Abstract:
A rotor ring and an armature for use in a toothed electromagnetic clutch or a toothed electromagnetic clutch brake. A method of manufacturing rotor rings and armatures used in toothed electromagnetic clutch or a toothed electromagnetic clutch brakes.

Description:
This application claims priority from (Japanese) Patent Application No. 2002-1655562 filed on Jun. 6, 2002. 
   BACKGROUND OF THE INVENTION 
   The rotating portion of an electric motor has angular momentum and kinetic energy during the motor&#39;s operation. Since both angular momentum and energy must be conserved, the rotating portion of the motor will continue to rotate until the angular momentum is transferred to other objects and the energy is dissipated. However, for a variety of applications using electric motors, it is advantageous to bring a motor, including its rotating shaft, to a prompt stop rather than allowing it to coast to a stop. Toothed electromagnetic clutch brakes are often employed for this purpose. A toothed electromagnetic clutch brake is a motor stopping device that utilizes a toothed electromagnetic clutch to transfer the motor&#39;s angular momentum and energy to an armature assembly that is sufficiently secured to a fixed structure to promptly stop the shaft&#39;s rotation. 
   Toothed electromagnetic clutches transmit angular momentum and energy through the use of interlocking teeth. In general, toothed electromagnetic clutches are comprised of an armature assembly, a rotor, and a coil. The rotor is coupled to a shaft that is driven by an electric motor or other similar device such that the rotor rotates with the shaft. The armature assembly may be enabled to rotate about the same axis as the rotor ring. Additionally, the armature assembly and the rotor possess mutually interlocking teeth. Further, the toothed portions of the armature assembly and the rotor are capable of relative axial movement such that when the coil is energized to create a magnetic field the toothed portions of the armature assembly and the rotor to come together. When the armature assembly and rotor come together, their teeth interlock causing the rotor to apply torque to the armature assembly. The application of this torque transmits energy and angular momentum from the rotor to the armature assembly. During engagement, which is when the toothed portions of the armature assembly and the rotor come together, toothed electromagnetic clutches unfailingly allow the rotor to apply compact, high torque to the armature assembly without the occurrence of slippage. During disengagement, toothed electromagnetic clutches unfailingly prevent the application of torque without the occurrence of entanglement. 
   A toothed electromagnetic clutch brake is a motor stopping device that utilizes an electromagnetic clutch to transfer the angular momentum and kinetic energy associated with a de-energized electric motor to an armature assembly that is sufficiently secured to a fixed structure to promptly stop the shaft&#39;s rotation. 
   In prior art toothed electromagnetic clutches, the toothed portion of the armature assembly (“the armature”) and the toothed portion of the rotor (“the rotor ring”) are either machined, or they are manufactured by powder metallurgical methods using sintered metal. Both of these methods have problems associated with them. 
   Machining of armatures and rotor rings, which is usually accomplished through the use of a one-reed hob, milling cutter, involute pinion cutter, or the like, is a time intensive and resultantly expensive process, since numerous processes are required to form the tooth flanks. Additionally, it is difficult to guarantee the dividing accuracy of the interlocking teeth and machining defects tend to occur. These problems are magnified when the number of interlocking teeth is large. 
   Manufacturing armatures and rotor rings through the use of powder metallurgical methods is less expensive and time consuming than machining them. However, the resulting materials are not as tough as the machined armatures and rotor rings, and it is difficult to guarantee the mechanical strength of the teeth. Moreover there is a major impact on product life and manufacturing cost due to the density and durability of the materials. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to guarantee the necessary mechanical properties and to reduce manufacturing costs with regard to the armature and rotor ring in a toothed electromagnetic clutch and in a toothed electromagnetic clutch brake. 
   These and other advantages are obtained when the rotor ring and armature are formed by stamping in accordance with the present invention. Stamping allows the mass production of rotor rings and armatures by metal dies using rolled steel sheet. Accordingly, manufacturing costs can be reduced. Additionally, it becomes easy to obtain the desired properties with regard to accuracy of tooth flank, mechanical strength, magnetic properties and so on. Moreover, the rotor ring and armature parameters, including the number of teeth, the pressure angle of the teeth, the number and shape of the U-shaped grooves and so on; can be arbitrarily set, and it is possible to conduct wide-ranging adjustments corresponding to clutch capacity, application, and the like. 
   An embodiment of the present invention comprises a rotor ring for use in an electromagnetic clutch, wherein the rotor ring is formed by stamping. 
   An embodiment of the present invention comprises an armature for use in an electromagnetic clutch, wherein the armature is formed by stamping. 
   A toothed electromagnetic clutch embodying the present invention comprises an armature assembly having a stamped armature, a rotor having a stamped rotor ring, and a coil that generates an electromagnetic field. When an electromagnetic field is generated by the coil, the armature and the rotor ring come together and their teeth mutually interlock. 
   A toothed electromagnetic clutch brake embodying the present invention comprises an armature assembly having a stamped armature, a rotor having a stamped rotor, ring, and a coil that generates an electromagnetic field. Additionally, the rotor is coupled to the rotating portion of a motor and the armature assembly is secured to a non-rotating structure. When an electromagnetic field is generated by the coil, the armature and the rotor ring come together and their teeth mutually interlock. 
