SWITCHING ROLLER FINGER FOLLOWER ECCENTRIC LATCH

Abstract

A switching rocker arm includes an inner arm, an outer arm pivotably secured to the inner arm and having a latch bore, and a latch pin configured for insertion into the latch bore. The latch pin includes a first portion having a first diameter, and a second portion having a second diameter. The second portion is eccentric to the first portion. The latch pin is selectively movable between a first position where the latch pin does not contact the inner arm, and a second position wherein the latch pin contacts the inner arm.

Description

FIELD

The present disclosure generally relates to switching roller finger followers in internal combustion engines and, more particularly, to a switching roller finger follower having an eccentric latch to facilitate preventing rotation thereof.

BACKGROUND

A switching roller finger follower or rocker arm allows for control of valve actuation by alternating between two or more states. In some examples, the rocker arm can include multiple arms, such as an inner arm and an outer arm. In some circumstances, these arms can engage different cam lobes, such as low-lift lobes, high-lift lobes, and no-lift lobes. Mechanisms are required for switching rocker arm modes in a manner suited for operation of internal combustion engines.

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY

According to various aspects of the present disclosure, a switching rocker arm is provided. The switching rocker arm includes an inner arm, an outer arm pivotably secured to the inner arm and having a latch bore, and a latch pin configured for insertion into the latch bore. The latch pin includes a first portion having a first diameter, and a second portion having a second diameter. The second portion is eccentric to the first portion. The latch pin is selectively movable between a first position where the latch pin does not contact the inner arm, and a second position wherein the latch pin contacts the inner arm.

In addition to the foregoing, the described switching rocker arm may include one or more of the following features: wherein the first diameter is larger than the second diameter; wherein the second portion defines a latch shelf configured to be engaged by the inner arm; wherein the latch shelf is crowned; wherein the latch bore includes a first bore sized to receive the latch pin first diameter portion; wherein the latch bore includes a second bore sized to receive the latch pin second diameter portion; wherein a diameter of the second bore is smaller than a diameter of the first bore; and wherein the second portion has a first end and a second end, and wherein the second portion is cylindrical from the first end to the second end.

In addition to the foregoing, the described switching rocker arm may include one or more of the following features: a cage disposed within the latch bore; a biasing mechanism disposed between the cage and the latch pin; wherein the biasing mechanism includes a first end and a second end, wherein the first end is disposed within a cage bore formed in the cage; wherein the biasing mechanism second end is disposed within a latch pin bore formed in the latch pin; wherein the latch pin bore is formed in the latch pin first portion; a hydraulic port fluidly coupled to the latch bore; and wherein the hydraulic port is directly coupled to the first bore.

According to other aspects of the present disclosure, a method of assembling a switching rocker arm is provided. The method includes providing an inner arm, providing an outer arm having a latch bore, pivotally securing the outer arm to the inner arm, providing a latch pin having a first portion with a first diameter, and a second portion with a second diameter, wherein the second portion is eccentric to the first portion, and inserting the latch pin into the latch bore such that the latch pin is selectively movable between a first position where the latch pin does not contact the inner arm, and a second position where the latch pin contacts the inner arm.

In addition to the foregoing, the described method may include one or more of the following features: providing the latch pin where the first diameter is larger than the second diameter; forming the latch pin second end with a latch shelf configured to be engaged by the inner arm; forming the latch shelf with a crown; forming the latch pin second portion as a cylindrical body extending between a first end and a second end of the second portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a front perspective view of a switching rocker arm constructed in accordance to one example of the present disclosure;

FIG. 2 is a cross-sectional view of another switching rocker arm constructed in accordance to one example of the present disclosure;

FIG. 3 is a perspective view of the switching rocker arm shown in FIG. 2;

FIG. 4 is a perspective view of a latch pin shown in FIGS. 2 and 3 in accordance to one example of the present disclosure;

FIG. 5 is a sectional view of an outer arm shown in FIGS. 2 and 3 configured to receive the latch pin shown in FIG. 4, in accordance to one example of the present disclosure;

FIGS. 6A and 6B are cross-sectional views of the switching rocker arm shown in FIG. 3 taken along lines 6A-6A and 6B-6B, and illustrating the latch pin in an equilibrium state, in accordance to one example of the present disclosure;

FIGS. 7A and 7B are cross-sectional view of the latch pin shown in FIGS. 6A and 6B, respectively, and illustrating the latch pin in an offset rotated state, in accordance to one example of the present disclosure; and

FIG. 8 is a perspective view of another latch pin constructed in accordance to one example of the present disclosure that may be used with the switching rocker arm shown in FIGS. 2 and 3.

