US3922845A

US3922845A - Watch drive pulse motor

Info

Publication number: US3922845A
Application number: US469904A
Authority: US
Inventors: Kenzi Miyasaka; Mikio Takemoto; Yoshiaki Kato; Hiroyuki Uematu; Munetaka Tamaru; Kazunari Kume; Hideshi Ohno; Mitsuo Onda
Original assignee: Citizen Watch Co Ltd
Current assignee: Citizen Watch Co Ltd
Priority date: 1973-05-15
Filing date: 1974-05-14
Publication date: 1975-12-02
Anticipated expiration: 1992-12-02
Also published as: GB1429100A; JPS505806U; DE2423705A1

Abstract

A spacial gap around the working tip end of an elongated reverse stop pawl shaped into an elongated spring bar adjustably fixed at its root end on the pillar plate of a watch and adapted for cooperation with a ratchet wheel concentrically rigid with a magnetized rotor of a pulse drive electric motor, and relative to the ratchet wheel is provided.

Description

United States Patent [191 Miyasaka et a1.

1 1 WATCH DRIVE PULSE MOTOR [75] Inventors: Kenzi Miyasaka, Tokyo; Mikio Takemoto, Sayama; Yoshiaki Kato, Higashimurayama; Hiroyuki Uematu, Narashino; Munetaka Tamaru, Tokyo; Kazunari Kume, Tokorozawa; Hideshi Ohno, Sayama; Mitsuo Onda, Fuchu, all of Japan [73] Assignee: Citizen Watch Co., Ltd., Tokyo,

Japan [22] Filed: May 14, 1974 211 Appl. No.: 469,904

[30] Foreign Application Priority Data May 15, 1973 Japan 48-56827 [52] US. Cl. 58/23 D; 310/37 [51] Int. Cl. G04C 3/00; HOZK 7/06 [58] Field of Search 53/23 R, 23 D; 310/37, 310/49 1 Dec. 2, 1975 [56] References Cited UNITED STATES PATENTS 3,151,440 10/1964 Schoenrock 310/37 X 3,783,608 1/1974 Miyazawa 3,810,354 5/1974 Naikaido et al.- i. 58/23 D FOREIGN PATENTS OR APPLICATlONS 693,719 9/1964 Canada 58/23 D Primary ExaminerEdith Simmons Jackmon Attorney, Agent, or Firm-Holman & Stern [57] ABSTRACT A spacial gap around the working tip end of an elongated reverse stop pawl shaped into an elongated spring bar adjustably fixed at its root end on the pillar plate of a watch and adapted for cooperation with a ratchet wheel concentrically rigid with a magnetized rotor of a pulse drive electric motor, and relative to the ratchet wheel is provided.

8 Claims, 8 Drawing Figures Sheet 2 of 3 3,922,845

US. Patent Dec. 2, 1975 s w m. e d llllllll 9 m & 01 l .E m m n n EE mEv O mscmok w ow m IHWI llllll IL- 3 FIG.6

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US. Patent Dec. 2, 1975 Shfiet 3 of3 3,922,845

FIG. 8

TO PULSE GENERATOR WATCH DRIVE PULSE Mo'roa BACKGROUND OF THE INVENTION This invention relates to improvements in and relating to a pulse drive electric motor adapted for use in a small timepiece, especially a watch.

More specifically, it relates to the above kind of an electric motor comprising, a pulse generator adapted for supply of a series of periodically and alternatively polarity-reversing pulse series under the control of a standard timebase, preferably a quartz oscillator, a stator, a drive coil wound thereon and electrically connected with said pulse generator, a radially magnetized rotor rotatable relative to saidstator, a ratchet wheel concentrically rigid .with said rotor and an elongated reverse stop pawl cooperating with said ratchet wheel.

