Abstract:
The structure for fixing a grommet to a housing is composed of a housing provided with a connector portion formed at least partly in a column shape, a wire harness connector coupled with the connector portion with a coupling gap and a tubular shaped grommet made of resilient material put on an outside circumferential surface of the connector portion to waterproof seal the coupling gap. The grommet includes a wall with openings that snap over protrusions on the connector portion to rigidly fix them together. The connector portion includes a locking through hole for receiving a latch on the wire harness connector. Seal lips on the grommet are angled downward so as to provide sealing for the locking hole.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of Japanese Patent Application No. H.11-21435 filed on Jan. 29, 1999, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a structure for fixing a grommet into a motor housing, in particular, a structure for fixing the grommet for waterproof sealing into a connector portion of the motor housing with which a connector of a wire harness is coupled, and a motor unit having the same structure and applicable to a power window regulator for vehicles. 
     2. Description of Related Art 
     A conventional power window regulator for opening/closing a vehicle door glass is composed of a motor unit and a regulator (a link mechanism). The motor unit is provided with a resin molding housing, a DC motor fixed to the housing, reduction gears housed in the housing, a wire harness with a connector coupled with a connector portion of the housing for current supply to the DC motor and a grommet fitted into the connector portion of the housing for waterproof sealing. The motor unit has a waterproof construction for its electrical circuit protection, since water running along the surface of the door window is likely to be entered into the motor unit. 
     As shown in FIGS. 9 and 10, the connector portion  52  of the housing  51  is formed in a column shape and the grommet  53  made of elastic rubber is formed in a tubular shape. For preventing water from entering into a coupling gap between the connector of wire harness and the connector portion  52 , the grommet  53  is fitted closely into an outside circumferential surface of the connector portion  52 . 
     To rigidly fix the grommet  53  to the connector portion  52 , there have been contemplated various ways that, for example, an inside circumferential surface of the grommet  53  and an outside circumferential surface of the connector portion  52  are glued, the grommet  53  is fastened tight from outside by fasteners such as a C-ring and a clip cord to the connector portion  52  after the grommet  53  is put on the connector portion  52 , a flange provided at a lower end of the grommet  53  is fastened by screws to a flange provided at a lower end of the connector portion  52  or an inwardly projecting portion of the grommet  53  is fitted into a groove or an undercut provided at a lower portion of the connector portion  52 . 
     However, these ways have such problems that not only more number of component parts or more complicated manufacturing processes are required but also reliability for fixing the grommet  53  to the connector portion  52  is not always sufficient, in particular, in case that these fixing means can not be provided all around circumferences of the connector portion  52  because of a restricted shape of the connector portion  52  integrally provided with the housing  51 . 
     Further, to cope with the problems mentioned above, it has been proposed that, as shown in FIGS. 9,  10  and  11 , the connector portion  52  is provided at a lower outside circumferential surface thereof with a plurality of locking claws  54 , to which a plurality of resilient locking pieces  55  provided at a lower end of the grommet  53  are respectively latched and fixed. Though this construction improves the fixing reliability, the manufacturing processes for fixing the grommet  53  to the connector portion  52  are still complicated and not suitable for automatic assembly thereof, since, after the grommet  53  is put on the connector portion  52 , each of the resilient locking pieces  55  has to be pulled in a lower direction so that the locking pieces  55  may be once deformed resiliently in order to be engaged with each of the locking claws  54  and, then, resiliently returned to the original positions thereof. 
     Furthermore, as shown in FIG. 11, the connector portion  52  is provided at an inside thereof with a locking concave  56  with which a locking convex C 1  of the connector C of the wire harness W is engaged for preventing the connector C from easily being left out the connector portion  52 . 