   A method of manufacture in accordance with the present invention is characterized by a process of forming a rotor ring by stamping a blank of metal sheet to form a ring having a plurality of teeth. 
   A method of manufacture in accordance with the present invention is characterized by a process of forming an armature by stamping a blank of metal sheet to form a ring having a plurality of teeth. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated by way of example and not limitation and the figures of the accompanying drawings in which like references denote like or corresponding parts, and in which: 
       FIG. 1  is a longitudinal section view of a toothed electromagnetic clutch according to one embodiment of this invention. 
       FIG. 2  is a lateral view of a toothed electromagnetic clutch according to one embodiment of this invention. 
       FIG. 3  is a frontal view of a toothed electromagnetic clutch according to one embodiment of this invention. 
       FIG. 4  is a rear view of a toothed electromagnetic clutch according to one embodiment of this invention. 
       FIG. 5  is longitudinal section view, which corresponds to line A—A as shown in  FIG. 6 , of a rotor ring according to one embodiment of this invention. 
       FIG. 6  is a frontal view of a rotor ring according to one embodiment of this invention. 
       FIG. 7  is a view showing an enlargement of the interlocking indentations of the rotor ring shown in FIG.  5 . 
       FIG. 8  is a longitudinal section view of an armature according to one embodiment of this invention 
       FIG. 9  is a frontal view of the armature shown in FIG.  8 . 
       FIG. 10  is a view showing an enlargement of the interlocking protuberances of the armature shown in FIG.  8   
   

   DETAILED DESCRIPTION 
   One embodiment of a toothed electromagnetic clutch embodying the present invention is shown in FIG.  1 . Toothed electromagnetic clutch  1  is comprised of field coil  2 , rotor  3 , and armature drive  4 . Rotor  3  is connected to a rotating shaft of an electric motor. 
   As shown in  FIG. 1 , field coil  2  is comprised of baseboard  5 , coil  6 , housing  7 , and bushing  8 . Housing  7  accommodates coil  6 , which is ring shaped. Baseboard  5  allows field coil  2  to be attached to an external frame or device, and bushing  8  connects field coil  2  to rotor  3  so as to allow relative rotation between field coil  2  and rotor  3 . 
   As shown in  FIGS. 1 ,  2 , and  4 , rotor  3  is comprised of cylindrical rotor ring  9 , shaft  10 , support shaft  11 , snap ring  12 , and rectangular coupler  17 . Cylindrical rotor ring  9  extends over the outer periphery of housing  7 , which is part of field coil assembly  2 , with a specified clearance. Additionally, cylindrical rotor ring  9  includes rectangular aperture  16  by which it is fixedly attached to a rectangular portion of shaft  10 . Shaft  10  extends through bushing  8 . A cylindrical portion of shaft  10  and bushing  8  form a bearing that allows shaft  10  to be rotatably supported by field coil  2 . Shaft  10  is fixed in the axial direction by the snap ring  12 . Support shaft  11 , which extends into armature drive  4 , is press fit into one side of shaft  10 . Rectangular coupler  17  is formed on the other side of shaft  10 . A rotating shaft (not shown) of a motor or similar device connects to shaft  10  through the use of rectangular coupler  17 . Accordingly, rotor ring  9 , shaft  10 , and support shaft  11  rotate with the rotating shaft (not shown). 
   As shown in  FIG. 5  to  FIG. 7 , eighteen interlocking indentations  13  are uniformly arranged at a central angle of 20° in the circumferential direction on the outer periphery of the outside end face of the bottom part of rotor ring  9 , forming annular teeth. On the inner periphery of the annular teeth (interlocking indentations  13 ), six arc-shaped long holes  15  are uniformly arranged at a central angle of 60° in the circumferential direction. Additionally, rectangular aperture  16  is formed at the center of the bottom part of rotor ring  9 . 
   In the preferred embodiment, rotor ring  9  is formed by press working (“stamping”) a 3.2 mm thick blank of cold rolled steel sheet (SPCE-SD), which is used for deep drawing. The arrow mark X shown in  FIG. 5  indicates the punching direction of long holes  15  and aperture  16 . Moreover, the surface of rotor ring  9  is hardened through the use a gas nitrocarbonizing method. As shown in  FIG. 5 , rotor ring  9  has the following dimensions: sheet thickness t 1 =3.2 mm, diameter D 1 =50 mm, axial measurement L 1 =12.3 mm. Additionally, as shown in  FIGS. 6 and 7 , rotor ring  9  includes eighteen interlocking indentations  13  that have the following dimensions: width W 1 =2.8 mm, depth d=0.8 mm, and pressure angle α=23°. 
