Abstract:
In a tensioner for a timing chain, a spring-biased plunger for urging a shoe into sliding engagement with the chain is temporarily held in a retracted condition, prior to installation of the tensioner, by a stopper having a pin that extends through a hole in the tensioner housing and engages a grove formed in the plunger. The stopper is bent so that its handle extends away form the pin axis at an angle greater than zero but not greater than 90°. Removal of the stopper from the tensioner can be carried out by rotating the handle to avoid interference with engine components in the vicinity of the tensioner.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to tensioners of the kind used to maintain tension in a chain of the timing drive of an internal combustion engine, and more particularly to improvements in a stopper for preventing a biased plunger from projecting or disengaging from the tensioner housing before the tensioner is mounted on the engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     In a conventional tensioner for maintaining tension in a flexible, endless, traveling transmission medium, such as the timing chain in an internal combustion engine, a plunger protrudes from a housing and has a shoe at its outer end for sliding contact with the traveling transmission medium. The plunger is urged in the protruding direction by a biasing device, such as a coil spring, inside the tensioner housing. Stoppers have been used to maintain the plunger in a retracted condition, and to prevent the plunger from separating from the tensioner housing during shipping and during installation on an engine. An example of a conventional stopper is depicted in  FIG. 6  of Japanese Laid-open Patent Publication No. Hei. 7-42805. Another example of a conventional stopper is described in U.S. Pat. No. 5,676,614, and shown in  FIGS. 8 and 9 ,  FIG. 8  being a front elevational view of a tensioner having a conventional stopper, and  FIG. 9  being a cross-sectional view taken on plane  9 - 9  of  FIG. 8 . In these figures, a tensioner  51  includes a shoe  56 , which comes into sliding contact with a chain  55 , and a cylindrical plunger  54 , which is caused to protrude from a housing  52  by a coil spring  58  in a direction to maintain tension in the chain. The plunger is slidable in a cylindrical bore  53  in the housing, which, together with the plunger  54 , defines a hydraulic chamber  57 . Oil is supplied under pressure to the chamber  57  from an oil passage (not shown) through a check valve  59 .  
         [0003]     A guide surface  60 , formed On a side of the housing  52 , extends in parallel relation to the protruding direction of the plunger  54 . An extension  62 , facing the guide surface  60 , is formed as an integral part of shoe  56 , and prevents rotation of plunger  54  about its axis. A pin-receiving hole  63  is formed in the guide surface  60 , and a through hole  64  is formed in the extension  62 . Hole  64  can be aligned with the pin-receiving hole when the plunger  54  is pushed into the cylindrical bore  53 .  
         [0004]     By aligning the holes  63  and  64 , a pin  61   a  of a stopper  61  which comprises the pin  61   a  and a handle  61   b,  can be inserted through hole  64 , and into hole  63 , to secure the shoe  56  in fixed relation to the housing  52 , and prevent the plunger from being pushed out of the housing by spring  58 . After the tensioner is mounted, when the stopper  61  is pulled out, the plunger  54  can protrude and press the shoe  56  against the chain to impart tension to the chain.  
         [0005]     Where a tensioner is used in the timing chain system of certain types of automobile engines for example a V-type, double overhead cam (V-DOHC) engine, it may be situated in a very restricted space. In the timing system shown in  FIG. 10 , for example, a first chain C 1  is in mesh with a crankshaft sprocket S 1  and two cam sprockets S 2  on the camshafts that operate the air intake valves of the engine. Second air-intake cam sprockets S 3  are coaxial with, and rotate with, sprockets S 2 , and chains C 2  mesh with sprockets S 3  on the air intake camshafts, and sprockets S 4  on the exhaust camshafts, so that the exhaust camshafts are driven in synchronism with the air intake camshafts. Tensioner T 1 , situated along the path of chain C 1  between sprocket S 1  and one of sprockets S 2 , controls tension in chain C 1  through a pivoting tensioner lever L 1 . Tensioners T 2 , each of which is situated between a sprocket S 3  and a sprocket S 4 , control tension in chains C 2 . Fixed guides G 1  and G 2  are also provided along the path of chain C 1 .  
