Abstract:
A connecting rod includes first and second ball joints made of ball-shanks and holders tiltably connected with the ball-shanks. A connecting portion, which connects the holders of the first and second ball joints, adjusts the distance between the centers of the ball-shanks. The connecting portion includes first and second connecting arms integrally formed with the holders of the first and second ball joints and on which a plurality of positioning concaves and convexes which are meshed with each other are respectively arranged in a longitudinal direction. A fixing device engages the first and second connecting arms with each other in the condition where the positioning concaves and convexes of the first and second connecting arms mesh with each other.

Description:
FIELD OF THE INVENTION AND RELATED ART STATEMENT 
     This invention relates to a connecting rod or a con rod which is provided with a pair of ball joints at both ends of a rod-like connecting portion, and more particularly, to an improvement of a connecting rod which is capable of freely adjusting the distance between pivoting centers of these ball joints by means of the connecting portion. 
     In transmission control parts of automobiles, link mechanism parts of height control sensors and various other automatic machines or the like, many examples where a link motion mechanism uses a connecting rod provided with a pair of ball joints at both ends of a rod-like connecting portion have been observed. To ensure the smooth and accurate operation of such a link mechanism, in some cases, it becomes necessary to perform the adjustment of the distance between pivoting centers of a pair of ball joints (hereinafter called the adjustment between the centers). 
     Conventionally, as such a connecting rod which is capable of performing the adjustment between the centers, connecting rods disclosed in Japanese laid-open patent publication Hei 10-159818 and the like have been known. In these connecting rods, female threaded portions for connection are respectively formed in a pair of ball joints such that the female threaded portions have threading directions opposite from each other, and on both ends of the rod-like connecting portion to which these ball joints are joined, male threaded portions which are engaged with the female threaded portions are formed. By rotating the connecting portion, an amount of thread engagement between the male threaded portion and the female threaded portion is adjusted and hence, the distance between the centers of a pair of ball joints can be adjusted. Furthermore, lock nuts are respectively engaged with respective male threaded portions of the connecting portion and they prevents the relative rotation between the connecting portion and respective ball joints by fastening these lock nuts after the completion of the adjustment so as not to spoil the adjusted distance between the centers by an unintentional rotation of the connecting portion. 
     In these conventional connecting rods, however, at the time of performing the adjustment between centers, a pair of lock nuts must be loosened first and then the connecting portion must be rotated to adjust an amount of thread engagement between the female threaded portion and the male threaded portion, and after the completion of the adjustment, a pair of lock nuts must be fastened again and hence, there has been a problem that the operation to perform the adjustment between the centers is cumbersome. 
     In addition, there has been a problem that it is necessary to perform tapping of the female threaded portions and the male threaded portions at respective ball joints and the connecting portion so that the machining cost is increased by an amount corresponding to such an additional machining, while a pair of lock nuts are necessary so that the number of parts is increased thus pushing up the manufacturing cost. 
     OBJECT OF SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above-mentioned problems and it is an object of the present invention to provide a connecting rod equipped with ball joints which can easily adjust the distance between pivoting centers of a pair of ball joints provided to both ends of a connecting portion and can manufacture the connecting rods at a low cost. 
     To achieve the above-mentioned object, in the connecting rod equipped with ball joints according to the present invention which comprises first and second ball joints which are made of ball-shanks and holders tiltably connected with ball-shanks and a connecting portion which connects the holders of the first and second ball joints and is capable of adjusting the distance between the centers of a pair of the ball-shanks, the improvement is characterized in that the connecting portion is comprised of first and second connecting arms which are integrally formed with the holders of the first and second ball joints and on which a plurality of positioning teeth which are meshed with each other are respectively arranged in a longitudinal direction, and fixing means which makes the first and second connecting arms engaged with each other in the condition that the positioning teeth of the first and second connecting arms are meshed with each other. 
     Due to such a technical means, by engaging the first and second connecting arms which are integrally formed with holders of the first and second ball joints with each other by means of the fixing means, the connecting portion which connects the holders of the first and second ball joints is formed. Here, a plurality of positioning teeth are arranged on the first and second connecting arms respectively in a longitudinal direction and the connecting arms are engaged with each other in the condition that these positioning teeth are meshed with each other and hence, by merely loosening the engaged condition produced by the fixing means and thereafter shifting the meshed position of the teeth of the first connecting arm and the teeth of the second connecting arm, the length of the connecting portion, that is, the distance between the centers of the first ball joint and the second ball joint can be easily adjusted. 