     It is very difficult to form the locking concave  56  at the inside of the connector portion  52  simultaneously when the housing  51  is molded or formed in view of the molding die construction of the connector portion  52 . Therefore, to form the locking concave  56 , a locking member  57  provided primarily with the locking concave  56  is separately provided as shown in FIG. 12 and, when the housing  51  is molded, the locking member  57  thus separately provided is inserted into the molding die at a position corresponding to the inside of the connector portion  52  as shown in FIG.  11 . The locking member  57  also has a plurality of grooves  59  for positioning a plurality of terminals  58  to be also inserted into the molding die when the housing  51  is molded. 
     The structure mentioned above, however, has a drawback that the locking member  57  is needed as an additional component part and the terminals  58  have to be primarily mounted on the locking member  57  before the locking member  57  is inserted into the die for molding. As a result, a higher manufacturing cost is required, compared with a case that only the terminals  58  are directly inserted into the die for molding. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above mentioned problem, and an object of the present invention is to provide a waterproof sealing structure for easily fixing a grommet to a connector portion with which a wire harness connector is coupled with higher fixing reliability, least number of component parts and/or lower manufacturing cost. 
     It is an another object to provide a motor unit having the same structure as mentioned above. 
     To achieve the above object, the structure is composed of a housing provided with a connector portion formed at least partly in a column shape, a wire harness connector coupled with the connector portion with a coupling gap and a tubular shaped grommet made of resilient material put on an outside circumferential surface of the connector portion to waterproof seal the coupling gap. A plurality of locking convex portions are provided respectively with an interval therebetween around the outside circumferential surface of the connector portion. On the other hand, a plurality of concave portions are provided respectively with an interval therebetween around an inside circumferential surface of the grommet. By simply pushing the grommet to put on the connector portion, the grommet is resiliently deformed outwardly at the plurality of the convex portions and, after the grommet passes through the plurality of the convex portions, the grommet outwardly deformed is resiliently returned substantially to an original shape thereof so that the plurality of the concave portions may be engaged respectively with the convex portions to rigidly fix the grommet to the connector portion. 
     It is preferable that each of the concave portions is a through-hole penetrating radially through the grommet from an inside surface to an outside surface thereof. 
     Further, in case that the housing is provided with a base unit and a bridging portion connecting the base unit and a part of the circumferential surface of the connector portion, the convex portions are arranged except the outside circumferential surface of the connector portion axially extending from the bridging portion and the grommet is provided with a cut in order not to interfere with the bridging portion when the grommet is put on the connector portion and the concave portions are arranged except the circumferential surface of the grommet axially extending from the cut. In this case, it is preferable that at least a part of the outside circumferential surface of the grommet axially extending from the cut comes in contact with and is inwardly pressed against a surface of the base unit when the grommet is put on the connector portion. As a result, the circumferential surface of the grommet may be rigidly fixed in almost all ranges around the circumferential surface of the connector portion. 
     Preferably, the grommet is further provided with one or more projections on the outside circumferential surface of the grommet axially extending from the cut. Therefore, the outside circumferential surface of the grommet axially extending from the cut is inwardly pressed through the projections against the surface of the base unit. The projections serve to reduce a friction with the surface of the base unit when the grommet is pushed so as to be put on the connector portion. 
     Furthermore, it is preferable that a plurality of annular sealing lips are provided at the inside circumferential surface of the grommet. The sealing lips are resiliently deformed to come closely in contact with the outer circumferential surface of the connector portion so that waterproof function may be much more enhanced. 
     Further, the connector portion is provided with an annular positioning portion and a connector fitting portion axially extending from the annular positioning portion. On the other hand, the grommet is provided with a grommet fitting portion, a guide portion, and a taper shaped annular step portion on an inside thereof and on a boundary between the grommet fitting portion and the guide portion. An inside diameter of the guide portion is slightly larger than an outside diameter of the connector fitting portion. An inside diameter of the fitting portion is slightly smaller than an outside diameter of the connector fitting portion. Therefore, when the grommet is placed at first on the connector portion, the annular step portion is easily positioned, with a help of the guide portion, on the annular positioning portion to align in axial direction the grommet with the connector portion. When the grommet is pushed to the connector portion, the grommet fitting portion is fitted into the connector fitting portion by being resiliently deformed outwardly without disturbing the axial alignment. 
