A leading-out device for a lead wire of a DC motor and a method of leading out a lead wire

Abstract: A leading-out device for a lead wire of a DC motor (2) comprising: a lead wire (21) composed of twisted wires, a leading-out portion (21a) at an end side of which is formed in a flat shape and is shortened with respect to the axial direction of a DC motor (2); and a grommet (13) through which said lead wire (21) passes from outside the DC motor (2) to inside thereof; said leading-out portion (21a) of the lead wire (21) is welded and connected to an inner conductor (10) of the DC motor at an end portion thereof.

Description: This invention relates to a leading-out device for a lead wire of a DC motor wherein a lead wire portion connected to a main circuit conductor of the motor and led outside thereof, is improved. Figure 3 is a side view of a starter motor wherein a lead wire is led from a direct current motor portion to outside thereof. A reference numeral 1 designates a starter motor composed as follows. A numeral 2 designates a DC motor, wherein a rear bracket 4 is connected to a rear end of a yoke 3 and a front bracket 6 is connected to a front end thereof through an intermediate bracket 5. Inside thereof, a speed reducing gear device is connected to an armature and a pinion 15 is extended therefrom through an overrunning clutch. A numeral 16 designates an electromagnetic switch wherein a lead wire 12 extended from the motor 2 to outside thereof, is connected to a main circuit terminal (M terminal) 17. A numeral 13 designates a grommet fitted to a cut-off portion of the yoke 3 through which the lead wire 12 passes and 14, an insulation tube fitted to the lead wire 12. A circuit diagram of the DC motor 2 is shown by Figure 4. A numeral 7 designates an armature, 8, a brush and 9, a field coil to a connection conductor 10 of which the lead wire 12 is connected at a connecting portion 11. When current flows in an electromagnetic switch 16, the contact of the circuit is closed, a current from a storage battery flows from the main circuit terminal 17 to the lead wire 12 and to the main circuit of the DC motor 2 thereby rotating the armature 7. In the meantime, a plunger of the electromagnetic switch 16 is operated, a shift lever (not shown) is swiveled and a pinion 15 is moved forward through an overrunning clutch which meshes with a ring gear of an internal combustion engine. The rotation of the armature 7 is reduced by the speed reducing gear device and rotates the pinion 15 through the overrunning clutch. In this way, the ring gear is rotated and the engine is started. Figure 5A is a sectional diagram of a conventional leading-out device for a lead wire. An end of the lead wire 12 composed of twisted wires is connected to the connecting portion 11 of the connecting conductor 10 of the motor 2 by a brasing material. As shown in Figure 5B by a sectional diagram, a lead wire 12 passing through the grommet 13 made of a gummy material is a twisted-wire conductor composed of a great number of copper wires. Especially, in the starter motor, since a large current flows in the lead wire 12 and in view of the vibration resistance, the diameter thereof is magnified. In the conventional leading-out device for a lead wire, the outer configuration of a lead wire 12 is circular and thick. The lead wire 12 reaches inside of the yoke 3 through the grommet 13. To maintain a clearance between the lead wire 12 and the inner field coil 9, the motor 2 is elongated in the axial direction, which hampers the downsizing thereof. US-4,985,654 discloses a brush device of a motor comprising two elongated lead wires, a brush connected to one of end of each lead wire and a terminal connecting the other ends of the lead wires together. The wires are ultrasonically welded together at an intermediate position to form a reduced cross-section portion which is sealingly surrounded by a rubber grommet. Furthermore, in the above conventional leading-out device for a lead wire, in passing the leading-out portion of the lead wire 12 through the grommet 13, a hole of the grommet 13 has an interference to provide a waterproof performance. Therefore the operation is difficult. Furthermore, a variation of the protruding length of the leading-out portion which passes through the grommet 13 should be avoided and the protruding length should conform to a predetermined length. Therefore, the operation becomes more difficult. It is an object of the present invention to solve the above problems and to provide a leading-out device for a lead wire of a DC motor wherein the thickness of the leading-out portion of the lead wire in the axial direction is reduced and the outer configuration of the motor in the axial direction is shortened and downsized. Furthermore, it is an object of the present invention to provide a method of leading out a lead wire wherein the lead wire is provided with the waterproof performance at the grommet portion and the operational performance in connecting the lead wire to an internally connected conductor, is promoted. It is an object of the present invention to provide a leading-out device for a lead wire of a DC motor wherein it is not necessary to pass the lead wire 12 through the grommet, the waterproof performance and the vibration resistance performance are promoted and the protruding length of the leading-out portion thereof from the grommet is conformed to a predetermined length. According to first aspect of the present invention, there is provided a leading-out device for passing an electrical conductor of DC starter motor of an internal combustion engine through a generally cylindrical housing thereof, comprising: a grommet disposed in an aperture in a side of the housing, an electrical conductor composed of a plurality of twisted wires, said wires being welded together to form a lead at an end portion of the conductor extending through the grommet and into an