar portion <NUM> of the valve stem <NUM> is press-fitted into the gear <NUM>, and other components (not illustrated) constituting the drive mechanism are assembled with the lower case <NUM>.

Next, as illustrated in <FIG>, the potentiometer shaft <NUM> is inserted into the attachment hole <NUM> of the valve stem <NUM>. Specifically, the potentiometer shaft <NUM> is inserted into the attachment hole <NUM> from the small-diameter portion <NUM>, and the large-diameter portion <NUM> is inserted into the attachment hole <NUM> following the small-diameter portion <NUM>. The diameter of the large-diameter portion <NUM> of the potentiometer shaft <NUM> is the same as the diameter of the guide portion <NUM>. The outer peripheral surface of the large-diameter portion <NUM> comes into contact with the inner peripheral surface of the guide portion <NUM> slidably in the insertion direction and the circumferential direction. As described above, since the large-diameter portion <NUM> and the guide portion <NUM> are provided, it is possible to prevent the potentiometer shaft <NUM> from being inserted in an inclined manner with respect to the valve stem <NUM>. The potentiometer shaft <NUM> is guided coaxially with the valve stem <NUM> along the axis L. Then, the potentiometer shaft <NUM> is further inserted until the small-diameter portion <NUM> abuts against the step portion <NUM> of the attachment hole <NUM>. At this time, the potentiometer shaft <NUM> is in the inserted state before being press-fitted. The fitting shaft portion <NUM> of the potentiometer shaft <NUM> protrudes from the attachment hole <NUM>.

Next, as illustrated in <FIG>, the fitting shaft portion <NUM> of the potentiometer shaft <NUM> is passed through the through hole 72d provided in the meter attachment portion <NUM> of the potentiometer base <NUM>. The potentiometer base <NUM> is disposed on the bosses 43c, 43c of the lower case <NUM>. Then, the screws <NUM>, <NUM> are screwed into the bosses 43c, 43c to fix the potentiometer base <NUM> to the lower case <NUM>. The lower case <NUM> is joined to the valve body <NUM> by ultrasonic welding. Thus, the potentiometer base <NUM> is fixed with respect to the valve body <NUM>.

Next, as illustrated in <FIG>, the fitting shaft portion <NUM> of the potentiometer shaft <NUM> is passed through the fitting hole 81a provided in the rotor <NUM> of the potentiometer <NUM>, and the fitting shaft portion <NUM> is fitted to the fitting hole 81a. The potentiometer <NUM> is disposed in the recess 72c of the meter attachment portion <NUM> of the potentiometer base <NUM>. The potentiometer <NUM> is attached and fixed by soldering or the like. Alternatively, the potentiometer base <NUM> may be fixed to the lower case <NUM> after the potentiometer <NUM> is attached to the potentiometer base <NUM>.

Next, the potentiometer shaft <NUM> is positioned around the axis L. That is, as illustrated in <FIG> and <FIG>, the potentiometer shaft <NUM> fitted to the fitting hole 81a of the rotor <NUM> is rotated around the axis L in the attachment hole <NUM> so that a correct signal is output from the potentiometer <NUM> with respect to the rotational position of the ball valve member <NUM>. After the positioning of the potentiometer shaft <NUM> is completed, as illustrated in <FIG>, the potentiometer shaft <NUM> is further inserted and pushed downward. In this manner, the small-diameter portion <NUM> of the potentiometer shaft <NUM> is press-fitted into the press-fit portion <NUM> of the attachment hole <NUM>. The potentiometer shaft <NUM> is fixed to the valve stem <NUM> in a state in which the potentiometer shaft <NUM> has been positioned.

Finally, the upper case (not illustrated) is attached to the lower case <NUM> to complete the flow channel switching valve <NUM>.

As described above, according to the flow channel switching valve <NUM> of the present embodiment, the potentiometer shaft <NUM> that is press-fitted into the attachment hole <NUM> provided in the end surface 51b of the valve stem <NUM> is supported rotatably around the axis L in the attachment hole <NUM> in the inserted state before being press-fitted into the attachment hole <NUM>. With this configuration, in the state in which the potentiometer shaft <NUM> has been inserted into the attachment hole <NUM>, the potentiometer shaft <NUM> can be rotated around the axis L to perform positioning. Accordingly, it is possible to further reduce an error of the output of the potentiometer <NUM> due to the tolerances of the ball valve member <NUM>, the valve stem <NUM>, and the potentiometer <NUM>. Thus, it is possible to effectively improve the precision of the rotational position of the ball valve member <NUM>.

Next, a flow channel switching valve <NUM> illustrated in <FIG> and <FIG> as a modification of the above-described flow channel switching valve <NUM> will be described.

