Torque limiting torsion joint

Abstract

A torque limiting torsion joint for connecting an electric motor to a camshaft phaser includes an elongated body configured to extend from one end of a motor shaft of the electric motor to an input of a planetary gear assembly of the camshaft phaser; an angular displacement resistant end of the elongated body configured to engage one end of the motor shaft; and a key positioned at the other end of the elongated body opposite the angular displacement resistant end and configured to be received in and engaged with a slot at the input of the planetary gear assembly of the camshaft phaser so as to transmit torque from the electric motor to the planetary gear assembly; the elongated body prevents angular displacement of the motor shaft relative to the input of the planetary gear assembly and allows angular displacement of the motor shaft relative to the input of the planetary gear assembly when a mechanical stop of the camshaft phaser is engaged.

Description

Technical Field

[0001] The present invention relates to camshaft phasers and, more particularly, to electric motors that control camshaft phasers. Background Art

[0002] A vehicle may include an electric motor that performs various vehicle functions, including, for example, adjusting the angular position of one or more camshafts relative to the angular position of the crankshaft or adjusting the position of a passenger or driver seat. The electric motor may be used to operate a camshaft phaser to advance or retard the timing of the camshaft relative to the crankshaft. The camshaft phaser may include a gearbox driven by the electric motor. Mechanical stops that limit the authorized range of the camshaft phaser may be included in the gearbox. When the camshaft phaser reaches the end of the range, the gearbox motion may stop relatively abruptly and a relatively large amount of torque may be applied to the output shaft of the electric motor. This relatively large amount of torque may cause unnecessary stress on the camshaft phaser, and it will be helpful to reduce this stress. Summary of the invention

[0003] In one implementation, a torque limiting torsion joint for connecting an electric motor to a camshaft phaser includes an elongated body configured to extend from one end of a motor shaft of the electric motor to an input of a planetary gear assembly of the camshaft phaser; an angular displacement resistant end of the elongated body configured to engage one end of the motor shaft; and a key positioned at the other end of the elongated body opposite the angular displacement resistant end and configured to engage the input of the planetary gear assembly of the camshaft phaser so as to transmit torque from the electric motor to the planetary gear assembly; the elongated body prevents angular displacement of the motor shaft relative to the input of the planetary gear assembly and allows angular displacement of the motor shaft relative to the input of the planetary gear assembly when a mechanical stop of the camshaft phaser is engaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 is a perspective exploded view depicting an implementation of an electrically actuated variable camshaft timing (VCT) assembly;

[0005] Figure 2 is a perspective exploded view depicting a portion of an implementation of an electrically actuated VCT assembly;

[0006] Figure 3 is a cross-sectional view depicting an implementation of an electrically actuated VCT assembly;

[0007] Figure 4 is a perspective view depicting the implementation of an elongated torque-limiting torsion universal joint;

[0008] Figure 5 is an exploded perspective view depicting the implementation of an elongated torque-limiting torsion universal joint;

[0009] Figure 6 is a cross-sectional view depicting an implementation of an elongated torque-limiting torsion universal joint;

[0010] Figure 7 is a cross-sectional view depicting another implementation of an elongated torque-limiting torsion joint. DETAILED DESCRIPTION

[0011] An elongated torque-limiting twist universal joint may couple a motor shaft of an electric motor to a gear assembly of a variable camshaft timing (VCT) device (also referred to as a camshaft phaser). The twist universal joint may include an elongated body that is fixed to one end of the motor shaft and is pivotally received by an input of a gearbox, thereby transmitting torque or rotational motion generated by the electric motor through the motor shaft to the input of the gear assembly of the camshaft phaser. During normal operation, the twist universal joint may maintain the angular position of the motor shaft relative to the input of the gear assembly. When the camshaft phaser reaches the limit of its authorized range, causing a mechanical stop to engage, the twist universal joint may momentarily deform in response to the torque applied to the gear assembly from the motor shaft to gradually allow angular displacement of the motor shaft relative to the input of the gear assembly by allowing twisting motion along its elongated body. Once the gear assembly of the camshaft phaser disengages from the mechanical stop and / or no more torque is applied to the twist universal joint through the motor shaft, the universal joint may return to its default shape and reestablish a default angular relationship between the input of the motor shaft and the gear assembly. The torsion universal joint may also include a key formed at a distal end configured to be received in a slot formed in an input of the gear assembly.The key and slot combination may allow the axis of rotation of the motor shaft to be angularly offset from the axis of rotation of the gearbox.

