Abstract:
A starter for starting in-vehicle internal combustion engines comprise a motor, an electromagnetic switch and an electrically conductive connection member. The electromagnetic switch comprises first and second fixed contacts, a movable contact, an electromagnet moving back and forth to the movable contact to electrically connect and disconnect the first and second fixed contacts, and a cover covering the first and second contacts and movable contact. The predetermined direction is parallel to an armature provided in the motor. The electromagnet is provided with only a single coil generating a drive force for moving the movable contact. A connection member is arranged to be through the casing and the cover and electrically connects a brush of the armature in the motor and the second fixed contact in the switch. The connection member includes an end part arranged in the casing of the switch. This end part functionally provides the second fixed contact.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2007-192442 filed Jul. 24, 2007, the description of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to a biaxial type of starter for starting internal combustion engines, and in particular, to such a starter in which the operative shaft of an electromagnetic switch and the armature shaft of a motor are disposed parallel to each other. 
     2. Related Art 
     Japanese Patent No. 3478211, for example, discloses a starter including: a main contact which is provided in a motor circuit for supplying current from batteries to the armature of the motor; and an electromagnetic switch for opening/closing the main contact. 
     The main contact consists of a B (i.e., battery)-fixed-contact connected to a high-potential side (battery side) of the motor circuit via a B-terminal bolt, an M-fixed-contact connected to a low-potential side (motor side) of the motor circuit via an M (i.e., motor)-terminal bolt, and a movable contact configured to move over against the B-fixed contact and the M-fixed contact. The movable contact comes into contact with both of the fixed contacts to make both of the fixed contacts electrically conductive and to thereby close the main contact. When both of the fixed contacts are apart from the movable contact and the electrical conduction is interrupted between these fixed contacts, the main contact is opened. 
     However, starters of the type mentioned above use a number of parts on the low-potential side of the motor circuit. In particular, other than the M-fixed contact, such a type of starter needs, for example, an M-terminal bolt to be fixed to an insulating contact cover of the electromagnetic switch, a sealing member (e.g., O-ring) for sealing a gap between the M-terminal bolt and the contact cover, a washer for fixing the M-terminal bolt to the contact cover, motor leads drawn from the side of the motor, and nuts for fixing the terminals of the respective motor leads to the M-terminal bolt. In this way, the number of parts is increased and thus the number of assembling processes is increased, producing factors of high cost. 
     In addition, since two terminal bolts (B- and M-terminal bolts) are radially juxtaposed in the electromagnetic switch, an insulation distance (creepage distance) is required to be ensured between the two terminal bolts. Under such conditions, there is a limitation in radially closely arranging the two terminal bolts, and this has prevented the downsizing (radial reduction) of such an electromagnetic switch. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in light of the circumstances provided above, and has as its object to provide a starter which is able to reduce cost by reducing the number of parts and thus to reduce the size of an electromagnetic switch, and to provide a method for manufacturing such a starter. 
     For the above object, the present invention provides a starter for starting an internal combustion engine of a vehicle, comprises an electric motor, an electromagnetic switch, and an electrically conductive connection member. The electric motor is provided with an armature, a brush, and a casing that encloses at least the armature and the brush, current being supplied to the armature via the brush. The electromagnetic switch is provided with first and second fixed contacts, a movable contact, an electromagnet that moves back and forth to the movable contact in a predetermined direction so as to electrically connect and disconnect the first and second fixed contacts, and a cover that covers at least the first and second contacts and the movable contact. The predetermined direction is parallel to a longitudinal direction of the armature of the motor. The electromagnet is provided with only a single coil generating a drive force for moving the movable contact. The electrically conductive connection member is arranged to link the motor and the electromagnetic switch through the casing of the motor and the cover of the electromagnetic switch and electrically connects the brush of the motor and the second fixed contact in the electromagnetic switch. The connection member includes an end part arranged in the casing of the electromagnetic switch, and this end part of the connection member functionally provides the second fixed contact. 
     With the above configuration, one end part of the connection member is connected to, for example, a pigtail of a plus-side brush, and the other end part of the connection member functionally forms the second fixed contact. Thus, various parts can be omitted, such as the conventional terminal bolt (called M-terminal bolt), sealing members, washer, motor leads and nuts, by which the number of assembling processes can be reduced. 
