Patent Application
20180223701
The present disclosure generally relates to hydraulic lash adjusters and, more particularly, relates to hydraulic lash adjusters used in engine valve actuator assemblies.
Each cylinder of an engine, for example a diesel engine, is equipped with one or more valves (e.g., intake and exhaust valves) that are cyclically opened during normal operation. The valves may be opened by way of an actuator assembly that includes a driving member, such as a camshaft, and a rocker arm. The camshaft includes one or more lobes arranged at particular angles corresponding to desired lift timings and amounts of the associated valves. The lobes are connected to stem ends of the associated valves by way of the rocker arm and associated linkage components. As the camshaft rotates, a lobe comes into contact with a first end of the rocker arm causing the rocker arm to pivot, thereby forcing a second end of the rocker arm against the stem end of a valve (via the linkage). This pivoting motion causes the valve to lift or open against a spring bias. As the lobe rotates away from the rocker arm, the valve is released and allowed to return to a closed position.
When a cylinder is equipped with more than one of the same type of valve (e.g., more than one intake valve and/or more than one exhaust valve), valves of the same type may be typically opened at about the same time. To reduce the number of camshafts, lobes, and/or rocker arms required to open multiple valves, a valve bridge, or the like, may be used to interconnect a plurality of valves with a common rocker arm.
For example, an exemplary valve bridge may be generally T-shaped, having arms that extend between the stem ends of two valves. The second end of the rocker arm may engage a portion of the valve bridge, between the bridge arms. With this configuration, the force imparted to the bridge by the pivoted rocker arm results in lifting of the paired valves off of their respective valve seats. A lash adjuster may be associated with the valve bridge and used to remove clearance that may exists between the valves and corresponding seats (and/or between other valve train components) during rocker arm cycle.
Publication WO2016/086067 (“McCarthy et al.”) published Jun. 2, 2016, describes an internal combustion engine that has a valvetrain that includes a rocker arm assembly on which is mounted an electronic device and at least part of a generator. A hydraulic lash adjuster is disclosed in McCarthy et al. to provide lash adjustment via relative movement of an inner sleeve and a middle sleeve. While beneficial, the disclosure does not address a replaceable hydraulic lash adjuster that can be slidably installed/removed from inside a compartment of a rocker arm by sliding the hydraulic lash adjuster in or out of the compartment in the rocker arm. As used herein, the terms “slidably” and “slidingly” each mean “able to be moved by sliding.”
In accordance with one aspect of the disclosure, a replaceable hydraulic lash adjuster for an actuator assembly for an engine valve is disclosed. The actuator assembly includes a rocker arm operatively connected to a valve stem of the engine valve. The rocker arm defines a compartment. The replaceable hydraulic lash adjuster comprises a body, a piston, a check valve and a spring. The body is configured to be slidably received in and released from the compartment of the rocker arm. The body has a top end and a bottom end. The top end of the body is configured to be disposed inside the rocker arm. The bottom end of the body may be configured to be disposed outside of the rocker arm. The body includes a sidewall surrounding a floor. The floor is disposed below the top end of the body. The sidewall and the floor define an upper cavity and a lower cavity. The floor includes a passage that extends between the upper cavity and the lower cavity. The lower cavity is configured to receive the piston. The floor may be configured to receive a boss that extends through the rocker arm into the upper cavity. The compartment and the upper cavity form an upper chamber when the body is positioned inside the compartment. The piston includes a plunger, a neck and a base. The neck is disposed between the base and the plunger. The base is disposed inside the lower cavity of the body. The base defines a pocket. The plunger is disposed below and outside of the bottom end of the body and may be configured to be received by a retention member. The check valve may be disposed inside the lower cavity and adjacent to the passage and to the base of the piston. The spring may be disposed inside the pocket. The replacable hydraulic lash adjuster is configured to be slidingly removeable from the compartment of the rocker.
In accordance with another aspect of the disclosure, a method of assembling a replaceable hydraulic lash adjuster for an actuator assembly for an engine valve is disclosed. The actuator assembly includes a rocker arm operatively connected to a valve stem of the engine valve. The rocker arm defines a compartment. The method may comprise: providing a body, the body configured to be slidably received in and released from the compartment of the rocker arm, the body having a top end and a bottom end, the top end of the body configured to be disposed inside the compartment, the bottom end of the body configured to be disposed outside of the rocker arm, the body including a sidewall surrounding a floor, the floor disposed below the top end of the body, the sidewall and the floor defining an upper cavity and a lower cavity, the floor including a passage that extends between the upper cavity and the lower cavity, the lower cavity configured to receive a piston, the floor configured to receive a boss that extends through the rocker arm into the upper cavity, wherein the upper cavity is configured to form an upper chamber with the compartment when the body is positioned inside the compartment; inserting a check valve inside the lower cavity of the body and adjacent to the passage; providing a piston, the piston including a plunger, a neck and a base, the neck disposed between the base and the plunger, the base defining a pocket; and disposing a spring inside the piston and inserting the piston into the body. The hydraulic lash adjuster disposed between the rocker arm and the engine valve.