[0012] Figures 1 to 3 An embodiment of an electrically actuated VCT assembly 10 (also referred to as an electrically actuated camshaft phaser or "phaser") is shown. The phaser 10 is a multi-piece mechanism having components that work together to transfer rotation from a crankshaft of an engine to a camshaft of the engine and that work together to angularly displace the camshaft relative to the crankshaft to advance and retard the opening and closing of the engine valves. The phaser 10 may have different designs and configurations depending on, among other possible factors, the application in which the phaser is used and the crankshaft and camshaft with which it operates. For example, in Figures 1 to 3 In the illustrated embodiment, the phaser 10 includes a sprocket 12 , a planetary gear assembly 14 , and a camshaft plate or plate 16 .

[0013] The sprocket 12 receives a rotational drive input from the engine crankshaft and rotates about an axis x 1Rotation. A timing chain or timing belt can be encircled around the sprocket 12 and around the crankshaft so that the rotation of the crankshaft is converted into the rotation of the sprocket via the chain or belt. Other technologies for transferring rotation between the sprocket 12 and the crankshaft are also possible. Along the outer surface, the sprocket 12 has a set of teeth 18 for cooperating with a timing chain, a timing belt or another component. In different examples, the set of teeth 18 can include thirty-eight individual teeth, forty-two individual teeth, or some other number of teeth that continuously span around the circumference of the sprocket 12. As shown, the sprocket 12 has a housing 20 that spans axially from the set of teeth 18. The housing 20 is a cylindrical wall surrounding a portion of the planetary gear assembly 14.

[0014] The planet gear stop 13 may be included on the inwardly facing surface of the sprocket 12 to limit the angular displacement between the camshaft and the crankshaft. The planet gear stop 13 is one implementation of a range limiting element. The planet gear stop 13 engages a portion of the planet gear assembly 14 and prevents further angular displacement between the camshaft and the crankshaft in the advance direction and the retard direction. However, the planet gear stop 13 may be implemented in a variety of different ways. For example, the planet gear stop may be movable rather than existing as a fixed protrusion extending radially inward from the sprocket 12. For example, in one implementation, the planet gear stop may be an element that fits into a recess of the camshaft ring gear so that the planet gear stop moves to engage an element included on the planet gear assembly. In one implementation, the planet gear stop may pivot about an axis or may slide radially inward or radially outward to engage or disengage the planet gear assembly 14. A variety of different planet gear stops are described in U.S. Patent Application No. 15 / 635,281, the entire contents of which are incorporated herein by reference.

[0015] In the embodiment shown here, the planetary gear assembly 14 comprises planetary gears 24. The sun gear 22 is driven by an electric motor 23 to rotate about an axis x. 1 Rotation. The sun gear 22 is engaged with the planetary gears 24 and has a set of teeth 32 on the exterior thereof that are in direct tooth-to-tooth mesh with the planetary gears 24. In different examples, the set of teeth 32 may include twenty-six individual teeth, thirty-seven individual teeth, or some other number of teeth that span continuously around the circumference of the sun gear 22. A cylindrical skirt 34 spans from the set of teeth 32. As described above, the sun gear 22 is an external spur gear, but it may be other types of gears. The electric motor 23 includes a stator and a rotor (not shown). The rotor may be coupled to the motor shaft 100 to prevent angular movement of the rotor relative to the motor shaft 100. Electric current may be received by windings included in the stator to cause rotational movement of the rotor relative to the stator. The rotational movement of the rotor is in communication with the motor shaft 100. In one implementation, the motor shaft 100 may include an inner diameter 114 (at Figure 6 and7 ) and outer diameter such that shaft 100 is tubular. A torsional universal joint 110 can be coupled to the distal end of motor shaft 100, extending within an inner diameter 114 of motor shaft 100, and an opposite end of the universal joint formed as a key 102 can pivotally engage sun gear 22. Key 102 can be shaped to engage sun gear 22 via slot 126 and transfer rotational motion from motor shaft 100 to planetary gear assembly 14. However, it should be understood that in other implementations, key 102 can engage the input of the planetary gear assembly differently. For example, the key can be welded or otherwise coupled to the input of the planetary gear assembly. This will be discussed below with reference to Figures 4 to 7 Discuss in more detail.

[0016] When the camshaft of the engine is placed in an intermediate position between the advanced angle position and the retarded angle position, the planetary gears 24 rotate about their respective axes of rotation x 2 When not advanced or retarded, the planetary gears 24 rotate together with the sun gear 22 and the ring gears 26 and 28 about the axis x. 1 Rotation. In the embodiment given here, there are a total of three discrete planetary gears 24, which are similarly designed and constructed relative to each other, but there may be other numbers of planetary gears, such as one, two, four or six. However, in many cases, each planetary gear 24 can be engaged with the first and second ring gears 26, 28 included in the sprocket 12 and the plate 16, respectively. Each planetary gear 24 can have a set of teeth 60 along its exterior for direct tooth-to-tooth engagement with the ring gears 26, 28. In different examples, the teeth 60 can include twenty-one individual teeth, or some other number of teeth that continuously span around the circumference of each planetary gear 24. In order to keep the planetary gears 24 in place and support them, a bracket assembly 62 can be provided. The bracket assembly 62 can have different designs and constructions. In the embodiment shown in the drawings, the bracket assembly 62 includes a first bracket plate 64 on one side, a second bracket plate 66 on the other side, and a cylinder 68 that serves as a hub for rotating the planetary gears 24. A planetary pin or bolt 70 can be used with the bracket assembly 62. It should be understood that other implementations of planetary gear assemblies are possible, and the term should be understood to include other such implementations, such as implementations using eccentric shafts and compound planetary gears or implementations using harmonic drives. An implementation with one ring gear and one planetary gear attached to the camshaft via a coupling is also possible.