     Also, the omission of the conventional terminal bolt can reduce the number of terminal bolts to one to establish connection with the motor circuit. In other words, only one terminal bolt may only have to be fixed to the contact cover in order to connect the first fixed contact (called B-fixed contact) to the high-potential side of the motor circuit. In this case, a large insulation distance (creepage distance) can be ensured between the connection member forming the second fixed contact (called M-fixed contact) and the single terminal bolt, because the connection member is inserted into the cover from the radial outer periphery thereof. As a result, the diameter of the cover can be reduced comparing with the conventional electromagnetic switch where two terminal bolts are juxtaposed along the radial direction of the cover. 
     Moreover, in a conventional two-coil electromagnetic switch, or in an electromagnetic switch having a suction coil and a retention coil, electrical connection is generally established between the suction coil and an M-terminal bolt via a connecting terminal. Accordingly, the omission of the M-terminal bolt may involve substantial structural change, for establishing connection between the suction coil and the motor circuit. In this regard, in the present invention, the switch coil of the electromagnetic switch is not required to be connected to the motor circuit, because the switch coil is structured by a single coil. In other words, the omission of the M-terminal bolt may cause no problem, and thus almost no structural change is required. Accordingly, the connecting terminal can be omitted together with the omission of the M-terminal bolt, and hence the process can also be omitted for connecting the end of the suction terminal to the connecting terminal such as by welding, whereby the number of parts and the number of processes can be reduced and thus more cost reduction can be achieved. 
     It is preferred that the starter comprises a holding member ( 28 ) that is made of insulating and elastic material and that fixedly holds, between the motor and the electromagnetic switch, the connection member inserted through the holding member and that is inserted through the casing of the motor and the cover of the electromagnetic switch. 
     In this way, the connection member is held and supported by the holding member, so that the starter can be assembled in the state where the connection member is fitted to the side of the electromagnetic switch through the holding member. In this case, since one end side of the connection member has already been inserted into the cover to form the second fixed contact, the starter can be assembled by only connecting the other end side of the contact member to the brush. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a side elevational view with a partial cross section illustrating a starter according to a first embodiment of the present invention; 
         FIG. 2A  is a side elevational view illustrating a contact cover according to the first embodiment; 
         FIG. 2B  is a front elevational view illustrating the contact cover as viewed from the axial direction, according to the first embodiment; 
         FIG. 3  illustrates a starting circuit diagram of the starter according to the first embodiment; 
         FIG. 4  is a cross-sectional view illustrating the procedure of assembling a starter ASSY, according to the first embodiment; 
         FIG. 5  is a perspective view illustrating a metal terminal and a rubber grommet used in the embodiment; and 
         FIG. 6  is a cross-sectional view illustrating the procedure of assembling a starter ASSY, according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter will be described in detail some embodiments of the present invention. 
     (First Embodiment) 
     Referring to  FIGS. 1-4 , a first embodiment of the present invention will now be described. 
     As shown in  FIGS. 1-3 , a starter  1  according to the first embodiment is provided. This starter  1 , which is to be mounted on a vehicle, is provided with an armature  2  having an armature shaft  2   a ; a motor  3  for generating torque for the armature  2 ; a motor circuit  50  for supplying current to the armature  2 ; a main contact  51  (described later) provided in the motor circuit  50 ; an electromagnetic switch  4  for opening/dosing the main contact  51 ; an output shaft (not shown) that rotates with the transmission of the driving torque from the motor  3 ; and a pinion gear  5  helical-spline-fitted to the outer periphery of the output shaft. 
     In the present embodiment, as shown in  FIG. 1 , the longitudinal direction along the output shaft, that is, the longitudinal direction along the armature  2  is defined as an axial direction and directions along a plane perpendicular to the axial direction are referred to as a radial direction. 
     The starter  1  has a well-known function of starting an engine by bringing the pinion gear  5  into engagement with a ring gear (not shown) of the engine, and transmitting the driving torque of the motor  3  to the engine through the pinion gear  5  and the ring gear. 
     The motor  3  includes: a cylindrical yoke  6  forming a magnetic circuit; field permanent magnets  7  (or field coils) fixed to the inner periphery of the yoke; the armature  2  having gaps and rotatably supported by the inner periphery of the permanent magnets; a brush  8  for passing current to the armature  2  through a rectifier provided at the armature  2 ; and an end frame  9  fitted to the rear-end opening of the yoke  6 . The “rear-end” side means the rightward side in  FIG. 1 . The motor  3  is fixed to and clamped on a housing  10  through a through bolt, not shown. 