     Furthermore, by arranging the positioning teeth at a given pitch relative to respective connecting arms, at the time of changing the distance between the centers of the first ball joint and the second ball joint, the distance between the centers can be easily shortened or extended by an aimed distance by counting the number of these positioning teeth. 
     Furthermore, the first and second connecting arms can be molded integrally with the holders by die casting or the like at the time of forming the holders. In such a case, since the above-mentioned positioning teeth can be simultaneously molded with respective connecting arms, the connecting rods can be easily manufactured and the manufacturing cost can be reduced. 
     On the other hand, with respect to the above-mentioned fixing means, the specific construction thereof can be properly changed so long as the first and second connecting arms can be engaged in the condition that the positioning teeth are meshed with each other. In the simplest case, the fixing means may be comprised of a bolt which passes through the first and second connecting arms and a nut which is engaged with the bolt so as to fasten these connecting arms. In case the bolt and the nut are used as the fixing means, the adjustment between the centers can be readily performed by merely loosening the connecting arms fastened by the bolt and the nut first, and then changing the meshed condition of the positioning teeth, and thereafter fastening the connecting arms by the bolt and the nut again. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawings which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of this invention. 
     FIG.  1 ( a ) is a plan view showing the first embodiment of a connecting rod to which the present invention is applied, FIG.  1 ( b ) is a front view of the embodiment, and FIG.  1 ( c ) is a right side view of the embodiment. 
     FIG.  2 ( a ) is a plan view showing a first ball joint of the first embodiment and FIG.  2 ( b ) is a front view of the first ball joint. 
     FIG. 3 is an enlarged view of an essential portion of the first ball joint according to the first embodiment. 
     FIG. 4 is a right side view of the first ball joint according to the first embodiment. 
     FIG.  5 ( a ) is a plan view showing the second embodiment of a connecting rod to which the present invention is applied and FIG.  5 ( b ) is a front view of the embodiment. 
     FIG.  6 ( a ) is a plan view of a first ball joint according to the second embodiment and FIG.  6 ( b ) is a front view of the embodiment. 
     FIG.  7 ( a ) is a plan view of the third embodiment of a connecting rod to which the present invention is applied and FIG.  7 ( b ) is a front view of the embodiment. 
     FIG.  8 ( a ) is a plan view of a first ball joint according to the third embodiment and FIG.  8 ( b ) is a front view of the embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A connecting rod equipped with ball joints of the present invention is explained in detail in conjunction with attached drawings hereinafter. 
     FIG.  1 ( a ) is a front view showing the first embodiment of a connecting rod to which the present invention is applied, FIG.  1 ( b ) is a plan view thereof and FIG.  1 ( c ) is a side view thereof. This connecting rod C 1  is provided with the first and second ball joints  2 ,  3  at both ends of a rod-like connecting portion  1 . By adjusting the length of the connecting portion  1 , the distance d between the centers of the first and second ball joints  2 ,  3  can be adjust freely. 
     Furthermore, the connecting portion  1  is comprised of the first and second connecting arms  5 ,  6  which respectively have positioning teeth  4  arranged on surfaces thereof, and a bolt  7  and a nut  8  as fixing means which makes the first and second connecting arms  5 ,  6  engaged with each other in the condition that the positioning teeth  4  of these connecting arms  5 ,  6  are meshed with each other. The connecting arms  5 ,  6  are respectively formed integrally with holders  20 ,  30  of the first and second ball joints  2 ,  3 . 
     As shown in FIG.  2 ( a ), FIG.  2 ( b ) and FIG. 3, the first ball joint  2  is comprised of the holder  20  with which a ball receiving portion  21  and the above-mentioned connecting arm  5  are integrally formed and a ball-shank  22  which is engaged with the ball receiving portion  21  of the holder  20 . This ball-shank  22  is provided with a ball portion  24  having a high sphericity at the distal end of the shank portion  23  and a connecting male threaded portion  25  is provided to the shank portion  23 . The ball portion  24  is rotatably and tiltably wrapped or received in the ball receiving portion  21  of the holder  20  while maintaining a necessary minimum gap. A hexagonal tool engaging portion  26  is formed on the ball-shank  22  and a spanner or a wrench for rotating the ball-shank  22  can be engaged with the tool engaging portion  26  at the time of joining the connecting male threaded portion  25  formed on the shank portion  23  to other movable part (not shown in drawings). 