interior of the housing, perpendicular thereto, and an inner conductor of the motor disposed within the housing at a terminus of the end portion, characterized by the cross-section of said end portion being flattened with respect to the axial direction of the motor, and a resistance weld establishing electrical connection between said inner conductor and said terminus. According to a second aspect of the present invention, there is provided a method of leading a twisted wires electrical conductor through an aperture in a side of a generally cylindrical housing of a DC starter motor, comprising the steps of: disposing a grommet (13,24,122) in the aperture, characterized by welding the twisted wires together to form a lead at an end portion of the conductor such that said end portion is pressed and deformed in a flattened shape, inserting the end portion through the grommet and into an interior of the housing such that the cross-section of said end portion is flattened with respect to the axial direction of the housing, welding a terminus of the end portion to an inner conductor of the motor disposed within the housing. According to a third aspect of the present invention, there is provided a method of leading a twisted wires electrical conductor through an aperture in a side of a generally cylindrical housing of a DC motor, comprising the steps of: welding an end of the twisted wires electrical conductor to form a lead at an end portion of the conductor such that said end portion is pressed and deformed to have a generally flattened shape, protruding the end portion by a predetermined length and integrally molding a resin with the end portion to form a grommet, installing the grommet and integral end portion in the aperture of the motor housing from the outside of the motor such that the cross-section of said end portion is flattened with respect to the axial direction of the housing, and welding a terminal of the motor to the protruded end portion In this invention, the leading-out portion at an end side of the lead wire from inside of the machine, is flatly shortened with respect to the axial direction of the motor, thereby shortening the outer configuration of the motor in the axial direction. Furthermore, in flattening the leading-out portion, the portion is pressed end formed by a resistance welding or by an ultrasonic welding along with a brazing material. Therefore, in a later step, the end portion of the leading-out portion is connected to an inner conductor by a resistance welding and no addition of a brazing material is required. In this way, the flattened leading-out portion prevents invasion of the outside moisture. In this invention, the grommet is integrally formed with the deformed and reduced leading-out portion on the one end side of the lead wire. The operation of passing the leading-out portion through the grommet is saved. The protruding length of the leading-out portion of the lead wire from the grommet is set to a predetermined length. Furthermore, the invasion of the outside moisture is firmly prevented. In the drawings: Figure 1A is a sectional diagram showing a first embodiment of a leading-out device for a lead wire of a DC motor according to the present invention, and Figure 1B is a sectional view taken along a line B 1 -B 1 of Figure 1A; Figure 2A is a sectional diagram showing a second embodiment of a leading-out device for a lead wire of a DC motor according to the present invention and Figure 2B, a sectional diagram taken along a line B 2 -B 2 of Figure 2A; Figure 3 is a side view of a starter motor provided with a leading-out device for a lead wire; Figure 4 is a circuit diagram of the motor in Figure 3; Figure 5A is a sectional diagram of a leading-out device for a lead wire of a conventional DC motor, and Figure 5B, a sectional diagram taken along a line B 5 -B 5 of Figure 5A; Figure 6A is a sectional diagram of a third embodiment of a leading-out device for a lead wire of a starter motor according to the present invention, Figure 6B, a sectional diagram taken along a line B-B of Figure 6A, and Figure 6C, a sectional diagram taken along a line C-C of Figure 6A; Figure 7A is a sectional diagram of a fourth embodiment of a leading-out device for a lead wire according to the present invention and Figure 7B, a sectional diagram taken along a line B-B. EXAMPLE 1 Figure 1A is a sectional diagram of a first embodiment of a leading-out device for a lead wire of a DC motor according to the present invention. As shown in Figure 1B, a leading-out portion of a lead wire 11 composed of twisted wires at an end side thereof passing through the grommet 13, is formed in a semicircular flattened form, shortened with respect to the axial direction of the motor 2 and widened in the peripheral direction thereof. Accordingly, as the grommet 13, the one which is shortened with respect to the axial direction of the motor 2 is employed. The flattening-deformation of the leading-out portion 21a of the lead wire 21 and the connection of the lead wire 21 to the inner conductor 10, are performed as follows. The leading-out portion of the lead wire 11 is pressed and deformed as shown in Figure 1B by a resistance welding along with a brazing material. The end portion of the leading-out portion 21a is connected to the connecting portion 11 of the inner conductor 10 by a resistance welding. At this occasion, the leading-out portion 21a already contains the brazing material and therefore, the addition of the brazing material is not necessary. The lead wire 21 is compressed in a flattened shape containing the brazing material at the grommet 13 and therefore, is excellent in the waterproof performance. EXAMPLE 2 Figure 2A is a sectional diagram of a second embodiment of a leading-out device for a lead wire according to the present invention. The leading-out portion 21a of the lead wire 11 composed of twisted wired at an end portion thereof, is