During the manufacture and assembly of said kind of pulse motor, it is necessary to make manual adjustments for properly setting the rotor at its correct initial position relativeto the stator. The thus once correctly, the established initial setting of the rotor should not be disturbed. The initial rotor setting must be maintained upon its connection, during assembly, with the timekeeping gearing when the rotor can be subjected to a load, thereby. For this purpose, the number of magnetic poles on the rotor is selected to be identical with that of the teeth on the ratchet wheel which is made concentrically rigid with the former and the rigid assembly is mounted on a rotatable common shaft and the tip end of the slightly resilient and elongated reverse stop pawllis brought into tight contact with one of the teeth of the ratchet wheel for provisional fixing of the correct initial phase of the rotor relative to the stator. v I

In such conventional arrangement, however, allowance for the manual adjustability during assembly of the rotor with the stator must be substantially limited by virtueof the unavoidablepresence of various machining errors in and of the ratchet teeth, rotor and its shaft, and the reverse stop pawl and/or the angular inaccuracy of the radially magnetized state of the rotor,

so far as the working end of the stop pawl should be in engagement with the ratchet tooth.

OBJECT OF THE INVENTION SUMMARY OF THE INVENTION For this purpose, according to this invention, the reverse stop pawl is so arranged that the working end thereof is kept positively and intentionally in complete separation from the ratchet tooth during the assemblying as well as assembled state of the rotor and stator. Therefore, the working pawl end is positioned at the very presence of a spacial idle gap relative to the ratchet tooth, so far as the rotor and stator are in their static condition which means that no electric current is passed through the drivecoil wound on the stator.

' Any 'person skilled in the art would deem that theworking stop pawl end should be kept in contact with the ratchet tooth for the desired reverse stop operation, thereby inviting a substantial limitation in the adjustable allowance, as'was-above referred to. However, such reverse-stopaction is brought about in effect, exclusively during the dynamic operation of the rotor-stator assembly, and according to our experimental results, the very provision of a spacial idle around the working end of the stop pawl provides a substantial loosening and broadening of the adjustability allowance during rotor assembly, without an appreciable loss of the stepping accuracy of the motor.

DESCRIPTION OF THE DRAWINGS This and further objects, features and advantages of the present invention will appear more apparent when read with the following detailed description of the invention with reference to the accompanying drawings illustrative substantially of a sole embodiment thereof.

In the drawings:

FIG. 1 is a, schematic plan view of a preferred embodiment of the pulse motor according to this invention wherein however, the drive coil has been shown in its schematic section.

FIG. 2 is an enlarged part of FIG. 1, illustrating of the relationship among three centers of the rotor and two slightly staggered stator halves.

FIG. 3 is an enlarged schematic and partial elevation, showing the improved provision of a spacial idle gap around the working end extremity of an elongated reverse stop ratchet pawl shown in FIG. 1, being provided relative to the related part of the ratchet wheel.

FIG. 4 is a schema illustrative of the transient move- I ment of the rotor appearing upon application of a drive pulse to the drive coil shown in FIG. 1 wherein, how- I ever, the rotational angle, in degrees, of the rotor has been plotted against the time in milliseconds.

FIGS. 5, 6 and 7 are three explanatory charts for the invention.

FIG. 8 is a more specific plan of several working parts of the pulse motor.

DISCUSSION OF THE PREFERRED EMBODIMENT Referring now to the accompanying drawings, a preferred embodiment of the invention will be described in detail.

In FIG. 1 schematically illustrative of a timepiece drive pulse motor, numeral 1 represents a stator made of a high permeable material such as permalloy, while numeral 2 represents a drive coil which surrounds a leg part In and through an opening lb of said stator as shown. The both ends of this drive coil 2 are formed into a pair of

terminals

2a and 2b These terminals are connected with a conventional pulse generator, not shown, so as to be fed with a series of periodically and alternatively polarity-reversed short and acute pulses, preferably, at every second under the control of a standard time base, such as, preferably, a conventional quartz oscillator, not shown. These pulses may be of about 15 milliseconds, as an example.

