Abstract:
A lash adjuster includes a plunger inserted into a body and defining a pressure chamber in the body, and a spacer. The plunger is moved axially when a working fluid flows into or out of the pressure chamber so that a volume of the pressure chamber is increased or reduced. The plunger has a bottom wall defining the pressure chamber, a peripheral wall rising from an outer periphery of the bottom wall and an outer peripheral surface having an annular groove located at a height position confined in a thickness range of the bottom wall. When fitted in the groove, the spacer has a plate width equal to a separating distance between a groove bottom and an inner peripheral face of the body to fill a gap between the body and the plunger. The spacer has a flow path through which the working fluid introduced into the pressure chamber leaks.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of patent application number 2007-175032, filed in Japan on Jul. 3, 2007, the subject matter of which is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a lash adjuster. 
     JP-A-2004-278377 discloses a lash adjuster and a valve apparatus of a background art. The lash adjuster includes a body and a plunger in a cylindrical shape. A pressure chamber is defined between the body and a bottom portion of the plunger inserted into the body by increasing or reducing a volume of the pressure chamber by a working fluid introduced into the pressure chamber. The plunger is moved in an axial direction, and a valve clearance in a valve apparatus of an internal combustion engine is automatically adjusted. A gap between an inner peripheral face of the body and an outer peripheral face of the plunger is constituted by a small clearance for leaking the working fluid from the pressure chamber. When the plunger is moved to a lower side relative to the body and the working fluid in the pressure chamber is compressed, the working fluid in the pressure chamber flows out of the pressure chamber by passing the small clearance, and a total length of the lash adjuster is slightly shortened. 
     The small clearance is required to be controlled highly accurately in order to ensure a performance of the lash adjuster. However, there is a situation that the control of the gap between the inner peripheral face of the body and the outer peripheral face of the plunger is technically difficult and productivity is poor. Particularly, a further deterioration in the productivity is concerned when it is necessary to further narrow the gap between the inner peripheral face of the body and the outer peripheral face of the plunger by a request for downsizing the lash adjuster. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention has been accomplished based on the above-described situation and it has an object to improve a productivity by facilitating a gap control. 
     The present invention provides a lash adjuster comprising a body in a cylindrical shape. The plunger is inserted into the body and defining a pressure chamber in the body when assembled to the body. The plunger is moved in an axial direction in the body when a working fluid flows into or out of the pressure chamber so that a volume of the pressure chamber is increased or reduced. The plunger has a bottom wall defining the pressure chamber, a peripheral wall rising from an outer periphery of the bottom wall and an outer peripheral surface formed with an annular groove located at a height position confined in a range of a thickness of the bottom wall out of an outer peripheral surface of the peripheral wall. A spacer is formed into a shape of an annular plate with elasticity and fittable into the annular groove of the plunger. When the spacer is fitted in the annular groove, the spacer has a plate width that is equal to a separating distance between a groove bottom of the annular groove and an inner peripheral face of the body thereby to fill a gap between an inner peripheral face of the body and an outer peripheral face of the plunger. The spacer has a flow path through which a working fluid introduced into the pressure chamber leaks. 
     According to the above-described lash adjuster, the spacer having a large control width is made to handle a gap control, and therefore, different from the background art, it is not necessary to strictly control a gap between the inner peripheral face of the body and an outer peripheral face of the plunger, the gap control is facilitated, and promotion of a productivity can be achieved. 
     The invention also provides a valve apparatus comprising a cam rotated by being transmitted with a power of an engine; a rocker arm pivoted with rotation of the cam; a cylinder head including a feeding path along which a working fluid flows and recessed to be formed with a support hole at an upper face thereof and opened with an oil feeding port intersected with the filling path at an inner peripheral face of the support hole; and a lash adjuster of automatically adjusting a valve clearance of a valve inserted to the cylinder head, wherein the lash adjuster comprises a body in a cylindrical shape inserted into the support hole of the cylinder head; a plunger pivotably supporting the rocker arm at an upper end portion thereof, inserted into the body, and defining a pressure chamber in the body when assembled to the body, the plunger being moved in an axial direction in the body when a working fluid flows into or out of the pressure chamber so that a volume of the pressure chamber is increased or reduced, the plunger having an outer peripheral surface formed with an annular groove; and a spacer formed into a shape of an annular plate with an elasticity and fittable into the annular groove of the plunger, wherein when the spacer is fitted in the annular groove, the spacer has a plate width that is equal to a separating distance between a groove bottom of the annular groove and an inner peripheral face of the body thereby to fill a gap between an inner peripheral face of the body and an outer peripheral face of the plunger, and the spacer has a flow path through which a working fluid introduced into the pressure chamber leaks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments 1 through 5 specifying the invention will be explained in reference to the drawings as follows. 