[0017] The first ring gear 26 receives a rotational drive input from the sprocket 12 such that the first ring gear 26 and the sprocket 12 rotate together about the axis x in operation. 1The first ring gear 26 may be an integral extension of the sprocket 12, i.e., the first ring gear 26 and the sprocket 12 may form a unitary structure together. The first ring gear 26 has an annular shape, engages with the planetary gears 24, and has a set of teeth 72 at its interior for direct tooth-to-tooth engagement with the planetary gears 24. In different examples, the teeth 72 may include eighty individual teeth, or some other number of teeth that span continuously around the circumference of the first ring gear 26. In the embodiment presented here, the first ring gear 26 is an internal spur gear, but may be other types of gears.

[0018] The second ring gear 28 rotates the drive output about the axis x 1 to the camshaft of the engine. In this embodiment, the second ring gear 28 drives the rotation of the camshaft via the plate 16. The second ring gear 28 and the plate 16 can be connected together in different ways, including interconnection by cutouts and tabs, press fit, welding, adhesion, bolting, riveting or by another technology. In embodiments not shown here, the second ring gear 28 and the plate 16 can be integral extensions of each other to form an integral structure. Similar to the first ring gear 26, the second ring gear 28 has an annular shape, engages with the planetary gears 24, and has a set of teeth 74 inside it for direct tooth-to-tooth engagement with the planetary gears. In different examples, the teeth 74 can include seventy-seven individual teeth, or some other number of teeth that continuously span around the circumference of the second ring gear 28. Relative to each other, the number of teeth between the first and second ring gears 26, 28 can differ by a multiple of the number of planetary gears 24 provided. Thus, for example, the teeth 72 can include eighty individual teeth, while the teeth 74 can include seventy-seven individual teeth, in this example, the three individual teeth of the three planetary gears 24 are different. In another example with six planetary gears, teeth 72 may include seventy individual teeth, while teeth 74 may include eighty-two individual teeth. Meeting this relationship provides advance and retard capability by imparting relative rotational motion and relative rotational speed between the first and second ring gears 26, 28 during operation. In the embodiment presented here, the second ring gear 28 is an internal spur gear, but may be another type of gear. Plate 16 includes a central hole 76 through which a central bolt 78 passes to fixedly attach plate 16 to the camshaft. In addition, plate 16 is also secured to sprocket 12 by a snap ring 80, which axially constrains the planetary gear assembly 14 between sprocket 12 and plate 16.

[0019] The two ring gears 26, 28 together form a split ring gear configuration for the camshaft phaser 10. However, it should be understood that other camshaft phaser designs can be used with buffer stops. For example, the camshaft phaser can be implemented using an eccentric shaft, a compound planetary gear, and two ring gears. Alternatively, the camshaft phaser can include more than two ring gears. For example, the camshaft phaser 10 can include an additional third ring gear, for a total of three ring gears. Here, the third ring gear can also transmit the rotational drive output to the camshaft of the engine like the second ring gear 28, and can have the same number of individual teeth as the second ring gear.

[0020] Go to Figures 4 to 7 , shows an implementation of a torque limiting torsion universal joint 110 for connecting the motor shaft 100 of the electric motor 23 to the planetary gear assembly 14. The rotor 112 of the electric motor 23 includes an inner diameter that engages the outer diameter of the motor shaft 100. The motor shaft 100 may be friction fit into the inner diameter of the rotor, or otherwise coupled to prevent angular displacement of the rotor 112 relative to the motor shaft 100.

