Stepping motor and motorized valve using it

To provide a stepping motor which can precisely and reliably detect stopping of a rotor with respect to a stopper with a simple structure, i.e., positioning of a base point of the rotor, and provide a motorized valve using it.The stepping motor includes a stator 55 and a rotor 57 rotationally driven by the stator 55, and a detection rotor 47 detecting a rotation position of the rotor 57. The detection rotor 47 is rotatably disposed on a co-axial center L with the rotor 57 and rotationally driven via a rotation drive mechanism between the rotor 57 and the detection rotor 47. The rotation drive mechanism has a drive play having a predetermined length or angle in the rotation direction.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a stepping motor and a motorized valve using it.

Description of the Conventional Art

Conventionally, in a motorized valve using a stepping motor, for example, reliable base point positioning of the stepping motor (it is also called initializing) is guaranteed by inputting a drive pulse signal which is over the maximum step numbers necessary to close the motorized valve. For example, Japanese Patent Application Laid-Open No. 2005-287152 discloses a solenoid coil device of a stepping motor of such a motorized valve. In this conventional technique, exciting coils, in which a pair of magnetic pole plate (magnetic pole teeth) is provided from the top and bottom inside thereof, are provided in the two-tiered up and down.

On the other hand, it has been known that some problems generate when continuing to input the drive pulse signal to a stepping motor after a rotor constituting the stepping motor is stopped by a stopper, or the like, at a base point position. These problems are generating of noise or vibration, and lowering of durability of the stepping motor.

For solving these problems, Japanese Patent No. 4,028,291 discloses a technique detecting contact of a rotor to a stopper at a time of the base point positioning of the stepping motor, and stopping the base positioning pulse energizing the drive coil.

In the drive device of the motorized valve disclosed in Japanese Patent No. 4,028,291, at a time of base point positioning of the motorized valve, the device outputs base point positioning pulse to the drive coil of a stator so as to return the rotor of the stepping motor to the base point position. At the same time, the device inputs a magnetic detection signal from a magnetic detection means. Then, the device recognizes a changing pattern of the magnetic detection signal corresponding to the difference of timing between when the stopper contacts and when the magnetic detection signal transfers from high level to low level or low level to high level. Then, the device detects the contact of the rotor to the stopper in the step corresponding to the changing pattern, and stops the pulse output for base point positioning.

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

On the other hand, as described above, after a rotor contacts a stopper at the base point position and stops, when the device continues to input the drive pulse signal, the rotor is attracted to an opposed phase (magnetic pole) at a certain step and reverses. Further, when the device continues to input the drive pulse signal more, the rotor reverses again and contacts the stopper again.

For example, a case that the magnetic pole pattern of the coil is repeated for each 8 steps by a predetermined excitation order to the stator coil, is described. As illustrated inFIG. 8, in step7to step4, the rotor rotationally drives at a predetermined angle for each input of the drive pulse signal, and the stopper on the rotor side approaches the stopper on the fixed side provided on the base point position of the rotor. Then, in step3, the stopper on the rotor side contacts the stopper on the fixed side and the rotor stops at the base point position. Then, from step2to step0, even when the drive pulse signal is input, the rotation drive is blocked, so that the rotor continues to stop (stepping) at the base point position. In addition, inFIG. 8, the mark drew by an imaginary line (two-dot chain line) indicates how the stopper on the rotor side continues to rotate when it is assumed that the stopper on the fixed side is not present.

However, when the excitation to the stator coil is transferred from step0to step7, the rotor is attracted to an opposed phase (magnetic pole) and reverses, so that the stopper on the rotor side leaves from the stopper on the fixed side (8 step reversion). That is, the stopper on the rotor side, which contacts the stopper on the fixed side in step2to step0, is attracted to the position indicated by the two-dot chain line. However, when the stopper on the rotor side transfers from the step0to step7again, the stopper on the rotor side is attracted to the following phase and the rotor reverses.

In the drive device disclosed in U.S. Pat. No. 4,028,291, the operations of the above contacting/reversing is digitized by using a Hall IC of an alternating type, or the like, and compared with a normal drive waveform, so that the stopping of the rotor is detected.