In accordance with a further aspect of the disclosure, an actuator assembly for an engine valve is disclosed. The engine valve includes a valve stem. The actuator assembly may comprise a rocker arm, a replaceable hydraulic lash adjuster, a boss and a retention member. The rocker arm includes a first arm end and a second arm end. The first arm end is operatively connected to a cam, or the like. The second arm end defines a compartment configured to receive the hydraulic lash adjuster. The second arm end defines a bore extending from an outer surface of the rocker arm to the compartment. The replaceable hydraulic lash adjuster is disposed between the rocker arm and the valve stem. The replaceable hydraulic lash adjuster includes a body, a piston, a check valve and a spring. The body is configured to be slidably received in and released from the compartment of the rocker arm. The body has a top end and a bottom end. The top end of the body is configured to be disposed inside the rocker arm. The bottom end of the body is configured to be disposed outside of the rocker arm and above a retention member. The body includes a sidewall surrounding a floor. The floor is disposed below the top end of the body. The sidewall and the floor define an upper cavity and a lower cavity. The floor includes a passage that extends between the upper cavity and the lower cavity. The lower cavity is configured to receive the piston. The floor is configured to receive the boss that extends through the rocker arm into the upper cavity. The compartment and the upper cavity form an upper chamber. The piston includes a plunger, a neck and a base. The neck is disposed between the base and the plunger. The base is disposed inside the lower cavity of the body. The base defines a pocket. The plunger is disposed below and outside of the bottom end of the body and may be disposed in a recessed surface of the retention member. The check valve is disposed inside the lower cavity and adjacent to the passage and to the base of the piston. The spring is disposed inside the pocket. The replacable hydraulic lash adjuster is slidingly removable from the compartment of the rocker. The boss has an engagement end and a nut end. The boss extends through the bore of the rocker arm into the upper cavity. The engagement end of the boss is configured to receive the floor and to adjust, in a direction parallel to the sidewall, a position of the replaceable hydraulic lash adjuster inside the compartment. The retention member is disposed between the valve stem and the bottom of the body. The retention member includes a recessed surface configured to receive the plunger of the piston.
The rocker arm 104 includes a first arm end 118 and a second arm end 120. The first arm end 118 is operatively connected to a driving member 122, such as a cam shaft 124 that includes one or more lobes 130 (a rocker arm 104 activated by the lobe 130 of a cam shaft 124 may be referred to as a cam-activated rocker arm). More specifically, the first arm end 118 may be operatively connected to a lobe 130 of a cam shaft 124. The driving member 122 is configured to actuate the rocker arm 104. The rocker arm 104 defines a compartment 126 and a bore 128, both disposed proximal to the second arm end 120. The compartment 126 is configured to receive the replaceable hydraulic lash adjuster 106. The bore 128 extends from an outer surface 132 of the rocker arm 104 to the compartment 126. In one embodiment, the compartment 126 may be cylindrical in shape.
The replaceable hydraulic lash adjuster 106 is disposed between the rocker arm 104 and one or more valve stems 204 of an engine valve 102. In the exemplary embodiment discussed herein, the replaceable hydraulic lash adjuster 106 is disposed between the rocker arm 104 and the bridge 110, however other embodiments may not include the bridge 110 or may, alternatively, include other interconnecting linkage between the rocker arm 104 and the one or more valve stems 204. As best shown in
The body 134 is configured to be slidably received in and released from the compartment 126 of the rocker arm 104. The body 134 is not configured or dimensioned to be a press-fit into the compartment 126. In one embodiment, such as the one shown in
The floor 152 may be disposed below the top end 146 of the body 134. The floor 152 may be disposed generally perpendicular to the sidewall 150. Herein, with respect to the orientation of the floor 152 in relation to the sidewall 150, generally perpendicular means plus or minus fifteen (15) degrees. The inventors have found that the positioning of the floor 152 between the top end 146 and the bottom end 148 of the body 134 inhibits or eliminates bulging of the sidewall 150 that might occur in some situations due to stress on the sidewall 150.
The sidewall 150 and the floor 152 define an upper cavity 158 and a lower cavity 160. In one embodiment, the upper cavity 158 (as defined by the distance between the top end 146 of the body 134 to the floor 152) is longer than the lower cavity 160 (as defined by the distance between the bottom end 148 to the floor 152). While not wishing to be bound by theory, the relative length of the upper cavity 158 to the lower cavity 160 also contributes to the elimination of deformation of the sidewall 150 due to stress.
The floor 152 includes a passage 162 that extends between the upper cavity 158 and the lower cavity 160. The floor 152 is configured to form with the boss 108 one or more fluid pathways 164 to the check valve 138.