     The annular positioning portion may be formed in an inclined direction relative to an axis of the connector portion to avoid the interference with the bridging portion. In this case, the annular step portion is also inclined to correspond to the shape of the annular positioning portion. 
     In case that both of the annular step portion and the annular positioning portion are formed obliquely, it becomes easier to align in axial and angular directions the grommet with the connector portion before the grommet is pushed toward the connector portion for assembly. 
     It is preferable that the convex portions are arranged on the connector fitting portion and the concave portions are arranged on the guide portion. With the construction above, the concave portions may be engaged respectively with the convex portions simultaneously when the grommet is pushed so as to make the grommet fitting portion fit into the connector fitting portion. 
     Further, preferably, the sealing lips are arranged on the inside circumferential surface of the grommet fitting portion in parallel with the annular step portion. Therefore, in case that the annular step portion is inclined relative to the axis of the grommet or the connector portion as mentioned above, the sealing lips are also inclined relative to the axis of the grommet or the connector portion so that the grommet fitting portion may be fitted into the connector fitting portion with the least axial travel distance when the grommet is pushed to the connector portion for assembly. 
     Furthermore, preferably, the connector portion is provided with a locking hole penetrating therethrough perpendicular to the axis of the connector portion and the wire harness connector is provided with a locking convex portion to be engaged with the locking hole for preventing the wire harness connector from being left easily out of the connector portion. An outside of the locking hole is covered with the grommet. It is more preferable that the locking hole is formed to penetrate a circumferential wall of the connector portion on a side opposite to the connector fitting portion with respect to the annular positioning portion. As a result, the penetrating locking hole may be sufficiently sealed without adversely affecting the fitting of the grommet into the connector portion. In case that the annular sealing lips are provided obliquely as mentioned above, there is a sufficient space where the penetrating locking hole may be formed without prolonging the height of the connector portion for securing waterproof sealing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings: 
     FIG. 1 is a perspective view of a grommet and a connector portion according to an embodiment of the present invention; 
     FIG. 2 is a perspective view of a power window regulator for vehicles incorporating the embodiment of the present invention; 
     FIG. 3 is an elevation view of the grommet fitted to the connector portion; 
     FIG. 4 is a cross sectional view taken along a line IV—IV of FIG. 3; 
     FIG. 5 is a cross sectional view taken along a line V—V of FIG. 3; 
     FIG. 6 is a cross sectional view of the grommet to be put on the connector portion; 
     FIG. 7 is a perspective view from a lower side of the grommet; 
     FIG. 8A is a cross sectional schematic view of locking concave and convex portions before engagement; 
     FIG. 8B is a cross sectional schematic view of locking concave and convex portions after engagement; 
     FIG. 9 is a perspective view of a grommet and a connector portion as a prior art; 
     FIG. 10 is an elevation view of the grommet fitted to the connector portion as a prior art; 
     FIG. 11 is a cross sectional view of the grommet to be put on the connector portion as a prior art; and 
     FIG. 12 is a perspective view of a locking member as a prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention is described hereinafter according to FIGS. 1 to  8 . 
     FIG. 2 shows a power window regulator for vehicles  10  to be disposed inside a vehicle door for opening or closing a door glass. The power window regulator  10  is composed of a motor unit  11  and a regulator (link mechanism)  12 . An upper arm  13  is moved upward or downward according to a rotation of the motor unit  11  in normal or in reverse direction so that the door glass (not shown) fixed to the upper arm  13  may be moved upward or downward. 
     As shown in FIG. 1, the motor unit  11  is composed of a housing  14  made of synthetic resin and integrally molded, a DC motor  15  fixed to the housing  14 , worm and wheel type reduction gears (not shown) housed in the housing  14 , a connector portion  16  integrally formed with the housing, a wire harness W with a connector C (shown in FIG. 5) coupled with the connector portion  16  for current supply to the DC motor  15  and a grommet  22 . 