Numeral 3 represents a rotor which is mounted rotatably on a conventional timepiece pillar plate, not shown, in a substantially circular opening formed through the stator l and comprising a pair of slightly staggered semi-circles 1c and 1d. These semi-circles have been drawn with a common radius, but the righthand one 10 has its centor O positioned slightly above the center 0 of the rotor 3, while the left-hand one 1d has its centor O" positioned slightly below said rotor center, as more specifically shown in FIG. 2. These three centers 0', O and O" are positioned on a separat- 3 ing axis AA of the stator 1. As seen, the stator comprises a pair of core halves l-l and 1-2 defining said semi-circular openings and 1 d respectively, and being rigidly united together by means of said leg portion In having generally a U-shape when seen in FIG. 1, by tongue-andgroove connection with riveting. although there is shown only a separating line in dotted manner at 1e. Rotor 3 has been diametrally magnetized, so as to represent a plurality of alternating magnetic poles N and S. as an example six in this embodiment; as shown schematically at 3a, 3b, 30, 3e and 3f, peripherally in succession, of which 3c, 3c and 3e being north and 312, 3d and 3f being south. The rotor is thus arranged in a soto-speak double eccentric relationship relative to the stator.

Numeral 4 represents a six tooth ratchet wheel which is made rigid with and concentric to the rotor 3, having a common shaft 5 rotatably mounted. Thus, the ratchet teeth are equal in their number with the rotor poles.

The rotor and the stator are arranged in their relatively stationary position with no current passing through the drive coil 2 in such a way that when seen in FIG. 1 the initial phase position of a magnetic pole as at 3a or 3d of the rotor establishes a predetermined included angle a relative to the separation line A A of the stator. The included angle may preferably be 7 Numeral 6 represents an elongated resilient reverse stop pawl the root end of which is fixedly mounted at 6a on the pillar plate, while the tip end 6b of the pawl is initially positioned, so as to establish a predetermined idle gap g relative to the trailing surface 4a of the nearest ratchet tooth 4, the central angle of said gap measured at the rotor center 0 amounts to 2-l0. This gap has a linear dimension of 30-180 microns for the regu- Iar size mens watch. In other words, it amounts generally to 3-18 units when the radius of the ratchet wheel is assumed to have a length of. 100 units. The stop pawl tip end 6b is positioned at a certain distance s, preferably being 30 l00 microns when measured from the tooth bottom or leading surface 4b on the ratchet wheel 4, as partially and schematically illustrated in FIG. 3. In this way, a spacial idle gap is provided around the working end of the stop pawl relative to the ratchet tooth when the ratchet wheel is stationary.

When a drive pulse is applied between the terminals and 2b under these ready-operational conditions, the rotor 3 will make a rotational stepping motion amounting to 60 in this case in the clockwise direction B in FIG. 1 at every second.

FIG. 4 illustrates a transient state appearing at the stepping movement of the rotor 3 wherein the rotor rotational angle in degrees has been plotted against the time in milliseconds. In this schema, the half full and half dotted line curve 7 represents a conventionally encountered transient movement of the rotor 3 for no provision of said pawl 6, while the full line curve 8 illustrates the transient rotor movement for the arrangement shown in FIG. I wherein such gap g was intentionally and definitely introduced.

From the curve 7, it will be seen that when rotor 3 4 this case. max. damping amplitude amounts to about 35 and the damping pcriod consumed until stabilized attainment at 6U-line extends for 38 milliseconds, as

shown.

With use of the stop pawl 6 and when provided no idle gap as at g, the transient curve will progress along initial curve portion 7a and a ripple curve portion 11 in succession. In this case, when an idle gap as at g is introduced according to this invention, the transient curve will progress along 7a and 8 in succession. In these cases, the maximum damping amplitude is substantially similar to that which is obtained in the first instance wherein use of reverse stop pawl has been abolished, while the damping period amounts generally to the order of 20 milliseconds. It will be seen from the foregoing that even with the provision of the said appreciable spacial idle gap around the working end of the reverse stop pawl, the damping effect has not been injured. Instead, the manual adjusting job during the rotor-stator assembly has been foundv highly quicker and easier, because the linear gap allowance is highly favored with the practically utilizable broad limitation (180 30) or microns in this embodiment. Thanks to the provision of lateral gap dimension s, otherwise appreciable loss in rotor driving energy could be substantially minimized.

