Hydraulic valve lash adjuster for a valve train of an internal combustion engine

Abstract

A hydraulic valve lash adjuster for a valve train of an internal combustion engine, for example for an automotive vehicle, said hydraulic valve lash adjuster comprising a piston ( 2 ) that is guided for displacement in a piston housing ( 4 ) and elastically supported against said housing, said piston ( 2 ) comprising a low pressure chamber ( 3 ) that communicates via an axial opening ( 26 ) in a piston bottom ( 19 ) with a high pressure chamber ( 5 ) defined by the piston housing ( 4 ) and the piston ( 2 ), and further comprising a control valve ( 6 ) acting between said pressure chambers ( 3, 5 ), said control valve ( 6 ) comprising a valve closing body ( 7 ) that can be brought to bear sealingly against a valve seat ( 24 ) that surrounds the axial opening ( 26 ) on a piston body undersurface ( 28 ) and is received in a closing body cap ( 9 ) whose cap bottom ( 21 ) acts as a stroke limitation of the valve closing body ( 7 ), and said control valve ( 6 ) further comprising a control valve spring ( 8 ) that loads the valve closing body ( 7 ) in opening direction, and, during a collapsing movement between the piston ( 2 ) and the piston housing ( 4 ), said valve closing body ( 7 ) being hydraulically loadable in closing direction against the biasing force of the control valve spring ( 8 ) by a pressure build-up in the high pressure chamber ( 5 ). To improve the valve lash adjuster so that undesired operational fluctuations are reduced, the valve closing body ( 7 ) is configured as a needle-shaped, elongate sealing piston whose valve seat-proximate end comprises a plate-shaped sealing surface ( 10 ) that cooperates with a correspondingly configured sealing surface ( 25 ) of the valve seat ( 24 ) and whose valve seat-distal end comprises a surface of application ( 12 ) for hydraulic loading, and the valve closing body ( 7 ) substantially fills a space volume of the closing body cap ( 9 ) surrounding the valve closing body ( 7 ).

1 . A hydraulic valve lash adjuster for a valve train of an internal combustion engine, said hydraulic valve lash adjuster comprising a piston that is guided for displacement in a piston housing and elastically supported against said housing, said piston comprising a low pressure chamber that communicates via an axial opening in a piston bottom with a high pressure chamber defined by the piston housing and the piston, and further comprising a control valve acting between said pressure chambers, said control valve comprising a valve closing body that can be brought to bear sealingly against a valve seat that surrounds the axial opening on a piston body undersurface and is received in a closing body cap whose cap bottom acts as a stroke limitation of the valve closing body, and said control valve further comprising a control valve spring that loads the valve closing body in opening direction, and, during a collapsing movement between the piston and the piston housing, said valve closing body being hydraulically loadable in closing direction against the biasing force of the control valve spring by a pressure build-up in the high pressure chamber, wherein the valve closing body is configured as a needle-shaped, elongate sealing piston whose valve seat-proximate end comprises a plate-shaped sealing surface that cooperates with a correspondingly configured sealing surface of the valve seat and whose valve seat-distal end comprises a surface of application for hydraulic loading, and the valve closing body substantially fills a space volume of the closing body cap surrounding the valve closing body. 
   
   
       2 . A hydraulic valve lash adjuster of  claim 1 , wherein the valve closing body is guided in the closing body cap with a guide clearance. 
   
   
       3 . A hydraulic valve lash adjuster of  claim 1 , wherein a guide means is arranged or configured on the valve closing body and/or the closing body cap. 
   
   
       4 . A hydraulic valve lash adjuster of  claim 3 , wherein the guide means acts as a anti-tilt device and/or a centering means and/or an anti-rotation device of the valve closing body. 
   
   
       5 . A hydraulic valve lash adjuster of  claim 1 , wherein at least a central region of the valve seat-distal, cap bottom-side end of the valve closing body has a shape mating the cap bottom. 
   
   
       6 . A hydraulic valve lash adjuster of  claim 1 , wherein the surface of application is configured as a circumferential chamfer on the valve seat-distal end of the valve closing body and can be hydraulically loaded through an oil passage in the valve body cap. 
   
   
       7 . A hydraulic valve lash adjuster of  claim 1 , wherein a dirt-collecting device is configured in the valve closing body. 
   
   
       8 . A hydraulic valve lash adjuster of  claim 7 , wherein the dirt-collecting device is configured in the valve closing body as a recess that is arranged coaxially to the axial opening and is open on the valve seat-proximate end of the valve closing body. 
   
   
       9 . A hydraulic valve lash adjuster of  claim 8 , wherein the recess is configured as a cylindrical collecting pocket. 
   
   
       10 . A hydraulic valve lash adjuster of  claim 8 , wherein the recess comprises a bottom-side sink.