         FIG. 1  is a vertical sectional view of a lash adjuster according to the invention. 
         FIG. 2  is a plane view of a spacer of Embodiment 1. 
         FIG. 3  is a plane view of a spacer of Embodiment 2. 
         FIG. 4  is a plane view of a spacer of Embodiment 3. 
         FIG. 5  is a plane view of a spacer of Embodiment 4. 
         FIG. 6  is a cross-sectional view enlarging a portion of a body formed with a flow path in a reference example. 
         FIG. 7  is a vertical sectional view of a valve apparatus of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiment 1 
     A lash adjuster  10  of Embodiment 1 details of which are shown in  FIG. 1 ,  FIG. 2  and  FIG. 7  is a lash adjuster of a hydraulic type for pivotably supporting a rocker arm  90  in an axial direction (up and down direction), including a body  20  and a plunger  60  made of a metal. 
     As shown by  FIGS. 1 and 7 , the body  20  constitutes a shape of a bottomed cylinder raising a cylinder portion  22  of a shape of a circular cylinder from a peripheral edge of a bottom portion  21  in a circular shape and is attachably and detachably inserted to a bottomed support hole  81  recessed to be formed at an upper face of a cylinder head  80  attachably and detachably while directing an axis core thereof in a depth direction (up and down direction) thereof. An inner peripheral face of the support hole  81  is opened with an oil feeding port  83  intersected with a feeding path  82  of the cylinder head  80 . A stem hole  84  of the cylinder head  80  is inserted with a valve stem  86  of a valve  85  movably in an axial direction, and a valve portion  87  provided at a front end of the valve stem  86  opens and closes an intake path  88  at inside of a cylinder, not illustrated. 
     An outer peripheral face of the cylinder portion  22  of the body  20  is formed with an outer side recess portion  23  over an entire periphery thereof at a position opposed to the oil feeding port  83 , further, an inner peripheral face of the cylinder portion  22  of the body  20  is formed with an inner side recess portion  24  in a constrained shape over an entire periphery thereof at a position opposed to the outer side recess portion  23 . Further, the cylinder portion  22  of the body  20  is bored with a body hole  25  opened to the outer side recess portion  23  and the inner side recess portion  24 . 
     On the other hand, the plunger  60  constitutes a shape of a bottomed cylinder raising a peripheral wall  62  in a shape of a circular cylinder from a peripheral edge of a bottom wall  61  in a circular shape, fitted to the body  20  and is made to be movable in an axial direction (up and down direction) while bringing an outer peripheral face thereof into sliding contact with an inner peripheral face of the body  20 . An upper end portion (top portion) of the plunger  60  is formed with a support portion  63  in a semispherical shape engaged with and supporting one end portion of the rocker arm  90  and the support portion  63  is formed with a vertical hole  64  capable of supplying a working fluid to the rocker arm  90 . 
     An inner portion of the plunger  60  is made to constitute a lower pressure chamber  65  surrounded by the bottom wall  61  and the peripheral wall  62 , and an inner portion of the body  20  includes a high pressure chamber  26  between the bottom portion  21  and the bottom wall  61  of the plunger  60  (in correspondence with a pressure chamber of the invention). A center of the bottom wall  61  is formed with a communicating hole  66  for communicating the lower pressure chamber  65  and the high pressure chamber  26 . 
     The high pressure chamber  26  is integrated with a retainer  92 , the retainer  92  is pressed to a lower face of the bottom wall  61  of the plunger  60  by an urge force of a retainer spring  93  brought into contact with the bottom portion  21  of the body  20 . Further, inside of the high pressure chamber  26  is provided with a check valve  94  in a spherical shape for opening and closing the communicating hole  66 , and a valve spring  95  is interposed between the check valve  94  and the retainer  92 . The check valve  94  is constituted to be normally urged to an upper side by the valve spring  95  and to be opened only when a hydraulic pressure in the lower pressure chamber  65  is elevated more than a hydraulic pressure in the high pressure chamber  26 . 
     A position of the outer peripheral face of the plunger  60  opposed to the inner side recess portion  24  of the body  20  is formed with a recess portion  67  over an entire periphery thereof. Further, the peripheral wall  62  of the plunger  60  is formed with a plunger hole  68  for communicating the lower pressure chamber  65  and the recess portion  67  on an upper side of the body hole  25 . 
     Now, the outer peripheral face of the peripheral wall  62  of the plunger  60  is formed with a ring-like groove  69  over an entire periphery thereof. The ring-like groove  69  is installed at a height position on a lower side of the recess portion  67  and confined in a range of a thickness of the bottom wall  61 . Further, the outer peripheral face of the peripheral wall  62  of the plunger  60  is mounted with one spacer  50  fitted to the ring-like groove  69 . 