     Furthermore, a connecting opening portion  27  is formed in the ball receiving portion  21  of the holder  20  and the shank portion  23  of the ball-shank  22  is protruded from this connecting opening portion  27 . Furthermore, at a portion of the ball receiving portion  21  opposed to the connecting opening portion  27 , a lubrication opening portion  28  which exposes the ball portion  24  of the ball-shank  22  is formed and a cap member  29  made of synthetic resin is mounted on this lubrication opening portion  28  so as to define a lubricant pocket which stores a lubricant such as grease. This cap member  29  is mounted-on the ball receiving portion  21  such that it slightly pushes the ball portion  24  of the ball-shank  22  and hence, for example, in case an axial external force suddenly acts on the ball-shank  22  or the like, the occurrence of metal sound which may be caused when the ball portion  24  and the ball receiving portion  21  impinge into each other can be attenuated. 
     Still furthermore, a seal member  9  is mounted between an outer periphery of the ball receiving portion  21  and the ball-shank  22 . This seal member  9  forms a lubricant pocket which stores a lubricant such as grease supplied to a gap defined between the ball portion  24  and the ball receiving portion  21  and prevents dust or the like from infiltrating into the gap from the connecting opening portion  27 . 
     On the other hand, the first connecting arm  5  which is integrally formed with the ball receiving portion  21  is formed of a flat plate which extends in a direction perpendicular to the axis of the ball-shank  22 . On a surface of the first connecting arm  5  at the same side as the shank portion  23 , a large number of previously-mentioned positioning teeth  4  are arranged at a given pitch in a longitudinal direction of the first connecting arm  5  thus forming a rack. Furthermore, at one sides of these arranged positioning teeth  4 , a side wall  10  is formed for stopping the lateral shift of the second connecting arm  6 . An elongated hole  11  through which the bolt  7  passes is formed in this first connecting arm  5  in a longitudinal direction and the distance d between the centers can be adjusted by shifting the engaged position of the first and second connecting arms  5 ,  6  along this elongated hole  11 . 
     The second ball joint  3  is comprised of the holder  30  and a ball-shank  32  as in the case of the first ball joint  2  and the structures of these holder  30  and the ball-shank  32  are substantially as same as those of the first ball joint  2 . As shown in FIG.  1 ( b ), however, in the connecting rod C 1  of this embodiment, in the condition that the first ball joint  2  and the second ball joint  3  are combined, the shaft ends of respective ball-shanks  22 ,  32  extend in directions 180° opposite to each other and hence, side walls  10  for stopping the lateral shift between the first connecting arm  5  and the second connecting arm  6  are formed on the first connecting arm  5  and the second connecting arm  6  at opposite sides from each other. 
     The first ball joint  2  can be manufactured using a method disclosed in Japanese patent publication Hei 5-7786. 
     First of all, a steel ball for bearing use which constitutes the above-mentioned ball portion  24 .is fixedly secured to the inside of a casting mold as a core. Molten metal made of zinc based alloy or aluminum based alloy (for example, grade  1 ,  2  of zinc alloy die casting, grade  3 ,  10  or  12  of aluminum alloy die casting of JIS) is poured into the casting mold so as to produce the holder  20  by die casting. Accordingly, the ball receiving portion  21  which wraps the steel ball for bearing use is formed and the connecting arm  5  on which the positioning teeth  4  are formed can be formed integrally with the ball receiving portion  21 . 
     Subsequently, the shank portion  23  is welded to the steel ball for bearing use which is wrapped by the holder  20  by way of the connecting opening portion  27  formed in the holder  20  thus forming the ball-shank  22 . As such a welding, a projection welding where the welding is performed by supplying an electric current to both of the shank portion  23  and the steel ball for bearing use in the condition that they are abutted to each other may preferably be used. When the ball-shank  22  is formed in the above manner, an external force is applied to the ball-shank  22  and the holder  20  so as to define a minute gap between the ball portion  24  of the ball-shank  22  and the ball receiving portion  21  of the holder  20  which are brought into close contact with each other at the time of die casting. Due to such a construction, the ball-shank  22  can perform the rotational movement and the tilting movement freely relative to the holder  20 . 
     The second ball joint  3  can be manufactured exactly in the same manner as in the case of the first ball joint  2 . 
     In this embodiment having the above-mentioned construction, the positioning teeth  4 ,  4  which are respectively formed on the first connecting arm  5  and the second connecting arm  6  are meshed with each other and, while holding such a meshed condition, the first connecting arm  5  and the second connecting arm  6  are fastened by engaging the nut  8  with the bolt  7  which is inserted into the elongated hole  11  thus completing the connecting rod C 1  equipped with a pair of ball joints  2 ,  3  at both ends of the connecting portion  1 . 
