STRUCTURE OF MOTOR HOUSING HAVING INTEGRALLY MOLDED ELECTRIC CONNECTOR

Abstract: A structure of a motor housing having a front flange (26) and a molded rear housing (28) fixed to the front and rear ends of the core (12) of the stator (10) of the motor, respectively, and a rotor (20) rotatably supported in the stator (10) with a gap therebetween through revolving bearings (30,32) retained by the front flange (26) and rear housing (28), wherein the front flange (26) is made of metal and the rear housing (28) is formed of a synthetic resin, light weight and provided with an electric connector (40) molded integrally with said housing (28) and capable of supplying electric power motor when coupled with an external electric connector (50) so that the connector (50) may be electrically coupled with the connector (40) when inserted thereinto in the same direction as that of the axis of the motor.

Description: TECHNICAL FIELD The present invention relates to an industrial motor for use as a rotative drive source for driving a machine tool or the like and, more particularly, to a housing structure for a motor, having a portion formed by molding a resin and integrally provided with a primary portion of an electric connector, to enable a supply of an electric drive current to the motor. BACKGROUND ART An industrial motor widely used as a rotative drive source for machine tools and other industrial machines has a construction comprising a laminated stator core having an outer circumference serving as a casing of the motor, a stator formed by inserting exciting coils in the laminated stator core, a front housing joined to the front end of the laminated stator core, a rear housing joined to the rear end of the laminated stator core, rotary bearings fitted in holes in the front and rear housings, and a rotor supported for rotation in the rotary bearings within the bore of the stator, with a gap between the outer circumference of the rotor and the inner circumference of the stator. Such an industrial motor is formed, by taking into consideration that the industrial motor is mostly subjected to severe running conditions due to a continuous long operation thereof, in a construction having a sufficient mechanical strength by forming the principal components, particularly, the front and rear housings joined respectively to the front and rear ends of the stator core, of a metal, and incorporating a means for transmitting and dispersing heat generated by copper loss and iron loss when an electric drive current is supplied to the exciting coils, to thereby prevent damage to and a reduction of the life of the motor due to an increase in the temperature of the motor to a high temperature. A motor having a greater output generates a greater amount of heat, and thus a metallic housing having a high heat conductivity is essential to a large-capacity industrial motor, to prevent a burning of the exciting coils. On the other hand, power, i.e., an exciting current, is supplied to an industrial motor having such a metallic housing, in most cases, by electrically connecting an electric connector, for example, a male electric connector, at the extremity of a power supply cable to a female electric connector screwed to a connector base projecting outward from a portion of the metallic rear housing of the motor. Figure 4 shows an exemplary industrial motor provided with such a conventional housing structure. This conventional industrial motor is constructed by joining a metallic front flange 3 and a rear housing 4 respectively to the front and rear ends of the core 2 of a stator 1, disposing a rotor, not shown, inside the stator 1 with its output shaft 5 projecting to the front from the front flange 3 so as to be connected mechanically to a driven member by a coupling or the like, and joining a cover 6 to the rear end of the rear housing 4 so as to cover the rear end of the motor. A connector base 7 is formed on the rear housing 4 so as to protrude radially outward from the outer circumference of the rear housing 4. An electric connector 8 is fastened to the connector base 7 by screws 9. Such a construction provided with the electric connector screwed to the connector base of the metallic housing requires a process for attaching the electric connector 8 on the market to the connector base 7 by screws 9 by hand during the fabrication of the motor. Furthermore, when the motor is intended for use as the rotative drive source of a machine tool, a packing 9′ is placed between the electric connector 8 and the connector base 7 to prevent a wetting the interior of the motor by machining liquid splashed out during the operation of the machine tool, the electric connector is fastened to the connector base 7 by the screws 8, and then the junction of the electric connector 8 and the connector base 7 is coated with a sealing grease to prevent a leakage of moisture into the motor. Thus, the motor manufacturing process requires an excessive amount of work, which is an impediment to a desired cost reduction. Furthermore, although the construction having the connector base 7 projecting from the outer circumference of the metallic rear housing 4 is intended to reduce costs through the employment of the available electric connector 8, the connector base 7 radially projecting from the outer circumference of the housing increases the overall size of the enveloping surface of the motor including the top of the connector base 7, and thus the motor requires a relatively large space for installation on a machine tool or the like. On the other hand, the conditions for dispersing heat generated by copper loss and iron loss are not very severe with an industrial motor having a comparatively small output capacity, and the rear housing need not be necessarily formed of a metal but may be formed of a resin, in view of forming a motor having a lightweight construction, provided that only the front flange is formed of a metal, to ensure satisfactory heat conduction and a sufficient mechanical strength for supporting the output shaft and for coupling the output shaft and the driven member. A motor housing structure having an integrally molded electrical connector is disclosed in U.S. Patent No. US-A-4 333 026. This document describes a motor housing structure for electric motors of the stepping or synchronous type, for use in translating a valve or rotatably driving a shaft. The disclosed structure has all the features according to the pre-characterising portion of claim 1 of the attached claims and in particular includes a rear housing formed of insulating material which defines a hollow bulge within which