JP6598366B2 - Stepping motor, watch movement, watch - Google Patents

Description

The present invention also relates stepping motor, the watch movement, a time meter.

  Conventionally, an analog electronic timepiece has been used in which display hands such as an hour hand and a minute hand are driven to rotate by a motor driving device. The motor drive device includes a stepping motor that rotationally drives the display hands and a drive unit that rotationally drives the stepping motor.

  The stepping motor includes a stator having a positioning hole (inner notch) that determines a rotor through hole and a stop position of the rotor, a rotor rotatably disposed in the rotor through hole, a magnetic core that contacts the stator, and a magnetic core. And a coil wound around.

  By alternately supplying drive pulses having different polarities from the drive circuit to the coils, leakage magnetic fluxes having different polarities are alternately generated in the stator, thereby causing the stepping motor, that is, the rotor to rotate 180 degrees in a predetermined direction (forward direction). And the rotor is stopped at a position corresponding to the positioning portion.

  In general, in order to easily obtain a leakage magnetic flux for driving the rotor, narrow portions with a narrow width are formed at two locations (180 degree intervals) around the rotor through-hole formed to dispose the rotor. An integrated stator that is easy to saturate the magnetic flux by using it is used.

  As a technique to make it easy to obtain the leakage magnetic flux that drives the rotor, first, the stator is divided into two parts by cutting it at two places (180 degree intervals) around the rotor through-hole where the cross-sectional area of the magnetic path is minimized. A so-called two-body type stator is known in which a slit material made of a low magnetic permeability material or a non-magnetic material is inserted into the cut portion and then welded and joined to reduce the magnetic permeability of the narrow portion. (See Patent Document 1).

Japanese Examined Patent Publication No. 5-56109

However, the conventional techniques still have problems in the following points.
In the case of an integrated stator in which narrow portions are formed at two positions around the rotor through-hole described above, as a driving principle of the rotor, first, the narrow portion is saturated with a magnetic flux, and the stator is magnetically divided to obtain two magnetic poles. After making it into pieces, leakage magnetic flux flows into the rotor and the rotor rotates. That is, the magnetic flux generated from the coil at the time of current supply is consumed in the narrow portion (electric power is consumed due to the saturation of the magnetic flux in the narrow portion), so that there is a problem that magnetic flux loss to the narrow portion occurs. there were.

  In addition, since the narrow portion exists, the magnetic flux from the rotor itself is also consumed in the narrow portion, so that it becomes difficult to obtain the peak of the magnetic potential, and the rotor is magnetically stopped and held. The holding power of will decrease. As a result, the operation of stopping the rotor at the position corresponding to the positioning portion may become unstable, and further, the rotor may rotate (step out) beyond 180 degrees.

In the technique described in Patent Document 1, since the stator is divided into two parts by machining and then joined by welding, distortion and displacement of members are likely to occur due to mechanical stress or welding process. Therefore, there is a problem that an error occurs in the distance between the rotor and the stator. For this reason, there are problems that problems such as deviation of the stop position of the rotor and deterioration of rotational accuracy are likely to occur.
Further, when the outer shape of the stator is distorted, the flatness of the stator is lowered, and the contact area between the coil and the stator is reduced, and the mutual position between the rotor and the stator is liable to occur. As a result, the magnetic efficiency may be reduced, or the stator may be damaged during the assembly process, which may cause a reduction in product quality.

Accordingly, the present invention has been made in view of such circumstances, and a stepping motor capable of reducing power consumption (power saving) and improving the stability of rotor rotation driving with high holding force. , and an object thereof is to provide a watch movement, the watch.

As a result of intensive studies to solve the above problems, the inventors of the present invention formed a Cr diffusion region composed of a molten and solidified portion of Cr, which is a nonmagnetic material, in a part of the magnetic path provided around the rotor through hole. Then, it has been found that by reducing the magnetic permeability of the region, the power consumption can be reduced and the holding power can be improved.
The gist of the present invention obtained by the findings is as follows.

[1] A stator formed of an integral Fe—Ni alloy, provided with a rotor through-hole, and provided with a magnetic path around the rotor through-hole, and in the rotor through-hole a rotatably disposed rotor, a coil provided in the stator, a stepping motor with, Cr diffusion region consisting of melt-solidified portion of Cr in a part of the magnetic path be formed The Cr diffusion region is formed in the irradiation direction irradiated with the laser when forming the Cr diffusion region, and is not formed on the side opposite to the irradiation side from the irradiation side irradiated with the laser. Feature stepping motor.
[2] In the Cr diffusion region, in the irradiation direction irradiated with the laser when forming the Cr diffusion region, the diameter of the region having a high weight ratio of Cr is different from the irradiation side than the irradiation side irradiated with the laser. The stepping motor according to the above [1], wherein the facing side is smaller.