However, the above contacting/reversing operation is a periodic movement and there is a possibility that the drive waveform according to the contacting/reversing operation and the normal drive waveform are synchronized depending on the detection position. That is, there is a possibility that the drive waveform according to the contacting/reversing operation and the waveform of the normal drive are not changed so much. Thus, in the above method detecting the base point position of the rotor by using the contacting/reversing operation, a problem, in which the stopping of the rotor by contacting to the stopper cannot be reliably detected, may occur.

The present invention is made in view of the above problem and directed to provide a stepping motor which can precisely and reliably detect stopping of a rotor to a stopper with a simple structure, i.e., positioning of a base point. The present invention is also directed to provide a motorized valve using it.

Means to Solve the Problems

For solving the above problem, a stepping motor according to the present invention includes a stator, a rotor rotationally driven by the stator. The stepping motor further includes a detection rotor for detecting a rotation position of the rotor. The detection rotor is rotatably disposed on a co-axial center with the rotor and rotationally driven through a rotation drive mechanism between the rotor and the detection rotor. The rotation drive mechanism has a drive play having a predetermined length or angle in the rotation direction.

In a preferable embodiment, the stepping motor has a rotation stop mechanism for stopping the rotation of the rotor. The length or angle of the drive play of the rotation drive mechanism is equal to or greater than a reversion length or a reversion angle of the rotor when the rotation of the rotor is blocked by the rotation stop mechanism.

Further, in a preferable embodiment, the rotation drive mechanism includes a plurality of projections of the rotor disposed having a predetermined length interval or angle interval in a rotation direction, and another projection of the detection rotor disposed between a plurality of projections of the rotor.

Further, in a preferable embodiment, the rotation drive mechanism includes a drive play concave portion of the rotor having a predetermined length interval or angle interval in a rotation direction, and projections of the detection rotor loosely fitted in the drive play concave portion of the rotor.

Furthermore, in a preferable embodiment, urging force inhibiting rotation of the detection rotor is applied to the detection rotor and preferably, the urging force is generated by a magnetic material provided on an outside of the detection rotor.

Further, the motorized valve according to the present invention includes the above stepping motor, a valve main body, a valve body, and a conversion mechanism. The valve main body has a valve chamber and a valve port opening to the valve chamber. The valve body is for opening/closing the valve port and disposed movably up and down in the valve chamber. The conversion mechanism converses the rotation movement of the rotor to the up and down movement of the valve body. The stepping motor rotationally drives the rotor by the stator, moves the valve body up and down by the conversion mechanism, and stops the rotation of the rotor by a rotation stop mechanism when the valve body reaches at a predetermined position.

In a preferable embodiment, the predetermined position is a position in which the valve body closes the valve port or a position in which the valve body fully open the valve port.

Further, in a preferable embodiment, a can is fixed to the valve main body, and the rotor and the detection rotor is disposed in the can.

Effect of the Invention

According to the stepping motor and the motorized valve using it, the detection rotor detecting a rotation position of the rotor is rotatably disposed on a co-axial center with a rotation axis of the rotor, and rotationally driven by the rotor. A rotational drive mechanism between the rotor and the detection rotor has a drive play of a predetermined length or angle in the rotation direction. Thus, when the rotor reverses, the length or angle of the drive play inhibits the transmission of rotation drive force from the rotor to the detection rotor, so that even when the rotor contacts a stopper and vibrates, the vibration is not transmitted to the detection rotor. Therefore, by detecting signals based on the detection rotor, it can be reliably detected that, for example, the valve body reaches to a predetermined position, so that positioning of the base point of the rotor can be precisely performed. Further, the length or angle of the drive play in the rotation drive mechanism is equal to or greater than a reversion length or a reversion angle of the rotor. Thus, the transmission of the rotation drive force from the rotor to the detection rotor is reliably inhibited more, so that the positioning of the base point of the rotor can be more precisely performed. Furthermore, since urging force inhibiting the rotation of the detection rotor is applied to the detection rotor, the signal based on the detection rotor at a time of reversion of the rotor becomes stable. Thus, the detection of the contacting state of the rotor to the stopper can be preciously performed more.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The exemplary embodiment of the stepping motor according to the present invention and the motorized valve using the stepping motor will be described, referring to drawings as follows.

FIG. 1is a basic constitution of the exemplary embodiment of the motorized valve according to the present invention. In this figure, the motorized valve is a state of closing. The motorized valve1illustrated inFIG. 1is used in, for example, a heat pumping type heating and cooling system, or the like. Further,FIG. 2is a schematic view illustrating the basic constitution of the stepping motor adapted in the motorized valve illustrated inFIG. 1.FIG. 3is a cross-sectional view along a line A-A illustrated inFIG. 2.

