FAST ACTING SWITCHING VALVE TRAIN SYSTEM FOR VALVE DEACTIVATION

Abstract

A fast acting valve train system for valve deactivation is provided that includes an actuator together with a switchable rocker arm. The actuator, controlled by the engine control unit and mounted to a structural housing, contains an actuator pin that retracts or extends facilitating either a deactivation or reactivation valve event. The switchable rocker arm is a two arm design that includes cam side and valve side arms that are coupled together with a locking mechanism assembly that interfaces with the actuator pin. The system is capable of fast switching times to meet the increased demands of cylinder deactivation systems.

Claims

1. A switchable rocker arm comprising: a cam arm assembly including a first housing with a first rocker shaft bore and a locking pin bore; a valve arm assembly, axially adjacent to the cam arm assembly, the valve arm assembly including a second housing with a second rocker shaft bore and a shuttle pin bore with two at least partially open ends; wherein, the second rocker shaft bore is axially aligned with the first rocker shaft bore; and a coupling assembly, including a locking pin arranged at least partially within the locking pin bore, and a shuttle pin arranged at least partially within the shuttle pin bore with a first end engaging the locking pin.

2. The switchable rocker arm of claim 1, including: a first locked position with the locking pin bore axially aligned with the shuttle pin bore, the locking pin arranged partially within the shuttle pin bore and partially within the locking pin bore with a first end of the locking pin at a first distance from a first axial face of the first housing, and a second end of the shuttle pin at a second distance from a first axial face of the second housing; and, a second unlocked position with the first end of the locking pin at a third distance from the first axial face of the first housing, and the second end of the shuttle pin at a fourth distance from the first axial face of the second housing, wherein the third distance is less than the first distance and the fourth distance is less than the second distance.

3. The switchable rocker arm of claim 2, including a resilient element in contact with the locking pin, the resilient element having a first compressed length in the first locked position and a second compressed length in the second unlocked position, wherein the first compressed length is greater than the second compressed length.

4. The switchable rocker arm of claim 3, wherein an external force acts upon the second end of the shuttle pin in the first locked position to axially urge the shuttle pin to the second unlocked position.

5. The switchable rocker arm of claim 4, wherein the external force is provided by an actuator.

6. The switchable rocker arm of claim 5, wherein the actuator includes an actuator pin.

7. The switchable rocker arm of claim 6, wherein a distal end of the actuator pin engages the second end of the shuttle pin, the distal end having an angled face.

8. The switchable rocker arm of claim 7, wherein the actuator pin is supported by a housing.

9. The switchable rocker arm of claim 6, wherein the distal end of the actuator pin is of frusto-conical form.

10. The switchable rocker arm of claim 1, wherein the second end of the shuttle pin is of frusto-conical form.

11. The switchable rocker arm of claim 1, further comprising a lost motion resilient element arranged to engage the cam side arm.

12. The switchable rocker arm of claim 1, further comprising a hydraulic lash adjuster arranged within the second housing.

13. The switchable rocker arm of claim 1, further comprising a cam roller follower arranged within the first housing.

14. A switchable rocker arm system comprising: a switchable rocker arm having: a cam arm assembly including a first housing with a first rocker shaft bore and a locking pin bore; a valve arm assembly, axially adjacent to the cam arm assembly, the valve arm assembly including a second housing with a second rocker shaft bore and a shuttle pin bore; wherein, the second rocker shaft bore is axially aligned with the first rocker shaft bore; a coupling assembly, including a locking pin arranged at least partially within the locking pin bore, and a shuttle pin arranged at least partially within the shuttle pin bore with a first end engaging the locking pin; and, an actuator having an actuator pin arranged to engage a second end of the shuttle pin.

15. The switchable rocker arm system of claim 14, further comprising a resilient element arranged to engage the cam side arm.

16. The switchable rocker arm system of claim 14, wherein a distal end of the actuator pin has an angled face.

17. The switchable rocker arm system of claim 14, wherein the actuator pin is supported by a housing.

18. The switchable rocker arm system of claim 14, wherein a distal end of the actuator pin is of frusto-conical form.

19. The switchable rocker arm system of claim 14, wherein a second end of the shuttle pin is of frusto-conical form.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] The above mentioned and other features and advantages of the embodiments described herein, and the manner of attaining them, will become apparent and be better understood by reference to the following descriptions of multiple example embodiments in conjunction with the accompanying drawings. A brief description of the drawings now follows.

[0016] FIG. 1 is a system response time diagram for a prior art electro-hydraulic switchable valve train system.

[0017] FIG. 2 is a system response time diagram for an electro-mechanical switchable valve train system.

[0018] FIG. 3 is a perspective view of a fast-acting switchable rocker arm.

[0019] FIG. 4 is a perspective view of the fast-acting switchable rocker arm of FIG. 3 together with an actuator and a first embodiment of an actuator pin.