According to the stepping motor described in [1] or [2] above, the non-austenite single phase is diffused by melting Cr in a part of the magnetic path provided around the rotor through hole. Since the magnetic region is formed, the magnetic permeability of the region can be reduced. As a result, since the magnetic flux consumed in the region is greatly reduced, it is possible to efficiently secure the leakage magnetic flux that drives the rotor and to save power.
In addition, according to the stepping motor described in [1] or [2] above, consumption of magnetic flux generated from the rotor itself is suppressed in the Cr diffusion region due to the low permeability of the Cr diffusion region, and loss of magnetic potential is caused. Therefore, the holding force for magnetically stopping and holding the rotor can be increased, and the stability of the rotational drive of the rotor can be improved.
Further, in the conventional integrated stator, it is necessary to rotate the rotor with one polarity and then rotate the rotor with the other polarity. In this case, the residual magnetic flux in the narrow portion is canceled out and the narrow portion is saturated with the magnetic flux. Thus, the stator must be magnetically divided into two pole pieces. In particular, when performing high-speed hand movement, it is necessary to finish the rotation of the rotor including the cancellation of the residual magnetic flux in a short period of time. However, according to the stepping motor described in [1] or [2] above, Since the magnetic flux is greatly reduced, the time required for canceling the residual magnetic flux can be shortened, so that the drive frequency can be increased.
Furthermore, according to the stepping motor described in [1] or [2] above, since the stator is integrally formed as a structure, mechanical stress and welding that have been a concern when manufacturing a conventional two-body type stator. -It is possible to avoid the occurrence of distortion and member misalignment due to the joining process, and it is possible to prevent a decrease in magnetic efficiency, damage to the stator, and a decrease in product quality.
Furthermore, according to the stepping motor described in [1] or [2] above, since the stator is integrally formed, there is no welded portion or joint portion where mechanical stress tends to be concentrated, and deterioration of strength is prevented. it can.

[ 3 ] The stator is provided with a narrow portion formed so that a cross-sectional area of the magnetic path is narrower than other portions, and the Cr diffusion region is formed in at least a part of the narrow portion. The stepping motor according to [1] or [2] above, wherein

According to the invention described in [ 3 ] above, a narrow portion is provided in a part of the magnetic path provided around the rotor through hole, and the Cr diffusion region is formed in at least a part of the narrow portion. Therefore, the leakage magnetic flux for driving the rotor can be secured more efficiently, and the power consumption can be greatly reduced.

[4] The melt-solidified portion includes the narrow portion, the [3, characterized in that provided in the notched portion that does not interfere with the provided rotor through holes for stable position securing of the rotor ] The stepping motor described in the above.

According to the invention described in [ 4 ] above, the melt-solidified portion does not hinder the function of securing a stable position in the rotation control of the rotor.

[ 5 ] The stepping motor according to any one of [1] to [ 4 ], wherein Cr is contained in the Cr diffusion region in an amount of 15% by mass to 80% by mass.

According to the invention described in [ 5 ] above, the magnetic permeability of the Cr diffusion region can be significantly reduced.

[ 6 ] The stepping motor according to [ 5 ], wherein the Cr diffusion region contains 18 mass% or more and 55 mass% or less of Cr.

According to the invention described in [ 6 ], the magnetic permeability of the Cr diffusion region can be significantly reduced.

[ 7 ] A timepiece movement comprising: the stepping motor according to any one of [1] to [ 6 ] above; and a hand that displays time by rotating by the stepping motor.

[ 8 ] A timepiece comprising the timepiece movement described in [ 7 ] above.

According to the inventions described in [ 7 ] and [ 8 ] above, it is possible to provide a timepiece movement and a timepiece having excellent magnetic characteristics by providing a stepping motor having both power saving and high holding power.

  According to the present invention, there are provided a stepping motor, a timepiece movement, a timepiece, and a manufacturing method of a stepping motor capable of reducing power consumption (power saving) and improving the stability of rotational driving of a rotor with high holding force. Can be provided.

It is a block diagram common to the stepping motor which concerns on this embodiment, a stepping motor drive device, the movement for timepieces, and a timepiece. It is a front schematic diagram of the stepping motor according to the present embodiment. FIG. 3A is a graph showing the change over time in the current value of the coil when the output condition of laser irradiation is changed (the volume of the Cr diffusion region is changed) (vertical axis: current value of the coil (mA). ), Horizontal axis: time (msec)), and FIG. 3B is a schematic view of a stator in which a conventional “narrow portion” is formed without melting and diffusing Cr, and FIG. FIG. 5 is a schematic view of a stator divided into two parts by cutting a conventional “narrow part”. It is a schematic diagram for demonstrating the form of Cr spreading | diffusion area | region. It is a schematic diagram for demonstrating the state of the magnetic potential by a magnetic pole angle. It is a front schematic diagram of the stepping motor according to the present embodiment. It is a schematic diagram for demonstrating the manufacturing method of the stepping motor which concerns on this embodiment. It is a scanning electron microscope (Scanning Electron Microscope, SEM) image of a cross section perpendicular to the thickness direction of Cr diffusion regions 210 and 211 in the example of # 2. FIG. 9 is a scanning electron microscope image in which FIG. 8 is partially enlarged. It is a scanning electron microscope (Scanning Electron Microscope, SEM) image of a cross section perpendicular to the thickness direction of Cr diffusion regions 210 and 211 in the example of # 4. It is the scanning electron microscope image which expanded FIG. 10 partially. Scanning electron microscope (SEM) image of a cross section perpendicular to the thickness direction of the Cr diffusion regions 210 and 211 in the example # 6 (direction parallel to the paper surface in FIGS. 4A and 4B). is there. FIG. 13 is a scanning electron microscope image in which FIG. 12 is partially enlarged. It is a ternary alloy phase diagram of Fe-Ni-Cr.

