Latch interface for a valve actuating device
A novel latch seat for a switching rocker arm assembly used in variable valve actuation (VVA) systems for internal combustion engines. The seat is formed interactively in the assembled switching rocker arm using a novel fixture and press. The press interactively creates a curved dimple of the correct curvature, position and depth while measuring several lash dimensions. Since the latch seat is formed on the assembled rocker arm assembly, the latch seat depth is designed to account for the inaccuracies in the rocker arm assembly parts which create lash. Therefore all of the parts may be made with less precision since the latch seat is sized to compensate for the inaccuracies of all of the parts. The rocker arm assembly parts now may be manufactured to less stringent standards, but result in a rocker arm assembly with same accuracy of rocker arm assemblies manufactured to previous standards.
1. A process for creating a latch for a switching rocker arm assembly, comprising:
providing an inner arm having a latch bore;
providing an outer arm;
assembling the inner and outer arms into a switching rocker arm assembly;
selecting a latch rod having dimensions of a desired latch;
fitting the latch rod into the latch bore;
mounting the switching rocker arm assembly into a manufacturing fixture that simulates installation of the switching rocker arm assembly into an engine;
pressing the outer arm into the latch rod to form a latch seat in the outer arm;
measuring a latch lash of the switching rocker arm assembly;
repeating the steps of pressing and measuring until the switching rocker arm assembly exhibits a desired latch lash.
2. The process of claim 1 , wherein the manufacturing fixture has a ball plunger post and a valve stem post with sizes, shapes, relative positions and orientations which allow the manufacturing fixture to receive the switching rocker arm assembly.
3. The process of claim 1 , wherein the manufacturing fixture employs a support shelf that supports the latch rod when the latch rod is pressed into the latch seat.
4. The process of claim 1 , wherein the steps of pressing and measuring are done interactively until the desired latch lash is created.
5. The process of claim 1 , wherein the latch rod has a hardness significantly higher than a hardness of the latch seat.
6. The process of claim 1 , wherein the latch seat is substantially flat prior to a first execution of the pressing step.
7. The method of claim 1 , wherein the latch bore comprises a round cross-section without a flat portion.
8. A process for creating a latch for a switching rocker arm assembly, comprising:
providing an outer arm;
providing an inner arm having a latch bore;
assembling the inner and outer arms into a switching rocker arm assembly;
selecting a latch rod having desired dimensions of a latch;
fitting the latch rod into the latch bore;
mounting the switching rocker arm assembly into a manufacturing fixture simulating installation of the switching rocker arm assembly into an engine;
applying a load to the outer arm to press the outer arm into the latch rod to form a latch seat; and
measuring a latch lash of the switching rocker arm assembly.
9. The process of claim 8 , wherein the selected latch rod is sized to have a tight slip fit into the latch bore.
10. The process of claim 8 , further comprising increasing the applied load and repeating the step of measuring until the switching rocker arm assembly has a desired latch lash.
11. The process of claim 8 , further comprising adding a cam lash or an expected cam lash of a valve for which the switching rocker arm assembly is intended to ensure that a total of the measured latch lash and the cam lash or expected cam lash meets specifications.
12. The process of claim 8 , wherein the latch rod comprises a material harder than a material of the outer arm.
13. The process of claim 8 , wherein the step of assembling results in the latch rod resting on a carbide support shelf of the manufacturing fixture.
14. The process of claim 8 , wherein operation of the switching rocker assembly results in non-point loading of the latch seat with the latch.
15. A process for creating a latch for a switching rocker arm assembly, comprising:
assembling an inner arm into an outer arm to create a switching rocker arm assembly;
inserting a latch rod into a latch bore of the inner arm;
coining a latch seat by pressing the outer arm into the latch rod; and
measuring a latch lash of the switching rocker arm assembly.
16. The process of claim 15 , further comprising placing the switching rocker arm assembly into a manufacturing fixture after the step of inserting and before the step of coining.
17. The process of claim 16 , wherein the latch seat is formed on a first surface of the outer arm adjacent the latch rod and opposite a second surface of the outer arm to which the force is applied.
18. The process of claim 15 , wherein the step of coining deforms a surface of the outer arm into a shape of the latch rod.
19. The process of claim 15 , further comprising increasing the latch lash by increasing a force applied to the outer arm in a subsequent step of coining.
20. The process of claim 15 , further comprising calculating a total lash for the switching rocker arm assembly by adding the latch lash to an actual or expected value of a camshaft lash for a valve or an engine in which the switching rocker arm assembly may be used.