     In case the adjustment of the distance between the axes of the ball-shanks  22 ,  32  of the ball joints  2 ,  3 , that is, the distance d of the centers is necessary, the fastening of the first and the second connecting arms  5 ,  6  by the bolt  7  and the nut  8  is loosened, subsequently, the meshed position of the positioning teeth  4  of the first and second connecting arms  5 ,  6  is shifted, and then the first and second connecting arms  5 ,  6  are fastened again by means of the bolt  7  and the nut  8  thus facilitating the adjustment of the distance d of the centers. Here, since the positioning teeth  4  are formed at a given pitch, an amount of adjustment of the distance d between the centers can be easily recognized by counting the number of the positioning teeth  4 . 
     Furthermore, the holders  20 ,  30  of the first and second ball joints  2 ,  3  can be formed by die casting, and the ball receiving portions and the connecting arms  5 ,  6  can be integrally formed during such a casting, and the positioning teeth  4  can be cast integrally and hence, the first and second ball joints  2 ,  3  per se can be manufactured extremely easily at a low cost. 
     Subsequently, FIG.  5 ( a ) and FIG.  5 ( b ) show the second embodiment of the connecting rod to which the present invention is applied, and FIG.  6 ( a ) and FIG.  6 ( b ) show the first ball joint  2  which constitutes the connecting rod of the second embodiment. 
     Although this connecting rod C 2  has substantially the same construction as that of the connecting rod C 1  of the previously mentioned first embodiment, the connecting rod C 2  differs from the connecting rod C 1  in only the shape of positioning teeth  42  formed on first and second connecting arms  40 ,  41 . 
     That is, in the connecting rod C 2  of the second embodiment, the positioning teeth  42 ,  42  formed on the first and second connecting arms  40 ,  41  are formed in a herring bone shape. Due to such a construction, when the positioning teeth  42  of the first connecting arm  40  and the positioning teeth  42  of the second connecting arm  41  are meshed with each other and then the first and second connecting arms  40 ,  41  are fastened by means of the bolt  7  and the nut  8 , the lateral shift of these connecting arms  40 ,  41  in a direction perpendicular to the longitudinal direction can be prevented. Accordingly, in the connecting rod C 2  of the second embodiment, the side walls  10  which are provided to the connecting rod C 1  of the first embodiment for preventing the lateral shift are not formed on the first and second connecting arms  40 ,  41 . With respect to other parts, the connecting rod C 2  has the same construction as that of the connecting rod C 1  of the first embodiment and hence, here, the same symbols are affixed to these parts in FIG.  5 ( a ) and FIG.  5 ( b ) and the detailed explanation of these parts is eliminated. 
     FIG.  7 ( a ) and FIG.  7 ( b ) show the third embodiment of the connecting rod to which the present invention is applied, and FIG.  8 ( a ) and FIG.  8 ( b ) show the first ball joint  2  which constitutes the connecting rod C 3  of the third embodiment. 
     Although this connecting rod C 3  has substantially the same construction as the connecting rod C 1  of the first embodiment, the connecting rod C 3  differs from the connecting rod C 1  of the first embodiment only in that instead of inserting the bolt  7  which fastens the first connecting arm  5  and the second connecting arm  6  into the elongated holes  11  of these connecting arms  5 ,  6  after making their positioning teeth  4  meshed with each other, the bolt  7  is formed as a part of a first connecting arm  50  at the time of die casting the holder  20  of the first ball joint  2 . Accordingly, in this embodiment, the construction of the second ball joint  3  is exactly as same as that of the connecting rod C 1  of the first embodiment. 
     That is, with the connecting rod C 3  of this third embodiment, casting of the holder  20  is performed in the condition that the bolt  7  is inserted into the inside of the casting mold so that the threaded portion of the bolt  7  can solidly erect from the surface of the first connecting arm  50  on which the positioning teeth  4  are formed. Accordingly, at the time of fastening the first connecting arm  50  and the second connecting arm  6  by means of the bolt  7  and the nut  8 , it is unnecessary to engage the nut  8  with the bolt  7  while holding the bolt  7  with one hand. That is, after adjusting the meshed position of the positioning teeth  4 ,  4  of the first connecting arm  50  and the second connecting arm  6 , while pinching the connecting arms  50 ,  6  with one hand, the nut  8  can be engaged with the bolt  7  with the other hand. Accordingly, making use of the connecting rod C 3 , the adjustment of the distance d of the centers can be performed more easily than the connecting rod C 1  of the first embodiment.