Patent Application
20210033006
Example aspects described herein relate to camshaft phasers, and, more particularly, to camshaft phasers utilized within an internal combustion (IC) engine.
Camshaft phasers are utilized within IC engines to adjust timing of an engine valve event to modify performance, efficiency and emissions. Hydraulically actuated camshaft phasers can be configured with a rotor and stator arrangement. The rotor can be connected to a camshaft and actuated hydraulically in clockwise or counterclockwise directions relative to the stator to achieve variable engine valve timing. The rotor can include a locking pin assembly that selectively locks the rotor to the stator.
In an example embodiment, a camshaft phaser includes a stator and a rotor, the rotor having a plurality of vanes that form fluid chambers with the stator. The stator can include an endless drive band interface that is arranged to non-rotatably connect the stator to a power source of an internal combustion engine. The rotor includes a locking assembly that has a first unlocked position and a second locked position. The locking assembly is configured to: (i) roll against the stator in the first unlocked position, and (ii) lock the rotor to the stator in the second locked position. In an example embodiment, the locking assembly rolls against a front cover that is non-rotatably attached to the stator.
The locking assembly can include a locking pin, a retention insert, and a rolling element arranged within the retention insert, the rolling element configured to roll against the stator in the first unlocked position. The locking assembly is configured to selectively lock the rotor to the stator. The rolling element can be a ball or a roller. The locking assembly can also include a force generator or bias spring arranged between the locking pin and the retention insert. At least a portion of the locking assembly, including, by not limited to the locking pin and retention insert, can be received by a locking pin aperture that is arranged within the rotor. In an example embodiment, the locking pin aperture is arranged within one of the plurality of vanes of the rotor. The locking pin can protrude from a locking end of the locking pin aperture to engage the stator (or rear cover) in the second locked position. A vent passage can be configured in an axial face of the rotor and is fluidly connected to the locking pin aperture. In an example embodiment, the vent passage is transverse to a central axis of the locking pin aperture.
The retention insert can include at least one outlet that is configured to provide an exit pathway for hydraulic fluid and/or air from the locking pin aperture. The at least one outlet can be fluidly connected to the vent passage.
A method for operating a camshaft phaser is provided that includes:
The rotor can include a locking pin aperture that receives at least a portion of the locking pin assembly. The locking assembly can be moved to the first unlocked position by hydraulic fluid pressure, and the rotor can be rotated relative to the stator by hydraulic fluid pressure.
A further step of operating the camshaft phaser can include actuating the locking assembly to a second locked position which prevents rotation of the rotor relative to the stator. The locking assembly can be actuated to the second locked position by a bias spring that is arranged within the locking assembly. The bias spring can provide a force that is greater than a hydraulic fluid force acting on the locking assembly.
The above mentioned and other features and advantages of the embodiments described herein, and the manner of attaining them, will become apparent and 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.
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 at least one embodiment, in at least one form, and such exemplification is not to be construed as limiting the scope of the claims in any manner. Certain terminology is used in the following description for convenience only and is not limiting. The words “inner,” “outer,” “inwardly,” and “outwardly” refer to directions towards and away from the parts referenced in the drawings. Axially refers to directions along a diametric central axis. Radially refers to directions that are perpendicular to the central axis. The words “left”, “right”, “up”, “upward”, “down”, and “downward” designate directions in the drawings to which reference is made. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import.
Referring to
The term “non-rotatably connected” can be used to help describe various connections of a camshaft phaser and respective adjacent components and is meant to signify two elements that are directly or indirectly connected in a way that whenever one of the elements rotate, both of the elements rotate in unison, such that relative rotation between these elements is not possible. Radial and/or axial movement of non-rotatably connected elements with respect to each other is possible, but not required.
The stator 40 of the camshaft phaser 10 is configured with an endless drive band interface 44 to rotationally connect the camshaft phaser 10 to any power source, such as the crankshaft 16 of an internal combustion (IC) engine. The endless drive band 18 can be a belt or a chain to facilitate a non-rotatable connection between the camshaft phaser 10 and the crankshaft 16, causing the camshaft phaser 10 to rotate around a rotational axis 12.
The rotor 20 of the camshaft phaser 10 is non-rotatably connected to the camshaft 14, achieved by an axial clamping of the rotor 20 to the camshaft 14 via the hydraulic fluid control valve 80. The hydraulic fluid control valve 80 is configured with external threads 82 that engage internal threads (not shown) of the camshaft 14 to facilitate the axial clamping. Other ways to attach the rotor 20 to the camshaft 14 are also possible. To ensure proper orientation or timing of the camshaft phaser 10 relative to the camshaft 14, a timing protrusion 28 is arranged on the rotor 20.