[0020] FIG. 5 is a perspective view of the system of FIG. 4 within a switchable valve train system of an internal combustion engine.

[0021] FIG. 6 is a perspective view of the system of FIG. 5 within a partial cylinder head section of an internal combustion engine.

[0022] FIG. 7A is a cross-sectional view of the system of FIG. 6, with the switchable rocker arm in a locked state.

[0023] FIG. 7B is a detailed view taken from FIG. 7A.

[0024] FIG. 8A is a cross-sectional view of the system of FIG. 6, with the switchable rocker arm in an unlocked state.

[0025] FIG. 8B is a detailed view taken from FIG. 8A.

[0026] FIG. 9 is a cross-sectional view of the system of FIG. 6, with a second embodiment of a solenoid valve actuator pin with the switchable rocker arm in a locked state.

[0027] FIG. 10 is a cross-sectional view of the system of FIG. 6, with a third embodiment of a solenoid valve actuator pin and a second embodiment of a shuttle pin with the switchable rocker arm in a locked state.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Identically labeled elements appearing in different figures refer to the same elements but may not be referenced in the description for all figures. The exemplification set out herein illustrates embodiments which should not be construed as limiting the scope of the claims in any manner.

[0029] Referring to FIG. 3, a fast-acting switchable rocker arm 1 for valve deactivation is shown that can achieve fast actuation and reactivation times to meet the demands of new cylinder deactivation systems. Referring now to FIG. 4, a fast-acting switchable rocker arm system 30 is shown that includes the switchable rocker arm 1 of FIG. 3 together with an actuator 11 that controls an actuator pin 13. FIG. 5 shows the fast-acting switchable rocker arm system 30 of FIG. 4 within a switchable valve train system 40. FIG. 6 shows the switchable valve train system 40 within a sectioned cylinder head 15 of an IC engine. FIG. 7A shows the switchable rocker arm 1 in a locked condition while FIG. 8A shows the switchable rocker arm 1 in an unlocked condition. The following discussion should be viewed in light of FIGS. 2-6 together with FIGS. 7A and 8A.

[0030] The switchable rocker arm 1 has a cam side arm assembly 4 and an adjacent valve side arm assembly 2. The cam side arm assembly 4 contains a cam side arm housing 18, a rocker shaft bore 28, a cam roller follower 8, a locking pin bore 24, a locking pin 21, and a locking pin bias spring 23, also referred to herein as a resilient element. Optionally, the cam roller follower 8 may be removed and another interface for a camshaft 17 can be implemented. The valve side arm assembly 2 contains a valve side arm housing 16, a hydraulic lash adjuster 5, a rocker shaft bore 10, a shuttle pin bore 25, and a shuttle pin 3. The shuttle pin bore 25 has a first open end 35 and a second end 36 that is at least partially open for actuation access. Optionally, the hydraulic lash adjuster 5 may be removed and another interface for the engine valve 19 can be implemented.

[0031] The switchable rocker arm 1 is capable of two discrete valve lift modes: full valve lift and no valve lift. Full valve lift is achieved when the cam side arm assembly 4 is locked to the valve side arm assembly 2, thereby, when the camshaft 17 rotates against the cam roller follower 8, which is attached to the cam side arm assembly 4, the switchable rocker arm 1 rotates as one unit about a rocker shaft 9, causing the valve 19 to open. FIG. 7A illustrates a locked condition that facilitates a full valve lift mode. With the actuator pin 13 in its retracted position the locking pin bias spring 23 acts upon the locking pin 21 which pushes the shuttle pin 3 against a stop 14. The stop 14 could also be in the form of another design element that offers containment, including the actuator pin 13. Since the locking pin 21 has simultaneous engagement with the valve side arm assembly 2 and the cam side arm assembly 4, both arms are rotationally locked, thereby, the valve side arm assembly 2 rotates with the cam side arm assembly 4 when the cam side arm assembly 4 is acted upon by the camshaft 17.

[0032] In order to facilitate a no valve lift or deactivated mode, the cam side arm assembly 4 is unlocked from the valve side arm assembly 2. FIG. 8A illustrates an unlocked condition that facilitates a no valve lift mode. With the actuator pin 13 in an extended position, the locking pin 21 is no longer engaged with the shuttle pin bore 25 of the valve side arm assembly 2. This position of the locking pin 21 detaches the valve side arm assembly 2 from the cam side arm assembly 4; thereby, when the camshaft 17 rotates against the cam roller follower 8, the cam side arm assembly 4 rotates about the rocker shaft 9, while the valve side arm assembly 2 remains stationary and the valve 19 is not actuated, fulfilling a no valve lift or deactivated mode. A lost motion spring 7, also referred to herein as a lost motion resilient element, is present within the switchable valve train system 40 to provide adequate force to maintain a controlled rotational motion of the cam side arm assembly 4 during the deactivated mode and to facilitate alignment of the locking pin 21 with the shuttle pin bore 25 during the base circle or non-lift portion of the camshaft 17. The force of the lost motion spring 7 is applied to the cam side arm assembly 4 via a lost motion interface 6. Other known methods, spring types and interfaces for lost motion management could also be applied.