electric connector means are formed. US-A-4 104 550 discloses a structure incorporating an end cap made from glass reinforced styrene modified polyphenylene oxide. Also German Patent No. D-A-3235622 discloses a one-piece end cap formed from a plastics material which includes a hollow bulged housing for electrical connector means. DISCLOSURE OF THE INVENTION A principal object of the present invention is to provide a motor housing structure capable of solving the foregoing problems. Another object of the present invention is to provide an industrial motor having a construction including a rear housing formed by molding a resin and having a portion integrally provided with an electric connector incorporated therein by molding. According to the present invention there is provided a motor housing structure with an integrally molded electrical connector, comprising a front flange made of metal and fixed to a front end of a core of a stator of a motor, a rear housing fixed to a rear end of the core, rotary bearings held by said front flange and said rear housing respectively, a rotor shaft rotatably supported via the rotary bearings, the rotor shaft having a rotor of the motor mounted thereon and positioned inside the stator via a gap extending between an outer circumference thereof and an inner circumference of the core and having an output shaft formed in it's front end and projecting outwardly from a front surface of said front flange toward a front of said motor, said rear housing including a molded housing which is provided with a hollow bulge at a portion thereof, an electrical connector means through which an electric drive current is supplied to the motor being formed integrally with said molded housing in said hollow bulge, the electrical connector means including wall means defining a socket for receiving an external electrical connector, said wall means defining a first opening in a direction along the axis of the output shaft of the motor, the electrical connector means further including conductive pin means electrically connected to the stator of the motor for electrically connecting with said external electrical connector through said first opening when the external electrical connector is inserted into the socket characterised in that said molded housing is formed by molding a resin, said first opening is disposed outside an outer peripheral wall of said rear housing, said wall means defines a second opening between the socket and an interior of said rear housing, and said conductive pin means have a holding element so as to be operatively insertable through said second opening into the socket from said interior of the rear housing so as to be electrically connectable with the external electrical connector. When molding the thus molded rear housing of the motor housing structure, the primary portion of the electric connector is molded integrally with the rear housing. Therefore, a locking mechanism for holding an external electric connector in place and an external electric connector guide groove for guiding the external electric connector so that the external electric connector can be correctly received in the electrical connector means in a given position can be formed when molding the rear housing, and therefore the motor housing structure does not need a sealing structure and eliminates the work needed for screwing the component parts of the electric connector. Preferably the wall means of the electrical connector means is provided with an upper wall, a lower wall opposite the upper wall and a pair of mutually facing side walls. Preferably the wall means of the electrical connector means is further provided with an innermost holding wall for holding the conductive pin means. Preferably the innermost holding wall is provided with a catch formed integrally therewith and operatively engageable with an elastic hook formed in the holding element of the conductive pin means. Preferably at least one of the upper or lower walls is provided with a guide groove for guiding the external electrical connector when the external electrical connector is inserted into the socket. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which: Fig. 1 is a partially cutaway front elevation of a motor provided with a molded housing provided with an integrally molded electric connector; Fig. 2 is a side elevation of the motor shown in Fig. 1; Fig. 3 is an exploded perspective view of a molded rear housing included in a motor housing in accordance with the present invention; and Fig. 4 is a partially sectional front elevation of a conventional industrial motor and a connector structure incorporated into the same industrial motor. BEST MODE OF CARRYING OUT THE INVENTION Fig. 1 shows an industrial motor to which the present invention can be applied. The servomotor has a stator 10 and a rotor 20 disposed in the central bore of the stator 10 with a gap between the inner circumference of the stator 10 and the outer circumference of the rotor 20. The stator 10 comprises a stator core 12 and exciting coils 14, and the rotor 20 has a rotor shaft 22 extended in its central portion thereof. The front end 24 of the rotor shaft 22 is formed as an output shaft projecting to the front, and a metallic flange 26 having the shape of a bell jar is fastened to the front end of the stator core 12 by screw bolts, not shown. A molded resin rear housing 28 formed by molding a resin is fastened to the rear end of the stator core 12 by screw bolts. The rotor shaft 22 is supported rotatably in rotary bearings 30 and 32 fitted in the respective central portions of the front metallic flange 26 and the molded rear housing 28, respectively, to enable the rotor 20 to rotate inside the stator 10, and a cover 34 is attached by suitable attaching means, such as screws or an adhesive, to the rear end of the molded rear housing 28. A rotation detector, not shown, is housed in the cover 34 for detecting the rotation of the output shaft of the servomotor. The molded rear housing 28 is formed of a heat-resistant resin material having a satisfactory moldability and capable of ensuring a sufficient mechanical strength for moldings, by a well-known molding process using an injection molding machine. The molding process is able to form the molded rear housing 28 with a high accuracy and is able to form an electric connector unit 40 integrally with the molded rear housing 28, whereas the conventional metallic rear housing is provided integrally with only a connector base. The electric connector unit 40 comprises a bulge 42 formed in one portion of the molded rear housing 28 by molding and internally