The rotor 20 includes vanes 22 that extend radially outward from a hub 33 of the rotor 20. The stator 40 includes protrusions 42 that extend radially inward from an outer ring portion 46 of the stator 40. A plurality of fasteners 52 extend through front apertures 58 of the front cover 50, through clearance apertures 48 of the stator 40, and attach to locking apertures 64 of the rear cover 60. The front cover 50 and rear cover 60, together with the vanes 22 of the rotor 20 and protrusions 42 of the stator 40, form hydraulic actuation chambers 38 that are circumferentially arranged within the camshaft phaser 10. The camshaft phaser 10 is hydraulically actuated by pressurized hydraulic fluid F that is managed by the hydraulic fluid control valve 80 to move the rotor 20 either clockwise CW or counterclockwise CCW relative to the stator 40 by means of first hydraulic fluid ports 54 and second hydraulic fluid ports 56. The first and second hydraulic fluid ports 54, 56 are radially arranged in the hub 33 of the rotor 20, and serve to fluidly connect the hydraulic fluid control valve 80 with the hydraulic actuation chambers 38. As the rotor 20 is connected to the camshaft 14, clockwise CW and counterclockwise CCW relative movements of the rotor 20 relative to the stator 40 can advance or retard an engine valve event with respect to a four-stroke cycle of an IC engine. With reference to
The locking assembly 70 includes a locking pin 74, a force generator 76, a retention insert 78, a rolling element 94, and a bushing 72. The rolling element 94 is arranged within the retention insert 78. The force generator 76 can be any component that provides a force on the locking pin 74 while permitting longitudinal movement of the locking pin 74. The force generator 76 can be a bias spring, elastomer or any component that meets the described functional attributes. In an example embodiment, the locking assembly 70 can either lock or unlock the rotor 20 from the stator 40, via the rear cover 60. The bushing 72 is received by a locking aperture 62 arranged within the rear cover 60. The bushing 72 can be hardened to suffice as a locking pin interface and can provide a low-cost alternative to hardening the rear cover 60. It could also be possible to eliminate the bushing 72 so that the locking pin interfaces directly with the locking aperture 62. The retention insert 78 is disposed within a locking pin aperture 23 of the rotor 20 and can provide: 1). an interface for the force generator 76; 2). an outlet 79 (at least one) for air and/or hydraulic fluid to exit a middle chamber 77 due to longitudinal movement of the locking pin 74 within the locking pin aperture 23; the outlet 79, as shown in
With view to
The retention insert 78 can be fabricated from many materials, including, but not limited to plastic. The plastic can be filled with glass fibers to increase the structural integrity of the retention insert 78. The plastic retention insert 78 can be held in place within the locking pin aperture 23 by either a slip-fit or a press-fit. A press-fit can be incorporated to facilitate retention of the locking assembly 70 during initial assembly of the camshaft phaser 10. However, due to thermal expansion and inherent creep and stress relaxation of plastic that occurs, the press-fit can change to a slip-fit, rendering the retention insert 78 movable within the locking pin aperture 23 during normal operation of the camshaft phaser 10. When the locking pin 74 is displaced within the locking pin aperture 23 by pressurized hydraulic fluid F, displacement of the retention insert 78 within the locking pin aperture 23 can occur. This displacement can be limited or restricted by an inner axial surface 51 of the front cover 50, which serves as an abutment surface for the rolling element 94. A first end 90 of the retention insert 78 is configured with a reception pocket 91 to receive the rolling element 94, formed as a ball that interfaces with or rolls against the inner axial surface 51 of the front cover 50. The reception pocket 91 includes a retention lip 95 that retains the ball 94 within the reception pocket 91. In an example embodiment, a first diameter D1 of the ball 94 is larger than a second diameter D2 of the retention lip 95 which facilitates an assembly process in which the ball is ‘snapped’ into the reception pocket 91 and then held in place by the retention lip 95.
For this disclosure, any component that is non-rotabably attached to the stator 40 can be classified as “the stator”. For example, since the front cover 50 is non-rotatably attached to the stator 40, it could be stated that the rolling element 94 rolls against the stator 40.
The locking assembly 70 selectively locks the rotor 20 to the stator 40 via the rear cover 60.
Given the previously described camshaft phaser 10 and respective retention inserts 78, 78A and respective rolling elements 94, 94A, the following method of operating a camshaft phaser can be utilized.
The first operation step involves providing a camshaft phaser 10 that includes: (i) a stator 40; (ii) a rotor 20 that has a plurality of vanes 22 that form fluid chambers 38 with the stator 40; and, (iii) a pressureless-locked locking assembly 70 that selectively locks the rotor 20 to the stator 40 or selectively unlocks the rotor 20 from the stator 40.
The second operation step involves actuating the locking assembly 70 to unlock the rotor 20 from the stator 40, defining a first unlocked position.
The third operation step involves rotating the rotor 20 relative to the stator 40, causing the locking assembly 70 to roll against the stator 40.
At least a portion of the locking assembly 70 can be received by the locking pin aperture 23 arranged within the rotor 20. Actuation of the locking assembly 70 to the first unlocked position and rotation of the rotor 20 relative to the stator 40 can be accomplished by hydraulic fluid pressure, as provided by the hydraulic fluid control valve 80. The hydraulic fluid control valve 80 is electronically controlled by the electronic controller 88, to manage the timing and control of hydraulic fluid from the pressurized hydraulic fluid source 87.
A third operation step involves actuating the locking assembly 70 to a second locked position, which prevents rotation of the rotor 20 relative to the stator 40. This actuation of the locking assembly 70 to the second locked position can be accomplished by the force generator 76 or bias spring arranged within the locking assembly 70, between the locking pin 74 and the retention insert 78, 78A. The force generator 76 or bias spring can provide a force F2 that is greater than a hydraulic fluid force F1 acting on the locking assembly 70.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.
