The present disclosure relates generally to a cam follower assembly, and more particularly, to a cam follower assembly having a swaged bushing.
Fuel injectors in an internal combustion engine are typically driven by a cam arrangement that is operably connected to a crankshaft of the engine. Rotation of the crankshaft results in a corresponding rotation of a cam that drives one or more cam followers. The movement of the cam followers results in actuation of the fuel injectors. The shape of the cam governs the timing and duration of the fuel injection. Each cam follower may include, among other things, a roller in contact with the cam, and a bushing that rotatably supports the roller.
An exemplary cam follower is disclosed in U.S. Pat. No. 7,703,984 that issued to Watanabe et al. on Apr. 27, 2010 (“the '984 patent”). Specifically, the '984 patent discloses a rocker arm operably connected to a valve on a first end and operably connected to a cam on a second end. At the second end, the rocker arm includes a cam follower having a bifurcated roller holder, a roller in contact with the cam, and rolling elements that rotatably support the roller along a roller shaft. Both ends of the roller shaft are swage-locked to beveled sides of the roller holder, such that the roller shaft is secured to the roller holder.
Although the cam follower of the '984 patent may be suitable for some applications, it may still be less than optimal. For example, because swage-locking the roller shaft causes deformation, excessive wear can result and replacement of the roller shaft may be needed. This replacement can be expensive in some situations. Also, the swage-locked ends of the roller shaft may not completely prevent axial movement of the rolling elements and/or the roller. Axial movement of the rolling elements and/or the roller can cause the roller to lock against the roller holder, thereby causing premature wear and/or failure of the roller.
The cam follower assembly of the present disclosure is directed towards overcoming one or more of the problems set forth above and/or other problems of the prior art.
One aspect of the present disclosure is directed to a bushing for a cam follower assembly having a cam roller and an inner race. The bushing may include a generally cylindrical body having an outer surface configured to be press-fitted with the cam roller. The bushing may also include a central bore formed within the generally cylindrical body and configured to receive the inner race. The bushing may further include at least one swaged end configured to inhibit axial movement of the bushing.
Another aspect of the present disclosure is directed to a cam follower assembly. The cam follower assembly may include a forked body having a main bore, and a cam roller disposed within the main bore. The cam roller may include a hollow and generally cylindrical body having an outer surface configured to engage a camshaft. The cam follower assembly may also include a bushing having a generally cylindrical body having an outer surface configured to be press-fitted with the cam roller, a central bore formed within the generally cylindrical body of the bushing, and at least one swaged end configured to inhibit axial movement of the bushing. The cam follower assembly may further include an inner race disposed within the central bore of the bushing and configured to rotatably support the bushing.
In yet another aspect, the present disclosure is directed to a method of forming a bushing having a generally cylindrical body, a central bore formed within the generally cylindrical body, and two opposing ends. The method may include press-fitting the bushing into a cam roller. The method may also include swaging at least one of the two opposing ends to inhibit axial movement of the bushing and secure the bushing to the cam roller.
Engine 10 may include an engine block 14 that at least partially defines a plurality of cylinders 16. A piston 18 may be slidably disposed within each cylinder 16 to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head 20 may be associated with each cylinder 16. Each cylinder 16, piston 18, and cylinder head 20 may together at least partially define a combustion chamber 28. A fuel injector assembly 36 may be at least partially disposed within each cylinder head 20 and configured to inject fuel into each respective combustion chamber 28 to support fuel combustion within engine 10. Engine 10 may also include a crankshaft 24 that is rotatably supported within engine block 14 by way of a plurality of journal bearings 25. A connecting rod 26 may connect each piston 18 to crankshaft 24 so that a sliding motion of piston 18 within each respective cylinder 16 results in a rotation of crankshaft 24.
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Fuel injector assembly 36 may be driven by a rocker arm 38 that is pivotally coupled to a rocker shaft 40. Each fuel injector assembly 36 may include an injector body 42, a plunger 44, and an injector tip 46. A first end 48 of rocker arm 38 may be operatively coupled to plunger 44. Plunger 44 may be biased by a spring 49 toward the first end 48 of rocker arm 38 in the general direction of an arrow 50.
