WO2018013464A1

WO2018013464A1 - Shifting cam with internal actuator shaft

Info

Publication number: WO2018013464A1
Application number: PCT/US2017/041333
Authority: WO
Inventors: Blaine R. Lingenfelter
Original assignee: Borgwarner Inc.
Priority date: 2016-07-14
Filing date: 2017-07-10
Publication date: 2018-01-18

Abstract

A valve actuation device for providing variable valve lift. The device employs a hollow shaft, lobe segments that are non-rotatably but axially slidably coupled to the hollow shaft, and an actuator for selectively moving the lobe segments along the hollow shaft. The actuator employs an actuator shaft, which is received in the hollow shaft and is maintained in a non-rotating condition. The actuator shaft is moved axially along the rotational axis of the hollow shaft to cause engagement of followers, which are coupled to the lobe segments, with cam surfaces formed on the actuator shaft.

Description

SHIFTING CAM WITH INTERNAL ACTUATOR SHAFT

FIELD

[0001] The present disclosure relates to a valve actuation device providing variable valve lift. BACKGROUND

[0002] Variable valve lift is an emerging technology that appears to be capable of providing improved fuel economy, performance and drive-ability by switching between two or more camshaft profiles that are optimized for various conditions. Commonly, a lower-lift profile is employed for relatively lower speed operation, and a higher-lift profile is employed for relatively high speed operation.

[0003] While the known valve actuation devices that provide variable valve lift are suited for their intended purposes, there remains a need in the art for an improved valve actuation device that provides variable valve lift. SUMMARY

[0004] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0005] In one form, the present disclosure provides a valve actuation device that includes a hollow shaft, a lobe segment and an actuator. The hollow shaft is rotatable about an axis. The lobe segment is coupled to the hollow shaft for rotation therewith and is axially slidable along the axis. The lobe segment has a cam lobe set with a plurality of discrete lift sections. The actuator has an actuator shaft and a follower. The actuator shaft is received in the hollow shaft such that the hollow shaft and the lobe segment are rotatable about the actuator shaft. The actuator shaft is configured to be coupled to an engine structure such that the actuator shaft is maintained in a non-rotating position. The actuator shaft defines a first cam, a second cam and a gap that is disposed axially between the first and second cams. The follower is coupled to the lobe segment. Contact between the follower and the first cam when the hollow shaft rotates in a predetermined rotational direction causes translation of the lobe segment relative to the hollow shaft in a first direction along the axis. Contact between the follower and the second cam when the hollow shaft rotates in the predetermined rotational direction causes translation of the lobe segment relative to the hollow shaft in a second direction along the axis that is opposite the first direction. The first and second cams do not interact with the follower when the follower is disposed in the gap and contacts neither of the first and second cams.

[0006] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

[0007] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0008] Figure 1 is a perspective view of an exemplary valve actuation device constructed in accordance with the teachings of the present disclosure;

[0009] Figure 2 is an exploded perspective view of the valve actuation device of Figure 1 ;

[0010] Figure 3 is a longitudinal section view of a portion of the valve actuation device of Figure 1 ;

[0011] Figure 4 is a section view taken along the line 4-4 of Figure 3;

[0012] Figure 5 is a side elevation view of a portion of the valve actuation device of Figure 1 , illustrating a lobe segment in more detail;

[0013] Figures 6 and 7 are perspective views of a portion of the valve actuation device of Figure 1 , illustrating an actuator shaft of an actuator in more detail;

[0014] Figures 8 and 9 are perspective, partly broken away views of a portion of the valve actuation device of Figure 1 ;

[0015] Figure 10 is a top plan view of a portion of the valve actuation device of Figure 1 , illustrating a shift collar of the actuator in more detail; [0016] Figure 1 1 is a perspective, partly broken away view of a portion of the valve actuation device of Figure 1 ;

[0017] Figure 12 is a perspective view of a portion of the valve actuation device of Figure 1 , illustrating the shift collar and lobe segments mounted on a hollow shaft and the actuator shaft received in the hollow shaft;

[0018] Figure 13 is an elevation view of a portion of the valve actuation device of Figure 1 , illustrating the actuator in more detail; and

[0019] Figure 14 is a plan view of a portion of an alternately constructed valve actuation device illustrating a somewhat different shift collar.