     In details, the spacer  50  is constituted as a plate in a shape of a circular ring made of a synthetic resin having heat resistance and predetermined elasticity of fluororesin (ethylene tetrafluoride (PTFE)) or the like. The spacer  50  is interposed in a gap between the inner peripheral face of the cylinder portion  22  of the body  20  and the outer peripheral face of the peripheral wall  62  of the plunger  60  in a compressed state while being fitted to the ring-like groove  69 , whereas in a single product state, the spacer  50  is provided with a plate width of a dimension slightly larger than a separating distance between a groove bottom of the ring-like groove  69  and the inner peripheral face of the cylinder portion  22  of the body  20 , in an integrated state, the spacer  50  is provided with a plate width of a dimension the same as the separating distance. Further, the inner peripheral face of the cylinder portion  22  of the body  20  and the outer peripheral face of the peripheral wall  62  of the plunger  60  are opposed to each other in parallel by being spaced apart from each other by a small clearance  40  therebetween in a state of interposing the spacer  50  between the two faces. 
     Further, the spacer  50  is notched to be formed with a flow path  51  for leaking a work fluid introduced into the high pressure chamber  26 . The flow path  51  is constituted by notching a portion of an outer peripheral edge of the spacer  50  by a small amount in a rectangular shape, and the working fluid at inside of the high pressure chamber  26  is made to be able to flow out to the upper side by only passing the flow path  51 . The opening dimension of the flow path  51  is determined in correspondence with an individual one of the lash adjuster  10 . 
     Next, an operation of the lash adjuster  10  according to the embodiment will be explained. A portion of the working fluid flowing in the feeding path  82  is introduced into the lash adjuster  10  by successively passing the oil feeding port  83 , the body hole  25 , and the plunger hole  68  and is stored at inside of the lower pressure chamber  65  and the high pressure chamber  26 . Further, when a cam  70  is rotated along with a cam shaft  71  transmitted with a power of an engine and the rocker arm  90  is pressed from an upper side by a cam nose  72 , the plunger  60  is moved to a lower side relative to the body  20  by being pressed by the rocker arm  90 , the working fluid flowing into the high pressure chamber  26  is compressed and a pressure in the high pressure chamber  26  is elevated. In accordance with elevation of the pressure in the high pressure chamber  26 , a small amount of the working fluid in the high pressure chamber  26  is moved up to meander through the gap between an inner peripheral face of the cylinder portion  22  of the body  20  and the outer peripheral face of the peripheral wall  62  of the plunger  60 , passes through the flow path  51  of the spacer  50  and the small clearance  40 , thereafter, made to flow into the lower pressure chamber  65  by way of the plunger hole  68 . An entire length of the lash adjuster  10  is shortened slightly by an amount of the working fluid flowing out from inside of the high pressure chamber  26 . Further, by elevating the pressure in the high pressure chamber  26 , the body  20  and the plunger  60  are integrated to be rigid and the lash adjuster  10  functions as a fulcrum of the operation of the rocker arm  90 . 
     When the cam nose  72  is brought into a state of being directed to the upper side from a lowermost point in accordance with rotation of the cam  70 , a force of pressing the rocker arm  90  is nullified, and the plunger  60  is pressed back to the upper side by the pressure in the high pressure chamber  26  and the urge force of the retainer spring  93 . When the pressure in the high pressure chamber  26  is lowered to be lower than the pressure in the lower pressure chamber  65  in accordance with movement of the plunger  60  to the upper side, the check valve  94  is opened against the urge force of the valve spring  95 , the working fluid introduced into the lower pressure chamber  65  flows into the high pressure chamber  26  by passing the communicating hole  66  and the entire length of the lash adjuster  10  is expanded. By the operation of expanding the lash adjuster  10 , a gap is prevented from being brought about between the support portion  63  of the plunger  60  and the rocker arm  90 . 
     According to Embodiment 1, by interposing the spacer  50  between the inner peripheral face of the cylinder portion  22  of the body  20  and the outer peripheral face of the peripheral wall  62  of the plunger  60  and making the working fluid in the high pressure chamber  26  flow out from the flow path  51  provided at the spacer  50 , the gap control is handled by the spacer  50  having a large control width, and therefore, different from the background art, the gap between the inner peripheral face of the cylinder portion  22  of the body  20  and the outer peripheral face of the peripheral wall  62  of the plunger  60  may not be controlled strictly and promotion of a productivity can be achieved. As a result, the lash adjuster  10  can be downsized. 
     Particularly, the flow path  51  is formed at the spacer  50  made of a synthetic resin, and therefore, a working performance of the flow path  51  is facilitated and a dimensional accuracy of the flow path  51  can be promoted in comparison with a case of being formed at the body  20  or the plunger  60  made of a metal. In this case, only one flow path  51  is formed at the spacer  50 , and therefore, the dimensional accuracy is further improved. 