DETAILED DESCRIPTION

With initial reference to FIG. 1, an exemplary switching rocker arm constructed in accordance to one example of the present disclosure is shown and generally identified at reference 10. The switching rocker arm 10 can include a three lobed cam 12, a lash adjuster 14, a valve 16, a spring 20 and a spring retainer 22. The cam 12 can have a first and second high-lift lobe 26, 28 and a low-lift lobe 30. The switching rocker arm 10 has an outer arm 40 and an inner arm 42. During operation, the high-lift lobes 26 and 28 contact the outer arm 40 while the low-lift lobe 30 contacts the inner arm 42. The lobes cause periodic downward movement of the outer arm 40 and the inner arm 42. The downward motion is transferred to the valve 16 by the inner arm 42, thereby opening the valve 16. The rocker arm 10 is switchable between a high-lift mode and a low-lift mode. In the high-lift mode, the outer arm 40 is latched to the inner arm 42.

During engine operation, the high lift lobes 26 and 28 periodically push the outer arm 40 downward. Because the outer arm 40 is latched to the inner arm 42, the high-lift motion is transferred from the outer arm 40 to the inner arm 42 and further to the valve 16. When the rocker arm 10 is in its switched mode, the outer arm 40 is not latched to the inner arm 42. As a result, high-lift movement exhibited by the outer arm 40 is not transferred to the inner arm 42. Instead, the low-lift lobe 30 contacts the inner arm 42 and generates low-lift motion that is transferred to the valve 16. When unlatched from the inner arm 42, the outer arm 40 pivots about an axle 50, but does not transfer motion to the valve 16. It will be appreciated that the rocker arm 10 is provided by way of example only. In this regard, the configuration of the rocker arm 10 is not limited to the configuration of the rocker arm 10 shown in FIG. 1, and it will be appreciated that the rocker arm 10 can be configured to have the outer arm normally latched to the inner arm or unlatched to the inner arm depending on configuration and/or application.

With additional reference to FIGS. 2-6, the rocker arm 10 can include a latching mechanism 60 for latching the inner arm 42 to the outer arm 40. The latching mechanism 60 can generally include a latch pin 62, a biasing mechanism 64 (e.g., a spring), and a cage 66 each configured to be mounted inside a bore 68 formed in the outer arm 40.

As shown in FIGS. 2 and 3, bore 68 includes a large diameter portion 70 and a small diameter portion 72. A hydraulic fluid port 74 is fluidly coupled to the large diameter portion 70 and is configured to supply a hydraulic fluid to bore 68 to selectively move the latching mechanism 60 between an activated position (FIG. 2) and a deactivated position (not shown). However, it will be appreciated that latching mechanism 60 is not limited to hydraulic actuation and may include other actuation methods such as, for example, mechanical, electrical, and/or magnetic actuation. As illustrated in FIG. 5, small diameter portion 72 is positioned eccentrically to large diameter portion 70 so as to define a generally crescent-shaped shoulder 76.

With continued reference to FIG. 4, latch pin 62 can generally include a first or major outer diameter portion 80 coupled to a second or minor outer diameter portion 82. In one example, first and second portions 80, 82 are formed as a single unitary component. In other examples, first and second portions 80, 82 are formed separately and subsequently coupled before insertion into bore 68.

Latch pin first portion 80 is generally cylindrical and includes a generally cylindrical body 84 having opposed walls 86 and 88. Latch pin body 84 extends along a longitudinal axis ‘A’ (FIG. 3). Latch pin first portion 80 is configured to be disposed within bore large diameter portion 70. In the example embodiment, longitudinal axis ‘A’ extends through a center point of a cross-section of the first portion 80.

As shown in FIG. 2, latch pin second portion 82 is configured to be disposed within bore small diameter portion 72. As shown in FIG. 4, latch pin second portion 82 can include a generally cylindrical body 90 extending along an axis ‘B’ (FIG. 3) and having a first end 92, an opposed second end 94, and an arm engaging surface or latch shelf 96. First end 92 is coupled to latch pin first portion wall 88 and is disposed in an orientation eccentric to the latch pin first portion 80 (e.g., eccentric to axis ‘A’). In the example embodiment, longitudinal axis ‘B’ extends through a center point of a cross-section of the second portion 82.