[0020] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0021] With reference to Figures 1 and 2 of the drawings, an exemplary valve actuation device is generally indicated by reference numeral 10. The valve actuation device 10 is configured to operate a set of valves 12, which could comprise some or all of the exhaust and/or intake valves of an internal combustion engine. The valve actuation device 10 can comprise a hollow shaft 20, one or more lobe segments 22 and an actuator 24. The hollow shaft 20 can be supported on an appropriate structure, such as a cylinder head or an engine block, for rotation about an axis 30. In the example provided, the hollow shaft 20 defines a plurality of bearing journals 32 that are received in bearing mounts 34 in a cylinder head 36 (only partly shown) and bearings (not specifically shown) are received between the bearing journals 32 and the bearing mounts 34.

[0022] With reference to Figures 2 through 4, each lobe segment 22 is non-rotatably but axially slidably coupled to the hollow shaft 20. In the particular example provided, each lobe segment 22 has an internally splined or toothed aperture 40 that engages a correspondingly splined or toothed section 42 of the hollow shaft 20 to thereby couple the lobe segment 22 to the hollow shaft 20 for common rotation about the axis 30 while permitting translation of the lobe segment 22 along the axis 30 relative to the hollow shaft 20.

[0023] Each lobe segment 22 can include a plurality of discrete lift sections 50a, 50b and 50c that can be grouped in one or more cam lobe sets 52. Each cam lobe set 52 is configured for use in the operation of a single one of the valves 12 (Fig. 1 ). More specifically, the lift sections 50a, 50b and 50c of a cam lobe set 52 can be alternately selected (as will be discussed in more detail, below) to operate a single one of the valves 12. Each cam lobe set 52 is configured to interact with an actuating element 56 (Fig. 1 ) to cause translation of a corresponding valve 12. The actuating element 56 (Fig. 1 ) is depicted as a finger follower in the example provided, but could be any type of actuating element, such as a rocker arm or a bucket tappet, for example.

[0024] With reference to Figure 5, the cam lobe set 52 can have a base circle portion 60 and two or more of the lift sections 50a, 50b and 50c. The base circle portion 60 is configured to interact with the actuating element 56 (Fig. 1 ) in a manner that positions (or maintains) the associated one of the valves 12 in a closed position, while each of the lift sections 50a, 50b and 50c can be configured to provide a desired amount of "valve lift" that opens or translates the associated one of the valves 12 (Fig. 1 ) in a desired manner (i.e., to a desired extent and at a desired rotational position of the hollow shaft 20). It will be appreciated that each of the lift sections 50a, 50b and 50c of a given cam lobe set 52 can be configured differently from one another. For example, each of the lift sections 50a, 50b and 50c in the cam lobe set 52 can be defined by a maximum radius r1 , r2 and r3, respectively, and each of the lift sections 50a, 50b and 50c in the cam lobe set 52 can have a different maximum radius. In the particular example provided, the maximum radius r2 of the lift section 50b is larger than the maximum radius r1 of the lift section 50a, which in turn is larger than the maximum radius r3 of the lift section 50c (i.e., r2 > r1 > r3). Additionally or alternatively, the maximum radius one two or more of the lift sections 50a, 50b and 50c of the cam lobe set 52 can be offset from one another about the axis 30. As will be appreciated, configuration in this manner permits the timing of the opening of the associated valve 12 (Fig. 1 ) to be changed (relative to another one of the lift portions). [0025] With reference to Figures 1 through 3, the actuator 24 can have an actuator shaft 70 and one or more followers 72. The actuator shaft 24 can be received in the hollow shaft 20 such that the hollow shaft 20 and the lobe segment 22 are rotatable about the actuator shaft 70. The actuator shaft 70 can be non-rotatably coupled to an engine structure, such as the cylinder head 36, such that the actuator shaft 70 is maintained in a non-rotating position. The actuator shaft 70 can have a quantity of actuator sections 75 that can correspond to the quantity of the lobe segments 22. Each of the actuator sections 75 can define a first cam 78, a second cam 78 and a gap 80 that is disposed axially between the first and second cams 76 and 78. In the example provided, the actuator sections 75 are unitarily and integrally formed with the remainder of the actuator shaft 70. In this regard, the actuator shaft 70 of the particular example provided is a solid cylindrical shaft having a plurality of necked-down sections in which the first and second cams 76 and 78 of an actuator section 75 are formed on opposite axial shoulders of a corresponding one of the necked-down sections.