     The electromagnetic switch  4  has a function of actuating (sucking or attracting) a plunger  12  with the magnetic force generated by a switch coil  11  to open/close the main contact  51 , and at the same time pushing the pinion gear  5  to the direction opposite to the motor (leftward in  FIG. 1 ) through a shift lever (not shown). As shown in  FIG. 1 , the electromagnetic switch  4  is fixed to the housing  10  so as to be close to the radial outer periphery of the motor  3 . The operative shaft of the plunger  12  is disposed parallel to a longitudinal direction O (i.e., axial direction) of the armature shaft of the motor  3 . 
     A switch coil  11  is made up of a single coil electrically separated from the motor circuit  50 , which coil has one end portion connected to a terminal  14  (which is frequently referred to as a “50-terminal”: see  FIG. 2B ) which is fixed to an insulating contact cover  13  of the electromagnetic switch  4 , and the other end portion connected to a grounding side. Specifically, the single switch coil  11  generates suction force for sucking the plunger  12  for closing operation of the main contact  51 , and retention force for retaining the plunger  12  to maintain the closed state. 
     As shown in  FIG. 3 , the terminal  14  is connected to an ignition switch  16  (hereinafter referred to an “IG switch”) via a starter relay  15 . When the IG switch  16  is turned on, current flowing from batteries  17  is supplied via the starter relay  15 . 
     As shown in  FIG. 3 , the IG switch  16  is configured to have two systems, that is: a relay circuit  52  for controlling the excitation current of the starter relay  15  by an ECU (electronic control unit)  18 ; and a terminal circuit  53  for supplying current flowing from the batteries  17  to the terminal  14  via the starter relay  15 . A neutral switch  19  is provided at the relay circuit  52  so that the shift position of the transmission, when it is neutral, can be brought into an on-state. When the IG switch  16  is turned with the neutral switch  19  being in an on-state, the excitation current is supplied to the starter relay  15  via the ECU  18  to close the relay contact. 
     The main contact  51  includes a B-fixed contact  20  connected to a high-potential side (battery side) of the motor circuit  50 , an M-fixed contact  21  connected to a low-potential side (motor side) of the motor circuit  50 , and a movable contact  22  for connecting/disconnecting the fixed contacts  20  and  21 . When the movable contact  22  comes into contact with the fixed contacts  20  and  21 , and the contacts  20  and  21  are electrically connected, the main contact  51  is in a closed state. When the movable contact  22  is apart from the fixed contacts  20 , and  21  and the contacts  20  and  21  are disconnected, the main contact  51  is in an opened state. 
     The B-fixed contact  20  is arranged in the contact cover  13  and integrated into a B-terminal bolt  23  which is molded and fixed onto the contact cover  13  of the electromagnetic switch  4 . 
     The B-terminal bolt  23  is axially projected from the rear-end surface of the contact cover  13 . A battery cable  54  is electrically connected to the tip end of the projected B-terminal bolt  23 . 
     The M-fixed contact  21 , which is a portion of a metal terminal  24  having electrical conductivity, is connected to a pigtail  8   a  of the plus-side brush  8  via the metal terminal  24 . The metal terminal  24  has a strip shape as can be seen in  FIG. 5 . 
     Incidentally, the shape of the metal terminal  24  is not always limited to a strip shape, i.e., a flat plate form, but may be modified such that only both ends thereof are formed-into flat plate portions and the remaining portion thereof is formed into a cylindrical shape, for example. 
     The movable contact  22  is attached to an end of a shaft  25  via an insulating member  26 , as shown in  FIG. 1 , and is prevented from coming off, with the aid of a washer  27  fixed to the end of the shaft  25 . The shaft  25  is fixed to the plunger  12  which is slidably provided in the electromagnetic switch  4 . 
     Hereinafter is provided a detailed explanation on the metal terminal  24 . 
     The metal terminal  24  is made, for example, of a copper plate and inserted into a slit hole  28   c  formed in a rubber grommet  28  (functioning as an elastic member having insulation properties). Lateral sides of the metal terminal  24  in the longitudinal direction are held by the grommet  28  in the state of being projected from the slit hole  28   c.    
     One end side of the metal terminal  24  is inserted into the motor  3  from an opening formed between the yoke  6  and the end frame  9  of the motor  3  (hereinafter referred to a “motor-side opening”), and electrically connected to the pigtail  8   a  of the plus-side brush  8 . The other end side of the metal terminal  24  is inserted into the contact cover  13  of the electromagnetic switch  4  from an opening formed in the contact cover  13  (hereinafter referred to a “switch-side opening”) and forms the M-fixed contact  21 . 
     As shown in  FIG. 4 , the grommet  28  is provided with a motor-side seal  28   a  for sealing the motor-side opening and a switch-side seal  28   b  for sealing the switch-side opening. Both seals  28   a  and  28   b  are integrally formed. 
