CAMSHAFT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S.

Provisional Patent Application No. 62/041,948, filed August 26, 2014, which application is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to torsional assembly for controllably providing torque to a camshaft, for example, a camshaft in a vehicular drive train. In particular, the torsional assembly includes a rocker arm, a switchable roller finger follower, or a tappet for engaging with lobes on the camshaft. The lobes are arranged to displace the rocker arm, the finger follower, or the tappet to compress one or two springs to generate and transmit to the camshaft a respective torque associated with compression of the two springs.

[0003] In vehicles including an engine with a drive train having a variable cam timing

(VCT) system, when the engine is turned off and the camshaft is retarded, the camshaft must be ratcheted to the mid-position when the engine is next started. Further, the ratcheting must be done within a relatively short time span, for example, while an operator is attempting to start the engine. VCT systems with midlock require certain magnitude of torsionals in order to engage the midlock pin, prior to oil pressure reaching a necessary threshold to disengage the pin during normal engine operation. Often start-up torsionals are not enough to engage the pin.

[0004] US patent 5, 107,805 discloses an extra cam on a camshaft to increase the magnitude of torsionals during engine operation. The extra cam shaft remains active during normal engine operation. Thus, once the engine is started, the camshaft torsionals are still present. However, the camshaft torsionals are not necessary for operation of the VCT system and can have detrimental effect on other engine components such as higher loads in the valve train, higher chain drive forces, poor chain drive performance, and poor performance in general for any component attached to or operated by the camshaft, such as a fuel pump. SUMMARY

[0005] According to aspects illustrated herein, there is provided a torsion assembly for providing controllable torsion to a camshaft, including: a spring assembly including a first spring; and, a contact element arranged to engage at least one lobe for the camshaft. For a locked mode: the contact element is arranged to be displaced by the at least one cam lobe; the contact element is arranged to compress the first spring; and the first spring is arranged to impart a first torque to the camshaft via the contact element. For an unlocked mode, the contact element is arranged to be displaced by the at least one cam lobe and the contact element is arranged to impart a second torque, less than the first torque, to the cam shaft via the contact element.

[0006] According to aspects illustrated herein, there is provided a torsion assembly for providing controllable torsion to a camshaft, including: a first spring with a first spring constant; a second spring with a second spring constant less than the first spring constant; a lock element including a distal end; and a contact element. For a locked mode: a position of the distal end is fixed; at least one lobe for the camshaft is arranged to displace the contact element; and the displaced contact element is arranged to compress the first spring and transmit a first torque to the camshaft. For an unlocked mode: the at least one lobe for the camshaft is arranged to displace the contact element; and the displaced contact element is arranged to compress the second spring and transmit second torque, less than the first torque, to the camshaft.

[0007] According to aspects illustrated herein, there is provided a torsion assembly for providing controllable torsion to a camshaft, including: a housing; a pressure chamber at least partially enclosed by the housing; at least one pin partially disposed in the pressure chamber; a first spring engaged with the at least one pin; a second spring engaged with the housing; a third spring; and a piston engaged with the second and third springs. For a locked mode: the first spring is arranged to displace the at least one pin to block displacement of the piston with respect to the housing; the at least one cam lobe is arranged to displace the housing in the first direction to compress the third spring in the first direction to generate a first torque; and the housing is arranged to transmit the first torque to the camshaft. For an unlocked mode: the pressure chamber is arranged to be pressurized to displace the at least one pin to enable displacement of the housing with respect to the piston; the at least one cam lobe is arranged to displace the housing to compress the second spring in the first direction to generate a second torque, less than the first torque; and the housing is arranged to transmit the second torque to the camshaft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which:

Figure 1 is a cross-sectional view of a cross-sectional view of a torsion assembly, including a rocker arm, for providing controllable torsion to a camshaft;

Figure 2 is a cross-sectional view of a cross-sectional view of a torsion assembly, including a switching roller finger follower, for providing controllable torsion to a camshaft;

Figure 3 is a cross-sectional view of a cross-sectional view of a torsion assembly, including a switching roller finger follower, for providing controllable torsion to a camshaft; and,

Figure 4 is a cross-sectional view of a cross-sectional view of a torsion assembly, including a tappet, for providing controllable torsion to a camshaft.

DETAILED DESCRIPTION

[0009] At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the disclosure. It is to be understood that the disclosure as claimed is not limited to the disclosed aspects.

[0010] Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure.

[0011] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure.

[0012] Figure 1 is a cross-sectional view of torsion assembly 100, including a rocker arm, for providing controllable torsion to a camshaft.

[0013] Figure 2 is a cross-sectional view of torsion assembly 100, including a switching finger follower, for providing controllable torsion to a camshaft. [0014] Figure 3 is a cross-sectional view of torsion assembly 100, including a switching finger follower and a fixed lock element, for providing controllable torsion to a camshaft.