defining a connector socket 42a having an opening 42b opening in the axial direction of the motor, conductive pins 46 provided in the depth of the connector receiving socket 42a and electrically connected to the exciting coils 14 of the stator 10, and a separate base wall 48 holding the conductive pins 46. An external electric connector 50 schematically illustrated by broken lines in Fig. 1 is plugged into the connector socket 42a to connect the external electric connector electrically to the conductive pins 46. The connector socket 42a is defined within the bulge 42 by an upper wall 43a, a lower wall 43b and side walls 43d and 43e and has a substantially rectangular cross section. When the electric connector unit 40 integrally formed with the molded rear housing 28 by molding can be completed by attaching the molded rear housing 28 to the rear end of the stator core 12 when assembling the motor. A locking projection 44 formed on the lower wall 43b to lock the external electric connector 50 in place and a guide groove 49 formed in the upper wall 43a defining the connector socket 42a so as to guide a projection formed on the outer surface of the external electric connector 50 enable the external electric connector 50 to be firmly plugged into the connector socket 42a in a correct position relative to the electric connector unit 40, so that a wrong connection of the electric connector unit 40 and the external electric connector 50 can be prevented and, consequently, the conductors of the external electric connector 50 for different phases can be correctly connected to the corresponding conductors of the electric connector of the electric connector unit 40 connected to the exciting coils 14 for different phases, respectively, without fail. Since the external electric connector 50 can be inserted deeply into the socket 42a of the electric connector unit 40, an effective internal water-proof sealing, hitherto obtained by a packing, can be obtained by providing a sealing structure on the inner surface of the socket 42a and the outer surface of the external electric connector 50. The molded rear housing 28 formed of a resin reduces the weight of the motor, and the electrical connector unit 40 integrally formed with the molded rear housing 28 and having the socket receiving the external electric connector 50 in a direction parallel to the axis of the motor reduces the size of the enveloping surface of the motor, compared with that of the enveloping surface of the conventional motor provided with the projecting connector base, and thus the motor can be formed in a compact construction. Accordingly, the motor requires a relatively small space for installation when operatively connecting the motor with the driven unit of a machine tool or the like. Although the invention is described as applied to a servomotor, naturally the present invention is not limited thereto in practical application. When the present invention is embodied in an industrial motor for example, an induction motor having a comparatively small output capacity, a bulge having a socket is formed in a portion of the rear housing when forming the rear housing by molding a resin, and conductors are fixedly provided in the depth of the socket to construct a motor housing structure having an integrally molded electric connector similar to that described above. Figure 3 is a perspective view of a motor housing structure according to the present invention. A molded rear housing 128 included in the motor housing structure shown in Fig. 3 is provided integrally with a hollow bulge 142 formed in molding the same. The bulge 142 has an upper wall 143a, a lower wall 143b opposite the upper wall 143b, opposite side walls 143b and 153e, and an end wall 143f. The upper wall 143a, the lower wall 143b and the side walls 143d and 143e define a socket 142e extending in a direction along the axis of the motor and having an opening 142b, and an opening 145 opening into the interior of the molded rear housing 128 is formed in the inner portion of the lower wall 143b. When assembling the motor, a holding member 148 holding conductive pins 146 is inserted upward in the opening 145 so that an elastic hook 149c formed in the middle portion of the upper end of a vertical section 148a of the holding member 148 engages a catch 149c formed on the inner surface of the end wall 143f, to hold the holding member 148 in place on the end wall 143f. The opposite side portions of the vertical section 148c are received respectively in grooves 141 formed respectively in the side walls 143d and 143e (only one of the grooves 141 formed in the side wall 143d is shown), and thus the holding member 148 is secured to the bulge 142. When secured to the bulge 142, the upper surface of a lower horizontal section 148b of the holding member 148 is flush with the upper surface of the lower wall 143b of the bulge 142, and a guide groove 149a formed on the upper surface of the lower horizontal section 148b is aligned with a guide groove 149 formed on the upper surface of the lower wall 143b. In this state, the conductive pins 146 are held horizontally in the socket 142a, so as to be electrically connected to an external electric connector when the external electric connector is plugged in the socket 142a. The lower ends 146a of the conductive pins 146 are electrically connected to the exciting coils, not shown, of the stator of the motor within the molded rear housing 128 by a connecting means such as soldering or caulking. A locking projection similar to the locking projection 44 of the first embodiment may be formed on the sidewall 143d or 143e of the bulge 142, by molding. As will be understood from the foregoing description of the invention, in accordance with the present invention a rear housing for industrial motors including a servomotor is formed by molding a resin, and the molded rear housing is integrally provided with an electric connector through which an electric drive current is supplied to the motor. Accordingly, a process for mounting an electric connector on the rear housing by screws can be omitted, to thereby reduce the steps of the motor manufacturing process and enable cost reductions and allow the use of a locking mechanism, a protective mechanism to prevent a wrong connection of an external electric connector, and a water-proof sealing mechanism having improved structural abilities, for a functional improvement of the structure of the motor. It should be noted that many modifications and variations of the present invention may occur without departing from the scope of the invention as defined by the appended claims.