     The motor-side opening is formed, for example, of a substantially U-shaped groove  29  (see  FIG. 4 ; in detail, see  FIG. 6 ) which is formed in an opening end of the yoke  6 . The motor-side seal  28   a  of the grommet  28  is fitted to the groove  29 , and then the end frame  9  is assembled to the opening end of the yoke  6 . Thus, the motor-side seal  28   a  is held between the yoke  6  and the end frame  9 . 
     The switch-side opening is formed of a recess  30  to which the switch-side seal  28   b  of the grommet  28  is elastically fitted, and a through hole  31  passing through the contact cover  13  from the recess  30  to the inside of the cover  13 . The end side of the metal terminal  24  projecting from the switch-side seal  28   b  is inserted into the contact cover  13  through the through hole  31 . 
     The motor-side opening (U-shaped groove  29 ) and the switch-side opening (recess  30  and through hole  31 ) are formed at such positions that the axial distances L from a motor-mount surface A (see  FIG. 1 ) of the housing  10  for fixing the motor  3  to these positions are substantially the same. 
     As shown in  FIG. 4 , the grommet  28  of the present embodiment is attached to the side of the motor in the state where the motor-side seal  28   a  is fitted to the motor-side opening. Then, when a starter ASSY is assembled by fixing the motor  3  and the electromagnetic switch  4  to the housing  10 , the switch-side seal  28   b  is elastically fitted to the recess  30  formed in the contact cover  13  to seal the switch-side opening. Thus, the waterproof is ensured for the motor  3  and the electromagnetic switch  4 . 
     Prior to sandwiching the motor-side seal  28  of the grommet  28  between the yoke  6  and the end frame  9 , that is, prior to assembling the end frame  9  to the rear end of the yoke  6 , one end of the metal terminal  24  is electrically connected, by welding, for example, to the pigtail  8   a  of the plus-side brush  8 . Then, in assembling the starter ASSY, the other end side of the metal terminal  24  is inserted into the contact cover  13  from the switch-side opening to thereby form the M-fixed contact  21 . In this case, the M-fixed contact  21  is held by the grommet  28  in the state of being pressed onto an insulating contact seat  13   a  (see  FIG. 1 ) provided at the contact cover  13 . In other words, the grommet  28  is assembled with its switch-side seal  28   b  being elastically fitted to the recess  30  of the contact cover  13 , in the state where the other end side of the metal terminal  24  forming the M-fixed contact  21  is pressed onto the contact seat  13   a.    
     Hereinafter, the operation of the electromagnetic switch  4  is explained. 
     When the IG switch  16  is turned on to supply current to the switch coil  11  of the electromagnetic switch  4 , the plunger  12 , being sucked by the magnetic force generated by the switch coil  11 , is shifted rightward RD of  FIG. 1 . Thus, the shaft  25  fixed to the plunger  12  is pushed out, and the movable contact  22  supported at the end of the shaft  25  is permitted to come into contact with the B-fixed contact  20  and the M-fixed contact  21  to close the main contact  51 . As a result, current is supplied from the batteries  17  to the armature  2  via the brush  8  to generate torque in the armature  2 . 
     After the engine start, when the IG switch  16  is turned off to stop the current supply to the switch coil  11  for elimination of the magnetic force, the plunger  12  is pushed back to the leftward LD by the reaction force of a return spring (not shown). Then, the movable contact  22  comes away from the B-fixed contact  20  and the M-fixed contact  21  to open the main contact  51 , whereby the current supply to the motor  3  is stopped. 
     The electromagnetic switch  4  of the present embodiment establishes direct connection between the metal terminal  24  forming the M-fixed contact  21  and the pigtail  8   a  of the plus-side brush  8 . This can omit use of the conventional M-terminal bolt, and accordingly, various parts can also be omitted, such as sealing members, washer, motor leads and nuts. In this way, the number of parts and the number of assembling processes can be reduced, whereby cost, size and weight can be reduced. 
     Also, the omission of the conventional M-terminal bolt can reduce the number of terminal bolts to one to establish connection with the motor circuit  50 . In other words, only one B-terminal bolt  23  may only have to be fixed to the contact cover  13  (see  FIG. 2 ) in order to connect the B-fixed contact  20  to the high-potential side of the motor circuit  50 . In this case, a large insulation distance (creepage distance) can be ensured between the metal terminal  24  forming the M-fixed contact  21  and the B-terminal bolt  23 , because the metal terminal  24  is inserted into the contact cover  13  from the radial outer periphery of the contact cover  13 . As a result, the diameter of the contact cover  13  can be reduced comparing with the conventional electromagnetic switch where two terminal bolts are juxtaposed along the radial direction of the contact cover. 