[0026] With reference to Figures 6 and 7, each of the first and second cams 76 and 78 can have a circumferentially extending portion 84 and a helical portion 86 that tapers from the circumferentially extending portion 84 toward an opposite axial shoulder of the necked-down section and terminates at the gap 80.

[0027] With reference to Figures 3, 8 and 9, the quantity of the followers 72 can be equal to the quantity of the lobe segments 22. Each follower 72 can be coupled to a corresponding one of the lobe segments 22. In the example provided, each follower 72 comprises a pin that is coupled to a corresponding one of the lobe segments 22 and received through a corresponding slotted aperture 90 formed in the hollow shaft 20. Contact between one of the followers 72 and an associated one of the first cams 76 when the hollow shaft 20 rotates in a predetermined rotational direction causes translation of the corresponding one of the lobe segments 22 relative to the hollow shaft 20 in a first direction along the axis 30, while contact between the one of the followers 72 and an associated one of the second cams 78 when the hollow shaft 20 rotates in the predetermined rotational direction about the axis 30 causes translation of the corresponding one of the lobe segments 22 relative to the hollow shaft 20 in a second direction along the axis 30 that is opposite the first direction. The first and second cams 76 and 78 of an actuator section 75 do not interact with the associated follower 72 when that follower 72 is disposed in the gap 80 and contacts neither of the first and second cams 76 and 78.

[0028] With renewed reference to Figures 3 and 8, it will be appreciated that the actuator shaft 70 is movable axially along the axis 30 between a plurality of discrete positions. At times when the actuator shaft 70 is not in its furthest position in the first direction along the axis 30, the actuator shaft 70 can be slid along the axis 30 in the first direction to cause engagement of the followers 72 to the first cams 76 while the followers 72 rotate about the actuator shaft 70. In this condition, the first cams 76 urge the followers 72 in the first direction along the axis 30 as they rotate about the axis 30 to thereby shift the lobe segments 22 in the first direction along the axis 30 relative to the hollow shaft 20. Once a follower 72 has fully traversed its associated first cam 78, the follower 72 will be aligned to the gap 80 between the first and second cams 76 and 78 in a given actuator section 75. Depending on the quantity of the lift sections in a lobe segment 22, it may be possible to shift the actuator shaft 70 further in the first direction along the axis 30 to cause the lobe segments 22 to shift correspondingly further in the first direction along the axis 30 (through appropriate interaction between the followers 72 and the first cams 76). Stepped movement of the actuator shaft 70 to produce corresponding stepped movement of the lobe segments 22 would be required to move the lobe segments 22 from a first position, in which the lift section 50a is aligned to the actuating element 56 (Fig. 1 ), to a second position in which the lift section 50b is aligned to the actuating element 56 (Fig. 1 ) and finally to a third position in which the lift section 50c is aligned to the actuating element 56 (Fig. 1 ).

[0029] It will also be appreciated that at times when the actuator shaft 70 is not in its furthest position in the second direction along the axis 30, the actuator shaft 70 can be slid along the axis 30 in the second direction to cause engagement of the followers 72 to the second cams 78 while the followers 72 rotate about the actuator shaft 70. In this condition, the second cams 78 urge the followers 72 in the second direction along the axis 30 as they rotate about the axis 30 to thereby shift the lobe segments 22 in the second direction along the axis 30 relative to the hollow shaft 20. Once a follower 72 has fully traversed its associated second cam 78, the follower 72 will be aligned to the gap 80 between the first and second cams 76 and 78 in a given actuator section 75. Depending on the quantity of the lift sections in a lobe segments 22, it may be possible to shift the actuator shaft 70 further in the second direction along the axis 30 to cause the lobe segments 22 to shift correspondingly further in the second direction along the axis 30 (through appropriate interaction between the followers 72 and the second cams 78). Stepped movement of the actuator shaft 70 to produce corresponding stepped movement of the lobe segments 22 would be required to move the lobe segments 22 from the third position, in which the lift section 50c is aligned to the actuating element 56 (Fig. 1 ), to the second position in which the lift section 50b is aligned to the actuating element 56 (Fig. 1 ) and finally to the first position in which the lift section 50a is aligned to the actuating element 56 (Fig. 1 ).