         [0006]     When the tensioners T 1  and T 2  are mounted on an engine, they are typically mounted in spaces that are restricted by the presence of various engine structures and fittings, including fittings associated with the cam sprockets. In particular, the tensioners T 2 , which apply tension to chain C 2 , are mounted in very restricted spaces on the insides of the loop-shaped paths of chains C 2 , where various engine structures are gathered. However, because the stopper  61  in the conventional tensioner  51  is straight, that is, its handle  61   b  and its pin  61   a  are aligned along a common axis, the stopper can come into contact with the engine frame or its sprocket fittings, which makes the mounting of the tensioner difficult. Moreover, after the tensioner is installed and the various parts of the timing system are assembled, there is little available space to allow removal of the stopper. Accordingly, in some engine configurations, it is not possible to utilize a tensioner having a stopper of the kind depicted in  FIGS. 8 and 9 .  
       SUMMARY OF THE INVENTION  
       [0007]     An object of this invention is to overcome the above-mentioned problems of conventional tensioners having plunger stoppers, and to provide a tensioner with a stopper that can be mounted in a very restricted space, and from which the removal of the stopper is not impeded by interference with various engine parts.  
         [0008]     The tensioner in accordance with the invention has a housing, and a plunger received in a plunger-receiving hole in the housing. The plunger protrudes outward from the housing, and is biased in its protruding direction. The plunger has a shoe connected to its outer end for sliding contact with an endless, flexible, power transmission medium for maintaining tension therein. A through hole is formed in the housing, and a locking recess, preferably in the form of an annular groove, is formed on the plunger. A stopper is provided, having an elongated pin extending along a pin axis, and a handle connected to the pin and extending along a handle axis. The pin can be extended through the through hole in the housing, for engagement with the locking recess of the plunger, to prevent the plunger from moving in the protruding direction relative to the housing during handling of the tensioner before the shoe is engaged with a power transmission medium. The axes of the pin and the handle intersect, and a part of the axis of the pin that extends beyond the intersection of the pin axis and the handle axis forms an angle with the pin axis on the pin side of the intersection. This angle is greater than zero but not greater than 90 degrees. The bent stopper construction allows the handle to be rotated about the pin axis while the stopper pin is in the through hole of the housing. As a result, the handle of the stopper can be rotated so that contact between the handle and interfering objects in the vicinity of the tensioner can be avoided, and the tensioner can be mounted in a very restricted space. If, after the is mounted tensioner and the various parts of the timing system are assembled, only a very narrow space is available, it is still possible to remove the stopper without difficulty by rotating it to avoid interfering parts. Consequently, assembly of an engine or other mechanism utilizing a tensioner can be greatly facilitated. Optionally, rotation of the stopper during handling and installation of the tensioner can be prevented by configuring the stopper so that its rotation is prevented or restricted until its pin is disengaged from the plunger of the tensioner by a relatively small outward movement of the stopper along its pin axis. Thereafter, the stopper can be easily removed from the tensioner by rotating the handle as necessary to avoid contact with interfering parts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of a tensioner equipped with a stopper  1  according to the invention;  
         [0010]      FIG. 2  is a diagrammatic front elevational view illustrating how the tensioner of  FIG. 1  maintains tension in a cam-to-cam power transmission chain;  
         [0011]      FIG. 3  is a diagrammatic plan view, partly in cross-section, showing how the tensioner of  FIGS. 1 and 2  is mounted on an engine block;  
         [0012]      FIG. 4  is a diagrammatic side elevational view, partly in cross-section, showing the tensioner of  FIGS. 1-3  mounted on an engine block,  
         [0013]      FIG. 5 (A) is a side elevational view of a stopper in accordance with a first embodiment of the invention;  
         [0014]      FIG. 5 (B) is a fragmentary front elevational view, partly in cross-section, showing the stopper of  FIG. 5 (A) positioned to lock the plunger of a tensioner;  
         [0015]      FIG. 5 (C) is a side elevational view of a tensioner in which the plunger is locked by the stopper of  FIG. 5 (A);  
         [0016]      FIG. 6 (A) is a top plan view of a stopper in accordance with a second embodiment of the invention;  
         [0017]      FIG. 6 (B) is a side elevational view of the stopper of  FIG. 6 (A);  