[0021] The torsion universal joint 110 includes an elongated body 116 extending from one end of the motor shaft 100 of the electric motor 23 to an input of a gearbox of a camshaft phaser, such as the sun gear 22. In this implementation, the motor shaft includes an inner diameter so that the torsion universal joint 110 can be received within the motor shaft 100 so that the torsion universal joint 110 is at least partially concentric with the shaft 100. At one end of the elongated body 116, an anti-angular displacement end 118 of the motor shaft 100 can mechanically engage an anti-angular displacement end 120 of the torsion universal joint 110. In this implementation, the anti-angular displacement end 118 can include a hexagonal cross-sectional shape that receives and engages with a similarly shaped end 120 of the torsion universal joint 110. When the anti-angular displacement end 118 engages with the similarly shaped end 120, the anti-angular displacement end 118 can prevent angular displacement of the torsion universal joint 110 relative to the shaft 100. It should be understood that the anti-angular displacement end may be achieved in other ways, such as by welding the end of a torsion universal joint to the motor shaft. The size and shape of the elongated body 116 may define the amount of angular deflection of the rotor 112 relative to the sun gear 22. For example, the length of the elongated body 116, the diameter of the elongated body 116, the material of the elongated body 116, and / or the cross-sectional shape of the elongated body 116 may be specified to define the amount of angular deflection.

[0022] At the opposite end 122 of the elongated body 116, the key 102 may be shaped to be received within and engage a slot 126 at the input of the planetary gear assembly 14 of the phaser 10 and transfer torque from the electric motor 100 to the assembly 14. The key 102 may be shaped in a variety of different forms and in this implementation includes a first wing 128 and a second wing 130, each wing extending from the planetary gear assembly rotation axis (x 1 ) extends radially outward. When each wing 128, 130 engages a portion of the slot 126, the motor shaft 100 and the electric motor 23 can rotate relative to the planetary gear assembly axis (x 1 ) is angularly displaced while still maintaining functional operation and minimizing friction and vibration. In this implementation, the torsion universal joint 110 can be formed from a unitary metal wire that is bent at certain axial points to form the first wing 128 and the second wing 130.

[0023] Figure 7 Another implementation of a torsion gimbal 110' is depicted. The torsion gimbal 110' includes an anti-angular displacement end 120' that can be formed by a portion of an elongated body 116' that is bent substantially perpendicularly relative to the main body 116'. The anti-angular displacement end 120' can include a tab 132 having a diameter that substantially matches or is slightly smaller than the width of a notch 134 in the distal end of the motor shaft 100'. The tab 132 can engage the notch 134 to prevent angular displacement of the torsion gimbal 110' relative to the motor shaft 100'.

[0024] It should be understood that the above is a description of one or more embodiments of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but is limited only by the following claims. In addition, the statements contained in the foregoing description relate to specific embodiments and should not be interpreted as limitations on the scope of the present invention or the definitions of the terms used in the claims, unless the terms or phrases are clearly defined above. Various other embodiments and various changes and modifications to the disclosed embodiments will become apparent to those skilled in the art. All of these other embodiments, changes and modifications are intended to fall within the scope of the appended claims.

[0025] As used in this specification and claims, the terms "eg," "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a list of one or more components or other items, are each interpreted as open-ended, meaning that the list is not to be construed as excluding other additional components or items. Other terms should be interpreted using their broadest reasonable meaning unless used in a context that requires a different interpretation.

Claims

1. A torque limiting torsion joint for connecting an electric motor to a camshaft phaser, comprising: an elongated body configured to extend from an end of a motor shaft of the electric motor to an input of a planetary gear assembly of the camshaft phaser; an angularly resistant end of the elongated body configured to engage an end of the motor shaft; and a key positioned at the other end of the elongated body opposite the anti-angular displacement end and configured to engage the input of the planetary gear assembly of the camshaft phaser to transmit torque from the electric motor to the planetary gear assembly, wherein the elongated body prevents angular displacement of the motor shaft relative to the input of the planetary gear assembly and allows angular displacement of the motor shaft relative to the input of the planetary gear assembly when a mechanical stop of the camshaft phaser is engaged, Wherein the motor shaft includes an inner diameter and an outer diameter, and the elongated body is received within the inner diameter of the motor shaft and is concentric with the motor shaft.

2. The torque limiting torsion joint of claim 1, wherein the key allows the axis of rotation of the motor shaft to be angularly offset from the axis of rotation of the planetary gear assembly.

3. The torque limiting twist joint of claim 1 wherein said angular displacement resistant end of said elongated body comprises a hexagonal cross-section.

4. The torque limiting twist joint of claim 1 wherein said angular displacement resistant end of said elongated body comprises a vertically curved portion of said elongated body.

5. The torque limiting torsion joint of claim 1, wherein the key includes a first wing and a second wing, the first wing and the second wing are each formed from a portion of the elongated body and extend radially away from the motor shaft rotational axis.

6. The torque limiting torsion joint of claim 1 further comprising a camshaft phaser.

7. The torque limiting torsion joint of claim 6, wherein the planetary gear assembly includes a sun gear and a plurality of planet gears.

8. The torque limiting twist universal joint of claim 1 further comprising a slot at said input of said planetary gear assembly, said slot receiving said key.

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