Hereinafter, a stepping motor, a timepiece movement, a timepiece, and a manufacturing method of a stepping motor according to embodiments of the present invention will be described with reference to the drawings.
The drawings shown below are for explaining the configuration of the stepping motor according to the embodiment of the present invention. The size, thickness, dimensions, etc. of each part shown in the drawing are the same as the dimensional relationship of the actual stepping motor. May be different.

  FIG. 1 is a block diagram showing a timepiece using a stepping motor and a timepiece movement according to an embodiment of the present invention. In the present embodiment, an analog electronic timepiece will be exemplified and described as an example of a timepiece.

In FIG. 1, an analog electronic timepiece includes an oscillation circuit 101 that generates a signal of a predetermined frequency, a frequency dividing circuit 102 that divides the signal generated by the oscillation circuit 101 and generates a clock signal that serves as a time reference, and an analog electronic timepiece. Control circuit 103 that performs control of each electronic circuit element constituting the control, change control of drive pulse, and the like, and a drive pulse selection circuit that selects and outputs a drive pulse for motor rotation driving based on a control signal from the control circuit 103 (Drive means) 104, a stepping motor 105 that is rotationally driven by a drive pulse from the drive pulse selection circuit 104, a rotation detection circuit 111 as a detection means that detects a detection signal generated by the stepping motor 105, and a rotational drive by the stepping motor 105 A train wheel (not shown) that is driven by the train wheel to display the time (In the example of FIG. 1 hour 107, minute hand 108, 3 types of second hand 109) of time hands and a analog display unit 106 having a or a calendar display section 110 for date display.
The stepping motor driving device in this embodiment includes a stepping motor 105, a device control circuit 103, a driving pulse selection circuit 104, and a rotation detection circuit 111.

  The analog electronic timepiece includes a watch case 113, an analog display unit 106 is provided on the outer surface side of the watch case 113, and a watch movement (movement) 114 is provided inside the watch case 113. Yes.

The oscillation circuit 101, the frequency dividing circuit 102, the control circuit 103, the drive pulse selection circuit 104, the stepping motor 105, and the rotation detection circuit 111 are components of the movement 114.
In general, a timepiece mechanical body composed of devices such as a timepiece power source and a time reference is called a movement. Electronic devices are sometimes called modules. When the watch is completed, a dial and hands are attached to the movement and housed in a watch case.
Here, the oscillation circuit 101 and the frequency dividing circuit 102 constitute a signal generation unit, and the analog display unit 106 constitutes a time display unit. The rotation detection circuit 111 and the load detection circuit 112 constitute a rotation detection unit. The control circuit 103 and the drive pulse selection circuit 104 constitute a control unit. The oscillation circuit 101, the frequency dividing circuit 102, the control circuit 103, the drive pulse selection circuit 104, the rotation detection circuit 111, and the load detection circuit 112 constitute a stepping motor control circuit.

Next, the stepping motor 105 according to the present embodiment will be described in detail.
FIG. 2 is a schematic front view of the stepping motor 105 according to the present embodiment.

  In FIG. 2, a stepping motor 105 is integrally formed by machining from an Fe—Ni alloy plate, provided with a rotor through hole 203, and a stator provided with a magnetic path R around the rotor through hole 203. 201, a two-pole rotor 202 rotatably disposed in the rotor through-hole 203, a magnetic core 208 joined to the stator 201, and a coil 209 wound around the magnetic core 208. Further, the stepping motor 105 according to the present embodiment is characterized in that Cr diffusion regions 210 and 211 made of a Cr solidified portion are formed in a part of the magnetic path R.

  When the stepping motor 105 is used in an analog electronic timepiece, the stator 201 and the magnetic core 208 are fixed to a base plate (not shown) with screws (not shown) and joined to each other. The coil 209 has a first terminal OUT1 and a second terminal OUT2.

  The rotor accommodating through hole 203 is a circular hole in which a plurality of (two in the example of FIG. 2) half-moon cutouts (inner notches) 204 and 205 are integrally formed at the opposing portion of the through hole having a circular outline. It is configured in shape. These notches 204 and 205 are configured as positioning portions for determining the stop position of the rotor 202. For example, the notch portion (inner notch) 204 has an action of lowering the potential energy when the rotor is in a predetermined position, and stabilizing the position of the rotor.

The rotor 202 is magnetized to two poles (S pole and N pole).
In a state where the coil 209 is not excited, the rotor 202 has a position corresponding to the positioning portion as shown in FIG. 2, in other words, a line segment connecting the notches 204 and 205 with the magnetic pole axis A of the rotor 202. Is stably stopped at a position orthogonal to the angle (angle θ0 position).