[0030] Returning to Figure 1 , any desired means can be employed to shift the actuator shaft 70 between its plurality of positions. For example, pneumatic or hydraulic cylinder or a solenoid-operated plunger could be employed to apply an axially directed force directly to the actuator shaft 70 to cause it to translate along the axis. In the particular example provided, however, the actuator 24 further includes a shift collar 100 and one or more actuator members 102.

[0031] With reference to Figures 2 and 10 through 12, the shift collar 100 can be non-rotatably but axially slidably coupled to the hollow shaft 20 and can define one or more shift grooves that extend about the circumference of the shift collar 100. In the example provided, the shift collar 100 has an internally splined or toothed aperture 120 (similar to that of the lobe segments 22), which is engaged to an externally splined or toothed segment 42 on the hollow shaft 20, and two discrete, axially spaced apart shift grooves 122a and 124b . The shift collar 100 can further be coupled to the actuator shaft 70 in a manner that causes the actuator shaft 70 to translate with the shift collar 100 along the axis 30 relative to the hollow shaft 20 while permitting rotation of the shift collar 100 about the actuator shaft 70. For example, one or more cylindrical pins 130 can extend radially from the shift collar 100 through corresponding slots 132 formed in the hollow shaft 20 and reside in a circumferentially extending groove 134 that is formed in the actuator shaft 70. The circumferentially extending groove 134 can be wider than a diameter of a portion of the pin(s) 130 that is/are received in the circumferentially extending groove 134.

[0032] With reference to Figures 2 and 13, the actuator member(s) can selectively engage the shift collar 100 to cause corresponding translation of the shift collar 100 along the axis 30 during rotation of the hollow shaft 20 in the predetermined rotational direction. In the example provided, each of the actuator members 102a and 102b is a plunger of a solenoid 140a and 140b, respectively, and is movable between an extended position, in which a plunger 102a, 102b of the solenoid, 140a, 140b is received into an associated one of the shift grooves 122 and 124, and a retracted position in which the plunger 102a, 102b of the solenoid 140a, 140b is retracted out of the associated one of the shift grooves 122 and 124. Each of the solenoids 140a, 140b can be fixedly coupled to a (stationary) structure, such as the cylinder head 36 (Fig. 1 ). Accordingly, positioning of the actuator member 102a in an extended position places the actuator member 102a in a first one of the shift grooves 122, while positioning of the actuator member 102b in an extended position places the actuator member 102b in the second shift groove 124b.

[0033] With additional reference to Figure 10, the first shift groove 122 is cam-shaped and configured so that when it is engaged by the actuator member 102a and the hollow shaft 20 is rotated in the predetermined rotational direction, a force is applied to the shift collar 100 that causes the shift collar 100 to translate in the first direction along the axis 30. In the particular example provided, the first shift groove 122 has first, second and third circumferentially-extending portions 150, 152 and 154, a first helical portion 156 that connects the first and second circumferentially-extending portions 150 and 152, an a second helical portion 158 that connects the second and third circumferentially-extending portions 152 and 154. Selective movement of the actuator member 102a into and out of the first shift groove 122 can be coordinated with the rotational position of the hollow shaft 20/shift collar 100 so that the actuator member 102a is introduced to the first circumferentially-extending portion 150 and is withdrawn from the second circumferentially-extending portion 152 or the third circumferentially-extending portion 154 or is introduced to the second circumferentially-extending portion 152 and is withdrawn from the third circumferentially-extending portion 154.