Claims: A motor housing structure with an integrally molded electrical connector, comprising a front flange (26) made of metal and fixed to a front end of a core (12) of a stator (10) of a motor, a rear housing (128) fixed to a rear end of the core (12), rotary bearings (30, 32) held by said front flange (26) and said rear housing (128) respectively, a rotor shaft (22) rotatably supported via the rotary bearings (30, 32), the rotor shaft (22) having a rotor (20) of the motor mounted thereon and positioned inside the stator (10) via a gap extending between an outer circumference thereof and an inner circumference of the core (12) and having an output shaft (24) formed in it's front end and projecting outwardly from a front surface of said front flange (26) toward a front of said motor, said rear housing (128) including a molded housing (128) which is provided with a hollow bulge (142) at a portion thereof, an electrical connector means through which an electric drive current is supplied to the motor being formed integrally with said molded housing (128) in said hollow bulge 142, the electrical connector means including wall means (143a to 143e) defining a socket (142a) for receiving an external electrical connector, said wall means (143a to 143e) defining a first opening (142b) in a direction along the axis of the output shaft (24) of the motor, the electrical connector means further including conductive pin means electrically connected to the stator (12) of the motor for electrically connecting with said external electrical connector through said first opening (142b) when the external electrical connector is inserted into the socket (142a) characterised in that said molded housing (128) is formed by molding a resin, said first opening (142b) is disposed outside an outer peripheral wall of said rear housing (128), said wall means (143b) defines a second opening (145) between the socket (142a) and an interior of said rear housing (128), and said conductive pin means (146) have a holding element (148) so as to be operatively insertable through said second opening (145) into the socket (142e) from said interior of the rear housing (128) so as to be electrically connectable with the external electrical connector. A motor housing structure according to claim 1, wherein the wall means of the electrical connector means is provided with an upper wall (143a), a lower wall (143b) opposite the upper wall (143a) and a pair of mutually facing side walls (143d, 143e). A motor housing structure according to claim 2, wherein the wall means of the electrical connector means is further provided with an innermost holding wall (143f) for holding the conductive pin means. A motor housing structure according to claim 3, wherein the innermost holding wall (143f) is provided with a catch (149b) formed integrally therewith and operatively engageable with an elastic hook (149c) formed in the holding element of the conductive pin means. A motor housing structure according to any one of claims 2 to 4, wherein at least one of the upper or lower walls (143a, 143b) is provided with a guide groove (144) for guiding the external electrical connector when the external electrical connector is inserted into the socket (142a).

Inventors: NISHINA MASASHI FANUC DAI- VIR, OKUDA KANEMASA FANUC MANSION H, SOGABE MASATOYO FANUC MANSION, UCHIDA HIROYUKI FANUC MANSION, YAMAMOTO TOMONAGA FANUC DAI- V, NISHINA, MASASHI FANUC DAI-3 VIRA-KARAMATSU, OKUDA, KANEMASA FANUC MANSION HARIMOMI 6-204, SOGABE, MASATOYO FANUC MANSION HARIMOMI 6-304, UCHIDA, HIROYUKI FANUC MANSION HARIMOMI, 7-107, YAMAMOTO, TOMONAGA FANUC DAI-3 VIRA-KARAMATSU
Applicants: FANUC LTD, FANUC LTD.
Application year: 1990
Main classification: H02K5
IPC codes: H02K5