  Cr diffusion regions 210 and 211 made of a melted and solidified portion of Cr, which is a nonmagnetic material, are formed in a part of the magnetic path R provided around the rotor through-hole 203 (two locations in the example of FIG. 2). Yes. Here, the width of the cross section of the narrow portion of the stator 201 is defined as a cross-sectional width t, and the width in the direction along the magnetic path is defined as a gap width w. The melted and solidified portions 210 and 211 are formed in a region defined by the cross-sectional width t and the gap width w. Note that the gap width w is formed to have a size equal to or greater than the cross-sectional width t (w ≧ t) due to a method for manufacturing a melt-solidified portion described later. In addition, the melt-solidified portions 210 and 211 are formed in a region up to the extent of not interfering with the notch portion (inner notch) 204 so as not to hinder the function of ensuring a stable position in the rotation control of the rotor 202. Note that the cross-sectional width t is defined as a width that does not include Cr that is applied to, or plated on, the stator base material in a method for producing a melt-solidified portion described later. The gap width w is defined as the width of the size of the surface where Cr to be coated, plated, etc. contacts the stator base material.

Here, the operation of the stepping motor 105 according to the present embodiment will be described.
First, a drive pulse is supplied from the drive pulse selection circuit 104 between the terminals OUT1 and OUT2 of the coil 209 (for example, the first terminal OUT1 side is positive and the second terminal OUT2 side is negative). , A magnetic flux is generated in the stator 201 in the direction of the broken line arrow.

In the present embodiment, Cr diffusion regions 210 and 211 which are low magnetic permeability regions are formed at locations conventionally designated as “narrow portions”, and the magnetic resistance of the regions is increased. Therefore, it is not necessary to magnetically saturate the region corresponding to the conventional “narrow portion” (Cr diffusion regions 210 and 211), and a leakage magnetic flux can be easily secured. Thereafter, the magnetic pole generated in the stator 201 and the magnetic pole of the rotor 202 , The rotor 202 rotates 180 degrees in the direction of the arrow in FIG. 2, and the magnetic pole axis stably stops at the angle θ1 position.
The rotation direction (counterclockwise direction in FIG. 2) for normal operation (the hand movement operation in each embodiment of the present invention is an analog electronic timepiece) by rotating the stepping motor 105 is positive. The reverse (clockwise direction) is the reverse direction.

Next, a drive pulse of reverse polarity is supplied from the drive pulse selection circuit 104 to the terminals OUT1 and OUT2 of the coil 209 (the first terminal OUT1 side is connected to the negative electrode and the second terminal so as to have the reverse polarity to the drive). When a current is passed in the direction indicated by the arrow in FIG. 2, the magnetic flux is generated in the stator 201 in the direction indicated by the broken line.
Thereafter, similarly to the above, Cr diffusion regions 210 and 211 that are low magnetic permeability regions are formed. Therefore, leakage magnetic flux can be easily secured, and the interaction between the magnetic pole generated in the stator 201 and the magnetic pole of the rotor 202 is achieved. As a result, the rotor 202 rotates 180 degrees in the same direction (positive direction) as described above, and the magnetic pole axis stably stops at the angle θ0 position.

  Thereafter, by supplying signals with different polarities (alternating signals) to the coil 209 in this way, the above operation is repeated, and the rotor 202 can be continuously rotated 180 degrees in the direction of the arrow. .

Thus, the Cr diffusion regions 210 and 211, which are low permeability regions, are formed in a part of the magnetic path around the rotor accommodating through hole 203, so that the magnetic flux consumed in the region can be greatly reduced. The leakage magnetic flux that drives the rotor 202 can be efficiently secured.
In addition, by forming Cr diffusion regions 210 and 211 in locations that have been conventionally defined as “narrow portions” to reduce the magnetic permeability, consumption of magnetic flux generated from the rotor 202 itself is also suppressed. The As a result, loss of magnetic potential can be prevented and the holding force for magnetically stopping and holding the rotor can be increased.
In addition, it is generated at the time of OUT1 side (negative electrode) in order to rotate on the OUT2 side (positive electrode) after being saturated with the magnetic flux on the OUT1 side (negative electrode) and rotating on the part that was previously regarded as the “narrow part” However, since the residual magnetic flux in the region is greatly reduced, the time required for canceling the residual magnetic flux becomes unnecessary, and the time until the rotation is converged can be shortened. Therefore, it is possible to maintain operational stability when performing high-speed hand movement, and to increase the drive frequency.

  The Cr diffusion regions 210 and 211 can be formed by melting and diffusing using a laser, but the diffusion amount of Cr changes by expanding the melting and diffusion range due to the amount of heat applied to the region by laser irradiation, The larger the output, the larger the Cr diffusion regions 210 and 211 formed.

In FIG. 3A, the vertical axis represents the current value (mA) of the coil 209, the horizontal axis represents time (msec), and the laser irradiation output condition (shown in parentheses in the graph) was changed, that is, Cr diffusion. The graph showing the time-dependent change of the electric current value of a coil at the time of changing the volume of the area | regions 210 and 211 is shown. This graph is a graph obtained by removing the rotor in order to confirm the saturation state only with the magnetic flux generated from the coil except for the influence of the magnetic flux generated from the magnet of the rotor.
In addition, as a comparative example of the present embodiment, an example in which Cr is melted and a conventional “narrow portion” is formed without being diffused (“no laser” in the graph, see FIG. 3B) and a conventional case. An example in which the “narrow part” is cut and the stator is divided into two parts (“separated type” in the graph, see FIG. 3C) is also shown.

