The invention relates to a step motor particularly for an electronic timepiece, comprising a stator whose two free ends constitute two pole pieces delimiting therebetween an air-gap in which is accommodated the rotor. Each pole piece is provided with a recess of cylindrical shape so that the axis of each cylinder is parallel with the axis of rotation Ar of the rotor. The two axes of the said cylinders are shifted from one another by a value comprised between 80.mu. and 200.mu. in a direction perpendicular to the plane defined by the axis of rotation Ar of the rotor and the main direction of the flux generated by an exciting coil associated with the stator. The radii of the rotor and the stator are in the order of about 800.mu. and 1500.mu. respectively.
BACKGROUND OF THE INVENTION
The present application is a continuation-in-part of co-pending appln. Ser. No. 572,432, filed Jan. 20, 1984, now U.S. Pat. No. 4,518,884 issued May 21, 1985, which is in turn a continuation of co-pending appln. Ser. No. 255,220 filed Apr. 17, 1981 and now abandoned.
A stator (1) is made up by bonding a first stator part (1a) made of a high-permeability material to a second stator part (1b) made of a high-permeability material respectively by welding through the intermediary of connections (1c,1d) made of a low-permeability material or a nonmagnetic material, interposed therebetween. Paired recesses (5a, 5b) serving as holding torque setting means for holding a rotor (3) by a magnetic action are formed on the inner, periphery of a rotor hole (2) defined inside the stator (1) at the position forming an initial phase angle (.theta..sub.1). A field coil (7) for excitation is magnetically bonded to opposite ends of the stator (1), thereby forming a two-pole step motor for a timepiece
A stator (1) is made up by bonding a first stator part (1a) made of a high-permeability material to a second stator part (1b) made of a high-permeability material respectively by welding through the intermediary of connections (1c, 1d) made of a low-permeability material or a nonmagnetic material, interposed therebetween. Paired recesses (5a, 5b) serving as holding torque setting means for holding a rotor (3) by a magnetic action are formed on the inner periphery of a rotor hole (2) defined inside the stator (1) at the position forming an initial phase angle (.theta..sub.1). A field coil (7) for excitation is magnetically bonded to opposite ends of the stator (1), thereby forming a two-pole step motor for a timepiece.