[0034] Similarly, the second shift groove 124 is cam-shaped and configured so that when it is engaged by the actuator member 102b and the hollow shaft 20 is rotated in the predetermined rotational direction, a force is applied to the shift collar 100 that causes the shift collar 100 to translate in the second direction along the axis 30. In the particular example provided, the second shift groove 124 has fourth, fifth and sixth circumferentially-extending portions 160, 162 and 164, a third helical portion 166 that connects the fourth and fifth circumferentially-extending portions 160 and 162, and a fourth helical portion 168 that connects the fifth and sixth circumferentially-extending portions 162 and 164. Selective movement of the actuator member 102b into and out of the second shift groove 124 can be coordinated with the rotational position of the hollow shaft 20/shift collar 100 so that the actuator member 102b is introduced to the sixth circumferentially-extending portion 164 and is withdrawn from the fifth circumferentially-extending portion 162 or the fourth circumferentially-extending portion 160 or is introduced to the fifth circumferentially-extending portion 162 and is withdrawn from the fourth circumferentially-extending portion 160.

[0035] It will be appreciated that the extension and retraction of the actuator members 102a and 102b can be coordinated with the rotational position of the hollow shaft 20 and as such, a conventional position sensor and controller (not shown) could be employed (i.e., the position sensor can sense a rotational position of the hollow shaft 20 and to responsively generate a rotational position signal, while the controller can receive the rotational position signal and can determine the rotational position of the hollow shaft as well as control the timing of the extension and retraction of the actuator members 102a and 102b). If desired, one or more detents (not shown) could be employed to resist axial movement of the shift collar 100 and/or each lobe segment 22 relative to the hollow shaft 20 when the first and second actuator members 102a and 102b are retracted from the first and second shift grooves 122 and 124, respectively. [0036] In the example of Figure 14, an alternately constructed shift collar 100' is illustrated. The shift collar 100' is similar to the shift collar 100 (Fig. 10), in that that each of the first and second shift grooves 122a' and 122b', respectively, is formed with a pair of circumferentially-extending portions (150' and 152', respectively, in the first shift groove 122a' and 160' and 162', respectively, in the second shift roove 122b') and a helical portion (156' and 166', respectively) that interconnect a respective pair of the circumferentially extending portions. However, each of the first and second shift grooves 122a' and 122b' also includes a circumferentially-extending retaining groove 200 and 202, respectively. The retaining groove 200 intersects the circumferentially-extending portion 152' of the first shift groove 122a', while the retaining groove 202 intersects the circumferentially- extending portion 162' of the second shift groove 122b'.

[0037] During operation, the actuator member 102a' can be engaged to the circumferentially-extending portion 150' in the first shift groove 122a' to cause the shift collar 100' to move axially in a first direction to switch from a first lift section to a second lift section. Because the retaining groove 200 intersects the circumferentially-extending portion 152', the actuator member 102a' can be maintained in the circumferentially-extending portion 152' and the retaining groove 200 to inhibit further axial movement of the shift collar 100'. The actuator member 102a' can subsequently be withdrawn from the circumferentially-extending portion 152' and the retaining groove 200 and the actuator member 102b' can be engaged to the circumferentially-extending portion 160' in the second shift groove 122b' to cause the shift collar 100' to move axially in a second direction opposite the first direction to switch from the second lift section to the first lift section. Because the retaining groove 202 intersects the circumferentially-extending portion 162', the actuator member 102b' can be maintained in the circumferentially-extending portion 162' and the retaining groove 202 to inhibit further axial movement of the shift collar 100'.