As shown in FIG. 3A, the “separated type” current waveform has a sharp rise in current value when a drive pulse is applied to the coil. On the other hand, it can be seen that the current waveform in the case of “without laser” has a gentle rise and consumes power to magnetically saturate the “narrow portion”.
Looking at the current waveform of the example in which the Cr diffusion regions 210 and 211 are formed (samples # 1 to # 6), the current waveform shifts to the “separated type” current waveform as the laser output intensity (heat amount) is increased. That is, it can be seen that by applying heat locally, the range of the melt-solidified portion is expanded, and as the Cr diffusion regions 210 and 211 are increased, it tends to approach the “separated” magnetic characteristics. Sample # 1 has an applied heat amount of 0.4 J (output intensity 1 kW), Sample # 2 has an applied heat amount of 0.6 J (output intensity 1.5 kW), and Sample # 3 has an applied heat amount of 0.8 J (output intensity 2.. 5 kW), sample # 4 with applied heat of 1.0 J (output intensity 2.5 kW), sample # 5 with applied heat of 1.2 J (output intensity 3 kW), sample # 6 with applied heat of 1.4 J (Output intensity 3.5 kW). The laser output intensity is the output power (kW) of the heat source, and the applied heat amount (J) is determined by considering the application time, aperture and the like.
From the above, in order to magnetically saturate the “narrow portion” in the conventional stepping motor having the “narrow portion” by forming the Cr diffusion regions 210 and 211 in the region corresponding to the “narrow portion”. It can be seen that the required power consumption (area filled in the graph of FIG. 3A) can be reduced (power saving).

FIGS. 4A and 4B are enlarged schematic views in the vicinity of the formation region of the Cr diffusion regions 210 and 211.
As shown in FIG. 4A, the Cr diffusion regions 210 and 211 are regions that are conventionally “narrow portions”, that is, the entire region from the end of the rotor accommodating through hole 203 to the end of the stator 201. It may be formed over a part of the region as shown in FIG.
From the viewpoint of ensuring the leakage magnetic flux for driving the rotor 202 more efficiently (reducing the above-described power consumption), the end of the stator 201 is extended from the end of the rotor accommodating through hole 203 as shown in FIG. It is desirable to form the Cr diffusion regions 210 and 211 over the entire region up to the portion, but as shown in the graph of FIG. 3A, when the Cr diffusion regions 210 and 211 are small, or the Cr diffusion regions 210 and 211 Even if the formation region is only a part of the conventional “narrow portion”, the above-described effects can be enjoyed.

In FIG. 5, the horizontal axis is the angle (deg) of the magnetic pole axis of the rotor 202, and the vertical axis is the magnetic potential (unit is arbitrary), and there are two “no laser” and “# 6” shown in FIG. The change of the torque in an example is shown.
The angle at which the magnetic potential is lowest is the rest position, and the highest angle is the peak that must be exceeded as the rotor rotates. The peak difference between the highest angle and the lowest angle indicates the holding force held by the rotor, which corresponds to the holding torque of the movement.
Since the stepping motor 105 of this embodiment includes the notches 204 and 205 so that the stationary position is 45 °, 45 ° has the lowest magnetic potential. On the other hand, 135 ° has the highest magnetic potential, and if this angle is not exceeded, the rotor 202 will reverse to 45 °, which is the stationary position, and the rotational force necessary for moving the watch cannot be obtained. .
From FIG. 5, it can be confirmed that the peak difference of the magnetic potential is higher for the example # 6 according to the present embodiment than the conventional “without laser”, and the holding torque is high.
In the case of # 6, the behavior of the magnetic flux changes from “no laser” because the narrow portion becomes a nonmagnetic region. That is, “# 6” and “no laser” show slightly different behaviors (the angle at which the magnetic potential shows a peak shifts) in the graph shown in FIG. 5 depending on the position and shape of the Cr diffusion region. In this specification, the angle at which each peak occurs is matched between “# 6” and “without laser” so that the above-described “peak difference”, that is, the change in the holding torque of the movement can be easily observed. It is written to let you do.

  In the stepping motor 105 according to the present embodiment, as shown in FIG. 6, narrow portions 213 and 214 formed so that the cross-sectional area of the magnetic path R is narrower than other portions may be provided. . The narrow portions 213 and 214 are formed in the Cr diffusion regions 210 and 211 unlike the conventional “narrow portion”. When the narrow portions 213 and 214 are provided, the Cr diffusion regions 210 and 211 are formed in at least a part of the narrow portions 213 and 214.

  The narrow portions 213 and 214 are formed by forming notches (outer notches) 206 and 207 at positions facing the outer end portion of the stator 201 and the rotor housing through-hole 203 therebetween. That is, narrow portions 213 and 214 are formed between the outer notches 206 and 207 and the rotor accommodating through hole 203.

  By providing the narrow portions 213 and 214, the leakage magnetic flux for driving the rotor can be secured more efficiently, and the power consumption can be greatly reduced.