Accordingly, the eccentric positioning between the latch pin first portion 80 and the latch pin second portion 82, and the corresponding eccentric positioning of the bore larger diameter portion 70 and the bore smaller diameter portion 72, cooperate to inhibit rotation of the latch pin 62 about the longitudinal axis ‘B’ of the latch pin second portion 82. The desired maximum rotational limits of the latch pin 62 about axis ‘B’ can be designed by varying the diameters and eccentricity of the first and second latch pin portions 80, 82. The size of large and small diameter portions 70, 72 of the bore 68 can then be designed to accommodate the latch pin 62 with the desired maximum rotational limits.

Latch shelf 96 is positioned to selectively engage a latch engaging surface 44 of the inner arm 42 (see FIGS. 2 and 3). In the latched or activated state (FIGS. 2 and 3), the latch shelf 96 of the latch pin 62 engages the latch engaging surface 44 of the inner arm 42. In the unlatched or deactivated state, the latch shelf 96 of the latch pin 62 is withdrawn into bore 68 such that latch engaging surface 44 does not contact the latch pin 62, thereby allowing relative movement between the outer arm 40 and the inner arm 42.

In the illustrated example, latch shelf 96 can be rounded or crowned to facilitate enabling rotation of the latch pin 62 to center (e.g., FIGS. 6A and 6B) when latch engaging surface 44 engages one edge 98 of the latch shelf 96 (e.g., see FIGS. 7A and 7B). FIGS. 6A and 6B illustrates latch pin 62 in an equilibrium position where a rotational axis 100 of the latch pin 62 is aligned with a rotational axis 102 of the bore 68. FIGS. 7A and 7B illustrate latch pin 62 in an offset rotated state such that pin rotational axis 100 is not aligned with bore rotational axis 102 (i.e., latch pin 62 is angularly rotated within bore 68).

Accordingly, in the event the latch pin 62 is angularly offset, the initial contact between the inner arm 42 and the latch shelf 96 will be offset from the latch pin second portion longitudinal axis ‘B’. As shown in FIGS. 7A and 7B, a load application ‘F’ at such an off-center point (e.g., 98) of the latch shelf 96 creates a moment across the latch pin second portion axis ‘B’. As the load increases, the latch pin 62 rotates to the equilibrium position that will have the tendency to reduce the moment, thereby enabling the latch pin 62 to self-align to the equilibrium position (FIGS. 6A and 6B).

With continued reference to FIG. 2, biasing mechanism 64 includes a first end 110 and an opposite second end 112. In the example embodiment, first end 110 is disposed within a bore 114 formed in latch pin 62, and second end 112 is disposed within a bore 116 formed in cage 66. In this way, biasing mechanism 64 is properly positioned within bore 68 between the latch pin 62 and the cage 66 to provide a biasing force to move the latch pin 62 away from cage 66 into the latched position.

In the example embodiment, cage 66 is generally cylindrical and includes a first end 120 and an opposite second end 122. Cage 66 is disposed within bore 68 and is configured to seal one end thereof. Moreover, bore 116 is configured to define a spring seat for biasing mechanism second end 112. A small diameter bore 124 extends from bore 116 through first end 120, for example, to provide pressure relief for bore 68.

FIG. 8 illustrates an alternative embodiment of latch pin 62 that is identified as latch pin 162. Latch pin 162 is similar to latch pin 62 except latch pin 162 does not include latch shelf 96 and rather just includes a round latch pin. In some configurations, the round latch pin lowers the portion for a rotational torque, thereby preventing or minimizing any sticking of the latch pin.

In more detail, latch pin 162 can generally include a first or major outer diameter portion 180 coupled to a second or minor outer diameter portion 182. In one example, first and second portions 180, 182 are formed as a single unitary component. In other examples, first and second portions 180, 182 are formed separately and subsequently coupled before insertion into bore 68.

Latch pin first portion 180 is generally cylindrical and includes a generally cylindrical body 184 having opposed walls 186 and 188. Latch pin body 184 extends along a longitudinal axis ‘C’. Latch pin first portion 180 is configured to be disposed within bore large diameter portion 70. In the example embodiment, longitudinal axis ‘C’ extends through a center point of a cross-section of the first portion 180.

As shown in FIG. 2, latch pin second portion 182 is configured to be disposed within bore small diameter portion 72. Latch pin second portion 182 can include a generally cylindrical body 190 extending along an axis ‘D’ and having a first end 192 and an opposed second end 194. First end 192 is coupled to latch pin first portion wall 188 and is disposed in an orientation eccentric to the latch pin first portion 180 (e.g., eccentric to axis ‘C’). In the example embodiment, longitudinal axis ‘D’ extends through a center point of a cross-section of the second portion 182.