   As shown in  FIGS. 1 ,  2 , and  3 , armature drive  4  comprises ring-shaped armature  18 , guide ring  19 , cylindrical sleeve  20 , bushing  21 , snap ring  22 , and clutch spring  27 . Ring-shaped armature  18  faces opposite rotor ring  9 . Guide ring  19  is affixed to and arranged behind armature  18  and it is affixed to cylindrical sleeve  20 . Support shaft  11 , which is part of rotor  3 , is inserted in sleeve  20  via bushing  21  such that it is capable of rotating. Snap ring  22  fixes support shaft  11  in the axial direction. Spring  27  serves to keep ring shaped armature  18  away from rotor ring  9  when coil  6  is not energized. Rectangular coupler  23  is formed on the end of cylindrical sleeve  20  that is opposite to guide ring  19 . Rectangular coupler  23  may be attached to a rotating shaft or if toothed electromagnetic clutch  1  is being used as a brake, then rectangular coupler  23  will be attached to a non rotating structure 
   As shown in  FIG. 8  to  FIG. 10 , nine interlocking protuberances  24  are uniformly arranged in the circumferential direction at a central angle of 40° on the surface of armature  18  that faces rotor ring  9 , forming annular teeth. The nine interlocking protuberances  24  (annular teeth) are capable of engaging with the eighteen interlocking indentations  13  (annular teeth), which are formed on rotor ring  9 . Three U-shaped grooves  25  are uniformly arranged at a central angle of 120° between interlocking protuberances  24  on the outer periphery of armature  18 . Additionally, Guide claws  19 A, which project from guide ring  19 , fit into U-shaped grooves  25  and cause guide ring  19  to rotate with armature  18 . Armature  18  can slide axially along guide claws  19 A. Spring seat  26  is formed at the inner periphery edge part of armature  18 . Clutch spring  27  engages with spring seat  26  to ordinarily maintain armature  18  away from the rotor ring  9  by the spring force. Guide holes  28  are provided in the armature  18  for the purpose of positioning U-shaped grooves  25  on guide claws  19 A during assembly. 
   In the preferred embodiment, armature  18  is formed by press working (“stamping”) a 2.8 mm thick blank of cold rolled steel sheet (SPCE-SD), which is used for deep drawing. The armature  18  can, for example, be formed by the following type of stamping processes: (1) the annular blank is formed; (2) nine interlocking protuberances  24  and three spring seats  26  are formed in the blank; (3) three U-shaped grooves  25  and guide holes  28  are formed; (4) the inner surface of the U-shaped grooves  25  are formed; (5) the inner surface of the U-shaped grooves  25  are finished by surface pressing. Furthermore, surface-hardening treatment is conducted by the gas nitrocarbonizing method. 
   As shown in  FIG. 8 , armature  18  has the following dimensions: sheet thickness t 2 =2.8 mm, outer diameter D 2 =46 mm, bore diameter D 3 =24 mm. Additionally, as shown in  FIGS. 9 and 10 , armature  18  includes nine interlocking protuberances  24  that have the following dimensions: width W 2 =2.6 mm, height H=0.7 mm, pressure angle β=23°. 
   The operation of toothed electromagnetic clutch is described with reference to FIG.  1 . When coil  6  is energized, armature  18  is attracted towards rotor ring  9  by an electromagnetic force that is greater than the spring force of clutch spring  27 . Armature  18  slides along guide claws  19 A until it is united with the rotor ring  9 . The nine interlocking protuberances  24  on armature  18  mesh with the eighteen interlocking indentations  13  on rotor ring  9 . Interlocking indentations  13  apply torque to interlocking protuberances  24  thereby transmitting angular momentum and energy from rotor  3 , including the kinetic energy and momentum of any rotating shaft or motor coupled to rotor  3  by rectangular coupler  17 , to armature drive  4 . Armature drive  4 , in turn, transmits energy and momentum to any rotating shaft or non-rotating structure coupled to armature drive  4  through rectangular coupler  23 . When the nine interlocking protuberances  24  are meshed with the eighteen interlocking indentations  13 , there is no occurrence of slippage between armature  18  and rotor ring  9 . Accordingly, torque can be unfailingly applied. 
   When coil  6  is deenergized, the electromagnetic field dissipates and an electromagnetic force is no longer applied to armature  18 . The spring force applied by clutch spring  27  causes armature  18  to move away from rotor ring  9 . Accordingly, Interlocking indentations  13  can no longer apply torque to interlocking protuberances  24  and the transmission of angular momentum and energy is blocked. Since interlocking protuberances  24  and the interlocking indentations  13  are unfailingly separated by the spring force of clutch spring  27  when coil  6  is deenergized, the application of torque can be unfailingly blocked without the occurrence of entanglement. 
   The drawings and descriptions of the preferred embodiment are made by way of example rather than to limit the scope of the inventions, and the claims are intended to cover all variations and modifications within the spirit and scope of the inventions. For example, the teeth on rotor ring  9  could be protuberances and the teeth on an armature  18  could be indentations. Additionally, clutch spring  27  could be configured to apply a spring force that pushes armature  18  towards rotor ring  9  and field coil  2  could be positioned on armature drive  4  to apply an electromagnetic force that pulls armature  18  away from rotor ring  9  such that armature  18  and rotor ring  9  unite when coil  6  is deenergized.