     The housing  14  is provided, in addition to the connector portion  16 , with a base unit  17  for fixing the DC motor  15 , a cylindrical portion  18  for housing a worm fixed to a rotational axis (not shown) of the DC motor  15  and a wheel portion  19  for housing a worm wheel (not shown) as an output axis of the motor unit  11 . Otherwise, the housing  14  is provided with a plurality of through-holes ( 20 ) for fixing the motor unit  11  to the vehicle door by bolts. 
     The connector portion  16 , as shown in FIG. 1, is formed nearly in a column shape as an appearance thereof and located on a side opposite to the wheel portion  19  with respect to the cylindrical portion  18 . A center axis of the connector portion  16  is nearly in parallel with a center axis of the worm wheel and a height of the connection portion  16  in an axial direction is nearly equal to a thickness of the wheel portion  19  in an axial direction. The housing  14  is also provided with a bridging portion  21  for connecting the connector portion  16  and the base unit  17 . The height of the bridging portion  21  in an axial direction of the connector portion  16  is lower than the height of the connector portion  16 . 
     The grommet  22  is of a tubular shape and made of integrally formed elastic (resilient) material such as rubber for waterproof sealing a connector coupling gap formed by coupling the wire harness connector C with the connector portion  16  as shown in FIG.  3 . 
     As shown FIGS. 4 and 5, the connector portion  16  is provided inside thereof with terminals  23  for lead wires connecting the DC motor  15  and signal wires for sensors such as a rotation sensor (hall-effect device) disposed in the housing  14 . Each of the terminals  23  is embedded in the housing  14  in such a manner that the housing  14  is molded by inserting the terminals  23  to a molding die. 
     As shown in FIG. 5, the connector portion is provided with a locking hole  24  formed perpendicular to a coupling direction of the wire harness connector C (in a direction shown by an arrow Y in FIG. 5) for engaging and locking with a locking convex portion C 1  of the wire harness connector C. The housing  14  is molded by cutting dies separable in a coupling direction of the connector portion  16  and the locking hole  24  is formed by drawing back a core piece separately provided in the cutting dies perpendicular to a separating direction of the cutting dies simultaneously when the housing  14  is molded. The locking hole  24  can be integrally molded with housing  14  without such an inserting molding as the conventional locking concave  56  is formed. The locking hole  24  is located on a circumferential surface of the connector portion on a side opposite to the bridging portion  21 . 
     As shown in FIGS. 1,  3  and  4 , a plurality of locking convex portions  25  are arranged on an outside circumferential surface of a connector fitting portion  36  of the connector portion  16  with a certain interval therebetween. Each of the locking convex portions  25  is formed, as shown in FIGS. 8A and 8B, in a tapered shape at least on a front side thereof (wire harness connector C side) that an outwardly protruding length thereof is shorter on a side of the wire harness connector C than that on a side opposite to the wire harness connector C. This tapered shape causes the grommet  22  to slidably move for fitting the grommet  22  easily into the connector portion  16 . 
     As shown in FIG. 1, an annular positioning portion  26  is formed on the outside circumferential surface of the connector portion  16 . The annular positioning portion  26  is formed obliquely in a coupling direction of the connector portion  16 , that is, the lowest in height on a side of the locking hole  24  and the highest in height on a side of the bridging portion  21 . The connector fitting portion  36  is an outside circumferencial surface of the connector portion  16  extending axially from the annual positioning portion  26 . 
     The grommet  22  has, as shown in FIGS. 6 and 7, a grommet fitting portion  27  for fitting into the connector portion  16 , a sealing portion  28  for sealing the wire harness connector side and a guide portion  31  for guiding properly the grommet  22  when the grommet  22  is simply pushed so as to be put on the connector portion  16 . Inside the grommet  22 , an inwardly protruding stopper  29  is provided between the fitting portion  27  and the sealing portion  28 . The stopper  29  serves to locate the grommet  22  at a predetermined axial position in a manner that the stopper  29  comes in contact with the leading end of the connector portion  16  when the grommet  22  is put on the connector portion  16 . 