         [0018]      FIG. 6 (C) is an elevational view of the stopper of FIGS.  6 (A) and  6 (B), as seen from the left-hand side of  FIG. 6 (B);  
         [0019]      FIG. 6 (D) is a fragmentary front elevational view, partly in cross-section, showing the stopper of FIGS.  6 (A)- 6 (C) positioned to lock the plunger of a tensioner;  
         [0020]      FIG. 7 (A) is a top plan view of a stopper in accordance with a third embodiment of the invention;  
         [0021]      FIG. 7 (B) is a side elevational view of the stopper of  FIG. 7 (A);  
         [0022]      FIG. 7 (C) is an elevational view of the stopper of FIGS.  7 (A) and  7 (B), as seen from the left-hand side of  FIG. 7 (B);  
         [0023]      FIG. 7 (D) is a fragmentary front elevational view, partly in cross-section, showing the stopper of FIGS.  7 (A)- 7 (C) positioned to lock the plunger of a tensioner;  
         [0024]      FIG. 8  is a front elevational view of a tensioner having a conventional stopper;  
         [0025]      FIG. 9  is a cross-sectional view taken on plane  9 - 9  of  FIG. 8 ; and  
         [0026]      FIG. 10  is a schematic front elevational view showing the timing drive of a dual overhead cam internal combustion engine, having tensioners in which stoppers are used to hold the plungers of the tensioners in place prior to installation of the tensioners. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Tensioner  1 , shown in  FIG. 1 , having a stopper  7  in accordance with the invention, is mounted on an engine block on the inside of the loop-shaped path of a drive chain C 2 , which, as shown in  FIG. 2 , is driven by an air-intake cam sprocket S 3 , and drives an exhaust cam sprocket S 4 . As shown in FIGS.  3  and  4 , the tensioner is mounted in a recess in an engine block  12 . The tensioner may be mounted to the engine block by fasteners which extend through mounting holes such as hole  11  in  FIG. 1 . Sprocket S 3  is coaxially fixed, by a fitting  13 , to a sprocket S 2 , which is driven from a crankshaft sprocket S 1  ( FIG. 10 . Sprocket S 4  is mounted on a fitting  14 .  
         [0028]     The tensioner  1  has a plunger  3  ( FIG. 5 (B)), and a shoe  2  is mounted at the outer end of the plunger. This shoe is disposed in sliding contact with chain C 2 , and is urged outward against the chain by a coiled biasing spring (not shown) within the tensioner housing  5 , or by another suitable biasing device. As shown in  FIG. 5 (B), stopper  7  holds the plunger  3  in the housing, preventing the force exerted by the biasing device from pushing the plunger out of the housing while the plunger is being installed on the engine. After installation of the tensioner, the stopper is removed, and the engagement of the shoe  2  with the chain C 2  limits outward movement of the plunger. As seen in  FIG. 1 , a shoulder  10  is formed on the tensioner housing. When the plunger  3  is pushed into the housing, the shoe  2  is brought into contact with shoulder  10  so that the rotation of the shoe  2  and the plunger  3  is prevented.  
         [0029]     As shown in  FIG. 5 (B), an annular locking groove  4  is provided on the outer circumferential surface of plunger  3  at a location such that the groove is positioned inside the housing when the plunger is pressed into the housing. A through hole  6  is drilled in the housing  5  for receiving the pin  8  of the stopper so that the pin can extend through hole  6  and enter groove  4  to hold the plunger in the retracted condition depicted in  FIG. 5 (B). Although the locking groove  4  is preferably in the form of an annular groove on the outer circumference of the plunger  3 , the pin it may also be in the form of a recess, formed only on a part of the outer circumference of the plunger  3 .  
         [0030]     As seen in  FIG. 5 (A), the stopper has a handle  9 , which extends along an axis  9   a.  As in the example shown in  FIG. 5 (A), the handle can be symmetrical, in which case the handle axis can be an axis of symmetry of the handle. The handle may also be elongated, in which case, the handle axis will ordinarily extend along the direction of elongation of the handle. However, the handle does not need to be symmetrical or elongated. In any case, the handle axis  9   a  defines the direction in which the handle extends away from the pin. The stopper is bent so that the handle axis is disposed at an angle a with respect to the axis  8   b  of the pin  8 . More specifically, the axes  8   b  of the pin, and  9   a  of the handle, intersect, and the portion of axis  9   a,  which extends from the handle beyond the intersection, forms an angle α with respect to the axis  8   b  of the pin  8  on the pin side of the intersection, that is, the side of the intersection on which the pin is located. The angle α must be greater than zero, but not greater than 90°. If the angle α is more than 90°, rotation of the stopper  7  while the front end  8   a  of the pin is inserted into the pin through hole  6  becomes impossible because the handle  9 , which rotates with the pin  8 , would come into contact with the tensioner housing  5 , making it difficult to remove the stopper  7  from the tensioner housing  5 .  