[0038] The foregoing description of the embodiments 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 embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, 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

CLAIMS What is claimed is:

1 . A valve actuation device (10) comprising:

a hollow shaft (20) that is rotatable about an axis (30);

a lobe segment (22) coupled to the hollow shaft (20) for rotation therewith, the lobe segment (22) being axially slidable along the axis (30), the lobe segment (22) having a cam lobe set (52), the cam lobe set (52) having a plurality of discrete lift sections (50a, 50b, 50c); and

an actuator (24) having an actuator shaft (70) and a follower (72), the actuator shaft (70) being received in the hollow shaft (20) such that the hollow shaft (20) and the lobe segment (22) are rotatable about the actuator shaft (70), the actuator shaft (70) being adapted to be coupled to an engine structure such that the actuator shaft (70) is maintained in a non-rotating position, the actuator shaft (70) defining a first cam (76), a second cam (78) and a gap (80) that is disposed axially between the first and second cams (76, 78), the follower (72) being coupled to the lobe segment (22), wherein contact between the follower (72) and the first cam (76) when the hollow shaft (20) rotates in a predetermined rotational direction causes translation of the lobe segment (22) relative to the hollow shaft (20) in a first direction along the axis (30), wherein contact between the follower (72) and the second cam (78) when the hollow shaft (20) rotates in the predetermined rotational direction causes translation of the lobe segment (22) relative to the hollow shaft (20) in a second direction along the axis (30) that is opposite the first direction, and wherein the first and second cams (76, 78) do not interact with the follower (72) when the follower (72) is disposed in the gap (80) and contacts neither of the first and second cams (76, 78).

2. The valve actuation device (10) of Claim 1 , wherein the cam lobe set (52) has a base circle portion (60) and wherein each of the discrete lift sections (50a, 50b, 50c) intersect the base circle portion (60).

3. The valve actuation device (10) of Claim 2, wherein each of the lift sections (50a, 50b, 50c) in the cam lobe set (52) is defined by a maximum radius (r1 , r2, r3), and wherein each of the lift sections (50a, 50b, 50c) in the cam lobe set (52) has a different maximum radius.

4. The valve actuation device (10) of Claim 2, wherein the maximum radius (r1 , r2, r3) of at least two of the lift sections (50a, 50b, 50c) of the cam lobe set (52) are offset from one another about the axis (30).

5. The valve actuation device (10) of Claim 1 , wherein the first and second cams (76, 78) are formed on opposite axial shoulders of a necked- down segment of the actuator shaft (70).

6. The valve actuation device (10) of Claim 1 , wherein the follower (72) is a pin that is coupled to the lobe segment (22) and received through a slotted aperture (90) formed in the hollow shaft (20).

7. The valve actuation device (10) of Claim 1 , wherein the actuator (24) further comprises a shift collar (100) and at least one actuator member (102), the shift collar (100) being non-rotatably but axially slidably coupled to the hollow shaft (20), the at least one actuator member (102) being configured to engage the shift collar (100) to cause corresponding translation of the shift collar (100) along the hollow shaft (20), the shift collar (100) being rotatable about the actuator shaft (70) but coupled to the actuator shaft (70) for common movement along the axis (30), the actuator member (102) being selectively engageable with the shift collar (100) to cause movement of the shift collar (100) along the axis (30) during rotation of the hollow shaft (20) in the predetermined rotational direction.

8. The valve actuation device (10) of Claim 7, wherein the actuator

(24) comprises a pair of actuator members (102) that are alternately engageable to the shift collar (100), wherein engagement of a first one of the actuator members (102) to the shift collar (100) when the hollow shaft (20) is rotated in the predetermined rotational direction coordinates movement of the shift collar (100) relative to the hollow shaft (20) in the first direction along the axis (30) and wherein engagement of the other one of the actuator members (102) to the shift collar (100) when the hollow shaft (20) is rotated in the predetermined rotational direction coordinates movement of the shift collar (100) relative to the hollow shaft (20) in the second direction along the axis (30).

9. The valve actuation device (10) of Claim 7, wherein a pin (130) is coupled to shift collar (100) and is received in a groove (134) in the actuator shaft (70), the groove (134) being wider than a diameter of a portion of the pin (130) that is received in the groove (134).

10. The valve actuation device (10) of Claim 1 , wherein the lobe segment (22) has a second cam lobe set (52), the second cam lobe set (52) having a plurality of discrete second lift sections (50a, 50b, 50c) and wherein the second cam lobe set (52) is offset from the cam lobe set along the axis (30).

1 1 . The valve actuation device (10) of Claim 1 , wherein the lift sections (50a, 50b, 50c) of the cam lobe set (52) number three in quantity.