The motorized valve1illustrated inFIG. 1mainly includes a valve chamber21, a valve main body20, a rod-shaped valve body25, and a stepping motor50. The valve main body20has a valve port22aopening to the valve chamber21. The rod-shaped valve body25is disposed movably up and down in the valve chamber21for opening/closing the valve port22a. The stepping motor50moves the valve body25up and down.

In the valve chamber21in the valve main body20, the valve port22ahaving a valve seat22opening to the valve chamber21is formed at a lower portion of the valve chamber21. A first inlet and outlet port11is opened on the side portion of the valve chamber21. A second inlet and outlet port12communicating to the valve port22ais opened at a lower portion of the valve port22a.

At an upper opening of the valve main body20, a lower end of a cylindrical can58having a ceiling portion is fixed. A lower end portion of a cylindrical guide bush26is press-fitted to an upper inner periphery portion of the valve main body20and the valve body25is slidably inserting-fitted inside the guide bush26. A male screw28is formed on an outer periphery of an upper reduced diameter portion26bof the guide bush26. A cylindrical valve body holder32is outer-fitted on a periphery of the male screw28. A female screw38is formed on an inner periphery of the valve body holder32. The male screw28of the guide bush26and the female screw38of the valve body holder32are screwed.

Further, an upper reduced diameter portion25bof the valve body25is fixed to a cylindrical rotation axis (a supporting axis)56by press-fitting, or the like, in a state of sildably inserting in an upper portion (a ceiling portion) of the valve body holder32. Further, a pressing coil spring34is disposed at an outer periphery of the upper reduced diameter portion25bof the valve body25, and between the ceiling portion of the valve body holder32and a step portion, which is between a lower large diameter portion25aand the upper reduced diameter portion25bof the valve body25. This coil spring34urges the valve body25downward (in the direction of valve closing).

On the other hand, a stepping motor50includes a yoke51, a bobbin52, a stator coil53, and a resin mold cover54, or the like. The stepping motor50has a stator55externally-fixed to a can58, and a rotor57disposed rotatably with respect to the can58inside the can58. The rotor57is formed, for example, by mixing a magnetic material and a resin, and is consisted of a magnet magnetized by N pole and S pole having a predetermined interval. A supporting ring36is integrally fixed on an upper end portion of the rotor57. An upper projection of the valve body holder32is caulking-fixed to the supporting ring36. Therefore, the rotor57, supporting ring36, and the valve body holder32are integrally connected, and slidably supported by the valve body25fixed with a rotation axis56via the coil spring34. Thus, the valve body25also moves up and down when the rotor57rotates and moves up and down.

Further, on the upper side of the rotor57and the inside the can58, a detection rotor47is disposed. The detection rotor47is placed on a projecting support portion56aformed on the rotation axis56of the rotor57, disposed relatively rotatably with respect to the rotation axis56of the rotor57, and co-axially to a rotation axial center L of the rotor57. The rotation drive force of the rotor57rotationally drives the detection rotor47. The detection rotor47has a same or a different diameter with a diameter of the rotor57, and is magnetized with a same pattern of the rotor57(a pattern in which the angle interval of N pole and S pole is the same as the pattern of the rotor57). The detection rotor47and the rotor57are disposed, separating having a distance in which each magnetic force does not affect each other. In addition, angle intervals of N pole and S pole of the magnetized pattern formed on outer periphery of the detection rotor47can be different with angle intervals of the rotor57.

On an upper surface of the rotor57, two projections57band57care disposed, having a predetermined length interval (or angle interval) R1in the rotation direction of the rotor57. On a lower surface of the detection rotor47, a rod-shaped projection47ais disposed, having a constitution in which the top end of the projection47ais disposed between the projections57band57c(refer toFIG. 2). Having such a constitution, in which the top end of the rod-shaped projection47ais disposed between the two projections57band57cof the rotor47, the detection rotor47is relatively slidable with respect to the rotor57inside the predetermined length interval (or angle interval) R1(that is, in a range of R1), (refer toFIG. 3). As described above, referring toFIG. 8, the interval R1is set so as to be equal to or greater than a length (reversion length) or an angle (reversion angle), in which the rotor57is reversed by the following phase (magnetic pole) after a rotor side stopper contacts a fixed side stopper.