[0015] Figure 4 is a cross-sectional view torsion assembly 100, including tappet, for providing controllable torsion to a camshaft. The following should be viewed in light of Figures 1 through 4. Assembly 100 includes spring assembly 101, including spring 102, and contact element 104 arranged to engage at least one lobe L of camshaft C. Hereinafter, "at least one cam lob C" is referred to as "cam lobe C" to simplify presentation. In an example embodiment, contact element 104 is arranged to contact a plurality of lobes L.

[0016] For a locked mode, contact element 104 is arranged to be displaced by cam lobe L in direction Dl and element 104 is arranged to compress spring 102 in direction Dl. Spring 102 urges at least a portion of element 104 in direction D2; therefore, the resistance of spring 102 to compression in direction Dl imparts torque Tl to lobe L and camshaft C via contact element 104. As camshaft C rotates, lobe L and spring 102 displace end El of element 104 in directions Dl and D2 in a cycle.

[0017] For an unlocked mode, contact element 104 is arranged to be displaced by cam lobe C and contact element 104 is arranged to impart torque T2, less than torque Tl, to cam shaft C via contact element 104. In an example embodiment, spring 102 is free of compression from contact element 104 during the unlocked mode. As camshaft C rotates, lobe L and spring 102 displace end E2 of element 104 in directions Dl and D2 in a cycle.

[0018] For a full 360 degree rotation of camshaft C in the locked mode, contact element 104 is arranged to transmit a cumulative torque to the cam shaft. For a full 360 degree rotation of camshaft C in the unlocked mode, the contact element is arranged to transmit a cumulative torque to the cam shaft, which is less than the cumulative torque transmitted by the contact element for a full 360 degree rotation of camshaft C in the locked mode.

[0019] In general, torque T2 is much lower than torque Tl and has little or no impact on the operation of camshaft C. In an example embodiment, spring 102 is configured to prevent full compression of spring 102 in the locked mode.

[0020] In an example embodiment, assembly 100 includes camshaft C.

[0021] The following discussion is directed to the example embodiment shown in

Figure 1. Assembly 100 includes lock element 106. End El is engaged with assembly 101 and end E2 is engaged with distal end 106A of lock element 106. For the locked mode, end E2 pivots on lock element 106 and for the unlocked mode, end El pivots on assembly 101.

[0022] Lock element 106 includes housing 112, component 114, including end 106A, and spring 116. Portion 114A of component 114 is disposed within housing 112. Spring 116 is disposed within housing 112. In an example embodiment, spring 116 urges component 114 in direction D2, opposite direction Dl, with force Fl due to preloading of spring 116. Fl increases as spring 116 is compressed. In an example embodiment, spring 116 is not preloaded and force Fl is generated when spring 116 is compressed. End E2 is engaged with end 106A. As further described below, spring 102 provides force F2, greater than Fl, in direction D2.

[0023] For the locked mode, component 114 is fixed with respect to housing 112 and end E2 pivots on component 114 so that end El displaces in direction Dl and compresses spring 102. In an example embodiment, spring 116 is not compressed in the locked mode. In an example embodiment, spring 116 is configured to prevent full compression of spring 116 in the unlocked mode.

[0024] For the unlocked mode, end El pivots on assembly 101 and component 114 is displaced, with respect to housing 112, by end E2 in direction Dl to compress spring 116. That is, since Fl is less than F2, in response to the displacement of element 104, spring 116 compresses before spring 102 compresses. In an example embodiment, spring 102 is not compressed in the unlocked mode.

[0025] In an example embodiment, assembly 101 includes piston 118 partially disposed in housing 119 and engaged with end El and end 120 of spring 102 and displaceable in directions Dl and D2. End 122 of spring 102 is arranged to be fixed with respect to cam shaft C. For example, spring 102 is installed in component CM of a valve train including cam shaft C, for example the cylinder head of an internal combustion engine, with end 122 engaged with CM. Piston 118 includes flange 118A which engages housing 119 to limit displacement of piston 118 in direction D2. In an example embodiment, spring 102 is preloaded to exert force F2, greater than Fl, in direction D2 on piston 118 and F2 increases as spring 102 is compressed. In an example embodiment, spring 102 is not preloaded and a spring constant for spring 102 is such that as spring 102 is compressed, force F2 is generated. [0026] In an example embodiment, lock element 106 includes piston 124, chamber

126, pins 128A and 128B at least partially disposed in chamber 126, and spring 130. Spring 130 urges pins 128A and 128B in opposite directions D3 and D4, respectively. Piston 124 is engaged with component 114 and end 131 of spring 116. For the locked mode, chamber 126 is substantially unpressurized and spring 130 is arranged to displace pins 128A and 128B directions D3 and D4, respectively, into slots 132A and 132B, respectively in housing 112. The placement of pins 129A and 129B into slots 132A and 132B fixes component 114 and housing 112 together. Movement of component 114 in direction Dl is prevented by pins 129A and 129B, and component 114 becomes a fixed component about which element 104 pivots. For example, a position of component 114, in particular, end 106A, is fixed with respect to camshaft C.