     Further, the ring-like groove  69  for fitting the spacer  50  is provided at a position in correspondence with the bottom wall  61  of the plunger  60 , and therefore, the groove depth is not particularly restricted by the thickness of the peripheral wall  62 , for example, the groove bottom face can also be disposed on the side of the bottom wall  61 , and a degree of freedom of design is improved. 
     Embodiment 2 
       FIG. 3  shows the spacer  50  of Embodiment 2 of the invention. Although Embodiment 2 differs from Embodiment 1 in a mode of a flow path  51 A of the spacer  50 , Embodiment 2 is the same as Embodiment 1 in constitutions of the spacer  50 , the lash adjuster  10 , and the valve apparatus excluding the flow path  51 A. The flow path  51 A of the spacer  50  in Embodiment 2 is formed by notching a portion of an outer peripheral edge of the spacer  50  in a circular arc shape, in details, in a shape of a true circular arc exceeding a semicircle. 
     EMBODIMENT 3 
       FIG. 4  shows the spacer  50  of Embodiment 3 of the invention. Although Embodiment 3 differs from Embodiment 1 in a mode of a flow path  51 B of the spacer  50 , Embodiment 3 is the same as Embodiment 1 in constitutions of the spacer  50 , the lash adjuster  10 , and the valve apparatus excluding the flow path  51 B. The flow path  51 B of the spacer  50  of Embodiment 3 is formed by penetrating a portion of the spacer  50  in a circular shape, in details, in a shape of a true circle. The flow path  51 B constituted as such an orifice hole is easy to achieve a dimensional accuracy. 
     Embodiment 4 
       FIG. 5  shows the spacer  50  of Embodiment 4 of the invention. Although Embodiment 4 differs from Embodiment 1 in a mode of a flow path  51 C of the spacer  50 , Embodiment 4 is the same as Embodiment 1 in constitutions of the spacer  50 , the lash adjuster  10 , and the valve apparatus excluding the flow path SiC. The flow path  51 C of the spacer  50  of Embodiment 4 is formed by cutting to remove a portion of the spacer  50  over an entire width thereof. Thereby, the spacer  50  is constituted by a shape of a character of C as a whole, and therefore, by expanding or contracting a groove width of the flow path  51 C constituting a cut portion of the character of C, in comparison with a case of an O ring described above, an error in integrating to between the body  20  and the plunger  60  is easy to be absorbed. In this case, the spacer  50  is not limited to a synthetic resin material but can use a spring member made of a metal. Further, in this case, by utilizing thermal expansion of a material constituting the spacer  50 , the groove width of the flow path  51 C can be widened at low temperatures and narrowed at high temperatures, and therefore, a flow rate of the working fluid passing the flow path  51 C can be maintained substantially constant in a state of a low fluidity at low temperatures and a state of a high fluidity at high temperatures. Further, although the flow path  51 C of the spacer  50  shown in  FIG. 5  is extended in a skewed direction relative to a diameter direction of the spacer  50 , the embodiment is not limited thereto but the flow path  51 C may be extended in the diameter direction of the spacer  50 . 
     Reference Example 
       FIG. 6  shows a reference example of the invention. A flow path  51 D of the reference example is provided not in the spacer  50  but in the inner peripheral face of the cylinder portion  22  of the body  20 . In details, the flow path  51 D in a shape of a semicircular groove extended in a height direction and communicating with the small clearance  40  is formed at a position of the inner peripheral face of the cylinder portion  22  opposed to the spacer  50 , a plurality of the flow paths  51 D are arranged in the peripheral direction at intervals, and individual flow paths  51 D are opened by small amounts. The spacer  50  of the reference example constitutes a shape of a true circular ring as a whole and is not provided with a cut portion, a notch, a hole or the like. 
     Otherwise, the flow path may be provided at the outer peripheral face of the peripheral wall  62  of the plunger  60 , or may be provided by penetrating the bottom wall  61  of the plunger  60  partitioning the high pressure chamber  26  and the low pressure chamber  65 . In this way, with regard to a mode of installing the flow path, a certain latitude may be provided to a variation, and therefore, by selecting a pertinent mode in accordance with a situation, a function characteristic of the lash adjuster  10  can sufficiently be achieved. 
     Further, a plurality of rectangular flow paths may be notched to be formed in an outer peripheral edge of a spacer. 
     Further, various modes of the flow paths of Embodiments 1 through 4 may mixedly be utilized such that a rectangular flow path and a circular flow path are mixedly provided to the outer peripheral edge of the spacer. 
     The invention is applicable to an internal combustion engine of a gasoline engine, a diesel engine or the like.