[0033] Referring now specifically to FIGS. 7A and 8A, extension and retraction of the actuator pin 13 along a central axis 20, which directly interfaces with an end 27 of the shuttle pin 3, provides for the respective unlocked (no valve lift mode) and locked (full valve lift mode) positions. The actuator pin 13 can be supported on one side by the cylinder head 15, which reduces pin deflection and provides repeatable switching performance. An angled interface 12 on the opposite side contacts the end 27 of the shuttle pin 3 to yield axial displacement of the shuttle pin 3 along a central axis 22. The timing of the stroke of the actuator pin 13 is controlled by a solenoid actuator 11 that is managed by the ECU. Given the electrical control, coupled with the previously described mechanical actuation, this system can be classified as electro-mechanical. FIG. 2 depicts a system response time diagram for this electro-mechanical actuation system. Compared to FIG. 1 which shows a system response time for an electro-hydraulic system, FIG. 2 combines segments 1 and 3, while eliminating segment 2. Combining segments 1 and 3 is possible because of the direct interface between the actuator pin 13 and the shuttle pin 3. Segment 2 can be removed because engine oil pressure is no longer required for actuation of the locking mechanism. This change in actuation method reduces the impact of oil temperature and resultant kinematic viscosity on the system response time. While oil still serves as a lubricating medium for the moving actuator 11 and switching rocker arm 1 components, the effect of cold oil temperature on response time is less pronounced in this role versus its additional actuation role within the electro-hydraulic system. Given the shorter system response time, this electro-mechanical system is able to meet the actuation time demands of new cylinder deactivation systems with expanded operating range and switching frequency requirements. In addition to the shorter system response time of the electro-mechanical system, the actuation system is made simpler by the fact that no oil galleries are required to deliver pressurized oil to actuate the locking mechanism. The elimination of the oil galleries reduces the manufacturing complexity which includes costly machining, deburring and washing processes. Yet another advantage of this electro-mechanical system is the independent mounting of the actuator 11 such that the mass of the actuation device is not part of the rotating mass of the rocker arm. Any additional rotating mass would potentially require additional valve spring force to maintain contact amongst the valve train components at higher speeds and, thus, increasing the stress, wear and resultant friction between the rubbing interfaces.

[0034] Referring now to FIGS. 7B and 8B, the respective locking pin 21 and shuttle pin 3 positions in the locked and unlocked modes are shown. For the locked positions shown in FIG. 7B, a length S1 indicates a distance from the end 27 of the shuttle pin 3 to an axial face 29 of the valve side arm housing 16; additionally, a length X1 indicates a distance from an end 31 of the locking pin 21 to an axial face 33 of the cam side arm housing 18. For the unlocked positions shown in FIG. 8B, a length S2 indicates a distance from the end 27 of the shuttle pin 3 to the axial face 29 of the valve side arm housing 16, while a length X2 indicates a distance from the end 31 of the locking pin 21 to the axial face 33 of the cam side arm housing 18. Comparison of the respective lengths from FIGS. 7B and 8B yields the following relationships:

X2<X1

S2<S1

[0035] As evident by the position change of the locking pin 21 relative to the axial face 33 of the cam side arm housing 18 in the locked and unlocked positions, the compressed length of the locking pin bias spring 23 is greater in the locked position than in the unlocked position.

[0036] FIG. 9 shows a second embodiment of an actuator pin 13 which contains a frusto-conical interface 12 for contact with the shuttle pin 3. The frusto-conical interface 12 eliminates a need to prevent rotation of the actuator pin 13.

[0037] FIG. 10 shows a second embodiment of a shuttle pin 3 which contains a frusto-conical interface 26 for contact with a third embodiment of an actuator pin 13. The form of the actuator pin 13 also eliminates the need to prevent rotation and also facilitates potential use of a current production component.

[0038] In the foregoing description, example embodiments are described. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto, without departing from the broader spirit and scope of the present invention.

[0039] In addition, it should be understood that the figures illustrated in the attachments, which highlight the functionality and advantages of the example embodiments, are presented for example purposes only. The architecture or construction of example embodiments described herein is sufficiently flexible and configurable, such that it may be utilized (and navigated) in ways other than that shown in the accompanying figures.

[0040] Although example embodiments have been described herein, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that this invention may be practiced otherwise than as specifically described. Thus, the present example embodiments should be considered in all respects as illustrative and not restrictive.