In addition, a top end of the rotation axis56is supported by being inserted through a hole formed at a center portion of a support member48. The support member48is disposed, inscribing in the can58.

Further, a magnetic material46is disposed outside the detection rotor47. The urging force (it is also called as detent torque) inhibiting the rotation of the detection rotor47is applied by a magnetic field, which is formed on the periphery of the detection rotor47by the magnetic material46. Furthermore, at the outside of the detection rotor47, a Hall IC45detecting change of the magnetism by the detection rotor47is disposed. The rotation position of the rotor57is detected based on an output signal detected by the Hall IC45.

Further, a stopper (fixed side stopper)27is fixed on the outside of the guide bush26and a stopper37is fixed on the outside of the valve body holder32. When the valve body25reaches a predetermined position, for example, when the rotor57rotationally lowers to a position in which a valve body portion24, which is a lower end of the valve body25, closes the valve port22a, the stopper37stops the rotor57to rotate more. That is, in the present exemplary embodiment, a rotation stop mechanism59to stop the rotation of the rotor57is constituted by the stopper27of the guide bush26and the stopper37of the valve body holder32.

In the above motorized valve1, when the drive pulse signal is supplied to the stator55in a first embodiment (drive embodiment in closing valve direction), the rotor57, the valve body holder32, the rotational axis56, and the like, rotate in one direction (for example, inFIG. 1, the clockwise rotation viewing from the upper side). According to this action, the valve body holder32is lowered by screw-feeding the male screw28of the guide bush26and the female screw38of the valve body holder32. Then, the valve body portion24of the valve body25is pushed to the valve port22avia the press-coil spring34, so that the valve port22ais closed. A conversion mechanism to convert the rotation movement of the rotor57of the stepping motor50to the up and down movement of the valve body25is constituted with the male screw28of the guide bush26and the female screw38of the valve body holder32. At this time, the projection47aon the lower surface of the detection rotor47contacts the projection57con the upper surface of the rotor57and the drive force is transmitted from the rotor57to the detection rotor47via the projection57cand the projection47a. Then, the detection rotor47follows the rotor57and rotates in one direction. In addition, the detection rotor47lowers according to the rotation of the rotor57, maintaining the interval between the detection rotor47and the rotor57to be substantially constant.

When the valve port22ais closed, the stopper37of the valve holder32impinges the stopper27of the guide bush26. Even when the drive pulse signal is supplied to the stator55, the lowering of the valve holder32is forcibly prevented and the rotation of the rotor57and the detection rotor47are stopped in a state that the projection47aof the detection rotor47contacts projection57cof the rotor57.

Further, when the drive pulse signal is supplied more to the stator55, the rotor57is attracted to an opposed phase (magnetic pole) in a certain step and reverses. For example, the stopper27of the guide bush26separates from the stopper37of the valve holder32. On the other hand, the detection rotor47is relatively rotatable with respect to the rotor57. The interval R1between the projection57band the projection57cof the rotor57in the rotation direction is set, in its inside, to have a length (or angle), in which the rod-shaped projection47aof the detection rotor47can rotate equal to or greater than the reversion length (or reversion angle) of the rotor57(refer toFIG. 3). Therefore, even when the rotor57is attracted to the opposed phase and reverses, the projection47aof the detection rotor47does not contact the projection57band the drive force is not transmitted from the rotor57to the detection rotor47, so that the detection rotor47urged by the magnetic material46does not rotate. That is, the detection rotor47once stopped at a position, in which the valve body25closes the valve port22a, continues to stop at the position even when the rotor57reverses. The magnetism generated in the detection rotor47is detected by using the Hall IC45and thereby, it can be reliably detected that the lowering of the valve body25stops and the valve port22ais closed (the positioning of the base point of the rotor57).

Further, then, when energization to the stator55is made to stop, the vibration and the noise by contacting the stopper27of the guide bush26to the stopper37of the valve body holder32is can be inhibited.

Furthermore, since the magnetic material46is disposed outside the detection rotor47, by the effect of the magnetism between the detection rotor47and the magnetic material46, the detection rotor47continues to stop at the position even when the rotor reverses.