The lower cavity 160 is configured to receive the piston 136. The floor 152 is configured to receive the boss 108 that extends through the rocker arm 104 into the upper cavity 158. The compartment 126 and the upper cavity 158 form an upper chamber 166 when the body 134 is positioned inside the compartment 126. The lower cavity 160 and the piston 136 form a lower chamber 168 when the piston 136 is positioned inside body 134.
As best shown in
The check valve 138 is disposed inside the lower cavity 160. The check valve 138 is disposed adjacent to the passage 162 and to the base 174 of the piston 136. The spring 140 is disposed inside the pocket 176.
The adjuster O-ring 142 is disposed around an outside surface 184 (
The retaining ring 144 is disposed below the base 174 of the piston 136 and is mounted to the inner wall 190 of the sidewall 150 inside the lower cavity 160. In some embodiments, the retaining ring 144 may be disposed in a furrow 192 that extends around the inner wall 190 of the sidewall 150 inside the lower cavity 160. The retaining ring 144 may be disposed perpendicular to the sidewall 150. In some embodiments, the retaining ring 144 may be a snap ring or the like.
The boss 108 has an engagement end 196 and a nut end 198. The boss 108 extends through the bore 128 of the rocker arm 104 into the upper cavity 158. The engagement end 196 of the boss 108 is configured to receive the floor 152 and to adjust, in a direction parallel to the sidewall 150, a position of the replaceable hydraulic lash adjuster 106 inside the compartment 126. The boss 108 further a plurality of conduits 200 disposed at the engagement end 196. In one embodiment, the conduits 200 extend radially outward from a center 202 of the boss 108. The floor 152 and the engagement end 196 of the boss 108 form one or more fluid pathways 164 to the passage 162, or more specifically, the floor 152 and each conduit 200 of the boss 108 forms a fluid pathway 164 to the passage 162.
The bridge 110, in the exemplary embodiment of
The retention member 112 is disposed between the engine valve 102 (valve stems 204) and the bottom of the body 134. In the exemplary embodiment shown in
The retention O-ring 116 is disposed on the recessed surface 182 of the retention member 112. More specifically, the retention O-ring 116 is disposed above the plunger 170 of the piston 136 when the piston 136 is disposed against the recessed surface 182 of the retention member 112.
The nut 114 is disposed on the rocker arm 104 and is configured to secure the boss 108 to the rocker arm 104.
Once assembled the replaceable hydraulic lash adjuster 106 (
During operation of the engine, the engine valves 102 of the engine (e.g., intake and exhaust valves) are cyclically opened and closed. The engine valves 102 are opened by way of the actuator assembly 100. The driving member 122 moves/pivots the rocker arm 104 (about a shaft 230) from a first position 208 (
In the exemplary embodiment shown in
In
As the cam shaft 124 rotates, the lobe 130 comes into contact with the first arm end 118 of the rocker arm 104 and the rocker arm 104 begins to pivot about the shaft 230 from the first position 208 of
As the rocker arm 104 continues to pivot about the shaft 230 to the second position 210, the pivoting motion causes each engine valve 102 operatively connected to the bridge 110 to lift or open against a bias provided by a valve spring 216 positioned around and operatively connected to the valve stem 204 of the engine valve 102. When the lobe 130 of the cam shaft 124 reaches the high-point position 214 the position of the lobe 130 forces the rocker arm 104 fully into the second position 210, the maximum lift of each engine valve 102 from its valve seat occurs.
As the lobe 130 rotates away from the rocker arm 104, the rocker arm 104 begins to pivot about the shaft 230, moving upward and back to the first position 208. The upward movement of the rocker arm 104 reduces the downward force exerted by the piston 136 on the bridge 110. At the same time the reaction force exerted on the piston 136 decreases. Both the combination of the decreasing reaction force exerted on the piston 136 and the bias of the spring 140 in the pocket 176 begin to move the piston 136 toward its primary position 218 at the beginning of the cycle. Movement of the piston 136 toward the primary position 218 increases the volume of the lower chamber 168, thus decreasing the pressure in the lower chamber 168. The check valve 138 opens and fluid begins to flow from the upper chamber 166 through the passage 162 to the lower chamber 168. When the rocker arm 104 reaches the first position 208, the bridge 110 no longer exerts a downward force on the valve stems 204 and the engine valves 102 have return to their closed position in which each engine valve 102 is sealed against its valve seat (not shown). In addition, the piston 136 has returned to its primary position 218 at the beginning of the cycle.
The features disclosed herein may be particularly beneficial to actuator assemblies that include a rocker arm 104 and a hydraulic lash adjuster installed in the compartment 126 of the rocker arm 104. The teachings of the present disclosure provide for a replaceable hydraulic lash adjuster 106 that can be slidably installed into the compartment 126 and slidably removed from the compartment 126, for maintenance or replacement. Conventional hydraulic lash adjusters are typically press-fit into a rocker arm 104. When the hydraulic lash adjuster needs to be replaced, it usually cannot be removed without damaging the rocker arm 104, thus, the rocker arm 104 and the hydraulic lash adjuster must be replaced together.