  In the stepping motor 105 according to the present embodiment, the Cr concentration in the Cr diffusion regions 210 and 211 is configured to be higher than the Cr concentration in the stator 201 made of an Fe—Ni alloy plate. Thereby, the magnetic permeability of the Cr diffusion regions 210 and 211 can be reduced. From the viewpoint of reducing the magnetic permeability of the Cr diffusion regions 210 and 211, the Cr concentration in the Cr diffusion regions 210 and 211 is preferably 15% by mass or more and 80% by mass or less.

  In the stepping motor 105 according to this embodiment, the stator 201 is made of an Fe—Ni alloy, but it is preferable to use an Fe—Ni alloy having a high magnetic permeability. For example, Fe-38% Ni-8% Cr (so-called 38 permalloy) can be exemplified. From the phase diagram of FIG. 14, the Curie temperature of Fe-38% Ni-8% Cr is 500K or more (point X), but when Cr is 15% by mass or more, the Curie temperature is 300K and the austenite phase is at room temperature. (Point X ′). That is, in the vicinity of the room temperature where the driving of the stepping motor 105 is required, the nonmagnetic state of the stator 201 can be ensured with Cr of 15% by mass or more. FIG. 14 is a state diagram quoted from 188 items of “Alternary alloys Between Fe, Co or Ni and Ti, V, Cr or Mn (Landolt-Bornstein new Series III / 32A)”.

  As described above, the stepping motor 105 according to this embodiment has been described by taking the two-pole stator including one stator and one coil as shown in FIG. 2 as an example. The present invention can also be applied to a stepping motor having a three-pole stator composed of two coils.

A stepping motor having a three-pole stator is known to operate stably while controlling the rotation direction of the rotor.
Here, when the reverse rotation drive is realized by the two-pole stator method, in order to rotate the rotor in the reverse direction, a pulse for guiding the rotor to a predetermined position is necessary before the reverse rotation pulse is output, and the excitation section is in the positive direction. It becomes 2-3 times or more than the case. Therefore, since there is a difference in the frequency that can be set between the forward rotation and the reverse rotation, there is a drawback that the reverse rotation is slow. However, the use of a three-pole stator has the merit that it can move with the same pulse form and frequency for forward rotation and reverse rotation because rotation is performed after supplying a pulse for determining the rotation direction.

However, since the 3-pole stator has a sub-magnetic pole, the holding force tends to be lower than that of the 2-pole stator.
In addition, since the polarity of the pulse is switched a plurality of times in one rotation, there is a problem in stable operation that it is necessary to rotate while canceling the residual magnetic flux that has been generated in the region that has been conventionally defined as the “narrow portion”.
Therefore, as in the case of the above-described two-pole stator, at least a part of the magnetic path around the rotor through-hole, or at least a part of the region conventionally referred to as a “narrow part”, is a Cr diffusion region. By forming the structure and reducing the magnetic permeability, the stability at the time of high-speed operation can be improved and further high-speed operation can be realized.

  According to the stepping motor of the present invention, since the Cr diffusion region is formed in a part of the magnetic path provided around the rotor through hole, the magnetic permeability of the region can be greatly reduced. As a result, since the magnetic flux consumed in the region is greatly reduced, it is possible to efficiently secure the leakage magnetic flux that drives the rotor and to save power.

  Further, according to the stepping motor according to the present invention, by reducing the magnetic permeability of the Cr diffusion region, the magnetic flux generated from the rotor itself is also suppressed in the region and the loss of magnetic potential can be prevented. Therefore, the holding force for magnetically stopping and holding the rotor can be increased, and the stability of the rotational drive of the rotor can be improved. In particular, when high-speed hand movement is performed, the time required for canceling the residual magnetic flux in the region can be shortened, and the drive frequency can be increased.

  Further, according to the stepping motor of the present invention, since the stator is integrally formed, the mechanical stress, the distortion caused by the welding / joining process and the position of the member, which have been a concern when manufacturing the conventional two-body stator, Generation | occurrence | production of a shift | offset | difference can be avoided and the fall of magnetic efficiency, the damage of a stator, and the fall of product quality can be prevented. In addition, since a welded part and a joint part where mechanical stress tends to concentrate are not formed, deterioration of strength can be prevented.

The stepping motor according to the present invention can be applied to various electronic devices using the stepping motor, but is particularly suitable as a timepiece movement, and can provide a timepiece movement having excellent magnetic characteristics.
Also, a timepiece having the timepiece movement can be improved in magnetic characteristics, and can be applied to various types of analog electronic timepieces such as an analog electronic wristwatch with a calendar function and a chronograph timepiece.

Next, a method for manufacturing the stepping motor 105 described above will be described.
The manufacturing method of the stepping motor 105 according to the present embodiment has a rotor through hole 203 and a magnetic path R disposed around the rotor through hole 203 by machining the Fe—Ni alloy plate. A step of forming the stator material 201a, a step of disposing a Cr material for diffusion on at least a part of the stator material 201a, and diffusing Cr by irradiating the Cr material with a laser to melt the Cr material inside the magnetic path R And forming the regions 210 and 211.
Hereinafter, each condition in the manufacturing method according to the present embodiment will be described.