In addition, the operation from the closing valve state of the valve port22ato the opening valve state of the valve port22a, i.e., in the second embodiment (the drive embodiment in the opening the valve embodiment) will be described as follows. When the drive pulse signal is supplied, and the rotor57, the valve body holder32, and the rotation axis56, or the like, are rotated in another direction to the guide bush26fixed with respect to the valve main body20(for example, inFIG. 1, in anti-clockwise direction viewing from the upper side), the valve body holder32rises by screw-feeding the male screw28of the guide bush26and the female screw38of the valve body holder32. The valve body portion24of the valve body25separates from the valve port22a, so that the valve port22ais opened and, for example, a refrigerant passes through the valve port22a. At this time, after the detection rotor47continues to stop only a partial step, the projection47aon the lower surface of the detection rotor47contacts the projection57bon the upper surface of the rotor57. Then, the drive force is transmitted from the rotor57to the detector rotor47via the projection57band the projection47a, so that the detection rotor47follows the rotor57and rotates in another direction.

Then, referring toFIG. 4, when the rotor57, or the like, rotates in one direction (for example, clockwise direction viewing from the upper side inFIG. 1), the drive of the detection rotor47and the rotor57will be described in more detail. For example, similarly as the case inFIG. 8, the case that the patterns of the magnetic pole of a stator coil are repeated for each 8 step by a predetermined excitation order to the stator coil, will be described. At first, in step7illustrated in the upper side inFIG. 4, the rotor57rotates in one direction based on the drive pulse signal in the stator55, so that the projection57cprovided on the upper surface of the rotor57contacts the projection47aprovided on the lower surface of the detection rotor47.

Then, in step7to step4, when the drive pulse signal is input, the drive force is transmitted from the rotor57to the detection rotor47via the projection57cand the projection47a. The detection rotor47rotationally drives with rotor57against the urging force by the magnetic material46. By this rotation drive, the stopper37of the valve body holder32(stopper on the rotor57side) approaches the stopper27of the guide bush26(stopper on the fixed side). Then, the projection57cof the rotor57and the projection47aof the detection rotor47approach the position corresponding to the base point position of the rotor57. In step3, when the drive pulse signal is input, the stopper37of the valve body holder32(stopper on the rotor57side) contacts the stopper27of the guide bush26(stopper on the fixed side). Then, the rotor57stops at the base point position in a state that the projection57cof the rotor57contacts the projection47aof the detection rotor47. Then, in step2to step0, even when the drive pulse signal is input, the rotations of the rotor57and the detection rotor47are inhibited, so that the rotor57continues to stop at the base point position (stepping).

Next, when the drive pulse signal is input after transferring from step0to step7, as illustrated in lower side view inFIG. 4, the rotor57is attracted to the opposed phase (magnetic pole) and reverses. As the result of this, the stopper37of the valve body holder32(stopper on the rotor57side) separates from the stopper27of the guide bush26(stopper on the fixed side). On the other hand, the detection rotor47is relatively rotatable to the rotor57. The interval R1between the projection57band the projection57cof the rotor57in the rotation direction, is set, in its inside, so as to have the position that the rod-shaped projection47aof the detection rotor47can rotate equal to or greater than the reversion length (reversion angle) of the rotor57. Therefore, even when the rotor57is attracted to the opposed phase and reverses, the drive force is not transmitted from the rotor57to the detection rotor47and the detection rotor47continues to stop at the base point position of the rotor57. The detection rotor47, which once stops at the base point position of the rotor57, continues to stop at the base point position of the rotor57even when the contacting/reversing action generates repeatedly. By detecting the magnetism generated in the detection rotor47using the Hall IC45, it can be reliably detected that the rotor57reaches at the predetermined base point position even when the rotor reverses (performing the base point positioning of the rotor57).

Referring toFIG. 5, the drive of the detection rotor47and the rotor57of the stepping motor50and the output signal of the Hall IC45, when the rotor57, or the like, rotates in one direction (for example, inFIG. 1, clockwise rotation viewing from the upper side), will be described in detail more. The stepping motor50includes a stator in which a coil is provided in two tiered up and down. The coil has a pair of magnetic pole teeth from up and down inside thereof. The stepping motor50is the similar one disclosed in Japanese Patent Application Laid-Open No. 2005-287152.