A second end 52 of rocker arm 38 may be operatively coupled to a camshaft 54. More specifically, a cam follower assembly 62 may be disposed in operative connection between camshaft 54 and injector rocker arm 38. Camshaft 54 may include a cam 56 having an outer profile that determines, at least in part, the fuel injection timing of fuel injector assembly 36 during operation of engine 10. In one embodiment, cam 56 may have at least one lobe 58. Camshaft 54 may be operably connected to crankshaft 24 (shown only in
When lobe 58 is rotated into contact with cam follower assembly 62, lobe 58 may exert a force F1 on cam follower assembly 62. In response, the second end 52 of rocker arm 38 may be urged in the general direction of arrow 50. As the second end 52 is urged in the general direction of arrow 50, rocker arm 38 may pivot about rocker shaft 40, thereby causing the first end 48 to be urged in the general direction of an arrow 60. The force F1 exerted on cam follower assembly 62 by lobe 58 may be greater in magnitude than a bias force F2 generated by spring 49, thereby causing plunger 44 to be likewise urged in the general direction of arrow 60. When camshaft 54 is rotated beyond a peak of lobe 58, the bias of spring 49 may urge plunger 44 in the general direction of arrow 50. As plunger 44 is urged in the general direction of arrow 50, the first end 48 of rocker arm 38 may likewise be urged in the general direction of arrow 50 to cause rocker arm 38 to pivot about rocker shaft 40. When this happens, the second end 52 may be urged in the general direction of arrow 60.
During operation of engine 10, axial forces may be generated between one or more components of cam follower assembly 62. For example, in one embodiment, a first force F3 and/or a second force F4 may be generated and urge the components of cam follower assembly 62 in opposite directions (e.g., into and out of page shown in
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Cam roller 66 may embody a hollow and generally cylindrical body having an outer surface configured to engage cam lobe 58 of camshaft 54, such that cam roller 66 rotates with a corresponding rotation of camshaft 54. Bushing 68 may also embody a hollow and generally cylindrical body having an outer surface configured to be press-fitted with an inner surface of cam roller 66. Bushing 68 may rotatably support cam roller 66. Bushing 68 may include a central bore configured to receive inner race 70. Inner race 70 may embody a hollow and generally cylindrical body having an outer surface configured to be slip-fitted with an inner surface of bushing 68. Inner race 70 may rotatably support bushing 68. Axle 72 may be a hollowed shaft configured to rotatably support inner race 70.
In some embodiments, cam roller 66 may be made of a hardened steel alloy with a hardness that substantially matches a hardness of camshaft 54. Bushing 68 may be made of a non-hardened mild steel backing ring with cast bronze material and a lead-tin outer coating. The outer coating may have a hardness substantially greater than a hardness of the cast bronze inner surface. Inner race 70 may be made of a hardened steel to provide a hard bearing outer journal surface to rotate against the soft inner bearing surface of bushing 68.
As discussed above, during operation of engine 10, forces F3, F4 may tend to urge components of cam follower assembly 62 to move axially (e.g., cam roller 66 and/or bushing 68). In some situations, these forces F3, F4 may gradually reduce a retention force of the press-fit connection between cam roller 66 and bushing 68. That is, the forces F3, F4 may loosen the connection between cam roller 66 and bushing 68, causing bushing 68 to move in an axial direction (indicated by arrows shown in
In order to inhibit movement of bushing 68, bushing 68 may be swaged or peened on at least one of opposing ends 92, 94. For example, bushing 68 may include at least one swaged end 100 that helps secure the axial connection between cam roller 66 and bushing 68. Specifically, swaged ends 100 may include an outwardly deformed protrusion in a radial direction. In the disclosed embodiment, both ends 92, 94 of bushing 68 are swaged. The swaged ends 100 of bushing 68 may inhibit movement of bushing 68 in an axial direction towards either tine 78, 80 of forked body 64. As a result, this may help to prevent roller 66 from contacting tines 78, 80 and causing lock up of cam roller 66.
In some embodiments, ends 92, 94 of bushing 68 may include generally flat, annular surfaces. Swaged ends 100 may be formed on either end 92, 94 by swaging around an entire periphery of the annular surfaces. In other words, swaging may occur at each point around the periphery (e.g., 360° around the annular surface). It is contemplated that, in other embodiments, swaged ends 100 may be formed by mechanically swaging or thermal-mechanically swaging only a discrete number of locations around the annular surface, for example, four equally distanced locations.
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The disclosed cam follower assembly 62 may be used with any internal combustion engine. The cam follower assembly 62 may include bushing 68 having at least one swaged end 100 to inhibit undesired axial movement of bushing 68 and cam roller 66. By inhibiting movement of these components, wearing of cam roller 66 and/or camshaft 54 may be reduced.
In addition, only an outer diameter 96 of bushing 68 may be swaged to maintain structural integrity of an inner diameter 98 of bushing 68. Also, in some applications, bushing 68 may include two swaged ends 100 to further increase retention of bushing 68 within cam roller 66. In other applications, swaged ends 100 may be formed by swaging an entire annular surface associated with the swaged end 100, resulting in a stronger connection between cam roller 66 and bushing 68.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cam follower assembly. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.