         [0031]     In the assembly of the tensioner, the plunger  3  is pushed into the housing  5  against the biasing device, and the annular locking groove  4 , formed on the outer circumferential surface of the plunger  3 , is aligned with the pin through hole  6  in the housing  5 , so that the front end pin  8   a  of the stopper pin  8  may be inserted through hole  6  and into engagement with the groove  4 . The pin holds the plunger  3  in the housing  5 . After the tensioner is mounted, and the drive chain with which the tensioner is to be associated is installed on its sprockets, the stopper  7  may be pulled out, allowing the plunger  3  to protrude under the force exerted by the biasing device, until the shoe  2  is brought into contact with, and applies tension to, the chain C 2 .  
         [0032]     The handle  9  of the stopper  7  is pivotable so that contact between the handle and interfering objects such as engine fittings and the like in the vicinity of the tensioner can be avoided. Consequently, the tensioner  1 , with the stopper  7  installed, can be mounted in a very restricted space. Furthermore, even if only a limited space is available after mounting the tensioner with the stopper installed in it, the handle  9  can be pivoted about the axis  8   b  of pin  8  so that interfering objects can be avoided, and the stopper  7  can be removed. Accordingly, assembly of the engine, or other mechanism in which the tensioner is used, can be greatly facilitated.  
         [0033]     In the second embodiment, shown in FIGS.  6 (A)- 6 (D), the stopper has a different construction. The stopper  21  is composed of a pin body portion  22  and a handle  23 . The pin body portion  22  is includes a pin holder  22   a  and a pin  22   b.  The pin holder  22   a  includes a top  22   c,  which abuts a shoe  2  when the stopper  21  is attached to the tensioner, as shown in  FIG. 6 (D). The handle  23  is bent at an angle α with respect to the pin body portion  22 . As in the case of the first embodiment, described above, the angle α is greater than zero, but not more than 90°.  
         [0034]     During assembly of the tensioner of FIGS.  6 (A)- 6 (D), the plunger  3  is pushed into the housing  5  against a biasing member until the annular locking groove  4  is aligned with the through hole  6  in the housing  5 . Pin  22   b,  at the front end of the pin body  22 , is inserted through hole  6  and into groove  4 , preventing the plunger from being pushed out of the housing until the tensioner is installed.  
         [0035]     Since the top  22   c  of the pin holder engages the shoe to prevent, or at least limit, rotation of the stopper, the handle remains substantially in the position depicted in  FIG. 6 (D) during installation of the tensioner. However, when the stopper is pulled a short distance so that the front end of the pin  22   b  disengages the locking groove  4  of the plunger, the plunger can move outward until the shoe applies tension to its associated chain. When the plunger moves forward, the shoe no longer restricts rotation of the stopper, and the stopper can be rotated, if necessary, to allow it to be fully removed from the tensioner  
         [0036]     In the third embodiment, depicted in FIGS.  7 (A)- 7 (D), the stopper  31  is composed of a pin body  32  and a handle  33 , and the pin body  32  is composed of a pin holder  32   a,  a fitting  32   b,  and a solid rectangular pin  32   c.  When the stopper  31  is attached to the tensioner, the fitting  32   b  fits into a through hole  6  in the housing  5 , and the rectangular pin  32   c  engages the locking groove  4  of the plunger  3 . As in the previously described embodiments, the handle  33  is disposed at an angle α with respect to the pin body  32 , the angle α being greater than zero, but not greater than 90°.  
         [0037]     Because the pin  32   c  is rectangular in shape, when it is engaged in the locking groove  4 , pivoting of the stopper is either limited or prevented altogether. The pin holds the plunger in its retracted condition prior to installation of the tensioner. After installation, the stopper can be pulled a short distance to disengage pin  32   c  from groove  4 . Thereupon, the plunger is urged outward by the biasing device of the tensioner, and into engagement with its associated chain. At the same time, when the pin disengages the locking groove, pivoting movement of the of the stopper is no longer prevented, and the stopper handle can be moved as required to clear any interfering parts so that the stopper can be fully removed from the tensioner.