The magnetic or static torque subjecting to the rotor by virtue of the magnetic coupling between the rotor and stator progress along a sinusoidal curve 9 shown by way of example in FIG. 5, in case where no use of the reverse stop pawl 6 has been made. In this chart, FIG. 5, the torque in mgmm has been plotted against the rotor rotational angle in degrees.

In a sector range of 60, shown in FIG. 5, of the rotor, being equal to one pole pitch thereof, there may be considered four

angular ranges

0,, 0,, 0;, and 0,. Within the first range 0,, when the rotor should be positioned at any point therein, it will move automatically under the mutual statical magnetic attraction between .the rotor and stator, to zero position which corresponds to the initial phase one inclined a predetermined angle a FIG. 5, again only for comparison.

If the effective gap g should invade into the remaining final angle range 0,, the output of the pulse motor will become adversely reduced, as may be seen from FIG. 7, showing test results.

In FIG. 6, the relationship between the variable range of gap 3 and ratchet teeth is shown. In this figure, a shaded area 0 represents said variable range relative to the ratchet teeth. In this figure, further, 0 represents again the minimum gap (about 2 of rotor central angle). 0, and 0, are also illustrated.

In FIG. 8, several main working parts of the pulse motor are shown again and ma more specific manner. These parts can be easily identified by reference to same reference numerals as those already shown.

As seen, the leg portion la has been connected with stator halves I--] and I-2 by use of tongue-and-groove connections 1e and 1e" and fixed by means of set screws lfand 1g.

Although, in the foregoing, the root end 6a of reverse stop pawl 6 has been shown and described only schematically as if it be fixedly attached to the pillar plate, not shown, but practically it is adjustable by use of a double adjusting unit 20 which comprises a mounting plate 10 pivotably mounted through a pivot pin on the pillar plate.

The root end 6a of the stop paw'l is rigidly attached to a mounting ring 11 which is mounted in turn frictionally on a pin 12 studded on the mounting plate 10.

By adjustingly turning the ring 11 around the pin 12 by means of a screw or the like tool, the lateral gap s at the tip end 6b can be modified as desired.

The mounting plate is formed with a round opening 14 in which an adjuster member 13 is eccentrically introduced and rotatably received in a tapped opening, not shown, of the pillar plate. By turning the adjuster properly by means of a screw driver or the like manual tool, the plate 10 will swivel to and fro around the pivot 15 so that the axial gap distance g can be adjusted as desired.

Upon satisfactory adjustment of the spacial gap around the tip end 6b of reverse stop pawl 6, the adjusted position of the latter can be fixed by tightening a fixing screw 16 which is received through a curved slot 17 formed through the plate 10, in and by a tapped opening, not shown, of the pillar plate.

We claim:

1. In a pulse drive electric motor for use in a small timepiece, especially watch, comprising a pulse generator adapted for supply of a series of periodically and alternatively polarity-reversing pulse series, a stator, a

drive coil wound thereon and electrically connected with said pulse generator, a radially magnetized rotor rotatable relative to said stator, a ratchet wheel having a plurality of teeth, each having a leading surface and a trailing surface, said ratchet wheel being concentrically rigid with said rotor and an elongated reverse stop pawl cooperating with said ratchet wheel, the improvement comprising: wherein said pawl is positioned so as to positively and intentionally provide a special gap at the working tip end of said pawl and relative to the trailing surface of the nearest, tooth on said ratchet wheel when said drive coil is deenergized between said pulses in said series.

2. The pulse drive electric motor of claim 1, wherein said spacial gap (having) has an axial dimension corresponding to 2l0 (in terms of central angle) with respect to the center of said ratchet.

3. The pulse drive motor of claim 2 wherein said spacial gap has a lateral dimension relative to said ratchet (and) of 30 180 microns.

4. The pulse drive motor of claim 3 wherein the root end of said reverse stop pawl is mounted on a pillar plate of the timepiece through a double-adjusting unit.