compressed and deformed in a flat shape with respect to the axial direction of the motor 2 by the same means as in Figure 1. The section of the leading-out portion 21a is shown in Figure 2B, which is deformed in a rectangular flattened shape. The lead wire 21 deformed as above is bent in the axial direction with respect to a portion thereof above the grommet 13. The bent portion is fitted with an insulation tube 14, an end of which is fitted to an upper end portion of the grommet 13. In case of Figure 2A, the device is more excellent in the waterproof performance and the vibration resistance performance. EXAMPLE 3 In the above Examples, the flattening-deformation of the lead wire 21 is performed by the resistance welding, but it may be performed by the following way. The leading-out portion 21a of the lead wire 21 composed of twisted wires is pressed and deformed in a flattened shape by an ultrasonic welding along with a brazing material. Thereafter, the leading-out portion 21a is connected to the inner conductor 10 by a resistance welding. According to this method of connecting the leading-out portion, the productivity is further promoted compared with the connection method in Example 1. Furthermore, in the above Examples, cases are shown wherein the flattened shape of the leading-out portion 21a of the lead wire 21 is semicircular or rectangular. However, the shape is not limited to the above Examples and may be oval or trapezoidal. As stated above, according to the present invention, since the leading-out portion of the lead wire composed of twisted wires is pressed and deformed in a flattened shape which is shortened with respect to the axial direction of the motor, the outer configuration with respect to the axial direction of the motor is shortened and downsized. Furthermore, according to the present invention, since the leading-out portion of the lead wire is pressed and deformed in a flattened shape by the resistance welding or by the ultrasonic welding along with the brazing material, and the leading-out portion of the lead wire is drawn into the machine while placing the area-reduced side in the axial direction of the motor and is connected to the inner conductor by the resistance welding, it is not necessary to add the brazing material in the welding-connection thereof to the inner conductor body thereby promoting the productivity. Furthermore, the device is excellent in the water proof performance. EXAMPLE 4 Figure 6A is a sectional diagram of a fourth embodiment of a leading-out device for a lead wire of a DC motor according to the present invention. A leading-out portion 121a of a lead wire 121 composed of twisted wires at an end side thereof is pressed and deformed so that the section is flattened into a rectangular shape or the like by a resistance welding or by an ultrasonic welding, along with a brazing material. A portion of the lead wire 121 above the leading-out portion 121a is bent in an arcuate form. A constricted portion 121b is formed at an upper portion of the bent portion by pressing and reducing the bent portion in a rectangular section or the like by a resistance welding or by an ultrasonic welding with or without a brazing material. Examples of sections of the leading-out portion 121a and the constricted portion 121b are shown in Figures 6B and 6C. Accordingly, even when the lead wire 121 is composed of twisted wires, by forming the constricted portion 121b, the bending by an angle of 90° or the like can firmly be maintained. An end side of the deformed lead wire 121 is inserted into a mold of forming a grommet (not shown), positioning the lead wire 121 in the mold employing the leading-out portion 121a and the constricted portion 121b, and a gummy material is charged in the mold thereby forming a grommet 122 by the integral forming. A synthetic gum, a synthetic resin series gum or the like is employed for the grommet 122. If the grommet requires the thermal resistance, a corresponding material is employed. EXAMPLE 5 Figure 7A is a sectional diagram showing a fifth embodiment of a leading-out device for a lead wire according to the present invention. A coating layer 123 is integrally formed on the outer periphery of the leading-out portion 121a at an end side of the lead wire 21 wherein the section thereof is reduced and formed into a rectangular shape, by a mold (not shown) employing a heat-resistant gum such as polybutylene terephthalate (PBT). The grommet 24 is integrally formed with an end side of the as coated lead wire 21 by a mold (not shown) employing a synthetic gum, a synthetic resin series gum, a thermoplastic elastomer or the like. In this way, the thermal resistance is promoted. The device can meet the required function by employing a gummy material corresponding to the requirement for the coating layer 123 and by laminating at least two kinds of forming materials for the coating layer 123 and the grommet 24. As stated above, according to the present invention, the leading-out portion at one end side of the lead wire is deformed in a rectangular form flattened with respect to the axial direction of the motor and the grommet is integrally formed with the one end side of the lead wire. Therefore, the integration operational performance is promoted, the waterproof can firmly be maintained and the protruding length of the leading-out portion from the grommet can be determined in a predetermined length. Moreover, in case of bending a portion of the lead wire above the leading-out portions, by providing the constricted portion at the other end of the bent portion which is reduced and deformed in a rectangular shape , the bent state of the lead wire is maintained and the integral forming of the grommet at the one side can easily be performed. Furthermore, the required performance can be promoted by forming the grommet by laminating at least two kinds of gummy materials at the leading-out portion of the lead wire.