First, machining such as punching is performed on the Fe—Ni alloy plate to form a stator material having a rotor through hole 203 and a magnetic path R disposed around the rotor through hole 203. The notches (inner notches) 204 and 205 can also be formed in this step.
Further, in the case where the notched portions (outer notches) 206 and 207 are formed and the narrow portions 213 and 214 are provided (see FIG. 6), they may be formed together in this step.

  The stator material 201a is preferably made of an Fe—Ni alloy having a high magnetic permeability. For example, Fe-38% Ni-8% Cr (so-called 38 permalloy) can be exemplified.

Next, a Cr material for melting diffusion is disposed on at least a part of the stator material 201a, and the Cr material is irradiated with a laser to melt and diffuse the Cr material inside the magnetic path R, thereby forming Cr diffusion regions 210 and 211. Form.
Specifically, for example, a paste containing powdered metal chromium may be applied to at least a part of the magnetic path, and the paste may be irradiated with a laser to be melted and diffused. Alternatively, a chromium plating layer may be formed on the surface of the stator material 201a in advance, and the chromium plating layer formed on at least a part of the magnetic path R of the chromium plating layer may be irradiated with a laser to be diffused. Good. In the case of plating, the mass ratio of Cr does not exceed 80% in consideration of the feasibility of covering the stator base material. Alternatively, powder may be used instead of the paste described above.
In the case where the narrow portions 213 and 214 are provided (see FIG. 6), as shown in FIGS. 7A and 7B, the above-described paste or chrome plating layer is formed in the notched portions (outer notches) 206 and 207. May be formed.

  By melting the Cr material, the laser irradiation conditions for diffusing are not particularly limited, and may be appropriately adjusted so that a desired Cr diffusion region is obtained.

Next, after forming the Cr diffusion regions 210 and 211 to obtain the stator 201, the rotor 202 is disposed in the rotor through-hole 203, and the magnetic core 208 is fixed by the stator 201 and any fixing means. The stepping motor 105 can be manufactured by winding the coil 209 around the magnetic core 208.
When the stepping motor 105 is used for an analog electronic timepiece, the stator 201 and the magnetic core 208 are fixed to a ground plane (not shown) with screws (not shown).

  The stepping motor 105 according to this embodiment can be manufactured by the manufacturing method described above.

Here, in the Cr diffusion regions 210 and 211, the molten state and the Cr content rate due to the difference in processing conditions were investigated.
8 shows a scanning type of a cross section perpendicular to the thickness direction of the Cr diffusion regions 210 and 211 in the example of “# 2 (0.6 J)” (direction parallel to the paper surface in FIGS. 4A and 4B). An electron microscope (Scanning Electron Microscope, SEM) image is shown. FIG. 9 is a scanning electron microscope image in which FIG. 8 is partially enlarged. In FIG. 9, regions 1, 2, and 3 surrounded by a square line correspond to the upper side 1, the center 2, and the lower side 3 of Table 1.
First, cross section polisher (CP) processing was performed using IB-09020CP (trade name) manufactured by JEOL Ltd. on the observation portion in the Cr diffusion regions 210 and 211. The acceleration voltage was 7 kV.
Energy dispersive x-ray spectroscopy (EDS) was performed on these regions 1, 2, 3 and the base material (region where Cr was not diffused by melting Cr). The results are shown in Table 1.
As the scanning electron microscope, a field emission scanning electron microscope (FE-SEM) (trade name: IB-09020CP, manufactured by JEOL Ltd.) was used. The acceleration voltage was 5 kV.
In the EDS mapping analysis, the acceleration voltage was set to 15 kV using NORAN SYSTEM 7 (trade name) manufactured by Thermo Fisher Scientific.

FIG. 10 shows a scanning type of a cross section perpendicular to the thickness direction of the Cr diffusion regions 210 and 211 in the example of “# 4 (1.0 J)” (a direction parallel to the paper surface in FIGS. 4A and 4B). An electron microscope (Scanning Electron Microscope, SEM) image is shown. FIG. 11 is a scanning electron microscope image in which FIG. 10 is partially enlarged. In FIG. 11, regions 1, 2, and 3 surrounded by a square line correspond to the upper side 1, the center 2, and the lower side 3 of Table 1.
For these regions 1, 2, 3 and the base material (region where Cr was not diffused by melting Cr), EDS analysis was performed in the same manner as in the case of “# 2 (0.6 J)”. . The results are shown in Table 1.

FIG. 12 shows a scanning type of a cross section perpendicular to the thickness direction of the Cr diffusion regions 210 and 211 in the example of “# 6 (1.4 J)” (a direction parallel to the paper surface in FIGS. 4A and 4B). An electron microscope (Scanning Electron Microscope, SEM) image is shown. FIG. 13 is a scanning electron microscope image in which FIG. 12 is partially enlarged. In FIG. 13, regions 1, 2, 3, and 4 surrounded by a square line correspond to the upper side 1, the center 2, the lower side 3, and the outer peripheral portion 4 of Table 1.
For these regions 1, 2, 3, 4 and the base material (the region where Cr is not diffused by melting Cr), EDS analysis is performed in the same manner as in the example of “# 2 (0.6 J)”. went. The results are shown in Table 1.