Like the flow channel switching valve <NUM>, the flow channel switching valve <NUM> includes a valve body <NUM>, a ball valve member <NUM>, seat members <NUM>, <NUM>, sealing members <NUM>, <NUM>, a drive unit 40A, a valve stem <NUM>, a potentiometer shaft <NUM> that is a rotation angle output shaft, a potentiometer base <NUM> that is a base body, and a potentiometer <NUM> that is a rotation angle detection unit. The flow channel switching valve <NUM> has a configuration similar to or the same as that of the flow channel switching valve <NUM> except that the flow channel switching valve <NUM> includes the drive unit 40A instead of the drive unit <NUM> in the flow channel switching valve <NUM> described above. The drive unit 40A will be described below. In <FIG> and <FIG>, the ball valve member <NUM>, the seat members <NUM> and <NUM>, and the sealing members <NUM>, <NUM> are not illustrated.

The drive unit 40A includes a lower case <NUM> and a drive mechanism <NUM>. The drive mechanism <NUM> includes a motor <NUM>, a driving gear <NUM>, a first intermediate gear <NUM>, a second intermediate gear <NUM>, and the gear <NUM>.

The driving gear <NUM> is attached to a rotating shaft 46a of the motor <NUM>. The first intermediate gear includes a shaft portion 48a, a large-diameter gear portion 48b, a small-diameter gear portion 48c, and a small-diameter disk portion 48d. The second intermediate gear <NUM> includes a shaft portion 49a, a spur gear portion 49b, a worm portion 49c, and a large-diameter disk portion 49d.

The large-diameter gear portion 48b of the first intermediate gear <NUM> meshes with the driving gear <NUM>, and the small-diameter gear portion 48c of the first intermediate gear <NUM> meshes with the spur gear portion 49b of the second intermediate gear <NUM>. The worm portion 49c of the second intermediate gear <NUM> meshes with the gear <NUM>. Thus, the rotation of the rotating shaft 46a is transmitted to the gear <NUM> via the driving gear <NUM>, the first intermediate gear <NUM>, and the second intermediate gear <NUM>. The gear <NUM> is fixed to the valve stem <NUM> by press-fitting, and the valve stem <NUM> is rotated by rotation of the gear <NUM>. Then, the ball valve member <NUM> attached to the valve stem <NUM> is rotated and positioned at each rotational position.

A peripheral surface 48e of the small-diameter disk portion 48d of the first intermediate gear <NUM> and a peripheral surface 49e of the large-diameter disk portion 49d of the second intermediate gear <NUM> are in contact with each other. Thus, an inter-shaft distance between the first intermediate gear <NUM> and the second intermediate gear <NUM> is ensured, and noise, poor lubrication, gear damage, and gear wear can be suppressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Those skilled in the art may appropriately perform addition, deletion, or design change of a component with respect to the above-described embodiments, or may appropriately combine features of the embodiments. The modified or combined embodiments are included in the scope of the present invention as long as not impairing the scope of the present invention as defined by the appended claims.

Claim 1:
A flow channel switching valve (<NUM>, <NUM>) including a valve body (<NUM>) provided with a valve chamber (<NUM>) and a plurality of flow channels (<NUM>, <NUM>, <NUM>) that communicate with the valve chamber (<NUM>), a valve member (<NUM>) that is rotatably housed in the valve chamber (<NUM>) and that switches connection of the flow channels (<NUM>, <NUM>, <NUM>) in accordance with a rotational position, a valve stem (<NUM>) that is attached to the valve member (<NUM>) along a rotation axis of the valve member (<NUM>), and a drive unit (<NUM>) that rotates the valve member (<NUM>) via the valve stem (<NUM>), the flow channel switching valve (<NUM>, <NUM>) comprising:
a rotation angle output shaft (<NUM>) that is press-fitted into an attachment hole (<NUM>) provided in an end surface of the valve stem (<NUM>); and
a rotation angle detection unit (<NUM>) that detects a rotation angle of the rotation angle output shaft (<NUM>) around the rotation axis,
wherein the attachment hole (<NUM>) and the rotation angle output shaft (<NUM>) are configured such that the rotation angle output shaft (<NUM>) is supported rotatably around the rotation axis in the attachment hole (<NUM>) in an inserted state before being press-fitted into the attachment hole (<NUM>),
wherein the attachment hole (<NUM>) includes a press-fit portion (<NUM>) into which a first portion (<NUM>) of the rotation angle output shaft (<NUM>) is press-fitted, and a guide portion (<NUM>) with which a second portion (<NUM>) of the rotation angle output shaft (<NUM>) comes into contact slidably in an insertion direction and a circumferential direction, and
wherein the second portion (<NUM>) is formed in a circular columnar shape having the same diameter as the diameter of the guide portion (<NUM>), and
the first portion (<NUM>) is formed in a circular columnar shape having a diameter smaller than the diameter of the second portion (<NUM>) and larger than the diameter of the press-fit portion (<NUM>).