At first, the rotor57rotates in one direction based on the drive pulse signal of the stator55, so that the projection57cprovided on the upper surface of the rotor57contacts the projection47aprovided on the lower surface of the detection rotor47({circle around (1)} inFIG. 5). When N pole and S pole in the stator55are replaced sequentially in a state that the projection57cof the rotor57contacts the projection47aof the detection rotor47, the drive force is transmitted from the rotor57to the detection rotor47. Via57cand47a, the rotor57made of magnet rotationally moves and the detection rotor47rotates with the rotor57. The output signal of a rectangular wave form changing, for example, 0 V to 5 V, 5 V to 0 V, or 0 V to 5 V is detected by the Hall IC45({circle around (1)} to {circle around (10)} inFIG. 5).

In the next step, the stopper37of the valve body holder32(stopper on the rotor57side) contacts the stopper27of the guide bush26(stopper on the fixed side) and the rotations of the rotor57and the detection rotor47are inhibited in the state that the projection57cof the rotor57contacts the projection47aof the detection rotor47(corresponding to {circle around (11)} inFIG. 5, and step3inFIG. 4). Even when N pole and S pole of the stator55are replaced sequentially in a state that the stopper37of the valve body holder32(stopper on the rotor57side) contacts the stopper27of the guide bush26(stopper on the fixed side), the rotor57and the detection rotor47do not rotate and continue to stop at the base point position of the rotor57. The Hall IC45detects a constant voltage, for example, 5 V in this condition (corresponding to {circle around (12)} to {circle around (14)} inFIG. 5, and step2to step0inFIG. 4).

In the next step, N pole and S pole of the rotor57are attracted to N pole and S pole of the opposed phase of the stator55(the magnetic pole), and the rotor57reverses one direction to the opposed direction (another direction) by only a reversion length of 4 steps. The detection rotor47is relatively rotatable with respect to the rotor57and the interval R1between the projection57band the projection57cof the rotor57is set to have interval in which the rotor57can idle equal to or greater than the reversion length (or the reversion angle). Therefore, even when the rotor57is attracted to the opposed phase and reveres by the reversion length (or the reversion angle), the projection47aof the detection rotor47does not contact the projection57cand the projection57bof the rotor57and the detection rotor47does not reverse, following the reversion of the rotor57. The detection rotor continues to stop at the base point position of the rotor57and the Hall IC45detects a constant voltage, for example, 5 V at this condition (corresponding to {circle around (15)} inFIG. 5and step7inFIG. 4).

Then, even when N pole and S pole of the stator55are replaced and the rotor57rotates, the projection47aof the detection rotor47is disposed between the projection57band the projection57cof the rotor57, so that the detection rotor47continues to stop at the base point position of the rotor57. At this time, since the urging force to inhibit the rotation of the detection rotor47is applied by the magnetic field formed at the periphery of the detection rotor47by the magnetic material46, the Hall IC45detects a constant voltage, for example, 5 V (corresponding to {circle around (16)} inFIG. 5, and step6inFIG. 4). By detecting the constant voltage of the Hall IC45, it can be reliably detected that the rotor57reaches the predetermined base point position (performing the positioning of the base point position of the rotor57).

In addition, when the rotor57rotates to another direction (for example, inFIG. 1, anti-clockwise direction), the detection rotor47continues to stop by a certain step, i.e., the detection rotor47continues to stop, having a predetermined drive play. At a certain step, the projection57bprovided on the upper surface of the rotor57contacts the projection47aprovided on the lower surface of the detection rotor47. Then, the drive force is transmitted from the rotor57to the detection rotor47via the projection57band the projection47a, so that the detection rotor47rotates with the rotor57. The Hall IC45provided outside of the detection rotor47detects the output signal having a rectangular wave.

As described above, in the present exemplary embodiment, a rotational drive mechanism transmitting rotationally drive force from the rotor57to the detection rotor47is constituted by two projections57band57cprovided on the upper surface of the rotor57and the rod-shaped projection47aprovided on the lower surface of the detection rotor47. The rotation drive mechanism has a drive play having a predetermined length or angle in the rotation direction of the rotor47. In particular, the drive play has a length or an angle equal to or greater than the reversion length or reversion angle of the rotor57. Having this constitution, when the rotor57reverses, the transmission of the rotationally drive force from the rotor57to the detection rotor47is suppressed by the length or the angle of the drive play. Thus, it can be reliably detected that the valve body25closes the valve port22a, (precisely performing the positioning of the base point of the rotor57). Thus, it can be inhibited to generate continuous noises and vibration of the motorized valve and lower the durability of the motorized valve. In addition, unnecessary drive of the stator55of the stepping motor50can be suppressed.