From the results in Table 1, it was confirmed that Cr diffusion regions 210 and 211 contain Cr, Fe, and Ni as main components and C, O, Al, and Si as trace components.
Further, from the results in Table 1, it was confirmed that the Cr diffusion regions 210 and 211 formed by irradiating the laser had a higher Cr content than the base material.
From the above results, it can be said that the Cr diffusion regions 210 and 211 form a low magnetic permeability region.

With the above configuration, when a magnetic flux acts alternately and continuously from both polar sides of the negative electrode and the positive electrode on the so-called narrow portion (near the portion where the cross-sectional area around the through hole for accommodating the rotor is minimal), By setting the mass% concentration of Cr formed as the melt-solidified portion to 15% by mass or more and 80% or less, the residual magnetic flux remaining due to the immediately preceding magnetic flux action can be reduced. Then, the time required to cancel the residual magnetic flux is shortened, and the time until the rotation of the rotor is converged can be shortened, thereby facilitating drive control of the next successive rotation. Therefore, for example, when performing high-speed hand movement, the drive frequency can be increased while maintaining operational stability.
Further, by setting the lower limit of the mass concentration of Cr in the so-called narrow portion to, for example, the vicinity of 18% to 20% shown in # 6, the residual magnetic flux can be made almost zero, which is necessary for canceling the residual magnetic flux. Time can also be minimized. Thereby, for example, stable operation can be performed even at a high driving frequency of about 256 Hz.
Further, by setting the upper limit value of the mass concentration of Cr in the so-called narrow portion to, for example, around 45% to 55% shown in # 2, the residual magnetic flux can be reduced, and the residual magnetic flux canceling time can be ignored in the high-speed operation. The amount of Cr coating (including plating and the like) can be suppressed to a practical range. Thereby, a stepping motor capable of high-speed hand movement with higher feasibility can be provided.

  According to the manufacturing method of the stepping motor of the present invention, since the stator is integrally formed, the magnetic efficiency is improved without causing mechanical stress such as cutting, distortion due to welding / joining process, and displacement of the member. Reduction, stator damage, product quality deterioration, and strength deterioration can be prevented. In addition, since a Cr diffusion region is formed in a part of the magnetic path to reduce the magnetic permeability, a stepping motor having both power saving and high holding power can be easily manufactured.

  Conventionally, when adjusting the low-permeability region, the number of processes has been increased, and many manufacturing conditions have been changed and adjusted, such as the machining method and conditions for mechanically dividing the stator and the adjustment of the non-magnetic material to be inserted. As a result, the manufacturing cost may increase. However, according to the present invention, the Cr diffusion region (low magnetic permeability region) can be adjusted to a desired one only by adjusting the laser irradiation conditions without performing processing such as cutting on the stator material.

DESCRIPTION OF SYMBOLS 101 ... Oscillator 102 ... Frequency divider 103 ... Control circuit 104 ... Drive pulse selection circuit (drive means)
105 ... Stepping motor 106 ... Analog display 107 ... Hour hand 108 ... Minute hand 109 ... Second hand 110 ... Calendar display 111 ... Rotation detection circuit 112 ... Load detection circuit 113 ... Clock case 114 ... Movement 201 ... Stator 201a ... Stator material 202 ... Rotor 203 ... Rotor through holes 204, 205 ... Notches (inner notches)
206, 207 ... Notch (outer notch)
208 ... Magnetic core 209 ... Coils 210, 211 ... Cr diffusion regions 213, 214 ... Narrow part OUT1 ... First terminal OUT2 ... Second terminal R ... Magnetic path

Claims (8)

A stator formed of an integral Fe-Ni alloy, provided with a rotor through-hole, and provided with a magnetic path around the rotor through-hole;
A rotor rotatably disposed in the rotor through hole;
A stepping motor comprising a coil provided on the stator,
A Cr diffusion region consisting of a Cr solidified portion is formed in a part of the magnetic path ,
The Cr diffusion region is formed in the irradiation direction irradiated with a laser when forming the Cr diffusion region, and is not formed on the side facing the irradiation side from the irradiation side irradiated with the laser.
Stepping motor characterized by that.   The Cr diffusion region is such that, in the irradiation direction irradiated with the laser when forming the Cr diffusion region, the diameter of the region having a high Cr weight ratio is opposite to the irradiation side from the irradiation side irradiated with the laser. Is smaller,
  The stepping motor according to claim 1. The stator is provided with a narrow portion formed so that a cross-sectional area of the magnetic path is narrower than other portions, and the Cr diffusion region is formed in at least a part of the narrow portion. The stepping motor according to claim 1 or 2 , characterized in that. The melt-solidified portion includes the narrow portion, according to claim 3, characterized in that provided in the part that does not interfere with the notch portion provided in the rotor through holes for stable position securing of the rotor Stepper motor. The stepping motor according to any one of claims 1 to 4 , wherein Cr is contained in the Cr diffusion region in an amount of 15 mass% or more and 80 mass% or less. The stepping motor according to claim 5 , wherein the Cr diffusion region contains 18 mass% or more and 55 mass% or less of Cr. A timepiece movement comprising: the stepping motor according to any one of claims 1 to 6 ; and a hand for displaying time by rotating by the stepping motor. A timepiece comprising the timepiece movement according to claim 7 .