[0027] For the unlocked mode, chamber 126 is pressurized to displace pins 128A and

128B directions D4 and D3, respectively, out of slots 132A and 132B, respectively. Component 114, pins 129A and 129B, and piston 124 are now displaceable. The displacement of end E2 in direction Dl

[0028] Contact element 104 includes rocker arm 132 with bearing 134. Arm 133 includes ends El and E2. Bearing 134 is arranged to engage lobe L to minimize frictional losses. Arm 132 is connected to bearing 134 so that bearing 134 and 132 displace in unison in responses to lobe L.

[0029] The following discussion is directed to the example embodiment shown in

Figure 2. The description of assembly 101 in Figure 1 are applicable to assembly 101 in Figure 2.

[0030] In an example embodiment, contact element 104 includes switchable roller finger follower 136 including arm 138, and shaft 140, about which arm 138 is disposed. Portion 138A of arm 138 includes end El and portion 138B of arm 138 includes end E2.

[0031] For the locked mode, arm 138 is non-rotatably engaged with shaft 140 (arm

138 and shaft 140 are fixed with respect to each other). In response to lobe L, portion 138B of arm 138, is displaced in direction D2 so that arm 138 pivots to compress spring 102 and generate torque Tl.

[0032] For the unlocked mode, rotation of arm 138 about shaft 140 is enabled. In response to lobe L, portion 138B of arm 138 is displaced in direction Dl. Since arm 138 is rotatable about shaft 140, arm 138 rotates with respect to shaft 140 to accommodate the displacement of portion 138B without compressing spring 102. The rotation of arm 138 generates torque T2.

[0033] The following discussion is directed to the example embodiment of Figure 3. The description of assembly 101 in Figure 1 is applicable to assembly 101 in Figure 3.

[0034] In Figure 3, contact element 104 includes switchable roller finger follower 136 including arm 138, and shaft 140, about which arm 138 is disposed. Portion 138A of arm 138 includes end El and portion 138B of arm 138 includes end E2. Lock element 106 is fixed with respect to component CM, in particular, end 106A is fixed with respect to component CM.

[0035] For the locked mode, arm 138 is non-rotatably engaged with shaft 140. In response to lobe L, follower 136, in particular, bearing 139 and arm 138, is displaced in direction Dl so that arm 138 pivots about lock element 106 to compress spring 102 and generate torque Tl.

[0036] For the unlocked mode, rotation of arm 138 about shaft 140 is enabled. In response to lobe L, bearing 139 is displaced in direction Dl. Since arm 138 is rotatable about shaft 140, arm 138 pivots about spring 102 and rotates with respect to shaft 140 to accommodate the displacement of bearing 139 without compressing spring 102. The rotation of arm 138 generates torque T2.

[0037] The following discussion is directed to the example embodiment of Figure 4. The description of spring 116 and assembly 101 in Figure 1 is applicable to assembly 101 in Figure 4.

[0038] In an example embodiment, for example as shown in Figure 4, element 104 includes: housing 142; pressure chamber 144 at least partially enclosed housing 142; pins 146A and 146B partially disposed in pressure chamber 144; spring 148 engaged with pins 146A and 146B and urging pins 146A and 146B in opposite directions D3 and D4, respectively; piston 150; spring 102; and spring 116. Spring 116 is engaged with piston 150 and housing 142. Spring 102 is engaged with piston 150 and component CM. In an example embodiment, piston 150 includes component 152 and at least one component 154 and pins 146A and 146B are disposed between component 152 and at least one component 154. Spring 116 is engaged with component 152. In an example embodiment, at least one component 154 includes piston 118 and component 154A. Pins 146A and 146B are disposed between component 152 and component 154A. Piston 118 is engaged with component 154A. [0039] For the locked mode, spring 148 is arranged to displace pins 146A and 146B in opposite directions D3 and D4, respectively, into slots 156A and 156B, respectively, in housing 142 to block displacement of the piston with respect to the housing. The at least one cam lobe L is arranged to displace housing 142 in direction Dl to compress spring 102 in direction Dl and generate torque Tl. Housing 142 is arranged to transmit torque Tl to camshaft C.

[0040] For the unlocked mode, pressure chamberl44 is arranged to be pressurized to displace pins 146A and 146B in directions D4 and D3, respectively, out of slots 156A and 156B, respectively, to enable displacement of housing 142 with respect to piston 150. The at least one cam lobe L is arranged to displace housing 142 in direction Dl to compress spring 116 in direction Dl and generate torque T2. Housing 142 is arranged to transmit torque Tl to camshaft C. Because force F2 is greater than force Fl, spring 102 is not compressed in the unlocked mode unless the spring 116 is fully compressed by housing 142 and housing 142 is displaced in direction Dl after fully compressing spring 116. However, in an example embodiment, element 104 is configured to prevent the fully compression of spring 116.

[0041] Advantageously, each of the respective example embodiments in Figures 1 through 4 solves the problems, noted above, associated with camshaft torsionals. For example, when extra torsion is needed to ratchet camshaft C, for example, the engine is turned off with the camshaft retarded, assembly 100 is operated in the locked mode, providing torque Tl to the camshaft. For example, when extra torsion is not required, assembly 100 is operated in the unlocked mode, which imparts negligible torque to the camshaft.

[0042] It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.