Claims: A leading-out device for passing an electrical conductor of a DC starter motor (2) of an internal combustion engine through a generally cylindrical housing thereof, comprising: a) a grommet (13,24,122) disposed in an aperture in a side of the housing, b) an electrical conductor (21,121) composed of a plurality of twisted wires, said wires being welded together to form a lead at an end portion (21a,121a) of the conductor (21,121) extending through the grommet (13,24,122) and into an interior of the housing, perpendicular thereto, and c) an inner conductor (10) of the motor disposed within the housing at a terminus of the end portion (21,121), characterized by d) the cross-section of said end portion (21a,121a) being flattened with respect to the axial direction of the motor (2), and e) a resistance weld establishing electrical connection between said inner conductor (10) and said terminus. A device according to claim 1, wherein said flattened end portion (21a,121a) has a semi-circular or rectangular cross-section. A device according to claims 1 or 2, wherein said twisted wires are welded together by one of resistance welding and ultrasonic welding, and include a brazing material for implementing the weld of sub-paragraph e). A device according to one of claims 1 to 3, wherein the grommet (13,24,122) is integrally formed with the end portion (21a,121a). A device according to claim 4, wherein the grommet (24) is integrally formed with the end portion (21a,121a) through a coating layer (123) which is coated on the end portion (21a,121a) with a material other than a mold resin. A device according to claim 4, wherein an unwelded portion (121b) of the electrical conductor (121) exterior of the housing is bent in an arcuate shape at a right angle to lie parallel to the housing, and the grommet (122) is molded about the welded end portion (121a) and the unwelded, bent portion (121b). A device according to claim 6, wherein the twisted wires in a portion of the electrical conductor (121) exiting the arcuate bend are welded together and flattened. A method of leading a twisted wires electrical conductor (21,121) through an aperture in a side of a generally cylindrical housing of a DC starter motor, comprising the steps of: a) disposing a grommet (13,24,122) in the aperture, characterized by b) welding the twisted wires together to form a lead at an end portion (21a,121a) of the conductor (21,121) such that said end portion (21a,121a) is pressed and deformed in a flattened shape, c) inserting the end portion (21a,121a) through the grommet (13,24,122) and into an interior of the housing such that the cross-section of said end portion (21a,121a) is flattened with respect to the axial direction of the housing, d) welding a terminus of the end portion (21a,121a) to an inner conductor (10) of the motor disposed within the housing. A method according to claim 8, wherein said flattened shape is one of semi-circular and rectangular. A method according to claims 8 or 9, wherein said twisted wires are welded together by one of resistance welding and ultrasonic welding, and include a brazing material for implementing the welding step of sub-paragraph d). A method of leading a twisted wires electrical conductor (21,121) through an aperture in a side of a generally cylindrical housing of a DC motor, comprising the steps of: a) welding an end of the twisted wires electrical conductor (21,121) to form a lead at an end portion (21a,121a) of the conductor (21,121) such that said end portion (21a,121a) is pressed and deformed to have a generally flattened shape, b) protruding the end portion by a predetermined length and integrally molding a resin with the end portion (21a,121a) to form a grommet (13,24,122), c) installing the grommet (13,24,122) and integral end portion (21a,121a) in the aperture of the motor housing from the outside of the motor (2) such that the cross-section of said end portion (21a,121a) is flattened with respect to the axial direction of the housing, and d) welding a terminal of the motor (10) to the protruded end portion (21a,121a). A method according to claim 11, wherein the flattened shape is one of semi-circular and rectangular. A method according to claim 11 or 12, wherein the welding in sub-paragraph d) comprises one of resistance welding and ultrasonic welding along with a brazing material. A method according to claims 11 or 12, wherein forming the end portion (21a,121a) is implemented by: providing a constricted portion (121b) in a mid-region of the electrical conductor (121) composed of twisted wires, wherein a section thereof is constricted and welded; welding a remaining end (121a) of the lead wire of a predetermined length beyond the constricted portion (121b) to form the flattened shape; and bending a twisted wire portion intermediate the mid-region and remaining end in an arcuate shape. A method according to claims 11 or 12, wherein the step of forming the grommet (122) in sub-paragraph b) comprises the steps of: forming a coating layer (123) on the end portion (121a) by coating the end portion with a material other than a molding resin, and integrally molding the resin on the coating layer (123).

Inventors: ISOZUMI SHUZOU, YAMAMOTO KYOHEI, ISOZUMI, SHUZOU, YAMAMOTO, KYOHEI, ISOZUMI, SHUZOU, C/O MITSUBISHI DENKI K. K., Yamamoto, Kyohei, c/o Mitsubishi Denki Eng. K. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: H02K5
IPC codes: H02K5