Acting valve gear

Abstract

A bucket tappet is provided for direct-acting valve gear having a body portion formed of a light weight material having a thermal expansion suitable for use in an aluminum engine head. The body of the tappet is formed with a tubular wall, an inner tubular hub and a transverse web joining and supporting the hub within the outer tubular wall. An hydraulic lash adjusting piston/plunger assembly formed of steel is received within the tubular hub. The leakdown control surfaces within the lash adjuster are formed on the mating interfaces between the steel piston and plunger. The body of the tappet has a cam face member formed of hardened material, preferably iron base, received thereover transversely of the outer tubular portion and retained thereon for providing a cam contacting surface. The inner tubular hub has the end adjacent the cam face closed by portions of the body for forming a portion of the hydraulic reservoir in conjunction with a cavity formed in the hydraulic piston. The outer periphery of the light weight body has a hardened surface adapted for wear-resistant sliding contacting with a guide bore formed in the aluminum engine head.

I claim: 
     
       1. An hydraulic lash adjusting tappet for use in the valve gear of an internal combustion engine, said tappet comprising: (a) body means, including structure defining, (i) an outer annular wall having the outer periphery thereof forming a wear resistant surface;   (ii) an annular hub disposed within said annular wall and spaced therefrom, said hub having one end thereof closed and the annular inner periphery thereof disposed in generally parallel relationship to said wear surface;   (iii) a plurality of webs disposed in circumferentially spaced arrangement about said annular wall and with each web extending inwardly therefrom to said hub and joined thereto for supporting same, wherein said body means structure is formed of material having a coefficient of thermal expansion not less than 22×10 -6  per unit length per degree centigrage as measured in the range 20-100 degrees C.     (b) a face member having a cam face formed thereon, said member being disposed over said hub end and extending outwardly to said annular wall and being joined thereto, said face member being formed of material having surface hardness value of at least 89 as measured on the Rockwell 15 N scale for the cam face;   (c) hydraulic lash adjusting means movably received in the open end of said hub, said lash adjusting means including structure defining a reaction surface adapted for contacting associated components of the engine valve gear, said reaction surface extending generally parallel to said cam face and being movable with respect thereto, said lash adjusting means including means defining a fluid pressure chamber and one-way valve means operable to admit fluid to said chamber for altering the position of said reaction surface with respect to said cam face for lash adjustment in said valve gear, said lash adjusting means further including means biasing said reaction surface away from said cam face;   (d) said body means including structure defining a fluid passage from said wear resistant surface to said one-way valve means for communicating fluid thereto upon installation of said tappet in an engine and supplying pressurized fluid to said passage; and,   (e) means retaining said lash adjusting means in said hub.   
     
     
       2. The tappet defined in claim 1, wherein said body means is formed of substantially aluminum material. 
     
     
       3. The tappet defined in claim 1, wherein said lash adjusting means includes structure cooperating with said body means to define a fluid reservoir communicating with said one-way valve means. 
     
     
       4. The tappet defined in claim 1, wherein said body means is formed of material having a density less than 2.85 grams per cm 3  hub structure, said annular wall and said web structure are integrally formed. 
     
     
       5. An hydraulic lash adjusting tappet for the valve gear of an internal combustion engine, said tappet comprising: (a) body means including structure defining: (i) an outer annular wall having a wear resistant surface on the outer periphery thereof;   (ii) an annular hub disposed within said outer wall and spaced therefrom, and,   (iii) an end wall attached respectively to and extending transversely across one axial end of said hub,   (iv) web structure extending inwardly from said outer annular wall and supporting said hub, wherein said body means is formed of material having a coefficient of thermal expansion of at least 22.0×10 -6  per unit length per degree centigrade as measured in the range 20-100 degrees C.;     (b) a member defining a cam face adapted to contact an engine cam, said face member being formed of material having a hardened surface adapted for contacting a cam;   (c) hydraulic lash adjsuting means movably received in said hub, said lash adjusting means including structure defining a reaction surface adapted for contacting associated valve gear components, said reaction surface extending generally parallel to said cam face and being movable with respect thereto, said lash adjusting means including means defining a fluid pressure chamber and plunger means including piston structure cooperating with said web to form a first fluid chamber of a fluid reservoir, and said plunger means including plunger structure cooperating with portions of said hub to form a second chamber of a fluid reservoir, and one-way valve means operable to admit fluid to said chamber for altering the position of said reaction surface with respect to said cam face, said lash adjusting means further including means biasing said reaction surface away from said cam face, said web including structure defining at least one by-pass channel operable to communicate said first reservoir portion with said second reservoir portion for all positions of said piston structure and said plunger structure in said hub;   (d) said body means including structure defining a fluid passage through said tubular wall portion from said wear resistant surface to said second reservoir chamber and one-way valve means for communicating fluid thereto upon installation of said tappet in an engine and supplying pressurized fluid to said passage;   (e) means retaining said lash adjusting means in said hub.   
     
     
       6. The tappet defined in claim 5, wherein said fluid passage defining structure includes a radial web extending between said outer tubular wall and said hub. 
     
     
       7. The tappet defined in claim 5, wherein said body means structure is formed of material having a bulk density less than 2.85 grams per cm 3 . ' 
     
     
       8. The tappet defined in claim 5, wherein said face member is formed of steel and said body, means outer wall, hub and web are formed of substantially aluminum material. .Iadd. 
     
     
       9.  A hydraulic lash adjusting tappet for use in the valve gear of an internal combustion engine, said tappet comprising: (a) a member defining a cam face, said member formed of material having a hardened surface adapted for contacting a cam;   (b) body means including structure defining: (i) an outer annular wall having the outer periphery thereof forming a wear resistance surface;   (ii) at a web extending radially inwardly from said outer wall;   (iii) an annular hub disposed centrally within said outer wall and supported from said web, wherein said body means is formed of material selected from the group consisting of aluminum, material having a thermal expansion coefficient not less than 22×10 -6  per unit length per degree centigrade as measured in the range 20-100 C., or material having a bulk modulus not greater than 2.85 grams per cubic centimeter     (c) hydraulic lash adjusting means movably received in the open end of said hub, said lash adjusting means including structure defining a reaction surface adapted for contracting associated components of the engine valve gear, said reaction surface extending generally parallel to said cam face and being movable with respect thereto, said lash adjusting means including means defining a fluid pressure chamber and one-way valve means operable to admit fluid to said chamber for altering the position of said reaction surface with respect to said cam face for lash adjustment in said valve gear, said lash adjusting means further including means biasing said reaction surface away from cam face;   (d) said body means including structure defining a fluid passage from said wear resistant surface to said one-way valve means for communicating fluid thereto upon installation of said tappet in an engine and supplying pressurized fluid to said passage; and,   (e) means retaining said lash adjusting means in said hub. .Iaddend.