In addition, in the above exemplary embodiment, when the valve body25closes the valve port22a, the stopper37of the valve body holder32impinges to the stopper27of the guide bush26, and the rotation of the rotor57stops at the closing valve position of the valve port22aby the rotation stopping mechanism. However, the motorized valve may have a constitution in which a slight leakage of a fluid is allowed at a time of closing the valve. Further, the rotation stop mechanism to stop the rotation of the rotor57can be set at an arbitrarily position, for example, a fully opened position of the valve body25(the end position of the rotor57) and the desired rotation position of the rotor57can be detected.

Further, in the above exemplary embodiment, the detection rotor47is placed on the support portion56aformed in the rotation axis56of the rotor57and disposed relatively rotatably to the rotation axis56of the rotor57. However, the motorized valve may have a constitution in which, for example, the detection rotor47and the rotation axis56are integrated and the rotation axis56is loosely fitted to the upper reduced diameter portion25bof the valve body25. The detection rotor47and the rotation axis56are integrated and relatively rotatably with respect to the rotor57, the support ring36, and valve body holder32.

FIG. 6is a view schematically illustrating a basic constitution of another exemplary embodiment of a stepping motor applied in the motorized valve inFIG. 1.FIG. 7is a cross-sectional view along a line B-B illustrated inFIG. 6.

The stepping motor50A in the exemplary embodiment illustrated inFIG. 6andFIG. 7have different constitutions of the rotation drive mechanism and the rotation stop mechanism with respect to the stepping motor50illustrated inFIG. 2andFIG. 3. The other constitutions are almost the same as the stepping motor illustrated inFIG. 2andFIG. 3. Therefore, the same codes are attached to the same constitutions of the stepping motor50illustrated inFIG. 2andFIG. 3and the detailed explanations are omitted.

On the upper surface of the rotor57A illustrated inFIG. 6, a concave portion (drive play concave portion)57Ad having a predetermined length interval (or angle interval) in the rotation direction of the rotor57A is formed. On the lower surface of a detection rotor47A disposed on the upper side of the rotor57A, a rod-shaped projection47Aa, in which a top end of the projection47Aa is loosely fitted in the concave portion57Ad of the rotor57A, is provided. The concave portion57Ad is formed inside of an outer edge of the upper surface of the rotor57A. Since the top end of the rod-shaped projection47Aa is loosely fitted in the concave portion57Ad like this constitution, the detection rotor57A is relatively rotatable to the rotor57A in the predetermined length (or angle) in the rotation direction of the rotor57A. The predetermined length (or angle) is the length interval (or angle interval) R2between the side surface57Ac and the side surface57Ac of the concave portion57Ad of the rotor57A. In the inside of R2(i.e., within the range R2), the detection rotor47A is relatively rotatable with respect to the rotor57A (refer toFIG. 7). Similar to the above interval R1, the interval R2is set so as to have a length (or angle), in which the rod-shaped projection47Aa can rotate equal to or greater than the reversion length (or reversion angle) of the rotor57A.

In a state that the rod-shaped projection47Aa of the detection rotor47A contacts the side surface57Ac of the concave portion57Ad of the rotor57A, when the rotor57A rotationally drives in one direction (for example, inFIG. 6, the clockwise direction viewing from the upper side), the drive force is transmitted from the rotor57A to the detection rotor47A. The detection rotor47A follows the rotor57A and forcibly rotates in the above one direction. On the other hand, in a state that the rod-shaped projection47Aa of the detection rotor47A contacts the side surface57Ab of the concave portion57Ad of the rotor57A, the rotor57A rotationally drives in another direction (for example, inFIG. 6, the anti-clockwise direction viewing from the upper side), the detection rotor47A follows the rotor57A and forcibly rotates in the above another direction.

Further, a stopper58Aa is fixed on the lower side of the rotor57A of the can58. A stopper57Aa is provided on a lower surface of the rotor47A. When the rotor57A rotates only a predetermined rotation number of times in the one direction, the stopper57Aa contacts the stopper58Aa to stop the rotation of the rotor57A. That is, in the exemplary embodiment inFIG. 6andFIG. 7, a rotation stop mechanism59A stopping the rotation of the rotor57A is constituted by the stopper57Aa provided on the rotor57A and the stopper58Aa provided inside the can58.