Accordingly, the eccentric positioning between the latch pin first portion 180 and the latch pin second portion 182, and the corresponding eccentric positioning of the bore larger diameter portion 70 and the bore smaller diameter portion 72, cooperate to inhibit rotation of the latch pin 162 about the longitudinal axis ‘D’ of the latch pin second portion 182. The desired maximum rotational limits of the latch pin 162 about axis ‘D’ can be designed by varying the diameters and eccentricity of the first and second latch pin portions 180, 182. The size of large and small diameter portions 70, 72 of the bore 68 can then be designed to accommodate the latch pin 162 with the desired maximum rotational limits.

Described herein are systems and methods for a latching mechanism for a switching roller finger follower. The latching mechanism includes a latch pin wherein the minor and major outer diameter portions are eccentrically positioned. The bores in the outer arm that correspond with the latch pin diameter are also eccentrically positioned. The eccentricity of the two paired cylinders facilitates limiting the rotation of the latch pin beyond a predetermined limit. The latch pin rotates around the axis generated by the latch pin minor outer diameter portion and bore minor inner diameter. The latch pin can be mathematically determined based on diameters and the eccentricity.

The latch pin can include a slightly rounded or crowned latch shelf that will self-orient the latch pin when the inner arm is lowered into contact with the latch pin. The crown can be large enough not to limit the angular rotation of the latch pin. After assembly, the latch pin may have an angular offset. In this case, the initial contact between the inner arm and the latch pin shelf is offset from the latch pin center axis (defined by the latch pin minor outer diameter). This offset point for the load application creates a moment across the latch pin axis. As the load increases, the latch pin will rotate to the equilibrium position that will have the tendency to reduce the moment. This will make the latch pin self-align. The initial gap between the latch pin and the inner arm is higher if a crown is used, however this can be compensated in the camshaft lobe design.

The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A switching rocker arm comprising: an inner arm;an outer arm pivotably secured to the inner arm and having a latch bore; anda latch pin configured for insertion into the latch bore, the latch pin having a first portion having a first diameter, and a second portion having a second diameter, wherein the second portion is eccentric to the first portion,wherein the latch pin is selectively movable between a first position where the latch pin does not contact the inner arm, and a second position wherein the latch pin contacts the inner arm.

2. The switching rocker arm of claim 1, wherein the first diameter is larger than the second diameter.

3. The switching rocker arm of claim 1, wherein the second portion defines a latch shelf configured to be engaged by the inner arm.

4. The switching rocker arm of claim 3, wherein the latch shelf is crowned.

5. The switching rocker arm of claim 1, wherein the latch bore includes a first bore sized to receive the latch pin first diameter portion.

6. The switching rocker arm of claim 5, wherein the latch bore includes a second bore sized to receive the latch pin second diameter portion.

7. The switching rocker arm of claim 6, wherein a diameter of the second bore is smaller than a diameter of the first bore.

8. The switching rocker arm of claim 1, wherein the second portion has a first end and a second end, and wherein the second portion is cylindrical from the first end to the second end.

9. The switching rocker arm of claim 6, further comprising a cage disposed within the latch bore.

10. The switching rocker arm of claim 9, further comprising a biasing mechanism disposed between the cage and the latch pin.

11. The switching rocker arm of claim 10, wherein the biasing mechanism includes a first end and a second end, wherein the first end is disposed within a cage bore formed in the cage.

12. The switching rocker arm of claim 11, wherein the biasing mechanism second end is disposed within a latch pin bore formed in the latch pin.

13. The switching rocker arm of claim 12, wherein the latch pin bore is formed in the latch pin first portion.

14. The switching rocker arm of claim 5, further comprising a hydraulic port fluidly coupled to the latch bore.

15. The switching rocker arm of claim 14, wherein the hydraulic port is directly coupled to the first bore.

16. A method of assembling a switching rocker arm, the method comprising: providing an inner arm;providing an outer arm having a latch bore;pivotally securing the outer arm to the inner arm;providing a latch pin having a first portion with a first diameter, and a second portion with a second diameter, wherein the second portion is eccentric to the first portion; andinserting the latch pin into the latch bore such that the latch pin is selectively movable between a first position where the latch pin does not contact the inner arm, and a second position where the latch pin contacts the inner arm.

17. The method of claim 16, further comprising providing the latch pin where the first diameter is larger than the second diameter.

18. The method of claim 16, further comprising forming the latch pin second end with a latch shelf configured to be engaged by the inner arm.

19. The method of claim 18, further comprising forming the latch shelf with a crown.

20. The method of claim 16, further comprising forming the latch pin second portion as a cylindrical body extending between a first end and a second end of the second portion.