     The guide portion  31  is provided with a cut at a position corresponding to the bridging portion  21  to avoid an interference with the bridging portion  21  and a plurality of locking concave portions  32  (through-holes) with a certain interval therebetween with which the locking convex portions  25  are respectively engaged and locked. Instead of the through-holes mentioned above, each of the locking concave portions  32  may be a hollow provided only on an inside surface of the guide portion  31  not to be penetrated to an outside surface thereof. When the locking convex portions  25  completely fit into the locking concave portions  32 , respectively, as shown in FIG. 8B, the grommet  22  is rigidly fixed to the connector portion  16 . 
     Further, inside the grommet  22 , a taper shaped annular step portion  33  is provided at a boundary between the grommet fitting portion  27  and the guide portion  31 . An inside diameter of the guide portion  31  is slightly larger than an outside diameter of the connector fitting portion  36 . An inside diameter of the grommet fitting portion  27  is slightly smaller than an outside diameter of the connector fitting portion  36 . 
     The annular taper shaped step portion  33  is provided obliquely in an axial direction of the grommet  22  and comes closely in contact with the annular positioning portion  26  when the grommet  22  is placed on the connector portion  16  so that the guide portion  31  may be nearly fitted into the connector fitting portion  36  without resiliently deforming. As a result, the grommet  22  can be easily aligned in axial and angular directions relative to the connector portion  16 , that is, a center axis of the grommet  22  is aligned in parallel with the coupling direction of the connector portion  16  and an angular position of the grommet  22  coincides with that of the connector portion  16 . 
     A plurality of sealing lips  30  are formed obliquely on an inside circumferential surface of the fitting portion  27  in parallel with the annular taper shaped step portion  33 . Therefore, the grommet fitting portion  27  may be fitted into the connector fitting portion  36  with the least axial travel distance when the grommet  22  is pushed toward the connector portion  26 . Further, as the sealing lips  30  is obliquely provided, the locking hole  24  penetrating a circumferential wall of the connector portion  26  can be located at a space on a side opposite to the connector fitting portion  36  with respect to the annular positioning portion  26 . As a result, the locking hole  24  may be sufficiently sealed by the grommet  22  without prolonging the height of the connector portion  16  for securing waterproof sealing. 
     As shown in FIG. 7, a plurality of projections  34  is provided with an interval therebetween on the outside surface of the grommet fitting portion  27  axially extending from the cut where the locking concave portions  32  are not provided. The projections  34  come in contact and are inwardly pressed against a surface of the base unit  17  of the housing  14 , as shown in FIGS. 3,  4  and  5 , so that the inside circumferential surface of the grommet fitting portion  27  may be rigidly fixed to the outside circumferential surface of the connector fitting portion  36 . 
     Each of the projections  34  is formed in such a shape that an area where the projection  34  comes in contact with the surface of the base unit  17  is as small as possible. This is for reducing a friction with the surface of the base unit  17  when the grommet  22  is pushed so as to be put on the connector portion  16 . Therefore, the circumferential surface of the grommet  22  can be rigidly fixed all around the circumference of the connector portion  16  with a locking engagement by the locking concave and convex portions  32  and  25  and a frictional engagement by the projections  34  and the base unit  17 . 
     However, when a space between the base unit  17  and the connector portion  16  is narrower, that is, when the bridging portion  21  is shorter, the projections  34  may be eliminated. Instead, a part of the grommet fitting portion  27  axially extending from the cut may be pushed into the space. With the construction mentioned above, the waterproof fitting of the grommet  22  into the connector portion  16  is more enhanced, though the friction with the base unit  17  becomes larger because of no projections  34 . 
     The present invention is applicable not only to the motor unit  11  for the power window regulator mentioned above but also to an any type of motor unit, for example, for a sun roof control or for a retractable headlight control. The motor  15  is not limited to the DC motor but may be an any type of motor including a brushless motor or a stepping motor.