5. In a pulse drive electric motor for use in a small timepiece, especially a watch, comprising a pulse generator adapted for supply of a series of periodically and alternatively polarity-reversing pulse series, a stator, a drive coil wound thereon and electrically connected with said pulse generator, a radially magnetized rotor rotatable relative to said stator, a ratchet wheel having a plurality of teeth, each having a leading surface and a trailing surface, said ratchet wheel being concentrically rigid with said rotor and an elongated reverse stop pawl cooperating with said ratchet wheel, the improvement comprising: wherein said pawl is positioned so as to positively and intentionally provide a spacial gap at the working tip end of said pawl and relative to the trailing surface of the nearest tooth on said ratchet wheel when said drive coil is deenergized between said pulses in said series and the root end of said reverse stop pawl mounted on a pillar plate of the timepiece through a double-adjusting unit which comprises a rotatable member mounting said pawl and a slidable member mounting said rotatable member wherein by rotating said rotatable member, the radial dimension of said gap is adjusted and by moving said slidable member, the peripheral dimension of said gap is adjusted.

6. In the pulse drive electric motor ofclaim 5, a unit comprising a mounting plate acting as said slidable member and pivotably mounted through a pivot pin on the pillar plate wherein the root end of the stop pawl is rigidly attached to a mounting ring acting as said rotatable ring and mounted frictionally in turn on a pin studded on the mounting plate, and by adjustably turning the ring around the pin, the lateral dimension of said gap at the tip end can be modified as desired and the mounting plate is formed with an opening in which an adjuster member can be eccentrically introduced and rotatably received in a tapped opening of the pillar plate where by turning the adjuster, the plate will swivel around the pivot so that the axial gap distance of the said gap can be adjusted as desired and upon satisfactory adjustment of the spacial gap around the tip end of reverse stop pawl, the adjusted position of the latter can be fixed by tightening a fixing screw which is received through a slot formed through the plate, in and by a tapped opening of the pillar plate.

7.. The pulse drive electric motor of claim 6 wherein the central angle of said spacial gap measured at the center of said ratchet amounts to 2l0.

8. The pulse drive motor of claim 7 wherein said spacial gap has a lateral dimension relative to said ratchet and of 30-180 microns.

Claims

1. In a pulse drive electric motor for use in a small timepiece, especially watch, comprising a pulse generator adapted for supply of a series of periodically and alternatively polarity-reversing pulse series, a stator, a drive coil wound thereon and electrically connected with said pulse generator, a radially magnetized rotor rotatable relative to said stator, a ratchet wheel having a plurality of teeth, each having a leading surface and a trailing surface, said ratchet wheel being concentrically rigid with said rotor and an elongated reverse stop pawl cooperating with said ratchet wheel, the improvement comprising: wherein said pawl is positioned so as to positively and intentionally provide a special gap at the working tip end of said pawl and relative to the trailing surface of the nearest, tooth on said ratchet wheel when said drive coil is deenergized between said pulses in said series.

2. The pulse drive electric motor of claim 1, wherein said spacial gap (having) has an axial dimension corresponding to 2*-10* (in terms of central angle) with respect to the center of said ratchet.

3. The pulse drive motor of claim 2 wherein said spacial gap has a lateral dimension relative to said ratchet (and) of 30 - 180 microns.

6. In the pulse drive electric motor of claim 5, a unit comprising a mounting plate acting as said slidable member and pivotably mounted through a pivot pin on the pillar plate wherein the root end of the stop pawl is rigidly attached to a mounting ring acting as said rotatable ring and mounted frictionally in turn on a pin studded on the mounting plate, and by adjustably turning the ring around the pin, the lateral dimension of said gap at the tip end can be modified as desired and the mounting plate is formed with an opening in which an adjuster member can be eccentrically introduced and rotatably received in a tapped opening of the pillar plate where by turning the adjuster, the plate will swivel around the pivot so that the axial gap distance of the said gap can be adjusted as desired and upon satisfactory adjustment of the spacial gap around the tip end of reverse stop pawl, the adjusted position of the latter can be fixed by tightening a fixing screw which is received through a slot formed through the plate, in and by a tapped opening of the pillar plate.

7. The pulse drive electric motor of claim 6 wherein the central angle of said spacial gap measured at the center of said ratchet amounts to 2*- 10*.

8. The pulse drive motor of claim 7 wherein said spacial gap has a lateral dimension relative to said ratchet and of 30- 180 microns.