     Moreover, in a conventional two-coil electromagnetic switch, or in an electromagnetic switch having a suction coil and a retention coil, electrical connection is generally established between the suction coil and an M-terminal bolt via a connecting terminal. Accordingly, the omission of the M-terminal bolt may involve substantial structural change, for establishing connection between the suction coil and the motor circuit  50 . In this regard, owing to the starter  1  of the present embodiment, the switch coil  11  of the electromagnetic switch  4  can be electrically disconnected from the motor circuit  50 , because the switch coil  11  is structured by a single coil. In other words, the omission of the M-terminal bolt may cause no problem, and thus no structural change is required. Accordingly, the connecting terminal can be omitted together with the omission of the M-terminal bolt, and hence the process can also be omitted for connecting the end of the suction terminal to the connecting terminal such as by welding, whereby more cost down can be achieved. 
     Also, since the metal terminal  24  is held by the rubber grommet  28 , relative vibration between the motor  3  and the electromagnetic switch  4  caused by engine vibration can be absorbed by the grommet  28 . Accordingly, the stress applied to the metal terminal  24  can be mitigated. 
     In addition, the grommet  28  is provided with the motor-side seal  28   a  for sealing the motor-side opening and the switch-side seal  28   b  for sealing the switch-side opening, and thus both of the motor-side and switch-side openings can be reliably sealed to ensure waterproof of the motor  3  and the electromagnetic switch  4 . 
     Further, the motor-side and switch-side openings are formed at the positions so that the axial distances from the motor-mount surface A of the housing  10  to the positions are substantially the same. Thus, in assembling the starter ASSY, the end side of the metal terminal  24  can be readily inserted into the contact cover  13  from the switch-side opening. 
     The metal terminal  24  held by the grommet  28  is fixed, with the end side of the terminal  24  that forms the M-fixed contact  21  being pressed onto the contact seat  13   a . Thus, when the movable contact  22  comes into contact with the M-fixed contact  21 , the M-fixed contact  21  will not move (will not vibrate). In this way, stable contact can be attained between the M-fixed contact  21  and the movable contact  22 , thereby preventing contact failure between the movable contact  22  and the M-fixed contact  21 . 
     The metal terminal  24  can be readily manufactured by forming a simple plate by presswork, for example. 
     Also, the connection between the pigtail  8   a  of the plus-side brush  8  and one end side of the metal terminal  24  can be readily attained because the pigtail  8   a  can be connected to the plane surface of the metal terminal  24 . Further, by permitting the thickness direction of the metal terminal  24  to coincide with the axial direction of the starter  1  (left-right direction of  FIG. 1 ), the axial direction of the starter  1  can be shortened. 
     (Second Embodiment) 
     Referring to  FIG. 6 , a second embodiment of the present invention will now be described. 
     In the present embodiment, the identical or similar components to those in the firs embodiment are given the same reference numerals for the sake of omitting explanation. 
     The second embodiment is directed to how to assembling the starter in steps modified from those in the first embodiment.  FIG. 6  is a cross-sectional view illustrating another procedure for assembling the starter ASSY. 
     The present embodiment presents an example in which the starter ASSY is assembled in the state where the metal terminal  24  held by the grommet  28  is attached to the side of the switch. 
     In the first embodiment, the starter ASSY has been assembled in the state where the metal terminal  24  held by the grommet  28  is attached to the side of the motor. Alternatively, as shown in  FIG. 6 , for example, the metal terminal  24  held by the grommet  28  may be attached to the side of the switch in advance, and then, in assembling the starter ASSY, an end side of the metal terminal  24  may be connected to the pigtail  8   a  of the plus-side brush  8 . After that, the end frame  9  may be assembled to the yoke  6  to sandwich the motor-side seal  28   a  of the grommet  28  between the yoke  6  and the end frame  9 , for fixation. 
     In this case, since one end of the metal terminal has already been connected to the pigtail of the plus-side brush, the assemblage of the starter ASSY can be attained by only inserting the other end side of the metal terminal into the contact cover from the opening formed in the contact cover. 
     The present invention may be embodied in several other forms without departing from the spirit thereof. The embodiment and modification described so far are therefore intended to be only illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them. All changes that fall within the metes and bounds of the claims, or equivalents of such metes and bounds, are therefore intended to be embraced by the claims.