In this way, in the exemplary embodiment illustrated inFIG. 6andFIG. 7, a rotation drive mechanism transmitting the rotation drive force from the rotor57A to the detection rotor47A is constituted by the concave portion57Ad provided on the upper surface of the rotor57A and the rod-shaped projection47Aa provided on the lower surface of the detection rotor47A. The rotation drive mechanism has a drive play having a predetermined length or angle in the rotation direction of the rotor57A. For example, the drive play has a length or angle equal to or greater than a reversion length or reversion angle. Having this constitution, when the rotor57A reverses, the transmission of the rotation drive force from the rotor57A to the detection rotor47A is inhibited only by the length or angle of the drive play. Thus, even when the drive current to the stator55is continued to supply after the rotor57A is forcibly stopped by the rotation stop mechanism59A, the rotor57A only vibrates and the detection rotor47A continues to stop. In this state, the magnetic material45detects precisely that the rotor57A contacts the stopper and the positioning of the base point of the rotor57A can be precisely performed. Thus, it is possible to suppress, for example, the generation of the continuous noise and vibration of the motorized valve, and lowering of the durability of the motorized valve. Further, it is possible to suppress unnecessary drive of the stator of the stepping motor.

In addition, in the above exemplary embodiments, the embodiment that two projections57band57cdisposed, having an interval in the rotation direction, are provided on the rotor57, and the projection47adisposed between the projections57band57cof the rotor57is provided on the detection rotor47, is described. Further, the embodiment that the concave portion57Ad is provided on the rotor57A, and the projection47Aa loosely fitted in the concave portion57Ad on the rotor57A is provided on the detection rotor47A. The concave portion57Ad has a predetermined length interval (or angle interval) in the rotation direction of the rotor57A. However, some other modified constitutions can be performed. For example, a constitution that a plurality of projections disposed, having intervals in the rotation direction, are provided on the detection rotor47and projections disposed between a plurality of projections of the detection rotor47are provided on the rotor57, can be performed. Further, a constitution that a concave portion having a predetermined length interval (or an angle interval) in the rotation direction is provided on the detection rotor47A and a projection loosely fitted in the concave portion of the detection rotor47A is provided on the rotor57, can be performed. It is possible to arbitrarily change the position and the shape of the projection or the concave portion of the rotor.

Further, in the above exemplary embodiments, when the rotor57or57A reversely rotates, for inhibiting the detection rotor47or47A to rotate together with the rotor57or57A, the interval R1or R2is made to have a length (or angle) equal to or greater than the reversion length (or the reversion angle) of the rotor. The interval R1is between the projections57cand57bon the rotor57. The interval R2is between the side surfaces57Ab and57Ac in the concave portion57Ad on the rotor57A. However, even when R1or R2is made to have a length (or angle) smaller than the reversion length (or the reversion angle) of the rotor, there is a range in which the detection rotor47or47A does not rotate to follow the rotor57or57A (i.e., there is a drive play). Thus, in this case, it can be detected that the drive waveform is clearly different from a conventional drive waveform, so that the positioning of the base point of the rotors57and57A can perform precisely.

Further, in the above exemplary embodiment, the rotation stop mechanism for stopping the rotation of the rotor is constituted by the stopper37provided in the valve body holder32and the stopper27provided in the guide bush26, or the stopper57Ac provided in the rotor57A and the stopper58Aa provided in the can58. However, if the rotation of the rotor disposed inside the stator can be stopped, the constitution of the rotation stop mechanism can be changed arbitrarily.

Further, in the above embodiment, the rotation of the rotor is inhibited by the magnetic field formed in the periphery of the rotor by the magnetic material46. However, the rotation of the rotor can be inhibited by an appropriate urging force, for example, frictional resistance, or the like.

Furthermore, in the above exemplary embodiment, the stepping motor according to the present invention is applied in the motorized valve and the embodiment, in which the base point positioning of the rotor is performed when the valve body reaches a predetermined position, is described. However, the stepping motor according to the present invention is applicable to other equipment other than the motorized valve, which is necessary to detect the predetermined rotation position of a rotor.

EXPLANATION OF NUMERALS